JPH04271121A - Forming method of contact hole - Google Patents

Abstract

PURPOSE:To obtain a contact hole forming method capable of surely forming a contact hole independently of the distribution of contact hole forming position, when a contact hole is formed in an interlayer insulating film formed of polyimide resin. CONSTITUTION:Firstly, a dummy post is formed at a position where a contact hole is formed. Secondly an interlayer insulating film of polyimide is formed. Finally the dummy post is eliminated, thereby forming the contact hole.

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 in highly integrated semiconductor devices.

0002

2. Description of the Related Art Conventionally, when polyimide resin is used for an interlayer insulating film of multilayer wiring in a high-density integrated semiconductor device, the process shown in FIGS. 3(A) and 3(B) is performed. A contact hole is formed in the polyimide resin through the process.

First, a polyimide resin layer 4, which is an interlayer insulating film, is formed on the semiconductor substrate 3 on which the first aluminum wiring layers 1a to 1c are formed. Then, on the polyimide resin layer 4, a titanium layer or a silicon nitride film layer 5 is formed to serve as a mask during this polyimide etching. Next, in order to form contact holes on the first aluminum interconnection layers 1a to 1c, the silicon nitride film layer 5 in those portions is removed. The longitudinal cross-sectional view at this time is as shown in FIG. 3(A). Then, in this state, the polyimide resin layer 4 is etched to form contact holes 6a to 6c on the first aluminum wiring layers 1a to 1c. The vertical cross-sectional view at this time is shown in Figure 3 (B
) as shown. After that, the silicon nitride film 5 is removed, and if necessary, a second aluminum wiring layer is formed and the first
Aluminum wiring layers 1a to 1c are electrically interconnected.

0004

[Problems to be Solved by the Invention] However, in such a conventional contact hole forming method, a region where contact hole formation positions where contact holes are to be formed are densely distributed, in other words, a contact hole formation method is difficult to solve. Etching of the polyimide resin layer 4 is performed reliably in regions where the mutual spacing between formation positions is narrowly distributed, but as shown in FIG.
In areas where contact holes 6a are relatively sparsely distributed, such as near the contact holes 6a shown in B), etching remains are likely to occur, and there is a problem in that the etching may not be performed reliably.

[0005] This phenomenon occurs because the moisture contained in the polyimide resin evaporates when the polyimide resin is etched, but in areas where the contact hole formation positions are sparsely distributed, the moisture evaporates. This is because the etching is concentrated on the contact holes, which hinders etching, and in the worst case, contact holes such as contact hole 6a will be left unetched.

The present invention has been made to solve these conventional problems, and provides a method for forming contact holes that can reliably form contact holes regardless of the distribution of contact hole formation positions. The purpose is to provide.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a contact hole forming method for forming a contact hole in an interlayer insulating film formed of polyimide resin. forming a dummy pillar at the desired contact hole formation position; forming a polyimide resin layer until the dummy pillar is completely covered; and etching the polyimide resin layer until the head of the dummy pillar is exposed. and a step of removing the dummy pillar to form a contact hole.

[0008]

[Function] If the contact hole is formed in this process, the contact hole will be formed by removing the dummy pillar, so there will be no need to consider the influence of moisture in the polyimide, and the contact hole formation position can be adjusted. Contact holes can be reliably formed regardless of the distribution of the contact holes.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1(A), FIG. 1(B), FIG. 2(A), and FIG. 2(B) are longitudinal cross-sectional views obtained by each step of an embodiment of the present invention. to form a contact hole.

First, a first aluminum wiring layer 1 is formed on the insulating layer 2.
A silicon oxide film is deposited on the entire surface of the semiconductor substrate 3 on which wirings a to 1c are formed, and dummy pillars 10a to 10c as shown in FIG.
1c. The dummy pillars 10a to 10c are formed by a photolithography process and an etching process. Specifically, after forming a silicon oxide film on the entire surface of the semiconductor substrate 3, a resist mask is formed on a predetermined portion of the silicon oxide film by a photolithography process, and the silicon oxide film is etched using the resist mask as a mask. By doing so, dummy columns 10a to 10c are formed. The height of the dummy pillars 10a to 10c is made to be about 3000 angstroms higher than the depth of the contact hole that is desired to be finally obtained. The reason for doing this is to facilitate the removal of the dummy pillars.

Next, a polyimide resin layer 4 is formed as shown in FIG. 1(B) on the substrate having the layered structure shown in FIG. 1(A). The thickness of this polyimide resin layer 4 is set to be about 7000 angstroms thicker than the target value which will be the final height of the contact hole. Then, the polyimide resin layer 4 is etched back to reduce its thickness to the target value. By this etching, the image shown in FIG. 2(A)
The heads of the dummy columns 10a to 10c are exposed as shown in FIG. At this time, about 3000 angstroms of the head is exposed. Finally, the dummy pillars 10a-10c made of silicon oxide film are removed by etching to form contact holes 6a-6c as shown in FIG. 2(B). Note that the dummy pillars are removed by wet etching using a hydrofluoric acid solution. When a contact hole is formed in this way, there is no need to etch the polyimide resin to form the contact hole, so the contact hole can be formed without considering the influence of moisture during etching of the polyimide resin. will be possible. Therefore, contact holes can be formed reliably regardless of how dense or dense the contact hole formation positions are.

0012

As is clear from the above description, according to the present invention, all contact holes can be reliably formed regardless of the distribution of contact hole formation positions.

[Brief explanation of the drawing]

FIGS. 1A and 1B are vertical cross-sectional views for explaining a method of forming a contact hole according to the present invention.

2A and 2B are vertical cross-sectional views for explaining the method of forming a contact hole according to the present invention, which is performed subsequent to the step of FIG. 1B.

FIGS. 3A and 3B are vertical cross-sectional views for explaining a conventional method of forming a contact hole.

[Explanation of symbols]

1a to 1c first aluminum wiring layer 2 insulating layer 3 semiconductor substrate
4 Polyimide resin layer (interlayer insulating film) 5 Titanium layer or silicon nitride film layer 6a to 6c
Contact holes 10a to 10c dummy pillars

Claims (1)

[Claims] 1. A contact hole forming method for forming a contact hole in an interlayer insulating film formed of polyimide resin, comprising: forming a dummy pillar at a contact hole formation position where the contact hole is to be formed; a step of forming a polyimide resin layer until the dummy pillar is completely covered; a step of etching the polyimide resin layer until the head of the dummy pillar is exposed; and a step of removing the dummy pillar to form a contact hole. A method for forming a contact hole, the method comprising: