JPH0677209A - Manufacture of fluororesin - Google Patents

Abstract

PURPOSE:To provide an interlayer insulating film material having a low apparent dielectric constant and consisting of fibril structure fluororesin of low dielectric constant containing a large void. CONSTITUTION:A fluororesin thin film is formed by fluorinating a fibril structure high molecule compound 4 thin film which is crossed at random and contains a gap 10a. The fibril structure high molecule compound 4 is composed of a polymer of chain-like aliphatic hydrocarbon having a polar radical to be replaced by a non-polarity side chain and fluorine. After the fibril structure high molecule compound 4 has been compounded by polymerizing a monomer in the polymerization catalyst solution 10 which is coated on a substrate 1, the polymerization catalyst solution 10 is removed, a process in which a thin film of fibril structure high molecule compound 4 containing a gap 10a, and a process, in which the fibril structure high molecule compound 4 is fluorinated, are conducted and a thin film, consisting of the fibril structure high molecule compound 4, is fluorinated by exposing the thin film to fluorine or fluorine radical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluororesin thin film having fibrils randomly intersecting with each other and having voids.

For the interlayer insulating film of the integrated circuit, an insulating material having a low dielectric constant is required in order to reduce the wiring delay of electric signals. Therefore, a thin film made of a material having a small dielectric constant and having a large amount of voids containing a gas having a low dielectric constant is required.

[0003]

2. Description of the Related Art A conventional integrated circuit, for example, an interlayer insulating film for insulating each layer of a multilayer wiring of a semiconductor integrated circuit is formed of SiO ₂
It is formed of a deposited film containing as a main component or a deposited film made of an organic polymer material.

However, SiO ₂ has a high dielectric constant. Also,
Although organic polymer materials, especially those using a fluorine compound, have a lower dielectric constant, since the deposited film is densely packed, the apparent dielectric constant is smaller than that of the material of the deposited film. You cannot do it.

Therefore, reduction of the dielectric constant of the interlayer insulating film is limited, and it is difficult to form an interlayer insulating film having a low dielectric constant suitable for a high speed device.

[0006]

As described above, in the conventional interlayer insulating film made of a deposited film, the apparent dielectric constant cannot be made smaller than that of the material of the interlayer insulating film because of its high packing density. .

It is an object of the present invention to provide a fluororesin thin film which is made of a fibril structure fluororesin having a large amount of voids and a low dielectric constant and serves as an interlayer insulating film having a low apparent dielectric constant, and a manufacturing method thereof.

[0008]

FIG. 1 is a diagram for explaining the principle of the present invention, which shows a process of forming a thin film of fibril structure fluororesin covering electric wiring arranged on a substrate, and FIG. FIG. 4 is a process drawing of a cross section of an embodiment of the invention, showing a process of forming a first layer of a multilayer wiring and its interlayer insulating film.

In order to solve the above problems, FIG. 1 and FIG.
Referring to, the first structure of the present invention is characterized in that it is manufactured by fluorinating a thin film composed of the non-oriented fibril structure polymer compound 4 formed so as to randomly intersect with each other and containing the voids 10a. In the method for producing a fluororesin thin film of the first construction, the fibril structure polymer compound 4 is composed of a nonpolar side chain and a polar group substituted with fluorine by fluorination. The present invention is characterized in that a chain aliphatic hydrocarbon which may be present is polymerized to be produced, and a third constitution is a method for producing a fluororesin thin film of the first or second constitution, wherein the substrate 1 After polymerizing the monomer in the polymerization catalyst solution 10 coated on the above to synthesize the fibril structure polymer compound 4 which is randomly crossed, the polymerization catalyst solution 10 is removed and the fibril structure polymer containing voids 10a. Compound 4 is formed, and a step of fluorinating the fibril structure polymer compound 4 is constituted, and the fourth constitution is manufactured in the third constitution, and is vacuum or non-polar. A non-polar gas is filled in the voids 10a of the fluororesin 6 thin film dried in a neutral gas, and a sealing film 17 is formed on the surface of the thin film.

