JPH0786401A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To restrain imperfect contact and increase of wiring resistance, and improve reliability of wiring, regarding the wiring formation of a multilayered structure of high melting point metal (upper layer)/Al, alloy (lower layer). CONSTITUTION:(1) Process wherein an Al alloy film 4 and a high melting point metal film 5 are formed in order on a semiconductor substrate 1 is prepared, and the film formation temperature of the Al, alloy film is made higher than that of the high melting point metal film 5. (2) The Al alloy film 4 does not contain Si. (3) TiN is used as the high melting point metal film 5 and Al-Cu-Ti (0.15% or lower) alloy is used as the Al alloy film 4. (4) The film formation temperature of the high melting point metal film 5 is set to be 400 deg.C, and preliminarily heating is performed within 10 seconds. (5) The film formation temperature of the Al alloy film 4 is set to be 500 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming wiring using a laminated film of refractory metal (upper layer) / aluminum (Al) alloy (lower layer).

[0002]

2. Description of the Related Art In a conventional semiconductor device, a single-layer Al alloy film or a laminated structure of an Al alloy film (upper layer) / refractory metal film (lower barrier metal) has been used as a wiring film.

However, with the miniaturization of the device, the reliability of the connection becomes a problem when connecting the upper and lower wirings through the contact holes formed in the interlayer insulating film, and a refractory metal film is further formed on the Al alloy film. is doing. Therefore, it has a three-layer structure of upper refractory metal film / Al alloy film / lower refractory metal film (barrier metal). The formation of the lower refractory metal film is a necessary technique for contacting the base,
Since it is not directly related to the present invention, it is omitted in the following description of the present invention, and the laminated structure of the upper refractory metal film / Al alloy film will be described.

[0004]

[Problems to be Solved by the Invention] Conventionally, there are the following problems when a refractory metal film is formed on an Al alloy film.

Since the refractory metal is deposited on the Al alloy, grain growth of Al due to the heat treatment in the subsequent process is suppressed, and the reliability of the wiring is inferior to that when the wiring is not stacked. In order to increase the Al grains before forming the refractory metal, increasing the Al film formation temperature causes silicon (Si) to be contained.
In Al alloys (for example, Al-Si-Cu), Si nodules (lumps,
The nodules become large, leaving a residue in the wiring formation process.

As the upper refractory metal film / Al alloy film,
In the TiN / Al-Cu-Ti laminated structure, Ti in TiN is Al-C.
It diffuses into u-Ti, and Ti exceeding the solid solution limit (0.15%) of the Al-Cu-Ti metal becomes excessive and exists at the grain boundaries, hindering grain growth.

If the film forming temperature of the refractory metal is 400 ° C. or higher, and if preheating is performed for about 30 seconds even at 400 ° C. or lower, hillocks are formed on the Al alloy film during the film formation of the refractory metal.
(Protrusions) are generated and become residues on the assumption that the wiring is formed.

If a refractory metal formed at a high temperature is used to improve the film quality, the above problem occurs. If a contact hole is opened in the interlayer insulating film on the upper refractory metal film / Al alloy film and heat treatment is performed in the opened state, the refractory metal is oxidized and contact failure occurs with the upper wiring.

In the laminated structure of the upper refractory metal film / Al alloy film, if the heat treatment temperature in the subsequent step is high, the sheet resistance of the wiring increases and a low wiring resistance cannot be obtained. The present invention solves the above problems and solves the problem of the upper refractory metal film / Al.
The purpose of the present invention is to improve the reliability of the wiring by suppressing the contact failure of the upper and lower wiring and the increase of the wiring resistance of the laminated structure of the alloy film.

[0010]

[Means for Solving the Problems] 1)
There is a step of sequentially forming an aluminum or aluminum alloy film 4 and a refractory metal film or refractory metal compound film 5 on the semiconductor substrate 1, and the film formation temperature of the aluminum alloy film is set to the film formation temperature of the refractory metal film. Semiconductor device manufacturing method in which the temperature is higher than the film temperature, or 2) the aluminum alloy film 4
Is a method for manufacturing a semiconductor device as described in 1) above, which does not contain silicon, or 3) uses titanium nitride (TiN) for the refractory metal film 5, and the aluminum alloy film (4)
Aluminum (Al) -copper (Cu) -titanium (Ti) alloy is used for
And the method for manufacturing a semiconductor device according to 1), wherein the concentration of titanium is 0.15% or less, or 4) the refractory metal film.
The film-forming temperature of 5 was 400 ° C, and the film-forming temperature was 10
1) The method for manufacturing a semiconductor device according to 1) above, wherein the preheating is performed for a time of not more than 2 seconds;
This is achieved by the method for producing a semiconductor device according to 1), wherein the film forming temperature is 500 ° C. or higher.

[0011]

In the present invention, in the upper layer refractory metal film / Al alloy film laminated structure, the Al alloy film formation temperature is raised and the refractory metal film formation temperature is lowered below this temperature. By increasing the Al film formation temperature before, the Al grains grow, and by decreasing the refractory metal film formation temperature, Al hillocks are not generated after the refractory metal film formation. .

Further, in the present invention, the temperature at the time of load-in / out of the wafer to / from the heat treatment apparatus is determined so that the refractory metal exposed in the contact hole is not oxidized by the heat treatment in the subsequent step, and the wiring resistance In order to prevent the rise, the maximum heat treatment temperature in the subsequent process is set.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view for explaining an embodiment of the present invention. This example shows the first layer wiring of 16M SRAM. Semiconductor substrate
A contact hole is formed in the interlayer insulating layer 2 deposited on the layer 1. Then, a TiN film with a thickness of 100 nm / 20 nm is formed as a barrier metal film (lower refractory metal film) 3 by sputtering or the like.
A laminated film consisting of two layers (upper layer) / Ti (lower layer) is applied.

Next, in order to improve the barrier property between the upper and lower layers and prevent electromigration of the upper Al alloy film, annealing of the barrier metal was performed in a nitrogen (N ₂ ) atmosphere.
Perform at 50 ℃ for 30 minutes.

Next, the step of forming the laminated structure of the upper refractory metal film / Al alloy film, which is the step of the present invention, is started. Al alloy film 4
Al-0.1% Cu-0.1% Ti alloy was used as the
Form a film with a thickness of 350 nm at ℃. Here, the Ti concentration is set to 0.15% or less, which is the solid solution limit in the alloy, and the excess titanium is Al
It is not deposited on the grain boundaries and hinders grain growth (corresponding to claim 3).

As the upper refractory metal film 5, a refractory metal compound film TiN is used, and the film is continuously grown in the same vacuum at 300 ° C. for 10 nm.
The film is formed to a thickness of (corresponding to claim 3). As described above, the temperature of the upper refractory metal film 5 is higher than that of the Al alloy film 4, and the Al grains are grown before the upper refractory metal film 5 is formed to improve the reliability of the wiring. Has been improved (claim 1
Correspondence).

Here, as the Al alloy film 4, since the Al-Si-Cu alloy that has been conventionally used produces Si nodules and remains as a residue even at this temperature, it is better not to use an Al alloy containing Si ( Corresponding to claim 2).

Before the upper refractory metal film (TiN) 5 is formed, preheating is performed at the film forming temperature, but this time was shortened to 5 seconds. The reason for performing preheating before TiN film formation is to degas the wafer in order to obtain good film quality and to perform film formation after stabilizing the film formation temperature by preheating. The minimum preheating time is based on the time during which the gas pressure in the film deposition system stabilizes, and the time during which the discharge within the film deposition system stabilizes is selected. If the preheat time exceeds 10 seconds, hillocks of Al will occur, so this time should be maximized. (Corresponding to claim 4).

Further, it has been known that the TiN / Al interdiffusion is suppressed as the TiN film forming temperature increases. For example, Ti
When N is formed at 500 ° C, the film quality is better than when it is formed at 300 ° C (see Fig. 2).

FIG. 2 is a diagram showing the heat treatment temperature dependence of the sheet resistance due to the mutual diffusion of TiN / Ti. In the figure, the parameters are
The TiN / deposition temperature is shown in (1) when TiN is formed at 500 ℃ and (2) when TiN is formed at 300 ℃.

When TiN is formed on Al at 500 ° C., hillocks are generated in Al. The hillocks can be prevented by forming Al at a higher temperature, for example, 550 ° C. (corresponding to claim 5).

Next, the wiring film having the three-layer structure is patterned to form wiring, and the interlayer insulating film 6 is deposited on the wiring,
A contact hole 7 for the upper wiring is formed. After opening the contact hole 7, heat treatment is usually performed for degassing the interlayer insulating film and the side wall of the contact hole.

In this heat treatment, load-in is performed at 300 ° C. in a nitrogen atmosphere, annealing is performed at 400 ° C. (corresponding to claim 7) for about 30 minutes, and load-out is performed at 300 ° C. If the load-in / out temperature is higher than 350 ° C, the wiring will be oxidized, so the temperature should be below this temperature. (Corresponding to Claim 6) FIG. 3 is a graph showing the elapsed time dependence of the change rate of the sheet conductance due to the mutual diffusion of TiN / Ti.

In the figure, the parameter indicates the heat treatment temperature,
(1) is heat treatment at 400 ℃ and (2) is heat treatment at 450 ℃.
From this result, the heat treatment in the post process after the wiring formation is performed at a temperature of 400 ° C. or less (corresponding to claim 7).

In the embodiment, the Al alloy film is used as the lower wiring film of the upper refractory metal film, but the present invention can be applied by using pure Al instead. Although TiN was used as the upper refractory metal compound film, Ti may be used instead of TiN or other refractory metal film (high melting point gold compound film).
The present invention can be applied by using

[0026]

According to the present invention, refractory metal (upper layer) /
The reliability of the wiring was improved by suppressing contact failure and increase in wiring resistance of the wiring of the laminated structure of Al alloy (lower layer).

[Brief description of drawings]

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

FIG. 2 is a diagram showing the heat treatment temperature dependence of sheet resistance due to TiN / Ti interdiffusion.

FIG. 3 is a diagram showing the elapsed time dependence of the change rate of the sheet conductance due to the TiN / Ti interdiffusion.

[Explanation of symbols]

1 semiconductor substrate 2 interlayer insulating layer 3 barrier metal film (lower layer refractory metal film) made of TiN (upper layer) / T
i (lower layer) film 4 Al alloy film, Al-0.1% Cu-0.1% Ti film 5 Upper layer, refractory metal film, TiN film 6 Upper interlayer insulating film 7 Contact hole opened in upper interlayer insulating film

Claims (5)

[Claims] 1. A metal film (4) containing aluminum and a refractory metal film or refractory metal compound film on a semiconductor substrate (1).
(5) is sequentially formed, and the film forming temperature of the aluminum alloy film is set higher than the film forming temperature of the refractory metal film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the aluminum alloy film (4) does not contain silicon as a component. 3. A titanium nitride (Ti) is formed on the refractory metal film (5).
N) is used, an aluminum (Al) -copper (Cu) -titanium (Ti) alloy is used for the aluminum alloy film (4), and the titanium concentration is 0.15% or less. A method for manufacturing a semiconductor device as described above. 4. The deposition temperature of the refractory metal film (5) is set to 400.
2. The method for manufacturing a semiconductor device according to claim 1, wherein preheating is performed at a film forming temperature of 10 seconds or less before film forming. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the film forming temperature of the aluminum alloy film (4) is 500 ° C. or higher.