Halftone mask and manufacturing method thereof and method for forming film using the same

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 25 Jun. 2009 and there duly assigned Serial No. 10-2009-0056941.

1. Field of the Invention

Embodiment relates to a halftone mask, and more particularly, to a halftone mask that can uniformly form the heights of underlying layers in two regions spaced from each other, a manufacturing method thereof and a method for forming a film using the same.

2. Discussion of Related Art

An organic light emitting display device has advantages in view of rapid response speed as well as wide view angle and excellent contrast so that it has been spotlighted as a next generation flat panel display device.

In manufacturing the organic light emitting display device, the integration of a panel and a driving circuit is very important for the lightweight and slimness and the reduction in production costs of the panel. For example, with a manufacturing process using a low temperature poly silicon (LTPS) technology, the number of masks is reduced, making it possible to enhance the productivity of the device and to seek for the cost reduction thereof.

One of the methods to reduce the number of masks is to use a halftone mask. If the halftone mask is used, pixel defining layers that cover a pixel electrode to expose some regions of the pixel electrode of the organic light emitting display device can be patterned using one mask.

However, when the pixel defining layers are patterned using one mask, a height difference is generated between the regions of the pixel defining layers on left and right sides of the exposed pixel electrode so that it may cause a defect in a subsequent process.

For example, the height difference between the regions of the pixel defining layers on both sides of the pixel electrode may cause a defect in an organic deposition such as a light emission layer, etc. or in a metal deposition such as an electrode layer, etc. Further, the pixel defining layer also functions as a spacer when masks for depositing the organic material or the electrode, etc. are attached but in that case, the masks get loose in some regions so it may cause a defect in deposition.

Embodiments provide halftone masks that can uniformly form the heights of underlying layers in two regions spaced from each other, and a manufacturing mask thereof. Further, an embodiment provides a method for forming a film that can enhance productivity and reduce manufacturing costs using the halftone mask.

According to one aspect of the present invention, there is provided a halftone mask including a first light blocking unit having a first length and blocking light, a second light blocking unit having a second length and blocking light, and a first semi-transmitting unit having a third length. The first and second light blocking units are spaced apart lengthwise from each other at a predetermined interval. The first semi-transmitting unit is disposed substantially next to the second light blocking unit in a manner that the second light blocking unit is disposed between the first semi-transmitting unit and the first light blocking unit. The first semi-transmitting unit reduces intensity of light passing through the halftone mask. Sum of the second length and the third length is larger than the first length.

The third length may be determined in an inverse proportion to the first length of the first light blocking unit while maintaining the sum of the second length and the third length. The first length and the third length may have a relationship of W 1 =A·W 3 +B, where W 1 is the first length, W 3 is the third length, A is a number in a range from −0.68 to −1.43, and B is a number in a range from 12 to 23.

The halftone mask may include a light transmitting unit transmitting light or a second transmitting unit disposed between the first light blocking unit and the second light blocking unit.

The first semi-transmitting unit may be made of the same material as the second light blocking unit, the first semi-transmitting unit having slits, light passing through the slits.

Each of the first light blocking unit and the second light blocking unit may include a light shielding layer disposed on a transparent base. The light shielding layer may include chrome (Cr) or chrome oxide. The semi-transmitting unit may include CrxOy, CrxCoy, CrxCoyNz, SizNy, or combinations thereof (herein, suffix x, y, and z are natural numbers, each representing the number of chemical elements).

According to another aspect of the present invention, there is provided a manufacturing method of a halftone mask, including forming a first light blocking unit having a first length and a second light blocking unit having a second length, and forming a first semi-transmitting unit having a third length. The first and second light blocking units block light. The first and second light blocking units are spaced apart lengthwise from each other at a predetermined interval. The first semi-transmitting unit is disposed substantially next to the second light blocking unit in a manner that the second light blocking unit is disposed between the first semi-transmitting unit and the first light blocking unit. The first semi-transmitting unit reduces intensity of light passing through the halftone mask. Sum of the second length and the third length being larger than the first length.

The third length may be determined in an inverse proportion to the first length while maintaining the sum of the second length and the third length.

The first semi-transmitting unit may include slits through which light passes.

The forming the first light blocking unit and the second light blocking unit may include forming a light shielding layer on a transparent base.

