JPS61114456A - Ion implantation equipment - Google Patents

Abstract

PURPOSE:To reduce the difference in the time of a beam irradiation staying on each part of the wafer by rotating a rotary plate having semiconductive wafers attached along the circumferential direction and reciprocating the rotary plate perpendicularly to the direction of ion beam irradiation. CONSTITUTION:A rotary plate 8 having several conductor wafers 9 attached along the circumferential direction is installed in an airtight chamber 1. A motor 6 installed in a small chamber 1, which is isolated from the airtight chamber 1 by means of a magnetic fluid seal 12 and a bellows 11, is used to rotate the rotary plate 8 with an angular velocity of omega. A motor 2 and a reciprocating-motion-converting mechanism 3 are used to reciprocate the small chamber 10 at a velocity of VR perpendicularly to an ion beam 13. When the distance between the ion beam 13 and the rotary plate 8 is supposed to be R, the reciprocating motion is controlled so that omega becomes constant and VR is in inverse proportion to R. Accordingly, it is possible to equalize the degree of ion implantation by making the amount of an ion beam irradiation upon each part of the wafer 9 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ion implantation apparatus for doping impurities into a wafer to be processed, such as a semiconductor wafer.

[Background technology] When performing high-current ion implantation into semiconductor wafers, a mechanical scanning method with a fixed ion beam is most suitable.
Truck-type ion implantation equipment is widely used.

Among these, in the 7 Ellis wheel type ion implantation device, a wafer support is rotated along a vertical plane by a motor drive, and a large number of semiconductor wafers are supported around this wafer support so that their main surfaces are always horizontal. It has a structure in which the entire device is placed in an airtight container in a vacuum state, and an ion source is provided at the top.

According to this method, as shown in Figure @1 (,), the rotation locus at the center of the semiconductor wafer is a solid circle (centered at 0), while the rotation locus at the periphery of the wafer is a broken line circle (O There is a drawback that the residence time of the ions in the wafer differs for the semiconductor wafer which is placed at the top of the wafer (centered on the wafer), and therefore the amount of ions implanted becomes non-uniform.

On the other hand, the race track type ion implantation device is shown in Figure 1 (
As shown in b), a belt is looped around a group of rollers and driven by a motor, and a semiconductor wafer is mounted on the belt. The ion beam is irradiated from the ion source.

In the case of this ion implantation equipment, the belt bends and it is difficult to irradiate each part of the semiconductor wafer with an ion beam of minute width perpendicularly, so the amount of ion beam irradiation on each part of the wafer is As a result, the amount of ion implantation becomes uneven.

In both of the above methods, the drive unit and rotation transmitter structure are structurally installed inside the ion implantation chamber, and since these have complex mechanisms, a large amount of fine dust due to wear of the drive unit floats in the airtight chamber. However, there was a problem of contamination of the semiconductor wafer surface.

In addition, US Patent No. 37786 discloses a method of fixing the beam and rotating the semiconductor wafer while moving the rotary plate up and down.
It is disclosed in the specification of No. 26.

[Object of the Invention] An object of the present invention is to equalize the amount of ion implantation by reducing the difference in the dwell time of ion beam irradiation to each part of a wafer to be processed.

The present invention provides an ion implantation apparatus that mechanically scans an ion beam onto a wafer by fixing the direction of the ion beam and moving the wafer to be processed. It is equipped with a rotary plate that rotates at an angular velocity ω in an airtight chamber, a rotary drive unit directly connected to the rotary plate within the container, and a reciprocating drive and control unit provided outside the container that causes the rotary drive unit to reciprocate and linearly move at a speed VR. death,
The distance between the ion beam and the rotation axis is R, VR is fixed, and the rotary drive unit is controlled so that ω is inversely proportional to R. This allows the ion beam to be directed to the wafer on the rotating plate. This averages the irradiation time.

[Embodiment] FIG. 2 shows an embodiment of the ion implantation apparatus of the present invention.

As shown in the figure, the vacuum evacuation airtight chamber 1 of the ion implantation device
A reciprocating drive section consisting of a motor 2 and a reciprocating motion converting mechanism 3 for converting the motor 2 into rotational motion is installed outside the external container having a reciprocating motion shaft 4 connected to the rotation drive section inside the container. This rotary drive unit consists of a support base 5 and a rotary drive motor 6, and a rotary plate 8 that rotates within the airtight chamber is connected to the tip of the pongee 7 of the rotary drive motor 6.

