JPH06151612A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form an inter layer insulating film adhering closely to a backing resin film by forming a flattening resin layer on a substratum wiring layer with organic silicon polymer used and also forming a layer insulating layer on the resin layer by the vacuum evaportion of ion beam assist to flatten a difference in level which is caused by a multilayer inter connection process. CONSTITUTION:The methanol solution of siniphenylene resin powder is applied by a spin-coat method to a silicon substrate 3 having the aluminum wiring of the first layer applied to. The substrate 3 provided with a resin layer is fixed in a dome 2 located within vacuum tank 1, and Ar ion beams from an ion gun 5 are applied to the substrate 3 to perform the bombardment of the surface of the substrate for clean-up. Next, light from a halogen lamp 7 is applied to the substrate 3, and after the temperature of the surface of the substrate is set at 300 deg.C, oxygen gas is introduced into the vacuum tank 1. Also, Ar gas is introduced into a gas control unit 10 and SiO2 is deposited on the substrate 3 from an evaporation source 4 which is heated by an electron gun with the Ar ion beams being applied to the substrate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device. More specifically, the present invention relates to a method of manufacturing a semiconductor device having a multi-layer wiring structure including a plurality of wiring layers and an interlayer insulating film arranged between them.

[0002]

2. Description of the Related Art In recent semiconductor devices having a high degree of integration such as IC and LSI, the surface step after element formation is increased with the increase in the degree of integration, and the reduction of the wiring capacity due to the miniaturization of wiring is prevented. As a result of the necessity of thickening the wiring for wiring, the step difference after the wiring tends to be severe. For this reason, it is necessary to form an interlayer insulating film that provides excellent flatness when forming the N + 1th layer wiring through the insulating film and then forming the multilayer wiring after forming the Nth layer wiring.

Conventionally, as materials for the interlayer insulating film, inorganic materials such as silicon dioxide, silicon nitride and PSG, organic polymer insulating materials such as polyimide and silicone resin, or these inorganic materials and organic polymers are used. Laminates with materials have been used.

In the multi-layer wiring process in the manufacture of a semiconductor device, since the surface of the semiconductor substrate having wiring between elements has steps due to the unevenness of the wiring, this is used as a base and chemical vapor deposition (CVD) method or the like is used as the base. When an inorganic film is formed as an interlayer insulating film, the surface of the interlayer insulating film reproduces the unevenness of the base as it is. The irregularities cause disconnection of upper layer wiring formed thereon and insulation failure. Therefore, it has been desired that the interlayer insulating film formed on the base having irregularities can make the surface of the substrate flat. Therefore, a method of obtaining a flat surface from an insulating film manufacturing process such as an etch back method or a bias sputtering method, and a method of obtaining a flat insulating film by forming a resin by a spin coating method have been studied.

Among these methods, the resin coating method which is simple in process requires that the resin is coated and then heat-cured. In addition, the conventionally used silicone-based hard coat material becomes a material with a low coefficient of thermal expansion close to that of a silicon oxide film after curing, and cracks easily occur due to internal strain and thermal shock of the film due to the curing reaction. However, there is a problem in that a film formed of this material has low electrical insulation. On the other hand, polyimide resin, silicon resin and the like have a drawback in that organic groups are oxidized or thermally decomposed at a temperature of about 400 ° C. and cracks are generated due to strain of the film.

As described above, it is difficult to use the organic polymer material alone as the material for the interlayer insulating film of the multi-layered wiring of the semiconductor device with a high degree of integration. Therefore, a method of further forming an inorganic material film such as SiO ₂ on the resin film as the flattening layer to form an interlayer insulating film has been studied. For forming this inorganic material film, a vacuum evaporation method or Plasma CV
Method D is used.

[0007]

In the vacuum deposition method, formation is performed.
In general, pinholes are likely to occur in the formed film, so
₂Insulates high-melting inorganic materials such as
To form a film, heat the substrate with the resin film to a high temperature
Must be 1 μm or more. For that, the vacuum
It takes time to form a film by the vapor deposition method, and the heat conduction of the integrated circuit
There are problems such as deterioration of characteristics and deterioration of characteristics.
It

On the other hand, in the plasma CVD method, a dense SiO ₂ film can be obtained as compared with the vacuum vapor deposition method, so that the SiO ₂ film thickness may be several thousand Å, but the resin film as the base film is formed by the plasma applied during the film formation. When the flattening layer is cracked as a result of being oxidized, the adhesiveness between the inorganic film and the non-dense resin film is low. In addition, there is a problem that the inorganic film is peeled off from the resin film.

According to the present invention, these problems can be solved to flatten a step generated in a multi-layer wiring process of a semiconductor device, without causing cracks or the like in the flattening base resin film, and Provided is a method for manufacturing a semiconductor device in which an inorganic material film such as SiO ₂ is sufficiently adhered to the base resin film to form an interlayer insulating film, and a highly reliable semiconductor device is manufactured. The purpose is to enable.

[0010]

A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having a multi-layer wiring structure composed of a plurality of wiring layers and an interlayer insulating film arranged between them. Then, a planarizing resin layer is formed of an organosilicon polymer on the lower wiring layer, and then an inorganic material film is formed on the resin layer by vacuum deposition by ion beam assist or ion plating by high frequency excitation. The method is characterized by including a step of forming an interlayer insulating film.

In the method of the present invention, when the inorganic material film is formed by ion beam assisted vacuum evaporation, the charge on the surface of the substrate to be evaporated may be neutralized by a neutralizer. Further, when forming the inorganic material film by ion plating by high frequency excitation, ion beam assist may be performed.

The organosilicon polymer used for forming the lower layer for flattening has heat resistance, and at the time of thermosetting at low temperature so that the surface step of the underlying wiring layer can be well flattened. It is desirable that it has a property of melting at 1, and is unlikely to cause cracks due to thermal shock.
A typical example of such an organosilicon polymer is a silphenylene resin (polysilphenylene siloxane).
Silphenylene resin has a silicon atom through an oxygen atom,
Further, it is a polymer substance having a network structure which is bonded via a phenylene group, and is represented by the following general formula.

[0013]

[Chemical 1]

In this formula, R ^{1 s} may be the same as or different from each other and each represents a lower alkyl group or a phenyl group, and R ² represents a triorganosilyl group. Further, n represents the number of values such that the weight average molecular weight of the organosilicon polymer is 5,000 to 5,000,000. When a polymer having a molecular weight outside this range is used, it becomes difficult to conveniently form the planarizing resin layer of the interlayer insulating film. The weight average molecular weight of the polymer is preferably 10,000 to 500,000.

The silphenylene resin represented by the above general formula has, for example, a lower alkyl group or a phenyl group represented by R ¹ and a hydrolyzable group such as an alkoxy group bonded to a silicon atom. It can be easily prepared by hydrolyzing disilylbenzene having two silyl groups and then dehydration condensation.

The inorganic material film forming the upper layer of the interlayer insulating film is preferably a silicon dioxide (SiO ₂ ) film.

[0017]

The organosilicon polymer used in the method of the present invention has a property of melting at a low temperature, so that it is easily fluidized at the time of heat curing and flattens the surface step of the underlying wiring layer. Moreover, this resin is less likely to crack due to thermal shock, and can be used in a thick film.

Furthermore, organosilicon polymers such as silphenylene resins are excellent in oxidation resistance. Therefore, it is necessary to use such organosilicon polymers for barrel type etching which is usually used in the resist stripping process. Allows use of the device.

Vacuum deposition by ion beam assist is
The deposition of a film-forming substance such as SiO ₂ is performed while irradiating the substrate with an inert gas such as argon as an ion beam in a vacuum of 10 ⁻⁴ to 10 ⁻⁵ Torr. Basically, the kinetic energy of the ion beam is used for the arrangement when a film-forming substance such as SiO ₂ molecules is deposited on the substrate, so that a film having a small internal stress and hence a dense and highly arranged film is formed. to enable. Further, since the internal stress of the obtained film is small, it is possible to uniformly form the pinhole-free inorganic material film on the resin film, so that the adhesion strength of the inorganic material film to the resin film is increased macroscopically.

The use of a neutralizer in forming an inorganic material film by vacuum deposition with ion beam assist means that the gas is accumulated on the surface of the substrate to be processed due to a charge-up phenomenon due to irradiation of inert gas ions, for example Ar ⁺ ions. The positive charge thus generated serves to neutralize the charge on the surface of the substrate for the purpose of eliminating the repulsion from the inert gas ions continuously applied to the surface of the substrate.

