JP2012220923A - Method for alignment between mask and work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a position of a pattern formed on a work by projection exposure from being deviated from a position of a pattern formed by previous exposure processing and a position of a mask pattern for screen printing or the like to be executed in the next step, even in the case of the occurrence of telescopic deformation on the work.SOLUTION: During alignment in a projection exposure device, a scale factor by which a pattern of a mask M is enlarged or reduced is adjusted so as to minimize a value obtained by adding the sum total of amounts of deviation dM between positions of mask marks MAM1 to MAM4 of the mask and reference positions of mask marks SAM1 to SAM4 of a screen mask for use in the next step to the sum total of amounts of deviation dR between mask marks MAM1 to MAM4 of the mask and work marks WAM1 to WAM4, and the mask M or the work W is moved to align the mask M and the work W with each other.

Description

  The present invention relates to a method of aligning a mask and a workpiece in a projection exposure apparatus that projects and exposes a mask pattern on the workpiece, and particularly to a workpiece whose size changes due to expansion and contraction in a processing step. At this time, by performing alignment in consideration of alignment in the next process, a mask having a fixed size such as solder screen printing, contact exposure, and proximity exposure is used in the next process of the projection exposure process. Even when the mask pattern is transferred onto the workpiece by bringing the workpiece into contact with or approaching the workpiece, the mask can be aligned with the fixed size mask without causing a large deviation. And the method of aligning the workpiece.

As an example in which projection exposure is performed and the mask and workpiece are brought into close contact with each other in the next step and the mask pattern is transferred to the workpiece, screen printing is described here as an example.
In the manufacture of printed circuit boards and the like, a process of transferring a mask pattern onto a work by a projection exposure apparatus to form a wiring pad pattern on the work, and then printing solder on the formed wiring pad by screen printing Is done.
FIG. 9 is a conceptual diagram of the wiring pads and the wiring pads on which solder is printed (applied).
As shown in FIG. 6A, a wiring pattern Pp and a wiring pad Pd made of a conductor such as copper are formed on a substrate (work) by a projection exposure process or the like, and as shown in FIG. The solder S is printed (applied) on the pad Pd by screen printing.

In the screen printing, a mask and a work on which the wiring pads are formed are overlapped, solder is applied on the mask, and solder is applied to a position on the work corresponding to the opening provided in the mask. . In the step of forming the wiring pad pattern on the work, the printed circuit board (work) expands and contracts. Therefore, during projection exposure, the magnification of the mask pattern image to be projected is changed according to the expansion and contraction of the work.
On the other hand, in the screen printing, since the mask is adhered to the workpiece and solder is applied, the magnification of the mask pattern image to be projected cannot be changed according to the expansion and contraction of the workpiece as in projection exposure, and the expansion and contraction of the workpiece is performed. This is performed using a mask whose size is set in advance in consideration of the above.

As described above, a process of forming a wiring pad pattern on a work such as a printed board and placing (printing) solder on the formed wiring pad is as follows.
(A) A pattern of a wiring pad is formed on a work on which a wiring pattern is formed by a projection exposure apparatus.
(A) Solder is printed on the wiring pad formed on the workpiece by the screen printing apparatus.

The above process will be described more specifically.
(A) Formation of wiring pad pattern on workpiece by projection exposure First, the process (A) will be described. Prior to this step, a wiring pattern has already been formed on the workpiece.
The projection exposure apparatus aligns the mask on which the wiring pad pattern is formed and the workpiece coated with resist (the wiring pattern is already formed) in a predetermined positional relationship, and then passes through this mask. Irradiate the workpiece with exposure light. Thereby, the pattern of the wiring pad is transferred (exposed) to the work at a predetermined position of the work.
An example of an exposure apparatus provided with a projection lens used for the above exposure process is described in Patent Document 1 (Japanese Patent Laid-Open No. 9-82615). The operation when the above alignment is performed by the exposure apparatus shown in FIG. 1 of the same publication will be described with reference to FIG. In FIG. 10, since the drawing is complicated, the wiring pattern formed on the workpiece is omitted.

As shown in FIG. 10A, a pattern P of wiring pads formed on the work W is formed on the mask M. The workpiece W is a resin substrate such as a printed circuit board.
The projection lens (see, for example, FIG. 1 of Patent Document 1) is a lens that projects the pattern P formed on the mask M onto the workpiece W, and the projection lens includes a zoom mechanism, and according to the expansion and contraction of the workpiece. The magnification of the pattern image to be projected can be changed.
In the exposure process, in order to form the wiring pad Pd at a predetermined position of the workpiece W, the mask M and the workpiece W are aligned before exposure. Therefore, as shown in FIG. 10A, a mask alignment mark (hereinafter, mask mark MAM) is formed on the mask M, and a work alignment mark (hereinafter, work mark WAM) is formed on the workpiece.
Since the alignment of the mask and the work is performed in two directions (X direction and Y direction) and the rotation direction (θ direction) in the plane, two or more mask marks MAM and work marks WAM are formed. In FIG. 10, four mask marks MAM and four work marks WAM are formed.

Detection of the mask mark MAM and the work mark WAM is performed by an alignment microscope (see FIG. 1 of Patent Document 1). The alignment microscope is provided according to the number of mask marks and work marks to be formed.
The procedure for aligning the mask M and the workpiece W is as follows.
(A) The mask mark MAM projected by the projection lens is detected by an alignment microscope. Further, the work mark WAM formed on the work W is detected by an alignment microscope.
(B) The mask mark MAM and the work mark WAM detected by the alignment microscope are subjected to image processing in the control unit of the apparatus, and the respective position coordinates are obtained.

(C) The mask M or the workpiece W is moved in the XYθ direction so that the total amount of displacement between the positions of the workpiece mark WAM and the mask mark MAM is preferably matched so as to be minimized. In addition, when the workpiece W is stretched and deformed to change its size, the magnification of the mask pattern image projected onto the workpiece W is changed by the zoom mechanism of the projection lens.
(D) As shown in FIG. 10B, the deviation amount between the upper left mask mark MAM1 and the work mark WAM1 is dR1, similarly, the deviation amount between the upper right marks MAM2 and WAM2 is dR2, and the lower left marks MAM3 and WAM30. If the shift amount between the two marks MAM4 and WAM4 in the lower right is dR4 (the shift amount dR4 between MAM4 and WAM4 is shown enlarged on the right side of the drawing), The total sum of WAM deviation amounts is expressed by the following equation (1).
Then, as shown in FIG. 10C, the magnification of the mask pattern image projected onto the work is changed (by the projection lens) so that the total sum of the shift amounts dR is minimized, and the mask and work are moved in the XYθ direction. Move relative to.

(E) After the alignment is completed, the work W is irradiated with exposure light through the mask M, and the pattern formed on the mask M is exposed on the work W. Thereby, a wiring pad is formed at a predetermined position of the wiring pattern formed on the workpiece W.

(A) Next, the screen printing process (A) will be described with reference to FIGS. 11, 12, and 13. FIG.
FIG. 11 is a view showing an example of a mask ScM (hereinafter referred to as a screen mask or a metal mask) used for screen printing, FIG. 12 is a view for explaining operations by the screen printing apparatus, and FIG. 13 is a flowchart showing the procedure. .
The screen printing technique is described in, for example, paragraphs 0004 to 0006 of FIG. 9 and FIG. 9 and paragraphs 0005 and 6 of patent document 3.

The outline of the procedure of solder application (screen printing) to the workpiece by the solder application apparatus will be described below with reference to FIGS.
(A) The workpiece W is placed and held on the workpiece stage 14 shown in FIG. A circuit pattern is formed on the workpiece.
(B) A work stage drive mechanism (not shown) is operated, and the work stage 14 is raised (moved in the Z direction) to a position where the screen mask ScM and the work W are close to each other (step S1 in FIG. 13).
As shown in FIG. 11, the screen mask ScM used for screen printing is provided with an opening at a position corresponding to the position where the wiring pad shown in FIG. 9 is formed. Although not shown, through-holes are formed in the screen mask ScM as alignment marks (alignment marks or second mask marks) SAM at four locations in the same manner as the mask used in the exposure apparatus.
(C) The alignment microscope 16 shown in FIG. 12A is inserted on the screen mask ScM (step S2 in FIG. 13).
The alignment microscope 16 simultaneously detects the mask mark SAM and the work mark WAM formed on the work W. That is, the alignment microscope 16 detects the work mark WAM in the through hole that is the mask mark SAM. (Step S3 in FIG. 13).

(D) The control unit (not shown) of the solder coating apparatus determines the work stage WAM so that the work mark WAM comes to the center of the mask mark SAM that is a through hole based on the detected position information of the mask mark SAM and the work mark WAM. The work mechanism 14 is moved by the drive mechanism 15 in the X direction (for example, the left-right direction in the figure), the Y direction (for example, the direction perpendicular to the paper surface in the figure), and the θ direction (rotated about an axis perpendicular to the work stage surface) The screen mask ScM and the workpiece W are aligned (alignment) (step S4 in FIG. 13).
The alignment of the screen mask ScM and the workpiece W may be performed by moving the mask stage 13 or by moving both the workpiece stage 14 and the mask stage 13.
(E) After the alignment is completed, the work stage 14 is raised by the work stage driving mechanism, and the screen mask ScM and the work W are brought into contact with each other (step S5 in FIG. 13).
(F) As shown in FIG. 12B, while the screen mask ScM and the workpiece W are in contact with each other, the top of the opening of the screen mask ScM is rolled while rolling the solder (cream solder) with a spatula called a squeegee 15. Is applied to the workpiece W. On the workpiece W, solder is applied only to a portion where the opening of the screen mask ScM is formed, and a solder pad is formed (step S6 in FIG. 13).

