JPH0449258B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a multilayer wiring structure in which a flat surface is obtained by forming a spin-coated glass film by spin coating and heat curing. The present invention relates to a method for manufacturing a semiconductor device.

(Prior Art) As semiconductor devices become more highly integrated, it becomes necessary to adopt a multilayer wiring structure. This multilayer wiring is formed by laminating an insulating film and a wiring film.

A conventional method for forming multilayer wiring will be explained with reference to FIG. In FIG. 1, 1 is a semiconductor substrate;
First, a PSG film (containing phosphorus) is placed on this substrate 1.
Form a SiO ₂ film) 2. Next, a first layer aluminum wiring 3 having a thickness of 4000 to 10000 Å is formed on this PSG film 2. Thereafter, an insulating film 4 of a PSG film having approximately the same thickness as the aluminum wiring 3 is formed on the PSG film 2 including the aluminum wiring 3. Thereafter, an aluminum layer 5 for forming a second layer aluminum wiring having a thickness of about 10,000 Å is formed on the insulating film 4, and a photoresist 6 is applied on the aluminum layer 5. Then, this photoresist 6 is exposed and developed into a pattern, and the aluminum layer 5 is etched using the patterned photoresist as a mask to form a second layer aluminum wiring.

In such a formation method, the step caused by the first layer aluminum wiring 3 causes a steep step in the insulating film 4 formed thereon. In particularly severe cases, a concave depression is formed at the lower end of the step.
Therefore, when the aluminum layer 5 is formed on the insulating film 4, breakage may occur at the shoulder portion 7 of the insulating film 4. In addition, in order to pattern the aluminum layer 5, the photoresist layer 6 is exposed and
When developed, unexposed portions 8 are generated on the sidewalls of the stepped portions of the aluminum layer 5, and resist remains.
When etching the aluminum layer 5, etching residue was left behind, which caused a short circuit.

In order to prevent such defects, it is necessary to flatten the insulating film on the first layer wiring as much as possible to reduce the level difference.

One method for flattening is a method of forming a spin-coated glass film. FIG. 2 is a diagram showing a multilayer wiring formed by applying this method. In this case, after forming the first layer aluminum wiring 3, a spin-coated glass film, such as a silica film 9 containing phosphorus, is formed by spin coating and heat curing, and then the insulating film 4 is formed by chemical vapor deposition (CVD).
After that, the process is similar to that shown in FIG. 1.

According to such a method, the surface shape of the silica film 9 formed by spin coating becomes flat;
The CVD insulating film 4 also becomes flat, and as a result, the above-mentioned drawbacks can be eliminated.

However, in the above-mentioned conventional method, as shown in FIG.
Cracks 11 enter the silica film 9 using the cracks 10 as cores, and in severe cases, cracks may also enter the CVD insulating film 4.

(Object of the Invention) The present invention has been made in view of the above points, and provides a semiconductor device which prevents cracks from occurring in the glass film due to cracks on the surface of the wiring layer that occur during heat treatment after spin-coating glass film formation. The purpose is to provide a manufacturing method.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 4a, 21 is a silicon semiconductor substrate. First, on this semiconductor substrate 21, as shown in FIG.
As shown in , a PSG film 22 is formed as a first insulating film. Next, a first layer aluminum wiring 23 (first wiring layer) having a thickness of 4,000 to 10,000 Å is patterned at a predetermined portion on this PSG film 22. After that, the above-mentioned area including the aluminum wiring 23 is
A silica film 24 (spin-coated glass film) is formed thickly and evenly on the PSG film 22 by spin coating and heat curing. At this time, silica film 2
4 is thicker on the PSG film 22 than on the first layer aluminum wiring 23, as is clear from FIG. 4a.

To form this silica film 24, for example, Si(OH) ₄ is added to an alcohol solution in terms of SiO ₂ .
Use one containing 4.8%. When the solvent is evaporated and dried, this solution forms a silicon dioxide layer according to the reaction formula: Si(OH) ₄ →SiO ₂ +2H ₂ O. Although this reaction occurs to some extent at room temperature, it is insufficient. Heating is necessary to complete this reaction. If there is aluminum wiring in the lower layer, the appropriate heating temperature is about 450°C or less. Heating is carried out at approximately 250°C after spin coating the solution, and also at approximately 450°C during the generation of the insulating film (CVD PSG film) described later.
It is carried out by.

After forming the silica film 24 in this way, next, a carbon fluoride gas such as
The entire surface of the silica film 24 is dry etched using a gas such as C ₂ F ₆ until the upper surface of the first layer aluminum wiring 23 is exposed. This results in
The silica film 24 disappears on the first layer aluminum wiring 23. On the other hand, the silica film 24 remains on the PSG film 22 except on the first layer aluminum wiring 23. (FIG. 4b) After that, an insulating film 25 (second insulating film) of CVD PSG film is coated on the silica film 24 including on the first layer aluminum wiring 23 to a thickness that is approximately the same as that of the first layer aluminum wiring 23. This insulating film 25
A second layer aluminum wiring 26 is formed thereon.

(Effects of the Invention) As is clear from the above examples, in the method of the present invention, after forming a spin-coated glass film, the entire surface of the spin-coated glass film is dry-etched to form a first spin-coated glass film. Remove from above the wiring layer. That is, the portions of the spin-coated glass film where cracks occur are removed. Therefore, the cracks generated in the first wiring layer no longer occur in the spin-coated glass film as before, and, of course, the second insulating film thereon does not suffer from cracks.

In addition, since the entire surface of the spin-coated glass film is dry-etched, the spin-coated glass film is thicker on the other underlying insulating film (first insulating film) than on the first wiring layer, so that Since the etching remains sufficiently on the entire underlying insulating film, the surface shape remains flat even after etching.
Therefore, the second insulating film and the second wiring metal layer formed thereon can form a uniform and flat surface, and the second wiring layer formed by steep steps can be This can prevent wire breakage and short circuits.

Furthermore, if the surface of the metal layer for the second wiring layer is flat, a photoresist layer with a uniform thickness and no unevenness can be obtained for patterning on the surface. It also becomes possible to obtain accurate photoresist mask patterns.

Further, according to the method of the present invention, after the spin-coated glass film is applied, the glass film is heated and hardened, so that the subsequent etching can be easily controlled. Moreover, in this invention, since dry etching is used as the etching method, the etching can be controlled with higher precision, and only the spin-coated glass film on the first wiring layer can be removed with higher precision.

Further, according to the present invention, since the spin-coated glass film is left on the entire base insulating film (first insulating film) other than on the wiring (first wiring layer), it is applied only to the side wall of the wiring. Compared to a method (referred to as a comparative example) in which the spin-coated glass film is left and the spin-coated glass film is removed from the base insulating film, the following effects are obtained.

In the case of a pattern with a small wiring pitch, when a spin-coated glass film is spin-coated, the spin-coated glass film is also spin-coated to a considerable thickness between the wirings, so as in the comparative example, the base insulation between the wirings is In order to remove the spin-coated glass film on the film, a considerable amount of the entire surface of the spin-coated glass film must be removed.
In the comparative example, the remaining amount of the spin-coated glass film on the side wall of the wiring, which is necessary for smoothing the level difference, is extremely small, and the effect of smoothing the level difference in the wiring becomes very weak. Furthermore, if there are patterns with very small wiring pitches (e.g. ~1 μm) and very large patterns (e.g. tens to hundreds of μm) on the same board surface (in reality, they always exist at the same time). ), in the comparative example, a large amount of removal is required as described above to remove the spin-coated glass film on the small-pitch inter-wiring insulating film ( If the spin-coated glass film is thin, a phenomenon occurs in which the insulating film is etched. On the other hand, as in the present invention, the etching of the spin-coated glass film is completed when the upper surface of the first wiring layer is exposed.
By leaving the spin-coated glass film not only on the sidewalls of the interconnect layer but also on the entire underlying insulating film, a sufficient smoothing effect can always be obtained, and the underlying insulating film can be etched at large pitches between interconnects. It is also possible to prevent insulation deterioration.

Note that if the spin-coated glass film is not heat-cured after application, the spin-coated glass film will be fragile and cracks may occur not only on the Al wiring surface but also on the underlying insulating film.
Therefore, it is necessary to remove the spin-coated glass film from above the base insulating film, but if the spin-coated glass film is hardened by heat treatment after coating as in this invention, the spin-coated glass film can be removed from the base insulating film. Even if it is left in place, cracks can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a conventional method for forming multilayer wiring, FIG. 2 is a cross-sectional view for explaining another conventional method for forming multilayer wiring, and FIG. FIG. 4 is a plan view showing how cracks occur in a silica film in the method, and a cross-sectional view for explaining an embodiment of the method for manufacturing a semiconductor device of the present invention. 21... Silicon semiconductor substrate, 22... PSG film,
23... First layer aluminum wiring, 24... Silica film, 25... Insulating film, 26... Second layer aluminum wiring.

Claims (1)

[Claims] 1 After forming the first insulating film on the semiconductor substrate,
A step of patterning a first wiring layer on this first insulating film, and forming a spin coat glass film on the first insulating film including on this first wiring layer. A step of spin-coating the first insulating film evenly so that it is thicker, and heating and hardening the spin-coat glass film, and then applying the spin-coat glass film so that only the upper surface of the first wiring layer is coated with a thin layer. a step of leaving the spin-coated glass film in a region other than on the first wiring layer by dry etching it flat until it is exposed, and then leaving the spin-coated glass film on the first wiring layer and the spin-coated glass film; A method of manufacturing a semiconductor device, comprising the step of forming a second insulating film.