JPS5894746A - Ion beam electrostatic scanner - Google Patents

Abstract

PURPOSE:To secure excellent injection uniformity, by scanning a beam in one direction by means of a fixed triangular wave signal, while sweeping the beam with a speed in proportion to the beam current quantity in the perpendicular direction to it. CONSTITUTION:A beam deflecting electrode 1 connets with an oscillator 10 generating a fixed triangular wave, through which an ion beam 3 is scanned in the x-axis direction. In addition, the deflecting electrode 2 connectes with the output of an integrator 4 and thereby scanning is carried out with a speed in proportion to be beam in the y-axis direction. Furthermore, with a beam current 1B flowing into a target 5, voltage V1 in proportion to the beam current 1B is generated in the output of an I/V converter 6 and this voltage is designed to be impressed to the integrator 4 by way of an analog switch 7. With this, excellent injection uniformity can be secured without being affected by variations in the beam current quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion beam beam scanning system, and more particularly to a static beam scanning system used in an ion implantation system.

Conventional devices of this type use two independent triangular wave generators as the sweep voltage for scanning the target surface with the ion beam, and the frequency ratio of the two independent triangular waves from these two oscillators is By adjusting the distance appropriately, uniform scanning of the entire target surface was achieved. Therefore, it has been impossible to avoid that variations in the ratio of the two frequencies and variations in the beam current affect the uniformity of ion implantation into the target.

SUMMARY OF THE INVENTION An object of the present invention is to provide an effective ion beam electrostatic scanning device that eliminates the above-mentioned drawbacks.

That is, the present invention scans the beam in one direction using a constant triangular wave signal, and at the same time sweeps the beam in a direction perpendicular to that at a speed proportional to the beam current flowing across the target surface, thereby eliminating the effects of variations in beam current. This is to obtain good injection uniformity without causing any damage.

The present invention will be explained in detail below using FIG.

The beam deflection electrode 1 is equipped with an oscillator l that generates a constant triangular wave.
O is connected, whereby the ion beam 3 is scanned in the two axial directions shown in the diagram #I1. The output of an integrating beam 4 is connected to the deflection electrode 2, thereby scanning in the V-axis direction at a speed proportional to the beam current I. Due to the beam current IB flowing through the target 5, the output of the I/V converter 6 has a voltage proportional to II! is generated and applied to the integrator 4 via the analog switch 7. Here, Vl
- to 11. However, if Kl... is the conversion constant and the gain of the integrator, then the scanning voltage applied to the deflection plate 2 will be KxfKsIsdt. Therefore, the V-axis direction of the beam spot on the target 5 is V y =
K t K s I yr and the beam current I1
The amount of injection into the target is DI, which is proportional to the number ζ.
m7Y, -17, and is not affected by fluctuations in the beam current 1. Note that the output frequency of oscillator 2 is v
Assume that it is sufficiently high compared to y+.

The sign inverter 8, the Schmitt trigger 9 and the analog switch 7 are for reversing the direction of movement of the beam spot at the end of the injection region. The upper and lower trip points of the Schmitt trigger 9 are each set to the deflection electrode voltage value when the beam spot is located at the upper end or lower end of the injection region. When the beam spot reaches the end of the injection region, the output of the Schmitt trigger 9 is reversed and the analog switch 7 is switched to start scanning in the opposite direction, so that the speed is proportional to the beam current 1 in the V-axis direction. A round trip scan is realized. Furthermore, as mentioned above, if the scanning speed in the -axis direction is made sufficiently larger than the speed in the V-axis direction, uniform scanning can be performed over the entire target surface without being affected by fluctuations in the beam current (1). That will happen.

By using the present invention, it is possible to eliminate implantation non-uniformity caused by changes in beam current during implantation, which could not be avoided with conventional methods, and implantation non-uniformity due to the synchronization phenomenon of the X-Y scanning signal, which is unique to conventional methods. sex is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ion beam electrostatic scanning device according to the present invention. In addition, as shown in the figure, l...1 axial deflection plate, 2
...1 directional deflection plate, 3... curved ion beam,
4...Integrator, 5...Target, 6
...I/V converter, 7...analog switch, 8...sign converter. 9... Schmidt) IJ, 1o... It is a curved ball square wave oscillator.

Claims (1)

[Claims] In the XY Seiden scanning device for ion beam, XI or Y
In order to scan one of the directions with a constant triangular wave and scan in the direction perpendicular to the other at a speed proportional to the ion beam current incident on the target, the incident ion beam current is integrated and the waveform is proportional to the integral value. An ion beam electrostatic scanning device characterized in that it generates a scanning voltage.