(G) When the solder application is finished, the work stage driving mechanism operates, and the work stage 14 is lowered as shown in FIG. 12C (step S7 in FIG. 13).
(H) The workpiece W on which solder application (solder pad formation) has been completed is carried out of the work stage 14 to the outside of the solder application device by a conveyance mechanism (not shown).
As shown in FIG. 9, the solder S is applied onto the wiring pad Pd. However, if the position of the wiring pad Pd formed on the workpiece W and the position of the screen mask ScM do not match, the wiring pad Pd The solder S is not printed (applied) on the surface, causing problems such as disconnection and short circuit.
In addition, after performing projection exposure as described above, the process of processing the mask in close contact with or approaching the workpiece is not limited to screen printing as described above. For example, contact after performing projection exposure is performed. The same applies to exposure and proximity exposure.

JP-A-9-82615 JP-A-8-264932 JP 2003-53932 A

In the screen printing, a screen mask (metal mask) M in which the opening shown in FIG. 14A is formed is placed on the workpiece W shown in FIG. 14B, and as shown in FIG. The screen mask ScM and the workpiece W are moved relative to each other in the XYθ directions so that the positions of the formed workpiece mark WAM and the second mask mark SAM coincide with each other. Then, as described above, with the squeegee 15, the opening of the screen mask ScM is filled with the solder S, and the solder S is printed on the wiring pads of the workpiece.
As shown in FIG. 14, if the workpiece W does not expand and contract and is the same size as the screen mask ScM, the opening of the mask ScM and the wiring pad Pd on the workpiece W coincide with each other without deviation.
However, the printed circuit board used as the workpiece W repeats the laminating and thermosetting processes for building up. By repeating this process, the printed circuit board often shrinks gradually.
When the substrate contracts, as shown in FIG. 15A, the position of the work mark WAM formed thereon also changes. Specifically, the size of the wiring pattern formed on the substrate is reduced as a whole by the contraction of the substrate.

By using the projection exposure apparatus shown in the prior art, the mask and workpiece can be changed by changing the magnification of the projection lens to change the size of the mask pattern with respect to the wiring pattern or work mark whose position has changed due to the contraction of the substrate. Can be aligned.
As a result, the exposure apparatus can be formed by shifting the positions of the wiring pads in accordance with the wiring pattern that is reduced as a whole by contraction of the workpiece.
However, the screen mask ScM of the screen printing machine for printing solder on the wiring pads basically has openings formed assuming the positions of the wiring pads formed on the substrate that does not expand and contract. That is, the opening is formed based on a pattern that is not stretched.
The screen mask is used by being directly mounted on the work, and the magnification of the opening pattern cannot be changed in accordance with the deformation of the substrate as in the case of projection exposure.

Therefore, in the projection exposure apparatus, as shown in FIG. 15A, for example, when the wiring pad Pd shifted in position is formed on the work W in accordance with the wiring pattern reduced by contraction of the substrate (work W), When the unreduced screak mask ScM shown in FIG. 15B is overlaid on the work W as shown in FIG. 15C, the position of the wiring pad formed on the work W and the screak mask ScM. The position of the opening will not match.
When solder printing is performed in such a state, the solder is not printed on the solder pads formed on the workpiece, which causes problems such as disconnection and short circuit.
However, when forming a wiring pad with an exposure device, the position of the wiring pad projected on the work must be changed unless the magnification is changed by reducing or enlarging the wiring pattern accompanying the expansion and contraction of the work. Since the position of the wiring pattern and the position of the wiring pad are not matched, this also causes problems such as disconnection and short circuit.
Further, the size of the screen mask ScM is set in consideration of the expansion and contraction of the work W, and the screen mask opening position and the alignment mark SAM position are matched with the predicted wiring pad position and work mark WAM position. Although it is conceivable to create the mask ScM, since the amount of expansion and contraction of the work is not necessarily constant, even if such a screen mask ScM can be created, the alignment mark SAM of the screen mask ScM and the work formed on the work W The alignment of the mark WAM is often difficult.

As described above, in screen printing, the mask is adhered to the work and solder is applied, so that the magnification of the mask pattern image to be projected cannot be changed according to the expansion and contraction of the work as in projection exposure. If the size of the mask used for screen printing differs greatly due to expansion and contraction, screen printing may not be possible.
The above-described problem also occurs when contact exposure and proximity exposure are performed after the above-described projection exposure.
The present invention has been made on the basis of the above circumstances, and the object of the present invention is to provide a pattern (which is formed on a workpiece by projection exposure) even when the workpiece is stretched and deformed and the pattern formed on the workpiece is reduced or enlarged. For example, the position of the wiring pad) and the position of the pattern (for example, wiring pattern) formed on the workpiece by the previous exposure process can be adjusted to the extent that there is no hindrance to the operation. The pattern formed on the workpiece is also used when transferring the mask pattern onto the workpiece by bringing the mask into contact with or approaching the workpiece, such as screen printing, contact exposure, and proximity exposure. This is to prevent a large shift between the mask patterns.

Conventionally, in an exposure process for forming a wiring pad pattern, the projection exposure apparatus performs a mask mark MAM of a mask M projected by a projection lens and a work mark WAM formed on the work W as shown in FIG. The mask M and the workpiece W are aligned so that the total sum of the positional deviation amounts dR is minimized.
On the other hand, according to the present invention, during the alignment in the projection exposure apparatus, the sum of the shift amount dR between the mask mark MAM of the mask M (first mask) and the work mark WAM is further added to the first. The sum of the position of the mask mark MAM of the mask M and the total amount dM of the reference position of the mask mark (for example, SAM) of the second mask (for example, the screen mask ScM) used in the next process is minimized. As described above, the magnification for enlarging or reducing the pattern of the first mask is adjusted, and the mask M or the workpiece W is moved to align the mask and the workpiece.
The reference position of the second mask is, for example, the position of a mask mark SAM (screen mask alignment mark) formed on the screen mask, and the position of the alignment mark of the mask is the work mark before the work is deformed. Or the position of the alignment mark in the second mask created assuming the expansion and contraction of the workpiece W.
That is, in the present invention, the above problem is solved as follows.
(1) A first mask pattern is enlarged or reduced and projected onto a workpiece having a size different from that of the mask, and a projection image of the alignment mark formed on the mask and an alignment mark formed on the workpiece An alignment method for aligning an image and exposing the mask pattern on a workpiece for exposure, wherein the mask and the workpiece are aligned, and a predetermined size used by overlapping the workpiece in the next step The position of the alignment mark of the second mask is stored in advance.
When aligning the first mask and the workpiece, the magnification for enlarging or reducing the first mask pattern onto the workpiece is adjusted, and the alignment mark image formed on the first mask is adjusted. Projected position on the workpiece, first displacement amount of the alignment mark formed on the workpiece, projected position of the alignment mark formed on the first mask on the workpiece, and formed on the stored second mask The first mask and the workpiece are aligned so that the total sum of the alignment mark positions and the second deviation amount is minimized.
(2) The work in the next step of the above (1) is a soldering process in which the second mask is overlapped with the work and the solder paste is injected into the opening formed in the mask and the solder is placed on the work. Printing operation or contact exposure or proximity exposure in which the pattern formed on the second mask is transferred onto the work.

In the present invention, in the alignment of the first mask and the work in the projection exposure apparatus, not only the relationship between the mask and the work but also the subsequent work is used by overlapping or approaching the work. Positioning is performed in consideration of the positional relationship with a second mask whose size is predetermined.
For this reason, even if the pattern formed on the work is reduced or enlarged due to the expansion / contraction of the work, the position of the pattern (for example, the wiring pad) formed on the work by the projection exposure is changed to the pattern ( For example, it can be brought close to the position of the wiring pattern), and it is also formed on the workpiece when transferring the mask pattern onto the workpiece by bringing the mask of a predetermined size into contact with or approaching the workpiece in the next process. There is no significant deviation between the formed pattern and the mask pattern.
Accordingly, when screen printing is performed in the next step, for example, the solder pad can be formed at a predetermined position of the wiring pattern, and the solder can be printed on the wiring pad without causing a large shift. be able to. For this reason, the board | substrate which apply | coated the solder can be created, without producing a disconnection and a short circuit.

It is a figure (1) which shows the structure of the projection exposure apparatus which concerns on this invention. It is a figure (2) which shows the structure of the projection exposure apparatus which concerns on this invention. It is a figure (1) explaining position alignment of a mask and a work. It is a figure (2) explaining position alignment of a mask and a work. It is a flowchart which shows the alignment procedure of the Example of this invention. It is a figure explaining the alignment in the flowchart of FIG. It is a flowchart of the other Example which shows the alignment procedure. It is a figure explaining the alignment in the flowchart of FIG. It is a conceptual diagram of the wiring pattern and wiring pad which are formed on a board | substrate (work). It is a figure explaining the alignment operation | movement of the mask and workpiece | work in exposure apparatus. It is a figure which shows an example of the mask used for screen printing. It is a figure explaining the operation | work by a screen printing apparatus. It is a flowchart which shows the operation | movement procedure by a screen printing apparatus. It is a figure explaining the case where the workpiece | work is not expanded-contracted in screen printing. It is a figure explaining the case where the workpiece is expanding and contracting in screen printing.

