CN110007555B

CN110007555B - Pattern drawing method, photomask and manufacturing method thereof, and manufacturing method of display device

Info

Publication number: CN110007555B
Application number: CN201811530914.3A
Authority: CN
Inventors: 金谷健一
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2017-12-18
Filing date: 2018-12-14
Publication date: 2022-07-08
Anticipated expiration: 2038-12-14
Also published as: CN110007555A; JP7126925B2; TWI710848B; TW201928508A; KR102229514B1; JP2019109499A; KR20190073276A

Abstract

The invention relates to a pattern drawing method, a method for manufacturing a photomask, and a method for manufacturing a display device. The variation of pattern CD is reduced, and stable yield is obtained. The pattern drawing method includes: a correction step of obtaining correction pattern data by correcting the design pattern data based on a correction value obtained in advance so that the CD of the hole/dot pattern obtained on the transfer object by exposing the photomask is equal to a target value; and a drawing step of applying the correction pattern data and drawing the image with a drawing device. The drawing device is driven by a driving method having different CD control accuracies in the X direction and the Y direction perpendicular to the X direction within a plane parallel to the surface of the photomask substrate. In the correction step, the CD of the hole/dot pattern is corrected in the design pattern data by changing the CD in the direction having high CD control accuracy in the X direction and the Y direction, thereby obtaining correction pattern data.

Description

Pattern drawing method, photomask and manufacturing method thereof, and manufacturing method of display device

Technical Field

The present invention relates to a photomask used for manufacturing an electronic device, and more particularly, to a method for manufacturing a photomask useful for manufacturing a photomask used for manufacturing a display device typified by a liquid crystal display panel (LCD), an organic EL display (OLED), or the like, and a pattern drawing method used in the manufacturing method.

Background

Patent document 1 (hereinafter, referred to as document 1) describes a method of correcting a pattern line width variation occurring in a development stage and performing exposure when manufacturing a photomask. The exposure method comprises the following steps: a step of forming a measurement pattern on the photomask substrate by a test pattern having a predetermined line width; a step of dividing the region on the photomask substrate into meshes, measuring the line width of the measured pattern for each mesh, and determining the pattern line width variation Δ CD which is the difference between the measured line width and the line width of the test pattern; a step of preparing a graph showing a distribution of the measured pattern line width variation Δ cd (r) with respect to the distance r from a grid having a distance r from an arbitrarily determined reference grid; predicting a pattern line width variation Δ cd (x) at an arbitrary position on the photomask substrate at a distance x from the reference grid based on the graph; a step of correcting pattern line width data by reducing the pattern line width of a region where the predicted pattern line width variation Δ cd (x) is positive in order to enlarge the pattern line width of a region where the predicted pattern line width variation Δ cd (x) is negative for each position on the photomask substrate; and a step of applying pattern line width data obtained by correcting each position on the photomask substrate to exposure equipment.

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-107665

Disclosure of Invention

According to document 1, when a photomask for manufacturing a semiconductor device is manufactured, a variation in pattern line width generated in a development stage is compensated for to improve uniformity of the pattern line width.

However, according to the studies of the present inventors, there is a factor of changing the line width of a pattern (i.e., CD: Critical Dimension) in addition to the line width of the pattern generated in the development stage when manufacturing a photomask. For example, in the production process of a photomask, there are also CD errors caused by a drawing device, and various stages such as a stage of exposing a pattern on a transfer object by using the photomask and a development of the exposed pattern have a factor causing CD variations. Therefore, it is difficult to obtain an excellent device (display device or the like) by exposure through a photomask only by the method of document 1.

Therefore, the present invention has been accomplished to solve the following problems: when manufacturing an electronic device (for example, a display device) as a final product, the variation of a pattern CD is reduced, and stable yield and production efficiency are obtained.

(1 st mode)

The 1 st aspect of the present invention is a pattern drawing method for drawing a pattern on a photomask substrate based on predetermined design pattern data to form a photomask having a transfer pattern including a hole/dot pattern,

the pattern drawing method is characterized by comprising:

a correction step of obtaining correction pattern data by correcting the design pattern data based on a correction value obtained in advance so that a CD of a hole/dot pattern obtained on a transfer object by exposing the photomask becomes equal to a target value; and

a drawing step of drawing with a drawing device by applying the correction pattern data,

the drawing device is driven by a driving method having different CD control accuracies in an X direction and a Y direction perpendicular to the X direction in a plane parallel to the surface of the photomask substrate,

in the correction step, the CD of the hole/dot pattern is corrected in the design pattern data by changing the CD in the direction having high CD control accuracy in the X direction and the Y direction, thereby obtaining correction pattern data.

(2 nd mode)

According to the pattern drawing method of the above-mentioned 1, the invention of claim 2 is characterized in that,

in the correction step, a target area of a hole/dot pattern of the transfer pattern is determined, and the CD of the hole/dot pattern obtained on the object to be transferred is equal to the target area,

the CD of the hole/dot pattern is corrected in the design pattern data in accordance with the target area of the hole/dot pattern of the transfer pattern, so that correction pattern data in which the CD in the X direction and the Y direction is changed with high CD control accuracy is obtained.

(3 rd mode)

The 3 rd aspect of the present invention is a pattern drawing method for forming a photomask having a transfer pattern including a hole/dot pattern by drawing on a photomask substrate based on predetermined design pattern data,

the pattern drawing method is characterized by comprising:

a correction step of obtaining correction pattern data by correcting the design pattern data based on a correction value obtained in advance so that an area of a hole/dot pattern obtained on a transfer object by exposing the photomask becomes equal to a target value; and

(4 th mode)

According to the pattern drawing method of the 3 rd aspect, the 4 th aspect of the present invention is characterized in that,

in the correction step, a target area of a hole/dot pattern on the transfer object is determined,

determining a target area of a hole/dot pattern of the transfer pattern from the target area of the hole/dot pattern on the object to be transferred,

(5 th mode)

According to the pattern drawing method of any one of the above-described 1 to 4 aspects, a 5 th aspect of the present invention is characterized in that,

the drawing device is a laser drawing device that performs drawing with a laser beam.

