JPH02129844A - Irradiation of ion beam - Google Patents

Abstract

PURPOSE:To reduce a difference in an irradiation quantity of an ion beam by a method wherein a target is bent symmetrically to an imaginary plane including a rotary center of a disk and a bus of a conical inner wall surface and in cylindrical shape convex to the conical inner wall side while being so constituted that a straight line passing through the center of the target placed and fixed may be parallel with the bus. CONSTITUTION:A pedestal 7 puts a target 5 between holding arms 71 for bending it in cylindrical shape while closing the tips of the arms 71 and pressing the target from both sides. In this way, the target is bent symmetrically to an imaginary plane including the disk rotary center O and a bus (g) of a conical inner wall surface while being convex to the conical inner wall surface, and at the same time being so constituted that a straight line going through the center of the placed target may be parallel with the bus (g). Thereby, a difference in scanning speed of an ion beam in the central part and at the end part of the target is reduced, moreover the incident direction of the ion beam at the end part nears to a right angle so that a difference in an irradiation quantity of the ion beam to the target can be reduced.

Description

[Detailed Description of the Invention] [Summary] Regarding equipment for manufacturing semiconductor devices, especially equipment for irradiating wafers with ion beams, the present invention relates to equipment for irradiating large-sized targets with ion beams, which reduces the difference in irradiation dose. An ion beam irradiation device that aims to provide a beam irradiation method, in which multiple disc-shaped targets are placed on the inner wall of a cone surrounding a disk, and ion beams are irradiated onto the targets from a fixed direction while rotating the disk. Curving the target into a cylindrical shape that is bilaterally symmetrical with respect to a virtual plane including the rotation center of the disk and the generatrix of the inner wall surface of the cone and convex toward the inner wall surface of the cone,
The configuration is such that a straight line passing through the center of the placed target is parallel to the generatrix g.

[Industrial application field]

The present invention relates to equipment for manufacturing semiconductor devices, and particularly to equipment for irradiating wafers with ion beams.

2. Description of the Related Art In recent years, wafers have rapidly increased in size in the manufacture of semiconductor devices, and as a result, it has become important to establish a technique for uniformly processing the wafer surface. For example, in an ion implantation process, an important issue is how to equalize the amount of ion beam irradiated onto a wafer.

[Conventional technology]

FIG. 3 is a side sectional view showing the main parts of the ion beam irradiation device.

In FIG. 3, the ion beam irradiation device has a disk 3 mounted inside a vacuum chamber 1, which is driven and rotated by a motor 2 outside the vacuum chamber 1, and a conical inner wall surface 4 is provided around the disk 3. A plurality of wafers to be irradiated, that is, disk-shaped targets 5 are placed on the inner wall surface 4 of the disk 3. In the conventional ion beam irradiation method, regardless of the size of the target 5, the target 5 is placed on the conical inner wall surface 4 in a flat plate shape without being bent.

On the other hand, a highly accelerated ion beam 6 formed by an ion beam generation mechanism and an acceleration mechanism (not shown) enters the vacuum chamber 1 from a fixed direction and irradiates the target 5 placed on the inner wall surface 4 of the cone. The area of the target 5 is wider than the spot diameter of the ion beam 6, but for example, if the disk 3 is
The entire surface of the target 5 can be irradiated with the ion beam 6 by rotating the disk 3 at a speed of 00 to 900 PPM and at the same time reciprocating the disk 3 in the direction of the rotation axis or in the direction of the surface including the ion beam.

[Problem to be solved by the invention]

FIG. 4 is a perspective view showing details of the mounted target.

When looking from above at the contact position between the conical inner wall surface 4 and the target 5, as shown in the figure, the linear target 5 is in contact with the conical inner wall surface 4 having an arcuate cross section at both ends, but is separated in the middle, and the disk 3 Target 5 from the rotation center of
The distance R1 is shortest at the center of the target 5 and increases as the distance from the center increases. The difference in R3 is the distance R2 from the rotation center of the disk to the conical inner wall surface 4.
and target radius R3, the difference in distance R1 increases as Rz/Rs decreases.

For this reason, even if the rotation of the disk is constant, the scanning speed of the ion beam is slow at the center of the target 5 and increases as it moves away from the center. Also target 5
The ion beam 6 is incident at the center from a right angle direction, but at a position away from the center, the ion beam 6 is incident from an oblique direction.

As a result, the amount of ion beam irradiation on the target 5 varies depending on the position.

FIG. 5 is a schematic diagram showing a conventional ion beam irradiation dose distribution.

In the figure, the arrows shown at various locations on the target 5 indicate the irradiation dose at that point, and the broken lines connecting the heads of the respective arrows represent the irradiation dose change on the corresponding coordinates. According to the figure, there was a problem in that the amount of ion beam irradiation per unit area of the target was large in the center and decreased significantly as the distance from the center increased.

By the way, the ratio R2/R:l of the distance from the center of rotation of the disk to the inner wall surface of the cone and the radius of the target is 3, the angle between the plane of the disk and the target is 80 degrees, and the angle of incidence of the ion beam on the target is When simulated at 7 degrees, the difference in ion beam irradiation amount, that is, the standard deviation value of the distribution anomaly was 1.136%.

An object of the present invention is to provide an ion beam irradiation method that reduces the difference in irradiation dose in an apparatus for irradiating a large target with an ion beam.

[Means to solve the problem]

FIG. 1 is a principle diagram showing the irradiation method according to the present invention. The same objects are represented by the same symbols throughout the plan.

The above problem involves a plurality of disc-shaped targets 5 being placed on a conical inner wall surface 4 provided around a disc 3, and an ion beam 6 is emitted from a certain direction while rotating the disc 3.
In an ion beam irradiation device that irradiates disk 3
The target 5 is curved into a cylindrical shape that is bilaterally symmetrical with respect to a virtual plane that includes the rotation center 0 and the generatrix g of the conical inner wall surface 4 and is convex toward the conical inner wall surface 4 side, and a straight line that passes through the center of the target 5. target 5 so that it is parallel to the generatrix g.
This is achieved by the ion beam irradiation method of the present invention.

[For production]

In Fig. 1, the target is curved into a cylindrical shape that is symmetrical with respect to a virtual plane that includes the rotation center O of the disk and the generatrix g of the inner wall surface of the cone, and is convex toward the inner wall surface of the cone. By configuring the target so that the straight line passing through the center is parallel to the generatrix g, the difference in scanning speed of the ion beam between the center and the edges of the target is reduced, and the direction of incidence of the ion beam at the edges approaches a right angle. Therefore, the difference in the amount of ion beam irradiation to the target can be reduced.

[Example] An example of the present invention will be described below with reference to FIG. Note that FIG. 2 is a plan view showing an example of the receiver.

The reason why the standard deviation value of the distribution abnormality becomes large in the conventional irradiation method is that, as shown in Figure 5, the ion beam irradiation dose in areas far from the center is significantly lower than the ion beam irradiation dose in the center. It's in what you're doing.

In other words, as is clear from the figure, the radiation dose distribution within the target is based on the generation line g between the rotation center of the disk and the inner wall surface of the cone.
The dotted line connecting the maximum irradiation dose point has a cylindrical shape with the conical inner wall side parallel to the generatrix g being concave.

Therefore, in order to correspond to the dose distribution in the conventional irradiation method, the target is arranged in a cylindrical shape that is symmetrical with respect to a virtual plane that includes the center of rotation of the disk and the generatrix g of the inner wall surface of the cone, and that is convex toward the inner wall surface of the cone. By curving the target and at the same time configuring it so that a straight line passing through the center of the mounted target is parallel to the generatrix g, the standard deviation value of the distribution abnormality of the ion beam irradiation amount can be brought close to zero.

In FIG. 1, the ion beam irradiation device used in the irradiation method of the present invention has a disk 3 mounted inside a vacuum container 1 and rotated by a motor 2.
A conical inner wall surface 4 is provided around the disk 3,
The target 5 is held by a stand 7 which is attached to the inner wall surface 4 of the cone. A highly accelerated ion beam 6 formed by an ion beam generation mechanism and an acceleration mechanism enters the vacuum chamber 1 from a fixed direction and irradiates a target 5 held by a receiver 7 .

For example, as shown in FIG. 2, the receiver pedestal 7 includes a holding arm 71 pivoted to the conical inner wall surface 4, and a link mechanism 72 for opening and closing the tip of the holding arm 71, as shown in FIG. 2(b). Insert the target 5 between the holding arms 71 as shown in FIG.
2, the tip of the holding arm 71 closes and the target 5 is pushed from both sides and curved into a cylindrical shape, as shown in FIG. 2(a).

The back surface of the target 5 curved into a cylindrical shape is supported by a holding arm 71, and the front surface is held down by a claw 73 provided at the tip of the holding arm 71, so that the receiver does not fall off the table 7. Note that the tip of the holding arm 71 that supports the back surface of the target 5 is formed parallel to the inner wall surface 4 of the cone. Therefore, a straight line passing through the center of the target is parallel to the generatrix g.

In this way, the rotation center 0 of the disk and the generatrix g of the inner wall surface of the cone
The target is curved into a cylindrical shape that is bilaterally symmetrical with respect to an imaginary plane containing and convex toward the inner wall surface of the cone, and at the same time, the straight line passing through the center of the mounted target is parallel to the generatrix g. As a result, the difference in scanning speed of the ion beam between the center and the edges of the target is reduced, and the direction of incidence of the ion beam at the edges approaches a right angle, making it possible to reduce the difference in the amount of ion beam irradiation to the target. can.

By the way, the ratio R, /R3 of the distance from the center of rotation of the disk to the inner wall surface of the cone and the radius of the target is 3, the angle between the plane of the disk and the target is 80 degrees, and the angle of incidence of the ion beam on the target is 7. When simulating the case where the target is curved into a cylindrical shape,
The standard deviation value of the distribution anomaly is 0.036%, which is 30% of the standard deviation value in the conventional method.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an ion beam irradiation method that reduces the difference in irradiation amount in an apparatus for irradiating a large target with an ion beam.

It is. In the figure 1 is a vacuum container, 3 is the disk, 5 is discoid Targera 7 is the uke, 72 is a link mechanism; respectively.

2 is a motor, 4 is a conical inner wall surface, G, 6 is an ion beam, 71 is a holding arm; 73 is a nail,

[Brief explanation of drawings]

Fig. 1 is a principle diagram showing the irradiation method according to the present invention, Fig. 2 is a plan view showing an example of a receiver, Fig. 3 is a side sectional view showing the main parts of the ion beam irradiation device, and Fig. 4 is a diagram showing the principle of the irradiation method according to the present invention. Figure 5 is a schematic diagram showing the conventional ion beam irradiation dose distribution. , -f
Pregnancy plan for pregnancy 5 Figure

Claims (1)

[Claims] A plurality of disc-shaped targets (5) are placed on a conical inner wall surface (4) provided around the disc (3), and the disc (3)
The ion beam (6) is emitted from a certain direction while rotating the
In the ion beam irradiation device for irradiating the target (5), the ion beam irradiation device is symmetrical with respect to a virtual plane including the rotation center o of the disk (3) and the generatrix g of the conical inner wall surface (4), and ) The target (5) is curved into a cylindrical shape convex to the ) side, and the target (5) is placed so that a straight line passing through the center of the target (5) is parallel to the generatrix g. An ion beam irradiation method characterized by: