JPH0261145B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for annealing a single crystal wafer, and more particularly to a method for annealing a single crystal wafer to prevent cracking of the single crystal wafer due to annealing.

By irradiating the surface of a silicon single crystal wafer damaged by ion implantation with energy beams such as high-power laser beams, ion beams, and electron beams, the damage on the surface of the single crystal wafer is recovered. It is well known to do so. That is, when a pulsed laser is used as the energy beam, the annealing mechanism is liquid crystal epitaxy in which the temperature on the wafer surface rises to the melting point and recrystallizes.
When using a CW laser, the wafer temperature is explained using the concept of solid-phase epitaxy, in which recrystallization occurs before the wafer temperature reaches the melting temperature.

Furthermore, in addition to crystal damage caused by ion implantation on the surface of a single crystal wafer as described above, damage to a polycrystalline layer previously formed on the surface of a single crystal wafer by CVD or an amorphous silicon layer formed by vacuum evaporation, etc. It is also known that polycrystalline or amorphous layers can be made into single crystals by irradiating them with energy rays.

Also, a technique of performing annealing simultaneously with ion implantation in order to dope the surface of a single crystal silicon wafer is well known.

When irradiating an energy beam onto a single crystal wafer or a wafer surface (hereinafter referred to as wafer) on which an amorphous layer or a polycrystalline layer is formed as described above, in the conventional configuration, as shown in the first diagram, A facet surface 3 is formed on the wafer 2 configured on the XY stage 1, and in the case of wafers for MOS, the surface orientation is (100).
are used.

Reference numeral 4 denotes an energy ray source such as a laser. Thermal energy from the energy ray source is reflected and focused by a prism 5 and a lens 6 to form a focal spot 7 on the wafer 2 and melt the surface of the wafer 2.

The wafer 2 placed on the XY stage 1 with the above configuration is accurately fixed so that the facet surface 3 is parallel to the Y-Y axis direction or the X-X axis direction of the XY stage.

In this state, with the focal spot 7 fixed,
By moving the XY stage 1 in the X-X axis or Y-Y axis direction, the surface orientation (100) of the above wafer 2
A scan 8 will be performed parallel to the 110> direction.
That is, scanning is performed in a direction parallel to or perpendicular to the facet plane 3.

Especially for such (100) wafers <110
The wafer surface is melted by energy ray irradiation and is rapidly cooled to become a single crystal.
It has been found that residual thermal strain parallel to the > direction also causes the wafer to be easily damaged. In particular, the wafer may be destroyed during the heat treatment process and handling process after the wafer surface is irradiated with energy rays.
Damage increases significantly.

The present invention provides a method for annealing single crystal wafers that eliminates the above-mentioned drawbacks, and is characterized in that during annealing, an energy beam is scanned in a direction that is deviated by 22.5° to 67.5° from the direction in which cleavage is likely to occur. In this way, cleavage of the wafer due to residual thermal strain is prevented.

An embodiment of the present invention will be described in detail below with reference to FIGS. 2 and 3.

What is shown in FIG. 2 is a plan view of the XY stage shown in FIG. Orthogonal axes F-F and X
- Install with an angle θ between the X-axis or Y-Y axis.

If the angle θ = 45°, when the plane orientation of the silicon wafer 2 is (100), the X-X axis and the Y-Y axis will be in the <110> direction, and this direction is also considered to be a direction in which cleavage is difficult from a crystallographic point of view. Become.

For this reason, the focus spot 7 of the energy beam is
Even if the wafer is scanned in the axial and Y-axis directions (direction parallel to <100>), the wafer will not be damaged during handling in the post-processing process.

Even if we take the above angle θ = 22.5° to 67.5°, <
Compared to the 110> direction, damage can be greatly reduced and the yield of the manufacturing process can be improved.

In FIG. 2, scanning 7 was performed by fixing the spot 7 and moving the XY stage 1 in the X-X, Y-Y axis directions, but as shown in FIG. This is a case where scanning is performed by moving the energy beam side in a direction parallel to the <100> direction having an angle θ with the Y axis and the X-X axis.

Of course, in this case as well, it is obvious that θ=22.5° to 67.5° can be selected.

As described above, in the present invention, the scanning direction of the energy beam is shifted from the direction in which cleavage is likely to occur, so that thermal distortion is caused by the irradiation of the energy beam on the wafer.
Even if it remains on top, it will not be damaged,
It has the characteristic that it can perform the initial purpose of single crystallization by annealing, doping, etc.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a conventional method for annealing a single crystal wafer, FIG. 2 is a plan view showing an embodiment of the wafer annealing method of the present invention, and FIG.
This figure is a plan view similar to FIG. 2 showing another embodiment of the present invention. 1...XY stage, 2...wafer, 3...
Facet surface, 4... Energy ray source, 5... Prism, 6... Lens, 7... Focal spot, 8
...scanning line.

Claims (1)

[Claims] 1. A method of annealing a single crystal wafer in which an energy beam is scanned in a direction deviated by 22.5° to 67.5° from the cleavage direction of the semiconductor single crystal wafer.