GaAs表面旋转超声雾化清洗新技术

研究了一种新型湿法化学清洗半导体GaAs表面的方法。通过简单设计清洗工艺能使GaAs表面产生最低的损伤。GaAs表面清洗必须满足三个条件：(1)清除热力学不稳定因素和表面粘附的杂质,(2) 除去GaAs表面氧化层,(3)提供一个光滑平整的GaAs表面。本文采用旋转超声雾化方式用有机溶剂除去GaAs表面的杂质,再用NH4OH:H2O2:H2O= 1:1:10和HCl:H2O2:H2O=1:1:20顺次腐蚀非常薄的GaAs层,去除表面的金属污染,并在GaAs表面形成一个非常薄的氧化层表面,最后用NH4OH:H2O= 1:5溶液来清除GaAs表面氧化层。测试GaAs表面的特性,分别用X射线光电光谱仪、X射线全反射荧光光谱仪和原子力显微镜测试了GaAs表面氧化的组分、GaAs表面金属污染和GaAs表面形貌,测试结果表明通过旋转超声雾化技术清洗可提供表面无杂质污染、金属污染和表面非常光滑的GaAs衬底,以供外延生长。     

TaN wet etch for application in dual-metal-gate integration technology

Wet-etch etchants and the TaN film method for dual-metal-gate integration are investigated. Both HF/HN O_3/H_2O and NH_4OH/H_2O_2 solutions can etch TaN effectively, but poor selectivity to the gate dielectric for the HF/HNO_3/H_2O solution due to HF being included in HF/HNO_3/H_2O, and the fact that TaN is difficult to etch in the NH_4OH/H_2O_2 solution at the first stage due to the thin TaO_xN_y layer on the TaN surface, mean that they are difficult to individually apply to dual-metal-gate integration. A two-step wet etching strategy using the HF/HNO_3/H_2O solution first and the NH_4OH/H_2O_2 solution later can fully remove thin TaN film with a photo-resist mask and has high selectivity to the HfSiON dielectric film underneath. High-k dielectric film surfaces are smooth after wet etching of the TaN metal gate and MOSCAPs show well-behaved C-V and J_g-V_g characteristics, which all prove that the wet etching of TaN has little impact on electrical performance and can be applied to dual-metal-gate integration technology for removing the first TaN metal gate in the PMOS region.     

LED用GaAs抛光片清洗技术研究

伴随着LED照明产业的迅猛发展,高质量的GaAs抛光片需求量日益增大.研究了一种有效的直径5.08 cm低阻GaAs免洗抛光片的清洗技术,采用异丙醇低温超声去蜡结合兆声温法清洗工艺,使晶片表面达到了低表面颗粒度、极低表面金属离子浓度,并形成了较薄的富As氧化层表面.表面颗粒度通过Tencor6220测试大于0.3 μm的颗粒少于10个,通过TXRF测试表面金属离子个数均控制在9×1010/cm2以内;通过台阶仪测量表面粗糙度为0.8 nm,通过偏振光椭圆率测量仪测得均一的2 nm厚表面氧化层.     

薄GaAs层化学腐蚀及它的表面结构

用pH=7±O.05的H_2O_2-NH_4OH溶液,在5±1℃,对晶句是(100)的高阻或浓度为2×10~(13)cm~(-3)的n型GaAs衬底进行腐蚀试验.发现腐蚀速率不但与搅拌有关,且在最初半分钟左右或开始250～500(?)的GaAs腐蚀,其腐蚀速率比更长时问或更深腐蚀时要快得多.分析表明,NH_4OH向GaAs与溶体界面的扩散很可能是腐蚀过程的限制步骤.对腐蚀后的残余氧化层进行测试分析,认为化学腐蚀后在表面有一层极薄的氧化物层,接着是过渡层.用HCI或NH_4OH水溶液清洗则可去除氧化物层并缩小过渡层.     

