Study of electrochemical etch-stop for high-precision thickness control of single-crystal Si in aqueous TMAH : IPA : pyrazine solutions

In this paper, we describe a method of controlling the thickness of single-crystal Si membranes, fabricated by wet anisotropic etching in aqueous tetramethyl ammonium hydroxide (TMAH) : isopropyl alcohol (IPA) : pyrazine solutions. The Si surface of the etch-stopped microdiaphragm is extremely flat with no noticeable taper or nonuniformity. The benefits of the electrochemical etch-stop method for the etching of n epilayer-embedded p-type single-crystal Si(0 0 1) wafers in aqueous TMAH became apparent when the reproducibility of the microdiaphragm’s thickness in mass production was realized. The results indicated that the use of the electrochemical etch-stop method for the etching of Si in aqueous TMAH provided a powerful and versatile alternative process for the fabrication of high-yield Si microdiaphragms (20 ± 0.26 μm s.d). With etch-stop, the pressure sensitivity of devices fabricated on the same wafer can be controlled to within ±2.3% s.d.     

TMAH单晶硅腐蚀特性研究

TMAH是一种具有优良的腐蚀性能的各向异性腐蚀剂,选择性好,无毒且不污染环境,最重要的是TMAH与CMOS工艺相兼容,符合SOC的发展趋势。TMAH正逐渐替代KOH和其他腐蚀液,成为实现MEMS工艺中微三维结构的主要腐蚀剂。本文着重介绍了TMAH的特性、工艺条件及应用。     

槽式湿法碱抛光技术在PERC太阳电池中的工艺研究

高效晶体硅太阳电池是光伏领域的热门研究之一,提高晶体硅太阳电池的转换效率是光伏研究者的重要研究方向。降低电池背面反射率是提高晶体硅电池转换效率的有效方法之一,实验采用激光掺杂制作选择性发射极,并利用槽式湿法碱抛光技术,去除发射极表面的重掺杂区,降低载流子在电池发射极表面区域的复合,提高载流子的有效寿命达到抛光效果,并最终提升电池转换效率。结果表明:硅片经过抛光处理后,减少了作为复合中心的悬挂键,降低了表面复合速率。发现了高反射率增强了光的反射,反射回电池内部的光被再吸收,提高了光的利用率。这是造成短路电流提升的主要原因。表面掺杂浓度的降低以及表面重掺杂区尺寸的减小将有效抑制载流子在发射极区域的俄歇复合,提高载流子的有效寿命。     

基于TMAH溶液的PN结自停止腐蚀的研究

MEMS器件的性能与尺寸密切相关.介绍了一种精确控制器件尺寸的各向异性腐蚀方法--基于改进TMAH溶液的PN结自停止腐蚀.这种方法几乎不刻蚀铝,从而与CMOS工艺良好地兼容.应用这种办法正面腐蚀,成功释放结构,尺寸与设计比较符合,证明了这种方法的可行性及易操作性.     

基于硅(111)晶面腐蚀的可控在线细化工艺及其对硅纳米线电学性能的改善

Nanoscale refinement on a (100) oriented silicon-on-insulator (SOI) wafer was introduced by using tetra-methyl-ammonium hydroxide (TMAH, 25 wt%) anisotropic silicon etchant, with temperature kept at 50 ℃ to achieve precise etching of the (111) crystal plane. Specifically for a silicon nanowire (SiNW) with oxide sidewall protection, the in situ TMAH process enabled effective size reduction in both lateral (2.3 nm/min) and vertical (1.7 nm/min) dimensions. A sub-50 nm SiNW with a length of microns with uniform triangular cross-section was achieved accordingly, yielding enhanced field effect transistor (FET) characteristics in comparison with its 100 nm-wide pre-refining counterpart, which demonstrated the feasibility of this highly controllable refinement process. Detailed examination revealed that the high surface quality of the (111) plane, as well as the bulk depletion property should be the causes of this electrical enhancement, which implies the great potential of the as-made cost-effective SiNW FET device in many fields.     

Non-chromatographic atomic spectrometric methods in speciation analysis: A review

In recent years, knowledge of the different chemical forms of the elements has gained increasing importance. There has been significant progress in methods that hyphenate chromatographic separations with atomic spectrometry. These hyphenated methods can provide the most complete information on the species distribution and even structure. However, they can be lengthy, relatively costly and difficult to bring to the routine. On the other hand, it is important to remember that chromatographic techniques represent only a minor part of the separation procedures available and, in certain cases, the application of basic chemistry to sample treatments can give quantitative information about specific chemical forms. In this sense, non-chromatographic procedures can provide methods that offer sufficient information on the elemental speciation for a series of situations. Moreover, these non-chromatographic strategies can be less time consuming, more cost effective and available, and present competitive limits of detection. Thus, non-chromatographic speciation analysis continues to be a promising research area and has been applied to the development of several methodologies that facilitate this type of analytical approach. In view of their importance, the present work overviews and discusses different non-chromatographic methods as alternatives for the speciation analysis of clinical, environmental and food samples using atomic spectrometry for detection.     

High-performance PIN photodiodes on TMAH thinned silicon wafers

The electro-optical characteristics of PIN photodiodes fabricated on high-resistivity silicon substrates locally thinned by bulk micromachining techniques are discussed. Experimental results and numerical simulations demonstrate that devices fabricated by the proposed approach have leakage current, quantum efficiency and speed performance comparable to the best commercially available Si PIN photodiodes, with the additional advantage of possible back-side illumination, making them suitable for the implementation of two-dimensional arrays having a read-out electronic chip connected to the front-side.     

10%TMAH硅湿法腐蚀技术的研究

研究了浓度为10%的四甲基氢氧化铵(TMAH)溶液,在不同量的Si粉掺杂下,对铝膜及硅衬底的腐蚀及其pH值的变化。测试了在满足铝膜极低的腐蚀速率(<1nm/min)时,不同温度下该腐蚀液对硅(100)、(111)和(110)晶面及SiO2介质膜的腐蚀速率。还介绍了添加剂—过硫酸铵(APODS)和吡嗪的加入对腐蚀表面形貌及腐蚀速率的影响。研究结果表明,存在着一个临界的硅粉添加量,超过此量后铝膜的腐蚀速率急剧降低。90℃时,在10%TMAH溶液中加入1 5mol/L硅粉、3 0g/LAPODS和2g/L吡嗪可以实现铝膜不被腐蚀,同时硅(100)面约有1μm/min的腐蚀速率,腐蚀表面平整。腐蚀后的铝膜表面同硅铝丝键合良好,实现了腐蚀工艺同CMOS工艺的完全兼容。     

TMAH腐蚀液的研究

IMAH是一种新型的、性能优异的各向异性腐蚀液.文章通过大量对比实验,对该腐蚀液用于＜100＞、＜111＞单晶Si片不同电阻率、不同晶向的样品研究了粗糙度和腐蚀速率,得出重要结论.此研究对正确使用rMAH腐蚀液有重要指导意义.