JPH0778816A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To uniform the quality of an SOG film, and reduce a part where film is locally weak on a step-difference or the like, by simultaneously performing the etch-back and the heat treatment of an SOG film. CONSTITUTION:SOG coating solution is spread on a substrate 4 provided with wiring layers 1a, 1b, and a P-SiO2 layer insulating film 3 covering the whole part of the wiring layers 1a, 1b and step-difference part 2a-2c, and an SOG coating film 5 is formed. Some amount of organic solvent in the SOG coating film 5 is evaporated by prebaking. The substrate 4 is heat-treated in a low pressure reaction vessel, and etching gas is supplied. The SOG film is subjected to etch-back process by plasma generated by applying high frequency to the etching gas. The SOG film 7 is left in the manner in which recessed parts 6a-6c on the step-difference parts 2a-2c are filled with the SOG film 7, and the superflous SOG film 7 is eliminated. A flattened interlayer insulating film 8 is formed of the P-SiO2 layer insulating film 3 and the SOG film 7.

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 in particular, a method for obtaining a semiconductor device having an interlayer insulating film including a flat SOG film having a uniform film quality by a simple and short process. Regarding

[0002]

2. Description of the Related Art Generally, in order to secure reliability of wiring in a semiconductor device, a technique for flattening an interlayer insulating film between wirings is required. In particular, with the progress of multilayering and complexity of wiring in recent years, a technique for planarizing an interlayer insulating film has become an important technique in order to secure reliability of the wiring. As a flattening technique for the interlayer insulating film, a coating solution obtained by dissolving a silanol compound in an organic solvent is applied by spin coating on a substrate on which a wiring layer, a SiO ₂ interlayer insulating film, etc. are formed. , Evaporate the organic solvent by pre-baking,
There is a method of forming an SOG film by vitrifying a silanol compound by heat treatment at a temperature of 400 to 450 ° C. in an atmosphere of N ₂ , air or the like. Since this SOG film is formed by spin-coating a liquid coating solution, it has characteristics that it is formed thin in the convex portion and thick in the concave portion, and is therefore suitable for flattening the interlayer insulating film. However, the SOG film has a problem that it tends to absorb moisture and the amount of degassing during heat treatment is large. for that reason,
When the SOG film is used as a part of the interlayer insulating film, a method is adopted in which etching back is performed so that the sidewalls of via holes and the like are not exposed and excess SOG on the wiring is removed.

[0003]

[Problems to be Solved by the Invention] However, the conventional SOG
In the film forming method, heat treatment at 400 to 450 ° C. is 2 to
It takes a long time of 3 hours, and since the SOG film is etched back thereafter, it takes a very long time to form a flat interlayer insulating film.

Moreover, the conventional N _2, in the heat treatment performed in an atmosphere of such air, uneven portions occurs in the film quality of the accumulated SOG film such as stepped portion, by degassing, etc., reliability of the semiconductor device obtained There is a problem that it causes the deterioration of sex.

Therefore, an object of the present invention is to provide a method capable of obtaining a semiconductor device having an interlayer insulating film including a flat SOG film having a uniform film quality by a simple and short-time process.

[0006]

In order to solve the above problems, the present invention is a method of manufacturing a semiconductor device having an interlayer insulating film including an SOG film, wherein an SOG film is formed on a substrate and prebaked. In the process and in a depressurized reaction container, the substrate is heated and heat-treated, an etching gas is supplied into the reaction container, and an SOG film is etched back by plasma generated by applying a high frequency to the etching gas. The present invention provides a method for manufacturing a semiconductor device including steps to be performed simultaneously.

Hereinafter, in the method of manufacturing a semiconductor device of the present invention (hereinafter referred to as the “method of the present invention”), a step of forming a flat interlayer insulating layer on a wiring layer formed on a substrate of the semiconductor device will be described. As an example, the process will be described in detail with reference to FIG. 1.

In the process shown in FIG. 1, first, as shown in FIG.
As shown in (a), the wiring layers 1a and 1b and the wiring layer 1
The SOG coating liquid is applied to the substrate 4 having the P-SiO ₂ interlayer insulating layer 3 covering the entire surfaces a, 1b and the step portions 2a, 2b, 2c by the spin coating method to form the SOG coating film 5. .