A fifth constitution is a method for producing a fluororesin thin film of the first, second or third constitution, in which the thin film made of the fibril structure polymer compound 4 is exposed to fluorine or a fluorine radical to be fluorinated. It is characterized by.

[0011]

The operation of the structure of the present invention will be described with reference to FIG. In the present invention, referring to FIG. 1A, first, a thin film made of a non-oriented fibril-structured polymer compound 4 in which fibrils are randomly crossed and includes voids 10a is formed.

Such a fibril-structured polymer compound 4 thin film is usually formed by a method of forming fibrils into a thin film, for example, after polymerizing a monomer in a polymerization catalyst solution 10 coated on a substrate 1, the polymerization catalyst solution 10 is used as a solvent. It can be manufactured by a method of forming a void 10a by dissolving it in and removing it.

Next, the fibril-structured polymer compound 4
The thin film is fluorinated and converted into a fibril-structured fluororesin 6. This fluorination can be carried out easily and without impairing the structure in which the fibrils are crossed by exposure to, for example, fluorine or fluorine radicals 5.

The fluororesin 6 according to the present invention produced by the above method has a fibril structure which is randomly crossed and forms a thin film of the fibril structure fluororesin 6 rich in the voids 10a.

Since the apparent density of the thin film having such a structure is smaller than that of the fluororesin, its apparent dielectric constant is also smaller than that of the fluororesin itself. Further, as the above-mentioned fibril-structured polymer compound, a polymer of a chain aliphatic hydrocarbon which may have a nonpolar side chain and a polar group substituted with fluorine by fluorination is used, and hydrogen of the side chain is fluorinated. Atoms and polar groups as well as hydrogen atoms in the main chain can be replaced with fluorine to convert into a fluorine resin having no polar group. Therefore, a low dielectric constant fluororesin thin film having no polar group can be manufactured.

Further, after filling the voids with a dry non-polar gas such as an inert gas or N ₂ gas, a sealing film 17, for example, a SiO ₂ film is formed on the surface of the thin film made of the fluororesin having the fibril structure. It is possible to form a film so as to have a structure in which the gas that fills the voids is sealed.

With this structure, it is possible to prevent molecules having polarity from entering the voids and to avoid an increase in the dielectric constant. Also, in the etching performed after the thin film formation,
It is possible to avoid damage to the fibril-structured fluororesin and realize an interlayer insulating film with excellent reliability.

[0018]

The present invention will be described in detail with reference to an embodiment in which the present invention is applied to an interlayer insulating film between multi-layer wirings of a semiconductor integrated circuit.

FIG. 3 is an explanatory view of the structure of a fibril-structured polymer thin film manufacturing apparatus according to an embodiment of the present invention, and schematically shows the structure of the main part. This apparatus is for forming a fibril-structured polymer thin film on the surface of a substrate, and referring to FIG. 3, a polymerization reaction including a spin coater 8, a vacuum stage 11 and a vacuum cap 12 in a glove box 7. A device is provided. Further, the inside of the glove box is filled with Ar gas.

First, referring to FIGS. 2A and 3, a semiconductor element is formed on the surface, and wiring 3 for connecting the semiconductor elements is formed on the lower insulating film 2 made of SiO ₂ formed on the surface.
The semiconductor substrate 1 on which is formed is placed on the turntable 9 of the spin coater 8, and the polymerization catalyst solution 10 is dropped on the substrate 1 rotating at 3000 rpm. For example, a thin layer of the polymerization catalyst solution 10 having a thickness of 1 μm covers the wiring 3. It is formed on the surface of the substrate 1.

This polymerization catalyst solution was prepared by adding a mixture of tetrabutoxy titanium and triethylaluminum mixed with titanium and aluminum at a ratio of 1: 4 to toluene so that the titanium concentration was 0.4 mol / liter. Dissolve in, and age for 1 hour at room temperature to adjust.

