JP2009271473A - Mask blank and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly evaluate the sensitivity of a resist film on a mask blank. <P>SOLUTION: The mask blank 10 with the resist film is obtained by depositing a thin film 14 for forming a transfer pattern on a top surface of a substrate 12, and by applying a chemically amplified regist film 16 on the top surface of the thin film 14. The resist film 16 is composed of the chemically amplified regist whose transmittance is changed by exposure of ultraviolet light. The resist film 16 applied to a region other than the region for forming the transfer pattern of the thin film 14 is exposed to the ultraviolet light at a plurality of portions and the reflectance to the ultraviolet light is changed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mask blank and a mask blank manufacturing method.

  In recent years, mask blanks (CAR mask blanks) coated with a chemically amplified resist film have become indispensable for leading edge mask processing. Further, the processing accuracy required at the time of processing the leading edge mask is becoming stricter year by year.

  Here, in tip mask processing, the sensitivity of the chemically amplified resist (CAR sensitivity) is an important factor that determines the mask processing accuracy. In advanced mask processing where accuracy is controlled in the order of several nanometers, high sensitivity stability (MTT: Mean To Target) and in-plane uniformity (CDU: Critical Dimension Uniformity) with respect to the sensitivity of chemically amplified resists. Is required. The characteristics of the chemically amplified resist are described in detail in Non-Patent Document 1, for example.

  Under such circumstances, the inventor of the present application examined quantifying and evaluating the sensitivity of the resist film before shipping the mask blank with respect to the mask blank coated with the chemically amplified resist film. In addition, by this evaluation, it was studied to guarantee the sensitivity of the resist film of the mask blank.

  As a method of quantifying the sensitivity of the resist film, for example, a method of evaluating the line width (CD: Critical Dimension) accuracy after patterning of the resist film and the residual film sensitivity can be considered. However, since the results obtained by these methods depend on the process conditions, it is difficult to correlate with the sensitivity of the resist film if the process conditions are different. In addition, these methods are destructive inspections because they require processes such as EB exposure, post-exposure baking (PEB), and development. Also, it takes a long time to complete the measurement, for example, at least one day or more. Therefore, conventionally, it has been required to quantitatively evaluate the sensitivity of the resist film by a more appropriate method. Then, an object of this invention is to provide the manufacturing method of a mask blank and mask blank which can solve said subject.

In addition, as a method for evaluating the performance of the resist film, for example, a method in which the exposure process is performed is also known (see, for example, Patent Document 1). However, this method also requires development processing and the like, and causes the same problems as described above.
Latest resist material handbook, Information Organization, ISBN 4-901676-45-4 JP 2005-326581 A

  The inventor of the present application has conducted extensive research on a new sensitivity evaluation method that is highly accurate and effective as a guarantee inspection before shipment. And it discovered that the sensitivity of a resist film could be evaluated by measuring the change of the reflectance with respect to the ultraviolet light which arises by exposure of the ultraviolet light with respect to a resist film. In order to solve the above problems, the present invention has the following configuration.

  (Configuration 1) A mask blank in which a thin film for forming a transfer pattern is formed on an upper surface of a substrate, and a resist film of a chemically amplified resist is applied on the upper surface of the thin film. The resist film consists of a chemically amplified resist with variable transmittance, and the resist film applied to areas other than the area for forming the thin film transfer pattern is exposed to UV light at multiple locations to provide reflectivity for UV light. It is changing.

  If comprised in this way, the sensitivity of a resist film can be quantified by measuring the reflectance of the location which exposed the ultraviolet light, for example. Thereby, for example, the sensitivity of the resist film can be appropriately evaluated.

  In this case, since the sensitivity of the resist film can be evaluated without performing a process such as development, the sensitivity of the resist film can be evaluated independently of the process conditions. Furthermore, the reflectance can be measured in a shorter time than when performing processes such as EB exposure and development. Therefore, the time required for evaluation can be greatly shortened. Therefore, if comprised in this way, the sensitivity of a resist film can be appropriately evaluated before shipment of a mask blank, for example. This also makes it possible to appropriately guarantee the sensitivity of the resist film, for example.

  In this configuration, the reflectance of the resist film is changed not by electron beam (EB) exposure but by ultraviolet light exposure. Therefore, if constituted in this way, the reflectance of the exposure part in a resist film can be changed with high throughput compared with the case where a reflectance is changed by electron beam exposure, for example. This also makes it possible to perform evaluation with sufficient throughput even when, for example, evaluation of the sensitivity of the resist film is performed by single wafer inspection on all manufactured mask blanks.

  (Configuration 2) The resist film is made of a chemically amplified resist whose transmittance changes upon exposure to deep ultraviolet light. If comprised in this way, the reflectance of the location which irradiated the ultraviolet-ray light can be changed more appropriately, for example. This also makes it possible to more appropriately evaluate the sensitivity of the resist film.

  (Configuration 3) A mask blank manufacturing method in which a thin film for forming a transfer pattern is formed on an upper surface of a substrate, and a resist film of a chemically amplified resist is applied on the upper surface of the thin film. An exposure measurement process that measures the amount of reflected UV light reflected from the resist film by exposing the surface of the resist film to UV light, and the amount of reflected light measured. And a sensitivity evaluation step for evaluating the sensitivity of the resist film.

  In this way, for example, the sensitivity of the resist film can be appropriately evaluated. In addition, the same effect as in Configuration 1 can be obtained. The evaluation of the sensitivity of the resist film may be performed by a single wafer inspection for all manufactured mask blanks, or by a sampling inspection for some mask blanks.

  (Configuration 4) In the exposure measurement step, exposure of ultraviolet light and measurement of the amount of reflected light are performed on the surface of the resist film in a region other than the region where the thin film transfer pattern is formed.

  In this way, for example, it is possible to appropriately evaluate the sensitivity of the resist film while avoiding the influence on the region where the transfer pattern is formed. This also makes it possible to appropriately evaluate the sensitivity of the resist film while avoiding the influence on the quality of the mask blank even when performing a single wafer inspection, for example.

  (Configuration 5) In the exposure measurement step, the entire resist film surface in the region where the thin film transfer pattern is to be formed is subjected to exposure of ultraviolet light and measurement of the amount of reflected light at a plurality of predetermined intervals. The sensitivity distribution of the resist film in the region to be formed is evaluated. The evaluation of the sensitivity of the resist film by the exposure measurement process and the sensitivity evaluation process is preferably performed by sampling inspection for a part of the mask blank.

  In this way, for example, the resist sensitivity can be appropriately evaluated for a region directly related to the formation of the transfer pattern. In addition, the in-plane distribution of the sensitivity of the resist film on the main surface of the mask blank can be appropriately evaluated.

  According to the present invention, for example, the sensitivity of a mask blank resist film can be appropriately evaluated.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a mask blank 10 with a resist film according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of a mask blank 10 with a resist film. The mask blank 10 with a resist film is a mask blank used for manufacturing a mask for photolithography, and includes a substrate 12, a thin film 14, and a resist film 16.

  The substrate 12 is a light-transmitting substrate such as a glass substrate. The thin film 14 is a thin film for forming a transfer pattern in the mask manufacturing process, and is formed on the upper surface of the substrate 12. In this example, the thin film 14 is, for example, a light shielding film or a semi-transparent film. The thin film 14 may be a laminated film of a plurality of types of films.

  The resist film 16 is a resist film of a chemically amplified resist applied on the upper surface of the thin film 14. In the mask manufacturing process, the resist film 16 is patterned and used, for example, as an etching mask when processing the thin film 14. The patterning of the resist film 16 is performed by a process such as electron beam (EB) exposure and development, for example.

  In this example, the resist film 16 is made of a chemically amplified resist whose transmittance changes upon exposure to ultraviolet light. This ultraviolet light is, for example, deep ultraviolet (DUV) light. The thin film 14 is exposed to ultraviolet light at a plurality of locations on the resist film 16 on the region other than the region for forming the transfer pattern. Thereby, the reflectance with respect to the ultraviolet light is changed at the plurality of locations in the resist film 16.

  The chemically amplified resist used for the resist film 16 is, for example, a resist containing PHS (polyhydroxystyrene) having an acetal protecting group, PAG (acid generator), and a quencher. Such a composition is common to a chemically amplified resist for KrF (wavelength 248 nm) laser exposure, for example, and reacts to deep ultraviolet light (particularly around 248 nm).

  Here, the principle of pattern formation at the time of patterning of the resist film 16 is a decomposition reaction (deprotection reaction) of the acetal protecting group by an acid generated from the PAG upon receiving irradiation energy by exposure with an electron beam or deep ultraviolet light. For example, when the resist film 16 is a positive resist, the decomposed protective group is replaced with a hydroxyl group, and the irradiated portion becomes alkali-soluble. Then, this portion is removed by subsequent development, and the resist film 16 is patterned.

  The basic reaction of the decomposition reaction of the acetal protecting group is the same as or similar to the known reaction. In order to promote the reaction with a small amount of irradiation energy, post exposure bake processing (PEB: Post-Exposure Bake) is performed following exposure in a normal process.

The acid concentration generated by exposure can be defined by the following equation as a result of analysis by FTIR (Fourier transform infrared spectroscopy).
[Hpag] = 1-EXP (-C * E) (Formula 1)

In this equation, [Hpag] is the normalized acid generation concentration, C is the acid generation reaction constant (cm ² / mJ), and E is the exposure energy (mJ / cm ² ). Details of this equation are described in Non-Patent Document 1, for example.

  FIG. 1B is a graph showing an example of a change in optical characteristics of the resist film 16 due to irradiation with ultraviolet light. In the chemically amplified resist having the above composition, the optical characteristics change due to PAG decomposition and deprotection reaction caused by energy irradiation. This graph shows the UV light (wavelength) generated by a deuterium lamp generated by applying a chemically amplified positive resist (model number: FEP171) manufactured by Fuji Film Electronics Materials, Inc., which is a chemically amplified resist having the above composition, on a glass substrate. An example of a transmittance spectrum before and after irradiation in the case of irradiation with 190 to 400 nm) is shown.

  In the mask blank 10 with a resist film, since there is a thin film 14 serving as a light shielding layer, even if the transmittance of the resist film 16 changes, the transmittance of the entire mask blank 10 with resist film does not substantially change. . However, when the transmittance of the resist film 16 changes, the reflectance also changes according to the change. Therefore, by measuring the reflectance, for example, the acid generation concentration in the resist film 16 can be quantified, and the sensitivity of the resist film 16 can be evaluated.

  FIG. 2 shows an example of the configuration of the sensitivity evaluation apparatus 100 used for evaluating the sensitivity of the resist film 16. The sensitivity evaluation apparatus 100 is an apparatus used in the exposure measurement process in the manufacturing process of the mask blank 10 with a resist film. The exposure measurement process is a process performed after the application of the resist film 16, and the surface of the resist film 16 is exposed to ultraviolet light, and the amount of reflected ultraviolet light reflected from the resist film 16 is measured. Moreover, in the manufacturing process of the mask blank 10 with a resist film, a sensitivity evaluation process is performed after the exposure measurement process. In the sensitivity evaluation step, the sensitivity of the resist film 16 is evaluated based on the amount of reflected light measured in the exposure measurement step.

  In this example, the sensitivity evaluation apparatus 100 includes a stage 102, a UV light source unit 104, a UV light irradiation unit 106, a light receiving unit 108, a spectroscope 110, a stage controller 112, and a control unit 114. The stage 102 is a table for holding the mask blank 10 with a resist film on the upper surface. The UV light source unit 104 is a light source that generates ultraviolet light. The UV light source unit 104 preferably generates deep ultraviolet light. In this example, the UV light source unit 104 is a deuterium lamp, and generates ultraviolet light having a wavelength of 190 to 400 nm, for example, according to an instruction from the control unit 114.

  The UV light irradiation unit 106 and the light receiving unit 108 are optical systems that face the surface of the resist film 16 in the mask blank 10 with a resist film. The UV light irradiation unit 106 is connected to the UV light source unit 104 by an optical fiber, for example, and irradiates the surface of the resist film 16 with ultraviolet light generated by the UV light source unit 104. The light receiving unit 108 receives reflected light from the resist film 16.