(mode 6)

According to the pattern drawing method of any one of the above-described 1 to 4 aspects, the present invention is characterized as the 6 th aspect,

the X-CD and Y-CD of the hole/dot pattern in the transfer pattern are smaller than the resolution limit size of an exposure apparatus that exposes the photomask.

(7 th mode)

According to the pattern drawing method of any one of the above-described 1 to 4 aspects, a 7 th aspect of the present invention is characterized in that,

the X-CD and Y-CD of the hole/dot pattern in the transfer pattern are less than 3 μm.

(8 th mode)

According to the pattern drawing method of any one of the above-described 1 to 4 aspects, an 8 th aspect of the present invention is characterized in that,

in the above-described drawing apparatus, the laser beam is fed in the X direction with a fixed feed width, and then is irradiated in the Y direction with a fixed width, and the drawing apparatus draws on the photomask substrate by repeating these operations alternately.

(9 th mode)

According to the pattern drawing method of any one of the above-described 1 to 4 aspects, a 9 th aspect of the present invention is characterized in that,

in the correction step, the CD of the design pattern data is replaced with a CD correction value obtained so that the area of the hole/dot pattern included in the design pattern data is equal to the area of the hole/dot pattern on the photomask substrate, thereby obtaining the correction pattern data.

(10 th mode)

According to the pattern drawing method of any one of the above-described 1 to 4 aspects, a 10 th aspect of the present invention is characterized in that,

a step of obtaining a preliminary mask obtained by performing pattern drawing by the drawing device before the correction step; and

and a correction value grasping step of grasping the correction value by X-CD and Y-CD of the preliminary mask.

(11 th mode)

An 11 th aspect of the present invention is a method for manufacturing a photomask, including the pattern drawing method according to any one of the 1 st to 4 th aspects.

(12 th mode)

The 12 th aspect of the present invention is a photomask including a transfer pattern including a plurality of hole/dot patterns,

the photomask is characterized in that,

the X-CD and Y-CD of the plurality of hole/dot patterns in the transfer pattern are less than 3 μm,

the plurality of hole/dot patterns in the transfer pattern include a hole/dot pattern group having a quadrangular shape in which X-CDs are different from each other and areas are equal to each other.

(mode 13)

A 13 th aspect of the present invention is a method for manufacturing a display device, including:

preparing the photomask according to claim 12; and

and transferring the transfer pattern to a transfer object by an exposure device having an optical system with a numerical aperture of 0.08 to 0.20.

(14 th mode)

The 14 th aspect of the present invention is a method for manufacturing a display device, including transferring a pattern for transferring a photomask to a transfer target by exposing the photomask formed based on predetermined design pattern data to light,

the method for manufacturing a display device is characterized by comprising the following steps:

a drawing step of drawing the photomask substrate by a drawing device using the correction pattern data,

a step of forming a photomask having the transfer pattern by developing and etching the photomask substrate; and

a step of exposing the photomask to light by an exposure device to form a hole/dot pattern on the transferred object,

the X-CD and Y-CD of the hole/dot pattern in the transfer pattern are less than 3 μm,

in the correction step, the CD of the hole/dot pattern in the design pattern data is corrected by changing the CD in a direction having high CD control accuracy of the drawing device, out of the X-CD in the X direction and the Y-CD in the Y direction, to obtain correction pattern data.

(15 th mode)

According to the method for manufacturing a display device of claim 14, a 15 th aspect of the present invention includes:

a step of obtaining a preliminary mask obtained by performing drawing by the drawing device before the correction step; and

and a correction value grasping step of grasping the correction value by a CD of the hole/dot pattern formed on the transfer target by exposing the preliminary mask to light by the exposure device.

Effects of the invention

By applying the present invention, it is possible to accurately correct design pattern data used for drawing a photomask and improve CD accuracy of a transferred image obtained on a transferred object (i.e., a processed object used in a manufacturing apparatus) by exposing the corrected photomask.

Drawings

Fig. 1 (a) is a schematic plan view of a binary mask having a hole pattern, and fig. 1 (b) and (c) are diagrams in which CD errors on the mask with respect to the design size of the square hole pattern are measured for CDs in the X direction and the Y direction perpendicular to the X direction, and the CD errors are plotted.

Fig. 2 is a diagram schematically showing a laser beam feeding operation of the laser drawing device.

Fig. 3 is a diagram showing a case of CD control of a pattern in the Y direction.

Fig. 4 is a diagram showing a case of CD control of a pattern in the X direction.

Fig. 5 is a diagram showing an example of a mask pattern as a simulation target.

Fig. 6 is an aerial image formed on the transfer object when the mask pattern shown in fig. 5 is exposed, and is an aerial image on the transfer object obtained by virtually cutting at a position corresponding to a broken line shown in each mask pattern of fig. 5.

FIG. 7 is a view showing the amount of variation of X-CD on a transfer image when X-CD and Y-CD are changed for each size of hole pattern.

Fig. 8 is a graph showing the result of the optical simulation.

Detailed Description

In the field of display devices, there is a strong demand for miniaturization and high integration of pixels, as well as for brighter display and power saving, and there is a demand for improvement in display performance such as high-speed display and wide viewing angle.

For example, in the case of a Thin Film Transistor (TFT) used in the display device, if a contact hole formed in an interlayer insulating Film among a plurality of patterns constituting the TFT does not have a function of reliably connecting patterns of an upper layer and a lower layer, an accurate operation cannot be ensured. On the other hand, in order to realize a bright and power-saving display device by increasing the aperture ratio of a liquid crystal display device as much as possible, for example, the diameter (CD) of a contact hole is required to be sufficiently small, and the diameter of a hole pattern is also required to be miniaturized (for example, less than 3 μm) in accordance with the demand for high density of the display device. For example, a fine hole pattern having a diameter of 0.8 μm or more and less than 3 μm is required, and a technique capable of stably and efficiently forming the hole pattern is required.

In addition, in the field of photomasks for manufacturing semiconductor devices (LSIs) in which integration is high and miniaturization of patterns is significantly improved as compared with display devices, there are the following processes: in order to obtain higher resolution, an optical system having a high numerical aperture NA (for example, more than 0.2) is used in an exposure apparatus, thereby promoting a shorter wavelength of exposure light. As a result, in this field, excimer lasers of KrF and ArF (single wavelengths of 248nm and 193nm, respectively) are used. An EB (electron beam) drawing apparatus is used as a drawing apparatus for manufacturing a photomask.

