JPS6336526A - Wafer exposure equipment - Google Patents

Abstract

PURPOSE:To make accurate exposure possible, by providing an exposure region measuring part an arithmetic circuit, a driving circuit and a wafer chuck having a plurality of piezoelectric driving pins, calculating correction quantity, and making a focal plane and an exposure region acurately coincide with each other in the exposure region of wafer surface. CONSTITUTION:Automatic correction of exposure region applying a wafer chuck 41 having piezoelectric driving pins 44, a driving circuit 45, an exposure region measuring part 55 and an arithmetic circuit 56 is executed as follows; a wafer chuck 41 is horizontally transferred under the condition where voltage is not applied to the piezoelectric driving pins 44, and the exposure region 50 of a wafer 42 fixed on the chuck is set at a specified position corresponding to a projection lense 40. Then the upper and the lower positions of a plurality of points on the exposure region 50 are measured. In this measurment, the output light 57 of a light emitting element 46 makes an incidence on the respictive positions corresponding to the piezoelectric driving pins 44. When the reflected light signals are input to the arithmetic circuit 56 via sensors 54, the arithmetic circuit 56 calcurates the difference between each incidence point on the exposure region 50 and the focal plane of the projection lense 40, and the correction quantity is output to a driving circuit 46. which applies a voltage corresponding to the correction quantity to the piezoelectric driving pins 44 corresponding to each point of the exposure region 50, and makes the wafer chuck shift according to the correction quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wafer exposure apparatus used in the manufacture of semiconductor integrated circuit devices, and more particularly to a position correction apparatus for an exposure area of a wafer.

(Prior Art) Conventionally, there have been technologies in this field as shown in FIGS. 2 and 3. FIG. 2 shows a schematic configuration of a conventional wafer exposure apparatus, as an example of a reduction projection exposure apparatus using light, and FIG. 3 shows the automatic focusing t! This shows the device.

In FIG. 2, reference numeral 1 denotes a mercury lamp as a light source of a reduction projection exposure apparatus, and this mercury lamp 1 has a concave mirror 2 that reflects and condenses the light. 3 is a first inverter I=liff for changing the direction of light from the mercury lamp 1, and a collimator 4 for collimating the reflected light and a collimator 4 at the optical axis position of the reflected light to equalize the light and eliminate uneven illuminance. The integrator 5 to make it smaller is being used. A second reflecting mirror 6 is provided in front of the integrator 5, and a condenser lens 7 for condensing light is provided at the forward optical axis position of the reflected light. Reference numeral 8 denotes a mask having a pattern that is, for example, 5 times or 10 times as large as the actual size pattern, and a reduction projection lens 9 is provided in front of the mask 8. This reduction projection lens 9 is used to reduce the pattern of the mask 8 to, for example, 115 or 1/10, and to form an image on the wafer 11 placed on the wafer stage 10.

In the reduction projection exposure apparatus configured as described above, the light from the mercury lamp 1 is reflected and focused by the concave mirror 2 as shown by the dashed line 12, and its direction is roughly changed by the first reflecting mirror 3. The light enters the collimator 4. The light collimated by the collimator 4 enters the integrator 5 and is made uniform, resulting in a uniform light beam with little unevenness in illuminance on the wafer 11.

The light emitted from the integrator 5 passes through the second reflecting mirror 6 and enters the condenser lens 7. The light focused by the condenser lens 7 irradiates the mask 8 and then enters the reduction projection lens 9 . The light emitted from the reduction projection lens 9 spreads the pattern of the mask 8 onto the surface of the wafer 11 by 15 mm x 15 m.
The image is formed on a quadrilateral exposure area of about m. By repeating such an operation while moving the wafer stage 10, different exposure areas are sequentially exposed and the second surface of the wafer 11 is exposed.

In the reduction projection exposure apparatus as described above, the wafer 11
Since the depth of focus at the surface is very shallow, about ±2 μm, in order to precisely align the surface of the wafer 11 with the focal plane, the third
An automatic focusing device as shown in the figure is used.

This automatic focusing device includes a light emitting diode 20, a first
Convex lens 21, first slit 22, second convex lens 23,
Third convex lens 24, (turbulence reflector 25, second slit 2
6 and a photodiode 27.

In the automatic focusing device configured as described above, the light emitted from the light emitting diode 20 is focused by the first convex lens 21 and passes through the first slit 22, as shown by the dashed line 28. The light passing through the first slit 22 is focused by the second convex lens 23 and is focused at a point 2 on the wafer 11.
The image of the first slit 22 is tied at 9.

Roughly speaking, the light reflected at the point 29 on the wafer 11 is
The light enters the vibration reflecting mirror 25 through the convex lens 24 .

The light that has been given a minute angle disturbance by this photographing reflector 25 forms an image again at the second slit 26 and reaches the photodiode 27. A predetermined position of the wafer stage 10 is detected based on the relationship between the reflected angle and the sensitivity of the photodiode 27 at that time. 10 is moved up and down to set the wafer 11 at a predetermined vertical position with respect to the reduction projection lens 9. With such an automatic focusing device, [the reduction projection lens 9 at the set point 29 on the wafer 11] The setting error for the focal point can be within ±0.25 μm.

(Problems to be Solved by the Invention) However, the reduction projection exposure apparatus and its automatic focusing device having the above configuration have the following problems.

That is, although the setting error between the two points set on the wafer 11 by the automatic focusing device can be within ±0.25 μm, in the actual device, the focal plane of the reduction projection lens 9 is not a perfect plane. In addition, because the flatness of the surface of the wafer 11 on which the image is projected cannot be perfect, there is a possibility that an error exceeding the depth of focus may occur.

As shown in FIG. 4, the central cross section of the focal plane is curved 31.
Since it is curved as expressed by It will be about.

Therefore, in order to minimize the difference between the exposure area and the focal point over the entire surface of the exposure area, the position of the exposure area is determined by the automatic focusing device to be approximately equal to the focal distance difference a, as shown by the broken line 32. Set near the center. However, since the actual surface of the wafer 11 is uneven, assuming that the central cross section of the exposure area on the surface of the wafer 11 is shown by the curve 33, the center point 34 of the exposure area is simply set at the position of the straight line 32. It turns out. On the surface of the wafer 11, there is usually a
2-3) Since there are irregularities on the order of μm, in the case shown in the figure, the maximum deviation b between the focal plane and the exposure area is likely to exceed ±2 μm in terms of the depth of focus of the reduction projection exposure system. It is in.

The present invention addresses the problems that the prior art had, in that it is extremely difficult to accurately match the focal plane and the exposure area in the exposure area on the surface of the wafer 11, and there is a possibility that a deviation greater than the depth of focus may occur. The object of the present invention is to provide a wafer exposure apparatus which solves the problem that the reduction projection lens 9 cannot fully utilize its resolving power due to the large amount of light, and therefore there is a possibility that accurate exposure may not be performed.

(Means for Solving the Problems) In order to solve the above problems, the present invention causes a wafer exposure apparatus to irradiate a plurality of light beams onto a plurality of points in the exposure area on the wafer surface, and based on the reflected light of the light beams, an exposure area measurement unit that obtains a signal regarding the vertical position of a point and outputs the signal; and a plurality of units that have a piezoelectric material that deforms by applying a voltage and that move up and down according to the deformation level of the piezoelectric material to deform the exposure area. a wafer chuck in which a piezoelectric drive pin is housed in a cavity; an arithmetic circuit that inputs the output signal of the exposure area measurement section to determine a correction amount for a predetermined position of the exposure area and outputs it; and an output correction of the arithmetic circuit. The piezoelectric drive pin is provided with a drive circuit that inputs a correction amount and applies a voltage to the piezoelectric drive pin to drive the piezoelectric drive pin based on the correction amount.

(Function) According to the present invention, since the wafer exposure apparatus is configured as described above, the exposure area measurement unit moves to accurately measure the vertical positions of multiple points in the exposure area on the wafer surface, and the arithmetic circuit moves to determine the amount of correction for a predetermined position of the exposure area based on the measurement value, the drive circuit moves to drive the piezoelectric drive pin based on the amount of correction, and roughly, the wafer chuck moves to a vacuum housing the piezoelectric drive pin. The negative pressure in the gap attracts and fixes the wafer, and at the same time, the vertical movement of the piezoelectric drive pin deforms the exposure area to align it with a predetermined position. Due to the above-mentioned function, the exposure area can be precisely aligned with a predetermined position, for example, the focal plane of the reduction projection lens, so that accurate exposure of the wafer surface can be performed. Therefore, the above problem can be eliminated.

