CN111381437A

CN111381437A - Mask plate and exposure method

Info

Publication number: CN111381437A
Application number: CN201811652807.8A
Authority: CN
Inventors: 任书铭; 章磊; 李成立
Original assignee: Shanghai Micro Electronics Equipment Co Ltd
Current assignee: Shanghai Micro Electronics Equipment Co Ltd
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2020-07-07
Anticipated expiration: 2038-12-28
Also published as: CN111381437B

Abstract

The invention provides a mask plate and an exposure method, wherein a mask pattern is formed by regularly arranging a plurality of polygonal unit patterns, each unit pattern comprises an opaque part and a light-transmitting part surrounding the opaque part, after a plurality of exposure areas of an LED substrate are exposed through the mask pattern, an exposure pattern can be formed in each exposure area, the exposure patterns are regularly spliced to form a PSS pattern, and the PSS pattern is spliced from the same exposure pattern, so that the pattern size and the pattern of each splicing area are consistent, the problem of inconsistent light intensity of the edge patterns of the splicing areas is solved, the uniformity of the edge patterns is improved, and the degree of chromatic aberration is weakened.

Description

Mask plate and exposure method

Technical Field

The invention relates to the technical field of semiconductor manufacturing, in particular to a mask plate and an exposure method.

Background

Patterning a Sapphire Substrate (PSS), namely growing a mask for dry etching on the Sapphire Substrate, forming a PSS pattern by using a standard photoetching process, etching the Sapphire by using an ICP (inductively coupled plasma) etching technology, removing the mask, and growing a GaN material on the mask to change longitudinal epitaxy of the GaN material into transverse epitaxy, so that on one hand, the dislocation density of the GaN epitaxial material can be effectively reduced, the non-radiative recombination of an active region is reduced, the reverse leakage current is reduced, and the service life of an LED (light-emitting diode) is prolonged; on the other hand, light emitted from the active region is scattered for multiple times through the interface of the GaN substrate and the sapphire substrate, the emergence angle of total reflection light is changed, the probability of the light of the LED emitting from the LED substrate is increased, and therefore the light extraction efficiency is improved. FIG. 1 is a schematic view showing a structure of a PSS pattern in which a plurality of hexagons are arranged in a honeycomb shape (a circular portion is protruded and the remaining portion is depressed) due to a sapphire substrate crystal image. As shown in fig. 2, since the existing exposure field Q 'is in a rectangular form, and due to the manufacturing of the exposure lens, the farther from the center of the pupil, the worse the image quality (the concentric circles in fig. 2 represent different image quality areas, and the closer to the center, the better the image quality, and the areas within the iv image quality area are all available image quality areas), the edge of the exposure field Q' spans the different image quality areas, especially, the four corners of the rectangular exposure field Q 'may be located in the worst available image quality area iv, and the process windows corresponding to the different image quality areas are not consistent, so the image appearance of the area image in the mosaic area beyond the process window may change, and the color difference may occur in the sense of human eyes, wherein the color difference may be the most serious in the four corners of the exposure field Q'. Therefore, in order to make the process quality of the splicing part of the PSS pattern reach the standard, the size of the exposure field is often required to be reduced by taking four corners of the rectangular exposure field Q' as boundaries, so that the image quality of the pattern in all the exposure fields can be used, thereby greatly reducing the yield of the lithography machine. In order to make the rectangular exposure view field Q' in the available image quality area, the size of the single exposure view field is limited, and to form the manufacture of the whole PSS pattern, a splicing exposure method needs to be used, the existing splicing area division method is shown in fig. 1 and fig. 3 (orthogonal line division), the virtual line in the figure is the splicing line, actual imaging cannot be performed, the splicing area may need 4 rectangular exposure view fields to complete, in this scheme, because the sizes of the patterns near the edges of the splicing area are not consistent, the light intensities received by the patterns during actual imaging are not consistent, thereby further aggravating the variation of the shapes of the patterns at the edges of the splicing area and aggravating the problem of chromatic aberration.

Disclosure of Invention

The invention aims to provide a mask plate and an exposure method, which are used for solving the problem that the graph light intensity at the edge of a splicing area is inconsistent in the existing PSS graph manufacturing process.

In order to achieve the above object, the present invention provides a mask plate for exposing an LED substrate to form a PSS pattern, wherein the mask plate comprises a substrate and a mask pattern formed on the substrate, the mask pattern comprises a plurality of polygonal unit patterns, and the unit patterns are regularly spliced to make the mask pattern in a gear shape as a whole.

Optionally, the unit pattern includes an opaque portion and a light-transmitting portion surrounding the opaque portion, a center of the opaque portion coincides with a center of the unit pattern, a gap is formed between an edge of the opaque portion and an edge of the unit pattern, and the gap forms the light-transmitting portion.

Optionally, the PSS pattern of the LED substrate has a protrusion corresponding to the opaque portion, and the total number of the protrusions is n times the total number of the opaque portion in the mask pattern, where n is the number of exposures.

Optionally, the unit pattern is a regular hexagon, and the opaque portion is a circle.

Optionally, the central points of the opaque portions at the outer edges of the mask patterns are sequentially connected to form a regular quadrangle or a regular hexagon, so that the area of the mask patterns in the usable image quality area of an exposure system is maximized.

Optionally, the splicing between the adjacent unit patterns is seamless.

The invention also provides an exposure method, which comprises the following steps:

providing the mask plate;

sequentially moving a plurality of exposure areas of an LED substrate to the lower side of a mask pattern of the mask plate for field-by-field exposure until the whole LED substrate is completely exposed, and regularly splicing the exposure patterns of each exposure area to form a PSS pattern on the LED substrate.

Optionally, the size and shape of an available image quality area of an exposure system are obtained, and the mask pattern is designed according to the size and shape of the available image quality area so as to maximize the area of the mask pattern within the available image quality area.

Optionally, the splicing between adjacent exposure patterns is seamless.

Optionally, the LED substrate is a sapphire substrate.

According to the mask plate and the exposure method provided by the invention, the mask pattern is formed by regularly splicing a plurality of polygonal unit patterns, the mask pattern is integrally in a gear shape, after a plurality of exposure areas of an LED substrate are exposed through the mask plate, an exposure pattern can be formed in each exposure area, and the plurality of exposure patterns are regularly spliced to form the PSS pattern.

Drawings

FIG. 1 is a schematic diagram of a PSS pattern;

FIG. 2 is a schematic diagram of a rectangular exposure field;

FIG. 3 is a schematic diagram of PSS graph stitching position splitting;

FIG. 4 is a schematic structural diagram of a unit pattern according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a mask pattern according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of an exposure pattern according to an embodiment of the present invention;

FIG. 7 is a partial enlarged view of the area A in FIG. 6 according to one embodiment of the present invention;

FIG. 8 is a schematic structural diagram of another mask pattern according to an embodiment of the present invention;

FIG. 9 is a schematic structural diagram of another mask pattern according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of a mask pattern according to a second embodiment of the present invention;

FIG. 11 is a schematic structural diagram of an exposure pattern according to a second embodiment of the present invention;

FIG. 12 is a schematic diagram of a hexagonal exposure field according to an embodiment of the present invention;

wherein the reference numerals are:

1-unit pattern; 11-a light-transmissive portion; 12-opaque portion;

q-hexagonal exposure field of view; q' -rectangular exposure field; a-region A;

a-characteristic angle of class quadrangle; a' -characteristic angle of a hexagon;

b1, b2, b3, b4, b 5-exposure pattern b1, exposure pattern b2, exposure pattern b3, exposure pattern b4, exposure pattern b 5;

c1, c2, c3, c4, c5, c6, c 7-exposure pattern c1, exposure pattern c2, exposure pattern c3, exposure pattern c4, exposure pattern c5, exposure pattern c6, and exposure pattern c 7.

Detailed Description

The following describes in more detail embodiments of the present invention with reference to the schematic drawings. Advantages and features of the present invention will become apparent from the following description and claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

Example one

Referring to fig. 4 to 5, which are schematic views of a mask according to the present embodiment, as shown in fig. 3 and 4, the mask is used for exposing an LED substrate to form a PSS pattern, the mask includes a substrate and a mask pattern formed on the substrate, the mask pattern includes a plurality of unit patterns 1 in a polygonal shape, and the unit patterns 1 are regularly spliced to make the mask pattern in a gear shape as a whole. The LED substrate uses a light transmitting material, which may be, for example, sapphire, silicon carbide (SiC), zinc oxide (ZnO), spinel (MgAL2O4), or the like. In this embodiment, the LED substrate is a sapphire substrate.

Specifically, as shown in fig. 4 and 5, the mask pattern includes a plurality of unit patterns 1 in a polygonal shape, in this embodiment, the unit patterns 1 are regular hexagons, and the unit patterns 1 are regularly spliced to form the gear-shaped mask pattern shown in fig. 5, that is, the edge of the mask pattern is zigzag. Each unit pattern 1 includes an opaque portion 12 and a light-transmitting portion 11 surrounding the opaque portion 12, in this embodiment, the opaque portion 12 is circular, the center of the opaque portion 12 coincides with the center of the unit pattern 1, and a gap is formed between the edge of the opaque portion 12 and the edge of the unit pattern 1 (the radius of the opaque portion 12 is smaller than the distance from the center to the side length of the unit pattern 1), and the gap constitutes the light-transmitting portion 11.

Wherein, the light transmission part 11 can also be called as "light transmission area", and the light transmission is, for example, greater than or equal to 98%; the opaque portion 12 may also be referred to as an "opaque region," and the opaque portion 12 has a light transmittance of, for example, 2% or less, and may be considered to be capable of blocking all light approximately. In this embodiment, the areas of the unit pattern 1 except the opaque portion 12 are all the transparent portions 11, that is, the unit pattern 1 in this embodiment includes two areas, i.e., the transparent areas 11 and the opaque areas 12. It should be understood that the light transmittances of the light transmitting portion 11 and the light non-transmitting portion 12 are not limited to the ranges described above, the light transmittance of the "light transmitting portion" is only higher than that of the "light non-transmitting portion" and does not mean complete light transmittance, and the light transmittance of the "light non-transmitting portion" is only lower than that of the "light transmitting portion" and does not mean complete light non-transmitting, and the light transmittance ranges of the two regions can be adjusted accordingly according to actual process requirements. It is understood that, except for the mask pattern, the rest of the unusable parts of the mask plate are not transparent. The material of the substrate of the mask plate is, for example, quartz glass (quartz), which may be covered with a patterned chrome film. The region of the substrate not covered with the chromium film may constitute the light-transmitting portion 11 (light-transmitting region), and the region of the substrate covered with the chromium film may constitute the light-non-transmitting portion 12 (light-non-transmitting region).

As shown in fig. 5, the mask patterns are closely spliced by a plurality of identical unit patterns 1 (a splicing line is not shown), and adjacent unit patterns 1 are seamlessly spliced, that is, the light-transmitting portions 11 of adjacent unit patterns 1 are continuous, or it can be understood that the light-transmitting portions 12 are formed on a whole light-transmitting area, the light-transmitting area covered by the light-transmitting portions 12 is no longer light-transmitting, that is, the light-transmitting portions 12 are formed, and the remaining light-transmitting area forms the light-transmitting portion 11. With reference to fig. 5, in the present embodiment, the opaque portions 12 in the mask pattern are uniformly distributed, that is, the size and the distance between adjacent opaque portions 12 are the same, and the centers of the opaque portions 12 at the outer edge (the outermost circle of the exposure field) of the mask pattern are sequentially connected to obtain a quadrangle, each side of the quadrangle is the same, in the present embodiment, each side of the quadrangle is connected to the centers of four opaque portions 12, and the quadrangle has 4 complete opaque portions 12 (the innermost circle of the exposure field), and the centers of the four complete opaque portions 12 are sequentially connected to form a quadrangle with a smaller size. In the mask pattern of the quadless shape, the characteristic angle a of the quadless shape may be 50 ° -70 °, preferably 57.8 °, to more conform to the characteristic of the quadless shape.

Further, the mask pattern in this embodiment has 7 rows of the opaque parts 12 in the Y direction, the opaque parts 12 in each row are uniformly distributed, that is, the intervals between adjacent opaque parts 12 are equal, and the number of the opaque parts 12 in each row gradually increases by 1 from the edge to the center of the mask pattern.

Further, an exposure process is performed on the LED substrate by using the mask pattern, so as to reduce the mask pattern to one exposure area of the LED substrate in an equal proportion, in order to enable an exposure field to be in an available image quality area and cannot be completely exposed at one time, the LED substrate needs to be divided into a plurality of exposure areas, and then the plurality of exposure areas are respectively exposed to form an exposure pattern in each exposure area, as shown in fig. 6, adjacent exposure patterns are spliced to form a PSS pattern. It should be understood that the stitching between the exposed patterns is also seamless, and that the stitching lines between adjacent exposed patterns are not actually imaged. Fig. 6 is a schematic diagram schematically showing only the stitching between 5 exposure patterns b1, b2, b3, b4 and b5, in which the upper left stitching line of the middle exposure pattern b1 coincides with the lower right stitching line of the upper left exposure pattern b2, the lower left stitching line of the middle exposure pattern b1 coincides with the upper right stitching line of the lower left exposure pattern b4, the upper right edge line of the middle exposure pattern b1 coincides with the lower left stitching line of the upper right exposure pattern b3, the lower right edge line of the middle exposure pattern b1 coincides with the upper left stitching line of the lower right exposure pattern b5, light-transmitting portions and light-opaque portions are not specifically shown in fig. 6, only adjacent exposure pattern stitching lines are shown, fig. 7 is a partially enlarged view of a region in fig. 6, a region is a boundary between the exposure pattern b1, the exposure pattern b2 and the exposure pattern b3, and it can be seen from fig. 7 that the opaque portion b11 of the exposure pattern b1 is located at the boundary between the exposure pattern b3, The opaque portion b21 of the exposure pattern b2 and the opaque portion b31 of the exposure pattern b31 are adjacent to each other, and it should be understood that the opaque portions at the boundaries of the remaining exposure patterns should follow the same rule, and they are not illustrated here. Next, b2, b3, b4 and b5 may be spliced with other exposure patterns as intermediate exposure patterns, and finally, adjacent exposure patterns are repeatedly spliced by increasing the number of the exposure patterns until the entire LED substrate is completely exposed, thereby forming the honeycomb-shaped PSS pattern.

It is understood that the mask pattern of the present embodiment schematically shows a mask pattern having 16 opaque parts 12, but actually, the number of the opaque parts 12 in the mask pattern is determined according to the available image quality area and the PSS pattern to be formed, because the PSS pattern is formed after the exposure of the LED substrate using the mask plate, the LED substrate has protrusions corresponding to the opaque parts, the total number of the protrusions in the LED substrate is fixed, and in order that the state of repeated exposure does not occur, the total number of the protrusions should be n times the total number of the opaque parts 12 in the mask pattern, where n is the number of exposure times (integer). If the number of the opaque portions 12 is satisfied, it is also necessary that the mask pattern does not exceed the available image quality area, for example, if the mask pattern in fig. 5 is formed by further splicing a unit pattern at each jagged notch, the mask pattern shown in fig. 8 is too large and exceeds the range of the available image quality area, and the exposed image quality cannot be guaranteed; if the mask pattern shown in fig. 9 is formed after one unit pattern is reduced at the edge of the mask pattern in fig. 5, the mask pattern is too small to maximize the mask pattern within the usable image quality area, and the PSS pattern can be formed through more exposures, which results in low production efficiency. Therefore, the mask pattern can be determined by the size and shape of the usable image quality area and the total number of protrusions in the LED substrate, so as to maximize the area of the mask pattern within the usable image quality area.

Based on this, the present embodiment further provides an exposure method for an LED substrate, including:

s1: providing the mask plate;

s2: sequentially moving a plurality of exposure areas of an LED substrate to the lower side of a mask pattern of the mask plate for field-by-field exposure until the whole LED substrate is completely exposed, and regularly splicing the exposure patterns of each exposure area to form a PSS pattern on the LED substrate.

Specifically, the size and shape of the usable image quality area of the exposure system may be first obtained (the pupil of the exposure system may not be a perfect circle but an ellipse, and the shape of the usable image quality area may also be changed), then the number of protrusions to be formed in the LED substrate is determined, the mask pattern is designed on the mask plate according to the size and shape of the usable image quality area and the number of protrusions, then the mask plate is mounted on a mask holder, then the LED substrate is transported over a workpiece stage, vacuum suction is started, and the LED substrate is sucked on a vacuum chuck to prepare for exposure. And then, selecting a stepping prescription according to the shape of an exposure field, moving the workpiece table, and sequentially moving the exposure area required by the LED substrate into the exposure field below the mask plate to carry out field-by-field exposure.

Example two

As shown in fig. 10, different from the first embodiment, in the present embodiment, after the centers of the opaque portions 12 at the outer edge (the outermost circle of the exposure field) of the mask pattern are sequentially connected, a hexagonal shape can be obtained, each side of the hexagonal shape is equal, in the present embodiment, each side of the hexagonal shape connects the centers of three opaque portions 12, and the inner side (the second outer circle of the exposure field) of the hexagonal shape further has 5 complete opaque portions 12, and the centers of the 5 complete opaque portions 12 can be sequentially connected to form a hexagonal shape with a smaller size. In a hexagonal-like mask pattern, the hexagonal-like feature angle a' may be 50 ° -70 °, preferably 57.8 °, to better conform to the hexagonal-like features.

Further, the mask pattern in this embodiment has 5 rows of the opaque parts 12 in the Y direction, the opaque parts 12 in each row are uniformly distributed, that is, the intervals between adjacent opaque parts 12 are equal, and the number of the opaque parts 12 in each row gradually increases by 1 from the edge to the center of the mask pattern.

