JP5937873B2 - Photomask substrate set, photomask set, and pattern transfer method - Google Patents

Description

  The present invention relates to a photomask substrate, a photomask, a photomask substrate set, a photomask set, a photomask manufacturing method, and a pattern transfer method.

  A liquid crystal display device included in a computer, a portable terminal, or the like includes a TFT substrate in which a TFT (thin film transistor) array is formed on a translucent substrate, and a color filter (hereinafter also referred to as CF) in which an RGB pattern is formed on the translucent substrate. And a structure in which liquid crystal is sealed between them. The color filter includes a step of forming a black matrix layer constituting a color boundary portion on one main surface of the translucent substrate, and an upper surface of the translucent substrate partitioned by the black matrix layer. It is manufactured by sequentially performing a step of forming a color filter layer (hereinafter also referred to as a color layer or a color plate) such as a red filter layer, a green filter layer, and a blue filter layer. Both the TFT and the color filter can be manufactured by applying photolithography using a photomask.

  On the other hand, when a photomask is set in an exposure machine and pattern transfer is performed, the photomask is slightly bent due to its own weight. Therefore, a support mechanism of an exposure machine for reducing this bending is described in Patent Document 1. Yes.

Japanese Patent Laid-Open No. 9-306832

  Expectations for performance improvement required for liquid crystal display devices are increasing. In particular, display devices that have small dimensions and require high-definition images, such as portable terminals, are required to have performances that exceed conventional products in several respects. The sharpness of color (there is no color turbidity), the reaction speed, the resolution, and the like. Because of these demands, the accuracy of pattern formation is required more than ever in photomasks for manufacturing TFTs and CFs.

  For example, in a photomask for TFT formation, in order to increase the reaction speed of the liquid crystal display device, the TFT pattern itself becomes finer, or a finer TFT is used in combination with the main TFT, etc. When forming a pattern, it is necessary to precisely form a fine line width. In addition, TFT and CF are used in an overlapping manner. If the positioning at the time of transfer is not controlled precisely together with the coordinate accuracy of each pattern on the photomask, the position shift between them There is a risk that the liquid crystal will malfunction.

  On the other hand, the photomask for forming CF also has the following problems. As described above, the black matrix layer and the color layer are used in an overlapping manner, so that the pattern formation on the mask is made precise, and there is a coordinate shift due to variations and variations in the pattern surface shape during transfer. When it occurs, inconvenience such as color turbidity occurs.

  In order to form a black matrix layer or a color filter layer on a light-transmitting substrate using a photomask, it is most advantageous to apply proximity (proximity) exposure. This is because the production efficiency is high because a complicated optical system is not required for the structure of the exposure machine and the apparatus cost is low as compared with projection exposure. However, when proximity exposure is applied, it is difficult to correct distortion at the time of transfer, so that transfer accuracy is likely to deteriorate compared to projection exposure.

  In proximity exposure, the transferred object on which the resist film is formed and the pattern surface of the photomask are held facing each other, the pattern surface is directed downward, and from the back side of the photomask (surface opposite to the pattern surface) By irradiating light, the pattern is transferred to the resist film. At this time, a predetermined minute gap (proximity gap) is provided between the photomask and the transfer target. Note that the photomask includes a transfer pattern in which a predetermined pattern is formed on a light shielding film formed on the main surface of the transparent substrate.

  Generally, when a photomask is set in a proximity exposure exposure machine, the outside of an area (also referred to as a pattern area) where a transfer pattern is formed on the main surface on which the transfer pattern is formed, Hold by the holding mechanism. Here, the photomask mounted on the exposure machine may bend due to its own weight, but such deflection can be corrected to some extent by the holding mechanism of the exposure machine. For example, the method of Patent Document 1 describes applying a predetermined pressure force from above the mask outside the support point of the holding member that supports the photomask from below.

  However, the present inventors have found that even if it is useful to reduce the influence on the pattern transfer due to the bending of the photomask, it is not sufficient for manufacturing a precise display device for the above-mentioned use alone. It was. For example, when the above-mentioned proximity exposure is performed, the overlay accuracy of the transfer pattern formed on the transfer target is not good even though the formation accuracy of the transfer pattern provided in the photomask is sufficiently high and within the reference range. It has been found that there is a possibility that inconvenience in operation of the liquid crystal display device and color turbidity may occur. As the resolution of liquid crystal display devices increases, such deterioration of the overlay accuracy of transfer patterns is becoming unacceptable.

  An object of the present invention is to improve the pattern transfer accuracy when a transfer pattern formed on a photomask is transferred to a transfer medium by proximity exposure. In particular, it is an object to improve pattern overlay accuracy when transferring a plurality of photomasks sequentially to the same transfer target.

According to a first aspect of the invention,
A photomask substrate for forming a transfer pattern on a main surface to form a photomask,
There is provided a photomask substrate in which the maximum value ΔZmax of the height variation of the pattern region on the main surface is 8.5 (μm) or less.

According to a second aspect of the invention,
The maximum value ΔZmax of the height fluctuation is the maximum value and the minimum value of Z, where Z is the height of each measurement point set at equal intervals with a predetermined separation distance P in the pattern region. There is provided a photomask substrate according to the first aspect which is a difference from the above.

According to a third aspect of the invention,
The photomask substrate according to the second aspect, in which the separation distance P is 5 (mm) ≦ P ≦ 15 (mm), is provided.

According to a fourth aspect of the invention,
A photomask substrate according to any one of the first to third aspects is prepared, an optical film is formed on a main surface of the photomask substrate, and a pattern for transfer is formed by patterning the optical film. A method of manufacturing a photomask including the step of performing is provided.

According to a fifth aspect of the present invention,
A photomask having a transfer pattern formed on the main surface,
A photomask is provided in which the maximum value ΔZmax of the height variation of the pattern region on the main surface is 8.5 (μm) or less.

According to a sixth aspect of the present invention,
The maximum value ΔZmax of the height fluctuation is the maximum value and the minimum value of Z, where Z is the height of each measurement point set at equal intervals with a predetermined separation distance P in the pattern region. The photomask as described in 5th aspect which is a difference with these is provided.

According to a seventh aspect of the present invention,
The photomask according to the sixth aspect, in which the separation distance P is 5 (mm) ≦ P ≦ 15 (mm), is provided.

According to an eighth aspect of the present invention,
A photomask according to any one of the fifth to seventh aspects, which is for proximity exposure, is provided.

According to a ninth aspect of the present invention,
The photomask as described in any one of 5th-8th aspect provided with the pattern for color filter manufacture in the said pattern area | region is provided.

According to a tenth aspect of the present invention,
There is provided a pattern transfer method in which the photomask according to any one of the fifth to ninth aspects is set in an exposure machine for proximity exposure and pattern transfer to a transfer target is performed.

According to an eleventh aspect of the present invention,
A first photomask substrate for forming a transfer pattern to be transferred to a transfer object on the main surface to form a first photomask, and a transfer to be transferred to the transfer object in an overlapping manner with the transfer pattern A photomask substrate set comprising: a second photomask substrate for forming a pattern for use on a main surface to form a second photomask;
The height of the arbitrary point M set in the pattern region on the main surface of the first photomask substrate with respect to the reference plane is Zm,
The height of the point N at a position corresponding to the point M on the first photomask substrate in the pattern region on the main surface of the second photomask substrate with respect to the reference plane is Zn,
When the difference Zd between the Zm and the Zn is obtained,
A photomask substrate set in which the maximum value ΔZdmax of Zd is 17 (μm) or less within the pattern region is provided.

According to a twelfth aspect of the present invention,
A first photomask in which a transfer pattern to be transferred to the transfer object is formed on the main surface, and a transfer pattern to be transferred to the transfer object are formed on the main surface so as to overlap the first transfer pattern. A second photomask, and a photomask set comprising:
The height of an arbitrary point M set in the pattern area on the main surface of the first photomask with respect to the reference plane is Zm,
The height of the point N at the position corresponding to the point M on the first photomask in the pattern region on the main surface of the second photomask with respect to the reference plane is Zn,
When the difference Zd between the Zm and the Zn is obtained,
A photomask set in which the maximum value ΔZdmax of Zd is 17 (μm) or less in the pattern region is provided.

According to a thirteenth aspect of the present invention,
The transfer pattern possessed by the first photomask according to the twelfth aspect and the transfer pattern possessed by the second photomask according to the twelfth aspect are applied to the same transfer object for proximity exposure. There is provided a pattern transfer method for transferring an image by using an exposure machine.

  According to the present invention, when a transfer pattern formed on a photomask is transferred to a transfer object by proximity exposure, the pattern transfer accuracy can be improved. In particular, when a plurality of photomasks are sequentially transferred to the same transfer object, the pattern overlay accuracy can be improved.

It is a flowchart which illustrates the outline of the manufacturing process of the color filter which concerns on this embodiment. (A) is a side view which illustrates a mode that proximity exposure is performed in the manufacturing process of the color filter concerning this embodiment, and (b) is the top view. (A) is a top view which illustrates the plane structure of the photomask which concerns on this embodiment, (b) is a top view which illustrates the modification. It is a schematic diagram which illustrates a mode that the transfer precision of a pattern deteriorates on the to-be-transferred material which superimposes and transfers a pattern, (a) is a cross-sectional enlarged view of the 1st photomask which forms a black matrix layer, (b) ) Is an enlarged cross-sectional view of the second photomask forming the red filter layer, and (c) shows how the pattern is transferred to the resist film. It is a flowchart which illustrates the manufacturing process of the photomask which concerns on this embodiment. It is a schematic diagram which illustrates a mode that flatness is measured by injecting a laser beam. It is a figure which shows the relationship between the superimposition of the substrate for photomasks, and a coordinate shift | offset | difference. It is a figure which illustrates the flatness profile of the main surface. It is the model which illustrates a mode that the transfer accuracy of a pattern deteriorates on the to-be-transferred material which superimposes and transfers a pattern, (a) is a cross-sectional enlarged view of the 1st photomask which shows a predetermined | prescribed flatness tendency, b) is an enlarged cross-sectional view of the second photomask showing the same flatness tendency as the first photomask, and (c) shows how the pattern is transferred to the resist film.

<One Embodiment of the Present Invention>
Hereinafter, an embodiment of the present invention will be described.

(1) Color Filter Manufacturing Process First, a color filter manufacturing process used in a liquid crystal display device and the like will be described with reference to FIGS. FIG. 1 is a flowchart illustrating the outline of the manufacturing process of the color filter according to this embodiment. FIG. 2A is a side view illustrating a state in which proximity exposure is performed in the manufacturing process of the color filter according to this embodiment, and FIG. 2B is a plan view thereof. FIG. 3A is a plan view illustrating the planar configuration of the photomask according to this embodiment, and FIG. 3B is a plan view illustrating a modification thereof.

  As shown in FIG. 1, the color filter 10 for a liquid crystal display device is a process of forming a black matrix layer 12p constituting a color boundary portion on one main surface of a translucent substrate 11 (FIG. 1A). And (e)) and a step of forming a color filter layer such as a red filter layer 14p, a green filter layer 15p, and a blue filter layer 16p on one main surface of the translucent substrate 11 partitioned by the black matrix layer 12p. (FIG. 1 (f)-(j)) is manufactured by implementing sequentially. Below, each process is demonstrated.

(Formation of black matrix layer)
First, a translucent substrate 11 made of a translucent resin, glass or the like is prepared, a light shielding material film 12 is formed on one main surface of the translucent substrate 11, and a resist film 13 is formed on the light shielding material film 12. Is formed (FIG. 1A).

  Then, the first photomask 100 for forming the black matrix and the translucent base material 11 on which the light shielding material film 12 and the resist film 13 as the transfer target are formed are disposed in the exposure machine 500 for proximity exposure. (FIG. 1 (b), FIG. 2).

  3A, the first photomask 100 has a predetermined light shielding film formed on one main surface of the transparent substrate 101 (the lower surface in FIG. 1B). The pattern region 133 having the transfer pattern 112p formed by the above patterning is provided (hereinafter, the region to be formed may be the pattern region 133 in addition to the region where the transfer pattern 112p is formed). ). The shape of the transfer pattern 112p is, for example, a lattice shape so as to form a black matrix layer 12p described later. In addition, the main surface of the transparent substrate 101 of the first photomask 100 has an exposure machine 500 in the vicinity of each of the two opposing sides that form the outer periphery of the main surface of the transparent substrate 101 outside the pattern region 133. A holding portion (supporting region) 103 that comes into contact with the holding (supporting) member 503 is provided. The holder 103 may be formed with a light shielding film, and one main surface of the transparent substrate 101 may be exposed.

  As shown in FIG. 2A, the holding unit 103 is supported from below by the holding member 503 of the exposure apparatus 500, so that the first photomask 100 is disposed in the exposure apparatus 500 in a horizontal posture. Then, the transfer pattern 112p included in the first photomask 100 and the resist film 13 formed on the translucent substrate 11 face each other, and are disposed close to a proximity gap distance of, for example, 10 μm to 300 μm. The

  When the first photomask 100 and the translucent base material 11 on which the light shielding material film 12 and the resist film 13 are formed are arranged in the exposure device 500 for proximity exposure, and alignment is completed, the light source 501 and the irradiation are performed. Using the system 502, the resist film 13 is exposed through the transfer pattern 112p by irradiating light such as ultraviolet rays from the back surface side of the first photomask 100 (that is, the second main surface side of the transparent substrate 101). A part of the film 13 is exposed (FIGS. 1C and 2A). A light source in a wavelength region including i-line, h-line, and g-line can be used for exposure.

  Then, the first photomask 100 and the light-transmitting base material 11 after the exposure on which the light shielding material film 12 and the resist film 13 are formed are removed from the exposure machine 500. Then, the resist film 13 is developed to form a resist pattern 13p that partially covers the light shielding material film 12 (FIG. 1D).

  Then, the light shielding material film 12 is etched using the formed resist pattern 13p as a mask to form a black matrix layer 12p on one main surface of the translucent substrate 11. When the black matrix layer 12p is formed, the resist pattern 13p is removed (FIG. 1E).

(Formation of red filter layer)
Subsequently, a red resist film 14 made of, for example, a photosensitive resin material is formed on one main surface of the translucent substrate 11 on which the black matrix layer 12p is formed (FIG. 1 (f)).

  Then, the second photomask 200 for forming the red filter layer and the translucent base material 11 as the transfer object on which the black matrix layer 12p and the red resist film 14 are formed are used for the above-described exposure apparatus for proximity exposure. It arrange | positions in 500 (FIG.1 (g)).

  As illustrated in FIG. 3A, the second photomask 200 has a light-shielding film on the main surface (the lower surface in FIG. 1G) of the transparent substrate 201 with a predetermined transfer. A pattern region 233 having a transfer pattern 212p processed into a pattern for use is provided. The shape of the transfer pattern 212p is a shape for forming the red filter layer 14p, and is different from the transfer pattern 112p of the first photomask 100. An exposure machine 500 is provided on one main surface of the transparent substrate 201 of the second photomask 200 on the outside of the pattern region 233 and in the vicinity of each of the two opposing sides constituting the outer periphery of the transparent substrate 201. A holding portion (support region) 203 on which the holding member 503 is provided is provided. A light shielding film may be formed on the holding unit 203, and one main surface of the transparent substrate 201 may be exposed.

  As shown in FIG. 2A, the holding unit 203 is supported from below by the holding member 503 of the exposure apparatus 500, so that the second photomask 200 is disposed in the exposure apparatus 500 in a horizontal posture. Then, the transfer pattern 212p included in the second photomask 200 and the red resist film 14 formed on the translucent substrate 11 face each other and are arranged close to the proximity gap distance described above.

  When the second photomask 200 and the translucent base material 11 on which the black matrix layer 12p and the red resist film 14 are formed are arranged in the exposure machine 500 for proximity exposure, and alignment is completed respectively, the light source 501 and The irradiation system 502 is used to irradiate light such as ultraviolet rays from the back side of the second photomask 200 to expose the red resist film 14 through the transfer pattern 212p, thereby exposing a part of the red resist film 14 ( FIG. 1 (h)).

