JPH04348516A - Method of forming contact hole - Google Patents

Abstract

PURPOSE:To provide a method which can easily provide a contact hole, whose sidewall is properly tapered, in an etching process being more simplified than before. CONSTITUTION:Method of forming a contact hole, characterized by performing anisotropic etching after heat-treating a resist film 3 when selectively removing the part fronting on the through hole 3a of an insulating film 2 and providing a hole for electrode contact by etching it after forming a resist film 3, which has a through hole 3a in the position in which to bring an electrode into contact with it, on the insulating film 2 of a semiconductor substrate 1 whose surface is covered with said insulating film 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming contact holes for forming electrode contacts in an insulating film on the surface of a semiconductor substrate.

0002

[Prior Art] In the conventional method for forming contact holes used in the manufacture of semiconductor devices, an insulating film (dielectric film) is slightly etched by isotropic wet etching, and then etched by anisotropic dry etching. A cup-shaped contact hole (with a diameter that gradually decreases from the surface side toward the bottom) is formed. This is to provide a gentle taper to the side wall of the hole to provide good step coverage of the electrode in the hole.

A conventional method for forming contact holes will be explained in more detail with reference to the drawings. First, as shown in FIG. 5, a resist film 33 is formed on an insulating film 32 covering the surface of a semiconductor substrate 31 in a pattern having through holes 33a at positions where electrodes (electrode wiring) are to be contacted. The insulating film 32 is made of SiO layered in order by CVD method.
2 layer 32c, BPSG layer 32b, SiO2 layer 32a
It has a three-layer structure.

Next, as shown in FIG. 6, parts of the SiO2 layer 32a and the BPSG layer 32b are etched by anisotropic dry etching, and then, as shown in FIG. 7, they are etched by isotropic wet etching. After creating a cup shape by utilizing the difference in etching speed between the SiO2 layer and the BPSG layer, the BPSG layer 3 is removed by anisotropic dry etching.
The remaining portion of 2b and the SiO2 layer 32c are etched to complete the contact hole 35.

After completing the hole 35, as shown in FIG. 8, the resist film 33 is peeled off, and then heat treatment (for example,
After adjusting the shape of the hole 35 at 900° C. for 5 minutes, a metal film such as aluminum is deposited to a desired thickness by sputtering and patterned by selective etching to form the electrode 39.
form. The electrode 39 is connected to the hole 3 as shown in FIG.
5 and is in contact with the n-type impurity region 31a (see above, Japanese Patent Laid-Open No. 1-194328).

[0006]

However, the above-described conventional contact hole forming method has the following problems. One is that the etching process is complicated. Both anisotropic etching and isotropic etching must be performed. Further, the insulating film needs to be a special one in which both the SiO2 layer and the BPSG layer are laminated, and the process for forming the insulating film is complicated, and there are disadvantages in that the applicable insulating films are limited.

Another problem is that it is difficult to obtain suitable contact holes. Although the difference in etching rate between each insulating layer is utilized, it is particularly difficult to accurately detect the end point of isotropic etching, and it is difficult to properly taper the sidewalls of the hole. Therefore, the step coverage of the hole portion is not appropriate, and problems such as electrode disconnection may occur.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a method for easily forming a contact hole having an appropriately tapered side wall using an etching process that is simpler than the conventional method.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the method for forming a contact hole of the present invention, an electrode is placed on the insulating film of a semiconductor substrate whose surface is covered with an insulating film at a position where the electrode is to be brought into contact with the insulating film. By forming a resist film in a pattern having through holes and performing an etching process, a portion of the insulating film facing the through holes is selectively removed to provide a hole for the electrode contact. On the other hand, after heat treatment is performed, anisotropic etching is performed as the etching treatment.

[0010] Hereinafter, the method for forming a contact hole according to the present invention will be explained in detail with reference to the drawings. first,
As shown in FIG. 1, an insulating film (
A photoresist film 3 is formed on the dielectric film 2 in a pattern with through holes 3a at positions where electrodes (electrode wiring) are to be contacted. The insulating film 3 does not need to have a specific multi-layer structure as in the conventional case, for example, it may be made of a thermally oxidized silicon layer, but it may not be made of a laminated SiO2 layer or BPSG layer as in the conventional case. There may be.

Then, as shown in FIG. 2, the photoresist film 3 is heat treated to form a taper (inclination) of about 60° on the side wall of the through hole, and anisotropic dry etching is performed to remove the insulation. A portion of the film 2 facing the through hole 3a is selectively removed to form a contact hole 5, as shown in FIG. Since the etching rate of the silicon oxide film is two to three times faster than the etching rate of the photoresist film, the side wall of the contact hole 5 naturally has an appropriate taper of about 70 to 80°.

After completing the hole 5, as shown in FIG. 4, the photoresist film 3 is peeled off, a metal film such as aluminum is deposited to a desired thickness by sputtering, and patterned by selective etching to form the electrode 8. form. Electrode 8
is in contact with n-type impurity region 1a through hole 5, as shown in FIG. Note that after the resist film 3 is peeled off, heat treatment may be performed to adjust the shape of the hole 5 as necessary.

In FIGS. 1 to 4, one contact hole is formed for convenience, but it is common to form a large number of contact holes at the same time.

[0014]

[Operation] In the contact hole forming method of the present invention,
The etching process is simplified. This is because if only anisotropic etching is performed, an appropriate taper will be formed on the side wall of the hole. This is because the side walls of the through holes in the resist film are tapered by heat treatment, so as the anisotropic etching progresses, the holes in the resist film gradually become larger and the etched surface expands. This is because the etching depth becomes shallower toward the edges, and an appropriate slope is naturally formed.

Furthermore, the insulating film does not need to have a specific multi-layer structure, which has the advantage of simplifying the insulating film forming process and widening the range of applicable insulating films. In addition, it is easy to implement because it does not require isotropic etching, which is difficult to control accurately. If appropriate contact holes are formed, step coverage will also be good, increasing the reliability of the electrode.

[0016]

[Example] Next, an example of the present invention will be described. In the example, contact holes were provided and electrodes (electrode wiring) were formed according to FIGS. 1 to 4 above. A layer with a thickness of 1.5 mm is formed on the semiconductor substrate 1 with the n-type impurity region 1a on the front side.
An insulating film 2 of thermally oxidized silicon having a thickness of μm was formed. Then,
A resist film with a viscosity of 30 cp and a thickness of 1.5 μm is provided on this insulating film 2 and patterned, as shown in FIG.
A photoresist film 3 was formed in a pattern with through holes 3a at positions where electrodes were to be contacted.

[0017] Then, the photoresist film 3 is
Heat treatment was performed at ~150°C for 30 seconds. As a result, Figure 2
As can be seen, the side wall of the through hole 3a of the photoresist film 3 was tapered (inclined) at about 60°. Next, using the photoresist film 3 as a mask, [CHF3 +C2
Anisotropic dry etching was performed using F6]-based gas to form contact holes 5 as shown in FIG. The side wall of contact hole 5 had an appropriate taper of approximately 70-80°.

After completing the hole 5, as shown in FIG. 4, the photoresist film 3 is peeled off, a metal film such as aluminum is deposited to a desired thickness by sputtering, and the electrode 8 is patterned by selective etching. was formed. Electrode 8
As shown in FIG. 4, it was in contact with the n-type impurity region 1a through the hole 5, and thanks to the appropriate taper attached to the side wall of the hole 5, the step coverage was also good.

The present invention is not limited to the above embodiments. Figure 1
4, n-type impurity region 1 on the surface side of the semiconductor substrate
Another example is where a is a p-type impurity region.

[0020]

[Effects of the Invention] In the contact hole forming method of the present invention, since the side surface of the through hole in the resist film is tapered, a contact hole with an appropriate taper can be formed simply by performing anisotropic etching. The process is simpler and easier to implement than before, and furthermore,
It has a wide range of applicable insulating films and is very useful.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a semiconductor substrate in the middle of forming a contact hole in an example of the present invention.

FIG. 2 is a cross-sectional view showing a semiconductor substrate in the middle of forming a contact hole in an example of the present invention.

FIG. 3 is a cross-sectional view showing a semiconductor substrate in which contact holes are formed in an example of the present invention.

FIG. 4 is a cross-sectional view showing a semiconductor substrate in which an electrode is formed to contact the surface of the substrate through a contact hole provided in an example of the present invention.

FIG. 5 is a cross-sectional view showing a semiconductor substrate in the middle of forming contact holes using a conventional method.

FIG. 6 is a cross-sectional view showing a semiconductor substrate in the middle of forming contact holes using a conventional method.

FIG. 7 is a cross-sectional view showing a semiconductor substrate in which contact holes are formed using a conventional method.

FIG. 8 is a cross-sectional view showing a semiconductor substrate on which an electrode is formed to contact the surface of the substrate through a contact hole formed by a conventional method.

[Explanation of sign]

1 Semiconductor substrate 1a N-type impurity region 2 Insulating film 3 Photoresist film 3a Through hole 5 Contact hole

Claims (1)

[Claims] 1. A resist film is formed in a pattern having through holes at positions where electrodes are to be contacted on the insulating film of a semiconductor substrate whose surface is covered with an insulating film, and etching is performed. In the method of selectively removing a portion of an insulating film facing the through-hole to provide a hole for the electrode contact, the resist film is heat-treated, and then anisotropic etching is performed as the etching treatment. A method for forming a contact hole, characterized in that: