JPH06232040A - Method for erasing resist film picture - Google Patents

Abstract

PURPOSE:To provide a method by which an unnecessary ion-implanted resist film picture on a semiconductor substrate can be erased during the course of manufacturing a semiconductor integrated circuit device. CONSTITUTION:When the method is used, a resist film picture on a substrate is removed by sticking an adhesive sheet, etc., to the upper surface of the picture and performing a heating process, to be concrete, by irradiating the picture with microwaves of 2.45 GHz in frequency so as to scatter the water contained in the sheet etc., and/or on the surface of the picture, and then, peeling the sheet, etc., from the semiconductor substrate together with the resist film picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing an ion-implanted resist film image on a semiconductor substrate which has become unnecessary, for example, in the manufacture of a semiconductor integrated circuit device.

[0002]

2. Description of the Related Art In manufacturing a semiconductor integrated circuit device,
A resist material is applied onto a semiconductor substrate such as a silicon wafer, and a predetermined resist film image is formed by a normal photo process. Using this as a mask, ions of P ⁺ , B ⁺ , As ⁺ , Sb ^+, etc. are implanted at a high concentration in the openings.
At this time, the ions are also injected into the upper surface layer of the resist film image. Next, the unnecessary resist film image is generally removed from the semiconductor substrate by ion-assisted etching (ashing means) or a solvent.

[0003]

However, when the above-mentioned ions are injected into the upper surface layer of the resist film image and the upper surface layer of the resist film image is cured and deteriorated, the upper surface layer has high heat resistance and reaction. Since it has a low property, the conventional ashing means has a problem that it takes a long time for the removing work and the removing is practically difficult. Further, when the usual ashing means is used, the impurity ions in the resist material and the implanted ions remain on the semiconductor substrate and are implanted into the semiconductor substrate by the subsequent heat treatment, which makes it impossible to construct the semiconductor integrated circuit as designed. However, there is also a problem that the characteristics of the semiconductor device are deteriorated. Therefore, the present invention provides a simple and reliable method for removing an unnecessary resist film image on a semiconductor substrate, particularly an ion-implanted resist film image, by a novel method completely different from the conventional method. To aim.

[0004]

The inventors of the present invention, when removing an unnecessary resist film image on a semiconductor substrate, apply a specific heat treatment after attaching adhesive sheets to the upper surface of the resist film image. It has been found that the application can easily and particularly remove the ion-implanted resist film image, and the present invention has been completed.

That is, according to the present invention, an adhesive sheet is attached to the upper surface of a resist film image of a semiconductor substrate on which an image made of a resist material is present, and water contained in the adhesive sheet and / or the surface of the resist film image is A resist film characterized by removing the resist film image on the substrate by subjecting the adhesive sheet and the resist material to an integral peeling after a heat treatment for diffusing existing water into the resist film image. An image removal method is provided.

[0006]

According to the method of removing a resist film image of the present invention, first, on the upper surface of the image formed of the resist film,
Stick adhesive sheets. Next, the adhesive sheets are preferably irradiated with microwaves having a frequency of 2.45 GHz so that the moisture existing in the adhesive sheets or on the resist film image absorbs the microwave power. The water that absorbs this microwave power and is heated diffuses and moves isotropically. As a result of such water being diffused and absorbed from the surface of the resist film image toward the inside of the resist film image, the adhesive force between the semiconductor substrate and the resist film image is reduced. Then, by peeling off the adhesive sheets, the ion-implanted resist film image can be satisfactorily removed from the semiconductor substrate together with the adhesive sheets.

The adhesive sheets used in the present invention are not particularly limited as long as they contain water, and ordinary pressure-sensitive adhesive sheets can be used, but from the viewpoint of preventing contamination of the semiconductor substrate, it will be described later. It is preferable to use a curable pressure-sensitive adhesive sheet.

The water-containing adhesive sheet is, for example, a normal pressure-sensitive adhesive sheet whose adhesive layer originally contains a small amount of water, or a water-soluble adhesive sheet which contains water in a microencapsulated state. Examples thereof include those containing water positively, such as containing.

The water present on the resist film image is, for example, water adsorbed on the resist film image from the atmosphere or water adsorbed on the resist film image.

In the present invention, the heat treatment for diffusing and absorbing the water inside the resist film image is particularly preferably irradiation of microwaves having a frequency of 2.45 GHz, and water absorbs microwaves at frequencies other than this. It is not preferable because it is difficult to do.

Further, the microwave irradiation time is not particularly limited because it changes depending on the water content of the adhesive sheet or the microwave power, but it is about 30 to 300 seconds when the microwave power of about 500 W is irradiated. . Irradiation with microwaves for a too long time is not preferable because evaporation of water from the resist film image is promoted and the effect of such treatment is reduced.

In the present invention, as described above, it is preferable to attach the adhesive sheets using the curable pressure-sensitive adhesive which has particularly good affinity with the resist agent. At this time, the resist material and the adhesive are favorably adhered and integrated, but in order to promote the adherence and integration, heating and / or pressure may be applied during the adhering.

Such a curable pressure-sensitive adhesive comprises a pressure-sensitive adhesive polymer containing a non-volatile compound having a good affinity for a resist material and having at least one unsaturated double bond in the molecule. Is preferred.

As the above-mentioned pressure-sensitive adhesive polymer, any of various known polymers applied to general pressure-sensitive adhesives can be used, and particularly preferable polymers are alkyl acrylate and / or methacrylic acid. An acrylic polymer having an alkyl ester as a main monomer can be used.

This acrylic polymer is a main monomer described above, that is, an ester of acrylic acid or methacrylic acid with an alcohol having a carbon number of usually 12 or less, a monomer having a carboxyl group or a hydroxyl group if necessary, and other modifications. It can be obtained by polymerizing these using a monomer for use by a conventional method such as solution polymerization, emulsion polymerization, suspension polymerization and bulk polymerization.

Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, maleic acid,
Itaconic acid or the like is used, and as the hydroxyl group-containing monomer, for example, hydroxyethyl acrylate, hydroxypropyl acrylate or the like is used. The amount of these monomers used is preferably 20% by weight or less based on the total amount of all the monomers.

As the above-mentioned other modifying monomers, vinyl acetate, vinyl propionate, styrene, acrylonitrile, acrylamide, couglycidyl methacrylate and the like are used. The amount of these modifying monomers used is preferably 50% by weight or less in the total amount with the main monomer.

The acrylic polymer composed of such monomers has a weight average molecular weight of usually 30.
It is preferably from 10,000 to 2,000,000. If the molecular weight is too low, the viscosity will be low when the non-volatile compound described below is blended therein, and problems such as flowing during storage are likely to occur, and if it is too high, handling problems are likely to occur. Further, the acrylic polymer preferably has a glass transition point of 250 ° K or lower in consideration of workability at the time of image removal. If it is higher than this, it tends to be too hard after curing and the peeling tends to be heavy. However, it does not try to eliminate all the use of acrylic polymers having such a high glass transition point,
Of course, it can be used in some cases.

In the present invention, the pressure-sensitive adhesive polymer contains a non-volatile compound having a good affinity with a resist agent and having at least one unsaturated double bond in the molecule. An adhesive sheet made of a pressure sensitive adhesive is preferably used. Here, having a good affinity with the resist material means that the phenomenon of dissolving, swelling or destroying the resist material is remarkable, and also includes the phenomenon of migration or diffusion into the resist material. As a guide for this, the resist material is sufficiently dried and the solvent is dipped in the non-volatile compound, and the resist material is dissolved, swelled or destroyed when stored at 130 ° C. for 24 hours. Further, that the compound is non-volatile means that it is not easily volatilized in the step of coating and drying the adhesive.

Such a non-volatile compound has a function of bonding adhesive sheets onto a semiconductor substrate on which a resist film image is present, the resist material and the adhesive are integrated by the action of this compound, and then cured. . Therefore, this non-volatile compound is required to have at least one unsaturated double bond capable of being cured by heat or light in the molecule and to have good affinity with the resist material. It is also required that the polymer has good compatibility with the water-soluble polymer and does not flow out during storage.

Examples of such non-volatile compounds include phenoxy polyethylene glycol (meth) acrylate, ε-caprolactone (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, and trimethylolpropane tri. (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, oligoester (meth) acrylate, and the like. Among these, the type of pressure-sensitive adhesive polymer used One or two or more of them can be appropriately selected and used depending on the target resist material.

The amount of the non-volatile compound used is usually 5 to 20 with respect to 100 parts by weight of the pressure-sensitive adhesive polymer.
The amount is 0 parts by weight, preferably 10 to 100 parts by weight. If the amount used is too small, the peeling effect of the resist material may not be sufficient, and if it is too large, the adhesive may flow out during storage, which is not preferable.

In the above-mentioned curable pressure-sensitive adhesive of the present invention, it is preferable that the pressure-sensitive adhesive polymer is crosslinked to enhance cohesive force in terms of workability when it is attached to a semiconductor substrate. For example, an acrylic polymer obtained by copolymerizing a carboxyl group- or hydroxyl group-containing monomer as a pressure-sensitive adhesive polymer is used, and a polyfunctional compound that reacts with the functional group of the polymer, such as polyisocyanate, polyepoxy, various metal salts, By containing a chelate compound or the like in the adhesive, the above reaction can be promoted in the step of forming a sheet or the like to crosslink the polymer.

The amount of the polyfunctional compound used is usually 20 parts by weight or less based on 100 parts by weight of the pressure-sensitive adhesive polymer. Within this range, the higher the molecular weight of the polymer, the lower the molecular weight of the polymer. , May be selected as appropriate.
If the amount of the polyfunctional compound used is too large, the adhesive strength will decrease, which is not preferable.

The curable pressure-sensitive adhesive may also contain a filler such as finely divided silica for the same purpose as the use of the above polyfunctional compound. Further, various additives such as a tackifier, a colorant and an anti-aging agent may be contained if necessary. The amount of these used may be in the usual range.

A polymerization initiator suitable for the curing means can be added to the curable pressure-sensitive adhesive which can contain such various components. For example, in the case of heat curing, benzoyl peroxide, a thermal polymerization initiator such as azobisisobutyronitrile that generates radicals by heating is used, and in the case of photocuring such as ultraviolet light, benzoin, benzoin ethyl ether, A photopolymerization initiator that generates radicals by light irradiation such as dibenzyl is used. These polymerization initiators are usually used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive polymer.

The curable pressure-sensitive adhesive used in the present invention having the above-described structure has an initial elastic modulus, that is, an elastic modulus before curing of usually about 0.5 to 50 g / mm ² , and that after curing. It is desirable that the elastic modulus is adjusted to about 3 to 400 g / mm ² . This is because when the elastic modulus is adjusted to such a range, favorable results can be obtained for both the pressure-sensitive adhesive property before curing and the resist releasability after curing. The elastic modulus can be adjusted by appropriately selecting the type of pressure-sensitive adhesive polymer, the amount of various non-volatile compounds added to it, the amount of other compounding components, the degree of crosslinking with a polyfunctional compound, the curing conditions, and the like. It can be done by

The above-mentioned elastic modulus was determined by applying a stress-strain to the adhesive having a cross-sectional area of 5 mm ² under a temperature of 23 ± 2 ° C. at a pulling speed of 50 mm / min with a marked line distance of 10 mm. It means a value measured by a method of obtaining a curve and obtaining it from an initial slope.

When used, such a curable pressure-sensitive adhesive can be formed into a sheet or tape by itself, but it is usually dried on a film substrate. To be about 10 to 180 μm, which can be used as an adhesive sheet used for removing the resist film image of the present invention. Examples of such a film substrate include polyethylene, polypropylene, polyethylene terephthalate, polyurethane, polyvinyl chloride,
Consisting of saponified ethylene-vinyl acetate copolymer,
Usually, a resin film having a thickness of about 12 to 100 μm is used, and particularly when the adhesive is cured by irradiation with light, a resin that transmits light such as ultraviolet rays is selected and used.

In the method of removing a resist film image of the present invention, an adhesive sheet using the curable pressure-sensitive adhesive having the above-mentioned constitution is attached onto the semiconductor substrate on which the resist film image is present, and then, preferably. Has a frequency of 2.45G
The adhesive sheets are irradiated with a microwave of Hz to diffuse and absorb moisture existing in the adhesive sheets or on the resist film image from the surface of the resist film image toward the inside of the resist film image to absorb the water. The adhesive force at the interface with the resist film image is reduced. Then, a predetermined curing treatment is performed by heating or light irradiation. At this time, when the heat effect on the semiconductor substrate is taken into consideration, the curing treatment by light irradiation is particularly suitable, and the irradiation amount is usually 3 for ultraviolet rays.
The range is preferably from 00 to 3000 mj / cm ² .
By this curing treatment, the adhesive is cured in a state of being integrated with the resist material, and its elastic modulus is remarkably increased as described above, and along with this, the adhesive force between the resist film image and the semiconductor substrate is further greatly reduced. To do. Then, by peeling off the adhesive sheets, the ion-implanted resist film image can be satisfactorily removed from the semiconductor substrate together with the adhesive sheets.

