JP2009223308A - Multi-gradation photomask and method of manufacturing the same, and pattern transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-gradation photomask which has a resist pattern having a desired remaining film value of thickness in a translucent area without reference to a pattern shape and a method of manufacturing the same, and a pattern transfer method. <P>SOLUTION: The multi-gradation photomask is provided with a light shielding area A, a first light-transluent area B (dark light-transluent area), a second light-transluent area C (light-transluent area), and a light-ttransluent area D on a transparent substrate 21. The first light-transluent area B has a pattern of a wide area, and the second light-transluent area C has a pattern including a narrow width. The first light-transluent area B and second light-transluent area C are different in film thickness, and nearly equal to effective transmissivity to exposure light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multi-tone photomask used in a photolithography process.

  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 mask.

  As a photomask, there is a multi-tone photomask having a light-blocking region that blocks exposure light, a light-transmitting region that transmits exposure light, and a semi-light-transmitting region that transmits part of the exposure light. In this multi-tone photomask, the amount of exposure light can vary depending on the region. Therefore, by performing exposure and development using this multi-tone photomask, the remaining film value (residual amount) of at least three thicknesses can be obtained. A resist pattern having a film value of zero) can be formed. In this way, a multi-tone photomask that realizes a resist pattern having a plurality of different remaining film values is very useful because the photolithography process can be made more efficient by reducing the number of photomasks used. It is.

  The semi-transparent region in the multi-tone photomask can be provided, for example, by forming a semi-transparent film having a desired transmittance that transmits part of the exposure light (Patent Document 1).

JP 2006-268035 A

  However, the transmissivity of the translucent film constituting the translucent region is defined using the transmissivity inherent to the translucent film, and in many cases, the transmittance of the representative wavelength included in the exposure light. Thus, the transmissivity of the semi-transparent film when the transmissivity of the translucent part (that is, only the transparent substrate) is 100% has been used. This is not a problem when specifying the transmittance of a pattern of a wide area above a certain level, but strictly speaking, for a pattern with a dimension of a certain degree or less, exposure at the time of actual pattern transfer The light transmittance is not accurately reflected. Since this is due to diffraction of exposure light, this tendency becomes more prominent as the exposure light wavelength becomes longer as the pattern becomes smaller. However, the present situation is that the change in transmittance with respect to light sources having different pattern dimensions and spectral characteristics is not accurately taken into consideration. For this reason, an attempt is made to form a resist pattern having two remaining film values in addition to a desired number, for example, an area having no remaining film (using a photomask having a light shielding area, a semi-transparent area, and a translucent area). However, if a pattern shape including a very narrow width and a pattern shape of a relatively wide area exist in the semi-transparent region, the semi-transparent region always remains on the resist film on the transfer target. Where a film value should be given, a resist pattern with a different remaining film value is formed due to the pattern shape, and when the variation of the remaining film value exceeds a desired tolerance, There is a problem of becoming an unstable factor.

  The present invention has been made in view of the above points, and a multi-tone photomask capable of obtaining a resist pattern having a residual film value having a desired thickness regardless of a pattern shape in a semi-transparent region, and a manufacturing method thereof The purpose is to provide.

  The multi-tone photomask of the present invention is formed by patterning a light-shielding film that shields exposure light and a semi-transparent film that partially transmits the exposure light, provided on a transparent substrate. A multi-tone photomask having a transfer pattern having a region, a light-shielding region, and a semi-transparent region, wherein the semi-transparent region includes a first semi-transparent portion with respect to a specific pattern shape, and the pattern shape. A second semi-transparent portion for different pattern shapes, and the first semi-transparent portion and the second semi-transparent portion have the same semi-transparent film so that the effective transmittance for the exposure light is substantially equal. It is characterized in that the transmittance specific to the film is different. Here, “substantially equal” is preferably 1% or less in terms of the effective transmittance described later. Depending on the use of the photomask, the reference value may be larger (for example, 3% or less).

  According to this configuration, the pattern of the resist pattern formed on the transfer object can be accurately considered with respect to the transmittance of the exposure light in the semi-transparent region in the patterns having different line widths and the transmittance to the light sources having different wavelengths. Since the gradation photomask is realized, a resist pattern having a desired remaining film value can be obtained on the transfer target regardless of the pattern shape in the semi-transparent region.

  In the multi-tone photomask of the present invention, the first semi-transparent portion and the second semi-transparent portion may transmit light unique to each film in the first semi-transparent portion and the second semi-transparent portion. It is preferable that the rate difference is set to a predetermined value of 10% or less. The lower limit of the transmittance difference is determined by the use of the photomask, but in general, it is preferably in the range of 1% to 10%. More preferably, it is 1% to 5%.

  In the present invention, it is preferable that the first semi-transparent portion and the second semi-transparent portion are formed with different thicknesses of the semi-transparent film. Alternatively, in the present invention, the first semi-transparent portion and the second semi-transparent portion may be formed with different film qualities of the semi-transparent film.

  In the multi-tone photomask of the present invention, the effective transmittance in the first semi-transmissive part and the second semi-transmissive part is preferably 15% to 60%, more preferably 20% to 50%. . In particular, in the region where the effective transmittance is 40% or more, the thickness of the semi-transparent film is relatively small, and the difference in thickness for making a difference in transmittance is even smaller. It is very difficult to quantitatively achieve such a small film thickness difference unless the present invention is applied, and the effect of the present invention is remarkable.

  In the multi-tone photomask of the present invention, the translucency of the semi-transparent film is relatively relative to the semi-transparent part including a pattern shape with a relatively narrow pattern width sandwiched on both sides adjacent to the light-shielding part. The transmissivity of the semi-transparent film is preferably relatively low in a semi-transparent portion including a pattern shape having a high pattern width and a relatively wide pattern width. Here, the pattern width of the semi-translucent portion is the width of the sandwiched portion in the pattern shape of the semi-translucent portion sandwiched between the light shielding portions on both sides. For example, when there are a plurality of values of the width, the minimum width can be set.

  In the multi-tone photomask of the present invention, the semi-transparent film preferably contains a metal silicide. More preferably, molybdenum silicide as the main component can be used. The main component is a content of Mo and Si in an atomic percentage exceeding 50% in total. More preferably, it can exceed 80%. Such a semi-transparent film material can be easily patterned by wet etching, and has an etching selectivity with Cr, which is a material generally used as a light shielding film. No thickness reduction occurs. Furthermore, the film thickness can be appropriately reduced by a chemical solution such as alkali, and the transmittance can be quantitatively controlled by modifying the surface film quality by irradiation with energy rays.

  The method for producing a multi-tone photomask of the present invention prepares a photomask blank provided with a semi-transparent film that transmits at least part of exposure light and a light-shielding film that blocks the exposure light on a transparent substrate. And a step of patterning each of the light shielding film and the semi-transparent film, and in the step of patterning the semi-transparent film, a first semi-transparent portion for a specific pattern shape, and the pattern A difference in effective transmittance with respect to the exposure light between the second semi-transparent part and the second semi-transparent part with a pattern shape different from the shape is the same in the first semi-transparent part and the second semi-transparent part. The semi-transparent film is patterned so as to be smaller than when the film is provided.

  In the conventional multi-tone mask, the translucent portions having different shapes included in the same plane have the same film transmittance. Therefore, the effective transmittance described later is necessarily different. It was. However, since the difference in these effective transmittances can be reduced according to the present invention, the in-plane distribution can be reduced in the effective transmittance of the semi-transparent portion during actual exposure. The amount of reduction at that time can be determined according to the application of the mask, but preferably, the effective transmittance of the semi-translucent portion is substantially equal.

  The method for producing a multi-tone photomask of the present invention prepares a photomask blank provided on a transparent substrate with at least a semi-transparent film that partially transmits exposure light and a light-shielding film that blocks the exposure light. And a step of patterning the semi-transparent film and the light-shielding film, respectively, a first semi-transparent portion for a specific pattern shape, and a second semi-transparent light for a pattern shape different from the pattern shape The semi-transparent film is patterned so that the effective transmittance with respect to the exposure light is substantially equal and the transmittance inherent to each film is different.

