半导体工艺基础第三章氧化.pptx

第 三 章Oxidation 氧化Oxidation氧化n简介n氧化膜的应用n氧化机理n氧化工艺n氧化设备nRTO快速热氧化简介n硅与O2直接反响可得；nSiO2性能稳定；n氧化工艺在半导体制造中广泛使用Si + O2 SiO2氧化层简介Oxidation氧化层简介Silicon氧化膜的应用n掺杂阻挡层n外表钝化(保护)n Screen oxide, pad oxide, barrier oxiden隔离层n Field oxide and LOCOSn栅氧化层氧化层应用掺杂阻挡氧化层nMuch lower B and P diffusion rates in SiO2 than that in SinSiO2 can be used as diffusion mask氧化层应用外表钝化(保护)氧化层nPad Oxide衬垫氧化层, Screen Oxide屏蔽氧化层 Sacrificial Oxide牺牲氧化层, Barrier Oxide阻挡氧化层nNormally thin oxide layer (150) to protect silicon defects from contamination and over-stress.氧化层应用Screen Oxide氧化层应用Pad and Barrier Oxides in STI Process氧化层应用USG: Undoped Silicate Glass未掺杂硅酸盐玻璃Application, Pad OxidenRelieve strong tensile stress of the nitridenPrevent stress induced silicon defects氧化层应用牺牲氧化层 Sacrificial OxidenDefects removal from silicon surface氧化层应用器件隔离氧化层n临近器件的绝缘隔离nBlanket field oxidenLocal oxidation of silicon (LOCOS)nThick oxide, usually 3,000 to 10,000 氧化层应用Blanket Field Oxide Isolation氧化层应用LOCOS Process氧化层应用LOCOSnCompare with blanket field oxiden Better isolation更好的隔离n Lower step height更低台阶高度n Less steep sidewall侧墙不很陡峭nDisadvantage缺点n rough surface topography粗糙的外表形貌n Birds beak鸟嘴n被浅的管沟(STI)所取代氧化层应用栅氧化层nGate oxide: thinnest and most critical layernCapacitor dielectric氧化层应用氧化膜(层)应用名称应用厚度说明自然氧化层不希望的15-20A屏蔽氧化层注入隔离，减小损伤200A热生长掺杂阻挡层掺杂掩蔽400-1200A选择性扩散场氧化层和LOCOS器件隔离3000-5000A湿氧氧化衬垫氧化层为Si3N4提供应力减小 100-200A热生长很薄牺牲氧化层去除缺陷1000A热氧化栅氧化层用作MOS管栅介质30-120A干氧氧化阻挡氧化层防止STI工艺中的污染100-200A氧化层应用Silicon Dioxide Grown on ImproperlyCleaned Silicon Surface外表未清洗硅片的热氧化层n热氧化生长的SiO2层是无定形的nSiO2分子间趋于交联形成晶体n未清洗硅片外表的缺陷和微粒会成为SiO2的成核点n这种SiO2层的阻挡作用很差n氧化前需要清洗硅片外表氧化前圆片清洗n颗粒n有机粘污n无机粘污n本征氧化层RCA清洗nDeveloped by Kern and Puotinen in 1960 at RCAnMost commonly used clean processes in IC fabsn(1号液)NH4OH:H2O2:H2O with 1:1:5 to 1:2:8 ratio at 70 to 80 to remove organic .n(2号液)- HCl:H2O2:H2O with 1:1:6 to 1:2:8 ratio at 70 to 80 to remove inorganic contaminates ，DI water rinsenHF dip or HF vapor etch to remove native oxide.Pre-oxidation Wafer Clean Particulate RemovalnHigh purity deionized (DI) water or H2SO4:H2O2 followed by DI H2O rinse.n高压清洗或者放在清洗液中加热漂洗，最后烘干High pressure scrub or immersion in heated dunk tank followed by rinse, spin dry and/or dry bake (100 to 125 C).被氧化的硅片上有机物的去除n强氧化剂去除有机污垢nH2SO4:H2O2 or NH3OH:H2O2 followed by DI H2O rinse.nHigh pressure scrub or immersion in heated dunk tank followed by rinse, spin dry and/or dry bake (100 to 125 C).