JPS62216320A - Laser annealing equipment - Google Patents

Abstract

PURPOSE:To prevent the output of a laser unit from decreasing due to an impact by mounting the laser unit on a stationary trestle, mounting X, Y stages and a heater on an X direction movable trestle, providing a portion parallel to the X direction on a laser beam passage, mounting a laser unit side optical system on the stationary trestle and a wafer side optical system on the movable trestle. CONSTITUTION:A laser unit 10 is secured to a trestle 32, a trestle 28 is movable, and both ends are suppressed by the projecting members 34a, 34b of the trestle 32 through springs 36a, 36b. Thus, the trestle 28 is movable between the projecting members, and the moving direction is matched to X direction. A laser beam from the unit 10 passes U-shaped optical path of mirrors 12, 14, 16. When a horizontal unit, i.e., between the mirrors 14 and 16 is selected to the X direction, laser unit side optical systems 12, 14 of the horizontal unit are supported by the trestle 32, and stage side optical systems 16, 18 are supported by the trestle 28. Then, even if the trestle 28 is moved to the X direction due to an impact, the length of the horizontal unit is altered, but no influence is exerted on the laser beam emission to a wafer 20.

Description

[Detailed Description of the Invention] [Summary] The mount of the laser device and the mounts of the X and Y stages are separated,
A laser annealing device in which the latter pedestal is held down by a spring and movable within a predetermined range relative to the former pedestal, thereby absorbing shocks caused by the reciprocating movement of the stage.

[Industrial application field]

The present invention relates to an apparatus for converting polycrystalline silicon on a wafer into a single crystal by laser annealing.

[Conventional technology]

The laser recrystallization method uses SOI (Silicon O
This is an effective method for manufacturing MOS FETs with a nIn5ul-ator structure. SO■ structure M(is
When using FIET, s.

High-speed and highly integrated ICs such as l-ICs and 3D ICs
(Integrated circuits) can be made, so much research and development has been carried out on the laser recrystallization method in recent years.

The laser recrystallization apparatus has a configuration schematically shown in FIG. 1
0 is a gas laser device, 12, 14.16 is a mirror, 18
2 is a focusing lens, and 20 is a silicon wafer, which is held by a heating device (hot chuck) 22. 26
is an X stage (X direction moving mechanism), on which a Y stage (Y direction moving mechanism) 24 is attached, and a heating device 22
rides the Y stage.

The wafer 20 is, for example, a
A silicon substrate St with a thickness of μm, and silicon dioxide Si with a thickness of about 1.0 μm formed by thermally oxidizing its surface.
It consists of O2 and polycrystalline silicon poli-3t formed thereon by CVD method. The laser device W10 is an argon gas laser, and as shown in FIG. 4 (bl), it is equipped with an oscillation tube 10a and oscillation mirrors 10b and 1Oc at both ends of the oscillation tube 10a.

The laser beam 30 emitted from the laser device 10 has a diameter of about 2 cranes,
The light is guided by mirrors 12, 14, and 16 as shown in the figure, focused by a lens 18 to a diameter of 20 to 100 μm, and projected onto a wafer 20. When the laser beam is projected onto the wafer, the polycrystalline silicon in the top layer of the wafer, which has already been heated to about 500°C by the heating device 22, immediately melts, and the X, Y
As the stages 26 and 24 move in the X and Y directions, the polycrystalline silicon layer is completely melted and solidified as shown in FIG. 4(C), thereby becoming a single crystal. 1, 2 in this Fig. 4 fcl.・・・・・・ is the first time, second time, etc.
. . . shows the regions melted and solidified by movement in the X direction (this is for illustration purposes only). These are narrow belt-like regions having a width equal to y to the diameter of the laser beam. Since this is a full-surface filling process, these band-shaped areas are slightly irregular in shape. Arrows indicate the direction of movement.

[Problem that the invention seeks to solve]

In laser annealing, the wafer is irradiated with a narrow laser beam of 20 μm (the irradiation position is fixed), then the wafer is moved in the X direction, then moved in the Y direction by a minute length, and then moved in the same X direction but in the opposite direction. The wafer is completely melted and solidified in a zigzag motion. The above-mentioned micro length in the Y direction is 20 μm or less in this example because the melting and solidifying zones overlap, and in order to melt and solidify the entire wafer, the processing will require a long time unless the moving speed is high. .

Therefore, to improve throughput, the scanning speed was set to 30Q mm.
/s is adopted, and since it is a reciprocating motion, the acceleration is 1 to 10 m/s2. By the way, although the wafer itself is lightweight and has no problem with high speed and high acceleration, the heating device 22 is heavy and has difficulty in high acceleration.

As shown in FIGS. 4(d) and 4(e), the heating device 22 consists of an intake/exhaust mechanism for vacuum suctioning the wafer, a heater for heating, and a water cooling mechanism for not heating the X and Y stages. For φ wafers, it will take more than 18 hours.When such a heavy object moves at high speed, for example, the acceleration will be 5 hours or more.
m/s2, and the weight of the Y stage is 2.0 Kg, and the impact during the acceleration movement of the X stage is 20 Kg・5 m/s2 =
100N, causing positional deviation or vibration in the mirror and optical system of the laser device, making precise positioning and stable laser irradiation for a long period of time difficult.

As shown in FIG. 3(b), the laser device 10 includes mirrors 10b and 10c for oscillation placed at both ends of an oscillation tube.
The mirror is held in place by a spring and pushed from the opposite side with a micrometer to set it in the desired position, so it is movable in the optical axis direction. Therefore, when the above-mentioned impact is applied in the optical axis direction of the laser device, the mirror position changes and the power value changes.

Although impact generation is unavoidable as long as reciprocating laser scanning is used, it is a problem that uniform laser annealing cannot be achieved due to a decrease in the output of the laser device. Therefore, the present invention aims to make this impact as harmless as possible.

[Means for solving problems]

The present invention includes a laser device (10), an x, an X stage (
26, 24) for holding and heating the wafer (20), and an optical system (12, 14, '16.18) for projecting laser light from a laser device onto the wafer. In a laser annealing apparatus, a wafer is reciprocated at high speed in the X direction and precisely moved in the Y direction by an X and Y stage while projecting a wafer to make a polycrystalline silicon layer on the wafer surface into a single crystal.
32), and the X, Y stage and heating device are mounted on a pedestal (28) which is held down via a spring and movable in the X direction within a predetermined range, and the laser beam path of the optical system is
The optical system on the laser device side of the passage is attached to a fixed pedestal, and the optical system on the wafer side of the passage is attached to a movable pedestal, with a portion parallel to the direction.

[Effect]

In laser annealing, the laser beam position is fixed and
, high-speed reciprocation of the wafer in the X direction by the Y stage, Y
This causes a slight skip in the X direction, which generates a strong impact force in the X direction. Therefore, as shown in FIG. 1, the pedestal of the laser device and the pedestal of the stage are separated to prevent shocks from high-speed reciprocating motion from being applied to the laser device.

In FIG. 1, reference numeral 32 denotes a fixed pedestal, and the laser device 10 is fixed to the pedestal 32. The pedestal 28 is movable and has springs 3 at both ends.
The protruding member 34a of the fixed frame 32 via 6a and 36b,
34b. Therefore, the movable pedestal 28 is movable between these projecting members.

This movable direction is aligned with the X direction. Since the impact generated by the high-speed reciprocation of the X stage is in the X direction, the impact causes the mount 2 to
8 moves, compressing one spring and stretching the other spring,
When the impact is released, the spring returns to its original position, and the impact is thus absorbed. It is advisable to provide suitable running resistance to the pedestal 28 to prevent it from vibrating.

The laser beam from the laser device 10 passes through a U-shaped optical path formed by mirrors 12, 14, and 16 as shown in the figure. The device side optical system 12.14 is mounted on the fixed mount 3
If the stage-side optical system 16.18 is supported from the movable pedestal 28, the impact will cause the movable pedestal 2 to move.
Even if 8 moves in the X direction, it only changes the length of the horizontal portion and has no effect on the laser beam projection onto the wafer 20.

It is possible to support all the optical systems on the fixed pedestal 32, but in this case, since the projection position of the laser beam does not change, the projection position will be shifted by the movement of the movable pedestal 28, and the X direction on the wafer will be the same. The start and end of the scan are separated. In this regard, according to the support method shown in FIG. 1, the mirror 16 and lens 18 move together with the movable pedestal 28, so the laser beam projection position on the wafer does not change, and the start and end of scanning in the X direction are not jagged. There isn't. Note that when laser annealing is performed by scanning the entire wafer 20 in the X and Y directions as shown in FIG. However, the X direction does not require high embedding precision (it is sufficient to have a slightly larger scanning width). However, in the case of local processing within a wafer, it is not preferable that there is a large excess or deficiency in the X direction as well.

〔Example〕

The movable frame 28 is movable in the X direction, but preferably fixed in the Y direction. FIG. 2 shows such an embodiment, in which rollers 38 a, 38 are attached to a fixed frame 32.
b, . . . suppress the side surface of the movable pedestal 28 to prevent movement of the pedestal 28 in the Y direction.

Between the movable pedestal 28 and the fixed pedestal 32, there are rollers, wheels,
Or provide a sliding bearing. The heating device 22 as described above
For example, the weight is 18Kg, the Y stage 24 is 2Kg, and the
The stage 26 weighs 4 kg, and if the weight of the movable pedestal 28 is added to this, the total weight becomes considerable, so it is better to use the above method rather than just contact or sliding.

(Effects of the Invention) As explained above, according to the present invention, it is possible to prevent the optical axis of the laser device from shifting and the output to decrease due to the impact caused by the high-speed reciprocating motion of the stage, and to improve the lifespan and characteristics of the laser annealing device. It is effective because it can stabilize the situation.

[Brief explanation of drawings]

1 is an explanatory diagram of the present invention, FIG. 2 is a schematic perspective view showing an embodiment, FIG. 3 is an explanatory diagram of a conventional device, and FIG. 4 is an explanatory diagram of each part of FIG. 3. In FIG. 1, 10 is a laser device, 24 is a Y stage, 26 is an X stage, 20 is a wafer, 22 is a heating device, 12,
14, 16, 18 are optical systems, 32 is a fixed pedestal, 28 is a movable pedestal, 36a, 36b are springs, and 14 to 16 are parts parallel to the X direction.

Claims (1)

[Claims] Laser device (10) and X, Y stages (26, 24)
A device (2) for holding and heating the wafer (20) placed on the
2) and an optical system (12, 14, 16, 18) that projects the laser beam from the laser device onto the wafer, and while projecting the laser beam, the wafer is reciprocated at high speed in the In a laser annealing device that single-crystallizes a polycrystalline silicon layer on the surface of a wafer by precisely moving it in a direction, the laser device is attached to a fixed pedestal (32),
The Y stage and the heating device are mounted on a pedestal (28) that is held down by a spring and movable in the X direction within a predetermined range, and the laser beam path of the optical system has a portion parallel to the X direction to extend the path. A laser annealing apparatus characterized in that an optical system on the laser device side of the passage is attached to a fixed pedestal, and an optical system on the wafer side of the passage is attached to a movable pedestal.