Search

In this study, we conduct a comparative analysis of single-beam laser annealing (SBLA) and dual-beam laser annealing (DBLA) techniques for semiconductor manufacturing. In the DBLA approach, two laser beams were precisely aligned to simultaneously heat a phosphorus-doped silicon (Si) wafer. The main objective was to investigate the impact of the two annealing techniques on the electrical properties, crystalline structure, and diffusion profile of the treated phosphorus-doped Si at equivalent laser powers. Both SBLA and DBLA improved the electrical properties of the phosphorus-doped Si, evidenced by increased carrier concentration and reduced carrier mobility. Additionally, the crystalline structure of the phosphorus-doped Si showed favorable modifications, with no defects and improved crystallinity. While both SBLA and DBLA produced similar phosphorus profiles with no significant redistribution of dopants compared to the as-implanted sample, DBLA achieved a higher activation ratio than SBLA. Although the results suggest improved dopant activation with minimal diffusion, further studies are needed to clearly confirm the effect of DBLA on dopant activation and diffusion. [ABSTRACT FROM AUTHOR]

As gallium oxide-based heterojunction devices gain prominence, low-resistance contacts to aluminum gallium oxide material are of increasing importance for high performance and access to modulation doped layers. Here, the activation of ion-implanted silicon donors is investigated as a function of donor density from 5 × 1018 cm−3 to 1 × 1020 cm−3, activation anneal duration from 6 s to 600 s, and activation temperature from 900°C to 1140°C. Importantly, ohmic behavior was achievable across a reasonably wide process window at moderate to high doping concentrations. Specific contact resistance of 1 × 10−3 Ω cm2 and sheet resistance of 2.8 kΩ/□ were achieved for a 60 nm-deep 1 × 1020 cm−3 box implant after activation at 1000°C for 6 s with standard Ti/Au contacts. Under these conditions, an activation efficiency of 7% was observed with Hall mobility of ~32 cm2/Vs. Furthermore, we demonstrate a Schottky diode formed of implanted material with a rectification ratio > 106 and further confirm the Hall carrier density results using capacitance–voltage profiling analysis. Finally, we show the significant impact of anneal duration and the potential for deleterious over-annealing which reduces the active carrier density, mobility, and resultant material conductivity. [ABSTRACT FROM AUTHOR]

Carrier (electron) compensation is an important issue in impurity (donor) doped ZnO thin films, which must be understood to achieve the desired electrical conductivity. Unprecedentedly, using trivalent Al, tetravalent Ti, and pentavalent Vanadium, (the atomic symbol is not used to avoid confusion with the conventional vacancy symbol) metal ion doping in ZnO thin films while keeping all the growth and annealing parameters similar, we demonstrate that donor–acceptor (D-A) compensation in the doped film is influenced largely by the dopant valence. Hall data show a drastic decrease in the conductivity and carrier concentration values indicating progressively more D-A compensation as the dopant valence increases. Post-growth annealing in special ambient recovers trapped free carriers due to dopants' activation. The activation of the dopants due to annealing in Ar + 10% H2 + excess Zn ambient is far more than that happened in only Ar + 10% H2 ambient. To support this, we further discuss the dark and photo-Hall electrical transport data of the as-grown and annealed films measured under sub-bandgap photo-excitations to release the electrons from the acceptor-like complexes. [ABSTRACT FROM AUTHOR]

The bit density is generally increased by stacking more layers in 3D NAND Flash. Lowering dopant activation of select transistors results from complex integrated processes. To improve channel dopant activation, the test structure of vertical channel transistors was used to investigate the influence of laser thermal annealing on dopant activation. The activation of channel doping by different thermal annealing methods was compared. The laser thermal annealing enhanced the channel activation rate by at least 23% more than limited temperature rapid thermal annealing. We then comprehensively explore the laser thermal annealing energy density on the influence of Poly-Si grain size and device performance. A clear correlation between grain size mean and grain size sigma, large grain size mean and sigma with large laser thermal annealing energy density. Large laser thermal annealing energy density leads to tightening threshold voltage and subthreshold swing distribution since Poly-Si grain size regrows for better grain size distribution with local grains optimization. As an enabler for next-generation technologies, laser thermal annealing will be highly applied in 3D NAND Flash for better device performance with stacking more layers, and opening new opportunities of novel 3D architectures in the semiconductor industry. [ABSTRACT FROM AUTHOR]

Differential Hall Effect Metrology (DHEM) technique was used to characterize highly n-type doped Si epi layers deposited on p-type Si wafers. Total dopant concentration, doping depth profile and post deposition annealing condition were changed for various sample sets and influence of such changes on the resistivity, mobility and carrier concentration depth profiles were studied. It was determined that samples annealed at 900 °C had higher activation compared to those annealed at 700 °C. Gradation in doping depth profiles did not result in similar gradation in resistivity values. Carrier concentration at the near-surface region was found to be lower in all samples. It is shown that electrical properties of films forming ultra-shallow junctions can be studied in detail and correlated with process parameters using DHEM data obtained at sub-nm depth resolution.

The state-of-the-art CMOS technology has started to adopt three-dimensional (3D) integration approaches, enabling continuous chip density increment and performance improvement, while alleviating difficulties encountered in traditional planar scaling. This new device architecture, in addition to the efforts required for extracting the best material properties, imposes a challenge of reducing the thermal budget of processes to be applied everywhere in CMOS devices, so that conventional processes must be replaced without any compromise to device performance. Ultra-violet laser annealing (UV-LA) is then of prime importance to address such a requirement. First, the strongly limited absorption of UV light into materials allows surface-localized heat source generation. Second, the process timescale typically ranging from nanoseconds (ns) to microseconds (μs) efficiently restricts the heat diffusion in the vertical direction. In a given 3D stack, these specific features allow the actual process temperature to be elevated in the top-tier layer without introducing any drawback in the bottom-tier one. In addition, short-timescale UV-LA may have some advantages in materials engineering, enabling the nonequilibrium control of certain phenomenon such as crystallization, dopant activation, and diffusion. This paper reviews recent progress reported about the application of short-timescale UV-LA to different stages of CMOS integration, highlighting its potential of being a key enabler for next generation 3D-integrated CMOS devices. [ABSTRACT FROM AUTHOR]

In view of 3D sequential integration, it is proposed to perform solid-phase epitaxial regrowth (SPER) of amorphous silicon, based on nanosecond laser pulses at energy densities (ED) kept right below the melting threshold. Si substrates were amorphized down to 29 nm by Ge and P implantation. The application of up to 1000 laser pulses at constant energy density values did not enable full regrowth. To overcome such limitations, an adaptive energy density strategy was developed. In this new approach, the ED was progressively increased in steps, with N pulses being applied at each ED value, while always remaining below the increasing melting threshold. Sequences with N = 100 pulses enabled complete recrystallization and dopant activation rates beyond 90 %. Sheet resistance and time-resolved reflectivity measurements proved to be efficient techniques to both monitor the progressive regrowth up to the surface and detect undesirable melting if any. Phosphorus atomic concentration depth profiles evidenced some snow-plow towards the surface upon regrowth and a very limited in-depth diffusion. Finally, the adaptive ED SPER strategy was successfully transposed to P-doped source and drain regions of 28 nm FD-SOI transistors that were fully regrown without any degradation of the gate stack. [Display omitted] • Complete regrowth of pre-amorphized phosphorus doped Si by nanosecond laser annealing. • Original processing strategy optimizing regrowth and dopant activation. • In-situ monitoring using time-resolved reflectometry. • Phosphorus depth profiles: redistribution upon recrystallization. • Application to 28 nm FD-SOI transistors: source and drain regrowth. [ABSTRACT FROM AUTHOR]

The bit density is generally increased by stacking more layers in 3D NAND Flash. Lowering dopant activation of select transistors results from complex integrated processes. To improve channel dopant activation, the test structure of vertical channel transistors was used to investigate the influence of laser thermal annealing on dopant activation. The activation of channel doping by different thermal annealing methods was compared. The laser thermal annealing enhanced the channel activation rate by at least 23% more than limited temperature rapid thermal annealing. We then comprehensively explore the laser thermal annealing energy density on the influence of Poly-Si grain size and device performance. A clear correlation between grain size mean and grain size sigma, large grain size mean and sigma with large laser thermal annealing energy density. Large laser thermal annealing energy density leads to tightening threshold voltage and subthreshold swing distribution since Poly-Si grain size regrows for better grain size distribution with local grains optimization. As an enabler for next-generation technologies, laser thermal annealing will be highly applied in 3D NAND Flash for better device performance with stacking more layers, and opening new opportunities of novel 3D architectures in the semiconductor industry.

Laser thermal annealing (LTA) has played an important role in the fabrication of scaled semiconductor devices by reducing the heat budget of the dopant activation process. During the laser annealing of entire wafer areas, the beam scanning pattern and overlap ratio have significant effects on uniform heating during the process. In this study, a numerical simulation of the LTA process was carried out using a three-dimensional transient heat transfer model. The temperature distribution produced by different laser scan paths and beam overlap ratios was analyzed. Additionally, the behavior of the dopant (phosphorus) diffusion induced under the multipath and beam overlapping conditions was numerically investigated. According to the simulation result, a zig-zag pattern generated hot spots around the corner areas of the beam path due to the greater heat accumulation per unit area; however, a bidirectional pattern induced cold spots due to the absence of laser heating around the corner areas. It was also found that the maximum temperature reachable in the beam overlapped region was much lower than that obtained along the beam scanning path, and the most uniform heating could be obtained when the zig-zag pattern and a 50% overlap ratio were used. According to the dopant diffusion and concentration distribution predicted for the case of the zig-zag pattern and 50% overlap ratio, the difference in the dopant diffusion length was approximately thirty times within the scanned area. [ABSTRACT FROM AUTHOR]

In this brief, we demonstrate the gate-first HfZrO2 (HZO) fully depleted silicon-on-insulator (FDSOI) negative capacitance field-effect transistor (NCFET) with self-aligned nickel-silicide (NiSi) source and drain (S/D). Although the gate-first process has advantages in terms of fabrication simplicity, the dopants of S/D cannot be fully activated since the polarization of ferroelectric HZO film is seriously degraded at high temperatures. To improve the S/D resistance without the polarization degradation, self-aligned S/D nickel silicidation, which induces dopant activation and dopant segregation at relatively low temperature, was simultaneously performed during ferroelectric post metal annealing (PMA). It is experimentally confirmed that 1) high concentrated dopants (As+) can be fully activated during silicidation through diode measurements and 2) S/D resistance can be reduced by NiSi silicidation through resistance measurements. Furthermore, it is verified that the electrical characteristic of NCFET with NiSi S/D exhibits superior current drivability without subthreshold swing (SS) degradation compared with that of NCFET without NiSi. [ABSTRACT FROM AUTHOR]

Electrical properties and microstructure of phosphorus (P) implanted p-type Si substrates were evaluated by four-point probe (4PP), Differential Hall Effect Metrology (DHEM), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) techniques, after RTA 750–950°C and CO2 laser 120–140W annealing. When RTA temperature was increased, defect concentration at a-Si/c-Si interface gradually disappeared. For CO2 laser annealing, defects were found to aggregate at the end of range (EOR) region. Sheet resistance (Rs) values decreased significantly with increasing RTA temperature due to defects disappearing at EOR. Rs did not change appreciably for the CO2 laser annealing case. The dopant activation ratio was less than 50% below RTA temperature of 850 °C, and it increased to 70% at 950 °C. For CO2 laser annealing, the activation ratio could reach to over 80% regardless of the laser power. The highest active concentration and the lowest resistivity or mobility were found to be within the top 20 nm region of the surface. Although RTA annealing conditions influenced dopant diffusion and the resulting electrical property depth profiles significantly, depth profiles did not change much with changes in CO2 laser power level. It was demonstrated that DHEM data in conjunction with SIMS and TEM data can be successfully employed to evaluate, in detail, the electrical properties of ultra-shallow junctions for metal oxide semiconductor field effect transistor (MOSFET) applications. [ABSTRACT FROM AUTHOR]

