JPH0330990B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for positioning a disk having a linear notch in a portion of its periphery, such as a semiconductor wafer, and more particularly to a wafer positioning apparatus suitable for an exposure apparatus for IC manufacturing. .

(Background of the Invention) In recent years, exposure equipment for IC manufacturing has been used in a so-called step process, in which a circuit pattern image of a mask or reticle is projected onto a wafer in a reduced size, exposed and transferred in one shot, and then the wafer is moved by a certain amount. BACKGROUND ART AND-REPEAT type reduction projection exposure apparatuses (steppers) are becoming popular.

Such a stepper for optical lithography typically includes a stage that moves a wafer two-dimensionally at high speed. By the way, the wafer needs to be positioned and placed on this stage within a predetermined error range.

This type of positioning is commonly referred to as an orientation flat because it uses a direct notch or flat in the wafer to orient the wafer in one direction. A conventionally known orientation flat (hereinafter referred to as an orientation flat) device is, for example, disclosed in Japanese Patent Application Laid-Open No. 1986-
As disclosed in No. 18713, it is installed in a wafer transfer device, and is designed to transfer a wafer that has been pre-aligned using a flat onto a stage using a transfer arm, slider, etc. Ta.

However, when a wafer is placed on a stage and vacuum suctioned, the positioning accuracy deteriorates due to the flatness of the wafer, causing a problem that the positioning accuracy is not within the positioning error range. Therefore, it has been considered to pre-align the wafer transferred onto the stage again using a flat.
Specifically, the wafer is pre-aligned by pressing the flat of the wafer against a reference member provided on a wafer holder (wafer chuck) on a stage.

That is, the accuracy of positioning the wafer with respect to the stage is improved by performing pre-alignment on the wafer/transfer device side and performing pre-alignment again on the wafer holder side of the stage, so-called two-time pre-alignment.

By the way, one chip (or one shot exposure area) of an IC is rarely a square area due to circuit pattern design, but is often a rectangular area. Therefore, it becomes necessary to determine the long sides and short sides of the rectangle according to the crystal structure of the wafer. However, with the above-mentioned device, it is only possible to always orient the flat in one direction (0° direction).
As the exposure area becomes more rectangular, wafer flatness
In response to the request for orientation in two directions, 0° and 90°, there was a drawback that positioning was impossible.

(Objective of the Invention) Therefore, the present invention solves these drawbacks, and in addition to positioning in the normal exposure direction (hereinafter referred to as 0° orientation flat), positioning at a position where the wafer is rotated 90° from there (hereinafter referred to as 0° orientation flat). The purpose of the present invention is to obtain a positioning device that also enables a 90° orientation flat.

(Summary of the Invention) Therefore, the present invention provides a holder for placing a disc-shaped wafer having a flat portion of a predetermined length around the periphery;
comprising a positioning reference member erected on the periphery of the holder, and a pressing member that presses the wafer placed on the holder in the direction of the reference member,
A device for positioning a wafer on a holder includes a turntable 2 that rotates the wafer (W ₁ , W ₂ ) in a horizontal plane, and a rotating wafer (W ₁ ;
Flat detection unit 40, PD, 1 that photoelectrically detects the periphery of _W2 ) to detect the center position of flat part F.
10 to 113, _G1 , and this flat detection section 40,
PD, 110-113, detection signal I ₁ from G ₁ ;
Based on the signal 119 for switching whether to orient the flat portion F in either the 0° direction or the 90° direction,
A pre-alignment means including control units 100, 114 to 118 for controlling the rotation stop position of the turntable 2, and a wafer _W2 positioned in the 0° direction or the 90° direction by the pre-alignment means. Conveying means 10, 12, 1 for conveying onto the holder 20
4 and 22, and the reference member is located at the position of the wafer _W2 that has been transported.
A first reference member consisting of three rollers 25a, 25b, and 25c arranged side by side facing the flat part F in the 0° direction, and a first reference member made up of three rollers 25a, 25b, and 25c arranged in parallel opposite to the flat part F in the 90° direction of the transferred wafer. three rollers 2
6a, 26b, and 26c, one roller 25a at the center of each of the first reference member and the second reference member; two rollers 25b, 25c; 26b, on both sides; The line connecting 26c is spaced apart from the outside of the holder 20 by a predetermined gap δ, and the predetermined gap δ is
The circumferential portion of W ₂ contacts the central roller 25a; 26a among the three rollers arranged in parallel, and the two rollers on both sides 25b, 25c; 26b, 26
The key point is to set the amount so that there is no contact with c.

(Description of Examples) Examples of the present invention will be described below based on the drawings.

FIG. 1 is a plan view of the overall configuration of an example of a wafer transfer device of a projection exposure apparatus, which is an embodiment of the present invention.

FIG. 2 is a partial sectional view of a pre-alignment mechanism provided in the wafer transfer device, and FIG. 3 is a plan view of a wafer holder on a stage.

The apparatus shown in FIGS. 1 and 2 is basically constructed in the same manner as in Japanese Patent Application Laid-open No. 18713/1983.

In FIG. 1, 1a to 1f are conveyor belts for the wafer W, 2 is an annular table, and the conveyor belts 1a to 1f are
The wafer W transported by 1f is placed on the upper surface of the circular table 2. circular table 2
is rotatable in the clockwise direction shown by the arrow, and is also capable of vacuum suction or airflow to the placed wafer W, which is the opposite of suction.
When the wafer W ₁ indicated by the broken line is located above the table 2 by belt conveyance, the belts 1a to 1f
At the same time, the feeding of belts 1c to 1f is stopped.
is lowered, and the wafer _W1 is transferred onto the table 2. Centering arms 4a to 4g are installed so as to be able to reciprocate in the radial direction while maintaining the same distance from the rotation center _O1 of the table 2.
The centering arms 4a to 4g abut and hold the periphery of the wafer _W1 that has been air-flowed by the table 2, and align the center of the wafer _W1 with the rotation center _O1 of the table 2. The center of wafer W ₁ and
If the center O ₁ matches, at this stage table 2
performs a vacuum suction operation to suction the wafer _W1 onto the table 2. After this, centering arm 4a
~4g will be evacuated.

Now, as shown in FIG. 2, the table 2 has an annular groove 2c formed in the mounting surface 2b, and air flow and vacuum suction are performed through this groove 2c.

Furthermore, a toothed portion 2a is carved on the lower circumferential end of the table 2. The tooth portion 2a meshes with a gear 5a rotated by a motor 5, and the rotation speed (rotation angle) of the motor 5 is controlled by a pulse generator 7 (hereinafter referred to as
PG7) is detected by the number of pulses.
Also, in order to detect the flat F of wafer _W1 ,
As shown in Fig. 1, the photoelectric element PD is provided at the 0° orientation flat position where the linear direction of the flat F _coincides with the X direction, and as shown in Fig. A floodlight 40 is provided that illuminates the end portion with a parallel beam of light.

Now, the table 2 is rotated by the motor 5,
When the flat F of wafer _W1 is optically detected by the photoelectric element PD, it is found that if the orientation is 0°, the flat F is detected.
The table 2 stops at a predetermined position where the rollers 6a and 6b are aligned in the X direction. In this position, the table 2 has airflow again, and the arm 8 is the center.
_{The wafer W 1 is} moved toward the roller 6a,
6b and 6d. At this time, an orientation flat (rough) is established, and the wafer is positioned so that the flat F is parallel to the x direction, as shown by the dashed line _W2 .

The center of wafer W ₂ positioned in this way is
It coincides with the center O ₂ of center up 10. Here, the center O ₁ and the center O ₂ are eccentric by the amount of movement of the wafer due to the pressure of the arm 8 .

Now, these rollers 6a and 6b come into contact with the flat F of the wafer during the 0° orientation and flat, and the roller 6d
comes into contact with one place on the circumferential end. On the other hand, during the 90° orientation/flating, as the arm 8 moves, the rollers 6c and 6d come into contact with the flat F of the wafer, and the roller 6b comes into contact with one location on the circumferential edge of the wafer.

Now, due to the increase in center up 10, the wafer
W ₂ is passed from table 2 to center up 10. At this time, the wafer is
W ₂ is adsorbed. 14 is a slider arm, which is equipped with suction holes 14a and 14b at its tip.
It reciprocates along the guide rail 12 in the y direction. This slider arm 14 moves below the wafer _W2 lifted by the center up 10, evacuates the suction holes 14a and 14b, and suctions the wafer _W2 . At this time, center up 10
releases the adsorption by the intake hole 10a and descends.
As a result, wafer W ₂ is attached to slider arm 1.
It will be handed over to 4. Then slider arm 14
The wafer W ₂ is placed in the wafer holder 20 on the stage.
Move in the y direction to pass to the side.

The wafer holder 20 is provided on a two-dimensional moving stage of an exposure apparatus (not shown in FIG. 1),
By moving this stage, the wafer can be exposed in a step-and-repeat manner at the projection exposure position. Note that 21 is a mounting surface of the wafer holder, and 22 is a center up that is installed at the center of the wafer holder 20 so as to be movable up and down.

