JP2576516B2 - Resist removal liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the production of a photomask used in the production of semiconductors, and an unnecessary resist that has undergone development and etching steps after irradiation with an electron beam or UV is applied to the photomask. The present invention relates to a resist removing solution for removing from a resist.

[Conventional technology]

A photomask used as an original for photolithography in LSI manufacturing is manufactured by processing a blank plate in which a thin chromium film is deposited on a low expansion glass plate or a quartz plate by vacuum evaporation or sputtering.

In recent years, a blank plate in which a chromium oxide film is laminated on a chromium film to suppress the light reflectance has been used in order to improve a pattern accuracy defect due to a standing wave at the time of exposure.

In the photomask manufacturing process, a UV resist or electron beam resist is applied to a blank plate, exposed using ultraviolet rays or electron beams, and then developed and etched to remove unnecessary resist on metal chromium or chromium oxide. The step of performing

Resist removal is a very important step in removing unnecessary resist on the mask to produce a defect-free mask.

Conventionally, as a method for removing the resist, a dry process using plasma or the like and a wet process using a liquid chemical have been used.

Dry processing is a method of ashing a resist using oxygen plasma or ozone, and is a method that has a wide range of application regardless of the type of resist. However, the apparatus is expensive, processing capacity is low, and productivity is poor. In addition, there is a problem that ash remains in the resist and foreign matter easily remains, and the cleaning cost is not very high. Therefore, there are many problems such as further cleaning with a liquid chemical after the dry treatment.

On the other hand, in the wet method, the resist is peeled off by a chemical, and although the productivity is high, there is a problem that various kinds of peeling liquids must be used depending on the type of the resist. There are four types of resists: ultraviolet-sensitive photoresists and electron-beam-sensitive resists, each of which has a positive type and a negative type.

The chemical which is most widely applied to these resists and has a high resist removing ability is a resist removing solution comprising sulfuric acid and hydrogen peroxide.

OEBR-1000 (manufactured by Tokyo Ohka, electron beam positive type), OEBR-100
(Tokyo Ohka, electron beam negative), OMR-83 (Tokyo Ohka,
Various resists such as photonegative type, JSR-PFR-3000 (made by Nippon Synthetic Rubber, photopositive type), OFPR-800 (made by Tokyo Ohka, photopositive type) are mixed with sulfuric acid hydrogen peroxide (general mixing ratio) Is concentrated sulfuric acid: 30% by weight hydrogen peroxide = 2: 1 vo
(l ratio). However, OEBR-1000 and OEBR-100
Has a problem that the peeling ability is slightly low.

In addition, when a mixed solution of sulfuric acid and hydrogen peroxide is applied to a photomask, the sulfuric acid remaining on the mask causes corrosion of the metal chromium film and chromium oxide film to progress even with traces of sulfuric acid, Alternatively, there is a problem that causes a fine defect of a mask, such as a peeling-off of a metal chromium film or a chromium oxide film on a glass substrate or generation of a pinhole. Even if the washing with water after removing the resist is strengthened, the photomask pattern has been miniaturized and complicated in recent years.
It is difficult to eliminate defects.

As a resist removing method using a low corrosive chemical, the present inventors have previously proposed a method of immersing in a 60% by weight aqueous hydrogen peroxide solution and then washing with a water-soluble solvent such as DMSO. No. 62-9630), this method uses two kinds of chemicals, so there is a problem that a washing tank is multi-stage and the washing process is complicated, so that it is not practical, and the target resist is limited to a negative type electron beam resist. Have been.

[Problems to be solved by the invention]

The present inventors have intensively studied for the purpose of providing a resist removing solution having low corrosiveness to a metal chromium film or a chromium oxide film and capable of removing various resists.

As a result, 30% by weight or more of hydrogen peroxide alone cannot remove the resist, but surprisingly, when a small amount of phosphate or condensed phosphate is added to this hydrogen peroxide, the electron beam on the photomask is The present invention has been found that not only a resist (including a positive type and a negative type) but also a photoresist (a positive type and a negative type) can be removed.

[Means for solving the problem]

The hydrogen peroxide used in the present invention is preferably hydrogen peroxide having a concentration of 30% by weight or more, but from the viewpoint of safety in use, hydrogen peroxide of 30% by weight to 75% by weight is more preferable. is there.

