JPH07122226A - Method and device for ion implantation - Google Patents

Abstract

PURPOSE:To enlarge the width of an acceleration voltage and thicken the implantation layer by installing an acceleration voltage modulating device between the mass-spectrograph and chamber of an ion accelerator. CONSTITUTION:An acceleration voltage modulating device 3 is installed between the mass-spectrograph 2 and chamber 4 of an ion accelerator. Thereby the acceleration voltage for each ion which has been accelerated with a constant acceleration voltage is varied with an ultrashort period in cycles before being cast onto a target 5. This permits enlarging the width of the acceleration voltage and thickening the implantation layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation method and apparatus for implanting ions into a base material to change the properties of the base material, and more particularly to doping impurities in the semiconductor field and forming circuits and electrodes. It is a method that can be advantageously applied to the formation of an insulating layer, a surface modification method for improving the corrosion resistance of highly corrosion-resistant materials, piping members, heat transfer tubes, valve rods, etc. in the nuclear field and the like.

[0002]

2. Description of the Related Art As a means for expanding the existing region width of implanted ions in the depth direction, a method of utilizing diffusion by heat or a method of changing the accelerating voltage and dividing into several times is adopted.

[0003]

In order to achieve high integration in VLSI, it is desired to structure fine elements represented by a three-dimensional structure. For that purpose, a technique of implanting ions at a shallow position on the surface at a low acceleration voltage is also required. In other words, there is a need for a technique of implanting a fixed amount of ions at a fixed depth from the surface of the substrate. On the other hand, in the ion implantation, there is a phenomenon that the width of the existing region of ions becomes smaller as the acceleration voltage becomes smaller. S
When As ions are implanted into the i-substrate, at 200 keV, the ions are distributed up to a depth of about 280 nm.
At keV, it is about one-third that is about 110 nm. The smaller the acceleration voltage, the smaller the distribution. Ion implantation is performed at an accelerating voltage of about 2 keV to 4 MeV in manufacturing a semiconductor element. However, when an implantation layer is formed near the surface at a low accelerating voltage, a layer thicker than the layer formed by implantation may be required. Occur. One way to address this problem is to use thermal diffusion. However, compared with the accuracy of the depth distribution reproducibility due to the acceleration voltage at the time of ion implantation, it is very difficult to control by heat, and there is a risk that the device may be destroyed. A method of changing the accelerating voltage and performing ion implantation in several times is also conceivable, but it takes extra time and labor when used in an actual process, which is an obstacle to shortening the process time.

In order to improve the corrosion resistance of a nuclear reactor material, surface modification is performed by implanting ions to form a highly corrosion-resistant layer on the surface. If the layer formed at this time is thin, when the crack expands due to a surface crack or the like, the base material cracks beyond the forming layer and causes corrosion, which leads to destruction in the worst case. To address this issue,
The layer to be formed may be thickened to form a stable and highly corrosion-resistant layer, but at this time, the problem described in the semiconductor arises.

It is an object of the present invention to provide an ion implantation method and apparatus capable of obtaining a thick implantation layer.

[0006]

In order to solve the above problems, the present invention uses the following method.

(1) An acceleration voltage modulator is installed between the mass spectrometer of the ion accelerator and the chamber (FIG. 1). By this modulator, the accelerating voltage of the ions accelerated to a constant accelerating voltage is changed in an extremely short period before being irradiated to the target, so that the accelerating voltage has a range.
Increase the thickness of the injection layer.

(2) A piezoelectric element or an electromagnetic coil is used for the support base of the target (FIGS. 2 and 3), and a high frequency is applied to the support so that the target has an amplitude corresponding to a target acceleration voltage width. Vibrate to the frequency to obtain a thick injection layer.

By the method as described above, a thick implantation layer which cannot be obtained by ordinary ion implantation can be obtained.

[0010]

[Action]

(1) Ions accelerated to a certain accelerating voltage in the ion source can change the accelerating voltage in an accelerating voltage modulator in an extremely short cycle. This is based on the following principle. Consider an electromagnetic coil in which ions pass through its center. By passing a high frequency current through the electromagnetic coil, the electric field in the electromagnetic coil is changed. By being affected by the change in the electric field, the ions are changed in accelerating voltage periodically, and the ions reach the target and are implanted. As a result, since the ion implantation can be performed with the acceleration voltage of the plus or minus arbitrary% continuous change without any change around the acceleration voltage in the ion source, the ion implantation depth corresponding to the acceleration voltage change can be obtained, and the thick implantation layer can be formed. Obtainable.

(2) By vibrating the target with a piezoelectric element or an electromagnetic coil, the accelerating voltage of the ions is changed relative to the target so that the implantation depth has a range. The target is vibrated by passing a high-frequency current through the piezoelectric element or electromagnetic coil to which the target is attached. The amount of current flowing at this time is set so that the frequency and amplitude of the target vibration correspond to plus or minus arbitrary% of the acceleration voltage of the implanted ions. By thus implanting while oscillating the target, the acceleration voltage of the ion is continuously changed relatively without interruption, and only the relative acceleration voltage increment corresponding to the oscillation is centered on the acceleration voltage of the implanted ion. It can have a width of depth.

