JPH0220043A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To uniformly form a contact hole having a taper by etching irrespective of the uneven surface of a semiconductor substrate, and to remarkably improve the coverage of wirings on this part by employing a mask material having a taper on an opening shape as a mask. CONSTITUTION:A phosphorus glass film 104 as an insulating film, a silicon nitride film 105 as a first mask material, and a photoresist 106 as a second mask material are formed on a semiconductor substrate 101, and a pattern of a contact hole is formed. The film 105 is formed by a vapor growing method, and uniformly formed irrespective of the uneven surface of the substrate. Then, with the photoresist 106 as a mask the film 105 is isotropically etched, and the photoresist 106 is then removed. With the film 105 as a mask the film 104 is eventually etched. Thus, the hole having a taper is formed in a uniform shape without respect to the uneven surface of the substrate.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for forming a contact hole.

[Conventional technology] Conventionally, when attempting to form a contact hole in an insulating film, the insulating film was dry etched using a photoresist as a mask, but in this case, since the shape of the contact hole was overlapping, .

As miniaturization and higher integration progress, the coverage of wiring in contact hole areas has become a problem.

It has become necessary to form a contact hole with a taper angle, and as a means to meet this requirement, photoresists such as those shown in Figures 2 (a) to (C) are used for A method that takes advantage of the regression of

That is, after forming a contact hole pattern with a photoresist 205 on the upper phosphor glass 204 of the semiconductor substrate 201, baking the photoresist 205 at 150'C to 200C to flow the photoresist 205.
A contact hole having a tapered angle was formed by etching the photoresist 205 and the phosphor glass 204 at the same time so that the etching speed was the same.

[Problems to be Solved by the Invention] However, in the above-mentioned technique, since the photoresist is spin-coated, if the surface of the semiconductor substrate is uneven, the photoresist film becomes thicker in the uneven areas. , to become thinner in the convex part.

The shape of the photoresist in each part of the ridges that flowed due to high-temperature baking is different, and in particular, there is a large taper in the part where the film thickness is slightly thicker.

Therefore, even after etching, the shape of the contact hole is not uniform, and it is very difficult to taper the opening.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a method for uniformly forming tapered contact holes in an insulating film on a semiconductor substrate.

[Means for Solving the Problems] A method for manufacturing a semiconductor device of the present invention includes a step of forming a contact hole in an insulating film formed above a semiconductor substrate.

(a) A step of forming a first mask material on the insulating film to have a uniform thickness regardless of irregularities on the surface of the semiconductor substrate.

(b) A step of forming a contact hole pattern on the first mask material using a photoresis l- as a second mask material.

(C) using the second mask material as a mask, the first mask material is isotropically etched;
The process of removing mask material.

(d) A step of opening a contact hole by etching the insulating film using the first mask material as a mask.

It is characterized by being more.

[Example] FIGS. 1(a) to (C) are process cross-sectional views showing an example of the present invention. The explanation will be given below in the order of the steps.

That is, first, as shown in FIG. 1(a), a phosphor glass film 104 is formed as an insulating film over the semiconductor substrate 101.
After forming a silicon nitride film 105 as a first mask material on the phosphorus glass film 104, a photoresist 106 is formed as a second mask material.
10,000 contacts are formed to form a contact hole pattern. At this time, since the photoresist 106 is spin coated, its film thickness is not uniform due to unevenness on the surface of the semiconductor substrate, but since the silicon nitride film 105 is formed by vapor phase growth, the unevenness on the surface of the semiconductor substrate is uneven. It is formed uniformly regardless of the Next, as shown in FIG. 1(b), the silicon nitride film 1 is coated using the photoresist 106 as a mask.
After etching 05 isotropically, the photoresist 106 is removed. At this time, the shape of the opening in the silicon nitride film is uniform regardless of the unevenness of the surface of the semiconductor substrate. Finally, as shown in FIG. 1(C), the silicon nitride film 10
Using No. 5 as a mask, the phosphor glass film 104 is etched. At this time, the etching conditions are set so that the etching speed of the silicon nitride film and the phosphorus glass film are equal, and in reality, CHF3 = 50 sec, 02 = 2
Etching was performed at 0 sec, gas pressure = 8 Pa, and RF power = 700 W, and the etching rate at this time was 500 people/mi.
It was n. The silicon nitride film 105 is completely removed by over-etching. In this way,
A contact hole having a taper angle is formed in a uniform shape regardless of irregularities on the surface of a semiconductor substrate.

Note that in this example, phosphorus glass,
Although a silicon nitride film is used as the first mask material, the insulating film may be any insulating thin film such as a non-doped silicon dioxide film or boron phosphorus glass. Any material can be used as long as it can be easily etched isotropically using a resist as a mask material; for example, the same effect can be obtained by using polycrystalline silicon or the like.

[Effects of the Invention] As described above, according to the present invention, when forming a contact hole, it is possible to uniformly form the contact hole above the semiconductor substrate regardless of the unevenness of the surface thereof, and the shape of the opening is tapered. By etching using the mask material as a mask, a tapered contact hole is created.
It has the effect that it can be formed uniformly regardless of the unevenness of the surface of the semiconductor substrate, and as a result, the coverage of the wiring in these parts can be dramatically improved, and the yield rate is 2.
We were able to improve reliability.

101° 102° 103° 104° 106, 205 semiconductor substrate Base insulating film wiring phosphorus glass membrane silicon nitride film photoresist that's all Applicant: Seiko Epson Corporation Agent: Patent attorney - Masayoshi Kamiyanagi and 1 other person

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) are process cross-sectional views showing an embodiment of the method for manufacturing a semiconductor device of the present invention.

Claims (1)

[Claims] In the step of forming a contact hole in an insulating film formed above a semiconductor substrate, (a) a first mask material is uniformly applied on the insulating film regardless of irregularities on the surface of the semiconductor substrate; (b) forming a contact hole pattern using photoresist as a second mask material on the first mask material; (c) using the second mask material as a mask; removing the second mask material after isotropically etching the first mask material; (d) etching the insulating film using the first mask material as a mask to form a contact hole; The process of opening a hole. A method for manufacturing a semiconductor device, characterized by comprising the following steps.