JPH0436447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a beam annealing method.

2. Description of the Related Art A method of heating a sample surface by irradiating the sample with a directional energy beam such as a laser beam or an electron beam is attracting attention in the field of manufacturing semiconductor devices. However, if a laser beam or electron beam is scanned using a rotating reflector or an electromagnetic coil, which is conventionally used to scan the beam over the sample surface at high speed, the sample 1
Since the irradiation power density is not constant due to the difference in the incident angle θ of the beams 12 and 12' on one surface and the deviation h from the focal point (focal plane 13), there has been a problem that non-uniformity occurs in the annealing of the sample.

An object of the present invention is to provide a new beam annealing method that can significantly improve the problems in the conventional methods described above.

The method according to the invention is characterized in that the incident beam is incident perpendicularly to the sample surface or an extended surface of the sample surface at one end of the sample or an external part of the sample, and the point of normal incidence on the sample surface or the extended surface of the sample surface is the focal point of the beam. Arrange the beam and sample so that Then, under conditions such that the irradiated area reaches the desired temperature, the beam is irradiated parallel to the first irradiation area from the end point of the first scan or its vicinity so that at least a portion thereof overlaps with the first beam irradiation area. This method is characterized in that the beam is scanned in a direction opposite to the first scanning direction.

In the method according to the invention, the positional relationship between the beam and the sample is selected such that the beam is focused on the sample surface or its extension at the edge of the sample or outside the sample. For example, in the schematic plan view of the sample stage shown in FIG. 2, the beam is arranged so as to be focused on the same level point F as the surface of the sample 22 on the sample stage 21. Therefore, if the beam is scanned for the first time in one direction at a constant speed from point F using a rotating mirror or electromagnetic coil, the temperature rise on the sample surface caused by beam irradiation as it moves away from point F will be decreases monotonically. This is because the incident angle of the beam becomes larger and the sample surface moves out of focus (aberration).
by. However, the beam is moved once from point F to point G (point G is the point symmetrical to point F across the sample).
The temperature distribution on the scanned line immediately after scanning at a constant power and constant speed (when the beam reaches point G) can be approximately represented by, for example, a curve 31 in FIG. 3. A characteristic feature is that the sample surface temperature increases as the distance from point F increases. this is,
This is because the closer the point is to F, the longer the time has elapsed after the beam has passed, so the temperature decreases more greatly due to the heat dissipation effect. Next, increase the power further from point G to point F, or decrease the scanning speed and turn around in the opposite direction.
When the second scan is performed, the temperature rise on the sample surface due to the second scan itself is high on the F point side, as approximated by the curve 32 in FIG. 3, due to the influence of the incident angle and aberration as described above. It becomes lower on the G point side. However, the actual sample surface temperature is
Since it can be approximated as the sum of the preheating effect due to the first scan and the temperature increase due to the second scan, a substantially uniform temperature increase as shown by the curve 33 in FIG. 3 can be achieved. Parameters such as the power of the first and second beams, the scanning speed, and the time interval between the first and second scanning may be adjusted so that this substantially uniform temperature becomes the desired heat treatment temperature. Further, the first and second irradiation portions may only partially overlap.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining problems in the conventional beam annealing method. FIGS. 2 and 3 are diagrams for explaining the method according to the present invention, in which FIG. 2 is a schematic plan view of the sample stage, and FIG. 3 is a diagram showing the relationship between position on the sample surface and temperature. 11, 22...sample, 12,12'...beam, 1
3... Focal plane, 21... Sample stage.

Claims (1)

[Claims] 1. At one end of the sample or outside of the sample, the incident beam is incident perpendicularly to the sample surface or an extended surface of the sample surface, and the point of normal incidence to the sample surface or the extended surface of the sample surface is the focal point of the beam. The beam and the sample are arranged, and the beam is first scanned in one direction from the vertical incidence point or outside thereof toward the other end of the sample surface under conditions that the irradiated part of the sample does not reach the desired heat treatment temperature. The first scan is performed parallel to the first irradiation area from or near the end point of the first scan so that at least a portion thereof overlaps with the first beam irradiation area under conditions such that the irradiated area reaches a desired temperature. A beam annealing method characterized by scanning a beam in the opposite direction.