JP2009244350A - Multi-tone photomask, method of manufacturing the same, and pattern transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-tone photomask of which the variation of in-plane transmittance can be reduced, and to provide a method of manufacturing the same. <P>SOLUTION: In the method of manufacturing the multi-tone photomask, a light-shielding film and a semi-transmissive film transmitting a portion of exposure light are formed on a transparent substrate and are respectively patterned as prescribed to form a transfer pattern including a light-shielding part, a semi-transmissive part transmitting a portion of exposure light, and a light-transmissive part. In this method, the semi-transmissive film and the light-shielding film are patterned by wet etching to form the transfer pattern, and at least part of the semi-transmissive film of the transfer pattern is subjected to surface modification treatment to change an exposure light transmittance of the semi-transmissive film, whereby a transmittance in-plan distribution range of the semi-transmissive part existing in the transfer pattern is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multi-tone photomask used in a photolithography process, a manufacturing method thereof, and a pattern transfer method.

  2. Description of the Related Art Conventionally, in the manufacture of electronic devices such as liquid crystal devices, a photolithographic process is used to form a predetermined pattern using a photomask having a predetermined pattern on a resist film formed on a layer to be etched. Exposure is performed under exposure conditions to transfer the pattern, and the resist film is developed to form a resist pattern. Then, the layer to be processed is etched using this resist pattern as a gradation mask.

In recent years, the usefulness of multi-tone masks with three or more gray levels has been recognized by electronic device manufacturers, and the use of such multi-tone photo masks has been expanding. This multi-gradation photomask having three or more gradations has a semi-transparent portion composed of a semi-transparent film that transmits part of the exposure light. As such a multi-tone photomask, there is one disclosed in Patent Document 1.
JP 2007-271696 A

  On the other hand, such a multi-tone photomask has been used as a large photomask for manufacturing a liquid crystal display device. In photomasks for this purpose, it is important to keep the resist residual film value formed on the transferred object constant when using the mask by reducing the in-plane transmittance variation in the photomask. is there. This is because the processing accuracy and stability of the transferred object are greatly improved. However, in the technique disclosed in Patent Document 1, the variation in transmittance between individual photomasks is reduced, but the variation in transmittance in the plane of the photomask is reduced. It does not solve the problem.

  The present invention has been made in view of this point, and an object of the present invention is to provide a multi-tone photomask that can reduce in-plane transmittance variation in the photomask and a method of manufacturing the same.

  The multi-tone photomask of the present invention forms a light shielding film and a semi-transparent film that transmits a part of the exposure light on a transparent substrate, and performs a predetermined patterning on each film, thereby shielding the light. A multi-tone photomask formed with a transfer pattern including a part, a semi-transparent part that transmits part of exposure light, and a translucent part, and at least a surface part of the semi-transparent film is modified The transmissivity in-plane distribution range of the semi-translucent portion existing in the transfer pattern is within 2%.

  In the multi-tone photomask of the present invention, the semi-transparent film is preferably made of a material containing metal silicide.

  In the multi-tone photomask of the present invention, it is preferable that the semi-transparent film is made of a material that does not substantially contain nitrogen.

  The method for producing a multi-tone photomask of the present invention comprises preparing a photomask blank in which a light-shielding film and a semi-transparent film that transmits part of exposure light are formed on a transparent substrate, In the method of manufacturing a multi-tone photomask for forming a light-shielding portion, a semi-transparent portion that transmits a part of exposure light, and a transfer pattern including the translucent portion by performing predetermined patterning, the semi-transparent film And patterning by etching each of the light shielding film to form the transfer pattern, and performing surface modification treatment on at least a part of the semi-transparent film in the transfer pattern, A surface modification step of changing the exposure light transmittance of the optical film to reduce the transmittance in-plane distribution range of the semi-translucent portion existing in the transfer pattern. With regard to the above-described etching, at least the etching of the semi-transparent film has a remarkable effect when the wet etching is applied.

  According to this method, it is possible to obtain a multi-tone photomask with a small variation in transmissivity of the semi-transparent portion in the plane. In addition, in this method, the surface modification treatment can be selectively applied to a region where the transmittance is low due to various factors, so that only an inappropriate portion of the transmittance can be corrected. In-plane variation can be suppressed. Therefore, it is preferable that the surface modification process includes performing a process different from the other parts on the selected part in the photomask surface.

