JP2557916B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to planarizing an insulating film covering a stepped portion such as wiring formed on a substrate. Regarding the method.

(Prior Art) In manufacturing a semiconductor device, an insulating film is usually formed on a semiconductor element or a wiring in order to maintain an insulating property from other regions. In this case, since the wiring or the semiconductor element usually has a step, the surface of the insulating film covering the wiring or the semiconductor element becomes uneven. Particularly in the corners of the unevenness of the insulating film, more stress is applied than in other parts, and therefore, there is a problem that the insulating property cannot be maintained, such as cracks in the insulating film.

In particular, this problem is remarkable in the multi-layer wiring structure used in recent years with the increase in capacity and integration of semiconductor devices. That is, in the case of forming the semiconductor device having the multilayer wiring structure, the wiring layer and the interlayer insulating film are repeatedly laminated, but the repetition causes a steep step, so that the insulating film is subjected to many physical stresses. In some cases, the wiring may be broken and the wiring may be broken.

In order to avoid the above-mentioned problems, the surface of the insulating film having irregularities is flattened so that physical stress does not occur in the insulating film. A resist etching back method and a bias sputtering method are mainly used as the planarization method. However, the former has a drawback that the process control becomes difficult as the miniaturization of the semiconductor device progresses, and the latter damages the device.

Therefore, as a method different from the above two methods, a method of flattening the step by a coating method using the fluidity of the liquid has become effective.

The coating film formed by the coating method is formed by coating the wiring or the semiconductor element with an insulating film, and then spin coating a coating film forming solution or the like in which a silicon compound is dissolved in a solvent on the insulating film, and then applying a solvent by heat treatment. Is vaporized and the film is cured to form the film.

However, the heat treatment cannot be performed at a high temperature in consideration of the influence on the semiconductor element and the like, and the solvent is not sufficiently volatilized. Therefore, there is a problem in moisture resistance such that moisture contained in the coating film reacts with residual elements of halogen gas used in the etching process to corrode wiring or semiconductor elements. Therefore, instead of using it alone as an interlayer insulating film, for example, plasma CVD insulating film / coating film / plasma C
In many cases, a laminated structure is formed in which a coating film such as a VD insulating film is sandwiched between other insulating films.

However, the coefficient of thermal expansion (α) of the wiring layer on the substrate is different from that of the insulating film and the coating film. In particular, the wiring layer is made of aluminum alloy, and the insulating film is made by plasma CVD CVD
_In the case of _two membranes, α differs by two digits. Therefore, even if the interlayer insulating film having a laminated structure is formed, thermal stress may occur between the wiring layer and the insulating film during the heat treatment for curing the coating film, which may cause a crack in the insulating film, which is a problem. There is.

(Problems to be Solved by the Invention) In the present invention, in the above-described conventional method of coating a wiring or a semiconductor element with an insulating film, the unevenness of the insulating film is flattened, and a crack is generated in the insulating film. This is done in view of the problem that it will occur. That is,
The present invention relates to a method for manufacturing a semiconductor device, in which an insulating film for covering a stepped portion such as a wiring layer and a coating film formed on the insulating film are formed at a low temperature to prevent cracks from occurring in the insulating film. The purpose is to provide.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention comprises a step of forming a first insulating layer covering at least the stepped portion on a substrate having a stepped portion on the surface, and the first step. Forming a coating film on the insulating layer and flattening the substrate surface on which the first insulating film is formed; thereafter, exposing at least the coating film to plasma; and the flattening coating. Second on the membrane
And a step of forming an insulating layer, the method for manufacturing a semiconductor device.

(Operation) By exposing the coating film on the first insulating layer covering the step portion to the plasma according to the present invention, the surface of the insulating film can be flattened at a low temperature, and the first insulating film is cracked. It never happens.

Further, in the curing treatment of the coating film, the reaction can be promoted by the plasma F at a low temperature, and the moisture resistance can be improved.

For example, when the coating film is a silicon compound such as Si (OH) ₄ , a dehydration condensation reaction occurs between Si--OH OH--Si, and Si--
By expanding the network of O-Si, the curing of the coating film can proceed and the moisture resistance can be improved. The processing temperature in this case is 40 for hardening by heat treatment.
While heating at 0 ° C. or higher is required (in this case, a crack is generated in the insulating film), the heating can be performed at a low temperature of 400 ° C. or lower without causing the crack. In addition, since no stress is applied to the wiring, no disconnection occurs.

This is because when the coating film is exposed to plasma, Si-OH
Alternatively, the O—H bond is activated by the energy of the plasma and is highly reactive.

Therefore, according to the present invention, a coating film having good flatness and moisture resistance can be formed at low temperature. This also gives
There is no occurrence of cracks in the insulating layer or disconnection of the wiring layer.

(Example) Hereinafter, the Example of this invention is described in detail using drawing. FIG. 1 is a sectional view of this step.

First, as shown in FIG. 1A, a first plasma CVD-SiO ₂ film (2) is formed on a substrate (6) on which a wiring (1) made of, for example, nth aluminum is formed. Next, as shown in FIG. 1 (b), a coating film forming solution containing a silicate compound is applied to the entire surface of the substrate on which the plasma CVD-SiO ₂ film (2) is formed, and then the coating film is formed under reduced pressure. The solvent of the forming solution is volatilized to leave the silicate compound film (3) as a coating film on the substrate. Subsequently, as shown in FIG. 1 (c), a silicate compound film (3a) which has been subjected to a curing treatment in oxygen plasma is formed. Here, after forming the silicate-based compound film (3a), etching may be performed to make the entire surface flat. Further, as shown in FIG. 1 (d), a second plasma CVD-SiO ₂ film (4) is formed as an interlayer insulating film, and further on it, as shown in FIG. 1 (e), (n + 1) th aluminum wiring. (5) is formed.

The n-th aluminum wiring (1) formed in the above embodiment is a line-and-space pattern having an aluminum width of 2 μm, a space width of 2 μm, and an aluminum thickness of 1 μm, and the first plasma CVD-SiO ₂ film (2) has a film thickness of 0.2. When the coating film (3) was cured by heat treatment at 450 ° C. under the condition of μm, the crack generation rate in the first plasma CVD-SiO ₂ film (2) was 30%. After that, the substrate temperature is further from room temperature to 300 ° C, oxygen pressure 1 Torr, RF power 800W, processing time
When the coating film (3) is cured by the oxygen plasma treatment for 60 minutes, no crack is generated in the CVD-SiO ₂ film (2).

The film quality of the coating film formed by the present invention is preferably as close as possible in order to suppress the influence of the stress generated between the coating film and the first or second insulating layer.

The results of investigating the etching rates of the two for comparison of the film quality will be described below.

FIG. 2 shows the etching rates of the coating film ((A) heat treatment, (B) plasma treatment) and the plasma CVD-SiO ₂ film (C) when the substrate temperature was changed during the curing treatment of the coating film. It is a characteristic diagram.

Here, the plasma treatment is performed in an oxygen (O ₂ ) atmosphere,
Oxygen pressure is 1 Torr, RF output is 800 W, and processing time is 60 minutes. Further, the etching rate of the plasma CVD-SiO ₂ film is almost constant regardless of the substrate temperature,
It was found that the etching rates were almost the same when the substrate temperature was around 300 ° C.

Further, when the etching rate after the hardening treatment of the coating film is compared between the case of performing the heat treatment (A) and the case of performing the plasma treatment according to the present invention (B), for example, the plasma treatment of 30
The etching rate at 0 ° C. was almost the same as that when the heat treatment was performed at 600 ° C.

For these reasons, the coating film cured by plasma treatment is more likely to be plasma CVD than cured by heat treatment.
It is inferred near the quality of -SiO ₂ film.

Further, it can be seen from FIG. 2 that the coating film subjected to the plasma treatment has a slower etching rate than that of the ordinary heat treatment at the same substrate temperature and the film is dense. Therefore, at the same substrate temperature, the hygroscopicity of the plasma treatment is smaller than that of the heat treatment.

This was clarified by immersing the coating film in boiling water for about 30 minutes and then measuring the relative amount of water released when the coating film was heated using a mass spectrometer.

That is, substrate temperature 300 ° C, oxygen pressure 1 Torr, RF.800
The coating film formed under the conditions of W and treatment time of 60 minutes is plasma C
It is similar to the VD-SiO ₂ film, and its hygroscopicity is greatly improved to about 1/10 of that of the film cured by heat treatment.

Although the coating film was exposed to oxygen plasma in the above embodiment, the same effect can be obtained by exposing it to a gas plasma of nitrogen, argon or the like. Further, the coating film forming solution may be any material as long as it cures when exposed to plasma, but preferably contains silicon (Si) and oxygen (O).

Further, if the substrate is subjected to heat treatment immediately before or during the exposure of the coating film to plasma, the curing treatment time can be shortened and the throughput can be improved.

〔The invention's effect〕

As described above, according to the present invention, the surface of the insulating layer covering the stepped portion such as the wiring of the substrate can be flattened at a low temperature, and the influence on the insulating layer or the wiring in the process can be suppressed. .

[Brief description of drawings]

FIG. 1 is a process sectional view showing one embodiment of the present invention, and FIG.
The figure is a characteristic diagram for explaining the effect of the present invention. 1,5 ... Wiring, 2 ... First insulating layer, 3 ... Coating film, 4
...... Second insulating layer, 6 ... Substrate.

Claims (6)

(57) [Claims] 1. A step of forming a first insulating layer covering at least the step portion on a substrate having a step portion on the surface,
Forming a coating film on the first insulating layer and flattening the surface of the substrate on which the first insulating film is formed;
A method of manufacturing a semiconductor device, comprising: exposing at least the coating film to plasma; and forming a second insulating layer on the planarized coating film. 2. The stepped portion on the surface of the substrate is a region where a wiring pattern or a semiconductor element is formed, and a first insulating film is formed on the region. A method for manufacturing a semiconductor device as described above. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the coating film is formed by coating a coating film forming solution on the first insulating layer by a spin coating method. . 4. The method for manufacturing a semiconductor device according to claim 3, wherein the coating film forming solution is a solution in which a silicon compound is dispersed or dissolved in a solvent. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the coating film forming solution contains at least a silicon (Si) element and O (oxygen). 6. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of performing heat treatment immediately before or during the exposure of the coating film to plasma.