Dry etching method

Abstract

The invention provides a method for processing vertical gate patterns while reducing the Si substrate recess dimension caused by overetching. The invention provides a dry etching method for processing a gate pattern by performing a main etching process (b) and then an overetching process on a gate pattern layer 12 of a semiconductor substrate 10, wherein the overetching process (c) is performed using a composite gas having added to an etching gas containing HBr gas a gas represented by a general formula of CxHy or at least one gas selected from CO and CO2 gases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating the schematic structure of a microwave plasma etching apparatus to which the dry etching method of the present invention is applied;

FIGS. 2A, 2B and 2C are cross-sectional views of the processing steps showing the relevant portion of the structure of the semiconductor substrate subjected to the dry etching method of the present invention; and

FIG. 3 is a graph showing the relationship between the ion injection energy and Si recess dimension, and the occurrence of side etch of polysilicon according to the dry etching method.

Claims

1. A dry etching method for processing a gate pattern by performing an overetching process after performing a main etching process on a gate pattern layer of a semiconductor wafer, the method comprising: performing the overetching process using a composite gas having added to an etching gas containing HBr gas a gas represented by a general formula of CxHy or at least one gas selected from CO and CO2 gases.

2. The dry etching method according to claim 1, wherein the gas represented by a general formula of CxHy added to the HBr gas during the overetching process is CH4, and the amount thereof is within the range of 2 to 20 percent of the HBr gas for performing the overetching process.

3. The dry etching method according to claim 1, wherein the gas added to the etching gas containing HBr during the overetching process is a gas containing carbon atoms.

4. The dry etching method according to claim 1, wherein the energy for injecting ions in the plasma to the Si substrate via RF bias is set to 400 eV or smaller for performing the overetching process.

5. The dry etching method according to claim 1, wherein the energy for injecting ions in the plasma to the Si substrate via RF bias is set to fall within the range of 150 eV to 400 eV for performing the overetching process.