半导体工艺基础第三章氧化

1、第 三 章Oxidation 氧化.Oxidation氧化简介氧化膜的运用氧化机理氧化工艺氧化设备RTO快速热氧化.简介硅与O2直接反响可得；SiO2性能稳定；氧化工艺在半导体制造中广泛运用Si + O2 SiO2氧化层简介.Oxidation氧化层简介Silicon.氧化膜的运用掺杂阻挠层外表钝化(维护) Screen oxide, pad oxide, barrier oxide隔离层 Field oxide and LOCOS栅氧化层氧化层运用.掺杂阻挠氧化层Much lower B and P diffusion rates in SiO2 than that in SiSiO2 ca

2、n be used as diffusion mask氧化层运用.外表钝化(维护)氧化层Pad Oxide衬垫氧化层, Screen Oxide屏蔽氧化层 Sacrificial Oxide牺牲氧化层, Barrier Oxide阻挠氧化层Normally thin oxide layer (150) to protect silicon defects from contamination and over-stress.氧化层运用.Screen Oxide氧化层运用.Pad and Barrier Oxides in STI Process氧化层运用USG: Undoped Silicat

3、e Glass未掺杂硅酸盐玻璃.Application, Pad OxideRelieve strong tensile stress of the nitridePrevent stress induced silicon defects氧化层运用.牺牲氧化层 Sacrificial OxideDefects removal from silicon surface氧化层运用.器件隔离氧化层临近器件的绝缘隔离Blanket field oxideLocal oxidation of silicon (LOCOS)Thick oxide, usually 3,000 to 10,000 氧化层

4、运用.Blanket Field Oxide Isolation氧化层运用.LOCOS Process氧化层运用.LOCOSCompare with blanket field oxide Better isolation更好的隔离 Lower step height更低台阶高度 Less steep sidewall侧墙不很峻峭Disadvantage缺陷 rough surface topography粗糙的外表形貌 Birds beak鸟嘴被浅的管沟(STI)所取代氧化层运用.栅氧化层Gate oxide: thinnest and most critical layerCapacito

5、r dielectric氧化层运用.氧化膜(层)运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氧化层运用.Silicon Dioxide Grown on ImproperlyCleaned Silicon Surface.外表未清洗硅片的热氧化层热氧化生长的S

6、iO2层是无定形的SiO2分子间趋于交联构成晶体未清洗硅片外表的缺陷和微粒会成为SiO2的成核点这种SiO2层的阻挠作用很差氧化前需求清洗硅片外表.氧化前圆片清洗颗粒有机粘污无机粘污本征氧化层.RCA清洗Developed by Kern and Puotinen in 1960 at RCAMost commonly used clean processes in IC fabs(1号液)NH4OH:H2O2:H2O with 1:1:5 to 1:2:8 ratio at 70 to 80 to remove organic .(2号液)- HCl:H2O2:H2O with 1:1:6

7、to 1:2:8 ratio at 70 to 80 to remove inorganic contaminates ，DI water rinseHF dip or HF vapor etch to remove native oxide.Pre-oxidation Wafer Clean Particulate RemovalHigh purity deionized (DI) water or H2SO4:H2O2 followed by DI H2O rinse.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 heat

8、ed 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强氧化剂去除有机污垢H2SO4:H2O2 or NH3OH:H2O2 followed by DI H2O rinse.High pressure scrub or immersion in heated dunk tank followed by rinse, spin dry and/or dry bake (100 to 125 C).无机物的清洗先用HCl:H2O液体浸泡再在大的玻璃杯中浸泡清洗 Immersion i

9、n dunk tank followed by rinse, spin dry and/or dry bake (100 to 125).Pre-oxidation Wafer Clean Native Oxide RemovalHF:H2OImmersion in dunk tank or single wafer vapor etcher followed by rinse, spin dry and/or dry bake (100 to 125).Oxidation MechanismSi+O2SiO2O来源于提供的氧气Si来源于衬底硅圆片O经过外表已有的氧化层向内分散并与Si反响生长

10、SiO2氧化薄膜越厚，生长速率越低干氧氧化Dry Oxidation.Oxide 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 OxidationSi + 2H2O SiO2 + 2H2At high temperature H2O is dissociated to H and H-OH-O diffuses faster in SiO2 than O2Steam oxidation has higher growth rate than dry oxidation. Silicon Wet

11、Oxidation Rate.湿氧氧化(Wet Oxidation)湿氧氧化法是将枯燥纯真的氧气，在通入氧化炉之前，先经过一个水浴瓶，使氧气经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。 Si+O2SiO2Si + 2H2O SiO2 + 2H2.氧化速率温度湿氧或干氧厚度压力圆片晶向(或)硅中杂质.氧化速率与温度氧化速率对温度很敏感，指数规律温度升高会引起更大的氧化速率升高物理机理：温度越高，O与Si的化学反响速率越高；温度越高，O在SiO2中的分散速率越高。.氧化速率与圆片晶向外表的氧化速率高于外表外表的Si原子密度高.湿氧氧化速率.氧化速率与杂质浓度杂质

12、元素和浓度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N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中挪动，这引起杂质堆积或滚雪球效应B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HCl is used to reduce mobile ion contaminationWidely used for gate oxidatio

13、n processGrowth rate can increase from 1 to 5 percent.氧化速率与不均匀氧化氧化层越厚，氧化速率越小对于更厚的氧化层，O需求更多的时间分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，等等湿氧氧化，厚氧化层 场氧化层 分散掩膜氧化层.Dry Oxidation System.氧化安装系统.Dry OxidationDry O2 as the main process gasHCl is used to remove mobile i

14、ons for gate oxidationHigh purity N2 as process purge gasLower grade N2 as idle purge gas.Dangling Bonds and Interface Charge.Wet Oxidation ProcessFaster, higher throughputThick oxide, such as LOCOSDry oxide has better quality.Water Vapor SourcesBoilerBubblerFlushPyrogenic.Boiler System.Bubbler Syst

15、em.Flush System.Pyrogenic Steam System.Pyrogenic SystemAdvantage All gas system Precisely control of flow rateDisadvantage Introducing of flammable, explosive hydrogenTypical H2:O2 ratio is between 1.8:1 to 1.9:1.Rapid Thermal OxidationFor gate oxidation of deep sub-micron deviceVery thin oxide film, 30 Need very good control of temperature uniformityRTO will