JPH0888208A - Adhesive tape and method for removing foreign matter adhering to semiconductor wafer - Google Patents

Abstract

PURPOSE: To remove foreign matters adhering to semiconductor wafers at a high elimination factor by using a dry cleaning system using an adhesive tape without causing such a problem as the contamination of the wafers or working efficiency in peeling the tape by a remaining adhesive paste. CONSTITUTION: An adhesive tape 1 for removing foreign matters is provided with an adhesive layer 12 on a substrate film 11, and the layer 12 is composed of such an adhesive agent that its molecular structure becomes a three- dimensional network when it is hardened by an active energy source. Foreign matters adhering to the front and/or rear surface of a semiconductor wafer are removed by removing the tape 1 form the front and/or rear surface of the wafer, after sticking the tape 1 to the front and/or rear surface of the wafer so that the foreign matters can be stuck to the adhesive layer 12 and supplying the active energy source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive tape for removing foreign matter adhering to a semiconductor wafer and a method for removing it, which is applied to a cleaning step in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art As the density of LSIs increases, the degree of integration increases, and the diversification of circuits progresses, foreign substances (particles) such as dust and metal impurities existing on semiconductor wafers increase the yield of products and increase the reliability of products. Has come to have a great influence on. For example, a foreign substance existing on the surface of a semiconductor wafer (circuit pattern forming surface) causes a disconnection or a short circuit of a circuit when the circuit is formed. In addition, foreign matter existing on the back surface of the semiconductor wafer (the surface opposite to the circuit pattern surface) may cause the focus to be deviated during the exposure process at the time of circuit formation. -It causes

Therefore, in the LSI manufacturing process, efforts are being made to improve the level of cleanliness in the manufacturing process and the level of wafer cleaning technology, and various cleaning technologies have been proposed and implemented. Especially, the washing process is about 3
It accounts for 0%, which is the key to improving yield and reliability. However, with the recent increase in the density and integration of LSIs, the problems of the conventional wafer cleaning method have become apparent.

The wafer cleaning method includes wet cleaning (using ultrapure water, chemical solution, etc.) and dry cleaning (UV ozone, O 2).
₍₂ plasma etc.), and in general, wet cleaning is frequently applied because of its good balance of versatility and economy. The problem of wet cleaning is that foreign matter removed from the wafer by cleaning is reattached to the wafer, and in particular foreign matter attached to the back surface of the wafer becomes a significant source of contamination. Also,
Since wet cleaning requires a drying process, the problem of wafer contamination during the drying process also exists.

As a cleaning method for compensating the disadvantages of wet cleaning, dry cleaning methods (UV ozone, O ₂ plasma, etc.) are being advanced, and advantages such as reduction of redeposition of foreign matters and omission of a drying step are utilized. However, it has been found that dry cleaning does not show a sufficient ability to remove foreign substances and is not suitable for removing a large amount of contaminants.

As another attempt, JP-A-48-35771
JP-A-53-92665, JP-A 1-1
Japanese Patent No. 35574 discloses a method of using an adhesive tape to adsorb foreign matter adhering to the surface of a semiconductor wafer onto the adhesive layer surface of the tape to remove it. Since this method can be said to be a kind of dry cleaning, it is possible to avoid the problem of reattachment of foreign matter in wet cleaning and the problem of contamination in the drying process, and it is also applicable to other dry cleaning such as UV ozone and O ₂ plasma. In comparison, it is expected that the ability to remove foreign matter will be further enhanced.

[0007]

However, in the method proposed above, when an adhesive tape having a high adhesive strength that is easily plastically deformed is used, the adhesive tape is peeled off,
There is a problem of workability and wafer damage, and further there is a problem of contamination of the wafer surface due to adhesive residue. On the other hand, in order to avoid these problems, if a hard and low adhesive tape is used, it adheres to the semiconductor wafer. There was a problem that it was difficult to sufficiently adsorb foreign matter on the surface of the adhesive layer.

In view of such circumstances, the present invention uses a specific adhesive tape in a dry cleaning method using an adhesive tape, which is more useful than the wet cleaning method, to remove the peeling operation. The problem of workability and wafer damage,
Further, it is intended to remove foreign matters adhering to the semiconductor wafer at a high removal rate without causing the problem of contamination of the wafer surface due to adhesive residue.

[0009]

Means for Solving the Problems The inventors of the present invention have made earnest studies for the above-mentioned object, and as a result, as an adhesive tape, a type that is cured by an active energy source is used.
When the adhesive force in the normal state is increased and the sticking operation is performed on the semiconductor wafer, the adhering foreign matter on the wafer can be effectively adsorbed and held. The adhesive force is reduced, the peeling operation becomes easy, and the problem of contamination of the semiconductor wafer due to adhesive residue and adhesive residue is reduced, and in the end, the foreign matter adhering to the semiconductor wafer can be removed at a high removal rate without causing the above problems. They have found that they can be easily adsorbed and removed, and completed the present invention.

That is, according to the present invention, firstly, as the above-mentioned specific adhesive tape, an adhesive layer is provided on a support film, and the adhesive layer is cured by an active energy source to have a molecular structure. The present invention provides a pressure-sensitive adhesive tape for removing foreign matter attached to a semiconductor wafer, which is characterized by having a three-dimensional reticulation property.

Secondly, by attaching the above-mentioned specific adhesive tape to the front surface and / or the back surface of the semiconductor wafer and peeling off the adhesive tape after supplying the active energy source, Provided is a method for removing foreign matter attached to a semiconductor wafer, which is characterized in that foreign matter attached to the front surface and / or the back surface of the wafer is adsorbed to the surface of the adhesive layer and removed from the semiconductor wafer.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a foreign matter removing adhesive tape of the present invention. 1 is adhesive tape,
An adhesive layer 12 is provided on a support film 11, and a separator 13 is superposed on the adhesive layer 12.

The support film 11 may be any one as long as it has a property of sufficiently transmitting the active energy source,
For example, the thickness of plastics such as polyester, polycarbonate, polyvinyl chloride, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyethylene, polypropylene, ethylene-propylene copolymer is usually The film has a thickness of 10 to 1,000 μm.

The pressure-sensitive adhesive layer 12 may be one having a pressure-sensitive adhesive force under normal conditions, that is, a pressure-sensitive adhesive property, and having a property of being cured by the supply of an active energy source to have a three-dimensional reticulated molecular structure. Various adhesives such as acrylic resin-based, silicone resin-based, fluorine resin-based, and rubber-based adhesives can be used. Here, the above-mentioned active energy source is, for example, an electromagnetic wave typified by ultraviolet rays, infrared rays (heat), an electron beam, an X-ray, or an elastic wave typified by ultrasonic waves.

The pressure-sensitive adhesive layer 12 is generally made of a polymer such as acrylic resin, silicone resin, fluorine resin, rubber (natural rubber or synthetic rubber) as a base polymer, on which a polymer is added. It has a composition in which a polymerizable compound having at least two carbon-carbon double bonds is mixed with a polymerization initiator that generates radicals by an active energy source, and the above-mentioned base polymer is It may have a carbon-carbon double bond in the molecule.

The above-mentioned polymerizable compound usually has a molecular weight of 1
The number of carbon-carbon double bonds in the molecule is preferably 2 to 6 and is preferably 20,000 or less. Specifically, tetramethylol methane tetraacrylate, pentaerythritol triacrylate, pentaerythritol pentachlorate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate. -, 1,4-butanediol diacrylate, polyethylene glycol diacrylate,
Examples include commercially available oligoester acrylate, urethane acrylate, epoxy acrylate, and the like. These polymerizable compounds may be used alone or in combination of two or more. The amount used is preferably in the range of 1 to 1,000 parts by weight with respect to 100 parts by weight of the base polymer.

The polymerization initiator may be any one as long as it can generate radicals by supplying the active energy source, and is appropriately selected depending on the kind of the active energy source. Specifically, isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, chlorothioxanthone, dodecyl thioxanthone, dimethyl thioxanthone, diethyl thioxanthone, acetophenone diethyl ketal, benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ester. Examples thereof include enyl ketone, 2-hydroxymethylphenyl propane, benzoyl peroxide, and azobisisobutyronitrile. These polymerization initiators may be used alone or in combination of two or more.
The amount used is 100 parts by weight of the polymerizable compound,
It is preferably in the range of 0.1 to 20 parts by weight. In addition,
If necessary, an amine compound such as triethylamine, tetraethylpentaamine, dimethylaminoethanol or the like may be used as a polymerization accelerator together with the above polymerization initiator.

A pressure-sensitive adhesive layer 12 having such a composition
Is the same as the above on the release paper by applying the pressure-sensitive adhesive composition containing the above base polymer, the polymerizable compound and the polymerization initiator onto the support film 11 and subjecting it to crosslinking treatment by heating or the like. It can be formed by sticking the pressure-sensitive adhesive layer formed by the method onto the support film 11. The thickness of the pressure-sensitive adhesive layer 12 may be appropriately determined, but is usually 5 to 10
It is 0 μm. The above-mentioned cross-linking treatment is carried out if necessary. For example, in the case of an acrylic resin-based pressure-sensitive adhesive, an acrylic resin having a cross-linkable functional group in its molecule is used as a base polymer, and this functional group is used. A polyfunctional compound having a functional group that reacts with, for example, polyisocyanate
Cross-linking agent consisting of
It may be pre-blended in the pressure-sensitive adhesive composition.

The adhesive strength of the adhesive layer 12 is determined according to JIS Z
180 degree peeling adhesive strength to silicon wafer measured according to -0237 (at room temperature, peeling speed 300 mm /
Min) is usually 500 g or more / 20 mm width, preferably 70
The width is 0 to 2,000 g / 20 mm. In addition, the 180-degree peeling adhesive strength (at room temperature, peeling speed 300 mm / min) after curing by supplying an active energy source is as follows.
Usually less than 500g / 20mm width, preferably 1-100g
/ 20 mm width.

The separator 13 is for protecting the surface of the pressure-sensitive adhesive layer 12 until it is attached to a semiconductor wafer from the viewpoint of preventing contamination during storage or distribution of the pressure-sensitive adhesive tape 1. Then, it is peeled and removed at the time of using the above-mentioned pasting. The separator 13 is usually a flexible thin sheet made of paper (dust-free paper), plastic film, metal foil or the like, and if necessary, surface-treated with a release agent to impart releasability.

In the present invention, the adhesive tape having the above-mentioned structure is used to remove foreign matters adhering to the semiconductor wafer.
In this method, first, an adhesive tape is attached to the entire front surface and / or the back surface of the semiconductor wafer so that the surface of the adhesive layer is sufficiently adapted to the foreign matter on the wafer. This can be done, for example, by pressing the adhesive tape on the wafer with a hand roller and then leaving it for a few minutes. Here, since the pressure-sensitive adhesive layer has plastic deformability and has the large pressure-sensitive adhesive force, foreign matter on the wafer is effectively adsorbed and held during the above-mentioned bonding operation.

After sticking in this way, a peeling operation of peeling off from the end of the adhesive tape is carried out. Prior to this peeling operation, active energy such as ultraviolet rays is applied from the side of the support film of this tape. Supply the source. As a result, the pressure-sensitive adhesive layer is cured, and the molecular structure is three-dimensionally reticulated. As a result, the pressure-sensitive adhesive layer is hard and exhibits the low adhesive strength. If you perform the above peeling operation in this state, peeling can be done very smoothly,
It causes almost no damage on the wafer surface or contamination due to adhesive residue. Moreover, the above-mentioned curing ensures that the foreign matter on the wafer is strongly and surely adsorbed on the surface of the adhesive layer.

By this method, foreign matter on a semiconductor wafer can be adsorbed and removed at a high removal rate as compared with conventional dry cleaning, as well as wet cleaning and a method using an already proposed adhesive tape. In particular, it is possible to obtain a high removal rate of 80% or more of foreign matters having a size of 0.2 μm or more.

By cleaning and removing the foreign matter on the semiconductor wafer at a high removal rate in this way, the occurrence of circuit disconnection, shots and exposure failures during circuit formation is reduced, and the yield of semiconductor devices finally manufactured is reduced. And reliability is greatly improved. Further, from the standpoint of global environment conservation, by replacing the conventional wet cleaning and dry cleaning methods that consume large amounts of pure water, chemicals, air, electric power, etc. with the method of the present invention, It can also contribute significantly to conservation.

[0025]

According to the adhesive tape for removing foreign matters and the method for removing the same according to the present invention, foreign matters adhering to a semiconductor wafer can be easily removed with a high removal rate, and at the same time, damage to the semiconductor wafer and adhesive residue It is possible to greatly contribute to the improvement of the yield and the reliability of the semiconductor device without causing the pollution and the problems caused by the above. Further, compared to other conventional cleaning methods, a contribution effect in terms of global environment conservation can be obtained.

[0026]

EXAMPLES Next, examples of the present invention will be described to more specifically describe. In the following, "parts" means "parts by weight".

Example 1 80 parts of n-butyl acrylate, 15 parts of acrylonitrile and 5 parts of acrylic acid were copolymerized in ethyl acetate by a conventional method to obtain an acrylic copolymer having a number average molecular weight of 800,000. Obtained. To 100 parts of this acrylic copolymer,
3 parts of cross-linking agent consisting of polyisocyanate compound, dipentaerythritol monohydroxypentaacrylate 8
0 part, α-hydroxycyclohexyl phenyl ketone 5
Parts were added to prepare a solution of an acrylic pressure-sensitive adhesive.

On the corona-treated surface of a polyester support film having a thickness of 50 μm, the above-mentioned acrylic adhesive solution was applied and heat-crosslinked at 120 ° C. for 5 minutes to give a thickness of 20 μm.
An adhesive tape having m adhesive layers was prepared. Adhesive strength to silicon wafer (mirror surface) is JIS Z-0
180 degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to 237, 1,000 g / 20
The width was mm. Also, ultraviolet rays (wavelength 365 nm, 1,000 mJ / cm ² ) are irradiated as an active energy source from the back side of the adhesive tape, that is, the support film side.
Similarly, the adhesive strength was measured and found to be 10 g / 20 mm width.

Next, a 5-inch silicon wafer (a mirror wafer without a circuit pattern) having no foreign matter having a size of 0.2 μm or more is passed through a predetermined process (ion implantation process process) to remove the foreign matter. Laser surface inspection device [LS-500 manufactured by Hitachi Electronics Engineering Co., Ltd.]
0; a device capable of counting the number of foreign matters only on the mirror surface of a silicon wafer],
The number of foreign matters having a size of 2 μm or more was counted. In addition,
In order to count the foreign matters adhering to the front and back of the wafer, the same inspection was performed for two cases in which the mirror surfaces were reversed.

As a foreign matter cleaning test, the adhesive tape prepared by the above method was attached to the mirror surface of the silicon wafer to which the foreign matter was adhered as described above by using a hand roller and left for 3 minutes. . Then, after irradiating with ultraviolet rays (wavelength 365 nm, 1,000 mJ / cm ² ) from the back side of the adhesive tape, the adhesive tape was peeled off and washed. After this cleaning, again using the laser surface inspection device,
The number of foreign matters having a size of 0.2 μm or more attached to the surface was counted. The foreign matter removal rate was calculated from the number of foreign matter after cleaning by this sticking and peeling operation and the number of foreign matter before cleaning.

Separately from this, as a contamination test with an adhesive, a 5-inch silicon wafer with no foreign matter having a size of 0.2 μm or more (a mirror wafer without a circuit pattern)
The adhesive tape prepared by the above-mentioned method was attached to the mirror surface of No. 1 using a hand roller, and left for 3 minutes. After that, ultraviolet rays (wavelength 365 nm, from the back side of the adhesive tape,
After irradiating with 1,000 mJ / cm ² ), the adhesive tape was peeled off. After this operation, the number of foreign matters having a size of 0.2 μm or more adhering to the mirror surface was counted by using a laser surface inspecting apparatus, and the contamination state due to the adhesion of the adhesive was examined.

In the above-mentioned foreign matter cleaning test (measurement of foreign matter removal rate) and adhesive contamination test (measurement of the number of foreign matter adhered), a series of work is carried out in a class 10 clean room (temperature 23 ° C., The humidity was 60%). The test results were as shown in Table 1 (wafer front surface) and Table 2 (wafer back surface) described later.

Example 2 100 parts of this rubber containing natural rubber as a main component, dipentaerythritol monohydroxypentaacrylate 80
Parts and 5 parts of α-hydroxycyclohexylphenyl ketone were added to prepare a solution of the rubber-based pressure-sensitive adhesive. Next, the solution of the above-mentioned rubber-based pressure-sensitive adhesive was applied to the corona-treated surface of a polyester support film having a thickness of 50 μm, and the temperature was adjusted to 5 ° C. at 150 ° C.
After heat treatment for minutes, an adhesive tape having an adhesive layer with a thickness of 20 μm was produced.

This adhesive tape silicon wafer (mirror
The adhesive strength to the surface) was a 1,200 g / 20 mm width as a 180 degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to JIS Z-0237. From the back side of the adhesive tape, ultraviolet rays (wavelength 365 nm, 1,000 mJ / cm ² ) were used as an active energy source.
When the adhesive strength was similarly measured, it was 30 g / 2.
It was 0 mm wide.

Using this adhesive tape, a foreign matter cleaning test (measurement of foreign matter removal rate) and an adhesive contamination test (measurement of the number of adhered foreign matters) were carried out in the same manner as in Example 1. The test results were as shown in Tables 1 and 2 below.

Comparative Example 1 80 parts of n-butyl acrylate, 15 parts of acrylonitrile and 5 parts of acrylic acid were copolymerized in ethyl acetate by a conventional method to obtain an acrylic copolymer having a number average molecular weight of 800,000. Obtained. To this acrylic copolymer solution, 3 parts of a crosslinking agent composed of a polyisocyanate compound was added to 100 parts of the copolymer to prepare an acrylic adhesive solution.

On the corona-treated surface of a polyester support film having a thickness of 50 μm, the above-mentioned acrylic adhesive solution was applied and heat-crosslinked at 120 ° C. for 10 minutes to give a thickness of 20.
An adhesive tape having an adhesive layer of μm was prepared. Adhesive strength to silicon wafer (mirror surface) is JIS Z-
The 180-degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to 0237 was 200 g / 20 mm width.

Using this pressure-sensitive adhesive tape, a foreign matter cleaning test (measurement of foreign matter removal rate) and an adhesive contamination test (adhered foreign matter) were carried out in the same manner as in Example 1 except that the ultraviolet irradiation treatment before the peeling operation was omitted. Number measurement). These test results are
The results are shown in Tables 1 and 2 below.

Comparative Example 2 A solution of a rubber-based pressure-sensitive adhesive containing natural rubber as a main component was prepared to a thickness of 5
The adhesive tape was applied to the corona-treated surface of a 0 μm polyester support film and heat-treated at 150 ° C. for 5 minutes to prepare an adhesive tape having an adhesive layer with a thickness of 20 μm. This adhesive tape
The adhesive strength to the silicon wafer (mirror surface) is 180 degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to JIS Z-0237.
The width was 30 g / 20 mm.

Using this pressure-sensitive adhesive tape, a foreign matter cleaning test (measurement of foreign matter removal rate) and an adhesive contamination test (adhered foreign matter) were carried out in the same manner as in Example 1 except that the ultraviolet irradiation treatment before the peeling operation was omitted. Number measurement). These test results are
The results are shown in Tables 1 and 2 below.

[0041]

[Table 1]

[0042]

[Table 2]

As is clear from the results shown in Tables 1 and 2 above, the adhesive tapes of Examples 1 and 2 of the present invention have a higher silicone content than the adhesive tapes of Comparative Examples 1 and 2. It is clear that the foreign matter attached to the front surface or the back surface of the wafer can be removed at a higher removal rate of about 90% without causing contamination of the wafer.

The cleaning methods shown in Examples 1 and 2 and Comparative Examples 1 and 2 were applied to a predetermined semiconductor wafer manufacturing process, and the yield of semiconductor devices finally obtained was totaled. It was found that the method of Examples 1 and 2 increased the yield by about 8% as compared with the methods of Comparative Example 1 and Comparative Example 2.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an adhesive tape for removing foreign matter of the present invention.

[Explanation of symbols]

 1 Adhesive Tape 11 Support Film 12 Adhesive Layer 13 Separator

Claims (2)

[Claims] 1. A semiconductor wafer characterized in that a pressure-sensitive adhesive layer is provided on a support film, and the pressure-sensitive adhesive layer has a property of being cured by an active energy source and having a three-dimensional reticulated molecular structure. Adhesive tape for removing foreign matter. 2. A semiconductor wafer by adhering the adhesive tape according to claim 1 on the front surface and / or the back surface of a semiconductor wafer and peeling off the adhesive tape after supplying an active energy source. A method for removing foreign matter adhering to a semiconductor wafer, which comprises adsorbing foreign matter adhering to the front surface and / or the back surface of the semiconductor wafer onto a pressure-sensitive adhesive layer to remove it from the semiconductor wafer.