JP5545994B2 - Multi-tone photomask manufacturing method and pattern transfer method for display device manufacturing - Google Patents

Description

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

  Conventionally, a photolithography process has been used in the manufacture of electronic devices such as liquid crystal display devices. In the photolithography process, a predetermined pattern is transferred using a photomask to a resist film formed on a transfer target to be etched, and the resist film is developed to form a resist pattern. The transferred object is etched using the pattern as a mask.

  As a photomask, it is known to use a multi-tone photomask to expose a resist film on a transfer target to form a resist pattern having a step (for example, Patent Document 1). A multi-tone photomask having a semi-transparent part that transmits part of the exposure light in addition to the light-shielding part and the translucent part can change the amount of the exposure light that passes through the mask by changing the part of the exposure light. On top of this, a first resist pattern having a remaining film value that differs depending on the part can be formed. Thereafter, the second resist pattern can be formed by reducing the entire first resist pattern by ashing. This is very useful because the number of photolithographic steps in the manufacturing process can be reduced and the number of photomasks used in the manufacturing process can be reduced. On the other hand, in such a multi-tone photomask manufacturing method, in order to form a resist pattern with a desired shape, the pattern shape of the semi-translucent portion, the film quality (film material) formed on the semi-transparent portion The determination of the film thickness is important.

JP 2006-268035 A

  When a photolithography process is performed using a multi-tone photomask, the shape of the first resist pattern to be formed is controlled by controlling the line width of thin film etching using the second resist pattern used in the next process as a mask. In many cases, however, the shape control of the first resist pattern is performed based on empirical rules. In particular, the factors that greatly affect thin film etching in the shape of the resist pattern are the line width and film thickness value of the resist pattern. Therefore, in developing the resist film after exposure, aiming that a desired resist residual film remains at the time when a desired line width is obtained (to obtain a resist residual film value in a desired range) Etching conditions were repeatedly determined and the optimum conditions were determined.

  However, when the optimum conditions are determined by repeatedly determining the conditions in each etching step, there is a problem that reproducibility and stability are poor and time is required. In addition, since the reproducibility and stability of the photolithography process are impaired as described above, there is a problem that adversely affects performance stability and manufacturing cost of an electronic device such as a liquid crystal display device.

  The present invention has been made in view of the above points, and a method and a pattern for manufacturing a multi-tone photomask capable of accurately controlling the shape of a resist pattern and improving reproducibility and stability in a photolithography process. Another object is to provide a transfer method.

  One embodiment of the present invention has a predetermined transfer pattern including a light-transmitting portion, a light-shielding portion, and a semi-light-transmitting portion that transmits part of exposure light, and a resist formed on a transfer target to be etched. This is a multi-tone photomask manufacturing method that transfers a predetermined pattern to a film and turns the resist film into a resist pattern that serves as a mask for etching, and grasps the resist characteristics of the resist used for the resist film with respect to the exposure light A step of determining an effective transmittance for the exposure light of the semi-transparent portion based on the resist characteristics, and a semi-transparent by patterning at least a light shielding film formed on the transparent substrate based on the effective transmittance Forming a portion.

  According to this configuration, the characteristics of the resist film used in the photolithography process are grasped in advance, and the multi-tone photomask is based on the effective transmittance of the semi-translucent portion determined in consideration of the shape of the resist pattern after development. Therefore, a multi-tone photomask capable of accurately controlling the shape of the resist pattern can be manufactured. Thereby, the reproducibility and stability of a photolithography process can be improved.

  In one aspect of the method for producing a multi-tone photomask of the present invention, the resist characteristic can be defined by a resist characteristic curve indicating a relationship between an exposure amount of exposure light and a film thickness of the resist with respect to the exposure amount.

  In one aspect of the method for producing a multi-tone photomask of the present invention, the film transmittance of the semi-transparent portion is determined based on the determined effective transmittance, the pattern shape of the semi-transparent portion, and the exposure conditions of the exposure machine. The semi-transparent portion can be formed based on the film transmittance of the semi-transparent portion. According to this configuration, during actual exposure, the transmittance of light that actually passes through the semi-transparent portion due to the pattern shape of the semi-transparent portion and the exposure conditions is suppressed from varying from the effective transmittance. It becomes possible.

  In one aspect of the method for producing a multi-tone photomask of the present invention, the semi-transparent portion is a light-shielding film pattern having a dimension not larger than the resolution limit of an exposure machine used for exposure of the multi-tone mask on a transparent substrate. Can be formed.

  In one embodiment of the method for manufacturing a multi-tone photomask of the present invention, the semi-transparent portion can be formed using a semi-transparent film formed on a transparent substrate.

  In one embodiment of the method for manufacturing a multi-tone photomask of the present invention, the effective transmittance of the semi-transparent portion is determined by the resist film of the resist pattern formed on the transferred body by the transmitted light of the semi-transparent portion. This can be done based on the film thickness reduction t with respect to the initial film thickness. According to this configuration, even when a positive resist is used, it is easy to design a photoresist because there is a correlation between the film reduction amount and the exposure amount.

  In one aspect of the method for producing a multi-tone photomask of the present invention, the semi-transparent portion of the multi-tone mask has a first semi-transparent portion and a second semi-transparent portion having different effective transmittances, and a resist. It can be set as the structure which has the process of determining the target effective transmittance | permeability of a 1st semi-transparent part and the target effective transmissivity of a 2nd semi-transparent part based on the characteristic, respectively.

