JPH01183049A - Ion radiation device - Google Patents

Abstract

PURPOSE:To improve the beam utilizing efficiency and to make it possible to implant ions at a high accuracy by measuring the ion beams continuously, and cutting the parallel driving of a target plate at the time other than the time of movement of an ion beam radiation member and its radius part in a specific distance. CONSTITUTION:A continued ion current is detected by a Faraday cup 16 with a disk-form target plate 11 at the bottom. The ion current is converted into a voltage by an I/V converter 18, and further converted into a constant frequency of pulse line. On the other hand, a reflection type photo-sensor 17 arranged at the rear side of the target plate 11 detects the reflected light from a mirror body 11a furnished at the rear side of the target plate 11, and the detected signal is given to a photo-sensor detector 22. The detector 22 closes a switch 20 only when the mirror body 11a passes by the sensor 17, and outputs a control signal to open the switch 20 in the other time. Consequently, it is not necessary to form slits in the target plate 11, the beam utilizing efficiency is improved, and a high accuracy of ion implantation can be made.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an ion irradiation device having a disk-shaped target plate, and more specifically, includes a mechanism for correcting temporal changes in beam current and changes in beam irradiation position on the disk-shaped target plate. The purpose of this project is to provide an ion irradiation device with a disk-shaped target plate that can achieve uniform ion implantation easily and with high precision, and that can also improve beam utilization efficiency. An ion irradiation device for irradiating an ion beam onto a disk-shaped target plate, comprising: a translation drive means for translationally driving the disk-shaped target plate in proportion to continuously measured ion beam current; and an ion beam irradiation section of the disk-shaped target plate. and a cutting means for cutting off a part of the translation drive means during a time other than the time required for a portion of the same radius to move a certain distance.

[Industrial application field]

The present invention relates to an ion irradiation device having a disk-shaped target plate, and more particularly to an ion irradiation device equipped with a mechanism for correcting temporal changes in beam current and changes in the beam irradiation position on the disk-shaped target plate.

[Conventional technology]

An ion irradiation device is a device that irradiates a solid with ions accelerated at a high voltage to perform impurity doping, control of physical properties of a solid surface, etc., and is used in various processes for manufacturing semiconductor devices.

Among these ion irradiation devices, those for large currents are
For example, a wafer receives 7W of electricity per unit time! In order to prevent problems such as overheating and charging due to excessive beam energy, a mechanical scanning method using a disk-shaped target on which a plurality of Ueno\ is mounted is generally used.

FIG. 4 is a configuration diagram showing an example of a conventional high-current ion irradiation device. In the drawing, the ion irradiation device has a large number of wafers 2 arranged circumferentially on the surface of a circular disk-shaped target plate 1. The target plate 1 is driven at a constant high speed rotation by a disk rotation motor 3, and at the same time is driven to translate by a disk translation motor 4, and an ion beam is irradiated onto the wafer \2 on the target plate 1 through a mask or the like. A slit portion 5 having a constant width is formed in the target plate 1 from the center to the circumferential direction. Also,
On the back side of the target plate 1, there is a Faraday cup 6 for detecting the ion current of the beam passing through the slit section 5.
and a suppressor 7 that prevents ion current measurement errors due to secondary electrons, and a T that converts the detected ion current into voltage.
A /V (current/voltage) converter 8, a V7F (voltage/frequency) converter 9 that converts voltage into frequency, a through controller 10 that applies drive pulses according to the frequency to the disk translation motor 4, and the like are provided.

In such an ion irradiation device, it is necessary to correct temporal changes in the beam current and changes in the beam irradiation position in the radial direction of the rotating target plate 1 in order to perform uniform ion implantation. This can be realized by driving the disk translation motor 4 in proportion to the amount of current of the beam passing through the section 5.

That is, the ion beam current irradiated onto the target plate 1 is IR, the slit width of the slit part 5 is IR, the beam irradiation position on the target plate 1 is R, the dose is D, and the rotation frequency of the disk translation motor 4 is f. , the number of round trips of translation is n
, the amount of charge of the ion is q, then the following equation holds true.

