KR101248689B1 - Method for evaluating multi-gray scale photomask - Google Patents

Abstract

For the transfer pattern of the multi-gradation photomask, spatial data under exposure conditions is acquired, and a threshold value of a predetermined effective transmittance is determined for the spatial data. The spatial data is binarized using the threshold value, and the transfer pattern is evaluated using the binarized spatial data.

Description

Evaluation method of multi-gradation photomask {METHOD FOR EVALUATING MULTI-GRAY SCALE PHOTOMASK}

This invention relates to the evaluation method of the multi-gradation photomask used in a photolithography process.

Background Art Conventionally, in the manufacture of electronic devices such as liquid crystal display devices, exposure is performed under predetermined exposure conditions using a photomask having a predetermined pattern to a resist film formed on a layer to be etched using a photolithography process. A pattern is transferred, and the resist film is developed to form a resist pattern. And a to-be-processed layer is etched using this resist pattern as a mask.

In a photomask, there is a multi-gradation photomask having a light shielding region for shielding exposure light, a light transmission region for transmitting the exposure light, and a semi-transmission region for transmitting a part of the exposure light. When a desired pattern is transferred to a resist film on a transfer object using a multi-gradation photomask including such a light blocking region, a semi-transmissive region, and a transmissive region, light is irradiated through the transmissive region and the semi-transmissive region of the multi-gradation photomask. do. At this time, the amount of light irradiated through the translucent region is smaller than the amount of light irradiated through the translucent region. For this reason, when developing the resist film to which light was irradiated in this way, the residual film value of a resist film differs according to the quantity of irradiated light. That is, the resist residual film value of the area irradiated with light through the semi-transmissive area of the multi-gradation photomask is thinner than the resist residual film value of the area where light is shielded by the light shielding area if it is a positive resist. In addition, the resist residual film value of the area | region irradiated with light through the translucent area | region becomes 0 (zero). Thus, by performing exposure and development using a multi-gradation photomask, a resist pattern having a residual film value (including zero residual film value) of at least three thicknesses can be formed.

As described above, in the case of etching a transfer member on which a resist film is formed by using a resist film including regions having different residual film values, first, a region having a residual film value of zero (an area to which the transfer member is exposed: a light-transmitting region of a multi-gradation photomask) is used. The corresponding region) is etched, and then the resist film is reduced by ashing. As a result, the region of the resist film having a relatively thin thickness (region corresponding to the semi-transmissive region of the multi-gradation photomask) is removed, thereby exposing the transfer member in that portion. Then, the exposed transfer target is etched. Therefore, a multi-gradation photomask that realizes a resist pattern having a plurality of different residual film values is very useful because the photolithography process can be made efficient by reducing the number of photomasks used.

In Japanese Patent Laid-Open No. 2004-309327 (Patent Document 1), in a defect inspection method of a gray tone mask, image processing is performed to create image data of a gray tone part and to make a defect of the gray tone part identifiable, A method of performing a defect inspection is described.

As described above, in the multi-gradation photomask, the semi-transmissive region becomes a region for forming a resist film having a relatively thin thickness with respect to the light shielding region. For example, in a TFT (thin film transistor) used in a liquid crystal display device, this portion can form a region corresponding to the channel portion, while the light shielding region can form a region corresponding to a source, a drain, or the like. The part formed by the semi-transmissive area does not significantly influence the performance of the electronic device to be obtained, such as a liquid crystal display device. Specifically, if the line width and the exposure light transmittance of the semi-transmissive region are not strictly controlled, problems arise in the accuracy and yield of the device to be obtained. For this reason, it is necessary to predict and evaluate the shape of the resist pattern formed on a to-be-transferred body beforehand in the exposure / transfer process, and to do it easily and with high precision.

However, in patent document 1, defect inspection is performed only by performing Gaussian varnish processing on image data, and photomask is not evaluated in the state which reflected the irradiation conditions and optical conditions at the time of actually using a photomask. For this reason, precise multi-gradation photomask evaluation cannot be performed based on the shape of the resist pattern which the photomask forms on a to-be-transferred body.

The present invention has been made in view of this point, and the multi-gradation is obtained by grasping the spatial image formed by the multi-gradation photomask under actual transfer conditions, and accurately reflecting the resist pattern formed by the multi-gradation photomask on the transfer object. An object of the present invention is to provide a method for evaluating a multi-gradation photomask that can evaluate a photomask.

In the method for evaluating a multi-gradation photomask according to an aspect of the present invention, at least a light-shielding film formed on a transparent substrate is patterned, thereby providing a multi-gradation photo having a transfer pattern including a light-transmitting region, a light-shielding region, and a semi-transmissive region. A method for evaluating a mask, the method comprising: obtaining spatial data of the transfer pattern under exposure conditions with respect to the transfer pattern to be evaluated; and determining a threshold value of a predetermined effective transmittance with respect to the spatial data. And binarizing the spatial data by using the threshold value, and evaluating the transfer pattern by using the binarized spatial data.

According to this method, the multi-gradation photomask can be evaluated using image data accurately reflecting a resist pattern formed on the transfer object using the actual transfer conditions.

In this multi-gradation photomask evaluation method, spatial data for a normal part having a normal transfer pattern is acquired in advance, and the threshold value can be determined using the spatial data of the normal part.

In the method for evaluating the multi-gradation photomask, the threshold may be a threshold determined based on a target line width after the transfer pattern is transferred onto the transfer object using the multi-gradation photomask.

In the evaluation method of this multi-gradation photomask, the threshold value may be a threshold value determined based on a line width design value of the transfer pattern formed on the multi-gradation photomask.

In this multi-gradation photomask evaluation method, the step of evaluating the transfer pattern includes previously acquiring the binarized spatial data for the top portion having the normal transfer pattern, and determining the acquired spatial data and the evaluation target. It is preferable to include comparing the binarized spatial data.

In this multi-gradation photomask evaluation method, the transfer pattern to be evaluated can be included in the same photomask together with the normal transfer pattern.

In the evaluation method of this multi-gradation photomask, it is preferable that the transfer pattern made into the said evaluation object has grasped | ascertained that the transflective part in the said transfer pattern contains a defect part before the said comparison.

In the evaluation method of the multi-gradation photomask, it is necessary to correct the transfer pattern to be evaluated by comparing the binarized spatial data in the transfer pattern to be evaluated with the binarized spatial data of the top part. It is preferable to include determining.

The evaluation method of the multi-gradation photomask is a line width for calculating the line width of the defective portion when the transfer pattern is transferred onto the transfer target based on the binarized spatial data in the transfer pattern to be evaluated. It is preferable to include a calculation process. In this case, it is preferable to make it the defect correction object, when the calculated line width differs more than a predetermined range from the line width obtained based on the binarized spatial data of the top part.

In the evaluation method of the multi-gradation photomask, the semi-transmissive region may be formed by forming a fine pattern below the resolution limit of an exposure machine in the light shielding film formed on the transparent substrate.

In the method for evaluating the multi-gradation photomask, the semi-transmissive region may be formed by forming a semi-transmissive film on the transparent substrate that transmits a part of the exposure light.

In this multi-gradation photomask evaluation method, the step of acquiring the spatial data includes irradiating exposure light under the exposure conditions to the photomask on which the transfer pattern is formed, and transmitting the transmitted light of the transfer pattern by the imaging means. It is preferable to include imaging.

According to another aspect of the present invention, there is provided a method of manufacturing a multi-gradation photomask, wherein at least a light shielding film formed on a transparent substrate is patterned to provide a multi-gradation including a light transmission region, a light shielding region, and a translucent region. A method of manufacturing a photomask, comprising a pattern forming step of forming the transfer pattern to form the transfer pattern, and an evaluation step of evaluating the formed transfer pattern, wherein the evaluation step is based on the evaluation method.

According to this method, since the multi-gradation photomask is evaluated with image data accurately reflecting the resist pattern formed on the transfer object, it is possible to manufacture a multi-gradation photomask without any problem in actual mask use.

In this manufacturing method of a multi-gradation photomask, it is preferable to manufacture the said photomask by which the in-line line | wire width distribution of the said transfer pattern at the time of being transferred on a to-be-transferred body becomes 0.15 micrometer or less.

The pattern transfer method according to still another aspect of the present invention is characterized in that the transfer pattern is transferred onto a transfer object using a photomask according to the method for producing a multi-gradation photomask.

According to this method, since the multi-gradation photomask is evaluated with image data accurately reflecting the resist pattern formed on the transfer target, the transfer pattern can be accurately transferred onto the transfer target.

The evaluation method of the multi-gradation photomask of the present invention includes a transfer pattern including a light-transmitting region, a light-shielding region, and a semi-transmissive region by patterning at least a light-shielding film formed on a transparent substrate, wherein the transfer is an evaluation target. With respect to the pattern, spatial data of the transfer pattern under exposure conditions is acquired, and a threshold value of a predetermined effective transmittance is determined for the spatial data, and the spatial data is binarized using the threshold value. Since the transfer pattern is evaluated using the binarized spatial data, the multi-gradation photo is image data that accurately reflects the resist pattern formed on the transfer object by using the actual transfer conditions. The mask can be evaluated.

(A) is a figure which shows an example of a transfer pattern, (b) is a figure which shows the relationship between an effective transmittance and the position of the transfer pattern of (a), and (c) is between CD and a threshold value. A diagram showing the relationship between
2 is a diagram showing an example of an apparatus for reproducing exposure conditions of an exposure machine.
(A) is a figure which shows an example of a transfer pattern, (b) is a figure which shows the space image of the transfer pattern, (c) uses (b), and transfer pattern is transferred onto a transfer body image. 2 is a diagram showing a binarized spatial image obtained by determining a threshold value based on a target line width after being transferred to (d), and (d) is obtained by determining a threshold value based on a design line width of a mask using (b). Chichi space.
Fig.4 (a)-(i) are the binarization space image of the top part and evaluation object which were obtained by determining a threshold value based on the target line width on a to-be-transferred body.
5 (a) to 5 (i) are binarized space images of a top portion and an evaluation target obtained by determining a threshold value based on a design line width.

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

The present inventors note that in order to obtain a desired resist residual film value on the transfer target, it is insufficient to merely control the film transmittance of the semi-transmissive film used in the semi-transmissive portion of the multi-tone mask. In order to determine the resist residual film value at the time of obtaining the portion of the film, not only the exposure transmittance (due to the film composition or the film thickness) of the semi-transmissive film used for the mask, but also the shape and pattern of the pattern formed on the mask It has been found that the transmittance in consideration of the diffraction phenomenon of light generated must be controlled by the optical characteristics of the light source to be used, the characteristics of the optical system, and the like. Therefore, the present inventors define an effective light transmittance (effective transmittance) T _A that transmits the mask in place of the film transmittance T _f of the semi-transmissive film, and propose to control the effective transmittance. In addition, this effective transmittance T _A can be considered as the transmittance | permeability which the translucent area | region of the mask transmits exposure light under the exposure conditions actually used, for example. In reality, the light transmittance of the semi-transmissive region has a distribution, for example, as shown in FIG. 1B due to the influence of an adjacent light shielding portion, and thus corresponds to the peak of the light transmission curve in the region. The transmittance value described above can be taken as a representative value of the effective transmittance.

Since the effective transmittance T _A is an index that considers optical conditions and pattern design in addition to the transmittance inherent to the film, it accurately reflects the light intensity due to exposure on the transfer object, and thus, as an index for managing the residual film value of the formed resist pattern. It is appropriate. In addition, as an effective transmittance of a semi-transmissive area, when the exposure light transmittance of a translucent area is 100%, it can be set as the transmittance | permeability of the part which has the maximum value in the light intensity distribution which permeates a translucent area. This is because, for example, using this photomask, when a resist pattern of a positive resist is formed on a transfer object, it has a correlation with the minimum value of the resist residual film value which arises in a semi-transmissive area | region. For such range management, for example, when a thin film transistor (TFT) is manufactured using a multi-gradation photomask, the semi-transmissive region corresponds to the channel region of the TFT, and the width of the channel is 5 µm. It is especially effective when it is below. In addition, "Ch-L (channel length)" in FIG. 3 etc. means the width | variety of this channel part.