Next, referring to FIG. 3, the substrate 1 is transferred onto the vacuum stage 11, the vacuum cap 12 is brought into close contact with the vacuum stage 11, and the inside thereof is 3 × 10 ⁻³ Torr by the vacuum pump 13. Exhaust to.

Then, the suction port of the vacuum pump 13 is closed,
Acetylene as a monomer is introduced into the vacuum cap 12 from the monomer gas reservoir ball 15 connected to the vacuum exhaust pipe of the vacuum cap 12.

The acetylene introduced is shown in FIG.
, The polymerization catalyst solution 10 applied to the surface of the substrate 1
It undergoes a polymerization reaction inside to become polyacetylene, which is a fibril-structured polymer compound that is randomly crossed. The polyacetylene synthesized by such a method contains a large amount of the polymerization catalyst solution 10 between the crossed fibrils.

The pressure of acetylene during the above reaction may be 200 Torr at room temperature, and the reaction time may be 5 minutes. In this example, the pressure and the reaction time during the reaction are such that the polymer compound having a fibril structure is sufficiently generated and the generated fibrils are pressed against the lower insulating film, and as a result, the fibril structure is formed in the vicinity of the lower insulating film 2 and the wiring 2. It is preferable to select the polymer compound so that it becomes dense.

By adopting such a structure, when the fibril-structured polymer compound is fluorinated later, fluorine can be blocked by the dense layer to prevent the lower insulating film 2 or the wiring 2 from being damaged.

However, when the pressure of the monomer is too high, a dense fibril-structured polymer compound layer is formed on the surface of the polymerization catalyst solution 10, and the fibril-structured polymer is formed near the lower insulating film 2 and the wiring 2. Formed sparsely. Therefore, these damages may occur in the subsequent fluorination step.

On the other hand, when the pressure of the monomer is low, the reaction is slow, which is a disadvantage. Further, the lack of reaction time hinders the formation of a sufficiently dense fibril structure polymer layer in the vicinity of the lower insulating film 2 and the wiring 2.

Next, referring to FIG. 3, after completion of the reaction, the gas recovery trap 14 is cooled with liquid nitrogen to recover unreacted acetylene. Further, the recovered acetylene cools the cold finger 15a, which is provided outside the monomer gas reservoir sphere 15 and comprises a closed tube that opens into the monomer gas reservoir sphere 15, and further the cooling gas recovery trap 1
By raising the temperature of No. 4, it is collected again in the monomer gas reservoir sphere 15.

Next, the cock connected to the exhaust pipe of the vacuum cap 12 is closed and the leak valve 12a of the vacuum cap 12 is opened to leak the vacuum cap 12 to atmospheric pressure.

Then, the substrate is taken out from the vacuum stage 11, and the fibril structure polymer compound 4 formed on the substrate 1 is washed with a solvent of the polymerization catalyst solution 10, for example, toluene, and the polymerization contained in the fibrils is carried out. Catalyst solution 10
To remove.

Then, the substrate 1 is placed on the vacuum stage 11 again and, for example, at room temperature to 2 in a vacuum of 3 × 10 ⁻³ Torr.
Hold at 00 ° C to dry. As a result, referring to FIG. 2 (c), the region of the polymerization catalyst solution contained between the fibrils remained as voids 10a, and a thin film of fibril-structured polymer compound 4 having a large amount of voids 10a and randomly intersecting. Are formed on the substrate 1.

Next, the substrate 1 is taken out from the glove box 7 using the load lock 16 and placed in the plasma generator. Next, referring to FIG. 2D, the thin film of the fibril structure polymer compound 4 is exposed to the fluorine radicals 5 generated from the plasma.

As a result of this exposure of the fluorine radicals 5,
Referring to (e), the fibril structure polymer compound 4 has its hydrogen atom replaced with fluorine and the double bond part undergoes an addition reaction to be converted into a fibril structure fluororesin 6, for example, a fibril structure fluorinated polyolefin. Thus, a thin film made of the fibril structure fluororesin 6 is manufactured.

