JPH09213797A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacture of a semiconductor device having an interlayer dielectric film of a low dielectric constant. SOLUTION: A wiring 2 and a silicon oxide film 3 covering the wiring 2 are formed on a substrate 1. Thereafter, a wet gel film 7 is formed on the substrate 1 where the wiring 2 and the silicon oxide film 3 are formed. Further, the wet gel film 7 is dried in accordance with a supercritical drying method to form a porous film, and an insulating film is formed in accordance with the CVD method on the porous film, and a second wiring 6 is formed on the insulating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device, and more particularly to a method for forming an interlayer insulating film having a low dielectric constant.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor integrated circuits has improved, the number of wiring layers of semiconductor devices has increased.
Along with the multi-layered wiring, there is a need for a technique for flattening a step caused by forming a wiring pattern in order to improve the reliability of the wiring. One of the widely used flattening techniques is the SOG method.

The technique of SOG described above is such that a sol solution obtained by dehydrating and condensing silicon hydroxide produced by hydrolyzing a silicon alkoxide is spin-coated on a stepped substrate and then heated to about 450 ° C. under normal pressure. Is a method of forming a planarization insulating film by performing heat treatment and baking.

Therefore, a conventional method of forming an interlayer insulating film using the SOG method will be described below with reference to FIG.

First, in FIG. 3A, after forming a wiring pattern 2 on a substrate 1, a silicon oxide film 3 is formed by a plasma CVD method. Next, as shown in FIG. 3 (B), a sol solution obtained by dehydration condensation of silicon hydroxide obtained by hydrolyzing silicon alkoxide is spin-coated on the silicon oxide film 3 and then at 450 ° C. for 30 minutes. Heat treatment is performed to form the coating film 4. Then, FIG.
As shown in (C), a silicon oxide film 5 is formed on the coating film 4 by a plasma CVD method, and subsequently a through hole (not shown in the figure) is formed in the silicon oxide film 5, and then a second film is formed. The wiring pattern 6 is formed.

[0006]

However, in the case of the coating film formed by the conventional SOG method, the relative dielectric constant of the inorganic SOG film is 4.0 to 5.0, and the relative dielectric constant of the organic SOG film is 3.0. Since it is up to 4.0, the inter-wiring capacitance is large when it is used for the interlayer insulating film, which is a problem in increasing the operating speed of the semiconductor device. Therefore, it has been difficult to form an insulating film having a low dielectric constant with a relative dielectric constant of 3.0 or less by the conventional SOG method.

In view of the above problems, it is an object of the present invention to provide a method for manufacturing a semiconductor device having a small inter-wiring capacitance by forming an insulating film having a low relative dielectric constant.

[0008]

Means for Solving the Problems The basic constitution of the present invention for achieving the above object is a step of forming a wet gel film, and the wet gel film is dried using a supercritical drying method to form a porous film. And a step of forming an insulating film on the porous film by a CVD method.

The film formed on the substrate by using the SOG method or the like is a wet gel which is formed by binding sol in a mesh shape, and the solvent is dispersed in the gaps of the mesh structure. This wet gel film is placed under high temperature and high pressure above the critical point of the solvent to bring the solvent molecules into a supercritical state in which there is no distinction between gas and liquid. If the solvent is removed in this state, the stress due to the capillary force is not applied to the network structure of the wet gel, so the film hardly shrinks,
It is possible to obtain a porous film having an extremely high porosity and a low dielectric constant.

Further, in order to protect the porous film, an insulating film is formed on the porous film by the CVD method.

In the present invention, the inter-wiring capacitance can be reduced by using the above-mentioned porous film formed by the supercritical drying method as an interlayer insulating film. Furthermore, by forming an insulating film on the porous film as a protective film by using the CVD method, deterioration of the porous film due to moisture absorption can be prevented.

Further, according to the present invention, there is provided a step of spin-coating a coating chemical solution coated with a synthetic resin wall or a glass wall, in which fine particles having a hollow structure or a capsule structure having a foaming agent dispersed, and heat treating the formed coating film. And a step of applying.

A coating film is formed by spin-coating a coating solution in which hollow fine particles having a synthetic resin wall or a glass wall are dispersed on a substrate. The coating film thus formed is a porous film because hollow fine particles are dispersed in the film. The porous film as described above is formed by spin-coating a coating solution in which a foaming agent coated on a synthetic resin wall or a glass wall is dispersed on a substrate, and heat-treating the coating film to form a foaming agent. It can also be obtained by vaporizing. Since the foaming agent is a capsule structure covered with a synthetic resin wall or a glass wall, when the foaming agent decomposes by heat treatment,
The capsule structure in the coating film becomes hollow and becomes a porous film.