As described above, the effective transmittance T _A is represented here as the transmittance at the maximum value of the light intensity distribution curve in the semi-transmissive region (if a positive resist is used, this corresponds to the bottom (minimum value) of the resist residual film). You can. That is, the effective transmittance T _A is sandwiched between two light shielding regions, and in the case of a semi-transmissive region adjacent to the light shielding regions, the light intensity distribution curve of the transmitted light becomes a steering curve and the transmittance corresponding to the peak. I shall say. This effective transmittance is determined by the film transmittance T _f , the actual exposure conditions (optical parameters, spectral characteristics of the irradiated light), and the actual photomask pattern shape. However, at the time of actual evaluation, in order to simplify, it can represent as exposure conditions according to model conditions. This condition is, for example, using an optical system having a numerical aperture NA of 0.08 and a coherence sigma of 0.8, wherein the intensities of the g-line, h-line, and i-line are 1: 1: 1. It can be set as exposure conditions using irradiation light.

On the other hand, the film transmittance T _f can be defined as the transmittance of the semi-transmissive region in a sufficiently large area with respect to the resolution limit under the exposure conditions when a semi-transmissive membrane is formed on the transparent substrate to form a semi-transmissive region. When the semi-transmissive region is not formed in the semi-transmissive region and the space of the fine line width in the light-shielding pattern functions as a semi-transmissive region, the "film transmittance" of the space of the semi-transmissive region is equal to 100. It becomes%. On the other hand, according to the evaluation method described later, since the transmittance of the semi-transmissive region is influenced by the line width of the pattern, the exposure light transmittance of the semi-transmissive region in the actual pattern is defined by the effective transmittance T _A. Become useful.

As mentioned above, evaluation of a multi-gradation photomask needs to be performed reflecting the resist pattern on a to-be-transferred body obtained through an actual exposure / transfer process, and process of a to-be-processed layer with evaluation of the completeness of a photomask. It is necessary to perform inspection (evaluation) of whether a phase problem arises easily and with high precision.

The present inventors pay attention to this point, obtain spatial data under actual exposure conditions, determine a threshold of a predetermined effective transmittance with respect to this spatial data, and binarize the spatial data at this threshold, By evaluating the transfer pattern with the binarized spatial image data, it was found that the multi-gradation photomask can be evaluated with image data accurately reflecting the resist pattern formed on the transfer object.

That is, at least the light shielding film formed on the transparent substrate is patterned, so that a transfer pattern including a light transmitting region, a light shielding region, and a semi-transmissive region is provided, and the transfer pattern under exposure conditions for the transfer pattern to be evaluated. Obtains spatial data of the spatial data, and determines a threshold value of a predetermined effective transmittance with respect to the spatial data, binarizes the spatial data by binarizing the binary data using the threshold value. By evaluating the transfer pattern, the multi-gradation photomask is evaluated by image data accurately reflecting a resist pattern formed on the transfer object under the actual exposure conditions.

The multi-gradation photomask, which is the object of the evaluation method according to the embodiment of the present invention, is provided with a transfer pattern including a light-transmitting region, a light-shielding region, and a semi-transmissive region because at least the light-shielding film formed on the transparent substrate is patterned. A photomask of more than gradation. In other words, in the multi-gradation photomask, by having a semi-transmissive region in addition to the light shielding region and the light transmissive region, a region having a plurality of film thicknesses is formed in a resist pattern formed on the transfer object. The light blocking region may substantially shield exposure light, and the light transmitting region may be formed by exposing a transparent substrate. The semi-transmissive region is a portion where the transmittance is relatively smaller than that of the transmissive region, and is a region for forming a desired resist residual film on the transfer object. This translucent region can be formed by, for example, forming a translucent film having a predetermined film transmittance on a transparent substrate. When the transmissive region is 100%, the film transmittance of the semi-translucent membrane is 10% to 70%, more preferably 20% to 60%. Moreover, you may make it a semi-transmissive area | region by forming the pattern of the line width below the resolution limit of an exposure machine in the light shielding film formed on the transparent substrate. In addition, the multi-gradation photomask which is an object of the evaluation method may be a 4-gradation or higher photomask having a resist pattern having three or more resist residual film values (other than the resist residual film value zero portion).

A glass substrate etc. are mentioned as a transparent substrate. Moreover, as a light shielding film which shields exposure light, metal silicide films, such as metal films, such as a chromium film, a silicon film, a metal oxide film, and a molybdenum silicide film, etc. are mentioned. In addition, the light shielding film preferably has an antireflection film on its surface, and examples of the material of the antireflection film include oxides, nitrides, carbides, and fluorides of chromium. As a semi-transmissive film which partially transmits the exposure light, an oxide of chromium, nitride, carbide, oxynitride, oxynitride carbide, metal silicide or the like can be used. In particular, metal silicide films such as chromium oxide films, chromium nitride films, and molybdenum silicide films, and oxides, nitrides, oxynitrides, carbides, and the like of the molybdenum silicide films are preferable. More preferably, a film of oxide, nitride, oxynitride, carbide, oxynitride carbide or the like of molybdenum silicide can be used.

As a transfer pattern of a multi-gradation photomask, a transfer pattern formed by forming a semi-transmissive film and a light shielding film on a transparent substrate, and performing predetermined patterning on each of them, or forming a light shielding film on a transparent substrate, and having a fine pattern below the exposure machine resolution And a transfer pattern that is patterned to give an intermediate tone by diffraction effect of light.

In the evaluation method of the multi-gradation photomask according to the embodiment of the present invention, spatial data of a transfer pattern under exposure conditions is acquired for a transfer pattern to be evaluated, and a threshold of a predetermined effective transmittance is given to the spatial data. A value is determined, and the threshold value is used to binarize the spatial data, and the transfer pattern is evaluated using the binarized spatial data.

In this evaluation method, spatial data of a transfer pattern under exposure conditions is acquired for the transfer pattern to be evaluated. That is, when acquiring spatial data, exposure light under exposure conditions is irradiated to the photomask on which the transfer pattern is formed, and the transmitted light of the transfer pattern is imaged by the imaging means. Exposure conditions here are exposure conditions at the time of using this multi-gradation photomask. Specifically, the exposure conditions use NA (number of apertures), sigma (coherency), and irradiation wavelength of the optical system when using this multi-gradation photomask. In addition, a space image means here the image (light intensity distribution) given on a to-be-transferred body, when a transfer pattern is exposed under the said exposure conditions. For example, as for the transfer pattern (channel length: 5.0 micrometers, film transmittance 40%) of TFT shown to Fig.3 (a), the intensity ratio by NA = 0.08, (sigma) = 0.8, and wavelength of exposure light is g line / h In the case of exposing under exposure conditions of line / i line = 1/1/1, the resulting spatial image is shown in Fig. 3B. In Fig. 3A, reference numeral 21 denotes a light shielding film and reference numeral 22 denotes a translucent film.

In this evaluation method, the threshold of predetermined effective transmittance is determined with respect to spatial data. For example, in the transfer pattern as shown in Fig. 1A, that is, the transfer pattern in which the semi-transmissive film 22 is formed between two light shielding films 21, the effective transmittance between ABs is obtained from As shown in b). The threshold value of the effective transmittance in this process is the threshold value TH1, TH2, TH3 with respect to the characteristic curve shown to Fig.1 (b). The difference in threshold is the difference in the exposure amount applied to the photomask.

Since the threshold value is necessary as a criterion when evaluating the transfer pattern, the determined method becomes important. As described above, the effective transmittance T _A means a transmittance through which, for example, a semi-transmissive region of the mask transmits the exposure light under the exposure conditions actually used. This effective transmittance varies with line width as described above, and as shown in Fig. 1C, the threshold of effective transmittance and the line width (CD (Critical Dimension)) of the portion corresponding to the semi-transmissive region are correlated. I think this is. The fact that the threshold value is large means that the line width of the portion corresponding to the translucent region is small. The threshold value of the effective transmittance can be determined based on the target line width after the transfer pattern is transferred onto the transfer object using a photomask. Alternatively, the threshold value can be determined based on the line width design value of the transfer pattern formed on the photomask.

For example, the spatial data at the time of applying exposure conditions to the top part which has a normal transfer pattern can be calculated | required previously. With reference to the spatial data, an effective transmittance for giving the target line width (for example, the target line width of the semi-transmissive region to be formed as the channel portion) can be obtained and this can be set as the threshold value. Alternatively, the effective transmittance for giving the line width design value of the photomask (for example, the design line width of the semi-transmissive region corresponding to the channel portion) can be obtained by referring to the spatial image of the top portion, and set this as the threshold value. do.

By using the threshold value of the effective transmittance determined above, the spatial data of the transfer pattern to be evaluated can be binarized to obtain the binary data of the binarization. The transfer pattern is evaluated using this binarized spatial data. For example, the absolute value of line width, white defect, and black defect can be judged from this binarized space data. For example, based on the binarized spatial data in the transfer pattern to be evaluated, the line width of the defective portion when the transfer pattern is transferred onto the transfer target is calculated (line width calculation step), and the line width calculated here. In the case where the difference exceeds the predetermined range, it may be a defect correction target.

In the evaluation of the transfer pattern, the binarized spatial image data for the top portion having the normal transfer pattern may be acquired in advance and compared with the binarized spatial image data of the evaluation target. And based on this comparison result, the line width distribution of a mask etc. are evaluated using the criterion of whether it is a defect, and also determines whether the defect correction is necessary in some cases. That is, by comparing the binarized spatial image data of the transfer pattern to be evaluated and the binarized spatial data of the top part, the completeness of the transfer pattern to be evaluated can be judged, or the necessity of correction is determined. It becomes possible.

Here, as a criterion of whether or not it is a defect, for example, the inspection image of the black defect part is generated by the method described above, and the semi-transmissive area (sandwiched between the light shielding regions 21 of FIG. 1A) ( In the semi-transmissive film 22 of FIG. 1A, when an island-like pattern below a threshold is detected, the reference which is to be corrected, or the threshold is defined as the maximum effective transmittance of the semi-transmissive region + As 2.0%, the inspection image of a white defect is produced | generated, and when a fall pattern is detected in a semi-transmissive area, the criteria etc. which make it a correction object are mentioned.

The transfer pattern to be evaluated may be included in the same photomask together with the normal transfer pattern. For example, mask evaluation in the case of the repeating pattern in which the unit patterns are arranged, as represented by TFT, can determine the presence or absence of a defect by simply comparing the patterns in different regions of the same photomask. It is useful.

In the transfer pattern to be evaluated, it may be understood that the translucent portion in the transfer pattern includes the defect portion prior to comparison with the top portion. For example, when a pattern defect is found in a multi-gradation photomask by the pattern shape defect inspection apparatus of a mask, the resist pattern which the photomask forms on a to-be-transferred body under an actual exposure condition produces a problem. It can be grasped | ascertained previously by the evaluation method mentioned above whether it is. Therefore, there is an advantage that can be secured before the actual exposure process, that is, at the stage of mask evaluation.

Conventionally, it is widely used to determine the presence or absence of a defect only by the specification of a mask pattern, but the transfer pattern determined by the method does not cause a problem under actual exposure conditions, or vice versa. Discovered by the present inventors. Furthermore, the inventors of the present invention may determine that black defects (excess defects) are determined by normal pattern shape defect inspection to act as white defects (missing defects) by the use of an actual photomask. Was found by. This is considered to arise by the synergistic effect of exposure wavelength ranges, such as i line | wire-g line | wire, and a pattern shape and a dimension.

When manufacturing a multi-gradation photomask including the above-mentioned evaluation method, at least a light shielding film is formed on a transparent substrate, the film | membrane on the said transparent substrate is patterned, a transfer pattern is formed, and the formed transfer pattern is evaluated by the said method. . In this evaluation, when defect correction is necessary, defect correction can be performed and evaluation can be performed in the same manner. Since the multi-gradation photomask obtained through such evaluation is evaluated with image data reflecting accurately the resist pattern formed on the transfer object, the multi-gradation photomask is a multi-gradation photomask without any problem in the actual mask use. In particular, by using this evaluation method, it becomes possible to manufacture a high quality multi-gradation photomask which can make the in-plane line width distribution of the transfer pattern when transferred onto a transfer object to be 0.15 µm or less.

Specifically, in the evaluation of the transfer pattern, the binarized spatial image data for the top portion having the normal transfer pattern is previously obtained and compared with the binarized spatial image data of the evaluation target. Thus, since binarized spatial data of the normal part having a normal transfer pattern is acquired in advance and compared with this spatial data, accurate mask evaluation can be performed. In addition, it is preferable that the transfer pattern to be evaluated is included in the same photomask together with the normal transfer pattern.

When the in-line line width distribution is 0.15 µm or less, the line width distribution (absolute value of the difference between the line width maximum value and the line width minimum value) with respect to the line width standard value can be 0.15 µm or less. For example, the line width design value of the transfer pattern in the photomask, or the target line width when the transfer pattern is transferred to the transfer target (workpiece) can be a standard value. Alternatively, the line width distribution can be within 0.15 µm between the same patterns in the transfer pattern.

The multi-gradation photomask thus obtained can transfer the transfer pattern onto the transfer target. Since the multi-gradation photomask is evaluated with image data reflecting accurately the resist pattern formed on the transfer target, the transfer pattern can be accurately transferred onto the transfer target.

Here, as an apparatus for making a transfer pattern into spatial data, the apparatus shown in FIG. 2 is mentioned, for example. This apparatus comprises a light source 1, an irradiation optical system 2 for irradiating light from the light source 1 to the photomask 3, and an objective lens system 4 for forming an image transmitted through the photomask 3. And the imaging means 5 for imaging an image obtained through the objective lens system 4.

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

The irradiation optical system 2 guides the light from the light source 1 to irradiate the photomask 3 with light. This irradiation optical system 2 is provided with an aperture mechanism (opening aperture 7) in order to make the numerical aperture NA variable. It is preferable that this irradiation optical system 2 is provided with the visual field stop 6 for adjusting the irradiation range of the light in the photomask 3. The light passing through this irradiation optical system 2 is irradiated to the photomask 3 held by the mask holder 3a. This irradiation optical system 2 is disposed in the case 13.

The photomask 3 is held by the mask holder 3a. The mask holder 3a supports the lower end of the photomask 3 and the vicinity of the side edges of the photomask 3 while the main plane of the photomask 3 is substantially vertical, and tilts the photomask 3. It is fixed and kept. This mask holder 3a is a photomask 3 that holds a large (for example, 1220 mm x 1400 mm, 13 mm thick) main surface and a photomask 3 of various sizes. It is supposed to be. In addition, an approximately perpendicular means that the angle from the perpendicular | vertical represented by (theta) in FIG. 2 is within about 10 degrees. Light irradiated to the photomask 3 passes through the photomask 3 and enters the objective lens system 4.

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

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

In this apparatus, since the numerical aperture of the irradiation optical system 2 and the numerical aperture of the objective lens system 4 are respectively variable, the ratio of the numerical aperture of the irradiation optical system 2 to the numerical aperture of the objective lens system 4, that is, The sigma value (σ: coherency) can be varied. By appropriately selecting the above conditions, the optical conditions at the time of exposure can be reproduced or approximated.

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

In the apparatus shown in Fig. 2 having such a configuration, the NA and sigma values are variable, and the source of the light source can also be changed, so that the exposure conditions of various exposure machines can be reproduced.

Here, the case where the presence or absence of defect correction is determined by the above-mentioned evaluation method is demonstrated concretely.

First, the transfer pattern for TFT manufacture of the shape shown to Fig.3 (a) is evaluated. The design value of this transfer pattern is a pattern including a semi-transmissive region having a channel length of 5.0 µm and a film transmittance of 40%. This transfer pattern is exposed and imaged using the apparatus shown in FIG. 2 to obtain a spatial image as shown in FIG. The exposure conditions at this time are NA = 0.08, sigma = 0.8, and the intensity ratio g line / h line / i line = 1/1/1 for each wavelength of exposure light.

First, a space image under the above exposure conditions is obtained for a top portion having a normal pattern. Using this spatial data, an effective transmittance for giving a target line width after transfer can be obtained, and this is determined as a threshold value. For example, if the target line width of the channel length after transfer is 4.2 占 퐉, the effective transmittance was 0.183, and this is set as the threshold value. Fig. 3C is a binarized space image on which this threshold value is applied.

If this is applied to the spatial data of the transfer pattern to be evaluated, this spatial data can be binarized. This is shown in Figs. 4B to 4I. Alternatively, in the spatial data of the normal pattern, an effective transmittance for giving a line width design value of a mask may be obtained instead of the target line width after transfer, and this may be set as a threshold value. For example, when the line width design value was 5.0 μm, the effective transmittance for giving this line width was 0.122 (FIG. 3 (d)). Therefore, using this threshold value, the data on the transfer pattern space of the evaluation target can be binarized. FIG.5 (b)-(i) is the binarization space image. In addition, Th in FIG.3 (c), (d) is a threshold value (threshold value) in effective transmittance | permeability.