The application of the SOG coating solution by the spin coating method is not particularly limited and can be performed according to a conventional method. The preparation of the SOG coating liquid is not particularly limited and can be performed according to a conventional method. Examples of silanol compounds used include monomethylsilanol, dimethylsilanol, and the like, and examples of organic solvents used include alcohols, esters, ketones, and the like, but the present invention is not limited thereto. Not limited.

Further, the film thickness of the SOG coating film is appropriately adjusted according to the type of the SOG coating liquid, the step difference of the base and the like. Usually, it is about 0.1 to 0.3 μm when using an inorganic SOG, and 0.3 to 0.6 μm when using an organic SOG.
It is preferably about the same.

Next, prebaking is performed to evaporate the organic solvent in the SOG coating film to some extent. This prebaking can be performed by heating the substrate at a temperature of about 100 to 250 ° C. using a hot plate or the like.

Then, in a depressurized reaction vessel, the substrate is heated to be heat-treated, an etching gas is supplied, and an SOG film is etched back by plasma generated by applying a high frequency to the etching gas. As shown in FIG. 1 (b), the excess SOG film is removed leaving the SOG film 7 so that the recesses 6a, 6b, 6c above the stepped portions 2a, 2b, 2c are filled with the SOG film 7. , P-SiO ₂ interlayer insulating layer 3 and the SOG film 7 form a planarized interlayer insulating film 8. The upper surfaces 9a and 9b of the P-SiO ₂ interlayer insulating layers 3a and 3b above the wiring layers 1a and 1b may be exposed as shown in FIG. 1B, or may be covered with the SOG film. Good.

The method of the present invention has been described above based on the steps shown in FIGS. 1 (a) and 1 (b), which are one embodiment of the method of the present invention. It is needless to say that the present invention is not limited to the steps shown in a) and (b) and can be applied to the manufacture of various semiconductor devices having an interlayer insulating film. For example, it can be applied to a bipolar semiconductor device having a multi-layer metal wiring having a memory or a logic element, a MOS semiconductor device, and the like.

In the method of the present invention, the reaction vessel for carrying out the heat treatment and the etchback treatment of the substrate is not particularly limited, and any equipment can be used as long as it can perform the heat treatment and the etchback treatment at the same time. Good.
As a specific example of this reaction container, an apparatus whose schematic sectional views are shown in FIGS. 2 and 3 can be mentioned.

The apparatus shown in FIG. 2 is a so-called batch type plasma etching apparatus, and comprises an outer tube 11 constituting the outside of the reaction vessel, an inner tube 12 arranged inside the outer tube 11, and a large number of substrates. 1
3 is held horizontally, and has a substrate support port 15 rotatably supported by a rotation base 14, and an injector 17 for supplying the substrate 13 with an etching gas introduced from a gas supply port 16. Further, on the outer side of the outer tube 11, at least a pair of high-frequency generating electrodes 19 connected to a high-frequency power source 18 and a heater 20 for heating the substrate are arranged, and further connected to an exhaust hole 21. The inside of the outer tube 11 is evacuated by a decompression device (not shown) so that the outer tube 11 can be decompressed.

In the apparatus shown in FIG. 2, the substrate 13
After mounting the substrate on the substrate support port 15, the atmosphere inside the outer tube 11 is exhausted by a decompression device to reduce the pressure, and the substrate 13 rotated in the direction of the arrow A by the rotating pedestal 14 is heated by the heater 20. At the same time as supplying the etching gas from the injector 17,
A high frequency power can be applied from the high frequency power generation electrode 19 by the high frequency power supply 18 to turn the etching gas into plasma to etch back the SOG film on the substrate 13.

The apparatus shown in FIG. 3 is a so-called single-wafer type plasma etching apparatus, which is a main body 31 of the reaction vessel.
And a gas introduction port 32 arranged on the upper part of the main body 31,
The main body 31 has an exhaust hole 33 disposed below the main body 31. Inside the main body 31, a lower electrode 35 for generating a high frequency on which a substrate 34 is mounted and an upper electrode 36 are disposed. Three
5 and the upper electrode 36 are connected to a high frequency power source 37. The substrate 34 is provided below the lower electrode 35.
A heater 38 for heating the upper electrode 3 is provided.
6 is provided with a gas supply hole 39 for supplying the etching gas introduced from the gas introduction port 32 onto the substrate 13.