  According to this method, a desired thickness can be obtained regardless of the pattern shape in the semi-transparent region, which accurately takes into account the transmittance of the exposure light in the semi-transparent region in patterns having different dimensions and the transmittance for light sources having different wavelengths. A multi-tone photomask from which a resist pattern having a remaining film value can be obtained can be obtained. Here, the pattern processing of the semi-transparent film includes not only transferring the pattern shape to the semi-transparent film but also controlling the film thickness or modifying the film quality. Specifically, in the step of patterning the semi-transparent film, a surface treatment is performed to make the film thickness of the semi-transparent film different in the first semi-transparent part and the second semi-transparent part. It is also possible to apply surface treatment that makes the film quality of the semi-transparent film different in the first semi-transparent part and / or the second semi-transparent part.

  It is preferable that the photomask blank applied to the present invention is obtained by providing at least the semi-transparent film and the light-shielding film in this order on a transparent substrate.

  In the multi-tone photomask manufacturing method of the present invention, a first resist pattern is formed on the light shielding film of the photomask blank prepared as described above, and the light shielding film is etched using the first resist pattern as a mask. Forming a first light-shielding film pattern, etching the semi-transparent film using the first resist pattern or the first light-shielding film pattern as a mask, and forming a light-transmissive region; Forming a second resist pattern on a predetermined region of the first light shielding film pattern, etching the light shielding film using the second resist pattern as a mask to form a second semi-transparent portion; Forming a third resist pattern on an area different from the predetermined area of the first light shielding film pattern, and using the third resist pattern as a mask; By comprising a third photolithography step to form a first semi-light-transmitting portion of the light shielding film by etching, it is preferred.

  In the method for producing a multi-tone photomask of the present invention, it is preferable that the semi-transparent film is subjected to a surface treatment so that a film thickness difference is formed between the first translucent part and the second translucent part. . In this case, the surface treatment is performed on the second semi-transparent portion exposed by the second photolithography step and / or on the first semi-transparent portion exposed by the third photolithography step. Preferably, it is performed together with the resist pattern removal in the second photolithography process and / or the third photolithography process.

  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.

  The multi-tone photomask of the present invention comprises a light-transmitting region, a light-shielding region, and a light-shielding film that is provided on a transparent substrate and shields exposure light, and a semi-transparent film that partially transmits the exposure light. A multi-tone photomask having a transfer pattern having a semi-transparent region, wherein the semi-transparent film includes a first semi-transparent portion for a specific pattern shape and a second pattern shape different from the pattern shape. The first semi-transparent part and the second semi-transparent part have different film thicknesses so that the effective transmissivity with respect to the exposure light is substantially equal. Regardless of the pattern shape in the region, a resist pattern with a desired film thickness value can be obtained on the transfer target. Manufacturing stability and yield when manufacturing electronic devices using this mask can be obtained. Can be improved.

(A), (b) is a figure which shows the light intensity distribution corresponding to the pattern of a light shielding film and a semi-transparent film, and it. It is a characteristic view which shows the relationship between channel width and the transmittance | permeability. It is a figure which shows an example of the apparatus which reproduces the exposure conditions of an exposure machine. It is a figure which shows the structure of the multi-tone photomask which concerns on embodiment of this invention. It is a characteristic view which shows the relationship between an integrated transmittance | permeability fluctuation amount and alkaline chemical | medical solution processing time. (A)-(j) is a figure for demonstrating the manufacturing method of the structure of the multi-tone photomask shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Until now, the transmissivity of the semi-transparent film constituting the semi-transparent region has been defined by the transmissivity specific to the film determined by the film and the exposure light, regardless of the pattern shape. In the case where the film material and thickness of the semi-transparent film are set based on the transmittance defined in this way, no particular problem occurs when the area of the semi-transparent area is sufficiently large with respect to the resolution of the exposure machine. . However, when the area or width of the semi-translucent region becomes small, the influence of the exposure light diffraction that occurs at the edge of the pattern cannot be ignored. Due to the influence of the portion, the transmittance inherent in the semi-transparent film may be different during actual exposure.