(Embodiment) FIG. 1 is a block diagram of a main part of a wafer exposure apparatus showing an embodiment of the present invention, and mainly shows a device for correcting the position of a wafer exposure area.

In the figure, reference numeral 40 denotes a fixed reduction projection lens, and this reduction projection lens 40 projects and exposes the mask pattern onto the surface of a wafer 42 placed on a movable wafer chuck 41. The chuck 41 has a gap 43-1 between it and the wafer 42 placed on its upper surface, and this gap 43-1 is evacuated by suctioning the air inside by the vacuum line 43-2. The wafer 42 is attracted and fixed on the wafer chuck 41. A plurality of piezoelectric drive pins 44 are fixed to the wafer chuck 41 in the gap 43-1. The pin 44 is made of a piezoelectric phenomenon such as a crystal, and has a temperature corresponding to the applied voltage.
The piezoelectric drive pin 44 is displaced in the vertical direction due to the deformation of the crystal or the like. Each piezoelectric drive pin 44 is electrically connected to its drive circuit 45.

Reference numeral 46 denotes a light emitting element such as a light emitting diode, and using this light emitting element 46 as a light source, a first convex lens 47, a first slit 48 having a plurality of notches, and a second convex lens 49 are sequentially provided on the optical axis of the light emitting element 46. . Said first slit 4
The plurality of notches 8 reduce the respective images through the projection lens 4.
It is set to connect to the exposure area 50 on the wafer 42 corresponding to 0. In addition, this exposure area 1. +! Each of the 50 imaging locations is set in one-to-one correspondence with each of the piezoelectric drive pins 44. In front of each reflected light beam, there is a third
A convex lens 51 and a reflecting mirror 52 are provided, and the reflecting mirror 52 is arranged so that each reflected light forms an image on the light receiving surface of a plurality of sensors 54 made of light receiving elements such as photodiodes installed directly in the second slit 53. is set to . That is, the sensors 54 are provided corresponding to the positions and number of cuts of the first slit 48. The optical system consisting of the above-mentioned light emitting element 46 to sensor 54 forms an exposure area measuring section 55.

Each of the sensors 54 is connected to an arithmetic circuit 56 that determines the amount of vertical displacement of the piezoelectric drive pin 44 corresponding to each sensor 54 according to its output.

This arithmetic circuit 56 is composed of, for example, a microcomputer, and its output is connected to the drive circuit 45 to control the drive circuit 45 of the piezoelectric drive pin 44.

As described above, the operation of the automatic exposure area correction apparatus constituted by the wafer chuck 41 having the piezoelectric drive pin 44, the drive circuit 45, the exposure area measuring section 55, and the arithmetic circuit 56 will be described next. First, with no voltage applied to the piezoelectric drive pin 44, the wafer chuck 41 is moved in the horizontal direction, and the exposure order Vi50 of the wafer 42 fixed thereon is set at a predetermined position corresponding to the reduction projection lens 40. do. At this time, the position information of the exposure order Vj, 50 is given to the arithmetic circuit 56 at the same time as the position setting. Further, it is assumed that the vertical position of the center of the exposure area 50 is set, for example, to a position that coincides with the focal point of the reduction projection lens 40, which is input into the arithmetic circuit 56 in advance. In this state, the exposure area measuring section 55 measures the vertical positions of a plurality of points in the exposure area 50. In this measurement, the emitted light 57 of the light emitting element 46 passes through the first convex lens 47 and then passes through the first slit 48.
This is done by each light beam passing through multiple incisions. The respective lights pass through the second convex lens 49 and enter the positions corresponding to the piezoelectric drive pins 44 in the exposure area 50, and the reflected lights pass through the third convex lens 51, the reflecting mirror 52, and the second slit 53, and then enter the respective positions corresponding to the piezoelectric drive pins 44 in the exposure area 50. Corresponding sensor 5
4. The signal from this sensor 54 is transmitted to the arithmetic circuit 5
6, the arithmetic circuit 56 calculates the deviation between each incident point of the exposure area 50 and the focal plane of the reduction projection lens 40,
The correction amount is output to the drive circuit 45. The drive circuit 45 applies a voltage corresponding to the amount of correction to the piezoelectric drive pin 44 corresponding to each point in the exposure area 50, and displaces the piezoelectric drive pin 44 up and down according to the amount of correction. As a result, the exposure area 50 is deformed to coincide with the focal plane of the reduction projection lens 40.

