Method for forming self-aligned contact hole by taking undoped silicon oxide as polycrystalline silicon cap layer

Abstract

The invention discloses a method for forming a self-aligned contact hole by taking undoped silicon oxide as a polycrystalline silicon cap layer. The method comprises the following steps of: 1, depositing a grid oxide layer on a silicon substrate and depositing a polycrystalline silicon layer on the grid oxide layer; 2, depositing an undoped silicon oxide cap layer on the polycrystalline silicon layer; 3, photoetching and etching polycrystalline silicon so as to form a polycrystalline silicon electrode; 4, injecting a laser detector diode (LDD); 5, manufacturing a side wall of the polycrystalline silicon; 6, performing source drain injection and thermally annealing quickly; 7, preparing a phosphorosilicate glass physical medium dependent (PMD) layer on a full silicon chip; and 8, etching the self-aligned contact hole. By the method, self-aligned polycrystalline silicon doping can be realized during source drain injection, so that the realization of a self-aligning double grid process is facilitated.

Description

technical field [0001] The invention belongs to the field of semiconductor integrated circuit manufacturing, in particular to a method for making self-aligned contact holes by using non-doped silicon oxide as a polysilicon cap layer. Background technique [0002] In a conventional CMOS (Complementary Metal Oxide Semiconductor) process, silicon nitride is usually used as a cap layer on polysilicon for self-aligned contact holes. In the etching process of the contact hole, the self-alignment process is realized by controlling the etching selectivity ratio of the PMD layer (pre-metal dielectric layer) and silicon nitride by etching. However, since silicon nitride has a very strong impurity blocking ability, this process method is not conducive to the realization of a self-aligned double gate process (Self-Align Dual Poly Process: that is, self-aligned polysilicon doping is achieved through source-drain implantation. ). Contents of the invention [0003] The technical proble...

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Problems solved by technology

However, since silicon nitride has a very strong impurity blocking ability, this process method is not conducive to the realization of a self-aligned double gate process (Self-Align Dual Poly Process: that is, self-aligned polysilicon doping is achieved through source-drain implantation. )

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