JPH0145217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure apparatus for printing a predetermined pattern onto a substrate.

FIG. 1 is a schematic configuration diagram showing a conventional projection exposure apparatus. A pattern 2 on the surface of the mask 1 indicated by an arrow in the figure is formed by concave mirror M ₁ ,
An image is formed on the wafer 4 via a mirror optical system consisting of a convex mirror M ₂ and a plane mirror M ₃ and is printed. Reference numeral 5 indicates an imaged pattern on the wafer. A carriage 6 carrying a wafer 4 and a mask 1 scans back and forth as indicated by arrow A in the figure, and the mask pattern 2 is transferred onto the wafer 4 in accordance with the scanning.
In order to attract the wafer 4 to the upper surface of the chuck 7, the wafer chuck 7 has a plurality of holes arranged on the upper surface forming an air passage connected to holes 8 on the lower surface, and the holes 8 are indicated by arrows 9. It communicates with a vacuum generator (not shown) via piping. Figure 2a
and b are an enlarged sectional view and a plan view of the wafer 4 placed on the wafer chuck 7, respectively. FIG. 2b shows the flatness of the surface of the wafer 4 using contour lines 10, which in this example show that it is formed into an upwardly protruding spherical shape. As shown in FIG. 2a, if the surface 11 of the wafer 4 does not coincide with the imaging plane 12 of the optical system, even if you try to transfer the line pattern 13 (see FIG. 2b), it will not be within the depth of focus. Since the image is formed only on the surface 11 of the wafer, only a portion of the line pattern 13 is transferred. The depth of focus of the imaging plane 12 is determined by the resolution of the optical system required for transfer, and the depth of focus at the resolution required to transfer a line width of 3 μm is ±3 μm.
Further, when the line width to be transferred is 2 μm, the depth of focus on the wafer side is allowed to be ±2 μm. On the other hand, the flatness of the surface 11 of the wafer 4 adsorbed on the flat chuck surface 15 is poor, and is usually ±4 μm.
or more, and some of them are more than ±10μm,
This results in a decrease in yield. On the other hand, it is extremely difficult to improve the flatness of the wafer itself.

Therefore, in order to image and print a mask pattern on a wafer with poor flatness, a method of focusing on the surface 11 of the wafer 4 can be considered. With reference to FIG. 3, printing of a circuit pattern onto the surface of a wafer by focusing will be described. The wafer 4 has a spherical shape projecting upward as in FIGS. 2a and 2b, and the depth of focus is defined by two contour lines 10. If you scan in the direction of the arrow in the burn range W1 without focusing,
The circuit pattern can only be printed within a ring-shaped area with a width R ₀ corresponding to the depth of focus. Next, the same range W
1 and scans along the center of range W1 while focusing, printing is performed in range R1. Next, in the narrow printing range W2, scanning is performed in the vertical direction three times while adjusting the focus in the figure, and printing is performed in the range R3.

From the above explanation, it will be understood that the yield is best if the exposure is performed in parts. However, if it is divided into three times, the throughput is reduced to 1/3, resulting in a significant loss, and it is also extremely difficult to connect patterns between printing areas, making it difficult to achieve high-precision pattern printing. Further, it requires complicated mechanisms and operations for detecting the focal position, adjusting the focal plane, etc., is expensive, and has the disadvantage that maintenance is difficult and troublesome.

Further, as a prior art, Japanese Patent Application Laid-Open No. 146580/1983 was known. In this conventional technology, the deformation of the substrate is corrected by using a displacement generating means such as an electrostrictive element to correct the deformation of the substrate by using a member that partially adsorbs the back surface of the substrate. This poses a problem in that it is difficult to arbitrarily position the entire surface of the substrate on the imaging plane. Further, as a prior art, Japanese Patent Application Laid-Open No. 48-88871 was known.
Similar to the prior art described above, this prior art also has a member that partially adsorbs the substrate attached to the vertical displacement generating element, which causes lateral positional displacement and deformation of the board between the partially adsorbed parts. is something that cannot be controlled,
There was a problem in that it was difficult to arbitrarily position the entire surface of the substrate on the imaging plane.

It is an object of the present invention to eliminate the above-mentioned drawbacks of the conventional art, and to provide a simple mechanism that allows arbitrary image formation on the image plane over the exposed area of the substrate without inducing local deformation or lateral positional displacement of the substrate. It is an object of the present invention to provide an exposure apparatus that can expose and print fine patterns by positioning with high accuracy, and can improve the yield of products such as semiconductors.