In one aspect of the method for producing a multi-tone photomask of the present invention, a resist pattern for forming a target effective transmittance of the first semi-translucent portion on a transfer target by using the transmitted light of the first semi-transparent portion. The effective transmittance of the second semi-translucent portion is determined on the transferred object by the transmitted light of the second semi-transparent portion, based on the film thickness t ₁ with respect to the initial film thickness of the resist film. The resist pattern can be formed based on the film thickness t ₂ with respect to the initial film thickness of the resist film. According to this configuration, even when the resist film formed on the transfer target having a step is exposed through the multi-tone photomask, the resist pattern exposed through the first semi-transparent portion. And the remaining film value of the resist pattern exposed through the second semi-transparent portion can be made substantially the same.

  In one embodiment of the pattern transfer method of the present invention, a resist film on a transfer target is exposed to light using the multi-tone photomask manufactured by any of the manufacturing methods described above. A pattern is formed.

  In one embodiment of the pattern transfer method of the present invention, a resist film is formed on a transfer target having a step, and the resist film on the transfer target is exposed to light using a multi-tone photomask. A multi-tone photomask having a first semi-transparent portion and a second semi-transparent portion manufactured by the manufacturing method described above as a multi-tone photomask. The resist residual film value of the resist pattern formed on the transfer target having each step is formed to be approximately equal.

  According to one aspect of the present invention, characteristics of a resist film used in a photolithography process are grasped in advance, and the multi-level is based on the effective transmittance of a semi-translucent portion determined in consideration of the shape of a resist pattern after development. A multi-tone photomask that can accurately control the shape of the resist pattern can be manufactured in order to produce a toned photomask. In addition, by performing a photolithography process using such a multi-tone photomask, reproducibility and stability can be improved.

It is a figure explaining an example of the order of the manufacturing method of a multi-tone photomask. It is a figure explaining the case where a photolithography process is performed using a multi-tone photomask. It is a figure explaining the case where a photolithography process is performed using a multi-tone photomask. It is a figure explaining the manufacturing method of the electronic device using a multi-tone photomask. It is a figure explaining the manufacturing method of the electronic device using a multi-tone photomask. It is a figure explaining an example of the multi-tone photomask applied to the manufacturing method of an electronic device. It is a figure explaining a resist characteristic curve. It is a figure which shows arrangement | positioning and an effective transmittance | permeability of a semi-transmissive film.

(Embodiment 1)
FIG. 2 shows a case where a photolithography process is performed using a multi-tone photomask 100 having a predetermined transfer pattern including a light transmitting portion 102, a light shielding portion 103, and a semi-light transmitting portion 104 that transmits a part of exposure light. Show. The resist film 105 is formed on the transferred object 106 to be etched, and the resist film 105 is transferred to the transferred object 106 by transferring the pattern of the multi-tone photomask 100 to the resist film 105. The first resist pattern 107 can be used as a mask in the first etching process (see FIGS. 2A and 2B). Subsequently, the first resist pattern 107 is entirely reduced by ashing to form a second resist pattern 108 that serves as a mask in the second etching process of the transfer target 106 (see FIG. 2C). Desired patterning can be performed by etching the transferred object 106 using the second resist pattern 108 (see FIG. 2D).

  Hereinafter, an example of a method for manufacturing the multi-tone photomask 100 used in the photolithography process illustrated in FIG. 2 will be described.

  First, resist characteristics used for the resist film 105 formed on the transfer target 106 in a stage before the photolithography process (a stage before manufacturing a multi-tone photomask (before FIG. 2A)). (See FIG. 1 (step 1)).

  The resist characteristics can be grasped by grasping the film thickness of the resist with respect to the light (exposure light) applied to the resist film 105. Specifically, the resist characteristics can be defined by a resist characteristic curve showing the relationship between the exposure amount of exposure light and the resist film thickness with respect to the exposure amount.

  An example of a method for creating a resist characteristic curve will be briefly described. First, a resist film having a predetermined film thickness is formed on a substrate. Next, after the resist film is developed by irradiating the resist film with exposure light at a predetermined exposure amount, the amount of film reduction from the initial film thickness of the resist film after development is obtained. In this way, a resist characteristic curve can be created by determining the film thickness of the resist for each predetermined exposure amount. However, the method of creating the resist characteristic curve is not limited to this, and any method can be used as long as it can define the relationship between the exposure amount of light irradiating the resist and the film thickness of the resist with respect to the exposure amount. Good.

  In creating the resist characteristic curve, as exposure light, a condition imitating an exposure condition in an exposure apparatus in an actual photolithography process can be set. Here, imitating the exposure conditions means that the exposure wavelength is approximate, for example, when the exposure light has a wavelength range, the exposure wavelength with the highest light intensity is the same. Alternatively, for example, irradiation light including i-line, h-line, and g-line at a ratio of 1: 1: 1 may be selected as an approximation of actual exposure light. Simulating exposure conditions means that the optical system is approximate, for example, that the NA (numerical aperture) of the imaging system is substantially the same or σ (coherence) is substantially the same. Here, the case where the NAs are substantially the same is exemplified when the NA is within a range of ± 0.005 with respect to the NA of the actual exposure apparatus. The case where σ is substantially the same is exemplified when the σ is within a range of ± 0.005 with respect to σ of an actual exposure apparatus.

Next, when the resist film 105 is actually developed in the photolithography process to form the first resist pattern 107, the semi-transparent portion 104 region (the region exposed through the semi-transparent portion 104) is formed. A target film reduction amount t of the resist film 105 is determined (see FIG. 1 (step 2)). The target film reduction amount t of the resist film 105 only needs to be smaller than the initial film thickness value t ₀ of the resist film 105 and can be set as appropriate by the practitioner. Note that the reduction amount of the resist film 105 in the light shielding portion 103 region can be 0, and the reduction amount of the resist film in the light transmission portion 102 region can be t ₀ .

