JPS63274942A - Polyimide pattern forming method - Google Patents

Abstract

PURPOSE:To improve the adhesiveness between a polyimide (PI) film and photoresist at the time of wet etching by providing a specific PI boundary face reforming film on the PI film and subjecting the photoresist to exposing and developing after coating, then etching the PI. CONSTITUTION:The film of the PI consisting of arom. diamine which is 1mol. 4,4'-diamino diphenyl ether and tetracarboxylic anhydride which is 1mol one kind of pyromellitic acid anhydride 3,3',4,4'-biphenyl tetracarboxylic dianhydride or the mixture composed thereof is formed as the PI boundary face reforming film on the PI film 3 (1 is a substrate, 2 is a wiring) and after the photoresist 5 is coated thereon, the photoresist is subjected to exposing and developing, then the PI film 3 is etched. The PI is preferably low thermally expandable PI having <=3X10<-6>K<-1> coefft. of thermal expansion and the photoresist 5 is preferably a cyclized rubber type negative resist. Hydrazine hydrate, etc., are used for an etching agent and the etching rate of the boundary face reforming film 4 is preferably 1/2-2 times the etching rate of the PI film 3. The extremely fine patterns of the inter-layer insulating films of a VLSI are thereby formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a polyimide pattern, and in particular, to improving the adhesion between a low thermal expansion polyimide and a photoresist when patterning the low thermal expansion polyimide. Regarding strategy.

[Conventional technology]

Previously, JP-A-52-22071, JP-A-55-78
No. 0, as described in Japanese Patent Publication No. 55-42497, in order to pattern a PIQ (trade name of Hitachi Chemical) film, which is a polyimide resin, a negative photoresist 0 is used.
PI such as MR83 and 0NNR20 (Tokyo Ohka product name)
After coating on the Q film, exposing and developing it, it was etched with a mixed etching solution of hydrazine hydrate and ethylenediamine to form a pattern.

Recently, a low thermal expansion polyimide with a thermal expansion coefficient of 1/1 to 1/2 that of PIQ has been developed, and its usefulness has attracted attention because the thermal stress caused by the difference in thermal expansion coefficient with Si wafer is extremely small. There is. but.

When this polyimide was patterned in the same process as the above-mentioned PIQ pattern formation, a problem arose that the polyimide and photoresist were easily peeled off at the interface during etching, making it impossible to form a good pattern.

[Problems to be Solved by the Invention] As mentioned above, it is quite difficult to form a pattern by directly coating a low thermal expansion polyimide with a photoresist.

An object of the present invention is to improve the adhesion between a polyimide film and a photoresist when patterning a low thermal expansion polyimide by wet etching.

[Means for solving problems]

A feature of the present invention is that in forming a pattern of low thermal expansion polyimide, a polyimide-based interface modification film is interposed at the interface between the low thermal expansion polyimide film and the photoresist.

In particular, low thermal expansion polyimides have poor adhesion to photoresists compared to conventional polyimides.

This has a so-called rod-like structure in which the low thermal expansion polyimide exhibits a linear and rigid skeleton, and is therefore considered to have poor adhesion to the photoresist.

The main chain of this low thermal expansion polyimide is: and/or (where R is selected from an alkyl group, a fluorinated furkyl group, an alkoxyl group, a fluorinated alkoxyl group, an acyl group, and a halogen; Ω is an integer of 0 to 4; m is an integer from O to 2,
n is an integer from 0 to 3).

Further, the unit structure of the polyimide molecule is selected from the following formula.

(In the formula, R is selected from an alkyl group, a fluorinated alkyl group, an alkoxyl group, a fluorinated alkoxyl group, an acyl group, and a halogen, K is an integer of 0 to 3, Q is an integer of 0 to 4,
(m is an integer of 0 to 2, n is an integer of 0 to 3) This polyimide molecule is further blended with another polymer,
Alternatively, it may be copolymerized.A0 Polyimide having such a skeleton can be obtained by homopolymerizing an aromatic aminodicarboxylic acid derivative, or by copolymerizing an aromatic diamine or an aromatic diisocyanate with an aromatic tetracarboxylic acid. It can be obtained by reaction with derivatives.

Tetracarboxylic acid derivatives include esters, acid anhydrides, and acid chlorides. The use of acid anhydrides is preferable in terms of synthesis. The synthesis reaction is generally performed in a solution of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone, dioxane, etc. ~20
It is carried out in the range of 0°C.

The aminodicarboxylic acid derivative used in the present invention is 4-
Aminophthalic acid, 4-amino-5-methylphthalic acid, 4
Examples include -(p-anilino)-phthalic acid, 4-(3,5-dimethyl-4-anilino)phthalic acid, and esters, acid anhydrides, and acid chlorides thereof.

Aromatic diamines include the following:

p-phenyl diamine, 2,5-diaminotoluene,
2,5-diaminoxylene, diaminoxylene (2,3
, 5,6-tetramethyl p-phsmy
lenediamine), 2,5-cyamitsubensitrifluoride, 2,5-diaminoanisole,
2,5-diaminoacetophenone, 2,5-diaminobenzophenone, 2,5-diaminodiphenyl, 2,5-
Diaminofluorobenzene, benzidine, o-tolidine, m-tolidine, 3.3'.

5.5'-tetramethylbenzidine, 3.3'-dimethoxybenzidine, 3,3'-di(trifluoromethyl)benzidine, 3,3'-diacetylbenzidine, 3,
3'-difluorobenzidine, octafluorobenzidine, 4,4'-diaminoterphenyl, 4,4''-diaminoquarterphenyl.

Further, these diisocyanate compounds can also be used in the same manner.

Examples of the tetracarboxylic acid derivatives include pyromellitic acid, methylpyromellitic acid, dimethylpyromellitic acid, di(trifluoromethyl)pyromellitic acid, 3.3', 4.
4'-biphenyltetracarboxylic acid, 5,5'-dimethyl-3,3', 4,4'-biphenyltetracarboxylic acid-p (3t 4-dicarboxyphenyl)benzene, or their acid anhydrides, acid chlorides Examples include compounds, esters, etc.

Also, S i , S i O2, A Q , S i
In order to improve adhesion to substrates such as N, the general formula % formula % (Rs, R7 are divalent organic groups, R number, Re are monovalent organic groups, p, q are integers greater than 1) The diaminosiloxane represented by → indicates a coordinate bond). Here, R1, Rz, and Ra are alkyl groups having 1 to 4 carbon atoms, and Xl* Xz+ x8
゜X4y Xs and Xs are ligands that form a coordination bond with aluminum,
~4 alkyl group).

Among these aluminum chelate compounds, aluminum monoethylacetoacetate diisopropylate, aluminum diethylacetoacetate monoisopropylate, aluminum triacetylacetonate, aluminum triethylacetoacetate, and the like are particularly useful.

As a result of various studies, the polyimide interface-modified membrane of the present invention has
It has been found that 4,4'-diaminodiphenyl ether is suitable. This is a polyimide with a flexible skeleton and probably has a strong affinity with both photoresist and low thermal expansion polyimide with a rod-like structure. Specifically, as a polymeric acid anhydride obtained from 4,4'-diaminodiphenyl ether and pyromellitic dianhydride, PMDA and 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3.3
A copolymer containing 4,4'-biphenyltetracarboxylic dianhydride is suitable. Furthermore, other polymers may be blended or copolymerized with these polymers.

In the present invention, when applying the polyimide interface modified film to the low thermal expansion polyimide film, it is preferable that the low thermal expansion polyimide film is in a semi-cured state from the viewpoint of adhesive properties. That is, on the film in which the so-called imidization reaction to completely cure the low thermal expansion polyimide film has been completed,
When a polyimide-based interface-modified film is formed, the adhesion at this interface is somewhat poor, and if etching takes a long time, a phenomenon of peeling at this interface can be observed. In addition, even if the polyimide film is completely cured in this way, the surface can be coated with Ar sputtering or
It is more desirable to form a polyimide-based interface-modified film in addition to the plasma treatment. This will significantly improve the adhesion between the two.

No peeling phenomenon occurs at the interface.

The photoresist that can be used in the present invention is a negative type photoresist that can be wet-etched with an alkaline etchant, and includes a cyclized rubber-based resist. For example, there are 0MR83, 85 or 0NNR20 (trade name) manufactured by Tokyo Ohka.

Etching solutions for low thermal expansion polyimide include aqueous alkaline solutions such as KOH, NaOH, (CHa)4No)((τe
tra+methyl Ammonium Hydro
(abbreviated as TMA), hydrazine hydrate, and ethylenediamine. Among these, a mixed solution of hydrazine hydrate and ethylenediamine (for example, 7 by volume)
=3 to 3 near) is desirable from the viewpoint of etching speed and contamination of semiconductor elements, but it also poses a serious problem of peeling at the interface between polyimide and photoresist.

In the present invention, it is important to balance the etching rates of the low thermal expansion polyimide film and the polyimide interfacially modified film. That is, it is not preferable that the etching speed of both is too fast or too slow; it is preferable that the etching speeds of both be about the same. Preferably,
The etching rate of the polyimide interface modified film is preferably about 1/2 to 2 times that of the low thermal expansion polyimide. The etching rate of the interface-modified film can be controlled relatively easily by adjusting the blending ratio of pyromellitic anhydride, biphenyltetracarboxylic anhydride, and benzophenonetetracarboxylic anhydride.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in order of steps with reference to the drawings.

<Examples 1 to 7. Comparative Examples 1 to 7> In FIG. 1, an aluminum wiring M2 is formed on a substrate 1,
The upper surface thereof is coated with a low thermal expansion polyimide resin 3. As shown in Table 1, this low thermal expansion polyimide is prepared by mixing 1 mol of aromatic diamine and 1 mol of aromatic tetracarboxylic dianhydride in N-methyl-2-pyrrolidone (NMP) at 0 to 50°C. A polyamic acid varnish obtained by reaction at a temperature of .

This varnish was spin-coded and cured at 100"C for one hour to obtain a film with a thickness of 1 to 40 μm. Next, as a polyimide-based interface modified film, 1 mol of aromatic diamine shown in Table 1 and aromatic A polyamic acid varnish obtained by reacting 1 mol of tetracarboxylic dianhydride in NMP was used. That is, as shown in FIG. It was cured at ~250°C for 0.5 hours to form a polyimide interface modified film 4 with a film thickness of 0.1 to 0.5 μm.Next, as shown in FIG.
As a negative photoresist 5, spin code Tokyo Ohka type 0MR83 or 0NNR20 (product name) and heat it at 90'C.
Dry for 0 minutes. Next, as shown in FIG. 4, in order to remove the polyimide interface-modified film and the low thermal expansion polyimide film in the connection hole 6, the photoresist film was exposed and developed. Then, it was cured at 150°C for 20 minutes. Next, using the photoresist pattern as a mask, a mixed solution of hydrazine hydrate and ethylenediamine (temperature 30
I etched it with "C)" and opened the window.

As shown in Table 2, the etching process was completed in 2 to 4 minutes, and a good pattern was formed without any problems such as peeling.

Next, as shown in FIG. 6, the photoresist film was removed by immersing it in resist stripping solution S-502.

Thereafter, in order to complete the imidization reaction between the low thermal expansion polyimide film and the interface modified film, the film was cured at 400° C. for 0.5 h.

<Example 8> The low thermal expansion polyimide used in Example 1 was cured at a temperature (400° C.) at which imidization was completed. After treating this surface with Oz plasma asher (200W for 5 minutes),
, 4'-diaminodiphenyl ether, 0.5 mole of pyromellitic anhydride, and 5 moles of BTDAo (solvent: NMP) was spin-coded and cured at 200°C. After coating this polyimide with photoresist 0MR83,35CP and baking it at 90°C, it was exposed and developed, and etched with an etching solution of hydrazine hydrate/ethylenediamine = 7/3 (volume ratio). As a result, it was completely etched in 3 minutes. Etching is completed,
Furthermore, no phenomena such as peeling were observed.

〔Effect of the invention〕

According to the present invention, wet etching of low thermal expansion polyimide becomes possible, and etching of α-ray shielding films for thick memory elements, which requires a long time, and ultrafine pattern formation of interlayer insulating films of VLSI become possible. Ta.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. As a polyimide interface modified film on a polyimide film,
4,4'-diaminodiphenyl ether 1 mol of aromatic diamine and pyromellitic dianhydride 3,3',4,4'
-benzophenonetetracarboxylic dianhydride, 3,3,
A polyimide consisting of 1 mole of tetracarboxylic dianhydride selected from '4,4'-biphenyltetracarboxylic dianhydride or a mixture thereof is applied, a photoresist is applied, and the polyimide is etched by exposure and development. A method for forming a polyimide pattern, characterized by: 2. The method for forming a polyimide pattern according to claim 1, wherein the polyimide is a low thermal expansion polyimide having a coefficient of thermal expansion of 3×10^-^5K^-^1 or less. 3. The method for forming a polyimide pattern according to claim 1, wherein the photoresist is a cyclized rubber-based negative photoresist. 4. The method for forming a polyimide pattern according to claim 1, wherein the etching agent is hydrazine hydrate or a mixture of hydrazine hydrate and ethylenediamine. 5. The method for forming a polyimide pattern according to claim 1, wherein the etching rate of the polyimide interface-modified film is 1/2 to 2 times that of the polyimide. 6. The polyimide-based interfacially modified membrane contains 4,4'-diaminodiphenyl ether and pyromellitic dianhydride, 3,3
2. The method for forming a polyimide pattern according to claim 1, wherein the copolymer is a copolymer whose main component is ',4,4'-benzophenonetetracarboxylic dianhydride.