半導(dǎo)體工藝基礎(chǔ)第三章氧化

1、第 三 章Oxidation 氧化.Oxidation氧化簡介氧化膜的運用氧化機理氧化工藝氧化設(shè)備RTO快速熱氧化.簡介硅與O2直接反響可得；SiO2性能穩(wěn)定；氧化工藝在半導(dǎo)體制造中廣泛運用Si + O2 SiO2氧化層簡介.Oxidation氧化層簡介Silicon.氧化膜的運用摻雜阻撓層外表鈍化(維護) Screen oxide, pad oxide, barrier oxide隔離層 Field oxide and LOCOS柵氧化層氧化層運用.摻雜阻撓氧化層Much lower B and P diffusion rates in SiO2 than that in SiSiO2 ca

2、n be used as diffusion mask氧化層運用.外表鈍化(維護)氧化層Pad Oxide襯墊氧化層, Screen Oxide屏蔽氧化層 Sacrificial Oxide犧牲氧化層, Barrier Oxide阻撓氧化層Normally thin oxide layer (150) to protect silicon defects from contamination and over-stress.氧化層運用.Screen Oxide氧化層運用.Pad and Barrier Oxides in STI Process氧化層運用USG: Undoped Silicat

3、e Glass未摻雜硅酸鹽玻璃.Application, Pad OxideRelieve strong tensile stress of the nitridePrevent stress induced silicon defects氧化層運用.犧牲氧化層 Sacrificial OxideDefects removal from silicon surface氧化層運用.器件隔離氧化層臨近器件的絕緣隔離Blanket field oxideLocal oxidation of silicon (LOCOS)Thick oxide, usually 3,000 to 10,000 氧化層

4、運用.Blanket Field Oxide Isolation氧化層運用.LOCOS Process氧化層運用.LOCOSCompare with blanket field oxide Better isolation更好的隔離 Lower step height更低臺階高度 Less steep sidewall側(cè)墻不很峻峭Disadvantage缺陷 rough surface topography粗糙的外表形貌 Birds beak鳥嘴被淺的管溝(STI)所取代氧化層運用.柵氧化層Gate oxide: thinnest and most critical layerCapacito

5、r dielectric氧化層運用.氧化膜(層)運用名稱應(yīng)用厚度說明自然氧化層不希望的15-20A屏蔽氧化層注入隔離，減小損傷200A熱生長摻雜阻擋層摻雜掩蔽400-1200A選擇性擴散場氧化層和LOCOS器件隔離3000-5000A濕氧氧化襯墊氧化層為Si3N4提供應(yīng)力減小100-200A熱生長很薄犧牲氧化層去除缺陷1000A熱氧化柵氧化層用作MOS管柵介質(zhì)30-120A干氧氧化阻擋氧化層防止STI工藝中的污染100-200A氧化層運用.Silicon Dioxide Grown on ImproperlyCleaned Silicon Surface.外表未清洗硅片的熱氧化層熱氧化生長的S

6、iO2層是無定形的SiO2分子間趨于交聯(lián)構(gòu)成晶體未清洗硅片外表的缺陷和微粒會成為SiO2的成核點這種SiO2層的阻撓作用很差氧化前需求清洗硅片外表.氧化前圓片清洗顆粒有機粘污無機粘污本征氧化層.RCA清洗Developed by Kern and Puotinen in 1960 at RCAMost commonly used clean processes in IC fabs(1號液)NH4OH:H2O2:H2O with 1:1:5 to 1:2:8 ratio at 70 to 80 to remove organic .(2號液)- 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.高壓清洗或者放在清洗液中加熱漂洗，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).被氧化的硅片上有機物的去除強氧化劑去除有機污垢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).無機物的清洗先用HCl:H2O液體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來源于提供的氧氣Si來源于襯底硅圓片O經(jīng)過外表已有的氧化層向內(nèi)分散并與Si反響生長

10、SiO2氧化薄膜越厚，生長速率越低干氧氧化Dry Oxidation.Oxide Growth Rate RegimeB/A為線性速率常數(shù)；B為拋物線速率常數(shù). 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.濕氧氧化(Wet Oxidation)濕氧氧化法是將枯燥純真的氧氣，在通入氧化爐之前，先經(jīng)過一個水浴瓶，使氧氣經(jīng)過加熱的高純?nèi)ルx子水，攜帶一定量的水汽，濕氧氧化法的氧化劑是氧氣和水的混合物。 Si+O2SiO2Si + 2H2O SiO2 + 2H2.氧化速率溫度濕氧或干氧厚度壓力圓片晶向(或)硅中雜質(zhì).氧化速率與溫度氧化速率對溫度很敏感，指數(shù)規(guī)律溫度升高會引起更大的氧化速率升高物理機理：溫度越高，O與Si的化學(xué)反響速率越高；溫度越高，O在SiO2中的分散速率越高。.氧化速率與圓片晶向外表的氧化速率高于外表外表的Si原子密度高.濕氧氧化速率.氧化速率與雜質(zhì)濃度雜質(zhì)

12、元素和濃度高摻磷的硅有更高的氧化層生長速率，更低密度的氧化層薄膜和更高的刻蝕速率通常，摻雜濃度越高，氧化層生長速率越高；在氧化過程的線性區(qū)(氧化層較薄時)更為顯著。.氧化：雜質(zhì)堆積和耗盡效應(yīng)N型雜質(zhì)(P、As、Sb)在Si中的溶解度高于在SiO2中的溶解度，當(dāng)SiO2生長時，雜質(zhì)向Si中挪動，這引起雜質(zhì)堆積或滾雪球效應(yīng)B傾向于向SiO2中運動，這引起雜質(zhì)耗盡效應(yīng).Depletion and Pile-up Effects.氧化速率與HCl摻雜氧化HCl is used to reduce mobile ion contaminationWidely used for gate oxidatio

13、n processGrowth rate can increase from 1 to 5 percent.氧化速率與不均勻氧化氧化層越厚，氧化速率越小對于更厚的氧化層，O需求更多的時間分散過氧化層與襯底硅發(fā)生反響.在干氧中的氧化速率.在合成水汽中的氧化速率.二氧化硅色譜.氧化工藝干氧氧化，薄氧化層 柵氧化層 襯墊氧化層，屏蔽氧化層，犧牲氧化層，等等濕氧氧化，厚氧化層 場氧化層 分散掩膜氧化層.Dry Oxidation System.氧化安裝系統(tǒng).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