The dielectric constant of the porous film obtained by the above method decreases with an increase in the porosity in the film. Therefore, by increasing the amount of the hollow fine particles or the foaming agent dispersed in the coating solution, the inter-wiring space can be increased. It is possible to obtain an interlayer insulating film having a low capacitance and a low dielectric constant. Further, each hole in the porous film obtained by the above method is an independent hole surrounded by a synthetic resin wall or a glass wall. Therefore, it is possible to minimize the deterioration of the film quality due to the hygroscopicity that is often found in a porous material having continuous pores such as airgel.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing a method of manufacturing a semiconductor device according to the present invention in the order of steps.

First, as shown in FIG. 1A, a first wiring layer 2 is formed on a substrate 1 on which a semiconductor device is to be formed, and an oxide film 3 is formed thereon by plasma CVD. This oxide film 3 is for improving the adherence between the coating film formed later and the substrate, and may be another film type, or may be omitted if the adherence does not matter. .
However, a thin film having an insulating property (for example, several hundreds) is desirable.
Å), and examples thereof include a silicon nitride film in addition to the above silicon oxide film.

Next, as shown in FIG. 1B, a solution prepared by mixing 25 g of tetraethoxysilane, 35 g of ethanol, 24 g of water and 0.3 g of hydrochloric acid on the silicon oxide film 3 is spin-coated by spin coating. The wet gel film 4 is formed by coating. As a result of gelation, the wet gel film 4 is formed by binding silica in a mesh shape, and ethanol as a solvent is dispersed in the gaps of the mesh structure. In addition, the above-mentioned wet gel refers to a state in which ethanol as a solvent is dispersed and remains in the skeleton of silica.

Examples of the wet gel include a sol solution obtained by dehydrating and condensing a metal hydroxide produced by hydrolyzing a metal alkoxide, a solution containing an organic polymer, and the like.

Subsequently, as shown in FIG. 1C, the wiring layer 2
Substrate 1 on which silicon oxide film 3 and wet gel film 4 are formed
Is put into an autoclave, and ethanol in the wet gel film 4 is removed by using a supercritical drying method. What is the supercritical drying method?
In this method, the wet gel is dried under conditions of high temperature and high pressure above the critical point of the solvent. Under the conditions of high temperature and high pressure above the critical point, the solvent is in a supercritical state in which gas and liquid are indistinguishable. If the solvent in the wet gel is removed in this state, a gas-liquid interface does not occur in the gel, so that stress due to capillary force is not applied to the skeleton of the gel, and the wet gel can be dried with almost no shrinkage. The thus-obtained dry gel is a porous substance having a very high porosity because the network structure of the wet gel remains as it is, and the relative dielectric constant is also extremely low.

In the present embodiment, since ethanol is the solvent, it is held for 1 hour at high temperature and high pressure conditions at which ethanol becomes a supercritical state, for example, 260 ° C. and 8 MPa. After reducing the pressure to 1 atm while maintaining the temperature at 260 ° C,
Reduce the temperature to room temperature. Since ethanol is removed from the film without a gas-liquid interface, gel contraction due to surface tension does not occur, and the wet gel network structure does not contract, resulting in a porous film with a porosity of 50% or more. . Further 40
Heat treatment is performed for 30 minutes at 0 ° C. to obtain the porous film 5. The relative permittivity of the porous film 5 thus formed was measured,
It was 1.8 to 2.2.

Finally, as shown in FIG. 1D, a silicon oxide film 6, for example, is formed on the porous film 5 by the CVD method. The silicon oxide film 6 plays a role of protecting the porous film 5 having high hygroscopicity. Thereafter, although not shown in the drawing, if necessary, a via hole is formed and the via hole is filled with metal to form the second wiring layer 7.

In this embodiment, as the wet gel film, SOG is used which is obtained by applying a sol solution containing tetraethoxysilane, ethanol, water, and hydrochloric acid as starting materials by a spin coating method. A sol solution obtained by dehydration condensation of a metal hydroxide produced by hydrolyzing another metal alkoxide, or a solution containing an organic polymer may be applied. The method of forming the wet gel film is SO
Not limited to the G method, the dip coating method or the C method
It may be formed by the VD method.

(Second Embodiment) Next, a method of manufacturing a semiconductor device according to a second embodiment of the present invention will be described with reference to the drawings. 2A to 2C are process sectional views of the method for manufacturing a semiconductor device according to the present embodiment.

First, as shown in FIG. 2A, a first wiring layer 2 is formed on a substrate 1 on which a semiconductor device is to be formed, and an oxide film 3 is further formed thereon by using a plasma CVD method. . This oxide film 3 is for improving the adherence between the coating film formed later and the substrate, and may be another film type, or may be omitted if the adherence does not matter. .

