JP5319193B2 - Multi-tone photomask for manufacturing liquid crystal display device, method for manufacturing multi-tone photomask for manufacturing liquid crystal display device, and pattern transfer method - Google Patents

Abstract

PURPOSE: A multi-gray scale photomask and a pattern transfer method are provided to obtain light density distribution including a flat region by increasing the transmissivity between a light-shielding layer and a half transmissive film. CONSTITUTION: A half transmissive film and a light-shielding layer are formed on a transparent substrate. The light shielding portion(2), a light-transmitting portion(4), and a half light-transmitting portion(3) are formed by light-shielding layer pattern and the half transmissive film. The half light-transmitting portion is located between two separated light shielding portions. The half light-transmitting portion is interposed between two light shielding portions and a first half transmissive film. The width of the half light-transmitting portion inserted between the light shielding portion is 3um~6um.

Description

  The present invention relates to a multi-tone photomask and pattern transfer method used for manufacturing an image sensor, a liquid crystal display (hereinafter referred to as LCD), a semiconductor device, and the like.

  Currently, in the field of LCDs, thin film transistor liquid crystal displays (hereinafter referred to as TFT-LCDs) are easier to make thinner and have lower power consumption than CRTs (cathode ray tubes). Commercialization is progressing rapidly. The TFT-LCD has a TFT substrate having a structure in which TFTs are arranged in pixels arranged in a matrix, and a color filter in which red, green, and blue pixel patterns are arranged in correspondence with each pixel. It has a schematic structure superimposed under the intervention of. The TFT-LCD has a large number of manufacturing steps, and the TFT substrate alone is manufactured using 5 to 6 photomasks. Under such circumstances, a method of manufacturing a TFT substrate using four photomasks has been proposed (for example, Non-Patent Document 1).

In this method, the number of masks to be used is reduced by using a multi-tone photomask (hereinafter referred to as a photomask) having a light shielding portion, a light transmitting portion, and a semi-light transmitting portion. Here, the semi-transparent portion means that when a pattern is transferred to a transfer object using a mask, the amount of exposure light transmitted therethrough is reduced by a predetermined amount, and the photoresist film on the transfer object after development is developed. A portion that controls the amount of remaining film is referred to, and a photomask including such a semi-transparent portion together with a light-shielding portion and a translucent portion is referred to as a multi-tone photomask.
“Monthly FP Intelligence”, May 1999, p. 31-35

  In recent years, especially with the miniaturization of the TFT channel pattern, an increasingly fine pattern is required even in a multi-tone photomask. For example, a multi-tone photomask in which a portion corresponding to the source and drain of the TFT is formed as a light shielding portion, and a portion corresponding to a channel portion located between the source and drain is formed as a semi-transparent portion is used. (See FIG. 3B). When the portion corresponding to the channel width (Channel Length) in the TFT channel portion pattern of the multi-tone photomask, that is, the width of the semi-transparent portion between the light shielding films is about 7 μm, the exposure apparatus when using this mask is used. FIG. 12 shows the light intensity distribution of the transmitted light of the semi-transparent part. As an exposure light source of the exposure machine, for example, a light source in a wavelength region of 350 nm to 450 nm including g-line (wavelength 436 nm) and i-line (wavelength 365 nm) is used. In accordance with the light intensity distribution, the resist film on the transfer object is exposed, and then a resist pattern is formed through a resist development process. For this reason, the light intensity distribution in the semi-transparent portion of the gray tone mask is reflected in the shape of the resist pattern to be formed.

  On the other hand, when the shape of the pattern of the semi-translucent portion is further miniaturized and the width of the semi-translucent portion between the light shielding films is, for example, 3.6 μm, the semi-translucent portion in the exposure machine when using this mask is used. The light intensity distribution of the transmitted light of the part is as shown in FIG. As can be seen from FIG. 13, the shape of the light intensity distribution curve is different from the shape of the light intensity distribution curve shown in FIG. 12, and there is almost no plateau region (flat portion) near the peak.

  In general, in the semi-transparent part near the boundary with the light-shielding part, a predetermined inclination is drawn by light diffraction according to the resolution of the exposure machine, but when the dimension (width) of the semi-transparent part is reduced to, for example, 6 μm or less, Since the influence of diffraction becomes so large that it cannot be ignored with respect to the exposure light wavelength and the resolution of the exposure machine, it is considered that the light intensity distribution shape has almost no plateau region as shown in FIG. For this reason, when exposure is performed using such a mask, the resist film on the transfer object is exposed, and the resist pattern formed through the development process is transferred with a normal distribution shape having almost no plateau region. . In general, it is desirable that the resulting resist pattern has a cross section that rises perpendicular to the substrate. However, in the above resist pattern, a tapered cross section is formed at the edge, and the taper angle is a conventional one with a large channel width. It tends to be smaller (inclination direction). When etching is performed on a transfer object using a resist pattern with a normal distribution type having such a tapered cross-sectional shape and almost no plateau region, the pattern size of the processed layer formed by etching changes. The pattern size control is very difficult, and the line width accuracy may be deteriorated.

  The present invention has been made in view of such points, and even if the pattern shape of the semi-translucent portion is miniaturized, the resist pattern on the transferred body facilitates dimensional control in subsequent processing steps. Thus, an object of the present invention is to provide a multi-tone photomask and a pattern transfer method that can improve line width accuracy.

The multi-tone photomask of the present invention has a semi-transparent film and a light-shielding film on a transparent substrate, and the light-shielding part, the translucent part, and the semi-transparent part are formed by the pattern of the semi-transparent film and the light-shielding film. A multi-gradation photomask formed, wherein the multi-gradation photomask is positioned between two light-shielding portions that are spaced apart in plan view, and has a width of 6 μm or less formed with a semi-transparent film. A semi-transparent portion, the semi-transparent portion is provided between a first semi-transparent region having a first transmittance, the two light-shielding portions and the first semi-transparent region, wherein a second translucent areas with a high second transmittance than the first transmittance, have a, wherein the second translucent areas, high transmittance than the first translucent areas semipermeable An optical film is formed, and a phase difference of the semi-translucent portion with respect to the translucent portion is 60 ° or less .

Multi-tone photomask of this invention, in a flat plane when viewed, the in light transmission intensity distribution curve of the light having a wavelength band within a wavelength range of 350nm~450nm for semi transparent portion, the transparent portion of the exposure light transmitted When the rate is 100% and the region including the center in the width direction of the semi-translucent portion and the variation amount of the transmittance is 2% or less is defined as the plateau region, the plateau region exceeds 50% of the width. It is characterized by being.

  According to these configurations, the transmittance of the boundary portion between the light shielding film and the semi-transparent film, particularly the boundary portion below the resolution limit under the exposure conditions for the multi-tone photomask, can be relatively increased. Thus, the light intensity on both sides of the peak in the light intensity distribution can be increased, and as a result, a shape including a plateau region can be realized. For this reason, even if the shape of the pattern of the semi-translucent portion is miniaturized, it is easy to control the size of the resist pattern on the transferred body, and the line width accuracy can be improved.

  In the multi-tone photomask of the present invention, it is preferable that the width of the second semi-transparent region is a dimension that is not more than a resolution limit in an exposure condition for the multi-tone photomask.

  In the multi-tone photomask of the present invention, the difference between the transmissivity of the first semi-transparent region and the transmissivity of the second semi-transparent region is preferably 10% to 50%. .

  In the multi-tone photomask of the present invention, the first semi-transparent region is formed by stacking a first semi-transparent film and a second semi-transparent film formed on a transparent substrate. The film is made of the first or second semi-transparent film formed on the transparent substrate, so that the second semi-transparent region has higher transmittance than the first semi-transparent region. Can do.

In the multi-tone photomask of the present invention, the first semi-transparent region is composed of a semi-transparent film having a first thickness formed on a transparent substrate, and the second semi-transparent region is on the transparent substrate. The second semi-transparent region can be made to have a higher transmittance than the first semi-transparent region.

In the multi-tone photomask of the present invention, the multi-tone photomask preferably forms a resist pattern having portions with different thicknesses on a resist film on a transfer target.
The multi-tone photomask of the present invention is preferably a photomask for manufacturing a thin film transistor substrate.

In the method for producing a multi-tone photomask of the present invention, a semi-transparent film and a light-shielding film are provided on a transparent substrate, and a light-shielding part, a light-transmitting part, and a pattern of the semi-transparent film and the light-shielding film, In the method of manufacturing a multi-tone photomask in which a semi-transparent portion is formed, the semi-transparent film having a width of 6 μm or less, in which a semi-transparent film is formed between the two light-shielding portions apart from each other in plan view The semi-transparent portion is provided between the first semi-transparent region having the first transmittance, the two light-shielding portions, and the first semi-transparent region, respectively. A second semi-transparent region having a second transmissivity higher than the transmissivity, and a semi-transparent film having a transmissivity higher than that of the first semi-transparent region is formed in the second semi-transparent region. by the by the phase difference der Rukoto below 60 ° with respect to the transparent portion of the semi-transparent portion, the exposure light transmitted through the semi-transparent portion The flat portion of the rate curve is increased.

  In the pattern transfer method of the present invention, a film thickness different from that of the light-shielding portion or the light-transmitting portion is formed on a portion corresponding to the semi-light-transmitting portion in a resist film formed on the transfer object using the multi-tone photomask. The latent image on which the resist film is formed is transferred to the resist film.

  The multi-tone photomask of the present invention has a semi-transparent portion located between two light-shielding portions spaced apart in plan view, and the semi-transparent portion has a first semi-transparent portion having a first transmittance. A light region, and a second semi-transparent region provided between the two light-shielding portions and the first semi-transparent region, and having a second transmittance higher than the first transmittance. Alternatively, in plan view, in a light transmission intensity distribution curve of light including a wavelength region within a wavelength range of 350 nm to 450 nm with respect to the semi-transparent part, the exposure light transmittance of the translucent part is set to 100%, and the semi-transparent part is obtained. When a region including the center in the width direction of the optical part and having a transmittance fluctuation amount of 2% or less is defined as a plateau region, the plateau region exceeds 50% of the width. When the resist pattern on the transfer target is flat enough When sharp edges cross rising is obtained. And in the etching process using this resist pattern, the dimension control of a to-be-processed object becomes easy, and line width accuracy can be improved.

  In the multi-tone photomask having a semi-transparent portion with a fine pattern by the light-shielding film, the present inventor makes the slope of the light intensity distribution as shown in FIG. We considered the shape to include. For example, a method of providing a semi-transparent part having a desired transmittance by arranging a light-shielding pattern below the resolution limit of the exposure machine in the semi-transparent part can be considered. In this case, it is possible to some extent to obtain a light intensity portion having a relatively flat portion in the semi-transparent portion. However, in this case, the light intensity of the transmitted light is lowered, and it is difficult to freely select the exposure amount of the transferred material to the resist film. Here, the appropriate transmissivity of the semi-translucent portion is a desired exposure amount of the mask user within a range of 10% to 70% when the exposure light transmittance in the transmissive portion is 100%. Preferably, it is in the range of 20% to 60%, more preferably in the range of 30% to 60%. In such a range, it is important to be able to select a wide range so as to suit the processing conditions such as the resist material and exposure environment applied by the mask user. Therefore, if the gap size of the light-shielding pattern of the semi-translucent portion is increased in order to obtain the light intensity, it is resolved at the time of exposure, and the light intensity distribution having a shape including the plateau region cannot be obtained. That is, in the conventional multi-tone photomask of the fine light-shielding pattern type, it is difficult to obtain both the pattern miniaturization of the semi-translucent portion and the light intensity distribution having a shape including the plateau region.

  The present inventor has intensively studied the light intensity distribution having a shape without a plateau region and the pattern of the semi-transparent film between the light-shielding films. Focusing on the boundary portion below the resolution limit in the exposure conditions for the photomask, and relatively increasing the transmittance of this boundary portion, the light intensity on both sides of the peak in the light intensity distribution can be increased, resulting in a plateau It was found that a shape including a region can be realized.

  That is, the essence of the present invention has a semi-transparent portion located between the two light-shielding portions spaced apart in plan view, and the semi-transparent portion is a first semi-transparent region having a first transmittance. And a second semi-transparent region provided between the two light-shielding portions and the first semi-transparent region and having a second transmittance higher than the first transmittance. Even if the shape of the pattern of the semi-translucent portion is miniaturized, the shape of the resist pattern on the transferred object can be easily controlled in size during etching of the processed object, and the line width accuracy can be improved. It is to realize a multi-tone photomask that can be used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a plan view showing a pattern in a multi-tone photomask according to an embodiment of the present invention. The multi-tone photomask is used in a manufacturing process of a thin film transistor (TFT), a color filter, a plasma display panel (PDP), or the like of a liquid crystal display device (LCD), for example. This is for forming a resist pattern having portions having different film thicknesses on the resist film on the transfer object by irradiation with exposure light. The pattern in the multi-tone photomask shown in FIG. 1 includes semi-transparent portions 12 and 13 sandwiched between the light shielding portions 11. Specifically, when the multi-tone photomask is used, the light shielding portion 11 that shields the exposure light (transmittance is approximately 0%), the light transmitting portion that transmits the exposure light approximately 100%, and the transmittance of the exposure light. And a semi-translucent portion that is reduced to about 20% to 60%. The light-shielding part 11, the light-transmitting part, and the semi-light-transmitting part are obtained by patterning a semi-light-transmitting film and a light-shielding film formed on a transparent substrate such as a glass substrate, respectively. As shown in FIG. 1, the pattern is arranged from the left in the order of a light transmitting part, a light shielding part, a semi-light transmitting part, a light shielding part, and a light transmitting part. Hereinafter, the width of the semi-translucent portion or the like refers to the width in the arrangement direction. Note that the pattern shapes of the light-shielding portion 11 and the semi-transparent portion shown in FIG. 1 are merely representative examples, and the present invention is not limited to this.

  Examples of the material constituting the translucent film include a chromium compound, MoSi, Si, W, and Al. Among these, chromium compounds include chromium oxide (CrOx), chromium nitride (CrNx), chromium oxynitride (CrOxN), chromium fluoride (CrFx), and those containing carbon and hydrogen. Examples of the material constituting the light shielding film include Cr, Si, W, and Al. The transmittance of the light shielding part 11 is set by selecting the film material and film thickness of the light shielding film. Further, the transmittance of the semi-translucent portion is set by selecting the film material and the film thickness of the semi-transparent film.

  The semi-transparent portion is provided between the first semi-transparent region 12 having the first transmissivity, and the light-shielding portion 11 and the first semi-transparent region 12, and the second transmissivity is higher than the first transmissivity. And a second semi-transparent region 13. As described above, by providing the second semi-transparent region 13 having the second transmittance higher than the first transmittance outside the first semi-transparent region 12, the outer side (both sides of the first semi-transparent region 12). ) Area can be relatively increased. The width of the second semi-translucent region 13 is preferably a dimension that is equal to or smaller than the resolution limit in the exposure conditions for the multi-tone photomask. By doing so, the shape of the second semi-transmission region is not resolved as it is, but the transmissivity of the semi-transmission part can be increased and the rise of the light intensity distribution can be made steep. That is, as shown in FIG. 2, the multi-tone photomask has a shape including a plateau region P in a semi-transparent portion of the light intensity distribution. Here, including the plateau region P in the semi-transparent portion of the light intensity distribution means that in the light transmission intensity distribution curve of light including a wavelength region in the range of 350 nm to 450 nm with respect to the semi-transparent portion, When the exposure light transmittance is 100%, the region including the center in the width direction of the semi-translucent portion and the variation amount of the transmittance is 2% or less is the plateau region, the plateau region exceeds 50% of the width A It means that.

