JPH043929A - Method of etching silicon material layer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of etching a layer of silicon-based material.

[Summary of the Invention] The present invention provides a method for etching a silicon-based material layer formed on a substrate, by using a mixed gas of a gas containing C and Br and a gas capable of generating fluorine radicals. The idea is to at least protect the side walls by the decomposition products of the etching gas while increasing the selectivity between the resist and the underlayer.

1. Prior art] For etching gate electrodes of ULSI, VLSI, etc.,
As design rules become increasingly finer, the thickness of the gate oxide film is also becoming thinner by about 100 degrees. Etching is required.

For this reason, reactive ion etching (RIE)
), various etching techniques have been developed, such as parallel plate etching, etching using electron microtron resonance (ECR), or etching using ECR and a magnetic field.

[Problem to be solved by the invention] In the etching using ECR and a magnetic field mentioned above, there are examples of achieving anisotropic etching with a single gas of chlorine (C12), or using a diverging magnetic field as the magnetic field. Therefore, there is an inconvenience that the etching shape is different between the central part and the peripheral part of the wafer. In addition, in etching using ECR and parallel plate etching, the etching gas is devised so that anisotropic etching can be performed in a low power range, but the etching gas is considered to be a cause of ozone layer depletion. CCl2F4 and C2
Freon gases containing two or more chlorines (CI) such as Cl3F3 and carbon tetrachloride (CC1), which is known to be carcinogenic.
, ) gas, and not only is it expected that it will no longer be usable in the future, but it has also been pointed out that undercuts may occur. This is etched using, for example, SP, /CCl4 gas as a typical etching gas,
To explain the case where a gate electrode is formed by etching (n-PolySi), F-rankal contributes to the etching, and CCl4 or DOPOS contributes to sidewall protection by depositing on the etched sidewalls and protecting them. Whether directional etching is performed, Cl silanol or D
A phosphorus abstraction reaction occurs in which the phosphorus (P) in the OPOS reacts and evaporates, resulting in an undercut.

By the way, the applicant has discovered that two chlorines (
Protects the sidewall of the silicon-based material layer with the reaction product of the Renost pattern and bromine (Br) without using harmful gases such as fluorocarbon gas containing C1) or carcinogenic carbon tetrachloride (CC1,). However, as a method of anisotropically etching the Noricon material layer without undercutting, Japanese Patent Application No. 2-10489 (etching using SF6 gas and HBr gas while using a reaction product of the resist and Br as a sidewall protective film) is proposed. together with a method of overetching using HBr gas alone), and an application filed on February 27, 1990 (SP
, etching the reaction product of renost and Br as a sidewall protective film using gas and HBr gas, and etching S.
This is a method of overetching using F6 gas alone.

"Means for Solving the Problems" Therefore, in the present invention, by using a mixed gas of a gas containing C and Br and a gas capable of generating fluorine radicals, the Noricone material layer is made anisotropic. etching.

[Operation] After forming a resist pattern on a silicon-based material layer on a substrate, using this resist pattern as a mask, for example, sidewall protection is performed using at least a decomposition product of CB r 4 gas using SFs/ CB r 4 gas. While performing etching, the above-mentioned Noricon-based material layer is etched.

[Example] As shown in FIG. 1(A), l is a substrate such as a silicon substrate, 2 is a gate oxide film formed on the substrate l, and 3 is a film of, for example, 3000 people on the gate oxide film 2. DOPOS (n-PolySi) as a thick silicon-based material layer
) layer, and a Renost pattern 4 is formed on this DOPOS using a photolithography technique.

Thereafter, as shown in FIG. 1(B), C etching is performed using an etching apparatus using ECR, which uses plasma gas as a raw material gas using microwaves, and etches the film to be etched using active species in the plasma gas. The resist pattern 4 is used as a mask using a raw material gas which is a mixed gas of a gas containing Br and Br and a gas capable of generating fluorine radicals.

The PO9 layer 3 was etched until the underlying gate oxide film 2 was exposed, and the DOPOS layer 3 was formed as the gate electrode 3A. The specific conditions for this etching are as follows: Source gas: SFa/CBr 4130/IO5CCM
Pressure car 100 mtorr power density;
0.06 W/cm".

In this etching, the DOPOS layer 2 is etched by F radicals generated from SF6 in the plasma gas, and CBrx generated by decomposition of CBr4 gas and carbon (C), which is a decomposition product of the cyst pattern 4, are etched.
CBrx, which is a reaction product between CBrx and Br generated by the decomposition of CBr4, is etched and deposited on the side wall of the DOPOS layer 3, which becomes the gate electrode, thereby protecting the side wall from etching by F radicals. ,
Since there is little reaction between Br in the source gas and phosphorus (P) in the DOPOS layer 3, the DOPO3 layer 3 is anisotropically etched into a rectangular shape without undercutting.

In this example, the flow rate of CBr needs to be optimized, but it was set to 1O5CCH with reference to 65CCM, which is the optimum flow rate of CCl4 in conventional etching.

Further, although the etching of the DOPOS layer 3 has been described, since F radicals are used as the main gas, the present invention can also be applied to etching of a W-polycide structure using WSix or a Mo-polycide structure.

Furthermore, the main gas is N, which can generate F radicals.
F3. ClF3. Gases such as CP, C as additive gas
HBr3. Gases such as CH2Brz, C7Bra, and CPBr may also be used. In addition, when using the above-mentioned CF gas and CBra gas, oxygen (02) is added and carphone (
It is sufficient to remove the deposits in C).

[Effects of the Invention j As described above, according to the present invention, since a mixed gas of a gas containing C and Br and a gas capable of generating fluorine radicals is used, two or more radicals that can destroy the ozone layer are used. Anisotropically nicking a silicon-based material layer into a rectangular shape without undercuts while protecting the sidewalls by the decomposition products of the etching gas without using harmful gases such as fluorocarbon gas containing C1 or carcinogenic CC14. Moreover, the selectivity ratio between the resist and the underlayer can be increased.

[Brief explanation of the drawing]

FIG. 1(A) is a cross-sectional view showing the patterning process of a resist pattern according to an embodiment of the present invention, and FIG. 1(B) is a cross-sectional view showing the etching gas for the five layers of DOPO in the same embodiment. DESCRIPTION OF SYMBOLS 1...Substrate, 3...Solicon material film, 3A/Kate electrode, 4...-Resist pattern. Figure 1 (A) ++ ↓ Shi-1111-F radical and CBrx
[Quality] Etching ゛' and cat of begging 11, v1 afternoon I mouth Figure 1 (B)

Claims (1)

[Claims] (1) In a method of anisotropically etching a silicon-based material layer formed on a substrate, a mixed gas of a gas containing carbon (C) and bromine (Br) and a gas capable of generating fluorine radicals is used. A method of etching a silicon-based material layer, characterized by: