JPH03222417A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent undercut induced by scattered active species by discharging mixed etching ga to which inactive dilution gas is added in an ECR ion source. CONSTITUTION:As impurities, phosphorous is added to an oxidizing silicon film 1 which forms an offset region. When a polysilicon film 2 is deposited thereon, mask patterns are formed on the silicon film by a photo resist film 3. Cl2 is used as an etching gas while N2 gas is used as a dilution gas. Under the pressure of 0.05Torr, the plasma generated in an ECR ion source is converged by a magnetic field and introduced into an etching chamber where etching is carried out. Then, a favorable etching shape, which is virtually free of undercut, is available. It is, therefore, possible to inhibit undercut induced by scattered active species.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a dry etching method using an ECR ion source.

[Conventional technology]

Conventional dry etching methods using ECR ion sources can obtain high-density active species under high-vacuum conditions, so they are excellent at anisotropic processing using active species that move in a straight line, and are becoming widely used. .

[Problem to be solved by the invention]

However, the above-mentioned etching method has the disadvantage that, due to the linear nature of the active species, they are scattered in the vicinity of the step region as shown in FIG. 2, resulting in undercuts.

Methods to compensate for this drawback include (1) a method of adding an additive gas to the etching gas for forming a sidewall protective film;

(2) A method of suppressing scattering of etching species by extremely low runner cooling of the substrate during etching.

etc. have been devised, but (1) has the disadvantage that the reproducibility of etching is significantly reduced, and (2) has the disadvantage that the configuration of the etching apparatus becomes complicated and operation becomes difficult.

[Means to solve the problem]

The present invention is a method of manufacturing a semiconductor device including a dry etching process using an ECR ion source, in which a mixed gas containing an etching gas and an inert diluent gas is discharged within the ECR ion source.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) and 1(b) are cross-sectional views of a semiconductor chip before and after an etching process for explaining one embodiment of the present invention.

A polysilicon film 2 doped with phosphorus as an impurity is deposited on a silicon oxide film 1 forming a step region, and a mask pattern is formed with a photoresist film 3 (FIG. 1(a)).

Using C12 as the etching gas and N2 as the diluent gas, the plasma generated in the ECR ion source under a pressure of 0.05 Torr is focused by a magnetic field and introduced into the etching chamber for etching, resulting in a good etched shape with almost no undercuts. (Fig. 1(b)).

The relationship between the N2 addition rate, polysilicon etching rate, and undercut amount is shown in FIG.

However, the index is 1°0 when the N2 partial pressure ratio is 0%.

Note that when the N2 partial pressure ratio is 50% or more, the etch rate decreases significantly and is not practical, and the amount of undercut is also unknown.

In addition, in practical use, the etch rate decreases due to the addition of N2, so by setting conditions in multiple stages, the initial C! From the viewpoint of processing efficiency, it is effective to perform etching with 12 alone and dilute with 11 N2, which has etched the polysilicon film halfway.

In the example, cJ22. Although N2 was used as the diluting gas in the explanation, other etching gases include NF3. CF4. HF.

HCJ, HBr or SF6. Similar effects can be obtained by using He, Ar, Ne, or a mixture thereof as the diluent gas.

In addition, although polysilicon was fried as the object to be etched, W, Mo, and Ti were used depending on the selection of the gas type mentioned above.

The same applies to Ta and its silicide.

〔Effect of the invention〕

As explained above, the present invention has the effect of suppressing undercuts due to scattering of active species by adding a diluent gas to the etching gas.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are sectional views before and after the etching process for explaining one embodiment of the present invention, FIG. 2 is a sectional view after etching according to a conventional example, and FIG. 3 is a sectional view of one embodiment of the present invention. FIG. 3 is a characteristic diagram showing the dependence of etching rate and undercut amount on N2 partial pressure in Examples. 1... Silicon oxide film, 2... Polysilicon film, 3
... Photoresist film, 4... Etching species, 5.
...Dilution gas.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device including a dry etching step using an ECR ion source, characterized in that a mixed gas in which an inert diluent gas is added to an etching gas is discharged within the ECR ion source. A method for manufacturing a semiconductor device. 2. Etching gas is SF_6, NF_3, CF_4,
2. The method of manufacturing a semiconductor device according to claim 1, wherein the diluent gas is HF, HCl, HBr, or Cl_2, and the diluent gas is N_2, He, Ar, or Ne.