半导体各工艺简介4

OxideThicknessMeasurementsSeveralmethodsareusedforthemeasurementofthermaloxidethickness.Theseincludecolor,mechanical,interference,andellipsometry.Color-theeasiestmethodforestimatingoxidethicknessistoobservethefilmunderilluminationbyawhitelight.Uniformcolorisevidenceofauniformoxidethickness.Thesensationofasinglecolorisduetotheabsenceofparticularfrequenciesinwhitelight.Themissingfrequenciesareduetodestructiveinterferenceasthelightisreflectedfromtheoxide-airinterface.Destructiveinterferenceoccurswhen2d=(2k-1)λ/2nwheredisoxidethickness,k=1,2,3order,n=indexofrefractionofSiO2filmk=123Grey100A--Tan300--Brown500--Blue800--Violet100028004600Blue150030004900Green180033005200Yellow210037005600ColorChartSiNBulksiliconnitride,Si3N4,isahard,dense,refractorymaterial.Nitrideiswidelyemployedinelectronicsasabarriermaterial.Evenhydrogendiffusesslowlyinadensifiednitridefilm,andothersmallpositiveions(Na+orK+)areeffectivelyblockedbythinnitridelayers.Sinceoxygendiffusesveryslowlythroughnitride,depositednitridecanpreventoxidationofunderlyingsilicon:thispropertyisexploitedinlocal-oxidation-of-silicon(LOCOS)transistorisolation.Nitridelayersarealsoemployedasetchstoplayersbothforwetetchingandplasmaetching.-----但SiN与Si之间应力大，界面态密度高。Si3N4/SiO2/Si结构;N-dopedSiO2;其他高介电常数薄膜