On the other hand, in the field of photolithography for manufacturing a display device, the above-described method is not generally applied in order to improve resolution. For example, the NA (numerical aperture) of an optical system included in an exposure apparatus used in this field is about 0.08 to 0.2. In addition, the exposure light source often uses i-line, h-line, or g-line, and by using a wide wavelength light source mainly including these i-line, h-line, or g-line, the light quantity for irradiating a large area (for example, a square with a side of 300 to 2000 mm) of the photomask is obtained, and the production efficiency and the cost tend to be emphasized strongly.

In this situation, as described above, the demand for finer patterns is increasing in the manufacture of display devices. Here, when the technology for manufacturing a semiconductor device is directly applied to the manufacture of a display device, there are several problems. For example, conversion to an exposure apparatus having a high resolution with a high NA (numerical aperture) is technically difficult, and requires a large investment. Further, in the case of changing the exposure wavelength (for example, in the manufacture of a semiconductor device, a single wavelength is used for a short wavelength such as ArF excimer laser), if it is applied to a display device having a large area, the production efficiency is lowered, and a considerable investment is required. That is, the photomask for manufacturing a display device has a problem that cost and efficiency, which are conventional advantages, cannot be secured while pursuing miniaturization of a pattern which has not been achieved in the past.

In an exposure apparatus for manufacturing a display device, the limit size of a pattern (for example, a hole pattern) that can be discriminated is about 3 μm in most cases. On the other hand, as a photomask for manufacturing a display device, a hole/dot pattern of a CD having a size close to 3 μm or smaller than 3 μm may be required. Therefore, a method of finely transferring even a minute CD that cannot be secured by an exposure apparatus is required.

[ necessity of CD correction ]

In the manufacture of display devices, there is a strong demand for small hole patterns and dot patterns in which CD (Critical Dimension, hereinafter used in the meaning of pattern width) is stably formed in a desired size. On the other hand, exposure to a photomask causes the sizes of the patterns formed on the transfer target (display panel substrate, etc.) to be out of design, and causes the sizes to vary.

For example, in a photomask manufacturing process, the CD of a hole pattern or a dot pattern provided in a photomask may deviate from a design value.

Although the following description will be given mainly with reference to the case of forming a hole pattern as an example, the present invention is applicable not only to a hole pattern but also to a dot pattern. In this connection, the "hole pattern or dot pattern" is simplified and expressed as a "hole/dot pattern" in the present specification.

In manufacturing a photomask, first, the photomask is designed in accordance with the design of a device (display device or the like) to be obtained, and pattern data (design pattern data) for drawing is generated. Then, the design pattern data is used to draw on the photomask substrate by a drawing device. The photomask blank may be one in which an optical film (such as a light-shielding film) and a resist film used as a photomask pattern are formed on a transparent substrate, or may be an intermediate photomask in which an optical film and a resist film are formed to pattern a part of a stacked optical film and then further patterned. The photomask substrate subjected to the drawing is transferred to a developing process. The resist pattern formed by development is used as an etching mask to pattern an optical film, thereby obtaining a photomask having a transfer pattern. Ideally, the resulting photomask design should be one that faithfully reflects the design pattern data, and the pattern CD on the photomask should conform to the data shown in the design pattern data.

However, as the pattern to be processed is miniaturized, when the CD of the obtained photomask is measured, there is a case where a deviation occurs between the measured CD and the CD based on the design pattern data. As the reason, there are the following: for example, when there is a difference in individual outputs among a plurality of laser beams divided by a laser oscillator provided in the drawing device, or when there is a slight variation in driving of the laser head, CD errors that occur reproducibly with the same tendency are included.

In such a case, it is considered that if a photomask conforming to the design can be obtained by creating a preliminary mask by preliminarily drawing using predetermined design pattern data, measuring the CD of the formed transfer pattern, grasping the CD error tendency, and correcting the design pattern data of the photomask to be actually obtained so as to reflect the CD error tendency (case 1: case of mask CD failure).

When a pattern is transferred onto a transfer target (such as a display panel substrate) by an exposure apparatus using a photomask, an error may occur between the transfer target and a target CD in the obtained transfer image. In such a case, even when no CD error occurs in the transfer pattern of the photomask used (case 2: case of a panel CD defect).

As the cause of case 2, for example, there are the following cases: in the case where an in-plane distribution occurs in the film thickness of a resist film formed on a transfer object before exposure, or in the case where an in-plane deviation occurs in the supply of a developer during development, or the like, the CD which should be the same varies depending on the position on the transfer object. In particular, when the substrate (mother glass or the like) for a display device has a large size (one side exceeds 1000mm to 3000mm or the like), the in-plane process condition cannot be completely avoided from being uneven due to the structure of a resist coating apparatus and a developing apparatus, a liquid flow of a wet process, or the like.

In an exposure apparatus used for exposing a photomask, an in-plane light amount distribution may occur due to an apparatus configuration.

Even when the above-described process conditions and exposure conditions are not uniform in the plane, it is considered that if the same apparatus is used, the CD error occurring in a reproducible manner can be reduced by grasping the tendency and adopting a strategy for reducing the tendency. Specifically, it can be estimated that: the CD nonuniformity of the transferred image due to these in-plane nonuniformity is reflected in the pattern data of the photomask in advance, and the increase and decrease of the CD due to these nonuniformity tend to be corrected.

[ difficulty in CD correction ]

Therefore, for example, a CD error caused by the drawing device in the photomask manufacturing process is considered. When CD measurement is performed on the photomask to be formed, and the CD is different from the CD based on the design pattern data, the CD error is canceled out in advance, and therefore, the CD of the design pattern data should be corrected. For example, if the X-CD (CD in the X direction is also referred to as X-CD) of the hole pattern on the photomask is too large, correction to reduce the X-CD of the corresponding hole pattern in the design pattern data may be performed, or if the Y-CD (CD in the Y direction is also referred to as Y-CD) is too small, correction to increase the corresponding Y-CD in the design pattern data may be performed, based on the result obtained by CD measurement based on the photomask. However, according to the studies of the present inventors, such correction of design pattern data sometimes produces a case where satisfactory results cannot be obtained.

[ difference in controllability between X-CD and Y-CD described ]

Next, a photomask having a hole pattern as a transfer pattern will be described as an example. The hole pattern (also referred to as a mask hole pattern herein) provided in the photomask is useful, for example, when used as a transfer pattern for forming a contact hole in a transfer target. In addition, in this pattern, miniaturization tends to be remarkable in order to realize a current high-definition display device.

On the other hand, as the fine CD, for example, a pattern having a size smaller than the resolution limit size of an exposure apparatus used for exposure of a photomask is exemplified. There are few examples of display devices that generate such fine patterns. When such a pattern of a CD is provided, it is difficult to manufacture a photomask, and it is difficult to form a pattern having an accurate dimension in accordance with a design on the photomask.

In addition, the resolution limit size R of the exposure apparatus is defined by the following formula.

R＝k×(λ/NA)

The coefficient k is a constant, here 0.61. λ is the wavelength of light used for exposure. For example, when light having a plurality of wavelengths including i-line, h-line, g-line, and the like (also referred to as broad wavelength light) is used, an average value of the plurality of wavelengths (weighted average taking into consideration the light intensity of the included wavelengths) is used as the wavelength λ. Alternatively, the representative wavelength (e.g., i-line) is simply taken as the wavelength λ. And NA is a numerical aperture on the mask side of the projection optical system of the exposure apparatus.

In this way, in the process of manufacturing a photomask, as a cause of difficulty in forming a transfer pattern conforming to a design, the following is concerned: with the tendency toward finer patterns, the CD accuracy is not sufficient even for the drawing device used for drawing the patterns.

Therefore, the present inventors have verified the CD accuracy of the photomask. Here, when a square hole pattern (punched hole pattern) is to be formed on a photomask in order to form a hole pattern on a transfer target, CD controllability thereof is studied.

A photomask blank was prepared by forming a Cr-based light-shielding film on a substrate made of a transparent material and forming a positive photoresist film on the surface of the film. Then, a plurality of hole patterns each having a square shape with one side having a design size W1(μm) were drawn on the photoresist film by a laser drawing apparatus. Here, W1 gradually decreased from 5.5 μm to about 1.0. mu.m.

After the drawing, a resist pattern is formed by development, and the light shielding film is wet-etched using the resist pattern as a mask, thereby producing a binary mask having a hole pattern on the photomask substrate (fig. 1 (a)).

Next, the size of the hole pattern of the formed binary mask was measured. That is, CD errors with respect to the design dimensions of the square hole pattern on the binary mask are measured for the X direction and the Y direction CD perpendicular to the X direction (referred to as X-CD and Y-CD, respectively), and are plotted to obtain (b) and (c) of fig. 1.

In both (b) and (c) of fig. 1, as the CD as the design size becomes smaller from 5.5 μm, the errors of the X-CD and the Y-CD of the binary mask change to the negative side, and then, when the CD as the design size is smaller than 3 μm, the absolute value of the CD error amount of the binary mask becomes large sharply.

On the other hand, the above-described actions are different between X-CD and Y-CD. While the change in the error amount of Y-CD draws a smooth curve, irregular unevenness is visible in the change in the error amount of X-CD. When compared with Y-CD, the change of the error amount of X-CD is unstable and difficult to predict.

The drawing device used in this case is a laser drawing device, and a laser beam is fed in the X direction with a fixed feed width, and then is irradiated in the Y direction with a fixed width, and drawing is performed on the photomask substrate by repeating these operations alternately. That is, with respect to the CD accuracy of the pattern formed on the photomask, the CD controllability in the X direction and the Y direction differs depending on the driving mechanism of the drawing device.

Fig. 2 schematically shows the feeding action of the bundle of the above-described drawing device. Here, a case is shown in which the entire drawing area is drawn while repeating an operation of feeding a laser beam having a predetermined beam diameter (in the case of a single-beam drawing machine shown here) in the X direction by a predetermined feeding width and then scanning the laser beam in the Y direction by a predetermined width. These operations may be realized by only moving the head that emits the laser beam, or may be realized by moving the relative position with respect to the mounting table on which the photomask substrate is mounted.

Fig. 3 and 4 show the CD control of the patterns in the respective directions X, Y. The Y-CD of the pattern (fig. 3) can be controlled by switching ON/OFF (ON/OFF) the power of the laser beam. On the other hand, the X-CD (fig. 4) can be controlled by the arrangement width of the laser beams (and adjusting the power of the laser beams at the end portions as needed). That is, since the control methods of X-CD and Y-CD are different, the control accuracy also differs. If examined in conjunction with the results of (b), (c) of fig. 1, it can be concluded that: in this drawing apparatus, the control accuracy of the Y-CD is higher than that of the X-CD, the reproducibility is good when the CD correction is performed on the pattern data, and the desired correction value can be reflected in the drawing to obtain a predetermined effect.

In the above description, the description has been given of the drawing apparatus that performs the laser irradiation while scanning the laser beam in the Y direction with a fixed width after performing the feeding operation of the laser beam in the X direction with a fixed width, and performs the drawing by repeating these operations alternately, but the present invention is not limited to this embodiment. For example, the irradiation operation of the laser beam may be an operation (scanning irradiation) of turning ON/OFF (ON/OFF) the irradiation while scanning an area of a fixed width extending in the Y direction, or an operation (single irradiation) of performing one-shot irradiation with power adjustment ON the area of the fixed width. The present invention is not limited to the laser, and can be applied to other energy beams (for example, LEDs) as long as the effects of the present invention can be achieved.

Further, although the description has been given of the single beam, in a drawing device that performs drawing by operating a plurality of (multiple) beams, the accuracy of CD control in the X direction and the accuracy of CD control in the Y direction may be different from each other, and it is needless to say that the present invention can be applied to this case.

[ relationship between CD on photomask and CD on transferred body ]

In addition, when the pattern CD formed on the transfer object indicates a CD error of in-plane unevenness, the following method can be adopted: the defect is eliminated by performing appropriate CD correction in the pattern data for manufacturing the photomask for each pattern in which a CD error is generated. Therefore, when changing the X-CD and Y-CD of the photomask by a predetermined amount, it has been studied by performing optical simulation on how the aerial image (light intensity distribution) formed on the transfer target changes and how the CD of the pattern transferred onto the transfer target changes.

Fig. 5 shows an example of a mask pattern as a simulation object. In general, when a hole pattern such as a contact hole is formed in a transfer target, the shape of the hole pattern is square. Here, a photomask having a square punch pattern (a) was prepared by making the resist on the transferred object positive, and the diameter (length of 1 side) was set to 10.0 μm (reference example 1) and 2.0 μm (reference example 2).

(B) A pattern in which X-CD was increased by 0.025 μm for the two square patterns (A) (reference examples 3 and 4, respectively).

(C) A pattern in which Y-CD was increased by 0.025 μm for the two square patterns (A) (reference examples 5 and 6, respectively).

In fig. 5, X and Y indicate directions perpendicular to each other in the photomask plane, regardless of the direction X, Y related to the driving method of the drawing device described in fig. 1 and 2.

The simulation conditions applied are as follows.

Optical system of exposure apparatus: NA is 0.08 and coherence factor σ is 0.7

The exposure wavelength is wide wavelength light including g line, h line and i line, and the intensity ratio is g: h: 1, i: 1: 1.

fig. 6 shows an aerial image formed on the transfer object when the mask pattern shown in fig. 5 is exposed. The aerial image is an aerial image (light intensity distribution) on the transfer object obtained by virtually cutting at a position corresponding to a broken line shown in each pattern of fig. 5.

The following points are clarified by fig. 6. When the CD is large (fig. 6 (a) and (b)), the change in CD on the mask is relatively faithfully reflected on the aerial image on the transferred body. Here, the increase in X-CD of the mask is shown as an increase in CD in the X direction on the aerial image. The increase in Y-CD on the mask does not affect the X-direction CD of the aerial image.

On the other hand, when the absolute value of the hole CD becomes smaller than the resolution limit size of the exposure apparatus ((c), (d) of fig. 6), the increase in the CD in the X direction is almost the same in the presented aerial image regardless of whether the X-CD is increased or the Y-CD is increased on the mask. In this case, it can be found that the aerial image on the transferred body is more correlated with the area of the hole pattern than the size of the hole pattern on the mask has in the X-CD and Y-CD. That is, it is predicted that the hole patterns having the same area draw almost the same aerial image, and thus it can be predicted that the CD of the hole/dot pattern obtained on the transfer object is almost the same as long as there is no factor other than the photomask.

In this case, the transferred image formed on the transfer target body has an influence of light diffraction to an extent that cannot be ignored, and thus corners of the square pattern on the mask are rounded to be close to a circle. Therefore, in the case of such a minute CD, it is not very meaningful to distinguish the X-CD and the Y-CD from each other with respect to the CD of the transferred hole pattern, and the CD approaches a diameter similar to a circle. In this case, the average value of X-CD and Y-CD of the hole/dot pattern formed on the transfer target may be simply referred to as CD.

This phenomenon can be more clearly understood from fig. 7. Here, the X-CD variation amount of the hole pattern formed on the object to be transferred is shown in the case where correction is performed by adding 0.025 μm to only X-CD (left side of the bar graph) or only Y-CD (right side of the bar graph) for each of the photomasks having 6 hole patterns which are square (X-CD ═ Y-CD) and have one side of 1.5 to 10 μm. As the X-CD and the Y-CD become smaller, the irradiation light amount of the exposure light corresponding to the smaller X-CD and the smaller Y-CD is increased, whereby a hole pattern of a target CD (here, each CD of 1.5 to 10 μm, similar to the CD on the photomask) is formed on the transfer target.

In fig. 7, X and Y represent directions perpendicular to each other in the plane of the photomask and the plane of the transfer target, and are not related to the X, Y direction relating to the driving method of the drawing device described in fig. 1 and 2.

Thus, when the CD is relatively large, the correction of the X-CD on the mask is reflected on the X-CD on the transferred body. On the other hand, as the CD is miniaturized, correction for only the X-CD on the mask and correction for only the Y-CD become factors for changing the X-CD on the transferred body. In particular, this tendency is remarkable in the case of a CD smaller than 3 μm, and it is known that, in the case of a CD of 2 μm or less, the correction of X-CD on the mask and the correction of Y-CD both exert almost the same action on X-CD of the transferred image on the transferred object. Further, here, the CD variation in the transferred image becomes large and exceeds the correction amount of X-CD (0.025 μm). This means that: the effect of the phenomenon (increase in MEEF: Mask Error Enhancement Factor) of the CD difference on the transferred body relative to the CD difference on the Mask is increased with the miniaturization of the pattern.

As can be seen from the above, when the design pattern data of the photomask is corrected, it is not necessary to equally distribute the correction amounts to the X-CD and the Y-CD, and it is not necessary to similarly adopt a square pattern before the correction. Further, as can be seen from the knowledge of fig. 1, the method of correcting in the direction in which the controllability of the CD accuracy is good (the direction of Y-CD in the drawing device) is more advantageous. The reason is that: if the determination is made from the drawing accuracy of X-CD, the reproducibility of CD errors is low, and when X-CD is corrected, there is a risk that a new CD error will be generated after correction. In view of this, it is preferable to improve the CD accuracy of the transferred image on the transfer target by correcting only the Y-CD as much as possible without correcting the X-CD.

As a result, the corrected pattern data includes not only the square pattern without correction but also a plurality of quadrangles (rectangles) having different X-CDs (fixed Y-CDs) or different Y-CDs (fixed X-CDs) as a result of CD correction performed only in a direction with high drawing accuracy. The photomask drawn by the correction pattern data includes a group of hole/dot patterns having the same area although the shapes are different from each other. That is, 1 or more of the following combinations are included: this combination is a combination of quadrilateral hole/dot patterns having different X-CDs (hence different Y-CDs) and equal areas, and is also referred to as a hole/dot pattern group of the same area.

From the results, the following can be determined. That is, when correcting the CD of the design pattern of the photomask, it is effective to correct only one CD having high CD control accuracy among the X-CD and the Y-CD, taking into consideration the configuration of the drawing device. With this method, a hole/dot pattern group having the same required area can be obtained on a photomask, and the following correction effect can be easily obtained by exposing the photomask: this correction effect is used to obtain a hole/dot pattern having a CD conforming to the design on the transferred object.

Here, the CD having the higher controllability can be determined by grasping the tendency of the controllability of the drawing device in advance.

