JPH0754798B2 - Beam annealing method - Google Patents

Description

DETAILED DESCRIPTION [Outline] In beam annealing in which a semiconductor layer on an insulator is swept and irradiated with an energy ray beam to melt and recrystallize the semiconductor layer, an irradiation area having a band shape is used and a cross section is used. By irradiating the semiconductor layer through the reflection of the concave reflecting surface having a parabolic shape, the beam energy can be effectively utilized when the melting shape of the semiconductor layer is made into a crescent shape.

[Industrial application field]

The present invention relates to a beam annealing method for sweeping and irradiating a semiconductor layer on an insulator with an energy beam to melt and recrystallize the semiconductor layer, and more particularly to a method for forming an irradiation beam.

The beam anneal is SOI (Silicon On Insulator)
It is used to form silicon single crystals on insulators in the technology.

The SOI technology is a technology that forms a silicon single crystal on an insulator on the surface of a substrate, and forms an element on this single crystal. It is expected to improve the isolation of the element and enable high integration by forming a three-dimensional circuit. Has been done.

Therefore, for this beam annealing, it is desired to be able to form a large single crystal.

[Conventional technology]

FIG. 3 is an explanatory perspective view of the beam annealing method according to the present invention.

That is, the semiconductor layer 2 such as polycrystalline silicon deposited on the insulator 1 on the surface of the substrate is swept and irradiated with an energy beam 3 such as argon laser light. In the figure, the semiconductor layer 2 is swept by moving as shown by the arrow.

Then, the irradiation part 4 of the semiconductor layer 2 is heated and melted,
When the melted region is solidified by the movement of the beam 3, it is recrystallized to form a band-shaped recrystallized region 5. And the single crystallization at the time of this reforming is utilized.

When the beam 3 has a normal Gaussian distribution, the fusion shape 6 of the irradiation part 4 is circular as shown in FIG. 4 (a) in the explanatory view of FIG. In such a case, recrystallization starts from both sides of the width of the recrystallized region 5, and crystals grow inward. At this time, since the recrystallization start points are located at both edges of the recrystallization region 5 and are in contact with the unmelted semiconductor layer 2, that is, the polycrystalline silicon, the growth nuclei cannot be united during the sweep. Therefore, the single crystal becomes small without being connected in the sweep direction.

It is known that as a measure for enlarging a single crystal, the melting shape 6 may be a crescent shape as shown in FIG. 4 (b). Here, the crescent shape refers to a shape including an arc shape, a radial shape, or a V-shape.

Since the central portion of the recrystallized region 5 serves as the recrystallization start point, the number of nuclei for growth during the sweep becomes one, and the growth goes to both outsides and is connected in the sweep direction. The single crystal region 7 having a width close to that of the recrystallized region 5 and long in the sweep direction
Is obtained.

In order to realize such a crescent-shaped melted shape 6, hitherto, for example, as shown in FIG. 5, a mask 9 provided with a crescent-shaped through hole 8 is interposed in the passage of the beam 3 and reaches the irradiation section 4. A method of limiting the cross-sectional shape to a crescent shape is used.

[Problems to be solved by the invention]

However, in the above-described conventional method using the mask 9, only the portion of the beam 3 that has passed through the through hole 8 reaches the irradiation portion 4, so the energy that contributes to the heating of the semiconductor layer 2 is extremely higher than the energy of the beam 3. The size is small, for example, about one-tenth to one-tenth, and the utilization efficiency of beam energy is extremely poor.

This imposes a restriction on the width of the recrystallized region 5 and hinders the expansion of the width of the single crystal region 7.

[Means for solving problems]

The above-mentioned problem is that the energy ray beam having a plurality of regions in a strip shape is obliquely incident on the concave reflecting surface having a parabolic cross section from the front thereof so that the strip longitudinal direction of the beam is aligned with the cross section direction and the reflection is performed. This is solved by the beam annealing method of the present invention in which a semiconductor layer to be melted and recrystallized is swept and irradiated with a reflected beam from a surface.

[Action]

Due to the reflection on the reflecting surface, the irradiation area of the reflected beam becomes a crescent shape, and the energy thereof is substantially the same as the energy before entering the reflecting surface.

Therefore, the utilization efficiency of the beam energy becomes extremely high as compared with the conventional one, and the width of the recrystallized region can be greatly expanded as compared with the conventional one.

Along with this, the width of the single crystal region is also expanded.

Thus, it becomes possible to form a single crystal region having a large width.

〔Example〕

An embodiment will be described below with reference to the perspective view of FIG. 1 showing an essential part of the method of the present invention and the perspective view of FIG. 2 showing a concave reflecting mirror used in the embodiment.

In FIG. 1, a laser beam 3a having a spot-shaped cross section emitted from a light source 11 is reflected by a reflecting mirror 12 that oscillates in the swinging direction of an arrow to form a belt-shaped beam 3b, which is a concave reflecting mirror shown in FIG. It is reflected by 20 and becomes a crescent beam 3c having a crescent-shaped cross section and focusing only in the width direction. Then, the crescent beam 3c irradiates the irradiation section 4 of the semiconductor layer 2 when the width reaches a predetermined size after passing through the focusing point 13.

The concave reflecting mirror 20 has a band-shaped concave reflecting surface 21 having a parabolic cross section. Therefore, when the belt-shaped beam 3b is obliquely incident on the concave reflecting surface 21 from the front thereof with the belt-shaped longitudinal direction aligned with the above-mentioned cross-sectional direction, the reflected beam has a crescent-shaped cross-section and only the width direction is focused on the focusing point 13. It becomes crescent beam 3c.

From the above, the melting shape in the irradiation unit 4 becomes a crescent shape as shown by 6 in FIG. 4 (b), and the energy of the beam 3c irradiating the irradiation unit 4 is still the beam 3a emitted from the light source 11. Is almost equal to the energy of. This enables the width of the recrystallized region 5 to be greatly expanded as compared with the conventional one, and accordingly, the single crystal region 7 having an extremely large width.
Can be formed.

According to the confirmation of the inventor of the present application, the recrystallized region 5 is formed by the conventional method.
The width of the light source 11 was about 10 μm and the width was about 20
Use a concave reflecting mirror 20 with a width of about 50μ for the recrystallized region 5.
Single crystal region 7 with a width of about 40 μm and a long length in the sweep direction.
I was able to get

In the above-described embodiment, the irradiation unit 4 irradiates the crescent moon beam 3c after passing the focus point 13, but it may be irradiated before the focus point 13.

Further, it can be easily analogized from the principle of the present invention that a prism having a reflecting surface similar to the concave reflecting surface 21 may be used instead of the concave reflecting mirror 20.

Further, a lens system may be inserted between the concave reflecting mirror 20 and the irradiation unit 4 to adjust the size of the fused shape.

〔The invention's effect〕

As described above, according to the configuration of the present invention, in the beam annealing in which the semiconductor layer on the insulator is swept and irradiated with the energy beam to melt and recrystallize the semiconductor layer, the melting shape of the semiconductor layer is a crescent shape. At this time, there is an effect that the beam energy can be effectively used and the width of the single crystal region can be greatly expanded.

[Brief description of drawings]

FIG. 1 is a perspective view showing an essential part of an embodiment of the method of the present invention, FIG. 2 is a perspective view of a concave reflecting mirror used in the embodiment, and FIG. 3 is an explanatory perspective view of a beam annealing method according to the present invention. FIG. 4 is an explanatory view (a) and (b) of a melting shape by a beam, and FIG. 5 is an explanatory perspective view of an example of a conventional method for forming the melting shape into a crescent shape. In the drawing, 1 is an insulator, is a semiconductor layer, 3 is a beam, 3a to 3d is a beam, 4 is an irradiation part, 5 is a recrystallized region, 6 is a molten shape, 7 is a single crystal region, 8 is a crescent-shaped through hole, Reference numeral 9 is a mask, 11 is a light source, 12 is a reflecting mirror, 13 is a focusing point, 20 is a concave reflecting mirror, and 21 is a concave reflecting surface.

Claims (1)

[Claims] 1. When performing beam annealing for sweeping and irradiating a semiconductor layer on an insulator with an energy ray beam to melt and recrystallize the semiconductor layer, the irradiation area is a band-shaped energy ray beam having a parabolic cross section. A beam annealing method, characterized in that a strip-shaped longitudinal direction of the beam is obliquely incident on a concave reflecting surface having a shape such that the longitudinal direction of the beam is aligned with the cross-sectional direction, and the reflected beam from the reflecting surface is applied to the semiconductor layer. .