When the stage has an orientation of 0°, the mounting surface 21 of the wafer holder 20 is at the transfer position, that is, the center O ₃ of the mounting surface 21 and the center of the center up 10.
The wafer W ₂ is fed in such a way that the line connecting the wafers W 2 is almost coincident with (parallel to) the y-axis direction. At this position, the center up 22 rises, releases the adsorption of the suction holes 14a and 14b, and removes the wafer W ₂ . Center up 22
hand it over to After that, the slider arm 14 retreats, and the center up _{2 which is adsorbing the wafer W 2}
2 is lowered, and the wafer W ₂ is placed on the mounting surface 21. Note that the mounting surface 21 is capable of vacuum suction and air flow. Thereafter, the stage moves to a position directly below a projection lens (not shown) (exposure position).

By the way, in such an apparatus, the flat F of the wafer W ₂ is moved to a predetermined position at each point in time when the wafer is transferred from the center up 10 to the slider arm 14 and when the wafer is transferred from the slider arm 14 to the center up 22. It is required that the wafer be transferred without shifting from the wafer holder 20 and placed accurately on the wafer holder 20.

FIG. 3 is a plan view showing a main part of an apparatus for repositioning a wafer on a stage in order to satisfy such requirements, and is a preferred embodiment of the present invention.

In FIG. 3, the mounting surface 2 of the wafer holder 20 is
1 is formed with a spiral groove 21a as disclosed in Japanese Patent Application Laid-Open No. 57-85235. This groove 21
In a, on the peripheral side of the center O ₃ of the mounting surface 21,
In addition, suction holes 21b for vacuum suction are provided at three locations that divide the mounting surface 21 into three equal parts. Also,
Airflow exhaust holes 21c are provided in the groove 21a at three locations in the radial direction from the center _O3 of the mounting surface 21.

Now, when the wafer conveyed by the 0° orientation flat is placed on the placing surface 21, three rotatable rollers 25a, 25b, 25c arranged in line along the flat F are moved. to face.

On the other hand, when the wafer transported by the 90° orientation flat is placed on the mounting surface 21, the flat F
is approximately from the three rollers 25a, 25b, 25c.
It faces three rotatable rollers 26a, 26b, and 26c arranged in parallel at positions rotated by 90 degrees.

Further, a plunger 23 for pressing the periphery of the wafer is provided on the wafer holder 20, and a pressing member 23 is provided to press the periphery of the wafer.
4 moves towards the center _O3 .
At this time, the pressing force of the wafer is such that the wafer is
The pressing direction is determined so as to work both in the direction of a to 25c and in the direction of rollers 26a to 26c.

Furthermore, among these six rollers, when a wafer with an orientation of 0° is pressed by the pressing member 24,
The flat F of the wafer contacts the rollers 25b and 25c, and one location on the circumference of the wafer contacts the roller 26a.

In the case of a wafer with an orientation of 90 degrees, the rollers 26b and 26c contact the flat F, and the roller 25a contacts the wafer at one location on its circumference. In this way, the positioning of the wafer on the mounting surface 21 is also
Ori-flat wafers in 0° and 90° directions are always subjected to three rollers.

As mentioned above, the position of the flat F of the wafer is on the rollers 25a to 25c side and the rollers 26a to 26a side.
6c side, so that part of the spiral groove 21a is made discontinuous to match the shape of the flat F.
The adhesion of the wafer to the mounting surface 21 is enhanced.
Note that the flats F of wafers W ₁ and W ₂ in FIGS. 1 and 2 represent what is called a main flat, and some wafers have a sub-flat with a smaller notch depth than the main flat. Sometimes it is formed.

Next, in an embodiment of the present invention, a specific control system of the above-mentioned wafer transfer device will be explained based on FIG.

All sequences of this device are controlled by the microcomputer 100, including vacuum suction of the table 2, air flow operation, vacuum suction and vertical movement of the center ups 10 and 22, movement of the slider arm 14, and movement of the centering arms 4a to 4g. Operation, movement of arm 8, operation of plunger 23, belt 1
All information is exchanged via the bus line 120 from the I/O port of the microcomputer 100 for driving a to 1h and moving the stage two-dimensionally.

In the following explanation, information on the I/O port of the microcomputer 100 is actually exchanged with an external device via a predetermined interface, but for convenience, the I/O port will be explained as a representative.

