KR101194151B1 - Multi-gray scale photomask, pattern transfer method, and method of manufacturing thin firm transistor - Google Patents

Abstract

The multi-gradation photomask includes a transfer pattern having a light-transmitting region, a light-shielding region, and a semi-transmissive region formed by a light shielding film for shielding exposure light and a semi-transmissive film partially transmitting the exposure light, formed on a transparent substrate. do. The semi-transmissive film has a transmittance having a wavelength dependency in the wavelength region of the exposure light, and the semi-transmissive region is substantially free of the wavelength dependency under exposure optical conditions of an exposure machine used at the time of transferring the transfer pattern. It includes an area having a dimension indicating the transmittance.

Light shielding film, transflective film, exposure machine, effective transmittance, wavelength dependence, transfer pattern, light shielding area, semi-transmissive area

Description

MULTI-GRAY SCALE PHOTOMASK, PATTERN TRANSFER METHOD, AND METHOD OF MANUFACTURING THIN FIRM TRANSISTOR}

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

Conventionally, in the photolithography step, a resist pattern is formed by exposing and developing under a predetermined exposure condition to a resist film formed on a layer to be etched using a photomask having a predetermined pattern. And a to-be-processed layer is etched using this resist pattern as a mask.

In a photomask, there is a multi-gradation photomask having a light shielding region for shielding exposure light, a light transmission region for transmitting the exposure light, and a semi-transmission region for transmitting a part of the exposure light. Since the amount of light of exposure light differs according to each area | region, this multi-gradation photomask has the residual film value (including the residual film value zero) of at least 3 thickness by performing exposure and image development using this multi-gradation photomask. A resist pattern can be formed. Thus, a multi-gradation photomask that realizes a resist pattern having a plurality of different residual film values is extremely useful because it is possible to reduce the photolithography process.

The semi-transmissive region in the multi-gradation photomask can be formed, for example, by forming a semi-transmissive film having a desired transmittance for transmitting a part of the exposure light (Patent Document 1).

Prior art literature

Patent literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2006-268035

SUMMARY OF THE INVENTION [

Problems to be Solved by the Invention

However, the transmissivity of the transflective film constituting the translucent region is usually a transmissivity in the case where a film is formed on the entire surface of a wide region, and, strictly speaking, differs from the transmissivity of exposure light during actual pattern transfer. In particular, it is a phenomenon that the transmittance of exposure light in a very narrow pattern and the transmittance with respect to light sources having different wavelengths are not accurately considered. In the future, when the precision in the pattern design is further improved, the desired resist pattern cannot be formed without accurately considering these factors (the difference in the pattern shape or the wavelength of the light source), and as a result, the pattern is accurately formed on the layer to be processed. There is a problem that I cannot do it.

This invention is made | formed in view of such a point, and it becomes easy to use a photomask in an optimal state irrespective of the exposure wavelength characteristic of an exposure machine, and it can stably and accurately form the pattern on a to-be-processed layer multi-gradation It is an object to provide a photomask.

MEANS FOR SOLVING THE PROBLEMS [

The multi-gradation photomask according to the first aspect of the present invention is a light-transmitting region, a light-shielding region, and a half formed of a light shielding film for shielding exposure light and a semi-transmissive film partially transmitting the exposure light, formed on a transparent substrate. A multi-gradation photomask having a transfer pattern having a transmissive region, wherein the semi-transmissive layer has a transmittance having a wavelength dependency in a wavelength region of exposure light, and the semi-transmissive region is used for transferring the transfer pattern. And an area having a dimension exhibiting a transmittance in which the wavelength dependence is substantially not generated under the exposure optical conditions of the exposure machine.

According to this configuration, since the multi-gradation photomask accurately considering the transmittance of the exposure light in the semi-transmissive region in the very narrow pattern and the transmittance with respect to the light source having different wavelengths can be realized, the precision in the pattern design is further improved, or Even if the pattern is further refined, a pattern having a desired residual film value can be accurately formed on the layer to be processed.

In the multi-gradation photomask of the present invention, the exposure optical condition preferably includes at least the wavelength, the numerical aperture, and the coherency of the light source of the exposure machine. Here, coherence means the ratio of the numerical aperture of the exposure machine to the numerical aperture of the projection optical system.

