JPH02121329A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent any Al spike from occurring without augmenting the contact resistance between an Si substrate and an Al wiring by a method wherein, during the formation process of Al films, an Ag film containing Si is higher concentration than the Si slid solubility at heat treatment temperature is formed in the first phase while another Al film containing Si in lower concentration than the Si concentration in the first phase is formed in the second phase. CONSTITUTION:The first layer insulating film 1 is deposited on an Si substrate 2. First, the photographic etching process is used together with the dry-etching process to remove oxide film 1 on the contact region for making a contact hole 3. Secondly, the Si substrate 2 is held on an anode of a sputtering device while the contact hole 3 is coated with the first phase Al film 4 as a wiring film on a cathode comprising Al-Si alloy (1wt.% of Si). Thirdly, the Al film 4 is coated with the second phase A film 5. In case of forming the second phase Al film 5, Al-Si alloy containing 0.4wt.% of Si is used for the cathode of the sputtering device while the second Al film 5 becomes another Al layer containing 0.4wt.% of Si.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of manufacturing a semiconductor device, and in particular, to a method of manufacturing a semiconductor device, and in particular, in manufacturing a highly integrated LSI, contact between a Si-containing Al film used as a wiring material and a Si substrate. The present invention relates to a method of manufacturing a semiconductor device in which the connection state of parts is improved.

[Conventional technology]

Conventionally, semiconductor devices have been fabricated by performing a hole-opening process (contact hole etching) on an insulating film on a Si semiconductor substrate, and then depositing AI, which is a wiring material, to form an Al wiring film on the semiconductor substrate. Manufacturing has been going on.

AI, which is a conventional wiring material, contains 1 to 2% Si (for example, LSI Handbook, p. 280, Ohmsha, 1984). The reason for containing Si is that during heat treatment,
This is to prevent the diffusion growth of AI (AI spike) into the Si substrate, which occurs as a reverse phenomenon of the diffusion of 31 from the Si substrate to the Al film. That is, by containing Si in Al, the diffusion of Si from the Si substrate into the AI is prevented, thereby preventing the diffusion of AI into the Si substrate, thereby avoiding the occurrence of AI spikes.

When this AI spike occurs, the source of the Si substrate.

Since AI grows through the drain, the substrate and the AI wiring film are short-circuited. Conventionally, such short circuits have been prevented by incorporating Si into the Al film.

[Problem to be solved by the invention]

However, the Si content of 1 to 2% by weight is
Heat treatment (sintering) temperature (400 to 500°C) to improve the electrical connection between the wiring film and the Si substrate
Since the solid solubility of Si is larger than that of Si, there is a problem in that during heat treatment, Si contained in the AI precipitates at the contact interface between the Si substrate and the AI wiring film, increasing the contact resistance. This problem has become particularly serious as the contact diameter becomes smaller as LSIs become more highly integrated.

In addition, conventionally, the solid solubility at the heat treatment temperature (0.28% by weight)
4400°C, o, so wt% 500°C, Hanse
n, M, Condition of binar
y alloys, McGraw-Hill, 195
8) The reason why a larger amount of Si was contained in the Al film is that in order to reliably prevent the diffusion of Si from the Si substrate to the Al wiring film, it is necessary to
This is because it needs to be included in I.

Therefore, according to the conventional semiconductor manufacturing method, there is a problem in that an increase in contact resistance between the Si, 33 board and the AI wiring cannot be avoided when trying to prevent AI spikes.

In order to solve such conventional problems, the present invention
It is an object of the present invention to provide a method for manufacturing a semiconductor device that can prevent the occurrence of AI spikes without increasing the contact resistance between the substrate and the AI wiring.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a semiconductor formed by performing hole-opening treatment on a Si substrate on which an insulating film is formed, forming an AI film containing Si on the substrate, and then heat-treating the Si substrate. In the method for manufacturing the device, the step of forming the AI film consists of a step of sequentially forming a plurality of Al films with different Si concentrations, and the first step of forming the AI film is based on the Si solid solubility at the heat treatment temperature. The second step is to form an AI film containing a high concentration of Si, and the next step of forming an AI film is to form an AI film containing a lower concentration of Si than the 5ifi degree of the first step. , is characterized by.

[Effect]

In the present invention, in the first step of forming an AI film, an AI wiring film with a high Si concentration is formed on the Si substrate. Therefore, during sinkling, Al
Since diffusion of Si into the film is blocked, generation of Al spikes can be prevented.

On the other hand, in the process of forming an AI film in the second and subsequent stages, an AI film containing low concentration of Si is formed on the AI film in the first stage.
A film is formed. Next, when heat treatment is performed, the first stage A
The Si in the I peritoneum diffuses into the AI peritoneum in the second stage, and the Si concentration becomes average, and the Si concentration in the AI peritoneum in the first stage can be reduced to the solid solubility or a value close to it.
It is possible to prevent Si from being deposited at the contact interface between the Si substrate and the AI film.

〔Example〕

Embodiments of the present invention will be described with reference to the process diagram shown in FIG.

First, the process shown in FIG. 1(1) will be explained.

Si semiconductor substrate "Orientation, (100), N type, ρ = 1 ~ 5
Ω・cm, diameter 75-100mmφ, thickness 450-600
MOS on a phosphorus-doped N-type Si single crystal wafer)
After forming the transistor element, a first layer insulating film 1 is grown on the Si substrate 2.

Next, using photolithography and dry etching, the oxide film 1 in the contact region is removed to form a contact hole 3.

Next, hold the Si substrate on the anode of a sputtering device,
On the other hand, the cathode of the spatter device is made of Al-S which is a wiring material.
A wiring film is formed on the contact hole 3 by holding an i alloy (containing 1% by weight of Si). First stage AI film 4 is deposited.

This first stage AI film 4 is formed to have a thickness of 20% of the total Al film thickness, and is an Al film containing 1% by weight of Si. After this first stage AI film 4 is formed, as shown in FIG.
As shown in the process, a second-stage Al film 5 is deposited on the AI film 4 in the same manner as in the sputtering process. This second
During the formation of the stage AI film 5, the cathode of the Svanta device is
．． An Al-Si alloy containing 4% by weight of Si is used, and the second stage Al film 5 is an Al layer containing 0.4% by weight of Si. This second stage AI film 5 is formed to have a thickness of 80% of the total Al film thickness.

After forming the second stage AI film 5, a pattern is formed using photolithography using a photoresist, and using the photoresist as a mask, unnecessary portions are removed by dry etching and the photoresist is washed away.

Next, by CVD method, A
A Si0g film (second interlayer insulating film) 6 is deposited on the I film 5. This second interlayer insulating film 6 connects the second AI wiring formed on this insulating film and the first AI wiring (Al film 4.
5).

After completing the formation of this second interlayer insulating film, the Si substrate is
A heat treatment for C230 minutes is performed to improve the electrical connection between Si and AI in the contact hole 3 (sintering).

In the embodiment described above, the first stage AI film 4 includes:
It contains 1% by weight of Si. The concentration of this Si is
Since the solid solubility of Si in At at the processing temperature during sintering and formation of the second interlayer insulating film 5 is higher than the solid solubility of At (0.3 to 0.8% by weight), Si diffuses from the substrate 2 into the Al film 4. can be prevented. From this point of view, the first stage AI film 4
It is necessary that the Si concentration is sufficiently higher than the solid solubility of Si at the heat treatment temperature. Specifically, the Al film 4 is
It is desirable that Si be contained in an amount of about 0.8 to 2.0% by weight.

If the amount is less than 0.8% by weight, when forming the Al film 4, there will be a portion where the sN4 degree is low, and in this portion, the SN will be removed from the substrate 2.
This is because there is a possibility that i diffuses into the At film 4 and Al spikes are generated as a reverse reaction. On the other hand, if Si is contained in an amount exceeding 2.0% by weight, Si will precipitate during heat treatment and the contact resistance of the contact hole 3 will increase.

On the other hand, the second stage Al film 5 contains 0.4% by weight of Si. This concentration is approximately equal to the solid solubility of Si at the heat treatment temperature and is lower than the Si concentration of the first stage Al film 4.

