JPH0291933A - Ion implantation device - Google Patents

Abstract

PURPOSE:To form a metallic thin film on a wafer during ion implantation so as to prevent electrification of the wafer by attaching metal which is sputtered by the use of ion beams to the surface of a semiconductor wafer, and installing the mechanism to form a metallic thin film to become a conductive layer. CONSTITUTION:A high purity aluminum target 15 is placed at a part that ion beams 7 over-scan a wafer along the inside diameter of the wafer holder 2 to press the wafer 3 placed on a platen 1. On the other hand, when the ion beams 7 during implantation over-scan the wafer and hit against the high purity aluminum target 15, aluminum hits against the convex high purity aluminum target 12 of a reflecting plate 11 according to a sputtering course 10, and the aluminum is resputtered anew and accumulated on the wafer 3 according to a resputtering course. The charge which is accumulated in the wafer during implantation escapes from a metallic cramp 14 pressing the wafer 3, and the electrification of the wafer 3 during implantation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation apparatus, and more particularly to a wafer holder within an implantation chamber.

[Conventional technology]

In ion implantation of semiconductor wafers, it is a well-known fact that the wafer is charged during implantation. In particular, with the recent increase in the density of LSI integration, the gate oxide film of transistors has tended to become thinner, and in order to achieve high throughput on equipment, the beam current for ion implantation has been reduced to several mA.
The current has increased from 10 mA to several tens of mA. As a result, the amount of charge on the wafer during implantation increases, and destruction of the gate oxide film has become an important problem. To prevent these,
Conventionally, a secondary electron generating device (hereinafter referred to as an electron shower device) installed near the wafer to be implanted generates secondary electrons during implantation, and these secondary electrons are directly applied to the wafer or implanted with an ion beam. The secondary electrons are caused to reach the wafer together with the ion beam, thereby preventing the wafer from being charged during implantation.

This conventional example will be explained with reference to FIG. The electron shower device is installed in front of a wafer 3 placed on a platen 1 and fixed with a holder 2, as shown in the figure. This device extracts primary electrons 6 by passing a current through a filament 4 and applying a voltage to a grid 5. The emitted primary electrons 6 hit a target (metal) 9 placed on the opposite side of the filament 4 and generate secondary electrons 8, which, depending on the orientation of the target 9, cause an ion beam 7 to be implanted into the wafer 3.
At the same time, the wafer is directly irradiated. It is possible to prevent the wafer 3 during injection from being charged by the secondary electrons 8 .

[Problem to be solved by the invention]

The above-mentioned conventional electron shower device has the disadvantage that (1) the filament is used, and therefore the filament is rapidly consumed and must be replaced frequently. ■The target is easily soiled, and the amount of secondary electrons changes depending on the state of soiling. (2) Since the amount of charge on the wafer varies depending on the wafer to be implanted and the beam current to be implanted, it is necessary to control the amount of secondary electrons, and it is quite difficult to find the optimal conditions.

■The secondary electrons change as the filament deteriorates, making it difficult to control.

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] While the above-mentioned conventional electron shower device that generates secondary electrons is used, the present invention does not use this type of electron shower device and uses an ion beam during implantation. The sputtered metal is attached to the wafer surface,
The difference is that a thin metal film is formed as a conductive layer.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an ion implantation apparatus that performs ion implantation into a semiconductor wafer using an ion beam, in which metal sputtered by the ion beam is attached to the surface of the semiconductor wafer to form a thin metal film that becomes a conductive layer. It is equipped with a mechanism.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) Figure 1 is a perspective view showing Example 1 of the present invention, and Figure 2 is a cross-sectional view of the same.The ion beam for implantation is an electrostatic scanning type ion implanter, so This is an example of the case where the incident angle is . The implantation conditions were an energy of 50 KeV,
Ionic arsenic (As), dose 1.0X1014C1
1-2. Beam current is 300 μA. A high-purity aluminum target 15 is installed along the inner diameter of a wafer holder 2 that holds a wafer 3 placed on a platen 1 at a portion where the ion beam 7 overscans the wafer. on the other hand,
Aluminum sputtered by the ion beam 7 during implantation is deposited onto the wafer 3; it has a reflector plate 11 in which a convex high-purity aluminum target 12 for re-sputtering is embedded.

When the ion beam 7 overscans and hits the high-purity aluminum target plates I to 15, aluminum is sputtered from there toward the convex high-purity aluminum target 12 of the reflection plate 11 along the sputtering path 10. Next, this sputtered aluminum hits a convex high-purity aluminum target 12 placed on a reflection plate 11, and new aluminum is re-sputtered and deposited as AΩ on the wafer 3 along a re-sputtering path 13. The deposition is done simultaneously with the ion implantation, and during the implantation, a thin layer of aluminum, i.e., a metal conductive layer, is formed on the wafer surface, and the charge that accumulates on the wafer during the implantation is transferred to the wafer 3.
The wafer can escape from the metal clamp 14 holding it down from the surface, thereby preventing the wafer from being charged during implantation.

(Example 2) FIG. 3 is a sectional view showing a second embodiment of the present invention.

This embodiment shows an example of a mechanical scanning type ion implantation apparatus. In this type of apparatus, since the ion beam for implantation is perpendicular to the wafer (incident angle OD), the angle and height of the reflecting plate 11 are different from those in the first embodiment.

In addition, the high-purity aluminum target 9 embedded in the holder 2 is a flat plate tilted outward as shown in the figure so that sputtered aluminum hits the convex high-purity aluminum target 12 installed on the reflection plate 11. . The process of repeating sputtering and re-sputtering of aluminum from two high-purity aluminum targets and depositing it on the surface of the wafer 3 by the ion beam of ion implantation is the same as in the first embodiment.

〔Effect of the invention〕

As explained above, the present invention has the effect of forming a thin metal film on the wafer during ion implantation, thereby preventing the wafer from being charged.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing Embodiment 1 of the present invention, FIG. 2 is a sectional view thereof, FIG. 3 is a sectional view showing Embodiment 2 of the present invention, and FIG. 4 is a conventional wafer holder and secondary electron generation. It is a figure showing an apparatus. 1...Platen 2...Holder 3...
Wafer 7...Ion beam 10...
Sputtering path 11...Reflector 12...Convex high-purity aluminum target 13...Re-sputtering path
14 River clamp 15...High purity aluminum target

Claims (1)

[Claims] (1) An ion implanter that implants ions into a semiconductor wafer using an ion beam, which is equipped with a mechanism that attaches metal sputtered by the ion beam to the surface of the semiconductor wafer to form a thin metal film that will become a conductive layer. Ion implantation equipment.