| 摘要 |
A method of forming and removing spacers used to mask lightly doped drain (LDD) regions in the formation of a field effect transistor (FET) involves depositing a thin silicon nitride (Si3N4) layer over the active region of a substrate, a gate structure formed on the active region, and over the field oxide regions. A silicon oxide (SiO2) film is provided over the nitride and then etched to form LDD spacers at the ends of the gate. The etchant used to etch the oxide layer selectively etches oxide at least 20 times faster than nitride. The nitride layer protects the field oxide regions from etching, thereby preventing oxide loss. The spacers are used to mask regions in the substrate during the implantation of source and drain regions, and the masked regions become the LDD regions. After implanting the source and drain regions, the nitride layer may be removed with a wet etchant which selectively etches nitride. The LDD spacers will be lifted off by the removal of the nitride layer or the spacer may be removed with a wet etchant which selectively etches silicon oxide followed by a nitride wet etchant which selectively etches nitride.
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