JPH01119668A - Ion implantation device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of charge-up phenomenon of wafer caused by implanted ions by implanting ions in a set wafer and then irradiating the above wafer with ultraviolet light. CONSTITUTION:In vacuum chamber 1 evacuated to the prescribed degree of vacuum, ions from an ion source 2 are drawn and accelerated in a drawing and accelerating part 3. These accelerated ions are subjected to mass spectrometry by means of a polarization electromagnet 4. The resulting ion beam 5 consisting of desired ions alone is implanted in a wafer 8 set in a disk 7 by means of a clamp 9. Simultaneously, the whole surface of the wafer 8 is irradiated with ultraviolet light from an ultraviolet light source 10, such as low-pressure mercury lamp. By the above irradiation, a thin insulating film of SiO2, etc., on the wafer 8 surface is excited, by which electric conductivity is provided. By this method, positive charge electrified on the wafer 8 surface due to the above ion implantation is rapidly discharged via the clamp 9 and the disk 7, by which charge-up can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation apparatus, and more particularly to an ion implantation apparatus that does not cause a wafer charge-up phenomenon caused by implanted ions.

[Conventional technology] Conventionally, as a technique for reducing charge-up caused by ion implantation, ion implantation is performed while rotating a stage on which a wafer is set at high speed, thereby reducing the amount of charge accumulated per unit area. Alternatively, there was a method using an electron flood gun, which traps electrons in flying ions and injects them in an electrically neutral state. .

[Problems to be Solved by the Invention] Of the conventional techniques described above, the method of reducing the amount of charge accumulated per unit area naturally reduces the throughput of the ion implantation apparatus. On the other hand, the method using an electron flood gun has the disadvantage that there is an optimum value for the amount of electrons to be captured by ions, and if it deviates from this, a sufficient charge-up reduction effect cannot be obtained.

An object of the present invention is to provide an ion implantation device that solves the above problems.

[Differences between the invention and the prior art] In contrast to the above-mentioned prior art, the present invention focuses on the fact that charge-up due to ion implantation is caused by the insulating film covering the wafer surface, and this insulating film is removed only during ion implantation. The difference is that charge-up can be reduced by imparting electrical conductivity to the material.

[Means for Solving the Problems] The present invention provides an ion implantation apparatus having an ion source, an ion analysis section, and an acceleration section, which is characterized in that it is equipped with a light source that irradiates a set wafer with ultraviolet light. It is a device.

[Principle/Operation] The basic structure of the present invention is that the ion implantation apparatus is equipped with a mechanism for simultaneously irradiating the entire surface of the wafer with ultraviolet rays during ion implantation. For example, the 5iOz insulating film covering the surface of the 3i substrate has an energy gap of 9.
OeV, and the energy difference between the conduction band of 3i and the conduction band of SiO2 is 3.1eV, and the difference in energy between the conduction band of 3i and the conduction band of SiO2 is 3.1eV.
The energy difference with the valence band of 2 is 4.8 eV. Therefore, for electrons it is less than 400 nm, and for holes it is less than 2
By irradiating ultraviolet light with a wavelength of 58 nm or less,
It is possible to make i02 electrically conductive. If this means is used, the ten charges charged by ion implantation will be quickly discharged, and no charge-up will occur.

[Example] Next, an example of the present invention will be described with reference to FIG. Vacuum chamber 1 evacuated to about 10-5 to 10' Torr
Ions are extracted from an ion source 2 provided therein, and the ions are accelerated by an extraction/acceleration section 3.

Next, ion interrogation analysis is performed through the polarized electromagnet 4,
An ion beam 5 consisting only of desired ions is formed and implanted into a wafer 8. Since the wafer surface is usually covered with an insulating thin film SiO2, the wafer surface is sufficiently charged by the ion implantation. 6 is the Faraday flag. The present invention is further equipped with an ultraviolet light source 10 (low-pressure mercury lamp) for irradiating ultraviolet light onto a wafer into which ions are to be implanted. That is, at the same time as the ion implantation into the wafer 8, the wafer surface is irradiated with ultraviolet light from the ultraviolet light source 10 (low-pressure mercury lamp) to excite carriers in SiO2, and the wafer 8 is charged through the disk 7 or clamp 9 on which the wafer 8 is set. discharge.

In the above embodiments, a low-pressure mercury lamp was used as the ultraviolet light source 10, but it is also possible to use a coherent excimer laser 1, especially an Ar or F laser (λ=193 nm), which is the most excellent in terms of efficiency and output. is obtained.

[Effects of the Invention] As explained above, according to the present invention, when implanting ions into a wafer, the entire surface of the wafer is irradiated with ultraviolet light, and SiO2
Since the carriers are excited in the ion implantation, the 10 charges caused by ion implantation can be immediately discharged through the disk or clamp, and this device can eliminate problems caused by charge-up due to ion implantation (such as dielectric breakdown of thin 5102). It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 2... Ion source, 3... Extraction/acceleration part, 4... Polarizing electromagnet, 5... Ion beam. 6...Faraday Flag, 7...Disc.

Claims (1)

[Claims] (1) An ion implantation apparatus having an ion source, an ion analysis section, and an acceleration section, characterized in that the ion implantation apparatus is equipped with a light source that irradiates a set wafer with ultraviolet light.