The reason why the Si concentration of the second stage AI film is lower than that of the first stage Al film is that during the heat treatment, the Si contained in the first stage AI film 4 is stage Al
Diffuses into the film 5 and averages the Si concentration between the AI films 4° and 5, reducing the overall Si concentration, which prevents Si precipitation during heat treatment and increases contact resistance. This is because it becomes possible to avoid. From this point, 5ii4 degree in the Al film 5 in the second stage is equal to A in the first stage.
It is sufficient if it is lower than the I film 5, but it is desirable that the solid solubility is at or below the solid solubility at the heat treatment temperature at that time. In this example, a 5tfi degree of 0.3 to 0.8% by weight is preferred. If it is less than 0.3% by weight, A! Membrane 4 of 5
This is because the degree of ifi becomes lower than necessary, and as a result, there is a possibility that Si is diffused from the substrate 2 and the above-mentioned aluminum spike occurs. - On the other hand, if Si is contained in excess of 0.8% by weight, the Si concentration in the AI film 4.5 will increase, resulting in an increase in contact resistance due to Si precipitation. .

Next, the thickness of the Al films 4 and 5 will be considered.

In the above embodiment, the film thickness of the first stage Al film 4 is the total A
The thickness is 20% of that of the I film.

Since the AI film 4 has the function of preventing the diffusion of Si from the substrate 2, it is sufficient if it has a thickness sufficient to fulfill this function. Specifically, the thickness is preferably 20 to 50%. On the other hand, it is preferable that the thickness of the second stage Al film 5 is 50 to 80% of the thickness of the AI film 4.

Next, for a comparative example in which a single layer of AI containing 1% by weight of Si was formed on a Si substrate in which a contact hole 3 of 1.5 μm×1.5 μm was formed, the contact resistance was measured and found to be 308Ω. On the other hand, similarly 1.
When the contact resistance was measured for a Si substrate in which a contact hole 3 of 5 μm x 1.5 μm was formed and two layers of AI film were formed based on the above example, it was 30Ω.
It became. From this experimental result, it can be seen that according to this example, the contact resistance is improved.

Further, when the substrate was cross-cut and visually observed under a microscope to determine whether aluminum spikes were generated, no aluminum spikes were observed.

In the embodiments described above, the Al film is formed in two stages, but the invention is not limited to this, and it is also possible to form the Al film in three or more stages. At this time, AI from the second stage onward
The Si1 degree of the film is formed to be lower than the Si1 degree of the first stage Al film. And the second. It is also possible to sequentially lower the Si concentration as it progresses to the third stage.

In the above embodiment, the AI film 4.5 was formed by sputtering, but it may also be formed by chemical plating, CVD, or vacuum evaporation.

The method of the present invention described above applies to bipolar integrated circuits, MO
It is possible to apply the present invention to various semiconductor devices such as 3 integrated circuits.

〔Effect of the invention〕

As explained above, according to the method for manufacturing a semiconductor device according to the present invention, the step of forming an Al film consists of the step of sequentially forming a plurality of AI films with different Si concentrations, and the first step of forming the Al film is is to form an AI film containing Si at a concentration higher than the Si solid solubility at the heat treatment temperature, and the next step of forming an AI film is to
To provide a semiconductor device which can prevent the occurrence of AI spikes without increasing the contact resistance between the Si substrate and the Al wiring because it forms an AI film containing Si at a concentration lower than i1 degrees. I can do it.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the steps of an embodiment of the present invention.

Claims (1)

[Claims] (1) A method for manufacturing a semiconductor device, in which a Si substrate on which an insulating film is formed is subjected to hole-opening treatment, an Al film containing Si is formed on the substrate, and then a heat treatment is performed. The step of forming a plurality of A
The first stage of the Al film forming step is to form an Al film containing Si at a higher concentration than the Si solid solubility at the heat treatment temperature,
A method for manufacturing a semiconductor device, wherein the next step of forming an Al film is to form an Al film containing Si at a lower concentration than the Si concentration in the first step.