JPS6063928A - Contact exposure device - Google Patents

Abstract

PURPOSE:To enable the accurate control of the amount of bending of a mask exposure by a method wherein the titled device is equipped with a position control mechanism to make the mask abut against or close to a plate object to be processed and an atmospheric pressure control mechanism to control the difference in atmospheric pressures between both surfaces. CONSTITUTION:A wafer 33 is held by adsorption by means of pipes 35 and 37 and a wafer chuck 32 drawn in vacuum V. Next, the mask 11 and a mask holer 10 are fixed by adsorption in vacuum V via pipes 8 and 9. A wafer 33 on the chuck 32 is made to abut against the mask 11 by control of the supply pressure of an air chamber 25 by setting the initial amount of rise by means of a transfer amount setter 49. A spherical base 31 is fixed to a receiver plate 30 by evacuation of the air chamber 45 after parallel leading. While the target position of the mask and the wafer is confirmed through an alignment scope 44, the mask pattern and the wafer pattern are brought to agreement by transfer of alignment tables 12, 13, and 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for aligning a photomask suitable for use, for example, in a mask exposure process when performing a selective photoetching process in the semiconductor industry, and particularly relates to an apparatus for aligning a photomask, which is suitable for use in a mask exposure process when performing a selective photoetching process in the semiconductor industry. Relates to devices for contacting and separating.

For example, an exposure apparatus for optically transferring a mask pattern is disclosed in Japanese Patent Application No. 4973/1983.

Conventionally, as shown in, for example, U.S. Pat. A one-piece mask alignment apparatus has been proposed that allows the wafer to be brought into close contact with the lower surface of the mask. In this type of equipment, care must be taken not to cause damage such as scratches to the mask, which has a pattern such as the circuit pattern of a semiconductor integrated circuit, and also to prevent damage to the wafer. , it is required to press the wafer against the mask, and in the arrangement for the final step of exposure after alignment between the wafer and the mask,
Accurate adhesion is required for pressure contact between the wafer and the mask. Especially in masks with fine patterns of interconnect lines and elements, such as circuit patterns of large-scale integrated circuit devices, inaccurate adhesion deteriorates the resolution of the fine patterns and, as a result, reduces the yield rate of wafers. cause it to happen.

In conventionally known devices of this type, precise control of the bending of the mask is not taken into account when the wafer and mask are pressed into contact during exposure. As a result, exposure was performed without the wafer and mask coming into precise contact with each other in the same plane.As a result, the resolution of the wafer after exposure deteriorated, resulting in a decrease in the quality of wafers, or the completion of exposure on the wafer. This has the disadvantage of causing errors in pattern dimensions.

SUMMARY OF THE INVENTION Therefore, a general object of the present invention is to provide a device for bringing a mask and a wafer into close contact for precisely controlling the amount of bending of a mask during exposure.1.Other objects of the present invention An object of the present invention is to provide a close contact device that prevents the relative positions of the mask and wafer, which have been aligned in advance, from shifting when the mask and wafer are brought into close contact with each other.

Still another object of the present invention is to provide an adhesion device that can shorten the adhesion time when adhering a mask and a mask, and easily separate them after adhesion.

In addition, another object of the present invention is to provide a device for detecting the degree of closeness or pressure contact between a mask and a mask, which is applicable to a mask alignment device according to the above-mentioned purpose. It is an object of the present invention to provide a device that can accurately detect the degree of pressure contact between two objects, such as for use in detecting the degree of pressure contact between a mask of an alignment device and a wet cloth.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 shows a mask alignment apparatus according to the invention. In the figure, the mask alignment device 1 has the following configuration.

A scan table consisting of a scan Y table 3 movable in the plane Y direction and a scan X table 4 movable in the plane X direction is provided on the fixed base 2. In addition, a support 5 is provided on the outer periphery of the scan X table 4.
are fixed, and an upper base 6 is fixed on these columns 5. The upper base 6 has a circular space in the center, and a donut-shaped mask holder adsorption/fixing plate 7 with flat upper and lower surfaces is fitted and fixed in this circular space.

The mask holder suction and fixing plate 7 is provided with pipes 8 and 9 for supplying vacuum pressure, and the mask holder 10 and the mask 1 placed on the mask holder suction and fixing plate 7 are provided with pipes 8 and 9 for supplying vacuum pressure.
1 is fixed by suction, respectively. Also,
A frame-shaped alignment Y table 12 and an alignment X table 13 are sequentially stacked on the inner upper surface of the scan X table 4 to form an alignment table that is movable in the plane X and Y directions. Further, a flange 14 is provided at the inner lower part of the alignment X table 13, and a donut-shaped retainer 15 is fixed on the flange 14. An alignment θ table 17 that moves in the θ direction of the plane is attached. Also, this alignment θ
Steel balls 18 are disposed on the top surface of the table 17, and the top surface of these steel balls 18 is held down by a doughnut-shaped holding plate 19 fixed to the top of the alignment X table 13.

Further, inside the alignment θ table 17, a cylindrical main body 20 of a vertical movement mechanism is fixed.

A block 22 having a leaf spring portion 21 on its periphery is fixed to the lower and upper surfaces of the cylindrical body 20, respectively.

Further, the central portions of these blocks 22 are fixed by a tubular connecting rod 23. Further, a dish-shaped lid 24 is fixed to the lower surface of the lower block 22, and an air chamber 25 is formed between the lower block 22 and the lid 24.

A displacement detector 26 made of an electric micrometer or the like is mounted inside the connecting rod 23, and its detection end passes through the block 22 on the lower surface and faces the inner wall surface of the lid body 24. Further, a seal 27 is arranged to surround the detection end. Further, compressed air is introduced into the air chamber 25 through a pipe 28. When compressed air A is sent into the air chamber 25 through the pipes 28 and 29, the peripheral plate 21 of each block 22 is elastically deformed, and the piston device consisting of the block 22 and the cylindrical body 23 moves upward. By the way, as explained later,
The air pressure in the air chamber 40 and the amount of displacement of the leaf spring section 21 are proportional to each other. Utilizing the rapid change in the constant, it is possible to detect the position where the mask and wafer slightly touch, and to precisely control the distance between the mask and the mask.

On the other hand, on the upper block 22 there is a plate 30 with a spherical floor support.
is fixed, and a wafer chuck 32 for fixing the Uni-No is attached to the plate 30 of this spherical floor support via a spherical seat 31. The upper surface of this Uni-No-1 chuck 32 has a pipe 35 connected to the suction hole 34 provided around the Uni-No-1 chuck, and a suction hole 36 provided on the central portion of the Uni-No-1 chuck. It has other pipes 37 in series, and these pipes supply vacuum pressure to the mask 33 or supply N2 gas.

In the spherical floor support, inert gas (Nt gas) or vacuum pressure is supplied to the space 45 between the plate 30 and the spherical seat 31 through an air guide hole (not shown).

In order to ensure close contact between the wafer 33 and the mask 11, a support plate 38 is fixed to the outer wall of the upper block 22, and a bellows 39 is attached to this support plate 38. Block 22゜Mask holder suction fixing plate 7. An air chamber 40 surrounded by the mask J1 is formed, and one pipe 41 for supplying vacuum pressure or gas to the air chamber 40 is provided on the mask holder suction and fixing plate 7.

Further, a wafer unloader table 43 having an air bearing mechanism 42 is attached to the upper surface of one side of the upper base 6.

On the other hand, an alignment scope 44 is disposed above the mask holder 10, and this alignment scope 4
4, the mask and wafer are aligned. Further, an exposure mechanism (not shown) is disposed above the mask holder 10, and serves as a trap so that exposure can be performed after the mask and wafer are brought into close contact with each other.

In such an alignment device according to the present invention,
It features the following configuration.

First, the semiconductor wafer 33 on the wafer chuck and the mask 1
A device is installed to constantly detect the state of pressure contact with 1 or the degree of proximity between the two.

As will be made clear from the overall operation of the alignment apparatus described below, the mask and wafer are pressed into contact with each other several times during the step before alignment between the mask and the wafer, and during the exposure step after alignment. It is required that the two be moved close to each other within a predetermined distance relationship. According to the present invention, in the above configuration, if air A is sent into the air chamber 25 through the pipe 28 and the pressure is controlled, the wafer chuck 32 can be moved up and down together with the shaft 23, and the amount of vertical movement thereof is the displacement detector 26
Detected by The inventors have noted that in this case, the relationship between the air supply pressure P and the displacement output E obtained from the output terminal 45b of the detector 26 is proportional as shown in FIG. That is, within the limits of elastic deformation that causes stress in the spring 21, the supply pressure P, which is the driving force, and the displacement output E, which is the movement l of the Unino chuck 32, have a linear relationship as shown by the straight line S1, and E-KP. Become. Here, K is a proportional g number, which is expressed by - Δe/Δ, which is an increment Δ1 of the supply pressure P and an increment Δ8 of the displacement output E. By the way, this proportionality constant remains constant until the Unino chuck 32 approaches the mask 11 and is then subjected to a resistance force, but when it receives a resistance force, it changes. That is, the displacement output is E as shown in FIG. Assuming that the wafer chuck 32 (or the unit 33 on top of it) comes into pressure contact with the mask 11 and experiences resistance, if the air supply pressure P is increased further, the supply pressure P and displacement output will change. The relationship with E is as shown by straight line S2, and the slope, that is, the constant of proportionality, is different from that of straight line SI. Therefore, it is proposed to accurately control the amount of vertical movement of the wafer chuck based on the mask position.

Such a control system will be explained with reference to FIG.

The pressure of air A supplied from the air pressure source 46 to the valves 29 and 28 is controlled by an air pressure control device 47. The control device 47 is a precision pressure reducing valve driven and operated by a pulse motor, for example, and controls the supply pressure P of the air A according to the control signal CA from the control signal generator 50. A detector 48 is provided for detecting the supply pressure P, and the output P of this detector is input to a control signal generator 50.

In addition, the displacement output E from the displacement amount detector 26 and the movement i signal M from the sea urchin-pachuck movement amount setting device 49 are added to the control signal generator 50. Control signal generator 5
0 are these input signals P, E.

Based on M, a control signal CA is generated which enables the control operations previously described with respect to FIG.

As shown in FIG. 3, the control signal generating device 50 is provided with a ratio calculation circuit 51 that calculates the ratio between the supply pressure P and the displacement amount E and generates an output according to the ratio. The coincidence circuit 52 compares the output of the ratio calculation circuit 51 with the input corresponding to the proportionality constant K of the straight line S2 set in advance, and sets the hold circuit 53 when the two match. This is to hold the displacement output E of. The hold circuit 53 holds the displacement output E in accordance with the set output of the matching circuit 52 to generate a control target value signal T, and sends this to one input terminal of the adder circuit 54. The other input terminal of the adder circuit 54 is given a movement amount signal M from the movement amount setter 49, and the amount of movement T
, M are added algebraically. The difference calculation circuit 55, which receives the addition output N at one input terminal and the displacement output E at the other input terminal, sends a control output CA corresponding to the difference between the human forces N and H to the pneumatic pressure control device 47. 1-ru.

In the apparatus shown in FIG. 1, when it is assumed that the Unino chuck 32 is initially in the holding position by only the leaf spring 21, the output E of the displacement detector 26 takes the minimum level. Therefore, by operating the movement amount setter 49, the movement amount signal M is applied to the addition circuit 54 in order to raise the edger sock 32 once to a position where it contacts or presses against the mask 11. In this case, the adder circuit 54 does not receive the target value signal T of the hold circuit 53 because it has not yet been established. Therefore, the set movement amount signal M is directly sent as an addition signal N to the difference calculation circuit 55, where the difference is calculated with the displacement output E, and a control signal output CA is generated according to the difference. This difference becomes smaller as the displacement output E becomes equal to the set value of the movement amount signal M. When the wafer chuck 32 comes into contact with the mask 11, the control target value is established as follows. That is, as described above, the circuit 51 that calculates the ratio between the supply pressure P and the displacement output E sends an output corresponding to the proportionality constant of the straight line S to the coincidence circuit when the wafer 33 and the mask 11 come into contact with each other. Therefore, in the matching circuit 52, a match is established between the received signal at this time and the proportional constant input set in advance, and therefore, the hold circuit 53 holds the value of the displacement output E at that time. The hold output T at this time is a target value signal and indicates the exact height position of the mask 11. Note that at the same time as this target value is established, the movement amount setter is reset and the control system is operated to follow the newly established target value, thereby maintaining the soft contact state in which the wafer 33 is in contact with the mask 11. . After this, in the control system shown in Figure 3,
Fine movement amount control can be performed by setting a corrected movement amount using the movement amount setter 49 based on the established target value.

For example, as shown in FIG.
The supply pressure P is slightly higher than the pressure when it contacts. By setting the amount of movement corresponding to the amount of movement, the wafer 33 can be slightly suppressed against the mask 11 and the amount of deflection of the mask can be controlled. It is also possible to create a state of so-called separation or proximity by slightly separating them without being separated from each other. The mask deflection amount control described above is performed when the air chamber 4o is evacuated to create a state of vacuum contact, as will be described later.

A second feature according to the invention is that the mask 11. Leaf spring 21.
An airtight chamber 40 is formed surrounding the sealing Perot-39 mask holder suction and fixing plate 7, and the wafer 33 is placed in this airtight chamber 40.
The point is to contain it. The vacuum pressure in this hermetic chamber 40 is adjustable by an air pressure adjusting means including a pipe 41. Further, in this airtight chamber 40, as shown in the schematic diagram of the alignment device in FIG. It is characterized by being larger than the area (determined by the inner diameter) Aw.

By forming such an airtight chamber 40, the chamber 40 is evacuated in the mask-to-wafer adhesion process after alignment of the wafer and mask, and as shown in the schematic diagram of FIG. 6, AM>Aw The mask 11 is bent downward using the relationship shown in FIG. Place them in close concentric circles. Thereby, the mask and the wafer can be brought into close contact without shifting the relative positions previously determined in the alignment process.

A third feature according to the present invention is that the Unino chuck 32 is provided with holes 34 and 36 for blowing out an inert gas (N gas). Of course these are some 5te
P is used to chuck the wafer by supplying a vacuum pressure V. In particular, in the embodiment of the present invention, the holes are divided into two parts, one in the center and one in the periphery of the wafer chuck. After bending the mask in the adhesion process, in order to promote adhesion concentrically from the center of the mask to the periphery, as shown in the schematic diagram of FIG. After that, as shown in the schematic diagram of FIG. 8, nitrogen and gas are also ejected from the holes 34 in the periphery to promote close contact between the wafer and the mask in the periphery. promote.

Such a mechanism can promote close contact between the mask and the wafer without interposing an air layer between the mask and the wafer. Separation between the wafer and the mask after contact and exposure can be easily achieved by performing the reverse of some of the steps described above.

A fourth feature according to the present invention is that it has a mechanism for adjusting the supply pressure P of the air chamber 25 mentioned above in the close contact process. When the chamber 40 is at atmospheric pressure, the above-mentioned control device memorizes the position (displacement output E) at which the unino contacts with respect to the reference plane of the mask as shown in FIG. In such a close contact process, N, gas flow rate QN
Experimentally determine the relationship between and the displacement amount ΔXN, input the value of ΔXN to the supply pressure control device of the air chamber 25, and supply the wafer chuck so that the position of the wafer chuck is lowered by ΔXN than the displacement output E of the reference plane. Control pressure P. This allows the bend of the mask to be reduced.

Next, the operation of the apparatus shown in FIG. 1 as a whole will be explained. First, a wafer 33 supplied from an automatic feeding mechanism (not shown) is held by suction by a vacuum chuck 32 drawn by a vacuum from pipes 35 and 37. Next, the mask 11 and mask holder 10 supplied from an automatic mask supply mechanism (not shown) are suctioned and fixed by vacuum V via the pipes 8 and 9. The initial rise amount is set by the movement amount setting device 49 mentioned above, and the supply pressure of the air chamber 25 is controlled.
The sea urchin 33 on the chuck 32 is brought into contact with the mask 11. At this time, the control target value corresponding to the height of the mask 11 is established by the above-described operation.

At this time, the air chamber 45 of the spherical seat 31 for parallelizing the Uninor chuck (to make it parallel to the mask) is at atmospheric pressure or low vacuum, so the spherical seat rotates freely.
Enables parallel alignment (・ru.

Furthermore, if necessary, a small amount of air, nitrogen, or gas is sent to the air chamber 45 in order to more completely align the Unicorn and the mask after the lifting of the Unicorn and the mask has stopped. After parallelization, that air AI knee Lp1!
The hard surface rot 31 is fixed to the notice plate 30.

Thereafter, the pressure supplied to the air chamber 25 is reduced by reversing the pulse motor (not shown) of the air pressure source, so that the distance between the mask and the wafer is approximately 20 μm. In this state, while confirming the target positions of the mask and wafer from the alignment table, the alignment tables 12, 13 and 17 are moved to match the mask pattern and the wafer pattern.

After this, the wafer is accurately aligned with the mask, the supply pressure in the chamber 25 is increased by -E again, the gap between the mask and the wafer is set to 5 to 10 μm, and at this position, the alignment between the mask and the wafer is 7 and corrected if necessary.

After this alignment step is completed, the supply pressure of the air chamber 25 is increased to bring the wafer and mask into contact.21 The contact process for the next exposure will be described with reference to FIGS. 5 to 8.

After the alignment step is completed, when a wafer mask is soft-touched by the control device for the air chamber 25, the mask qualitatively bends as shown in FIG. 5, and an air layer 56 is created between the wafer and the mask. It will exist. In order to eliminate this air layer 56 and achieve complete adhesion, first, as shown in FIG. 6, the chamber 40 is brought to a pressure lower than atmospheric pressure (negative pressure). When the pressure in the chamber 40 is made negative, since AM>AJ, the mask 11 receives a force from above to below and bends downward. As a result, as mentioned above, Unino 33 and Mask 1 are located almost in the center of the mask.
Press 1.

Next, as described above, in order to promote concentric contact from the center of the mask to the periphery, N2 gas is blown out from the center of the wafer chuck 32 toward the wafer, as shown in FIG.

Furthermore, as shown in FIG. 8, N gas is also blown out from the peripheral edge of the wafer chuck to complete the close contact. In this state, the air layer between the wafer 33 and the mask 11 is removed, but both the mask and the wafer may bend slightly upward due to the flow of N and gas ejected from the wafer chuck. In order to correct this bend, the supply pressure P in the chamber 25 is controlled by the control system as described above.

In the above-mentioned adhesion process, the process of preferentially supplying N and gas from the center of the wafer chuck shown in FIG. Yes.

In this way, according to the present invention, the close contact between the wafer and the mask can be completed at an early stage without creating an air layer between the mask and the wafer. Also, mask and unino
After the central portions of the masks come into contact with each other, the entire surface becomes in close contact with each other, so that the positional deviation between the mask and the unino when they are in close contact with each other can be significantly reduced.

After the close contact, a mask pattern is exposed onto the wafer by an exposure device (not shown).

The first method of separating the mask and the mask from the close contact between the mask and the mask as shown in FIG. 8 is as follows:
As shown in FIG. 7, only the periphery of the wafer chuck is switched to a vacuum state, the central part of the wafer is bent, and the mask is separated from the periphery of the wafer to promote the inflow of air. In the second method, in the state shown in FIG. 6, when the pressure in the air layer 25 is reduced while the pressure in the chamber 40 is kept negative, the wafer chuck 32 is gradually lowered by the action of the leaf spring 21. At this time, the mask is exposed to atmospheric pressure from the upper surface of the mask and becomes slanted downward, which promotes the inflow of air from around the wafer between the mask and the wafer.Afterwards, the chamber 40 is returned to atmospheric pressure, and the mask and completes the separation of the wafer.

The first and second methods allow air to enter the vacuum between the wafer and the mask, thereby:
This can solve the problem of the wafer and mask becoming stuck together.

By using the apparatus and method according to the present invention described above, it is possible to smoothly bring the mask and the wafer into close contact with each other without causing a shift in their relative positions. can be achieved in a short period of time. As a result 2
This can be expected to improve the yield of products manufactured from wafers and prevent damage to masks during the mask alignment process.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a cross-sectional view showing a mask alignment device according to the present invention, and FIG. 2 is a cross-sectional view showing the supply pressure control device of the present invention. 3 is a cross-sectional view schematically showing the mask alignment device of the present invention shown in FIG. figure. ■...mask alignment device, 20... cylindrical body,
24... 20 and 24 constitute a chamber in the lid body, 2
2...Block, 23...Connecting rod, 30...Spherical floor support 1-J-plate, 22.23 and 30 constitute a piston device, 32...Wafer cha, 25...Air chamber , 46... Air pressure source, 47... Air pressure control device 2
5. 46 and 47 constitute a driving device, 21... plate spring part for applying stress, 26... position detector, 48
...Detector, 49...Wafer chuck movement amount setting device,
50...26, 48, 49 and 5 in the control signal generator
0 constitutes a drive control means, 33...Unino., 10.
・Mask holder, 11... Mask, 39... Perot for airtight sealing, 40... Air chamber, 41... Vacuum pressure or gas supply pipe, 34... Adsorption hole or gas ejection hole, 35... Pipe, 36... Adsorption hole or gas ejection hole, 37... Pipe. Agent Patent Attorney Akio Takahashi Figure 2-□ Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. (at) a mask holder that holds the mask at its periphery; (bl) a mounting table that holds the plate-like object to be processed facing the mask; (cl) the mask and the plate-like object to be processed; A contact exposure apparatus comprising: a position control mechanism for bringing the two surfaces into contact with each other or close to each other; and an air pressure control mechanism for controlling the air pressure difference between the two surfaces of the mask.