Organic doping is widely used for defining the majority charge carriers of organic thin films, tuning the Fermi level, and improving and stabilizing the performance of organic light‐emitting diodes and organic solar cells. However, in contrast to inorganic semiconductors, the doping concentrations commonly used are quite high (in the wt% range). Such high concentrations not only limit the scope of doping in organic field‐effect transistors (OFETs), but also limit the doping process itself resulting in a low doping efficiency. Here, the mechanism of doping at ultralow doping concentrations is studied. Doped C60 metal‐oxide‐semiconductor (MOS) junctions are used to study doping at the 100 ppm level. With the help of a small‐signal drift‐diffusion model, it is possible to disentangle effects of traps at the gate dielectric/organic semiconductor interface from effects of doping and to determine the doping efficiency and activation energy of the doping process. Doped C60 OFETs with an ultralow operation voltage of 800 mV and an excellent on/off ratio of up to 107 are realized. The devices have low subthreshold swing in the range of 80 mV dec−1 and a large transconductance of up to 8 mS mm−1. [ABSTRACT FROM AUTHOR]

Heavily doped epitaxial films with an active dopant concentration over 1 × 1021/cm3 in the source/drain regions are key requirements for advanced metal-oxide-semiconductor field-effect transistors (MOSFETs) with ultralow contact resistance. In this study, we investigated the microstructure, strain characteristic, and electrical property with dopant behavior of heavily in-situ B-doped (ISBD) SiGe films (chemical B concentration >3 × 1021 atoms/cm3) treated by nanosecond laser annealing (NLA). The lattice parameters of the B-doped SiGe films considerably decreased in the regrown regions because of increased substitutional B concentrations. The substitutional B atoms decreased the accumulated strain energy per unit area of the regrown regions, leading to epitaxial regrowth of B-doped SiGe film without strain relaxation. Additionally, electrical analyses demonstrated that the active B concentrations in the regrown regions increased above 3 × 1021 atoms/cm3. In the unmelted region, the active B concentrations were close to that of the as-grown film, which was similar to the relative ratio of the active and inactive states in the B 1s spectra measured through X-ray photoelectron spectroscopy (XPS). Our results revealed that nonsubstitutional B atoms in the as-grown heavily ISBD SiGe films were converted into substitutional B atoms and activated in the recrystallized region via NLA. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NLA treatment prevents undesired dopant-diffusion and removes defects induced by ion-implantation in the near-surface region, effectively achieving highly active B concentration over approximately 1021 cm−3. • Using XPS, new chemical bonding states related to Si-B and Ge-B bonds in the near-surface region were identified in XPS Si 2 p and Ge 3 d spectra, which show the substitutionality of B-atoms upon NLA process. • Based on the depth profiles of the B 1 s peaks from the surface to melted depth, the relative ratios of active state in the NLA-treated films were confirmed and compared with the electrical activation rate measured by Hall measurements. Given that transistor dimensions are approaching atomic scale in metal–oxide–semiconductor field-effect-transistors (MOSFETs), attaining low-contact resistivity (ρ c) between contact-metal and Si is a primary challenge for source/drain (S/D) fabrications. To reduce ρ c , it is necessary to increase active dopant concentration in the semiconductor region underneath the contact-metal. High-dose ion-implantation and nanosecond laser-annealing (NLA) have been intensively investigated to produce highly activated layers in S/D regions. Particularly for the B-doped SiGe layers, which are used as S/D stressor for p-MOSFETs, non-substitutional B species are generated in the highly doped films at concentrations exceeding ∼ 1021 cm−3. These non-substitutional B are electrically non-activated and thus should be minimized to reduce ρ c. In this study, we investigated the chemical states and electrical activation in highly B-doped SiGe layer. Using X-ray photoelectron spectroscopy (XPS), we examined the substitutionality of B-atoms and identified new chemical states of Si-B and Ge-B bonds in Si 2 p and Ge 3 d peaks. In the B 1 s spectra, electrical activation states are determined by quantifying relative area ratios of the active/inactive B peaks, which are well matched with activation rates calculated by Hall measurements. Our findings systematically explained the activation behavior of NLA-treated B-doped SiGe films in high B-concentration ranges. [ABSTRACT FROM AUTHOR]

In this work an extensive characterization over XeCl multishot laser irradiation was performed at different energy densities and with different thicknesses of graphitic coating superimposed on P and Al implanted 4H–SiC epitaxial layers. It was noted that at 0.6 J/cm2 the 180 nm coating provides a smooth surface unlike lower thicknesses or uncoated treatments. The μ-Raman investigation showed the crystalline quality as a function of the energy density. Through Medium Angle Annular Dark Field-Scanning Transmission Electron Microscopy (MAADF-STEM) and High Angle Annular Dark Field (HAADF)-STEM investigations, the absence of extended defects and the presence of regions with higher density of carbon interstitials (C i) was revealed. Circular Transfer Length Method (CTLM) measurements demonstrated how irradiation at 0.9 J/cm2 succeeded to reach values of (7.28 ± 1.15) × 102 Ω/sq, lower than the findings achieved with furnace treatment at 1650 °C. However, electrical characterization carried out through μ-Raman investigation over the Folded Transverse Acoustic (FTA) modes showed consistent activation of the order of 7 × 1019 cm−3 at 0.6 J/cm2 while exhibited CTLM extracted sheet resistance of (3.17 ± 0.06) × 104 Ω/sq. Therefore, this work highlights the contrast between fast processes as the accommodation and ionization of dopant atoms in substitutional positions and slow processes such as the recovery of ion implantation damage. By offering faster processing rates, lower thermal budgets, and high spatial control over the annealing process, laser annealing on 4H–SiC as a post-implantation thermal treatment approach presents several advantages over conventional annealing methods. This study marks a significant progress in comprehending and improving the effectiveness of laser annealing on 4H–SiC. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we present an enhanced differential Hall effect measurement method (DHE) for ultrathin Si and SiGe layers for the investigation of dopant activation in the surface region with sub-nanometre resolution. In the case of SiGe, which constitutes the most challenging process, we show the reliability of the SC1 chemical solution (NH4OH/H2O2/H2O) with its slow etch rate, stoichiometry conservation and low roughness generation. The reliability of a complete DHE procedure, with an etching step as small as 0.5 nm, is demonstrated on a dedicated 20 nm thick SiGe test structure fabricated by CVD and uniformly doped in situ during growth. The developed method is finally applied to the investigation of dopant activation achieved by advanced annealing methods (including millisecond and nanosecond laser annealing) in two material systems: 6 nm thick SiGeOI and 11 nm thick SOI. In both cases, DHE is shown to be a uniquely sensitive characterisation technique for a detailed investigation of dopant activation in ultrashallow layers, providing sub-nanometre resolution for both dopant concentration and carrier mobility depth profiles.