[0031]

As described above, according to the present invention, an image of a resist film on a semiconductor substrate, into which ions which are usually difficult to remove are implanted, can be removed very easily and reliably, and further, the image in the resist material can be removed. This has the effect of reducing the problem that the impurity ions are injected into the semiconductor substrate.

[0032]

EXAMPLES The present invention will be described below based on examples. In addition, "parts" means "parts by weight".

Reference Example A positive type photoresist consisting of cresol novolac resin, naphthoquinone diazide sulfonic acid ester of polyhydroxy compound, and ethyl lactate was coated on the surface of a silicon wafer (semiconductor substrate), heated, exposed and developed to form a resist. After forming a film image on the entire surface, As ⁺ ions were implanted over the entire surface at a high concentration with an acceleration energy of 80 keV and a dose amount of 1 × 10 ¹⁶ ions / cm ² .

Example 1 80 parts of n-butyl acrylate, 15 ethyl acrylate
Part of the monomer mixture consisting of 5 parts of acrylic acid and 150 parts of ethyl acetate and 0.1 part of azobisisobutyronitrile were subjected to solution polymerization at 60 ° C. for 12 hours under a nitrogen stream to give a weight average molecular weight of 56. The glass transition point is 231 °
An acrylic polymer solution of K was obtained.

To 250 parts of this acrylic polymer solution,
100 parts of urethane acrylate as a non-volatile compound,
3 parts of benzyl methyl ketal as a polymerization initiator and 3 parts of diphenylmethane diisocyanate as a polyfunctional compound were uniformly mixed to obtain a curable pressure-sensitive adhesive solution.

Next, this curable pressure-sensitive adhesive solution was added to
A curable pressure-sensitive adhesive sheet for removing a resist film image used in the present invention is coated on a polyester film having a thickness of 50 μm so as to have a thickness after drying of 50 μm and dried at 150 ° C. for 10 minutes. It was made.

The obtained curable pressure-sensitive adhesive sheet was pressure-bonded to the entire surface of the resist film image of the reference example at room temperature, and then a microwave having a frequency of 2.45 GHz and a power of 500 W was applied to the adhesive sheet. Irradiate the entire surface for 60 seconds,
Then, using a high pressure mercury lamp, it is possible to emit ultraviolet light at 1000 mJ / cm ²
The curable pressure-sensitive adhesive sheet was cured by irradiating the curable pressure-sensitive adhesive sheet. After this curing, when the adhesive sheet was peeled off, the resist film image was peeled off together with the adhesive sheet. The surface of the silicon wafer was observed with a fluorescence microscope, but no resist material was observed.

Example 2 A monomer mixture consisting of 60 parts of 2-ethylhexyl acrylate, 30 parts of butyl acrylate, 5 parts of vinyl acetate and 5 parts of acrylic acid was polymerized in the same manner as in Example 1 to give a weight average molecular weight of 62. By the way, an acrylic polymer solution having a glass transition point of 207 ° K was obtained.

To 250 parts of this acrylic polymer solution,
Oligoester acrylate 10 as non-volatile compound
0 part, 3 parts of tolylene diisocyanate as a polyfunctional compound, and 5 parts of benzylmethyl ketal as a polymerization initiator were uniformly mixed to obtain a curable pressure-sensitive adhesive solution. An adhesive tape for image removal was prepared.

Using the obtained adhesive sheet, the resist film image was removed in the same manner as in Example 1.
The same result as in Example 1 was obtained.

[Measurement of Elastic Modulus] The initial elastic modulus of the pressure-sensitive adhesive of the adhesive sheet obtained in each example and ultraviolet rays were irradiated at a dose of 1000 mj / cm ² using a high pressure mercury lamp to cure the adhesive sheet. As a result of measuring the elastic modulus after the test, it was as shown in Table 1 below.

[0042]

[Table 1]

Claims (3)

[Claims] 1. A method of removing an image made of a resist material existing on a semiconductor substrate, wherein an adhesive sheet is attached to the upper surface of the resist film image, and moisture or / and a resist contained in the adhesive sheet are adhered. Characteristic of removing the resist film image on the substrate by performing a heat treatment for diffusing the water present on the surface of the film image into the resist film image and then peeling the adhesive sheet and the resist material together. A method for removing a resist film image. 2. The method for removing a resist film image according to claim 1, wherein the heat treatment for diffusing water into the resist film image is irradiation with microwaves. 3. The method for removing a resist film image according to claim 2, wherein the microwave frequency is 2.45 GHz.