JPH0136696B2 - - Google Patents

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 more particularly to a means for keeping the angle of incidence of charged particles on a semiconductor substrate (hereinafter referred to as wafer) constant and a means for cooling the wafer. It is. 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 a scanning means 2 within a region 3 indicated by a broken line, and are implanted into a wafer 4 supported by a 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, conventional equipment based on the above principle has encountered problems in controlling impurity addition because the ion implantation angle to both ends of the wafer is different from the implantation angle to the center of the wafer. has arisen. In other words, a mask formed on the wafer surface may cast a shadow on the area where the ion is implanted, or when the crystal structure of the material forms a certain angle with the ion implantation angle, the ion implantation may occur. Due to the so-called channeling effect, in which impurities are deeply implanted into the material, problems such as uneven doping of impurities 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 of this is that, as shown in FIG. 2, the scanning means is divided into two parts 22 and 24, and ions are always implanted into the wafer at a constant angle. This device had the disadvantage that two magnetic fields had to be used as scanning means, making the device bulky including the power supply. On the other hand, since the wafer is heated by ion implantation, it is necessary to cool the wafer in order to protect the crystallinity that affects the quality of the wafer and the mask formed on the surface. An object of the present invention is to provide an ion implantation apparatus that can efficiently cool a wafer by efficiently dissipating heat generated by ion implantation. The present invention is characterized in that a thermally conductive elastic material is disposed between a recess of the wafer support means and the wafer supported in the recess, the support means is connected to a heat disk filled with a coolant, and the support means is connected to a heat disk filled with a coolant. The point is that the heat disk is connected to the cooling mechanism. 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 a circular arc having a radius R, where R is the distance from the ion scanning means to the wafer. Depending on the deflecting 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 always be kept constant with respect to 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 the arrow 3 and implanted onto the entire surface of the wafer 42, but the wafer 42 is concave in the ion implantation direction as shown in the figure, and is supported by a support mechanism. 504 on the support means 50 . 6 is a part of the rotating disk. A cushion material (hereinafter referred to as a cool sheet) 502 having a high thermal conductivity is interposed between the wafer 42 and the support means 50 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=1000
Since the pressing distance D when mm is as shown in Table 1, damage is not inevitable.

[Table] 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. Reference numeral 6 in FIG. 5 is a rotating disk of the ion implantation device that rotates around the axis I, and a large number of supporting means 50 are attached around the disk. After evacuation, the heat disk part 602 is filled with a sufficient amount of refrigerant (usually pure water) compared to the amount of heat taken from the support means 50, and a reinforcing material 606 to supplement the strength during evacuation is used to prevent condensation. They are arranged at important points so that they do not interfere with the movement of the refrigerant from the inner shaft side of 602 to the support means 50 by centrifugal force. The heat generated by ion implantation is transferred to the wafer 42.
The heat is conducted from there to the support means 50 through the cool sheet 502, and further to the cooling section 604 by the heat disk section 602. That is, the support means 50
The heat transfer from the cooling part 604 to the cooling part 604 is caused by the evaporation of the refrigerant on the side of the support means 50 and the resulting vapor cooling part 604.
The vapor is condensed on the side of the cooling part 604, and the condensed refrigerant moves to the side of the support means 50, in the form of latent heat of vaporization, between the cooling part 604 and the support means 50. The refrigerant is moved to the support means 50 side forcibly by centrifugal force, so that the refrigerant is moved toward the support means 50 by the cushion material 502 provided in the recess of the support means 50. In addition to improved adhesion, the wafer 4 is cooled extremely effectively. The cool sheet 502 may be thin or thin, and may be made of a solid material made of a polymeric material with the shape shown in the figure, or a semi-solid material that is highly viscous even at high temperatures (~100°C), such as vacuum grease. It may also be applied between the wafer 42 and the support means 50. The cooling section 604 has a structure in which the outer wall of the rotary disk 6 is connected to a double 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. This structure has the effect of suppressing the rotational moment to a smaller value than the conventional example in which cooling water is led to the vicinity of the wafer, 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, cooling of the wafer during ion implantation can be performed extremely effectively.

[Brief explanation of drawings]

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. FIG. 4 is a diagram showing the principle of the embedding device, FIG. 4 is a diagram showing one embodiment of the present invention, and 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, 502
...Cushion material with high thermal conductivity, 504...Support mechanism, 6...Rotating disk, 602...Heat disk part,
604...Cooling part, 606...Reinforcement material, 608...Spring, 610...Partition disk.

Claims (1)

[Claims] 1. In an ion implantation apparatus in which a support member attached to a rotating disk has a concave portion for supporting a wafer in a curved manner, and implants ions into the wafer while scanning, the back surface of the wafer and the support member A thermally conductive elastic material is disposed between the recesses, and the rotating disk is provided with a cooling section through which a refrigerant flows near the center of rotation, and between the cooling section and the support member. An ion implantation device comprising: a heat disk having a sealed chamber filled with cold soot.