According to still another aspect of the present invention, there is provided a method for forming a film using a halftone mask including arranging the halftone mask on a underlying layer formed on a substrate, emitting light to the underlying layer through the halftone mask; and developing the underlying layer. The halftone mask includes a first light blocking unit having a first length and blocking light, a second light blocking unit having a second length and blocking light, and a first semi-transmitting unit having a third length. The first and second light blocking units are spaced apart lengthwise from each other at a predetermined interval. The first semi-transmitting unit is disposed substantially next to the second light blocking unit in a manner that the second light blocking unit is disposed between the first semi-transmitting unit and the first light blocking unit. The first semi-transmitting unit reduces intensity of light passing through the halftone mask. Sum of the second length and the third length is larger than the first length. A first height of a first portion of the underlying layer corresponding to the first light blocking unit and a second height of a second portion of the underlying layer corresponding to the second light blocking unit are substantially the same.

The underlying layer may be made of photosensitive polymer material.

The film includes a pixel defining layer that covers the upper part of a substrate on which a pixel electrode is formed so that a portion of the pixel electrode of an organic light emitting display device is exposed.

With the embodiment, the heights of two underlying layers spaced to each other corresponding to the regions of the two light blocking units of the mask can be formed uniformly. For example, in the manufacturing process of the organic light emitting display device, the heights of the pixel defining layers can be formed uniformly, while reducing the number of masks. Further, the generation of the defect during the subsequent process is prevented using the pixel defining layers having the uniform height, making it possible to enhance the productivity of the organic light emitting display device and to reduce the manufacturing costs thereof.

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 is a diagram explaining a mask layout compared with an embodiment of the present invention and a underlying layer formed using the mask;

FIG. 2 is a diagram explaining a halftone mask layout according to an embodiment of the present invention and a underlying layer formed using the halftone mask;

FIGS. 3A to 3D are diagrams explaining halftone masks adoptable to the present invention;

FIGS. 4A and 4B are diagrams showing layouts of halftone masks according to an embodiment of the present invention and profiles of underlying layers corresponding thereto;

FIGS. 5A to 5G are graphs showing the changes in heights of first and second light blocking units according to the changes in lengths of the first light blocking unit and semi-transmitting unit of the halftone mask according to the present invention;

FIG. 6 is a graph showing the length relationship between the first light blocking unit and semi-transmitting unit of the halftone mask according to the present invention;

FIG. 7A is a pixel circuit view explaining an example of an organic light emitting display device to which a method for forming a film according to the present invention is applied;

FIG. 7B is a plan view showing one example of a pixel structure wherein the pixel circuit of FIG. 7A is implemented;

FIGS. 8A to 8C are cross-sectional views explaining manufacturing processes of the organic light emitting display device to which the method for forming the film according to the present invention is applied;

FIG. 9 shows a flow chart for manufacturing a halftone mask; and

FIG. 10 is a graph showing a relationship between the first length W 1 (the length of the first light blocking unit DK 1 ) and the third length W 3 (the length of the semi-transmitting unit HT 1 ) in an extended range.

In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the another element or be indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the another element or be indirectly connected to the another element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements. In the drawings, the thickness or size of the respective constituents may be exaggerated for the convenience and clarity of explanation.

Hereinafter, exemplary embodiments of the present invention, proposed so that a person having ordinary skill in the art can easily carries out the present invention, will be described in more detailed with reference to the accompanying drawings.

FIG. 1 is a diagram explaining a mask layout compared with an embodiment of the present invention and an underlying layer formed using the mask. Referring to FIG. 1 , the mask according to the present comparative example includes two light blocking units DK 1 and DK 0 , a semi-transmitting unit HT 0 between the two light blocking units DK 1 and DK 0 , and two light transmitting units CL 1 and CL 2 positioned at both outsides of the two light blocking units DK 1 and DK 0 . The two light blocking units include one light blocking unit DK 1 having a first length W 1 in one direction and the other light blocking unit DK 0 spaced apart from the light blocking unit DK 1 at a predetermined interval and having a second length W 2 .

When patterning the underlying layer on a substrate structure using the mask according to the present comparative example, if the first length W 1 is different from the second length W 2 , for example, if the second length W 2 is larger than the first length W 1 , the thickness H 0 of a portion 2 of the underlying layer formed in the region corresponding to the light blocking unit DK 0 becomes larger than the thickness H 1 of a portion 1 of the underlying layer formed in the region corresponding to the light blocking unit DK 1 .

As described above, if the thicknesses of the underlying layers in the regions corresponding to the two light blocking units of the mask, which are spaced apart from each other, are different from each other when forming the underlying layers using the mask, defects may he easily generated in depositing a film having a desired thickness or pattern, etc.

For example, pixel defining layers that cover a pixel electrode to expose some regions of the pixel electrode of an organic light emitting display device may be patterned using one halftone mask, and at that time, a height (thickness) difference may be generated between the regions of the pixel defining layers on left and right sides of the exposed pixel electrode. In that case, the height difference between the regions of the pixel defining layers on the left and right sides of the pixel electrode may cause a defect in an organic deposition such as a light emission layer, etc. or in a metal deposition such as an electrode layer, etc. Further, the pixel defining layer also functions as a spacer when masks for depositing the organic material or the electrode, etc. are attached but in that case, the masks get loose in some regions so it may cause a defect in deposition.

FIG. 2 is a diagram explaining a halftone mask layout according to an embodiment of the present invention and an underlying layer formed using the halftone mask. Referring to FIG. 2 , the halftone mask according to the present embodiment includes two light blocking units DK 1 and DK 2 that are spaced apart from each other in one direction, a semi-transmitting unit HT 2 disposed between the two light blocking units DK 1 and DK 2 , and two light transmitting units CL 1 and CLS that are disposed at either outside of the two light blocking units DK 1 and DK 2 . Another semi-transmitting unit HT 1 is disposed between the light blocking unit DK 2 and the light transmitting unit CL 2 .

The light blocking unit DK 1 and DK 2 blocks light not to allow the light to reach the lower regions of the mask corresponding to the light blocking units. The semi-transmitting units HT 1 and HT 2 serves to allow a reduced amount of light to reach the lower regions of the mask corresponding to the semi-transmitting units by partially blocking light or attenuating the intensity of light. The light transmitting units CL 1 and CL 2 substantially transmit light.

Herein, the underlying layer may be made of polymer material having photosensitive properties, while having electrically sufficient insulating effects such as photoresist, polyimide, and silicon nitride. For example, the underlying layer may be made of the polymer material including photo active compound (PAC) material, wherein the PAC is changed into carboxylic acid when exposed to light. The carboxylic acid is neutralized when exposed to an alkaline developer. In other words, if the underlying layer is made of the polymer material having the photosensitive properties, the underlying layer having a desired pattern can be formed through an exposure process and a development process.

An intensity of light in a predetermined wavelength range is reduced while passing through the semi-transmitting unit HT 1 of the halftone mask. Accordingly, the thickness of the underlying layer corresponding to the semi-transmitting unit HT 1 is different from the thickness of the underlying layer corresponding to the light blocking unit DK 2 after the lithography process. However, if the semi-transmitting unit HT 1 is disposed adjacent to the light blocking layer DK 2 as shown in FIG. 2 , a portion of the underlying layer corresponding to the light blocking unit DK 2 flows to a portion of the underlying layer corresponding to the semi-transmitting unit HT 1 so that the height of the portion of the underlying layer corresponding to the light blocking unit DK 2 is lowered. In other words, if the semi-transmitting unit HT 1 is disposed adjacent to the light blocking layer DK 2 , the height of the underlying layer of the light blocking unit DK 2 can be lowered due to the factors such as diffraction of light used in the exposure process, the flow of the underlying layer, the shrinkage of the underlying layer, etc.

In a mask that has two light blocking units DK 1 and DK 0 spaced from each other in one direction (for example, in direction parallel to a straight line passing the two light blocking units DK 1 and DK 0 ) and having different lengths, if the length W 2 of one light blocking unit DK 0 is larger than the length W 1 of the other light blocking unit DK 1 , the difference of the lengths causes the aforementioned problem that the heights of the regions of the two underlying layers corresponding to the two light blocking units DK 1 and DK 0 are different. In the present embodiment, in order to solve this problem a portion of the light blocking unit DK 0 , whose length W 2 is larger than the length W 1 of another light blocking unit DK 1 , is replaced by a semi-transmitting unit HT 1 .

In other words, in the present invention, a portion of the light blocking unit DK 0 , having a relatively larger length than another light blocking units DK 1 , is replaced by the semi-transmitting unit HT 1 . The length of the semi-transmitting unit HT 1 is determined in a manner that the heights H 1 and H 2 of the regions of the two underlying layers 11 and 12 corresponding to the two light blocking units DK 1 and DK 2 , respectively, after the lithography process, become substantially the same.

Hereinafter, the rest of the light blocking unit DK 0 , which is not replaced by the semi-transmitting unit HT 1 , is referred to as a second light blocking unit DK 2 . The length of the first light blocking unit DK 1 is referred to as a first length W 1 . The sum of the length of the second light blocking unit DK 2 and the length of the semi-transmitting unit HT 1 is referred to as a fourth length W 2 . The length of the semi-transmitting unit HT 1 is referred to as a third length W 3 , and the length of the second light blocking unit DK 2 is referred to as a second length W 4 . In the present embodiment, the fourth length W 2 is larger than the first length W 1 .

FIGS. 3A to 3D are cross-sectional views explaining halftone masks adoptable to the present invention. Referring to FIG. 3A , a halftone mask 10 a of the present embodiment includes a first light blocking unit DK 1 (or 13 a ) having a first length W 1 and blocking light, a second light blocking unit DK 2 (or 13 b ) having a second length W 4 and blocking light, and a first semi-transmitting unit HT 1 having a third length W 3 . The first and second light blocking units DK 1 and DK 2 are spaced apart lengthwise from each other at a predetermined interval. The first semi-transmitting unit HT 1 is disposed substantially next to the second light blocking unit DK 2 in a manner that the second light blocking unit DK 2 is disposed between the first semi-transmitting unit HT 1 and the first light blocking unit DK 1 . Herein, the meaning of the “substantially next to” is that the first semi-transmitting unit HT 1 is disposed very close to the second light blocking unit DK 2 so that only a negligible gap or no gap is allowed between the first semi-transmitting unit HT 1 and the second light blocking unit DK 2 . Herein the negligible gap means a gap (or interval) that is determined in a manner that the heights of the underlying layers corresponding to the second light blocking unit DK 2 and the semi-transmitting unit HT 1 are, after lithography process, substantially the same. This gap is described in detail later referring to FIG. 3C .

The first light blocking unit DK 1 and the second blocking unit DK 2 of the halftone mask 10 a correspond to portions 13 a and 13 b on which metallic material exists. The first semi-transmitting unit HT 1 corresponds to a portion on which slits 14 are formed between metallic materials (slit structure or slit pattern portion). Light passes through the slits 14 , but overall intensity of the light passing through the first semi-transmitting unit HT 1 is reduced. The light transmitting units CL 1 , CL 2 , and CL 3 correspond to portions on which metallic material is not formed. The light transmitting unit CL 3 is formed between the first light blocking unit DK 1 and the second light blocking unit DK 2 of the halftone mask 10 a . The light transmitting units CL 1 , CL 2 , and CL 3 transmit light.

Referring to FIG. 3B , a halftone mask 10 b of the present embodiment is substantially the same as the halftone mask 10 a explained with reference to FIG. 3A , excepting for the feature that a second semi-transmitting unit HT 2 is provided between the first light blocking unit DK 1 and the second light blocking unit DK 2 . The second semi-transmitting unit HT 2 corresponds to a portion on which slits 15 are formed between metallic materials. Light passes through the slits 15 , but overall intensity of the light passing through the second semi-transmitting unit HT 2 is reduced.

The transmittances of the first and second semi-transmitting units HT 1 and HT 2 may be the same or be different. If the transmittances of the first and second semi-transmitting units HT 1 and HT 2 are different, a thickness of an underlying layer corresponding to a semi-transmitting unit having a lower transmittance may be smaller that a thickness of another underlying layer of the semi-transmitting unit having a higher transmittance. If the transmittances of the first and second semi-transmitting units HT 1 and HT 2 are the same, the thicknesses of regions of the corresponding underlying layers are the same, such that they may be etched to be removed during a subsequent process.

The halftone masks 10 a and 10 b explained with reference to FIGS. 3A and 3B may be provided by forming the semi-transmitting unit HT 1 having slits 14 in one portion of the light blocking unit DK 0 having a relatively longer length among two light blocking units DK 1 and DK 0 , which are spaced from each other and having different lengths in one direction in the metallic structure that forms a body of the halftone mask. The slits 14 may be formed through a metal processing process such as a molding and/or a cutting process, etc.

