JP2013142777A - Exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure method capable of aligning a mask and a work without forming any alignment mark on the work or mask and capable of forming element patterns (chip) as many as possible on the work.SOLUTION: A mask pattern is formed on a mask M to be larger than a conventional mask pattern by one line added outside vertically and horizontally respectively, and an area to be irradiated by exposure light is set to be larger by at least one line of patterns vertically and horizontally according to the mask pattern with respect to a work W. When exposing, a desired pattern in plural patterns repeatedly formed on the mask and a pattern formed at a position corresponding to the pattern on the work W are aligned, and the exposure light larger by one line of the pattern is radiated to the work W through the mask M. With this, even when the position of the work on a work stage WS is displaced to the side by one element, the exposure light through the mask M is radiated over entire area on the work W, and thus element patterns are formed.

Description

  The present invention relates to an exposure method for forming a pattern on a workpiece by irradiating the workpiece with exposure light through a mask in which a plurality of patterns having the same shape are formed vertically and horizontally, and in particular, a mask without using special alignment marks. And an exposure method for aligning the workpiece and exposing the mask pattern onto the workpiece.

An exposure apparatus is used in a process of manufacturing a pattern of a semiconductor element, an LED element, a printed board, a liquid crystal board, or the like by photolithography. The exposure apparatus aligns the mask on which the mask pattern is formed and the work to which the pattern is transferred in a predetermined positional relationship, and then irradiates light including exposure light through the mask. As a result, the mask pattern is transferred (exposed) to the workpiece.
FIG. 6 is a diagram showing a configuration example of a conventional exposure apparatus.
As shown in FIG. 6, the exposure apparatus includes a light irradiation unit 1 that emits exposure light, a mask stage MS that holds a mask M on which a pattern is formed, a work stage WS that holds a workpiece W that performs exposure processing, and a mask M. The projection lens 2 that projects this pattern onto the workpiece W on the workpiece stage WS, and the like.
On the mask M, a mask alignment mark (mask mark) MAM for alignment with the workpiece W and a pattern (mask pattern) MP exposed to the workpiece W are formed. The mask pattern MP is a pattern in which a plurality of element patterns having the same shape are repeatedly formed across a boundary line called a scribe line.

Also on the work W, a work alignment mark (work mark) WAM for alignment with the mask M is formed. Two or more mask marks MAM and work marks WAM are formed on the mask M and the work W, respectively.
Between the projection lens 2 and the work stage WS, alignment microscopes 10 that are movable in the direction of the arrows in the figure are provided at a plurality of locations according to the number of mask marks MAM and work marks WAM. The alignment microscope 10 includes a plurality of lenses 10a for enlarging the detection target mask mark MAM and work mark WAM at a predetermined magnification, and a CCD camera 10b for receiving the mask mark MAM image and work mark WAM image enlarged by the lens. A half mirror 10c and the like are provided.

Before the mask pattern MP is exposed on the workpiece W, the alignment microscope 10 is inserted into the position shown in the figure, the mask mark MAM and the workpiece mark WAM are detected, and the positions of the mask M and the workpiece W are determined based on the positional relationship between them. Align. After the alignment, the alignment microscope 10 is retracted from the workpiece W. In FIG. 6, only one alignment microscope among a plurality of places is shown.
A mask stage driving mechanism 3 is attached to the mask stage MS, and a work stage moving mechanism 4 is attached to the work stage WS. The mask stage driving mechanism 3 and the work stage moving mechanism 4 respectively move the mask stage MS and the work stage WS in the XY directions (left and right and front side in the drawing) in the plane of the stage and the Z direction (up and down directions) perpendicular to the stage surface. Then, it is moved in the θ rotation direction about an axis perpendicular to the stage surface.
Some exposure apparatuses do not include a projection lens.

FIG. 7 is a view of the workpiece W on which the exposure process is performed as viewed from the side on which the exposure process is performed. Here, a case where a plurality of LED elements are formed on a circular sapphire substrate (work) will be described as an example.
The LED element 100 formed on the workpiece W is a quadrangular shape having a side of about 0.5 mm to 3 mm, and is formed so as to fill the entire surface of the workpiece. Each element pattern (chip) is divided by a boundary line called a scribe line SL. The completed LED element 100 is cut off by the scribe line SL to become individual LED elements.
In FIG. 7, only the scribe line SL is shown, and the pattern of the LED element 100 formed therein is omitted. In addition, the size of each chip is actually smaller, but is shown here large for easy understanding.
As shown in the figure, the LED element 100 is formed on the entire surface of the workpiece W, but a chip in which the element is cut halfway occurs in the peripheral portion of the wafer (shaded portion in the figure). Since such a chip is not completed as an element, it cannot be used as an LED element and is a discarded part.

