JPH03120826A - Formation of metal wiring of semiconductor device - Google Patents

Abstract

PURPOSE:To restrain the generation of protrusions in metal wiring, and obtain a highly reliable semiconductor integrated circuit with high yield, by a method wherein the heat treatment after metal wiring is patterned is performed after an insulating film is formed so as to cover the metal wiring. CONSTITUTION:The following processes are included; a process wherein a metal wiring film 3 is stuck on a substrate 1 and then shaped into a metal wiring having a specified pattern, a process wherein an insulating film 5 is formed so as to cover the metal wiring, and a process wherein heat treatment is performed in an atmosphere containing hydrogen. For example, after functional elements like a transistor and the like are formed on a P-type Si substrate 1, a silicon dioxide film 2 is grown, and contact holes for connecting the functional elements are formed. An Al film 3 is formed and shaped into a specified pattern. After a silicon dioxide film 5 is formed so as to cover the Al film 3, heat treatment at 350-450 deg.C is performed in an atmosphere containing hydrogen, and the contact resistance of an N-type diffusion layer 4 and the Al film 3 is decreased. Thus the stabilizing process of a transistor is performed. After that, a silicon nitide film 6 is formed, and an aperture 7 for connection with an outer terminal is formed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for forming metal wiring in a semiconductor device.

[Conventional technology]

Conventionally, metal wiring of semiconductor devices such as semiconductor integrated circuits has been made of a metal containing aluminum as a main component. A conventional technique using metal wiring mainly composed of aluminum will be explained with reference to FIG.

FIGS. 3A to 3E are vertical cross-sectional views of semiconductor chips arranged in the order of steps for explaining a conventional method of forming metal wiring in a semiconductor device.

First, as shown in the 3rd U (a>), a P-type silicon substrate 1
After forming a functional element such as a transistor (the N-type diffusion layer 4 is shown as a representative) on top, it is deposited to a thickness of 0.8 mm using a known CVD technique.
A silicon dioxide film 2 having a thickness of μm is grown, and contact holes are formed for connections between functional elements. After depositing the aluminum film 3 to a thickness of 1.0 μm, it is shaped into an aluminum wiring using a known photoetching technique.

After that, in order to lower the contact resistance between the N-type diffusion layer 4 and the aluminum wiring (3) in the contact hole,
Perform heat treatment at ℃.

Usually, this heat treatment also serves to stabilize the transistor, so it is carried out in an atmosphere containing hydrogen (hydrogen gas and nitriding gas mixed at a ratio of approximately 1:1). At this stage, as shown in Figure 3 (b)
), the aluminum film 3 has protrusions 10a, 10
b may occur.

Thereafter, as shown in FIG. 3(c), a silicon dioxide film 9 is formed using CVD technology to protect the surface of the semiconductor chip.
A thickness of 2.0 μm is applied.

Then, as shown in FIG. 3(d), the photoresist film 1
Openings 7 are formed in the silicon dioxide film for connection to the semiconductor chip and external terminals using a photoetching technique using No. 1.

[Problem to be solved by the invention]

The conventional method for forming metal wiring in a semiconductor device described above is usually performed after shaping a metal film into a predetermined pattern for the purpose of lowering the contact resistance between the metal film and the N-type diffusion layer at the contact hole portion and for the purpose of stabilizing the transistor. 350 in an atmosphere containing hydrogen
A heat treatment is performed at a temperature of 450°C to 450°C. However, there is a drawback in that when a metal film containing aluminum as a main component is subjected to heat treatment at 350 DEG C. to 450 DEG C., protrusions (hillocks) are generated. This metal wiring protrusion is particularly likely to occur in wiring with a thick line width, and occurs on both the front surface (10a) and the side surface (10b).
As shown in Figure 2, the surface of the silicon dioxide film is exposed without being covered with the photoresist film, and the insulating film (
9) may be etched and the protrusions may be exposed. In addition, the protrusions 10b generated on the side surfaces of the metal wiring cause a short circuit with the adjacent metal wiring, lowering the manufacturing yield and hindering microfabrication.

[Means to solve the problem]

The method for forming metal wiring in a semiconductor device according to the present invention includes a step of depositing a metal film on a substrate and then shaping the metal wiring into a predetermined pattern, a step of forming an insulating film covering the metal wiring, and a step of forming an insulating film to cover the metal wiring. The process includes a step of performing heat treatment in an atmosphere containing

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) to 1(d) are longitudinal cross-sectional views of semiconductor chips arranged in the order of steps for explaining one embodiment of the present invention.

First, as shown in FIG. 1(a), a P-type silicon substrate 1
After forming a functional element such as a transistor (the N-type diffusion layer 4 is shown as a representative) on top, it is deposited to a thickness of 0.8 mm using a known CVD technique.
A silicon dioxide film 2 having a thickness of μm is grown, and contact holes are formed for connections between functional elements. An aluminum film 3 is formed to a thickness of 1.0 μm and shaped into a predetermined pattern by known photoetching. Using this state as a substrate, as shown in FIG. 1(b), a silicon dioxide film 5 with a thickness of 0.2 μm was formed covering the aluminum film 3 shaped by the plasma CVD method, and an atmosphere containing hydrogen was formed. (1:1 mixture of hydrogen gas and nitrogen gas) 350~4
A heat treatment is performed at 50° C. to lower the contact resistance between the N-type diffusion layer 4 and the aluminum film, and to stabilize the transistor.

Thereafter, as shown in FIG. 1(c), a silicon nitride film is formed to a thickness of 2.0 μm by CVD. And the first
As shown in Figure (d), an opening 7 for connection to an external terminal is provided using known photoetching.

In practice, if the thickness of the silicon dioxide film is 0.1 μm, the generation of protrusions during heat treatment can be suppressed.

Further, in the embodiment, a silicon dioxide film was formed before the heat treatment, and a silicon nitride film was formed after the heat treatment, but either the silicon dioxide film or the silicon nitride film may be deposited in two parts. In any case, first, the type and thickness of the insulating film covering the aluminum film must be such that it has sufficient mechanical strength to suppress the occurrence of hillocks during heat treatment, and is capable of permeating hydrogen to stabilize the functional element. It should be determined experimentally so that it can be done. The second insulating film is
Since the glabella insulating film and the cover insulating film are deposited to compensate for the insufficiency in the first insulating film, they may be omitted depending on the case.

FIGS. 2(a) and 2(b) are longitudinal sectional views of a semiconductor chip for explaining a modification of one embodiment.

After forming the contact hole as explained using FIG. 1, a titanium nitride film 8 with a thickness of 0.1 μm and an aluminum film 3 with a thickness of 1.0 μm are formed by sputtering, followed by known photoetching. 2(a)) to form a predetermined pattern. Thereafter, a silicon dioxide film 9 is formed to a thickness of 1.
Formed with a thickness of 0 μm and heated in an atmosphere containing hydrogen at 350~4
Heat treatment is performed at 50° C. (FIG. 2(b)). Then, as described in one embodiment, openings are provided in the silicon dioxide film on the aluminum wiring to obtain a semiconductor integrated circuit.

In this way, metal films are not limited to single-layer aluminum films;
It may be a metal thin film or a multilayer film containing aluminum as a main component. Further, since silicon dioxide film is more permeable to hydrogen than silicon nitride film, functional elements such as transistors can be stabilized even when deposited to a thickness of 1 to 2 μm.

Further, in the embodiment, a contact structure between an aluminum wiring and an N-type diffusion layer has been described, but the present invention can also be applied to a contact structure between an aluminum wiring and other wiring layers such as a P-type diffusion layer or a polycrystalline silicon wiring layer. Can be applied.

〔Effect of the invention〕

As explained above, in the present invention, by performing heat treatment after patterning the metal wiring after forming an insulating film, it is possible to suppress the occurrence of protrusions on the metal wiring, thereby increasing reliability and manufacturing yield. This has the effect of making it possible to obtain a semiconductor integrated circuit with good quality.

[Brief explanation of the drawing]

Figure 1 (a) to (d), Figure 2 (a), (b) and Figure 3
Figures (a) to (e) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining an embodiment of the present invention, a modification of the embodiment, and a conventional example, respectively. 1... P-type Si substrate, 2... Silicon dioxide film, 3
... Aluminum film, 4... N-type diffusion layer, 5...
Silicon dioxide film, 6... Silicon nitride film, 7...
Opening, 8...Titanium nitride film, 9...Silicon dioxide film, 10a, 10b...Protrusion, 11...Photoresist film.

Claims (2)

[Claims] (1) A step of depositing a metal film on a substrate and then shaping it into metal wiring in a predetermined pattern, a step of forming an insulating film covering the metal wiring, and a step of performing heat treatment in an atmosphere containing hydrogen. A method for forming metal wiring in a semiconductor device, the method comprising: (2) The method for forming metal wiring in a semiconductor device according to claim (1), wherein the metal film has at least one metal thin film containing aluminum as a main component.