The CD control in the photomask drawing device is not limited to the cases shown in fig. 3 and 4, and the same considerations as described above can be made in a drawing device in which the control accuracy of X-CD and Y-CD is poor.

As a method for determining a more quantitative determination of the direction of high CD controllability, in the curves shown in fig. 1 (b) and (c), the standard deviation of the CD error amount is calculated for each design size of 2.5 μm or more in which no recess is observed in the negative direction of the CD error amount, and the smaller standard deviation may be set as the direction of high CD controllability. In fig. 1, it is apparent that the standard deviation in the Y direction ((c) of fig. 1) is small.

Further, for the CD error amount in each design size, least square fitting may be performed using an approximation curve, standard deviations, which are differences between the approximation curve and the CD error amount, may be calculated, and the smaller standard deviation may be set as the direction in which CD controllability is high.

Such a correction method is particularly effective in the case where X-CD or Y-CD (preferably, X-CD and Y-CD) of the mask pattern is applied to a fine pattern close to the resolution limit size R of the exposure apparatus. In a projection exposure apparatus for manufacturing a display device, a resolution limit dimension R is generally as follows. Here, 0.061 may be applied as the coefficient k. Further, the value of NA may be 0.08 or more (more specifically, 0.08 to 0.2), and thus, considering about 3.0 μm as the resolution limit size, a size smaller than 3.0 μm is generally regarded as smaller than the resolution limit size. Since the value of the resolution limit dimension R changes in the future if the value of NA increases (for example, to the order of 0.1 to 0.2), the CD of the hole/dot pattern to which the present invention is applied changes, but the method of the present invention is also applicable.

R＝k*λ/NA

For example, in the above example, the control accuracy of the Y-CD of the drawing device is higher than that of the X-CD, and therefore, it is preferable to form a photomask having a hole/dot pattern of a desired area only by correcting the Y-CD of the mask pattern. Here, the required area is an area required as a hole/dot pattern on a photomask in order to form a hole/dot pattern having a required CD on a transfer target. When only the Y-CD is corrected to obtain the required area, if the value of the Y-CD exceeds the R (for example, 3.0 μm), the Y-CD is made smaller than the R, and the shortage of the CD to obtain the required area is compensated by the correction of the X-CD.

Specifically, the present invention is preferably applied to a photomask for manufacturing a display device, in which the X-CD and the Y-CD of a transfer pattern formed on the photomask are smaller than R, and the present invention is advantageously applied to a case where the transfer pattern includes a hole/dot pattern. As a specific example, the effect is remarkable in the case where X-CD and Y-CD are less than 3 μm. Further, X-CD and Y-CD are preferably 0.8 μm or more. More preferably, X-CD and Y-CD are 1.0 to 2.5 μm, and still more preferably 1.5 to 2.5 μm.

By using the transfer pattern, a transfer image having a CD (X-CD and Y-CD) of about 1.0 to 4.0 μm can be obtained on a transfer-receiving body. In other words, the present invention can be preferably applied when the CD of the hole/dot pattern to be obtained on the transfer target is 1.0 to 4.0. mu.m.

The preferable range of the correction width (increase/decrease) in the case of correcting X-CD or Y-CD is about + - ((0.01-0.15)) mu m. When the correction width is too large, there is a problem that the correlation accuracy of the pattern area on the photomask and the aerial image on the transferred body is lowered, and when the correction width is too small, the benefit after correction cannot be sufficiently obtained. If the correction width is within the above range, the size of the mask can be corrected more finely, and the pattern accuracy obtained on the transferred object can be brought closer to the desired value. A more preferable range of the correction width is + - (0.01-0.10 μm).

(example 1)

Fig. 8 shows the results of the optical simulation.

In FIG. 8 (c), it is assumed that a photomask having a square hole pattern is exposed to form a hole pattern of 2.5 μm in both X-CD and Y-CD on a transfer target (panel). Here, in the design pattern data for drawing, both X-CD and Y-CD were 2.5 μm. Also, it is assumed that hole patterns of the same size are formed on the photomask.

However, it is assumed that the X-CD varies within a range of 2.4 to 2.6 μm in the hole pattern of the obtained photomask (serving as a preliminary mask) due to the accuracy of the drawing apparatus. In this case, the preliminary mask is exposed to light to form an optical image on the transferred object, and the optical image is dotted in X-CD and Y-CD as shown in FIG. 8 (c). The preliminary mask has a preliminary transfer pattern obtained by drawing with a drawing device. In each graph of fig. 8, the horizontal axis represents the amount of variation in X-CD on the photomask, and the vertical axis represents the amount of variation in X-CD (dotted line) and Y-CD (solid line) in the optical image formed on the transfer target.

In FIG. 8 (c), only the X-CD fluctuates on the preliminary mask, but the X-CD and the Y-CD of the optical image formed on the transferred object fluctuate almost similarly between about 2.35 and about 2.6 μm according to the fluctuation of the X-CD on the preliminary mask.

Next, the design pattern data is corrected. Specifically, the area of a square with an aperture design value of 2.5 μm was calculated (2.5 × 2.5 — 6.25 μm)²) And obtaining a corrected pattern data by obtaining a Y-CD necessary for forming the area by X-CD of the hole pattern actually formed on the preliminary mask without changing the X-CD of the design pattern data (in a state where the design value X-CD is 2.5 μm), and correcting the Y-CD of the design pattern data (correction step). Then, a photomask is formed using the corrected pattern data obtained in this manner.

For example, when a hole pattern having an X-CD of 2.400 μm and a Y-CD of 2.500 μm is formed on the preliminary mask, the area is 6.000 μm². However, it is preferable to obtain a photomask having a thickness of 6.25 μm²The area of (a). Therefore, the X-CD (═ 2.50 μm) on the preliminary mask, which is the design pattern data corresponding to the hole pattern, is not changed, but the Y-CD of the design pattern data is corrected to be the same as that of the hole pattern2.604 μm. Then, drawing is performed by the drawing device (drawing step).

The obtained photomask was matched with the design pattern data and had a rectangular hole pattern in which Y-CD was corrected in accordance with the variation of X-CD, except for the hole pattern of a square (X-CD — Y-CD 2.5 μm) that was not corrected. The hole patterns are different from the X-CD and the Y-CD in the design pattern data, but the areas are equal. In the design pattern data, the areas of the hole/dot patterns having the same X-CD and Y-CD on the photomask are also equal to each other. That is, here, the CD of the design pattern data is replaced with a CD correction value obtained by equalizing the areas of the transfer patterns formed on the photomask, thereby obtaining corrected pattern data.

When the photomask is exposed to light and the transfer pattern is transferred to the object, a hole pattern of CD (2.5 μm. + -. 0.05 μm) with almost constant X-CD and Y-CD is obtained in the optical image (FIG. 8 (d)). It is understood that if this method is used, a hole pattern having a target size and a fixed CD can be stably formed on a transfer target. Because a range within ± 0.1 μm (more preferably, ± 0.05 μm) with respect to the target CD to be obtained on the transferred body is within the allowable range.

In addition, the target CD of the hole/dot pattern to be formed on the transferred body does not necessarily have to be equal to X-CD, Y-CD on the photomask. In the specification of the present application, design pattern data indicates data of dimensions on a photomask. If necessary, the design pattern data of the photomask is formed by adding (or subtracting) a predetermined offset value to or from the target CD of the pattern to be formed on the transferred object, and this is used as the X-CD or Y-CD of the design pattern data.

On the other hand, in the case where the square hole patterns of 4.0 μm in both X-CD and Y-CD are assumed as the design pattern data in (a) and (b) of FIG. 8, the same operations as described above are performed. When the X-CD on the photomask fluctuates in a range of 3.9 to 4.1 μm and the Y-CD is the original value of the design value, the X-CD and the Y-CD of the optical image formed on the transferred object are shown in FIG. 8 (a). Further, the area of a square with a hole design value of 4.0 μm was calculated, and without changing the X-CD of the design pattern data (in a state where the design value X-CD is 4.0 μm), the Y-CD required to be equal to the area was obtained from the X-CD of the hole pattern actually formed on the preliminary mask, and the Y-CD of the design pattern data was corrected. Then, a photomask is formed using the corrected pattern data obtained in this manner. The X-CD and Y-CD of the optical image on the transferred object obtained by using the photomask are shown in FIG. 8 (b).

However, in the case of this size (larger than the resolution limit size of the exposure apparatus), the X-CD and the Y-CD of the optical image formed on the transfer object by exposing the photomask to light largely fluctuate compared to the design value of 4.0 μm as compared to example 1.

From the above, a method of obtaining correction pattern data when correcting a hole/dot pattern obtained on a photomask (corresponding to example 1) on a photomask having a CD smaller than the resolution limit size of an exposure apparatus is examined.

Let X-CD be Xm (des), Y-CD be ym (des), and area be Sm (des) in the design pattern data of the photomask,

the actual X-CD on the formed preliminary mask is Xm (act), Y-CD is ym (act), and the area is Sm (act),

when X-CD in the calibration pattern data is Xm (cor), Y-CD is ym (cor), and the area is Sm (cor),

Ym(cor)＝{Sm(des)/Sm(act)}*Ym(act)…(1)。

here, (des), (act), and (cor) respectively represent a design value, an actual value, and a correction value, and xm (cor) is xm (des).

That is, when the mask CD defect is corrected, the CD (here, Y-CD) in the direction in which the CD controllability is high is corrected while maintaining the area of the hole/dot pattern in the design pattern data, thereby forming corrected pattern data. As a result, the obtained transfer image is almost the same as the transfer image targeted in the design pattern data.

In the step of determining the correction value, the correction amount of the CD (here, Y-CD) can be determined by determining the correlation between the area of the hole/dot pattern included in the design pattern data for the preliminary mask used to obtain the preliminary mask and the area of the hole/dot pattern formed on the preliminary mask. Of course, since the area of the hole/dot pattern is correlated with each of the values of X-CD and Y-CD, as a result, in order to obtain the value of the above expression (1), calculation may be performed in an arbitrary order using any value in the stage of calculating the correction value.

(example 2)

It is assumed that when a photomask having a pattern for transfer is formed on the basis of design pattern data of the photomask formed on the basis of design of a pattern to be obtained on a transfer object and the pattern is transferred by an exposure apparatus, a CD obtained on the transfer object deviates from a target value (in the case of example 2). In this case, the X-CD and the Y-CD in the transfer pattern are also smaller than the resolution limit size of the exposure apparatus.

In this case, in order to match the CD of the transferred image formed on the transferred object with the target value, the misalignment may be fed back in the photomask manufacturing process, and a newly corrected photomask may be prepared using the correction pattern data. The deviation from the target value of the CD may be caused by the deviation of the CD of the photomask, the exposure process, or both.

In this case, the correction of the CD is performed by changing the value of the one with higher CD control accuracy (here, Y-CD) instead of uniformly changing the values of the X-CD and the Y-CD in the generation of the correction pattern data.

First, a preliminary mask is prepared. The preliminary mask is manufactured by a drawing process using preliminary design pattern data.

Here, let X-CD be Xm (des), Y-CD be ym (des), and area be Sm (des) in the design pattern data of the photomask,

let X-CD as the pattern target to be obtained on the transferred object be Xp (tar), Y-CD be Yp (tar), area be Sp (tar),

let the actual X-CD in the formed preliminary mask be Xm (act), Y-CD be ym (act), and area be Sm (act),

exposing the preliminary mask with an exposure device to obtain a transfer image having an X-CD (xp (act), a Y-CD (Yp (act), and an area Sp (act) on the transfer object,

let X-CD be Xm (cor), Y-CD be ym (cor), and area be Sm (cor) in the corrected pattern data.

Here, (tar) represents a target value, and sp (tar) is preferably obtained in advance from xp (tar), yp (tar), and a pattern shape (circle, ellipse, or the like).

At this time, sm (cor) is obtained by the following relational expression.

Sm(cor)＝Sm(act)*{Sp(tar)/Sp(act)}

Then, correction pattern data for satisfying sm (cor) is obtained. That is, since the pattern on the mask is a quadrangle, ym (cor) ═ sm (cor)/xm (act).

Here, xm (cor) is also set to xm (des).

