MEMS工艺湿法腐蚀.pdf

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1、MEMS工艺--腐蚀董海峰改编自美国西北大学ChangLiu教授《微机电系统》课程相关课件2012.10考核方式考核方式Þ提出问题或发表评论(≤10个/人):每个满分5分Þ回答问题(≤10个/人):每个满分5分Þ问题、评论和回答重复得0分纪律要求纪律要求Þ课上关上手机Þ上课不出勤，必须提出具体意见回顾ThinFilmsPolishPatternedwaferDiffusionPhotoEtchTest/SortImplant*腐蚀工艺•湿法腐蚀•干法腐蚀KOHetching•Relationshipbetweenetchingrateandtempe

2、rature?•Relationshipbetweenetchingrateandconcentration?•SelectivityofKOHetching?•Etchingstopmethod?KOHetching•Relationshipbetweenetchingrateandtemperature?•Relationshipbetweenetchingrateandconcentration?•SelectivityofKOHetching?•Etchingstopmethod?KOHetching•Relationshipbetweene

3、tchingrateandtemperature?•Relationshipbetweenetchingrateandconcentration?•SelectivityofKOHetching?•Etchingstopmethod?KOHetching•Relationshipbetweenetchingrateandtemperature?•Relationshipbetweenetchingrateandconcentration?•SelectivityofKOHetching?•Etchingstopmethod?晶面的选择性通常{111}

4、面腐蚀速率最慢，与{100}比可达400：1zz11(100)(110)(111)PlanePlaneyPlaney11x11FeaturesthatareallconvexKOHetching•Relationshipbetweenetchingrateandtemperature?•Relationshipbetweenetchingrateandconcentration?•SelectivityofKOHetching?•Etchingstopmethod?EtchStops•Often,itisrequiredthatoneetchareg

5、ionofsiliconandstoponawell-defined“etch-stop”thatthenstopstheetchabruptly.•Thereareseveraletchstoptechniques？•Theseetchstopsallowonetocontrolthethicknessofamicrostructureaccurately(<1µm),andhaveveryuniformandreproduciblecharacteristics停止层技术（1）¢控制时间停止层技术（2）--重掺杂¢控制掺杂浓度浓硼掺杂自停止腐蚀技

6、术：KOH、EPW腐蚀，在掺杂浓度小于阈值时，腐蚀速率为常数，大于阈值时，腐蚀速率急剧降低—重掺杂导致腐蚀停止。停止层技术（2）--重掺杂•浓硼自停止HeavilydopedLightlydopedHeavilydoped停止层技术（3）--电钝化PN结自停止腐蚀：P衬底生长N外延层（结构层）SiO，SiN掩膜，恒压源加在N区和CE之间，电压略大于Vpp2停止层技术（4）--介质停止层•Silicon-On-Insulator(SOI)wafersarebecomingandabundantbecauseoftheiruseinICmanufactu

7、ring•TheSiontheinsulator(whichisusuallyasilicondioxide)canbeeithersingle-crystal,orpolycrystalline•ThesiliconoxideactsasanexcellentetchstopbecauseitdoesnotetchappreciablyinetchantlikeKOHorEDP.•Thethicknessofthesiliconontopoftheinsulatorcanbecontrolledveryaccuratelywithbettertha

8、n5%uniformity.•SOIwafersaretypicallymuchmoreexpensivet