JPH11111819A - Wafer fixing method and light exposing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit a wafer fixing method in which a wafer is hard to be bent by a foreign matter and local focus position deviations are hard to occur, by a method wherein only a marginal part of a wafer is brought into contact with an light exposing pedestal of a light exposing device and the marginal part of the wafer is fixed to the light exposing pedestal. SOLUTION: A light exposing pedestal 1 is a circular pedestal having the substantially same plane shape as a wafer W, and a marginal part of the light exposing pedestal 1 is a standing member of a height about several mm to form a ring type chuck 2. A plurality of attracting holes 2a for attracting and holding the wafer W are punched ranging over the entire periphery at an upper end of the ring type chuck 2 when the wafer W is brought into contact therewith. A first pump 21 is operated by a controller 23, and the wafer W is attracted by an attraction hole 2a, whereby the wafer W is fixed onto the light exposing pedestal 1. As a result, only the marginal part of the wafer W comes into contact with the ring type chuck 2 of the light exposing pedestal 1, and the other portion is held into non-contact with the light exposing pedestal l.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing a wafer on an exposure table in an exposure apparatus and an exposure apparatus, and more particularly to a method for fixing a wafer so that the wafer surface does not bend during exposure. The present invention relates to a wafer fixing method and an exposure apparatus.

[0002]

2. Description of the Related Art An exposure table of a conventional exposure apparatus has a structure as shown in FIGS. FIG. 7A is a plan view of the exposure table of the first conventional example, and FIG. 7B is a side sectional view of the exposure table with the wafer mounted thereon in the conventional example. FIG. 8A is a plan view of an exposure table of a second conventional example, and FIG. 8B is a side sectional view of the exposure table with a wafer mounted thereon.

As shown in FIG. 7A, an exposure table 51 of a first conventional example is a circular table having a plane having substantially the same shape as a wafer. The exposure table 51 has a ring-shaped chuck 52 formed at a higher peripheral portion and a lower portion at a central portion to form a space.
54 are formed. In this space 54, a large number of support protrusions 53 having the same height as the ring-type chuck 52 are arranged in a matrix.

For this reason, as shown in FIG. 7B, when the wafer W is placed on the exposure table 51, the wafer W
Is supported by the ring-shaped chuck 52 and a large number of support projections 53, and the space 54 is an airtight space sandwiched between the wafer W and the exposure table 51. The circular wafer W is
One end is omitted due to the necessity of positioning, and a notch portion called an orientation flat (hereinafter, referred to as an orientation flat) is formed here.
The flat portion 52a is also formed to conform to this shape.

With the wafer W placed at a predetermined position on the exposure table 51 as described above, the space 54 is
When the air is removed, the pressure in the space 54 becomes low, and the wafer W can be suction-fixed on the exposure table 51.

The exposure table 61 of the second conventional example shown in FIGS. 8 (a) and 8 (b) has a ring-shaped chuck 62 formed with a higher peripheral portion and a central portion, similarly to the first conventional example. Is lowered to form a space 64. Also, a flat portion 62a for matching the orientation flat of the wafer W is formed in the same manner.

In the exposure table of this conventional example, a concentric support stripe 63 is provided instead of the support projection 53 of the first conventional example. When the wafer W is mounted, the ring type chuck 62 and the support circle are provided. Article 63 supports this.

[0008] Similarly, when the air in the space 64 is evacuated using the suction pump 55, the wafer W is suction-fixed on the exposure table 61 by the suction force. In the conventional exposure table 61,
Since the space 64 is divided into a plurality of rooms by each of the supporting ridges 63, the airtightness can be maintained in each room, and the wafer can be more securely fixed.

[0009]

SUMMARY OF THE INVENTION The above-described first and second embodiments
A photoresist is applied to the wafer W fixed on the exposure tables 51 and 61 of the conventional example, and a mask pattern is transferred by a lithography process. The mask pattern used here has become extremely fine with the recent high integration of semiconductor elements.

For this reason, it comes into contact with the back surface of the wafer W,
Ring-type chucks 52, 62, or support protrusion 53, support circle 63
If foreign matter (dust) of the order of 10 μm or more is present on the upper surface of the wafer, the foreign matter will distort the wafer W and cause swelling on the surface on which the mask pattern is transferred.
Then, since the swelling shifts the focal position of the pattern image from the projection optical system of the exposure apparatus, the pattern image may not be partially formed on the surface of the wafer W and the resolution may be deteriorated. For this reason, these conventional exposure apparatuses have a problem that a pattern defect may be caused in a lithography process, and a large number of product defects may be caused.

It is an object of the present invention to provide a method for fixing a wafer in a semiconductor exposure process and an exposure apparatus for performing the method, wherein the wafer is hardly distorted by foreign matter,
An object of the present invention is to provide a wafer fixing method and an exposure apparatus which are unlikely to cause a curved focal position shift. Another object of the present invention is to propose a wafer fixing device and an exposure device capable of positively correcting a warp of a wafer when the warp occurs and improving the resolution at the time of mask pattern transfer. Is to do.

[0012]

In order to solve the above-mentioned problems, a method for fixing a wafer according to the present invention comprises contacting only a peripheral portion of a wafer with an exposure table of an exposure apparatus, and attaching the peripheral portion of the wafer to the exposure table. The above-mentioned subject is solved by fixing to.

[0013] Also, in the method of fixing a wafer, a pressure adjusting chamber is provided between a central portion of the wafer and the exposure table, and the pressure is adjusted by applying a positive pressure or a negative pressure to the pressure adjusting chamber. Alternatively, a configuration may be employed in which the deflection generated at the center of the wafer is corrected.

Further, as an apparatus embodying the above method,
The exposure table can be configured to have an annular chuck that contacts only the peripheral portion of the wafer and fixes the peripheral portion of the wafer.

Furthermore, the space surrounded by the annular chuck is
By providing a pressure adjustment chamber that corrects the deflection generated at the center of the wafer by adjusting the pressure by applying a positive pressure or a negative pressure, an exposure apparatus that can positively correct the deflection generated on the wafer can be configured. it can.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a connecting device according to the present invention will be described with reference to FIGS. FIG. 1 is a structural view of an exposure apparatus according to the present embodiment, FIG. 2 is a plan view of an exposure table of the exposure apparatus, FIG. 3 is an explanatory view of the operation of the exposure table of the exposure apparatus, and FIG. It is a flowchart.

The exposure apparatus A according to the present embodiment includes an exposure table 1 on which a wafer W is mounted and fixed, and a laser or L
An inspection device 10 for measuring the flatness of the surface of the wafer W by aiming with ED light or the like. The exposure apparatus A is a composite apparatus for transferring a mask pattern onto the surface of the wafer W on the exposure table 1, which includes a mask holding unit, a projection unit, and the like. Not shown.

As shown in FIGS. 1 and 2, the exposure table 1
Diameter 15 to 30 having substantially the same planar shape as wafer W
It is a circular table of about cm. The periphery of the exposure table 1 is several meters high
The ring-shaped chuck 2, which is an annular chuck, is formed as standing pieces of about m. A plurality of suction holes 2a for sucking and holding the wafer W when the wafer W comes into contact with the upper end of the ring type chuck 2 are formed in the entire circumference. The ring type chuck 2 is provided with a flat portion 2b so as to coincide with the orientation flat of the wafer W.
a is also provided along the flat portion 2b. The ring type chuck 2 is formed of a titanium alloy or ceramic, and the upper surface thereof is
It is finished horizontally in order to increase the adhesion with the.

Along the lower end of the ring type chuck 2,
A bottom portion 3 is formed on the exposure table 1, and a pressure adjustment chamber 4 is formed in this portion. A plurality of pressure adjusting holes 3a are formed in the bottom 3 radially.

At the upper end of the ring type chuck 2, a plurality of protruding elevating pins 5 are attached at equal angles (three in the present embodiment).
Is raised, a gap S can be formed between the wafer W and the ring-type chuck 2 when the wafer W is placed.

A first pump 21 having only a suction function is provided outside the exposure table 1, and is connected to a suction hole 2a of the ring type chuck 2 through a ventilation path 21a. Further, the second pump 22 capable of switching between pressurization and suction is provided.
Are also provided in parallel, and are connected to the pressure adjusting hole 3a of the bottom portion 3 through the ventilation path 22a.

The inspection apparatus 10 on the exposure table 1 includes a transmitter 11 for irradiating the surface of the wafer W with a laser or LED light and a sensor 12 for receiving the laser light reflected from the surface of the wafer W.
The cross measurement is performed to measure the flatness of the surface of the wafer W. The sensor 12 is connected to the control device 23,
Based on the measurement result of 12, the controller 23 controls the second pump
22 is controlled. The control device 23 is also connected to the first pump 21, and the first pump 21 is sequence-controlled together with the lifting pins 5 and the wafer W transfer means (not shown).

Next, the operation of the exposure apparatus of this embodiment will be described with reference to FIGS. First, the wafer W is lowered onto the exposure table 1 with the lift pins 5 raised, and the wafer W is supported by the lift pins 5 (see FIG. 1). At this time, the back surface of the wafer W is gripped by the suction-type hand (not shown) by the suction-type hand (not shown) and is positioned at a predetermined position. Can enter and evacuate without interference. Thereafter, the elevating pins 5 are lowered, and the elevating pins 5 are placed on the exposure table 1 so that the peripheral edge of the wafer W is brought into contact with the upper end of the ring type chuck 2.

In this state, as shown in FIG.
The controller 23 activates the first pump 21 to suck the wafer W through the suction hole 2a, thereby fixing the wafer W on the exposure table 1. As a result, the upper surface of the pressure adjustment chamber 4 of the exposure table 1 is closed by the wafer W, and the upper end of the ring-type chuck 2 and the peripheral edge of the wafer W are in close contact over the entire periphery. Becomes

Since the central portion of the wafer W is not supported, the wafer W may be bent by its own weight, and may be bent by heat treatment or the like in a process leading to this exposure step. Therefore, as shown in FIGS. 3B and 3C, the bending (hereinafter referred to as bend) is detected by the operation of the inspection device 10. Specifically, laser light or the like is emitted from a transmitter 11 such as a laser or LED light, and the reflected laser light or the like is received by the sensor 12, and the flatness of the surface of the wafer W is scanned. This scanning is performed on the surface of the wafer W in a cross shape from two orthogonal directions, and if a bend is generated, and if a vent is generated, it is detected whether the surface is convex or concave, and the amount of distortion is also detected. Grasp at the same time.

If the vent is generated below the surface of the wafer W, that is, if it is concave, FIG.
As shown in (b), the control device 23 operates the second pump 22 in the pressurizing mode to apply a positive pressure. The air sent by the second pump 22 increases the internal pressure of the pressure adjustment chamber 4 of the exposure table 1, which raises the central portion of the wafer W upward to correct the dent. The measurement by the inspection device 10 and the scanning of the wafer are also performed during the operation of the second pump 22, and the control device 23 stops the depression when the dent of the wafer W enters the range of the allowable flatness.

When the vent is formed above the surface of the wafer W, that is, when the vent is convex, the control device 23 sets the second pump 22 to the suction mode as shown in FIG. And apply a negative pressure. As a result, the swelling is corrected by lowering the internal pressure of the pressure adjustment chamber 4 and lowering the central portion of the wafer W. Similarly,
The stop timing of the second pump 22 is determined by the measurement performed by the inspection device 10 in parallel.

The operation of the exposure table 1 described above will be described again as a control flow of the control device 23 with reference to FIG.

First, the wafer W is placed on the ring type chuck 2 by using a suction hand (not shown) (S1).
Next, the bend amount (bending amount) is measured based on this information by performing cross-focus measurement on the surface of the wafer W using the inspection device 10 (S2) (S3).

Range of bend amount (tolerance) that causes no problem in transferring a mask pattern in a lithography process
Is set in advance, and it is determined whether the measured amount is within the tolerance (within the allowable range) (S4). If the measured value is outside the tolerance, the bending shape of the wafer W is determined based on whether the bend amount is plus (convex) or minus (concave) (S5).

Based on the above results, if it is determined that the shape of the wafer W is convex and bulges, the second pump 22 is operated in the suction mode, the pressure in the pressure adjustment chamber 4 is reduced, and the wafer W The shape is corrected by pulling in the central part of (S6). When the shape of the wafer W is concave and it is determined that the wafer W is concave, the second pump 22 is operated in the pressurizing mode, the pressure in the pressure adjustment chamber 4 is increased, and the central portion of the wafer W is pressed upward. To correct the shape (S7).

When each correction operation is completed, the bend amount is measured again by using the inspection device 10 (S8), and it is determined whether the tolerance is within the tolerance (S9). If it is out of tolerance in spite of the above correction work, the flow returns to S5 again to measure the bend amount, and the above work is repeated thereafter.

If the judgment result in S4 and the judgment result in S9 are within the tolerance, the sequence shifts to the next sequence control for performing a wafer alignment operation, an exposure operation and the like (S10). Then, the wafer W is carried out to complete a series of operations (S11).

As described above, according to the exposure apparatus of the present embodiment, only the peripheral portion of the wafer W comes into contact with the ring-type chuck 2 of the exposure table 1, and the other portions are not in contact with the exposure table 1. The contact state is maintained. For this reason, even if foreign matter such as dust is present in the exposure work space, it is possible to prevent the foreign matter from being trapped between the back surface of the wafer W and the exposure table 1 and deteriorating the flatness of the surface of the wafer W. it can.

In addition, in the exposure apparatus of the present embodiment, since the bend of the wafer W can be more positively corrected by using the pressure adjustment chamber, the flatness of the surface of the wafer W can be improved. By improving the resolution of the mask pattern, the yield of semiconductor elements to be produced can be improved.

A second embodiment and a third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is an explanatory view of a clamp type exposure table according to the second embodiment, and FIG. 6 is an explanatory view of a clamp type exposure table according to the third embodiment.
The exposure tables 31 and 41 shown in these figures are the exposure tables 1 of the first embodiment in which the wafer W is fixed by suction through the suction holes 2a.
Unlike this, it has a structure for fixing the wafer W using a clamp.

The exposure apparatus in which the exposure table of these embodiments is incorporated is similar to the first embodiment in that the wafer W
Inspection equipment for inspecting the flatness of the surface, lifting pins for avoiding interference of the suction type hand for transferring the wafer W, pressurization /
It has a pump that can switch suction, a control device that controls a series of operations, and the like.

FIG. 5A shows a plan view of an exposure table with a wafer mounted thereon according to the second embodiment.
b) shows a side sectional view of the exposure table. Exposure table of this embodiment
Reference numeral 31 denotes a pressure adjusting chamber 34 having a ring-type chuck 32 and a bottom 33.
Is composed. A plurality of pressure adjusting holes 33a are formed in the bottom portion 33. The pressure adjusting holes 33a are connected to a pump (corresponding to the second pump of the first embodiment) having a pressure / suction switching mechanism (not shown). Have been.

On the outside of the ring-type chuck 32, a plurality of (four in this case) claws 35
Is arranged. The claw-type clamp 35 has an L-shaped cross section, a horizontal piece 35a partially overlaps the ring-type chuck 32, and has a mechanism capable of moving up and down. By lowering the claw-type clamp 35, the peripheral edge of the wafer W can be sandwiched between the upper end of the ring-type chuck 32 and fixed.

According to the exposure apparatus having the exposure table 31 of the present embodiment, the wafer W can be compared with the exposure apparatus of the first embodiment.
(First pump in the first embodiment) and an air passage are not required, so that the structure is advantageously simplified. Further, since it is not necessary to open a suction hole on the upper surface of the ring-type chuck 32, the thickness of the ring-type chuck 32 can be reduced, and the wafer W
The contact area with the exposure table 1 can be further reduced, and the influence of foreign matter can be made extremely small.

Next, the exposure table 41 of the third embodiment will be described with reference to FIG. FIG. 3A is a plan view of the exposure table of the embodiment with a wafer mounted thereon, and FIG.
Shows a side sectional view of the exposure table. The exposure table 41 has a ring-shaped chuck 42 and a bottom 43 and forms a pressure adjustment chamber 44, similarly to the exposure table 31 of the second embodiment.
A plurality of pressure adjusting holes 43a are formed in the bottom 43, and the pressure adjusting holes 43a are connected to a pump having a pressure / suction switching mechanism (not shown).

In the exposure table 41, a ring clamp 45 is arranged along the outer periphery of the ring chuck.
The ring-shaped clamp 45 is an annular body having an L-shaped cross section. The inner diameter of the horizontal piece 45a is smaller than that of the ring-shaped chuck 42, and a part thereof overlaps the ring-shaped chuck 42. By lowering the ring-shaped clamp 45, the entire periphery of the peripheral portion of the wafer W can be sandwiched between the upper end of the ring-shaped chuck 42.

According to the exposure apparatus having the exposure table 41 of the present embodiment, the ring-shaped clamp 45 is fixed to the ring-shaped chuck 42 over the entire periphery of the wafer W.
It has the effect of further improving the airtightness of 44.

[0044]

As described above, according to the present invention,
In a method of fixing a wafer performed in a semiconductor manufacturing process, and an exposure apparatus that executes the method, a wafer is fixed to an exposure table by contacting only a peripheral portion of the wafer, thereby preventing foreign matter such as dust from entering between the two. be able to.
For this reason, in the wafer exposure step, the wafer can be hardly distorted by foreign matter, and a wafer fixing method and an exposure apparatus that are unlikely to cause a curved focal position shift can be provided.

Further, in the wafer fixing method and the exposure apparatus of the present invention, a positive pressure or a negative pressure is applied to a pressure adjusting chamber formed between the wafer and the exposure table.
The deflection at the time of mask pattern transfer can be further improved by positively correcting the deflection of the wafer.

[Brief description of the drawings]

FIG. 1 is a structural diagram of an exposure apparatus according to a first embodiment.

FIG. 2 is a plan view of an exposure table of the exposure apparatus according to the first embodiment.

FIG. 3 is an explanatory diagram of an operation of the exposure apparatus according to the first embodiment.

FIG. 4 is a control flowchart of the exposure apparatus according to the first embodiment.

FIG. 5 is an explanatory diagram of an exposure table of an exposure apparatus according to a second embodiment.

FIG. 6 is an explanatory diagram of an exposure table of an exposure apparatus according to a third embodiment.

FIG. 7 is an explanatory view of an exposure table of an exposure apparatus according to a first conventional example.

FIG. 8 is an explanatory diagram of an exposure table of an exposure apparatus according to a second conventional example.

[Explanation of symbols]

 A: Exposure device W: Wafer 1: Exposure table 2: Ring type chuck (annular chuck) 2a: Suction hole 2b: Flat portion 3: Bottom portion 3a: Pressure adjustment hole 4: Pressure adjustment chamber 5: Lifting pin 10: Inspection device 11 … Transmitter of laser light or LED light 12… Sensor 21… First pump 21a… Ventilation passage 22… Second pump 22a… Ventilation passage 23… Control device 31… Exposure table 32… Ring type chuck (annular chuck) 33… Bottom 33a… Pressure adjustment hole 34… Pressure adjustment chamber 35… Claw type clamp 35a… Horizontal piece 41… Exposure table 42… Ring type chuck (annular chuck) 43… Bottom 43a… Pressure adjustment hole 44… Pressure adjustment chamber 45… Ring type Clamp 45a ... Horizontal piece 51 ... Exposure table 52 ... Ring type chuck 52a ... Flat part 53 ... Support projection 54 ... Space 55 ... Suction pump 61 ... Exposure table 62 ... Ring type chuck 62a ... Flat part 63 ... Support circle Article 64… space

Claims (10)

[Claims] 1. A method for fixing a wafer to an exposure apparatus, wherein only a peripheral portion of the wafer is brought into contact with an exposure table of the exposure apparatus, and the peripheral section of the wafer is fixed to the exposure table. Wafer fixing method. 2. The method for fixing a wafer according to claim 1, wherein a space between a central portion of the wafer and the exposure table is a pressure adjustment chamber, and a positive pressure or a negative pressure is applied to the pressure adjustment chamber. A method of fixing a wafer, comprising correcting a deflection generated at a central portion of the wafer by adjusting a pressure. 3. The wafer fixing method according to claim 2, wherein the fixing of the peripheral portion of the wafer to the exposure table is performed by a vacuum chuck method. 4. The wafer fixing method according to claim 2, wherein the fixing of the peripheral portion of the wafer to the exposure table is performed by a clamping method. 5. The method of fixing a wafer according to claim 2, wherein the correction of the deflection of the wafer by adjusting the pressure of the pressure adjustment chamber is performed by measuring the focus of the surface of the wafer in a cross shape and determining the state of the deflection. A method for fixing a wafer, wherein the method is performed based on the result obtained. 6. An exposure apparatus for holding a wafer on an exposure table and transferring an electronic circuit pattern onto a surface of the wafer by using a mask, wherein the exposure table contacts only a peripheral portion of the wafer, and An exposure apparatus comprising an annular chuck for fixing a part. 7. The exposure apparatus according to claim 6, wherein the space surrounded by the annular chuck is adjusted by applying a positive pressure or a negative pressure to reduce a deflection generated at a central portion of the wafer. An exposure apparatus comprising a pressure adjustment chamber for correction. 8. An exposure apparatus according to claim 6, wherein said annular chuck has a suction hole opened at an upper end of said annular chuck, and fixes a peripheral portion of said wafer by a vacuum chuck method using said suction hole. An exposure apparatus, comprising: 9. An exposure apparatus according to claim 6, wherein said annular chuck has a clamp which can be raised and lowered above said annular chuck, and said clamp sandwiches said wafer between said clamp and said annular chuck. An exposure apparatus, wherein a peripheral portion of the wafer is fixed by means of: 10. An exposure apparatus according to claim 6, wherein:
Correction of the deflection of the wafer by adjusting the pressure of the pressure adjustment chamber, focus measurement of the wafer surface in a cross,
An exposure apparatus, wherein the exposure is performed based on a result of a control device that determines a state of bending.