JPH01117320A - Ion implanting method - Google Patents

Abstract

PURPOSE:To prevent the electrostatic breakdown and to contrive an improvement in productivity by a method wherein the substrate to be treated is charged with electricity by projecting electrons on the substrate in advance, and then ions are implanted by projecting an ion beam. CONSTITUTION:A plurality of semiconductor wafers 2 are arranged on a disc 4, and the disc 4 is rotated in the direction as shown by the arrow in the diagram with a rotating shaft as the center point. When the semiconductor wafer 2 passes the part of a target box 6, electrons are projected on the semiconductor wafer 2 by an electron projecting device 5, and when the wafer passes an ion beam introducing tube 1, an ion beam is projected on the wafer. At this time, the electron beam projecting device 5 is positioned on the front side of the ion beam introducing tube 1 against the rotating direction of the disc 4. Accordingly, electrons are projected on the wafer 2 by the electron projecting device 5, probably negative electricity is charged on the surface of the wafer, and the state of charge on the wafer surface is switched over to the positive side by projecting an ion beam subsequently.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an ion implantation method.

(Prior Art) Generally, ion implantation technology is widely used as a technology for doping a target object with impurities.

When impurities are doped into a semiconductor wafer using such an ion implantation technique, positively charged ions are accelerated and implanted. For this reason, when positive ions collide with the semiconductor wafer surface, the surface of the semiconductor wafer tends to become positively charged due to factors such as electrons being knocked out and positive charges accumulating in the insulating parts. This was not a big problem for devices with low power, but as the integration becomes extremely high (1M, 4M, etc.), the distance between adjacent elements becomes shorter, and this charging causes electrostatic breakdown in the insulating parts of semiconductor devices. This is a cause of decreased productivity.

As a means of solving this problem, there is an ion implantation method in which electrons are irradiated with an ion beam to prevent the surface of the semiconductor from becoming positively charged, thereby preventing electrostatic damage.

(Problems to be Solved by the Invention) However, as a result of detailed investigation by the present inventor, as explained above, in the conventional method of irradiating an ion beam while irradiating an electron beam, electrons are caused by the electric field of the ion beam. It has been previously discovered that electrostatic damage can occur on the surface of a semiconductor wafer because the ion beam is attracted and concentrated around the ion beam, and the ion beam is concentrated on a part of the semiconductor wafer.

The present invention has been made in response to such conventional circumstances, and aims to provide an ion implantation method that can prevent electrostatic damage to semiconductor wafers and improve productivity compared to conventional methods. There is something to be said.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention, when implanting ions into a substrate to be processed, irradiates the substrate with electrons in advance and then irradiates the substrate with ions. It is characterized by injection.

(Function) In the ion implantation method of the present invention, the substrate to be processed is irradiated with electrons in advance, and then the substrate to be processed is irradiated with an ion beam to implant ions.

Therefore, it is possible to prevent electrostatic damage caused by the accumulation of positive charges, and it is also possible to prevent electrons from being attracted by the electric field of the ion beam and being irradiated in a concentrated manner, which is caused by the accumulation of negative charges. Electrostatic damage can be prevented.

(Example) Examples of the ion implantation method of the present invention will be described below with reference to the drawings. Since the configuration of the ion implantation device is well known, its details will be omitted.

As shown in FIGS. 1 and 2, at the terminal end of the ion beam introduction tube 1, there is a disk 4 that holds a plurality of semiconductor wafers 2 and is configured to rotate in the direction of the arrow in the figure about a rotating shaft 3. is located.

In addition, near the ion beam introduction tube 1, for example, on the lower side,
An electron irradiation device 5 is arranged parallel to the ion beam introduction tube 1. This electron irradiation device 5 includes a target box 6 having an opening on the side of the disk 4 and a cooling I! 1′! It consists of an electron gun 8 connected via N7.

This electron gun 8 is configured so that electrons generated by a filament 9 are reflected by a reflecting plate 10 to which a reverse bias voltage is applied. Then, the primary electrons from the electron gun 8 are accelerated by an accelerating voltage of about ◆300V, for example,
Collision with the upper inner wall of the target box 61. The semiconductor wafer 2 held on the disk 4 is irradiated with low-energy secondary electrons generated by this collision.