Referring to FIG. 3C , a halftone mask 10 c of the present embodiment includes a first light blocking unit DK 1 ( 16 a ) having a first length W 1 in a lengthwise direction, a second light blocking unit DK 2 ( 16 b ) spaced apart lengthwise from the first light blocking unit 16 a and having a second length W 2 , a first semi-transmitting unit HT 1 ( 17 a ) disposed adjacent to one side of the second light blocking unit 16 b , which is a side of the second light blocking unit 16 b positioned far away from the first light blocking unit 16 a in the lengthwise direction.

The semi-transmitting unit 17 a is formed to be spaced apart from the one side of the second light blocking unit 16 b at a predetermined interval G. The size of the predetermined interval G is determined in a manner that the heights of the profile of the underlying layers corresponding to the second light blocking unit 16 b and the semi-transmitting unit 17 a respectively, are not substantially changed. In other words, the semi-transmitting unit 17 a may be formed to contact the second light blocking unit 16 b or may be formed to be spaced apart from the second light blocking unit 16 b at the predetermined interval G.

The halftone mask 10 c includes a third semi-transmitting unit HT 3 ( 18 a ). The third semi-transmitting unit 18 a is formed to contact one side of the first light blocking unit 16 a , which is a side of the first light blocking unit 16 a positioned far away from the second light blocking unit 16 b in the lengthwise direction.

The first light blocking unit 16 a and the second light blocking unit 16 b are formed of a light shielding layer (or a light shielding pattern) on a transparent base 20 . The light shielding layer includes a material and a structure not transmitting light. The light shielding layer may be made of chrome (Cr) or chrome oxide. The transparent base 20 completely transmits light in a predetermined wavelength range. The transparent base 20 may be made of quartz.

The semi-transmitting units 17 a and 18 a may be formed by disposing a predetermined material on the transparent base 20 . The semi-transmitting units 17 a and 18 a may be made of at least any one of CrxOy, CrxCoy, CrxCoyNz, SizNy (herein, suffix x, y, and z are natural numbers, each representing the number of chemical elements), preferably, chrome (CrxOy) including oxygen.

In the halftone mask 10 c of the present embodiment, when one portion of the light blocking unit DK 0 having a relatively larger length among two different lengths W 1 and W 2 of the two light blocking units DK 1 and DK 0 is replaced by the semi-transmitting unit 17 a , the third length W 3 of the semi-transmitting unit 18 a in the present embodiment may be further adjusted in consideration of the third semi-transmitting unit HT 3 contacting the light blocking unit DK 1 having a relatively smaller length. For example, if the height of the underlying layer of the first light blocking unit DK 1 is lowered by the third semi-transmitting unit 18 a , the third length W 3 of the first semi-transmitting unit 17 a can be increased.

Referring to FIG. 3D , a halftone mask 10 d of the present embodiment includes a first light blocking unit DK 1 ( 19 a ) and a second light blocking unit DK 2 ( 19 b ) formed on a transparent base 20 , and first and second semi-transmitting units HT 1 and HT 2 formed on the transparent base 20 . The first semi-transmitting unit HT 1 is formed to contact one side of the second light blocking unit 19 b , which is a side positioned far away from the first light blocking unit 19 a , and the second semi-transmitting unit HT 2 is formed between the first light blocking unit 19 a and the second light blocking unit 19 b.

The first and second light blocking units 19 a and 19 b may be provided by forming a light shielding layer on the transparent base 20 made of quartz, etc. and patterning the formed light shielding layer. The light shielding layer may be made of chrome (Cr) or chrome oxide.

The first semi-transmitting unit HT 1 and the second semi-transmitting unit HT 2 may be formed by disposing at least one material 17 b selected from a group consisting of CrxOy, CrxCoy, CrxCoyNz, SizNy, and combinations thereof (herein, suffix x, y, and z are natural numbers, each representing the number of chemical elements) on the transparent base 20 on which the first and second light blocking units 19 a and 19 b are formed. As shown in FIG. 3D , the material of the first semi-transmitting unit HT 1 and the second semi-transmitting unit HT 2 may cover the first and second light blocking units 19 a and 19 b .

FIG. 9 shows a flow chart for manufacturing a halftone mask The manufacturing method of the halftone mask 10 d of the present embodiment is briefly explained referring to FIG. 9 . First, a light blocking layer formed of Cr or CrO 2 and a first photoresist having positive characteristics are formed sequentially on the transparent base 20 (S 1 ) and a laser beam is emitted from the upper side of the first photoresist, thereby drawing a desired pattern on the first photoresist (S 2 ).

Next, the first photoresist is developed to remove the portion which is exposed to the laser beam. The light blocking layer exposed to the outside through the removal of the first photoresist is etched, thereby forming a first light blocking unit 19 a and a second light blocking unit 19 b (S 3 ).

Next, the first photoresist is completely removed and a second photoresist having positive characteristics is formed on the transparent base 20 on which the first and second light blocking units 19 a and 19 b are formed (S 4 ).

Next, a pattern corresponding to semi-transmitting units HT 1 and HT 2 is drawn on the second photoresist with a laser beam (S 5 ). The second photoresist is developed to remove the portion which is exposed to the laser beam (S 6 ).

Next, semi-transmitting layer material is sputtered on the transparent base 20 exposed to the outside through the removal of the second photoresist and the remaining second photoresist (S 7 ). The semi-transmitting material formed on the second photoresist is removed together with the remaining second photoresist (S 8 ).

The portion, on which the semi-transmitting layer material is disposed, is formed into the semi-transmitting units HT 1 and HT 2 . The semi-transmitting units HT 1 and HT 2 , which can reduce intensity light, may be implemented with various materials other than chrome or chrome oxide, and may have various structures, having no limitation in light transmission. For example, the semi-transmitting units HT 1 and FIT 2 may reduce the intensity of light by about 90% to 10%.

The wavelength range of the light may vary according to an exposure device so that it is not limited, while a wavelength range of about 300 to 400 nm may be generally used.

FIGS. 4A and 4B are diagrams showing layouts of halftone masks according to the present invention and profiles of underlying layers corresponding thereto. As shown in FIG. 4A , the respective heights (or thicknesses) H 3 and H 4 of the two regions 21 and 22 of the underlying layer patterned using a halftone mask 10 e of the present embodiment are substantially the same. Actually, the thicknesses H 3 and H 4 of the two underlying layer regions are substantially the same in an error range of −0.01 μm to 0.01 μm based on the thickness of 3.65 μm. The two regions 21 and 22 of the underlying layer correspond to the first light blocking unit DK 1 and the second light blocking unit DK 2 of the halftone mask 10 e , respectively.

Similarly, as shown in FIG. 4B , the heights (or thicknesses) H 5 and H 6 of the two regions 23 and 24 of the underlying layer patterned using a halftone mask 10 f of the present embodiment are substantially the same. Actually, the thicknesses H 5 and H 6 of the two underlying layer regions are substantially the same in an error range of −0.01 μm to 0.01 μm based on the thickness of 2.15 μm. The two regions 23 and 24 of the underlying layer correspond to the first light blocking unit DK 1 and the second light blocking unit DK 2 of the halftone mask 10 f , respectively.

In the two halftone masks 10 e and 10 f , the length of the first light blocking unit DK 1 of the mask 10 f is reduced to W 1 b from W 1 a of the mask 10 e . The length of the first semi-transmitting unit HT 1 disposed next to the second light blocking unit DK 2 of the mask 10 f is increased to W 3 b from W 3 a of the mask 10 e . As described above, in the halftone mask of the present embodiment, when the length of the first light blocking unit DK 1 is relatively small, the length of the semi-transmitting unit HT 1 is relatively large, and when the length of the first light blocking unit DK 1 is relatively large, the length of the semi-transmitting unit HT 1 is relatively small. Meanwhile, the sum of the length W 4 a of the second light blocking unit DK 2 and the length W 3 a of the semi-transmitting unit W 3 a of the halftone mask 10 e is the same as the sum of the length W 4 b of the second light blocking unit DK 2 and the length W 3 b of the semi-transmitting unit W 3 b of the halftone mask 10 f . In the mask having two light blocking units spaced apart from each other and having different lengths, the semi-transmitting unit is installed on one side of the light blocking unit having a relatively long length, of the two light blocking units.

FIGS. 5A to 5G are graphs showing the changes in heights of underlying layers corresponding to the first and second light blocking units as a function of the changes in lengths of the first light blocking unit and first semi-transmitting unit of the halftone mask according to the present invention.

