JPH07263549A - Manufacture of multilayer interconnect structure - Google Patents

Abstract

PURPOSE:To obtain a multilayer interconnect structure which has a good adhesiveness and a high reliability even when a polyimide film of a stiff structure is used as an upper-layer insulator layer by etching the surface of a patterned thermal oxide film. CONSTITUTION:This is a method for manufacturing a multilayer interconnect structure which includes the following processes. (A) A thermal oxide film is formed on a silicon substrate. (B) The thermal oxide film is patterned and the surface of the thermal oxide film is etched. (C) A metal layer is formed on the silicon substrate on which the thermal oxide film is formed. (D) The metal layer is patterned and a part of the thermal oxide film is exposed. (E) An insulator layer is formed on the silicon substrate on which the metal layer is formed. And, other processes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer wiring structure, and more particularly to a method for manufacturing a high density packaging multilayer wiring structure using a thermal oxide film as an interlayer insulating film. Is.

[0002]

2. Description of the Related Art As a multilayer wiring structure for high-density mounting using polyimide as an interlayer insulating film, a copper-polyimide multilayer wiring structure using copper for metal wiring is known (for example, "Nikkei Electronics"). 145-158 pages,
(August 27, 1984 issue). As an example of the multilayer structure of the multilayer wiring structure, a thermal oxide film is formed on a silicon substrate, a metal layer is formed thereon, and the metal layer is partially etched to form a pattern, and A polyimide layer may be formed. In this case, since the underlying thermal oxide film is partially exposed when the metal layer is partially etched,
It comes into contact with the upper polyimide layer.

[0003]

However, the adhesiveness between the thermal oxide film and the polyimide is often not good, and the adhesiveness is very poor, especially when the polyimide has a rigid structure. Therefore, when a multilayer wiring structure having the above-described structure is manufactured by using a polyimide having a conventional rigid structure, it has often been encountered that peeling occurs between the thermal oxide film and the polyid.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a method for producing a multilayer wiring structure having good adhesion between a thermal oxide film and an upper polyimide film and high reliability. .

[0005]

The object of the present invention is as follows.
This is achieved by the following configuration.

That is, it is a method of manufacturing a multi-layered wiring structure characterized by including the following steps. (A) A step of forming a thermal oxide film on a silicon substrate. (B) A step of patterning the thermal oxide film and etching the surface of the thermal oxide film. (C) A step of forming a metal layer on the silicon substrate on which the thermal oxide film is formed. (D) A step of patterning the metal layer to partially expose the thermal oxide film. (E) A step of forming an insulator layer on the silicon substrate on which the metal layer is formed.

The thermal oxide film in the present invention is a film formed by oxidizing the surface of a silicon substrate, the main component of which is silicon dioxide. The method for forming the thermal oxide film is not particularly limited, and examples thereof include a method of heating the silicon substrate in an oxygen atmosphere, a method of burning hydrogen in oxygen and oxidizing the silicon substrate in the atmosphere. Further, a method of oxidizing a silicon substrate under a gas in which hydrochloric acid or chlorine is mixed in oxygen or a mixed gas of oxygen and hydrogen is also included.

As a method of patterning the thermal oxide film in the present invention, generally, a method of forming a pattern of a photoresist on the thermal oxide film and etching the lower thermal oxide film using the photoresist pattern as a mask is used. To be At this time, the method of etching the thermal oxide film is not particularly limited, but a method using a hydrofluoric acid aqueous solution is generally used. The hydrofluoric acid concentration of the hydrofluoric acid aqueous solution is 1 to
50% by weight is preferable, and more preferably 5 to 30% by weight.
Is. Further, ammonium fluoride may be added to the aqueous solution of hydrofluoric acid.

The method of etching the surface of the thermal oxide film in the present invention is not particularly limited, but a method of wet etching using an etching solution and a method of dry etching using gas can be mentioned.

Examples of the etching solution include hydrofluoric acid aqueous solution and sodium hydroxide aqueous solution, with hydrofluoric acid aqueous solution being most preferred. When etching is performed using a hydrofluoric acid aqueous solution, the hydrofluoric acid concentration is preferably 0.01 to 50% by weight, more preferably 0.5 to 30% by weight. If the concentration is low, it takes a long time for etching, and if the concentration is high, etching is excessive and the thickness of the thermal oxide film tends to be remarkably reduced. Ammonium fluoride or the like can be added to the aqueous solution of hydrofluoric acid. The etching rate is stabilized by adding ammonium fluoride or the like. Examples of the wet etching method include a method of immersing in an etching solution and a method of coating on a substrate by spraying, and the method of immersing is generally used. The etching time varies depending on the concentration of the etching solution, but it is sufficient if the extreme surface of the thermal oxide film can be etched.

In the case of dry etching using a gas, gaseous neutral atoms, gaseous neutral molecules, ions, radicals, plasma and electrons can be used as the gas.
Specifically, argon, oxygen, tetrafluoromethane,
Examples thereof include, but are not limited to, a mixed gas of tetrafluoromethane and hydrogen, hexafluoroethane, argon ions, oxygen ions and the like. As the etching device, a plasma etching device, an ashing device,
A known device such as a reverse sputtering device can be used.

The etching depth is preferably 0.001 μm or more from the surface of the thermal oxide film. If it is shallower than this, it is difficult to obtain good adhesion between the thermal oxide film and the upper insulating layer (such as polyimide). Note that the etching depth here means roughness of the surface of the thermal oxide film.

By etching the surface of the thermal oxide film in this manner, the surface of the thermal oxide film is roughened and irregularities are formed, so that the adhesiveness between the thermal oxide film and the upper insulating layer (such as polyimide) is increased. Can be improved.

Either the etching of the surface of the thermal oxide film or the patterning may be performed first.

A metal layer is formed on the silicon substrate on which the thermal oxide film is formed. As the metal layer in the present invention,
Copper, nickel, copper alloy, nickel alloy, aluminum,
Examples thereof include those using gold, chromium, platinum, silver or the like alone, or those having a multilayer structure of two or more of these metals. Examples of the method for forming the metal layer include known methods such as a sputtering method, a vacuum evaporation method, an electrolytic plating method, an electroless plating method, and an electron beam evaporation method.

The metal layer is patterned. As a method of patterning the metal layer, a method of forming a pattern of a photoresist on the metal layer and using the mask as a mask to etch the underlying metal layer to pattern the metal layer is generally used. At this time, the lower thermal oxide film is exposed at the portion where the metal layer is etched.

After forming the metal layer, a treatment using a coating liquid containing an organosilicon compound can be carried out if necessary. By performing the treatment, the adhesiveness between the partially exposed thermal oxide film and the insulating layer is further improved.

Examples of the organosilicon compound include compounds represented by the following formula.

[Chemical 1] Here, n is an integer of 1 or more. In addition, R ₁ , R ₂ , R ₃
Represents a monovalent hydrocarbon group or an alkoxy group. Examples of the monovalent hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a phenyl group and a tolyl group, or a group of these groups. Examples include groups in which some or all of the hydrogen atoms are substituted with organic groups such as amino groups and methacryl groups. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propyl group and a butyl group. R ₄ represents a monovalent hydrocarbon group or hydrogen. Examples of the monovalent hydrocarbon group are the same as above.

Specific preferred examples of such organosilicon compounds include N-β (aminoethyl) γ-aminopropyltriethoxysilane and N-β (aminoethyl) γ-
Aminosilanes such as, but not limited to, aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane and the like can be mentioned.

These organic silicon compounds are dissolved in an organic solvent and then water is added to prepare a coating solution. The organic solvents used are alcohols, esters,
Known compounds such as ketones and aromatic hydrocarbons can be used alone or in combination. Further, as the coating liquid containing the organosilicon compound, a commercially available coating liquid can be used. For example, AP-420 (manufactured by Toray Industries, Inc.), VM-6
51 (manufactured by Du Pont) can be used.

A known method such as a spinner method, a spray method or a dipping method may be used as a method for applying these coating solutions.
After coating, it is dried to form an organosilicon compound film.
Drying conditions are less than 100 ° C, preferably 10 to 90
A temperature of 1 to 40 minutes is suitable.

An insulating layer is formed on the silicon substrate on which the metal layer is formed, and the insulating layer is usually patterned. Polyimide is generally used as such an insulating layer.

To form an insulating layer made of polyimide and pattern it, a polyimide precursor composition is applied,
After drying, pattern processing and curing may be performed.

