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Overlay metrology is crucial to process control in manufacturing semiconductor devices. Diffraction-based overlay (DBO) is an effective overlay measurement approach because it exhibits multiple advantages. This study analyzed measurement errors caused by sidewalls in the bottom gratings of DBO targets. Accordingly, improvement was proposed using a neural network. First, rigorous coupled wave analysis was employed to calculate the pupil images generated by an overlay target. These images were then used as a data set. Next, two-directional two-dimensional principal component analysis was used to reduce the dimension of features in these images. The features were then used to train a neural network and determine weighting coefficients in each network layer to create a DBO model. This study used virtual metrology to analyze 30 types of overlay targets and generated 18900 pupil images to create a data set. Each overlay target model was measured 10 times, and shot noise, dark noise, and quantization noise in the pupil images were accounted for. The simulation results revealed that when the dose level was 1000 mJ/ $\text{s}\cdot $ cm2, the overlay mean square error of the testing data was 0.40nm2, indicating notable improvement in the measurement results of overlay targets with bottom grating sidewalls. Therefore, the proposed neural network-based DBO model can be applied to overlay targets with sidewalls and effectively improve the overlay accuracy.

Titanium nitride (TiN) thin films were prepared by RF magnetron sputtering on a bare Si surface and a silicone-oil-covered Si surface as surface-enhanced Raman scattering (SERS) substrates. The TiN film deposited on the bare Si surface had a flat surface with densely packed grains measuring 18 nm in diameter, whereas the TiN film deposited on the oil surface had a wrinkly pattern made of grains measuring 19 nm in diameter. To analyze the SERS effect, Rhodamine 6G (R6G) was used as a Raman probe molecule at various concentrations ranging from 10−4 to 10−8 M. The analytical enhancement factor (AEF) values at 10−6 M R6G were respectively 6.2 × 103 and 1.3 × 104 for the flat TiN film and wrinkly TiN film. The SERS effect could be attributed to the enhancement of the local electromagnetic field at the top of the nano-sized grains. The wrinkly TiN film had a higher AEF than the flat TiN film, possibly due to the increased area of the Raman active spots. The wrinkly TiN film exhibited high level of SERS activity and achieved an R6G detection limit of 10−8 M.

This study used a digital micromirror device (DMD) to produce point-array patterns and employed a self-developed optical system to define line-and-space patterns on nonplanar substrates. First, field tracing was employed to analyze the aerial images of the lithographic system, which comprised an optical system and the DMD. Multiobjective particle swarm optimization was then applied to determine the spot overlapping rate used. The objective functions were set to minimize linewidth and maximize image log slope, through which the dose of the exposure agent could be effectively controlled and the quality of the nonplanar lithography could be enhanced. Laser beams with 405-nm wavelength were employed as the light source. Silicon substrates coated with photoresist were placed on a nonplanar translation stage. The DMD was used to produce lithographic patterns, during which the parameters were analyzed and optimized. The optimal delay time-sequence combinations were used to scan images of the patterns. Finally, an exposure linewidth of less than 10 µm was successfully achieved using the nonplanar lithographic process.

As the complexity of mask patterns increases, the standard off-axis illumination in 193-nm immersion systems is increasingly becoming inadequate for high-quality lithography. In this study, a source optimization (SO) technique was employed for improving lithographic resolution. A pixel-based optimization process was developed for constructing freeform sources on a PC platform to enhance contrast and improve process window (PW). In the proposed SO algorithm, the metaheuristic binary ant colony optimization algorithm was applied for constructing the freeform sources. Moreover, the proposed algorithm converged to the optimal solution between the 300th and 400th iterations. The performance of this algorithm was assessed using the half pitch (hp) 45-nm line/space (L/S) and 55-nm SRAM contact hole (CH) patterns. The fitness function was quality of aerial image, exposure latitude (EL), and depth of focus (DOF); the constructed freeform sources enhanced the contrast and extended the PW for the patterns. The DOF increased from 0.91 to 1.1 μm and 0.042 to 0.061 μm for the L/S and SRAM CH patterns, respectively, at an EL of 5% when using the freeform source. Moreover, the freeform source improved the mask error enhancement factor by 22% for the SRAM pattern.