By moving the wafer chuck 41 and repeating the above operations sequentially for each exposure area, the entire surface of the wafer 42 can be exposed to a predetermined amount.

In this embodiment, since the entire surface of each exposure area of the wafer 42 can be exposed in alignment with the focal plane of the reduction projection lens 40, the resolution of the reduction projection lens 40 is always in the best condition and accurate. This has the advantage that it is possible to perform precise exposure.

Note that the present invention is not limited to the illustrated embodiment and can be modified in various ways, for example, the following modifications can be considered.

(1) In this embodiment, a reduction projection exposure apparatus using light is shown, but the present invention is not limited to this. For example, it is possible to use it for other exposure apparatuses that use light, such as a same-magnification projection exposure apparatus and an exposure apparatus that uses X-rays, ion beams, and the like.

(2) The configuration of the automatic exposure area correction device is not limited to that of this embodiment. That is, any number of piezoelectric drive pins 44, sensors 54, etc. may be installed. Furthermore, for the piezoelectric drive pin 44, other materials having a piezoelectric effect, such as Rochelle salt, barium titanate crystal, and piezoelectric ceramic, can be used in addition to crystal. Light emitting element 46
may be a laser diode, and is not limited to a semiconductor device, but may be a light source lamp. Similarly, the light receiving element of the sensor 54 may be a phototransistor, a phototube, or the like.

(3) In this embodiment, the position of the incident light on the exposure area 50 and the position of the piezoelectric drive pins 44 and the number of each correspond to each other, but they do not have to correspond.

However, in this case, it is necessary to determine the amount of correction of the exposure area 50 to be made at the position of the piezoelectric drive pin 44 by estimating calculation by the arithmetic circuit 56 or the like.

(4) In this embodiment, the focal plane of the reduction projection lens 40 and the irregularities on the surface of the wafer 42 are corrected, but the present invention is not limited to this, and it may be used to correct only one of them. It can also be used to correct for other factors.

(5) The automatic exposure area correction device of this embodiment can be applied to devices other than wafer exposure devices, such as mask manufacturing devices such as photorepeater.

(Effects of the Invention) As described above in detail, according to the present invention, the wafer chuck having the exposure area measurement section, the arithmetic circuit, the drive circuit, and the piezoelectric drive pin is provided, so that the exposure area on the wafer surface can be adjusted, for example. Rather than partially or approximately matching a predetermined focal plane, it is possible to match the entire plane. Therefore, since extremely accurate exposure can be performed on the wafer surface, it is expected that not only will the yield in the manufacturing process of semiconductor integrated circuit devices and the like be improved, but also that the reliability will be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a main part configuration diagram mainly showing the automatic exposure area correction device part of a wafer exposure apparatus according to an embodiment of the present invention, FIG. 2 is a schematic diagram of the components of a conventional wafer exposure apparatus, and FIG. FIG. 4 is a block diagram of the main parts of the wafer exposure apparatus mainly showing the automatic focusing device, and is a cross-sectional curve diagram of the focal plane and the exposure area. 40... Reduction projection lens, 41... Wafer chuck, 42... Wafer, 43-1...
...Gap, 43-2...Vacuum line, 4
4... Piezoelectric drive pin, 45... Drive circuit, 46... Light emitting element, 48... First
Slits 1~. 50... Exposure area, 54...
...Sensor, 55...Exposure area measuring section, 56.
... Enfeng circuit. Applicant's agent Kaki Mizu Kyo Sei7mon 1, 1j Current configuration of conventional wafer exposure equipment Figure 2 Configuration of main parts of conventional wafer exposure equipment Figure 3 Figure 4

Claims (1)

[Claims] Irradiating a plurality of points in an exposure area on a wafer surface with a light beam,
an exposure area measurement section that obtains a signal regarding the vertical position of the plurality of points based on the reflected light of the light beam and outputs the signal; and a piezoelectric material that deforms when a voltage is applied, and moves up and down according to the amount of deformation of the piezoelectric material. a wafer chuck in which a plurality of piezoelectric drive pins for deforming the exposure area are housed in a cavity; and a calculation unit that inputs an output signal from the exposure area measurement unit, calculates a correction amount for a predetermined position of the exposure area, and outputs it. A wafer exposure apparatus comprising: a circuit; and a drive circuit that inputs an output correction amount of the arithmetic circuit and applies a voltage to the piezoelectric drive pin based on the correction amount to drive the piezoelectric drive pin.