Further, an exposure process is performed on the LED substrate by using the mask pattern to reduce the mask pattern to one exposure area of the LED substrate in an equal proportion, then the LED substrate is divided into a plurality of exposure areas, and then the plurality of exposure areas are respectively exposed to form an exposure pattern in each exposure area, as shown in fig. 11, the same as in the first embodiment, in this embodiment, the splicing between the adjacent exposure patterns is also seamlessly spliced, and the splicing line between the adjacent exposure patterns is not actually imaged. Fig. 11 is a schematic diagram showing only the stitching among 7 exposure patterns c1, c2, c3, c4, c5, c6 and c7, wherein the exposure patterns c2, c3, c4, c5, c6 and c7 are stitched around the middle exposure pattern c1, and the side edges of the exposure patterns c2, c3, c4, c5, c6 and c7 are sequentially stitched, and then, c2, c3, c4, c5, c6 and c7 can also be stitched with other exposure patterns as the middle exposure pattern, and finally, the stitching of the adjacent exposure patterns is repeated by increasing the number of the exposure patterns until the entire LED substrate is completely exposed, so that the honeycomb-shaped PSS pattern is formed.

As shown in fig. 12, in this embodiment, the hexagonal exposure field Q is also located in the usable image quality area, and the hexagonal exposure field Q can be well matched with the crystal image of the PSS pattern, and compared with the rectangular exposure field Q 'shown in fig. 2, the hexagonal exposure field Q has a larger area passing through the usable image quality area and can accommodate more patterns, thereby increasing the yield, and the area of the hexagonal exposure field Q is about 30% larger than that of the rectangular exposure field Q', so the theoretical yield can be increased by 30%.

Based on this, the present embodiment also provides an exposure method for an LED substrate, including:

s1: providing the mask plate;

The exposure method of the LED substrate and the design method of the mask pattern are described in detail in the first embodiment, and are not described herein again.

It should be understood that the present invention only shows the schematic diagrams of the mask patterns of two mask plates, but not limited thereto, as long as the mask patterns of the mask plates form exposure patterns that can be regularly and repeatedly spliced and form honeycomb-shaped PSS patterns (without repeated exposure), and the mask patterns are within the scope of the present invention within the usable image quality area.

In summary, in the mask and the exposure method provided by the present invention, the mask pattern is formed by regularly splicing a plurality of polygonal unit patterns, and the mask pattern is entirely in a gear shape, after the exposure is performed on a plurality of exposure areas of the LED substrate by the mask, an exposure pattern can be formed in each exposure area, and the plurality of exposure patterns are regularly spliced to form the PSS pattern.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A mask plate is used for exposing an LED substrate to form a PSS pattern and is characterized by comprising a substrate and a mask pattern formed on the substrate, wherein the mask pattern comprises a plurality of polygonal unit patterns, and the unit patterns are regularly spliced to enable the whole mask pattern to be in a gear shape.

2. A mask according to claim 1, wherein the unit pattern includes an opaque portion and a light-transmitting portion surrounding the opaque portion, a center of the opaque portion coincides with a center of the unit pattern, an edge of the opaque portion has a gap with an edge of the unit pattern, and the gap constitutes the light-transmitting portion.

3. A mask as claimed in claim 2, wherein the PSS pattern of the LED substrate has therein projections corresponding to the opaque portions, the total number of the projections being n times the total number of the opaque portions in the mask pattern, where n is the number of exposures.

4. A mask according to claim 2, wherein the unit pattern is a regular hexagon, and the opaque portion is a circle.

5. A mask according to claim 4, wherein the central points of the opaque portions of the outer edges of the mask pattern are sequentially connected to form a regular quadrangle or a regular hexagon, so as to maximize the area of the mask pattern within the usable image quality area of an exposure system.

6. A mask plate according to any one of claims 1 to 5, wherein the joint between adjacent unit patterns is a seamless joint.

7. An exposure method, comprising:

providing a mask according to any one of claims 1 to 6;

8. The exposure method according to claim 7, wherein the size and shape of an available image quality area of an exposure system are acquired, and the mask pattern is designed according to the size and shape of the available image quality area so as to maximize the area of the mask pattern within the available image quality area.

9. The exposure method according to claim 7, wherein the joint between adjacent exposure patterns is a seamless joint.

10. The exposure method according to any one of claims 7 to 9, wherein the LED substrate is a sapphire substrate.