As described above, the binarized spatial image data (Fig. 4 (a), Fig. 5 (a)) for the top portion and the binarized spatial image data (Fig. 4 (b) to (i) ) And (b) to (i)) of FIG. 5, it is possible to determine whether black defects or white defects are necessary for correction.

This invention is not limited to the said embodiment, It can change suitably and can implement. For example, the material, the pattern structure, the number of members, the size, the processing procedure, and the like in the above embodiments are examples, and various modifications can be made.

Claims (16)

At least the light shielding film formed on the transparent substrate is patterned to provide a transfer pattern including a light transmitting region, a light blocking region, and a semi-transmissive region, and on the transfer object, a portion having a resist residual film value different in accordance with the amount of irradiation light. As an evaluation method of a multi-gradation photomask for forming a resist pattern,
A step of acquiring spatial data of the transfer pattern under exposure conditions with respect to the transfer pattern to be evaluated;
Determining a line width for obtaining a threshold value based on one of a target line width when the semi-transmissive region of the transfer pattern is transferred onto the transfer target, or a design line width of the semi-transmissive region of the transfer pattern;
Obtaining a threshold value of an effective transmittance corresponding to the determined line width based on the spatial data;
And binarizing the spatial data by using the threshold value, and evaluating the transfer pattern using the binarized spatial data. The method of claim 1,
The threshold value is obtained by acquiring spatial data of a normal part having a normal transfer pattern in advance and determined using the spatial image data of the normal part. The method of claim 1,
The threshold value is a threshold value determined based on a target line width after transferring the translucent region of the transfer pattern onto a transfer object using the multi-gradation photomask. . The method of claim 1,
And said threshold value is a threshold value determined based on a design line width of said translucent region of said transfer pattern formed on said multi-gradation photomask. delete The method of claim 2,
The transfer pattern to be evaluated is included in the same photomask together with the normal transfer pattern. The method of claim 1,
The evaluation pattern of the multi-gradation photomask of the said transfer pattern made into the said evaluation object grasped that the translucent part in the said transfer pattern contains a defect part. delete The method of claim 7, wherein
And a line width calculating step of calculating the line width of the defective portion when the transfer pattern is transferred onto the transfer target based on the binarized spatial image data of the transfer pattern to be evaluated. Evaluation method of gradation photomask. 10. The method of claim 9,
When the calculated line width differs by more than a predetermined range from the line width obtained based on the binarized spatial image data of the top portion having the normal transfer pattern, the multi-tone photo characterized by the above-mentioned. Evaluation method of the mask. The method of claim 1,
The said semi-transmissive area | region is the evaluation method of the multi-gradation photomask characterized by the fine pattern below the resolution limit of an exposure machine formed in the said light shielding film formed on the said transparent substrate. The method of claim 1,
The semi-transmissive region is a method for evaluating a multi-gradation photomask, wherein a semi-transmissive film is formed on the transparent substrate to transmit part of the exposure light. The method of claim 1,
The step of acquiring the spatial data includes irradiating exposure light under the exposure conditions to the photomask on which the transfer pattern is formed, and imaging the transmitted light of the transfer pattern by an imaging unit. Evaluation method of gradation photomask. A method for producing a multi-gradation photomask having a transfer pattern including a light transmitting region, a light blocking region, and a semi-transmissive region by forming at least a light shielding film formed on a transparent substrate, wherein the patterning is performed to form the transfer pattern. The pattern forming process to form, and the evaluation process of evaluating the formed said transfer pattern are included, The said evaluation process is in any one of Claims 1-4, 6, 7 and 9-13. The manufacturing method of the multi-gradation photomask characterized by the evaluation method in any one of Claims. 15. The method of claim 14,
The method for producing a multi-gradation photomask, wherein the photomask has an in-line line width distribution of 0.15 µm or less in the plane of the transfer pattern when transferred onto the transfer target by the evaluation method. The pattern transfer method, wherein the transfer pattern is transferred onto a transfer object using the photomask according to the method for manufacturing a multi-gradation photomask according to claim 14.

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