JPH03165442A - Wafer installing device for ion implanter - Google Patents

Abstract

PURPOSE:To relax the charging of a conductor wafer by furnishing a holder provided to hold the wafer on the surface side of a plate body and an uneven part provided on the surface of the plate body. CONSTITUTION:In a wafer installing disk 20, clamps 4 to hold semiconductor wafers 2 are provided at the surface side of a disk-form plate body 1, while an uneven part 5 is provided on the surface of the disk 1 at the part other than the clamps 4, and the both parts 1 and 5 are formed integrally with the same material such as Al material. By facing the tapered surface 5b of the uneven part 5 to the upper side of the semiconductor wafer 2, the discharge rate of the secondary electrons is increased, and at the same time, the secondary electrons can reach to the semiconductor wafer 2 easily. As a result, a large amount of secondary electrons can be fed effectively. Consequently, the plus charging of the semiconductor wafer 2 is relaxed, and an electrostatic breakdown of the gate oxide membrane of a MOS transistor formed in the wafer 2, for example, can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer mounting device used in an ion implantation device for implanting impurity ions into a semiconductor wafer.

[Conventional technology]

2. Description of the Related Art A high current ion implantation device called a bridle deposition type is used as an ion implantation device for implanting impurities at a high concentration into a semiconductor device.

FIG. 5 is a conceptual diagram showing how impurity ions are implanted into a plurality of semiconductor wafers mounted on a wafer mounting device. In the figure, a plurality of semiconductor wafers 2 are mounted on a wafer mounting disk 10. As shown in FIG. The semiconductor wafers 2 are often arranged concentrically in consideration of temperature rise during ion irradiation. In addition, in FIG. 5, only four semiconductor wafers 2 are shown for convenience of illustration.

When implanting the impurity ion beam IB, the disk 10 is rotated at a high speed of 300 to 1500 rpm and translated vertically or horizontally.

Then, an ion beam IB formed with desired energy and ion species is implanted, and the above translation operation is performed in several steps until the desired implantation amount is reached.

FIG. 6 is a plan view of the wafer mounting disk 10, and FIG. 7 is a sectional view taken along the line AA'. As shown in these figures, the semiconductor wafer 2 is mounted on the front surface side of the disk 1o by a clamp 4 as a holding member.

[Problem to be solved by the invention]

In ion implantation, positive ions are usually implanted, so when implanting impurity ions at a high concentration with a large current, the surface of the sea urchin 11 becomes positively charged.

As a result of this charging, a MOS is formed inside the semiconductor wafer 1.
There have been problems in that electrostatic discharge phenomena such as deterioration of the gate oxide film of the transistor and scattering of contact holes occur.

The present invention was made in order to solve the above-mentioned problems in the prior art, and it is an object of the present invention to provide a mounting device for an ion implanter that can alleviate the charging of a semiconductor wafer 1 caused by ion implantation. With the goal.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a plate-shaped body and a wafer on one surface side of the plate-shaped body in an ion implantation device used in an ion implantation apparatus for implanting impurity ions into a semiconductor wafer. 1, and an uneven portion provided on the surface of the plate-like body.

[Effect]

Since the uneven portion increases the surface area of the plate, the amount of secondary electrons emitted when ions are incident on the uneven portion is
This is more than when there are no uneven parts.

These secondary electrons reach the positively charged surface of the wafer and relieve the charge on the semiconductor wafer.

〔Example〕

FIG. 1 is a plan view showing a wafer mounting disk as an embodiment of the present invention, and FIG. 2 is a BB' cross-sectional view thereof.

This wafer mounting disk 20 has a disk-shaped disk portion 1
A clamp 4 for holding the semiconductor wafer 2 is provided on the surface side of the disk portion 1, and uneven portions (convex portions in this figure) 5 are provided on other parts of the surface of the disk portion 1. It is being The disk portion 1 and the uneven portion 5 are integrally formed of the same material. The material for the disk portion 1 is preferably a metal such as aluminum, which has good electrical and thermal conductivity. In this embodiment, the clamp 4 is also made of the same material as the disk portion 1 and the uneven portion 5.

A portion of the uneven portion 5 is formed concentrically around the semiconductor sea urchin/X2. In addition, in FIG. 1, for convenience of illustration, the second
The top horizontal surface 5a of the uneven portion 5 shown in the figure is indicated by a sandy area. As can be seen from FIG. 2, the uneven portion 5 has a trapezoidal vertical cross-sectional view, and the side surface of this trapezoid facing toward the Ueno\2 side is a tape-shaped side surface that descends toward the Uni/"t. 5b (hereinafter referred to as a tapered surface).

Note that when mounting a semiconductor wafer 12 with a normal diameter of 6 inches, the radius Rd of the wafer mounting disk 20 is 30 to 1
oOc+n.

The height H can be 1 to 5 cm. Further, the length W of the lower side of the trapezoidal cross section of the uneven portion 5 may be approximately 1 mark, and the angle θ of the tapered surface 5b may be 0 to 90''.

By providing the uneven portion 5 as described above, the number of secondary electrons emitted during ion implantation increases for the following reasons.