That is, in order to achieve the above object, the present invention uses an exposure apparatus that prints a pattern on a substrate. A chuck plate obtained by deforming a chuck plate by applying a force to the back surface of the chuck plate having a partially changed chuck plate, a support means for supporting the chuck plate, and a chuck plate having a partially changed material or cross-sectional shape. a deforming means that deforms the substrate by following the deformed curved surface over the entire area;
The control means operates the deforming means based on the surface shape of the substrate to deform the substrate to follow the deformed curved surface of the chuck plate, and arbitrarily positions the surface on the pattern imaging plane. It is something to do. In other words, by partially changing the material or cross-sectional shape of the chuck plate, the deformation of the chuck plate can be partially changed, so that the desired deformation can be obtained, and as a result, the substrate surface can be raised to the image plane. It is possible to match the precision and realize deformation of the substrate with less distortion. Furthermore, when the deformation means is configured with vertical displacement generating means, it is possible to eliminate the need to arrange a large number of vertical displacement generating means, and the deformation means can also be configured with fluid pressure applying means that applies a uniform force. can.

The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 4 is an overall configuration diagram of a 1:1 projection type exposure apparatus showing an embodiment of the exposure apparatus of the present invention. That is, this exposure apparatus includes a deforming device 16 that flattens the wafer 4 and serves as a chuck, and a flatness detecting device 1.
7. Deformation controller 18, wafer 4 and mask 1
a carriage 6 for loading and scanning wafers, a wafer cartridge 19 for storing wafers before and after baking, a wafer transport mechanism 20 for transporting wafers between the wafer cartridge 19 and the deforming device 16, and a projection optical system 2.
1 and a base 22. wafer 4
is carried out by the cartridge 19 and the transport mechanism 20,
The wafer 4 is set on the deformation device 16 which has been flattened in advance, and the controller 18 operates the deformation device 16 by the required amount using the flatness detection device 17 to make the wafer 4 into the required shape, that is, flat in this case. Make it. Next, the flatness is detected by the flatness detection device 17, and if it is not within the specified value, the deformation operation is repeated a predetermined number of times, and after the flatness is within the specified value, the carriage 6 is moved under the projection optical system 21. Burn the pattern of mask 1. The wafers that have been baked are transferred to the wafer cartridge 19 for baked wafers by the transfer mechanism 20. Repeat the above steps until there are no more unbaked wafers left. Here, the deformed shape of the wafer 4 is preferably made to match the imaging plane of the mask surface pattern at the time of printing. However, in a normal exposure apparatus, the imaging plane of the mask surface pattern is made flat, and it is sufficient to align the surface 11 of the wafer 4 with the flat surface. When aligning with the mask image plane, a means not shown in the figure is required to detect the mask image plane in advance. This is done through the projection optical system 21.
It is sufficient to detect the image formation of the mask pattern on the wafer surface 11 while moving the deforming device 16. In addition, a simple method is to detect the flatness of the mask and
Knowing the deviation from the imaging position when the mask is flat,
It is also possible to consider a method of adjusting to the previously determined shifted imaging position based on several reference points on the wafer surface and the flatness of the wafer surface.

Figures 5a, b, c and d show the principle of the deforming device. As shown in the figure, a convex lens-shaped wafer 4
As shown in Figure b, a conventional flat vacuum chuck 23
When the surface 11 of the wafer 4 is suctioned, the surface 11 of the wafer 4 becomes convex. At this point, the surface 11 of the wafer 4 can be flattened by suction using the chuck 24 having a concave center as shown in FIG. The force deforming the wafer 4 is, in this example, atmospheric pressure 25 generated by the vacuum force of the chuck 24.
is the force that presses the wafer 4 against the chuck 24. Other possible deforming forces include electrostatic force, adhesive force, force due to contact with the surface 11 of the wafer 4, and force applied to the periphery of the wafer 4. Further, although the deformation of the wafer 4 is arbitrary, it is determined by the deformation curve of the wafer 4 determined by the elastic deformation coefficient and deformation force of the wafer 4,
In the case of a small deforming force 26 as shown in d of the figure, the chuck 24 may not be followed. However, in the case of the wafer 4, the amount of deformation is approximately 10 μm in most cases, and the shape is simple enough to be approximated by a quadratic curve within ±2 μm, so deformation due to atmospheric pressure is sufficient.

FIG. 4 shows an embodiment in which a convex lens-shaped wafer 4 is deformed into a flat shape by a deforming device 16 that sucks the wafer over the entire area based on the above principle.