Hereinafter, embodiments of the present invention will be described. In the following embodiments, a case where a workpiece contracts and a pattern shrinks will be described as an example. However, the present invention can be similarly applied even when the workpiece expands and the pattern expands.
1 and 2 are diagrams showing the configuration of a projection exposure apparatus according to the present invention. In this embodiment, the exposure apparatus exposes the entire workpiece (substrate) in a lump, and four workpiece marks are formed, and four mask marks are formed correspondingly.
In the following embodiments, the entire workpiece is exposed at once, but the present invention can also be applied to exposure in which the workpiece is divided into a plurality of exposure areas and the areas are exposed in order.
In FIG. 1 and FIG. 2, MS is a mask stage. On the mask stage MS, a mask M on which a mask mark MAM and a mask pattern MP are formed is placed and held. The mask stage MS is moved in the XYθ direction by the mask stage drive mechanism 3.
Exposure light is emitted from the light irradiation device 1. The emitted exposure light is irradiated onto the workpiece W coated with a resist, which is placed on the workpiece stage WS, through the mask M and the projection lens 2, and the mask pattern MP is projected onto the workpiece W and exposed. .

The projection lens 2 includes a projection lens zoom drive mechanism 2a. The projection lens zoom drive mechanism 2a changes the magnification of the projected image of the mask pattern MP projected onto the workpiece W.
Between the projection lens 2 and the workpiece W, there are provided four alignment microscopes 10 that can move in the direction of the arrow in FIG. Before the mask pattern MP is exposed on the work W, the alignment microscope 10 is inserted into the position shown in the figure, the mask mark MAM and the work mark WAM formed on the work W are detected, and the positions of the mask M and the work W are detected. Align. After the alignment, the alignment microscope 10 is retracted from the workpiece W. In FIGS. 1 and 2, only one alignment microscope 10 out of four is shown.

The alignment microscope 10 includes a half mirror 10a, a plurality of lenses L1, L2, and the like, and a CCD camera 10b. The mask mark MAM image, work mark WAM image, etc. received by the CCD camera 10 b of the alignment microscope 10 are sent to the control unit 11.
The control unit 11 includes an image processing unit 11a that processes an image received by the CCD camera 10b, a storage unit 11b that stores various parameters such as positional coordinate information of the mask mark MAM, and a position coordinate of a pattern detected as a work mark. The mask pattern projected by the projection lens by the projection lens zoom drive mechanism is moved by moving the work stage WS and / or the mask stage MS so as to coincide with the position coordinates of the mask mark image stored in the storage unit 11b. An alignment control unit 11d for changing the magnification of the MP image is provided.

The work stage WS or the mask stage MS is driven by the work stage drive mechanism 4 and the mask stage drive mechanism 3 that are controlled by the alignment control unit 11d, and is in the XY directions (X, Y: mask stage MS, work stage WS surface). And move around an axis perpendicular to the XY plane.
The projection lens 2 is driven by a projection lens zoom drive mechanism 2a controlled by the positioning control unit 11d, and a part of the lens in the lens tower is driven to change the magnification of the mask pattern MP image to be projected. The mask pattern MP projected above is enlarged or reduced.
A mirror 5 is provided on the surface of the work stage WS at a position where the four mask marks MAM are projected. This mirror 5 reflects the mask mark MAM image projected onto the work stage WS. The reflected mask mark MAM image is taken into the alignment microscope 10.
A monitor 12 is connected to the control unit 11, and an image processed by the image processing unit 11 a is displayed on the screen of the monitor 12.

As described above, since the screen printing apparatus aligns the screen mask ScM and the workpiece W, four alignment marks SAM are formed on the screen mask ScM as well as the mask M used in the exposure apparatus. Yes. Therefore, the positional information of the alignment marks (second mask marks) SAM1 to SAM4 of the screen mask (metal mask) ScM used in the screen printing apparatus for solder printing is input in advance to the registration unit 11e of the control unit 11 of the exposure apparatus. Keep it.
The position of the alignment mark SAM on the screen mask is the position of the work mark WAM in consideration of the contraction of the work, or the position of the work mark WAM in a state where the work is not deformed such as contraction (that is, the position of the design value of the work mark). ) Etc. to set.
This is because the screen mask is basically created in consideration of the assumed amount of expansion / contraction of the substrate or on the assumption that the substrate is not deformed, and the position of the second mask mark SAM of the screen mask is also set. This is because the position of the second mask marks SAM1 to SAM4 of the screen mask ScM is also adjusted to the position of the workpiece mark of the workpiece with the expected expansion / contraction amount or the position of the workpiece mark where the substrate is not deformed. Set according to these.
Thereby, the control part 11 memorize | stores the positional information on 2nd mask mark SAM of a screen mask in the memory | storage part 11b.