  As described above, the width of the second semi-transparent region 13 is preferably a dimension that is equal to or smaller than the resolution limit in the exposure condition for the multi-tone photomask, and is determined according to the dimension of the semi-translucent portion. For example, for a semi-transparent portion having a width of 6 μm or less, it is preferable that the width of the second semi-transparent region 13 is 2 μm or less, preferably 1 μm or less and 0.1 μm or more. The exposure conditions in this case are the exposure light source wavelength, the resolution of the exposure machine to be used, and the like. The multi-tone photomask of the present invention is suitable for an exposure wavelength of 350 nm to 450 nm (i line to g line). In the present invention, a remarkable effect can be obtained when the exposure apparatus applied to the multi-tone photomask has an optical system with a numerical aperture NA of about 0.1 to 0.07.

  Furthermore, it is preferable to consider the width of the second semi-transmissive region 13 with respect to the width A of the semi-transmissive portion so that the light intensity distribution of the transmitted light has a shape including the plateau region P in the semi-transmissive portion. One of the widths of the second semi-transparent regions 13 is preferably (2/5) A or less (when both sides are added, (4/5) A or less). More preferably, one of the widths of the second semi-transmissive regions 13 is (1/4) A or less. In particular, one is preferably (1/10) A (both sides (1/5) A) or more. The widths of the second semi-transparent regions 13 on both sides of the first semi-transparent region 12 are preferably substantially the same, but may be different as long as the effects of the present invention are not impaired.

  The width of the semi-translucent portion sandwiched between the light shielding portions 11 is preferably 3 μm to 6 μm in consideration of the operation speed of the TFT to be obtained and the processability of the multi-tone mask. Further, the difference between the transmittance of the first semi-transmissive region 12 and the transmittance of the second semi-transmissive region 13 is as shown in FIG. 2 based on the resolution of the optical system of the large mask exposure apparatus. In consideration of obtaining a bell-shaped transmittance curve having a flat portion, it is preferably 10% to 50%. Further, the phase difference of the semi-translucent part with respect to the translucent part is preferably 60 ° or less in consideration of the fact that dark lines are preferably not formed above and below the channel part.

  Light intensity distribution received by a resist film when exposed to light using a three-tone photomask having a transfer pattern including a light-shielding part, a light-transmitting part, and a semi-light-transmitting part and transferring the pattern to the resist film on the transfer target Is approximately in the shape shown in FIG. FIG. 3A shows a transmittance curve of the semi-transparent part B sandwiched between the light shielding parts A shown in FIG. Therefore, the resist pattern formed on the transfer body has a shape that is upside down in FIG. 3A, and the mortar-shaped minimum value corresponds to, for example, the resist residual film value (Rt). When a thin film is to be processed by etching using such a resist pattern, it is preferable that the cross section of the resist pattern is substantially rectangular, that is, the rising edge is vertical. This is because when the resist pattern is reduced and this is used as a mask, the lower layer thin film can be etched with high dimensional accuracy. For this reason, for example, it is conceivable to use a resist material having a sensitive photosensitivity with respect to a change in light intensity. However, such a resist material is not desirable because the residual film value changes due to a slight change in the exposure amount, and eventually the shape of the resist pattern becomes unstable.

  Therefore, it is required to increase the verticality (steepness of rising) of the cross-sectional shape of the resist pattern with the performance of the mask without changing the photosensitive characteristics of the resist. That is, when considering the resist pattern shape of a portion having a narrow line width, for example, a pattern corresponding to the channel portion of the TFT (a pattern having a semi-translucent portion sandwiched between light shielding portions), the larger the area of the bottom region, the better. The wall surface is desirably a vertical surface that rises as steeply as possible. As in the present invention, by using a plurality of semi-transparent portions having different film transmittances, a semi-transparent portion having a desired transmittance can be designed, and the degree of design freedom is widened.

  Although it does not specifically limit about the film | membrane structure of the 1st semi-transmission area | region 12 and the 2nd semi-transmission area | region 13 in a semi-transmission part, For example, the structure shown to Fig.4 (a)-(c) is mentioned. In the configuration shown in FIG. 4A, the semi-transparent film 14 is formed on the transparent substrate 10, and the thickness of the semi-transparent film 14 is different in the semi-transparent portion of the semi-transparent film 14. That is, the film thickness of the second semi-transparent region 13 is relatively thin (high transmittance), the film thickness of the first semi-transparent region 12 is relatively thick (low transmittance), and the light shielding unit 11 blocks light. It is the structure which provided the film | membrane. That is, the semi-transparent portion having this configuration is composed of one film, and the first semi-transparent region 12 and the second semi-transparent region 13 are formed by changing the thickness thereof.

  In the configuration shown in FIG. 4B, a semi-transparent film 14 is formed on the transparent substrate 10, and another semi-transparent region is formed on the first semi-transparent region 12 of the semi-transparent portion of the semi-transparent film 14. The light film 15 is provided, and the light shielding part 11 is provided with a light shielding film. That is, the semi-transparent portion of this configuration is composed of two semi-transparent films 14, 15, and the second semi-transparent region 13 is configured by one semi-transparent film 14 (high transmittance). The first semi-transparent region 12 is composed of a laminated film of two semi-transparent films 14 and 15 (low transmittance).

  In the configuration shown in FIG. 4C, the semi-transparent film 14 is formed on the transparent substrate 10, and another semi-transparent region is formed on the first semi-transparent region 12 of the semi-transparent portion of the semi-transparent film 14. The light film 15 is provided, and the light shielding part 11 is provided with a light shielding film. That is, the semi-transparent portion of this configuration is composed of two semi-transparent films 14 and 15, and the second semi-transparent region 13 is configured by one semi-transparent film 15 (high transmittance). The first semi-transparent region 12 is composed of a laminated film of two semi-transparent films 14 and 15 (low transmittance).

  The structure shown in FIG. 4A can be manufactured by the steps shown in FIGS. 5A and 5B, for example. In addition, the manufacturing method of the structure shown to Fig.4 (a) is not limited to these methods. Here, the material of the translucent film 14 is molybdenum silicide, and the material of the light shielding film is chromium. 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. 5A, a semi-transparent film 14 is formed on a transparent substrate 10, a light-shielding film is formed thereon, and then the semi-transparent film 14 in the second semi-transparent region 13 is exposed. The light shielding film is patterned so as to do this. Next, as shown in FIG. 5B, the semi-transparent film 14 is etched using the patterned light-shielding film as a mask to reduce the film thickness. Thereafter, the light shielding film in the first semi-transmissive region 12 is removed.

  The structure shown in FIG. 4B can be manufactured by, for example, the steps shown in FIGS. In addition, the manufacturing method of the structure shown in FIG.4 (b) is not limited to these methods. Here, the material of the semi-transparent film 14 is molybdenum silicide, the material of the semi-transparent film 15 is chromium oxide, and the material of the light shielding film is chromium. 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 semi-transparent film 14 is formed on the transparent substrate 10, a light-shielding film is formed thereon, and then the semi-transparent film 14 in the semi-transparent portion is exposed. The light shielding film is patterned. Next, as shown in FIG. 6B, a semi-transparent film 15 is formed on the entire surface, and a resist film 16 is formed thereon. Thereafter, the first semi-transparent region 12 is exposed to cure the resist (reference numeral 16a in the figure). Next, as shown in FIG. 6C, the resist is developed, and the semi-transmissive film 15 is etched using the remaining resist film as a mask.

  The structure shown in FIG. 4C can be manufactured by the steps shown in FIGS. 7A to 7G, for example. In addition, the manufacturing method of the structure shown in FIG.4 (c) is not limited to these methods. Here, the material of the semi-transparent film 14 is molybdenum silicide, the material of the semi-transparent film 15 is chromium oxide, and the material of the light shielding film is chromium. 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. 7A, a semi-transparent film 14 is formed on the transparent substrate 10, a light-shielding film is formed thereon, and then the semi-transparent film 14 in the semi-transparent portion is exposed. The light shielding film 11 is patterned. Next, as shown in FIG. 7B, a resist film 16 is formed on the entire surface. Thereafter, the first semi-transparent region 12 is exposed to cure the resist (reference numeral 16a in the figure). Next, as shown in FIG. 7C, the resist is developed, and as shown in FIG. 7D, the semi-transmissive film 14 is etched using the remaining resist film as a mask.

  As shown in FIG. 7E, a semi-transparent film 15 is formed on the entire surface, and a resist film 16 is formed thereon. Thereafter, the region including the semi-translucent portion is exposed to cure the resist (reference numeral 16b in the figure). Next, as shown in FIG. 7F, the resist is developed, and as shown in FIG. 7G, the semi-transmissive film 15 is etched using the remaining resist film as a mask.

  Such a light intensity distribution in the semi-transparent portion of the multi-tone photomask of the present invention is formed by exposing the resist film of the transfer object using the multi-tone photomask of the present invention and developing the same. This is also reflected in the shape of the resist pattern. That is, using the multi-tone photomask of the present invention, a resist film having a film thickness different from that of the light shielding portion or the light transmitting portion is formed in a portion corresponding to the semi-light transmitting portion in a resist film formed on a transfer target. In the case where a latent image to be formed is transferred to the resist film, in a portion corresponding to the semi-transparent portion having a width A in a multi-tone photomask, development corresponding to the light-transmitting portion or the light-shielding portion. When the subsequent resist film thickness is set to 100%, and the region including the center in the width direction of the developed resist film corresponding to the semi-translucent portion and having a film thickness variation of 2% or less is defined as the plateau region, A resist pattern having a width exceeding 50% of the width A can be formed.

  Therefore, when the semi-transparent portion is transferred to the resist film of the transfer object using the multi-tone photomask of the present invention, the resist has a flat portion with a substantially constant film thickness and a desired film thickness range. A pattern can be formed. As a result, it becomes easier to control the dimensions of the pattern formed on the transfer object, and the line width accuracy of the pattern is improved.

  Further, according to the present invention, in addition to the effects described above, the pattern of the semi-translucent portion is higher than that of the conventional semi-translucent portion (fine pattern type multi-tone photomask) in which the fine pattern is formed by the light shielding film. The permissible line width range of the (semi-transparent film forming part formed of a semi-transparent film) is wide, and the line width management at the time of mask manufacture is easy. Therefore, there is a great advantage in mass production. Further, when a mask user considers a processing process to be applied (resist material, development conditions, etching conditions, etc.), a mask having a desired transmittance for obtaining a resist pattern having a desired height is obtained. be able to. In this design, the transmittances of the two types of semi-transparent regions included in the semi-transparent portion may be set to desired values, respectively. Further, according to the present invention, it is not necessary to prepare an extremely high resolution (optical NA) exposure device for device manufacturing, and even with the use of the current exposure device, it can sufficiently cope with the miniaturization of the TFT channel portion. This is a great advantage in device manufacturing.

Next, examples performed for clarifying the effects of the present invention will be described.
(Example)
In the pattern shown in FIG. 1, the width of the semi-translucent portion is 3.6 μm, and the width of the second semi-transparent region 13 is 0.8 μm (the width of the first semi-transparent region 12 is 2.0 μm). A multi-tone photomask having a semi-translucent portion was manufactured by the above method. At this time, the configuration of the pattern is the configuration shown in FIG. 4B, chromium is used as the material constituting the light shielding film, MoSi is used as the material constituting the second semi-transparent region 13, and the first semi-transparent light is used. Chromium oxide was used as a material constituting the other semi-transparent film of the laminated film constituting the region 12. Further, the thickness of the semi-transparent film was adjusted so that the transmittance of the first semi-transparent region 12 was 45% and the transmittance of the second semi-transparent region 13 was 25%. In addition, the transmittance | permeability of a semi-transparent film here is the transmittance | permeability intrinsic | native to a film | membrane, and is not the effective transmittance mentioned later.

Such multi-tone photo curves of effective transmission rate T _A when performing a pattern transferred to the resist film on the transfer body by using a mask FIG 8 (a), (b) ( FIG. 8 (b) This is shown in FIG. Effective transmittance can be cited as one that directly controls the range of the remaining film value of the resist pattern actually formed. By managing the remaining film value by managing the effective transmittance, a resist pattern having a desired remaining film value can always be stably obtained even when the pattern has a narrow width.

  Here, the effective transmittance is a predetermined value when the transmittance of the exposure light that actually passes through the mask is 100% when the transmittance of the light transmitting portion (wide enough for the resolution of the exposure machine) is 100%. Partial transmittance. When the pattern width is reduced, the transmittance changes due to the influence of diffraction and the influence of adjacent patterns, but the transmittance reflects such an influence. Effective transmittance is an index that takes into account the optical conditions and pattern design in addition to the inherent transmittance of the film, and therefore accurately reflects the status of the remaining film value. Is appropriate. Note that the effective transmittance of the predetermined semi-translucent portion may be the transmittance of the portion having the maximum value in the light intensity distribution transmitted through the semi-translucent portion. This is because, for example, when a positive resist pattern is formed on the transfer object using this photomask, there is a correlation with the minimum value of the residual resist film value generated in the semi-translucent portion. Such range management is particularly effective when, for example, the width of the channel region of the thin film transistor is 5 μm or less.

  As a means for measuring the above effective transmittance, it is preferable to reproduce or approximate the exposure conditions by the exposure machine. An example of such a device is the device shown in FIG. This apparatus is obtained through a light source 21, an irradiation optical system 22 that irradiates the photomask 23 with light from the light source 21, an objective lens system 24 that forms an image of light transmitted through the photomask 23, and the objective lens system 24. The imaging unit 25 mainly captures the captured image.

  The light source 21 emits a light beam having a predetermined wavelength. For example, a halogen lamp, a metal halide lamp, a UHP lamp (ultra-high pressure mercury lamp), or the like can be used. For example, an exposure machine using a mask can be used with a light source having spectral characteristics approximating.

  The irradiation optical system 22 guides light from the light source 21 and irradiates the photomask 23 with light. The irradiation optical system 22 includes an aperture mechanism (aperture stop 27) in order to make the numerical aperture (NA) variable. The irradiation optical system 22 preferably includes a field stop 26 for adjusting the light irradiation range in the photomask 23. The light that has passed through the irradiation optical system 22 is irradiated onto the photomask 23 held by the mask holder 23a. The irradiation optical system 22 is disposed in the housing 33.

  The photomask 23 is held by a mask holder 23a. The mask holder 23a supports the vicinity of the lower end portion and the side edge portion of the photomask 23 with the main plane of the photomask 23 being substantially vertical, and holds the photomask 23 in a tilted manner. It is like that. The mask holder 23a 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 23 and various sizes. It has become. Note that “substantially vertical” means that the angle from the vertical indicated by θ in FIG. 9 is within about 10 degrees. The light irradiated on the photomask 23 passes through the photomask 23 and enters the objective lens system 24.

  The objective lens system 24 receives, for example, a first group (simulator lens) 24a in which light that has passed through the photomask 23 is incident and this light flux is corrected to infinity to obtain parallel light, and the light flux that has passed through the first group. It is composed of a second group (imaging lens) 24b that forms an image. The simulator lens 24a is provided with a diaphragm mechanism (aperture diaphragm 27), and its numerical aperture (NA) is variable. The light beam that has passed through the objective lens system 24 is received by the imaging means 25. The objective lens system 24 is disposed in the housing 33.

  The imaging unit 25 captures an image of the photomask 23. As this imaging means 25, for example, an imaging device such as a CCD can be used.

  In this apparatus, since the numerical aperture of the irradiation optical system 22 and the numerical aperture of the objective lens system 24 are variable, the ratio of the numerical aperture of the irradiation optical system 22 to the numerical aperture of the objective lens system 24, that is, The sigma value (σ: coherency) can be varied.

  Further, in this apparatus, calculation means 31 for performing image processing, calculation, comparison with a predetermined threshold value, display, and the like for the captured image obtained by the imaging means 25, a control means 34 having a display means 32, and a housing 33. A moving operation means 35 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. 9 having such a configuration, the NA and σ values are variable, and the radiation source of the light source can be changed, so that the exposure conditions of various exposure machines can be reproduced. In general, in order to easily approximate an exposure apparatus for a large-sized photomask for manufacturing a liquid crystal device or the like, irradiation light with the same light intensity by i-line, h-line, and g-line is used, and NA is 0 as an exposure optical system. The condition that the coherency σ that is the NA ratio of the irradiation system and the objective system is about 0.8 may be applied.

  Considering the above, in the present invention, based on the pattern shape and the semi-transparent film to be used (preferably considering the light source wavelength distribution of the exposure machine and the conditions of the optical system), the transmission of the photomask to be actually obtained It is preferable to design the photomask by calculating the transmittance (transmittance in a sufficiently large area) of the semi-transparent film to be used from the transmittance (effective transmittance).

  As can be seen from FIGS. 8A and 8B, the resist film after development corresponding to the light-transmitting portion or the light-shielding portion in the portion corresponding to the semi-transparent portion having the width A in the multi-tone photomask. When the thickness of the plateau region is defined as a plateau region having a thickness of 100% and including a center in the width direction of the developed resist film corresponding to the semi-translucent portion and having a thickness variation of 2% or less, the width of the plateau region is It is considered that a resist pattern exceeding 50% of the width A can be formed.

(Comparative example)
In the pattern shown in FIG. 1, the width of the semi-transparent portion is 3.6 μm, and the semi-transparent portion is made of a semi-transparent film (MoSi film) having a transmittance of 40%. A multi-tone photomask was manufactured. Figure 8 curve of effective transmission rate T _A when performing a pattern transferred to the resist film on the transfer member by using such a multi-tone photomask (a), shown in (b). As can be seen from FIGS. 8A and 8B, the resist pattern has a shape having no plateau region in the portion corresponding to the semi-transparent portion having the width A in the multi-tone photomask.

Next, an example of a manufacturing process of a TFT substrate using the multi-tone mask of the present invention will be described with reference to FIGS. A metal film for a gate electrode is formed on the glass substrate 41, and the gate electrode 42 is formed by a photolithography process using a photomask. Next, a gate insulating film 43, a first semiconductor film 44 (a-Si), a second semiconductor film 45 (N ⁺ a-Si), a source / drain metal film 46, and a positive photoresist film 47 are formed (FIG. 10 (a)). Next, as shown in FIG. 10B, the positive photoresist film 47 is exposed and developed using a multi-tone photomask 50 having a light shielding portion 51, a light transmitting portion 52, and a semi-light transmitting portion 53. As a result, a first resist pattern 47a that covers the TFT channel portion and the source / drain formation region and the data line formation region and whose channel portion formation region is thinner than the source / drain formation region is formed.

  Next, as shown in FIG. 10C, the source / drain metal film 46, the second semiconductor film 45, and the first semiconductor film 44 are etched using the first resist pattern 47a as a mask. Next, as shown in FIG. 11A, the thin resist film in the channel portion formation region is removed by ashing with oxygen to form a second resist pattern 47b. Next, as shown in FIG. 11B, using the second resist pattern 47b as a mask, the source / drain metal film 46 is etched to form the source / drains 46a and 46b, and then the second semiconductor film 45 is etched. Finally, as shown in FIG. 11C, the remaining second resist pattern 47b is peeled off.

  As described above, when the TFT pattern is transferred to the resist film using the multi-tone photomask of the present invention, a resist pattern having a flat portion with a substantially constant film thickness and a desired film thickness range can be formed. Therefore, it becomes easy to control the dimension of the TFT pattern formed on the transfer object, and the line width accuracy of the TFT pattern is improved.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. The number, size, processing procedure, and the like of the members in the above embodiment are merely examples, and various changes can be made within the range where the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

It is a top view which shows the multi-tone photomask which concerns on embodiment of this invention. It is a figure which shows the light transmission intensity distribution curve with respect to wavelength 365nm -436nm of the semi-translucent part in the multi-tone photomask which concerns on embodiment of this invention. (A) is a figure which shows the transmittance | permeability curve, (b) is a figure which shows the pattern containing a light-shielding part and a semi-translucent part. (A)-(c) is a figure which shows the structure of the multi-tone photomask which concerns on embodiment of this invention. (A), (b) is a figure for demonstrating the manufacturing process of the structure shown to Fig.4 (a). (A)-(c) is a figure for demonstrating the manufacturing process of the structure shown in FIG.4 (b). (A)-(g) is a figure for demonstrating the manufacturing process of the structure shown in FIG.4 (c). (A), (b) is effective transmission when pattern transfer is performed on a resist film on a transfer object using the multi-tone photomask according to the embodiment of the present invention and the conventional multi-tone photomask. It is a figure which shows a rate. It is a figure which shows schematic structure of the apparatus for measuring an effective transmittance | permeability. (A)-(c) is a figure for demonstrating the manufacturing process of the TFT substrate using the multi-tone photomask which concerns on embodiment of this invention. (A)-(c) is a figure for demonstrating the manufacturing process of the TFT substrate using the multi-tone photomask which concerns on embodiment of this invention. It is a figure which shows the light transmission intensity distribution curve with respect to wavelength 365nm -436nm of the semi-translucent part in the conventional multi-tone photomask. It is a figure which shows the light transmission intensity distribution curve with respect to wavelength 365nm -436nm of the semi-translucent part in the conventional multi-tone photomask.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Glass substrate 11 Light-shielding part 12 1st semi-light-transmitting area 13 2nd semi-light-transmitting area 14, 15 Semi-light-transmitting film 16 Resist film

Claims (9)

A multi-storey for manufacturing a liquid crystal display device having a semi-transparent film and a light-shielding film on a transparent substrate, wherein the light-shielding part, the translucent part, and the semi-translucent part are formed by a pattern of the semi-transparent film and the light-shielding film. A toned photomask,
The multi-tone photomask has a semi-transparent part with a width of 3 μm to 6 μm located between two spaced apart light shielding parts in plan view,
The semi-translucent portion has a first semi-transparent region having a first transmittance,
Between the two light-shielding portions and the first semi-transparent region, each is a second semi-transparent region having a second transmittance higher than the first transmittance, and i line to g line The second semi-transparent region having a dimension not larger than the resolution limit under the exposure conditions by the exposure apparatus for manufacturing a liquid crystal display device including the wavelength range of Placed in
In the second semi-transparent region, a semi-transparent film having a higher transmittance than the first semi-transparent region is formed,
A multi-tone photomask for manufacturing a liquid crystal display device , wherein a phase difference of the semi-translucent portion with respect to the translucent portion is 60 ° or less. Before having a light source comprising a wavelength range within the range of i-line ~g lines for Kihan transparent portion, when the light transmission intensity distribution curve of the exposure conditions with a liquid crystal display device manufacturing exposure apparatus in plan view, the magnetic When the exposure light transmittance of the light portion is 100%, the region including the center in the width direction of the semi-light-transmitting portion and the variation amount of the transmittance is 2% or less is defined as the plateau region, the plateau region has the width. 2. The multi-tone photomask for manufacturing a liquid crystal display device according to claim 1, wherein the multi-tone photomask is more than 50%. The liquid crystal according to claim 1 or claim 2, wherein the difference between the transmittance of the transmittance and the second translucent areas of said first translucent areas is 10% to 50% Multi-tone photomask for manufacturing display devices . The first semi-transparent region is formed by stacking a first semi-transparent film and a second semi-transparent film formed on a transparent substrate, and the second semi-transparent film is formed on the transparent substrate. by becoming the first or second HanToruHikarimaku, the second translucent areas may be any of claims 1 to 3, wherein a higher transmittance than the first translucent areas A multi-tone photomask for manufacturing a liquid crystal display device according to 1 . The first semi-transparent region is a semi-transparent film having a first thickness formed on a transparent substrate, and the second semi-transparent region is a semi-transparent film having a second thickness formed on the transparent substrate. by becoming the transparent film, the second translucent areas, the liquid crystal display device according to any one of claims 1 to 3, wherein the higher transmittance than the first translucent areas Multi-tone photomask for manufacturing . The multi-tone photomask, the resist film on the transfer member, characterized in that to form a resist pattern with a different portion of the film thickness, according to any one of claims 1 to 5 Multi-tone photomask for manufacturing liquid crystal display devices . The multi-tone photomask for manufacturing a liquid crystal display device according to any one of claims 1 to 6 , wherein the multi-tone photomask is a photomask for manufacturing a substrate for a thin film transistor. Manufacture of a multi-tone photomask having a semi-transparent film and a light-shielding film on a transparent substrate, and having a light-shielding part, a translucent part, and a semi-transparent part formed by the pattern of the semi-transparent film and the light-shielding film In the method
In a plan view, the semi-transparent portion having a width of 3 μm to 6 μm, in which a semi-transparent film is formed between the two light-shielding portions that are separated from each other,
The semi-translucent portion has a first semi-transparent region having a first transmittance,
Between the two light-shielding portion and the first translucent areas, respectively, a second translucent areas with a high second transmittance than the first transmittance, and i-line ~g line The flat part of the light transmission intensity distribution of the semi-translucent part is larger in the second semi-transparent area having a dimension not larger than the resolution limit under the exposure condition by the exposure apparatus for manufacturing a liquid crystal display device including the wavelength range of placed,
In the second semi-transparent region, a semi-transparent film having a higher transmittance than the first semi-transparent region is formed,
Wherein by the phase difference with respect to the transparent portion of the semi-light transmitting portion is 60 ° or less, the multi-use liquid crystal display device manufacturing is characterized by increasing the flat part of the exposure light transmittance curve of the semi-transparent portion A method of manufacturing a gradation photomask. Using a multi-tone photomask for liquid crystal display device manufactured according to claims 1 to claim 7, the portion corresponding to the semi-transparent portion of the resist film formed on the transfer member, the light shielding portion Or transferring a latent image on which a resist film having a film thickness different from that of the light transmitting portion is formed to the resist film using an exposure apparatus for manufacturing a liquid crystal display device including a wavelength region of i-line to g-line. A characteristic pattern transfer method.

Images