JPH06224310A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To increase the area of a contact and to lower the resistance of the contact by forming a second conductive layer to be insulated from the first conductive layer on the sidewall of a contact hole, filling in the contact hole and a slit with a third conductive layer, and obtaining a contact with the first conductive layer. CONSTITUTION:A first conductive layer 13 is formed on a semiconductor substrate 11, and a second conductive layer 14 is formed on the sidewall of a contact hole formed in a first insulating film 12 on the semiconductor substrate 11. On the second conductive layer 14, a second insulating film 15 is formed. Besides, a thin third insulating film 16 is formed on the sidewall of the contact, and a conductive sidewall 17 composed of polycrystalline silicon is formed on it. Furthermore, a slit 18 is formed at the bottom part of the conductive sidewall 17, and a contact with the first conductive layer is obtained by filling in the insides of the contact hole and the slit 18. Accordingly, it becomes possible to form a low-resistance contact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a method of manufacturing a contact thereof.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field,
For example, there were the following. 3 and 4
FIG. 3 is a sectional view of such a conventional semiconductor device. First, FIG.
As shown in, a contact hole 3 is opened in an insulating film 2 made of a first insulating material on a silicon substrate 1, and a sidewall 5 made of a second insulating material is formed around the contact hole 3.
A conductive film 6 made of a conductive material is in contact with the high-concentration impurity diffusion layer 4 near the surface of the silicon substrate. This allows
When the conductive film 6 is wired, the conductive film 6 and the high-concentration impurity diffusion layer 4 are electrically connected. Incidentally, 7 is another conductive film.

However, as shown in FIG. 4, a misalignment ΔL ₁ such as photolithography occurs at the time of contact opening,
Even when the other conductive film 7 is exposed in the contact hole 3, the sidewall 5 serves as an insulator. Hereinafter, a method of manufacturing the semiconductor device shown in FIG. 4 will be described. First, after the contact hole 3 is opened, a wiring portion exposed in the contact hole 3 is insulated by a misalignment ΔL ₁ such as contact photolithography. Therefore, an insulating film having a thickness larger than that of the wiring portion ΔL ₁ is formed. Isotropically grown, then etched back by anisotropic etching, sidewalls 5 are formed, impurities are implanted by ion implantation, and annealing for impurity activation is performed to form high-concentration impurity diffusion layers 4. After that, the conductive film 6 is grown to make contact with the high-concentration impurity diffusion layer 4.

[0004]

However, in the above-described conventional semiconductor device, since the insulating sidewall is formed, there is a problem that the contact area is reduced and the contact resistance is increased. This means that if a sidewall having a width of Y μm is formed in the contact opening diameter φX μm, the contact diameter becomes substantially φ (X−2Y).

The contact resistance R _c is R _c = R as compared with the resistance R _co when the sidewall is not formed.
_co the ^{[X 2 / (X-2Y)} 2 ]. Here, when the sidewall width is constant, there is a problem that the contact resistance R _c becomes extremely high when the contact opening diameter X is reduced due to the miniaturization of the element.

Further, when the contact misalignment ΔL ₁ occurs, the insulating film for forming the side wall is required to have a film thickness exceeding ΔL ₁ at least, and the contact resistance R _c is remarkably increased. There was a problem. The present invention has a low-resistance contact structure in which a thin insulating film is formed on the sidewall in order to eliminate the problem of increasing the contact resistance due to the reduction of the contact area due to the formation of the sidewall made of the insulating material. An object is to provide an excellent method for manufacturing a semiconductor device.

[0007]

In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor device in which a contact hole is formed on a semiconductor substrate having a first conductive layer, in which a sidewall of the contact hole is provided. Forming a second conductive layer insulated from the first conductive layer, forming a sidewall of the contact hole, and forming a slit in the bottom of the sidewall by isotropic etching. And a step of burying a third conductive layer in the contact hole and the slit to obtain a contact with the first conductive layer.

Further, in the method of manufacturing a semiconductor device in which a contact hole is opened on a semiconductor substrate having a first conductive layer, a second conductive layer insulated from the first conductive layer on a sidewall of the contact hole. Forming a thin insulating film in the contact hole, forming a sidewall by anisotropic etching of the insulating film, and using the sidewall as a mask, the thin insulating film at the bottom of the sidewall is formed. The film isotropically etched to form a slit, and the contact hole and the slit are filled with a third conductive layer to obtain a contact with the first conductive layer. It is a thing.

[0009]

According to the present invention, as described above, the step of forming the second conductive layer which is insulated from the first conductive layer on the side wall of the contact hole, and the side wall of the contact hole are formed. A step of forming a slit in the bottom of the sidewall by isotropic etching, and a step of filling a third conductive layer in the contact hole and the slit to obtain a contact with the first conductive layer. And apply.

In addition, a step of forming a second conductive layer which is insulated from the first conductive layer on the side wall of the contact hole, a step of growing a thin insulating film in the contact hole, and anisotropy of the insulating film. Forming a sidewall by reactive etching, and using the sidewall as a mask,
Isotropically etching the thin insulating film at the bottom of the sidewall to form a slit; and filling the contact hole and the slit with a third conductive layer to form the first conductive layer.
And a step of obtaining a contact with the conductive layer.

Therefore, it is possible to insulate the portion where misalignment occurs during the formation of the contact hole with the thinnest possible insulating film, increase the contact area, and form a contact with low resistance. it can.

[0012]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a semiconductor device showing a first embodiment of the present invention. As shown in this figure, the semiconductor substrate 11 has a first conductive layer (high-density impurity diffusion layer).
13 is formed, the second conductive layer 14 is formed on the side wall of the contact hole formed in the first insulating film 12 on the semiconductor substrate 11, and the second conductive layer 14 is formed on the second conductive layer 14. The second insulating film 15 is formed. Further, a thin third insulating film 16 is formed on the side wall of the contact hole, and the conductive side wall 1 made of polycrystalline silicon is formed thereon.
7 are formed. Further, a slit 18 is formed at the bottom of the conductive sidewall 17, and a third conductive layer 19 is filled in the contact hole and the inside of the slit 18 to obtain a contact with the first conductive layer 13. Is configured.

With this structure, the contact opening 20 is formed.
Even if a misalignment ΔL ₂ occurs in the photolithography process and an opening is formed on the second conductive layer 14 that should be insulated,
A short circuit is prevented by the third insulating film 16. Furthermore,
Since the third conductive film 19 is embedded in the slit 18, the contact area is large. Then the first
A method of manufacturing the semiconductor device of the embodiment will be described.

FIG. 2 is a sectional view of a semiconductor device manufacturing process showing the first embodiment of the present invention. First, as shown in FIG. 2A, a 5000 Å first interlayer insulating film 22, a 1000 Å N-type polycrystalline silicon film (second conductive layer) 23, a 5000 Å first P-type silicon substrate 21 are formed. Interlayer insulating film 2
4 are successively grown, and then a contact hole 25 of φ0.5 μm is opened by photolithography etching.
Here, this is an example of the case where the misalignment ΔL ₃ occurs due to the photolithography process. Next, the N-type impurity diffusion layer (first conductive layer) 26 which is the first conductive layer is formed.

Next, after forming the N-type impurity diffusion layer 26,
As shown in FIG. 2B, after the insulating film 28 of about 300Å is isotropically grown (for example, NSG growth by the CVD method), N
A conductive film 29 made of polycrystalline silicon is grown by the CVD method. At this time, the thickness of the conductive film 29 is set larger than the misalignment ΔL _{3 of} photolithography. Next, as shown in FIG. 2C, the conductive film 29 is etched back by anisotropic etching to form sidewalls 30. At this time, the conductive film 29 is thicker than the misalignment ΔL ₃ , so that the insulating film at the edge portion 31 of the N-type polycrystalline silicon film 23 is not exposed by controlling the amount of etch back. To

Next, as shown in FIG. 2D, the insulating film 28 is isotropically etched by using the sidewall 30 as a mask, and a slit 32 is formed at the bottom of the sidewall 30.
To form. Next, as shown in FIG. 2E, the third conductive layer 33 is isotropically grown to form a contact.

Next, a method of manufacturing the semiconductor device of the second embodiment will be described. FIG. 5 is a sectional view of a semiconductor device showing a second embodiment of the present invention. As shown in this figure, a first interlayer insulating film 42, such as N, is formed on a P-type silicon substrate 41.
SG5000Å is formed, and a second conductive layer 43 electrically separated from the substrate, for example, an N-type polycrystalline silicon film 1000Å is formed on the first interlayer insulating film 42, and a second conductive layer 43 is formed thereon. The interlayer insulating film 44, for example, NSG5000Å
Is growing. Therefore, a contact hole is formed,
A thin sidewall such as C in the contact hole
The silicon nitride film 45 is isotropically grown to about 200Å by the VD method, the contact hole is filled with the third conductive layer 47, and the N-type impurity diffusion layer (first conductive layer) 46 is contacted. Here, the first conductive layer 43 and the second conductive layer 47 are sidewalls of the silicon nitride film 4 which is a sidewall.
Insulated by 5.

FIG. 6 is a sectional view of a semiconductor device manufacturing process showing the second embodiment of the present invention. First, as shown in FIG. 6A, the first interlayer insulating film 5 is formed on the P-type silicon substrate 51.
2. Grow NSG 5000Å, for example. In addition, the second conductive layer 53 electrically separated from the substrate, for example, N
Type polycrystalline silicon film 1000Å is the first interlayer insulating film 52
A second interlayer insulating film 54, for example N.
SG5000Å is formed. In this state, contacts are opened by photolithography etching. At that time, the contact opening is misaligned with the second conductive layer 53, and Δ
L _{4 is} the overlap. On top of that, the third
As the insulating film, a silicon nitride film 57 is isotropically grown to about 200 Å by the CVD method, and a PSG 58 is grown to 1000 Å isotropically as the fourth insulating film. The thickness of the fourth insulating film is made thicker than ΔL ₄ . Further, 55 is a high concentration impurity diffusion layer (first conductive layer).

Next, as shown in FIG. 6B, the PSG 58 which is the fourth insulating film is etched back by anisotropic etching. Since the fourth insulating film 58 is thicker than the misalignment ΔL ₄ , the third insulating film 57 is not exposed in the contact hole at the contact sidewall portion, and the sidewall 59 is formed by the fourth insulating film. Next, as shown in FIG. 6C, the silicon nitride film 57 as the third insulating film is isotropically etched using the sidewalls 59 made of the fourth insulating film as a mask. At this time, the etching amount is such that an insulating film that can electrically separate the second conductive layer 53 remains.

Next, as shown in FIG. 6D, the sidewall 59 is removed by isotropic etching. Finally, as shown in FIG. 6E, the second conductive layer 60 is grown by the CVD method or the like to complete the contact. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0021]

As described above in detail, according to the present invention, it is possible to insulate a portion where misalignment occurs during formation of a contact hole with an insulating film which is as thin as possible, thereby increasing the contact area. And a low resistance contact can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor device in the manufacturing process showing the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional semiconductor device.

FIG. 4 is a cross-sectional view of a conventional semiconductor device in which misalignment of photolithography of contact holes has occurred.

FIG. 5 is a sectional view of a semiconductor device showing a second embodiment of the present invention.

FIG. 6 is a sectional view of a semiconductor device manufacturing process showing the second embodiment of the present invention.

[Explanation of symbols]

11 semiconductor substrate 12 first insulating film 13 first conductive layer 14, 43, 53, 60 second conductive layer 15 second insulating film 16 thin third insulating film 17 conductive sidewall 18, 32 slits 19, 33, 47 third conductive layer 20 contact openings 21, 41, 51 P-type silicon substrate 22, 42, 52 first interlayer insulating film 23 N-type polycrystalline silicon film (second conductive layer) Layer) 24, 44, 54 Second interlayer insulating film 25 Contact hole 26, 46 N-type impurity diffusion layer (first conductive layer) 28 Insulating film 29 Conductive film 30, 59 Sidewall 31 Edge part 45, 57 Silicon nitride film 55 High-concentration impurity diffusion layer (first conductive layer) 58 Fourth insulating film (PSG) ΔL _{2 to} ΔL ₄ Misalignment

Claims (2)

[Claims] 1. A method for manufacturing a semiconductor device having a contact hole opened on a semiconductor substrate having a first conductive layer, comprising: (a) a second side wall insulated from the first conductive layer on a side wall of the contact hole. Forming a conductive layer; (b) forming a sidewall of the contact hole; (c) forming a slit by isotropic etching on the bottom of the sidewall; (d) the contact. And a step of filling a hole and a slit with a third conductive layer to obtain a contact with the first conductive layer. 2. A method for manufacturing a semiconductor device having a contact hole opened on a semiconductor substrate having a first conductive layer, comprising: (a) a second side wall insulated from the first conductive layer on a side wall of the contact hole. A step of forming a conductive layer, (b) a step of growing a thin insulating film in the contact hole, (c) a step of forming a sidewall by anisotropic etching of the insulating film, (d) the side Isotropically etching the thin insulating film at the bottom of the sidewall using the wall as a mask to form a slit, and (e) filling the contact hole and the slit with a third conductive layer to form the first conductive layer. And a step of obtaining a contact with the conductive layer.