  For example, a multi-tone photomask for a thin film transistor is often used in which a region corresponding to a channel portion is a semi-transparent region, and regions corresponding to adjacent sources and drains are sandwiched by a light-shielding portion. The This photomask is normally exposed using exposure light in the wavelength band of i-line to g-line, but as the size (width) of the channel portion becomes smaller, the boundary with the adjacent light-shielding portion is the actual exposure. Under the condition, the exposure light transmittance of the channel portion becomes lower than the transmittance of the semi-transparent film. That is, as shown in FIGS. 1A and 1B, the light intensity distribution of the transmitted light in the semi-transparent region B sandwiched between the light shielding portions A is as follows. The whole is lowered and the peak is lowered. For example, as shown in FIG. 2, when the channel width is 5 μm or less, the transmittance of light contributing to actual exposure in the semi-transparent region having a width corresponding to the channel width is significantly reduced. Here, the film transmittance of the semi-transparent film is defined by the ratio of the exposure light irradiation amount and the transmission amount in a sufficiently wide area where the film is formed on the transparent substrate. It is determined by the composition and film thickness. A sufficiently wide region refers to a region where the transmittance does not change substantially due to a change in the width of the region. In FIG. 2, the transmittance of the semi-transparent region B is represented by the peak value of the light intensity distribution of the transmitted light in the semi-transparent region B. The transmittance of this portion has a correlation with the resist residual film value on the transfer target when the multi-tone mask is used for exposure.

  In recent thin film transistors (TFTs), the operation speed of the liquid crystal is increased by reducing the width of the channel part as compared with the prior art, or the brightness of the liquid crystal is increased by reducing the size of the channel part. Technology has been proposed, and these requirements tend to make the pattern finer. On the other hand, it is expected that the required accuracy of the resist pattern to be obtained will be further increased. In such a situation, the present inventors must consider not only the transmissivity specific to the semi-transparent film but also the transmissivity including factors such as a difference in pattern shape for the area of the photomask having a small area or width. It was considered that a desired resist pattern could not be formed.

  Therefore, the present inventors have captured the light intensity distribution received by the transferred object when the exposure light is actually irradiated on the photomask under the exposure conditions of the exposure apparatus, by imaging means, thereby causing factors such as a difference in pattern shape. Focusing on the ability to analyze the transfer pattern image containing the light, it was found that the film material and thickness of the semi-transparent film in the semi-transparent region can be determined based on the transfer pattern image obtained from this light intensity data . And based on this knowledge, by changing the thickness of the semi-transparent film in accordance with the pattern shape in the semi-transparent region, the remaining film value of the resist film in the semi-transparent region is the same regardless of the pattern shape. I found out what I can do.

  Therefore, in the present invention, a film configuration in which the semi-transparent region includes a first semi-transparent portion having a specific pattern shape and a second semi-transparent portion having a pattern shape different from the pattern shape, To do. In this case, for example, for a pattern having a narrow area, the transmittance actually contributing to exposure is relatively low as shown in FIG. 2, while for a pattern having a relatively wide line width, as shown in FIG. As shown in FIG. 2, the transmittance contributing to actual exposure is relatively high. Considering these, in order to obtain a desired transmittance (transmittance that actually contributes to exposure), the former and the latter film thickness and / or film quality are adjusted respectively. By providing such a film thickness difference or film quality difference, the effective transmittance with respect to the exposure light in the first semi-transmissive part and the second semi-transmissive part becomes substantially equal. That is, the film-specific transmittance difference between the first semi-transparent part and the second semi-transparent part due to the pattern shape is adjusted by the film thickness difference and / or the film quality, whereby the first semi-transparent part And the effective transmissivity between the second semi-transparent part and the second semi-transparent part. By performing pattern transfer using such a multi-tone photomask, the residual film value of the resist film in the semi-transparent region can be made equal regardless of the pattern shape.

  When the effective transmissivity between the first semi-transparent part and the second semi-transparent part is substantially the same by providing a film thickness difference between the first semi-transparent part and the second semi-transparent part. The difference between the film thickness of the first semi-transparent part and the film thickness of the second semi-transparent part is the difference in transmittance inherent to each film in the first semi-transparent part and the second semi-transparent part. 10% or less, more preferably 1% to 10%, and further 1% to 5%, the effect of the present invention is remarkable. More preferably, it is 1% to 5%. Therefore, the first and second semi-transparent portions are formed so as to have a film thickness difference so as to satisfy this condition. Here, the film-specific transmittance means the transmittance in a region having a relatively large film area. Here, the effective transmittance can be the transmittance at the peak of the light intensity distribution curves of FIGS. 1A and 1B when the exposure light transmittance of the light transmitting portion is 100%. . The light intensity distributions of FIGS. 1A and 1B can be obtained by, for example, a method described later.

