JPS6242523A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the dimension control of a contact hole by a method wherein a hole is formed with isotropic etching, and after a resist film has been baked, a mask by means of the second resist film is formed on an opening section and etched. CONSTITUTION:An insulation film 12 and the first positive-type resist film 13 are formed on a substrate 11 in order, and the film 13 is patterned. Then, a hole 14a' is formed with the film 13 as a mask with isotropic etching. The film 13 is baked with irradiation of far ultra violet ray to increase the absorption ratio of ultra violet ray. After that, the same kind of a resist as the film 13 is coated so that the hole 14 is completely filled to form the second resist film 14. Then, it is exposed, developed, and etched with the section 14a of the film 14 remaining under the opening 13a as a mask until it reaches the substrate 11. With this method, the etching advances in accordance with the shape of the hole, thereby forming the contact hole, with favorably controlled its dimension and shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This is a method for improving the dimensional controllability of contact holes when forming contact holes in the manufacture of semiconductor devices.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and more specifically, when forming a contact hole in an insulating film formed on the surface of a semiconductor substrate and providing an electrode therein,
The present invention relates to a method for forming contact holes with good dimensional control.

[Conventional technology]

The method of making a connection (contact) with a semiconductor substrate will be explained with reference to FIG. 2. As shown in FIG. A contact hole 24 is formed by forming a film 23, patterning the resist film 23 as shown, and etching and removing the diagonally shaded portion of the insulating film 22 using the resist remaining after development as a mask. Then, as shown in fb) of the same figure, [25
The contact hole 24 is filled with Al to make contact with the substrate. The contact hole is a circular hole with a diameter of, for example, 1.5 to 2.0 μm when viewed in a plan view.

Accordingly, as seen in FIG. 2 fal, the lateral dimension of the contact hole 24 is 1.5 to 2.0 μm.

The above-mentioned etching of the insulating film 22 is anisotropic etching, and a contact hole standing straight according to the pattern of the resist film 23 is created. When deposited, Al becomes the second
As shown in FIG.

In order to improve the coverage (adhesion) problem of contact holes, a method for forming contact holes as shown in FIG. 3 was developed. Referring to FIG. 3, a resist film 23 is formed on the insulating film 22 on the semiconductor substrate 2I in the same way as in the case described above.
), and first, about half of the thickness of the insulating film 22 is etched by isotropic etching as shown in FIG. As a result, a contact hole having the same width as the pattern of the resist 11ff is formed as shown in FIG. Since the upper part of the contact hole has a gently slanted shape, the problem explained with reference to FIG. 2 (bl) is solved and the coverage of A7! is improved.

[Problem that the invention seeks to solve]

In the above-mentioned anisotropic etching, the surface of the substrate to be exposed is scraped and cleaned so that good contact with Al can be made by excessively etching (over-etching). In such over-etching, the insulating film 22 is etched in the direction shown by arrow I in FIG. If the contact hole is shifted to the right or left as shown in the figure, the diameter of the predetermined contact hole is, for example, 2
There is a problem in that a contact hole that should have a diameter of 0 μm is formed with a diameter larger than that.

The present invention was created in view of these points, and an object of the present invention is to provide a method for forming a contact hole with good controllability in shape and size.

[Means for solving problems]

FIG. 1 is a sectional view of a main part of a semiconductor device, that is, a contact hole forming part, in a step of carrying out the method of the present invention.

In FIG. 1, as shown in fa), a first resist film 13 is formed using a positive resist on an insulating film 12 on a semiconductor substrate 11, and the resist film 13 is patterned. The insulating film 12 is partially etched by isotropic etching using a mask, and then the insulating film 12 is etched as shown in FIG.
As shown by the arrow, the resist is irradiated with deep ultraviolet rays and baked, and then a resist of the same type as the first resist film is applied to the entire surface as shown in FIG. A second resist film 15 is applied to completely fill the area, and then the entire surface of the resist film 15 is exposed to near ultraviolet rays as shown by the arrow in dl in the same figure (dl), and developed to form an eave-shaped opening in the resist film 13. The second resist film portion 15a is left under the portion 13a (FIG. 3(e)), and then the remaining portion of the insulating film 12 is etched by anisotropic etching and notching using the resist film 13 and the resist film portion 15a as masks. etching.

[Effect]

When a positive resist is baked, its absorption rate of ultraviolet rays increases, so it becomes a mask for the second resist, and the resist film 1
The second resist film portion 15a remains under the eave-shaped opening 13a of No. 3, and an apparently anisotropic hole is formed.
When anisotropic etching is then performed, the etching progresses in accordance with the shape of the anisotropic hole described above, so that the contact hole can be formed with good controllability in both size and shape.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG. 1 again.

FIG. 1 (see al: For example, phosphorus silicate glass (P) is placed on the semiconductor substrate 11.
An insulating film 12 with a thickness of 1 μm is formed using SG'), and a positive resist (for example, Tokyo Ohka Chemical Co., Ltd.
A first resist film 13 is formed by applying a resist (trade name: 0FPR-800), and after patterning the resist film 13, the insulating film 12 is partially isotropically formed using the resist film 13 as a mask. The hole 14a is formed by etching, for example, about half the initial film thickness. This can be done by wet etching using a hydronic acid (HF) based etchant or by dry etching using a CF4 based gas. By such etching, the insulation P
Since t112 is etched not only in the vertical direction but also in the horizontal direction, the hole 14a has a gentle shape, and the insulating film under the opening 13a of the resist film 13 is also removed.
The opening 13a overhangs like a canopy.

See FIG. 1(b): Next, the resist film 13 is baked at a temperature of about 200° C. while irradiating the entire surface with deep ultraviolet light as indicated by the arrow in the figure. When a positive resist is beta-aged at the above-mentioned temperature, its ultraviolet absorption rate increases and its maskability improves.

Refer to FIG. 1C: When the same resist as the first resist film is applied by the spin code method to fill the hole 14a, the upper part of the first resist film 13 is also thinly covered with the resist film 15.

Since the resist film 15 is formed by coating by a spin code method, the lower part of the eave-shaped opening 13a of the resist film 13 is also completely filled with the same resist. Note that when the hole 14a is formed by dry etching, it is preferable to ash the surface of the insulating film using, for example, 02 plasma in order to improve the wettability when applying the second resist.

Refer to FIG. 1(d): Near ultraviolet rays are irradiated as shown by the arrows in the figure to expose the entire surface of the second resist film 15.

See FIG. 1+e+: Next, the second resist film 15 is developed. Resist film 1
3 has been baked as described above and has a high absorption rate of ultraviolet rays, so in the near ultraviolet ray irradiation described with reference to FIG. 1(d), the second resist below the opening 13a is Since near ultraviolet rays are not transmitted, the opening 13a
A second resist film portion 15a remains below, and a hole 14b having the same shape and size as the apparently anisotropic opening of the resist film 13 is formed.

Refer to FIG. 1(f): Using the first resist film 13 and the remaining second resist 15a as a mask, the remaining portion of the insulating film 12 is etched by anisotropic etching. This etching cleans the surface of the substrate 11 by over-etching, but since the hole 14b is made with a predetermined shape and size as described above, the contact hole 14 finally formed by this over-etching has a certain size. Both shape and shape can be easily controlled. Subsequently, all the resist is removed and a predetermined i-electrode is formed.

In other embodiments of the invention, the second resist includes a first resist.
A resist that is sensitive to electron beams (EB) and deep ultraviolet rays, such as PMMA, is used, which is different from the resist used in the above. The steps in this case are the same as those in the previous example, but since this resist has high resolution, it is effective in forming fine patterns using deep ultraviolet rays.

〔Effect of the invention〕

As described above, according to the present invention, a contact hole can be formed with good controllability in terms of shape and size, there is no risk of disconnection of the i-wire formed in the contact hole, and fine control can be achieved by selecting the type of resist. This has the effect that a contact hole can be formed.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(f) are sectional views of an embodiment of the present invention, and FIGS. 2 and 3 are sectional views of a conventional example. In FIG. 1, 11 is a semiconductor substrate, 12 is an insulating film, 13 is a first resist film, 13a is an opening in the first resist film, 14 is a contact hole, 14a and 14b are holes, and 15 is a second resist film. The resist film 15a is the second resist film portion remaining under the opening. Houishi e month 9ζ dialect example 1 no. 1t7 Tomoe 9 Fig. 1

Claims (1)

[Claims] An insulating film (12) and a first resist film (13) are sequentially formed on a semiconductor substrate (11), and the resist film (13) is patterned in correspondence with contact holes to be formed. a step of partially etching the insulating film (12) using isotropic etching using a mask to form a hole (14a); a step of baking the resist film (13) while irradiating it with deep ultraviolet rays; Step 13) of applying the same type of resist to the entire surface to completely fill the hole (14a) to form a second resist film (15);
A step of exposing the entire surface of the resist film (15) to light, and developing the second resist film (15) so that the resist film (15) remains under the first resist film (13) and the opening (13a) of the resist film (13). A method for manufacturing a semiconductor device, comprising the step of etching the insulating film (12) using the second resist film portion (15a) as a mask until it reaches the substrate (11).