In situ phosphorus‐doped epitaxial silicon films have attracted significant attention as source and drain materials because low specific contact resistivities have been achieved on such films by increasing the active carrier concentration using millisecond laser annealing. However, the active phosphorus concentration that can be achieved using millisecond laser annealing is much less than the incorporated concentration. To increase the activation efficiency, nanosecond laser annealing with a dwell time ≈104 times shorter than that of millisecond laser annealing is investigated and the diffusion, strain, microstructure, and electrical properties of single‐ and multipulse nanosecond laser‐annealed samples are examined. The melting depth simulation classifies the energy density regions and explains the limited diffusion in nanosecond laser annealing. After multipulse nanosecond laser annealing, more phosphorus is activated without diffusion than by millisecond laser annealing. Moreover, almost all the incorporated phosphorus atoms are activated by the nanosecond laser, which melts in situ phosphorus‐doped epitaxial silicon films without major strain loss. The increased active carrier concentration presents an opportunity to achieve low contact resistivity characteristics. [ABSTRACT FROM AUTHOR]

Laser thermal annealing (LTA) has played an important role in the fabrication of scaled semiconductor devices by reducing the heat budget of the dopant activation process. During the laser annealing of entire wafer areas, the beam scanning pattern and overlap ratio have significant effects on uniform heating during the process. In this study, a numerical simulation of the LTA process was carried out using a three-dimensional transient heat transfer model. The temperature distribution produced by different laser scan paths and beam overlap ratios was analyzed. Additionally, the behavior of the dopant (phosphorus) diffusion induced under the multipath and beam overlapping conditions was numerically investigated. According to the simulation result, a zig-zag pattern generated hot spots around the corner areas of the beam path due to the greater heat accumulation per unit area; however, a bidirectional pattern induced cold spots due to the absence of laser heating around the corner areas. It was also found that the maximum temperature reachable in the beam overlapped region was much lower than that obtained along the beam scanning path, and the most uniform heating could be obtained when the zig-zag pattern and a 50% overlap ratio were used. According to the dopant diffusion and concentration distribution predicted for the case of the zig-zag pattern and 50% overlap ratio, the difference in the dopant diffusion length was approximately thirty times within the scanned area.

An N‐doped TiO2 model reveals a conceptually different mechanism for activating the N dopant based on delocalized orbital hybridization through O vacancy incorporation. Synchrotron‐based X‐ray absorption spectroscopy, time‐resolved fluorescence, and DFT studies revealed that O vacancy incorporation can effectively stimulate the delocalization of N impurity states through p‐band orbital modulation, which leads to a significant enhancement in photocarrier lifetime. Consequently, this effect also results in a remarkable increase in the incident photon‐to‐electron conversion efficiency in the range of 400–550 nm compared to that of conventional N‐incorporated TiO2 (15 % versus 1 % at 450 nm). This work reveals the fundamental necessity of orbital modulation in the band engineering of metal oxides for driving solar water splitting and beyond. [ABSTRACT FROM AUTHOR]

This study reports the comprehensive investigation of the green laser annealing (GLA) technique for phosphorus (P)-doped silicon (Si). The aim of this study was to examine the suitability of GLA in improving the properties of P-doped Si for semiconductor devices. This study explored the electrical, chemical, and crystalline characteristics of P-doped Si under major laser-annealing conditions. Multiple characterization techniques, including the four-point probe method, Hall effect measurement, transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS), X-ray diffraction (XRD), and atomic force microscopy (AFM), were used to investigate the interaction between the laser beam and P-doped Si under different laser annealing conditions. A considerable decrease in the sheet resistance, carrier mobility, and Hall resistance and an increase in the carrier concentration of the material were observed after GLA. The TEM images indicated a transition from partial polycrystallization to complete crystallization with epitaxial growth, depending on the GLA conditions. The SIMS data showed low P diffusion in the depth direction of the Si and relatively uniform P concentrations near the surface of the Si after annealing. Furthermore, XRD analysis revealed no considerable changes in the lattice spacing for the main (400) XRD peak, confirming insignificant strain effects from GLA. AFM analysis showed a minimal increase in the surface roughness compared to that of the as-implanted sample, indicating that GLA did not significantly alter the surface morphology of the material. GLA is a promising method for enhancing the electrical properties of P-doped Si without considerable dopant diffusion or changes in the atomic structure, making it suitable for industrial applications. [ABSTRACT FROM AUTHOR]

Significant research effort has been placed into the use of III–V compound semiconductors, including InGaAs as channel materials in CMOS logic devices due to their superior electron mobilities compared to Si and other more conventional semiconductor materials. One of the major factors preventing industrial adoption of InGaAs as a channel material involves the minimization of source and drain contact resistances. To understand challenges to minimization of contact resistance, this work will outline the effectiveness of several doping approaches that have been attempted for n-type InGaAs including the use of silicon as a dopant and the effectiveness of each approach in achieving the highest level of activation possible. Previous and recently reported dopant diffusion behaviors are also included and discussed. [ABSTRACT FROM AUTHOR]

Germanium n+/p junctions with high phosphorus dopant activation (>1020 cm−3) and minimal dopant diffusion were achieved by $P$ implantation and laser spike annealing (LSA) at temperatures ≥794 °C for 400 \mu \text{s} . In addition, there is no evidence of any residual extended defectivity near the junction after LSA. The effect of F co-doping was also investigated, demonstrating the reduction in both diffusion and activation. The thermal stability and electrical characteristics of Ge n+/p junction activated by LSA were evaluated. [ABSTRACT FROM PUBLISHER]

BF+ implantation is used for the first time for the formation of source/drain (S/D) junctions in Ge MOSFETs. It offers a higher B activation level ( \sim 2.0\times 10^20 cm ^-3) and a shallower junction depth in Ge compared with B+ and BF2+ implantation for the same projected range, after rapid thermal annealing at 800 °C. Germanium pMOSFETs using BF+ implantation demonstrate a high ON/OFF ratio of \sim 10^7 and an enhancement of ON current, due to the reduction of S/D series resistance compared with B+ or BF2+ implanted junctions. [ABSTRACT FROM PUBLISHER]

The possibility of direct writing thin semiconductive channels and structures on insulating substrates in a clean room-free process is attractive for its simplicity, cost effectiveness, and possibility of a wide choice of substrates. A broad range of applications, such as large-area electronic devices (touch screens, flexible displays), sensors, or optical wave guides could benefit from such a process. In this work, we directly write on doped hydrogenated amorphous silicon (a-Si:H), with thickness in the range 10 nm-1 μm, using a Nd-YAG laser operating at 532 nm that is part of a Witec Raman confocal system. The contrast in conductivity between the exposed and unexposed areas is so high that the a-Si:H matrix needs not to be removed after exposure. B- and P-doped films were deposited on plastic, glass, and oxidized silicon wafers. The laser power threshold for crystallization was studied. The highest conductivity (886 Ω−1 cm−1) was obtained on wafer. On hard substrates, it is possible to tune the mesoscopic electrical conductivity in a very broad range of values (∼10−4-103) by design of the pattern to be transferred. Patterned films are piezoresistive with gauge factors as high as +18 and −29 for p - and n-type patterns, respectively. SEM image of laser written lines on a 10 nm thick a-Si:H film deposited on a Si/SiO2 substrate. Four regions are clearly distinguishable: the metal contact on the top area; the laser eroded area (lines); the crystallized areas adjacent to lines; the amorphous region at the bottom right. [ABSTRACT FROM AUTHOR]

Defect evolution and dopant activation are intimately related to the use of ion implantation and annealing, traditionally used to dope semiconductors during device fabrication. Ultra-fast laser thermal annealing (LTA) is one of the most promising solutions for the achievement of abrupt and highly doped junctions. In this paper, we report some recent investigations focused on this annealing method, with particular emphasis on the investigation of the formation and evolution of implant/anneal induced defects and their impact on dopant activation. In the case of laser annealed Silicon, we show that laser anneal favours the formation of “unconventional” (001) loops that, following non-melt anneals, act as carrier scattering centres, leading to carrier mobility degradation. In contrast, in the case of melt anneals, the molten region itself is of excellent crystalline quality, defect-free and with very high activation rates. As for laser annealed Germanium, we studied in detail the amorphous to crystalline Ge phase transition as a function of the increasing LTA energy density and we found that using LTA, very high carrier concentrations (above 10 20 cm −3 ) were achieved in As doped regions, which are unachievable with conventional rapid thermal annealing (RTA) processes. [ABSTRACT FROM AUTHOR]

Aluminum-doped zinc oxide (AZO) films have been synthesized using reactive high power impulse magnetron sputtering (HiPIMS) in a wide range of Al contents, 0.6–14.7 at.%. The film structure and microstructure investigated by X-ray diffraction and transmission electron microscopy evolves from nanocrystalline columnar film towards ultrafine nanocrystalline films of wurtzite ZnO structure upon increasing the Al content. Electrical properties measured by 4-point probe and Hall effect setups revealed that effective doping maybe achieved up to 3 at.% Al by using HiPIMS. Most importantly, optical transmittance and electronic structure measurements at the Al L 2,3 of electron energy loss near edge structure (ELNES) contain signatures of dopant activation, and dopant segregation that may serve to investigate on the origin of electrical properties degradation and to optimize the electrical properties of AZO films. • Al-doped ZnO films synthesized by reactive HiPIMS of preserved wurtzite structure up to 14.7 at.% Al • Increasing the dopant content above 1 at.% Al decreases the crystallinity. • High density of charge carriers is induced by Al doping up to 3 at.% Al. • Al contents above 3 at.% inactivate a significant fraction of Al dopant. • Electronic structure at the Al L 2,3 edge can be used to extract the fractions of active/inactive Al dopant. [ABSTRACT FROM AUTHOR]

We demonstrate Ge enhancement-mode nMOS FinFETs fabricated on 300-mm Si wafers, incorporating an optimized gate-stack (interface trap density D\mathrm{ it} below 2 \times 10^11 eV ^-1\cdot \mathrm cm^-2) , n+-doping (active doping concentration N\mathrm{ act} exceeding 1 \times 10^20~\mathrm cm^-3) , and metallization (contact resistivity \rho c below 2 \times 10^-7\Omega \cdot \mathrm cm^2) modules. A new circular transmission line \rho c extraction model that captures the parasitic metal resistance is proposed. At a supply voltage V\mathrm{ DD} of 0.5 V, 40-nm-gate-length FinFET devices achieved an ON-performance I\mathrm{\scriptscriptstyle ON} of 50 \mu \textA/\mu \textm at an OFF-state current I\mathrm{\scriptscriptstyle OFF} of 100 nA/ \mu \textm , a subthreshold swing S\mathrm{ sat} of 124 mV/decade, and a peak transconductance gm of 310 \mu \textS/\mu \textm . The same gate-stack and contacts were deployed on planar devices for comparison. Both FinFET and planar devices in this paper achieved the highest reported gm/S\mathrm{ sat} at V\mathrm{ DD} = 0.5 V to date and the shortest gate lengths for Ge nMOS enhancement-mode transistors. [ABSTRACT FROM AUTHOR]

Microwave annealing (MWA) and rapid thermal annealing (RTA) of dopants in implanted Si are compared in their abilities to produce very shallow and highly activated junctions. First, arsenic (As), phosphorus (P), and BF2 implants in Si substrate were annealed by MWA at temperatures below 550^\circC. Next, enhancing the substitutional carbon concentration ([C]sub) by cluster carbon implantation in (100) Si substrates with MWA or RTA techniques was investigated. Annealing temperatures and time effects were studied. Different formation mechanisms of SiCx layer were observed. In addition, substrate temperature is an important factor for dopant activation during MWA and in situ doped a-Si on oxide/Si substrate or glass were compared to elucidate the substrate temperature effect. After the discussion of dopant activation in Si substrates, low temperature formation of ultrathin NiGe layer is presented. Ultrathin NiGe films with low sheet resistance have been demonstrated with a novel two-step MWA process. In the two-step MWA process, the first step anneals the sample with low power MWA, and the second step applies higher power MWA for reducing sheet resistance. During fixed-frequency microwave heating, standing wave patterns may be present in the MWA chamber resulting in nodes and antinodes and thermal variations over the process wafer. Therefore, the effects of Si or quartz susceptor wafers on dopant activation and sheet resistance uniformity during fixed-frequency MWA were investigated. [ABSTRACT FROM PUBLISHER]

