JPH0218851A - Ion implanter - Google Patents

Abstract

PURPOSE:To improve the precision of ion implantation in response to the fluctuation of a beam current by detecting a radiated ion beam via a through hole provided on a disk mounting an object to be radiated and controlling the radiation position based on the detected value. CONSTITUTION:A wafer 1 to be implanted with ions is mounted on the front face of a disk 2 rotated around a rotary shaft 4, an ion beam B is radiated on it. The disk 2 is moved in the perpendicular direction to the rotary shaft 4 via a driver 9 and a stepping motor 8. A through hole 3 or a notch is provided on the disk 2 the ion beam 3 passes the through hole 3 end enters an ion beam detector 10, the current value of the ion beam is measured by a controller 11, the driver 9 is controlled based on it. Ions can be implanted with high precision by this control even if the fluctuation of the ion beam current occurs during radiation.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an apparatus for implanting predetermined ions into a semiconductor wafer, and more particularly to an ion implanter capable of performing highly accurate ion implantation even when there are fluctuations in ion beam current (also simply referred to as beam current). Note that in the following figures, the same reference numerals indicate the same or corresponding parts.

[Conventional technology]

As this type of ion implantation apparatus, a system in which a rotating disk holding a semiconductor wafer is not provided with a slit for measuring the ion beam current (hereinafter referred to as a slitless system) is known. This device first measures the beam current only once, and uses that data to determine the disk scanning speed and control the ion implantation.

[Problem to be solved by the invention]

However, the above-mentioned slitless method has the disadvantage that it cannot cope with changes in beam current during the process. SUMMARY OF THE INVENTION An object of the present invention is to provide ion implantation in which the scanning speed can be changed even when the beam current changes during ion implantation, and the amount of ions implanted into a wafer can be controlled.

[Means to solve the problem]

In order to solve the above problems, the device of the present invention provides one surface (such as 2a, hereinafter referred to as the front surface) of the r disk (such as 2).
Semiconductor wafers (1, etc.) are mounted side by side on the top, and while this disk is rotated around a rotation axis (4, etc.) perpendicular to the front surface, the support for the rotation axis is moved in a predetermined direction perpendicular to this rotation axis. In an ion implantation device that is reciprocated in a scanning direction Y1, Y2, etc., and irradiates an ion beam (B, etc.) parallel to the rotation axis toward the front surface of the disk, an area of the semiconductor wafer on the disk. at least one through hole or cutout (such as slit 3)
and ion beam detection means (ion beam detector 10, etc.) for detecting the ion beam through the through hole or notch on the rear surface side of the disk, Measure the beam current value,
and a control means (such as 11) for controlling the speed of the reciprocating drive.

[For use]

In this invention, a slit of a constant width is provided at one or more locations on the disk so that the beam current can be sampled, and this sampling data is input to the V/F converter inside the control device, and an output proportional to the converter output is output to the disk. By inputting data to the scanning motor, the disk scanning speed can be changed even if the beam current changes during ion implantation, making it possible to control the ion implantation in a predetermined manner.

【Example】

The present invention will be explained in detail below based on FIGS. 1 and 2. FIG. 1 is a configuration block diagram of a control circuit including a cross section of a disk as an embodiment of the present invention, and FIG. 2 is a diagram similarly showing the configuration of the front surface of the disk. In FIGS. 1 and 2, 1 is a disk-shaped semiconductor wafer, and 2 is a disk that supports a plurality of wafers l and rotates them in the X direction. They are arranged at approximately equal intervals on a circumference centered on the rotating shaft 4 of the disk 2, while avoiding the slits 3, which will be described later, on the disk 2a. 3 is a predetermined position on this disk 2 (one location in this example)
This is a slit serving as an elongated through hole provided so as to penetrate through the disk 2. Reference numeral 5 denotes a disk support stand that supports the rotating shaft 4 of the disk 2, and 6 a disk rotation motor that is provided on this support stand and rotates the rotating shaft 4 at a predetermined speed. 7 is a feed screw that is screwed into disk support 5, and 8 is a stepping motor that rotates this screw 7. This stepping motor 8 is reversely driven to the left or right via a driver 9. For example, the disk support base 5 is rotated in response to right or left rotation of the stepping motor 8.
moves in the scanning direction Y1 or Y2. This reversal of the scanning directions Y1 and Y2 is repeated every predetermined feeding amount of the disk-supporting table 5. B is an ion beam irradiated from an ion beam generating means (not shown) toward the front surface 2a of the disk 2;
passes through a spatially defined position and runs on a path parallel to the rotation axis 4. Therefore, based on the rotation of the disk 2 in the X direction and the repeated movement of the disk support 5 in the scanning directions Yl and Y2, the beam B is projected onto the surface of the wafer l when the wafer 1 enters the path of the beam B. The ionic material is implanted into the wafer 1 while scanning the wafer. Also, due to the rotation of disk 2 (in this example, disk 2
(once per rotation of the disk) When the slit 3 comes within the path of the ion beam B, the ion beam B passes through the slit 3 and enters the ion beam detector 10 provided on the rear side of the disk 2. Then, the current of the ion beam is detected as described below. Reference numeral 11 denotes a control device that controls the entire device. That is, in the control bag W 11, I6 is a CPU which is the main body of control execution, 15 is a timing generator, and this generator 1
5 is an encoder (not shown) attached to the disk rotating motor 6, and the slit 3 is detected in front of the ion beam detector 10, that is, the ion beam B is detected through the slit 3 as indicated by the broken line arrow in FIG. At a position where it can enter the vessel 10,
It detects that the timing signal 15a has arrived and sends the timing signal 15a to the CPU 6.
give to Reference numeral 12 denotes a sample and hold amplifier, which samples the current value of the ion beam B based on the command 16a of the CPtJ 16 into which the timing signal 15a is input, holds this sampling value 12a until the next sampling time, and outputs the V/F converter 13. give to The V/F converter 13 converts the sampled value 12a of the beam current into a frequency 13a. 17 is a beam counter that outputs V/l” convert output signal (
frequency) 13a and output the count signal 17a to CP.
Give to U16. Thereby, IOCP tJ16 can determine the ion implantation amount as a so-called dose amount. ■4 is the frequency divider and the same < V/F converter output signal 13
a is frequency-divided based on the control command 16b of the CPU 16, and the frequency-divided output signal 14a is given to the driver 9. The driver 9 drives the steering and ping motor 8 at a speed proportional to the frequency-divided output signal 14a. As a result, the rotational speed of the feed screw 7 (and therefore the moving speed of the disk support 5, that is, the scanning speed) is proportional to the frequency-divided output signal 14a. Further, the CPU 16 inputs the output 14a of the frequency divider 14 and can know the number of scans, the amount of movement of the disk support 5 (therefore, the relative position of the ion beam B with respect to the disk support 5), and the like. In this way, the CPU 16 performs predetermined calculations based on the frequency-divided output signal 14a, the output signal 17a of the beam counter 17, etc., issues a control command 16b, and sends a control command 16b to the frequency divider 14.
The frequency division ratio, and therefore the frequency division output signal 14a, that is, the scanning speed of the ion beam B with respect to the disk (or wafer 1) is variably controlled. In the above description, the disk 2 is provided with a slit 3 as a through hole, but the present invention is also applicable even if the slit is not a hole but a long and narrow cutout around the disk 20. it is obvious.

【Effect of the invention】

According to this invention, the ion beam current is sampled and measured at a relatively high frequency by providing a slit in the disk, and the scanning speed of the ion beam with respect to the wafer can be variably controlled according to the sampling value, so that the ion beam current can be variably controlled during ion implantation. Highly accurate ion implantation control is possible even when there are fluctuations in the beam current.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control device including a cross section of a disk as an embodiment of the present invention, and FIG. 2 is a front view of the disk. B: Ion beam, 1: Wafer, 2: Disk, 3 Nislit, 4: Rotating shaft, 5: Disk support stand, Disk rotating motor, 7: Feed screw, 8 Nistemping motor, 9
: Driver, 10: Ion beam detector, 11: Control device.

Claims (1)

[Claims] 1) Semiconductor wafers are mounted side by side on one surface (hereinafter referred to as the front surface) of a disk, and while the disk is rotated around a rotation axis perpendicular to the front surface, a support for the rotation axis is attached. is reciprocated in a predetermined direction perpendicular to the rotation axis to irradiate the front surface of the disk with an ion beam parallel to the rotation axis. , ion beam detection means for detecting the ion beam through the through hole or notch on the rear surface side of the disk, and at least one through hole or notch; An ion implantation apparatus comprising: control means for measuring the current value of the ion beam and controlling the speed of the reciprocating drive.