  In the method for producing a multi-tone photomask of the present invention, it is preferable that the surface modification step includes a process for increasing the chemical resistance of the semi-translucent film. In the method of manufacturing a multi-tone photomask according to the present invention, it is preferable that the surface modification process is a process of irradiating a semi-transparent part in the transfer pattern with a predetermined energy.

  In the multi-tone photomask manufacturing method of the present invention, it is preferable that the surface modification process is a process of heating the semi-translucent portion in the transfer pattern.

  In the method of manufacturing a multi-tone photomask of the present invention, the method includes a step of measuring transmittances of the plurality of semi-translucent portions after the pattern forming step, and based on the measurement result in the surface modification step. Then, the surface modification treatment is performed on at least a part of the semi-transparent film so that the in-plane distribution range of the transmissivity of the plurality of semi-transparent parts of the transfer pattern is reduced, and preferably 2% or less. It is preferable. In addition, it is preferable that the measurement of the said transmittance | permeability is a measurement of the effective transmittance | permeability mentioned later.

  The pattern transfer method of the present invention is characterized in that the transfer pattern of the multi-tone photomask is transferred to a layer to be processed by irradiating exposure light from an exposure machine using the multi-tone photomask. In this case, it is preferable to use exposure light including a wavelength band of i-line to g-line as the exposure light.

  In the multi-tone photomask of the present invention, the translucent film and the light-shielding film that transmit part of the exposure light are patterned by wet etching to form the transfer pattern, and the translucent film in the transfer pattern It is obtained by subjecting at least a part of the surface modification treatment to change the exposure light transmittance of the semi-translucent film. Furthermore, chemical resistance can be increased. According to this multi-tone photomask, the in-plane transmittance variation of the photomask can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In a multi-tone photomask, it is known to use metal silicide as a material for a semi-translucent portion. However, this material may not necessarily have high chemical resistance, light resistance, etc. for a given drug. In a multi-tone photomask used in large photomasks for liquid crystal display manufacturing, for example, MoSix can be used effectively as a material for a semi-transparent film, but in that case, in the mask manufacturing process or defect correction process Depending on the chemical used, the chemical resistance may not be sufficient, and even if a semi-transparent film having a desired transmittance is formed at the stage of the photomask blank, the transmittance will be increased in the subsequent development and cleaning processes. There are changing problems.

  Originally, MoSix has a slight difference depending on the film forming method, but the chemical resistance to acid and alkali is not necessarily large. For example, the surface is slightly eluted by contact with alkali, and this changes (increases) the transmittance of the film. There are things to do. Usually, in the production of a photomask, acid or alkali is used in the cleaning process, and alkali is used in the resist development process. These steps are performed for each photolithography during the manufacture of the photomask (for example, at least twice for a normal three-tone photomask). Therefore, it is not possible to completely prevent the surface of MoSix from being damaged every time it comes into contact with acid or alkali. In particular, in the photolithography of the second layer, since MoSix contacts the resist developer, there is a concern about damage due to this.

  On the other hand, a large photomask for manufacturing a liquid crystal display device or the like has a large size, so that it is not easy to perform dry etching in a vacuum chamber. For this reason, wet etching is advantageous for patterning. Therefore, as a material of the semi-translucent film, it is necessary to form a pattern accurately with an appropriate etching time by wet etching. That is, when a material having a very high chemical resistance is used as the material of the semi-translucent film, there is a disadvantage that the speed of the wet processing is reduced.

  By the way, in a multi-tone photomask, a resist pattern having a predetermined level difference is formed on a resist film on a transfer object by partially selectively reducing the amount of exposure light transmitted through the photomask. To do. By doing so, there is an advantage that the photolithography process in the manufacturing process of an electronic device such as a liquid crystal display device can be simplified and two photolithography processes can be performed using one mask. However, for this purpose, it is important to calculate in advance the resist step required in the processing steps (development and etching steps) of the electronic device to be obtained, and to realize the resist residual film value corresponding to this in a stable manner. is there. That is, the exposure light transmittance of the multi-tone photomask for creating such a desired resist residual film value must also be accurately controlled. This becomes more important not only in a three-tone photomask but also in a multi-tone photomask having four or more tones.

  Furthermore, it is ideal that the wet processing steps such as the cleaning step, the development step, and the resist stripping step are performed under the same conditions on the transfer pattern formed on the large substrate as described above, but the size is further increased. Considering the size of the substrate, it is not always easy, and if in-plane non-uniformity occurs in this process, the product specifications may not be satisfied.

  Therefore, in the present invention, the transmittance is changed by applying a predetermined surface modification treatment to the semi-transparent portion (for example, formed of MoSix) after patterning. Furthermore, the chemical resistance of a photomask having a desired transmittance can be increased, and the subsequent treatment can prevent the transmittance from changing. In this case, the transmittance is inspected after patterning, and based on the result of the transmittance inspection, a surface modification process can be selectively performed on a predetermined portion in the plane different from other portions.

Here, the present inventors use MoSix as the material of the semi-transparent film, and the transmittance when the surface is modified by means such as irradiating energy to the semi-transparent film or heating. We examined changes. Here, as a process for irradiating energy, a vacuum ultraviolet ray irradiation process (VUV process) is performed under the conditions of a wavelength of 172 nm, an output of 40 mW / cm ² , and an irradiation distance of 3 mm, and as a heating process, a transparent substrate temperature is set using a halogen heater. The temperature was raised to 250 ° C., 300 ° C., and 400 ° C. and heated for 10 minutes. The result is shown in FIG. As can be seen from FIG. 1, the light transmittance was increased by irradiating the semi-translucent film with energy or heating it.

  Therefore, the present inventors prepared photomask blanks on which a semi-transparent film and a light-shielding film were formed, and produced a photomask in which a transfer pattern was formed by performing predetermined patterning on each film by wet etching. . As this transfer pattern, a pattern having a repeated pattern in which the same semi-transparent portions were regularly arranged was used. An experiment was conducted to reduce in-plane variation in transmittance of the semi-translucent portion by selectively performing the surface modification treatment on a part of the semi-transparent film in the transfer pattern.

  FIG. 2A shows the light transmittance distribution (for i-line to g-line) of the photomask on which the transfer pattern is formed before the surface modification treatment. Here, the size of each bubble represents the fluctuation rate of the white bubble toward the low transmittance side, and the shaded bubble represents the fluctuation rate (relative value) of the high transmittance side. Here, the VUV treatment was selectively performed on the white bubble portion, reflecting the variation rate of the transmittance, and then the heat treatment was performed. As a result, as shown in FIG. 2B, the in-plane distribution of transmittance could be reduced. Here, finally, the in-plane distribution of the exposure light transmittance could be reduced to 2% or less. Note that the transmittance measurement performed here will be described later.

  In the surface modification treatment, the VUV treatment and the heat treatment may be locally performed individually or simultaneously. Or you may perform VUV processing in multiple times so that it may become a desired transmittance | permeability range locally or entirely. In this case, transmittance measurement may be performed during a plurality of processes. Furthermore, for the purpose of increasing the light transmittance and / or improving the chemical resistance of the entire mask surface, VUV treatment or heat treatment may be performed on the entire photomask. Further, both processes may be performed on the entire surface at the same time.

The effect of increasing the light transmittance is particularly remarkable in the VUV treatment, and the effect of increasing the light transmittance and chemical resistance is remarkable in the heat treatment. As a preferable mode, for example, the VUV treatment is performed at a predetermined position in the surface, and then the entire surface is subjected to the heat treatment so as to obtain a desired light transmittance, and the light transmittance is not further changed. Can do. Alternatively, the VUV treatment may be performed at a predetermined position in the surface, and then the VUV treatment and the heat treatment may be performed on the entire surface. Note that the heat treatment is highly effective in increasing the chemical resistance of the translucent film, and is preferably performed at the end of the surface modification treatment. As surface treatment conditions, the temperature of the heat treatment can be about 100 ° C. to 500 ° C., and the output of the VUV treatment can be 20 W / cm ^{2 to} 100 W / cm ² (irradiation distance 1 mm to 20 mm).

