JPH01173621A - Method for etching process of polyimide resin - Google Patents

Abstract

PURPOSE:To use a high-molecular siloxane-modified polyimide resin as a coating for a semiconductor device, by exfoliating a negative resist using ultrasonic waves in an organic solvent which does not contain an interface activator. CONSTITUTION:In etching processes, a polyimide resin is used as a negative resist. The polyimide resin is made by reaction of an organic tetracarbonic acid dianhydride and a diamine component which contains 0.05-50mol% of a silicon diamine expressed by the formula I. After the etching process with such a polyimide used as a negative resist, the negative resist is exfoliated using ultrasonic waves in an organic solvent which does not contain an interface activator. In the formula I, R1 and R2 are methylene, pherylene or metathesis pherylene, n is an integer 1-4 and m is an integer 10-500. By this method, a high-molecular siloxane-modified polyimide resin can be used as a protective film for a semiconductor device by etching, without deteriorating any of the characteristics including a thermal resistance, electric and mechanical characteristics.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of etching polyimide resin for the purpose of protecting semiconductor elements.

[Traditional techniques]

Conventionally, polyimide resins with excellent heat resistance, electrical properties, mechanical properties, and processability have been used as surface protective films for semiconductor devices and the like. Recently, polyimide resins with a lower modulus of elasticity than before are required to absorb thermal stress caused by heat cycles and heat shocks of epoxy resin sealing materials, which are widely used as puff casing materials for semiconductor devices. The most effective way to lower the ratio is to introduce polymeric siloxane into the polyimide resin structure because it does not reduce other properties such as heat resistance and electrical properties.However, this polymeric siloxane-modified polyimide resin If the etching process is carried out in the same way as for ordinary polyimide resin, it has the disadvantage that the properties will be lost.The ordinary etching process for polyimide resin is to first apply the polyimide resin to a semiconductor wafer by spin coating using a spinner, etc. Next, apply a cyclized rubber-based resist as a negative resist, dry for 30 minutes at 80°C, and expose and develop with a photomask in close contact with the polyimide resin. Alternatively, etching is performed with a mixture of hydrazine and ethylenediamine.Then, only the '7 non-gare resist is dissolved and removed by heating at 100°C for 10 minutes with a phenolic stripper containing a surfactant. When etching molecular siloxane-modified polyimide resin, there is a problem that the polyimide resin dissolves in the cyst removal process. It contains surfactants and phenol, chlorinated solvents, or cellosolve-based solvents. The activator enters the interface between the polyimide and the resist and causes the resist to peel off.Finally, the surfactant alkylbenzenesulfonic acid acts as a catalyst for the decomposition of the double bonds in the cyclized rubber and dissolves the resist. This alkylbenzene sulfonic acid has a strong 'G%E ability, and when applied to a polymer siloxane-modified polyimide resin, the polymer siloxane component is also attacked and dissolved. 100
If the temperature is lower than .degree. C., for example 50.degree. C. or lower, dissolution of the polymeric siloxane-modified polyimide resin can be considerably prevented, but the ability to dissolve the negative resist will be markedly reduced and a large amount of resist will remain. On the other hand, if a positive resist is used in the etching process, the polyimide resin will not dissolve because the resist is removed using ketones such as acetone or alcohols such as methanol. However, the adhesion between the positive resist and the polymeric siloxane-modified polyimide resin is very poor, so during etching, the etching solution gets under the resist film, increasing the side etch and making it difficult to obtain the desired through-hole dimensions. It is not suitable for practical use because it is not available. [Object of the Invention] The present invention was developed as a result of extensive research into a method for removing negative resist without dissolving the polyimide resin in the etching process of polymeric siloxane-modified polyimide resin. They discovered and perfected a method of peeling using sound waves. The purpose of this method is to use the etched polymer siloxane-modified polyimide resin as a protective film for semiconductor devices without deteriorating its properties such as heat resistance, electrical properties, and mechanical properties. [Structure of the Invention] The present invention relates to an organic tetracarboxylic dianhydride and a general formula (1) % formula % (wherein R is a menalene group, a phenylene group or a substituted phenylene Ws, and Rz is a methyl group, a phenyl group or a substituted phenylene group) A polyimide resin made by reacting a diamine component containing 0.05 to 50 mol% of a silicone diamine represented by a phenyl group, n is an integer of 1 to 4, and m is an integer of 10 to 500, is etched using a negative resist. This is a polyimide resin etching method characterized by peeling off the negative resist using ultrasonic waves in an organic solvent containing no surfactant after processing. Examples of the organic tetracarboxylic dianhydride used in the present invention include pyromellitic dianhydride, 3.3'-4゜4'-benzophenonetetracarboxylic dianhydride, 2.3,6.7-
These include naphthalenetetracarboxylic dianhydride, and two or more of these may be used in combination. The silicone diamine used in the present invention has a siloxane bond←
The number m of 0-Si→ is 1O to 500, and it contains 0.05 to 50 mol% of the total diamine component, O,O
If it is less than S mol %, the effect of lowering the elastic modulus cannot be obtained, and if it is more than 50 mol %, the heat resistance will be significantly reduced. In addition to the long-chain silicone diamines mentioned above, examples of diamine components used in the present invention include p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl ether. Aromatic diamines such as can also be used in combination. In the reaction method of the present invention, a diamine component is blended in a ratio of 0.5 to 1.5 mol to 1 mol of organic tetracarboxylic dianhydride, and 1 to 1.
Stir for O hours. As the organic solvent, N,N'-dimethylacetamide,
Polar solvents such as N-methyl-2-pyrrolidone are preferred. In the etching method of the polymer siloxane-modified polyimide resin in the present invention, first, a polyimide resin is coated on a wafer of a semiconductor element with a spinner, and
Dry at a temperature of ℃ for 10 minutes to 10 hours in two or more steps as necessary to form a membrane J ¥0.5 to 50 μm.
Forms a film. Next, apply negative resist and 80~
After drying at 100°C for 10 to 60 minutes, expose and develop using a photomask.
Redry the resist for 0-60 minutes. Next, the polyimide resin is etched using a strong alkali such as hydrazine, ethylenediamine or tetramethylammonium hydroxide as an etching liquid. Furthermore, the resist is peeled off using ultrasonic waves in an organic solvent that does not contain a surfactant. Organic solvents used for resist stripping include aromatic hydrocarbons such as toluene and xylene, chlorinated solvents such as methylene chloride, trichloroethylene, and dichlorobenzene, cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, or acetates thereof. , N, N'-dimethylacetamide, N-
One or more polar solvents such as methyl-2-pyrrolidone may be used in combination. Resist? , it is also essential to apply ultrasonic waves in the lI#i steps. This is because the negative resist is swollen by infiltration into an organic solvent, and then ultrasonic waves are applied to infiltrate the solvent into the interface between the resist and polyimide, thereby physically peeling off the resist. Ultrasonic waves are carried out using a normal ultrasonic cleaner for 1 minute to 5 hours at an oscillation frequency of 20 to 50 Klz and an output of 20 to 500 W, depending on the capacity. The temperature is from 10° C. to the boiling point of the organic solvent used. Since the resist peeled off by the ultrasonic waves floats in the organic solvent, after performing the cyst peeling process, ultrasonic cleaning is performed once again using an organic solvent to prevent the resist from adhering to the polyimide surface. Finally, if necessary, heat treatment is performed at a temperature of 150 to 350° C. for 30 minutes to 2 hours to fully cure the polyimide. [Effects of the Invention] According to the method of the present invention, the resist can be removed efficiently in the etching process of the polymeric siloxane-modified polyimide resin, and the dissolution and deterioration of the polyimide resin, which are the drawbacks of conventional removal methods, are eliminated. It becomes possible to apply the polymer siloxane-modified polyimide resin to the coating of semiconductor devices, and the heat cycle resistance and heat shock resistance of semiconductor devices can be improved. [Example] [Example 1] 4.4 0.95 mol of '-diaminodiphenyl ether and 0.05 mol of siloxane diamine Cl1l CH3 of the following formula were dissolved in 7 volumes of N-methyl-2-pyrrolidone 'A.
Then, 140 mol of pyromellitic dianhydride was added, stirred at 20°C for 5 hours, and further diluted with N-methyl-2-pyrrolidone to obtain a polymeric loxane-modified polyimide with a viscosity of 20 poise and a solid content of 11%. A resin solution ill was obtained. This varnish (1) was applied with a spinner at 1000 rpm for 30 seconds onto a semiconductor element wafer having a passivation film of plasma silicon nitride (PSiN), and then heated at 100°C.
A 0-order negative resist was heated at 250°C for 30 minutes each to form a film with a thickness of 5 μm, and then applied with a spinner, and then heated at 80°C.
After drying for 30 minutes using a photomask, the resist is developed with a developer after exposure. Next, the polyimide of the bonding pad and the scribe line was etched with a 1:1 mixture of hydrazine and ethylenediamine.Then, the polyimide was heated in trichlorethylene for 10 minutes using a sonic cleaner (oscillation frequency: 45 KHz, output: 200 W). Then, change the trichlorethylene to a new one, perform ultrasonic cleaning for 5 minutes, and then wash at 250℃ and 350℃.
and heated for 30 minutes each. No resist residue was observed, and the surface condition of the polyimide film was good, with no dissolution or discoloration observed. This wafer was scribed into chips, mounted on a lead frame, and transfer molded with epoxy resin material. A heat cycle test was performed for 500 cycles, each cycle consisting of 30 minutes each at -65° C. and 150° C. When the molding material was opened, no cracks were observed in the passivation film on the chip surface. [Comparative Example] The resist was removed in the same manner as in Example 1, except that the resist was removed using a commercially available phenolic stripper containing a surfactant at 100° C. for 10 minutes. The polyimide film was partially dissolved, and the color changed from yellow to brown after final curing. 100~ in heat cycle test
A passivation crank was occurring. that's all

Claims (1)

[Claims] Organic tetracarboxylic dianhydride and general formula (1) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (1) (In the formula, R_1 is a methylene group, a phenylene group, or a substituted phenylene group, and R_2 is a A polyimide resin obtained by reacting a diamine component containing 0.05 to 50 mol% of a silicone diamine represented by a methyl group, a phenyl group, or a substituted phenyl group, where n is an integer of 1 to 4 and m is an integer of 10 to 500. A method for etching polyimide resin, which comprises etching using a negative resist and then peeling off the negative resist using ultrasonic waves in an organic solvent that does not contain a surfactant.