通过添加表面活性剂和螯合剂改进硅片化学清洗工艺的研究

通过在传统RCA清洗法所用的SC-1液中,添加表面活性剂四甲基氢氧化铵(TMAH)和/或螯合剂乙二胺四乙酸(EDTA),实验比较了不同清洗方法对颗粒粘污、金属粘污的去除效率;并测试了其对硅片表面粗糙度的影响。用MOS电容结构的击穿电场强度Weibull分布,评价了不同清洗方法所得氧化层的质量。结果表明,上述改进能够显著提高对颗粒粘污和金属粘污的去除效果,同时能省去RCA的SC-2清洗步骤,具有节省工时、化学试剂消耗量小的优势。     

CdZnTe材料的表面钝化新工艺

研究了一种新的钝化CdZnTe(CZT)器件表面的工艺，即先采用KOHKCl溶液对CZT表面进行处理，再用NH4F/H2O2溶液对其进行表面氧化的二步法钝化工艺．并借助俄歇电子能谱（AES）、微电流测试仪等手段对其表面钝化层的质量进行了鉴别，同时与KOH KCl和NH4F/H2O2两种工艺进行了比较．AES能谱分析表明，采用二步法工艺钝化，既可获得化学计量比较好的CZT表面，又可在表面形成一层起保护作用的氧化层．I-V特性曲线显示，两步法钝化后CZT器件的漏电流与KOH KCl和NH4F/H2O2钝化相比都有一定程度的下降．说明文中提出的新工艺在CZT器件制备方面具有良好的应用前景．     

GaAs表面处理及其椭圆偏振仪、俄歇电子能谱与X-光电子谱的特性测定

用椭圆偏振仪、俄歇电子能谱仪(AES)和X-光电子谱仪(XPS)等对经pH=7±0.05的H_2O_2-NH_40H溶液化学腐蚀或用NH_4OH:H_20=1:10和HCl:H_2O=1:1进行清洗后的GaAs表面残余氧化层厚度、折射率、纵向组分分布和Ga(3d)与As(3d)结合能变化等进行测定.三者实验结果对应很好.化学腐蚀后的GaAs表面有一层氧化物层,然后是氧化物与GaAs混合的过渡层,直至GaAs衬底.从NH_4OH:H_2O=1:10清洗后GaAs表面残余氧化层厚度,表面C吸附量和Ga/As的波动看,它均比用HCl:H_2O=1:1清洗为优,故用它作为GaAs在化学腐蚀后的清洗是可取的.     

制绒Si片清洗工艺的研究

研究对比了不同清洗工艺对制绒Si片性能的影响,采用原子力显微镜和少子寿命测试仪测试经不同化学清洗工艺处理之后的Si片表面微粗糙度和少子寿命。研究发现,使用浓硫酸、双氧水混合液和稀释的氢氟酸溶液清洗Si片能够有效改善Si片表面的质量,Si片表面的微粗糙度由原先的5.96μm降低到4.45μm;采用等离子体增强化学气相沉积法在清洗之后的Si片上生长本征氢化非晶Si层,对Si片进行表面钝化,钝化之后的Si片少子寿命可达107.88μs。测试结果还表明,采用此种清洗方法处理的Si片少子寿命稳定性有很大提高。     

Alkaline cleaning of silicon wafers: additives for the prevention of metal contamination

The paper presents a new strategy for cleaning of silicon wafers. A novel class of chelating agents added to alkaline cleaning mixtures provides promising performance without negative effects such as metal redeposition due to residual metal contamination of the cleaning solution. The superior capability of the new cleaning process is confirmed by the results obtained from wafer surface metal analysis as well as from minority carrier lifetime and diffusion length measurements and gate oxide integrity tests. Particle densities and surface roughness are not influenced by the presence of the chelating agents in the cleaning solution. TOF–SIMS measurements do not indicate any deposition of chelating agent on the wafer surface. With this type of modified SC-1 cleaning procedure the acid SC-2 step used in conventional RCA cleans to remove the metals deposited in the preceding SC-1 step is unnecessary resulting in substantial cost savings with respect to chemicals, waste, equipment and space.     

