JPH1167908A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device with an improved step coverage and a contact hole, and to provide a manufacturing method of the semiconductor device. SOLUTION: In a semiconductor device which is connected through a contact hole 4, wherein the conductors 6 and 7 to be arranged on the upper and the lower sides of an insulating film 2 or a semiconductor, is provided on the insulating film 2, the contact hole 4 is provided in two stage form, and side faces 41 and 42 of the two-staged contact hole are formed in to a tapered shape. The taper angle θ2 of the lower stage of the two staged contact hole has an angle smaller than the taper angle θ1 of the upper stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device for connecting conductors or semiconductors disposed above and below an insulating film via contact holes provided in the insulating film, and a method of manufacturing the same. More specifically, the present invention relates to a semiconductor device in which the shape of a contact hole provided in an insulating film is improved to improve the step coverage of a metal wiring provided in the contact hole, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a conventional semiconductor device such as an IC, a complicated circuit formed on a semiconductor substrate is connected by wiring.
In some cases, wiring is formed in multiple layers via an interlayer insulating film. In this case, there is no room between the patterns as the circuit is integrated, and the size of the contact hole provided in the insulating film needs to be accurately formed with a certain size. Therefore, the contact holes are formed by anisotropic etching so as to be formed perpendicular to the pattern of the mask. However, if an insulating film having a thickness of about 1 μm is completely formed as a vertical contact hole, metal wiring is difficult to be deposited on the vertical portion, step coverage is deteriorated, and current density per unit area is increased. In addition, electromigration resistance deteriorates. Therefore, in order to improve the step coverage, various etching methods that combine isotropic wet etching, isotropic dry etching, and anisotropic dry etching have been disclosed. For example, Japanese Patent Application Laid-Open No. 8-191103 discloses An opening method is disclosed in which an opening is formed by anisotropic dry etching so as to have the same size as the mask pattern in about the lower half of the insulating film, and an isotropic wet etching or dry etching is performed on the upper side. I have.

That is, in this method, for example, as shown in FIG.
A resist mask 3 is provided on an insulating film 2 provided on a surface of a semiconductor substrate 1, and an opening 30 for forming a necessary contact hole 4 is formed. Then, about 1/4 of the thickness of the insulating film is etched by isotropic wet etching, and then about 1/4 of the thickness of the insulating film is further etched by isotropic dry etching. This is performed by isotropic dry etching. As a result, as shown in FIG. 3, the thickness of the insulating film 2 on the side of the semiconductor substrate 1 is about half the thickness of the vertical contact hole 4, and the upper half is formed in a tapered shape.

[0004]

As described above, when the upper half of the insulating film is formed into a tapered shape by isotropic etching and the remaining portion is formed vertically by anisotropic etching, about half of the insulating film is formed. However, the coverage of the metal layer in the vertical portion is poor, and disconnection or the like is likely to occur at the corner. On the other hand, if the depth of the isotropic etching is close to the back surface of the insulating film, the isotropic etching is likely to be etched in the lateral direction, so that a contact hole having an accurate size (dimension) is formed. There is a problem that it is difficult.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a semiconductor device having a contact hole with improved step coverage and a method of manufacturing the same.

[0006]

In a semiconductor device according to the present invention, conductors or semiconductors provided above and below an insulating film are connected via contact holes provided in the insulating film. The two-stage contact hole is formed in a tapered shape, and both side surfaces of the two-stage contact hole are formed in a tapered shape, and the taper angle of the lower inner stage of the two stages is smaller than that of the upper stage. Is formed.

Here, the tapered shape means that the side surface of the contact hole is inclined with respect to the vertical direction. Even when the side surface is bowl-shaped and the cross section is not straight, the line connecting the upper and lower ends is inclined. In this case, the angle of the taper means a line connecting the upper and lower ends or an average inclination angle.

By forming the contact hole in such a two-stage shape, the vertical portion of the contact hole where the step coverage becomes a problem can be made much thinner than the thickness of the metal wiring deposited thereon. Therefore, a sufficiently reliable step coverage can be obtained, and the size of the contact hole can be accurately controlled.

A method of manufacturing a semiconductor device for obtaining a contact hole having such a shape is as follows. (A) A resist film is provided on the insulating film to provide an opening, and (b) an isotropic film is formed using the resist film as a mask. The insulating film is etched by wet etching, and (c) the remaining portion of the insulating film is etched by dry etching in which an isotropic element is added to the anisotropic element.

[0010]

Next, a semiconductor device of the present invention and a method of manufacturing the same will be described with reference to the drawings.

As shown in FIG. 1, a semiconductor device according to the present invention has, for example, a first metal wiring 6 and a first metal wiring 6 on a first insulating film 5 on a semiconductor substrate 1. The second metal wiring 7 is provided via the insulating film 2, and the first metal wiring 6 and the second metal wiring 7 are electrically connected via the contact hole 4 provided in the insulating film 2. . In the present invention, as shown in FIG. 1, the contact hole 4 is formed in a two-stage shape, and the side surface is provided so as to have a tapered shape (bowl-shaped curved surface). The inclination angle θ2 between the lower side surface 42 of the first metal wiring 6 and the vertical direction (the angle between the average inclined surface of the curved surface and the vertical direction) is the inclination angle of the upper side surface 41 with the vertical direction. It is characterized in that it is formed to be smaller than θ1.

The insulating film 2 has a thickness of about 0.5 to 1 μm.
Normal thickness of SiO_Two, Si_ThreeN_Four And B and P
BPSG, PSG, which are doped silicon oxide films,
Low melting point soft glass such as BSG is used. Ma
In addition, the first and second metal wirings 6 and 7 are
1, 0.5-1.3 μm thickness by Al-Si etc.
Is provided.

The contact hole 4 is formed as described below.
A first hole 4a (see FIG. 2B) having a large diameter formed by isotropic etching mainly using wet etching and formed at a depth of about half of the insulating film 2; It is formed in a two-stage shape with a small diameter second hole 4b mainly formed by anisotropic dry etching formed in the remaining portion. The angle θ1 between the side surface 41 of the first hole and the vertical direction is larger than the angle θ2 between the side surface 42 of the second hole and the vertical direction. That is, the first hole is formed by etching with a wet isotropic etchant, which is etched more in the horizontal direction than in the vertical direction, and the second hole is formed in the vertical direction more than the horizontal direction. It is formed by etching mainly using anisotropic dry etching which is often etched.

Next, a method of manufacturing the semiconductor device shown in FIG. 1 will be described with reference to FIG. In FIG. 2,
The semiconductor substrate 1 and the first insulating film 5 of FIG. 1 are omitted, and the upper part from the first metal wiring 6 is illustrated.

The first insulating made of (SiO ₂ which is formed of SiO ₂ and heat treatment was used as a mask when forming the element) to the transistor and the semiconductor substrate surface on which semiconductor elements are formed, such as a diode SiO ₂ A film is formed, and a first metal wiring 6 is formed thereon by vapor deposition of Al or the like and patterning. Then, FIG.
As shown in (1), an insulating film 2 made of, for example, a Si ₃ N ₄ film is formed thereon, and a resist film 3 is formed on the surface thereof. Then, patterning is performed such that an opening window 30 is formed on the contact hole formation location of the resist film 3.

Next, using the resist film 3 as a mask, H
Buffered hydrofluoric acid (BH) which is a mixed solution of F and NH ₄ F
F) isotropic wet etching is performed. At this time, the etching in the lateral direction proceeds faster than the etching in the depth direction due to the adhesion between the insulating film 2 and the resist film 3 described above. Therefore, etching is performed more in the horizontal direction than in the vertical direction, and a first hole 4a having a diameter larger than the opening window 30 of the resist film 3 is formed as shown in FIG. Since the side surface 41 of the first hole 4a is largely etched in the lateral direction on the front surface side, the diameter decreases as it becomes deeper, and is formed in a tapered shape that forms an angle of θ1 with the vertical direction. The angle θ1 is relatively large because the etching in the lateral direction is fast. And, continuously, CF ₄
Dry etching using / O ₂ gas
About 10% of the thickness of the insulating film 2 is etched. This dry etching is performed for adjusting the remaining film. At this time, as shown in the figure, a bowl-shaped concave surface is formed.