Next, the semi-light-transmitting portion 104 of the multi-tone photomask 100, determines the effective transmission rate _{T A} with respect to the exposure light (see FIG. 1 (step 3)). In this specification, the effective transmittance means the pattern shape (dimension or line width (CD (Critical Dimension)) and the optical conditions (optical wavelength, numerical aperture, σ value) of the pattern in addition to the film-specific transmittance. And the like, and the transmittance that reflects the actual exposure environment (effective transmittance that determines the amount of light that passes through the photomask and is irradiated). When the target effective transmittance of the part is determined and the pattern shape of the semi-transparent part and the optical conditions in the exposure environment are fixed, the semi-transparent part of the photomask can be designed based on this effective transmittance. It becomes possible.

The effective transmittance T _A is expressed by the following equation using the exposure amount E _L corresponding to the target reduction amount t of the resist film 105 obtained in step 2 above and the exposure amount E _T of the exposure light in the photolithography process. It can be obtained from (1). The exposure amount E _L corresponding to film reduction amount t of the resist film 105 can be obtained from the resist characteristic curve created in step 1, the exposure amount E _T is the exposure amount necessary for actual exposure in the photolithography process do it.

T _A = E _L / E _T (1)

By determining the effective transmission rate T _A of the semi-light-transmitting portion in the step 3, it is possible to determine the production conditions of the semi-light-transmitting portion 104 of the multi-tone photomask 100. When providing a plurality of semi-translucent portions having different effective transmission rate to each other in the multi-tone photomask 100, depending on the film reduction amount of each of the resist film of the semi-translucent regions, respectively determined effective transmission rate T _A do it.

Then, based on the obtained effective transmission rate T _A, to prepare a multi-tone photomask (see FIG. 1 (Step 4)). For example, by patterning at least a light-shielding film formed on a transparent substrate, a predetermined transfer including a translucent portion 102, a light-shielding portion 103, and a semi-transparent portion 104 that transmits a part of exposure light on the transparent substrate 101 A multi-tone photomask 100 having a pattern is manufactured. At this time, the transmittance of the semi-light-transmitting portion 104 is determined based on the effective transmission rate T _A obtained in Step 3.

The configuration of the semi-transparent portion 104 may be provided by using a semi-transparent film as a solid film, or a fine pattern is formed by patterning the light-shielding film or the semi-transparent film below the resolution limit under exposure conditions. May be provided. When forming a semi-light-transmitting portion 104 by HanToruHikarimaku, based on the effective transmission rate T _A was previously determined, it may be determined to be capable membrane permeability and the pattern shape realizing it. When forming a semi-light-transmitting portion in a fine pattern of the light-shielding film or HanToruHikarimaku, based on the effective transmission rate T _A was previously determined, it may be determined to be capable membrane permeability and the pattern shape realizing it. Note that the fine pattern may be formed by disposing a fine light-transmitting part and / or a light-shielding part in a semi-light-transmitting part made of a semi-light-transmitting film.

Through the above steps, a multi-tone photomask can be manufactured. In the present embodiment, in advance to understand the characteristics of the resist film used in the photolithography process, on the basis of the effective transmission rate T _A of the semi-light-transmitting portion, which is determined by considering the shape of the resist pattern after development multi-tone Since a photomask is manufactured, a multi-tone photomask capable of accurately controlling the shape of a resist pattern can be manufactured. Further, in this embodiment, when there is a film thickness (residual film value) of the resist pattern to be obtained on the transfer target after development, it is not based on the residual film value but from the initial film thickness of the resist film by development. A multi-tone photomask is designed based on the decreasing film thickness. In this way, designing a photomask based on the film thickness reduction makes it possible to design easily. This is because in the case of using a positive resist, there is a direct correlation between the film thickness reduction value and the exposure dose (there is no direct correlation between the remaining film value and the exposure dose).

(Embodiment 2)
In the present embodiment, specifically described for the case of producing a semi-light-transmitting portion of the multi-tone photomask based on the effective transmittance T _A determined in Step 3 of FIG. 1.

When forming a semi-light-transmitting portion of the multi-tone photomasks using HanToruHikarimaku to determine the membrane permeability of the semi-light-transmitting portion on the basis of the previously obtained effective transmission rate T _A, membrane permeability What is necessary is just to control the film quality and film thickness of a semi-transmissive film | membrane so that it may implement | achieve. In this specification, the film transmittance is a sufficiently large area (for example, 20 μm) with respect to the resolution limit under exposure conditions when a semi-transparent film is formed on a transparent substrate to form a semi-transparent region. □ or more) means the transmissivity of the semi-transparent region. Therefore, when the pattern shape of the semi-transparent part of the multi-tone photomask is sufficiently large, control the film quality and film thickness of the semi-transparent film as “effective transmittance ≒ film transmissivity of the semi-transparent part” By doing so, a photomask can be designed.

On the other hand, if a small pattern of the semi-light-transmitting portion (area and width is small), such as by considering the pattern shape and the optical conditions of the exposure light translucent portion, the effective transmission rate T _A It is preferable to reflect the film transmittance of the semi-translucent portion. This is because when the pattern shape of the semi-translucent portion is reduced, the transmittance of the semi-transparent portion changes during actual exposure due to the influence of diffraction of the exposure light generated at the end of the pattern of the semi-translucent portion. It is. That is, when forming a semi-light-transmitting portion of the photomask using HanToruHikarimaku, setting film transmittance of semi-light-transmitting portion to the same value as the effective transmittance T _A by controlling the film quality and film thickness , depending on the optical conditions such as the wavelength of the pattern shape and the exposure light semi-light-transmitting portion, it is if the effective transmission rate T _a to be obtained at the time of actual exposure can not be obtained. In this case, the film thickness reduction amount of the first resist pattern is different from a predetermined film thickness reduction amount t.

Therefore, as described above, the effective transmission rate T _A obtained in advance, and the pattern shape of the semi-light-transmitting portion, based on the exposure conditions apparatus determines the membrane permeability of the semi-light-transmitting portion, the By forming the semi-transparent portion based on the film transmittance, the transmittance of light that actually passes through the semi-transparent portion due to the pattern shape of the semi-transparent portion and the exposure conditions is obtained. it is possible to suppress that variation in transmittance from T _a (to approximate the actual transmission to be sought the transmittance of the transmitted light effective transmission rate T _a). Determining the membrane permeability of the semi-light-transmitting portion, in FIG. 1, it may be performed after determining the effective transmission rate T _A (after step 3).

Usually, as the pattern of the semi-transparent portion becomes finer or the wavelength of the exposure light becomes longer, the light intensity distribution of the actually transmitted light is lower than the film transmittance of the semi-transparent portion. Therefore, in the multi-tone photomask to be manufactured, when the pattern shape of the semi-transparent portion is small, the film transmittance of the semi-transparent film formed in the semi-transparent portion is set to the effective transmittance obtained in advance. Setting to be higher than T _A is effective.

  Note that, when the pattern shape of the semi-translucent portion is small, the determination of the film transmittance of the semi-translucent portion is performed in the predetermined pattern shape of the semi-transparent portion, and the effective corresponding to the film transmittance. The correlation with the transmittance can be grasped and determined based on the grasped correlation. For example, performing a test exposure on a test mask on which a predetermined test pattern is formed, acquiring a transmitted light pattern of the test mask by an imaging unit, and obtaining transmitted light pattern data based on the acquired transmitted light pattern; The correlation between the film transmittance and the effective transmittance in the pattern shape of the semi-translucent portion is grasped by performing the step of obtaining the effective transmittance of the test pattern under the exposure condition based on the transmitted light pattern data. be able to. Thereby, according to the obtained effective transmittance and the pattern shape of the semi-transparent portion, the film transmittance of the semi-transparent portion can be determined, and the film quality and film thickness to be formed in the semi-transparent portion can be determined. it can. Further, in the step of obtaining transmitted light pattern data, the light transmitting portion has a light shielding portion, a light transmitting portion, and a semi-light transmitting portion, and the pattern shape of the semi-light transmitting portion, the film quality or the film thickness of the semi-light transmitting portion is formed. Using a test mask with multiple test patterns with different light section characteristics, and using the multiple transmitted light pattern data obtained from the multiple test masks, the semi-transparent section characteristics and the effective corresponding to the semi-transparent section characteristics By grasping the correlation with the transmittance, it is possible to accurately determine the quality or thickness of the film formed in the semi-transparent portion based on the pattern shape of the semi-translucent portion and the obtained effective transmittance.

In addition, a database of the relationship between the semi-transmission part characteristics such as the pattern shape, film quality, and film thickness of the semi-transmission film and the effective transmittance corresponding to the semi-transmission part characteristic is prepared as a database. by performing a simulation based on the pattern shape and previously obtained effective transmission rate T _a of the optical unit, it is possible to determine the membrane permeability of the semi-light-transmitting portion. For example, a plurality of tests having a light-shielding portion, a light-transmitting portion, and a semi-light-transmitting portion and different semi-light-transmitting portion characteristics of the pattern shape of the semi-light-transmitting portion, the film quality or film thickness forming the semi-light-transmitting portion Test exposure is performed on the mask, the transmitted light patterns of these test masks are acquired by the imaging means, transmitted light pattern data is obtained based on the acquired transmitted light patterns, and exposure is performed based on the transmitted light pattern data. By obtaining the effective transmittance under the conditions, the characteristics of the semi-translucent portion and the effective transmittance corresponding thereto can be compiled into a database according to a certain rule. Thereby, based on the pattern shape of the semi-translucent portion and the obtained effective transmittance, the film quality and film thickness to be formed on the semi-translucent portion can be quickly determined.

(Embodiment 3)
In this embodiment mode, a method for manufacturing a multi-tone photomask having a first semi-transparent portion and a second semi-transparent portion having different effective transmittances, and a photolithography process using the multi-tone photomask are performed. The case where it performs is demonstrated.

  3A and 3B, a photolithography process is performed using a multi-tone photomask 200 having a light-transmitting portion 202, a light-shielding portion 203, and a first semi-transmissive portion 204a and a second semi-transmissive portion 204b having different effective transmittances. Shows the case. Hereinafter, an example of a method for manufacturing the multi-tone photomask 200 used in the photolithography process illustrated in FIGS. 3A to 3C will be described. In the following description, a resist film 205 is formed on the transferred object 206 having a step, and a first resist pattern is formed on the transferred object 206 by the transmitted light of the first semi-translucent portion 204a. A case where the film thickness of 207 and the film thickness of the first resist pattern 207 formed on the transferred body 206 by the transmitted light of the second semi-translucent portion 204b are approximately equal will be described.

First, after grasping the resist characteristics of the resist film 205 in steps 1 to 3 of FIG. 1 described above (step 1), the amount of reduction of the resist film 205 is determined (step 2), and the first half with respect to the exposure light. translucent portion 204a and the effective transmission rate _{T a} of the second semi-light-transmitting portion 204b respectively determined (step 3). Here, after the development, the film thickness of the first semi-translucent portion 204a is approximately equal to the film thickness of the resist pattern in the second semi-transparent portion 204b region. t ₁ and the film reduction value t ₂ of the second semi-translucent portion are determined. In the case shown in FIG. 3, since the first semi-transparent portion 204a is provided in the stepped portion, t ₁ <t ₂ is satisfied. Specifically, as compared with the film reduction value t ₁ of the first translucent portion, the film reduction value t ₂ of the second semi-light-transmitting portion by the film thickness of the step portion of the transfer member 206 (height) Just make it bigger.

Next, film reduction value of the first semi-light-transmitting portion 204a _{t 1} and on the basis of the film reduction value _{t 2} of the second semi-light-transmitting portion 204b, the effective transmittance of the first semi-light-transmitting portion 204a _{T A} and the second the respectively determined effective transmission rate _{T a} of the semi-light-transmitting portion 204b. Then, based on the obtained effective transmission rate T _A, can be prepared a multi-tone photomask 200 (Step 4). Membrane permeability of the membrane permeability of the first semi-light-transmitting portion 204a and the second semi-light-transmitting portion 204b of the multi-tone photomask 200 is determined based on the effective transmission rate T _A respectively obtained. Note that in the case where a plurality of semi-transparent portions having different film transmittances are provided in the same photomask, the film quality and film thickness of the semi-transparent film formed in each semi-transparent portion may be controlled. Further, as described in Embodiment 2, after the effective transmission rate T _A of the first semi-light-transmitting portion 204a of the effective transmission rate T _A of the second semi-light-transmitting portion 204b respectively determined, first semipermeable Based on the pattern shapes of the light part 204a and the second semi-transparent part 204b and the exposure conditions of the exposure machine, the film transmittance of the first semi-transparent part and / or the second semi-transparent part is determined. It is preferable to form the first semi-transmissive portion and / or the second semi-transmissive portion based on the film transmittance.

  As described above, even when a multi-tone photomask having a first semi-transparent portion and a second semi-transparent portion having different effective transmittances is manufactured, the initial thickness of the resist film is reduced by development. By designing a multi-tone photomask based on the film reduction value, it is possible to form a resist pattern having substantially the same film thickness on a transfer target having a step.

  In the above description, the case of manufacturing a multi-tone photomask having two types of semi-transparent portions having different effective transmittances is described. However, the present invention is not limited to this, and three or more types having different effective transmittances can be used. It is also possible to form a multi-tone photomask having a semi-translucent portion.

(Embodiment 4)
In this embodiment mode, a case where an electronic device is manufactured using a multi-tone photomask and a method for manufacturing the multi-tone photomask will be described with reference to the drawings. Here, as an example, a manufacturing process of a liquid crystal display device including a transistor will be described.

  First, after a conductive layer is formed over the insulating surface 300, a first resist film is formed over the conductive layer, and the conductive layer is etched using a photolithography process to form the gate electrode 301 ( (See FIG. 4A). Next, a gate insulating layer 302, an amorphous silicon layer 303, an impurity silicon layer 304, and a conductive layer 305 are sequentially stacked over the gate electrode 301 (see FIG. 4B).

Next, after a second resist film 306 is formed over the conductive layer 305 (see FIG. 4C), the second resist film 306 is developed using the first multi-tone photomask 307. Then, a first resist pattern 308 of the second resist film 306 is formed (see FIG. 4D). As the first multi-tone photomask 307, as shown in FIG. 2, a structure having a predetermined transfer pattern including a light transmitting portion, a light shielding portion, and a semi-light transmitting portion on a transparent substrate may be used. It can be manufactured using the method shown in the first and second embodiments. That is, after grasping the characteristics of the resist used for the second resist film 306 and determining the film thickness reduction value of the second resist film in the semi-translucent portion region, the effective of the semi-translucent portion is determined from the film thickness reduction value. The transmittance T _A is determined, and the first multi-tone photomask 307 is manufactured based on the effective transmittance T _A. When the pattern shape of the semi-translucent portion is small, the effective transmission obtained in consideration of the pattern shape of the semi-translucent portion, the optical conditions of the exposure light, etc., as described in the second embodiment. The ratio may be used when determining the film transmittance of the semi-translucent portion.

  Next, the conductive layer 305, the impurity silicon layer 304, and the amorphous silicon layer 303 are etched using the first resist pattern 308 as a mask (see FIG. 4E). Next, the first resist pattern 308 is ashed and reduced as a whole, and a second resist pattern 309 of the second resist film 306 is formed (see FIG. 4F). Next, the conductive layer 305, the impurity silicon layer 304, and the amorphous silicon layer 303 are etched using the second resist pattern 309 as a mask, so that a channel formation region, a source region, a drain region, a source electrode, and A thin film transistor having a drain electrode is formed (see FIG. 4G). Note that here, as an example, a case where a channel etch transistor in which a recess is formed in part of an amorphous silicon layer functioning as a channel formation region is shown. Next, after the passivation film 310 is formed, a third resist film 311 is formed over the passivation film 310 (see FIG. 4H). As the passivation film, a silicon nitride film or the like can be used. In addition, since the third resist film 311 is formed by a coating method (spin coating method), the surface of the third resist film 311 is formed even when the third resist film 311 is formed on the step. Becomes substantially flat.

Next, the third resist film 311 is developed by using the second multi-tone photomask 312 having at least a first semi-transmission part and a second semi-transmission part having different effective transmittances from each other. The first resist pattern 313 of the third resist film 311 is formed (see FIG. 4I). The second multi-tone photomask 312 may be configured to have a predetermined transfer pattern including a translucent portion, a light-shielding portion, a first semi-transparent portion, and a second semi-transparent portion on a transparent substrate. It can be manufactured using the method shown in Embodiment Mode 3 above. That is, by grasping the characteristics of the resist used for the third resist film 311, the film thickness reduction value t ₁ of the second resist film 311 in the _first semi-translucent portion region and the third value in the second semi-transparent portion region. resist after the film reduction value t ₂ of the film 311 were set respectively, to determine the effective transmission rate T _a of effective transmission rate T _a and the second semi-light-transmitting portion of the first semi-light-transmitting portion from the reduced film values, _A second multi-tone photomask 312 is manufactured based on the effective transmittance TA. In order to make the film thickness (residual film value) of the first resist pattern 313 in the first semi-transparent part region and the first resist pattern 313 in the second semi-transparent part region approximately equal after development, the film reduction value t ₁ of the first semi-light-transmitting portion of the film reduction value t ₂ of the second semi-light-transmitting portion may be previously adjusted (see Figure 6). In addition, when the pattern shape of the first semi-transmissive part and / or the second semi-transmissive part is small, as shown in the second embodiment, the first semi-transmissive part and / or the second semi-transmissive part. by considering the pattern shape and the optical conditions of the exposure light of the light unit, if reflects the effective transmission rate T _a obtained in the first semi-light-transmitting portion and / or membrane permeability of the second semi-light-transmitting portion Good.

  Next, using the first resist pattern 313 as a mask, the passivation film 310 is etched to expose part of the conductive layer functioning as a source electrode or a drain electrode (see FIG. 4J). Next, the first resist pattern 313 is ashed to reduce the overall thickness, and a second resist pattern 314 of a third resist film is formed (see FIG. 5K). Here, since the film thickness of the first resist pattern 313 in the first semi-transparent part region and the first resist pattern 313 in the second semi-transparent part region are formed to be substantially equal, The first resist pattern formed in both regions can be completely removed. Next, the transparent conductive layer 315 is formed so as to be electrically connected to the conductive layer functioning as a source electrode or a drain electrode (see FIG. 5L). At this time, the transparent conductive layer 315 is also formed on the second resist pattern 314 of the third resist film. As the transparent conductive layer 315, a light-transmitting conductive layer (for example, ITO, IZO, or the like) can be used. Next, the second resist pattern 314 of the third resist film is removed (lifted off) to form the pixel electrode 316 (see FIG. 5M). After that, a liquid crystal display device can be formed by providing a liquid crystal material between the counter substrate and the counter substrate.

As shown in this embodiment mode, by using a multi-tone photomask, the manufacturing process of the electronic device can be simplified and the member cost can be reduced. Further, by using a multi-tone photomask fabricated based on the effective transmittance T _A obtained previously, precisely performs shape control of the resist pattern in a photolithography process, to improve the reproducibility and stability Can do. As a result, the performance stability of the electronic device can be improved and the manufacturing cost can be reduced.

  In addition, this invention is not limited to the said Embodiment 1-Embodiment 4, It can change and implement suitably. Further, Embodiments 1 to 4 can be implemented in appropriate combination. For example, the material, the pattern configuration, the number of members, the size, the processing procedure, and the like in the above embodiment are merely examples, and various modifications can be made within the scope of the effects of the present invention. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  In this example, a multi-tone photomask having a first semi-transparent portion and a second semi-transparent portion having different effective transmittances was manufactured, and a photolithography process was performed using the multi-tone photomask. Show the case. In this embodiment, a resist film is formed on the transfer target having a step, and the resist film formed on the transfer target portion having the step is exposed through the first semi-transparent portion. It implemented about the case (refer FIG. 3) which exposes the resist film formed in the part which does not have through a 2nd semi-translucent part. In the present embodiment, the following four types of multi-tone photomasks are obtained by changing the film thickness (height) of the step of the transferred body and the pattern shapes of the first and second semi-transparent portions. (Multi-tone photomask (a) to multi-tone photomask (d)) were manufactured, and a photolithography process was performed using each multi-tone photomask.

First, multi-tone photomasks (a) to (d) to be designed are shown.
Multi-tone photomask (a)
-Level difference of the transfer object in the first semi-translucent part region: 0.4 μm
・ Pattern shape of the first semi-translucent part: 50 μm □ or more ・ Pattern shape of the second semi-translucent part: 50 μm □ or more

Multi-tone photomask (b)
-Level difference of the transfer object in the first semi-translucent part region: 0.4 μm
-Pattern shape of the first semi-translucent portion: width 4.0 μm surrounded by the light shielding portion
・ Pattern shape of the second semi-translucent part: 50 μm □ or more

Multi-tone photomask (c)
-Step difference of the transfer object in the first semi-transparent part region: 0.2 μm
・ Pattern shape of the first semi-transparent part: 50 μm or more ・ Pattern shape of the second semi-translucent part: width 4.0 μm surrounded by the light shielding part

Multi-tone photomask (d)
-Step difference of the transfer object in the first semi-transparent part region: 0.2 μm
-Pattern shape of the first semi-translucent portion: width 4.0 μm surrounded by the light shielding portion
-Pattern shape of the second semi-translucent portion: width 8.0 μm surrounded by the light shielding portion

  Next, the film transmissivity of the first semi-transparent part and the film transmissivity of the second semi-transparent part of the multi-tone photomasks (a) to (d) are obtained, and the multi-tone photomask (a) A method for producing (d) will be described.

  First, in the stage before manufacturing each multi-tone photomask (a) to (d), the conditions of the actual photolithography process were set as follows.

Exposure machine optical conditions: NA = 0.08, σ = 0.8, exposure wavelength (the ratio of the intensity of each wavelength is g-line / h-line / i-line = 1.0 / 1.0 / 1.0)
Exposure amount in photolithography process: 120 mJ / cm ²
Resist film: positive resist Initial film thickness of resist film: 2.4 μm

  Note that the conditions of the photolithography process are common to the multi-tone photomasks (a) to (d).

  Subsequently, the characteristics of the resist used in the photolithography process were grasped. In this example, a positive resist having an initial film thickness of 2.4 μm is irradiated with exposure light under the above exposure machine optical conditions, and the relationship between the exposure amount of the exposure light and the reduction amount of the resist due to development is shown. By obtaining this, a resist characteristic curve was created (see FIG. 7). In FIG. 7, the horizontal axis indicates the exposure amount of the exposure light under the above exposure machine optical conditions, and the vertical axis indicates the film thickness of the resist with respect to the exposure amount of the exposure light.

Next, the resist target film in the first semi-transparent part region is set so that the residual film values of the resist pattern in the first semi-transparent part region and the resist pattern in the second semi-transparent part region after development are the same. weight loss t _1, a targeted decrease film amount t ₂ of the resist of the second translucent region. In this example, the target film loss of the resist in the first semi-transparent region of the multi-tone photomasks (a) to (d) is set so that the residual film value of the resist pattern is 0.8 μm, and the second after determining translucent region of the resist of the target decreased film weight, respectively, was determined effective transmission rate T _a corresponding to the target decrease film weight as follows. Incidentally, each of the effective transmission rate T _A is after obtaining the exposure amount corresponding to each of the target decrease film weight from the resist characteristic curve can be determined by using the above equation (1).

Multi-tone photomask (a)
-Decrease amount t ₁ of the first semi-transparent film: 1.2 μm (effective transmittance T _A = 42.2 mJ / 120 mJ = 35.2%)
-Decrease amount t ₂ of the second semi-transparent film: 1.6 μm (effective transmittance T _A = 52.1 mJ / 120 mJ = 43.4%)

Multi-tone photomask (b)
-Decrease amount t ₁ of the first semi-transparent film: 1.2 μm (effective transmittance T _A = 42.2 mJ / 120 mJ = 35.2%)
-Decrease amount t ₂ of the second semi-transparent film: 1.6 μm (effective transmittance T _A = 52.1 mJ / 120 mJ = 43.4%)

Multi-tone photomask (c)
-Decrease amount t ₁ of the first semi-transparent film: 1.4 μm (effective transmittance T _A = 47.2 mJ / 120 mJ = 39.3%)
-Decrease amount t ₂ of the second semi-transparent film: 1.6 μm (effective transmittance T _A = 52.1 mJ / 120 mJ = 43.4%)

Multi-tone photomask (d)
-Decrease amount t ₁ of the first semi-transparent film: 1.4 μm (effective transmittance T _A = 47.2 mJ / 120 mJ = 39.3%)
-Decrease amount t ₂ of the second semi-transparent film: 1.6 μm (effective transmittance T _A = 52.1 mJ / 120 mJ = 43.4%)

  Next, the film transmittance of the first semi-transmissive film and the film transmittance of the second semi-transmissive film of the multi-tone photomasks (a) to (d) were respectively determined as follows, and the photomask was manufactured. .

In the multi-tone photomask (a), since the pattern shape of the first semi-transparent portion and the pattern shape of the second semi-transparent portion are sufficiently large, the effective transmittance and the film transmittance should be set to the same value. Can do. In this example, the film transmittance of the first semi-transparent portion is 35% (effective transmittance T _A 35.2%), and the film transmittance of the second semi-transparent portion is 43% (effective transmittance T _A 43). .4%), a multi-tone photomask (a) was produced.

In multi-tone photomask (b), since the pattern shape of the first semi-light-transmitting portion is small, it was determined membrane permeability by simulation based on the effective transmission rate T _A. FIG. 8A shows the aerial image simulation result of the first semi-transparent portion at this time. In FIG. 8A, the horizontal axis indicates the arrangement of the semi-transparent film, and the vertical axis indicates the effective transmittance when the width of the pattern shape is 4.0 μm and the film transmittance is 40%. On the other hand, the pattern shape of the second semi-light-transmitting portion is sufficiently large, the effective transmission rate T _A and membrane permeability can be made equal value. As a result, in this example, the film transmittance of the first semi-transparent portion is 40% (effective transmittance T _A 35.2%), and the film transmittance of the second semi-transmissive portion is 43% (effective transmittance). _A multi-tone photomask (b) was manufactured as TA 43.4%).

In the multi-tone photomask (c), since the pattern shape of the first semi-translucent portion is sufficiently large, the effective transmittance and the film transmittance can be set to the same value. On the other hand, since the pattern shape of the second semi-transparent portion is small, the membrane transmittance was obtained by simulation based on the effective transmittance. FIG. 8B shows the aerial image simulation result of the second semi-transparent portion at this time. In FIG. 8B, the horizontal axis indicates the arrangement of the semi-transparent film, and the vertical axis indicates the effective transmittance when the width of the pattern shape is 4.0 μm and the membrane transmittance is 49%. As a result, in this example, the film transmittance of the first semi-transparent portion was 39% (effective transmittance T _A 39.3%), and the film transmittance of the second semi-transmissive portion was 49% (effective transmittance). _A multi-tone photomask (c) was manufactured as TA 43.4%).

