JPS5941828A - Ion implanter - Google Patents

Abstract

PURPOSE:To keep the angle of ions implanted by simple constitution by processing a support means for a wafer in a recessed shape in the direction of implantation of the ions, bending the wafer toward the recessed section and supporting it. CONSTITUTION:The angle of ions implanted is kept constant at all times to a wafer by supporting the wafer in a recessed shape such as a circular arc of a radius R at a time when a distance up to the wafer 42 from a scanning means for the ions is made R. The ions such as charged particles, which are generated by an ion source, accelerated and selected, are scanned, and implanted to the whole surface of the wafer 42, but the wafer 42 is supported to the support means 50 by a support mechanism 504 in a recessed shape in the direction of implantation of the ions. A cushion material 502 of high thermal conductivity is interposed between the wafer 42 and the support means 50 in predetermined thickness, and the wafer 42 is supported to a cylindrical surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion implantation device used for adding impurities in the manufacture of semiconductor devices, and in particular, to a constant angle of incidence of charged particles onto a semiconductor substrate (hereinafter referred to as a wafer). It concerns the cooling means for sea urchins.

Conventionally, attempts have been made to perform uniform ion implantation by scanning charged particles.

That is, as the principle is shown in FIG. 1, the charged particles 1 are scanned by the scanning means 2 within a region 3 indicated by broken lines, and are implanted into the wafer 4 supported by the supporting means 5.

Here, the wafer 4 is usually supported on a flat surface, or supported in a slightly convex shape in the ion implantation direction in order to bring the wafer 4 into close contact with the support means 5 without creating a gap and increase the cooling effect. ing.

In recent years, as wafers have become larger in diameter, based on the above principle, in conventional equipment, the ion implantation angle to both ends of the wafer is different from the implantation angle to the center of the wafer, so it is difficult to control impurity addition. A problem has arisen.

In other words, the mask formed on the wafer surface casts a shadow on the part that was originally implanted, and when the crystal structure of the material forms a certain angle with the ion implantation angle, the ions are removed from the material. Problems such as non-uniform doping of impurities due to the so-called channeling effect caused by deep implantation have become impossible to ignore.

An ion implantation device that corrects the ion implantation angle has been proposed as a device to solve this problem. The principle behind this is that, as shown in Figure 2, the scanning means is divided into two parts 22 and 24, and ions are implanted into the wafer at a constant angle at all times.In this device, two magnetic fields must be used as the scanning means. However, there was a drawback that the device, including the power supply, was rated 9 times.

On the other hand, since the wafer is heated by ion implantation,
The wafer must be cooled to protect the crystallinity and the mask formed on the surface, which determine the quality of the sea urchin.

SUMMARY OF THE INVENTION An object of the present invention is to provide a supporting means capable of maintaining a constant ion implantation angle with a simple structure, in order to solve the drawbacks of the conventional apparatus described above.

The present invention is characterized in that the wafer support means is processed to have a concave shape with respect to the ion implantation direction, and the wafer is supported by being curved toward the concave portion.

FIG. 3 shows a diagram of the principle of the present invention. Means labeled with the same numbers as in FIG. 1 have the same concept. The concave shape is an arc with a radius approximately equal to the distance from the ion scanning means to the wafer. Depending on the deflection means, the concave shape may not be a circular arc, but may be a quadratic curve or a curve corrected by a trigonometric series taking into account the deflection angle.

By supporting the wafer in this manner, the ion implantation angle can be kept constant throughout the wafer. Further, the scanning means 2 scans the charged particles by changing a magnetic field or an electric field.

FIG. 4 shows an embodiment of the present invention.

The charged particles generated by the ion source, accelerated, and selected are scanned as shown by arrow 3 and implanted into the entire surface of the wafer 42.
As shown in the figure, the wafer 42 is supported by a support means 50 by a support mechanism 504 in a concave shape with respect to the ion implantation direction, and 56 is a part of a rotating disk. A cushioning material (hereinafter referred to as a cool sheet) 5o2 having a high thermal conductivity is interposed between the wafer 42 and the support means 5o with a constant thickness. The wafer is linear in the front and back directions of the paper in the figure. That is, the wafer 42 is supported by a cylindrical surface.