Processes inducing micro- and nano-structural modifications of materials play a crucial role in the advanced technology. In particular, laser irradiation attracts a great interest as a tool for the localized thermal treatment (laser thermal annealing) when the global heating of the sample could be detrimental. With the expansion of the application fields, a research effort is required to understand the kinetics in systems subjected to extreme transient excitations induced by the interaction with the laser light. Modeling and simulations cover a relevant part of this research effort. In this paper we review the current status of the laser annealing modeling. The theoretical analysis will be restricted to the heating stage of the irradiation, i.e. the ultrafast energy transfer from the electronic states to the lattice vibrations will not be considered. Therefore, the timescale of the process must be larger than ∼1 ns. Models, numerical methods and applications to the experiments will be presented to deal with different questions. Among them: the simulation of the thermal field when the heat absorption depends consistently on the temperature, the prediction of a phase change kinetics in a melting process including the redistribution of alloyed systems, the damage evolution in the transient non-uniform thermal field promoted by the irradiation induced kinetics, the related dopant activation kinetics. Numerical techniques include: continuum, kinetic Monte Carlo and molecular dynamics approaches. [ABSTRACT FROM AUTHOR]

We propose a new strategy for in-situ observation of dopant activation process using scanning tunnelling microscopy (STM) technology. Two factor techniques are established within our original STM system combined with liquid-metal-ion-source ion-gun (LMIS-IG/STM): (1) in-situ real-time observation of Si(001)-2×1 surface modified with dopant ions, and (2) in-situ hydrogen passivation of Si(001)-2×1 surface. Sequential STM images of the surface morphological changes are successfully obtained with keeping the original observation area. The hydrogenated Si(001)-2×1 surface is stable enough even under the degraded vacuum conditions which are unavoidable in ion irradiation processes. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Microwave annealing of arsenic-doped silicon was employed to achieve nearly complete dopant activation and repair of damage caused by ion implantation. Analysis of Rutherford backscattering spectra suggested that volumetric heating from microwaves can repair ion-implantation damage. Secondary ion mass spectroscopy depth profiling revealed that even with high damage due to implanted arsenic, microwave annealing achieves repair of lattice damage, and electrical activation of dopants without allowing any significant dopant diffusion into the silicon substrate. Surface temperatures greater than 700°C were achieved within ~100s with assisted microwave heating, marking this as a quick annealing technique when compared to un-assisted annealing. This temperature was sufficient for solid phase epitaxial growth in Si. The temperature profile recorded by a thermocouple-calibarated IR pyrometer was explained based upon the type of losses the sample undergoes while heating. The mechanism for susceptor-assisted microwave heating was dominated by dipole polarization losses in the initial stages of anneal and by Ohmic conduction losses at higher temperatures. Cross-section transmission electron microscopy, along with ion channeling spectra indicated that the silicon lattice regained nearly all of its crystallinity during the microwave anneal. Hall measurement and sheet resistance characterization were used to assess the extent of dopant activation. [Copyright &y& Elsevier]

Abstract: Ion-implantation characteristics and dopant activation behavior of P in Ge have been investigated. A Monte Carlo simulation indicates a smaller projected range and consequently a smaller critical dose of amorphization for Ge compared to Si. The solid-phase epitaxial (SPE) regrowth characteristics of damaged layers for Ge clearly depend on crystal orientation of the substrate in completely amorphized samples, while no orientation dependent regrowth is observed in the partially amorphized samples. These phenomena were explained on the basis of the damage cluster model. In addition, maximum carrier activation coincides with the complete regrowth at annealing temperatures of 300–400°C in completely amorphized samples. However, higher temperature annealing (500–550°C) is necessary for maximum carrier activation in partially amorphized samples, although SPE regrowth completes around 250–300°C. Analysis of the temperature dependence of carrier activation ratio in partially amorphized samples suggests that carrier-activation should be mediated by vacancy-migration. [Copyright &y& Elsevier]

Abstract: The electrical activation of B+ implantation at 2keV to doses of 5.0×1013–5.0×1015 cm−2 in crystalline and pre-amorphized Ge following annealing at 400°C for 1.0h was studied using micro Hall effect measurements. Preamorphization improved activation for all samples with the samples implanted to a dose of 5.0×1015 cm−2 displaying an estimated maximum active B concentration of 4.0×1020 cm−3 as compared to 2.0×1020 cm−3 for the crystalline sample. However, incomplete activation was observed for all samples across the investigated dose range. For the sample implanted to a dose of 5.0×1013 cm−2, activation values were 7% and 30%, for c-Ge and PA-Ge, respectively. The results suggest the presence of an anomalous clustering phenomenon of shallow B+ implants in Ge. [Copyright &y& Elsevier]

In this paper, the contact resistivity of NiGe on n-doped Ge is extracted. Although phosphorus is the slowest n-type dopant in terms of diffusion in Ge, the corresponding contact resistivity data for this dopant are sparse. Contact resistivity dependence on implant dose will be determined, as well as a comparison of phosphorus- and arsenic-doped Ge layers. The impact of high contact resistance is evaluated for future technology n-type metal–oxide–semiconductor germanium devices. [ABSTRACT FROM PUBLISHER]

Preserving the integrity (e.g., Ge concentration, strain, and lattice perfection) of pseudomorphically grown silicon germanium (SiGe) heterostructure channels on Si substrates is one of the most critical factors in obtaining optimal pMOSFET performance from high hole mobility of strained SiGe. A millisecond Flash-assisted rapid thermal annealing (RTA) technique was applied to source/drain (S/D) dopant activation of high-Ge-concentration SiGe channel MOSFETs with a high-k/metal gate stack. Flash annealing of SiGe channel pMOSFETs is shown to be an effective way to preserve channel integrity while achieving a low S/D resistance. Excellent mobility and short-channel device performance are realized. In addition, as the concentration of Ge in the SiGe layer is increased, high B activation can be achieved with a lower peak temperature Flash anneal. As a result, the sheet resistance of the implanted \p^+ junction can be comparable with that of higher temperature Flash-annealed (or optimal spike-annealed) Si. Furthermore, minimizing Ge diffusion reduces performance variation (such as statistical threshold voltage variation), which may be caused by the introduction and/or growth of defects in the strained SiGe heterostructure channel. It is shown that high-performance SiGe channel pMOSFETs with high Ge concentrations and a scaled high-k/metal gate can be achieved by a millisecond Flash-assisted RTA technique while preventing undesirable effects in the SiGe channel, such as within-wafer statistical performance variation. [ABSTRACT FROM PUBLISHER]