In the multi-gradation photomask of the present invention, it is preferable that the transmittance of the semi-transmissive film is 20% to 80% in the wavelength region of i-g line included in the exposure light. According to this structure, the process control in the electronic device manufacturing process using this mask becomes easy.

In the multi-gradation photomask of the present invention, the wavelength dependence is a dependency in which the transmittance increases as the wavelength becomes longer, and is represented by a characteristic line having a transmittance difference of 1% or more in the wavelength region of i-g line included in the exposure light. It is desirable to lose. In this case, the transmittance of the transmissive region of the photomask is set to 100%.

In the multi-gradation photomask of the present invention, the semi-transmissive film is preferably a chromium oxide film, a chromium nitride film, or a metal silicide film.

The multi-gradation photomask of the present invention is for manufacturing a thin film transistor, and it is preferable that a region having a dimension showing a transmittance in which the wavelength dependency does not substantially occur corresponds to a channel region of the thin film transistor. In this case, the width of the channel region is preferably 1.0 µm to 5.0 µm.

The multi-gradation photomask according to the second aspect of the present invention is a light-transmitting region, a light-shielding region, and a half formed of a light-shielding film for shielding exposure light and a semi-transmissive film for partially transmitting the exposure light, formed on a transparent substrate. A multi-gradation photomask having a transfer pattern having a transmissive region, wherein the semi-transmissive layer has a transmittance having wavelength dependence in the wavelength region of i-g line, and the translucent region is in the range of 0.075 to 0.085. When the exposure optical system has a numerical aperture, a coherency of 0.5 to 1.0 and a wavelength region of i to g lines, the transmittance in which the wavelength dependence is substantially not generated in the wavelength region of the i to g lines is obtained. It is characterized by including the area of the dimension shown.

In the pattern transfer method according to the third aspect of the present invention, a light-transmitting region, a light-shielding region, and a half by patterning a light-shielding film for shielding exposure light and a semi-transmissive film for partially transmitting the exposure light, respectively, formed on a transparent substrate. A pattern transfer method for transferring a transfer pattern to a layer to be processed by irradiating exposure light with an exposure machine using a multi-tone photomask having a transfer pattern having a light transmission region, wherein the semi-transmissive film is a wavelength region of the exposure light. Has a transmittance having a wavelength dependence, and the exposure optical condition of the exposure machine is characterized in that the wavelength dependence of the transmittance is substantially not generated in the translucent region having a predetermined dimension.

The manufacturing method of the thin film transistor which concerns on the 4th structure of this invention is characterized by patterning a thin film transistor by the said pattern transfer method.

EFFECTS OF THE INVENTION [

The multi-gradation photomask of the present invention has at least a light-transmitting region, a light-shielding region, and a semi-transmissive region formed by a light shielding film for shielding exposure light and a semi-transmissive film partially transmitting the exposure light, formed on a transparent substrate. A multi-gradation photomask provided with a transfer pattern, wherein the semi-transmissive film has a transmittance having wavelength dependence in a wavelength region of exposure light, and the semi-transmissive region is an exposure optical of an exposure machine used at the time of transferring the transfer pattern. It includes an area having a dimension exhibiting a transmittance in which the wavelength dependence is substantially not generated under the conditions, so that the pattern design becomes finer, or even if the required precision of the resist pattern obtained by the mask becomes higher, it is optimized for the exposure machine. It is easy to use a mask under the conditions. Moreover, according to the pattern transfer method using the multi-gradation photomask of this invention, stable resist pattern formation can always be performed and accurate patterning can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows an example of the apparatus which reproduces the exposure conditions of an exposure machine.

2 shows a pattern of narrow areas;

3 is a characteristic diagram showing wavelength dependence of transmittance;

4 (a) and 4 (b) show channel profiles with respect to effective transmittance.

5 (a) and 5 (b) show the structure of a multi-gradation photomask.

6A to 6F are views for explaining mask exposure of TFTs.

<Mode for carrying out the invention>

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail with reference to an accompanying drawing.

