Gold Stripe Optical Waveguides Fabricated by a Novel Double‐Layered Liftoff Process

To fabricate uniform and reliable thin gold stripes that provide low‐loss optical waveguides, we developed a novel liftoff process placing an additional SiN_x layer under conventional photoresists. By patterning a photoresist and over‐etching the SiNx, the photoresist patterns become free‐standing structures on a lower‐cladding. This leads to uniform metal stripes with good reproducibility and effectively removes parasitic structures on the edge of the metal stripe in the image reversal photolithography process. By applying the newly developed process to polymer‐based gold stripe waveguide fabrication, we improved the propagation losses about two times compared with that incurred by the conventional image‐reversal process.     

SEM-EDAX analysis of interaction of photoresist with thick films

The SEM-EDAX analysis of the interaction of Shipley's positive photoresist AZ-1350J with thick film pastes DP 9596 and DP 1441 is reported. The interaction is found to make the resistor surface smoother and conductor surface denser than those of processed conventionally. The gold from DP 9596 (Pt-Au) paste is also observed to pass through the photoresist during firing and settle underneath on alumina substrate in the form of 0.5 μm sized grains. The interaction is found useful for fabricating microlines and cantilevered structures for sensor development.     

Biaxial initial stress characterization of bilayer gold RF-switches

An analysis as been conducted to determine the biaxial initial stress state of gold bilayer switches. Results are shown that the sensitivity of the sacrificial photoresist layer to process parameters make the wafer curvature technique unreliable to determine the initial stress state of the evaporated gold seed layer. An analytical method based on the cantilever deflection method is proposed to determine the biaxial stress state on this layer. Assumptions were validated numerically using FEM and cantilevers gold bilayer of various length were elaborated and characterized.     

Measurement of minority-carrier lifetime in silicon at microwave frequencies using microstrip techniques

A method is described for measuring minority-carrier lifetime in semiconductor samples of any thicknes and dimensions (e.g. silicon is used in device fabrication). The semiconductor sample is used as the dielectric of a microstrip line sandwitched between a ground plane of electroplated gold (or other metal) and electroplateted strip conductor delineated using standard photoresist masking techniques.     

Lithography factors that determine the aspect ratio of electron cyclotron resonance plasma etched HgCdTe trenches

Factors that affect width and aspect ratio in electron cyclotron resonance (ECR) etched HgCdTe trenches are investigated. The ECR etch bias and anisotropy are determined by photoresist feature erosion rate. The physical characteristics of the trenches are attributed to a combination of photoresist feature geometry and ECR plasma etch chemistry. This knowledge has led to production of trenches suitable for two-color, 20 μm pitch detectors.     

The effect of ultrasonic agitation on the stripping of photoresist using supercritical CO2 and co-solvent formulation

A novel technology for removing high-dose ion-implanted photoresist (HDI PR) from semiconductor wafers using supercritical carbon dioxide (scCO₂) and several co-solvent formulations have been described. A combination of ultrasonic agitation with scCO₂/co-solvent stripping was found to be an effective method for photoresist removal. Ultrasonic agitation was an efficient technique for achieving higher stripping rates. The effects of temperature, pressure, reaction time and the type of organic co-solvent on the stripping rate of HDI PR were investigated. The microstructures of sample wafers after stripping were characterized by scanning electron microscopy and energy dispersive X-ray spectrometer.     

Novel Single-Wafer Single-Chamber Dry and Wet Hybrid System for Stripping and In Situ Cleaning of High-Dose Ion-Implanted Photoresists

There is increasing demand for moving from batch immersion tools to single-wafer spin tools for silicon wafer cleaning, etching, and photoresist/residue removal in advanced semiconductor manufacturing. However, high-dodse ion-implanted photoresist removal using a conventional single-wafer spin tool is very difficult. We have developed a novel single-wafer single-chamber dry and wet hybrid system in combination with dry ashing and moderate-temperature wet-cleaning treatments by implementing an atmospheric-pressure plasma unit into a conventional single-wafer spin cleaning tool. This compact single-wafer single-chamber system can completely remove the hardened photoresist due to high-dose ion-implantation by an atmospheric-pressure plasma ashing process followed by an in situ wet chemical process in the same single chamber within 2 min. This single-wafer single-chamber dry/wet hybrid system offers less than 1/3 smaller footprint, less than 1/4 shorter cycle time (for 50 wafer processing), and potentially better process control and less contamination risk, as well as lower equipment cost, compared to the conventional combination of two separate dry- and wet-processing systems.      

High aspect ratio electrodeposited Ni/Au contacts for GaAs‐based III–V concentrator solar cells

We report on a photolithographic and electro‐deposition process that results in an optimized front grid structure for high efficiency multi‐junction III–V concentrator solar cells operating under flux concentrations up to 1000 suns. Two different thick photoresists were investigated to achieve a 6 µm wide grid line with an aspect ratio of 1:1. A positive photoresist, SPR220 manufactured by Rohm and Haas was compared with a negative photoresist, nXT15 manufactured by AZ. A gold sulfite electrolyte was employed to prevent underplating as well as for environmental and safety considerations. An initial layer of nickel was discovered to be necessary to prevent delamination of the fingers during the removal of the contact layer. When deposited on a purpose grown, heavily doped GaAs contact layer, this Ni/Au contact exhibits an acceptable specific contact resistance in the low 10⁻⁴ to mid 10⁻⁵ Ohm cm² range along with excellent adhesion without sintering. Copyright © 2014 John Wiley & Sons, Ltd.     

Designing Multicolor Micropatterns of Inverse Opals with Photonic Bandgap and Surface Plasmon Resonance

Structural coloration provides unique features over chemical coloration, such as nonfading, color tunability, and high color brightness, rendering it useful in various optical applications. To develop the structural colors, two different mechanisms of coloration–photonic bandgap (PBG) and surface plasmon resonance (SPR)–have been separately utilized. In this work, a new method is suggested to create structurally colored micropatterns by regioselectively employing SPR in a single film of inverse opal with PBG. The inverse opals are prepared by thermal embedding of opal into a negative photoresist and its subsequent removal. The inverse opals have a hexagonal array of open pores on the surface which serves as a template to make SPR‐active nanostructures through a directional deposition of gold, a perforated gold film and an array of curved gold disks are formed. With a shadow mask lithographically prepared, the gold is regioselectively deposited on the surface of the inverse opal, which results in two distinct regions of gold‐free inverse opal with PBG and gold nanostructure with SPR. As PBG and SPR develop their own structural colors respectively, the resultant micropatterns exhibit pronounced dual colors. More importantly, the micropatterns show the distinguished optical response for evaporation of volatile liquids that occupy the pores.     

光刻胶段差对光刻图形的影响与改善

TFT光刻制程中,光刻胶段差使光胶在同一个光刻平面上,各区域的光刻程度不同,严重影响着光刻图形的质量。文章从光刻胶段差对光刻图形影响的原因进行分析,根据光强在投影光刻机光刻系统中焦点附近与光刻胶内部的变化特点,推导并计算出光刻胶段差区域内光强变化量为零时,光刻系统中光刻平面所应处于的位置,同时结合当前光刻系统焦平面的位置,计算出光刻平面的调整量,并以该调整量对当前光刻平面进行调整。结果表明:对于极限分辨率为2.41μm的投影光刻机,要使厚0.52μm的光刻胶段差内光强变化量为零,光刻平面调整量为9.434 42μm,且对光刻平面调整后10μm后,在DICD(Develop Inspection Critical Dimension)变化量较小的情况下,可显著改善沟道长为2.5μm的GOA(gate drive on array)区域的光刻胶残留。     

A self-aligned offset polysilicon thin-film transistor usingphotoresist reflow

A simple fabrication method for a self-aligned offset structure, which uses photoresist reflow, is developed to reduce the leakage current of polysilicon thin-film transistors (poly-Si TFTs). The reflow of photoresist can be controlled by varying photoresist thickness and reflow temperature. It is found that the reflow length increases in proportion to the photoresist thickness, and increases with increasing reflow temperature at less than 200°C for the AZ5214A photoresist. Poly-Si TFTs are successfully demonstrated with offset lengths of 0.4 and 0.6 μm, which show apparent reduction of the leakage current     

Thermal and mechanical analysis of photoresist and silylated photoresist films: Application to AZ 5214™

Combined thermal and mechanical analysis of spun-on photoresist, and silylated photoresist films after each lithographic step was done using Differential Scanning Calorimetry (DSC) and Thermomechanical Analysis (TMA). For reacting photoresist systems the DSC method is excellent for determination of both the baking-temperature ranges in which the reactions take place, and the heat of reaction. For calculation of the glass transition temperature (T_g), and mechanical deformation of resists however, TMA proves most appropriate. This methodology was applied for a commercial photoresist AZ 5214™ to determine the thermally or melamine induced crosslinking temperature regions, the T_g of crosslinked samples, and to show that wet HMCTS (Hexamethyl-Cyclo-Tri-Silazane) silylated films have higher T_g values than the original photoresist.     

基于制作COF精细线路的液态光致抗蚀液性能研究

卷对卷丝网印刷机在超薄挠性覆铜箔层压板上丝网印刷液态光致抗蚀液,实现COF精细线路的制作。研究了液态光致抗蚀液的感光性能与分辨率力等性能,考察了制作出COF的线路效果。实验结果表明,液态光致抗蚀液网印的针孔数随厚度的减小而增加,液态光致抗蚀剂曝光级数随曝光能量的变化趋势与干膜是一致的,11μm厚液态光致抗蚀剂分辨的最小线路宽达到25μm,满足COF精细线路制作的要求。     

Effects of HgCdTe on the Optical Emission of Inductively Coupled Plasmas

Inductively coupled plasmas (ICP) are the high-density plasmas of choice for processing HgCdTe and related compounds. Real-time examination of the ICP plasmas used to process HgCdTe would be desirable. In this preliminary study, the feasibility of using optical emission spectroscopy (OES) of ICP plasma used for processing HgCdTe has been examined. We have examined the utility of OES as a real-time diagnostic tool for HgCdTe device fabrication. In this preliminary study it has been found that mercury and cadmium can be detected but are dependent on several factors: sample area, material composition, etch rate, sample temperature, photoresist area, and plasma power. Furthermore, we found strong correlation between the amount of hydrogen detected by OES for samples with photoresist versus samples without photoresist while processing with hydrogen-based plasma. Hydrogen emission intensity decreased dramatically in samples with photoresist, contrary to the theory that photoresist adds hydrogen to the plasma effluent. It appears that hydrogen complexes with photoresist, reducing the global amount of hydrogen during the process. Furthermore, this phenomena may help to explain macroloading issues whereby additional photoresist area slowed HgCdTe, CdTe, and photoresist etch rates.     

Advanced development process for ultrafine photoresist patterns

Addition of appropriate surfactant to developer will improve wettability of the developer, thus promoting uniformity of dissolution of exposed photoresist. Surface smoothness of the Si substrate is also improved when developer contains surfactant. The only disadvantage is that surfactant is adsorbed onto the wafer surface; however, it can be removed by a Pt-H₂O₂ treatment without degrading the photoresist pattern. The optimal tetramethylammonium hydroxide (TMAH) concentration in the developer was investigated by measuring the developing selectivity of the photoresist against various TMAH concentration levels. The developing selectivity is considered to directly affect the photoresist profile and resolution in the development process     

对胶体球光刻中单层胶体晶体曝光特性的研究

对胶体球光刻中单层胶体晶体(MCC)的曝光特性进行了研究。利用磁控溅射的方法在蓝宝石衬底上生长SiO2薄膜并旋涂光刻胶,通过固液界面自组装的方法在光刻胶上制备了单层胶体晶体。胶体球光刻利用单层胶体晶体作为微透镜阵列,通过紫外曝光的方法在光刻胶上制备微孔阵列。光刻胶上图形的周期性与胶体球的直径有关,并且大直径的胶体球的聚光性能要强于小直径胶体球,在曝光过程中随着曝光时间的增加,由于曝光量的增加以及光刻胶的漂白现象,光刻胶上微孔的尺寸也在增加。最后以曝光后的光刻胶为掩膜,将感应耦合等离子体刻蚀技术(ICP)以及湿法腐蚀相结合,制备出了图形化蓝宝石(PSS)衬底。     

抗蚀剂AZ4562曝光参数的变化趋势分析

针对厚胶曝光参数随不同光刻胶厚度及工艺条件变化的特点,在原有Dill曝光模型基础上,建立了适合于描述厚胶曝光过程的增强Dill模型,并将统计分析的趋势面法引入到厚胶曝光参数变化规律的研究中,给出了厚胶AZ4562曝光参数随胶厚及工艺条件的变化趋势,为开展厚胶光刻实验研究和曝光过程模拟提供指导性依据。     

ToF-SIMS and XPS study of ion implanted 248 nm deep ultraviolet (DUV) photoresist

Arsenic implanted 248 nm DUV photoresist films were characterized by ToF-SIMS and XPS analysis methods. The effect of the implant dose and energy on the formation of the crust layer on top of the bulk photoresist was studied. The crust layer thickness was found to be dependent on the implant energy and dose. The elemental and chemical changes induced by various implant doses and implant energies were investigated. Emphasis was put on the effect of the aging time on the composition of the ion implanted photoresist.     

Investigation of the Photoresist Pattern Profile Contrast Improvement in Interference Lithography Technique Using 488-nm Laser

The interference lithography technique at 488 nm is explored theoretically and experimentally, and the effect of photoresist pattern profile contrast improvement is presented. In order to produce high contrast photoresist patterns using interference lithography, the system setup and process have to be optimized strictly, and process optimization can be facilitated by simulation. In the proposed simulation method, the absorption coefficient of photoresist varying with wavelength is considered by using photoresists with lower absorption coefficients, or, for the same photoresist, using laser sources with longer wavelengths. The visibility of aerial fringe patterns of the photoresist can be improved greatly. However, after developing, the contrast of photoresist patterns was not improved. The reason is that the photo sensitivity and etching rate V of photoresist decrease at 488 nm. This offsets the effect of lower absorption coefficients even though a 488-nm argon ion laser source is useable for some photoresists. This opens up a new window for the interference lithography technique.      

Effect of photoresist-feature geometry on electron-cyclotron resonance plasma-etch reticulation of HgCdTe diodes

The factors that affect the trench width and aspect ratio in electron-cyclotron resonance (ECR) etched HgCdTe and CdTe are investigated. The ECR etch bias and anisotropy are found to be predominately determined by the photoresist feature-erosion rate. The physical characteristics of the trenches are attributed to ECR plasma-etch chemistry. A method for fabricating high aspect-ratio, HgCdTe isolation trenches is demonstrated through a combination of advanced photolithography and ECR etching.