In this embodiment using the apparatus configured as described above, a plurality of semiconductor wafers 2 are placed on a disk 4, and the disk 4 is rotated about the rotating shaft 3 in the direction of the arrow shown in the figure. and,
When passing through the target box 6, the semiconductor wafer 2 is irradiated with electrons by the electron irradiation device 5, and when passing through the ion beam introduction tube 1, the ion beam is irradiated. At this time, the electron irradiation device 5 is located at a position 6 located in front of the ion beam introduction tube 1 with respect to the rotational direction of the disk 4.
Therefore, as shown in the graph of FIG. 3, where the vertical axis is the charge amount of the semiconductor wafer 2 and the horizontal axis is time, the semiconductor wafer 2 is first irradiated with electrons at the electron irradiation amount W5,
Although it is not clear, it is likely that the surface of the semiconductor wafer 2 becomes negatively charged, and by subsequently irradiating the ion beam, the charged state of the surface of the sea urchin shifts to the positive side.

At this time, it is necessary to control the amount of electron irradiation so that the charging voltage of the semiconductor wafer 2 is lower than the voltage that causes dielectric breakdown. For this reason, for example, a capacitance type charge detector is provided and configured to measure the charged voltage of the semiconductor wafer 2 after ion beam irradiation, and the amount of emission current of the electron irradiation device 5 is controlled according to the measurement result. The amount of electron irradiation can be automatically controlled and set.

That is, in the ion implantation method of this embodiment, the rotational movement speed of the disk 4 is controlled to control the amount of electron irradiation to the semiconductor wafer 2 to negatively charge it, and then the ion beam is irradiated for a predetermined period of time to inject the ions. inject. Therefore, it is possible to prevent electrostatic damage due to the accumulation of positive charges, and it is also possible to prevent electrons from being attracted by the electric field of the ion beam and being irradiated in a concentrated manner.
Electrostatic damage caused by accumulation of negative charges can be prevented.

In the above embodiment method, an example was explained in which the electron irradiation device Wt5 was placed outside the ion beam introduction tube 1 and an electron irradiation area and an ion beam irradiation area were separately provided. As shown in the figure, a conventional ion implantation device configured to irradiate electrons from an electron gun 8 into the ion beam introduction tube 1 can also be used. In this case, the beam gate is kept closed and electrons are irradiated with the ion beam blocked, and then the beam gate is opened and the ion beam is irradiated.

Further, in the above embodiment, an example in which secondary electrons were irradiated was explained, but primary electrons may also be irradiated.

[Effects of the Invention] As described above, according to the ion implantation method of the present invention, electrostatic damage caused by ion implantation can be prevented, and electrons can be attracted by the electric field of the ion beam and irradiated in a concentrated manner. Therefore, it is possible to prevent electrostatic damage caused by accumulation of negative charges. Therefore, productivity can be significantly improved compared to the conventional method.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an ion implantation apparatus for explaining an ion implantation method according to one embodiment of the present invention, FIG. 3 is a graph showing the charging state of a semiconductor wafer, and FIG. 4 is a diagram showing another embodiment of the ion implantation method. FIG. 2 is a cross-sectional view of an ion implantation apparatus for explaining an example method. 1... Ion beam introduction tube, 2... Semiconductor wafer, 3... Rotating shaft, 4... Disk, 5... Electron irradiation Device, 6...
Target box, 7... Cooling mechanism, 8...
...Electron gun, 9...Filament, 10.
·····a reflector. Applicant Tokyo Electron Co., Ltd. Agent Patent Attorney Sasa Suyama − +Naka−〇 −1ya 1 +Total −″−81

Claims (2)

[Claims] (1) In an ion implantation method in which ions are implanted by irradiating an ion beam onto a substrate to be processed, the substrate to be processed is irradiated with electrons in advance to charge it, and then the substrate to be processed is irradiated with an ion beam to ionize. An ion implantation method characterized by implanting. (2) A region to be irradiated with electrons is provided separately from and parallel to the region to be irradiated with an ion beam, and the substrate to be processed is placed on a rotating disk surface, and electrons are irradiated by passing through these regions alternately. 2. The ion implantation method according to claim 1, wherein irradiation with an ion beam is performed after the ion implantation.