Digital-mask lithography systems, with a digital micromirror device (DMD) as their central piece, have been widely used for defining patterns on printed circuit board (PCB). This study designed optical module parameters for point-array projection lithography based on field tracing technique to improve the quality of the aerial image on the exposure plane. In the realized optical module for the point-array projection lithography, a DMD was used as the dynamic digital-mask, and a 405-nm-wavelength laser was used to illuminate the DMD. The laser was then focused through the micro-lens array in the optical module to form a point array and was projected onto a dynamic scanning stage. By calculating the beam-overlapping rate, stage velocity, spot diameter, and DMD frame rate and programming them into the stage- and DMD-synchronized controller, the point array formed line patterns on the photoresist. Furthermore, using pulse width modulation (PWM) technique to operate the activation periods of the DMD mirrors effectively controlled the exposure and achieved a feature linewidth of less than 10 μm.

With the dramatically increase of design complexity and the advance of semiconductor technology nodes, huge difficulties appear during design for manufacturability with existing lithography solutions. Sub-resolution assist feature (SRAF) insertion and optical proximity correction (OPC) are both inevitable resolution enhancement techniques (RET) to maximize process window and ensure feature printability. Conventional model-based SRAF insertion and OPC methods are widely applied in industrial application but suffer from the extremely long runtime due to iterative optimization process. In this paper, we propose the first work developing a deep learning framework to simultaneously perform SRAF insertion and edge-based OPC. In addition, to make the optimized masks more reliable and convincing for industrial application, we employ a commercial lithography simulation tool to consider the quality of wafer image with various lithographic metrics. The effectiveness and efficiency of the proposed framework are demonstrated in experimental results, which also show the success of machine learning-based lithography optimization techniques for the current complex and large-scale circuit layouts.

This paper investigates the manufacturability-aware process of p-n junction formation for photovoltaic cells involving with Si nanoparticle layer. The furnace-based dopant diffusion process of forming a p-n junction consumes a substantial amount of energy. In addition, repetitive production steps prevent the possibility of Si ink-based cells integrating onto flexible substrates. This research examined the local heating dopant diffusion process by using a fiber laser at a wavelength of 1064 nm. The infrared beam is delivered onto the wafer stack with a nanoparticle carbon layer and n-type Si ink layer on p-type Si substrates. The nanoparticle carbon film absorbs infrared beam energy and converts photon energy as a thermal source to diffuse the n-type dopant in Si ink into the p-type Si wafer. The Si ink in this paper contains a mixture of Si nanoparticles and an n-type spin-on dopant solution. The TEM results show that Si nanoparticles are uniformly dispersed on the Si wafer surface. This research investigated sheet resistance as a function of laser parameters, including laser power, scanning speed, and pulse frequency for the samples coated with Si ink. Secondary ion mass spectroscopy measurements indicate the presence of an n-type dopant in p-type substrates, with an approximate diffusion depth of 100 nm. The results indicate that the proposed infrared laser treatment technique is promising for the formation of p-n junctions with Si ink-based photovoltaic cells.

Core-shell-isolated nanorods can be used to amplify the signals of target cancer antigen molecules. Recent research has suggested that these nanorods feature surface-enhanced Raman scattering (SERS) signals superior to those of nanoparticles. In this study, nanorod geometrical models based on core-shell-isolated nanocapsule morphology were employed to analyze the scattered power density in three-dimensional spaces. Superior to the conventional cross-section field analysis method, the average scattered power density based method in this presentation could verify the enhancement effects from all possible positions on the nanorod surface. The numerical results in this study were also compared with the experimental results described in the literature. The resonance scattering power reached the maximal value when the radius of the ${\rm Au/SiO}_{2}$ and ${\rm Ag/SiO}_{2}$ nanorods was 20 nm. At an incident wavelength of 751 nm, the ${\rm Au/SiO}_{2}$ and ${\rm Au/Al}_{2}{\rm O}_{3}$ nanorods achieved maximal scattered power density when spacing $d=30~{\rm nm}$ . Conversely, the ${\rm Au/TiO}_{2}$ nanorods achieved maximum scattered power density when spacing $d=40~{\rm nm}$ . When the core was Au, nanorods with shell thickness $h$ of 1 nm produced a resonant scattering intensity same as it by the nanorods without shells. The numerical results also indicated a stronger resonance peak when the incident ray illuminated the major-axis plane of the ${\rm Au/SiO}_{2}$ nanorods. When the incident ray illuminated the curvature plane of the nanorods, the resonance wavelength clearly shifted toward the UV wavelength range. The four ${\rm Au/SiO}_{2}$ nanorods with symmetric arrangement achieved the highest resonance peak when the nanorod spacing was 30 nm. This presentation can serve as a key reference for the design of core-shell-isolated nanorods as highly sensitive SERS substrates.