[0012]

EXAMPLES The present invention will be specifically described below based on examples.

When manufacturing an LSI device, a depth of 50 nm
In order to form an n-type implantation layer having a concentration peak, As ions are implanted into a Si substrate at an acceleration voltage of 50 keV using an accelerator. At this time, the silicon substrate is attached to the sample support base on the piezoelectric element fixed to the sample holder. When As ions are implanted at an acceleration voltage of 50 keV, the implantation depth is about 100 nm,
Acceleration voltage plus or minus 10 to increase injection depth
Change in the range of%. Therefore, 1kV1 is applied to the piezoelectric element.
Apply a high frequency of 00MHz. Then, the vibration of the piezoelectric element causes the target to have an amplitude ± 100 at a frequency of 100 MHz.
It vibrates at 1.1 μm. Due to this vibration, the apparent accelerating voltage seen from the implanted ions changes with an extremely short period, and an implantation layer having a target depth width is formed. Since the frequency and amplitude for giving an apparent accelerating voltage width have upper limits determined by the piezoelectric element, if a higher apparent accelerating voltage is to be applied, a diaphragm as shown in FIG. Used for holder. By adjusting the length of the vibrating plate so as to correspond to the desired acceleration voltage change and using it, the amplitude is mechanically amplified and an injection layer having a larger injection width can be obtained.

In order to improve the corrosion resistance of the stainless steel reactor piping, a surface treatment is performed by ion implantation. Cr is ionized in the ion source of the accelerator. In order to inject this into the target in the chamber, an acceleration voltage is applied and the target acceleration voltage is injected. At this time, it is advantageous to be able to form a thick injection layer in order to enhance the corrosion resistance,
In order to form such an implantation layer, the acceleration voltage of ions is continuously changed. That is, the ions accelerated by the ion source are selected to pass through the mass spectrometer and only Cr ions can reach the chamber. The ions that have passed through the mass spectrometer are steplessly modulated with an accelerating voltage modulator in front of the chamber in an extremely short cycle, and as ions having an accelerating voltage width of plus or minus a few percent,
Injected into the sample. At this time, the accelerating voltage modulator modulates the accelerating voltage by passing a high frequency current through the coil. By implanting ions in this manner, a thick and strong implantation layer can be obtained, and a surface treatment exhibiting high corrosion resistance can be performed.

Although only two examples have been shown above, the present invention is not limited to this example only, and is intended for all purposes for making the thickness of the injection layer obtained by a kind of accelerating voltage thicker than that originally obtained. , Can be applied effectively.

[0016]

According to the present invention, the thickness of the implantation layer can be increased without changing the acceleration voltage of the ion source. Until now, the accelerating voltage was changed to inject several times or thermal diffusion was used, but to change the accelerating voltage to inject, the current of the mass spectrometer is changed each time the voltage is changed. Moreover, the currents of other ion beam control devices have to be manipulated, and it takes a lot of time to apply it to an actual process, which causes a lot of loss in time. In addition, it is not practical to control the diffusion itself due to heat as well. By using the method and apparatus according to the present invention, it is possible to solve the above-mentioned problems and to have very good controllability and reproducibility of the implantation depth and to eliminate time loss.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an ion implantation apparatus including an accelerating voltage modulator.

FIG. 2 is an explanatory diagram of an ion implantation apparatus including an electromagnetic coil for vibrating a target.

FIG. 3 is an explanatory diagram of an ion implantation apparatus including a piezoelectric element for vibrating a target.

FIG. 4 is an explanatory diagram of a sample holder including a vibration plate for mechanically increasing the vibration of the piezoelectric element and transmitting the vibration to the target.

FIG. 5 is a diagram showing a distribution of implanted ions in the sample in the depth direction.

[Explanation of symbols]

1 ... Ion source, 2 ... Mass spectrometer, 3 ... Accelerating voltage modulator,
4 ... Chamber, 5 ... Target, 6 ... Sample stand, 7 ... Holder, 8 ... Pipe, 10 ... Vibration controller.

Claims (8)

[Claims] 1. An ion implantation method using an ion implantation apparatus comprising an ion source, an accelerating tube, and a target sample stage, wherein a method for controlling a relative velocity of ions accelerated by the accelerating tube with respect to a sample is added. Ion implantation method. 2. The ion implantation method according to claim 1, wherein the acceleration voltage is modulated. 3. The ion implantation method according to claim 1, wherein the target sample is vibrated at a high frequency for ion relative velocity control. 4. An ion implanter comprising an ion source, an accelerating tube, and a target sample stage, the ion implanting apparatus having means for controlling a relative velocity between the ions accelerated by the accelerating tube and the target. 5. The ion implanter according to claim 4, wherein the ion relative velocity control means is an accelerating voltage modulator. 6. The ion implantation apparatus according to claim 4, wherein the ion relative velocity control means has a device for vibrating a sample at a high frequency. 7. An ion implanter using a piezoelectric element as a device for vibrating the sample according to claim 6 at a high frequency. 8. An ion implanter using an electromagnetic coil as the device for vibrating the sample according to claim 6 at a high frequency.