That is, when there is a deviation between the CD of the pattern formed on the transferred object and the target value, the required area of the mask required to obtain the target area based on the target CD on the transferred object is determined, and based on this, the CD in the direction in which the CD controllability is high (here, Y-CD) is corrected, and the corrected pattern data is formed.

Further, when the influence of MEEF cannot be ignored due to the miniaturization of the pattern, the correction amount obtained as described above may be multiplied by a coefficient based on the value of MEEF.

In the above description, the case where the hole pattern is formed in the transferred object is taken as an example, but it is obvious that the same method can be applied to the dot pattern.

In the actual design pattern data, a plurality of hole/dot patterns are arranged as the same hole/dot pattern on the transfer target (plate). In order to obtain the correction pattern data of the present invention, it is preferable to perform the above calculation for each of the respective hole/dot patterns. This is because the cause of CD shift may vary depending on the position in the photomask plane, for example.

In example 2, the same procedure as in example 1 may be used to calculate the results, and the same results may be obtained.

The present invention is not limited to the above-described

embodiments

1 and 2.

The present invention also includes a method of manufacturing a photomask to which the above-described drawing method is applied.

The present invention also includes a method of manufacturing a display device including transferring a pattern for transfer onto a transfer-receiving body using the photomask manufactured in this manner. Here, the display device includes a device for display device for assembly into a display device as a final product.

The exposure apparatus is useful as a projection type, equal magnification exposure apparatus using an optical system having a numerical aperture NA of 0.08 to 0.20 and a coherence factor σ of about 0.2 to 0.7, and is mainly used as a known exposure apparatus for FPD. As the exposure wavelength, any of i-line, h-line, and g-line is preferably used, and light having a wide wavelength including these may be used.

The transfer pattern may be transferred to a positive resist on the transfer object, or a negative resist may be used. The resist on the transferred object may be used as a resist pattern as an etching mask, or may be transferred to a photosensitive resin for forming a three-dimensional structure.

The application of the photomask manufactured by applying the present invention is not particularly limited.

For example, a photomask for manufacturing a display device is preferably used as a photomask for forming a contact hole. In particular, the photomask may be used for the formation of so-called isolated hole patterns. Further, a structure such as a resist gap of the color filter may be formed.

The photomask may be a so-called binary mask or a multi-tone photomask for forming a three-dimensional resist pattern having a plurality of residual film amounts on a transfer target. Alternatively, a phase shift mask capable of improving contrast or the like by using a phase shift film may be used.

The present invention also includes a photomask obtained by the above-described manufacturing method.

When the pattern for transfer provided in the photomask includes a plurality of rectangular hole patterns, and the size of the long side of each rectangle is X-CD, the plurality of hole patterns have shapes having the same area and different X-CDs. When the dimension of the short side is Y-CD, it is preferable that X-CD and Y-CD are 3 μm or less.

Alternatively, when the transfer pattern provided in the photomask includes a plurality of rectangular dot patterns, and the size of the long side of each rectangle is X-CD, the plurality of dot patterns have shapes different from each other in X-CD and the same in area. When the dimension of the short side is Y-CD, it is preferable that X-CD and Y-CD are less than 3 μm.

Alternatively, the transfer pattern may further include a square hole/dot pattern having the same area as the rectangular hole/dot pattern.

Here, the pattern having a plurality of areas is a pattern having the same CD (X-CD and Y-CD) in the design pattern data based on the design of the device to be obtained (i.e., the pattern data before correction), and therefore, a pattern exhibiting the same function can be obtained in the final product.

If the drawing method according to the present invention and the method for manufacturing a photomask using the drawing method are applied, the CD error amount can be suppressed to the allowable range or less over the entire surface of the transferred object, which is advantageous in improving the yield and the production efficiency.

The application of the photomask to which the present invention is applied is not particularly limited. The following applies preferably: in the case of manufacturing various layers of display devices including liquid crystals and organic ELs using photomasks for manufacturing these display devices.

The photomask may be a so-called binary mask, or may be a photomask (multi-tone photomask, phase shift photomask, or the like) having a functional film pattern with a predetermined transmittance.

Claims

1. A pattern drawing method for forming a photomask having a transfer pattern including a hole/dot pattern by drawing on a photomask substrate based on predetermined design pattern data,

the pattern drawing method is characterized by comprising:

the drawing device is driven by different driving methods in an X direction and a Y direction perpendicular to the X direction with CD control precision in a plane parallel to the surface of the photomask substrate,

2. The pattern drawing method according to claim 1,

in the correction step, a target area of the hole/dot pattern of the transfer pattern is determined in which the CD of the hole/dot pattern obtained on the object to be transferred is equal to a target value,

3. A pattern drawing method for forming a photomask having a transfer pattern including a hole/dot pattern by drawing on a photomask substrate based on predetermined design pattern data,

the pattern drawing method is characterized by comprising:

4. The pattern drawing method according to claim 3,

5. The pattern drawing method according to any one of claims 1 to 4,

6. The pattern drawing method according to any one of claims 1 to 4,

7. The pattern drawing method according to any one of claims 1 to 4,

8. The pattern drawing method according to any one of claims 1 to 4,

in the drawing apparatus, the laser beam is fed in the X direction with a fixed feeding width and then irradiated in the Y direction with a fixed feeding width, and the drawing apparatus draws on the photomask substrate by repeating these operations alternately.

9. The pattern drawing method according to any one of claims 1 to 4,

in the correction step, the CD of the design pattern data is replaced with a CD correction value obtained so that the area of the hole/dot pattern included in the design pattern data is equal to the area of the hole/dot pattern on the photomask substrate, thereby obtaining correction pattern data.

10. The pattern drawing method according to any one of claims 1 to 4, comprising:

11. A method for manufacturing a photomask, comprising the pattern drawing method according to any one of claims 1 to 4.

12. A photomask produced by the method for producing a photomask according to claim 11, which has a transfer pattern including a plurality of hole/dot patterns,

the photomask is characterized in that,

the X-CD and Y-CD of the plurality of holes/dots pattern in the transfer pattern are less than 3 μm,

13. A method of manufacturing a display device, comprising:

preparing the photomask according to claim 12; and

14. A method for manufacturing a display device, comprising exposing a photomask formed based on predetermined design pattern data to light to transfer a pattern for transferring the photomask to a transfer object,

15. The method for manufacturing a display device according to claim 14, comprising: