JPS6194323A - Apparatus for correcting surface shape of laminar plate - Google Patents

Abstract

PURPOSE:To enable the surface shape of a laminar plate to be corrected, by providing a diaphragm for attracting and deforming the laminar plate, means for determining the surface shape and means for controlling the driving of the diaphragm. CONSTITUTION:A wafer is disposed on a wafer chuck body 2 and is attracted to the body 2 and a diaphragm 5 by means of vacuum grooves 22 and 52. The surface shape of the wafer 1 is determined by a flatness measuring device 9, output of which is supplied to an arithmetic circuit 12. The arithmetic circuit 12 computes a difference between said output and a shape data from a commanding section 8, and the output thereof is supplied to a driving section 7. The driving section 7 controls the pressure to be supplied to the diaphragm 5 in accordance with the computation output such that the diaphragm 5 is deformed for displacing the working surface 51 of the diaphragm. In this manner, the surface shape of the wafer 1 can be corrected to either flat or curved as required.

Description

Detailed Description of the Invention [Field of the Invention] The present invention relates to an apparatus for correcting the surface shape of a thin plate such as a semiconductor wafer, and is applied to a wafer chuck of a semiconductor exposure apparatus, for example, to correct the flatness of a wafer and use it as a mask. The present invention relates to a surface shape correction device used to correct defocus of a wafer.

[Background of the invention]

Conventionally, in the process of exposing a wafer in a semiconductor exposure apparatus, in order to eliminate focus deviation between the mask and the wafer, the flatness of a wafer chuck is improved, and the wafer is suctioned and fixed so as to follow the flatness. But in this case,
Wafer chucks are required to have highly accurate flatness on the surface, and the flatness must be constantly controlled, which has the disadvantage of increasing the cost of the wafer chuck and requiring strict maintenance methods. In addition, with this method of suctioning the entire surface of the wafer, the flatness of the wafer does not necessarily follow the flatness of the wafer chuck and is fixed.
In this case, there is a problem that a focus shift occurs between the mask and the wafer, and the image of the mask cannot be faithfully transferred to the wafer.

On the other hand, in order to eliminate such drawbacks, the vacuum suction force of each part of the wafer is adjusted independently.
No. 6, etc.) have also been proposed.

However, with such a method using only suction, it is relatively easy to correct a convex warp at the center of the wafer, but it is difficult to correct a concave warp.

Furthermore, when the mask and wafer are out of focus on the wafer surface, that is, when the optically best focus position is not a flat surface, conventionally it has not been possible to match the wafer surface shape to the best focus surface shape.

[Object of the Invention] In view of the above-mentioned problems in the conventional example, the present invention is capable of correcting the flatness of a wafer in a fast follow-up time even if the original wafer is warped in an uneven direction. The present invention aims to provide a surface shape correction device. In addition, even in projection exposure equipment where the best focus surface is not a flat surface, by applying this surface shape correction device, the surface shape of the wafer to be exposed can be adjusted to match the shape of the best focus surface, and the entire surface of the wafer can be set at the focus position. A further object of the present invention is to provide a surface shape correction device capable of correcting the surface shape.

[Description of Embodiment] FIG. 1 shows the configuration of a wafer chuck to which a surface shape correction apparatus according to an embodiment of the present invention is applied.

In the figure, 1 is a wafer on which a mask image is printed;
2 is a wafer chuck body; 3 is a pressure supply tube for wafer adsorption (hereinafter referred to as tube); the wafer 1 is placed on a wafer support part 21 provided in a ring shape around the wafer chuck body 2; A wafer suction pressure supply groove (hereinafter referred to as
By applying a vacuum to the wafer chuck body 2 (referred to as a vacuum groove) 22 through the tube 3, the wafer is suctioned and fixed to the wafer chuck body 2.

5 is a diaphragm attached to a recess 23 formed inside the wafer support portion 22 of the wafer chuck body 2, and a working surface 51 of the diaphragm 5 that contacts the wafer 1;
An annular wafer suction pressure supply groove (vacuum groove) 52 is provided in the groove. This diaphragm 5 attracts and engages the wafer 1 when the wafer 1 is placed on the wafer chuck body 2 and a vacuum is applied to the vacuum groove 52 via the tube 3.

7 is a drive circuit that deforms the diaphragm 5, such as a servo valve; 8 is a command unit that sets the surface shape of the wafer 1; 9
is a flatness measuring instrument. As this flatness measuring device 9,
For example, it is configured to measure displacements at multiple locations on the wafer 1 using a displacement measuring device such as a capacitance type displacement measuring device or a laser type displacement measuring device, and calculate flatness by comparing these measured values. do it.

10 is an air tube that supplies vacuum or pressurized air into the diaphragm 5, 11 is a pressure sensor, and 12 is a value obtained by the flatness measuring device 9 or a value obtained by the pressure sensor 11 and given from the command unit 8. This is an arithmetic circuit that provides the difference from the command value to the drive circuit 7 as an operation amount.

Next, the operation of the wafer chuck according to the above configuration will be explained.

When the wafer 1 is placed on the wafer chuck body 2, a vacuum is supplied to the tube 3, and the wafer 1 is attached to the wafer chuck body 2 and the diaphragm 5 by the vacuum grooves 22 and 52.
is adsorbed to. Next, the flatness measuring device 9 measures the surface shape of the wafer 1, such as flatness, and the output of the flatness measuring device 9 is supplied to the calculation circuit ''12. The difference between the output of the device 9 and the surface shape data of the wafer 1 output by the command unit 8 is calculated.The drive unit 7 controls the supply pressure to the diaphragm 5 according to the calculation output of the calculation circuit 12, and 5 and displaces its working surface 51 to change the surface shape of the wafer 1 to concave, flat, convex, etc. The above flatness measurement or diaphragm deformation operation is repeated in a negative feedback manner, that is, by feedback control. The surface shape of the wafer 1 is corrected to the shape given by the command unit 8.

Note that when the surface profile measuring device shown in FIG. 1 is applied to a semiconductor exposure device, it is difficult to measure the flatness of the wafer 1 with the flatness measuring device 9 during exposure, so the wafer is measured by the above operation before exposure. In addition to correcting the surface shape of the diaphragm 1, during exposure, the flatness measuring device 9 is moved out of the exposure optical path, and instead, the value of the pressure sensor 11 is fed back to maintain the supply pressure to the diaphragm 5 at a constant value. I try to keep it deformed.

In this way, in the wafer chuck shown in FIG. 1, the wafer 1 is supported and fixed only at the periphery, and the diaphragm 5 is provided at the center, and by controlling the pressure supplied to the diaphragm 5, the center of the wafer is fixed. The mask and wafer can be driven up and down to correct the surface shape to a flat surface or a concave or convex shape with a desired curvature. It is possible to eliminate defocus within the plane of the wafer, and to prevent deterioration of the image transferred to the wafer due to the defocus.

[Modifications of Embodiments] The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications. For example, in the above-mentioned embodiment, the wafer chuck fixes the wafer by vacuum suction, but the wafer may be fixed by other means such as a pressing fixing means that mechanically presses and fixes the wafer from above against the wafer support. You can do it like this. Also, in the above, 1
However, if a plurality of diaphragms are used and each diaphragm is individually controlled, more precise surface shape correction can be performed.

[Effects of the Invention] As described above, according to the present invention, a part of a thin plate such as a wafer is fixed, and the other part is adsorbed to the diaphragm and displaced up and down, so that the thin plate is free from unevenness. Even if the surface is warped, the surface shape can be corrected to a desired flat or curved surface. Therefore, if this surface shape correction device is applied to a semiconductor exposure device, even if the best focus surface of the projection system of the exposure device is a curved surface, the entire surface of the wafer can be set at the focus position by warping the wafer to a desired curvature. be able to. Furthermore, since the surface of the thin plate is displaced by the diaphragm, the follow-up time for surface shape correction is also fast.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a wafer chuck according to an embodiment of the present invention. 1: wafer, 2: wafer chuck body, 3: pressure supply pipe for wafer suction, 21: wafer support section, 22.52: pressure supply groove for wafer suction, 5: diaphragm, 51: working surface, 7: drive section, 8: Command unit, 9: Flatness measuring device, 10:
Air pipe, 11: Pressure sensor, 12: Arithmetic circuit. Figure 1

Claims (1)

[Claims] 1. A fixing means for fixing a part of the thin plate, and a thin plate suction means on the working surface, and the suction means engages at least a part of the thin plate other than the fixed part to displace the part. A surface shape correction device for a thin plate, comprising: a diaphragm for adjusting the surface shape of the thin plate, a means for measuring the surface shape of the thin plate, and a means for controlling the amount of drive of the diaphragm based on the output of the surface shape measuring means. 2. The thin plate surface shape correction device according to claim 1, wherein the fixing means adsorbs and fixes the thin plate using vacuum pressure. 3. The thin plate surface shape correction apparatus according to claim 1 or 2, wherein the thin plate suction means is a vacuum suction means. 4. Claim 1, wherein the thin plate is a semiconductor wafer.
The surface shape correction device for a thin plate according to any one of items 1 to 3.