First, by forming the uneven portion 5, the surface area of the wafer mounting disk 20 is increased. This increases the number of secondary electrons emitted when ions are implanted.

Next, as shown in FIG. 2, by making the side surface 5b of the concavo-convex portion tapered at an angle θ with the horizontal surface, the ion beam IB
is incident on the tapered surface 5b at an incident angle θ. When the ion beam is incident at an incident angle θ that is not 0'', the number of secondary electrons emitted increases compared to when the ion beam is incident at an incident angle 0''. Third
The figure shows the relationship between the incident angle θ and the secondary electron emission rate δ when primary electrons are incident on NiC. Here, the secondary electron emission rate δ is the ratio of the output current (the number of secondary electrons emitted) to the incident current (the number of incident primary electrons). Such a relationship can be seen, for example, in ``electron tube engineering'' (part of Sakuraba).

Morikita Publishing, September 1981), page 52.

As can be seen from FIG. 3, when the incident angle θ is larger than 0°, the secondary electron emission rate δ is larger than when it is 0°.

This is because when electrons (or ions) are incident at an incident angle θ that is not 0°, secondary electrons are generated at a shallower position from the incident surface than when they are incident at 0°, and This is thought to be due to the fact that if the generation position is shallow, more secondary electrons will be emitted to the outside without being captured inside the member into which they are incident. Figure 3 shows the case where electrons are incident.
A similar tendency exists when ions are incident.

Furthermore, most of the secondary electrons emitted from the tapered surface 5b are in the normal direction to the tapered surface 5b. This is because when the secondary electrons generated inside the uneven portion 5 go in the normal direction of the tapered surface b, the flight distance inside the uneven portion 5 becomes the shortest, so the probability of being captured is reduced. This is because it is the smallest.

Since the tapered surface 5b faces toward the top of the semiconductor wafer 2, the secondary electrons are emitted from the tapered surface 5b toward the top of the semiconductor wafer 2. Since the semiconductor wafer 2 is significantly positively charged by the implantation of positive ions, the secondary electrons emitted from the uneven portions 5 are attracted to the semiconductor wafer 2 and absorbed.

In this way, the tapered surface 5b of the uneven portion 5 is aligned with the semiconductor wafer 2.
By directing the secondary electrons toward the top, the emission rate of secondary electrons increases and the secondary electrons can more easily reach the semiconductor wafer 2, so a large amount of secondary electrons can be efficiently supplied to the surface of the semiconductor wafer 2. can. As a result, the positive charging of the semiconductor wafer 2 is alleviated, and it is possible to prevent electrostatic damage to, for example, the gate oxide film of a MOS transistor formed within the semiconductor wafer 2.

In the above embodiment, the vertical cross section of the uneven portion 5 is trapezoidal, and the tapered surface 5b is formed to face the upper part of the semiconductor wafer 2. However, the cross-sectional shape of the uneven portion 5 is not limited to the trapezoidal shape. , other shapes such as a rectangle are also possible.

Further, in the above embodiment, the concave and convex portions 5 are formed concentrically around the semiconductor wafer 2, but they do not need to be concentric; it is sufficient that the concave and convex portions are formed on the surface of the disk portion 1. FIG. 4 is a plan view showing a wafer mounting disk 20a as another embodiment of the present invention. In this wafer mounting disk 2°a, projection-like uneven portions (convex portions) 50 are formed on the surface of the disk portion 1 in a scattered manner. In addition, in FIG. 2 and FIG. 4, the uneven portions of the wafer mounting disk are formed as convex portions, but they may be formed as four portions. In other words, it is sufficient that the surface of the disk portion 1 has some kind of unevenness.

In the above embodiment, the material forming the uneven portion is the same metal as the disk portion, such as aluminum, but it is made of a compound such as an oxide such as MgO or a nitride such as TEN, which emits a large amount of secondary electrons. The uneven portions may be formed using other materials.

〔Effect of the invention〕

As explained above, according to the present invention, since the uneven portion increases the surface area of the plate-like body, the amount of secondary electrons emitted when ions are incident on the uneven portion is lower than that in the case where there is no uneven portion. It becomes more compared. Since these secondary electrons reach the positively charged wafer surface, there is an effect that the charging of the semiconductor wafer can be alleviated.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a wafer-mounted disk according to an embodiment of the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a diagram showing the relationship between the incident angle and the secondary electron emission rate, and FIG. 4 is a diagram showing the relationship between the incident angle and the secondary electron emission rate. A plan view showing a wafer mounting disk according to another embodiment of the present invention, FIG. 5 is a conceptual diagram showing how ions are implanted into a semiconductor wafer in an ion implantation apparatus, and FIG. 6 is a plan view showing a conventional wafer mounting disk. 7 are cross-sectional views thereof. In the figure, 1 is a disk portion, 2 is a semiconductor wafer, 5 is an uneven portion, and 2o is a wafer mounting disk. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A wafer mounting device used in an ion implantation device for implanting impurity ions into a semiconductor wafer, which includes a plate-shaped body and a holder provided on one surface side of the plate-shaped body to hold the wafer. A wafer mounting device for an ion implantation apparatus, comprising: a concavo-convex portion provided on the surface of the plate-like body.