JPH05211129A - Mold working method for pressing rubber plate for wafer mounting in ion implanter - Google Patents

Abstract

PURPOSE:To improve a mold which is used to stick a rubber plate for mounting a wafer to a wafer retaining part of an ion implanter, and make said mold contribute to the adhesion between the rubber plate and the wafer and the sticking prevention of the wafer. CONSTITUTION:A mold 25 is brought into a fixed state on the peripheral part. The surface to be worked is subjected to milling under the state that a pressing force is applied to the central part of a surface of the mold which surface is opposite to the surface to be worked. Thereby the surface to be worked is turned into a recessed spherical surface. A rubber plate is set on a wafer retaining part in the manner in which the recessed spherical surface is used as the pressing surface against the rubber plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement for cooling a wafer in an ion implantation apparatus for irradiating a wafer held on a wafer holding portion on a disk with an ion beam, and more specifically, to promoting the cooling of the wafer and the wafer cooling. The present invention relates to an improvement for improving the installation state of a rubber plate installed on a wafer holding part to prevent sticking with the rubber plate.

[0002]

2. Description of the Related Art An example of an ion implantation apparatus will be briefly described with reference to FIG. In FIG. 3, the disc chamber 20
A disk 21 for holding a wafer is rotatably arranged therein. The disk 21 is rotated at high speed around the central axis 22 by a driving device (not shown). A plurality of wafer holders are provided at equal intervals in the circumferential direction in an annular region near the peripheral edge of the disk 21, and the wafer 23 is held by each wafer holder. An ion beam 24 is generated from an ion generation source (not shown), and the ion beam 24 is scanned in the radial direction of the disk 21 to implant ions into each wafer 23 on the rotating disk 21.

By the way, the wafer 23 is held in the wafer holder via a rubber plate (for example, room temperature curable silicone rubber) having a high cooling effect for the purpose of suppressing a temperature rise during the ion implantation process. This rubber plate is set on the wafer holder by a jig called a mold. This will be briefly described with reference to FIG. 4. The mold 25 is a pressing die for attaching the rubber plate 27 to the wafer holding portion 26 of the disk 21, and the surface shape and surface roughness of the mold 25 are the same as the rubber. It is reflected in the surface shape and surface roughness of the plate 27. As an example of the mold, there is a mold finished by lathe processing so that the pressing surface against the rubber plate is a concave spherical surface. However, this mold uses an old type ion implanter, that is, a disk with a wafer surface clamp mechanism for pressing the wafer against the rubber plate, and the disk is released to the atmosphere each time the wafer is loaded and unloaded on the rubber plate. It was used for an ion implanter of the type described above.

However, in the current upgraded ion implanter, that is, the ion implanter having a load lock mechanism for loading and unloading in a vacuum, which uses a clampless disk without a wafer surface clamp mechanism, The rubber plate set by using the above-described mold has an insufficient wafer cooling effect. As the cause, firstly, since the mold is processed into a concave spherical surface by a lathe, concentric cutting tools remain in steps on the processed surface,
The surface roughness is also rough and the adhesion between the rubber plate and the wafer is insufficient. The second cause is that in the load lock type ion implanter, the disk is always placed in a vacuum, so that the rubber plate is hardened and uniform and sufficient heat conduction is not performed.

Various improvements have been made to the mold in order to solve the above problems. As a first example, there is provided a mold whose surface (the surface on the side in contact with the wafer) is a flat surface and whose surface roughness is improved by finishing the surface by polishing. By using such a mold, the adhesion of the wafer to the rubber plate can be improved and the wafer cooling effect can be enhanced. However, since the adhesion is improved, the sticking of the wafer (the wafer sticks to the rubber and becomes difficult to separate) easily occurs. In addition, during the polishing process, a shoulder sagging phenomenon (the peripheral portion forms a smooth arc) is likely to occur at the peripheral portion of the mold. The rubber plate set by such a mold forms a smooth concave surface at the peripheral edge thereof, further promoting the sticking of the wafer. In addition, it is difficult to control surface roughness in polishing.

[0006]

As a second example for solving the problems of the first example, there is provided a mold surface whose surface is finished by milling. According to the milling process, there is no shoulder sagging phenomenon at the periphery of the mold,
By specifying the processing conditions (rotation speed, feed rate, depth of cut, etc.), it is easy to control the surface roughness. In this way, by eliminating the shoulder sagging phenomenon at the peripheral edge of the mold,
Not only can a good wafer cooling effect be obtained, but
The sticking of the wafer is less likely to occur as compared with the mold of the above example. However, it is desired to improve sticking so that it is more difficult to occur. An object of the present invention is to provide a method of processing a mold which is effective in improving the cooling effect of the wafer and preventing the sticking of the wafer.

[0007]

In the method of processing a mold according to the present invention, the mold is fixed at its peripheral edge, and a pressing force is applied to the center of the surface of the mold opposite to the surface to be processed. By milling the surface to be processed, the surface to be processed becomes a concave spherical surface.

