JP4099658B2 - Photomask blank substrate handling and storage method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for handling a photomask blank substrate in which a resist film is laminated in a process for producing a photomask blank substrate in which a resist film used for manufacturing a semiconductor integrated circuit is laminated, and a photo in which the resist film is laminated. With regard to the mask blank substrate storage method, particularly when the resist film is handled or stored in contact with air, the resist film does not cause a change over time and the resolution of the resist film does not decrease. About.
[0002]
[Prior art]
Photomasks used in a wide range of applications, including the manufacture of semiconductor integrated circuits such as IC and LSI, basically consist of a light-shielding film composed mainly of chromium, molybdenum and silicon on a light-transmitting substrate. A phase shift film or the like as a component is formed in a predetermined pattern. In recent years, pattern miniaturization has been rapidly progressing along with market demands such as higher integration of semiconductor integrated circuits, and a resist exposure method used for pattern formation with this pattern miniaturization is also the conventional i. It is changing from line drawing to electron beam drawing.
[0003]
However, the resist for electron beam lithography exposure has the property that, instead of being highly sensitive, it deteriorates due to the influence of a very small amount of basic gas or acid gas in the outside air, and the resolution tends to decrease. Yes. Therefore, when handling in a state where the resist film is in contact with air in each step of manufacturing a photomask blank substrate on which a resist film is laminated, for example, when forming a resist, and then storing it in a storage container, the resist film When storing the photomask blank substrate on which is stacked, there is a problem that the resolution of the photomask blank decreases due to deterioration with time due to basic gas or acid gas in the outside air.
[0004]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems. In the process of manufacturing a photomask blank substrate on which a resist film is laminated, the resist film on the substrate is handled in a state where it is in contact with air or the resist film is laminated. It is an object of the present invention to provide a handling method and a storage method that do not cause a change in the resist film with time and do not reduce the resolution of the photomask blank when the stored photomask blank substrate is stored.
[0005]
Means for Solving the Problem and Embodiment of the Invention
As a result of intensive studies to solve the above problems, the present inventor, in each step of manufacturing a photomask blank substrate on which a resist film is laminated, particularly when handling the substrate in a state where the resist film is in contact with air, In the process of applying a resist to a photomask blank or the process of storing a photomask blank substrate on which a resist film is laminated in a storage container, the basic gas concentration is set to NH ₄ ⁺ concentration on the photomask blank substrate on which the resist film is laminated. If handled in an air atmosphere where the standard gas concentration is ₃ ppb or less and the acid gas concentration is reduced to 3 ppb or less based on the SO ₄ ^2- standard, the resolution of the photomask blank decreases due to deterioration with time due to basic gas or acid gas in the outside air. It was found that this can be prevented.
[0006]
Further, when storing a photomask blank substrate on which a resist film is laminated, an air atmosphere in which the basic gas concentration is reduced to 3 ppb or less on the NH ₄ ⁺ concentration basis and the acidic gas concentration is reduced to 3 ppb or less on the SO ₄ ²⁻ basis. If it is stored below, it has been found that the resolution of the photomask blank can be prevented from being deteriorated with time by the basic gas or acid gas in the outside air, and the present invention has been made.
[0007]
Therefore, the present invention provides the following photomask blank substrate handling method and storage method.
Claim 1:
In a process of manufacturing a photomask blank substrate on which a resist film is laminated, the substrate is handled in a state in which the resist film is in contact with air, the basic gas concentration is ₃ ppb or less on the NH ₄ ⁺ concentration standard, and the acid gas A method for handling a photomask blank substrate, wherein the substrate is handled in an air atmosphere having a concentration of ₃ ppb or less based on SO ₄ ²⁻ standard.
Claim 2:
2. The method according to claim 1, wherein the step is a step of forming a resist film on a photomask blank.
Claim 3:
2. The method according to claim 1, wherein the step is a step of storing a photomask blank substrate on which a resist film is laminated in a storage container.
Claim 4:
A method of storing a photomask blank substrate on which a resist film not patterned is laminated, wherein the basic gas concentration is ₃ ppb or less based on NH ₄ ⁺ concentration, and the acidic gas concentration is ₃ ppb or less based on SO ₄ ²⁻ A method for storing a photomask blank substrate, comprising storing the substrate in an air atmosphere.
Claim 5:
The method according to any one of claims 1 to 4, wherein the air is obtained by reducing the basic gas concentration and the acid gas concentration by passing the air through a basic chemical filter and an acid chemical filter. .
Claim 6:
6. The method according to claim 1, wherein the resist film is an electron beam drawing resist film.
[0008]
According to the present invention, it is possible to prevent deterioration of a resist film of a photomask blank substrate on which a resist film is laminated, and in particular, there is a substantial influence upon use within its practical use deadline (for example, within 30 days). It can be suppressed to the extent that
[0009]
Hereinafter, the present invention will be described in more detail.
The method for handling a photomask blank substrate according to the first aspect of the present invention is a basic gas when the substrate is handled in a state where the resist film is in contact with air in the process of manufacturing the photomask blank substrate on which the resist film is laminated. It is handled in an air atmosphere having a concentration of 3 ppb or less based on NH ₄ ⁺ concentration and an acid gas concentration of ₃ ppb or less based on SO ₄ ²⁻ .
[0010]
The photomask blank substrate on which the resist film is laminated is patterned with a light-shielding film and a phase-shift film on a photomask blank on which a light-shielding film mainly composed of chromium and a phase-shift film composed mainly of molybdenum and silicon are formed. A resist film is laminated for the purpose of annealing. In addition, the target processes in the first invention are all processes for handling the photomask blank substrate on which the resist film is laminated in a state where the resist film is in direct contact with air. A photomask blank substrate on which a resist film is laminated is manufactured, for example, by a process as shown in FIG. 1. In this case, a resist application (resist film formation) process, and storage of the substrate in a storage container The process is the target.
[0011]
In the first invention, in the above-described process, when the photomask blank on which the resist film is laminated is handled in an air atmosphere, that is, when the resist film and the air are in direct contact with each other, the basicity in air. The gas concentration is ₃ ppb or less on the NH ₄ ⁺ concentration basis, and the acid gas concentration is ₃ ppb or less on the SO ₄ ²⁻ basis.
[0012]
The photomask blank substrate storage method according to the second invention of the present invention is such that when storing a photomask blank substrate on which a resist film is laminated, the basic gas concentration is ₃ ppb or less on the NH ₄ ⁺ concentration basis, and It is stored in an air atmosphere having an acid gas concentration of ₃ ppb or less based on SO ₄ ²⁻ .
[0013]
In the second invention, the basic gas concentration in the air in direct contact with the resist film during storage is ₃ ppb or less on the NH ₄ ⁺ concentration basis, and the acidic gas concentration is ₃ ppb or less on the SO ₄ ²⁻ basis.
[0014]
In the first and second invention, the basic gas concentration of NH ₄ ⁺ concentration standards was calculated ammonia gas in the air, the NH ₄ ⁺ ion concentration of the basic gas such as a lower organic amine gas as the standard substance concentration For example, it can be measured by analyzing an aqueous solution in which a basic gas component in the air is absorbed by a wet method by ion chromatography. The SO ₄ ^2- standard acid gas concentration refers to the concentration of acid gas such as hydrogen halide gas such as hydrogen chloride in the air, sulfur oxide gas such as sulfurous acid gas, nitrogen oxide gas such as nitrogen dioxide, etc. This is a value calculated using SO ₄ ^2- ion as a standard substance, and can be measured by analyzing an aqueous solution in which an acidic gas component in the air is absorbed by a wet method by ion chromatography.
[0015]
In the first and second inventions described above, the basic gas concentration in the air is 3 ppb or less on the NH ₄ ⁺ concentration basis, and the acid gas concentration is ₃ ppb or less on the SO ₄ ²⁻ basis. A method of reducing the basic gas concentration and the acid gas concentration by passing through a basic chemical filter and an acid chemical filter can be mentioned.