As described above, the workpiece W is formed with a plurality of workpiece marks WAM. In FIG. 7, black circle (●) -shaped work marks WAM are formed at two locations.
The alignment and exposure procedures of the mask M and the workpiece W will be described with reference to FIGS.
8A shows the mask M, and FIG. 8B shows the work W. The mask M is formed with a scribe line SL, an L-shaped mask pattern MP surrounded by the scribe line SL, and two mask marks MAM. In the figure, a mask mark MAM is an annular (o) -shaped mark, which is registered in the control unit 11 of the exposure apparatus as a mask mark.
Also on the work W, two work marks WAM are formed at positions corresponding to the scribe line SL and the mask mark MAM. In the figure, a work mark WAM has a black circle (●) shape, and this is registered in the control unit 11 of the exposure apparatus as a work mark.

As shown in FIG. 9C, the mask mark M of the mask M held on the mask stage MS.
The workpiece mark WAM of the workpiece W held on the workpiece stage WS is detected using the alignment microscope 10, and the mask M and the workpiece W are aligned. In this figure, the workpiece W (or the mask M or both) is moved so that the center of the annular mask mark MAM and the center of the black circle-shaped workpiece mark WAM coincide.
As shown in FIG. 9D, after the alignment of the mask and the work is completed, the work W is irradiated with the exposure light matched to the shape of the work W through the mask M and the projection lens 2. In the figure, the shaded area is the area where the exposure light is irradiated (light irradiation area).

As shown in FIG. 10E, an L-shaped mask pattern MP is exposed inside the scribe line SL of the workpiece W. In the figure, a chip with a black L-shape is a chip that is a product of an LED element, and a chip with a white L-shape is a chip that is missing and does not become a product. In this case, 70 chips are products.
Patent Document 1 describes an alignment method and an alignment apparatus for aligning a mask and a workpiece using the alignment mark formed on the mask and the alignment mark formed on the workpiece as described above. Yes.

Japanese Patent No. 3152133

As described above, a plurality of work marks WAM are formed in the plane of the work W. However, as can be seen from FIGS. 7 and 10, the LED element cannot be formed at the place where the work mark WAM is formed. That is, the number of LED elements to be completed from one workpiece W is reduced by the number of workpiece marks WAM provided (at least two, or more in some cases).
Recently, in order to form as many LED elements as possible from a single work from a user who manufactures LED elements, without forming work marks on the work (that is, without forming alignment marks on the mask), There is a demand to align the mask and workpiece.
The present invention has been made based on the above circumstances, and an object of the present invention is to align the mask and the workpiece without forming an alignment mark on the workpiece or the mask, and to make as many element patterns (chips) as possible on the workpiece. ) Can be formed.

In order to meet this demand, the inventor diligently studied and considered to perform alignment using a plurality of patterns formed vertically and horizontally like a scribe line formed on a workpiece.
As described above, scribe lines (also called dicing lines or scribe streets) for separating a plurality of completed elements (chips) are formed in a grid pattern (vertical and horizontal) on the workpiece. For example, the square shape of the scribe line surrounding this element (chip) is used as an alignment mark to align the mask and the workpiece. In this way, patterns such as LED elements can be formed on the portion where the conventional work mark has been formed, and the number of elements such as LED elements formed per wafer can be increased.

However, when a plurality of patterns formed vertically and horizontally on a work such as a scribe line are used as alignment marks, there are the following problems.
The workpiece is carried using a workpiece conveyance mechanism that conveys the workpiece by sucking and holding the workpiece and placed on the workpiece stage. Before the workpiece is transported from the workpiece transfer mechanism, the edge position of the workpiece is detected by a sensor, or the edge of the workpiece is pressed against a pin, and the center position of the workpiece is positioned based on the edge. The center position is set so as not to cause a large positional shift with respect to the work stage. The main reason for this positioning is to ensure that the work mark is within the field of view of the alignment microscope.
However, such positioning based on the edge of the workpiece is caused when the workpiece is placed on the workpiece stage due to the error in the size of the workpiece or the operation accuracy and repeatability of the workpiece transfer mechanism. A positional shift of about 0.5 mm to 1 mm may occur.
Therefore, when using a plurality of patterns formed vertically and horizontally such as scribe lines as work marks, the same pattern is continuously formed on the entire surface of the work. If the size (for example, the size of the square formed by the scribe line) is 0.5 mm □ and the workpiece is placed on the work stage with a displacement of 0.5 mm, alignment should be performed within the field of view of the alignment microscope. A pattern next to the pattern enters and this pattern is detected as a work mark.
Thus, when the mask and the work are aligned using the adjacent pattern as a work mark, the area irradiated with the exposure light is shifted to the next by one pattern (one element), so that the work is not irradiated with light. An area will be created.

In order to solve this problem, the present inventor made a mask pattern to be formed on the mask more than the conventional one by at least one round (one by one row in the vertical and horizontal directions), and a region for irradiating the exposure light, In accordance with the increased mask pattern, the pattern was made larger (wider) by at least one pattern (element (chip)) in the vertical and horizontal directions with respect to the workpiece.
Then, when aligning and exposing, alignment between an arbitrary pattern among a plurality of patterns formed repeatedly on the mask and a pattern on a work formed at a position corresponding to this pattern is performed. Then, the workpiece is irradiated with exposure light through the mask with the pattern enlarged by one column.
Thereby, even when the position of the workpiece is shifted by one element when the mask and the workpiece are aligned, an area where the exposure light is not irradiated does not occur on the workpiece, and the entire area on the workpiece is passed through the mask. Exposure light is irradiated to form an element pattern.

In the present invention, the following effects can be obtained.
(1) Since the pattern on the workpiece is used as the alignment mark, it is not necessary to form the workpiece alignment mark on the workpiece, and the number of elements (chips) formed from one workpiece can be increased.
(2) Since the mask pattern to be formed on the mask is made larger by one column in the vertical and horizontal directions, and the area irradiated with the exposure light is enlarged (widened) by at least one column in the vertical and horizontal directions, Even if a shift of one element occurs, the entire workpiece can be irradiated with exposure light through a mask, and an element pattern can be formed.

It is a figure which shows the structural example of the projection exposure apparatus which is one of the application objects of this invention. It is a figure (1) explaining the procedure of position alignment and exposure of a mask and a workpiece | work of the Example of this invention. It is FIG. (2) explaining the procedure of the alignment of a mask and a workpiece | work of a Example of this invention, and exposure. It is FIG. (3) explaining the procedure of position alignment and exposure of a mask and a workpiece | work of the Example of this invention. It is a figure explaining the case where a workpiece | work raise | generates position shift on a work stage. It is a figure which shows the structural example of the conventional exposure apparatus. It is the figure which looked at the workpiece | work W in which an exposure process is performed from the side in which an exposure process is performed. It is a figure (1) explaining the procedure of position alignment and exposure of the mask M and the workpiece | work W in a prior art example. It is FIG. (2) explaining the procedure of alignment and exposure of the mask M and the workpiece | work W in a prior art example. It is a figure (3) explaining the procedure of alignment and exposure of the mask M and the workpiece | work W in a prior art example.

FIG. 1 is a diagram showing the configuration of a projection exposure apparatus that is one of the objects to which the present invention is applied.
Compared with the conventional example of FIG. 6, the area where the mask pattern MP of the mask M is formed is wider, and the light irradiation area of the exposure light irradiated to the work W via the mask M is accordingly One size larger than W. Further, neither the mask M nor the work W is formed with alignment marks (mask mark and work mark). The rest of the configuration of the apparatus is the same as in FIG. 6, and the same components are denoted by the same reference numerals.
In FIG. 1, 1 is a light irradiation unit that emits exposure light, MS is a mask stage that holds a mask M, WS is a work stage that holds a workpiece W, and 2 is a projection lens that projects a pattern of the mask M onto the workpiece W. is there.
On the mask M, a pattern (mask pattern) MP that is exposed to the workpiece W is formed. The mask pattern MP is a pattern in which a plurality of element patterns having the same shape are repeatedly formed across a boundary line called a scribe line.

A pattern such as a scribe line is repeatedly formed in the work W in the vertical and horizontal directions. In the following, a description will be given of a case where alignment is performed using this scribe line. However, when a pattern corresponding to the mask pattern MP is repeatedly formed on the workpiece W vertically and horizontally, this pattern is used for alignment. Can be used as a pattern.
Between the projection lens 2 and the work stage WS, an alignment microscope 10 that can move in the direction of the arrow in FIG. The alignment microscope 10 includes a plurality of lenses 10a for enlarging a pattern to be detected at a predetermined magnification, a CCD camera 10b for receiving a pattern image enlarged by the lens 10a, a half mirror 10c, and the like.

Before the mask pattern MP is exposed on the workpiece W, the alignment microscope 10 is inserted into the position shown in the figure, the pattern formed on the mask M and the workpiece W is detected, and the mask M and the workpiece W are detected based on the positional relationship between them. Perform position alignment. After the alignment, the alignment microscope 10 is retracted from the workpiece W. In FIG. 1, only one alignment microscope among a plurality of places is shown.
A mask stage driving mechanism 3 is attached to the mask stage MS, and a work stage moving mechanism 4 is attached to the work stage WS. The mask stage driving mechanism 3 and the work stage moving mechanism 4 respectively move the mask stage MS and the work stage WS in the XY directions (left and right and front side in the drawing) in the plane of the stage and the Z direction (up and down directions) perpendicular to the stage surface. Then, it is moved in the θ rotation direction about an axis perpendicular to the stage surface.

The alignment and exposure procedures of the mask M and the workpiece W according to the present invention will be described with reference to FIGS.
(1) FIG. 2A shows a mask M. The mask M has a scribe line SL and an L-shaped mask pattern MP formed between the scribe lines SL.
As compared with the conventional example of FIG. 8A, the mask pattern MP is formed in one row of elements (chips) in the vertical and horizontal directions (up and down and left and right). In the case of FIG. 8A of the conventional example, 16 × 8 = 128 chips are formed on the mask. On the other hand, in the case of FIG. 2A of the present invention, 18 chips × 10 chips = 180 chips are formed.
A mask mark MAM for alignment as in the prior art is not formed on the mask M. However, some reference mark is necessary for alignment with the workpiece. Therefore, in this embodiment, an L-shaped pattern having a specific shape in the circuit of the element (chip) to be formed is registered in the control unit 11 of the exposure apparatus as a mask mark MAM.

FIG. 2B shows the work W. A scribe line SL is formed on the work W, but a work mark WAM for alignment is not formed. Therefore, the shape of a square scribe line surrounding the element (chip) is registered as a work mark WAM in the control unit 11 of the exposure apparatus.
Then, the alignment of the mask M and the workpiece W is set such that the center of gravity of the L-shaped mask mark MAM is positioned at a predetermined position inside the workpiece mark WAM on the square scribe line, for example.

(2) Insert the alignment microscope 10 onto the workpiece W. As shown in FIG. 3C, the alignment microscope 10 detects an L-shaped pattern as a mask mark MAM, and displays a pattern surrounded by a square scribe line at a position corresponding to the mask mark MAM as a work mark WAM. And detect.
Then, the work W and / or the mask M is moved so that the center of gravity of the L-shaped mask mark MAM comes to a predetermined position inside the square work mark WAM, and the mask M and the work W are aligned.
That is, in FIG. 1, light for alignment from the light irradiation unit 1 is irradiated onto the mask M to project the pattern of the mask M onto the workpiece W, and any of the mask patterns projected onto the workpiece W is projected. The mask stage MS or the work stage WS is moved so that the barycentric position of the projected image of the pattern (which may be determined in advance) is located at a predetermined position inside the pattern on the work adjacent to the pattern. Align.

(3) After alignment is completed, the light irradiation unit 1 irradiates the workpiece W with exposure light through the mask M. At this time, the size (width) of the region irradiated with the exposure light is increased by at least one row of elements (chips) in the vertical and horizontal directions (up and down, left and right in the drawing) as compared with the conventional example. In FIG. 3D, the shaded area is the area irradiated with the exposure light (light irradiation area). In the case of FIG. 9D of the conventional example, the light irradiation area is the same size as the workpiece W. On the other hand, in the case of FIG. 3D of the present invention, the light irradiation region is larger (wider) by one chip than the size of the workpiece W.