FIG. 3 and FIG. 4 are diagrams for explaining the alignment of the mask and the workpiece in the exposure apparatus of the present embodiment. With reference to FIG. 3, an outline of the alignment of the mask and the workpiece of the present embodiment will be described. Details of the alignment procedure will be described later. In the following description, the case where screen printing is performed in the next step of the projection exposure process will be described. However, as described above, the same can be applied to the case where contact exposure and proximity exposure are performed in the next step.
FIG. 3A shows the workpiece W. As described above, the printed circuit board used as the workpiece expands and contracts by repeating the process, but in FIG. The workpiece W is provided with workpiece marks WAM1 to WAM4 as shown in FIG. FIG. 3B shows a mask M projected onto the work stage WS, and FIG. 3 shows a case where the scale is projected onto the work stage WS at a scale of 1, for example. On the mask M, mask marks MAM1 to MAM4 are provided as shown in FIG.
FIG. 3C shows the screen mask ScM, and the second mask marks SAM1 to SAM4 are provided on the screen mask ScM, and the positions of the second mask marks SAM1 to SAM4 are set in the storage unit of the control unit 11 as described above. 11b.

In FIG. 4, the workpiece W, the mask M, and the screen mask ScM shown in FIGS. 3A to 3C are overlapped so that the centers coincide with each other, and the alignment marks provided on each of them are arranged closest to each other. When the workpiece W, the mask M, and the screen mask ScM are overlaid, for example, as shown in FIG.
Note that the control unit 11 of the exposure apparatus only stores the position coordinates of the alignment marks SAM1 to SAM4 of the screen mask ScM, and the pattern of the opening of the screen mask ScM and the wiring pad (solder pad) on the workpiece W. ) Since the position of Pd is not stored, the workpiece W, the mask M, and the screen mask ScM are not overlapped as shown in the figure, but the figure is easy to understand. These are shown superimposed.
When the workpiece W, the mask M, and the screen mask ScM are overlapped, as shown in FIG. 4A, the alignment marks WAM1-4, MAM1-4, and SAM1-4 provided on the workpiece W overlap each other, for example, If the alignment marks WAM4, MAM4, and SAM4 at the lower right are enlarged, they are as shown in FIG.
Here, the deviation amount between the work mark WAM4 and the mask mark MAM4 is dR4, and the deviation amount between the mask mark MAM4 and the second mask mark SAM4 is dM4.
Similarly, the deviation amounts of the work mark WAM1-3 and the mask mark MAM1-3 are dR1 to dR3, respectively, and the deviation amounts of the mask mark MAM1-3 and the second mask mark SAM1-3 are dM3, respectively.

In the present embodiment, the sum of the deviations dR1 to dR1 between the mask mark MAM and the work mark WAM, the position of the mask mark MAM of the mask M, and the second mask of the screen mask ScM used in the next step are used. The magnification for enlarging or reducing and projecting the pattern of the mask M is adjusted so that the sum of the shift amounts dM1 to dM4 of the mask marks SAM1 to SAM4 is minimized, and the mask M or the workpiece W is moved. Align the mask and workpiece.
That is, the sum of the shift amounts dR1 to dR4 between the position coordinates of the four mask marks MAM1 to MAM4 and the corresponding position coordinates of the four work marks WAM1 to WAM4 is expressed by the following equation (1). It is.
Further, the sum of the shift amounts of the four mask marks MAM1 to MAM4 and the second mask marks SAM1 to SAM4 of the screen mask ScM is expressed by the following equation (2).
Conventionally, alignment is performed so that the total sum (equation (1)) of the shift amounts dR1 to dR4 is minimized.

In the present embodiment, the sum of the shift amounts dR1 to dR1 between the mask mark MAM and the work mark WAM represented by Expression (1), and the shift amount dM1 between the mask mark MAM and the second mask mark SAM represented by Expression (2). The magnification for enlarging or reducing and projecting the pattern of the mask M is adjusted so that the sum of the sums of .about.4 is minimized, and the mask M or workpiece W is moved to align the mask and workpiece.
The sum of the deviation amounts of the mask mark MAM and the work mark WAM and the sum of the deviation amounts of the mask mark MAM and the second mask mark SAM of the screen mask are expressed by the following equation (3). That is, the exposure apparatus aligns the mask and the workpiece so that the value of Expression (3) is minimized.

As a result, the position of the wiring pad formed on the workpiece W by the exposure process is an intermediate position between the wiring pattern reduced with the contracted workpiece W and the opening of the screen mask ScM.
For this reason, the solder pad Pd formed on the workpiece W by exposure does not completely coincide with a predetermined position where the solder pad of the reduced wiring pattern Pp is to be formed, but cannot be disconnected so as to cause a disconnection or a short circuit. Formed in position.
Thereafter, the solder printing formed by screen printing is also formed at a position that does not completely coincide with the position of the solder pad Pd formed by exposure, but does not deviate enough to cause a disconnection or a short circuit.
In the equation (3), α is a coefficient that gives weight to the alignment between the mask mark MAM and the work mark WAM and the alignment between the alignment mark SAM of the screen mask and the mask mark MAM.