[0016]
In this case, the basic gas filter removes the basic gas component by the acid chemical filter and the acid gas component by the adsorbent in each filter. Examples of the chemical filter include a filter having a structure in which an adsorbent that adsorbs a basic gas component or an acidic gas component is supported on a base material such as a non-woven cloth. The adsorbent of the basic chemical filter includes activated carbon, inorganic salt Examples of adsorbents for acid chemical filters, such as inorganic minerals impregnated with activated carbon, include activated carbon and aminosilicate metal salt minerals.
[0017]
In addition, since the basic chemical filter and the acid chemical filter may generate particles, it is preferable to remove the particles using a ULPA filter at the subsequent stage of the basic chemical filter and the acid chemical filter.
[0018]
The method of the present invention is suitable for handling or storing a photomask blank on which an electron beam drawing resist film is laminated. In particular, resist films formed using chemically amplified resists such as chemically amplified positive resists and chemically amplified negative resists are particularly susceptible to the effects of basic and acidic gases. This is effective when handling or storing a photomask blank.
[0019]
Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 2 is a diagram for explaining a method of transferring a photomask blank substrate on which a resist film is laminated and storing it in a storage container by applying the photomask blank substrate handling method of the present invention. 1 is shown.
[0020]
A basic chemical filter 21, an acid chemical filter 22, and a Ulpa filter 23 are provided in the upper part of the processing chamber 1 in this order from the upper layer, and an outside air intake 51 is provided by a fan 3 provided below the filter layer 2. The outside air is taken in, the basic air and acid gas are adsorbed by these filters with the filter, and the particles are filtered, so that the basic gas concentration in the air in the work space 11 is 3 ppb based on the NH ₄ ⁺ concentration standard. Hereinafter, the acid gas concentration is set to 3 ppb or less on the basis of SO ₄ ²⁻ , and the purified air is introduced into the work space 11 with a downflow of about 0.3 m / sec. The air that has passed through the work space 11 is discharged from the discharge port 52 through the net-like bottom plate 4.
[0021]
A substrate transfer device 6 is provided in the work space 11, whereby a photomask blank substrate a on which a resist film carried on the container d from the resist film formation step is stacked is stored in a storage container. The operation of replacing with (shipping container) b is performed. The storage container b containing the substrate a is covered with a lid c by the lid opening / closing device 7 and sealed.
[0022]
Therefore, the photomask blank substrate on which the resist film is laminated is stored in a storage container in an air atmosphere in which the basic gas concentration is ₃ ppb or less on the NH ₄ ⁺ concentration basis and the acidic gas concentration is ₃ ppb or less on the SO ₄ ²⁻ basis. , Sealed. In this case, since the basic gas and acid gas concentrations in the air in the sealed container are in the same state as in the processing chamber, the resist film was laminated even when the storage container was taken out to the atmosphere. The basic gas concentration in the air in contact with the photomask blank substrate can be stored at 3 ppb or less on the NH ₄ ⁺ concentration basis, and the acidic gas concentration can be stored at 3 ppb or less on the SO ₄ ²⁻ basis.
[0023]
In this case, the case where the photomask blank substrate on which the resist film is laminated in the processing chamber is stored in the storage container has been described as an example. However, the processing chamber is used in the resist coating (resist film forming) step. Similarly, if used as a processing chamber, the resist in an atmosphere in which the basic gas concentration in the air in direct contact with the resist film is ₃ ppb or less on the NH ₄ ⁺ concentration basis and the acid gas concentration is ₃ ppb or less on the SO ₄ ²⁻ basis is used. A film can be formed.