FIGS. 6a and 6b are diagrams showing the deforming device 16 in detail. This deforming device 16 includes a chuck plate 33 having flexibility formed of a thin metal plate such as steel, aluminum, or stainless steel or a thin resin plate such as Teflon;
A chuck body (supporting means) that supports the chuck plate 33 on the outside of the outer periphery of the wafer 4 of the chuck plate 33, a vertical shaft 34 connected to the center of the chuck plate 33, and a chuck body formed between the chuck body and the chuck plate 33. A deforming air chamber 35 for deforming the wafer 4 by air pressure; a vertical shaft air chamber 36 like a cylinder provided in the center of the chuck body for vertically moving the vertical shaft 34; A vacuum hole 37 formed through the center of the vertical shaft 34 for vacuum suction to the plate 33, the respective atmospheric pressure controllers 38, 39, the flatness detection device 17, and the flatness detected from the flatness detection device 17. It is composed of a controller 18 that controls atmospheric pressure controllers 38 and 39 according to the temperature. The vertical shaft 34 and the deformed air chamber 35 are connected to the chuck plate 3.
3 constitutes a deforming means for deforming the chuck plate 33 by applying a force to the back surface of the chuck plate 33. A protrusion 42 is provided on the surface of the chuck plate 33 and has a ring-shaped outer periphery 41 and a protrusion 42 whose upper end is at the same height as the protrusion 42 to form a vacuum suction groove. Further, the controller 18 includes a flatness detection device 1
Based on the flatness of the wafer surface detected by 7, the pressure in the deforming air chamber 35 and the amount of displacement of the vertical axis 34 are calculated and determined, and the atmospheric pressure controllers 38, 39 are operated based on the determined control data. It controls the The wafer 4 comes into contact with the outer peripheral ring 41 provided to form a vacuum suction groove on the surface of the chuck plate 33 at the tip of the protrusion 42, and is vacuum suctioned over the entire area by suction from the vacuum hole 37. to follow the surface shape of the chuck plate 33. The flatness detection device 17 detects the flatness of the surface of the attracted wafer 4. The controller 18 controls the pressure in the deformation chamber 35 and the vertical axis 34 based on the flatness of the wafer surface detected by the flatness detection device 17.
The amount of displacement is calculated and determined, and the atmospheric pressure controllers 38 and 39 are controlled based on the determined control data, and the chuck plate 33 is deformed based on the pressure in the deforming air chamber 35 and the displacement of the vertical shaft 34. to obtain a desired elastically deformed curved surface, and the obtained chuck plate 33
The flatness of the wafer 4 is controlled by deforming the wafer 4 so as to follow the elastic deformation curved surface.

FIGS. 7a, b, and c are center cross-sectional views showing how the chuck plate 33 is deformed. The elastic deformation curved surface W of the flexible chuck plate 33 changes as shown by WR in FIG. (Indicated by arrow 45)
changes as shown by Ws. Note that arrow 44,
45 shows atmospheric pressure, vertical axis displacement, and their methods. The overall elastic deformation curved surface W is a combination of a and b in the figure, as shown in figure c, and is expressed by the following equation (1). Note that the figure shows a cross section of the elastically deformed curved surface.

W=WR+Ws...(1) The limit of deformation is determined by the elastic limit of the material. Further, intermediate variations in FIG. 7c are also possible.

Therefore, the deformation phase of the surface of the wafer 4 when the wafer 4 is attracted to the flat chuck 23 shown in FIG. Assuming the deformation curved surface WV of the surface, the following equation (2) holds true.

WV=WF+W...(2) Therefore, the elastic deformation curved surface of the chuck plate 33 is as follows.
It can be found using equation (3).

W=WV-WF (3) By the way, if the allowable flatness on the surface of the wafer 4 is d, then the following equation (4) should be followed.

WV≦d ...(4) From the above formulas (1), (3), and (4), the optimal amount of deformation of the deforming means for deforming the chuck plate 33, that is, the deforming air chamber in the embodiment shown in FIG. The atmospheric pressure PR of 35 and the displacement of the vertical axis 34 can be determined. The controller 18 performs the above calculations and controls the air pressure controllers 38 and 39 to control the wafer 4.
flatten. The vacuum need not be drawn at the center of the vertical axis 34. Further, the displacement of the vertical shaft 34 may be performed by any electric, magnetic, or mechanical method such as a motor, magnet, thermal deformation, or mechanical method.

