JPH01268042A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve dimensional accuracy when contact holes having tapered cross sections are formed, by filling the contact holes halfway with conductive films, and expanding the diameters of the part above the conductive films in the contact hole by etching. CONSTITUTION:Contact holes 9 are formed so as to connect wirings on a semiconductor substrate 1 on which specified integrated circuits are formed and to connect the semiconductor substrate 1 and the wirings. At this time, the contact hole 9 which has the same diameter as the size of a resistor mask 7 that is deposited and formed on the surface of the semiconductor substrate 1 is formed. Then, each contact hole 9 is filled with a conductive film 10 to the intermediate part. Then, the diameter of the part of the contact hole 9 higher than said conductive film 10 is expanded by etching. In the process for filling the contact hole 9 to the intermediate part, a low temperature film forming method such as a light-selective CVD method and a low temperature epitaxial growing method is used. Thus the deterioration of photoresist 7 due to heat is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a technology for manufacturing semiconductor devices, and particularly to a technology that is effective when applied to improving interconnection reliability.

[Conventional technology]

As semiconductor devices become more highly integrated and interconnects become finer, the aspect ratio (contact hole depth/contact As the diameter of the hole increases and the deposition rate of the conductive film inside the contact hole decreases, the connection reliability of the wiring has decreased.

As a countermeasure against this problem, a so-called Taber etching technique has been put into practical use, which aims to improve the deposition rate of the conductive film by making the cross-sectional shape of the contact hole tapered.

Regarding the above-mentioned Taber etching technology, for example, in 1984
Published in April, “Solid State Technology,”
i Selective reactive ion etching of oxide film (5ol
id 5tate Technology”5elec
t-ive Reactive Ion Etchin
g of Sin,') J, as a specific example of the taper etching technique, isotropically wet-etching up to the middle of the contact hole, and then vertically etching the rest using highly anisotropic dry etching. It also describes a method of performing vertical dry etching up to the middle of a contact hole, then retreating the resist mask by ashing, and performing additional dry etching.

[Problem to be solved by the invention]

However, according to studies by the present inventors, the conventional taper etching technique described above has a drawback in that the diameter of the bottom of the contact hole becomes larger than the original resist mask dimension due to repeated etching.

Even if the error between the contact hole diameter and the resist mask dimension is extremely small,
In high-density integrated circuits in which the distance between contact holes is extremely narrow, short circuits between wiring lines may occur.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a technique that can improve the dimensional accuracy when forming a contact hole having a tapered cross section. .

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, first, a contact hole having a diameter matching the dimensions of the resist mask is formed, and then the contact hole is filled up to the middle with a conductive film, and then the diameter of the contact hole above the conductive film is etched. This is a method of forming a contact hole with a tapered cross section by enlarging it.

[action,]

According to the above-mentioned means, since the portion filled with the conductive film inside the contact hole is not etched, the diameter of the portion is maintained as per the dimension of the resist mask.

[Embodiment 1] FIGS. 1(a) to 1(6) are sectional views of essential parts of a semiconductor substrate showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

The first embodiment is applied, for example, to a method of manufacturing an MO3 type semiconductor device, and the process will be described below as shown in FIG. 1(a).
This will be explained according to (d).

First, a field insulating film 2, a gate oxide film 3, a gate electrode 4, a field insulating film 2, a gate oxide film 3, a gate electrode 4,
After forming the diffusion layers 5a and 5b, an insulating film 6 made of phosphosilicate glass (PSG) or the like is deposited on the surface of the substrate 1.

Next, a photoresist 7 is deposited on the surface of the insulating film 6,
The location where the contact hole is to be formed is etched to form an opening 8.8 (FIG. 1(a)).

Next, using the photoresist 7 as a mask, the openings 8.
The insulating film 6 exposed from the substrate 8 and the gate oxide film 3 below it are removed by etching, and the diffusion layers 5a, 5 of the substrate 1 are removed.
A contact hole 9.9 is formed to reach point b (FIG. 1(5)).

In this etching process, a highly anisotropic dry etching method such as reactive ion etching is used to match the diameter of the contact hole 9 with the diameter of the opening 8.

Next, a conductive film 10 made of a high melting point metal or low resistance polysilicon is selectively deposited, and the contact hole 9 is filled up to the middle with the conductive film 10 (FIG. 1C).

In this step, a low-temperature film forming method such as a photo-selective CVD method or a low-temperature epitaxial growth method is used to prevent deterioration of the photoresist 7 due to heat. At this time, the thickness of the conductive film 1O deposited inside the contact hole 9 is preferably made thicker than the gate oxide film 3.

Next, by etching the absolute μ film 6 inside the contact hole 9 using a highly isotropic etching method such as wet etching, the diameter of the contact hole 9 is made smaller than the diameter of the opening 8. Increase the size (Figure 1 (
d)).

In this etching step, by increasing the selectivity between the insulating film 6 and the conductive film 10, the conductive film 10 is prevented from being excessively etched.

Finally, by removing the photoresist 7, a contact ball 9 having a tapered cross-sectional shape above the conductive film 10 is obtained.

As described above, according to the first embodiment, the following effects can be obtained.

(1) After filling the hole 9 up to the middle with the conductive film 10 in advance, the insulating film 6 above it is etched in the same direction, so that the diameter of the part filled with the conductive film 10 is can be made to match the diameter of the opening 8.

(2) Due to the above (1), the dimensional accuracy of the contact hole 9 is improved, and the contact hole 9.9 in contact with 1lJP is
Even if the distance between the wires is extremely narrow, short circuits in the wires can be reliably prevented.

(3) The above (2) promotes the miniaturization of wiring,
High density and high integration of semiconductor devices can be achieved.

(4) Since the conductive film 10 is deposited inside the contact hole 9 under low temperature conditions where the photoresist 7 does not deteriorate, only one masking process is required, improving the throughput of the process of forming the contact hole 9. .

[Embodiment 2] FIGS. 2(a) and 2(b) are sectional views of essential parts of a semiconductor substrate showing a method for manufacturing a semiconductor device according to another embodiment of the present invention.

The second embodiment is the same as the first embodiment up to the step of filling the contact hole 9 with the conductive film 10, so only the subsequent steps will be described below.

That is, after filling the contact hole 9 up to the middle with a conductive film 10 using a low-temperature film forming method such as a photo-selective CVD method or a low-temperature epitaxial growth method, dry etching (ashing) is performed using a mixture of oxygen or ozone in the etching gas. (ashing) causes the photoresist 7 to retreat, thereby increasing the diameter of the opening 8 (see Fig. 2(a)).

Next, by etching the insulating film 6 exposed through the enlarged opening 8, a contact hole 9 having a tapered cross-sectional shape above the conductive film 10 is obtained, as in the case of Example 1. (Figure 2 (c)).

In this way, also in the case of the second embodiment, since the contact hole 9 is filled up to the middle with the conductive film 10 in advance and the insulating film 6 above it is etched, the hole is filled with the conductive film 10. It is possible to obtain the same effects as in the case of the first embodiment described above, such as being able to match the diameter of the opened portion with the diameter of the opening 8.

As above, the invention made by the present inventor has been specifically explained based on Examples, but the present invention is not limited to the above-mentioned Examples, and it is understood that various changes can be made without departing from the gist thereof. Needless to say.

For example, in Example 1.2, the case where the application is applied to a contact hole for connecting a wiring and a substrate is described, but it can also be applied to a contact hole for connecting an upper layer wiring and a lower layer wiring. .

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, when forming a contact hole for connecting between wirings on a substrate on which a predetermined integrated circuit is formed, or between a substrate and wirings, first, the dimensions of the resist mask formed on the surface of the substrate are determined. After forming a contact hole with the same diameter, the middle of the contact hole is filled with a conductive film, and then the diameter of the contact hole above the conductive film is enlarged by etching. Since the diameter of the contact hole can be made to match the dimension of the resist mask, the dimensional accuracy when forming a contact hole having a tapered cross section can be improved.

[Brief explanation of the drawing]

1(a) to 1(6) are cross-sectional views of main parts of a semiconductor substrate showing a method of manufacturing a semiconductor device according to an embodiment of the present invention, and FIG.
Figures (a) to (a) are sectional views of essential parts of a semiconductor substrate showing a method of manufacturing a semiconductor device according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Field insulating film, 3...
... Gate oxide film, 4... Gate electrode, 5a, 5b.
... Diffusion layer, 6... Insulating film, 7... Photoresist,
8... Opening, 9... Contact hole, 10...
・Conductive film. Figure 1 Figure 1 Figure 2

Claims (1)

[Claims] 1. When forming a contact hole for connecting between wirings on a semiconductor substrate on which a predetermined integrated circuit is formed, or between the semiconductor substrate and wirings, a contact hole is formed on the surface of the semiconductor substrate. After forming a contact hole having a diameter matching the dimensions of the deposited resist mask, the contact hole is filled up to the middle with a conductive film, and then the diameter of the contact hole above the conductive film is etched. A method for manufacturing a semiconductor device characterized by expanding the semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the contact hole is filled at a temperature lower than the allowable temperature limit of the resist mask.