Until now, the transmittance | permeability of the transflective film which comprises the translucent area | region was prescribed | regulated to the transmittance | permeability peculiar to the film | membrane determined by the film | membrane and exposure light irrespective of a pattern shape. In the case of setting the film material and thickness of the transflective film on the basis of the prescribed transmittance in this way, there is no particular problem when the area of the transflective area is sufficiently large with respect to the resolution of the exposure machine, and the wavelength of the exposure light is constant. However, when the area or width of the semi-transmissive region becomes small, the transmittance of the semi-transmissive region differs from the transmittance inherent in the semi-transmissive membrane due to the influence of the light blocking portion and the transmissive portion adjacent to the semi-transmissive region. May be a value.

For example, in the multi-gradation photomask for thin film transistors, the region corresponding to the channel portion is a semi-transmissive region, and the region corresponding to the adjacent source and drain is constituted by the light shielding portion. In this photomask, as the dimension (width) of the channel portion is reduced, the boundary with the adjacent light shielding portion is applied under actual exposure conditions, and the exposure light transmittance of the channel portion is lower than that of the semi-transmissive film. Here, the film transmittance of the semi-permeable membrane is defined by the ratio of the irradiation amount of the exposure light and the transmission amount in a sufficiently wide region in which the film is formed on the transparent substrate, and is determined by the composition and the film thickness of the film. A sufficiently wide region refers to a region in which the transmittance is not substantially changed by the change in the area of the region.

In addition, although the wavelength of the exposure light of a general exposure machine extends from i line | wire to g line | wire, the actual exposure conditions are not uniform, but the spectral characteristic changes with each exposure machine or even the same exposure machine with time. If the spectral characteristics are different, that is, the wavelengths included in the exposure light are different, the resolutions are different. Therefore, even in the same pattern shape, the transmittance of the semi-transmissive region under the actual exposure conditions is different.

In recent thin film transistors (TFTs), by reducing the width of the channel portion in comparison with the prior art, for example, increasing the operating speed of the liquid crystal with respect to liquid crystal driving, or increasing the brightness of the liquid crystal by reducing the size of the channel portion, etc. The technique has been proposed and it is expected that the pattern will be finer or the required precision of the resist pattern to be obtained will be further higher. In such a situation, the present inventors do not consider the transmittance including the pattern shape, the difference in the wavelength of the light source, and the like, not the transmissivity inherent in the transflective film, for the area having a small area or width of the photomask. It was thought that the desired resist pattern could not be formed.

Therefore, the present inventors pay attention to the fact that the pattern obtained when the exposure to the photomask is actually exposed to the photomask under the exposure conditions of the exposure machine is performed by the imaging means to obtain a transfer pattern image including factors such as a pattern shape and a difference in wavelength of the light source. Based on this transfer pattern, it was found that the film material and thickness of the transflective film in the translucent region can be determined.

As mentioned above, as an apparatus which reproduces the exposure conditions of an exposure machine, the apparatus shown in FIG. 1 is mentioned, for example. This apparatus comprises a light source 1, an illumination optical system 2 for irradiating light from the light source 1 to the photomask 3, and an objective lens system 4 for forming an image passing through the photomask 3. And the imaging means 5 for imaging the image obtained through the objective lens system 4.

The light source 1 emits a light beam having a predetermined wavelength, and for example, a halogen lamp, a metal halide lamp, a UHP lamp (ultra high pressure mercury lamp), or the like can be used.

The illumination optical system 2 guides the light from the light source 1 and irradiates the photomask 3 with light. This illumination optical system 2 is provided with the aperture mechanism (opening aperture 7) in order to make numerical aperture NA variable. It is preferable that this illumination optical system 2 is provided with the visual field stop 8 for adjusting the irradiation range of the light in the photomask 3. Light passing through the illumination optical system 2 is irradiated to the photomask 3 held by the mask holder 3a. This illumination optical system 2 is disposed in the case 13a.