In the apparatus shown in FIG. 3, the substrate 34
Is placed on the lower electrode 35, and then the main body 31 of the reaction container is removed by a pressure reducing device (not shown) connected to the exhaust hole 33.
The inside is evacuated to reduce the pressure, the substrate 34 is heated by the heater 38, and the etching gas introduced from the gas inlet 32 is supplied onto the substrate 34 through the gas supply hole 39, and at the same time, the high frequency power supply 37 is used to supply the upper electrode 36.
A high frequency can be applied from the lower electrode 35 to turn the etching gas into plasma to etch back the substrate 34.

In the method of the present invention, the pressure inside the reaction vessel is usually adjusted to about 0.1 to 0.8 Torr by reducing the pressure.

In the method of the present invention, the heating temperature in the heat treatment of the substrate is usually about 300 to 450 ° C.,
The temperature is preferably about 350 to 400 ° C. from the viewpoint of reducing thermal stress on the Al wiring. Also, at this time,
When heated rapidly at high temperature, in the case of thickened SOG film,
Cracks are likely to occur, and as shown in FIG. 4 showing the etching rate of the SOG film at each temperature, the etching rate also changes rapidly, making it difficult to control the etching amount. Moreover, in order to make the quality of the SOG film uniform,
It is not good to heat rapidly. Therefore, it is desirable to raise the temperature in at least two steps. First, in the first step, the temperature is kept constant at around 200 ° C., the SOG film is dried, and the excess SOG film on the wiring is removed by about 80%. Next, it is preferable that the temperature is raised to about 400 ° C. and the remaining excess SOG film is etched while the etching rate is close to that of the underlying oxide film.

The etching gas used in the etch-back process is not particularly limited and may be a conventional gas used in this type of process. For example, CF ₄ + O ₂ gas, CF ₄ +
Examples include CHF ₃ gas and NF ₃ gas. Especially CF
_{When the} SOG film is etched back with a CF ₄ -based etching gas such as ₄ + O ₂ gas or CF ₄ + CHF ₃ gas, the SOG film surface after the etching back becomes hydrophobic, and the upper insulating film is formed after the etching back. If so, there may be a problem in adhesion. Therefore, it is effective to perform the surface modification after the etch back with O ₂ plasma by using only O ₂ as the etching gas after the etching back of the SOG film is completed.

The SOG film obtained by the method of the present invention is denser and has a uniform film quality deep inside the film, as compared with the SOG film heat-treated in a normal N ₂ or air atmosphere.

[0023]

According to the method of the present invention, the SOG film is etched back and heat-treated at the same time, and
The quality of the film becomes uniform, and the number of locally weak parts (fast etchback) such as stepped parts decreases. Further, the steps can be significantly shortened by simultaneously performing the etch back and the heat treatment. Further, by devising a temperature raising step at the time of etching back, it is possible to reduce the occurrence of cracks when the SOG film is made thicker, which has an advantage of improving the reliability of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating main steps in an embodiment of the method of the present invention.

FIG. 2 is a schematic sectional view of an example of a batch type plasma etching apparatus.

FIG. 3 is a schematic cross-sectional view of an example of a single-wafer plasma etching apparatus.

FIG. 4 is a diagram showing a relationship between a curing temperature and an etching rate.

[Explanation of symbols]

1a, 1b wiring layers 2a, 2b, 2c stepped portion 3 P-SiO ₂ interlayer insulating layer 4 substrate 5 SOG coating 6a, 6b, 6c recess 7 SOG film 8 interlayer insulating film 9a, the 9b P-SIO ₂ interlayer insulation layer Upper surface 11 Outer tube 12 Inner tube 13 Substrate 14 Rotating pedestal 15 Substrate supporting port 16 Gas supply port 17 Injector 18 High frequency power source 19 High frequency generating electrode 20 Heater 21 Exhaust hole 31 Reaction vessel body 32 Gas inlet 33 Exhaust hole 34 Substrate 35 Lower electrode 36 Upper electrode 37 High frequency power supply 38 Heater 39 Gas supply hole

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device having an interlayer insulating film including an SOG film, comprising the steps of forming an SOG film on a substrate and pre-baking, and using a depressurized reaction container,
A method of manufacturing a semiconductor device, including the steps of heating the substrate for heat treatment, supplying an etching gas into a reaction vessel, and simultaneously performing an etchback process of an SOG film by plasma generated by applying a high frequency to the etching gas. .