Ion plating by high frequency excitation is performed by heating and evaporating SiO in a vacuum of 10 ^-4 to 10 ^-5 Torr using an inert gas such as argon as a carrier gas.
This is a carrier gas for transporting a film-forming substance such as ₂ onto the substrate with this carrier gas, and ionizes the carrier gas by high-frequency excitation before reaching the substrate to be processed, and the substrate gas is grounded or negatively bias-charged. A potential gradient is applied to the substrate, and a film-forming substance such as SiO _{2 is} accelerated and vapor-deposited on a substrate together with a carrier gas.

According to this method, carrier gas ions such as argon are accelerated straightly and with good directivity to the substrate, so that the underlying resin film is formed only in a very thin surface layer portion, for example, from the surface to a depth of several Å. Only the portion is oxidized, and the oxidation reaching the inside of the film as in plasma CVD does not occur. Further, as one of the characteristics of film formation by high-frequency ion plating, even if there is unevenness or a large step on the substrate surface, it is possible to uniformly and evenly deposit the entire surface of the substrate by the beam accelerated with good directivity. It has been shown that the wraparound property is high, and this property also meets this purpose, and enables formation of an inorganic material film having a macroscopically high adhesion strength with a resin film.

Ion beam assisting when forming an inorganic material film by ion plating by high frequency excitation is performed by irradiating an ion beam onto a substrate to be processed on which a film forming substance such as SiO ₂ is deposited. The kinetic energy of the ions enhances the ordering of the molecules of the film-forming material, thus enabling the formation of very dense films, especially resistant to acid treatment.

[0024]

The present invention will be further described with reference to the following examples.
Needless to say, the following examples are for illustrating the present invention and not for limiting the present invention.

Example 1 This example illustrates the synthesis of silphenylene resin for use as an interlayer insulating film for multi-layer wiring.

1,4-bis (methyldiethoxysilyl)
Nitric acid was added to a mixed system of 35 g of benzene and 20 g of methanol, and then 7 g of water was dropped and stirred at 50 ° C. for 3 hours to dehydrate and condense the starting material 1,4-bis (methyldiethoxysilyl) benzene. To produce a polymer.

After cooling the reaction solution, 150 g of methyl isobutyl ketone (MIBK) was added, and the mixture was allowed to stand to remove the aqueous layer, and further washed sufficiently with water. To the MIBK solution after washing with water, 50 g of triethylamine and 80 g of phenyldimethylchlorosilane were added, and silylation was performed while heating at 70 ° C. and stirring for 2 hours to change the hydroxyl group at the polymer terminal to a silyloxy group.

Then, the reaction solution was cooled, the aqueous layer was removed,
Then, sufficient washing with water was performed. Methanol was added to the MIBK solution after washing with water to precipitate a polymer, and the polymer was dissolved in benzene and freeze-dried to obtain a powdered silphenylene resin. The weight average molecular weight of this resin was about 10,000.

Example 2 A methanol solution of the resin powder synthesized in Example 1 was used to form a semiconductor element and a silicon substrate on which a first layer of aluminum wiring was formed (wiring thickness 1 μm, minimum line width 1 μm, minimum line spacing 1
μm) was applied by spin coating. 15 after application
The solvent was dried at 0 ° C. for 15 minutes and then heat-treated at 450 ° C. for 1 hour to form a film having a thickness of 1.5 μm. The step difference on the substrate surface after the heat treatment was 0.2 μm or less, and the step difference caused by the first-layer aluminum wiring was flattened.

On the substrate thus provided with the resin layer, a SiO ₂ film was formed as follows. The vacuum vapor deposition apparatus used for forming the SiO ₂ film is shown in FIG. In this figure, 1 is a vacuum chamber, 2 is a dome, 3 is a substrate, 4 is an evaporation source,
Reference numeral 5 is an ion gun, 6 is an ion gun shutter, 7 is a halogen lamp, 8 is a neutralizer, 9 is a power supply control unit, 10 is a gas control unit, 11 is an oxygen inlet, and 12 is a connecting pipe to an exhaust system.

The dome 2 in the vacuum chamber 1 of this vacuum deposition apparatus
The substrate 3 provided with the above resin layer was fixed to the substrate. After fixing, 1
Evacuate to × 10 ^-6 Torr and then increase the pressure in the vacuum chamber 1 to 5
The substrate 3 was irradiated with an Ar ion beam from the ion gun 5 for 30 seconds while maintaining the pressure at × 10 ^-5 Torr, and the surface of the substrate 3 was bombarded for cleaning. Next, the substrate 3 was irradiated with a halogen lamp 7 to set the substrate surface temperature to 300 ° C., and then oxygen gas was introduced into the vacuum chamber 1 at a flow rate of 10 cc / s. Further, Ar gas was introduced into the gas control unit 10 at a flow rate of 3 cc / s, and the ion acceleration voltage was set to 500.
While irradiating the substrate 3 with an Ar ion beam generated with V and current values set to 50 mA, SiO ₂ was vapor-deposited on the substrate 3 from an evaporation source 4 heated by an electron gun at a rate of 25 Å / s. . During the deposition, the degree of vacuum in the tank was maintained at 5 × 10 ⁻⁵ Torr, and in order to avoid charge-up of the substrate surface due to Ar ion beam irradiation, charge was neutralized using the neutralizer 8 at the same time as ion beam irradiation. .

The obtained SiO _{2 had} a film thickness of 5000 Å and a refractive index of 1.45, and it was found that a dense film having a refractive index of 1.45 of bulk SiO ₂ was obtained. . The refractive index of SiO _{2 formed} by vacuum evaporation without ion beam assist is about 1.35. SiO ₂
After formation of the film, the presence or absence of cracks in the resin film and the SiO ₂ film was examined by an optical microscope, and none was observed.

Next, a thermal cycle shock test was conducted at 400 ° C. to room temperature, and in the case where an inorganic material film was formed by plasma CVD or the like, innumerable cracks were formed in the lower resin film. No cracks were found in the resin film. Further, in the etching treatment with hydrofluoric acid, the SiO ₂ film or the resin film was peeled off when the conventional method was used, whereas the film formed in this example did not peel off at all.

A thermal cycle shock test and an etching treatment were performed, and then an electrical insulation test was further conducted. As a result, the insulation film produced in this example had an insulation property sufficient to be used as an interlayer insulation film of a multilayer wiring. It was confirmed that

Example 3 Si was formed by vacuum deposition with ion beam assist in Example 2.
A substrate to be treated having a silphenylene resin film similar to that used to form the O ₂ film was used to form an SiO ₂ film by ion plating as described below.

The ion plating apparatus used is shown in FIG.
Shown in. In this figure, 21 is a vacuum chamber, 22 is a dome, 23 is a substrate, 24 is an evaporation source, 25 is a high frequency excitation coil, 26 is a halogen lamp, 27 is a high frequency power supply, 28 is a matching box, 29 is a direct current power supply, and 30 is An argon gas inlet, 31 is a connecting pipe to the exhaust system.

Vacuum chamber 2 of this ion plating apparatus
A substrate 23 coated with a resin film was fixed to the dome 22 inside 1. After fixing, exhaust to 1 × 10 ^-6 Torr, and high frequency (13.56 MHz) output 100 W, argon gas pressure 2
The surface of the substrate was bombarded and cleaned under × 10 ⁻⁴ Torr. Next, the substrate 23 is irradiated with a halogen lamp 26 to set the substrate surface temperature to 300 ° C., and then 10 cc of oxygen gas is maintained with the internal pressure kept at 2 × 10 ⁻⁴ Torr.
It was introduced into the vacuum chamber 21 at a flow rate of / s. In this state, the high frequency output was set to 1 KW, argon of the carrier gas was excited, and SiO ₂ was vapor-deposited on the substrate from the evaporation source 24 heated by the electron gun. Deposition rate is 20Å / s, final film thickness is 5
It was 000Å.

The obtained SiO _{2 has} a refractive index of 1.42, and a film having a refractive index of 1.45 that is substantially the same as that of bulk SiO ₂ can be obtained. As a thin film, a dense film equivalent to that of bulk can be obtained. I understand that it is being done. After forming the SiO ₂ film,
When the presence or absence of cracks in the resin film and the SiO ₂ film was examined by an optical microscope, none was observed.

Next, after forming a through hole according to a conventional method, the resist was peeled off using a barrel type etching apparatus, and no cracks due to oxidation or receding of the film was observed at all. Next, the second layer wiring is applied,
A PSG film was formed as a cover film by the CVD method, and a semiconductor device was prototyped.

After conducting a thermal cycle shock test at 400 ° C. to room temperature using this semiconductor device, a high temperature storage test at 200 ° C. was performed, and no defect was observed even after 1000 hours.

In the apparatus shown in FIG. 2 used in this example, by negatively charging the substrate side, the effect of accelerating ions can be enhanced, and a film having a higher degree of adhesion can be obtained.

Example 4 Using the apparatus shown in FIG. 3, an SiO ₂ film is formed on a substrate to be processed having a silphenylene resin film by ion plating with ion beam assist. 3, parts corresponding to those of the device shown in FIG. 2 are given the same reference numerals. In the figure, 41 is an ion gun, 42 is a shutter of the ion gun, 43 is a gas control unit connected to the ion gun, and 44 is a power source control unit for the evaporation source 24 and the ion gun 41.

The operation in this case is basically the same as in the third embodiment.
Same as the above, but the pressure in the chamber was 8 × 10 ^-5 Torr during vapor deposition.
The SiO ₂ film is formed by irradiating the substrate with an ion beam while oscillating the high frequency ion plating. By ion beam irradiation, the kinetic energy of the ions enhances the alignment of the SiO ₂ molecules during the SiO ₂ deposition, and a very dense film, particularly strong against acid treatment, can be formed. In the apparatus shown in FIG. 3 as well, by negatively charging the substrate side, the effect of accelerating ions can be enhanced, and a film having a higher degree of adhesion can be obtained.

[0044]

As is apparent from the above description, according to the present invention, it is possible to flatten a step formed in a multi-layer wiring process of a semiconductor device, and to coat the resin on the flattening base resin film. It is possible to form a high-quality low-dielectric-constant inorganic dielectric film that does not cause cracks or the like in the film and has sufficient adhesion strength to withstand thermal shock and post-treatments such as heat treatment. The interlayer insulating film thus formed, which is composed of the planarizing base resin film and the inorganic material film thereon, maintains the same insulating characteristics as the conventional interlayer insulating film formed using the inorganic material film. Therefore, it is possible to manufacture a highly reliable semiconductor device such as a semiconductor integrated circuit.

Further, the film made of a normal resin having an organic group is for preventing the side surface exposed in the through hole portion from being oxidized by the stripping solution in the resist stripping process after forming the through hole. While it was necessary to suppress the damage of the resin film by using an expensive ECR etching device, by using the silphenylene resin excellent in the oxidation resistance according to the present invention, it is used in the usual resist stripping process. It becomes possible to use a barrel type etching apparatus.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating an ion beam assisted vacuum vapor deposition apparatus.

FIG. 2 is a schematic diagram illustrating an ion plating device by high frequency excitation.

FIG. 3 is a schematic diagram for explaining a high frequency excitation ion plating apparatus with ion beam assist.

[Explanation of symbols]

 1, 21 ... Vacuum tank 3, 23 ... Substrate 4, 24 ... Evaporation source 5, 41 ... Ion gun 8 ... Neutralizer 25 ... High frequency excitation coil

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor device having a multi-layer wiring structure composed of a plurality of wiring layers and an interlayer insulating film arranged between the wiring layers, the method comprising: forming an organic silicon polymer on a lower wiring layer; And a step of forming an interlayer insulating film by forming an inorganic material film on the resin layer by vacuum deposition with ion beam assist or ion plating by high frequency excitation. Of manufacturing a semiconductor device. 2. The method according to claim 1, wherein the vacuum deposition by the ion beam assist is performed while neutralizing the charge on the surface of the substrate to be deposited. 3. The method according to claim 1, wherein the ion plating by the high frequency excitation is performed while performing ion beam assist. 4. The method according to claim 1, wherein the organosilicon polymer forming the planarizing resin layer is a silphenylene resin. 5. The method according to claim 1, wherein the inorganic material film is a silicon dioxide film.