Fluorine radicals have a pressure of 1 atm and a flow rate of 500 sccm.
NF ₃ was produced by exciting plasma with a microwave having an output of 1 kW. The time required for fluorination is, for example, 10 minutes. Incidentally, instead of the fluorine radicals, it can be fluorinated by exposing it to nitrogen gas containing 5% fluorine gas at 1 atm for 1 hour.

Next, the substrate 1 is placed in the glove box 7, heated and dried in vacuum or Ar at 100 to 200 ° C., and then exposed to dry 1 atmosphere of Ar or nitrogen,
The void 10a in the fibril structure fluororesin 6 thin film is filled with a nonpolar gas such as Ar or nitrogen.

Next, referring to FIG. 3F, for example, a SiO ₂ film is SOG on the surface of the fibril structure fluororesin 6 thin film.
Method (spin coating method) to form a sealing film 17. The fibril-structured fluororesin 6 thin film having such a structure does not contaminate the voids and the fibril-structured fluororesin or damage the fibril-structured fluororesin even when it is exposed to the manufacturing process of the semiconductor device. It can be used stably as a small thin film.

In this example, a polymer of fibril-structured aliphatic hydrocarbon, which is an alternative to acetylene, such as a polymer of diacetylene can be used. As described above, the interlayer insulating film according to the present embodiment is made of the fibril structure fluororesin having a small dielectric constant, and since it contains many voids, the apparent dielectric constant of the thin film is smaller than that of the fibril structure fluororesin. Since it is small and the void is sealed with a non-polar gas having a small dielectric constant, it functions as an insulating layer having a small dielectric constant as a whole. Therefore, it is possible to form an interlayer insulating layer with a small wiring delay.

[0039]

According to the present invention, since it is possible to easily form a thin film made of a fibril structure fluororesin having a low dielectric constant and having a large amount of voids on a substrate, an interlayer insulating film having a low apparent dielectric constant can be obtained. A fluororesin thin film can be formed, which greatly contributes to the performance improvement of integrated circuits.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a sectional process drawing of an embodiment of the present invention.

FIG. 3 is an explanatory view of the structure of an apparatus for producing a fibril-structured polymer thin film according to an embodiment of the present invention.

[Explanation of symbols]

 1 Substrate 2 Base Insulating Layer 3 Wiring 4 Fibril Structure Polymer Compound 5 Fluorine Radical 6 Fluorine Resin 7 Glove Box 8 Spin Coater 9 Turntable 10 Polymerization Catalyst Solution 10a Void 11 Vacuum Stage 12 Vacuum Cap 12a Leak Valve 13 Pump 14 Gas Recovery Trap 15 Monomer gas reservoir sphere 15a Cold finger 16 Load lock 17 Sealing film

Claims (5)

[Claims] 1. A fluororesin thin film produced by fluorinating a thin film of a non-oriented fibril structure polymer compound (4) formed so as to randomly intersect with each other and containing voids (10a). Production method. 2. The method for producing a fluororesin thin film according to claim 1, wherein the fibril structure polymer compound (4) has a nonpolar side chain and a chain which may have a polar group substituted with fluorine by fluorination. A method for producing a fluororesin thin film, characterized by polymerizing and producing aliphatic hydrocarbons. 3. The method for producing a fluororesin thin film according to claim 1, wherein the fibrils are formed by polymerizing monomers in a polymerization catalyst solution (10) coated on a substrate (1) and randomly crossing them. A step of synthesizing a structural polymer compound (4) and then removing the polymerization catalyst solution (10) to form a thin film comprising the fibril structure polymer compound (4) containing voids (10a); And a step of fluorinating the polymer compound (4). 4. The non-polar gas is filled in the voids (10a) of the fluororesin (6) thin film produced by the method according to claim 3 and dried in a vacuum or non-polar gas, and the thin film surface is sealed. A method for producing a fluororesin thin film, which comprises forming a film (17). 5. The method for producing a fluororesin thin film according to claim 1, 2 or 3, wherein the thin film composed of the fibril-structured polymer compound (4) is exposed to fluorine or fluorine radicals for fluorination. And a method for producing a fluorine resin thin film.