Next, as shown in FIG. 2B, for example, a capsule structure in which a foaming agent such as azodicarbonamide is coated with a siloxane polymer wall is dispersed in a SOG chemical liquid to form a coating chemical liquid, which is an oxide film. A coating film 4 is formed by applying the coating film 3 on the surface 3 by a spin coating method. At this time, as the above-mentioned foaming agent, 100-200 without foaming when applied.
What foams at a temperature of ° C is desirable, and those which do not adversely affect the device itself such as nitrogen and carbon dioxide when foaming are desirable.

Subsequently, as shown in FIG. 2C, the substrate 1 is subjected to heat treatment at about 200 ° C. to 205 ° C. with a hot plate. By this heat treatment, the azodicarbonamide generates a gas such as nitrogen or carbon dioxide and decomposes, the capsule structure in the coating film becomes pores surrounded by siloxane polymer walls, and the coating film 4 is porous. Turn into. After the heat treatment on the hot plate, the film is further cured by heat treatment at 400 ° C. for 30 minutes to obtain the porous film 5.

Finally, as shown in FIG. 2D, a silicon oxide film 6, for example, is formed on the porous film 5 by the CVD method. Thereafter, although not shown in the figure, if necessary, a via hole is formed and the via hole is filled with metal to form a second wiring layer 7.

According to the present embodiment, after the coating film 4 in which the azodicarbonamide coated with the siloxane polymer wall is dispersed is formed by the spin coating method, the azodicarbonamide in the coating film 4 is vaporized by heat treatment. Thus, the coating film 4 can be made porous to obtain the porous film 5. By increasing the amount of the foaming agent mixed in the coating chemical, the dielectric constant of the porous film 5 can be lowered, and a porous film having a dielectric constant of about 2.0 to 2.5 can be obtained, resulting in Is
By using the porous film 5 having a low dielectric constant as the interlayer insulating film between the first wiring layer 2 and the second wiring layer 7, it is possible to manufacture a semiconductor device having a small wiring capacitance.

Further, in the present embodiment, since the foaming agent azodicarbonamide is a capsule structure coated with a siloxane polymer, when the azodicarbonamide is vaporized by heat treatment, the capsule structure in the film becomes a hollow capsule. Therefore, the hollow capsules are not bonded to each other, the respective pores in the porous film obtained in the present embodiment are independent of each other, the hygroscopicity is low, and the deterioration of the film quality due to the moisture absorption is small. Is obtained.

In this embodiment, the case where the foaming agent coated on the siloxane polymer wall is dispersed in the SOG chemical liquid has been described, but the capsule structure dispersed in the coating chemical liquid is a hollow structure having a synthetic resin wall or a glass wall. The same porous film can be obtained with fine particles.

[0032]

As described above, according to the present invention, the porous film 5 formed by the supercritical drying method is used as the interlayer insulating film between the first wiring layer 2 and the second wiring layer 7. As a result, a semiconductor device having a small wiring capacitance can be manufactured. Furthermore, by forming the insulating film 6 on the porous film 5 by using the CVD method, the porous film 5 having high hygroscopicity can be protected from moisture and a stable interlayer insulating film with little deterioration with time can be obtained. it can.

Further, according to the present invention, by using the porous film 5 as an interlayer insulating film between the first wiring layer 2 and the second wiring layer 7, a semiconductor device having a small wiring capacitance is manufactured. be able to. Further, the porous film 5 obtained by the present invention
Since the pores inside are independent from each other, the moisture absorption of the film is small and the deterioration of the film quality due to the moisture absorption is small.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufacturing process of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a manufacturing process of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a manufacturing process of a semiconductor device using a conventional SOG method.

[Explanation of symbols]

 1 substrate 2 wiring layer 3 silicon oxide film 4 coating film 5 silicon oxide film 6 wiring layer 7 wet gel film 8 porous film

Claims (4)

[Claims] 1. A step of forming a wet gel film on a substrate on which wiring is formed, a step of drying the wet gel film by a supercritical drying method to form a porous film, and a step of forming the porous film on the porous film. A method of manufacturing a semiconductor device, which comprises a step of forming an insulating film by a CVD method. 2. A sol solution obtained by hydrolyzing a metal alkoxide produced by hydrolyzing a metal alkoxide or a solution containing an organic polymer is applied in the step of forming a wet gel film. The method of manufacturing a semiconductor device according to claim 1. 3. A step of forming a coating film by coating a sol containing fine particles coated with a synthetic resin wall or a glass wall on a substrate on which wiring is formed, and a heat treatment is applied to the coating film to perform insulation. A method for manufacturing a semiconductor device, comprising a step of forming a film. 4. A step of forming a coating film by coating a sol containing a foaming agent coated with a synthetic resin wall or a glass wall on a substrate on which wiring is formed, and heat treating the coating film. A method for manufacturing a semiconductor device, comprising the step of forming an insulating film.