In FIG. 4, the photoelectric output of the photoelectric element PD is amplified by an amplifier 110, and its output signal E ₁
is the following bandpass filter 111 (hereinafter referred to as BPF)
111. ). and
The output signal _E2 of the BPF 111 is sent to a first detection circuit 112 for detecting only the main flat with a large amount of notch among the notches on the wafer, and for detecting the positions of the centers of the notches of the main flat and subflat. and the second detection circuit 113. The output signals E ₃ and E ₄ of the first detection circuit 112 and the second detection circuit 113 are generated as digitized binary signals, and the signals E ₃ and E ₄ are sent to the I of the microcomputer 100 via the AND circuit G ₁ . Of the /O ports, input to port _I1 , which performs manual operation.

On the other hand, the drive and sudden stop of the motor 5 are controlled by two transistors (hereinafter referred to as Tf) 17 and 118 connected in series. Therefore, Tr,
Each of the bases 117 and 118 is a port that performs an output operation among the I/O ports of the microcomputer 100.
Input digital signals from _P3 and _P4 . In addition, motor 5 is a pnp Tr117 with the emitter connected to the power supply.
Power is supplied from the collector by only the current being conductive. Then, the sudden stop of the motor 5 short-circuits the terminals of the motor 5 by making only the npn Tr 118 connected in parallel to the terminals of the motor 5 conductive. This is done using a so-called dynamic brake.
The power supply voltage supplied to the motor 5 can be switched between a high voltage HV and a low voltage LV by a switch 116, and the rotation speed of the motor 5 can be selected in two stages. This switch 116 is a microcomputer 100
Among the I/O ports, the port that performs output operation
Digital signal from P ₂ , e.g. logical value "H",
Switching operation is performed by "L".

Further, the pulse signal of PG 7 connected to the rotating shaft of motor 5 is sent to counter 11 via switch 115.
Enter 4.

The counter 114 counts the number of pulses of this pulse signal and sends the counted value to port D _S of the I/O ports of the microcomputer 100. Note that the counter 114 can be preset to an arbitrary digital value from the microcomputer 100 via the port _DS . In addition, the switch 115 switches whether or not to input the pulse signal of PG7 to the counter 114 by inputting a digital signal from port _P1 , which performs an output operation among the I/O ports of the microcomputer 100, and a logical value of "H", " Controlled by "L". Further, the switch 119 is used to switch between the 0° orientation and flat and the 90° orientation and flat.

When the switch 119 is switched to the terminal a side, it is assumed that "H" is applied to the port _I2 that performs the input operation of the microcomputer 100, and the 0° ori
Hula is specified. When the terminal is on the b side, it is assumed that "L" is applied to port _I2 , and the orientation is 90°.
Hula is specified.

Next, the overall operation of this apparatus will be explained with reference to FIGS. 5 to 10.

FIG. 5 is a flowchart of the microcomputer 100 for executing 0° ori-flat and 90° ori-flat with the wafer transfer apparatus shown in FIGS. 1 and 2. FIG. 6 is a time chart of each signal in FIG. 4, and shows the case of 0° ori-flat.

Now, with the wafer centered as shown in FIG. 1, vacuum suction of the table 2 is performed. Then, in step 200 of _FIG.
“L” to port _P2 , “H” to port _P4 , “L” to port P4
is output to initialize switch 115 to OFF, switch 116 to high voltage HV side, and Tr 118 to OFF. In the next step 201, the microcomputer 100 reads port _I2 and switches the switch 119.
If is in "H" (released) state, proceed to step 202;
If the state is "L" (grounded), the process advances to step 203. Step 202 sets the data preset in the counter 114 for the 0° orientation and flattening equal to the number of pulses generated from PG7 during one rotation (360°) of table 2, and outputs it from port D _S. It is.

Also, in step 203, data to be preset in the counter 114 for the 90° orientation/flat is set.
The number of pulses is made equal to the number of pulses generated from PG7 during 3/4 rotation (270 degrees) of table 2, and is output from port D _S.

Next, in step 204, the microcomputer 100 outputs "L" to the port _P3 , makes the Tr 117 conductive, and applies the high voltage HV to the motor 5. As a result, the motor 5 starts rotating at high speed.

