JPH06112336A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To furnish an organic insulating material which is excellent in a coverage and of which the dielectric constant is small, regarding a layer insulating film of a semiconductor device. CONSTITUTION:A manufacture of a semiconductor device wherein a paraxylylene radical obtained by thermal decomposition of a diparaxylylene gas is led onto a semiconductor substrate on which a first wiring layer is formed, it is polymerized on the first wiring layer, so that a thin film of polyparaxylylene be formed, the thin film thus formed is then fluorinated to be fluorinated polyparaxylylene and this thin film is used as a layer insulating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device using fluorinated polyparaxylylene as an interlayer insulating film.

Since it is necessary to process a large amount of information quickly, the semiconductor device that constitutes the main body of an information processing device has been integrated by miniaturization of unit elements, and LSI and VLSI have been put to practical use.

Here, the integration by miniaturization of the unit element is carried out by making the wiring pattern finer and multilayering.
That is, the minimum line width of the conductor line is
Cron), and the conductor lines that connect the unit elements are complicated, so a three-dimensional wiring structure is adopted.

On the other hand, the development of a multi-chip module (MCM) capable of high-density mounting is under way even for a multilayer wiring board on which these semiconductor devices are mounted. The present invention relates to an interlayer insulating film forming a three-dimensional structure.

[0005]

2. Description of the Related Art Necessary conditions for a material forming an interlayer insulating film are high insulation resistance value, low dielectric constant, excellent heat resistance, etc. As an inorganic insulating material, silicon dioxide ( SiO ₂ ), silicon nitride (Si ₃ N ₄ )
_Thus, phosphosilicate glass (abbreviated as PSG) is used, and polyimide is used as the organic insulating material.

[0006] Here, as the integration progresses and the frequency of the signal increases, the need for a small dielectric constant is increasing more and more. That is, when the thickness of the interlayer insulating film is 1 μm or less due to high integration, when the electrodes and wirings are vertically opposed to each other with the interlayer insulating film interposed, the capacitance ( Cross-talk for C)
In this case, the magnitude of the electrostatic capacitance (C) is proportional to the dielectric constant (ε).

C = εA / 3.6 πd (pF) ... (1) where A is the area of the opposing electrodes (cm ² ) d is the thickness (cm), and the signal passing through the electronic circuit The delay time (τ) of is required to be as small as possible, but this delay time (τ) is proportional to the dielectric constant (ε) of the substrate on which the electronic circuit is formed, as expressed by the following equation. , It is necessary to use a material with a low dielectric constant.

Τ∝ = ε ^1/2 / c (2) Here, c is higher than the speed of light, so that the dielectric constant (ε) is small as a constituent material of the interlayer insulating film. However, inorganic insulating materials such as SiO ₂ and Si ₃ N ₄ generally have excellent heat resistance and high insulation resistance, and even if SiO ₂ is the smallest material, it generally has a large dielectric constant. The permittivity value is 3.8.

On the other hand, polyimide, which is an organic insulating material, has a dielectric constant of 3.2, which is smaller than that of an inorganic insulating material, and is suitable as a constituent material of an interlayer insulating film. However, the problem with using organic insulating materials such as polyimide is the coverage (Cover
age) is bad.

That is, as a method of coating the substrate to be processed, a method of coating an organic insulating material dissolved in an organic solvent on the substrate to be processed by a spin coating method is generally used. In the case of polyimide, a solvent such as hydrazine is used. As a characteristic of this, spin coating is carried out by dissolving in the polyimide film 3 regardless of the unevenness due to the wiring 2 of the first layer patterned on the semiconductor substrate 1 as shown in FIG. The surface is to be formed flat.

Here, although the line width of the wiring 2 is becoming finer as the degree of integration is improved, the amount of current required to drive the semiconductor element must be kept constant. The height / width) tends to increase.

When the second-layer wiring 2 is present immediately above the first-layer wiring 2, the intervening capacitance of the polyimide film 3 is extremely thin, and therefore the mutual capacitance is increased. There is a problem that it will increase.

On the other hand, when the film is formed by the vapor phase epitaxy method, a film having a similar shape is grown in proportion to the unevenness of the underlying substrate, which is suitable for this purpose. Therefore, an organic insulating material having a dielectric constant smaller than that of polyimide and capable of forming a film by a vapor phase growth method is required as a constituent material of the interlayer insulating film.

[0014]

A material having a small dielectric constant and good coverage is required for an interlayer insulating film of a semiconductor device having an improved integration degree and a multilayer structure.

Here, inorganic insulating materials such as SiO ₂ , Si ₃ N ₄ and PSG are known as materials that can be formed into a film by the sputtering method or the vapor phase growth method, but these materials have good coverage. "Although the permittivity is large, on the other hand, polyimide has a relatively low permittivity," but it has a problem of poor coverage.