The wafer 42 is often single crystal, but R,=1000r
Since the pressing distance 11iID at the time of rrrn is as shown in Table 1, there is no fear of damage.

Table 1 Relationship between wafer diameter and presser distance FIG. 5 shows another embodiment of the present invention.

In this embodiment, the centrifugal force generated when the rotary disk rotates is used to perform the concave support, which is a feature of the present invention, and the advantage is that the support mechanism 504 shown in FIG. 4 is not required, and the concave support means 50 This has the effect of allowing the shape of the concave portion to be freely set.

That is, it is possible to support it concavely with the same radius R both in the front and back directions of the plane of the drawing. If this support is performed, it is possible to support the charged particles concavely not only in the scanning direction of the charged particles but also in the rotational direction of the rotating disk.

5 is a rotating disk of an ion implantation device that rotates around an axis t, and a large number of supporting means 5o are attached around the disk.

After evacuation, a reinforcing material 606 to supplement the strength during evacuation is added to the heat disk portion 602, which is filled with a sufficient amount of refrigerant (usually pure water) compared to the amount of heat removed from the support means 5o. They are arranged at important points so as not to obstruct the movement of the refrigerant inside 602 from the shaft side to the support means 5o by centrifugal force.

The heat generated by ion implantation is conducted from the wafer 42 to the support means 5o through the cool sheet 502, and further transferred to the cooling section 604 by the heat disk section 602.

The cool sheet 502 may be thinner, and a solid material made of a polymeric material having the shape shown in the figure may be used as the material, or a semi-solid material such as vacuum grease, which is highly viscous even at high temperatures (~100 C), may be used as the material for the wafer 42. and the support means 5o.

The cooling section 604 has a structure in which the outer wall of the rotating disk is connected to a double pipe as the outer pipe, and the refrigerant flows in and out in the direction of the arrow in FIG. 5 or in the opposite direction. The partition disk 610 is fixed to the rotating disk 6 with a spring 608 so that it is supported without being affected by thermal expansion.

With this structure, cooling water is guided to the Ueno area and its vicinity.It has the effect of keeping the rotational moment to a smaller value than conventional examples, and at the same time has the effect of increasing the heat capacity related to cooling when performing high-current ion implantation. .

Usually, a coolant such as freon is circulated in the cooling unit 604, but liquid nitrogen may be introduced depending on the amount of heat generated by ion implantation.

However, in this case, it is necessary to control the amount of liquid nitrogen flowing in so that the refrigerant in the heat disk section 602 does not freeze.

As described above, according to the present invention, the ion implantation angle can always be set at a constant angle with respect to the sea urchin.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a conventional ion implantation apparatus using a scanning means, FIG. 2 is a principle diagram of a conventional ion implantation apparatus using two scanning means, and FIG. 3 is an ion implantation apparatus according to the present invention. The principle diagram of the loading device, Figure 4, is based on the present invention! FIG. 5 is a diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Charged particle beam, 2... Scanning means, 3... Scanning range, 42... Semiconductor substrate, 50... Supporting means, 5
02...Cushion material with high thermal conductivity, 504...
Support mechanism, 6... Rotating disk, 602... Heat disk section, 604... Cooling section, 606... Reinforcement material, 6
08...Spring, 610...Partition disk.

Claims (1)

[Claims] 1. Ion implantation in which ions generated in an ion source are accelerated by an accelerating means, selected by a selecting means, and scanned by a scanning means to be implanted into a semiconductor substrate supported by a supporting means. An ion implantation device characterized in that the supporting means has a recessed portion formed on the side where the ions are implanted into the semiconductor substrate, and the semiconductor substrate is supported by being curved toward the recessed portion side. 2. The ion implantation apparatus according to claim 1, wherein the semiconductor substrate is supported using centrifugal force generated by rotating the support means.