  Then, the second photomask 200 and the translucent substrate 11 on which the red resist film 14 is exposed are removed from the exposure machine 500. Then, the red resist film 14 is developed to remove excess red resist film 14, and the remaining red resist film 14 is baked and cured to form a red filter layer 14p (FIG. 1 (i)). .

(Formation of green filter layer and blue filter layer)
Subsequently, the green filter layer 15p and the blue filter layer 16p are formed in the same manner as the red filter layer 14p, and the red filter layer 14p is formed on one main surface of the translucent substrate 11 divided by the black matrix layer 12p. Then, the process of forming the color filter layers such as the green filter layer 15p and the blue filter layer 16p is completed (FIG. 1 (j)).

(Formation of ITO electrode)
Thereafter, although not shown, an ITO film is formed so as to cover the upper surfaces of the color filter layers such as the black matrix layer 12p, the red filter layer 14p, the green filter layer 15p, and the blue filter layer 16p, thereby forming a transparent electrode. Exit.

(2) Pattern transfer accuracy As described above, the color filter 10 is manufactured using a photomask or the like that forms the black matrix layer 12p, the red filter layer 14p, the green filter layer 15p, and the blue filter layer 16p. Multiple exposures by proximity exposure are performed. However, when proximity exposure is performed, the transfer accuracy provided by each photomask is sufficiently high and within the reference range, the transfer accuracy may be insufficient as a result of overlaying the transfer patterns. It was found.

  According to the earnest studies by the inventors, it has been found that the deterioration of the transfer accuracy is caused by the transfer coordinate fluctuation caused by the slight height fluctuation of the pattern area in each photomask. Furthermore, it has been found that this deterioration in transfer accuracy may affect the function of the final product without considering that it can be amplified by superimposing transfer patterns of a plurality of photomasks on the transfer target. . 4A and 4B are schematic views illustrating a state in which the pattern transfer accuracy deteriorates when the proximity exposure is continuously performed. FIG. 4A is an enlarged cross-sectional view of the photomask 100 ′ forming the black matrix layer. ) Is an enlarged cross-sectional view of the photomask 200 ′ for forming the red filter layer, and (c) shows how the pattern is transferred to the resist films 13 and 14. Of course, these may be photomasks used for forming other layers.

  As shown in FIG. 4C, the exposure light irradiated from the exposure device 500 to the resist films 13 and 14 via the photomasks 100 ′ and 200 ′ is perpendicular to one main surface of the photomasks 100 ′ and 200 ′. It is assumed that the light is incident on. However, in reality, this incident angle that is slightly inclined cannot be completely excluded, and may be incident at a predetermined angle (for example, θ). In reality, the upper limit of θ is about 1 degree. In such a case, the position of the pattern transferred to the resist films 13 and 14 is obliquely projected, so that a predetermined amount is shifted in the horizontal direction in accordance with the magnitude of the inclination θ of the exposure light. In FIG. 4C, exposure light is incident at an angle θ with respect to the normal of the main surface of the photomasks 100 ′ and 200 ′, so that the pattern transfer position is shifted by S0 in the horizontal direction. Is shown.

  Even if the above-described transfer deviation occurs, if the deviation amount S0 is constant over the entire surfaces of the resist films 13 and 14, the transfer accuracy is hardly affected. However, according to the earnest studies by the inventors, it has been found that the deviation amount S0 locally changes according to the flatness of the main surface of the transparent substrates 101 'and 201'. Then, it was found that local deterioration of the pattern transfer accuracy occurred with the fluctuation of the deviation amount S0. In particular, even if the amount of local variation in the amount of deviation is within the permissible range for each photomask alone, when the patterns are superimposed using multiple photomasks in sequence, the variation at a predetermined overlay position If the directions are different from each other (for example, one photomask may change so that the amount of deviation increases at a predetermined overlapping position, and the other photomask may change so that the amount of deviation decreases at that position. In other words, it has been found that the accumulated value of the amount of fluctuation when superimposed may locally exceed the allowable range of transfer accuracy.

  FIG. 4A shows an enlarged cross-sectional view of a photomask 100 ′ in which a concave structure having a depth of Zm exists on one main surface of the transparent substrate 101 ′ in the transfer pattern 112 p ′. When proximity exposure is performed using such a photomask 100 ′, as shown in FIG. 4C, the height position (Z position) of the transfer pattern 112p ′ formed in the concave structure is as follows. Compared to the height position (Z position) of the transfer pattern 112p ′ in the flat area, the height is higher by Zm (at the point M). As a result, the amount of deviation S1 of the concave structure caused by the exposure light being inclined by the angle θ is locally larger than the amount of deviation S0 of the flat portion (S1> S0).

  On the other hand, FIG. 4B shows an enlarged cross-sectional view of a second photomask 200 ′ in which a convex structure having a height of Zn exists on one main surface of the transparent substrate 201 ′ in the transfer pattern 212 p ′. As shown in FIG. 4C, when proximity exposure is performed using such a second photomask 200 ′, the height position (Z position) of the transfer pattern 212p ′ formed on the convex structure is the same. The height is lower by Zn at the maximum (at the N point) than the height position (Z position) of the transfer pattern 212p ′ in other flat regions. As a result, the deviation amount S2 of the convex structure portion caused by the exposure light being inclined by the angle θ is locally smaller than the above-described deviation amount S0 of the flat portion (S2 <S0).

  The deterioration of the pattern transfer accuracy described above is a problem caused by one proximity exposure using a single photomask, but according to the inventors' earnest research, the variation of the shift amount S0 is In particular, it has been found that when a plurality of photomasks are sequentially used to perform proximity exposure on the same transfer target, the pattern transfer accuracy may be further deteriorated. That is, for example, as shown in FIG. 4C, when the concave structure existing in the first photomask 100 ′ and the convex structure existing in the photomask 200 ′ overlap on the vertical axis, the proximity exposure is continued. As a result, the coordinate positions of the transfer patterns of the black matrix layer and the red filter layer in the concavo-convex structure portion are locally shifted by the maximum | S1-S2 | (= | −Zm − (+ Zn) | · tan θ). . In other words, even if the coordinate accuracy of a single photomask is within the standard, the photomask that constitutes the photomask set that uses the transfer pattern superimposed is processed and selected in consideration of the above factors. Must-have. In addition, it has been clarified that a stricter evaluation is required for the flatness of a photomask substrate that is likely to produce a photomask constituting a photomask set.

  As a result of earnest research, the inventors have found that it is effective to control the height fluctuation of one main surface of the transparent substrate in the pattern region in order to improve the pattern transfer accuracy when performing proximity exposure. Got.

  According to the present embodiment to which such knowledge is applied, a photomask substrate for forming a transfer pattern on the main surface to become a photomask, the maximum fluctuation in the height of the pattern area on the main surface A photomask substrate having a value ΔZmax of 8.5 (μm) or less is used.

  That is, a photomask substrate in which the maximum value ΔZmax in the pattern region of | −Zm − (+ Zn) | mentioned above is 8.5 μm or less is used. Beyond this, the coordinate deviation that occurs on the transferred body may exceed the allowable range due to the combination with the height variation of the pattern area of the photomask for overlay exposure on the same transferred body. Incidentally, the allowable range of the coordinate deviation here will be described later.

  The photomask substrate of the present embodiment can be obtained by precision polishing of a transparent substrate and further by substrate selection. However, if this numerical value is excessively small, the surface processing of the substrate may exceed the capacity of the processing apparatus or may require an excessive processing time. Therefore, the maximum value ΔZmax in the pattern region is preferably 1 μm or more.

  The maximum value ΔZmax of the height fluctuation of the pattern area can be a difference between the maximum value and the minimum value when the height Z with respect to the reference plane at any point in the pattern area is obtained.

  An arbitrary point can be defined and standardized as follows, for example. That is, points set at equal intervals with a predetermined separation distance P in the pattern area can be set as arbitrary points. For example, the height Z of all lattice points when a lattice is drawn in the XY direction at a predetermined separation distance P (preferably 5 mm or more and 15 mm or less, for example, 10 mm) in the pattern region of the photomask substrate. Is the measurement point, the difference between the maximum value and the minimum value can be the maximum value ΔZmax.

  Here, as described later, the height Z can be measured using a flatness measuring device, and can be obtained using a reference plane defined by the apparatus. Note that when measuring the height Z at each point in the pattern region, it is preferable to perform the measurement in a state where the photomask substrate is vertical and the influence of bending due to its own weight is substantially eliminated.

  Such flatness control of the photomask substrate has the following advantages.

  The device pattern of a liquid crystal display device has been miniaturized. There is a strong demand for thinning a black matrix (hereinafter also referred to as BM) used for a color filter. Conventionally, it is expected that a BM width of about 10 μm is about 8 μm or about 6 μm, and the difficulty of manufacturing technology is further increased.

  For example, consider a case where a BM having a BM width of 6 μm or less is to be formed (FIG. 7A). When the color plate is superimposed on the BM, the maximum value of the coordinate deviation allowed on one side (for example, on the BM, the same applies hereinafter) is 3 μm (FIG. 7B). This is because inconvenience such as color turbidity occurs when the boundary between the color plates (for example, red and blue) protrudes from the width of the BM. Further, considering that there is a line width error of the color plate itself and a line width error of the BM itself, one of the coordinate deviations must be within (3 μm × 1/2 × 1/2 =) 0.75 μm. (Fig. 7 (c)).

  Incidentally, since the drawing reproducibility of the drawing apparatus is about 0.15 μm, the margin on the photomask substrate side is (0.75−0.15 =) 0.60 μm. This is the allowable value of the coordinate deviation caused by the photomask (FIG. 7D).

  However, the cause of the coordinate shift caused by the photomask substrate is not only due to the flatness (height variation) of the main surface of the photomask. According to the study by the inventors, there are a plurality of factors, and as a significant one (a factor that cannot be ignored), in addition, distortion of the transfer pattern due to contact between the holding member 503 of the exposure device 500 and the photomask, There is an element such as the shape of the second main surface (back surface) corresponding to the pattern region. Here, the shape of the second main surface is not negligible because it is related to the coordinate shift that occurs when the transfer pattern is drawn.

  Therefore, in order to distribute the allowable coordinate deviation amount to the above three main factors (FIG. 7 (e)) and satisfy Cpk (process capability index) 1.3, it is caused by the variation in the height of the pattern region. The allowable amount of deviation to be performed must be within 0.15 μm in a single photomask (therefore, the amount of deviation caused by the combination of two photomasks must be within 0.3 μm) (FIGS. 7F and 4C). ) S1-S2).

As described above, the deviation amount is [ΔZmax · tan θ], and the upper limit of θ is 1 degree.
ΔZmax · tanθ ≦ 0.15 (μm)
Therefore, ΔZmax ≦ 8.59 (deg)
If the maximum height variation ΔZmax is 8.5 μm or less, the coordinate shift caused by this element can be suppressed to such an extent that the BM performance is not affected.

  More preferably, the pattern region height variation maximum value ΔZmax is 7.5 (μm) or less. In this case, the coordinate accuracy of the next liquid crystal display device having a black matrix line width of about 5.5 μm can be satisfied.

  The plurality of measurement points can be set at equal intervals with a predetermined separation distance P in the pattern transfer region on the main surface. The main purpose of this embodiment is to suppress the deterioration of coordinate accuracy during transfer due to the non-uniform surface shape in the pattern area. If the separation distance of the measurement points is too large, the obtained height fluctuation The accuracy of the value decreases. However, since the transparent glass substrate for photomask has been subjected to precision polishing, unevenness with a small period has been removed, so that a sufficient height variation profile can be obtained by setting the measurement point at a separation distance of 5 mm or more. It is done. Specifically, the distance between the measurement points can be 5 ≦ P ≦ 15 (mm). For example, it is preferable to set a grid point of a 10 mm wide grid as a measurement point.

(3) Photomask Manufacturing Method A photomask manufacturing method according to the present embodiment will be described below with reference to FIGS. FIG. 5 is a flowchart illustrating the manufacturing process of the photomask according to this embodiment. FIG. 6 is a schematic view illustrating a state in which flatness is measured by entering laser light. In the following description, the case where the first photomask 100 for forming the black matrix is manufactured will be described as an example. However, the manufacture of the second photomask to the fourth photomask for forming the color filter layer is also the first photomask. This can be performed in the same manner as the manufacturing of the mask 100.

(Preparation of transparent substrate and inspection of flatness)
First, a transparent substrate 101 as a photomask substrate is prepared (FIG. 5A). 3A, the transparent substrate 101 has a rectangular plate shape in plan view, and the dimensions thereof are, for example, 600 to 1400 (mm) for the long side L1 and 500 for the short side L2. ˜1300 (mm) and thickness T can be about 6 to 13 (mm). The transparent substrate 101 can be made of, for example, quartz (SiO ₂ ) glass, low expansion glass containing SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , RO, R ₂ O, or the like. On one main surface of the transparent substrate 101 (upper surface in FIG. 5A), the above-described transfer pattern 112p is to be formed. In addition, the holding unit 103 outside the region where the transfer pattern 112p is to be formed and in the vicinity of the two opposite sides (long side L1 in the present embodiment) constituting the outer periphery of the transparent substrate 101 is exposed to light. The holding member 503 of the machine 500 abuts.

  The main surface (front surface and back surface) of the transparent substrate 101 is polished to be flat and smooth. As described above, the flatness of one main surface of the transparent substrate 101 is precisely polished so that the maximum value ΔZmax of the height fluctuation of the pattern region 133 is 8.5 (μm) or less. Alternatively, a transparent substrate 101 that satisfies this criterion is selected.

  The flatness is measured as follows. In order to obtain the maximum value ΔZmax of the height fluctuation, the height Z of each measurement point is measured. The height Z of each point is the distance between each measurement point and the reference plane when a plurality of measurement points are defined on the main surface. Further, the in-plane variation of the height Z is the above-described height variation. For example, when measuring the distance using a flatness measuring instrument, the reference plane of the measuring instrument can be the reference plane. For example, as shown in FIG. 6, the inspection can be performed by using a method in which laser light is incident on one main surface in the support region. For example, it can be performed using a flatness measuring device FFT-1500 (registered trademark) manufactured by Kuroda Seiko Co., Ltd. or a device described in JP-A-2007-46946.

  FIG. 8 illustrates the profile of the height variation in the pattern region 133 of the transparent substrate 101 as the photomask substrate thus obtained.

  As described above, as described above, grid points having a separation distance P (preferably not less than 5 mm and not more than 15 mm, for example, 10 mm) are used throughout the pattern region 133, and the heights Z of all measurement points are obtained. Then, the maximum value ΔZmax of the height fluctuation is obtained. At this time, even if only the photomask having ΔZmax of 8.5 μm or less is combined and exposed to the same transfer target, the deterioration of the coordinate accuracy due to the variation in the height of the pattern region 133 is not substantially a problem. On the other hand, even if it exceeds 8.5 μm, it can be used as a mask set if the behavior of the height fluctuation of other photomasks used in combination is the same. This point will be described later.

(Formation of light shielding film and resist film)
Subsequently, a light shielding film 112 containing, for example, Cr as a main component is formed on the main surface of the transparent substrate 101 (FIG. 5B). The light shielding film 112 can be formed by a technique such as sputtering or vacuum deposition. The thickness of the light shielding film 112 is sufficient to block the irradiation light of the exposure device 500, and can be, for example, about 90 to 140 nm. Note that an antireflection layer mainly composed of, for example, CrO is preferably formed on the upper surface of the light shielding film 112. Further, the light shielding film 112 may not be formed on the holding portion 103.

  Then, a resist film 113 is formed on the light shielding film 112 (FIG. 5B). The resist film 113 can be composed of a positive photoresist material or a negative photoresist material. In the following description, it is assumed that the resist film 113 is formed from a positive photoresist material. The resist film 113 can be formed by a technique such as spin coating or slit coating.

(Patterning process)
Subsequently, drawing exposure is performed on the resist film 113 by a laser drawing machine or the like, and a part of the resist film 113 is exposed. Thereafter, a developing solution is supplied to the resist film 113 by a method such as a spray method and developed to form a resist pattern 113p that covers a part of the light shielding film 112 (FIG. 5C).

  Then, a part of the light shielding film 112 is etched using the formed resist pattern 113p as a mask. The light shielding film 112 can be etched by supplying a chromium etching solution onto the light shielding film 112 by a spray method or the like. As a result, a transfer pattern 112 p formed by patterning the light shielding film 112 is formed on one main surface of the transparent substrate 101. Then, the resist pattern 113p is removed, and the manufacture of the first photomask 100 is completed (FIG. 5D).

  The flatness measurement described above may be performed after the photomask is formed. The method can be similar to the above.

<Other Embodiments of the Present Invention>
In the above-described embodiment, the case where the photomask substrate that satisfies the requirement that the maximum value ΔZmax of the height variation is 8.5 (μm) or less has been described. However, the present invention is not limited to the above-described embodiment, and a photomask substrate set as described below can be used.

That is,
A first photomask substrate for forming a transfer pattern to be transferred to a transfer object on the main surface to form a first photomask, and a transfer to be transferred to the transfer object in an overlapping manner with the transfer pattern A photomask substrate set comprising: a second photomask substrate for forming a pattern for use on a main surface to form a second photomask;
The height of the arbitrary point M set in the pattern area on the main surface of the first photomask substrate with respect to the reference plane is Zm,
The height of the point N at the position corresponding to the point M on the first photomask substrate in the pattern region on the main surface of the second photomask substrate with respect to the reference plane is Zn,
When the difference Zd between the Zm and the Zn is obtained,
A photomask substrate set in which the maximum value ΔZdmax of Zd is 17 (μm) or less in the pattern region can be used.

  As a result, it is possible to manufacture a liquid crystal display device or the like with excellent coordinate accuracy. That is, even if the photomask substrate alone does not satisfy the criterion that “the maximum value ΔZmax of height fluctuation is 8.5 (μm) or less”, a plurality of photomask substrate sets have the above-described profile of height fluctuation. In other words, when a plurality of photomask substrates having common height variation behaviors are combined to satisfy the criterion that “maximum height variation ΔZdmax as a set is 17 (μm) or less” These photomask substrates can be satisfactorily used as a photomask substrate set for superimposing patterns on the same transfer target.

  For example, as shown in FIG. 9, at least one of the substrate for the first photomask 100 ′ and the substrate for the second photomask 200 ′ to be exposed with the transfer pattern superimposed on the same transfer target is “high”. In addition to the case where the maximum variation ΔZmax satisfies the criterion of 8.5 (μm) or less, for example, when both of the pattern surfaces are concave, these “mask sets for photomasks” The maximum value ΔZdmax of the height fluctuation can be set to 17 μm or less ”. This is because the allowable deviation amount due to the variation in the height of the pattern region is within 0.15 μm in a single photomask (therefore, the deviation amount caused by the combination of two photomasks is within 0.3 μm). (S1-S2 in FIG. 4C). In other words, if the flatness profile of the partner photomask is known, the height variation ΔZmax of each photomask is allowed to exceed 8.5 μm. As a result, it is possible to relax the requirement standard for flatness of the photomask substrate alone, and to reduce the production cost of the photomask without deteriorating the coordinate accuracy.

  Note that, in the above, the same transferred object is one in which thin films to be patterned are laminated or laminated in the patterning process, and the transfer pattern of each photomask is aligned. These are the objects to be transferred in sequence. For example, a black matrix or a color plate photomask can be sequentially superimposed and transferred to the transfer object, and a color filter can be manufactured, or a thin film transistor photomask can be further overlapped and transferred to the transfer object. A liquid crystal display device can be manufactured. Note that the transfer target includes a state in which a resist film serving as a mask for patterning is applied.

  The maximum value ΔZdmax of the difference in height (Zd = | −Zm − (− Zn) |) between the substrate for the first photomask 100 ′ and the substrate for the second photomask 200 ′ constituting the photomask substrate set is obtained. The method can be similar to the above.

  That is, a plurality of measurement points M1, M2, M3... Are set on the first photomask 100 'substrate. A plurality of measurement points M1... Are set at equal intervals in the pattern region on the first photomask 100 'substrate. For example, it can be set as a lattice point when a lattice is drawn in the XY direction at a predetermined interval (for example, 10 mm) in the pattern region. And about M1, M2, M3 ..., the value of height Zm1, Zm2, Zm3 ... with respect to a reference plane is obtained. On the other hand, in the second photomask 200 ′ substrate, similarly, when lattice points N1, N2, N3... Are set at positions corresponding to the first photomask 100 ′ substrate, their reference planes are set. Heights Zn1, Zn2, Zn3... Are obtained. Then, the maximum value ΔZdmax can be obtained from the difference in height between the substrates at the corresponding positions (Zd = | −Zn − (− Zm) |).

  In addition, the same evaluation as described above can be performed for a photomask group formed by forming a transfer pattern on each of these photomask substrates. Therefore, the present invention can use a photomask set as described below, as in this embodiment.

That is,
A first photomask having a transfer pattern to be transferred to a transfer target body formed on the main surface, and a transfer pattern to be transferred to the transfer target body superimposed on the transfer pattern; A photomask set comprising two photomasks,
The height of an arbitrary point M set in the pattern area on the main surface of the first photomask with respect to the reference plane is Zm,
The height of the point N at the position corresponding to the point M on the first photomask in the pattern region on the main surface of the second photomask with respect to the reference plane is Zn,
When the difference Zd between Zm and Zn is obtained, a photomask set in which the maximum variation ΔZdmax of Zd is 17 (μm) or less in the pattern region can be used.

  In the above-described photomask substrate set and photomask set, ΔZdmax is more preferably 15 (μm) or less.

  Furthermore, in this embodiment, a transfer method using these photomask sets can be performed. That is, the transfer pattern included in the first photomask and the transfer pattern included in the second photomask are transferred to the same transfer object by using an exposure machine for proximity exposure. Thereby, it is possible to obtain an electronic device such as a liquid crystal display device excellent in coordinate accuracy.

  For example, a color filter is manufactured using a black matrix and the above-described three color plates, and in any of four photomasks for these applications (or five photomasks with photo spacers added thereto) Even if two photolithographic processes are combined, the overlay accuracy is high and the yield is high as long as the above standard (ΔZdmax is 15 (μm) or less) is satisfied. It is.

<Still another embodiment of the present invention>
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

  For example, the holding units 103 and 203 are not limited to a pair provided as in the above-described embodiment, and more holding units 103 and 203 may be provided along the periphery of the photomask. That is, as shown in FIG. 3B, the main surfaces of the transparent substrates 101 and 201 that are rectangular in plan view are formed outside the pattern formation region 133 and constitute the outer periphery of the transparent substrates 101 and 201. Four band-shaped holding portions 103 and 203 may be provided in the vicinity of each of the sides (L1, L2). For example, the four holding portions 103 and 203 are outside the pattern formation region 133 and are separated by 10 mm from each of the four sides constituting the outer periphery of the photomasks 100 and 200 and 50 mm from each of the four sides. It can be configured as four belt-like regions parallel to the four sides, sandwiched between straight lines. Furthermore, the holding portions 103 and 203 can be provided on the second main surface side of the transparent substrates 101 and 201.

  Further, for example, the black matrix layer 12p is not limited to a case where a metal material such as Cr is a main component, but may be formed of a photosensitive resin having a light shielding property. When the photosensitive resin is used, the black matrix layer 12p can be formed by sequentially performing exposure, development, and baking, like a color filter layer.

  Furthermore, although the above-mentioned embodiment demonstrated the case where the transparent glass substrate manufactured by grind | polishing quartz etc. was used as a photomask substrate, this invention is not limited to the form which concerns. For example, as a photomask substrate, a photomask blank in which any one of an optical film and a resist is formed on the transparent glass substrate, or a photomask intermediate in a process of forming a predetermined transfer pattern on the photomask is used. Even when used, the present invention is preferably applicable.

  According to the present invention, the transfer performance of each photomask substrate used for overlay transfer can be evaluated from the stage of the transparent substrate prior to the formation of the transfer pattern. Moreover, from the analysis of the height fluctuation of the pattern area, it was possible to provide the merit in mass production using the performance evaluation of each photomask and the performance evaluation of the photomask set used in combination. This merit is useful not only for color filters but also for the manufacture of products to which proximity exposure can be applied, such as thin film transistors and organic EL.

100 First photomask 101 Transparent substrate (first photomask substrate)
103 Support region 112p Transfer pattern 133 Pattern region 200 Second photomask 201 Transparent substrate (second photomask substrate)
203 Support Area 212p Transfer Pattern 233 Pattern Area 500 Exposure Machine 503 Support Member

Claims (5)

A first photomask substrate for forming a transfer pattern to be transferred to a transfer object on the main surface to form a first photomask, and a transfer to be transferred to the transfer object in an overlapping manner with the transfer pattern A photomask substrate set comprising: a second photomask substrate for forming a pattern for use on a main surface to form a second photomask;
The height of an arbitrary point M set in the pattern area on the main surface of the first photomask substrate with respect to a reference plane is Zm, and the height in the pattern area on the main surface of the second photomask substrate is Zm. When the height of the point N at the position corresponding to the point M on the first photomask substrate with respect to the reference plane is Zn and the difference Zd between the Zm and the Zn is obtained, in the pattern region, A photomask substrate set, wherein the maximum value ΔZdmax of Zd is 17 (μm) or less. Each of the first photomask substrate and the second photomask substrate has a main surface with a side of 500 mm or more, and a transfer pattern for manufacturing a display device is formed on the main surface, respectively. The photomask substrate set according to claim 1 , wherein the photomask substrate set is used as a mask. A first photomask having a transfer pattern to be transferred to a transfer target body formed on the main surface, and a transfer pattern to be transferred to the transfer target body superimposed on the transfer pattern; A photomask set comprising two photomask substrates,
The height of an arbitrary point M set in the pattern region on the main surface of the first photomask with respect to a reference plane is Zm, and the first photomask in the pattern region on the main surface of the second photomask When the height of the point N at the position corresponding to the upper point M with respect to the reference plane is Zn, and the difference Zd between the Zm and the Zn is obtained, the maximum value ΔZdmax of the Zd in the pattern region Is a photomask set, wherein the photomask set is 17 (μm) or less. The first photomask and the second photomask are photomasks for proximity exposure, each having a main surface with a side of 500 mm or more, and a transfer pattern for manufacturing a display device formed on each main surface. The photomask set according to claim 3 , wherein the photomask set is a feature. A transfer pattern having a first photo-mask according to claim 3, a transfer pattern having a second photo mask according to claim 3, identical to the material to be transferred, the exposure for the proximity exposure A pattern transfer method characterized by superimposing and transferring using a machine.