JP2007012974A - Method of forming resist film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a less defective resist film by reliably and efficiently removing microcontamination causing micro defects in a resist liquid, and preventing fine bubbles from being produced. <P>SOLUTION: The method of forming a resist film by coating a board with a resist liquid after filtering the resist liquid at a filtering pressure of 9,500 Pa or less, using a high polymer material-made filter having a hole diameter of 0.02 μm. This reliably and efficiently removes microcontamination in the resist liquid causing micro defects from which no problem arises in the prior art, prevents fine bubbles from being produced to lessen the defect of the resist film down to a required quantity of defects, and improves the yield of a resist film-coated product such as photo mask blank formed with the resist film and a work under process such as finely processed photo masks using the resist film. Thus, the resist film is formed efficiently by keeping the productivity of the resist film forming at a maximum with meeting the requirements of the resist film for lessening the defect. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming a resist film used for processing a photomask, a semiconductor integrated circuit, a CCD (charge coupled device), and the like, and in particular, removes minute foreign matters in a resist solution reliably and efficiently, The present invention relates to a method of forming a resist film with few defects by preventing generation of bubbles.

  In recent years, circuit processing has been miniaturized due to semiconductor processing, in particular, high integration of large-scale integrated circuits. As a result, wiring patterns constituting a circuit have been thinned and wiring between layers constituting a cell has been reduced. Therefore, there is an increasing demand for miniaturization technology for contact hole patterns. Also, in the manufacture of a photomask in which a mask pattern used in photolithography for forming a wiring pattern or a contact hole pattern is written, there is a technique capable of writing a finer and more accurate mask pattern with the miniaturization. It has been demanded.

  Therefore, for example, in the processing of a photomask that is an original plate when performing photolithography, a mask pattern with higher accuracy must be formed on the photomask, and for this purpose, a highly accurate resist pattern is formed on the photomask blank. It is necessary to form.

  Since optical lithography when processing an actual semiconductor substrate performs reduction projection, the mask pattern is about four times as large as the size of the transferred pattern that is actually required, but that does not mean that the accuracy is loosened. Photomasks that are original plates are required to have higher accuracy than that required for transferred pattern accuracy after exposure. Furthermore, in the lithography that is currently being performed, the circuit pattern (transfer pattern) to be drawn is a size that is considerably smaller than the wavelength of the light to be used. If it is used, the shape as the mask pattern is not transferred as a circuit pattern due to the influence of light interference or the like that occurs during photolithography.

  In order to reduce these effects, a technique for processing a mask pattern into a more complicated shape than an actual circuit pattern by a technique such as OPC (Optical Proximity Correction) is used, and a resist pattern necessary for photomask blank processing is used. In addition, there is a demand for a finer and more accurate lithography technique. Also, the resist material used is a chemically amplified type that provides high sensitivity and high resolution.

  On the other hand, as the circuit pattern to be drawn becomes finer and the film thickness of the resist film decreases with the miniaturization of the circuit pattern, the resist pattern defect also becomes more fine, for example, about 0.2 to 0.3 μm. Or defects of a smaller size have become a problem. In the production of photomasks that transfer a fine circuit pattern compared to conventional ones, the problem of such fine defects is not only when forming a mask pattern using a resist pattern, but also when a circuit is transferred using a photomask. Since it affects the accuracy of the pattern, if a defective defect occurs in the resist pattern, it will be repaired in some way. However, the finer the resist pattern, the greater the effort required to repair it. And cost.

  There are many possible causes for the defect of the resist pattern, one of which is a defect that occurs during the application of the resist solution. This is due to foreign matter present in the resist solution. Therefore, foreign matter is filtered through a filter when applying a resist solution. Recently, a filter having a small pore diameter of 0.02 μm has been used as a filter for removing the foreign matter. ing.

  However, if a filter with a small pore size is used, foreign matters having a size corresponding to the pore size of the filter cannot be completely removed. Even if such a filter with a small pore size is used, the size is about 0.2 μm or more. It is a problem that the foreign matter causing the defect cannot be sufficiently removed. Furthermore, when the resist solution is filtered using such a filter, there is a concern that minute bubbles are generated and defects derived therefrom are generated.

  The prior art document information related to the present invention includes the following.

JP-A-10-305256 JP-A-9-171955 JP 2004-221975 A

  The present invention has been made to solve the above-mentioned problems, and it is possible to reliably and efficiently remove minute foreign matters in a resist solution that cause fine defects that have not been a problem in the past, and to generate microbubbles. It is an object of the present invention to provide a method capable of preventing the above and forming a resist film with few defects.

  In order to prevent fine defects in the resist film, the present inventor examined a method for removing fine foreign matters in the resist solution by filtering through a filter. However, the present inventor generally uses a filter having a pore diameter of 0.02 μm and is generally applicable. Even when the resist solution was filtered under the conditions as described above, it was not possible to significantly reduce fine defects, particularly 0.2 μm size defects of the resist film coated on the photomask blank.

  Therefore, as a result of intensive studies in view of the above circumstances, the present inventors have found that the resist solution has a pore size of 0.02 μm or less, for example, a polymer material filter having a pore size of 0.02 μm, particularly a polyolefin filter, 9, When filtration is performed at a filtration pressure of 500 Pa or less, preferably 7,000 to 9,500 Pa, and the filtered resist solution is applied onto the substrate to form a resist film. Photomask blank in which a mask pattern of 100 nm or less in which, for example, a 0.2 μm size defect is a problem is formed, without significantly reducing the amount of filtered resist solution per unit time compared to The present inventors have found that a resist film with very few defects can be formed on a substrate such as the above, and have made the present invention.

That is, the present invention provides the following resist film formation method.
Claim 1:
A method of forming a resist film by applying a resist solution on a substrate, and applying the resist solution by filtering with a polymer material filter having a pore size of 0.02 μm or less at a filtration pressure of 9,500 Pa or less. A method for forming a resist film.
Claim 2:
2. The film forming method according to claim 1, wherein the polymer material is polyolefin.
Claim 3:
3. The film forming method according to claim 1, wherein the substrate is a photomask blank on which a mask pattern of 200 nm or less is formed.

  According to the present invention, it is possible to reliably and efficiently remove minute foreign matters in a resist solution that cause fine defects that have not been a problem in the past, and to prevent generation of microbubbles, thereby requiring a required amount of defects. To improve the yield of workpieces such as photomasks that have been finely processed using a resist film. Can do. In addition, the resist film can be efficiently formed while maintaining the resist film formation productivity to the maximum while satisfying the demand for reducing the defects of the resist film.

Hereinafter, the present invention will be described in more detail.
In the present invention, the resist film is formed by filtering the resist solution through a filter made of a polymer material having a pore diameter of 0.02 μm or less at a filtration pressure of 9,500 Pa or less and applying the resist solution onto the substrate.

  In the present invention, a filter made of a polymer material having a pore size of 0.02 μm or less is used for filtering the resist solution in order to more surely remove minute foreign matters, particularly 0.2 μm size foreign matters. Considering the removal rate of foreign substances and the filtration efficiency (productivity), it is particularly preferable to use a filter having a pore diameter of 0.02 μm. The filter material is preferably a polyolefin such as ultrahigh molecular weight polyethylene or polyethylene-polypropylene. A commercially available product can be used as the filter having the above pore diameter formed of the above material.

  Further, in the present invention, the filtration pressure (differential pressure) of the resist solution is filtered at a filtration pressure of 9,500 Pa or less, preferably 7,500-9,500 Pa. A conventionally known apparatus described in JP-A-9-171955 (Patent Document 2) can be used, has a resist solution supply pump, measures the filtration pressure, that is, the differential pressure before and after the filter, It can be carried out by setting the filtration pressure of the resist solution within the above range by a filtration mechanism capable of adjusting the discharge pressure of the pump automatically or manually.

  Then, the resist solution filtered as described above is discharged from the nozzle and applied onto the substrate. Many methods such as spin coating, roll coating, and flow coating are known as coating and film forming methods, and the coating of the present invention is not particularly limited to these specific methods. Is a preferable method for obtaining a small and uniform film.

  In the present invention, the resist solution is filtered at a filtration pressure that is significantly lower than the conventionally applied filtration pressure. When this filtered resist solution is applied onto a substrate to form a resist film, the amount of defects is reduced. In particular, processing of a photomask used to form a resist film for forming a resist pattern of 200 nm or less, for example, a circuit pattern of 100 nm or less, in which a finer defect having a size of 0.2 μm becomes a problem is particularly problematic. Therefore, it is useful for forming a resist film to be applied on a photomask blank, and a resist film with extremely few defects can be formed.

  In the case of processing a photomask, a photomask blank in which a metallic light-shielding film typified by a chromium compound is formed on a transparent substrate is used as a substrate to which a resist solution is applied. In this case, the resist film formed on the photomask blank is subjected to pattern exposure and development to form a resist pattern, and the light shielding film of the photomask blank is patterned using this resist pattern as a mask to form a mask pattern. In addition, the presence or absence of the defect of the resist film used for such pattern formation can be test | inspected using commercially available defect inspection machines, such as Hitachi High-Technologies GM-1000.

  Any known resist solution can be applied to the present invention. For example, for forming a circuit pattern of 100 nm or less, or for processing a photomask having a mask pattern of 200 nm or less. As the resist material, a chemically amplified resist solution having high resolution is preferable, and a positive type or a negative type can be selected as necessary.

  In addition, as a resist solution for processing a photomask, an etching selectivity for a metallic film containing chromium or the like is required, so that a resist material resin having an aromatic skeleton is selected. There are many known examples of these, but any of these can be applied, and excimer laser light resist solutions and electron beam irradiation resist solutions are also applicable.

  Furthermore, the present invention is particularly effective when a resist film having a thickness of 250 nm or less is formed. The viscosity of the resist solution varies depending on the solid content of the resin, etc. used, the type of solvent, and their blending ratio, particularly the solid content concentration, but the resist solution used when forming a resist film with a film thickness of 250 nm or less is generally Since the solid content concentration is low and the viscosity is relatively low, the effect of the present invention is particularly exhibited, which is preferable. In addition, the solid content concentration and the viscosity of the resist solution to be filtered are not particularly limited. For example, the solid content concentration is preferably 4 to 10% by mass and the viscosity is 1 to 200 Pa · s.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to the following Example.

[Examples 1 and 2 and Comparative Examples 1 to 3]
Using a 152 mm × 152 mm × 6.35 mm quartz glass substrate, a chromium compound (CrON) light-shielding film was formed on the quartz glass substrate by sputtering to a thickness of 70.0 nm.

  Next, a filter having a pore size of 0.02 μm (CWAX061S2 manufactured by Nihon Micro Lease Co., Ltd.) is attached to a spin coater equipped with a filtration mechanism capable of measuring filtration pressure, and the following negative resist solution for electron beam drawing exposure is used as a filter. Filtration pressures were adjusted to 7,000 Pa, 9,500 Pa, 13,000 Pa, 20,000 Pa, and 27,500 Pa, respectively, and 4 ml of the resist solution after filtration was applied onto the chromium light-shielding film on the substrate.

Negative resist solution for electron beam drawing Hydroxystyrene-indene (85:15) copolymer (Mw = 3,000) 80 parts by mass Tri (4-ethylphenyl) sulfonium trifluoromethanesulfonate 10 parts by mass tetramethoxymethyl glycol Uril 10 parts by mass Tri-n-butylamine 0.6 parts by mass Fluorosurfactant 0.2 parts by mass Propylene glycol dimethyl ether acetate 900 parts by mass Ethyl lactate 400 parts by mass

  Next, the substrate coated with the resist solution was pre-baked by a conventional method, cooled, and the number of defects in the resist film was measured with a defect inspection machine (GM-1000 manufactured by Hitachi High-Technologies Corporation). The results are shown in Table 1.

  From the above results, when the filtration pressure is 7,000 to 9,500 Pa, the filtration amount of the resist solution per unit time is 1/2 to 3 as compared with the filtration pressure higher than this, for example, 13,000 Pa. Although the number of defects is reduced to / 4, the total number of defects is reduced to 1/5 to 2/5, particularly to 1/6 to 1/3 for fine defects having a size of more than 0.2 μm and not more than 0.3 μm. Therefore, if the filtration pressure is set to 9,500 Pa or less, the number of defects in the resist film is remarkably reduced, that is, the defect rate per unit filtration flow rate is reduced as shown in FIG. It can be seen that the number of defects in the resist film can be remarkably reduced without greatly reducing the productivity of the resist solution coating when the number of defects is set to 1,000 to 9,500 Pa.

It is the graph which plotted the number of defects of the resist film with respect to the filtration pressure of the resist liquid of an Example and a comparative example.

Claims (3)

  A method of forming a resist film by applying a resist solution on a substrate, and applying the resist solution by filtering with a filter made of a polymer material having a pore size of 0.02 μm or less with a filtration pressure of 9,500 Pa or less. A method for forming a resist film.   2. The film forming method according to claim 1, wherein the polymer material is polyolefin. 3. The film forming method according to claim 1, wherein the substrate is a photomask blank on which a mask pattern of 200 nm or less is formed.

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