Substances to be added and blended with this include alkali metal salts of orthophosphoric acid such as disodium orthophosphate, trisodium orthophosphate, dipotassium orthophosphate, and tripotassium orthophosphate, sodium pyrophosphate, potassium pyrophosphate, sodium tripolyphosphate, and tripolyphosphate. Alkali metal salts of condensed phosphoric acid such as potassium acid and sodium hexametaphosphate can be used alone or in combination of two or more.

The amount of these additives is 0.003% by weight in terms of anhydrous salt.
To 1% by weight, more preferably 0.003% to 0.5% by weight. Addition of 1% by weight or more is not practical because hydrogen peroxide is easily decomposed when the resist is stripped, and the bath life is shortened. If the content is less than 0.003% by weight, the effect of removing the resist is not sufficient.

The resist removing solution of the present invention can be used in a step of removing a resist on a mask that is no longer required after a resist coating, exposure, development, and etching steps, by immersing a photomask in a processing bath and oxygen. After the resist is removed by a dry process such as plasma, it can be used for a step of removing and cleaning fine resist and foreign matter remaining on the mask.

The material of the treatment tank is preferably a fluororesin such as PTFE, quartz or glass from the viewpoint of decomposing hydrogen peroxide.

Next, the treatment temperature and immersion time at the time of removing the resist vary depending on the type of the resist, but are usually about 40 to 100 ° C., about 5 to 20 minutes, preferably 60 to 90 ° C., and 5 to 15 minutes are suitable. It is.

〔The invention's effect〕

The resist removing agent of the present invention has high performance of removing the resist and cleaning the mask surface, and has less residual resist and residual foreign substances than the dry ashing method.

In addition to the photoresist, the electron beam resist can also remove the resist on the photomask irrespective of whether it is a positive type or a negative type, so that it is not necessary to change the resist removing solution depending on the type of the resist.

〔Example〕

Next, the present invention will be described in detail with reference to Examples and Comparative Examples.

 In Examples and Comparative Examples, “%” indicates “% by weight”.

Example 1 (Manufacture of test mask) A chromium blank plate in which a chromium film having a thickness of 100 m is deposited on a glass plate and a chromium oxide blank plate in which a chromium oxide film is further laminated on the chromium film are prepared. After applying the various resists shown in Table 1 to this blank plate and pre-baking, develop a test pattern by irradiating UV or electron beam, etch with an etchant composed of cerium nitrate / perchloric acid, wash with pure water, and test A mask for use was made.

(Removal of resist) The mask prepared as described above was immersed in a resist removal solution having the composition shown in Table 2 at 80 ° C for 10 minutes, washed with pure water, and inspected with a differential interference microscope. The results are shown in Table 2.

Comparative Example 1 Using the mask prepared in Example 1, it was immersed in a resist removing solution having the composition shown in Table 3 at 80 ° C. for 10 minutes, and the peeling state was inspected in the same manner as in Example 1. Table 3 shows the results.

Example 2 OEBR-100 was applied to a chrome blank plate (100 mm square)
After pre-baking, it is irradiated with an electron beam. Then, the test mask, which was immersed in an etching solution composed of potassium nitrate / perchloric acid and washed with pure water, was manufactured. The test mask was prepared by adding 0.05% of sodium pyrophosphate / 10 hydrate to 60% of hydrogen peroxide. Soak at 80 ° C for 10 minutes.

Thereafter, after washing with pure water and drying, the foreign matter on the mask was measured by a foreign matter inspection device.

Comparative Example 2 The same test mask as in Example 2 was treated with an oxygen plasma asher, then washed with pure water and dried.

As a result of measuring foreign matter on the mask with a foreign matter inspection machine, the number of foreign matter having a size of 1 μm or more was about 10 times that of Example 2.

Claims (1)

(57) [Claims] 1. A method for removing a resist from a photomask for semiconductor production, comprising mixing an alkali metal salt of orthophosphoric acid or an alkali metal salt of condensed phosphoric acid in anhydrous hydrogen peroxide in an amount of 0.003% by weight to 1% by weight in terms of an anhydrous salt. liquid.