A plurality of semiconductor wafers 9 are arranged and mounted on the rotary plate 8 along the circumferential direction as shown in FIG. A fixed ion beam is irradiated from a predetermined position in the airtight chamber. The rotational drive section is surrounded by a small container 10, and a bellows 11 is interposed between the small container 10 and the external container 1, so that the rotational drive section inside the small container 10 can be moved outside the airtight chamber. At the same time, the elasticity of the bellows 11 enables linear reciprocating motion in the direction perpendicular to the rotating shaft of the rotary drive unit within the external container 6. On the other hand, a magnetic fluid seal is provided between the rotating shaft 7 and the small container 10. 12 is inserted to maintain airtightness between the airtight chamber 1 and the small container 10 in which the rotary plate 8 rotates. Reference numeral 13 denotes an ion implantation hole provided in a part of the airtight chamber 1, in which an ion source (not shown) is placed.

Next, the operation will be briefly explained.

While the vacuum pump 14 is operated to create a vacuum inside the airtight chamber 1, the reciprocating drive section and the rotation drive section are driven.

The rotary drive motor 6 is rotated to rotate the rotary plate 8 at a constant angular velocity ω, and the surface of the semiconductor wafer 9 mounted in advance on the rotary plate 8 is irradiated with an ion beam from the ion implantation hole 13 at right angles. do. By reciprocating the reciprocating part when facing outward, the entire rotary drive part moves within the external container through the reciprocating axis, and therefore the entire rotary plate reciprocates in the direction (plane) connecting the axis and the ion implantation direction. do. At this time, the distance between the axis and the ion implantation direction is R, and the reciprocating movement speed is VR. If the above VR is constant and ω is controlled so that ω is inversely proportional to R, ω is slow when the beam position is on the outer periphery of the rotary plate, and becomes faster as it approaches the center. The dwell times of the wafer sections are averaged.

The above-mentioned VR can be controlled by detecting the distance with a moving distance measuring magnet scale provided in the reciprocating mechanism and controlling the motor 2 by the control section.

[Effects] According to the present invention described in the above embodiments, the intended purpose is achieved for the following reasons.

That is, the rotary plate on which the wafer is placed is rotated at a constant angular velocity, and at the same time, the rotary plate is reciprocated in the radial direction at a moving speed that is inversely proportional to the distance from the center of the disk to the ion beam irradiation position.

Therefore, if the surface of a semiconductor wafer mounted on a rotary plate is irradiated with an ion beam, all parts of the semiconductor wafer will have the same opening during ion beam irradiation. Therefore, the amount of ion implantation becomes uniform.

According to the present invention, since the ion beam is irradiated perpendicularly to the surface of the semiconductor wafer on the rotating plate, a constant plane is maintained unless the rotating plate is eccentric, and the width of each part of the semiconductor wafer is small. It is possible to irradiate the entire ion beam perpendicularly, and in combination with the above-mentioned ω control to average the beam residence time, it is possible to equalize the amount of ions implanted into each part of the semiconductor wafer.

Further, according to the present invention, since the rotary drive and reciprocating drive parts are installed outside the airtight chamber, ions can be implanted into the airtight chamber without any fine dust from the drive mechanism floating in the airtight chamber. . Therefore, contamination of the semiconductor wafer can be reliably prevented.

The present invention is not limited to the above embodiments.

The reciprocating motion conversion mechanism may utilize a cam or ring mechanism, or the like.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams of the principle of a conventional ion implantation device, FIG. 2 is a schematic diagram of an embodiment of the ion implantation device of the present invention, and FIG. 3 is an explanation of its rotary plate. It is a diagram. 1. Airtight chamber, 2. Motor, 3. Reciprocating motion conversion mechanism,
4. Reciprocating shaft, 5. Support stand, 6. Rotation drive motor, 7. Axis, 8. Rotating plate, 9. Semiconductor wafer, 1
0... Small container, 11... Bellows, 12... Magnetic fluid seal, 13... Ion implantation hole, 14... Vacuum pump. Figure 1 (a) (b) Figure 2

Claims (1)

[Claims] 1. In an ion implantation device in which the ion beam direction is fixed and the ion beam is mechanically scanned over the wafer by moving the wafer to be processed, an external container having an airtight chamber that is evacuated to vacuum, and the airtightness of this container are used. A rotary plate that rotates at an angular velocity ω indoors, a rotary drive unit connected to the rotary plate within the container, and a reciprocating drive and control unit provided outside the container that reciprocates the rotary drive unit at a speed V_R, Let the distance between the ion beam and the axis of the rotating plate be R, and keep ω constant and V
An ion implantation device characterized in that the operation of the reciprocating drive unit is controlled so that _R is inversely proportional to R.