  Moreover, it is preferable that the effective transmittances in the first semi-transmissive part and the second semi-transmissive part are 15% to 60%, more preferably 20% to 50%.

  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, based on the effective transmittance, it becomes possible to determine the design (composition, film thickness, degree of modification) of each of the first semi-transmissive part and the second semi-transmissive part. Alternatively, the degree of film modification can be determined.

  As an apparatus for reproducing the exposure conditions of the exposure machine as described above, for example, an apparatus shown in FIG. This apparatus is obtained through a light source 1, an illumination 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, a light source having spectral characteristics approximating an exposure machine that uses a mask can be used.

  The illumination optical system 2 guides light from the light source 1 and irradiates the photomask 3 with light. The illumination optical system 2 includes an aperture mechanism (aperture stop 7) in order to make the numerical aperture (NA) variable. The illumination 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 illumination optical system 2 is applied to the photomask 3 held by the mask holder 3a. The illumination 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. 3 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 illumination optical system 2 and the numerical aperture of the objective lens system 4 are variable, the ratio of the numerical aperture of the illumination 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. 3 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.

  A multi-tone photomask according to the present invention comprises a light-transmitting region, a light-shielding region, a light-shielding film that is provided on a transparent substrate and shields exposure light, and a semi-transparent film that partially transmits the exposure light. And a transfer pattern constituting a semi-translucent region. The semi-transparent region has a first semi-transparent portion for a specific pattern shape and a second semi-transparent portion for a pattern shape different from the pattern shape. About each translucent part, the effective transmittance | permeability is match | combined by changing a film thickness and / or film quality.

  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. Further, 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 (MoSix) film is preferable. MoSix is more effective when the film thickness is adjusted with a chemical solution such as alkali as compared to MoSiON, MoSiN, etc., which are frequently used as phase shifters for LSI photomasks.

Example 1
As shown in FIG. 4, the multi-tone photomask described above has a light shielding region A, a first semi-transparent region B (dark semi-transparent region), and a second semi-transparent region C (bright semi-transparent region) on a transparent substrate 21. A translucent area) and a translucent area D are provided. The first semi-transparent area B is a pattern of a wide area sandwiched between the light shielding parts, and the second semi-transparent area C is a pattern including a narrow width sandwiched between the light shielding parts. In such a multi-tone photomask, for example, as shown in FIG. 4, a semi-transparent film 24 is formed on the light shielding region A, the first semi-transparent region B, and the second semi-transparent region C of the transparent substrate 21. The light-shielding film 22 and the antireflection film 23 are formed on the light-shielding region A of the semi-transparent film 24, and the thickness of the semi-transparent film 24 in the first semi-transparent region B is thick. The semi-transparent film 24 in the region C has a thin structure. Accordingly, the first semi-transmission region B has a low film transmittance (dark semi-transmission region) because the thickness of the semi-transmission film 24 is thick, and the second semi-transmission region C is the semi-transmission film 24. Since the thickness of the film is thin, the membrane transmittance is high (bright semi-translucent region). The multi-tone photomask having the structure shown in FIG. 4 has four gradations in the four regions A to D, and the effective of the semi-transparent region B and the semi-transparent region C in actual exposure. Since the transmittance is designed to be substantially the same, the resist residual film value formed on the transferred body is also equivalent, and as a result, the photomask forms a three-tone resist pattern.

  Such a multi-tone photomask having semi-transparent films having different film thicknesses can be manufactured as follows. A photomask blank provided with a semi-transparent film that partially transmits the exposure light and a light-shielding film that shields the exposure light on a transparent substrate, a first semi-transparent portion for a specific pattern shape, and the Manufactured by patterning the semi-transparent film so that the effective transmissivity for the exposure light is approximately equal and the film thicknesses are different in the second semi-transparent part for a pattern shape different from the pattern shape. be able to.

  When the structure shown in FIG. 4 is manufactured, a first resist pattern is formed on the light shielding film, the first light shielding film pattern is etched by using the first resist pattern as a mask, and the first light shielding film pattern is formed. A first photolithography process (see FIGS. 6A to 6D) for forming the light-transmitting region by etching the semi-transparent film using the resist pattern or the first light-shielding film pattern as a mask; A second photolithography step (FIG. 5) forming a second resist pattern on a predetermined region of the first light shielding film pattern and etching the light shielding film using the second resist pattern as a mask to form a second semi-translucent portion. 6 (e) to FIG. 6 (g)), and a third resist pattern is formed on a region different from the predetermined region of the first light shielding film pattern, and the third resist pattern is used as a mask. A light shielding film and the third photolithography step of forming a first semi-light-transmitting portion by etching (see FIG. 6 (h) ~ FIG 6 (j)), it will be preferable to include.

  In the above example, the semi-transparent film is subjected to a surface treatment to make a film thickness difference between the first semi-transparent part and the second semi-transparent part. This surface treatment can be performed on the second semi-transparent portion exposed by the second photolithography process. That is, in the state where the second semi-transparent portion is exposed by the second photolithography process (the portion corresponding to the first semi-transparent portion is covered with the light-shielding film), the surface treatment is applied to the semi-transparent film of that portion. Apply. Alternatively, in addition, in the third photolithography step, the surface treatment can be performed on the semi-transparent film in the portion where the first semi-transparent portion is exposed. At this time, if the second semi-transparent portion is in an exposed state, the second semi-transparent portion is also affected by the surface treatment. Keep it.

  The surface treatment can be performed by bringing a chemical solution into contact therewith. As the chemical solution, an acid (such as sulfuric acid) or an alkali (such as sodium hydroxide) can be used. For example, the second resist pattern may be formed, and after the light-shielding film is etched using the second resist pattern as a mask, the second resist pattern may be removed simultaneously with the surface treatment with the alkaline solution for the second semi-transparent portion. Alternatively, after the third resist pattern is formed, the light shielding film is etched using the third resist pattern as a mask, and then the surface treatment with the alkaline solution is performed on the first semi-translucent portion, and at the same time, the third resist pattern is removed. Good. In other words, it is preferably performed together with the resist pattern removal in the second photolithography process and / or the third photolithography process.

  By using a film material whose film thickness changes with respect to a specific surface treatment for the semi-transparent film, the thickness of the semi-transparent film can be reduced when removing the resist pattern. It is possible to increase the inherent transmittance of the membrane. For example, when MoSi is used as the film material, the transmittance can be changed by alkaline chemical treatment as shown in FIG. By utilizing this characteristic, it is possible to cancel the change in effective transmittance due to the pattern shape or arrangement difference.

  Actually, the amount of transmittance adjustment required due to the difference in line width is often several percent, and such fine adjustment of transmittance is extremely difficult. The method of the present invention is very effective for such fine adjustment of transmittance. According to the present invention, it is possible to make the difference in exposure light transmittance (specific to the film) of the first and second semi-transparent portions within 5%, for example, 2 to 3%. Therefore, it is possible to form a resist pattern that is precisely controlled, and it is possible to increase the production yield and efficiency of the panel user.

  In addition, after adjusting the transmittance by chemical treatment, that is, after manufacturing the photomask, it is preferable to improve the chemical resistance by modifying the surface of the semi-translucent film by UV treatment or heat treatment. When the transmittance is changed by such processing, the amount of transmittance adjustment by the chemical solution processing is determined in consideration of this amount in advance.

  FIG. 6 shows a process for manufacturing the photomask of the present invention. However, here, the arrangement of the patterns is different from that shown in FIG. 4 in order to simplify the description. Specifically, for example, the steps shown in FIGS. In addition, the manufacturing method of the structure shown in FIG. 4 is not limited to these methods. Here, the material of the translucent film 24 is molybdenum silicide (MoSi). 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 conventional 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. 6A, a photomask blank having a translucent 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 26 is formed on the photomask blank, and as shown in FIG. 6B, the resist layer 26 is exposed and developed so that only the translucent region D is exposed, thereby forming an opening. Next, as shown in FIG. 6C, the exposed antireflection film 23, light shielding film 22, and semi-translucent film are etched using this resist pattern as a mask, and thereafter, as shown in FIG. 6D. Then, the resist layer 26 is removed.

  Next, as shown in FIG. 6E, a resist layer 26 is formed on the light shielding region A and the first semi-transparent region B of the antireflection film 23, and this resist pattern is formed as shown in FIG. 6F. Then, the exposed antireflection film 23 and the light shielding film 22 are etched, and then the resist layer 26 is removed as shown in FIG. At this time, the thickness of the semi-translucent film 24 is reduced to form a thin semi-transparent film 24a by performing an alkaline chemical treatment that is a surface treatment. In the case where an alkaline chemical solution is used for removing the resist layer 26, when the resist layer 26 is removed, a process for reducing the thickness of the semi-transparent film 24 can be performed at the same time.

  Next, as shown in FIG. 6 (h), a resist layer 26 is formed on the light shielding region A of the antireflection film 23, and as shown in FIG. 6 (i), the antireflection exposed using the resist pattern as a mask. The film 23 and the light shielding film 22 are etched, and then the resist layer 26 is removed as shown in FIG. When an alkaline chemical solution is used to remove the resist layer 26, the thickness of the semi-transparent film 24 can be reduced when removing the resist layer 26, so that the film thickness of the semi-transparent film 24 can be finely adjusted. It can be performed. In this way, a configuration as shown in FIG. 4 can be produced.

  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. As a result, a resist pattern having a desired film thickness can be obtained regardless of the pattern shape in the semi-transparent region.

(Example 2)
In the step of FIG. 6 (f), instead of subjecting the exposed semi-translucent portion to surface treatment with a chemical solution, energy of UV light or the like is irradiated, so that a half of the exposed second semi-transparent portion is obtained. The translucent film can be modified. For example, the transmittance can be increased by forming an oxide layer on the surface. This brings about the same effect as reducing the film thickness by the chemical solution. Here, since only the semi-transparent part (second semi-transparent part) other than the first semi-transparent part is exposed, this part can be selectively film-modified. Further, in addition to or instead of this, energy may be irradiated in the same manner with the first semi-transparent portion exposed by the third resist pattern at the stage of FIG. 6 (i). In short, in the present invention, the surface treatment can be selectively applied to the first or second semi-transparent portion by forming the second and third resist patterns, respectively.

  According to the present invention, a three-tone resist pattern can be precisely formed on a transfer target by using a photomask having four gradations. That is, in the resist pattern formed using this mask, the remaining film value of the portion corresponding to the semi-translucent portion is substantially constant regardless of the dimension of the pattern. Therefore, when manufacturing an electronic device such as a liquid crystal display device The photolithography process is facilitated. Furthermore, when manufacturing such a four-tone photomask, the semi-transparent film in the present invention can be a single layer film of the same composition formed by a single film formation process. In this case, there is no demerit that the film forming process increases.

  In the above description, the advantage of applying the present invention has been described with respect to the transmissivity of the semi-transparent region sandwiched adjacent to the light shielding portion. However, in the semi-translucent portion sandwiched between the translucent portions, the same consideration is made, so that when the electronic device is manufactured using the mask of the present invention, the residual resist pattern formed on the transfer object is left. The membrane value can be controlled. In this case, the effective transmittance of the semi-transmissive region tends to be higher than the intrinsic transmittance of the semi-transmissive film used for the semi-transmissive region. Even in such a case, the transmittance that actually contributes to the exposure is obtained by the above-described means so that the effective transmittances of the first and second semi-transparent portions having different shapes are substantially equal. It can be adjusted.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. For example, in the above embodiment, the case where there are two semi-transparent regions in which the effective transmittance is uniform in the semi-transparent film is described, but the present invention is not limited to this, and the semi-transparent film Even in the case where there are three or more semi-transparent regions in which the effective transmittance is uniformed, it can be similarly applied by changing the film configuration according to the same technical idea. 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.

DESCRIPTION OF SYMBOLS 1 Light source 2 Illumination optical system 3 Photomask 4 Objective lens system 4a Simulator lens 4b Imaging lens 5 Imaging means 6 Field stop 7 Aperture stop 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 Semitranslucent film 24a Thin semitranslucent film 26 Resist layer

Claims (16)

  The light-transmitting region, the light-blocking region, and the semi-light-transmitting region are each formed by patterning a light-blocking film that blocks exposure light and a semi-transparent film that partially transmits the exposure light, provided on the transparent substrate. The semi-transparent region includes a first semi-transparent portion for a specific pattern shape and a second semi-transparent portion for a pattern shape different from the pattern shape. And the first semi-transmission part and the second semi-transmission part have different film-specific transmissivities so that the effective transmissivity for the exposure light is substantially equal. A multi-tone photomask which is formed.   The first semi-transparent part and the second semi-transparent part have a predetermined difference in transmittance of 10% or less between the first semi-transparent part and the second semi-transparent part. 2. The multi-tone photomask according to claim 1, wherein the multi-tone photomask is set as follows.   3. The multi-tone photomask according to claim 2, wherein the first semi-transparent part and the second semi-transparent part are formed with different thicknesses of the semi-transparent film.   3. The multi-tone photomask according to claim 2, wherein the first semi-transparent part and the second semi-transparent part are formed with different film qualities.   5. The multi-tone photomask according to claim 1, wherein an effective transmittance in the first semi-transmissive part and the second semi-transmissive part is 15% to 60%. .   A pattern in which the transmissivity of the semi-transparent film is relatively high and the pattern width is relatively wide in a semi-transparent part including a pattern shape with a relatively narrow pattern width sandwiched between the light shielding parts on both sides 6. The multi-tone photomask according to claim 1, wherein a transmissivity of the semi-transparent film is relatively low in a semi-transparent portion including a shape.   The multi-tone photomask according to claim 1, wherein the semi-translucent film contains a metal silicide.   Preparing a photomask blank provided with a semi-transparent film that transmits at least part of exposure light and a light-shielding film that shields the exposure light on a transparent substrate; and the light-shielding film and the semi-transparent film. A pattern processing step, and in the step of patterning the semi-transparent film, a first semi-transparent portion for a specific pattern shape and a second semi-transparent portion for a pattern shape different from the pattern shape The difference in effective transmittance with respect to the exposure light between the first semi-transmission part and the second semi-transmission part is smaller than when the same semi-transmission film is provided in the first semi-transmission part. A method of manufacturing a multi-tone photomask, comprising patterning the semi-transparent film for each of the first semi-transparent part and the second semi-transparent part.   A step of preparing a photomask blank provided with at least a semi-transparent film that partially transmits exposure light and a light-shielding film that shields the exposure light on a transparent substrate; and the semi-transparent film and the light-shielding film In the step of patterning the semi-transparent film, a first semi-transparent portion for a specific pattern shape and a second semi-transparent portion for a pattern shape different from the pattern shape In the method of manufacturing a multi-tone photomask, wherein the semi-transparent film is patterned so that the effective transmittance with respect to the exposure light is substantially equal and the transmittance inherent to each film is different .   The step of patterning the semi-transparent film is characterized in that a surface treatment is performed to make the thickness of the semi-transparent film different in the first semi-transparent part and the second semi-transparent part. Item 10. The method for manufacturing a multi-tone photomask according to Item 8 or Item 9.   The step of patterning the semi-transparent film is characterized in that a surface treatment is performed to make the film quality of the semi-translucent film different in the first semi-transparent part and the second semi-transparent part. A method for producing a multi-tone photomask according to claim 8 or 9.   12. The photomask blank according to claim 8, wherein at least the semi-transparent film and the light-shielding film are provided in this order on the transparent substrate. A method for manufacturing a multi-tone photomask.   Forming a first resist pattern on the light-shielding film of the photomask blank; etching the light-shielding film using the first resist pattern as a mask to form a first light-shielding film pattern; Etching the semi-transparent film using the first light shielding film pattern as a mask to form a light transmissive region; forming a second resist pattern on a predetermined region of the first light shielding film pattern; A second photolithography step of etching the light shielding film using the second resist pattern as a mask to form a second semi-transparent portion; and a third resist on a region different from the predetermined region of the first light shielding film pattern Forming a pattern, and etching the light-shielding film using the third resist pattern as a mask to form a first semi-transparent portion. Method for producing a multi-tone photo mask according to claim 8 according to claim 12, characterized by comprising the Rafi step.   The surface treatment is performed on the second semi-transparent portion exposed by the second photolithography step and / or on the first semi-transparent portion exposed by the third photolithography step. The method for manufacturing a multi-tone photomask according to claim 10.   The multi-tone photomask according to any one of claims 10 to 13, wherein the surface treatment is performed together with a resist pattern removal in the second photolithography process and / or the third photolithography process. Manufacturing method.   A transfer pattern of the multi-tone photomask is transferred to a processing layer by irradiating exposure light from an exposure machine using the multi-tone photomask according to claim 1. Pattern transfer method.

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