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We report the epitaxy of n-Ge layer with in situ phosphorus (P)-doping using metal-organic chemical vapor deposition (MOCVD) method with tertiary-butyl-germane and tri-ethyl-phosphine precursors. The crystalline and electrical properties of n-Ge epitaxial layers have been investigated using X-ray diffraction, atomic force microscopy, and Hall effect measurements in detail. In situ P-doping with MOCVD demonstrates the incorporation of P in Ge as high as 1 × 1020 cm−3. The electron concentration in P-doped Ge epitaxial layers are achieved as high as 1.7 × 1019, 1.8 × 1019, and 2.2 × 1018 cm−3 at growth temperatures of 400, 350, 320 °C, respectively.

Selective epitaxial growth of Ge and Ge1−xSnx layers on Si substrates was performed by using metal-organic chemical vapor deposition (MOCVD) with precursors of tertiary-butyl-germane (t-BGe) and tri-butyl-vinyl-tin (TBVSn). We investigated the effects of growth temperature and total pressure during growth on the selectivity and the crystallinity of the Ge and Ge1−xSnx epitaxial layers. Under low total pressure growth conditions, the dominant mechanism of the selective growth of Ge epitaxial layers is the desorption of the Ge precursors. At a high total pressure case, it is needed to control the surface migration of precursors to realize the selectivity because the desorption of Ge precursors was suppressed. The selectivity of Ge growth was improved by diffusion of the Ge precursors on the SiO2 surfaces when patterned substrates were used at a high total pressure. The selective epitaxial growth of Ge1−xSnx layer was also realized using MOCVD. We found that the Sn precursors less likely to desorb from the SiO2 surfaces than the Ge precursors.

We examined the formation of locally strained Ge nanostructures sandwiched between Ge1−x Sn x stressors using metal-organic chemical vapor deposition method. We have investigated the microscopic local strain and stress in the Ge/Ge1−x Sn x heterostructures using synchrotron microdiffraction and finite element method calculation. The microdiffraction measurement for an asymmetric lattice plane enables directly quantitative evaluation of the strain value of an individual Ge fine line structure with a few tens of nanometers width. An in-plane compressive strain value of 0.9% is achieved for a 30 nm-width Ge line with Ge1−x Sn x stressors, which corresponds to a compressive stress of 1.2 GPa.

The epitaxial growth of a Ge1 − xSnx layer was examined using metal-organic chemical vapor deposition (MOCVD) with two types of Ge precursors; tetra-ethyl-germane (TEGe) and tertiary-butyl-germane (TBGe); and the Sn precursor tri-butyl-vinyl-tin (TBVSn). Though the growth of a Ge1 − xSnx layer on a Ge(001) substrate by MOCVD has been reported, a high-Sn-content Ge1 − xSnx layer and the exploration of MO material combinations for Ge1 − xSnx growth have not been reported. Therefore, the epitaxial growth of a Ge1 − xSnx layer on Ge(001) and Si(001) substrates was examined using these precursors. The Ge1 − xSnx layers were pseudomorphically grown on a Ge(001) substrate, while the Ge1 − xSnx layer with a high degree of strain relaxation was obtained on a Si(001) substrate. Additionally, it was found that the two Ge precursors have different growth temperature ranges, where the TBGe could realize a higher growth rate at a lower growth temperature than the TEGe. The Ge1 − xSnx layers grown using a combination of TBGe and TBVSn exhibited a higher crystalline quality and a smoother surface compared with the Ge1 − xSnx layer prepared by low-temperature molecular beam epitaxy. In this study, a Ge1 − xSnx epitaxial layer with a Sn content as high as 5.1% on a Ge(001) substrate was achieved by MOCVD at 300 °C.

Research and development of GeSn and related group-IV semiconductor materials have been widely extended in recent years for not only electronic transistors but also various optoelectronic applications [1,2]. Design and engineering of the energy band structure of group-IV semiconductor materials are swiftly blossoming with establishing the crystal growth technology of GeSn and related materials. We have successively developed the crystalline growth technology of GeSn and GeSiSn thin films on various substrates mainly by using molecular beam epitaxy [1-7]. Recently, we also achieved the epitaxial growth of GeSn layer by using metal organic chemical vapor deposition method [8]. In this presentation, we will report our recent achievements of our study for the crystalline growth and electronic properties including energy band structure of GeSn and related group-IV materials. Controlling the composition of elements and the strain structure of the group-IV semiconductor alloys promises prospective energy band engineering technology. Increasing in the Sn content over about 10% or tensile strain over about 1% achieve the indirect-to-direct crossover, which is a strong driving force of the optical applications of GeSn material. In addition, we recently achieved the formation of polycrystalline SiSn thin layers with a very high Sn content of 20%, and demonstrated that the direct bandgap decreases to 1.05 eV with Si-Sn alloying, which is just 0.22 eV higher than the indirect bandgap of the poly-SiSn even by using Si matrix material [9]. Also, the ternary alloy GeSiSn promises the control of the energy band structure independently on the lattice constant by changing each content of three elements. We found that unstrained GeSiSn/Ge heterostructure realizes a type-I energy band alignment without using strain structure, that promises various electronic and optoelectronic applications [10]. We will demonstrate the experimental results of the energy band engineering with GeSn and related materials. The energy band engineering also provides controlling technology of the electronic property at the interface such as metal/Ge contact. Recently, we found that the Sn/Ge or GeSn/Ge contacts effectively reduces the Schottky barrier height at the metal/n-Ge interface [11,12]. In our presentation, we will also discuss the influence of the energy band structure on the interface properties for Ge and GeSn. This work was partially supported by Grant-in-Aid for Scientific Researches of the JSPS and the JSPS Core-to-Core Program, A. Advanced Research Networks. References [1] S. Zaima, Jpn. J. Appl. Phys. 52, 030001 (2013). [2] S. Zaima et al., Sci. Technol. Adv. Mater., submitted. [3] S. Zaima et al., ECS Trans. 41, 231 (2011). [4] S. Zaima et al., ECS Trans. 50, 897 (2012). [5] O. Nakatsuka et al., ECS Trans. 58, 149 (2013). [6] S. Zaima et al. ECS Trans. 64, 147 (2014). [7] O. Nakatsuka et al. ECS Trans. 64, 793 (2014). [8] Y. Inuzuka et al., ECS Solid State Lett., submitted. [9] M. Kurosawa et al., Appl. Phys. Lett. 106, 171908 (2015). [10] T. Yamaha et al., in Abstr. of ICSI-9, Montreal, Canada, May, 2015. [11] Suzuki et al., Jpn. J. Appl. Phys. 53, 04EA06 (2014). [12] A. Suzuki et al., SSDM2015, Hokkaido, Japan, Sept. 2015, to be submitted.

In this study, we have examined the formation of uniaxially strained Ge microstructures with embedded Ge 1 − x Sn x epitaxial layers and the microscopic local strain structure in Ge and Ge 1 − x Sn x using synchrotron X-ray microdiffraction and the finite element method. We achieved local heteroepitaxial growth of Ge 0.947 Sn 0.053 layers on the Ge recess regions. Microdiffraction measurements reveal that an average uniaxial compressive strain of 0.19% is induced in Ge locally with Ge 1 − x Sn x stressors. In addition, we found that the Sn precipitation near the Ge 1 − x Sn x /Ge(001) interface occurs after post-deposition annealing at 500 °C without the introduction of dislocation. It is considered that the local Sn precipitation occurs preferentially due to the larger residual stresses near the Ge 1 − x Sn x /Ge interface.

In this study, we have examined the local growth of Ge1 − x Sn x heteroepitaxial layers on micrometer-scale-patterned Ge substrates with molecular beam epitaxy method. We have investigated the strain relaxation behavior and microscopic local strain structure in both Ge and Ge1 − x Sn x by using x-ray microdiffraction and finite element method calculation. We found that the anisotropic strain relaxation of embedded Ge1 − x Sn x layers preferentially occurs along the direction which is perpendicular to the stripe line. Microdiffraction method revealed that the elastic strain relaxation of the embedded Ge1 − x Sn x layer occurs near the edge region. We demonstrated that the uniaxial compressive strain of 0.2% is locally induced in Ge with Ge1 − x Sn x stressors.

We have developed the epitaxial growth technology of Ge 1−x Sn x and related group-IV materials. The crystalline properties and energy band structure have been investigated for integrating group-IV semiconductors into Si ULSI platform.

We have investigated the structural and electrical properties of n-type doped Si1− x Ge x epitaxial layers (x = 24–26%) grown by chemical vapor deposition with conventional [SiH2Cl2 (DCS)/GeH4] and high-order (Si2H6/Ge2H6) precursor combinations. X-ray diffraction, atomic force microscopy, and deep-level transient spectroscopy (DLTS) measurements were performed for characterization. The crystalline properties and surface morphology of the Si1− x Ge x layer with Si2H6/Ge2H6 grown at temperatures as low as 550 °C show good structural quality similar to that with DCS/GeH4 grown at 615 °C. On the other hand, in terms of electrical properties, the DLTS measurement reveals the existence of vacancy-related complexes in the as-grown layer with Si2H6/Ge2H6. We found that post-deposition annealing at 200 °C for the Si1− x Ge x epitaxial layer is effective for annihilating vacancy-related defects with densities down to as low as that of conventional precursors.

We have investigated the selective growth of a Ge1− x Sn x epitaxial layer on a line/space-patterned SiO2/Si substrate by metal–organic chemical vapor deposition. We examined the behavior of a Sn precursor of tributyl(vinyl)tin (TBVSn) during the growth on Si and SiO2 substrates and investigated the effect of the Sn precursor on the selective growth. The selective growth of the Ge1− x Sn x epitaxial layer was performed under various total pressures and growth temperatures of 300 and 350 °C. The selective growth of the Ge1− x Sn x epitaxial layer on the patterned Si region is achieved at a low total pressure without Ge1− x Sn x growth on the SiO2 region. In addition, we found that the Sn content in the Ge1− x Sn x epitaxial layer increases with width of the SiO2 region for a fixed Si width even with low total pressure. To control the Sn content in the selective growth of the Ge1− x Sn x epitaxial layer, it is important to suppress the decomposition and migration of Sn and Ge precursors.

The strain engineering is a promising technology not only for low-power CMOS but also for optoelectronic applications of germanium (Ge) devices compatible with the conventional silicon (Si) process technology [1]. In terms of CMOS applications, a uniaxial compressive strained Ge has drawn attention as high-mobility channel material in p-MOSFET which is expected to transcend that of conventional strained Si channel [2]. We are focusing on germanium-tin (Ge1−x Sn x ) as a source/drain (S/D) stressors to apply a uniaxial compressive strain into Ge in analogy with Si1−x Ge x S/D for strained Si channel. However, there are few reports of the local epitaxial growth of Ge1−x Sn x on patterned Ge substrate and the local strain technology of the Ge/Ge1−x Sn x heterostructures. Since the recent device dimensions of Si CMOS devices have reached the sub-100 nm scale in accordance with Moore’s law, the investigation of the microscopic crystalline and the strain structures for various next generation semiconductor materials has grown increasingly important. In this study, we experimentally characterized the local strain structure in Ge/Ge1−x Sn x fine heterostructures by using synchrotron x-ray microdiffraction method [3,4]. We prepared Ge stripe structures with various line widths (25–100 nm) sandwiched with Ge1−x Sn x stressors. Patterned Ge(001) substrate with a SiO­ 2 cap layer was formed by anisotropic wet/dry etching as lines parallel along to the direction. The pitch of a Ge stripe is 500 nm. The Ge1−x Sn x layers were grown with solid-source molecular beam epitaxy (MBE) system and metal-organic chemical vapor deposition (MOCVD) system [5]. The Sn content in the Ge1−x Sn x was 2.9–6.5%. The x-ray microdiffraction measurement was performed at the beamline BL13XU in SPring-8 to analyze the local strain distribution and crystalline structure in Ge/Ge1−x Sn x samples. A synchrotron radiation light with an energy of 8 keV (λ=0.155 nm) was used. The cross-section size of an incident x-ray microbeam was estimated to be 0.16×0.20–0.82×0.26 μm2 in preliminary experiments. Transmission electron microscope observations revealed that Ge1−x Sn x were epitaxially grown on both sides of a Ge line, while the crystalline structure of Ge1−x Sn x on SiO2 on the top of Ge line was polycrystalline. We consider that the stressors of locally grown epitaxial Ge1−x Sn x can induce a local strain into the Ge line. In order to directly characterize the in-plane strain status in strained Ge region, we examined two-dimensional reciprocal space mapping (2DRSM) around the Ge1—1—3 asymmetric Bragg reflection with step scans of the microbeam position across the Ge lines with a step of 50 nm. Three diffraction peaks related to the bulk Ge, the epitaxial Ge1−x Sn x stressors, and the strained Ge are clearly observed in 2DRSM results. The intensity of diffraction peak of the strained Ge periodically varied corresponds to the stripe pitches. The diffraction peak position of the strained Ge in 2DRSM indicates an in-plane compressive strain is induced into a Ge line sandwiched with Ge1−x Sn x stressors. From the 2DRSM results for various Ge stripe widths, an in-plane strain value can be estimated from the lattice spacing with respect to that of bulk Ge. The in-plane compressive strain value in the Ge increases with narrowing the Ge line width and increasing the Sn content in the Ge1−x Sn x stressors, which is consistent with the simulated results of finite element method calculations. For the Ge0.943Sn0.057 stressors, the in-plane compressive strains were estimated to be 0.84%, 0.46% and 0.38% for 30, 60, and 100 nm-wide Ge lines, respectively. In summary, the formation of Ge/Ge1−x Sn x fine heterostructures were achieved by MBE and MOCVD, and experimentally characterized the local strain distribution in the Ge/Ge1−x Sn x by synchrotron radiation microdiffraction method. The microdiffraction enables a quantitative analysis of strain and an investigation of local crystalline structure in sub-100 nm-scale Ge lines sandwiched with Ge1−x Sn x stressors. This work was partly supported by the JSPS through the FIRST Program initiated by the CSTP, a Grant-in-Aid for Scientific Research (S) (Grant No. 26220605) and Core-to-Core Program ICRC-ACP4ULSI from the JSPS in Japan. The synchrotron radiation experiments were performed at SPring-8 with the approval of JASRI (Nos. 2012B1783, 2013A1682, 2013B1779, 2015A1874, and 2015B1813/BL13XU). [1] S. Zaima et al., Sci. Technol. Adv. Mater. 16, 043502 (2015). [2] T. Krishnamohan et al., IEDM Proc., 899 (2008). [3] S. Takeda et al., Jpn. J. Appl. Phys. 45, L1054 (2006). [4] Y. Imai et al., AIP Conf. Proc. 1221, 30 (2010). [5] Y. Inuzuka et al., Thin Solid Films 602, 7 (2016).

In this paper, we discuss the effectiveness of a new human interface device for PC user support. Recently, as the Internet utilization rate has increased every year, the usage of PCs by elderly people has also increased in Japan. However, the digital divide between elderly people and PC beginners has widened. To eliminate this digital divide, we consider improving the users' operability and visibility as our goal. We propose a new hemispherical humancomputer-interface device for PCs, which integrates a hemispherical subdisplay and a pointing device. Then we evaluate the interface device in terms of its effectiveness of operability and visibility. As seen from the analyses of a subjective evaluation, our interface device obtained good impressions results for both elderly people and PC beginners.

We have investigated the formation of the locally strained Ge nanostructure with epitaxial Ge1−xSnx stressors and characterized the microscopic strain field in the Ge1−xSnx/Ge fine-heterostructures by synchrotron X-ray microdiffraction and finite element method (FEM) calculations. We achieved local epitaxial growth of Ge1−xSnx with Sn contents of 2.9% and 6.5%, sandwiching the 25 nm-wide Ge fine line structure. Microdiffraction measurements revealed that out-of-plane tensile strain induced in the Ge line effectively increased with decreasing Ge width and increasing Sn content of Ge1−xSnx stressors, which is in good agreement with FEM calculations. An out-of-plane tensile strain of 0.8% along the Ge[001] direction is induced in a 25 nm-wide Ge line, which corresponds to an in-plane uniaxial compressive strain of 1.4% in the Ge line sandwiched between Ge0.935Sn0.065 stressors.

In order to realize fine microstructures with high aspect ratio, tow kind of thick-resist-based metal molding processes were studied. A novel technique obtaining fine line/space and high aspect ratio thick photoresist patterns on a glass substrate by the simple UV lithography was developed. A three-layer resist method using reactive ion etching (RIE) for patterning thick photoresist was also examined. The former method is to use fine thin metal patterns formed on the glass substrate as the exposure mask. A thick negative photoresist is coated on it and UV light is illuminated from the backside. Perfect contact between mask and photoresist is obtained and the influence of light diffraction is also avoided. By using SU-8 as the negative photoresist, minimum line/space of 1 micrometers and high aspect ratio of about 5 was achieved. The metal layer is served as a seed layer for Ni electroplating as well. Metal microstructures were also fabricated by the three-layer resist method using the thick photoresist-thin SiO2-thin photoresist structure. Even an usual contact UV lithography was applied to pattern the thin photoresist layer and a usual CCP-RIE was used to etch the SiO2 and thick photoresists layer, at least 1 micrometers gap microstructures were obtained by the Ni electroplating. Micro-packaging method using SiO2-SiO2 bonding with hydrofluoric acid was also studied. HF bonding conditions suitable for micropackaging were examined under different HF concentration, pressure, and temperature. Reasonable bond strength equal to that by the anodic bonding is obtained under high-applied pressure during bonding. Packaging method is posed using combination of the thick-resist-based molding and the HF bonding.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.