JPH0587008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a wafer adhesion method for adhering a wafer mounted on a wafer chuck to a mask held in a mask holder in a contact exposure type semiconductor exposure apparatus.

[Background of the invention]

In a lithography step of a semiconductor manufacturing process, a semiconductor wafer coated with a resist is exposed to light through a mask or a reticle to transfer a pattern. As such exposure methods for pattern transfer, a contact method, a proximity method, a reflective projection method, a reduction lens projection method, etc. are used. In the contact method, since exposure is performed with the mask and wafer in close contact, a relatively high-resolution pattern can be obtained. In such a contact exposure type semiconductor exposure apparatus, a wafer is suctioned and held by a vacuum chuck, and a mask is aligned and mounted on the wafer. In this case, if gas is sealed between the mask and the wafer, a high-resolution pattern cannot be obtained due to light diffraction or the like. Therefore, in order to obtain a high-resolution pattern, it is necessary to prevent gas traps and ensure that the mask and wafer are in close contact with each other, and the mask must be precisely aligned with the wafer.

[Conventional technology]

In a conventional contact type exposure apparatus, vacuum pressure is applied between a wafer chuck carrying a wafer and a mask holder holding a mask to bring the wafer and mask into close contact with each other. however,
In such a conventional adhesion method, as shown in FIG. 3, air is sealed near the center between the wafer 5 and the mask 6, creating a so-called gas trap 3.
There were disadvantages in that 0 was generated, the adhesion was lowered, a high-resolution pattern could not be obtained, and the pattern accuracy was also lowered.

In order to prevent the occurrence of such gas traps, a method has been proposed in which radial grooves are provided on the upper surface of the wafer chuck and the wafer is vacuum-suctioned through the groove to deform the wafer and release air from the upper surface of the wafer. An example of a wafer chuck having such radial grooves is shown in Japanese Utility Model Application No. 54-54270. In this known wafer chuck, radial grooves are formed on the upper surface of the wafer mounting holding table over a wide area until reaching the outer peripheral edge.
If vacuum pressure is applied to this groove, the wafer will be greatly deformed, which will cause large pattern distortions due to wafer deformation during printing, and the wafer deformation will reduce the accuracy of alignment between the mask and the wafer, which is a practical problem. It was hot.

[Purpose of the invention]

The present invention has been made in view of the drawbacks of the prior art.The present invention suppresses pattern distortion by reducing the amount of wafer deformation during vacuum suction, and improves the alignment precision between the mask and the wafer to achieve high resolution. The purpose of the present invention is to provide a wafer adhesion method that enables highly accurate pattern printing.

〔Example〕

FIG. 1 is a top view of a wafer chuck used in the method of the present invention, and FIG. 2 is a longitudinal sectional view thereof taken along line -C-. A plurality of concentric grooves 3 and two radial grooves 2 extending from the vicinity of the center to the inner part of the outer peripheral edge are formed on the upper surface of the wafer mounting table 20 constituting the wafer chuck 1. The two radial grooves 2 are formed at symmetrical positions with respect to the center C. Each radial groove 2 communicates with a vacuum source (not shown) via a through hole 4. Further, each concentric groove 3 communicates with a vacuum source (not shown) via a conduction hole 14. The communication holes 4 and 14 can be switched to communicate with a vacuum source or the atmosphere via electromagnetic valves 8 and 18, respectively. The concentric grooves 3 are for holding the wafer, and the radial grooves 2 are for releasing gas between the wafer and the mask. Each radial groove 2 is provided at a position apart from a wafer alignment mark 11 and a mask alignment mark 12 for positioning the wafer 5 and mask 6 when they are set. A seal rubber 9 is attached to the outer periphery of the wafer mounting table 20.
A mask holder 7 is provided with a mask 6 mounted thereon.
A vacuum chamber 10 can be formed between the wafer 5 and the wafer mounting table 20 on which the wafer 5 is mounted.

In the wafer chuck with the above configuration,
When vacuum pressure is applied to the radial grooves 2 and the concentric grooves 3 via the electromagnetic valves 8 and 18, the wafer 5 is appropriately deformed into a concave shape at the radial grooves 2, as shown in FIG. The gas between the wafer 5 and the mask 6 is released to prevent gas traps from occurring. At this time, since the concentric groove 3 has a small groove width (approximately 1 mm), the wafer 5 hardly deforms.