This paper investigated pixel-based source shape optimization to enhance the resolution in a projection extreme UV (EUV) lithography system. The particle swarm optimization method was proposed to optimize the source shapes. The layout patterns of the masks were corrected using model-based optical proximity correction. The optimal source shape in an EUV lithography system was verified using numerical calculations, through which the aerial image of two types of mask pattern exposure was determined. The two types of mask patterns were a logic line/space (L/S) pattern with a critical dimension (CD) of 16 nm and a SRAM contact hole (CH) pattern with a CD of 45 nm. Two significant metrics were used to evaluate the modified source performance: the latent image intensity and process window. Results from the numerical calculations showed that for L/S target patterns, using the optimal source produced a latent image error of 13.02% after exposure that was superior to that of traditional off-axis source exposure. The latent image intensity of the mask between the lines and the gaps differed substantially, corner rounding situations had effectively improved, and no bridges were observed. Concerning CH target patterns, using the optimal source produced a latent image error of 0.04% after exposure that was also superior to that of traditional sources. The latent image intensity between the holes and the gaps also differed significantly, and the latent image intensity distribution at the four corners of the CH had straight angles. Because the source shapes calculated in this study comprised pixel-based sources, the controllable microelectromechanical system mirror array chip was used to match each mirror to each pixel source, and the calculated source shapes were successfully projected.

Source Optimization is a key techniques to enhance the process window in ArF 193i-nm lithography process. This paper proposes a source optimization algorithm combining metaheuristic-based binary ant colony source optimization (BACO) and an artificial neural network (ANN). The purpose of this study is to establish the optimal freeform source for improving the process window of the critical patterns and maintaining the quality of aerial images. The source plane is pixelated and divided into 25 sectors. In this study, a set of the input data for training the ANN includes the pattern edge contours resulting from the various process conditions with respect to each searching agent at each iteration. The trained ANN selects sectors with effective pixel sources illuminating the target pattern to enhance the aerial image quality and improve the process window. The combination of the B-ACO and ANN methods decreases the searching space and speed up the convergence of the B-ACO. PROLITHTM (KLA-Tencor) is used to calculate the aerial image when using the optimized freeform source. The developed algorithm is tested using the 17 clips of 1D line/space pattern with various line widths, pitches and line orientations. The testing pattern includes nine horizontal line features and eight vertical line features. The minimum line width is 40 nm with a pitch of 80nm, and the maximum linewidth is 120nm with a pitch of 500nm. An optimized freeform source is simultaneously constructed for these 17 clips. The imaging performance for these 17 clips is presented.

Core-shell-isolated nanoparticles are commonly used in the surface-enhanced Raman scattering (SERS) technique to detect binding events and in analyte identification at the molecule level. In this paper, an opticalscattering theoretical model was used in which the core-shell-isolated nanoparticles are considerably smaller than incident light wavelengths, and the finite difference time domain method of numerical electromagnetics was adopted to compute the scattered opticalpower density per unit volume of the nanoparticles. In addition, the power densities were analyzed using various shell materials and the influences of differing parameters (i.e., the size of metal nanoparticles, shell thickness, nanoparticle size, and the distance between nanoparticles) on power-density functions were explored. The results indicated that when the nanoparticle shells were coated with silicon dioxide (SiO 2 ) and aluminum oxide (Al 2 O 3 ) to a thickness of 1 nm and the nanoparticle core was gold (Au), a particle size of 35 nm was the optimal design. The optimal distance between Au nanoparticles possessing SiO 2 shells was 5 nm and that between Au nanoparticles possessing Al 2 O 3 or titanium dioxide (TiO 2 ) shells was 10 nm. Based on the format results of nanoparticle arrangement, the distance between the shell-isolated Au nanoparticles was 10 nm and generated a stronger scattered power density with an asymmetric arrangement than that generated using symmetrically arranged nanoparticles. The advantage of the proposed method in this paper over the conventional method is its ability to relate the scattered power density to the required number of nanoparticles used in the SERS technique.

