JPH10116814A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device by which the number of operations for forming tapered contact holes is reduced. SOLUTION: An SiO2 film 2 which is a first film to be etched is formed on a semiconductor substrate 1. An Si3 N4 film 3 having a slower etching rate than the SiO2 film 2 is formed as a second film to be etched on the SiO2 film. The Si3 N4 film 3 and the SiO2 film 2 are subjected to an anisotropic etching through a resist film 6 to form a contact hole 8 having tapered parts 7 on its upper side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a technique for reducing the number of steps in a step of forming a tapered portion above a contact hole.

[0002]

2. Description of the Related Art A method of manufacturing a semiconductor device according to a conventional example, in particular, a process of forming a contact hole will be described below with reference to FIGS. First, a resist film 54 having an opening 53 as shown in FIG. 5 is formed on an SiO2 film 52 as a film to be etched formed on a semiconductor substrate 51 as shown in FIG. The SiO2 film 52 in the region where the contact hole is to be formed is anisotropically etched by, for example, RIE (Reactive Ion Etching: reactive etching) to form a contact hole 55 for contacting the surface of the substrate 51 as shown in FIG. I was

However, the thickness of the film to be etched is, for example, 1
If the contact hole diameter becomes as large as 0000 ° or more and the contact hole diameter becomes as small as, for example, 0.5 μm or less, there arises a problem that the step coverage is deteriorated. Therefore, conventionally, in order to form a tapered portion above a contact hole, a technique of forming a contact hole by performing isotropic etching and then performing anisotropic etching is performed. That is, as shown in FIG. 7, the SiO2 film 52 is selectively and isotropically etched using, for example, a hydrofluoric acid (HF) -based etchant to form the concave portion 56.

[0004] Next, as shown in FIG. 8, the SiO 2 film 52 under the concave portion 56 is anisotropically etched by RIE to form a contact hole 58 having a tapered portion 57 formed on the upper surface of the substrate 51. This solves the problem of step coverage degradation.

[0005]

However, in the conventional process of forming a contact hole having a tapered portion, the contact hole is formed by performing anisotropic etching after performing isotropic etching as described above. Therefore, the number of steps was increased. Further, with respect to a device having a fine rule in which a tapered portion cannot be formed by isotropic etching, step coverage deteriorates, and a problem arises in that sufficient step coverage cannot be secured.

Accordingly, it is an object of the present invention to provide a method of manufacturing a semiconductor device in which the number of steps for forming a contact hole having a tapered portion is reduced.

[0007]

In the present invention, an Si3N4 film having a lower etching rate than the SiO2 film is formed as a second film on a SiO2 film as a first film to be etched on a semiconductor substrate. Thereafter, the Si3N4 film and the SiO2 film are anisotropically etched through a resist film to form a contact hole having a tapered portion above the contact hole.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a semiconductor device according to the present invention will be described below. First, as shown in FIG. 1, an SiO2 film 2 as a first film to be etched is formed on a semiconductor substrate 1 to a thickness of about 12000 DEG, and then a second film to be etched is formed on the SiO2 film 2 as a second film to be etched. An etching target film 4 is formed by forming, for example, a silicon nitride film (hereinafter, referred to as a Si3N4 film) 3 having a lower etching rate than the film 2 to a thickness of about 1000 to 2000 degrees.

Next, as shown in FIG. 2, a resist film 6 having an opening 5 is formed, and using this resist film 6 as a mask, etching conditions are, for example, power 700 W, pressure 250 mTorr, CHF 3 at a flow rate of 15 sccm, flow rate of 10 sccm. By performing anisotropic etching of the film 4 to be etched by RIE using CF4 and Ar at a flow rate of 300 sccm, in the Si3N4 film 3 having a high selectivity to the SiO2 film 2 (slow etching rate), the etching progresses. On the other hand, a large amount of the deposit is supplied, and a tapered shape can be formed. Therefore, as shown in FIG. 3, a contact hole 8 having a tapered portion 7 on the upper surface thereof can be formed in the surface layer of the substrate 1.

In the embodiment of the present invention, a first film to be etched consisting of an SiO2 film 2 is formed on a semiconductor substrate 1, and an Si3N4 film 3 having a lower etching rate than the SiO2 film 2 is formed on the SiO2 film 2. By forming the second film to be etched to a thickness sufficient to form a desired tapered portion 7 above the contact hole 8, only the upper portion of the contact hole 8 is tapered by a single anisotropic etching step. A contact hole 8 having a portion 7 can be formed.

Therefore, in order to improve the step coverage as in the prior art, the isotropic etching is performed as a process of forming a tapered portion above the contact hole, and then the anisotropic etching is performed in two steps. The steps that have been performed can be performed in one step, and the number of steps can be reduced and the lead time can be reduced. Further, even in a device having a fine rule in which a tapered portion cannot be formed by isotropic etching, a tapered portion can be formed above a contact hole by applying the present invention.

[0012]

As described above, according to the present invention, a contact hole having a tapered portion only above the contact hole can be formed by a single anisotropic etching step, so that the number of steps can be reduced and the lead time can be shortened. . Further, even in a device having a fine rule in which a tapered portion cannot be formed by isotropic etching, the tapered portion can be formed in the present invention, so that step coverage can be improved.

[Brief description of the drawings]

FIG. 1 is a first sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention;

FIG. 2 is a second cross-sectional view illustrating the method for manufacturing the semiconductor device according to one embodiment of the present invention;

FIG. 3 is a third sectional view illustrating the method for manufacturing the semiconductor device according to one embodiment of the present invention;

FIG. 4 is a cross-sectional view illustrating a conventional method for manufacturing a semiconductor device.

FIG. 5 is a cross-sectional view illustrating a conventional method for manufacturing a semiconductor device.

FIG. 6 is a cross-sectional view illustrating a method for manufacturing a conventional semiconductor device.

FIG. 7 is a cross-sectional view illustrating a method for manufacturing a conventional semiconductor device.

FIG. 8 is a cross-sectional view illustrating a conventional method for manufacturing a semiconductor device.

Claims (2)

[Claims] A step of forming a first film to be etched on a semiconductor substrate; and a step of forming a second film to be etched having a lower etching rate than the film to be etched on the first film to be etched. And the first film to be etched and the second film via a resist film.
And anisotropically etching the film to be etched. 2. The method of manufacturing a semiconductor device according to claim 1, wherein said first film to be etched and said second film to be etched are respectively composed of a SiO2 film and a Si3 N4 film.