Now, as wafer W ₂ rotates, amplifier 11
The zero signal _E1 changes as shown in FIG. In FIG. 6, the horizontal axis is time and the vertical axis is electric potential. When the motor 5 starts rotating at high speed at time t ₀ and the center of the subflat of the wafer is located directly above the photoelectric element PD, the amplifier 110 generates a peak P _S at which the signal E ₁ reaches its maximum value at time t ₁ . do.
As the wafer continues to rotate further, at time _t2 when the center of the main flat is located directly above the photoelectric element PD, the amplifier 110 generates a peak PM at which the signal _E1 reaches its maximum value. The amount of notch on the main flat is larger than that on the subflat, so the peak as shown in Figure 6
The peak value of P _M is larger than the peak P _S.
Therefore, by distinguishing and detecting only the peak PM, the main flats of the wafer can be accurately detected. However, if eccentricity occurs in the wafer due to rotation, the signal E ₁ will not be generated neatly as shown in Figure 6, and the signal E ₁ generated at the circumference of the wafer will be
The DC potential of will fluctuate with eccentricity, and in the worst case, the relationship between the peak values of peaks P _S and _PM may become reversed. Taking this point into consideration, this device uses a centering operation to remove the eccentricity of the wafer, so that one photoelectric element PD
is sufficient to enable discrimination and detection of flatness.

Then, the signal E ₁ as described above is differentiated by the BPF 11 to obtain the signal E ₂ as shown in FIG.
When P _S occurs in the signal E ₁ , a simple harmonic transient response wave T _S occurs in the signal E ₂ , and when a peak P _M occurs, a transient response wave T _M with larger oscillation than the transient response wave T _S occurs. arise. The vibration centers of the response waves T _S and _TM correspond to times t ₁ and t ₂ of the peak values of the peaks P _S and _PM .

This signal E ₂ is input to the first detection circuit 112,
It compares it with a predetermined threshold level ±Vr, detects only the response wave T _M with large vibration, and generates a signal E ₃ that generates a pulse D ₁ before and after time t ₂ . Furthermore, the signal E ₂ is transmitted to the second detection circuit 113.
A signal E ₄ that generates pulses D ₂ and _{D 3 at} times t ₁ and t ₂ is obtained by inputting a signal E ₄ to occurs.

Now, the microcomputer 100 goes to step 205 in Figure 5.
Then, from time t ₀ when motor 5 starts rotating, port I ₁
Load.

And at time t ₂ , pulse D ₁ and pulse D ₃
When the AND is obtained, that is, when the center of the main flat is located directly above the photoelectric element PD while the wafer W ₂ is rotating, the microcomputer 100 detects I ₁ = "H" and proceeds to step 206. , outputs logic "H" to port _P1 and closes the switch 115,
The port D _S is set to input operation and reading of the digital value of the counter 114 is started. Then, as shown in FIG. 7, from time _t2 , the pulse signal E _P of PG7 is input to the counter 114, and the counter 114 sequentially subtracts the pulse from the preset digital value as described above. After time _t2 , the microcomputer 100 determines the position of the main flat based only on the count value of the counter 114.

To explain in detail, the microcontroller 100 is a step
When it is detected in step 207 that the count value has reached a predetermined value n approaching _zero , for example at time _t3 in FIG. is switched to the low voltage LV side to rotate the motor 5 at low speed. That is, the rotation of the wafer is decelerated before the wafer completes one rotation or 3/4 rotation from time _t2 to prevent the influence of overrun due to inertia. Furthermore, in this state, microcontroller 1
00, it is determined in step 209 whether or not the count value of the counter 114 has become zero, and when it is zero at time _t4 , the process proceeds to step 210, and outputs logic "H" from both ports _P3 and _P4 . Make Tr117 non-conductive,
Switch Tr118 to conduction state.

As a result, the back electromotive force of the motor 5 is short-circuited by the Tr 118, and the rotation of the wafer is abruptly stopped.

Therefore, the main flat F of wafer _W2 is the photoelectric element.
From time t ₂ , which is located directly above PD and coincides with the linear notch direction of main flat F, wafer W ₂
stops after making exactly one rotation (360°) or 3/4 rotation (270°).

Now, the main flat F of wafer _W2 is in the 0° direction or
When facing in a 90° direction, the microcomputer 100 is on the table 2.
Release vacuum suction and switch to air flow.
Then, the arm 8 presses the wafer W ₂ to bring the wafer W ₂ into contact with the rollers 6 a to 6 d. Therefore
Positioning on the wafer transfer device in the 0° direction and 90° direction will be explained based on FIGS. 7 and 8.

Positioning in the 0° direction is performed as shown in FIG. In Figure 7, arm 8 presses wafer _W2 ,
In the positioned state, the main flat F is in contact with rollers 6a and 6b arranged on a straight line in the x direction, and one place on the circumference of the wafer _W2 is in contact with the roller 6d. As a result, the notch direction of the main flat F of _W2 is positioned to coincide with the x direction. In addition, when positioning in the 0° direction is achieved,
Center of wafer W ₂ O ₄ and center of center up 10
It is set to match O ₂ .

