JPH0734432B2 - Laser annealing equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, in particular, a laser annealing apparatus for manufacturing a highly integrated, high-speed, high-performance, fully-insulated and separated semiconductor integrated circuit, that is, a substrate for an SOI device. Is.

2. Description of the Related Art In recent years, semiconductor integrated circuits have tended to have higher densities and higher speeds, and there has been an increasing demand for insulating and semiconductor isolated circuits. Conventionally, for the formation of a semiconductor integrated circuit with insulation isolation, for example, a poly-Si single crystal is irradiated by irradiating a poly-Si laser beam deposited on an insulator substrate such as a silicon (Si) wafer having an insulating film formed on the surface thereof. Is performed and circuit elements are formed on this Si wafer. A conventional laser annealing apparatus will be described below with reference to FIG. FIG. 3 is a block diagram of the most common laser annealing apparatus. The laser beam L emitted from the laser light source 1 is subjected to optical path conversion by the total reflection mirror 3 so as to be vertically incident on the light collecting lens 4, and the laser beam diameter on the silicon wafer 5 is adjusted by the light collecting lens 4. , Irradiate the silicon wafer 5, and XY
By scanning the stage 6, the entire surface of the silicon wafer 5 was irradiated with the laser.

Problems to be Solved by the Invention In the laser annealing apparatus shown in FIG. 3, the total reflection mirror 3 and the light collecting lens 4 are coated with an antireflection film in order to prevent energy loss due to reflection of the laser beam L. Therefore, the reflected light of the laser beam L from the silicon wafer 5, that is, the so-called return light, travels backward in the completely same optical path as the optical path of the laser beam L without any attenuation, and the laser light source 1
However, there is a problem that the output of the laser light source 1 becomes unstable and the single crystallized state becomes unstable.
In view of such a point, the present invention has an object to provide a laser annealing apparatus in which a laser output is returned and is not affected by light.

Means for Solving the Problems The present invention, in order to solve the above problems, in performing laser annealing of a semiconductor substrate, in an optical path from a laser light source to the semiconductor substrate, an antireflection film on one main surface. Is applied, but a glass substrate not coated with the antireflection film on the opposite main surface is arranged so that the antireflection film application surface is on the laser beam incident side.

Action According to the present invention, the laser beam from the laser light source enters the semiconductor substrate without being substantially attenuated because the laser beam is incident from the antireflection film coated surface side of the glass substrate. On the other hand, the return light from the semiconductor substrate is incident from the non-reflection film non-surface side, and a part of the return light is reflected according to the incident angle to the anti-reflection film non-surface. Therefore, by adjusting the incident angle of the returning light on the glass substrate, the returning light can be reflected by a desired amount, and the returning light becomes unstable when the returning light enters the optical resonator of the laser light source. It is possible to solve the problem.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
The figure is a block diagram of a laser annealing apparatus according to the present invention. Between the laser light source 1 and the total reflection mirror 3, one main surface is the antireflection film coated surface 7A, 7B, and the other main surface is the antireflection film non-surface 8A, 8B, the glass substrate 2A, 2B
However, both are installed so that the incident angle of the returning light is θi with respect to the antireflection film surfaces 8A and 8B. Therefore, the laser light emitted from the laser light source 1 passes through the glass substrates 2A and 2B, the total reflection mirror 3 and the light collecting lens 4 with almost no energy loss and is irradiated onto the semiconductor substrate, for example, the silicon wafer 5. On the other hand, part of the returning light is first reflected by the antireflection film surface 8B of the glass substrate 2B at a reflectance R (%) corresponding to the incident angle θi, and further, the antireflection film surface 8A of the glass substrate 2A. However, a part of it is reflected with the reflectance R (%) corresponding to the incident angle θi, and finally the return light R (2-R / 10
FIG. 2 shows the measurement results of the reflectance with respect to the incident angle θi of the glass substrate used in this example in which 0% is reflected. For example, when the glass substrates 2A and 2B are installed so that R = 20% and the laser beam L is irradiated on the silicon wafer 5 with the output 3W of the laser light source 1, 36% of the returning light is the glass substrates 2A and 2B.
Instability was not recognized in the output of the laser light source 1, and it became possible to stabilize the laser output during laser irradiation.

Effects of the Invention As described above, according to the present invention, when performing laser annealing of a semiconductor substrate, fluctuations in laser output due to returning light do not occur even during laser irradiation, and stable single crystallization is always performed. A possible laser annealing device is realized, and its practical effect is extremely great in the mass production process of single crystallization.

[Brief description of drawings]

FIG. 1 is a block diagram of a laser annealing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between an incident angle θi of returning light and reflectance R, and FIG. 3 is a block diagram of a conventional laser annealing apparatus. Is. 1 ... Laser light source, 2A, 2B ... Glass substrate, 3 ... Total reflection mirror, 4 ... Light collecting lens, 5 ... Silicon wafer,
6 ... XY stage, 7A, 7B ... Anti-reflection film coated surface, 8A, 8B ... No anti-reflection film surface.

Claims (1)

[Claims] 1. When performing laser annealing of a semiconductor substrate, an antireflection film is applied to one main surface of an optical path from a laser light source to the semiconductor substrate, while the other main surface is coated with the antireflection film. A laser annealing apparatus in which a glass substrate not coated with the antireflection film is arranged such that the antireflection film coating surface is on the laser light incident side.