The method of using the wafer chuck as described above will be explained below. First, the wafer 5 is placed on the wafer mounting table 20.
The electromagnetic valves 8 and 18 are switched to the vacuum source side to introduce vacuum pressure into each of the concentric grooves 3 and the radial grooves 2. As a result, the wafer 5 is placed on the wafer mounting table 2.
While the wafer 5 is suctioned and fixed onto the wafer 0, the wafer 5 is deformed as described above, and a recess is formed along the radial groove 2 on the upper surface of the wafer 5. Next, the mask 6 and the wafer 5 are aligned using the mask alignment mark 12 and the wafer alignment mark 11. At this time, since both alignment marks 11 and 12 are at positions shifted from the positions of the radial grooves 2, they are not affected by wafer deformation and no alignment errors occur. Next, the vacuum chamber 10 is evacuated and the mask 6 and wafer 5 are removed.
and in close contact with each other. At this time, air between the wafer 5 and the mask 6 is released through the recesses along the radial grooves 2 on the upper surface of the wafer 5, and gas traps do not occur. Next, the solenoid valve 8 is switched to the atmosphere side to open the radial groove 2 to the atmosphere. As a result, the deformation of the wafer 5 is returned to its original state, and the entire surface of the wafer is brought into complete contact with the mask without any gas traps. At this time, the radial grooves 2 may be pressurized above atmospheric pressure. Subsequently, an exposure step is performed according to normal operations.

〔Effect of the invention〕

As explained above, in the wafer chuck used in the method of the present invention, radial grooves are provided on the top surface of the wafer mounting table, extending from near the center to inside the outer periphery. By applying vacuum pressure to the grooves, the wafer is appropriately deformed and the gas on the top surface of the wafer can be discharged uniformly and reliably, improving the degree of adhesion between the mask and the wafer, allowing for high-resolution and highly accurate pattern printing. becomes possible. Further, since each radial groove is provided at a position away from the alignment mark for positioning the mask and wafer, positional deviation due to wafer deformation does not occur during positioning, and the reliability of positioning accuracy is increased.

[Brief explanation of the drawing]

FIG. 1 is a top view of a wafer chuck used in the method of the present invention, FIG. 2 is a sectional view taken along line -C- in FIG. 1, and FIG. 3 is an explanatory diagram of a gas trap in a conventional wafer bonding method. 1... wafer chuck, 2... radial grooves, 3
... Concentric grooves, 4, 14 ... Conduction holes, 5 ...
Wafer, 6...Mask, 11...Wafer alignment mark, 12...Mask alignment mark, 20...Wafer mounting stand.

Claims (1)

[Scope of Claims] 1. In a wafer adhesion method for bringing a wafer mounted on a wafer chuck into close contact with a mask held in a mask holder, the top surface of a wafer mounting table includes a groove for holding the wafer and a center of the top surface of the wafer mounting table. A wafer chuck is provided with radial grooves extending from the vicinity to the inner vicinity of the outer periphery, and is capable of introducing each vacuum pressure into each of the grooves, and by introducing vacuum pressure into the radial grooves, the wafer is removed from the wafer. While adsorbing the wafer onto the mounting table, the wafer is deformed along the radial grooves, a recess is formed on the top surface of the wafer to release air between the wafer and the mask, and then atmospheric pressure or higher pressure is applied to the radial grooves. A wafer adhesion method characterized by introducing a method to restore wafer deformation to its original state. 2. A sealant is provided on the outer periphery of the wafer mounting table to seal between the wafer mounting table and the mask holder, and a vacuum chamber is provided between the wafer mounting table on which the wafer is mounted and the mask holder on which the mask is mounted. 2. The wafer adhesion method according to claim 1, wherein the wafer and the mask are brought into close contact by introducing vacuum pressure into the vacuum chamber. 3. The device according to claim 1 or 2, characterized in that the wafer is sucked and fixed by introducing vacuum pressure into the radial groove and simultaneously introducing vacuum pressure into the wafer holding groove. Wafer adhesion method. 4. The upper surface of the wafer mounting table is substantially circular;
4. The method for adhering a wafer according to claim 1, wherein the wafer holding groove comprises a plurality of concentric grooves. 5. The method for adhering a wafer according to any one of claims 1 to 4, wherein the radial groove is provided at a position away from an alignment mark between the wafer and the mask. . 6. Any one of claims 1 to 5, characterized in that the wafer holding groove and the radial groove can be switched to communicate with a vacuum source or the atmosphere through each electromagnetic valve. The wafer adhesion method described in Section 1. 7. The wafer adhesion method according to any one of claims 1 to 6, characterized in that the radial grooves are constituted by two grooves symmetrical with respect to the center of the upper surface of the wafer mounting table. . 8. The wafer-holding groove according to any one of claims 1 to 7, wherein the width of the groove for holding the wafer is narrowed to such an extent that the wafer is not deformed when vacuum pressure is introduced. Method.