  The spectroscope 110 is, for example, a fiber spectroscope, and receives and separates the reflected light received by the light receiving unit 108 via an optical fiber or the like. In addition, the spectroscope 110 notifies the control unit 114 of the spectroscopic result. The stage controller 112 is a controller that moves the stage 102 relative to the UV light irradiation unit 106 and the light receiving unit 108, and moves the stage 102 according to an instruction from the control unit 114, for example. Thereby, the stage controller 112 changes the position of the resist film 16 where the ultraviolet light is irradiated from the UV light irradiation unit 106.

  The control unit 114 is a control device such as a PC, for example, and controls the operation of each unit of the sensitivity evaluation device 100. For example, in this example, the control unit 114 monitors the reflectance at a specific wavelength, for example, based on the spectral result received from the spectroscope 110. Further, in the sensitivity evaluation step after the exposure measurement step, the control unit 114 calculates a change in reflectance with respect to the irradiation amount of ultraviolet light based on the monitoring result. Furthermore, based on this result, the control unit 114 quantifies the acid generation concentration in the resist film 16 generated by, for example, irradiation of ultraviolet light from the UV light irradiation unit 106. Accordingly, the control unit 114 evaluates the sensitivity of the resist film 16.

  According to this example, for example, the sensitivity of the resist film 16 can be appropriately quantified. Thereby, the sensitivity of the resist film 16 can be appropriately evaluated. Further, according to this example, it is not necessary to perform a process such as development in the evaluation of the sensitivity of the resist film 16. Therefore, the sensitivity of the resist film 16 can be appropriately evaluated independently of the process conditions. In addition, by performing exposure at the time of evaluation not by electron beam (EB) exposure but by exposure to ultraviolet light, sensitivity can be evaluated with high throughput.

  FIG. 3 shows an example of an exposure part where exposure to ultraviolet light is performed in the sensitivity evaluation apparatus 100. FIG. 3A shows a first example of the exposure location. In this example, the exposure measurement step performs exposure to ultraviolet light and measurement of the amount of reflected light on the surface of the resist film 16 in a region other than the region where the transfer pattern of the thin film 14 (see FIG. 1) is formed. In this case, for example, as shown in FIG. 3A, the sensitivity evaluation apparatus 100 performs ultraviolet light exposure on a plurality of irradiation spots 202 arranged on the peripheral edge of the main surface of the mask blank 10 with a resist film. Then, the reflected light is measured according to the irradiated ultraviolet light. In the sensitivity evaluation step, the sensitivity evaluation apparatus 100 evaluates the sensitivity distribution of the resist film 16 based on the measurement result of the reflected light. In this way, for example, the sensitivity of the resist film 16 can be appropriately evaluated while avoiding the influence on the region where the transfer pattern is formed. Thereby, for example, the sensitivity of the resist film 16 can be appropriately evaluated by the single wafer inspection.

  FIG. 3B shows a second example of the exposure part. In this example, in the exposure measurement step, the entire surface of the resist film 16 in the region where the transfer pattern of the thin film 14 is to be formed is exposed at a plurality of positions at predetermined intervals, and exposure to ultraviolet light and measurement of the amount of reflected light are performed. In this case, for example, as shown in FIG. 3B, the sensitivity evaluation apparatus 100 exposes ultraviolet light to a plurality of irradiation spots 202 arranged in the vertical and horizontal directions on the entire main surface of the mask blank 10 with a resist film. The reflected light is measured according to the irradiated ultraviolet light.

  In the sensitivity evaluation step, the sensitivity evaluation apparatus 100 evaluates the sensitivity distribution of the resist film 16 in the region where the transfer pattern is formed, based on the measurement result of the reflected light corresponding to these irradiation spots 202. In this way, for example, the resist film 16 can be appropriately evaluated for a region directly related to the formation of the transfer pattern. In addition, the in-plane distribution of the sensitivity of the resist film 16 on the main surface of the mask blank with resist film 10 can be appropriately evaluated. The sensitivity evaluation of the resist film 16 by this method is preferably performed by sampling inspection for some mask blanks.

  Subsequently, the present invention will be described in more detail with reference to examples. As a mask blank 10 with a resist film according to Examples 1 to 3, a mask blank having the following configuration was manufactured. Moreover, the evaluation which performs irradiation of an ultraviolet-ray and the measurement of reflected light was performed with respect to the mask blank 10 with a resist film which concerns on Examples 1-3.

Example 1
The synthetic quartz glass substrate was mirror-polished and subjected to predetermined cleaning to obtain a substrate 12 of 152 mm × 152 mm × 6.35 mm. Next, a thin film 14 containing Cr as a main component was formed on the upper surface of the substrate 12 with a thickness of 1000 angstroms by a DC magnetron sputtering apparatus to obtain a mask blank. Specifically, a Cr target is used, a mixed gas of argon gas and nitrogen gas (Ar: N = 80: 20% by volume) is introduced into the apparatus, and a CrN film is formed to a thickness of 150 Å. At the target, a mixed gas of argon, methane and helium (Ar: CH ₄ : He = 30: 10: 60% by volume) was introduced into the apparatus, and a CrC film was formed to a thickness of 600 Å, and finally the same As a target, a mixed gas of argon gas and nitric oxide gas (Ar: NO = 80: 20% by volume) was introduced into the apparatus, and a CrON film was formed to a thickness of 250 Å. Finally, a chemically amplified positive resist (model number: FEP171) for electron beam drawing manufactured by Fuji Film Electronics Materials was applied as a resist film 16 to the surface of the thin film 14 to obtain a mask blank 10 with a resist film. The film thickness of the resist film 16 was 3000 angstroms.

(Example 2)
Using a mask blank manufactured by the same process as in Example 1, another chemically amplified positive resist for electron beam lithography (model number: PRL009) manufactured by Fuji Film Electronics Materials is used as a resist film 16 on the surface of the thin film 14. It applied and the mask blank 10 with a resist film was obtained. The film thickness of the resist film 16 is 2500 angstroms.

(Example 3)
Using a mask blank manufactured by the same process as in Example 1, the surface of the thin film 14 was coated with another chemically amplified negative resist (model number: NEB22) for electron beam drawing manufactured by Sumitomo Chemical as the resist film 16. A mask blank 10 with a resist film was obtained. The thickness of the resist film 16 is 3000 angstroms.

(Evaluation)
An evaluation similar to the sensitivity evaluation apparatus 100 described with reference to FIG. 2 was performed to perform irradiation with ultraviolet light and measurement of reflected light. A deuterium lamp was used as the UV light source unit 104. In addition, the irradiation spot 202 was repeatedly irradiated with ultraviolet light and the measurement of reflectance at intervals of 1 second, and the change in reflectance at that point was monitored. Further, the analysis software (product name: IGOR) was used to fit R% = A + B * EXP (−C ′ * T) with respect to the reflectance R% as a measurement value. T is the irradiation time of ultraviolet light.

  As a result of this fitting, in Example 1, A = 6.30, B = 3.59, and C ′ = 0.13. In Example 2, A = 9.02, B = 1.26, and C ′ = 0.03. In Example 3, A = 13.51, B = 1.87, and C ′ = 0.25.

  FIG. 4 is a graph showing the measurement result of the reflectance in each example and a curve fitted to the measurement result. As shown in the graph, the measurement result and the fitted curve (theoretical formula) are in good agreement.

  Here, the constants A and B used for the fitting depend on the reflectance component (substrate reflectance) determined by the influence of the thin film 14 and the substrate 12 as the base film of the resist film 16 and the film thickness of the resist film 16. It is a constant. It is considered that the constants A and B can be normalized as shown in Equation 1 described with reference to FIG.

  In addition, since the degree of coincidence between the fitted curve and the measured value is high, the constant C ′ used in the EXP function is considered to be a constant related to the acid generation constant in Equation 1. Therefore, the acid generation constant in the resist film 16 can be quantitatively evaluated by quantifying the constant C ′ by measuring the reflectance.

  The acid generation constant is a numerical value that defines the reaction speed inherent to the resist film 16. Therefore, it is possible to evaluate the sensitivity of the resist film 16 by evaluating the acid generation constant. From the above, it can be seen that the sensitivity of the resist film 16 can be appropriately evaluated by performing irradiation with ultraviolet light and measurement of reflected light.

  For the value of the constant C ′, in-plane distribution was further measured for the resist film 16 on the main surface of the mask blank. In this measurement, C ′ was calculated for the irradiation spot 202 of 25 points similar to that shown in FIG. 3B for each mask blank 10 with a resist film of 132 mm. Moreover, the same measurement was performed with respect to the mask blank 10 with a resist film of several lots. As a result, it has been confirmed that C ′ can obtain the same value without depending on the film thickness distribution of the resist film 16 and the difference in lots.

  Further, in each example, the line width (CD) accuracy after patterning of the resist film 16 was measured for the plurality of mask blanks 10 with resist film after calculating the constant C ′. As a result, it was confirmed that there is a correlation between the constant C ′ and the CD accuracy, and that the CD accuracy can be predicted by evaluating the constant C ′. Thereby, it can be seen that, for example, by confirming that the constant C ′ is within a predetermined range, it is possible to select the mask blank 10 with a resist film that can obtain good CD accuracy.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The present invention can be suitably used for, for example, a mask blank with a resist film coated with a resist film.

It is a figure showing an example of mask blank 10 with a resist film concerning one embodiment of the present invention. FIG. 1A shows an example of the configuration of a mask blank 10 with a resist film. FIG. 1B is a graph showing an example of a change in optical characteristics of the resist film 16 due to irradiation with ultraviolet light. It is a figure which shows an example of the structure of the sensitivity evaluation apparatus 100 used for the sensitivity evaluation of the resist film 16. FIG. It is a figure which shows an example of the exposure location which exposes with ultraviolet light in the sensitivity evaluation apparatus. FIG. 3A shows a first example of the exposure location. FIG. 3B shows a second example of the exposure part. It is a graph which shows the measurement result of the reflectance in each Example, and the curve fitted with respect to the measurement result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mask blank with resist film, 12 ... Substrate, 14 ... Thin film, 16 ... Resist film, 100 ... Sensitivity evaluation apparatus, 102 ... Stage, 104 ... UV light source part 106 ... UV light irradiation unit, 108 ... light receiving unit, 110 ... spectrometer, 112 ... stage controller, 114 ... control unit, 202 ... irradiation spot

Claims (5)

A mask blank in which a thin film for forming a transfer pattern is formed on the upper surface of a substrate, and a resist film of a chemically amplified resist is applied on the upper surface of the thin film,
The resist film is made of a chemically amplified resist whose transmittance is changed by exposure to ultraviolet light,
A mask blank, wherein a resist film applied to a region other than the region for forming the thin film transfer pattern is exposed to ultraviolet light at a plurality of locations to change the reflectance with respect to the ultraviolet light. .   2. The mask blank according to claim 1, wherein the resist film is made of a chemically amplified resist whose transmittance changes upon exposure to deep ultraviolet light. A method of manufacturing a mask blank in which a thin film for forming a transfer pattern is formed on the upper surface of a substrate, and a resist film of a chemically amplified resist is applied on the upper surface of the thin film,
The resist film is made of a chemically amplified resist whose transmittance is changed by exposure to ultraviolet light,
An exposure measurement step of exposing the surface of the resist film with ultraviolet light and measuring the amount of reflected ultraviolet light reflected from the resist film;
And a sensitivity evaluation step of evaluating the sensitivity of the resist film from the measured amount of reflected light.   4. The mask blank according to claim 3, wherein in the exposure measurement step, exposure of ultraviolet light and measurement of a reflected light amount are performed on the surface of the resist film in a region other than a region where the transfer pattern of the thin film is formed. Manufacturing method. In the exposure measurement step, the entire resist film surface in a region where the thin film transfer pattern is formed is measured at a plurality of locations at predetermined intervals, exposure to ultraviolet light and measurement of the amount of reflected light.
4. The method of manufacturing a mask blank according to claim 3, wherein the sensitivity evaluation step evaluates a sensitivity distribution of a resist film in a region where a transfer pattern is formed.

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