无机物的清洗n先用HCl:H2O液体浸泡n再在大的玻璃杯中浸泡清洗 Immersion in dunk tank followed by rinse, spin dry and/or dry bake (100 to 125)Pre-oxidation Wafer Clean Native Oxide RemovalnHF:H2OnImmersion in dunk tank or single wafer vapor etcher followed by rinse, spin dry and/or dry bake (100 to 125)Oxidation MechanismnSi+O2SiO2nO来源于提供的氧气nSi来源于衬底硅圆片nO通过外表已有的氧化层向内扩散并与Si反响生长SiO2n氧化薄膜越厚，生长速率越低干氧氧化干氧氧化Dry OxidationDry OxidationOxide Growth Rate RegimeB/A为线性速率常数；B为抛物线速率常数 Silicon Dry Oxidation水汽氧化(Steam OxidationnSi + 2H2O SiO2 + 2H2nAt high temperature H2O is dissociated to H and H-OnH-O diffuses faster in SiO2 than O2nSteam oxidation has higher growth rate than dry oxidation Silicon Wet Oxidation Rate湿氧氧化(Wet Oxidation)n湿氧氧化法是将枯燥纯洁的氧气，在通入氧化炉之前，先经过一个水浴瓶，使氧气通过加热的高纯去离子水，携带一定量的水汽，湿氧氧化法的氧化剂是氧气和水的混合物。

nSi+O2SiO2nSi + 2H2O SiO2 + 2H2氧化速率n温度n湿氧或干氧n厚度n压力n圆片晶向(或)n硅中杂质氧化速率与温度n氧化速率对温度很敏感，指数规律n温度升高会引起更大的氧化速率升高n物理机理：温度越高，O与Si的化学反响速率越高；温度越高，O在SiO2中的扩散速率越高氧化速率与圆片晶向n外表的氧化速率高于外表n外表的Si原子密度高湿氧氧化速率氧化速率与杂质浓度n杂质元素和浓度n高掺磷的硅有更高的氧化层生长速率，更低密度的氧化层薄膜和更高的刻蚀速率n通常，掺杂浓度越高，氧化层生长速率越高；在氧化过程的线性区(氧化层较薄时)更为显著氧化：杂质堆积和耗尽效应nN型杂质(P、As、Sb)在Si中的溶解度高于在SiO2中的溶解度，当SiO2生长时，杂质向Si中移动，这引起杂质堆积或滚雪球效应nB倾向于向SiO2中运动，这引起杂质耗尽效应Depletion and Pile-up Effects氧化速率与HCl掺杂氧化nHCl is used to reduce mobile ion contaminationnWidely used for gate oxidation processnGrowth rate can increase from 1 to 5 percent氧化速率与不均匀氧化n氧化层越厚，氧化速率越小n对于更厚的氧化层，O需要更多的时间扩散过氧化层与衬底硅发生反响在干氧中的氧化速率在合成水汽中的氧化速率二氧化硅色谱氧化工艺n干氧氧化，薄氧化层 栅氧化层 衬垫氧化层，屏蔽氧化层，牺牲氧化层，等等n湿氧氧化，厚氧化层 场氧化层 扩散掩膜氧化层Dry Oxidation System氧化装置系统Dry OxidationnDry O2 as the main process gasnHCl is used to remove mobile ions for gate oxidationnHigh purity N2 as process purge gasnLower grade N2 as idle purge gasDangling Bonds and Interface ChargeWet Oxidation ProcessnFaster, higher throughputnThick oxide, such as LOCOSnDry oxide has better qualityWater Vapor SourcesnBoilernBubblernFlushnPyrogenicBoiler SystemBubbler SystemFlush SystemPyrogenic Steam SystemPyrogenic SystemnAdvantage All gas system Precisely control of flow ratenDisadvantage Introducing of flammable, explosive hydrogennTypical H2:O2 ratio is between 1.8:1 to 1.9:1.Rapid Thermal OxidationnFor gate oxidation of deep sub-micron devicenVery thin oxide film, 30 nNeed very good control of temperature uniformitynRTO will be used to achieve the device requirement.High Pressure OxidationnFaster growth ratenReducing oxidation temperature: 1 amt. = 30 CnHigher dielectric strengthn缺点:设备复杂，存在平安问题氧化小结n氧化层稳定性好，容易获得n应用：栅氧化层，场氧化层，衬垫氧化层，掺杂阻挡层，牺牲氧化层，阻挡氧化层，注入屏蔽氧化层n干氧氧化和湿氧氧化。