Therefore, it is an object to put into practical use a material having a smaller dielectric constant than polyimide and good coverage.

[0017]

The above-mentioned problems are solved by introducing para-xylylene radicals obtained by thermally decomposing diparaxylylene gas onto a semiconductor substrate having a first wiring layer formed thereon. A method for manufacturing a semiconductor device characterized in that after a thin film of polyparaxylylene is polymerized on a wiring layer to form a thin film of fluorinated polyparaxylylene, the thin film is used as an interlayer insulating film. Can be solved by configuring

[0018]

The inventor has paid attention to the polyparaxylylene represented by the general formula (5) in FIG. Polyparaxylylene is a material marketed by Union Carbide under the name of Parylene, and has a dielectric constant of about 2.6, which is smaller than that of polyimide.
It can be made by the vapor growth method.

The method for producing the same will be described. The raw material is diparaxylylene represented by the formula (3) in FIG. When it is heated to ℃, it decomposes into para-xylylene radicals represented by the formula (4).

Next, when this para-xylylene radical is brought to room temperature, the polymerization proceeds and polyparaxylylene represented by the formula (5) can be obtained. Since this polyparaxylylene has excellent coverage, a method of covering the surface of the package of a semiconductor device such as an LSI to prevent radiation damage due to α rays or the like has been proposed. (For example, JP-A-57-99758) However, the problem with polyparaxylylene is that it has an excellent heat resistance of about 400 ° C. This value is in an inert gas atmosphere such as N ₂ or H _2. The heat resistance in the atmosphere is insufficient.

Therefore, the inventor fluorinated the polyparaxylylene and replaced the hydrogen (H) atom constituting the phenyl group with a fluorine (F) atom as shown in the formula (6) of FIG. It improves the heat resistance of the inside.

The substitution position and substitution amount of the H atom of the phenyl group are arbitrary, and the formula (6) is merely an example. Such fluorination improves heat resistance and reduces the dielectric constant to about 2.3.

[0023]

EXAMPLE 1 FIG. 2 shows the structure of an apparatus for forming a polyparaxylylene film as an interlayer insulating film on a semiconductor substrate by a vapor phase growth method.

That is, diparaxylylene 6 is added to the sample tube 5.
Then, when heated to 160 ° C. by the heater 7, the diparaxylylene 6 starts sublimation. When the cock 8 is opened and the sublimed diparaxylylene 6 is heated to about 600 ° C. by the heater 9, the diparaxylylene is decomposed into paraxylylene radicals.

When the paraxylylene radical is introduced into the deposition chamber 10 under reduced pressure, there is a stage 11 which is water-cooled to a temperature of about 25 ° C., on which a semiconductor substrate 12 is placed. However, the polymerization of para-xylylene radicals proceeds on this, and a thin film of poly-para-xylylene can be obtained.

In this state, the film was treated for 30 minutes to obtain a thin film having a thickness of 3 μm. Next, the substrate with the thin film of polyparaxylylene was used at room temperature in N ₂ gas with F ₂ gas 5%
Fluorination was able to be performed by carrying out a minute treatment.

The thus-obtained fluorinated polyparaxylylene had a heat resistance of 400 ° C. or higher in the atmosphere, and the dielectric constant could be reduced to about 2.3. Example 2 After a polyparaxylylene thin film having a thickness of 3 μm was formed on a Si semiconductor substrate by the method of Example 1, this substrate was placed at a position downstream of the plasma processing apparatus, and nitrogen trifluoride was placed in the plasma processing apparatus. While supplying (NF ₃ ) and reducing the pressure to 1 torr by the exhaust system, microwaves were irradiated at an output of 750 W to form plasma, and the plasma was processed at the downflow position for 40 minutes for fluorination.

The thus-obtained fluorinated polyparaxylylene exhibited a heat resistance of 400 ° C. or higher in the atmosphere and a dielectric constant of about 2.3.

[0029]

According to the present invention, an interlayer insulating film having excellent heat resistance and a low dielectric constant can be obtained.

[Brief description of drawings]

FIG. 1 is a general formula illustrating the formation of fluorinated polyparaxylylene according to the present invention.

FIG. 2 is a sectional view showing a configuration of a polyparaxylylene film forming apparatus.

FIG. 3 is a cross-sectional view illustrating a problem of the spin coating method.

[Explanation of symbols]

 2 Wiring 3 Polyimide film 6 Diparaxylylene 12 Semiconductor substrate

Claims (2)

[Claims] 1. A paraxylylene radical obtained by thermally decomposing diparaxylylene gas is introduced onto a semiconductor substrate on which a first wiring layer is formed, and polymerized on the first wiring layer. A method for manufacturing a semiconductor device, comprising forming a thin film of polyparaxylylene, fluorinating the thin film to form fluorinated polyparaxylylene, and using the thin film as an interlayer insulating film. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the thin film is fluorinated by down-flowing a fluorine compound gas plasma.