FIG. 8 shows variations in the vertical axis position. Depending on the flatness of the surface of the wafer 4 that is attracted to the entire surface of the chuck plate 33, the number of vertical axes 34 may be increased and arranged appropriately. 9th
The figure shows the relationship between the cross-sectional shape 46 of the chuck plate 33 and the elastically deformed curved surface W. That is, by changing the thickness of the cross section of the chuck plate 33, the elastically deformable curved surface W can be changed. Further, even if the material of the cross section is changed or a cut is made to locally change the thickness of the cross section, it is possible to realize an elastically deformed curved surface that is partially changed in the same way. By partially changing the material or cross-sectional shape of the chuck plate 33 in this way, it is possible to match the flatness of the target wafer 4. In other words, the flatness of the target wafer 4 (in equation (2)
If the material or cross-sectional shape of the chuck plate 33 is appropriately selected and designed according to the structure and arrangement of the deforming device 16 (W in equation (2)), the target surface shape of the wafer (( 2) formula WV) is obtained.

FIG. 10 is a diagram showing how the chuck plate deforms when a moment 47 of the vertical shaft 34 is applied. Simply displacing it up and down is a centrosymmetric deformation, but when making an asymmetrical deformation,
Just add moment 47.

There are various types of flatness detection devices such as air micro, optical, and capacitive types, but the type and number of measurement points can be determined depending on the required accuracy. In addition, the protrusions 42 on the chuck plate 33 significantly reduce the contact points between the front surface of the chuck plate and the back surface of the wafer, allowing foreign matter such as dust and resist present on the back surface of the wafer to escape into the groove, and causing sudden wafer contact. This is to prevent deformation of the

As explained above, according to the present invention, by partially changing the material or cross-sectional shape of the chuck plate, it is possible to generate a large local deformation of the chuck plate and obtain the desired deformation. As a result, the image forming surface can be arbitrarily distributed over the exposed area of the substrate without inducing local deformation or lateral positional shift on the substrate that has "warpage", "undulation", "unevenness in thickness", etc. It enables highly accurate positioning of
Fine patterns can be exposed and printed on LSI
It has a practical effect that can significantly improve the yield of products such as. Further, according to the present invention, when the deformation means is configured with a vertical displacement generating means, the number of vertical displacement generating means can be significantly reduced, and the deformation means is configured with a fluid pressure applying means that applies a uniform force. This has the effect of simplifying the deforming device.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing a conventional projection exposure apparatus, Figures 2a and b are diagrams showing the relationship between wafer flatness and image formation in the exposure apparatus shown in Figure 1, and Figure 3 is a diagram showing the relationship between wafer flatness and image formation in the exposure apparatus shown in Figure 1. A diagram for explaining divided exposure, FIG. 4 is a schematic configuration diagram showing an embodiment of the exposure apparatus of the present invention,
Figures 5a, b, c, and d are diagrams showing the principle of the present invention;
FIG. 6a is a plan view specifically showing an enlarged deformation device etc. provided in the exposure apparatus of the present invention, and FIG. 6b
is a partial sectional view of FIG. 6a, FIGS. 7a, b, and c are views showing cross-sectional lines of the elastic deformation curved surface of the chuck plate shown in FIGS. 6a and b, and FIGS. A diagram showing an example of the arrangement of the vertical axes shown in Figure 6 a, b, Figure 9 a, b,
c is a diagram showing the correspondence between the cross-sectional shape of each chuck plate and the cross-sectional line of its elastic deformation curved surface, and Fig. 10 is a diagram showing the shape of the flexible chuck plate when a moment is applied to the vertical axis shown in Fig. 6 b. FIG. 3 is a diagram showing a cross-sectional line of an elastically deformed curved surface. Explanation of symbols, 4...Wafer, 16...Deformation device, 17...Flatness detection device, 18...Controller, 33...Chick board, 34...Vertical axis, 3
6... Air chamber for transformation, 36... Air chamber for vertical axis, 37
...Vacuum hole, 41...Outer ring, 42...
…protrusion.

Claims (1)

[Scope of Claims] 1. In an exposure device that prints a pattern on a substrate, a chuck board that is adsorbed to follow the chuck surface over the entire back surface of the substrate and whose material or cross-sectional shape is partially changed. , a support means for supporting the chuck plate, and a deformed curved surface of the chuck plate obtained by deforming by applying a force to the back surface of the chuck plate whose material or cross-sectional shape is partially changed. a deforming means for deforming the substrate by following the deformation curved surface of the chuck board by actuating the deforming means based on the surface shape of the substrate to deform the substrate so as to follow the deformed curved surface of the chuck plate, and arbitrarily transform the surface into a pattern image formation plane. An exposure apparatus characterized by comprising a positioning control means. 2. The deforming means is provided on the back surface of the chuck plate.
An exposure apparatus according to claim 1, characterized in that the exposure apparatus is constructed by installing a plurality of vertical displacement generating means. 3. The exposure apparatus according to claim 1 or 2, wherein the deforming means is configured to apply fluid pressure to the back surface of the chuck plate.