半導(dǎo)體生產(chǎn)過程培訓(xùn)課件-在線瀏覽
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【正文】 ore soluble in the developer. The exposed resist is then washed away by the developer solution, leaving windows of the bare underlying material. The mask, therefore, contains an exact copy of the pattern which is to remain on the wafer. Photolithography PhotoresistNegative resistsExposure to the UV light causes the negative resist to bee polymerized, and more difficult to dissolve. Therefore, the negative resist remains on the surface wherever it is exposed, and the developer solution removes only the unexposed portions. Masks used for negative photoresists, therefore, contain the inverse (or photographic negative) of the pattern to be transferred.aonphotomaskprojectedtimesidesidethethisknownstepping andphotomaskcalledreticle.An mon reticle is the 5XThe patterns on the 5X reticle are reduced 5 times when projected onto the wafer. This means the dies on the photomask are 5 times larger than they are on the final product. There are other kinds of reduction reticles (2X, 4X, and 10X), but the 5X is the most monly used. Reduction reticles are used on a variety of steppers, the most mon being ASM, Canon, Nikon, and GCA.PhotolithographyPhotomasks and ReticlesExamples of 5X Reticles:PhotolithographyPhotomasks and Reticles Once the mask has been accurately aligned with the pattern on the wafer39。lastofisprocessashing.processthewaferswithmixtureanicthatportionsthe.ConventionalofrequireoxygenplasmaoftenbinationhalogentotheandthetheashingalsoacleaningwetchemicalsacidsremoveresiduesnonvolatilethatafterthisitnottothepluscycleorderpletelyallandSilicon ManufacturingOxidation of Siliconw SiO2 growth is a key process step in manufacturing all Si devices 173。 1181。 Thin gate oxides (173。) control MOS devices 173。simplestofanlayerofawaferanatmosphere.wDry oxide 173。PureoxygenemployedDisadvantage oxideveryAdvantagelayersveryRelativelydefectsatoxidesilicon(TheseinterferetheoperationsemiconductorItespeciallysurfacechargesmakedielectricsMOS Insameasoxides,steaminjectedDisadvantage atomsbydepositionthemoleculesimperfectionsmaythequality.WetgrowsUsefulgrowthickofoxideDeposited Oxidesisemployedanbetweenlayersmetalization.Incases,formdeposited oxideberathertheoxides.w Depositedcanproducedvariousbetweensiliconandoxidizers.Depositedtendpossessdensitieslargeofsites.NotforasdielectricsMOSbutacceptableuseinsulatingbetweenconductororprotectiveKeyin reaction rate 173。 wet oxidation is much faster than dry oxidation w Surface cleanliness 173。 quality of oxide grown (interface states)EtchingEtchingthewhereareasfilmsremovedeitherthemachemical(Wet Etching )bythemgasesatovolatile(Dry Etching).Resistareasareremain.IncaseshardusuallylayersSiO2Si3N4,usedtheselectivityphotoresistlowtheenvironmentresistdelaminate.isoftransfer.Wet Chemical Etchingw Wet etches: 173。m) 173。 capable of high throughputs 173。 can have resist adhesion problems 173。 HF + NH4F+H20 (buffered oxide etch or BOE) w For Si3N4 173。C 173。 Nitric, HF, acetic acids 173。 Acetic, nitric, phosphoric acids at 35173。C 173。etchin
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