The photomask 3 is held by the mask holder 3a. The mask holder 3a supports the lower end of the photomask 3 and the vicinity of the side edges of the photomask 3 while the main plane of the photomask 3 is substantially vertical, and tilts the photomask 3. It is fixed and kept. This mask holder 3a is capable of holding a large size (eg, a main plane having a size of 1220 mm x 1400 mm and a thickness of 13 mm) and a photomask 3 having various sizes. In addition, substantially vertical means that the angle from the vertical shown by (theta) in FIG. 1 is within about 10 degrees. Light irradiated to the photomask 3 passes through the photomask 3 and enters the objective lens system 4.

The objective lens system 4 includes, for example, a first lens group (simulator lens) 4a which receives light passing through the photomask 3 and applies infinity correction to the light beam to form parallel light, and It consists of the 2nd lens group (imaging lens) 4b which forms the light beam which passed through the 1st lens group. The simulator lens 4a is provided with an aperture mechanism (opening aperture 7), and the numerical aperture NA is variable. The light beam passing through the objective lens system 4 is received by the imaging means 5. This objective lens system 4 is disposed in the case 13b.

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

In this apparatus, since the numerical aperture of the illumination optical system 2 and the numerical aperture of the objective lens system 4 are respectively 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: coherence) can be varied.

Moreover, in this apparatus, the control means which has the calculation means 11 and the display means 12 which perform image processing, an operation, the comparison with a predetermined threshold value, and display with respect to the picked-up image obtained by the imaging means 5, etc. The movement operation means 15 which changes the position of 14 and the case 13a is provided. For this reason, predetermined control is performed by the control means 14 using the obtained captured image or the light intensity distribution obtained based on this, and the picked-up image under the conditions using other exposure light, or light intensity distribution and transmittance | permeability. Can be obtained.

In the apparatus shown in Fig. 1 having such a configuration, the NA and sigma 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.

MEANS TO SOLVE THE PROBLEM The present inventors acquired the following knowledge, when the transmittance | permeability was examined and reproduced by changing the exposure conditions of the exposure machine using the apparatus shown in FIG. In this case, a MoSi film (a film having a transmittance of 52% by g-rays) was used as the semi-transmissive film, and the channel pattern shown in FIG. 2 was used as the narrow region. The pattern shown in FIG. 2 is a pattern in which the transflective area 21 is located in the center part, and the light shielding area 22 which consists of chromium films is located in the both sides of the transflective area 21. As shown in FIG. That is, the semi-transmissive region 21 corresponds to the channel region (about 5 mu m in width) of the TFT, and the light shielding region 22 corresponds to the source and drain regions. In addition, g line | wire, h line | wire, and i line | wire were used as a source. The result is shown in FIG. In FIG. 3, the solid line represents the inherent transmittance of the film, and the broken line represents the transmittance in the channel region. In addition, the transmittance | permeability in a channel area | region is a transmittance | permeability when the exposure conditions of an exposure machine are reproduced with NA as 0.080 and (sigma) value as 0.9 in the apparatus shown in FIG. 3 is a figure which shows the tendency of the wavelength dependence of a transmittance | permeability, The numerical value in FIG. 3 is an example, It is not limited to this.

As can be seen from FIG. 3, the inherent transmittance of the film has a wavelength dependency (about 4% in g-line to i-line). That is, as the wavelength becomes longer, the transmittance increases. On the other hand, about the transmittance | permeability (transmittance obtained under the exposure conditions in actual exposure machine: effective transmittance | permeability) in a channel area | region, it becomes flat without almost wavelength dependence. Thus, the absence of wavelength dependence on the transmittance in the channel region can be considered as follows.

According to Rayleigh's equation d = k? (Λ / NA) (d: resolution line width, k: coefficient, λ: wavelength, NA: aperture degree), the shorter the wavelength, the smaller the resolution line width (the higher the resolution). 4A and 4B are diagrams showing channel profiles of the pattern shown in FIG. 2. Fig. 4A shows a channel profile (low resolution) when NA = 0.88 and sigma = 0.9, and Fig. 4B shows a channel profile (high resolution) when NA = 0.15 and sigma = 1.0. Indicates. Here, as can be seen from Fig. 4A, in low resolution, the effective transmittance is substantially the same (about 0.45) for g line, h line, and i line. On the other hand, at high resolution, the effective transmittance of g line is the highest (about 0.53), the effective transmittance of h line is high (about 0.50), and then the effective transmittance of i line is high (about 0.48). As can be seen from (a) and (b) of FIG. 4, the decrease in the effective transmittance due to the difference in resolution has the largest g line (0.53-0.45 = 0.08), followed by the larger h line (0.50). -0.45 = 0.05), followed by the larger i line (0.48-0.45 = 0.03).