[0008]

According to this processing method, the surface to be processed of the mold is milled in a state where the peripheral portion is fixed and the central portion projects more than the peripheral portion. Is higher than the peripheral region, and as a result, the surface to be processed becomes a concave spherical surface with a large radius of curvature. The concave spherical surface serves as a pressing surface when the rubber plate is attached to the wafer holding portion of the disc. The wafer mounting surface of the rubber plate attached to the wafer holding portion by such a mold becomes a convex spherical surface. When the wafer is placed on such a rubber plate, a minute gap is created between the wafer and the rubber plate at the peripheral edge of the wafer, and therefore it becomes easy to separate the wafer from the rubber plate. The gap between the peripheral edge of the wafer and the rubber plate is very small, and the wafer is pressed against the rubber plate by the centrifugal force component of the rotation of the disk during the ion implantation process. In close contact. Therefore, the adhesion between the rubber plate and the wafer is good, and the wafer cooling is not adversely affected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. In FIG. 2, the processing method according to the present invention is
A characteristic is a method of holding the mold 25 while milling the mold 25 with a milling machine (not shown). That is, the mold 25 has the grooves 25-1 at the side edges thereof at positions with an angular interval of 90 °. As a means for holding the mold 25 by tightening, a holding mechanism including a plate 30, two split rings 31 and 32 for holding the mold 25, and a push bolt 33 for giving the mold 25 a bend is used. ..

The split rings 31 and 32 are connected to the connecting portions 34 and 35.
In the mold 25, they are joined in a mechanically separable state, and projecting portions 31a, 31b, 32a, 32b that can be fitted into the grooves 25-1 are provided at positions corresponding to the grooves 25-1 of the mold 25. The split rings 31, 32 also have protrusions 31a, 3
Mounting portions 36, 37, 38, 39 to the plate 30 with screws are provided at the installation locations of 1b, 32a, 32b. That is, screws (not shown) at each of the mounting portions 36 to 39
By screwing into the screw hole of the plate 30, the split rings 31 and 32 are fixed to the plate 30, and the mold 25 on the plate 30 is held. Push bolt 33
Is provided in the central portion of the plate 30 so as to be retractable from the plate 30, and the central portion of the surface to be processed (upper surface in the drawing) of the mold 25 held by the split rings 31 and 32 is shown in the drawing. It is for projecting upward.

Next, the processing method according to the present invention will be described step by step with reference to FIG. In FIG. 1 (a), first,
A mold 25 having a flat surface and grooves 25-1 at a plurality of side edge portions is fixed. In FIG. 1B, the mold 25 is set on the holding mechanism described in FIG. 2 with its surface to be processed facing up. In FIG. 1C, the center portion of the mold 25 is pushed up by the push bolt 33 to bend it. That is, when the push bolt 33 is screwed in, the mold 25 has its peripheral portion fixed by the split rings 31 and 32.
Only the center bends upward. Of course, the amount of deflection of the mold 25 can be adjusted by the push bolt 33, and is set to a desired value calculated in advance. In FIG. 1 (d), FIG.
The surface to be processed is subjected to milling with a milling grinder (not shown) in a state where the deflection is given in (c). By milling, a machined surface with good surface roughness can be obtained. After the milling is completed, the push bolt 33 is returned to its original position as shown in FIG. When the mold 25 is removed from the holding mechanism, as shown in FIG. 1 (f), the mold 25 has a concave spherical surface having good surface roughness and having a gentle curvature with the deepest center of the surface to be processed.

Using such a mold 25, a rubber plate 27 is attached to the wafer holding part 26 as shown in FIG. The rubber plate attached in this way has its wafer mounting surface (upper surface).
Is a convex spherical surface with a gentle surface roughness. When a wafer is placed on such a rubber plate, a minute gap is formed between the wafer and the rubber plate at the peripheral edge of the wafer, so that sticking does not occur when the wafer is removed from the rubber plate after the ion implantation process is completed. On the other hand, during the ion implantation process, the disk rotates at a high speed and the wafer is pressed by the centrifugal force so as to come into close contact with the rubber plate, so that the adhesion between the rubber plate and the wafer is good and the desired wafer cooling effect is obtained. Obtainable.

[0013]

As described above, according to the processing method of the present invention, by making the mold surface for pressing the rubber plate into a concave spherical surface having a good surface roughness by milling,
It is possible to provide a bonded state of a rubber plate that has very little sticking and has a high wafer cooling effect.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a molding method according to the present invention.

FIG. 2 is a view showing a mold holding mechanism used in the processing method according to the present invention.

FIG. 3 is a diagram schematically showing an ion implantation apparatus to which the present invention is applied.

FIG. 4 is an enlarged view showing a part of the disc shown in FIG.

[Explanation of symbols]

 30 plate 31, 32 split ring 33 push bolt

Claims (1)

[Claims] 1. A mold having a predetermined shape is fixed at its peripheral edge, and a milling process is performed on the surface to be processed with a pressing force being applied to the center of the surface of the mold opposite to the surface to be processed. As a result, the surface to be processed is formed into a concave spherical surface, and a molding method for pressing a rubber plate for wafer placement in an ion implantation apparatus is characterized.