  Further, it is grasped in advance that the transmittance change occurs in the surface modification treatment, and the amount of fluctuation in the transmittance in the surface modification treatment for increasing the transmittance is determined in advance. Furthermore, it is also a preferable aspect to design the film transmittance (composition, film thickness) of the semi-translucent film in advance by assuming the light transmittance rising by the surface modification treatment.

  The above transmittance measurement can be performed by a membrane transmittance measuring device. For example, when a film thickness distribution occurs in the surface due to the formation of a semi-translucent film, the transmission of individual semi-transparent parts is repeated in a pattern in which a large number of semi-transparent parts having the same shape are repeated. When the rates differ, the above measurement is performed, and the surface modification treatment of the present invention can be performed according to the result.

  On the other hand, when the mask is actually exposed by an exposure machine, the effective transmissivity of each semi-translucent portion (hereinafter referred to as effective transmissivity) is not only the film quality and film thickness of the semi-translucent film, but the pattern shape May change under the influence of Therefore, it is preferable to perform the surface modification treatment after grasping the effective transmittance reflecting all of these.

  For example, in a photomask for manufacturing a liquid crystal display device, a portion corresponding to a channel portion can be formed by a semi-transparent portion, and portions corresponding to a source and a drain can be formed by a light shielding portion. In such a pattern, the translucent part having a part adjacent to the light-shielding part has lower transmittance near the adjacent part due to the influence of diffraction under the optical conditions of the exposure machine (in the resolution of the exposure machine). . For example, as shown in FIGS. 3A and 3B, the light intensity distribution of the transmitted light in the semi-transparent region B sandwiched between the light shielding portions A is lowered as a whole and the peak is lowered. This tendency becomes more prominent as the line width of the semi-transparent region B becomes smaller. In particular, in the channel portion having a small line width surrounded by the source and drain, the exposure light transmittance is the same as that of the used semi-transparent light. The transmittance is lower than the inherent transmittance of the membrane. In short, the transmissivity of the semi-transparent portion actually used in the pattern is different from the intrinsic transmissivity of the semi-transparent film grasped in a sufficiently large area. Therefore, the inspection of the transmittance after the patterning is desirably performed based on the effective transmittance rather than the intrinsic transmittance of the semi-translucent film.

  Of course, in the semi-transparent part adjacent to the translucent part, the smaller the line width of the semi-transparent part, the more effective the light transmittance inherent in the semi-transparent film due to the influence of diffraction of the exposure light. Also has a high transmittance.

  Therefore, in the present invention, each of the semi-transparent film and the light-shielding film is subjected to patterning by wet etching to form a transfer pattern, and after this pattern formation step, the effective transmissivity of a plurality of semi-translucent portions is measured, Based on the measurement results, surface modification is performed on at least a part of the semi-transparent film in the transfer pattern, and the exposure light transmittance of the semi-transparent film is changed, thereby providing an in-plane distribution. Make it smaller. Furthermore, it is more preferable to increase chemical resistance. That is, the gist of the present invention is to measure the effective transmittance of the plurality of semi-translucent portions after the pattern formation step, and in the surface modification step, based on the measurement result, The surface modification treatment is performed on at least a part of the semi-translucent film so that the in-plane distribution range of the transmittance is 2% or less.

  Here, in addition to the transmittance specific to the film, the effective transmittance is the shape (dimension or line width (CD (Critical Dimension)) of the pattern and the optical conditions of the exposure machine (light source wavelength, numerical aperture, σ value, etc.) This is the transmittance that reflects the actual exposure environment, so the width in the pattern is specified, the effective transmittance for that width is specified, and the optical conditions are fixed. Then, it becomes possible to determine the design (composition, film thickness, degree of modification) of the semi-transparent film of the semi-transparent part based on the effective transmittance, or to determine the degree of modification of the film It becomes possible.

  Furthermore, after the photomask is manufactured, when the transmissivity distribution of the in-plane semi-translucent portion is generated by the chemical treatment used in the processing step, this distribution is grasped in advance, and based on the result, The surface modification treatment of the invention can be performed to reduce the in-plane distribution.

  As a means for measuring the above effective transmittance, it is preferable to reproduce or approximate the exposure conditions by the exposure machine. An example of such a device is the device shown in FIG. This apparatus is obtained through a light source 1, an irradiation optical system 2 that irradiates the photomask 3 with light from the light source 1, an objective lens system 4 that forms an image of light transmitted through the photomask 3, and the objective lens system 4. It is mainly comprised from the imaging means 5 which images the obtained image.

  The light source 1 emits a light beam having a predetermined wavelength. For example, a halogen lamp, a metal halide lamp, a UHP lamp (ultra-high pressure mercury lamp), or the like can be used. For example, an exposure machine using a mask can be used with a light source having spectral characteristics approximating.

  The irradiation optical system 2 guides light from the light source 1 and irradiates the photomask 3 with light. The irradiation optical system 2 includes a diaphragm mechanism (aperture diaphragm 7) in order to make the numerical aperture (NA) variable. The irradiation optical system 2 preferably includes a field stop 6 for adjusting the light irradiation range in the photomask 3. The light that has passed through the irradiation optical system 2 is irradiated onto the photomask 3 held by the mask holder 3a. The irradiation optical system 2 is disposed in the housing 13.

  The photomask 3 is held by a mask holder 3a. The mask holder 3a supports the vicinity of the lower end portion and the side edge portion of the photomask 3 with the main plane of the photomask 3 being substantially vertical, and holds the photomask 3 in a tilted manner. It is like that. The mask holder 3a can hold the photomask 3 having a large size (for example, a main plane of 1220 mm × 1400 mm and a thickness of 13 mm or more) as the photomask 3 and various sizes. It has become. Note that “substantially vertical” means that the angle from the vertical indicated by θ in FIG. 4 is within about 10 degrees. The light irradiated to the photomask 3 passes through the photomask 3 and enters the objective lens system 4.

  The objective lens system 4 receives, for example, a first group (simulator lens) 4a in which light that has passed through the photomask 3 is incident and this light beam is corrected to infinity to obtain parallel light, and a light beam that has passed through the first group. It is composed of a second group (imaging lens) 4b that forms an image. The simulator lens 4a is provided with a diaphragm mechanism (aperture diaphragm 7), and its numerical aperture (NA) is variable. The light beam that has passed through the objective lens system 4 is received by the imaging means 5. The objective lens system 4 is disposed in the housing 13.

  The imaging unit 5 captures an image of the photomask 3. As this imaging means 5, for example, an imaging element such as a CCD can be used.

  In this apparatus, since the numerical aperture of the irradiation optical system 2 and the numerical aperture of the objective lens system 4 are variable, the ratio of the numerical aperture of the irradiation optical system 2 to the numerical aperture of the objective lens system 4, that is, The sigma value (σ: coherency) can be varied.

  Further, in this apparatus, the calculation means 11 for performing image processing, calculation, comparison with a predetermined threshold value, display, and the like for the captured image obtained by the imaging means 5, the control means 14 having the display means 12, and the housing 13. A moving operation means 15 for changing the position of is provided. For this reason, using the obtained captured image or the light intensity distribution obtained based on the obtained captured image, a predetermined calculation is performed by the control means, and the captured image or light under the condition using other exposure light. The intensity distribution and transmittance can be obtained.

  In the apparatus shown in FIG. 4 having such a configuration, the NA and σ values are variable, and the source of the light source can be changed, so that the exposure conditions of various exposure machines can be reproduced. In general, when an exposure apparatus for a large-sized photomask for manufacturing a liquid crystal device or the like is simply approximated, irradiation light having the same light intensity by i-line, h-line, and g-line is used, and NA is used as an exposure optical system. A condition that the coherency σ that is the NA ratio of the irradiation system and the objective system is about 0.8 may be applied.

  In the multi-tone photomask according to the present invention, a photomask blank having a semi-transparent film and a light-shielding film is prepared, and each film is subjected to patterning by wet etching to form the transfer pattern. A surface modification treatment is performed on at least a part of the semi-transparent film to change the exposure light transmittance of the semi-transparent film. Furthermore, it is preferable to improve chemical resistance by the above treatment. Accordingly, the transmissivity in-plane distribution range of the semi-translucent portion, which is present in the transfer pattern and is intended to obtain a predetermined exposure light transmissivity, is within 2%.