In multi-tone photomask (d), since the pattern shape and a pattern shape of the second HanToruHikarimaku the first semi-light-transmitting portion is small, was determined membrane permeability by simulation based on the effective transmission rate T _A . FIG. 8C shows the aerial image simulation results of the first semi-transmissive part and the second semi-transmissive part at this time. In FIG. 8C, the horizontal axis represents the arrangement of the semi-transparent film, and the vertical axis represents the effective transmittance T _A when the width of the pattern shape is 4.0 μm and the membrane transmittance is 43%, and the width of the pattern shape is 8 The effective transmittance is 0.0 μm and the membrane transmittance is 44%. As a result, in this example, the film transmissivity of the first semi-transmissive part of the multi-tone photomask (d) is 43% (effective transmissivity T _A 39.3%), and the film of the second semi-transparent part. _A multi-tone photomask (d) was manufactured with a transmittance of 44% (effective transmittance T _A 43.4%). In the multi-tone photomask (d), the difference between the film transmittance of the first semi-transmissive portion and the film transmittance of the second semi-transmissive film is 1%. May be produced.

  Table 1 shows the results of performing a photolithography process using the produced multi-tone photomasks (a) to (d).

  From the results of Table 1, the residual film value of the resist pattern in the first semi-transparent part region of the multi-tone photomasks (a) to (d) is equal to the residual film value of the resist pattern in the second semi-transparent part region. Value (near 0.8 μm).

DESCRIPTION OF SYMBOLS 100 Multi-tone photomask 101 Transparent substrate 102 Translucent part 103 Light-shielding part 104 Semi-transparent part 105 Resist film 106 Transfer object 107 1st resist pattern 108 2nd resist pattern 200 Multi-tone photomask 202 Translucent part 203 Light-shielding portion 204a First semi-transparent portion 204b Second semi-transparent portion 205 Resist film 206 Transfer object 207 First resist pattern 208 Second resist pattern 300 Insulating surface 301 Gate electrode 302 Gate insulating layer 303 Amorphous Silicon layer 304 Impurity silicon layer 305 Conductive layer 306 Second resist film 307 First multi-tone photomask 308 First resist pattern 309 Second resist pattern 310 Passivation film 311 Third resist film 312 Second multi-layer Gradation photomask 13 the first resist pattern 314 second resist pattern 315 transparent conductive layer 316 pixel electrode

Claims (7)

A transfer object having a predetermined transfer pattern including a translucent part, a light-shielding part, and a semi-transparent part that transmits a part of the exposure light, and is formed on the transferred object having a step. In the method of manufacturing a multi-tone photomask for manufacturing a display device, the predetermined transfer pattern is transferred to the resist film, and the resist film becomes a resist pattern that serves as a mask in the etching process.
The semi-translucent part has a first semi-translucent part and a second semi-translucent part having different effective transmittances from each other,
The step of grasping the resist characteristics of the resist used for the resist film with respect to the film thickness with respect to the light amount of the exposure light;
A step of the resist characteristics based, determines the effective transmission rate of the effective transmittance of the first semi-light-transmitting portion and the second semi-light-transmitting portion respectively,
The first half for forming a resist pattern having a predetermined film thickness on the step by patterning at least a light shielding film formed on the transparent substrate based on the determined effective transmittance. A method of manufacturing a multi-tone photomask for manufacturing a display device , comprising: forming a light- transmitting portion and a second semi-light- transmitting portion. Based on the determined effective transmittance, the pattern shape of the semi-translucent portion, and the exposure conditions of the exposure machine, the film transmissivity of the semi-transparent film used for the semi-transparent portion is determined, and the semi-transparent forming the semi-light transmitting portion based on the membrane permeability of light film, a method of manufacturing a display device for producing multi-tone photo mask according to claim 1. 2. The display according to claim 1, wherein the semi-transparent portion is formed by forming a light-shielding film pattern having a dimension not larger than a resolution limit of an exposure machine used for exposure of the multi-tone photomask on a transparent substrate. A method of manufacturing a multi-tone photomask for manufacturing an apparatus . The method for manufacturing a multi-tone photomask for manufacturing a display device according to claim 1, wherein the semi-transparent portion is formed by forming a semi-transparent film on a transparent substrate. The effective transmittance of the first semi-transparent portion is determined by reducing the film thickness t with respect to the initial film thickness of the resist film of the resist pattern formed on the transferred body by the transmitted light of the first semi-transparent portion. ₁ based on
The effective transmissivity of the second semi-transparent part is determined by reducing the film thickness t with respect to the initial film thickness of the resist film of the resist pattern formed on the transferred body by the transmitted light of the second semi-transparent part. performed based on the _2, a method of manufacturing a display device for producing multi-tone photo mask according to claim 1. By using the display device for manufacturing multi-tone photomasks produced by the production method described in any one of claims 1 to 5, by exposing the resist film on the transfer member, the transferred object A pattern transfer method for forming a resist pattern thereon. Forming a resist film on the transfer target having a step;
Forming a resist pattern on the transferred body by exposing the resist film on the transferred body using a multi-tone photomask, and
As the multi-tone photomask, a multi-tone photomask for manufacturing a display device manufactured by the manufacturing method according to any one of claims 1 to 5 ,
A pattern transfer method for forming substantially the same residual film value of a resist formed on each step of the resist pattern.

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