On the other hand, positioning in the 90° direction is performed as shown in FIG.

FIG. 8 shows a state in which the wafer W ₂ is positioned in the 90° direction, and the main flat F is in contact with rollers 6c and 6d arranged on a straight line in the y direction, and the wafer W 2 is positioned in the 90° direction.
One place on the circumference of W ₂ contacts the roller 6d. Thereby, the wafer _W2 is positioned so that the notch direction of the main flat F coincides with the y direction.
In this case, the center O ₄ of the wafer W ₂ is positioned offset from the center O ₂ of the center up 10 .

In addition, in order to improve positioning accuracy and reproducibility, the distance between rollers 6a and 6b and the distance between rollers 6c and 6
It is desirable that the distance d be set so that two points of the flat F that are as far apart as possible come into contact with each other, that is, set to be slightly shorter than the length of the flat F.

As described above, on the wafer transfer device, the two rollers 6a and 6b are placed on a straight line in the x direction as the abutting portions of the first reference member, and the rollers 6a and 6b are placed on a straight line in the y direction perpendicular to the x direction. Two rollers 6c and 6d are provided as abutting portions of the second reference member, and when positioning the wafer so that the linear direction of the flat F coincides with the x direction, the flat F contacts the roller 66.
a, 6b, and one place on the circumference of the wafer contacts the roller 6d. When positioning the flat F by aligning the linear direction with the y direction, the flat F contacts the rollers 6c, 6d and The wafer is positioned in two directions by arranging four rollers 6a to 6d such that one point on the circumference of the wafer contacts the roller 6d.

In addition, in FIG. 7 (FIG. 8), the rollers 6a, 6
With b, 6c, and 6d in contact with flat F,
One location on the circumference of the wafer _W2 contacts the rollers 6d and 6b, but may also contact the rollers 6c and 6a depending on the arrangement of each roller.

Now, the wafer W ₂ which has been pre-aligned on the table 2 is placed at the center up 1 as mentioned above.
0 and is transferred to the wafer holder 20 on the stage by the movement of the slider arm 14. First, in the case of an orientation flat of 0°, a second pre-alignment is performed as shown in Figure 9. When the wafer W ₂ is placed on the mounting surface 21, air flows through the exhaust hole 21c shown in FIG. 3, and the wafer W ₂ floats slightly. Then, the plunger 23 operates and the pressing member 24 presses the peripheral edge of the wafer _W2 . As a result, as shown in FIG. 9, the main flat of wafer W ₂ comes into contact with rollers 25b and 25c, and one place on the circumference of wafer W ₂ comes into contact with roller 26a.
comes into contact with. At this time, it is desirable that the rollers 25b and 25c contact the main flat at two locations as far apart as possible, and the roller 26a should contact the wafer _W2.
To define the radial direction of the wafer W 2, the center of the wafer W ₂ O ₄
, and the straight line l ₁ parallel to the main flat F and the wafer
It is desirable that the contact be made at a position where the circumferences of the wafer W ₂ intersect, that is, at the position of the maximum diameter of the wafer W ₂ . By arranging the three rollers 25b, 25c, and 26a in this manner, the positioning of the wafer _W2 with respect to the holder 20 becomes extremely accurate. Further, at this time, the roller 25a is at a position retracted by δ from the main flat F in the y direction, and the rollers 26b, 26
c is located at a distance of δ from the roller 26a in the x direction. Therefore, when the wafer W ₂ is positioned by the pressure of the pressing member 24, the rollers 25a,
26b and 26c never come into contact with the wafer _W2 .

Now, in the case of a 90° angle, it is done as shown in Figure 10. At this time, the main flat F of the wafer _W2 comes into contact with the rollers 26b and 26c, and one place on the circumference of the wafer _W2 comes into contact with the roller 25a. In this case, similar to the conditions for the 0° orientation flat, the rollers 26b and 26c abut on the main flat F at two locations as far apart as possible, and the roller 25a passes through the center _O4 of the wafer _W2 , It comes into contact with wafer W ₂ on a straight line l ₁ parallel to .

As mentioned above, the six rollers 25a to 25c,
Of 26a to 26c, three rollers contact the wafer W ₂ under the same conditions for each of the 0° and 90° orientation flats, so there is no difference in positioning accuracy in both directions. , extremely reproducible positioning is achieved.

Now, when the pressing member 24 presses the wafer W ₂ and the 90° orientation/flat is achieved,
Vacuum suction is performed through the intake hole 21b shown in FIG. 3, and air flow through the exhaust hole 21c is stopped. When suction completion is confirmed based on the vacuum sensor during vacuum suction, the operation of the plunger 23 is stopped and the pressing member 24 is retracted from the wafer _W2 . Thus wafer W ₂ is 2
After the second pre-alignment is achieved, the wafer is flattened and fixed on the mounting surface 21 of the wafer holder 20.

Furthermore, if the exhaust hole 21c is configured to not only exhaust gas for airflow, but also take in air in the same way as the intake hole 21b, the exhaust hole 21c can be used to
Since vacuum is applied at only one location, the wafer is attracted more uniformly and its flatness is improved.

As can be seen from FIGS. 9 and 10, the center O ₄ of the wafer W ₂ relative to the center O ₃ of the wafer holder 20 is slightly different between 0° and 90°. It's off. Therefore, the transfer position from the slider arm 14 to the wafer holder 20 will be slightly shifted between the 0° orientation and flatness and the 90° orientation and flatness.

This control is performed by the microcomputer 100 reading port _I2 and making slight corrections when moving the stage to the delivery position. this center ₄
As shown in Figures 7 and 8, the deviation is due to the first pre-
The same thing occurs during alignment, so
The stage is moved so as to correct the position at which the wafer is transferred to the stage, including the deviation at this time.

In this embodiment, the wafer is placed on the table 2 in the wafer transfer device by rollers 6a, 6b, 6.
After contacting the rollers 25a to 25c and 6d, the wafer holder 20 on the stage is moved again.
It was positioned by making it contact with 6a to 26c. However, if it is desired to shorten the total time until the completion of positioning on the wafer holder 20, the step of bringing the wafer into contact with the rollers 6a, 6b, 6c, and 6d may be omitted. In this embodiment, after the wafer is transferred to the table 2, a centering operation is performed to align the center of the wafer with the rotation center of the table 2, so there is no eccentricity due to rotation, and the flat F is placed on the table 2. This is because accurate positioning is possible.

Specifically, when the table 2 is rotated and the flat F is located directly above the photoelectric element PD, the rotation of the table 2 is stopped. Then, vacuum suction of the center up 10 is started, the center up 10 is raised, the vacuum suction of the table 2 is released, and the wafer is transferred to the setter up 10. Thereafter, it is only necessary to transport it to the stage in the same manner as in this embodiment.

Now, in the above embodiment, the pressing member 24 presses the wafer from one direction at an angle of 45 degrees.
This force was used to position the wafer in the x and y directions. However, the pressure in the x and y directions is
They may be performed independently as shown in Figure 1.

In FIG. 11, a swing member 30 that presses the wafer W ₂ in the x direction and a swing member 31 that presses the wafer W 2 in the y direction are provided.

Now, when the wafer W ₂ with an orientation and flat orientation of 0° is placed, the swinging member 31 swings, and the rotatably mounted roller 30a presses the wafer W ₂ toward the roller 26a. do. After that, the swinging member 31
The roller 31a is attached to be able to swing and rotate freely.
presses the wafer W ₂ toward the rollers 25b and 25c. At this time, the roller 30a is at the center of the wafer _W2.
The wafer W 2 passes through O ₄ and is separated from the flat F by an angle θ with respect to the straight line l ₁ parallel to _the flat F.
and generates a pressing force toward the center _O4 .

By doing this, when the wafer W 2 is sandwiched between the roller 30a and the roller 26a, the wafer W ₂ can be rotated, and the wafer W ₂ can be rotated without floating toward the swinging member 31. 25b,2
It tries to come into contact with the 5c side. Then, since the roller 31a presses the wafer _W2 , even if the flat F is slightly tilted, the rollers 25b and 2
5c, accurate positioning is achieved.

The same applies to the case of a 90° orientation/flat wafer, in which case the center of the wafer W ₂ becomes the center O ₄ ′, and the straight line l ₁ becomes the straight line l ₁ ′.

First, the swinging member 31 swings to sandwich the wafer W ₂ between the rollers 25a and 31a, and then the swinging member 30 swings to move the flat F of the wafer W ₂ onto the rollers 26b and 26c. bring it into contact.

Therefore, the roller 31a generates a pressing force toward the center O ₄ ' at a position separated from the flat F by an angle θ with respect to the straight line l ₁ '.

According to the above embodiment, the floating wafer W ₂ can be reliably pressed, and more stable positioning can be achieved than when pressing from a diagonal direction of 45 degrees.

Although not directly related to the present invention, the contact portion of the reference member may be formed as a mere protrusion instead of a roller. For example, as shown in Figure 12, the first
The reference member 40 and the second reference member 41 are arranged along the x direction and the y direction, respectively. The first reference member 40 has a roller 25 shown in FIGS. 3, 9, 10, and 11.
Projections 40a, 4 instead of a, 25b, 25c
0b, 40c, and the second reference member 41 has a protrusion 4 instead of the rollers 26a, 26b, 26c.
1a, 41b, and 41c are provided. A line segment connecting the protrusions 40b and 40c coincides with the x direction, and the protrusion 40
A is formed to be displaced outward of the wafer holder 20 by δ from the line segment. Further, the line segment connecting the protrusions 41b and 41c coincides with the y direction, and the protrusion 41
A is formed to be displaced outward of the wafer holder 20 by δ from the line segment a.

(Effects of the Invention) As described above, according to the present invention, there are two directions: 0° direction and 90° direction.
It can be used to position the wafer in both directions, and since the three rollers only come into contact with the wafer in both positions, when the wafer is pressed, the wafer rotates easily and is positioned with extremely high accuracy.

Furthermore, since the first and second reference members that come into contact with the wafer are provided only at two locations, one in the 0° direction and the other in the 90° direction, the position of the wafer upon completion of positioning in the 0° direction and the 90° There is only a slight deviation from the position of the wafer when positioning is completed in both directions, and there is no need to make a special shape for the mounting surface of the wafer holder in consideration of subsequent vacuum suction, and the wafer positioned in both directions can be Another advantage is that it can be fixed securely. Furthermore, since the first and second reference members are only provided in the 0° direction and the 90° direction, there is no spatial interference on the circumference of the wafer or in other directions, and the pressing member The degree of freedom in wafer placement is increased, and wafer loading and unloading
This also has the effect of increasing the degree of freedom in the directionality of the load.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the overall configuration of a projection exposure apparatus using the apparatus according to the present invention, showing an embodiment of the present invention for positioning on a wafer transfer device, and FIG. 2 is a partial cross-section of the wafer transfer device. 3 is a plan view of a wafer holder showing a more preferable embodiment of the present invention, FIG. 4 is a circuit block diagram of a control circuit for positioning a wafer in a wafer transfer device, and FIG. 5 is a circuit block diagram of the control circuit. Figure 6 is a flowchart of the microcomputer used in the control circuit, and Figure 6 is a time chart showing the state of each signal in the control circuit. FIGS. 9 and 10 are diagrams for explaining the positioning operation of the apparatus according to the embodiment of the invention, and FIGS. 1
FIG. 2 is a plan view of a positioning device according to another embodiment of the present invention. [Explanation of symbols of main parts] 2...Rotary table, 6a, 6b, 25a, 25
b, 25c...roller as a contact portion of the first reference member, 6c, 6d, 26a, 26d, 26c...second
A roller as a contact portion of the reference member, 8...arm,
20... Wafer holder, 24... Pressing member, 30, 3
1... Swinging member, 40... First reference member, 41... Second
Reference member.

Claims (1)

[Scope of Claims] 1. A holder on which a disc-shaped wafer is placed having a flat portion of a predetermined length on the periphery, a reference member for positioning provided upright on the periphery of the holder, and a wafer placed on the holder. A press member that presses a placed wafer in the direction of the reference member, and an apparatus for positioning the wafer on the holder, comprising: a turntable that rotates the wafer in a horizontal plane; a flat detection section that photoelectrically detects the central position of the flat section; a detection signal from the flat detection section; and switching between the orientation of the flat section in the 0° direction or the 90° direction. a control section for controlling a rotation stop position of the turntable based on a signal; and a control section for controlling a rotation stop position of the turntable based on a signal; a conveying means for conveying the wafer onto the holder, and the reference member includes a first reference member consisting of three rollers arranged in parallel to face a flat portion of the conveyed wafer in the 0° direction; a second reference member consisting of three rollers disposed in parallel to face the flat portion of the wafer in the 90° direction;
The two rollers are provided at a predetermined distance from the outside of the holder from a line connecting the two rollers on both sides, and the predetermined gap is such that the circumferential portion of the wafer is located at the center of the three rollers arranged side by side. 1. A wafer positioning device, characterized in that the amount is determined such that it makes contact with one roller and does not come into contact with two rollers on both sides. 2 3 of each of the first reference member and the second reference member
When the line segment connecting the two rollers on both sides of the two rollers is the chord of a circle centered approximately at the center of the holder, the constant gap is such that the perpendicular bisector of the chord is the arc of the circle. 2. The device according to claim 1, wherein the length is smaller than the length of the device until it intersects.