Extreme ultraviolet (EUV) lithography is the leading candidate for 22 nm node technology and beyond. This research studies the influence of focal contributor on critical dimension (CD) variation in the EUV lithography and calculates the CD sensitivity to focal contributor based on the resist CD. EUV lithography parameters used in the simulation include NA = 0.25, 6 degrees oblique incident on the mask and source wavelength at 13.6 nm. The reflection design of EUV mask consists of 40 alternating Si/Mo layers, a ruthenium capping layer, and an absorber layer. The Rayleigh-Sommerfeld diffraction theory is adapted to solve the aerial image of contact hole (CH) feature layouts on the EUV mask. Then the resist CDs for the CH feature are measured at the position of the 10% from the bottom of resist profile. The target CD is 35 nm on wafer. The simulation results reveal the 2 nm discrepancy of spatial position for the aerial image curves measured between on the X metrology and Y metrology planes. The CDs of CH features with the iso-pitch are more sensitive to focal variation than the CDs of the features with the dense pitch. The maximum CD uniformity is 3.1 nm for the focal range at 90 nm.

According to the International Technology Roadmap for Semiconductors report, extreme ultraviolet (EUV) lithography is a key lithography tool for manufacturing devices at the 22-nm node and above. The current findings suggest that the lithographic image affects the critical dimensions (CDs) of wafers used in EUV lithography differently from those used in conventional lithography because of off-axis illumination and reflective optics design. The process windows of line/space (L/S) were explored, using a target CD of 22 nm and illuminating target contact hole (CH) features of a CD of 35 nm by using conventional, annular, dipole, and quasor source shapes. The diffraction amplitudes of the L/S and CH EUV masks and corresponding aerial images were calculated. The results indicate that the dipole is the favorable illumination source shape for printing the L/S features and the quasor is favorable for printing the CH features. In addition, the optimal dipole and quasor illumination settings are reported for the L/S and CH features, respectively. The exposure latitude was 4% and the depth of focus (DOF) was 100 nm to illuminate the L/S feature by using the dipole to print the target at a CD of 22. The exposure latitude was 24% and the DOF was 300 nm to illuminate the CH feature by using the quasor to print the target CD at 35 nm.

This paper discusses the integration of an end-to-end optical interconnect testbed on printed circuit boards using inexpensive off-the-shelf, bare die, optoelectronic components. We developed a process for efficient and simultaneous in-plane optical coupling between edge emitting laser and waveguides, and between photodetector and waveguide. We demonstrated an optically smooth buffer layer separating the printed circuit layer from the optical transport layer. The demonstrated radically new optical interconnect technology, which we refer to as interface optical coupling, is able to efficiently and simultaneously form optical interfaces between waveguides, lasers and photodetectors by photolithographic technique, thereby eliminating the need for micro-lenses and manual alignment. The measured laser to waveguide coupling efficiency is 45% and measured waveguide to photodetector coupling is 35%. The optical link is demonstrated to operate at 10 Gbps.

Source mask optimization (SMO) was considered to be one of the key resolution enhancement techniques for node technology below 20 nm prior to the availability of extreme-ultraviolet tools. SMO has been shown to enlarge the process margins for the critical layer in SRAM and memory cells. In this study, a new illumination shape optimization approach was developed on the basis of the ant colony optimization (ACO) principle. The use of this heuristic pixel-based ACO method in the SMO process provides an advantage over the extant SMO method because of the gradient of the cost function associated with the rapid and stable searching capability of the proposed method. This study was conducted to provide lithographic engineers with references for the quick determination of the optimal illumination shape for complex mask patterns. The test pattern used in this study was a contact layer for SRAM design, with a critical dimension and a minimum pitch of 55 and 110 nm, respectively. The optimized freeform source shape obtained using the ACO method was numerically verified by performing an aerial image investigation, and the result showed that the optimized freeform source shape generated an aerial image profile different from the nominal image profile and with an overall error rate of 9.64%. Furthermore, the overall average critical shape difference was determined to be 1.41, which was lower than that for the other off-axis illumination exposure. The process window results showed an improvement in exposure latitude (EL) and depth of focus (DOF) for the ACO-based freeform source shape compared with those of the Quasar source shape. The maximum EL of the ACO-based freeform source shape reached 7.4% and the DOF was 56 nm at an EL of 5%.

Optical scatterometry has attracted extensive interest in extracting the geometric shape information of nanolithography patterns because of the trend of shrinking device size and complicated stack structure. RCWA is the numerical algorithm implemented in the current scatterometry tool to calculate the diffraction efficiency. However, the known weakness for the RCWA method is the analysis of metallic gratings illuminated by the TM wave. This research applies the FDTD method using the Gaussian beam excitation source to analyze the diffraction efficiency of HKMG gratings for the use in the optical scatterometry and verifies the numerical diffraction efficiency discrepancy between the Gaussian beam and plane wave excitation methods. The numerical study is carried out with the line/space nanolithography patterns on the HKMG process stacks at 45 nm node technology. The nanolithography patterns are modeled as 1-D surface relief gratings. The 0th order diffraction efficiency is analyzed as a function of CDs, SWAs, incident angles and pitches of the gratings. The study presents the impact of the polarizations of the incident waves on the diffraction efficiency. In addition, this research investigates the phase of the 0th diffraction order as a function of the SWAs and illustrates the corresponding SWA parameter effect on the phase distribution. This research suggests the minimum beam radius to converge the numerical diffraction efficiency using Gaussian beam excitation to it using the plan wave.

This paper describes the use of ArF immersion lithography to verify the feasibility of a self-developed freeform illumination source that exposes features on masks and forms resist patterns. After development inspection (ADI) was used to measure the results and inspect whether the critical dimension (CD), process window, line-edge roughness (LER), and line-width roughness (LWR) of the resist pattern attained the standards of existing manufacturing processes. The testing features include nine horizontal and eight vertical features. Ant colony optimization (ACO) can provide optimal freeform illumination sources for these horizontal and vertical features. This paper considers each feature’s particular weighting in order to test the complexity and adaptability of the ACO algorithm applied to semiconductor manufacturing processes. The results of source calculations show that all 17 testing features can be satisfied with the X symmetry freeform source. When using this freeform source in an ArF lithography system, the ADI resist CD of all testing features is located within ±10% target CD tolerance. The ADI target CD set by dense patterns is 40 nm. Resist pattern ADI CD measurements show that, under a through-focus condition, the resist pattern CD between 40 and 42 nm is within tolerance, the depth of focus can reach up to $0.1~\mu \text{m}$ , LER is approximately 5 nm, and LWR is approximately 7 nm. These ADI CD measurements show that this ACO-based freeform source can be integrated into existing advanced semiconductor lithography processes.

International Technology Roadmap for Semiconductors (ITRS) report proposes extreme ultraviolet (EUV) lithography to be the key candidate of lithography tools to manufacture devices at the 22nm node and beyond. The image effects on wafer critical dimensions (CDs) in the EUV lithography are different from the effects in the conventional lithography caused by the off-axis illumination and refelective optics design. This research investigates process windows of line/space (L/S) with the target CD 22nm and contact hole (CH) features with the target CD 35nm illuminated by the conventional, annular, dipole, and quasor source shapes. The diffraction amplitudes by the EUV mask are summarized. The research suggests that the dipole is the better illumination source shape to print L/S features and the quasor is the better one for CH features. In addition, the research reports the best dipole illumination setting for the L/S features and the best quasor illumination setting for the CH features. The exposure latitude and depth of focus (DOF) for L/S feature illuminated by the dipole to print the target CD 22nm are 4% and 100nm respectively. The exposure latitude and DOF for CH feature illuminated by the quasor to print the target CD 35nm are 24% and 300nm respectively. Full field analysis of CH CDs displays the minimized CD error through slit due to the quasor illumination in the EUV lithography.

