JPH088221B2 - Ion implantation method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation method for implanting impurity ions into a semiconductor wafer [hereinafter referred to as a wafer].

2. Description of the Related Art Ion implanters include a medium current type ion implanter and a high current type ion implanter. The medium current type ion implantation apparatus is an apparatus for irradiating a fixed wafer by deflecting a medium current ion beam. The high-current type ion implantation apparatus is an apparatus for irradiating a fixed high-current ion beam on a rotating and vertically moving wafer from a certain direction.

Since the present invention is carried out in a high current type ion implantation apparatus, the high current type ion implantation apparatus will be described with reference to FIGS. 2 to 4.

In FIG. 2, (1) is a main body for irradiating the ion beam (10), (2) is a disk-shaped wafer holder [hereinafter referred to as "wafer holder"], and a plurality of them are provided at predetermined circumferential positions on the front surface thereof. The wafer (3) is supported and placed at a fixed position in front of the body (1). (4) is a drive mechanism for rotating and vertically moving the wafer holder (2). The main body (1) comprises an ion source (5), an electrode (6), a mass spectrometer (7), an accelerating tube (8), and an ion focusing system (9). Ion beam (10) from ion source (5) by means of electrode (6)
Is withdrawn. Only predetermined target ions are extracted by the mass spectrometer (7). The ion beam (10) accelerated by the accelerating tube (8) has a focusing point on the wafer (3) by the ion focusing system (9).

Since the ion beam (10) is fixed and is irradiated in a fixed direction at a fixed incident angle, the wafer holder (2) is rotated and moved up and down to move each wafer (3).
(3) ... Are sequentially sent to the incident position of the ion beam (10), and the wafers (3), (3), ... .

By the way, the wafer holder (2) can support, for example, 13 wafers (3) as shown in FIG. Therefore, 25 sheets per carrier, 50 per batch
When the wafers (3) are sequentially supported by the wafer holder (2), a portion where the wafer (3) is insufficient appears in a part of the wafer holder (2) every fourth time, for example. When the portion not supporting the wafer (3) is irradiated with the ion beam (10), the wafer supporting portion is made of rubber in order to improve the adhesion with the wafer (3), so that the ions hit the rubber. It will be. Then, the scattered matter from that portion will contaminate the wafer (3).

Therefore, in order to prevent the ions from hitting the rubber, a dummy wafer (11) is attached to a portion of the wafer holder (2) where the regular wafer (3) is insufficient for ion implantation. As this dummy wafer (11),
Conventionally, a silicon wafer of the same material as the regular wafer (3) has been used.

By the way, not only the dummy wafer (11) but also the wafer (3) includes a plurality of pairs of positioning pins (12) and a pair of clampers (13) for holding the wafer (3) as shown in FIG. ), Supported by the wafer holder (2).

In order to prevent the wafer (3) from being damaged by the heat generated when the ions are implanted, cooling water for heat dissipation is flown behind the wafer holder (2).

Problems to be Solved by the Invention By the way, since the semiconductor device is not obtained in the dummy wafer (11) differently from the regular wafer (3), generally, the same thing is repeated many times for cost reduction. Since it is used for a long time, not only the strain at the time of ion implantation is accumulated, but also the material becomes brittle due to the implantation of a large amount of ions. When ions are implanted into such a dummy wafer (11), the kinetic energy of the ions is converted into heat energy to generate heat, and not only the back surface of the dummy wafer (11) but also the pins (12) and clampers. (13)
Heat is radiated from the part in contact with. Therefore pins (12)
The temperature is low in the area close to the clamper (13) and the pin (1
2) and the place separated from the clamper (13) have high temperature, so the temperature distribution in the dummy wafer (11) is not constant,
Thermal distortion occurs in the dummy wafer (11). In addition, since the wafer holder (2) rotates and moves up and down, the pins (12) and clamper (13) on the rear side in the traveling direction exert a reaction force on the dummy wafer (11), causing mechanical distortion, and the dummy wafer Combined with the residual strain due to ion implantation and the material becoming brittle, (11) was much more easily damaged than the regular wafer (3).

When the dummy wafer (11) is damaged, the fragments are scattered to damage the entire regular wafer (3) or adhere to the non-uniformity of ion implantation to cause a defect.

Means for Solving the Problems In order to solve the above problems, the present invention supports a plurality of regular semiconductor wafers and at least one dummy wafer at a predetermined cylindrical position of a disk-shaped wafer holder. In the high current type ion implantation method of implanting ions by ion implantation, an aluminum wafer whose surface is aluminized is used as the dummy wafer to perform ion implantation.

Action By making the dummy wafer of aluminum, it is possible to prevent the dummy wafer from breaking and scattering of fragments.

Further, since the surface is made of alumina, it is resistant to corrosion, and the surface is not hardened so that it itself does not become dust.

Embodiment An embodiment according to the present invention will be described with reference to FIG.

(2) is a disk-shaped wafer holder, and for example, 13 regular wafers (3) (3) ... Are supported circumferentially on the front surface thereof at regular intervals, but when the regular wafers (3) are insufficient , The aluminum dummy wafer (1
4) support. It is also convenient because aluminum is also used for the disk of the wafer holder (2).

As described in the prior art [see FIG. 2],
The ion beam (10) is irradiated from the main body (1) at a certain incident angle in a certain direction, and the wafer holder (2) is rotated and moved up and down so as to implant ions into the entire surface of the wafer (3). Since the dummy wafer (14) has substantially the same specific gravity as the wafer (3), even if a part of the dummy wafer (14) is supported, the rotation and vertical movement are the same as when the normal wafer (3) is supported. The operation is the same as before.
The aluminum dummy wafer (14) is also irradiated with the ion beam (10). However, since the dummy wafer (14) is made of aluminum, it is not damaged by heat or mechanical external force. The dummy wafer (14) irradiated with the ion beam (10) can be used any number of times.

The surface of the aluminum dummy wafer (14) is smoothed and aluminized by electrolytic polishing.
Then, the dummy wafer (14) is resistant to dust adhesion and corrosion, dust generation from the dummy wafer (14) can be prevented, and dust and the like does not adhere to the wafer (3).

The above is the description of the embodiment according to the present invention, and the present invention is not limited to this embodiment and can be modified in design within the scope of the present invention.

EFFECTS OF THE INVENTION By using an aluminum wafer having an aluminized surface as a dummy wafer, the dummy wafer is not damaged, and therefore, the regular wafer itself is not damaged or damaged to be defective.

Further, since the surface of the aluminum wafer is made alumina, it does not become dust and contaminates the regular wafer.

The cost can be reduced by using the aluminum dummy wafer as compared with the case of using the silicon dummy wafer.

[Brief description of drawings]

FIG. 1 is a schematic front view of a wafer holder for explaining an embodiment of an ion implantation method according to the present invention.
FIG. 3 is a schematic configuration diagram of a high-current type ion implantation apparatus, FIG. 3 is a schematic front view of a wafer holder, and FIG. 4 is an enlarged front view of essential parts of a wafer held by the wafer holder. (2) …… Wafer holder, (3) …… Regular semiconductor wafer, (14) …… Dummy wafer.

Claims (1)

[Claims] 1. A plurality of regular semiconductor wafers and at least one dummy wafer are supported at predetermined positions on the circumference of a disk-shaped wafer holder, and ions are generated while rotating and reciprocating the wafer holder. In the high current type ion implantation method for implanting, an aluminum wafer having an aluminized surface is used as the dummy wafer.