Abstract: In this work we investigate CO2 laser annealing at millisecond time scale for the fabrication of Ultra Shallow Junctions, able to fulfill the requirements imposed for sub-45nm CMOS nodes. Silicon samples doped with Boron using BF3 plasma implantation technique at low energy (0.4 and 0.6keV) were used to ensure ultra shallow as implanted boron concentration profiles. Our aim is to achieve high electrical activation level of the dopant, while maintaining the Boron concentration profile as immobile as possible. Samples have been irradiated at a variety of annealing conditions regarding the duration of the irradiation and the power density; however, in every case the peak surface temperature was kept in the range of 1080–1320°C. Sheet resistance measurements indicate significant enhancement in the activation levels, while chemical characterization by means of SIMS, shows very limited movement of the dopant concentration profile, especially for short pulse duration conditions. [Copyright &y& Elsevier]

Off-axis electron holography has been used to measure the electrostatic potential profile across the p-n junction of an AIGaAs/GaAs light-emitting diode with linearly graded triangular AIGaAs barriers. Simulations of the junction profile showed small discrepancies with experiment when the nominal dopant concentrations of Si and Be impurities were used. Revised simulations reproduced the measurements reasonably using reduced dopant levels that reflected the efficiency of dopant activation. Band-edge diagrams simulated with the nominal and revised dopant concentrations were also compared in terms of the effect that activation efficiency had on the AIGaAs barrier shape and carrier transport. It is concluded that electron holography measurements combined with modeling offer device designers and growers a helpful tool for analyzing and confirming doping profiles in complex heterostructures. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the p- and n-type dopants in thin SGOI (20nm) material obtained by Ge enrichment. The samples are doped with either BF2 or arsenic or phosphorus and then annealed with either a spike or a 15s rapid thermal annealing in a temperature range of 850–1050°C. We have observed that sheet resistance (R sh) obtained in SGOI for p-type is approximately independent of annealing conditions. In addition, these values are lower than the SOI (20nm) reference. Result reveals that almost all BF2 atoms remain in SGOI substrate giving rise to low R sh, whereas dopant out diffuses and segregates in SOI. In contrast, R sh measured with arsenic and phosphorus implanted SGOI samples is higher than SOI. [Copyright &y& Elsevier]

A high-performance In0.53Ga0.47As n-channel MOSFET integrated with a HfAIO gate dielectric and a TaN gate electrode was fabricated using a self-aligned process. After HCI cleaning and (NH4)2S treatment, the chemical vapor deposition HfAlO growth on In0.53Ga0.47As exhibits a high-quality interface. The fabricated nMOSFET with a HfAIO gate oxide thickness of 11.7 nm shows a gate leakage current density as low as 2.5 × 10-7 A/cm2 at Vg of 1 V. Excellent inversion capacitance was illustrated. Silicon implantation was self-aligned to the gate, and low-temperature activation for source and drain was achieved by rapid thermal annealing at 600 °C for 1 mm. The source and drain junction exhibited an excellent rectifying characteristic and high forward current. The result of an In0.53Ga0.47As nMOSFET shows well-performed Id-Vd and Id-Vg characteristics. `The record high peak electron mobility of 1560 cm2 /Vs has been achieved without any correction methods considering interface charge and parasitic resistance. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides an overview of the current state-of-the-art in the formation of shallow junctions in germanium by ion implantation, covering the issues of dopant activation, diffusion and defect removal. As will be shown, for the case of p+ implantations, the application of rapid thermal annealing (RTA) to B implants yields good sheet resistance values, corresponding with activation levels well above the maximum solid solubility. A further improvement can be achieved by the use of a Ge pre-amorphization implant (PAI), which also removes the stable extended defects observed after high-dose B implantations. It will be shown that the formation of shallow n+ junctions is a more challenging field due to the rather low dopant solubilities and high diffusivities. However, encouraging results will be reported on the application of laser and flash-lamp annealing of P implantations in Ge. Also point-defect engineering is shown to be successful in controlling the junction formation. [Copyright &y& Elsevier]

Abstract: For CMOS technology, generations beyond the 65nm node a major goal is achieving highly activated, ultra-shallow and abrupt profiles. In the case of p-type (boron) implants, one method to achieve this is using Ge preamorphization (PAI) prior to ultra-low energy B implantation. However, for future technology nodes, new issues arise when bulk silicon is supplanted by silicon-on-insulator (SOI). Understanding the strong impact of the buried Si/SiO2 interface, will enable tests of fundamental models on defect evolution, electrical activation and diffusion. In the present study, boron has been implanted in germanium-preamorphized silicon and SOI wafers. Subsequent to implantation, an isochronal and isothermal annealing study of the samples was carried out. Electrical and structural properties were measured by Hall effect and SIMS techniques. The results show a range of effects in both substrate types, including TED and deactivation driven by interstitials from the end-of-range (EOR) defects. However, in the SOI material there is a lower boron deactivation and the EOR defects are eliminated at a lower thermal budget in SOI than in the bulk silicon due to competition between the upper SOI interface and the Si surface which both act as sinks for interstitials. [Copyright &y& Elsevier]

Abstract: First results on the effects of strain on transient enhanced diffusion and deactivation of As-implanted ultrashallow junctions are presented. A significant effect of strain on the magnitude and timescale of transient enhanced diffusion is observed, which is consistent with the stabilization of interstitial-type defects by tensile strain. Our results show no significant impact of strain on As electrical activity during the deactivation timescale accessed in this study. [Copyright &y& Elsevier]

