JPH02122628A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a highly reliable semiconductor device without failure in electrode wiring by a method wherein after etching is performed under such conditions that an approximately perpendicular shape of a contact hole can be obtained, only an upper portion of the contact hole is subject to post- treatment so that its side is in a tapered shape. CONSTITUTION:Since first etching enables an approximately perpendicular shape to be obtained, deterioration in final detecting accuracy can be prevented by processing a contact hole 3 stably and reliably. By adopting dry etching with easy control of taper processing with sulfur hexafluoride added to etching gas, only an area of a contact hole upper portion can be selectively increased, thereby improving coverage of a conductive film 1. Further by preventing a bottom area of the contact hole 3 from being increased, electrical contact, leakage and interference with other wiring layers can be prevented, thereby improving stability and reliability of a semiconductor device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for manufacturing contact holes in a semiconductor device, particularly a method for processing fine contact holes by dry etching.

We make full use of a highly stable and reliable process for dry etching this contact hole.

Only the top part is intended to provide a tapered contact hole.

After the side surfaces of the contact hole are formed substantially perpendicular to the substrate, only the upper part of the contact hole is enlarged so that the side surface has a tapered shape by quasi-anisotropic etching using an etching gas containing sulfur hexafluoride.

[Industrial application field]

The present invention provides a method for manufacturing a contact hole in a semiconductor device,
In particular, it relates to a method of processing fine contact holes by dry etching.

As semiconductor devices become more highly integrated, contact hole diameters are required to become smaller and smaller.

Even if the diameter of the contact hole is reduced, the thickness of the insulating film to be etched cannot necessarily be reduced proportionally due to device characteristics.

Therefore, the ratio of the depth and diameter of the contact hole.

That is, the aspect ratio increases with miniaturization, and in the formation of a conductive film by sputtering in a subsequent process.

The thickness of the film at the contact hole area becomes partially thinner.
This may cause problems such as wire breakage. For this reason, to improve the stability and reliability of semiconductor device performance.

It is necessary to improve the coverage of the conductive film, which has deteriorated due to the increase in the aspect ratio of the contact hole.

(Prior Art) A conventional method for forming contact holes in a semiconductor device is shown in FIG.

In the conventional forming method, when a contact hole 12 is formed in the insulating film 11 on the underlying conductive film 10 by dry etching, a substantially vertical cross-sectional shape as shown in FIG. 3(a) is obtained. A conductive film 13 is applied to this contact hole 12 by sputtering.

As shown in FIG. 3(b), a thin portion is formed.

When the thickness of the conductive film at the flat part is 1, the ratio of the thickness of the conductive film at the thinnest part of the contact hole is "
It is called "coverage". This coverage decreases as the aspect ratio of the contact hole increases, and the reliability of the semiconductor device decreases significantly.

Therefore, several methods have been proposed for improving the coverage by processing the contact hole into a tapered shape and enlarging the upper surface portion as shown in FIG. 3(c). For example to obtain a tapered shape.

There is a method (Example 1) in which oxygen is added to the etching gas to lower the selectivity to the resist and make the upper part larger.

There is a method (Example 2) in which tapered etching is performed by lowering the etching rate under gas conditions with high deposition properties to reduce the lower area. Example 1 In FIG. 3(c) showing the shape of a contact hole processed by the method of Example 2, 14 is a conductive film, 15 is an insulating film, and 16 is a contact hole 117 having a tapered shape.

[Problems to be Solved by the Invention] When a contact hole is processed by the method described above, compared to the case where a contact hole having a nearly vertical shape is processed, in Example 1, there is a decrease in the selectivity with respect to the resist, In Case 2, problems such as a decrease in etching end point detection accuracy occurred.
In addition to a decrease in the accuracy of etching end point detection, problems such as a shortening of the cleaning cycle due to equipment contamination and the like occur.

As a result, the stability of the contact hole processing process,
Reliability decreases, causing malfunction of the semiconductor device.

An object of the present invention is to provide a contact hole whose upper portion is post-processed into a tapered shape by making full use of a highly stable and reliable dry etching process.

(Means for Solving the Problems) It is known that when a contact hole is subjected to anisotropic etching, a polymer film will adhere to the side surfaces of the contact hole.

On the contrary, the polymer membrane protects the side walls and is the reason why it maintains its almost vertical shape. As mentioned above, etching a contact hole in a nearly vertical shape is a process method with high stability and reliability, and the process itself of etching a contact hole is aimed at obtaining a vertical shape. It is desirable to carry out the test under the following conditions.

However, in this state, the tapered shape of the upper side surface of the contact hole cannot be obtained.

Therefore, in the present invention, after etching is performed under conditions that allow a nearly vertical shape of the contact hole to be obtained, only the upper part of the contact hole is post-processed so that the side surface becomes tapered, thereby expanding the area and increasing the coverage of the conductive film. It is something that makes things better.

FIG. 1 is a diagram explaining the principle of the present invention. First.

As shown in FIG. 1(a), using a conventional method, the insulating film 2 on the underlying conductive film 1 is masked with resist or the like, and a first etching is performed in a nearly vertical shape to form a contact. Pattern hole 3. In Figure 1, 1
is a conductive film, and 2 is an insulating film.

3 is a contact hole.

Next, as shown in FIG. 1(b), a second etching is performed under gas conditions such that the resist recedes from the etching and under conditions that allow etching of the insulating film. the result,
A tapered shape 4 at the top of the contact hole is obtained by retreating the resist.

[Effect]

In the present invention, as shown in FIG. 1(a), the first etching is an etching to obtain a substantially vertical shape as in the conventional etching, so that the contact hole is stable.

Processing with good reliability can avoid problems such as a decrease in end point detection accuracy.

Then, as shown in Figure 1(b), sulfur hexafluoride was added to the etching gas, and dry etching was adopted, which made it easier to control the taper process.

By selectively increasing only the area above the contact hole, the coverage of the conductive film can be improved. Furthermore, by not increasing the bottom area of the contact hole, electrical contact, leakage, and interference with other wiring layers can be avoided, and in this respect as well, the stability and reliability of the semiconductor device are increased.

〔Example〕

An embodiment of the invention is shown in FIG.

The etching process is divided into two stages: a first etching process to obtain a substantially vertical cross-sectional shape of the contact hole, and a second etching process to process only the upper part of the contact hole into a tapered shape.
Perform processing.

The first etching is performed by forming an insulating film such as phosphosilicate glass or a silicon dioxide film grown by chemical vapor deposition or thermal diffusion on the underlying conductive film 5, as shown in FIG. 2(a). 6 is formed, a resist 7 is applied by a conventional method, and a contact hole 8 is patterned. After that, using a two-reactive ion etching (RIB) device, carbon tetrafluoride (CF4) and trifluoromethane (C
HF,) is used.

The gas flow rate is CI'4=40sec, CHF,=
50sec+ Pressure: 0°3 Torr, Output: 60
Anisotropic etching is performed under 0- conditions to obtain a substantially vertical shape.

Next, a second etching process is performed to process only the upper part of the contact hole 8 into a tapered shape, for example, under the following quasi-anisotropic etching conditions.

Using the same RIE apparatus as above, CF4. Add sulfur hexafluoride (sp, ) to ClIF5 and change the gas flow rate to CF4=405CC111, CHF5=5
03CC111SF&=100! IccI+pressure 0.4
Etching is performed for 60 seconds to form a tapered shape 9 as shown in FIG. 2(b) under conditions of a Torr output of around 60.

The etching time depends on the etching conditions, but if the etching time is short, the taper will be insufficient only at the -E portion, whereas if the etching time is long, the taper will extend to the lower part, and if the etching time is longer, the area of the bottom portion will become larger. The optimum etching time is selected depending on the design and device performance.

〔Effect of the invention〕

As explained above, according to the present invention, since the side surface of the contact hole is first processed in a substantially vertical shape as in the conventional method, stability and reliability due to processing are not impaired.
Furthermore, by subsequently processing only the upper part of the contact hole into a largely tapered shape, it is possible to obtain a shape with good coverage, and a highly reliable semiconductor device without failure of electrode wiring can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention. FIG. 2 is a schematic sectional view of one embodiment of the present invention. FIG. 3 is a schematic sectional view of a conventional example. In fig. 1 is a conductive film. 2 is an insulating film. 3 is the contact hole. 4 is a tapered shape 5 is a conductive film. 6 is an insulating film. 7 is resist. 8 is a contact hole. 9 is a tapered shape for the main island.

Claims (1)

[Claims] In dry etching for forming contact holes in semiconductor devices, the side surfaces of the contact holes are formed almost perpendicular to the substrate, and then the upper part of the contact holes is etched by quasi-anisotropic etching using an etching gas containing sulfur hexafluoride. 1. A method of manufacturing a semiconductor device, comprising enlarging only the side surface of the semiconductor device so that the side surface thereof has a tapered shape.