Next, in a state where the resist film 3 is left as it is, dry etching having an isotropic element while having anisotropy is performed by a parallel plate type etching apparatus using SF ₆ gas as shown in FIG. As shown in (c),
The insulating film 2 is etched until the first metal layer 6 is exposed. Since this etching has an isotropic element, it is also etched in the horizontal direction. However, since the anisotropy mainly consisting of the etching in the vertical direction is mainly performed, the first hole 4a A second hole 4b having a small diameter is formed. Since the second hole 4b has a small amount of etching in the lateral direction, the second hole 4b is formed to be almost the same size as the diameter of the opening window 30 of the resist film 3 at the lowermost end of the insulating film 2 and at the upper end side in the lateral direction. The side surface 42 has a tapered shape and is formed so as to form an angle of θ2 with the vertical direction. Therefore, the taper angle θ2 is formed smaller than the taper angle θ1 of the first hole 4a.

Next, as shown in FIG.
The second metal wiring 7 is formed by forming a film by vapor deposition or the like and patterning it. And Si ₃
By forming a protective film 8 (not shown) (see FIG. 1) by depositing N ₄ or the like on the entire surface, the semiconductor device shown in FIG. 1 is obtained.

According to the present invention, since the contact holes are formed in two stages, the size of the first hole in the upper stage does not matter so much, and it is the first hole in the side wall having a large inclined surface. be able to. Then, it is only necessary to form the final precise dimension of the contact hole with the insulating film which is reduced to about half, and the control becomes very easy, and even if the etching including the isotropic element is performed, the precision is improved. Since the contact hole can be formed with a good size and the thickness of the second metal wiring laminated thereon is much larger, the step coverage does not become a problem. In addition, since the thickness of the insulating film is thin and the size of the contact hole can be easily controlled, the second hole can also be formed in a tapered shape so that the diameter increases as going upward. 1 (see FIG. 1) can be shifted in the lateral direction from the position of the diameter of the contact hole. As a result, the shortest distance L1 (see FIG. 1) of the second metal layer 7 on the lower corner A can be sufficiently increased, and there is no fear of disconnection. Of course, the shortest distance L2 of the second metal wiring 7 on the upper corner B (see FIG. 1) is also gently tapered, so that it can be made sufficiently large, and there is no fear of disconnection. Therefore, a very reliable step coverage can be obtained.

Further, according to the manufacturing method of the present invention, a two-stage contact hole is formed by a combination of isotropic wet etching and anisotropic dry etching including isotropic elements. Therefore, it is only necessary to form a resist mask once, and a two-stage contact hole can be formed by a simple manufacturing process.

In the above-described example, the connection between the first and second metal wirings is described. However, the same applies to the connection between the semiconductor substrate and the metal wiring. Further, the material of the insulating film is not limited.

[0022]

According to the present invention, the step coverage of the conductor or semiconductor connecting portion above and below the insulating film is improved through the contact holes provided in the insulating film, and the reliability of the semiconductor device is greatly improved. Get higher.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a structure of an embodiment of a semiconductor device of the present invention.

FIG. 2 is an explanatory cross-sectional view illustrating a manufacturing process of one embodiment of a method for manufacturing the semiconductor device of FIG. 1;

FIG. 3 is a diagram illustrating an example of a conventional method for forming a contact hole in a semiconductor device.

[Explanation of symbols]

 2 Insulating film 3 Resist film 4 Contact hole 6 First metal wiring 7 Second metal wiring 41 Side surface of first hole 42 Side surface of second hole θ1 Upper taper angle θ2 Lower taper angle

Claims (2)

[Claims] 1. A semiconductor device in which conductors or semiconductors provided above and below an insulating film are connected via contact holes provided in the insulating film, wherein the contact holes are formed in a two-stage shape. Each side surface of the step-shaped contact hole is formed in a tapered shape,
A semiconductor device in which the lower taper angle of the two stages is formed in a taper shape smaller in angle than the upper taper angle. 2. A method of manufacturing a semiconductor device in which conductors or semiconductors provided above and below an insulating film are connected through contact holes provided in the insulating film, wherein (a) a resist film is provided on the insulating film. An opening is provided, (b) the insulating film is etched by isotropic wet etching using the resist film as a mask, and (c) the remaining portion of the insulating film is dry-etched by adding an isotropic element to the anisotropy. A method of manufacturing a semiconductor device, characterized by etching.