Means for supporting a mask

To prevent tilting or bending of a large mask frame holder and at the same time to prevent distortion when the mask holding frame is attached to a support base by ball plungers in three of the four corner areas of a mask holding frame that engage V groove bodies which face the ball plungers on the surface of the base, compression springs are provided in those three corners which pre-stress the mask holding frame toward the support base while a compression spring is provided between the remaining corner area of the mask holding frame and the base which acts in a direction pressing the mask holding frame away from the support base, thereby preventing the mask holding frame from bending or tilting. As an alternative, in each of the three pre-stressed corner areas of the mask holding frame, instead of a compression spring, an elastic attachment component in the form of a bracket with spring-like legs mounted to the supporting component can be provided.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a means for supporting a mask holding frame for 
suction and attachment of a mask which is used for an exposure device, a 
proximity exposure device and the like. The invention especially relates 
to a means for supporting a mask holding frame with a device which adjusts 
the vertical angle of the mask holding frame and holds the mask surface 
perpendicular to the optical axis. 
2. Description of Related Art 
FIGS. 9 and 10 each schematically show a conventional means for supporting 
a mask holding frame. FIG. 10 is a cross-sectional view taken along line 
A--A in FIG. 9. In the drawing, a mask holding frame 1 and a base 2 are 
shown which, together form a mask carrier. 
Mask holding frame 1 has a means which suctions a mask (not shown) by 
vacuum or similar methods. Furthermore, in the three corner areas A, B, 
and C of mask holding frame 1, there are screw openings in which ball 
plungers 3 are installed. In the vicinity of the openings for the ball 
plungers 3, there are through openings which are penetrated by mounting 
pins 4. On the respective mounting pin 4, are a washer 6 and a compression 
spring 5 (disk spring or helical spring). 
In base 2 are V-sleeves 7 which are engaged by ball plungers 3, and screw 
openings 8 to which mounting pins 4 are joined. Mask holding frame 1, as 
shown in FIG. 10, is installed on base 2 by means of the mounting pins 4 
and ball plungers 3, and is prestressed by compression springs 5 toward 
the base 2. 
By the arrangement of ball plungers 3 in three corner areas A, B, and C the 
height of ball plungers 3 which are located on two orthogonally 
intersecting axes can be adjusted. Thus the vertical angle of mask holding 
frame 1 can be adjusted. Therefore the adjustment process can be 
simplified. 
In FIGS. 9 and 10, the position adjustment of mask holding frame 1 is done 
in the manner described below. 
(1) In mask holding frame 1, a mask (not shown) is attached by means of a 
vacuum chuck. 
(2) By screwing ball plungers 3 up or down the vertical angle of mask 
holding frame 1 with respect to base 2 is changed and adjusted such that 
the mask surface becomes perpendicular to the optical axis of the exposure 
light of the exposure device. 
(3) Mounting pins 4 are screwed down and mask holding frame 1 is attached. 
This holding means has a simple configuration, and can be easily produced 
and adjusted. Furthermore, mask holding frame 1 is always pressed with a 
constant force in the direction toward base 2 by the compression springs 5 
installed on mounting pins 4. The distance between mask holding frame 1 
and the base 2 does not change. This holding means therefore has the 
feature that the tilt of the mask relative to the optical axis does not 
change even after use over a long time. 
Recently, there has been a need for holding a large mask (for example, one 
with dimensions of 400 mm.times.400 mm) which is used for exposure of a 
liquid crystal substrate. The mask holding frames are therefore becoming 
larger and larger. As a result, the arrangement shown in FIGS. 9 and 10 
has the following defects: 
(1) When the mask holding frame 1 becomes larger, in the arrangement shown 
in FIGS. 9 and 10, the corner area D which is provided neither with ball 
plunger 3 nor V sleeve 7, is bent or tilted by its own weight, as shown in 
FIGS. 11(a) or 11(b). 
When bending/tilting occurs in mask holding frame 1, the mask installed 
therein is also bent or tilted. The distance between the mask and the 
workpiece is therefore no longer constant. The mask surface is no longer 
perpendicular to the optical axis. Furthermore, in the mask image which is 
projected onto the workpiece there are points at which no imaging takes 
place. Therefore, the exposure accuracy is reduced. 
(2) To eliminate the tilt of the holding frame for a large mask, in the 
arrangement shown in FIGS. 9 and 10, the spring constant of the 
compression springs 5 of mounting pins 4 or the number of disk springs can 
be increased, and thus, the force is increased with which the three corner 
areas A, B, and C of mask holding frame 1 are pressed in the direction 
toward base 2, so that corner area D which is not provided with a ball 
plunger is raised without being tilted. 
However, if the force with which mask holding frame 1 is pressed in the 
direction toward base 2 is increased, the force with which ball plungers 3 
are loaded also becomes greater. In the arrangement shown in FIGS. 9 and 
10, the points which are exposed to the force of the mounting pins 4 
differ from the points which are exposed to the force of ball plungers 3. 
If the above described pressing force becomes greater, distortions occur 
in mask holding frame 1 between the points at which mounting pins 4 are 
installed and the points on which plungers 3 are installed. Therefore, the 
defect of bending of the mask holding frame cannot be eliminated solely by 
increasing the pressing force. 
(3) In a proximity exposure device, for parallel adjustment of the mask and 
workpiece relative to one another with a constant distance, a distance 
setting process is used which, for example, is described in Japanese 
patent disclosure document HEI 7-74096. In the distance setting process, 
the workpiece is moved upward, pushed against the bottom of the mask and 
then moved farther upward. The overall surface of the workpiece is brought 
into contact with the mask, and the mask and the workpiece are positioned 
parallel to one another (hereinafter this actuation is called "parallel 
arrangement"). While maintaining this state, the workpiece is separated 
from the mask only to a given degree and the two are set parallel to one 
another, and at the same time, with a constant distance relative to one 
another. 
In the case of distance setting by this process, in the arrangement shown 
in FIGS. 9 and 10 mounting pins 4 for attaching mask holding frame 1 are 
located only in three corner areas A, B, and C. When the workpiece is 
pressed from underneath and brought into contact with the mask to bring 
the entire surface of the mask and the entire surface of the workpiece 
into contact with one another, corner area D of mask holding frame 1 is 
bent upward. Therefore, parallel arrangement of the mask and workpiece 
relative to one another cannot be done correctly. 
SUMMARY OF THE INVENTION 
The invention was devised to eliminate the above described defects in the 
prior art. Therefore, a first object of the invention is to devise a means 
for holding a mask carrier in which the tilting and bending of a large 
mask holding frame, which corresponds to a large mask, can be prevented. 
A second object of the invention is to devise a means for holding a mask 
carrier in which no distortion occurs in the mask holding frame, even if 
the force with which the mask holding frame is pressed in the direction 
toward the base is increased. 
The third object of the invention is to devise a means for holding a mask 
carrier in which the mask holding frame does not bend upwards if distance 
setting is done in a proximity exposure device. 
The above described objects are achieved in accordance with the invention 
in a means for supporting a mask holding frame which has a rectangular 
mask holding frame for attachment of a mask and a supporting component to 
support the mask holding frame as follows: 
(1) In three of the four corner areas of the mask holding frame there are 
three support axes which can each be moved in a direction which 
orthogonally intersects the surface of the mask holding frame. At points 
opposite these three support axes of the surface of the supporting 
component are three V-groove bodies. In the vicinity of the support axes 
of the mask holding frame there is a respective through opening. The 
through openings are penetrated by mounting pins, one end of the 
respective mounting pin being installed in a screw opening which is 
located in the supporting component. Between the other ends of the 
mounting pins and the mask holding frame there are first elastic 
components by which the mask holding frame is prestressed on the side of 
the supporting component. Furthermore, between the remaining corner area 
of the mask holding frame and the supporting component there is a second 
elastic component which prestresses the mask holding frame towards the 
side opposite the supporting component. 
(2) In at least three of the four corner areas of the mask holding frame 
there are protrusions. In three of these protrusions are three support 
axes which can be moved in a direction which orthogonally intersects the 
surface of the mask holding frame. At points opposite these three support 
axes of the surface of the supporting component are three V-groove bodies. 
The three protrusions are attached in the supporting component such that 
the support axes are pressed directly from overhead by plate-like, elastic 
attachment components which surround the protrusions. 
(3) In solution (2) between the mask holding frame or the protrusion of the 
remaining one corner area of the four corner areas of the mask holding 
frame and the supporting component there is a second elastic component 
which prestresses the mask holding frame towards the side opposite the 
supporting component. 
(4) In solutions (1), (2), and (3) in the corner area of the mask holding 
frame provided with the second elastic component or on the protrusion 
located in this corner area there is a position control component, by 
which position control is done so that the corner area of the mask holding 
frame does not move when the mask holding frame is exposed to a 
compressive force from the side of the supporting component. 
In accordance with the first embodiment of the invention, between the 
remaining one corner area of the four corner areas of the mask holding 
frame and the supporting component is the second elastic component which 
prestresses the mask holding frame towards the side opposite the 
supporting component, as was described above in solution (1). Therefore, 
in a large mask holding frame the latter is prevented from tilting or 
bending. Furthermore, by the support of one corner area of the mask 
holding frame by the second elastic component, it is not necessary to 
increase the screw-down force of the mounting pins. Distortions of the 
mask holding frame can be prevented. 
In the second embodiment of the invention, in at least three of the four 
corner areas of the mask holding frame are protrusions which are attached 
in the supporting component in such a way that the support axes are 
pressed directly upward by plate-like, elastic attachment components which 
surround the protrusions, as was described in solution (2). This measure 
prevents distortions from occurring in the mask holding frame even if the 
screw-down force by the attachment components is increased. Therefore, 
tilting of the mask holding frame can be prevented by the screw-down force 
of the attachment components. 
In accordance with a further aspect of the second embodiment of the 
invention, the measure described above in solution (3) prevents the mask 
holding frame from tilting or bending even if the mask holding frame is 
large. 
In accordance with the measure described above in solution (4), that the 
corner area of the mask holding frame provided with the second elastic 
component, or that there is a component for position control on the 
protrusion located in this corner area, prevents the corner area from 
being raised even when the mask holding frame, in a parallel arrangement 
of the mask and workpiece relative to one another in proximity exposure, 
is subjected to a compressive force from the side of the supporting 
component. Therefore, parallel arrangement can be done correctly. 
In the following, the invention is further described using several 
embodiments shown in the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following descriptions, to facilitate comparison, the parts of the 
inventive embodiments that are shared with the above-described known 
device bear the same reference numerals. 
(1) Embodiment 1 
FIGS. 1 and 2 schematically show a first embodiment of the invention in 
which tilting and bending of a large mask holding frame under its own 
weight is prevented. In FIG. 1, a mask holding frame 1 has ball plungers 3 
installed in three corner areas A, B and C as was described above using 
FIG. 10. In the vicinity of plungers 3 are through openings which are 
penetrated by mounting pins 4. On each mounting pin 4 is a respective 
washer 6 and a compression spring 5 (plate spring or helical spring). The 
mounting pins 4 are screwed into screw openings 8 which are located in 
base 2 and the tips of the ball plungers 3 are engage these V-sleeves 7 
located in base 2, as was described above. 
In corner area D of mask holding frame 1, which is not provided with ball 
plunger 3, and in base 2, are concave parts 11, 12, as is shown in FIG. 2. 
In recesses 11, 12, there is a helical compression spring 13. The spring 
constant of helical compression spring 13 is selected to be large enough 
to support a weight defined essentially by (W.sub.f +W.sub.m)/4 (where 
W.sub.f is the weight of mask holding frame 1 and W.sub.m is the weight of 
the mask) when compression spring 13 is compressed to a length which 
corresponds to the distance between the mask holding frame 1 and base 2. 
In this embodiment, installation of the mask holding frame 1 is performed 
as in the above described conventional example in the manner described 
below. 
(1) A mask (not shown) is attached by means of a vacuum chuck in the mask 
holding frame 1. 
(2) By screwing ball plunger 3 up or down, the vertical angle of mask 
holding frame 1 is changed with regard to base 2 and is set such that the 
mask surface becomes perpendicular to the optical axis of the exposure 
light of the exposure device. 
(3) Mounting pins 4 are screwed down and mask holding frame 1 is attached. 
In this embodiment, as was described above, between mask holding frame 1 
in corner area D which is not provided with ball plunger 3, and base 2 
there is helical compression spring 13 by which 1/4 of the sum of the 
weight of mask holding frame 1 and the weight of the mask is supported. 
Mask holding frame 1 is, therefore, neither tilted nor bent when the 
screw-down force of mounting pins 4 is low. Furthermore, mask holding 
frame 1 is not distorted because the screw-down force can be reduced in 
the above described manner. 
In this embodiment, the above described measure that, in corner area D of 
mask holding frame 1 which is not provided with ball plunger 3, there is a 
compression spring 13 which supports roughly 1/4 of the sum of the weight 
of mask holding frame 1 and the weight of the mask, even in a larger mask 
holding frame 1, mask holding frame 1 can be prevented from tilting or 
bending under its own weight. Also, mask holding frame 1 is prevented from 
being distorted because the screw-down force of mounting pins 4 can be 
reduced. 
(2) Embodiment 2 
FIGS. 3, 4(a), 4 (b) and 5 schematically show a second embodiment of the 
invention. In it, the tilting and bending of mask holding frame 1 is 
prevented, and at the same time, an arrangement for holding mask holding 
frame 1 is shown in which no distortion occurs in mask holding frame 1, 
even if the force with which mask holding frame 1 is pressed in the 
direction toward base 2 is increased. 
In FIG. 3, protrusions 21, 21' are shown installed in the four corner areas 
A, B, C and D of mask holding frame 1 with screws and the like. The 
protrusions 21 in the three corners areas A, B, and C are each installed 
on base 12 by an attachment bracket 22. 
Attachment bracket 22, as shown in FIG. 4 (a), has the shape of a recessesd 
plate and surrounds protrusion 21, its two ends being installed on the 
base 2 by means of a pair of mounting screws 23. The recess of attachment 
bracket 22 has an opening positioned to align with a screw opening in the 
respective protrusion 21. The ball plungers 3 penetrate the openings of 
attachment brackets 22, and thus, can be installed in the screw openings 
of the protrusions 21 so that the tips of ball plungers 3 engage the 
V-sleeves 7 located in base 2. 
In the protrusion 21' which is installed at the remaining corner area D, 
there is recess 24, as shown in FIG. 5. Between recess part 25 located in 
base 2 and the recess 24, there is a helical compression spring 13. The 
spring constant of helical compression spring 13 is selected to have a 
size with which a weight is supported which is defined essentially as 
(W.sub.f +W.sub.m)/4 (where W.sub.f is the weight of mask holding frame 1 
and W.sub.m is the weight of the mask) when compression spring 13 is 
compressed to a length which corresponds to the distance between mask 
holding frame 1 and base 2, as in the above described example. 
In this embodiment, the installation of mask holding frame 1 is performed 
as follows. 
(1) In mask holding frame 1, a mask (not shown) is attached by means of a 
vacuum chuck. 
(2) By screwing ball plungers 3 up or down, the vertical angle of the mask 
holding frame 1 is changed with regard to base 2 and is set such that the 
mask surface becomes perpendicular to the optical axis of the exposure 
light of the exposure device. 
(3) Mask holding frame 1 is attached by screwing down mounting pins 23 of 
attachment brackets 22. In doing so, attachment brackets 22 deform and act 
as springs as is shown in FIG. 4(b), so that they always press the 
protrusions 21 with a constant force in the direction toward the base 2. 
Here, a case was described in which in four corner areas of mask holding 
frame 1 are protrusions 21, 21'. However, without placing the protrusion 
21' in the corner area D which is not provided with ball plunger 3, 
compression spring 13 can be placed between the mask holding frame 1 and 
base 2, as was described on the first embodiment. 
Since mask holding frame 1 is not very large, attachment of attachment 
brackets 22 with the installed in protrusions 21 can prevent the mask 
holding frame 1 from tilting. In the case in which bending of mask holding 
frame 1 is not a problem, compression spring 13 need not be installed. 
By the above described arrangement of the holding means in this embodiment, 
protrusions 21 are pressed essentially vertically in the direction toward 
base 2 when mounting screws 23 are screwed down and, by means of 
attachment brackets 22, mask holding frame 1 is attached on base 2. 
Therefore, ball plunger 3 can be pressed essentially directly from 
overhead. This prevents distortion from occurring in mask holding frame 1 
even if the screw-down force by mounting screws 23 is increased. In the 
case of a mask holding frame 1 which is not too great, it is therefore 
possible to prevent tilting of mask holding frame 1 by screwing down with 
the mounting screws 23. 
Furthermore, the measure that attachment brackets 22 always press 
protrusions 21 with a constant force in the direction of the base prevents 
the distance between mask holding frame 1 and base 2 from growing and the 
tilt with respect to the optical axis of the mask from changing. 
In addition, the arrangement of helical compression spring 13 between base 
2 and the protrusion 21' which is installed in corner area D which is not 
provided with ball plunger 3, even in a larger mask holding frame 1, mask 
holding frame 1 can be prevented from tilting or bending under its own 
weight. 
(3) Embodiment 3 
FIG. 6 shows a third embodiment of the invention. In this embodiment, there 
is a means which prevents the corner area D of the mask holding frame 1 
which is not provided with a ball plunger 3 from being raised when the 
workpiece is pressed against the bottom of the mask in a proximity 
exposure device and the mask and workpiece are arranged parallel to one 
another. 
FIG. 6 schematically shows a means for supporting the protrusion 21' shown 
in FIG. 3. The other parts are identical to the parts in FIG. 3. 
In this embodiment, in the same way as in FIG. 5, between recess 24 located 
in protrusion 21' and recess 25 located in base 2, there is helical 
compression spring 13, as is apparent from the drawing. A stopper 
component 32 which is installed on base 2 and in which there is micrometer 
31. On mask holding frame 1 is a flat insert 33 with which the tip of 
micrometer 31 is in contact. 
FIG. 7 schematically shows the arrangement of a proximity exposure device 
for which the third embodiment is used. In the drawing, mask carrier 40 is 
comprised of the mask holding frame 1 and base 2. On the bottom of mask 
holding frame 1, a mask M is attached by means of a vacuum chuck or the 
like. Furthermore, as was described above, protrusions 21, 21' are 
installed in the four corner areas of mask holding frame 1. Protrusions 21 
provided with ball plungers 3 are attached to base 2 using attachment 
brackets 22. Between protrusion 21' and base 2 is helical compression 
spring 13. Upward motion of protrusion 21' is controlled by micrometer 31 
and stopper component 32 shown in FIG. 6. 
A workpiece W is placed on workpiece carrier 41 and is moved by X-Y-.THETA. 
carrier 43 in the X-Y-.THETA. directions (for example, X: to the right and 
left in FIG. 7, Y: in the direction which orthogonally intersects the 
X-direction and which is parallel to the surface of the workpiece; and 
.THETA.: in the direction of rotation around the axis which orthogonally 
intersects the X-Y plane). Furthermore, workpiece W is moved by means of Z 
carrier 44 in the Z-direction (to the top and bottom in FIG. 7: in the 
direction which orthogonally intersects the X-Y plane). 
Between X-Y-.THETA. carrier 43 and workpiece carrier 41 is a distance 
setting device 42 by which the mask M and workpiece W are set parallel to 
one another at a predetermined distance from each other. For distance 
setting device 42, the distance setting device disclosed by the applicant 
in Japanese patent disclosure document HEI 7-74096 can be used. 
Above mask M is an exposure light irradiation device (not shown). After 
setting the distance between mask M and workpiece W, and after alignment 
of mask M and workpiece W, exposure light is irradiated from the exposure 
light irradiation device via mask M onto workpiece W, and a mask pattern 
is exposed onto the workpiece. 
In the following, installation of mask holding frame 1 and setting of the 
distance between mask M and workpiece W in this embodiment is described. 
(1) Mask M is mounted in mask holding frame 1. Mask M is held by a vacuum 
chuck or the like located in mask holding frame 1. 
(2) Control of mask M and the optical axis of the exposure light, movement 
of workpiece carrier 41 in the Z direction and parallel adjustment of mask 
carrier 40 are carried out in the manner described below. 
(A) By controlling the height of ball plungers 3 of mask holding frame 1, 
its vertical angle is changed with respect to base 2 and the measure of 
the vertical position is set between the optical axis of the exposure 
light and mask M. 
(B) The height of ball plungers 3 is fixed. Mounting screws 23 of 
attachment brackets 22 are screwed down and mask holding frame 1 is 
attached. 
(C) By means of an alignment device (not shown) which is located in 
Z-carrier 44, setting is accomplished such that the Z-motion direction of 
workpiece carrier 41 becomes perpendicular to mask M. 
(D) Micrometer 31 is set such that mask holding frame 1 is not raised from 
a given position if, in parallel placement of mask M and workpiece W to 
one another, workpiece W collides with mask M. 
The above described setting of micrometer 31 is performed, for example, as 
follows: 
First of all, a state is established in which the tip of micrometer 31 and 
flat insert 33 of mask holding frame 1 are not in contact with one 
another. A dial gauge (not shown) is brought into contact with the surface 
of mask holding frame 1, the reading of the dial gauge being stored at 
this time. Next, the tip of micrometer 31 is moved down, brought into 
contact with flat insert 33 of mask holding frame 1, and pushed slightly 
in. This changes the reading of the dial gauge. The position of the tip of 
micrometer 31 is set such that the reading of the dial gauge becomes 
identical to its stored value. 
(3) Workpiece W is placed on workpiece carrier 41 and held by a vacuum 
chuck or the like. 
(4) Workpiece carrier 41 is moved upward by Z-carrier 44. Workpiece W and 
mask M held in mask holding frame 1 are brought into contact with one 
another. 
(5) Workpiece carrier 41 is moved farther up. This shifts distance setting 
device 42, and workpiece W and mask M tightly adjoin one another and lie 
on top of one another over their entire surfaces. This means that the 
inclination of mask M and workpiece W agree with one another and the two 
become parallel to one another. In doing so, pressure is applied to the 
mask holding frame 1 in an upward direction; but, it is also held down by 
micrometer 31. This prevents mask holding frame 1 from being pushed up. 
(6) While keeping the shifted state of distance setting device 42 constant, 
workpiece W is moved down by a given amount by means of Z-carrier 44. In 
this way, the workpiece W and the mask M are set parallel to one another, 
and at the same time, at a predetermined distance relative to one another. 
(7) Workpiece W and mask M are aligned by an alignment system (not shown). 
(8) Workpiece W and mask M are set relative to one another with the 
exposure distance. An exposure light irradiation device (not shown) emits 
exposure light and workpiece W is exposed. 
Above, the second embodiment was used and protrusion 21' was pressed down 
by micrometer 31 from overhead. However, the above descriptions also apply 
to use of the first embodiment, i.e., in the vicinity of the corner region 
D of mask holding frame 1 which is not provided with ball plunger 3, 
stopper component 32 can be installed and corner area D of mask holding 
frame 1 can be pressed down from overhead by micrometer 31. 
An embodiment was described above in which in the stopper component 32 is a 
micrometer 31, and thus, mask holding frame 1 is prevented from being 
raised when parallel placement is performed. However, instead of the 
micrometer, for example, a ball plunger 51 as shown in FIG. 8, or a 
component for positioning with another arrangement, can be used. 
As was described above, in this embodiment, a stopper component 32 is 
installed on the base 2 in which micrometer 31 or ball plunger 51 is 
located. Micrometer 31 or ball plunger 51 presses down mask holding frame 
1 from overhead. This prevents mask holding frame 1 from being raised in 
parallel placement of mask M and workpiece W to one another. Therefore, 
parallel placement of mask M and workpiece W correctly relative to one 
another can be achieved. Furthermore, precision position setting can be 
easily performed using micrometer 31. 
While various embodiments in accordance with the present invention have 
been shown and described, it is understood that the invention is not 
limited thereto, and is susceptible to numerous changes and modifications 
as known to those skilled in the art. Therefore, this invention is not 
limited to the details shown and described herein, and includes all such 
changes and modifications as are encompassed by the scope of the appended 
claims. 
Action of the Invention 
As was described above, the following effects can be obtained by the 
invention. 
(1) The measure that there is a second elastic component which prestresses 
the mask holding frame towards the side opposite the supporting component 
in a large mask holding frame between the remaining corner area, of the 
four corner areas of the mask holding frame, which is not provided with a 
ball plunger and the supporting component, prevents bending or tilting of 
the mask holding frame. Furthermore, by supporting one corner area of the 
mask holding frame by the second elastic component, it is unnecessary to 
increase the screw-down force of the mounting pins so that distortions of 
the mask holding frame can be prevented. 
(2) The measures that there are protrusions in at least three of the four 
corner areas of the mask holding frame, that in three of these protrusions 
there are three support axes which can be moved in the direction which 
orthogonally intersects the surface of the mask holding frame, and that 
the three protrusions are attached in the supporting component such that 
the support axes are pressed down directly from overhead by plate-like, 
elastic attachment components which surround the protrusions, prevents 
distortions in the mask holding frame even if the screw-down force by the 
attachment components is increased. Therefore, tilting of the mask holding 
frame by the screw-down force of the attachment components can be 
prevented. 
(3) In solution (2), between the mask holding frame or the protrusion of 
the remaining one corner area of the four corner areas of the mask holding 
frame and the supporting component, there is a second elastic component 
which prestresses the mask holding frame towards the side opposite the 
supporting component. This measure prevents the mask holding frame from 
tilting or bending, even if the mask holding frame is large. 
(4) In solutions (1), (2), and (3), in the corner area of the mask holding 
frame provided with the second elastic component, or on the protrusion 
located in this corner area, there is a component for position control. 
This measure prevents the corner area of the mask holding frame from being 
raised, even when the mask holding frame is exposed to a compressive force 
from the side of the supporting component in parallel placement of the 
mask and workpiece relative to one another in proximity exposure. 
Therefore, parallel placement can be correctly performed.