微腐蚀去除硅衬底表面损伤及污染物研究

硅片CMP工艺会引入表面缺陷和沾污,通常采用NaOH和KOH作为腐蚀溶液,利用微腐蚀法将硅片表面的损伤污染层剥离,以免导致IC制备过程中产生二次缺陷,但会不可避免地引入金属离子。制备了一种用螯合剂和表面活性剂复配的新型清洗液,利用螯合剂对硅片表面损伤层进行微腐蚀,同时采用表面活性剂去除硅片表面吸附的微粒。经台阶仪和原子力显微镜检测,该清洗液能有效去除硅片表面损伤层和颗粒,同时螯合剂本身不含金属离子,并且对金属离子有螯合作用,可有效避免传统腐蚀液中金属离子带来的二次污染。     

兆声清洗在GaAs PHEMT栅凹槽工艺中的应用

对GaAs赝配高电子迁移率晶体管(PHEMT)在栅凹槽光刻和栅凹槽腐蚀过程中光刻窗口内经常出现的一些沾污颗粒进行了分析.设计了一系列实验来分析残留在芯片上的颗粒度参数,采用4英寸(1英寸=2.54 cm)圆片模拟实际的栅凹槽清洗工艺过程,利用颗粒度测试仪分别测试了4英寸圆片表面不同粒径的沾污颗粒数在喷淋和兆声清洗两种条件下的变化情况.比较两种清洗结果,兆声清洗方法可以有效去除栅凹槽颗粒沾污.在实际流片过程中,采用兆声清洗方法大幅降低了源漏间沟道漏电数值,同时芯片的直流参数成品率由之前的75％提高到了93％.     

半导体单晶抛光片清洗工艺分析

通过对Si,CaAs,Ge等半导体材料单晶抛光片清洗工艺技术的研究,分析得出了半导体材料单晶抛光片的清洗关键技术条件.首先用氧化性溶液将晶片表面氧化,然后用一定的方法将晶片表面的氧化物去除,从而实现对晶片进行清洗的目的.采用这种先氧化再剥离的方法,可有效去除附着在晶片表面的杂质及各种沾污物.对于不同的材料,氧化过程以及剥离过程可以在不同的溶液中相互独立地进行;也可以组合在一起,使用一种混合液同时实现氧化及剥离.采用氧化、剥离的清洗原理,可提高半导体材料抛光片的清洗工艺技术水平,同时也对新材料抛光片的清洗工艺起到一定的指导作用.     

清洗工艺对锗外延片表面点状缺陷的影响

锗外延片表面的雾、水印及点状缺陷等会影响太阳电池的性能和成品率,其中点状缺陷出现的比例最高。研究了锗抛光片清洗工艺对外延片表面点状缺陷的影响,获得了无点状缺陷、低粗糙度及高表面质量的锗单晶片。采用厚度为175μm p型<100>锗单面抛光片进行清洗试验,研究了SC-1溶液的不同清洗时间、清洗温度和去离子水冲洗温度对锗抛光片外延后点状缺陷的影响,分析了表面SiO_2残留和锗片表面粗糙度对外延片表面点状缺陷的影响。结果表明点状缺陷主要是由于锗单晶抛光片表面沾污没有彻底清洗干净以及清洗过程中产生新的缺陷造成的。采用氢氟酸溶液浸泡、SC-1溶液低温短时间清洗结合低温去离子水冲洗后的锗抛光片进行外延,用其制备的太阳电池光电转换效率由原来的25%提高到31%。     

Remote plasma-enhanced atomic layer deposition of gallium oxide thin films with NH_3 plasma pretreatment

High quality gallium oxide(Ga_2O_3) thin films are deposited by remote plasma-enhanced atomic layer deposition(RPEALD) with trimethylgallium(TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga_2O_3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 ?/cycle at 250 °C,respectively. The increasing of deposition rate is attributed to more hydroxyls(–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga_2O_3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga_2O_3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.     

硅晶片热氧化前的清洗技术探索

阐述了硅晶片表面的各种沾污对热氧化生长的氧化膜质量的影响。进行了数组热氧化前硅晶片表面沾污清洗的实验,分析清洗液浓度、温度、超声等因素对清洗效果的影响。在显微镜下观察试验结果,对清洗后硅晶片表面出现的微粗糙度、蚀点及损伤等情况做了详细分析．并对引起这些情况的因素重新制定考察水平,进行优化改进,得到最佳的清洗效果。     

激光辐照下GaAs表面腐蚀液滴自然浸润过程及其边缘刻蚀特性

研究了激光辐照下GaAs表面酸性腐蚀液滴的浸润及其腐蚀特性,实验获得了激光辐照下H2SO4-H2O2液滴在GaAs表面的浸润过程以及液滴边缘方位、晶体取向等差异对GaAs半导体表面刻蚀效果的影响,得到了有价值的结论.实验结果表明,腐蚀液液滴在GaAs表面随着时间向外扩散,腐蚀现象由中心向四周逐渐减弱,并在边缘部分出现不完全腐蚀现象;通过对同一液滴的不同位置的边缘进行观察发现液滴边缘的腐蚀图样不完全相同,由于晶体的各向异性使腐蚀图样具有明显的方向性,此结论对半导体器件的加工工艺起着重要的理论补充作用.     

用于悬浮纳米结构制作的氢氟酸气相刻蚀研究

针对纳米悬浮结构的制作,对不同温度和不同气相条件下的氢氟酸(HF)气相刻蚀进行了研究.利用自制的研究装置,使用HF/水混合气体和HF/乙醇混合气体分别进行了HF对PECVD SiO_2的气相刻蚀实验,同时测量了不同衬底温度下刻蚀速率的变化.研究结果表明,在常温常压下,HF/乙醇混合气体气相刻蚀速率约为7.6 nm/s,而HF/水混合气体气相刻蚀速率约为11.5 nm/s.在衬底温度分别为35,40和50℃时,HF/水混合气体的气相刻蚀速率分别为10.25,7.95和5.18 nm/s.利用HF气相腐蚀进行SiO_2牺牲层释放,得到了悬浮的纳米梁结构,梁与衬底的间距为400 nm.     

Hafnium or zirconium high-k fab cross-contamination issues

Hf and Zr contamination during immersion in process solutions is most likely to occur in neutral and caustic solutions. Both Hf and Zr contamination are introduced onto the wafer surface if they are present in an ammonium hydroxide peroxide mixture solution (which is caustic), but such contamination is removed using existing acid cleans. Large amounts of wafer-to-wafer cross contamination occurs in plasma etch tools. Particles can cause cross contamination in a thermal reactor during high-temperature anneals of high-k dielectric layers. Residual surface cross contamination does not diffuse into the wafers during thermal processing. If contamination remains on a wafer, gate oxide integrity degradation is only observed at high concentrations. Near surface minority carrier lifetime is also affected, but bulk lifetime is not.     

纳米磨料对GaAs晶片的抛光研究

通过均相沉淀法制备了纳米CeO2和Al2O3粉体,研究了在相同抛光条件下纳米CeO2、SiO2和Al2O3磨料对GaAs晶片的抛光效果,并用原子力显微镜观察抛光表面的微观形貌并测量表面粗糙度。结果表明,使用纳米CeO2磨料抛光后的表面具有最低的表面粗糙度,在1μm×1μm范围内表面粗糙度Ra值为0.740nm,而且表面的微观起伏更趋于平缓。文中还探讨了GaAs晶片化学机械抛光材料去除机理,考虑了纳米磨料在抛光条件下所发生的自身变形,并分析了纳米磨料硬度对抛光表面粗糙度的影响,初步解释了在相同的抛光条件下不同硬度的纳米磨料为什么具有不同的抛光表面粗糙度。     

Influence of initial wafer cleanliness on metal removal efficiencyin immersion SC-1 cleaning: limitation of immersion-type wet cleaning

When contaminated silicon wafers are immersed in an ultra-pure cleaning solution of an NH₄OH/H₂O₂/H ₂O mixture known as the RCA Standard Clean 1 (SC-1), in which the impurity concentration is negligibly low, the level of wafer-surface metallic contamination after the cleaning treatment depends on the amount of metallic impurities brought into the solution by the to-be-cleaned wafers themselves. Even if the chemicals are disposed of after each wafer cleaning, the surface metallic contamination is still dominated by the amount of impurities brought into the fresh solution by the wafers themselves. In the past, purer chemicals have been sought to improve metal removal efficiency, but after reasonably purer chemicals are obtained the efficiency is not governed by the initial chemical purity but by the initial wafer cleanliness. Because of this, scrubbing of dirty wafers-both the backand front-surfaces-before immersion-type wet cleaning is recommended. However, to meet future stricter wafer cleanliness requirements, new cleaning methods in which fresh chemicals are continuously supplied, such as single-wafer spin cleaning, will have to be employed