U.S. patent application number 11/872081 was filed with the patent office on 2008-05-08 for apparatus and method for measuring chuck attachment force.
Invention is credited to Hyoung Kyu Son.
Application Number | 20080108154 11/872081 |
Document ID | / |
Family ID | 39360198 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080108154 |
Kind Code |
A1 |
Son; Hyoung Kyu |
May 8, 2008 |
APPARATUS AND METHOD FOR MEASURING CHUCK ATTACHMENT FORCE
Abstract
An apparatus and method for measuring a chuck attachment force
are provided. The apparatus is capable of measuring loads applied
to a measurement substrate, while the measurement substrate is
detached from a chuck, and precisely calculating necessary force
through a process of comparing and analyzing values of the measured
loads. This may prevent errors in the application of attachment
force during a semiconductor manufacturing process. In the
semiconductor manufacturing process, when the substrate is detached
from a chuck, the substrate may be prevented from being deformed or
cracked.
Inventors: |
Son; Hyoung Kyu; (Seoul,
KR) |
Correspondence
Address: |
KED & ASSOCIATES, LLP
P.O. Box 221200
Chantilly
VA
20153-1200
US
|
Family ID: |
39360198 |
Appl. No.: |
11/872081 |
Filed: |
October 15, 2007 |
Current U.S.
Class: |
438/17 ;
257/E21.529; 361/234 |
Current CPC
Class: |
H01L 21/6831 20130101;
H01L 21/67253 20130101 |
Class at
Publication: |
438/17 ; 361/234;
257/E21.529 |
International
Class: |
H01L 21/66 20060101
H01L021/66; H01L 21/687 20060101 H01L021/687 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 3, 2006 |
KR |
10-2006-0108175 |
Nov 3, 2006 |
KR |
10-2006-0108176 |
Nov 3, 2006 |
KR |
10-2006-0108177 |
Claims
1. An apparatus for measuring a chuck attachment force, comprising:
a chuck configured to receive and attach a substrate thereto; a
separating device that detaches the substrate from the chuck; a
variable load applying device connected to the separating device,
the variable load applying device operating the separating device
by changing a load of the variable load applying device; and a
controller that measures both a load of the variable load applying
device when the substrate is attached to or contacts the separating
device and a load of the variable load applying device when the
substrate is detached from the chuck, to calculate a chuck
attachment force.
2. The apparatus of claim 1, wherein the separating device
comprises: a vacuum device that creates a vacuum to adsorb the
substrate; and a drive device that transmits power to move the
vacuum device.
3. The apparatus of claim 2, wherein the drive device comprises a
power transmitting device that connects the variable load applying
device to the vacuum device to move the vacuum device.
4. The apparatus of claim 3, wherein the power transmitting device
comprises at least one pulley and at least one power transmitting
member coupled to the at least one pulley.
5. The apparatus of claim 4, wherein the at least one power
transmitting member comprises of a wire or chain.
6. The apparatus of claim 2, wherein the vacuum device comprises:
at least one vacuum suction member that adsorbs the substrate; and
a vacuum pump to draw air through the at least one vacuum suction
member.
7. The apparatus of claim 6, wherein the at least one vacuum
suction member comprises one selected from a vacuum suction pad or
a vacuum suction pin.
8. The apparatus of claim 1, further comprising: at least one
sensor provided in or on the chuck to detect whether the substrate
is attached to or detached from the chuck.
9. The apparatus of claim 8, wherein at least one sensor comprises
one selected from a pressure sensor, a magnetic sensor, or an
optical sensor.
10. The apparatus of claim 1, wherein the separating device
comprises: a lift device that detaches the substrate from the
chuck; and a drive device that transmits drive force to move the
lift device.
11. The apparatus of claim 10, wherein the lift device comprises at
least one lift pin that contacts the substrate to transmit the
force applied from the drive device to the substrate.
12. The apparatus of claim 11, further comprising: a lift plate
that supports the at least one lift pin and a lift shaft that
supports the lift plate.
13. The apparatus of claim 11, further comprising: a contact
detecting sensor provided in the at least one lift pin that
contacts the substrate to detect whether the at least one lift pin
contacts the substrate.
14. The apparatus of claim 10, wherein the drive device comprises a
power transmitting device that connects the variable load applying
device to the lift device to transmit the drive force to the lift
device.
15. The apparatus of claim 14, wherein the power transmitting
device comprises at least one pulley and at least one power
transmitting member coupled to the at least one pulley.
16. The apparatus of claim 15, wherein the at least one power
transmitting member comprises of a wire or chain.
17. The apparatus of claim 1, wherein the chuck comprises an
electrostatic chuck and the apparatus measures electrostatic
force.
18. A method of measuring a chuck attachment force, comprising:
placing a substrate onto a chuck; attaching the substrate to the
chuck using an attachment force; moving a separating device by
changing a load of a variable load applying device to detach the
substrate from the chuck; measuring a load of the variable load
applying device when the substrate is detached from the chuck; and
calculating a difference value between the load of the variable
load applying device measured when the substrate is detached from
the chuck and a load of the variable load applying device measured
when the separating device is attached to or contacts the
substrate, and determining a chuck attachment force using the
difference value.
19. The method of claim 18, wherein the chuck comprises an
electrostatic chuck and the attachment force comprises an
electrostatic force.
20. The method of claim 18, wherein the separating device comprises
a vacuum device, wherein the moving step comprises moving the
vacuum device upwards by changing the load of the variable load
applying device to detach the substrate from the chuck, and wherein
the calculating step comprises calculating a difference value
between the load of the variable load applying device measured when
the substrate is detached from the chuck and a load of the variable
load applying device measured when the vacuum device is attached to
the substrate, and determining the chuck attachment force using the
difference value.
21. The method of claim 20, wherein the chuck comprises an
electrostatic chuck and the attachment force comprises an
electrostatic force.
22. The method of claim 18, wherein the separating device comprises
a lift device, wherein the moving step comprises moving the lift
device upwards to detach the substrate from the chuck, and wherein
the calculating step comprises calculating a difference value
between the load of the variable load applying device measured when
the lift device comes into contact with the substrate and the load
of the variable load applying device measured when the substrate is
detached from the chuck, and determining the chuck attachment force
using the difference value.
23. The method of claim 22, wherein the chuck comprises an
electrostatic chuck and the attachment force comprises an
electrostatic force.
24. An apparatus for measuring a chuck attachment force,
comprising: a chuck configured to receive and attach a substrate
thereto; a separating device, comprising a lift device that
detaches a substrate from the chuck and a drive device that
operates the lift device; and a load measuring apparatus that
measures a first load of the lift device before the separating
device contacts the substrate and that measures a second load of
the lift device when the substrate is detached from the chuck, the
load measuring device calculating an attachment force of the chuck
using a difference value between the first load and the second
load.
25. The apparatus of claim 24, further comprising: a support device
that supports the chuck.
26. The apparatus of claim 25, wherein the support device comprises
a stage onto which the chuck is placed and a support frame that
supports the stage.
27. The apparatus of claim 26, wherein the lift device comprises:
at least one lift pin that vertically moves through at least one
corresponding opening provided in the chuck; and a lift plate that
supports the at least one lift pin.
28. The apparatus of claim 27, further comprising: at least one
sensor provided on or in the support device that detects whether
the substrate is attached to or detached from the chuck and whether
the at least one lift pin come into contact with the substrate.
29. The apparatus of claim 28, further comprising: at least one
guide bar provided on the stage such that the at least one lift
plate is slidably coupled to the guide bar, wherein the at least
one guide bar guides vertical movement of the lift device.
30. The apparatus of claim 27, wherein the drive device comprises:
a lift screw that supports the lift plate, the lift screw being
vertically movable; and a power generating and transmitting device
that rotates the lift screw.
31. The apparatus of claim 24, wherein the load measuring apparatus
comprises: a load measuring device that measures the first load and
the second load; a memory that stores a value of the first load
value and the second load therein; an arithmetic device that
calculates a difference value between the first load value and the
second load value; and a display device that displays the
difference value.
32. The apparatus of claim 24, wherein the chuck comprises an
electrostatic chuck and the apparatus measures electrostatic
force.
33. A method of measuring chuck attachment force, comprising:
placing a substrate on a chuck; attaching the substrate to the
chuck using an attachment force; moving a lift device to detach the
substrate from the chuck; measuring a first load of the lift device
before the lift device contacts the substrate attached to the
chuck; measuring a second load of the lift device when the
substrate is detached from the chuck; and calculating a chuck
attachment force using the measured first and second loads.
34. The method of claim 33, further comprising: attaching the
substrate to the chuck using an electrostatic force generated by
applying power to the chuck, before measuring the first load.
35. The method of claim 34, further comprising: determining an
electrostatic force using a difference value between the first load
and the second load.
36. The method of claim 33, wherein the chuck comprises an
electrostatic chuck and the method measures electrostatic force
Description
BACKGROUND
[0001] 1. Field
[0002] An apparatus and method for measuring chuck attachment force
are disclosed herein.
[0003] 2. Background
[0004] Apparatus and method for measuring chuck attachment force
are known. However, they suffer from various disadvantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Embodiments will be described in detail with reference to
the following drawings in which like reference numerals refer to
like elements, and wherein:
[0006] FIG. 1 is a schematic diagram of an apparatus for measuring
electrostatic force according to an embodiment;
[0007] FIG. 2 is a flow chart of a method of measuring
electrostatic force according to an embodiment;
[0008] FIG. 3 is a schematic diagram of an apparatus for measuring
electrostatic force according to another embodiment;
[0009] FIG. 4 is a bottom view of the electrostatic force measuring
apparatus of FIG. 3;
[0010] FIGS. 5 and 6 are views illustrating operation of the
electrostatic force measuring apparatus of FIG. 3;
[0011] FIG. 7 is a flow chart of a method of measuring
electrostatic force according to another embodiment;
[0012] FIG. 8 is a schematic diagram of an apparatus for measuring
electrostatic force according to another embodiment;
[0013] FIG. 9 is a block diagram of a load measuring device of FIG.
8;
[0014] FIGS. 10 and 11 are views illustrating operation of the
electrostatic force measuring apparatus of FIG. 8; and
[0015] FIG. 12 is a flow chart of a method of measuring
electrostatic force according to another embodiment.
DETAILED DESCRIPTION
[0016] Embodiments disclosed herein are directed to an apparatus
and method for measuring chuck attachment force. Certain
embodiments are disclosed employing an electrostatic chuck and
measuring electrostatic force. However, the apparatus and method
may be utilized with other types of chucks, such as a vacuum chuck,
and to measure other types of forces, such as a vacuum force.
Further, features of each of the disclosed embodiments may be
utilized with any of the other embodiments as desired based on, for
example, the desired application.
[0017] Generally, in processes of treating substrates, such as
semiconductor wafers, thin film transistors (TFTs) used in flat
panel displays, glass substrates or similar devices, the
substrates, which are carried into chambers, are moved to desired
positions, dropped onto support surfaces, and thereafter, are
arranged. Recently, according to the integration and lightness of
circuits in the semiconductor field, and according to the increase
in display area in the field of manufacturing flat panel displays,
the significance of a technique of holding substrates to arrange
the substrates and drop the substrates at desired positions has
been emphasized.
[0018] As representative examples of such substrate holding
techniques, there are a method using a clamp, a method using vacuum
force, and a method using an electrostatic chuck (ESC). In the
method using the clamp, a substrate is fixed by clamping an edge of
the substrate using the clamp. The clamp may be made of ceramic or
other material. In the method using the electrostatic chuck, the
electrostatic chuck adsorbs and holds a substrate using
electrostatic force generated at contact surfaces between the
electrostatic chuck and the substrate.
[0019] Recently, of such substrate holding methods, application of
the method using the electrostatic chuck, which enhances uniformity
of the manufacturing process, has increased. A representative
example of related art pertaining to an electrostatic chuck was
disclosed in U.S. Pat. No. 6,134,096, entitled "ELECTROSTATIC
CHUCK". In this patent, the electrostatic chuck has a structure
including an insulation layer, an electrode layer, and a dielectric
layer, and is constructed such that a substrate is attached to the
electrostatic chuck by applying power of -1000V to +1000V to the
electrostatic chuck. In the case of the method of holding the
substrate using the electrostatic chuck, because the chuck holds
the substrate by adsorbing it using electrostatic force, various
operations may be stably conducted during a semiconductor
manufacturing process, thus preventing the substrate from being
damaged and reducing the defective proportion of products.
[0020] The electrostatic chuck for adsorbing and holding the
substrate using electrostatic force may include a base plate, which
may be made of ceramic, an electrode, which may be provided on the
base plate, and a dielectric, which may be supplied with power
through the electrode.
[0021] In the electrostatic chuck, when power is applied to the
electrode to adsorb the substrate, the surfaces of the substrate
and the electrode may be polarized. At this time, electrostatic
force is generated on the electrostatic chuck, by which the
electrostatic chuck adsorbs and holds the substrate.
[0022] Recently, according to an increase in the area of flat panel
displays, such an electrostatic chuck may include a plurality of
dielectrics, which may be provided on a base plate and adsorb a
substrate. The plurality of dielectrics, which adsorb and hold the
substrate, must ensure even electrostatic force.
[0023] Electrostatic force may be set depending on a material and
thickness of the substrate. If the dielectrics do not ensure even
electrostatic force, an error of electrostatic force may occur, so
that, when the substrate is detached from the electrostatic chuck,
the substrate may not be correctly detached from the electrostatic
chuck, and a sticking phenomenon, in which the substrate may snap
back onto the electrostatic chuck, may be induced. Further, the
substrate may be deformed or cracked. Therefore, a problem of
reduced manufacturing efficiency results.
[0024] As shown in FIG. 1, an electrostatic force measuring
apparatus 10 according to an embodiment may include an
electrostatic chuck 100, onto which a measurement substrate S may
be seated, a power supply device 150 that applies voltage to the
electrostatic chuck 100, and a separating device 120 that detaches
the measurement substrate S from the electrostatic chuck 100 to
which voltage is applied. The electrostatic force measuring
apparatus 10 may further include a variable load applying device
110, which may be connected to the separating device 120 and
operate the separating device 120 through a process of changing a
load thereon, and a controller 160 that measures the load of the
variable load applying device 110 when the measurement substrate S
is attached to the separating device 120 and measures the load of
the variable load applying device 110 when the measurement
substrate S is detached from the electrostatic chuck 100, thus
calculating the electrostatic force using a change in the load of
the variable load applying device 110.
[0025] The electrostatic chuck 100 absorbs the measurement
substrate S using electrostatic force generated by a polarization
phenomenon occurring on surfaces between the measurement substrate
S and the electrostatic chuck 300 when power is applied thereto. A
dummy substrate that meets the same conditions as a thin film
transistor and a glass substrate of semiconductor water of flat
panel display may be used as the measurement substrate S. In
addition, a separate chuck carrying device and a separate substrate
carrying device may be provided to move the chuck 300 and the
substrate S, although not shown in the drawings.
[0026] The electrostatic chuck 100 may be supported by a support
device 150. The support device 150 may include a support plate or
stage 151 and support legs 153 and may be charged by voltage
applied from the power supply device 155. The support plate 151 may
serve to hold the electrostatic chuck 100, on which the measurement
substrate S is loaded. When voltage is applied from the power
supply device 155 to the electrostatic chuck 100, electric charges
having a polarity opposite to that of the electric charges applied
to the electrostatic chuck 100 may be induced at a contact surface
between the electrostatic chuck 100 and the measurement substrate
S, so that induced electromotive force may be generated by the
induced electric charges, by which the measurement substrate S may
be attached to the electrostatic chuck 100.
[0027] The electrostatic chuck 100 may have a dielectric ceramic
coating layer between it and the measurement substrate S. Depending
on a thickness of the dielectric ceramic coating layer, the
attaching force with which the measurement substrate S may be
chucked to the electrostatic chuck 100 may be changed.
[0028] Further, one or more sensor(s) 102 that detect whether the
measurement substrate S is attached to or detached from the
electrostatic chuck 100 may be provided in the surface of the
electrostatic chuck 100 that contacts the measurement substrate S.
The sensor(s) 102 may comprise a pressure sensor that detects a
change in pressure, or a magnetic sensor that detects a change in
the magnetic field between the measurement substrate S and the
electrostatic chuck 100.
[0029] The power supply device may include a direct current
generator (not shown) that supplies direct current to the
electrostatic chuck 100. The separating device 120 may include a
vacuum device 130 that creates a vacuum to adsorb the measurement
substrate S, and a drive device 140 that transmits power to move
the vacuum device 130. The vacuum device 130 may include a vacuum
suction device 131a having vacuum suction members 131b that adsorb
the measurement substrate S, a vacuum pump 132 that suctions air
through the vacuum suction members 131b, and a vacuum pipe 133,
which may be connected between the vacuum suction members 131b and
the vacuum pump 132. Vacuum suction pads, which may be made of
rubber, or vacuum suction pins, which may be made of a ceramic
nonconductor, may be used as the vacuum suction members 131b to
prevent the vacuum suction member 131b from affecting the
electrostatic force generated between the measurement substrate S
and the electrostatic chuck 100.
[0030] The vacuum pump 132 suctions air through the vacuum suction
members 131b to attach the measurement substrate S to the vacuum
suction device 131a, such that, when the measurement substrate S is
detached from the electrostatic chuck 100, the measurement
substrate S, which may be adsorbed by the vacuum suction members
131b, may be moved along with the vacuum suction device 131a in a
vertical direction. As set forth above, the vacuum pipe 133 may
serve to connect the vacuum suction device 131a and the vacuum pump
132 to each other.
[0031] The drive device 140 may include at least one, or, in the
example of this embodiment, two pulleys 141 and 142, and a power
transmitting member 143, which may be coupled to the pulleys 141
and 142 and the vacuum suction member 131 to conduct a power
transmitting function. In this embodiment, the pulleys 141 and 142
include a first pulley 141 and a second pulley 142. The first
pulley 141 may support the power transmitting member 143, which may
be connected to the vacuum suction device 131a, such that the power
transmitting member 143 may pull the vacuum suction device 131a and
the measurement substrate S adsorbed and held by the vacuum suction
members 131b with force corresponding to tension applied to the
power transmitting member 143 by the variable load applying device
110.
[0032] Further, the second pulley 142 may also serve to support the
power transmitting member 143 along with the first pulley 141 such
that the force applied from the variable load applying device 110
may be transmitted to the measurement substrate S, attached to the
electrostatic chuck 100, through the power transmitting member 143,
the direction of which may be changed by the first and second
pulleys 141 and 142. A stationary pulley or a movable pulley may be
used as each of the first and second pulleys 141 and 142. Further,
a plurality of pulleys may be used to change the direction in which
force is transmitted.
[0033] The power transmitting member 143 may connect the vacuum
suction device 131a, the first pulley 141, the second pulley 142,
and the variable load applying device 110 to each other and
transmit force, generated by the variable load applying device 110,
to the vacuum suction device 131a. A wire rope or a chain, which
may be capable of withstanding a load of several tons, may be used
as the power transmitting member 143.
[0034] In the separating device 120 having the above-mentioned
construction, the vacuum device 130 creates a vacuum, thereby
adsorbing the measurement substrate S, and the drive device 140
moves the vacuum suction device 131a, thus detaching the
measurement substrate S from the electrostatic chuck 100.
[0035] The variable load applying device 110 adjusts the load
thereof in response to an intensity of electrostatic force applied
between the measurement substrate S and the electrostatic chuck
100. That is, the force generated in the variable load applying
device 110 may be proportional to the intensity of the
electrostatic force. The load changing operation of the variable
load applying device 110 may be conducted by a method in which one
weight may be replaced with another using a separate machine, or by
a method in which the load may be increased or reduced using a
vertical load cylinder.
[0036] The controller 160 may receive, from the sensor(s) 102,
information about whether the measurement substrate S is detached
from the electrostatic chuck 100. Also, the controller 160 may
adjust the load of the variable load applying device 110 until the
measurement substrate S is detached from the electrostatic chuck
100, and measure the load of the variable load applying device 110
when the measurement substrate S is detached from the electrostatic
chuck 100. In addition, the controller 160 may serve to calculate
the electrostatic force using the measured load of the variable
load applying device 110.
[0037] The operation of the electrostatic force measuring apparatus
according to the above-described embodiment, having the
above-mentioned construction, will be described herein below.
[0038] As shown in FIG. 2, the measurement substrate S, which may
be adsorbed by the vacuum suction members 131b, may be seated on
the electrostatic chuck 100, in step S110. Thereafter, when voltage
is applied from the power supply device 155 to the electrostatic
chuck 100, the electrostatic chuck 100 may be charged, and
electrostatic force generated between the measurement substrate S
and the electrostatic chuck 100. Then, the measurement substrate S
may be attached to the electrostatic chuck 100 by the electrostatic
force, in step S120.
[0039] After the measurement substrate S has been attached to the
electrostatic chuck 100, the controller 160 may gradually increase
the load of the variable load applying device 110 until the
measurement substrate S is detached from the electrostatic chuck
100, in step S130. Then, the tension of the power transmitting
member 143, which may be coupled to the variable load applying
device 110, may be gradually increased, and pulling force may be
applied to the vacuum suction members 131b. The force by which the
vacuum suction members 131b adsorb the measurement substrate S must
be greater than the electrostatic force between the electrostatic
chuck 100 and the measurement substrate S to make it possible to
detach the measurement substrate S from the electrostatic chuck
100.
[0040] The load of the variable load applying device 110 may be
increased until the measurement substrate S is detached from the
electrostatic chuck 100. When the measurement substrate S is
detached from the electrostatic chuck 100, the sensor(s) 102, which
may be provided in the electrostatic chuck 100, may detect the
detachment of the measurement substrate S from the electrostatic
chuck 100, in step S140. The detected information of the sensor(s)
102 may be transmitted to the controller 160, so that a load of the
variable load applying device 110 when the measurement substrate S
is detached from the electrostatic chuck 100 may be determined, in
step S150.
[0041] Subsequently, the difference between the load of the
variable load applying device 110 when the measurement substrate S
is attached to the vacuum suction members 131b and the load of the
variable load applying device 110 when the measurement substrate S
is detached from the electrostatic chuck 100 may be calculated, and
the exact value of electrostatic force from this difference value
may be determined, in step S160.
[0042] In the above-described electrostatic force measuring
apparatus and method of measuring electrostatic force, an exact
value of electrostatic force may be determined from the difference
between the load of the variable load applying device 110 when the
measurement substrate S is attached to the vacuum suction members
131b and the load of the variable load applying device 110 when the
measurement substrate S is detached from the electrostatic chuck
100, thus preventing an error in the application of electrostatic
force in a semiconductor manufacturing process, and preventing a
substrate from being cracked or damaged when it is detached from an
electrostatic chuck in the semiconductor manufacturing process.
[0043] Hereinafter, an apparatus for measuring electrostatic force
and a method of measuring electrostatic force according to
additional embodiments will be described in detail with reference
to FIGS. 3 and 7.
[0044] As shown in FIG. 3, the electrostatic force measuring
apparatus 20 according to this embodiment may include an
electrostatic chuck 200, onto which a measurement substrate S may
be seated, a power supply device 255 that applies voltage to the
electrostatic chuck 200, and a separating device 220 that detaches
the measurement substrate S from the electrostatic chuck 200 to
which voltage is applied. The electrostatic force measuring
apparatus 20 may further include variable load applying devices
210, which may be connected to the separating device 220 and
operate the separating device 220 through a process of changing a
load thereof, and a controller 260 that measures the load of the
variable load applying devices 210 when the measurement substrate S
is attached to the separating device 220 and measures the load of
the variable load applying devices 210 when the measurement
substrate S is detached from the electrostatic chuck 200, thus
calculating electrostatic force using a change in the load of the
variable load applying devices 210.
[0045] The electrostatic chuck 200 absorbs the measurement
substrate S using electrostatic force generated by a polarization
phenomenon occurring on surfaces between the measurement substrate
S and the electrostatic chuck 200 when power is applied thereto. A
dummy substrate that meets the same conditions as a thin film
transistor and a glass substrate of semiconductor water of flat
panel display may be used as the measurement substrate S. In
addition, a separate chuck carrying device and a separate substrate
carrying device may be provided to move the chuck 200 and the
substrate S, although not shown in the drawings.
[0046] The electrostatic chuck 200 may be supported by a support
device 250. The support device 250 may include a support plate or
stage 251 and support legs 253. A through hole 236a may be formed
in the support plate 251, and a plurality of holes 203 may be
formed through the electrostatic chuck 200. The electrostatic chuck
200 may be made of ceramic and may have a ceramic coating layer
between the measurement substrate S and the electrostatic chuck
200. The ceramic coating layer may provide elasticity when the
measurement substrate S is attached to the electrostatic chuck 200,
thus increasing attachment ability therebetween.
[0047] Further, one or more sensor(s) 202 that detect whether the
measurement substrate S is attached to or detached from the
electrostatic chuck 200 may be provided in a surface of the
electrostatic chuck 200 that contacts the measurement substrate S.
When the measurement substrate S is detached from the electrostatic
chuck 200, the sensor(s) 202 may detect and transmit a signal(s) to
the controller 260. The sensor(s) 202 may include a pressure sensor
or a magnetic sensor. The power supply device 255 may include a
direct current generator (not shown) that supplies direct current
to the electrostatic chuck 200.
[0048] The separating device 220 may include a lift device 230 that
moves the measurement substrate S upwards, and a drive device 240
that transmits power to operate the lift device 230. The lift
device 230 may include a plurality of lift pins 231, which may be
brought into contact with the measurement substrate S through the
holes 203 formed through the electrostatic chuck 200, a lift plate
232, which may be coupled to the lift pins 231, a lift shaft 233,
which may extend from the lift plate 232 to transmit power from the
drive device 240 to the lift plate 232, and guide bars 234, which
may be provided between the support plate 251 and the lift plate
232 to guide the movement of the lift plate 232.
[0049] When voltage is applied from the power supply device 255 to
the electrostatic chuck 200, electric charges having a polarity
opposite to that of the electric charges applied to the
electrostatic chuck 200 are induced on a surface of the measurement
substrate S that contacts the electrostatic chuck 200. If the lift
pins 231, which may be made of a conductor, are used, when the lift
pins 231 contact the measurement substrate S to detach the
measurement substrate S from the electrostatic chuck 200, electric
charges of the measurement substrate S may be discharged through
the lift pins 231, so that the electrostatic force may not be
precisely measured. Thus, the lift pins 231 may be nonconductors
made, for example, of ceramic material to prevent the discharge of
electric charges of the measurement substrate S.
[0050] Further, in this embodiment, the measurement substrate S may
be detached from the electrostatic chuck 200 by applying a pushing
force to the lift pins 231, which may be in a state of contact with
the measurement substrate S, so that the attractive force between
the electrostatic chuck 100 and the measurement substrate S, that
is, the electrostatic force therebetween, may be measured.
Therefore, to precisely measure electrostatic force, contact
detecting sensors 235, which may detect whether the lift pins 231
are brought into contact with the measurement substrate S, may be
provided on ends of the lift pins 231 that contact the measurement
substrate S.
[0051] The lift plate 232 may serve to transmit force from the
drive device 240 to the measurement substrate S and may vertically
move along the guide bars 234. That is, the lift pins 231 may
transmit force to the measurement substrate S using upward movement
of the lift plate 232 such that the measurement substrate S may be
detached from the electrostatic chuck 100. The lift pins 231 may be
provided on an upper surface of the lift plate 232, and the lift
shaft 233 may be coupled at a central portion to a lower surface of
the lift plate 232. The lift shaft 233 may serve to transmit the
force of the drive device 240 to the lift plate 232 and to maintain
a horizontally leveled state of the lift plate 232 along with the
guide bars 234.
[0052] The guide bars 234 may serve to maintain the lift plate 232
in the horizontally leveled state such that several lift pins 231
may evenly transmit force, which may be applied from the drive
device 240 to the lift plate 232, to the measurement substrate S.
In addition, the guide bars 234 may serve to define a movement
space 236b such that the lift plate 232 may be vertically moved in
the movement space 236b. Further, a stop pin 237 may be provided in
a lower end of each guide bar 234 to prevent the lift device 230
from being removed from the movement space 236b defined by the
guide bars 234.
[0053] The drive device 240 may include at least one set of pulleys
241, and power transmitting members 243, which may be connected to
the pulleys 241 and the lift shaft 233 to conduct a power
transmitting function. The power transmitting members 243 may be
coupled at first ends thereof to a lower end of the lift shaft 233.
Each power transmitting member 243 may be coupled at a second end
thereof to the corresponding variable load applying device 210. The
upper end of the lift shaft 233 may be coupled to the central
portion of the lift plate 232.
[0054] A stationary pulley may be used, for example, as each pulley
241, and a wire rope or a chain, which is capable of withstanding a
load of several tons, may be used as each power transmitting member
243.
[0055] As shown in FIG. 4, in this embodiment, four power
transmitting members 243, each of which may be connected to the
lift shaft 233, may be oriented in four respective directions and
may be wrapped around the respective pulleys 241, which may be
provided on four respective support legs 253. Further, the four
pulleys 241 may be installed to maintain balance of the lift device
230 and to disperse the force that is applied to the lift device
230.
[0056] In the case of four pulleys 241, if the loads generated in
the variable load applying devices 210 are equal to each other, the
force applied to the lift device 230 is four times as much as the
force applied to each pulley 241. Further, even if the loads
generated in the variable load applying devices 210 differ from
each other, the force applied to the lift device 230 is equal to
the sum of the loads generated in the variable load applying
devices 210.
[0057] The loads of the variable load applying devices 210 may be
controlled by the controller 260. The vertical position of the lift
device 230 may be changed depending on the change in the load of
the variable load applying devices 210.
[0058] When the load of the variable load applying devices 210,
which may be connected to respective power transmitting members
243, is increased, an upward moving force may be transmitted to the
lift plate 232, coupled to the lift shaft 233. Thereby, the lift
plate 232 may be moved upwards. Here, as a modification of the
method of vertically moving the lift plate 232, a lift cylinder may
be used. Further, the load changing operation of each variable load
applying device 210 may be conducted using counterbalances or using
a vertical load cylinder.
[0059] The controller 260 may receive information about whether the
lift pins 231 have been brought into contact with the measurement
substrate S, measure the load of the variable load applying devices
210 when the lift pins 231 have been brought into contact with the
measurement substrate S, and increase the load of the variable load
applying devices 210 until the measurement substrate S is detached
from the electrostatic chuck 200. Thereafter, the controller 260
may measure the load of the variable load applying devices 210 when
it detects the detachment of the measurement substrate S from the
electrostatic chuck 200 using the sensor(s) 202.
[0060] Meanwhile, as shown in FIG. 5, in the drive device 240,
which uses the pulleys 241, when the load of the variable load
applying devices 210 connected to the first ends of the respective
power transmitting members 243 is increased, the tension of the
power transmitting member 243 increases, and thus pulls the lift
shaft 233. Thereby, the lift plate 232 may be moved upwards.
[0061] However, if a distance between the measurement substrate S
and the lift device 230 is relatively large, when detaching the
measurement substrate S from the electrostatic chuck 200, because
the force required for moving the lift device 230 to the
measurement substrate S may also be included in the calculation of
the load of the variable load applying devices 210, it is difficult
to precisely measure electrostatic force. Therefore, as shown in
FIG. 6, when the lift pins 231 are moved to the contact surface of
the measurement substrate S, the load of the lift device 230 may be
measured, and when the measurement substrate S is detached from the
electrostatic chuck 200, the load of the lift device 230 may be
measured. Thereafter, electrostatic force may be calculated using
the difference between the loads. Then, the electrostatic force may
be measured more precisely.
[0062] The operation of the electrostatic force measuring apparatus
according to this embodiment, having the above-mentioned
construction, will be described herein below.
[0063] As shown in FIG. 7, the measurement substrate S may be
seated on the electrostatic chuck 200, in step S210. Thereafter,
when voltage is applied from the power supply device 255 to the
electrostatic chuck 200, the electrostatic chuck 200 may be
charged, and electrostatic force generated between the measurement
substrate S and the electrostatic chuck 200. Then, the measurement
substrate S may be attached to the electrostatic chuck 200 by the
electrostatic force, in step S220.
[0064] After the measurement substrate S has been attached to the
electrostatic chuck 200, the controller 260 may gradually increase
the load of the variable load applying devices 210. Then, the
tension of the power transmitting members 243 connected to the
respective variable load applying devices 210 may be gradually
increased, so that the lift shaft 233 may be pulled, by which the
lift device 230 may be slowly moved upwards.
[0065] To reduce an error in the measurement of the electrostatic
force, the lift device 230 may be first moved upwards until the
lift pins 231 are brought into contact with the measurement
substrate S. When the lift pins 231 are brought into contact with
the measurement substrate S, the contact detecting sensors 235,
which may be provided in the lift pins 231, may detect the contact
therebetween. At this time, the controller 260 may measure the load
of the variable load applying devices 210, in step S230. In the
case where each variable load applying device 210 uses a method in
which a load is varied by replacing a counterbalance with another,
the load may be a value resulting from multiplying the weights of
the counterbalances by the acceleration of gravity. This value may
be equal to the force applied to the lift device 230.
[0066] The load of the variable load applying devices 210 may be
gradually increased. Then, the lift device 230 may be moved further
upwards. Ultimately, the measurement substrate S is detached from
the electrostatic chuck 200. As such, when the measurement
substrate S is detached from the electrostatic chuck 200, the
sensor(s) 202 installed in the electrostatic chuck 200 may detect
such detachment, in step S240. The detected information of the
sensor(s) 202 may be transmitted to the controller 260, and the
controller 260 may measure the load of the variable load applying
devices 210 when the measurement substrate S is detached from the
electrostatic chuck 200, in step S250.
[0067] Thereafter, electrostatic force may be precisely calculated
using the difference between the load of the variable load applying
devices 210 when the measurement substrate S is detached from the
electrostatic chuck 200 and the load of the variable load applying
devices 210 when the lift pins 235 are brought into contact with
the measurement substrate S, in step S260.
[0068] In the above-described electrostatic force measuring
apparatus and method of measuring electrostatic force, the exact
value of electrostatic force may be determined from the difference
between the load of the variable load applying devices 210 when the
lift pins 235 are brought into contact with the measurement
substrate S and the load of the variable load applying devices 210
when the measurement substrate S is detached from the electrostatic
chuck 200, thus preventing an error in the application of
electrostatic force in a semiconductor manufacturing process, and
preventing a substrate from being cracked or damaged when it is
detached from an electrostatic chuck in the semiconductor
manufacturing process.
[0069] Hereinafter, an apparatus for measuring electrostatic force
and a method of measuring electrostatic force according to
additional embodiments will be described in detail with reference
to FIGS. 8 and 12.
[0070] As shown in FIG. 8, the electrostatic force measuring
apparatus 30 according to this embodiment may include an
electrostatic chuck 300, onto which a measurement substrate S may
be seated, and a separating device 320 that detaches the
measurement substrate S from the electrostatic chuck 300. The
electrostatic force measuring apparatus 30 may further include a
load measuring apparatus 310 that measures the load when the
separating device 320 is brought into contact with the measurement
substrate S and measures the load when the measurement substrate S
is detached from the electrostatic chuck 300.
[0071] The electrostatic chuck 300 may be supported by a support
device 350. The support device 350 may include a stage 351, onto
which the electrostatic chuck 300 may be placed, and support frames
353, which may be provided under a perimeter of a lower surface of
the stage 351 to support the stage 351.
[0072] The electrostatic chuck 300 adsorbs the measurement
substrate S using electrostatic force generated by a polarization
phenomenon occurring on surfaces between the measurement substrate
S and the electrostatic chuck 300 when power is applied thereto. A
dummy substrate that meets the same conditions as a thin film
transistor and a glass substrate of a semiconductor wafer or a flat
panel display may be used as the measurement substrate S. In
addition, a separate chuck carrying device and a separate substrate
carrying device may be provided to move the electrostatic chuck 300
and the substrate S, although not shown in the drawings.
[0073] In detail, the electrostatic chuck 300 may be placed on an
upper surface of the stage 351. An electrode (not shown) for
applying power to the electrostatic chuck 300 may be provided in
the stage 351.
[0074] The separating device 320 may include a lift device 330,
which may be disposed below the stage 351 and push the substrate S
to detach it from the electrostatic chuck 300, and a drive device
340 that vertically moves the lift device 330. The lift device 330
may include a plurality of lift pins 331, which may be vertically
moved through the stage 351 and the electrostatic chuck 300, a lift
plate 332 that supports the lift pins 331, and guide bars 334,
which may be provided between the support device 350 and the lift
plate 332 to guide the movement of the lift plate 332.
[0075] Here, the lift pins 331 and the lift plate 332 may be
vertically moved under guidance of the guide bars 334 in a state in
which the lift plate 332 is parallel to the substrate S attached to
the electrostatic chuck 300. Thus, the lift pins 331, which may be
supported by the lift plate 332, may evenly contact the substrate
S, attached to the electrostatic chuck 300. Therefore, a
measurement error by the load measuring device 310 measuring a load
may be reduced.
[0076] At least two guide bars 334 may be provided at respective
opposite positions under the perimeter of the stage 351. Further, a
coupler 337, which is vertically movable along the corresponding
guide bar 334, may be provided on each lift plate 332.
Alternatively, through holes (not shown) may be formed through the
lift plate 332 such that the lift plate 332 may be vertically
movable along the guide bars 334 through the through holes.
[0077] Meanwhile, one or more sensor(s) 302 may be provided in the
stage 351 to detect whether the substrate S is placed on the
electrostatic chuck 300 and whether the lift pins 331 are brought
into contact with the substrate S. The sensor(s) 302 may be
connected to the load measuring apparatus 310 to transmit
information about placement of the substrate S and contact between
the lift pins 331 and the substrate S to the load measuring device
310.
[0078] In detail, when the substrate S is placed on the
electrostatic chuck 300, the sensor(s) 302 may transmit information
about the placement of the substrate S to the load measuring device
310. The load measuring apparatus 310 may measure a first load W1,
which may be the load of the lift device 330 before it pushes the
substrate S. Further, when the lift pins 331 are brought into
contact with the substrate S, the sensor(s) 302 may transmit
information about the contact between the lift pins 331 and the
substrate S to the load measuring apparatus 310. The load measuring
device 310 may measure a second load W2, which may be the load of
the lift device 330 when the substrate S is detached from the chuck
300.
[0079] Here, as shown in FIG. 8, the sensor(s) 302 may comprise a
pair of optical sensors, which may face each other and be located
on opposite sides of the measurement substrates. Alternatively, a
pressure sensor or a magnetic sensor, which may be installed in an
upper surface of the chuck 300, on which the measurement substrates
is seated, may be used as the sensor(s) 302, although not shown in
the drawings.
[0080] The drive device 340 may include a lift screw 341, which may
move vertically, and a power generating and transmitting device
342, which may be coupled to the lift screw 341 and supply power to
vertically move the lift screw 341. The lift screw 341 may be
provided below the lift device 330 and may be constructed such that
the lift plate 332 and the lift pins 331, which may be supported on
the lift plate 332, may be vertically moved together with the
vertical movement of the lift screw 341.
[0081] The power generating and transmitting device 342 may include
a power transmitting screw 343, which may have a rotating shaft
oriented in a direction perpendicular to the lift screw 341, a
bevel gear 344, which may be provided in a junction between the
lift screw 341 and the power transmitting screw 343, and a power
source 345, which may rotate the power transmitting screw 343.
[0082] The power source 345 may be in the form of a manual handle
so that power may be supplied by rotating the handle using the
manual power of a user. Alternatively, a mechanical power source,
such as a drive motor, may be used to supply power.
[0083] The load measuring apparatus 310 may be disposed between the
lift device 330 and the drive device 340. The upper surface of the
load measuring apparatus 310 may be in contact with the lower
surface of the lift plate 332, and the lower surface thereof may be
coupled to the lift screw 341.
[0084] As shown in FIG. 9, the load measuring apparatus 310 may
include a load measuring device 311 that measures the first load W1
and the second load W2, a memory 312 that stores the first load
value W1 and the second load value W2, an arithmetic device 313
that calculates a difference value between the first load value W1
and the second load value W2, which may be stored in the memory
312, and a display 314 that displays the difference value.
[0085] Here, a typical electron scale may be used as the load
measuring device 311. Alternatively, a piezoelectric sensor, which
uses the phenomenon in which, when mechanical force is applied to a
substance made of material such as ceramic, an internal stress is
generated and electric polarization is induced in the substance,
may be used as the load measuring device 311.
[0086] When the lift screw 341 is moved upwards to detach the
substrate S from the electrostatic chuck 300, the pressure of the
lift screw 341 may be transmitted to the load measuring apparatus
310. Then, the load measuring apparatus 310 moves the lift plate
332 upwards using the pressure of the lift screw 341, by which the
lift pins 331, which may be supported on the lift plate 332, may be
moved upwards.
[0087] During this process, the load measuring device 311 measures
both the pressure of the lift screw 341 that is applied to the lift
device 330 before the substrate S, attached to the chuck 300, is
pushed by the lift pins 331, and the pressure of the lift screw 341
that is applied to the lift device 330 when the substrate S is
detached from the chuck 300. In other words, the load measuring
device 311 measures both a first load W1, which is the load of the
lift device 330 before it pushes the substrate S attached to the
chuck 300, and a second load W2, which is the load of the lift
device 330 when the substrate S is detached from the chuck 300.
[0088] The operation of the electrostatic force measuring apparatus
according to this embodiment, having the above-mentioned
construction will be described herein below.
[0089] As shown in FIGS. 10 through 12, the electrostatic chuck 300
may be first placed on the stage 351 of the support device 350, and
the substrate S may be seated on the upper surface of the
electrostatic chuck 300, in step S310. As such, when the
electrostatic chuck 300 is placed on the stage 351 of the support
device 350 and the substrate S is seated on the electrostatic chuck
300, the sensor(s) 302 may detect the presence of the substrate S,
in step S320, and transmit this to the load measuring apparatus
310. At this time, the load measuring device 311 of the load
measuring apparatus 310 may measure a first load W1, which may be
the load of the lift device 330 before the substrate attached to
the electrostatic chuck 300 is pushed by the lift device 330, and
store the measured value in the memory 312, in step S340.
[0090] Thereafter, power may be supplied to the electrode (not
shown) of the stage 351 to generate electrostatic force between the
substrate S and the electrostatic chuck 300, in step S340. The
power, which may be supplied to the electrode of the stage 351, may
be applied to the electrostatic chuck 300. At this time, an
electric polarization phenomenon may be induced in the surfaces
between the electrostatic chuck 300 and the substrate S. The
electrostatic chuck 300 may adsorb the substrate S using the
electrostatic force generated by the electric polarization.
[0091] After the substrate S is attached to the electrostatic chuck
300 by electrostatic force, the power generating and transmitting
device 342 of the drive device 340 may rotate the lift screw 341 to
move the lift screw 341 upwards. While the lift screw 341 is
gradually moved upwards, the load measuring apparatus 310, which
may be coupled to the lower surface of the lift plate 332 of the
lift device 330, may transmit the pressure of the lift screw 341 to
the lift plate 332.
[0092] The lift plate 332, which may receive the pressure of the
lift screw 341 through the load measuring apparatus 310, may move
upwards under the guidance of the guide bars 334 in a state in
which it is parallel to the substrate S, and thus, move the lift
pins 331 upwards. Then, the lift pins 331 may pass through the
stage 351 and the chuck 300 and come into contact with the
substrate S.
[0093] At this time, the sensor(s) 302 may detect the contact
between the lift pins 331 and the substrate S and transmit this to
the load measuring apparatus 310. Subsequently, the load measuring
device 311 of the load measuring apparatus 310 may measure a second
load W2, which may be the load of the lift device 330 when the
substrate S is detached from the chuck 300, and store the measured
value in the memory 312, in step S350.
[0094] Before the substrate S is detached from the electrostatic
chuck 300, because the substrate S maintains the state in which it
is attached to the electrostatic chuck 300 by adsorbing force,
electrostatic force is applied in a direction opposite the
direction in which the lift pins 331 are moved upwards. Therefore,
the second load W2 is the load of the lift device 330, including
the load resulting from electrostatic force.
[0095] Further, the first load W1 and the second load W2
respectively correspond to the pressure of the lift screw 341 which
is applied to the lift device 330 before the lift device 330 pushes
the substrate S attached to the chuck 300, and the pressure of the
lift screw 341 which is applied to the lift device 330 in the state
in which electrostatic force is applied between the substrate S and
the chuck 300.
[0096] Therefore, the electrostatic force may be calculated using
the following equation.
P=W2-W1
[0097] Here, P denotes the electrostatic force of the electrostatic
chuck 300, W1 denotes a first load, which may be the load of the
lift device 330 before it pushes the substrate S attached to the
electrostatic chuck 300, and W2 denotes a second load, which may be
the load of the lift device 330 when the substrate S is detached
from the electrostatic chuck 300.
[0098] Thereafter, the arithmetic device 313 of the load measuring
apparatus 310 may calculate the difference between the first load
W1 and the second load W2 and determine the electrostatic force P
of the chuck 300, in step S360. The display 314 may display the
electrostatic force P.
[0099] In the electrostatic force measuring method according to
this embodiment, the electrostatic force P required for attaching a
substrate to an electrostatic chuck may be precisely measured, so
that the electrostatic force P may be evenly applied to the
electrostatic chuck in a semiconductor manufacturing process. As
such, in the electrostatic force measuring apparatus according to
this embodiment and the method of measuring electrostatic force, an
exact value of electrostatic force may be determined from the
difference between the first load of the lift device 330 before it
contacts the substrate S, attached to the electrostatic chuck 300,
and the second load of the lift device 330 when the substrate S is
detached from the electrostatic chuck 300. Therefore, the exact
value of electrostatic force may be applied to an electrostatic
chuck in a semiconductor manufacturing process, thus preventing a
substrate from being cracked or damaged in the semiconductor
manufacturing process, and enhancing the efficiency of the
semiconductor manufacturing process.
[0100] As described above, in an apparatus for measuring
electrostatic force and a method of measuring electrostatic force
using the apparatus according to embodiments disclosed herein,
electrostatic force may be precisely measured, such that whether
the measured electrostatic force value is a value appropriate for
conducting a semiconductor manufacturing process may be determined.
Therefore, an error in applying electrostatic force during the
semiconductor manufacturing process may be prevented, so that, when
the substrate is detached from an electrostatic chuck in the
semiconductor manufacturing process, the substrate may be prevented
from being deformed or cracked.
[0101] Embodiments disclosed herein provide an apparatus and method
for measuring electrostatic force through the calculation of force
applied to a substrate when the substrate is released from
electrostatic force, preventing the occurrence of an error in the
determination of electrostatic force in a semiconductor
manufacturing process, preventing the substrate from being
damaged.
[0102] An embodiment disclosed herein provides an apparatus for
measuring electrostatic force that includes a power supply unit or
device that applies a voltage to an electrostatic chuck, a
separating unit or devices that detaches a substrate, which is
attached to the electrostatic chuck supplied with the voltage, from
the electrostatic chuck, a variable load applying unit or device
connected to the separating unit, the variable load applying unit
operating the separating unit by changing a load of the variable
load applying unit, and a control unit or device that measures both
a load of the variable load applying unit, when the substrate is
attached to the separating unit, and a load of the variable load
applying unit, when the measurement substrate is detached from the
electrostatic chuck, and to calculate electrostatic force. The
separating unit may include a vacuum unit or device that creates a
vacuum to adsorb the measurement substrate, and a drive unit or
device that transmits power to move the vacuum unit.
[0103] Further, the vacuum unit may include a vacuum suction member
to adsorb the substrate, and a vacuum pump to draw air through the
vacuum suction member. The vacuum suction member may comprise one
selected from a vacuum suction pad and a vacuum suction pin.
[0104] The apparatus may further include a sensing unit or device
provided in the electrostatic chuck to detect whether the substrate
is attached to or detached from the electrostatic chuck. The
sensing unit may comprise one selected from a pressure sensor or a
magnetic sensor. The separating unit may include a lift unit or
device that detaches the measurement substrate, which may be
attached to the electrostatic chuck, from the electrostatic chuck,
and a drive unit or device that transmits drive force to move the
lift unit.
[0105] In addition, the lift unit may include a lift pin to contact
the substrate to transmit the force, applied from the drive unit,
to the substrate. A contact detecting sensor may be provided in a
part of the lift pin that contacts the substrate to detect whether
the lift pin contacts the substrate. The drive unit may include a
power transmitting member, which may connect the variable load
applying unit to the lift unit to transmit the drive force to the
lift unit.
[0106] Another embodiment disclosed herein provides an apparatus
for measuring electrostatic force that includes a chuck to seat a
substrate thereon, a separating unit or device comprising a lift
unit or device that detaches a substrate from the electrostatic
chuck and a drive unit or device that operates the lift unit, and a
load measuring device that measures a first load of the lift unit
before the separating unit compresses the substrate and measures a
second load of the lift unit when the substrate is detached from
the chuck, the load measuring device calculating an electrostatic
force of the chuck using a difference value between the first load
and the second load. The apparatus may further include a support
unit or device that supports the chuck, and may have a stage onto
which the chuck is placed, and a support frame to support the
stage.
[0107] The lift unit may include a plurality of lift pins to
vertically move through the chuck and a lift plate supporting the
lift pins. A sensor may be provided in the support unit to detect
whether the substrate is attached to or detached from the chuck and
whether the lift pins come into contact with the substrate.
[0108] In addition, a guide bar may be provided on the stage such
that the lift plate may be slidably coupled to the guide bar, thus
guiding vertical movement of the lift unit. The drive unit may
include a lift screw supporting the lift plate, the lift screw
being vertically moved, and a power generating and transmitting
unit or device that rotates the lift screw.
[0109] The load measuring device may include a load measuring unit
or device that measures the first load and the second load, a
memory unit or device that stores the first load value and the
second load value therein, an arithmetic unit or device that
calculates a difference value between the first load value and the
second load value, which may be stored in the memory unit, and a
display unit or device that displays the difference value.
[0110] Further, another embodiment disclosed herein provides a
method of measuring electrostatic force that includes placing a
substrate onto an electrostatic chuck, applying a voltage to the
electrostatic chuck to charge the electrostatic chuck and attaching
the substrate to the electrostatic chuck using electrostatic force
generated by the voltage, moving a vacuum unit or device upwards by
changing a load of a variable load applying unit or device that
detaches the substrate from the electrostatic chuck, measuring a
load of the variable load applying unit when the substrate is
detached from the electrostatic chuck by the variable load applying
unit, and calculating a difference value between the load of the
variable load applying unit, measured when the substrate is
detached from the electrostatic chuck, and a load of the variable
load applying unit, measured when a vacuum unit or device adsorbs
and holds the substrate, and determining an electrostatic force
using the difference value.
[0111] Another embodiment disclosed herein provides a method of
measuring electrostatic force that includes placing a substrate
onto an electrostatic chuck, applying a voltage to the
electrostatic chuck to charge the electrostatic chuck and attaching
the substrate to the electrostatic chuck using an electrostatic
force generated by the voltage, moving a lift unit or device
upwards to detach the substrate from the electrostatic chuck and
measuring a load of a variable load applying unit or device when
the lift unit comes into contact with the substrate, measuring a
load of the variable load applying unit when the substrate is
detached from the electrostatic chuck by the upward movement of the
lift unit, and calculating a difference value between the load of
the variable load applying unit, measured when the lift unit comes
into contact with the substrate, and the load of the variable load
applying unit, measured when the substrate is detached from the
electrostatic chuck, and determining an electrostatic force using
the difference value.
[0112] Another embodiment disclosed herein provides a method of
measuring electrostatic force that includes measuring a first load
of a lift unit or device before the lift unit compresses a
substrate attached to a chuck, and measuring a second load of the
lift unit when the substrate is detached from the chuck.
[0113] The method may further include attaching the substrate to
the chuck using an electrostatic force generated by applying power
to the chuck, before the first measuring is conducted. In the
second measuring, a difference value between the first load of the
lift unit before the lift unit compresses the substrate attached to
the chuck and the second load of the lift unit when the substrate
is detached from the chuck may be calculated, and an electrostatic
force may be determined using the difference value.
[0114] Any reference in this specification to "one embodiment," "an
embodiment," "example embodiment," etc., means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
invention. The appearances of such phrases in various places in the
specification are not necessarily all referring to the same
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with any embodiment, it
is submitted that it is within the purview of one skilled in the
art to affect such feature, structure, or characteristic in
connection with other ones of the embodiments.
[0115] Although embodiments have been described with reference to a
number of illustrative embodiments thereof, it should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this disclosure. More particularly, various
variations and modifications are possible in the component parts
and/or arrangements of the subject combination arrangement within
the scope of the disclosure, the drawings and the appended claims.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
* * * * *