  A glass substrate etc. can be mentioned as a transparent substrate. Examples of the light shielding film that shields the exposure light include a metal film such as a chromium film, a silicon silicide film such as a silicon film, a metal oxide film, and a molybdenum silicide film. In addition, it is preferable to use a laminated antireflection film as the light shielding film, and examples of the antireflection film include chromium oxide, nitride, carbide, fluoride and the like. As the semi-transparent film that partially transmits exposure light, chromium oxide, nitride, carbide, oxynitride, oxynitride carbide, metal silicide, or the like can be used. In particular, a metal silicide film such as a molybdenum silicide compound (MoSix, MoSiO, MoSiN, MoSiON, MoSiCON, etc.) film is preferable. However, in order to have an appropriate wet etching property, it is preferable that the translucent film is made of a material that does not substantially contain nitrogen.

  As described above, according to the present invention, it is possible to obtain a multi-tone photomask having a small in-plane transmittance variation. In addition, in this method, various factors (for example, non-uniform transmittance plane due to line width distribution, non-uniform transmittance plane due to film thickness variation during film formation, wet processing such as development / etching, etc. In-plane transmittance non-uniformity due to the surface) can be comprehensively taken into account, and surface modification treatment can be selectively applied to areas with low transmittance, so that the transmittance is corrected to approach the desired value. In-plane variation can be effectively suppressed. Furthermore, the resistance of the semi-transparent film can be improved so that the change in transmittance due to the subsequent chemical contact is suppressed.

  An example of the process for producing the photomask of the present invention is shown in FIG. Specifically, for example, the steps shown in FIGS. In addition, the manufacturing method of the structure shown in FIG. 5 is not limited to these methods. Here, the material of the semi-translucent film 24 is molybdenum silicide (MoSix). In the following description, a resist material constituting the resist layer, an etchant used for etching, a developer used for development, and the like that can be used in known photolithography and etching processes are appropriately selected. For example, the etchant is appropriately selected according to the material constituting the film to be etched, and the developer is appropriately selected according to the resist material to be used.

  As shown in FIG. 5A, a photomask blank having a semi-transparent film 24 and a light-shielding film 22 (having an antireflection film 23 formed on the surface) on a transparent substrate 21 is prepared. A resist layer 25 is formed on the photomask blank, and as shown in FIG. 5B, the resist layer 25 is exposed and developed so that only the light transmitting region is exposed, thereby forming an opening. Next, as shown in FIG. 5C, using this resist pattern as a mask, the exposed antireflection film 23, light shielding film 22, and semi-transparent film 24 are etched, and thereafter, as shown in FIG. 5D. Then, the resist layer 25 is removed. The resist pattern may be peeled off before the semi-transparent film 24 is etched, and the semi-transparent film 24 may be etched using the antireflection film 23 and the light-shielding film 22 as a mask.

  Next, as shown in FIG. 5E, a resist layer 25 is formed on the light-shielding region of the antireflection film 23, and as shown in FIG. 5F, the antireflection film exposed using this resist pattern as a mask. 23, the light shielding film 22 The semi-transparent film is etched, and then the resist layer 25 is removed as shown in FIG.

  Next, for the photomask patterned in this way, the effective transmittance of each semi-translucent portion is measured using the apparatus shown in FIG. Then, based on the obtained in-plane variation of the effective transmittance, the semi-transparent film 24 of the semi-transparent portion having a low effective transmittance is subjected to a VUV process that is a surface modification process, thereby making the semi-transparent film. The surface of the optical film 24 is modified to form a modified layer 24a. About this modified layer 24a, the transmittance | permeability rises and chemical resistance improves. As a result, a multi-tone photomask with small variations in transmissivity of the semi-transparent portion in the surface can be obtained. Thereafter, the same portion may be further subjected to heat treatment, or the entire surface may be subjected to heat treatment.