Halftone masks used in the embodiments hereinafter are substantially the same as the halftone mask 10 e or 10 f shown in FIG. 4A or 4 B, excepting for the feature that the lengths of the first and second light blocking units and the length of the first semi-transmitting unit vary. In FIGS. 5A to 5G , the thickness of the underlying layer corresponding to the first light blocking unit DK 1 is represented by TH_DK 1 , the thickness of the underlying layer corresponding to the second light blocking unit DK 2 is represented by TH_DK 2 , and the thickness of the underlying layer corresponding to the semi-transmitting unit HT 1 is represented by TH_HT 1 .

The graphs of FIGS. 5A to 5G shows thicknesses TH_DK 1 , TH_DK 2 , and TH_HT 1 of the underlying layer, when the lengths W 1 of the first light blocking units DK 1 were 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, and 15 μm, respectively. The length of the semi-transmitting unit HT 1 was increased by 1 μm from 1 μm to 14 μm.

As a result of the measurement, when W 1 =2 μm, TH_DK 1 was about 1.25 μm, when W 1 =4 μm, TH_DK 1 was about 2.25 μm, when W 1 =6 μm, TH_DK 1 was about 3.10 μm, when W 1 =8 μm, TH_DK 1 was about 3.50 μm, when W 1 =10 μm, TH_DK 1 was about 3.70 μm, when W 1 =12 μm, TH_DK 1 was about 3.80 μm, and when W 1 =15 μm, TH_DK 1 was about 3.90 μm. TH_DK 1 was about 1.1 μm, almost irrespective of the length W 1 of the first light blocking unit DK 1 . When the length of the semi-transmitting unit HT 1 is increased by 1 μm from 1 μm to 4 μm, TH_DK 2 is reduced from about 3.90 μm to 1.55 μm.

As shown in FIGS. 5A to 5G , it can be appreciated that when the length W 1 of the first light blocking unit DK 1 has a predetermined size, there is a predetermined length of the semi-transmitting unit HT 1 that can make TH_DK 1 and TH_DK 2 the same.

Meanwhile, although not shown in the drawing, if W 1 is smaller than 2 μm, TH_DK 1 and TH_DK 2 may be the same by making the length of the semi-transmitting unit HT 1 larger (for example, about 0.02 to 0.03 μm) than 14 m from the range of 14 μm to 15 μm.

By way of example, when the maximum set height of the underlying layer is about 25 μm, if W 1 is 15 μm or more, TH_DK 1 and TH_DK 2 may be substantially the same by making the length of the semi-transmitting unit HT 1 somewhat smaller (for example, about 0.01 to 0.03 μm) than about 2 μm by the height that W 1 exceeds 15 μm.

The experimental example as described above is examples for one embodiment having a predetermined defocus value in a predetermined exposure device using a predetermined light, but the length of the first light blocking unit DK 1 and the length of the semi-transmitting unit HT 1 of the halftone mask, together with the height of the underlying layer, intended to be formed, may naturally be controlled within a predetermined range, according to the wavelength-range of the emitted light, the sort of the exposure device, and the defocus degree.

FIG. 6 is a graph showing the length relationship between the first light blocking unit and the first semi-transmitting unit of the halftone mask, which makes the heights of the respective underlying layers the same, according to the present invention. As shown in FIG. 6 , in the respective halftone masks in the embodiments, the length of the first light blocking unit DK 1 is in inverse proportion to the length of the semi-transmitting unit HT 1 .

The graph in FIG. 6 including the experimental results of FIGS. 5A to 5G shows that in the process of forming a film using the halftone mask of the present embodiment, in order to form the film having the same heights on the lower parts of the two light blocking units spaced apart from each other and having different heights, when one portion of the light blocking unit having a relatively larger length of the two light blocking units is replaced by the semi-transmitting unit, the length of the semi-transmitting unit is formed at a predetermined range (a portion marked in the graph of FIG. 6 ) in inverse proportion to the size of the length of the light blocking unit DK 1 having a relatively small length, thereby making it possible to make the target heights of the two underlying layer regions constant.

FIG. 10 is a graph showing a relationship between the first length W 1 (the length of the first light blocking unit DK 1 ) and the third length W 3 (the length of the semi-transmitting unit HT 1 ) in an extended range, which can be applied to the present embodiment. This range is found through experiments and is acceptable to the present embodiment. FIG. 10 shows two lines that defines an acceptable range of the first length W 1 and the third length W 3 . The first length W 1 and the third length W 3 has a relationship of W 1 =A·W 3 +B. The upper line represents a line of W 1 =−1.43 W 3 +23, and the lower line represents a line of W 1 =−0.68 W 3 +12. In the present embodiment, the first length W 1 and the third length W 3 are determined in the range bounded by these upper and lower lines. In other words, the first length W 1 and the third length W 3 have a relationship of W 1 =A·W 3 +B, where A is a number in a range from −0.68 to −1.43 (−1.43≦A≦−0.68), and B is a number in a range from 12 to 23 (12≦B≦23).

FIG. 7A is a pixel circuit view explaining an example of an organic light emitting display device to which a method for forming a film according to the present invention is applied. FIG. 7B is a plan view showing one example of a pixel structure wherein the pixel circuit of FIG. 7A is implemented. Referring to FIG. 7A , the organic light emitting display device in an active matrix scheme basically includes two transistors T 1 and T 2 and one capacitor Cst. In other words, the organic light emitting display device includes a switching transistor T 1 that transfers a data signal on a data line Dm in response to a selection signal on a scan line Sn, a capacitor Cst that stores the data signal received through the switching transistor T 1 , a driving transistor T 2 connected to a power supply line VDD to generate driving current according to the data signal stored in the capacitor Cst, and an organic light emitting diode OLED that performs a light emission operation according to the driving current.

Referring to FIG. 7B , the respective transistors Ti and T 2 of the organic light emitting display device include a semiconductor layer 111 , a gate electrode 112 , source/drain electrodes 113 a and 113 b , respectively. The capacitor Cst includes a lower electrode 120 a and an upper electrode 120 b opposed to each other. The source/drain electrode 113 b on one side of the driving transistor T 2 is coupled to a first electrode 130 . The organic light emitting diode is coupled between the first electrode and a second electrode (or a ground electrode) in series.

When manufacturing the organic light emitting display device having the pixel structure, a pixel defining layer is formed on the upper part of the first electrode 130 . At this time, if any one of halftone masks in the embodiments is used, the heights of the two pixel defining layers adjacent to the pixel region at least in one direction can be formed to be constant.

FIGS. 8A to 8C are cross-sectional views explaining manufacturing processes of the organic light emitting display device to which the method for forming the film according to the present invention is applied. As shown in FIG. 8A , a pixel defining layer may be formed on a substrate structure using a halftone mask 10 g of the present embodiment. In other words, the material 128 a for forming the pixel defining layer coated on the substrate structure is exposed through the halftone mask 10 g so that a partial region of the first electrode 130 positioned on the upper part of the substrate structure is exposed to be used as a pixel region.

The substrate structure may be provided by sequentially forming a buffer layer (not shown), a semiconductor layer 111 , a gate insulating film 120 , a gate electrode 112 , an interlayer insulating film 122 , source/drain electrodes 113 a and 113 b coupled to the source/drain regions on both ends of the semiconductor layer 111 by penetrating through the interlayer insulating layer 122 , a protective film 124 , a planarization film 126 , a first electrode 130 coupled to the source/drain electrode 113 b on one side by penetrating through the planarization layer 126 and the protective film 124 on a insulating substrate 100 made of glass or plastic material.

As shown in FIG. 8B , in a pixel defining layer 128 provided by selectively transmitting ultraviolet rays using the halftone mask 10 g , the heights H 7 and H 8 of the two regions positioned on both sides of the pixel region where an organic layer 150 (in FIG. 8C ) is to be formed become substantially the same.

As shown in FIG. 8C , an organic layer 150 having desired structure and pattern and a second electrode 170 are formed on the structure where the pixel defining layer 128 on which the pixel region is exposed is provided. At this time, if the pixel defining layer 128 having the heights substantially the same on both sides of the pixel region is used, it can prevent a deposition defect from being generated when depositing organic material for the organic layer 150 or when depositing an electrode for the second electrode 170 on the structure where the organic layer 150 is formed.

As described above, if the halftone mask of the present embodiment is used, the organic light emitting display device having excellent reliability and durability can be manufactured.

While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.