The polyimide precursor composition of the present invention includes pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 4,4'. ′ -Diaminodiphenyl ether, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 3,3 ′ (or 4,4 ′)- Diaminodiphenyl sulfone, pyromellitic dianhydride and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride and 3,3 ′ (or 4,
4 ')-diaminodiphenyl sulfone, 3,3', 4
4'-benzophenone tetracarboxylic dianhydride and 3,
3 '(or 4,4')-diaminodiphenyl sulfone, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 3,3' (or 4,4 ')-diaminodiphenyl sulfone, Pyromellit Acid dianhydride and 4,4'-
Diaminodiphenyl sulfide, 3,3 ', 4,4'-
Benzophenone tetracarboxylic dianhydride and 4,4'-
Diaminodiphenyl sulfide, 3,3 ', 4,4'-
Biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl sulfide, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and paraphenylenediamine, 3,3', 4,4'-biphenyl Tetracarboxylic dianhydride and paraphenylenediamine, pyromellitic dianhydride and 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and paraphenylenediamine, pyromellitic dianhydride and 3,3 ', 4, 4'
-Biphenyltetracarboxylic dianhydride and paraphenylenediamine, 3,3 ', 4,4'-diphenyl ether Tetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether, 3,3', 4,4'-diphenyl ether Polyimide precursor synthesized from tetracarboxylic dianhydride and paraphenylenediamine, pyromellitic dianhydride and 4,4′-diaminodiphenyl ether and bis (3-aminopropyl) tetramethyldisiloxane, and polyimides thereof A compound having a structure in which a carboxyl group of a precursor is esterified with alcohol, and a polyimide obtained by imidizing these polyamic acids are dissolved in an aprotic polar solvent such as N-methylpyrrolidone or γ-butyrolactone. You can list the following.

Among the polyimide precursors exemplified above, the acid component is pyromellitic dianhydride or 3,3 ', 4.
Since the structure of 4'-benzophenone tetracarboxylic acid dianhydride and the like, and those containing paraphenylenediamine in the diamine component are rigid, the adhesiveness to the lower thermal oxide film tends to be a problem, According to the invention,
When the surface of the thermal oxide film is etched, the adhesiveness with such a rigid polyimide film is also improved, and a practical multilayer wiring structure can be obtained.

Photosensitivity can be imparted to these polyimide precursor compositions. The method of imparting photosensitivity is not particularly limited, but a methacrylic group, an acrylic group,
Examples thereof include a method of mixing a compound having a vinyl group and the like, a method of ester-bonding a group having a double bond to a carboxyl group portion of a polyimide precursor, and a method of introducing a methyl group into a polyimide skeleton. The method of imparting photosensitivity is described in, for example, JP-B-55-30207 and JP-B-59-52.
822 and JP-A-53-127723.

A known method may be used to pattern the polyimide precursor coating. When a polyimide precursor composition having no photosensitivity is used, a photoresist pattern is formed on the polyimide precursor film, and the lower layer polyimide precursor film is etched and patterned using the photoresist pattern as a mask. When the photosensitive polyimide precursor composition is used, the polyimide precursor coating may be directly patterned by a photolithography method.

As a method of curing the polyimide precursor coating, a temperature of room temperature to 450 ° C. is selected in a nitrogen atmosphere,
A method is preferred in which the temperature is raised stepwise or a certain temperature range is selected and the temperature is continuously raised for 5 minutes to 5 hours. The maximum temperature of this heat treatment is 120 to 450 ° C., preferably 13
It is preferable to carry out at 0 to 450 ° C. As an example of the temperature raising method,
Examples include a method of performing heat treatment at 130 ° C., 200 ° C., and 400 ° C. for 30 minutes each, or a method of linearly increasing the temperature from room temperature to 400 ° C. over 2 hours and performing heat treatment at 400 ° C. for 1 hour.

The multi-layer wiring structure is manufactured in this manner, and by repeating the lamination of the metal layer and the insulating layer, it is possible to obtain a multi-layer wiring structure having more layers.

[0030]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 A thermal oxide film was formed on the upper surface of a silicon substrate by burning hydrogen in oxygen and oxidizing the silicon substrate in that atmosphere. A photoresist OMR85 is formed on the thermal oxide film.
(Tokyo Ohka Co., Ltd.) was applied using a spinner at 3000 rpm for 10 seconds, and a mask was applied after prebaking. 2
After exposure with an exposure amount of 0 mJ / cm ² , development was performed using a dedicated developer (manufactured by Tokyo Ohka). After that, heat treatment was performed at 140 ° C. for 30 minutes to form a photoresist pattern. Next, using this photoresist as a mask, the lower thermal oxide film was etched for 10 minutes using a 10% hydrogen fluoride aqueous solution. Next, the photoresist was stripped using a stripping solution 502 (manufactured by Tokyo Ohka) to complete patterning of the thermal oxide film. Then, the surface of the patterned thermal oxide film was dipped in a 3% hydrofluoric acid aqueous solution and etched for 2 minutes.

Thereafter, a 0.1 μm chromium layer was formed on this substrate by sputtering. A photoresist OMR85 (manufactured by Tokyo Ohka Co., Ltd.) was applied on the chromium layer using a spinner at 3000 rpm for 10 seconds, and a mask was applied. After exposure with an exposure amount of 20 mJ / cm ² , a dedicated developer (manufactured by Tokyo Ohka). Was used for development. Then 140 ° C
And heat-treated for 30 minutes to form a photoresist pattern. Next, using this photoresist as a mask, chromium was etched for about 10 minutes using a 5% aqueous sodium hydroxide solution containing 15% potassium ferricyanide. As a result, the thermal oxide film was exposed at the portion where the chromium was etched.

Next, equimolar amounts of 3,3 ', 4,4 are formed on this substrate.
A photosensitive polyimide precursor (having a rigid structure) obtained by adding dimethylaminoethyl methacrylate to twice the molar amount of paraphenylenediamine to a polyimide precursor composed of 4′-biphenyltetracarboxylic dianhydride and paraphenylenediamine was used as a spinner. Use at 2000 rpm to apply,
Apply a mask after pre-baking, expose with an exposure amount of 200 mJ / cm ² , and use a developing solution DV-605 (manufactured by Toray),
Development was performed for about 5 minutes to perform pattern processing. Then 35
Curing was carried out at 0 ° C. for 3 hours to form a polyimide layer.

This substrate was placed at 120 ° C. under 1.5 atmospheric pressure to 70
After performing a PCT (pressure cooker test) test for a time, the adhesiveness between the polyimide and the thermal oxide film was examined by the cellotape peeling test described below. As a result, no peeled pieces were found and the adhesiveness was good.

[Cellotape Peeling Test] The surface of the polyimide layer is cut into a grid pattern having a width of 2 mm, a scotch tape having a width of 1 cm is attached, and then the tape is peeled vertically. Check the number of 2 mm square pieces peeled off with tape.

Example 2 Instead of patterning the thermal oxide film and then etching the surface in Example 1, the surface of the thermal oxide film was etched and then the thermal oxide film was patterned to form a multilayer wiring structure. It was constructed and tested for adhesion. As a result, there was no peeled piece, and the adhesion between the polyimide and the thermal oxide film was good.

Example 3 In Example 1, the surface of the thermal oxide film was etched with tetrafluoromethane plasma for about 2 minutes using an ashing device instead of using a 3% hydrofluoric acid aqueous solution.
A multilayer wiring structure was constructed and an adhesion test was conducted. As a result, there was no peeled piece, and the adhesion between the polyimide and the thermal oxide film was good.

Example 4 In Example 2, the surface of the thermal oxide film was etched with tetrafluoromethane plasma for about 2 minutes using an ashing device instead of using a 3% hydrogen fluoride aqueous solution to form a multilayer wiring structure. It was constructed and tested for adhesion. As a result, there was no peeled piece, and the adhesion between the polyimide and the thermal oxide film was good.

Comparative Examples 1 and 2 In Examples 1 and 2, a multilayer wiring structure was constructed without etching the surface of the thermal oxide film, and an adhesion test was conducted. As a result, 60% of the pieces peeled off in each case, and the adhesion between the polyimide and the thermal oxide film was poor.

[0040]

According to the present invention, since the surface of the patterned thermal oxide film is etched, the adhesiveness is good and reliable even when a rigid polyimide film is used as the upper insulating layer. It is possible to obtain a multilayer wiring structure having high properties.

Claims (7)

[Claims] 1. A method for manufacturing a multilayer wiring structure, comprising the following steps. (A) A step of forming a thermal oxide film on a silicon substrate. (B) A step of patterning the thermal oxide film and etching the surface of the thermal oxide film. (C) A step of forming a metal layer on the silicon substrate on which the thermal oxide film is formed. (D) A step of patterning the metal layer to partially expose the thermal oxide film. (E) A step of forming an insulator layer on the silicon substrate on which the metal layer is formed. 2. The method of manufacturing a multilayer wiring structure according to claim 1, wherein in the step (B), the surface of the thermal oxide film is etched after patterning the thermal oxide film. 3. The method for manufacturing a multilayer wiring structure according to claim 1, wherein in the step (B), the surface of the thermal oxide film is etched and then the patterning of the thermal oxide film is performed. . 4. The method for manufacturing a multilayer wiring structure according to claim 1, wherein in the step (B), the surface of the thermal oxide film is etched with a hydrofluoric acid aqueous solution. 5. The method for manufacturing a multilayer wiring structure according to claim 1, wherein in the step (B), the surface of the thermal oxide film is etched with a gas. 6. The method for manufacturing a multilayer wiring structure according to claim 1, wherein the insulating layer is a polyimide resin. 7. The method for manufacturing a multilayer wiring structure according to claim 6, wherein an insulating layer made of a polyimide resin is formed by using a photosensitive polyimide precursor composition.