Is ・1/f = q(D/n)2πRΔRf=IE/
(q(D/n)2πRΔRl -----
-(1) Here, if the average value of the current passing through the slit portion 5 is defined as the king, then 1=(separate/2πR) 1. −−−−−−−−
−−−−−− (2) From formulas (1) and (2), f = I / (q(D/n)WΔ11) −−
−−−−−−−−−−−−(3) holds true. this(
3) Equation shows that Q+D+n+JΔ, R is a constant, and f is proportional to T. Therefore, by detecting and controlling this T, temporal changes in the beam current and changes in the beam irradiation position on the target plate 1 can be automatically performed. This allows for uniform ion implantation.

[Problem that the invention seeks to solve]

However, in the above-mentioned ion irradiation apparatus, since the slit section 5 must be provided in a part of the target plate 1, the area for placing the wafer 2 is reduced, and the beam utilization efficiency is reduced accordingly. In addition, since the beam current is measured only when passing through the slit section 5, short-term fluctuations are ignored, and the input of the first stage amplifier of the beam current measurement system is
In some cases, the current is extremely small, on the order of several μΔ, and pulsed currents must also be amplified with high precision of 1% or less, so conditions such as high gain, high slew rate, low drift, and low offset must be met. However, there was a drawback that the design was difficult.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ion irradiation apparatus having a disk-shaped target plate, which can easily and accurately perform uniform ion implantation and improve beam utilization efficiency.

[Means for solving problems]

The above problem is solved by an ion irradiation device that irradiates a rotating disk-shaped target plate with an ion beam. An ion irradiation device comprising a cutting means for cutting a part of the translation drive means during a time other than the time required for a portion of the ion beam irradiation part of the shaped target plate to move a certain distance. solved by.

[Effect]

In the present invention, the ion beam current irradiated to the disk-shaped target plate is continuously measured, and the translational drive of the disk-shaped target plate is controlled to be cut off at times other than the time when a portion with the same radius as the ion beam irradiation part moves a certain distance. be done. Therefore, since the translational movement is controlled in proportion to the ion beam current and inversely proportional to the radius, temporal changes in the ion beam current and changes in the beam irradiation position on the disk-shaped target plate can also be automatically corrected. The time it takes for a portion of the same radius as the ion beam irradiation part to move a certain distance can be done on the back side of the disk-shaped target plate, which improves beam utilization efficiency and increases the detection distance in the circumferential direction. By providing a large number of them, it is possible to respond to minute changes in the ion beam current, making it possible to perform highly accurate ion implantation. Furthermore, by measuring a continuous thick ion beam current, it becomes easier to design the first stage amplifier of the control system.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an ion irradiation device according to an embodiment of the present invention, and FIG. 2 is a rear view of the disk-shaped target plate of FIG. 1. In these figures, the ion irradiation device is
It has a circular disk-shaped target plate 11, and a large number of wafers 12 are arranged on the circumference of the surface thereof. This disk-shaped target plate 11 is connected to a disk rotating motor 13.
At the same time, it is driven by the disk translation motor 14 to perform reciprocating translational movement in a direction perpendicular to the rotation axis. An ion beam generated from an ion source (not shown) passes through a mask, etc., and further passes through a suppressor 15 and a Faraday cup 16 on the surface side of the disk-shaped target plate 11 on which the wafers 12 are arranged.
irradiated onto the surface of The Faraday cup 16 is placed close to the disk-shaped target plate 11, and detects the ion beam current using the target plate 11 as its bottom.
The suppressor 15 prevents errors in ion current measurement due to secondary electrons. On the other hand, as shown in FIG. 2, the back surface of the disk-shaped target plate 11 has a constant width, a length longer than the scanning width, and a large number of mirror-finished parts 1 radially extending from the center of rotation.
1a is formed. In addition, a reflective optical sensor 17 that detects light irradiated onto the mirror surface portion 11a from a light source (not shown) is fixed to the apparatus main body at a position opposite to the back surface (indicated by a dotted line) of the beam irradiation position of the disk-shaped target plate. ing. Continuous current of ion beam detected by disk-shaped target plate 11 and Faraday cup 16 (I8)
is converted into a voltage by an I/V converter 18, converted into a frequency by a V/F converter 19, and further converted into a frequency by a switch 20.
The through controller 21 converts the signal into a drive pulse, which will be described later, and applies it to the disk translation motor 14, which includes a pulse motor or the like. The detection signal of the reflective optical sensor 17 is given to the optical sensor detecting section 22, and the optical sensor detecting section 22 detects that the reflective optical sensor 17 is connected to the mirror surface portion 11a.
Close the switch 20 only when light from the
The switch 20 is controlled to be opened when no light is detected.

That is, a pulse train of a constant frequency corresponding to the continuous ion beam current IB is periodically applied to the through controller 21 only when the switch 20 is closed. The through controller 21 smoothes the rising and falling portions of the periodically applied pulse train to make them gentler and applies them to the disk translation motor 14 as drive pulses.

The operation of the ion implantation apparatus having the above configuration will be explained.

The ion beam generated from the ion source passes through a mask,
Further, the ions pass through a suppressor 15 and a Faraday cup 16, and are irradiated onto a disk-shaped target plate 11 driven by a disk rotation motor 13 at a constant high speed rotation, whereby ions are implanted into a wafer 12. At this time, a continuous ion beam current (Il) is detected by the Faraday cup 16 having the disk-shaped target plate 11 as the bottom. This ion current (■,) is converted into a voltage by the I/V converter 18, and this voltage is further converted into a pulse train of a constant frequency. That is, the ion beam current (1B) is converted into a pulse train proportional to the current value. On the other hand, a reflective optical sensor 17 provided on the back side of the beam irradiation position of the disk-shaped target plate 11 detects the reflected light from the mirror surface 11a formed on the back side of the disk-shaped target plate 11, and outputs the detection signal. It is applied to the optical sensor detection section 22.

The optical sensor detection section 22 outputs a control signal that closes the switch 20 only during the time when the mirror surface section 11a passes by the reflective sensor 17, and opens the switch 20 at other times.

That is, the optical sensor detection unit 22 detects the distance (R) between the rotation center of the disk-shaped target plate 11 and the beam irradiation position.
The switch 20 is opened and closed using a control signal corresponding to a time interval that is inversely proportional to the constant width (W) of the mirror surface portion 11a.

Therefore, the pulse train proportional to the ion beam current (I8) is transmitted to the switch 2 controlled by the optical sensor detection section 22.
0 to the through controller 21. The through controller 21 generates a drive pulse that smooths out the rising and falling parts of a periodically applied pulse train, and this drive pulse drives the disk translation motor 14.
given to. The disk translation motor 14 applies a translational motion to the disk-shaped target plate 11 using a drive pulse given from the through controller 21 . As a result, the disc-shaped target plate 11 is proportional to the ion beam current (tn), inversely proportional to the distance (R) between the rotation center of the disc-shaped target plate 11 and the beam irradiation position, and the mirror surface part 11
Performs a translational movement proportional to the width of a. Therefore, based on the same principle as in the conventional example, temporal changes in the ion beam current and changes in the beam irradiation position on the disk-shaped target plate 11 are corrected.

As described above, since the slit portion 5 is not formed in the disk-shaped target plate 11, the area on which the wafer 12 is arranged can be increased by that amount, and the beam utilization efficiency can be improved.

Furthermore, on the back surface of the disk-shaped target plate 11, a large number of mirror surfaces 11a having a constant width are formed radially, so that it is possible to detect short-term fluctuations in the ion beam current while the disk-shaped target plate 11 rotates. This allows highly accurate ion implantation.

FIG. 3 is a configuration diagram showing an ion irradiation device according to another embodiment of the present invention. The parts corresponding to Figure 1 are as follows:
The same reference numerals will be used, and detailed explanations thereof will be omitted. In this ion irradiation device, a measurement disk 23 is disposed coaxially with the rotation axis of the disk-shaped target plate 11 and is driven by the same disk rotation motor 13 at the same rotation.

This detection disk 23 has holes 24 which have a constant width, a length longer than the scanning width, and are formed radially from the center of rotation.
There are many. Then, the detection disk 2
A light source section 25 such as a lamp and a transmission type optical sensor 26 are arranged with the hole 24 of No. 3 in between. This transmission type optical sensor 26 detects the light that passes through the hole 24 from the light source section 25 and provides the detection signal to the optical sensor detection section 22.

The other configuration is the mirror surface part 1 on the back of the disk-shaped target plate 11.
It is the same as the previous example except for 1a.

In the ion irradiation device having the above configuration, the light from the light source section 25 passing through the hole 24 of the detection disk 23 which rotates in the same rotation as the disk-shaped target plate 11 is detected by the transmission type sensor 26, and is applied to the optical sensor detection section 22. The switch 20 is opened and closed. Therefore, it functions similarly to the previous embodiment. In the embodiment, the mirror surface portion 11 of the disk-shaped target plate 11
In order to detect a, the reflection type optical sensor 17 and the like must be placed in a vacuum system, but in this embodiment, the detection disk 23, light source section 25, and transmission type optical sensor 26 are placed outside the vacuum system. becomes possible.

In addition, in the above embodiment, the disk-shaped target plate 1
1 or a hole 24 formed in the detection disk 22 is detected by an optical sensor (17, 26). It may be any means that measures the time required for the object to move a certain distance, and is not limited to the embodiment.

Further, the number of mirror surface portions 11a and holes 24 can be set arbitrarily, and the detection of minute changes becomes more effective when the number is increased.

〔Effect of the invention〕

As described above, according to the present invention, the ion beam current irradiated to the disk-shaped target plate is continuously measured, and the translation of the disk-shaped target plate is Since the drive is cut off, there is no need to form slits in the disc-shaped target plate as in the conventional method, improving beam utilization efficiency and making it possible to control the ion beam according to short-term fluctuations in the ion beam current. This allows highly accurate ion implantation.

Furthermore, since a continuous large ion beam current is detected, the design of the first stage of the beam current detection circuit becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ion irradiation device according to an embodiment of the present invention, FIG. 2 is a rear view of the disk-shaped target plate of FIG. 1, and FIG. 3 is a diagram of an ion irradiation device according to another embodiment of the present invention. Configuration Diagram, FIG. 4 is a configuration diagram of a conventional ion irradiation device. In the figure, 11 is a disk-shaped target plate, 11a is a mirror surface, 12 is a wafer, 13 is a disk rotation motor, 14 is a disk translation motor, 15 is a suppressor, 16 is a Faraday cup, 17 is a reflective optical sensor, 18 is an I C converter, 19 is a V/F converter, 20 is a switch, 21 is a through controller, 22 is a light sensor detection section, 23 is a measurement disk, 24 is a hole, 25 is a light source section, 26 is a transmission type sensor .

Claims (3)

[Claims] (1) In an ion irradiation device that irradiates a rotating disk-shaped target plate (11) with an ion beam, a translation drive means that drives the disk-shaped target plate (11) in translation in proportion to the continuously measured ion beam current. and measuring means (17, 22) for measuring the time required for a portion of the disk-shaped target plate (11) with the same radius as the ion beam irradiation part to move a certain distance;
7. An ion irradiation apparatus characterized by comprising a cutting means for cutting a part of the translational drive means during times other than the time measured by 7 and 22). (2) The measuring means includes the disc-shaped target plate (
11) The ion irradiation device according to claim 1, characterized in that an optical sensor (17) measures passage through a mirror surface (11a) formed with a constant width on the back surface. (3) The measuring means includes a disk-shaped target plate (11
), the light passing through a hole (24) of a constant width formed in a detection disk (23) that rotates at the same time as the detection disk (23) is measured by an optical sensor (26). ion irradiation equipment.