  Thereby, as shown in FIG. 4E, the L-shaped mask pattern MP is exposed inside the scribe line SL of the workpiece W. In the figure, a chip with a black L-shape is a chip that is a product of an LED element, and a chip with a white L-shape is a chip that is missing and does not become a product. In the present invention, since elements can be formed in a region where a work mark has been conventionally formed, 72 chips can be manufactured. Note that there are only two differences per workpiece, but this will become a big difference as hundreds and thousands are made.

Next, the case where the position shift occurs when the workpiece W is placed on the workpiece stage WS will be described with reference to FIG.
In this embodiment, there is no work mark having a unique shape, and the square shape of the scribe line SL is used as the work mark WAM. However, the square shape of the scribe line SL exists continuously on the top, bottom, left, and right (vertical and horizontal) of the chip to be used for alignment.
As described above, when the workpiece W is placed on the workpiece stage WS by the workpiece conveyance mechanism, a positional deviation of about 0.5 mm to 1 mm may occur. The chip size of the LED element formed on the workpiece W is about 0.5 mm □ when it is small. Therefore, when a position shift of 0.5 mm occurs when the work W is placed on the work stage WS, it is possible to detect not the chip to be used for alignment but the scribe line SL of the next chip as the work mark WAM. is there.

As a countermeasure, the mask M is formed with at least one row of elements (chips) in the vertical and horizontal directions (outside one round) as compared with the conventional case. Then, the size of the region irradiated with the exposure light is increased by at least one row of elements (chips) in the vertical and horizontal directions (outside one round) as compared with the conventional example.
FIG. 5 is a diagram showing a state of exposure when alignment is performed in a state where a positional deviation of one chip has occurred in alignment between the mask and the workpiece. FIG. 5A shows a case where the work is shifted to the right side of the drawing by one chip, and FIG. In the figure, the mask pattern MP is omitted except for those used as mask marks.
As shown in the figure, even if the mask M and the work W are shifted and aligned by one chip, the mask M has at least one row of elements (chips) in the vertical and horizontal directions with respect to the work W. A large mask pattern is formed, and the light irradiation area is also irradiated with at least one element (chip) in the vertical and horizontal directions corresponding to the mask pattern. There is no area where the exposure light is not irradiated (the work W does not protrude from the light irradiation area), and the entire work W is irradiated with the exposure light through the mask M, and a desired number of patterns are formed on the work W. Is done.

Note that when the number of chips formed on the mask M is increased, the size of the mask M increases accordingly, and the manufacturing cost of the mask M also increases. Moreover, if the area | region which irradiates exposure light is enlarged, illumination intensity will fall correspondingly. Therefore, how much the number of chips formed on the mask M is increased in length and width and how much the light irradiation area is increased is determined by the mechanical accuracy and reproducibility of the work transport mechanism that places the work W on the work stage WS.
If it does not shift to more than one chip, it only needs to be increased by one chip vertically and horizontally. However, if there is a possibility of shifting by two chips or more, it must be increased accordingly. However, since the conveyance accuracy of the workpiece conveyance mechanism used in the LED manufacturing process currently used is about ± 0.5 mm, it is considered unnecessary to increase it by 1 mm or more.
In the above embodiment, the exposure apparatus provided with the projection lens has been described as an example. However, the present invention can be applied to a proximity exposure apparatus and a contact exposure apparatus that do not include a projection lens. .

DESCRIPTION OF SYMBOLS 1 Light irradiation part 10 Alignment microscope 10a Lens 10b CCD camera 2 Projection lens 3 Mask stage drive mechanism 4 Work stage moving mechanism M Mask MAM Mask alignment mark (mask mark)
MP pattern (mask pattern)
MS Mask stage W Work WAM Work alignment mark (work mark)

Claims (2)

A plurality of patterns formed on the mask are formed on the workpiece by irradiating the workpiece on which the same pattern is repeatedly formed vertically and horizontally with a mask formed by repeating the same pattern vertically and horizontally. In the exposure method to
Using a mask in which a large number of the above patterns are formed for at least one column vertically and horizontally than the size of the workpiece,
Aligning an arbitrary pattern among a plurality of patterns repeatedly formed on the mask and a pattern on the work formed at a position corresponding to this pattern,
An exposure method comprising: irradiating an irradiation area of exposure light applied to the workpiece through the mask while increasing the length and width of the workpiece by at least one row of the pattern. 2. The exposure method according to claim 1, wherein the pattern formed on the workpiece is a scribe line.

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