The actual transmittance in the channel region is a transmittance (effective transmittance) obtained based on the image picked up by the apparatus shown in FIG. 1, and a transmittance in which the width and the optical conditions (NA, σ values) are considered. The effective transmittance in the channel region (semi-transmissive region) varies depending on its dimensions and optical conditions such as NA and σ. As described above, in the narrow region, the effective transmittance tends to be lowered. The fall amount of this effective transmittance is so large that it is a long wavelength side. In addition, as effective transmittance | permeability, it can be set as the transmittance | permeability of the part which has the maximum value in the light intensity distribution which permeate | transmits a semi-transmissive area | region. This correlates with the minimum value of the resist residual film value which arises in a semi-transmissive area, for example, when the resist pattern of a positive resist is formed on a to-be-transferred body using this photomask.

As described above, the decrease in the effective transmittance tends to increase as the wavelength becomes longer, as indicated by the broken line in FIG. 3. As for the effective transmittance in which the pattern dimensions and the optical conditions are considered, the result is that the transmittance becomes almost flat over the exposure wavelength.

Based on the above-described findings, the inventors of the present invention have found that the effective transmittance is constant at a source of an arbitrary range of wavelengths in a semi-transmissive region of a specific dimension under specific optical conditions, and the present invention has been made. Thereby, it becomes easy to use a photomask in an optimal state irrespective of the exposure wavelength characteristic of an exposure machine, and can form patterns on a to-be-processed layer stably and correctly. In particular, in a multi-gradation photomask for pattern transfer of a flat panel display using a plurality of sources as an exposure light source, it is very effective that the effective transmittance is constant at a source of an arbitrary range of wavelengths.

That is, the core of the present invention has at least a light-transmitting region, a light-shielding region, and a semi-transmissive region formed by a light shielding film for shielding exposure light and a semi-transmissive film partially transmitting the exposure light, formed on a transparent substrate. And a semitransmissive film having a wavelength dependence in the wavelength region of said exposure light, and said semitransmissive region being said wavelength dependent under exposure optical conditions of an exposure machine used for transferring said transfer pattern. The multi-gradation photomask including a region having a width exhibiting a substantially non-transmittable transmittance makes it easy to use the photomask in an optimal state irrespective of the exposure wavelength characteristic of the exposure machine, thereby stably and accurately Pattern formation on a process layer.

The multi-gradation photomask according to the present invention has a light-transmitting region, a light-shielding region, and a semi-transmissive region formed by a light shielding film for shielding exposure light and a semi-transmissive film partially transmitting the exposure light, formed on a transparent substrate. It has a transfer pattern.

A glass substrate etc. are mentioned as a transparent substrate. Moreover, as a light shielding film which shields exposure light, metal silicide films, such as metal films, such as a chromium film, a silicon film, a metal oxide film, and a molybdenum silicide film, etc. are mentioned. As the semi-transmissive film that partially transmits the exposure light, an oxide of chromium, nitride, carbide, oxynitride, oxynitride carbide, metal silicide or the like can be used. In particular, metal silicide films such as chromium oxide films, chromium nitride films, and molybdenum silicide films are preferred. This is because the above-described suitable wavelength dependence (inclination of characteristics) of the transmittance of the semi-permeable membrane is easily obtained by adjusting the composition and the film thickness. By forming the light shielding film and the semi-transmissive film on the transparent substrate, it is possible to form a transfer pattern having a light transmitting region, a light blocking region, and a semi-transmissive region.

The semi-transmissive film has a transmittance having a wavelength dependency in the wavelength region of the exposure light. This wavelength dependence is a dependence of the increase in transmittance as the wavelength becomes longer, and is represented by a characteristic line having a transmittance difference of 1% or more, more preferably 3% or more in the wavelength range of i to g lines included in the exposure light. desirable. As a range of preferable transmittance difference (tilt), it is 1%-15%, More preferably, it is 1%-10%, More preferably, it is 3-7%. When the transmittance of the semi-permeable membrane is in such a transmittance difference (tilt), the pattern region "having transmittance in which wavelength dependence does not substantially arise" of the present invention is more easily obtained. Moreover, it is preferable that the transmittance | permeability of a semi-transmissive film is 20%-80% in the wavelength range of i line | wire to g line | wire contained in exposure light. More preferably, the transmittance of the semipermeable membrane is 20% to 60%. This is because, when the semi-transmissive film having such transmittance is used, the remaining film value of the resist pattern obtained in the layer to be processed becomes appropriate by the processing process of the layer to be processed.

The semi-transmissive region constituted of the semi-transmissive film includes a region having a dimension showing a transmittance in which the wavelength dependency of the semi-transmissive film is substantially not generated under the exposure optical conditions of the exposure machine used in transferring the transfer pattern. Here, the exposure optical conditions include at least the wavelength of the light source of the exposure machine, the numerical aperture (NA), and preferably the coherence (σ: ratio of the numerical aperture of the illumination optical system of the exposure machine to the numerical aperture of the projection optical system). It includes more.

In addition, the transmittance | permeability which does not produce the wavelength dependence of a semi-transmissive film substantially means the effective transmittance | permeability which the wavelength dependency of the inherent transmittance | permeability does not produce substantially at the time of actual exposure, For example, in the wavelength region of i line | wire g line | wire, It is preferable that the change range of the transmittance | permeability is 1% or less, More preferably, it is 0.5% or less. This means that the above-mentioned effective transmittance becomes substantially flat as shown in FIG. The dimension indicating the transmittance in which the wavelength dependence of the semi-transmissive film is not substantially generated means that the effective transmittance obtained when exposed by the exposure apparatus or the apparatus shown in FIG. 1 in which exposure conditions are set based thereon is shown in FIG. 3. As mentioned, the dimension of a pattern becomes substantially flat. In such a case, since the resist pattern formed on the layer to be processed is formed in a constant shape without being affected by individual differences or changes in the light source of the exposure machine over time, it contributes to stabilization of the processing process of the layer to be processed.

In addition, the semi-transmissive film has a transmittance having wavelength dependence in the wavelength region of i-g line, and the semi-transmissive region has a numerical aperture within the range of 0.075-0.085, coherency of 0.5-1.0 and i-line. When it exposes by the exposure optical system which has a wavelength region of-g line | wire, it includes the area | region of the dimension which shows the transmittance which the said wavelength dependency does not produce substantially in the wavelength region of the i line | wire-g line | wire. For example, the channel region of a transistor is mentioned as an area | region which has the width | variety which shows the transmittance which substantially does not produce the wavelength dependence of a transflective film. It is preferable that the width | variety of this channel area is 1.0 micrometer-5.0 micrometers. In particular, the width of the channel region is preferably 2.0 µm to 4.0 µm. In the TFT used for driving the liquid crystal, the channel width is in the direction of miniaturization in order to further improve the speed and brightness of the liquid crystal, and the present invention is particularly useful in a multi-gradation photomask for producing such a fine channel.

The effective transmittance in the present invention is a transmittance including not only the inherent transmittance of the film but also the dimensions of the pattern, or factors such as CD (Critical Dimension) and optical conditions (light source wavelength, opening degree,? Value, etc.). Even in a narrow area, the transmittance reflects the actual exposure environment. For this reason, if the width in a pattern is specified and the effective transmittance of the width is calculated | required, it becomes possible to determine the thickness of a semi-permeable film based on the effective transmittance. In addition, when the effective transmittance of any region is specified, the film material or transmittance of the semi-permeable membrane can be determined so as to achieve the effective transmittance.

In the above-described multi-gradation photomask, as shown in FIG. 5A, a semi-transmissive film 32 is formed on the light shielding area A and the semi-transmissive area B of the transparent substrate 31, and the semi-transmissive film ( The structure which forms the light shielding film 33 on the light shielding area A of 32, and the light shielding film 33 and the semi-transmissive film on the light shielding area A of the transparent substrate 31 as shown in FIG. (32) is laminated | stacked, and there exists a structure which forms the transflective film 32 on the translucent area | region B of the transparent substrate 31. FIG.

The structure shown in FIG. 5A can be produced as follows, for example. That is, the photomask blank formed by laminating | stacking the semi-transmissive film 32 and the light shielding film 33 in this order on the transparent substrate 31 is prepared, and is formed in the light shielding area A and the semi-transmissive area B on this photomask blank. A resist pattern of a corresponding region is formed, and the exposed light shielding film 33 is etched using this resist pattern as a mask. Next, using the resist pattern or the light shielding film 33 as a mask, the exposed semi-transmissive film 32 is etched to form a light transmissive region. Next, a resist pattern is formed in the area | region containing at least the light shielding area A, and the exposed light shielding film 33 is etched using this resist pattern as a mask.

The structure shown in FIG. 5B can be produced as follows, for example. That is, the photomask blank in which the light shielding film 33 was formed on the transparent substrate 31 is prepared, the resist pattern of the area | region corresponding to the light shielding area A is formed on this photomask blank, and this resist pattern is used as a mask. The exposed light shielding film 33 is etched. Next, after removing the resist pattern, the semi-transmissive film 32 is formed on the entire surface of the transparent substrate 31. Then, a resist pattern is formed in a region corresponding to the translucent region B (or the translucent region B and the light shielding region A), and the exposed semitransmissive film 32 is etched using the resist pattern as a mask.

As described above, by patterning the light shielding film for shielding the exposure light and the transflective film for partially transmitting the exposure light, a transfer pattern having a light transmission region, a light shielding region, and a semi-transmissive region is formed. A gradation photomask is obtained. In the pattern transfer using such a multi-gradation photomask, the semi-transmissive film has a transmittance having a wavelength dependency in the wavelength region of the exposure light when the transfer pattern is transferred to the processing layer by irradiating the exposure light by the exposure machine. Under the conditions described above, the exposure optical condition of the exposure machine is a condition such that the wavelength dependency of the transmittance is not substantially generated in the semi-transmissive region having a predetermined dimension.

EMBODIMENT OF THE INVENTION Hereinafter, the Example performed in order to clarify the effect of this invention is demonstrated.

<Examples>

A photomask blank formed by laminating in this order a MoSi film, which is a semi-transmissive film having a transmittance of 50% with respect to a source g line, and a chromium film, which is a light shielding film, is prepared on the glass substrate. A resist pattern of a region corresponding to the region was formed, and the exposed chromium film was wet etched using an etching solution mainly composed of dicerium ammonium nitrate as an etchant, using the resist pattern as a mask. Next, using the chromium film as a mask and using hydrofluoric acid and an oxidant etching solution as an etchant, the exposed MoSi film was wet etched to form a transmissive region. The etching solution may be any of an etching solution containing at least one fluorine compound selected from hydrofluoric acid, hydrofluoric acid and ammonium bifluoride, and at least one oxidizing agent selected from hydrogen peroxide, nitric acid and sulfuric acid. . Next, a resist pattern was formed in the area | region containing at least the light shielding area | region, and the chromium film which was exposed was wet-etched using the etching liquid which uses this resist pattern as a mask as an etchant as a main component of ammonium dicerium nitrate.

Thus, the multi-gradation photomask 100 of the Example which has the light transmission area | region 102, the light shielding area | region 101, and the transflective area | region 103 as shown in FIG.6 (b) was produced. This multi-gradation photomask includes a pattern of TFTs having a channel width of 5.0 mu m. In addition, the thickness of the semi-permeable membrane was attached to the apparatus shown in FIG. 1, the test mask produced as mentioned above was calculated | required, and the effective transmittance was calculated | required based on this effective transmittance.

Next, as shown in Fig. 6B, the resist pattern was exposed using the produced multi-gradation photomask. As a to-be-exposed object, the laminated body shown to Fig.6 (a) was used. That is, the laminate includes a gate insulating film 203, a first semiconductor film (a-Si) 204, and a second semiconductor film (N + a-Si) on a glass substrate 201 having a gate electrode 202. 205, the source drain metal film 206, and the positive photoresist film 207 are sequentially formed.

The first resist pattern 207A was formed by exposing and developing the positive photoresist film 207. This first resist pattern 207A covered the channel portion, the source drain formation region and the data line formation region of the TFT, and the TFT channel portion formation region was thinner than the source drain formation region.

Next, as shown in FIG. 6C, the source drain metal film 206, the second and first semiconductor films 205 and 204 are etched using the first resist pattern 207A as a mask. . Next, as shown in Fig. 6D, the resist film 207 is reduced as a whole by ashing with oxygen to remove the thin resist film in the channel portion forming region, thereby removing the second resist pattern 207B. Formed. Thereafter, as shown in Fig. 6E, the source / drain metal film 206 is etched using the second resist pattern 207B as a mask to form source / drain 206A and 206B. Next, the second semiconductor film 205 was etched. Thereafter, as shown in FIG. 6F, the remaining second resist pattern 207B was peeled off.

When the pattern of the obtained TFT channel part was observed by AFM (atomic force microscope), it became a pattern as designed. Moreover, since this pattern shape can be formed stably regardless of the light source characteristic of an exposure machine, it could always be used stably as an optimal mask with respect to an exposure machine. This is considered to be because the effective transmittance is obtained using the apparatus shown in Fig. 1, and a multi-gradation photomask is produced based on the effective transmittance, so that a desired resist pattern is formed even in a narrow region such as a TFT channel portion.

This invention is not limited to the said embodiment, It can change suitably and can implement. The number, size, processing procedure, etc. of the member in the said embodiment are an example, It can change and implement in various ranges within the range which exhibits the effect of this invention. In addition, as long as it does not deviate from the range of the objective of this invention, it is possible to change suitably and to implement.

<Code description>

1: light source

2: illumination optical system

3: photomask

4: objective lens system

4a: simulator lens

4b: imaging lens

5: imaging means

6: wavelength selection filter

7, 7a: aperture aperture

8: field of view aperture

11: calculation means

12 display means

13a, 13b: case

14 control means

15: moving operation means

31: transparent substrate

32: semi-permeable membrane

33: light shielding film

Claims (12)

A multi-gradation photomask having a light-transmitting region having a light-transmitting region, a light-shielding region, and a semi-transmissive region formed on a transparent substrate, the light-shielding film shielding exposure light and a semi-transmissive film partially transmitting the exposure light. , The intrinsic transmittance of the semi-transmissive film has a wavelength dependency having a slope such that the transmittance increases as the wavelength becomes longer in the wavelength region of the i-g line, and further, The pattern size of the semi-transmissive region is about the wavelength region when exposed by an exposure optical system having a numerical aperture within a range of 0.075 to 0.085, a coherency of 0.5 to 1.0, and a wavelength region of i to g lines. It is a multi-gradation photo mask in which the wavelength dependence of the transmittance is set to a dimension flattening, whereby the wavelength dependence of the transmittance substantially does not occur during transfer. The multi-gradation photo mask, wherein the transmittance in which the wavelength dependence is not substantially generated is a transmittance change range of 1% or less in the wavelength range of the i line to the g line. delete delete The method of claim 1, The intrinsic transmittance of the semi-transmissive film is 20% to 80% in the wavelength region of i-g line included in the exposure light. The method of claim 1, The wavelength dependence in the intrinsic transmittance of the semi-transmissive film is a dependence of increasing the transmittance as the wavelength becomes longer, and is represented by a characteristic line having a transmittance difference of 1% or more in the wavelength region of i-g line included in the exposure light. Multi-gradation photomask, characterized in that. The method of claim 1, The semi-transmissive film is a chromium oxide film, a chromium nitride film, or a metal silicide film. The method of claim 1, The multi-gradation photomask is for manufacturing a thin film transistor, and the semi-transmissive region corresponds to the channel region of the transistor. The method of claim 7, wherein A multi-gradation photomask, wherein the channel region has a width of 1.0 µm to 5.0 µm. delete delete By using the multi-gradation photomask of claim 1, The pattern transfer method which transfers the said transfer pattern to a to-be-processed layer by irradiating the exposure light by an exposure machine. The thin film transistor is patterned by the pattern transfer method of claim 11, wherein the thin film transistor is manufactured.

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