When α> 1, the alignment is performed so that the total sum of the shift amounts dM1 to dM4 between the mask mark MAM and the second mask mark SAM is reduced. That is, the alignment is performed so that the deviation between the mask M and the screen mask ScM is small.
When α <1, the alignment is performed so that the sum of the shift amounts dR1 to dR1 between the mask mark MAM and the work mark WAM becomes small. That is, the alignment is performed so that the deviation between the mask M and the workpiece W is small.
When α = 1, alignment is performed so that the sum of the shift amounts dM1 to dM1 between the mask mark MAM and the second mask mark SAM and the sum of the shift amounts dR1 to dR4 between the mask mark MAM and the work mark WAM are equal. Is done.
The value of α depends on whether the wiring pattern Pp formed on the workpiece W and the solder pad Pd are weighted or whether the weight of the solder S to be printed and the solder pad Pd is weighted. Set as appropriate.

FIG. 5 is a flowchart showing the alignment procedure, and FIG. 6 is an explanatory diagram of the alignment. Hereinafter, a specific alignment procedure will be described with reference to FIGS.
First, as described above, the positional information of the second mask marks SAM1 to SAM4 of the screen mask (metal mask) ScM used in the screen printing apparatus for solder printing is set in the registration unit 11e of the control unit 11 of the exposure apparatus. (Step S1 in FIG. 5).
Next, the mask mark MAM is searched (step S2 in FIG. 5). That is, light is irradiated from the light irradiation device 1 to the mask M on which the four mask marks MAM are formed in a state where the workpiece W is not on the workpiece stage WS (see FIG. 2). Mask mark MAM is projected onto mirror 5 provided on the surface of work stage WS via projection lens 2 and half mirror 10a of alignment microscope 10. The mask mark MAM is reflected by the mirror 5 and enters the CCD camera 10b through the half mirror 10a and the lenses L1 and L2. The incident mask mark MAM image is subjected to image processing by the image processing unit 11a of the control unit 11, and the position coordinates of the mask marks MAM1 to MAM4 are stored in the storage unit 11b. When the position of the mask mark MAM can be stored, the light irradiation from the light irradiation unit 1 is stopped. Note that the magnification of the projected image of the mask pattern MP by the projection lens zoom drive mechanism 2a at this time may be 1 as described above, or may be set according to the size of the workpiece. Good.

Next, the workpiece W is conveyed by a conveyance system (not shown), and the workpiece W is placed on the workpiece stage WS (see FIG. 1). A wiring pattern is formed on the workpiece W and a resist is applied. The work mark WAM of the work W is searched (step S3 in FIG. 5).
That is, the image of the work mark WAM formed on the work W is picked up by the CCD camera 10b through the half mirror 10a of the alignment microscope 10 and the lenses L1 and L2. The captured work mark WAM image is subjected to image processing by the image processing unit 11a of the control unit 11, and the position coordinates of each of the work marks WAM1 to WAM4 are obtained.

The work marks WAM1 to WAM4, the mask marks MAM1 to MAM4, and the second mask marks SAM1 to SAM4 obtained as described above are illustrated in FIG. 6A, for example. The figure shows a case where the work marks WAM1 to WAM4 are arranged on the outermost side, the mask marks MAM1 to MAM4 are arranged on the inner side, and the second mask mark SAM is arranged on the innermost side.
The calculation part 11c of the control part 11 calculates | requires the center position of the said work marks WAM1-4 and the mask marks MAM1-4. On the basis of this, the alignment control unit 22d of the control unit 11 matches the center positions of the second mask marks SAM1 to SAM4, the work marks WAM1 to 4, the mask marks MAM1 to 4, and the second mask. The work stage WS or the mask stage MS is moved in the XYθ direction so that the rectangular sides formed by the marks SAM1 to SAM4 are parallel to each other (step S4 in FIG. 5).
Thereby, the work marks WAM1 to 4, the mask marks MAM1 to 4, and the second mask marks SAM1 to SAM4 are arranged as shown in FIG.

The calculation unit 11c of the control unit 11 calculates the difference between the position coordinates of the work mark WAMi (i = 1 to 4) and the mask mark MAMi (i = 1 to 4) and sets this as ai (i = 1 to 4). . Further, the difference between the mask mark MAMi (i = 1 to 4) and the second mask mark SAMi (i = 1 to 4) is calculated and set to bi (i = 1 to 4) (step S5 in FIG. 5). .
Then, the sum E of the shift amounts of the work mark WAMi, the mask mark MAMi, and the second mask mark SAMi is obtained by the following formula (4), and the pattern of the mask M that minimizes the total shift amount E is enlarged or reduced and projected. The magnification to be calculated is calculated (step S6 in FIG. 5). The alignment control 11d drives the projection lens zoom drive mechanism 2a to set the magnification of the projection lens 2 (step S7 in FIG. 5).

When the alignment of the mask M and the workpiece W is performed as described above, the exposure light is irradiated from the light irradiation unit 1 to the workpiece W through the mask M as described above, and the mask M is formed on the mask M. The exposed pattern is exposed on the workpiece W. Thereby, a wiring pad is formed at a predetermined position of the wiring pattern formed on the workpiece W.
Next, as described with reference to FIGS. 11-13, the work W and the screen mask ScM are aligned, the screen mask ScM and the work W are brought into contact, and solder is applied onto the wiring pads on the work W. Form a solder pad.
As a result, the wiring pad formed on the workpiece is not formed at a position greatly deviated from the position where the wiring pattern is formed, and the position of the solder applied by screen printing in the next process is also Although not completely coincident with the position of the wiring pad, it does not greatly deviate.

Next, another embodiment of the alignment procedure will be described with reference to FIGS. FIG. 7 is a flowchart showing an alignment procedure, and FIG. 8 is an explanatory diagram of alignment.
5 and 6, the procedure for setting the magnification of the projection lens so that the total amount E of the shift amounts is minimized after the mask M and the center position of the work W are aligned has been described. Reference numeral 8 denotes a case where the alignment is performed without performing the operation of aligning the center position as described above.

First, as described above, the positional information of the second mask marks SAM1 to SAM4 of the screen mask (metal mask) ScM used in the screen printing apparatus for solder printing is set in the registration unit 11e of the control unit 11 of the exposure apparatus. (Step S1 in FIG. 7).
Next, the mask mark MAM is searched (step S2 in FIG. 7). Then, the position coordinates of the mask marks MAM1 to MAM4 are stored in the storage unit 11b.
Next, the work mark WAM of the work W is searched (step S3 in FIG. 7).
When the work marks WAM1 to WAM4, the mask marks MAM1 to MAM4, and the second mask marks SAM1 to SAM4 obtained as described above are illustrated, for example, as illustrated in FIG. the same).

The calculation unit 11c of the control unit 11 calculates the difference between the position coordinates of the work mark WAMi (i = 1 to 4) and the mask mark MAMi (i = 1 to 4) and sets this as ai (i = 1 to 4). . Further, the difference between the mask mark MAMi (i = 1 to 4) and the second mask mark SAMi (i = 1 to 4) is calculated and set to bi (i = 1 to 4) (step S4 in FIG. 7). .
Then, the sum E of the shift amounts of the work mark WAMi, the mask mark MAMi, and the second mask mark SAMi is obtained by the equation (4), and the pattern of the mask M that minimizes the total shift amount E is enlarged or reduced and projected. The magnification and the XYθ movement amount of the mask stage MS or the work stage WS are calculated (step S5 in FIG. 7).
Then, based on this, the alignment control unit 22d of the control unit 11 matches the center positions of the second mask marks SAM1 to SAM4, the work marks WAM1 to 4, the mask marks MAM1 to 4, The work stage WS or the mask stage MS is moved in the XYθ directions so that the mask marks SAM1 to SAM4 of each of them are closest, and the projection lens zoom drive mechanism 2a is driven to set the magnification of the projection lens 2 (FIG. 7 step S6). Thereby, as shown in FIG.8 (b), the mask M and the workpiece | work W are aligned.

DESCRIPTION OF SYMBOLS 1 Light irradiation apparatus 2 Projection lens 2a Projection lens Zoom drive mechanism 3 Mask stage drive mechanism 4 Work stage drive mechanism 5 Mirror 10 Alignment microscope 10a Half mirror 10b CCD camera 11 Control part 11a Image processing part 11b Storage part 11c Operation part 11d Position alignment Control unit 11e Green climbing unit 12 Monitor 13 Mask stage (for screen printing)
14 Work stage (for screen printing)
15 Squeegee 16 Alignment microscope (for screen printing)
L1, L2 Lens M Mask MS Mask stage MAM Mask mark (Mask alignment mark)
Pd Wiring pad Pp Wiring pattern S Solder ScM Screen mask (metal mask)
SAM Second mask mark (Screen mask alignment mark)
W Work WS Work stage WAM Work mark (work alignment mark)

Claims (2)

A pattern of the first mask is enlarged or reduced and projected onto a workpiece having a different size from the mask, and a projected image of the alignment mark formed on the mask and an alignment mark image formed on the workpiece are obtained. A method of aligning a mask and a workpiece, exposing the mask pattern on the workpiece by aligning the mask pattern,
In advance, the position of the alignment mark of the second mask of a predetermined size that is used by being overlapped with the workpiece in the next step is stored in advance,
When aligning the first mask and workpiece,
The magnification at which the first mask pattern is enlarged or reduced and projected onto the work is adjusted, the projection position of the alignment mark image formed on the first mask on the work, and the first position of the alignment mark formed on the work. 1 shift amount,
The sum of the projected position of the alignment mark formed on the first mask on the workpiece and the second displacement amount of the position of the alignment mark formed on the second mask stored is minimized. And aligning the first mask and the workpiece with each other. The work in the next step is a solder printing work in which the second mask is overlapped with the work and the solder paste is injected into the opening formed in the mask and solder is placed on the work, or the second work 2. The method for aligning a mask and a workpiece according to claim 1, wherein contact exposure or proximity exposure is used to transfer a pattern formed on the second mask onto the workpiece.

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