With the growing consumption of oil, the most popular energy for environmental protection is "solar cell". In a solar cell module, the surface will affect the overall yield efficiency of power generation. This study utilizes an optical grade Epoxy (EPO-TEK 301–2FL) to replace the Ethylene Vinyl Acetate (EVA) for solar cell modules, and to explore the electrical characteristics (IV) of Epoxy-based solar cell modules. In the manufacturing process of Epoxy-based solar cell modules, the effect of controlled parameters such as Epoxy thickness, curing temperature and curing time for module packaging results is studied for optimization of multiple quality of control factor by using the Grey Relational Analysis (GRA). Then, nine sets of measured electrical properties such as power and fill factor (F.F) are used to obtain the best of the analysis process.

Recent progress toward implementing high-density, optical-digital building blocks necessary to accomplish efficient, end-to-end optical interconnect architecture on low cost FR-4 boards has been demonstrated. The optical interconnect system consists of fabricating an optical buffer layer separating board metallurgy from the optical lightwave circuit layer, and implementing optical links between embedded lasers and detectors. We will show an example of 1310 nm light from an edge emitting distributed-feedback or Fabry-Perot laser operating at 10 Gb/s being guided to the photodetector by a polymer waveguide. Both lasers and detector are embedded in the waveguide and all construction is built on a low-cost FR-4 board with 3 levels of metallurgy.

In this paper, the first embedded optical interconnection using separately grown and fabricated, heterogeneously integrated thin film lasers and thin film photodetectors that are connected with a polymer waveguide is demonstrated.

This paper describes the fabrication and integration of a thin film edge emitting laser (EEL) whose optical output is coupled into a polymer waveguide integrated on the same electrical interconnection substrate. This embedded laser/waveguide structure is a fundamental building block toward the realization of planar lightwave circuits using embedded optical interconnections. The demonstration of a thin film laser embedded with a waveguide eliminates the need for either an external optical source coupled to the waveguide or a bump bonded optical source with a beam turning element to launch an optical wave into the waveguide.

This paper reports the first demonstration of a thin film (microns thick) heterogeneously integrated edge emitting laser bonded to a Si host substrate. Preliminary processing for embedding these thin film lasers into BCB polymer waveguides has also been discussed toward the implementation of embedded edge emitting sources in planar lightwave circuits.

The integration of thin film optoelectronic devices with polymer waveguides creates optical signal propagation, distribution, and processing in a planar waveguide format. These planar lightwave integrated circuits are appropriate for applications such as optical interconnections, sensors, and ultra fast optical signal processing.

We have fabricated and tested fibers having a thin AlCu alloy film strip covering a 15 degree of arc along the core cladding boundary. The fabrication of these fibers had a dual purpose. In order for the metal film to deform smoothly during the fiber pulling process from a coating on the 1 mm diameter core rod in the preform to a coating of the 10 micrometer core in the fiber the viscosity of the metal must be less than the viscosity of the surrounding glass. The viscosity of the AlCu film can be conveniently changed by varying the composition of the alloy. These fibers can, eventually, be used as polarizers. Light polarized parallel to the metal strip is absorbed more than light polarized perpendicular to the strip. We tested both the spectral and polarization transmission properties of these fibers.

The passivation of modulation-doped Al 0.1 Ga 0.9 N/GaN Schottky surfaces by treatment with (NH 4 ) 2 S and P 2 S 5 /(NH 4 ) 2 S has been investigated. The current-voltage (I-V) curves of these Schottky diodes demonstrate that the Ti/Pt/Au-Al 0.1 Ga 0.9 N/GaN Schottky diodes prepared by P 2 S 5 /(NH 4 ) 2 S treatment have the lowest reverse-leakage current (7.5 nA/cm 2 ) and the highest Schottky-barrier height (0.98 eV). Detailed X-ray photoelectron spectroscopy analysis indicates that a thin sulfide layer on the samples with the (NH 4 ) 2 S treatment has an improvement for these favorable characteristics. Further, a thin phosphide layer on the samples with the P 2 S 5 /(NH 4 ) 2 S treatment exhibits a larger improvement on the Schottky-barrier height and the reverse-leakage current.