JPH04328126A - Protection film for semiconductor and its production - Google Patents

Abstract

PURPOSE:To obtain a protection film having excellent moisture resistance and heat-resistance and low dielectric constant and useful for the protection of IC, etc., by reacting a specific tetracarboxylic acid dianhydride with a specific diamine and imidating the obtained wholly fluorinated polyamic acid. CONSTITUTION:A tetracarboxylic acid dianhydride of formula I (R1 is group of formula II, etc.; Rf is fluorine, perfluoroalkyl, etc.) or the tetracarboxylic acid and its derivative is made to react with a diamine of formula III (R2 is group of formula IV, etc.) and the resultant wholly fluorinated polyamic acid of formula V is imidated to obtain the protection film composed of the polyimide of formula VI.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a semiconductor protection device that uses fully fluorinated polyimide and has excellent heat resistance, low water absorption, and low dielectric constant, and can be used for ICs and LSIs with multilayer wiring structures. Concerning membranes and their manufacturing methods.

0002

[Prior Art] Inorganic materials such as silicon dioxide, silicon nitride, aluminum oxide, and glass, and polyimide resin are used as materials for interlayer insulating films when forming a multilayer wiring structure of two or more layers on a semiconductor substrate. Typical polymer materials are used. Among these, polyimide resins are increasingly being used because they have characteristics such as high heat resistance despite being able to be coated at low temperatures, low manufacturing costs, and easy manufacturing rationalization. JP-A-50-8469 uses polyimides produced from pyromellitic dianhydride and diaminodiphenyl ether as these polyimides. Also, U.S. Patent Nos. 4001870 and 40
No. 17886, No. 4040083, No. 40608
No. 28 discloses the use of polyimide as a material for an insulating film in multilayer wiring. Polyimide has excellent heat resistance and insulating properties, and because it can be easily obtained in thin films from a solution of its precursor polyamic acid by spin coating or casting, it is useful for protecting interlayer insulating films in multilayer wiring and semiconductor elements from external natural radiation. It is known to be useful as a protective film for

0003

[Problems to be Solved by the Invention] However, polyimide, which has a highly polar imide ring in its molecular structure, has a high water absorption rate, which may cause leakage at the PN junction of a semiconductor device.
There have been problems in that it causes corrosion of the aluminum wiring, and that it is not possible to achieve higher signal speeds due to its high dielectric constant.

That is, polyimide materials used as protective films for semiconductor devices have a major problem of water absorption. The present invention was made in view of the current situation, and its purpose is to provide a polyimide composition and a protective film that have sufficient low water absorption, heat resistance, and low dielectric constant to be used as a protective film for semiconductor devices. There is a particular thing.

[0005]

[Means for Solving the Problems] The present inventors have discovered that perfluorinated polyimide, which does not have hydrogen in its molecular structure, has a high degree of transparency in the near-infrared region and heat resistance. Next, as a result of intensive studies on the moisture resistance and dielectric constant of these polyimides, polyimide copolymers, and polyimide mixtures, we found that perfluorinated polyamic acid or perfluorinated polyimide obtained by dehydrating and ring-closing it can be used as a protective film composition. It has been found that the intended purpose can be achieved by using it as the main component of

That is, the first aspect of the present invention relates to a composition for a protective film, which has the following general formula I:

[0007]

[C7] (Here, R1 and R2 are the following structural formulas: R1:

[
0008

[Chemical formula 8] R2:

[0009]

[Image Omitted] In the formula, Rf is fluorine or a perfluoroalkyl group, and X is the following structural formula:

0010

embedded image In the formula, Rf represents fluorine or a perfluoroalkyl group, and Rf' represents a perfluoroalkylene group. ) Perfluorinated polyamic acid having a repeating unit represented by
Or the following general formula [II]:

[0011]

The main component is a perfluorinated polyimide having a repeating unit represented by the following formula (wherein R1 and R2 have the same meanings as those in formula [I] above), and a copolymer or mixture thereof. It is characterized by

Another invention of the present invention relates to a protective film for semiconductors, which has the following general formula [II]:

[0013]

It is characterized by containing a perfluorinated polyimide having a repeating unit represented by the following formula (wherein R1 and R2 have the same meanings as in formula [I] above).

[0014] Still another invention relates to a method for manufacturing a protective film for semiconductors, which has the following structural formula [III]:

[0015]

[Chemical formula 13] (In the formula, R1 has the same meaning as the above formula [I].) Tetracarboxylic dianhydride or its tetracarboxylic acid, and its derivatives, and the following general formula [IV]: H2N
-R2 -NH2 [IV] (In the formula, R2 has the same meaning as the above formula [I].) It is characterized by imidizing a perfluorinated polyamic acid obtained by reacting with a diamine represented by the above formula.

[0016] The present inventors have conducted extensive studies on various existing polyimides regarding their heat resistance, water absorption, etc. As a result, it was revealed that by replacing hydrogen atoms in the molecular structure of polyimide with fluorine atoms, the water repellency of fluorine was imparted to the polyimide, and the water absorption rate of the polyimide film could be significantly reduced.

The perfluorinated polyimide used in the present invention has a high fluorine content by using fluorine or a perfluoroalkyl group as the monovalent element bonded to carbon such as an alkyl group or a phenyl ring, and also has imide bonds as the main component. By introducing it into a chain structure to form polyimide, the protective film can have sufficient heat resistance to ensure reliability.

In the tetracarboxylic acid or derivative thereof used in producing the perfluorinated polyamic acid and polyimide of the present invention, all monovalent elements bonded to carbon atoms such as alkyl groups and phenyl rings in the molecule are replaced with fluorine, Alternatively, any perfluoroalkyl group may be used. Examples of tetracarboxylic acids and their derivatives such as acid anhydrides, acid chlorides, and esters include the following. Here, examples of tetracarboxylic acids include 1,4-difluoropyromellitic acid,
1-trifluoromethyl-4-fluoropyromellitic acid, 1,4-di(trifluoromethyl)pyromellitic acid,
1,4-di(pentafluoroethyl)pyromellitic acid,
Hexafluoro-3,3',4,4'-biphenyltetracarboxylic acid, hexafluoro-3,3',4,4'-
Benzophenonetetracarboxylic acid, 2,2-bis(3,
4-dicarboxytrifluorophenyl)hexafluoropropane, 1,3-bis(3,4-dicarboxytrifluorophenyl)hexafluoropropane, 1,4-
Bis(3,4-dicarboxytrifluorophenoxy)
Tetrafluorobenzene, hexafluoro-3,3',
Examples include 4,4'-oxybisphthalic acid. Among them, 1,4-di(trifluoromethyl)pyromellitic dianhydride, 1,4-di(trifluoromethyl)pyromellitic dianhydride, which is a fluorine-containing dianhydride with a fluoroalkyl group introduced into the benzene ring of pyromellitic dianhydride;
A method for producing 4-di(pentafluoroethyl)pyromellitic dianhydride and the like is described in Japanese Patent Application No. 165056/1983.

Examples of diamines that can be used in the present invention include those in which all monovalent elements bonded to carbons such as alkyl groups other than amino groups and phenyl rings in the molecule are fluorine or perfluoroalkyl groups. Any compound may be used as long as it is 3,4,5,6-tetrafluoro-1,2-phenylenediamine, 2,4,5,6-tetrafluoro-1,3-phenylenediamine, 2, 3,
5,6-tetrafluoro-1,4-phenylenediamine, 4,4'-diaminooctafluorobiphenyl, bis(2,3,5,6-tetrafluoro-4-aminophenyl)ether, bis(2,3, 5,6-tetrafluoro-4-aminophenyl)sulfone, hexafluoro-
2,2'-(bistrifluoromethyl)-4,4'-diaminobiphenyl, and the like.

[0020] If the polyimide is soluble, it is also possible to use corresponding diisocyanates instead of these diamines.

[0021] The method for producing the perfluorinated polyamic acid, which is the perfluorinated polyimide precursor used in the present invention, may be the same as the manufacturing conditions for ordinary polyamic acid, and generally N
- The reaction is carried out in a polar organic solvent such as methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide. In the present invention, diamines or tetracarboxylic dianhydrides are not only used as a single compound, but also a plurality of diamines and tetracarboxylic dianhydrides may be used as a mixture. In that case, the total number of moles of multiple or single diamines and the total number of moles of multiple or single tetracarboxylic dianhydride are made to be equal or approximately equal. In the above-mentioned polymerization solution of polyamic acid or the like, the concentration of the solution may be 5 to 40% by weight, preferably 10 to 25% by weight. This reaction proceeds rapidly by stirring in an inert solvent at a temperature around room temperature, and the viscosity of the solution after the reaction gradually increases. The rotational viscosity of this polymer solution is preferably between 50 and 500 poise (at 25°C).

In the present invention, the above-mentioned polyamic acid solution may be used as a mixture of two or more types, and furthermore, the above-mentioned polyamic acid solution may be mixed with other polyamic acid solutions or polyimide solutions within an allowable range in terms of water absorption and heat resistance. ,
It is also possible to mix and use other resin solutions other than polyimide.

[0023] As a method for manufacturing the protective film for semiconductors of the present invention, a conventional method for manufacturing polyimide films can be used. For example, a polyamic acid solution is spin-coated onto a semiconductor element on a substrate, and heated from 70°C to 20°C under a nitrogen atmosphere.
The mixture is heated stepwise to 0°C (70°C for 2 hours, 160°C for 1 hour, 250°C for 30 minutes, and 350°C for 1 hour) to imidize.

[0024] Furthermore, as shown in the examples, if it becomes soluble in a polar solvent even after imidization is completed, the imidized product is dissolved in a solvent to a concentration of 10 to 25% and applied. A protective film can also be produced by heating the mixture at 70 to 100° C. for about 2 to 6 hours to remove the solvent. In order to achieve the intended purpose, it is preferable that all the components of the protective film composition be perfluorinated polyamic acid or perfluorinated polyimide, but non-perfluorinated acid anhydrides or diamines may be used. Even if a certain amount is used as a raw material, it will not be a big problem if the proportion is small.

[0025]

EXAMPLES The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to these Examples.

In each of the following examples, imidization was confirmed by the characteristic absorption due to the symmetrical and asymmetrical stretching vibrations of the carbonyl group in the infrared absorption spectrum. The thermal decomposition temperature was expressed as the temperature at which the weight decreased by 10 wt% when the temperature was increased at a rate of 10° C./min under a nitrogen stream. In addition, the water absorption rate is 20 to 30μ thick.
A polyimide film of m was prepared, and the weight increase was determined by soaking it in water at 23° C. and saturating it. Further, the dielectric constant of the polyimide protective film is a value measured at a frequency of 1 kHz. Example 1 1,4-bis(3,
4-Dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride

[0027]

embedded image 11.644g (20.0mmol) and 2,4,5,6-tetrafluoro-1,3-phenylenediamine represented by the following structural formula

[0028]

embedded image 3.602 g (20.0 mmol) and 86 g of N,N-dimethylacetamide (DMAc) were added. This solution was stirred at room temperature in a nitrogen atmosphere for 3 days to obtain a DMAc solution of polyamic acid. This material was spin-coated on an aluminum slope and heated at 70°C for 2 hours in a nitrogen atmosphere for 1 hour.
Heat imidization was performed at 60°C for 1 hour, at 250°C for 30 minutes, and at 350°C for 1 hour. This sample was immersed in a 10% aqueous hydrochloric acid solution, and the aluminum plate was dissolved to obtain a polyimide film. When the infrared absorption spectrum of this polyimide film was measured, an absorption characteristic of imide groups appeared at 1790 cm<-1 >and it was confirmed that imidization had progressed completely. Table 1 shows the thermal decomposition temperature, saturated water absorption rate, and dielectric constant of this polyamide film. Example 2 In an Erlenmeyer flask, 11.644 g (20.0 mmol) of 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride and bis(2,3, 5,6-tetrafluoro-4
-aminophenyl)ether

[0029]

embedded image 6.883 g (20.0 mmol) and 105 g of N,N-dimethylacetamide (DMAc) were added, and a polyimide film was obtained in the same manner as in Example 1. Table 1 shows the thermal decomposition temperature and saturated water absorption rate of this polyimide film. Example 3 In a separable flask, 11.644 g (20.0 mmol) of 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride and bis(
6.883 g (20.0 mmol) of 2,3,5,6-tetrafluoro-4-aminophenyl)ether and m-
100 g of cresol was added. This mixture was stirred and dissolved at room temperature under a nitrogen atmosphere, and then reacted at 180° C. for 5 hours. Next, the reaction solution was poured into methanol, and the resulting solid was pulverized with a mixer. After thoroughly washing this with methanol, it was dried under vacuum at 100° C. for a day and night to obtain a powder of perfluorinated polyimide. Dissolve this in DMAc and
A wt% polyimide solution was obtained. The viscosity of this solution was approximately 80 poise. This was spin-coated onto an aluminum plate, and the solvent was removed at 100° C. for 4 hours in a nitrogen atmosphere. This sample was immersed in a 10% aqueous hydrochloric acid solution, and the aluminum plate was dissolved to obtain a polyimide film. This film did not lose weight even after being held at 400°C for 2 hours, and as shown in Table 1, the water absorption rate was 0.10% and the dielectric constant was 2.
It was 5. Example 4 1,4-difluoropyromellitic dianhydride having the following structural formula in an Erlenmeyer flask

[0030]

[Chemical formula 17] 5.082g (20.0mmol) and 2,4,5,6-
Tetrafluoro-1,3-phenylenediamine 3.60
2 g (20.0 mmol) and 49 g of N,N-dimethylacetamide (DMAc) were added, and a polyimide film was obtained in the same manner as in Example 1. Table 1 shows the thermal decomposition temperature and saturated water absorption rate of this polyimide film. Example 5 In an Erlenmeyer flask, 5.082 g (20.0 mmol) of 1,4-difluoropyromellitic dianhydride and bis(2,3
, 6.883 g (20.0 mmol) of 5,6-tetrafluoro-4-aminophenyl)ether, and N,N-
A polyimide film was obtained in the same manner as in Example 1 by adding 68 g of dimethylacetamide (DMAc). Table 1 shows the thermal decomposition temperature and saturated water absorption rate of this polyimide film. Example 6 In an Erlenmeyer flask, 5.082 g (20.0 mmol) of 1,4-difluoropyromellitic dianhydride and bis(2,3
,5,6-tetrafluoro-4-aminophenyl) sulfide 7.205g (20.0mmol) and N,N-
A polyimide film was obtained in the same manner as in Example 1 by adding 70 g of dimethylacetamide (DMAc). Table 1 shows the thermal decomposition temperature and saturated water absorption rate of this polyimide film. Example 7 Instead of 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride used in Example 3, 5.082 g of 1,4-difluoropyromellitic dianhydride ( A polyimide film was obtained in the same manner as in Example 1 using 20.0 mmol). This film did not lose weight even after being held at 400° C. for 2 hours, had a water absorption rate of 0.2%, and a dielectric constant of 2.7. Example 8 1,4-di(trifluoromethyl)pyromellitic dianhydride represented by the following structural formula in an Erlenmeyer flask

0031
]

[Chemical formula 18] 7.082g (20.0mmol) and bis(2,3,5
, 6-tetrafluoro-4-aminophenyl) sulfide (7.205 g (20.0 mmol)) and 57 g of N,N-dimethylacetamide (DMAc) were added, and a polyimide film was obtained in the same manner as in Example 1. Table 1 shows the thermal decomposition temperature and saturated water absorption rate of this polyimide film. Example 9 Instead of 2,4,5,6-tetrafluoro-1,3-phenylenediamine used in Example 1, 2,4
, 5,6-tetrafluoro-1,3-phenylenediamine 1.801 g (10 mmol) and bis(2,3,5,
6-tetrafluoro-4-aminophenyl)ether 3
．． A polyimide film was obtained in the same manner as in Example 1 using a mixture of 442 (10 mmol). This film did not lose weight even after being held at 400°C for 2 hours, had a water absorption rate of less than 0.2%, and a dielectric constant of 2.
It was 7 or less.

Example 10 7.26 g of the polyamic acid solution prepared in Example 1 and 8.90 g of the polyamic acid solution prepared in Example 3 were mixed, and a polyimide film was obtained in the same manner as in Example 1. This film did not lose weight even after being held at 400° C. for 2 hours, had a water absorption of 0.2% or less, and a dielectric constant of 2.7 or less.

Example 11 The polyamic acid solution prepared in Example 1 was spin-coated onto an aluminum wiring pattern prepared on a silicon substrate with a silicon oxide surface so that the final film thickness after imidization was about 2 μm. , Heat imidization was performed at 70° C. for 2 hours, at 160° C. for 1 hour, at 250° C. for 30 minutes, and at 350° C. for 1 hour in a nitrogen atmosphere. This sample was placed in a pressure cooker tester and treated for 20 hours at 120° C. and a water vapor pressure of 20 atmospheres. After the treatment was completed, the aluminum of the wiring was observed using a microscope. As a result, almost no corrosion was observed on aluminum. Comparative Example 1 Pyromellitic dianhydride having the following structural formula was placed in an Erlenmeyer flask.

[0034]

embedded image 4.362g (20.0mmol) and 4,4'-diaminodiphenyl ether represented by the following structural formula

003
5]

embedded image 4.005 g (20.0 mmol) and 75 g of N,N-dimethylacetamide (DMAc) were added, and a polyimide film was obtained in the same manner as in Example 1. Table 1 shows the thermal decomposition temperature, saturated water absorption rate, and dielectric constant of this polyimide film. Comparative Example 2 In Example 11, the same steps as in Example 11 were carried out using the polyamic acid solution prepared in Comparative Example 1 instead of the polyamic acid solution prepared in Example 1. Corrosion was observed in some parts of the aluminum after the pressure cooker test.

[0036]

[Table 1]

[0037]

As described above, according to the present invention, a composition for a protective film having excellent heat resistance, low water absorption, and low dielectric constant can be obtained. It has been found that this film has superior water resistance and sufficient heat resistance compared to conventional polyimide resin films.

Claims (4)

[Claims] [Claim 1] The following general formula [I]: [Formula 1] (wherein R1 and R2 are the following structural formula: R1:
[Formula 2] R2: [Formula 3] Here, Rf is fluorine or a perfluoroalkyl group, and X is the following structural formula: [Formula 4] Here, Rf is fluorine or a perfluoroalkyl group, Rf' represents a perfluoroalkylene group. ), a polyamic acid copolymer thereof, and a polyamic acid mixture. [Claim 2] A perfluorinated polyimide represented by the following general formula [II]: [Chemical formula 5] (wherein R1 and R2 have the same meanings as the formula [1] of claim 1), and a polyimide copolymer thereof A composition for a semiconductor protective film comprising a polyimide mixture. 3. A protective film for a semiconductor, comprising the perfluorinated polyimide represented by the general formula [II] according to claim 2. [Claim 4] A tetracarboxylic dianhydride or its tetracarboxylic acid represented by the following structural formula [III]: [Chemical formula 6] (wherein R1 has the same meaning as the formula [I] of claim 1), and its derivatives, and the following general formula [IV]:H
2 N-R2 -NH2 [IV] (wherein R2 has the same meaning as the formula [I] of claim 1). Characteristics and manufacturing method of protective film for semiconductors.