  Using the above-described multi-tone photomask, the transfer pattern of the multi-tone photomask is transferred to the processing layer by irradiating exposure light from an exposure machine. In this case, it is preferable to use exposure light including a wavelength band of i-line to g-line as exposure light. As a result, a resist pattern having a desired film thickness can be obtained regardless of the pattern shape in the semi-transparent region.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. For example, in the above embodiment, a case where a photomask blank in which a semi-transparent film and a light shielding film are formed in this order on a transparent substrate is described, but a light shielding film pattern is formed on the transparent substrate. The photomask may be formed by coating a semi-transparent film and patterning it later. In addition, the number, size, processing procedure, and the like of the members in the above embodiment are merely examples, and various changes can be made within the range where the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

It is a figure which shows the relationship between a surface modification process and the transmittance | permeability fluctuation amount. (A), (b) is a figure which shows the in-plane dispersion | variation in the photomask before and behind surface modification. (A), (b) is a figure for demonstrating the transmittance | permeability of a semi-transparent area | region. It is a figure which shows the apparatus for measuring an effective transmittance | permeability. (A)-(g) is a figure for demonstrating the manufacturing method of the multi-tone photomask which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Irradiation optical system 3 Photomask 4 Objective lens system 5 Imaging means 11 Calculation means 12 Display means 13 Case 14 Control means 15 Moving operation means 21 Transparent substrate 22 Light-shielding film 23 Antireflection film 24 Semi-translucent film 24a Modification Layer 25 Resist layer

Claims (12)

  A light-shielding film and a semi-transparent film that transmits part of the exposure light are formed on the transparent substrate, respectively, and each film is subjected to predetermined patterning, thereby transmitting the light-shielding part and part of the exposure light. In a multi-tone photomask formed with a semi-transparent portion and a transfer pattern including the translucent portion, at least a surface portion of at least a part of the semi-transparent film is modified and is present in the transfer pattern. A multi-tone photomask characterized in that the transmissivity in-plane distribution range of the semi-translucent portion is within 2%.   2. The multi-tone photomask according to claim 1, wherein the semi-transparent film is made of a material containing metal silicide.   3. The multi-tone photomask according to claim 2, wherein the semi-translucent film is made of a material that does not substantially contain nitrogen.   Prepare a photomask blank in which a light-shielding film and a semi-transparent film that transmits part of the exposure light are formed on a transparent substrate, and apply a predetermined pattern to each film, thereby creating a light-shielding portion and exposure light. In the method of manufacturing a multi-tone photomask for forming a translucent part that transmits part of the light-transmitting part and a transfer pattern including the translucent part, patterning by etching is performed on each of the semi-transparent film and the light shielding film, A pattern forming step for forming the transfer pattern; and at least a part of the semi-transparent film in the transfer pattern is subjected to a surface modification process to change an exposure light transmittance of the semi-transparent film, and the transfer And a surface modification step of reducing a transmittance in-plane distribution range of the semi-transparent portion existing in the pattern.   5. The method of manufacturing a multi-tone photomask according to claim 4, wherein the surface modification treatment includes performing a treatment different from that of other portions on a selected portion in the photomask surface. .   6. The method for manufacturing a multi-tone photomask according to claim 4, wherein the surface modification step includes a process for increasing chemical resistance of the semi-translucent film.   7. The method of manufacturing a multi-tone photomask according to claim 5, wherein the surface modification treatment includes a treatment of irradiating a semi-translucent portion in the transfer pattern with a predetermined energy. .   The multi-tone photomask manufacturing method according to claim 4, wherein the surface modification process includes a process of heating a semi-translucent portion in the transfer pattern. Method.   After the pattern formation step, the method has a step of measuring the transmittance of the plurality of semi-translucent portions, and in the surface modification step, based on the measurement result, the transmission of the plurality of semi-translucent portions of the transfer pattern 9. The multi-tone photo according to claim 4, wherein the surface modification treatment is performed on at least a part of the semi-transparent film so as to reduce an in-plane distribution range of the rate. Mask manufacturing method.   10. The method for manufacturing a multi-tone photomask according to claim 9, wherein in the surface modification step, an in-plane distribution of transmittance of the semi-translucent portion is set to 2% or less.   Using the multi-tone photomask according to any one of claims 1 to 3 or the multi-tone photomask according to the manufacturing method according to claim 4 to 10, the multi-tone photomask is irradiated with exposure light from an exposure machine. A pattern transfer method comprising transferring a transfer pattern of a gradation photomask to a layer to be processed.   The pattern transfer method according to claim 11, wherein exposure light including a wavelength band of i-line to g-line is used as the exposure light.

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