[0024]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0025]
[Example 1]
A photomask blank is obtained by forming a light-shielding film (film thickness 700 mm) mainly composed of a chromium film on a quartz glass substrate of 152 mm × 152 mm × 6.35 mm, and then in a processing chamber as shown in FIG. The basic gas concentration in the air is ² ppb on the NH ₄ ⁺ concentration standard, the acid gas concentration is 1 ppb on the SO ₄ ^2- standard, and the electron beam drawing resist (chemically amplified positive resist) is 4000 mm thick by a resist coating machine. Then, a photomask blank substrate on which a resist film was laminated was obtained and loaded in a container.
[0026]
Subsequently, the photomask blank substrate on which the resist film loaded in the container in the processing chamber was stacked was stored in a shipping storage container, sealed with a lid opening / closing device, and taken out from the processing chamber. Further, the substrate was stored for 15 days or 30 days in a storage container, a line & space pattern having a line width of 1 μm was drawn on the resist with an electron beam to pattern the light-shielding film, and the line width of the obtained pattern was evaluated. The results are shown in FIG. The substrate that had been stored had little degradation over time, and had a resolution equivalent to that obtained by patterning immediately after manufacturing without storage.
[0027]
[Comparative Example 1]
A resist film is laminated in the same manner as in Example 1 except that no basic chemical filter is installed in the processing chamber and the basic gas concentration in the air in the working space is 8 ppb on the NH ₄ ⁺ concentration standard. A photomask blank substrate was obtained and sealed in a storage container. This was stored in the same manner as in Example 1, and the line width of the pattern was evaluated. The results are shown in FIG. The substrate that was stored was more rapidly deteriorated with time than Example 1, and the resolution was lowered.
[0028]
[Comparative Example 2]
The resist film was laminated in the same manner as in Example 1 except that the acid chemical filter was not installed in the processing chamber and the acid gas concentration in the air in the work space was 6 ppb on the basis of SO ₄ ²⁻ . A photomask blank substrate was obtained and sealed in a storage container. This was stored in the same manner as in Example 1, and the line width of the pattern was evaluated. The results are shown in FIG. The substrate that was stored was more rapidly deteriorated with time than Example 1, and the resolution was lowered.
[0029]
【The invention's effect】
According to the present invention, it is possible to provide a photomask blank substrate having a high resolution with little change in the resist film over time, whereby a photomask having a highly accurate fine pattern can be manufactured.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an example of a manufacturing process of a photomask blank in which resist films are laminated.
FIG. 2 is a view for explaining a method of transferring a photomask blank substrate on which a resist film is laminated and storing it in a storage container by applying the photomask blank substrate handling method of the present invention.
FIG. 3 is a diagram showing a change with time (change in line width of an obtained pattern) of a resist film of a photomask blank obtained in Examples and Comparative Examples.
[Explanation of symbols]
1 Processing chamber 2 Filter layer 21 Basic chemical filter 22 Acid chemical filter 23 Urpa filter a Substrate b Storage container c Lid

Claims (6)

In a process of manufacturing a photomask blank substrate on which a resist film is laminated, the substrate is handled in a state in which the resist film is in contact with air, the basic gas concentration is ₃ ppb or less on the NH ₄ ⁺ concentration standard, and the acid gas A method for handling a photomask blank substrate, wherein the substrate is handled in an air atmosphere having a concentration of ₃ ppb or less based on SO ₄ ²⁻ standard.   2. The method according to claim 1, wherein the step is a step of forming a resist film on a photomask blank.   2. The method according to claim 1, wherein the step is a step of storing a photomask blank substrate on which a resist film is laminated in a storage container. A method of storing a photomask blank substrate on which a resist film not patterned is laminated, wherein the basic gas concentration is ₃ ppb or less based on NH ₄ ⁺ concentration, and the acidic gas concentration is ₃ ppb or less based on SO ₄ ²⁻ A method for storing a photomask blank substrate, comprising storing the substrate in an air atmosphere.   The method according to any one of claims 1 to 4, wherein the air is obtained by reducing the basic gas concentration and the acid gas concentration by passing the air through a basic chemical filter and an acid chemical filter. .   6. The method according to claim 1, wherein the resist film is an electron beam drawing resist film.

Images