Abstract: The formation of highly activated ultra-shallow junctions (USJ) is one of the key requirements for the next generation of CMOS devices. One promising method for achieving this is the use of Ge preamorphising implants (PAI) prior to ultra-low energy B implantation. In future technology nodes, bulk silicon wafers may be supplanted by Silicon-on-Insulator (SOI), and an understanding of the Solid Phase Epitaxial (SPE) regrowth process and its correlation to dopant electrical activation in both bulk silicon and SOI is essential in order to understand the impact of this potential technology change. This kind of understanding will also enable tests of fundamental models for defect evolution and point-defect reactions at silicon/oxide interfaces. In the present work, B is implanted into Ge PAI silicon and SOI wafers with different PAI conditions and B doses, and resulting samples are annealed at various temperatures and times. Glancing-exit Rutherford Backscattering Spectrometry (RBS) is used to monitor the regrowth of the amorphous silicon, and the resulting redistribution and electrical activity of B are monitored by SIMS and Hall measurements. The results confirm the expected enhancement of regrowth velocity by B doping, and show that this velocity is otherwise independent of the substrate type and the Ge implant distribution within the amorphised layer. Hall measurements on isochronally annealed samples show that B deactivates less in SOI material than in bulk silicon, in cases where the Ge PAI end-of-range defects are close to the SOI back interface. [Copyright &y& Elsevier]

Abstract: The deliberate use of H- and He-related phenomena in crystalline Si (c-Si) has at times been hampered by concerns of the mobility of these light elements and hence potential device instability. However H is inevitably present in many Si processing steps, though not necessarily in the finished device. Accordingly one could differentiate between a transient or catalytic interaction of H with c-Si, and one where H resides permanently during device operation. We have uncovered phenomena on both domains, and these involve trapping and de-trapping of H by defective regions, thermal activation of latent defects in hydrogenated c-Si, and low-temperature activation of ion implanted dopant atoms. He differs from H principally by its electrical inactivity, but plays a significant role in altering the microstructure. The strong interaction of He with vacancy clusters results in nanocavities that act as excellent gettering sites and also enable localized minority carrier lifetime control. H and He thus offer possibilities for defect and impurity engineering in Si. [Copyright &y& Elsevier]

Abstract: Ion shower doping with a main ion source of P2Hx using a source gas mixture of PH3/H2 was conducted on excimer-laser-annealed (ELA) poly-Si. The crystallinity of the as-implanted samples was measured using a UV transmittance. The measured value of as-implanted damage was found to correlate well with the one calculated using TRIM-code simulation. The sheet resistance decreases as the acceleration voltage increases from 1 to 15 kV at the moderate doping conditions. It, however, increases as the acceleration voltage increases under the severe doping conditions. Uncured damage after activation annealing seems to be responsible for the rise in sheet resistance. Three different annealing methods were investigated in terms of dopant activation and damage recovery, such as furnace annealing (FA), excimer laser annealing (ELA) and rapid thermal annealing (RTA), respectively. [Copyright &y& Elsevier]

Abstract: We present a detailed study of the thermal stability of activated junctions as a function of the post-annealing conditions. p+/n junctions were formed by implanting 500eV boron (1 × 1015 cm−2) into Ge+ preamorphised Si followed by solid phase epitaxial growth (SPEG) at 650°C. Post-annealing temperatures ranged from 250 to 950°C, with times ranging from 3 to 1800s. Four point probe (4PP), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) analysis were then used to investigate the evolution of boron activation, boron diffusion and of the implantation induced extended defects. During isothermal anneals in the 750–900°C range, it is found that the sheet resistance initially increases (deactivation) and then decreases (reactivation) with rates proportional to the temperature itself. TEM results elucidate the crucial role of the extended defects in the deactivation process. On the other hand, the combination of 4PP and SIMS measurements allows to separate the respective contribution of both cluster dissolution and dopant in-diffusion to the reactivation process. [Copyright &y& Elsevier]

The need of an ultrashallow junction technology for the extension of p-FinFETs has been investigated by integrated process and device simulations. For devices with 60 nm physical gate length, whose extensions are activated in a low thermal-budget process (spike anneal), it is found that the Ioff-Ion performance is invariant with respect to the extension implant energy. Nevertheless, the short-channel behavior worsens. This can be remedied by adding spacers to both sides of the gate before the extension implant, resulting in virtually identical dc characteristics and speed. Devices with gate lengths of 18 nm and below require dopant activation with negligible diffusion. Under those circumstances the short channel behavior of the FinFET is limited by the lateral straggle of the ion implant. Spacers may remedy what is otherwise poor short channel behavior due to a relatively high energy extension implant. However, this comes at the price of drastically worse drive current at a fixed off-current. [ABSTRACT FROM PUBLISHER]

State-of-the-art semiconductor devices require accurate control of the full two-dimensional dopant distribution. In this work, we report results obtained on 2D electrical characterization of ultra shallow junctions in Si using off axis electron holography to study two-dimensional effects on diffusion. In particular, the effect of a nitride diffusion mask on lateral diffusion of phosphorous is discussed. Retardation of lateral diffusion of P under the nitride diffusion mask is observed and compared to the lateral diffusion of P under an oxide diffusion mask. The ultra shallow junctions for the study were fabricated by a rapid thermal diffusion process from heavily P doped spin-on-dopants into a heavily B doped Si substrate. These shallow junctions are needed for fabricating source/drain extensions in nanoscale MOSFETs. One-dimensional electrical characterization of the junction was carried out to determine the electrical junction depth and compared to the metallurgical junction depth from SIMS analysis. [Copyright &y& Elsevier]

This study extends electron holography as a quantitative characterization tool for nanoscale charge distributions associated with ultra shallow PN junctions in Si, which are needed for fabricating nanoscale MOSFETs, Si quantum dots and single electron transistors. The ultra shallow junctions were fabricated using rapid thermal diffusion from a heavily doped n-type surface source onto a heavily doped p-type substrate. Chemical characterization of the dopant profiles was performed using secondary ion mass spectrometry, which were analyzed to derive the metallurgical junction depth. 1-D characterization of the electrical junction depth associated with the electrically activated fraction of the incorporated dopants was performed using off-axis electron holography in a transmission electron microscope. 1-D potential profiles across the p–n junctions derived from electron holographic analysis were used to calculate the electric field and total charge distributions in the space charge region of the p–n junctions using numerical derivatives. Quantitative comparison between calculated electric field and total charge from the measured potential profiles and the simulated distributions using the secondary ion mass spectrometry profiles provide a reasonable estimate of the electrical activation of dopants in the ultra shallow junctions considered for this investigation. [Copyright &y& Elsevier]