JPH0888205A - Adhesive tape for removing foreign matter adhering to semiconductor wafer and removal method - Google Patents

Abstract

(57) [Abstract] [Purpose] In a dry cleaning method using an adhesive tape, a foreign matter adhering to a semiconductor wafer can be removed at a high removal rate without causing problems such as contamination of the wafer surface due to adhesive residue and wafer damage. Intended to be removed. [Structure] As an adhesive tape 1 for removing foreign matter, an adhesive layer 12 is provided on a support film 11, and this adhesive layer 1
2 has a (meth) acrylic acid alkyl ester polymer as a main component, has a gel fraction of 50% or more, and has a 180 ° peeling adhesive strength of 50 to a silicon wafer (mirror surface).
Use the adhesive tape of 0g or less / 20mm width.
After attaching the substrate 1 to the front surface and / or the back surface of the semiconductor wafer, the peeling operation is performed to
Alternatively, the foreign matter attached to the back surface is adsorbed to the surface of the adhesive layer 12 and removed from the semiconductor wafer.

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, according to the method proposed above, even if a tacky tape having a high tackiness that is easily plastically deformed is used, the foreign matter removing effect is not sufficiently enhanced, and conversely the peeling operation is performed. On this occasion, problems such as contamination of the wafer surface due to adhesive residue and damage to the wafer are likely to occur, and there is also a problem of corrosion of aluminum wiring due to impurities contained in the adhesive.

In view of the above 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, so that the adhesive residue causes It is an object of the present invention to remove foreign substances adhering to a semiconductor wafer at a high removal rate without causing problems such as contamination of the wafer surface and damage to the wafer, and corrosion of aluminum wiring due to impurities.

[0009]

Means for Solving the Problems The inventors of the present invention have diligently studied the above object, and as a result, as an adhesive tape,
When a polymer containing a (meth) acrylic acid alkyl ester polymer as a main component and having a specific gel fraction and a specific adhesive strength is used, problems such as contamination of the wafer surface due to adhesive residue and wafer damage, as well as impurities The present invention has been completed by discovering that foreign substances adhering to a semiconductor wafer can be removed at a high removal rate without causing any problem of corrosion of aluminum wiring due to the above.

That is, according to the present invention, firstly, as the above-mentioned specific adhesive tape, an adhesive layer is provided on a supporting film, and this adhesive layer is composed of an alkyl (meth) acrylate polymer. (Hereafter, referred to as acrylic polymer)
With a gel fraction of 50% or more, a 180 degree peeling adhesive strength to a silicon wafer (mirror surface) of 5
(EN) A pressure-sensitive adhesive tape for removing foreign matter attached to a semiconductor wafer, which has a width of 00 g or less / 20 mm.

Secondly, after sticking the above-mentioned specific adhesive tape on the front surface and / or the back surface of the semiconductor wafer, a peeling operation is performed to remove foreign matters attached to the front surface and / or the back surface of the semiconductor wafer. Disclosed is a method for removing foreign matter adhering to a semiconductor wafer, which is characterized in that it is adsorbed on the surface of an 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 is made of, for example, polyester, polycarbonate, polyvinyl chloride, ethylene-
The film made of plastic such as vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyethylene, polypropylene, ethylene-propylene copolymer and the like has a thickness of usually 10 to 1,000 μm.

The pressure-sensitive adhesive layer 12 is mainly composed of an acrylic polymer and has an adhesive force under normal conditions, that is, a pressure-sensitive adhesive property, and has a gel fraction of 50% or more, preferably 55-9.
At 5%, the 180 ° peeling adhesive force to the silicon wafer (mirror surface) is 500 g or less / 20 mm width, preferably 50 to 300 g / 20 mm width. The gel fraction is a value calculated by peeling off the pressure-sensitive adhesive layer 12 from the support film 11, immersing it in toluene (20 ° C.) for 24 hours, and changing the weight before and after immersing. In addition, the above-mentioned 180 degree peeling adhesive strength is JIS Z-
According to 0237, it is a value measured at room temperature and a peeling speed of 300 mm / min.

The pressure-sensitive adhesive layer 12 containing an acrylic polymer as a main component contains less ionic impurities than other pressure-sensitive adhesives containing a natural rubber or a synthetic rubber as a main component.
Even if this is applied to a semiconductor wafer, the problem of corrosion of aluminum wiring due to impurities does not occur. Further, when the gel fraction is 50% or more, the foreign matter adsorption and fixing force is increased, the removal effect is dramatically improved, and the adhesive residue on the wafer surface during the peeling operation is reduced. Pollution is avoided. Further, since the 180 degree peeling adhesive strength is 500 g or less / 20 mm width, the peeling operation is easy and there is no fear of damaging the semiconductor wafer during the peeling operation.

This adhesive layer 12 is made of an acrylic polymer.
A polyisocyanate compound, an epoxy compound, a melamine compound, a peroxide, etc. as a cross-linking agent, and a pressure-sensitive adhesive composition containing other additives as necessary, after coating on the support film 11, It can be formed by cross-linking by heating or by sticking the pressure-sensitive adhesive layer formed on the release paper by the same method as above on the support film 11. At that time, the gel fraction and the adhesive strength can be easily set within the above ranges by selecting the type and amount of the cross-linking agent, the conditions for the cross-linking treatment, etc. according to the composition and molecular weight of the acrylic polymer. The thickness of the pressure-sensitive adhesive layer 12 thus formed is not particularly limited,
Usually, it is good to be 5 to 100 μm.

Generally, the above-mentioned acrylic polymer is
A main monomer is (meth) acrylic acid alkyl ester, and a copolymerizable monomer having a crosslinkable functional group on it.
Further, if necessary, a monomer mixture to which other modifying monomers are added can be synthesized by radical polymerization by a polymerization method such as an emulsion polymerization method, a bulk polymerization method, a solution polymerization method. The acrylic polymer thus obtained preferably has a low content of low molecular weight substances, and its number average molecular weight is at least 400,000, particularly 40,000.
Those in the range of 10,000 to 3,000,000 are desirable.

Examples of the (meth) acrylic acid alkyl ester which is a main monomer include, for example, methyl group, ethyl group, propyl group, butyl group, isodecyl group, isoamyl group, hexyl group, 2-ethylhexyl group, isooctyl group and isononyl. An alkyl ester of acrylic acid or methacrylic acid having an alkyl group having a carbon number of 30 or less, especially 14 or less, such as a group, an isodecyl group or a dodecyl group, is used.

As the copolymerizable monomer having a crosslinkable functional group, acrylic acid, methacrylic acid, maleic anhydride,
Carboxyl group-containing monomers such as itaconic acid, hydroxy group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and N-methyl acrylamide. -, Amide group-containing monomers such as acrylamide, methacrylamide,
Examples thereof include epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and amino group-containing monomers such as N, N-dimethylaminoethyl acrylate. These monomers are used for adjusting the gel fraction and the adhesive strength of the adhesive, and generally,
It is used in a proportion of 0.1 to 30 parts by weight, preferably 2 to 10 parts by weight, relative to 100 parts by weight of the (meth) acrylic acid alkyl ester which is the main monomer.

Other reforming monomers that may be used as required include, for example, vinyl acetate, styrene, N-
All of those commonly used for so-called acrylic pressure-sensitive adhesives such as vinylpyrrolidone, acrylonitrile, methacrylonitrile, etc. can be used. The amount of these modifying monomers used is preferably 50% by weight or less based on the total amount of the (meth) acrylic acid alkyl ester which is the main monomer.

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 matter 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 may be done by pressing the adhesive tape on the wafer with a hand roller and then leaving it for a few minutes.

When the adhesive tape is attached in this manner and then peeled off from the end portion of the adhesive tape, a foreign matter on the semiconductor wafer is strongly adsorbed and fixed to the adhesive layer surface, and the foreign matter on the semiconductor wafer is effectively removed. To be removed. At that time, problems such as damage on the surface of the semiconductor wafer and contamination due to adhesive residue hardly occur. Moreover, there is no particular concern if the impurities in the adhesive will corrode the aluminum wiring portion and the like thereafter.

In this way, a high removal rate of foreign matter on the semiconductor wafer (usually 75% of foreign matter having a size of 0.2 μm or more)
It is possible to wash and remove with the above removal rate), which reduces the occurrence of circuit breaks and shots during circuit formation and exposure defects, and greatly improves the yield and reliability of the finally manufactured semiconductor devices. Improve to. 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]

As described above, according to the adhesive tape for removing foreign matters and the method for removing the same according to the present invention, there is a problem such as damage due to damage of the semiconductor wafer and contamination due to adhesive residue, and further, impurities due to the adhesive. It has the effect of cleaning and removing foreign matter adhering to semiconductor wafers with a high removal rate without causing corrosion problems such as aluminum wiring, and also contributes to global environmental protection compared to other conventional cleaning methods. The effect is also 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 contain an acrylic polymer having a number average molecular weight of 800,000. A polymer solution was obtained. An adhesive solution was prepared by adding 3 parts of a cross-linking agent composed of a polyisocyanate compound to 100 parts of an acrylic polymer in the polymer solution.

The above adhesive solution was applied to the corona-treated surface of a polyester support film having a thickness of 50 μm, and 120
A heat-crosslinking treatment was performed at 10 ° C. for 10 minutes to prepare an adhesive tape having an adhesive layer having a thickness of 20 μm. The gel fraction of the adhesive layer of this adhesive tape is 55%, and the silicon wafer (mirror
The adhesive strength to the surface) was 200 g / 20 mm width in 180 degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to JIS Z-0237.

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. After that, peel off the adhesive tape,
Washed. After this cleaning, the number of foreign matters having a size of 0.2 μm or more attached to the mirror surface was counted again using the laser surface inspection device. 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 the above using a hand roller and left for 3 minutes, and then 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 As a crosslinking agent, 3 parts of polyisocyanate compound was used,
An adhesive tape was produced in the same manner as in Example 1 except that 0.5 part of the epoxy compound was used. The adhesive layer of this adhesive tape has a gel fraction of 81% and a silicon wafer (mirror
The adhesive strength to the surface) was 120 g / 20 mm width in 180 degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to JIS Z-0237. Next, using this adhesive tape, in the same manner as in Example 1,
A foreign matter cleaning test (measurement of foreign matter removal rate) and a pressure-sensitive adhesive contamination test (measurement of the number of adhered foreign matters) were performed. The test results were as shown in Tables 1 and 2 below.

Comparative Example 1 The amount of the polyisocyanate compound used as the crosslinking agent was 3
Same as Example 1 except that the number of parts is changed to one,
An adhesive tape was prepared. The gel fraction of the adhesive layer of this adhesive tape is 45%, and the adhesive force to a silicon wafer (mirror surface) is measured according to JIS Z-0237. 1
80 degree peeling adhesive strength (at room temperature, peeling speed 300 mm /
Min) and the width was 320 g / 20 mm. Next, 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 performed in the same manner as in Example 1. These test results are shown in Table 1 below.
And as shown in Table 2.

Comparative Example 2 As a crosslinking agent, 3 parts of polyisocyanate compound was used,
An adhesive tape was produced in the same manner as in Example 1 except that 0.02 part of the epoxy compound was used. This adhesive tape
The gel fraction of the adhesive layer is 41%, and the adhesive force to the silicon wafer (mirror surface) is 180 degree peeling adhesive force measured at JIS Z-0237 (normal temperature, peeling speed 300 mm / min) It was 330 g / 20 mm wide. Next, using this pressure-sensitive 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 performed in the same manner as in Example 1. The test results were as shown in Tables 1 and 2 below.

Comparative Example 3 The amount of the polyisocyanate compound used as the crosslinking agent was changed to 3
An adhesive tape was produced in the same manner as in Example 1 except that the number of parts was changed to 0.5. The gel fraction of the pressure-sensitive adhesive layer of this pressure-sensitive adhesive tape is 29%, and the pressure-sensitive adhesive force to the silicon wafer (mirror surface) is 180 degree peeling pressure-sensitive adhesive force (normal temperature, peeling speed 300 mm
/ Min) and the width was 685 g / 20 mm. Next, 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 performed in the same manner as in Example 1. The test results were as shown in Tables 1 and 2 below.

Comparative Example 4 A solution of a rubber-based pressure-sensitive adhesive containing natural rubber as a main component was prepared to a thickness of 5
It is applied to the corona-treated surface of a 0 μm polyester support film and heat-crosslinked at 150 ° C. for 5 minutes to give a thickness of 20 μm.
An adhesive tape having m adhesive layers was prepared. The gel fraction of the adhesive layer of this adhesive tape is 66%, and the adhesive force to the silicon wafer (mirror surface) is JIS Z-0.
The 180-degree peeling adhesive strength (normal temperature, peeling speed 300 mm / min) measured according to 237 was 330 g / 20 mm width. Next, using this adhesive tape, Example 1
In the same manner as the above, a foreign matter cleaning test (measurement of foreign matter removal rate) and an adhesive contamination test (measurement of the number of adhered foreign matter) were performed. The test results were as shown in Tables 1 and 2 below.

[0038]

[Table 1]

[0039]

[Table 2]

As is clear from the results of Tables 1 and 2 above, according to the adhesive tapes of Examples 1 and 2 of the present invention, foreign substances adhering to the front surface and the back surface of the silicon wafer were contaminated. It can be seen that the removal can be performed with a high removal rate of about 80% without causing any trouble. It was also confirmed that the adhesive tapes of Examples 1 and 2 of the present invention did not cause damage such as cracks to the semiconductor wafer during the peeling operation.

On the other hand, the adhesive tapes of Comparative Examples 1 to 3 have a low foreign matter removal rate, and in particular, the adhesive tapes of Comparative Example 3 have a cohesive force of the adhesive layer due to the low gel fraction. It can be seen that due to the lack of pressure, the adhesive component is transferred to the surface of the wafer and the foreign matter removal rate becomes a negative value, that is, the adhered foreign matter increases. Also, the adhesive tape of Comparative Example 3 is
It was also confirmed that the adhesive strength was too large, and the wafer was damaged such as cracked during the peeling operation. Further, in the pressure-sensitive adhesive tape of Comparative Example 4 using a rubber-based pressure-sensitive adhesive, the foreign matter removal rate is slightly higher, but it is still inferior to the pressure-sensitive adhesive tapes of Examples 1 and 2. I know there is.

The above-mentioned Examples 1 and 2 and Comparative Example 1
The cleaning methods shown in FIGS. 4 to 4 are applied to a predetermined semiconductor wafer manufacturing process, and the yields of semiconductor devices finally obtained are tabulated.
It was found that the yield was increased by about 13 to 46% as compared with the method of No. 4. In addition, Examples 1 and 2 and Comparative Examples 1 to 1
In the method of 3, the aluminum wiring portion did not cause a problem such as corrosion after the aluminum wiring was applied, but in the method of Comparative Example 4 in which a rubber-based adhesive was used, the aluminum wiring portion was significantly corroded. Admitted.

[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 pressure-sensitive adhesive layer is provided on a support film, and this pressure-sensitive adhesive layer contains a (meth) acrylic acid alkyl ester-based polymer as a main component and has a gel fraction of 50% or more. Adhesive tape for removing foreign matter adhering to a semiconductor wafer, characterized by having a 180 degree peeling adhesive strength to the mirror surface) of 500 g or less / 20 mm width
Pu. 2. The adhesive tape according to claim 1 is attached to the front surface and / or the back surface of a semiconductor wafer, and then a peeling operation is performed to adhere foreign substances attached to the front surface and / or the back surface of the semiconductor wafer. A method for removing foreign matter adhering to a semiconductor wafer, which comprises adsorbing the agent layer surface to remove it from the semiconductor wafer.