JPS62216321A - Laser annealing apparatus - Google Patents

Abstract

PURPOSE:To prevent an optical axis from varying and the output of a laser from decreasing disposing an X stage directly under a heater, and disposing a Y stage under the X stage and a rotating unit in the lowermost position to reduce an impact due to the acceleration or deceleration of the high speed stage. CONSTITUTION:An X stage 26 is placed directly under a heater 22, a Y stage is disposed under the stage 26, and a rotating unit is disposed in the lowermost stage. Thus, the load of the high speed stage 26 is reduced to decrease an impact due to acceleration or deceleration, thereby reducing an influence to a laser unit and an optical system. That is, when the high speed stage is placed at an upper position, the load of the high speed stage is reduced, and a mechanical strength may be reduced, but since the accurate stage placed at a lower position is increased at its load, it must be rigid and increased in size to increase the weight as a whole, but the load of the high speed X stage is only the heater to reduce the acceleration between back and forth reciprocations. When the rotating unit 28 is disposed at the lowermost stage, a wafer 20 can be rotated at the optical axis as a center by matching the rotating center to the optical axis of a lens 18 to rotate the wafer 20 at the optical axis as a center, thereby facilitating the operation such as matching of the side and the scanning direction of a region to be processed.

Description

[Detailed Description of the Invention] [Summary] A laser annealing device in which a high-speed stage is placed on a precision stage in order to prevent optical axis deviation and deterioration of the laser device.

[Industrial application field]

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

[Conventional technology]

The laser recrystallization method uses SOI (Silicon O
nIn5u-1ator) structure MOS FET
It is an effective method for manufacturing. MOS with So■ structure
Since FETs can be used to create high-speed, highly integrated ICs (integrated circuits) such as 5OI-ICs and three-dimensional ICs, much research and development has been carried out on laser recrystallization in recent years.

The laser recrystallization apparatus has the configuration shown in FIG. 1
0 is a gas laser device, 12, 14.16 is a mirror, 18
2o is a focusing lens, and 2o is a silicon wafer, which is held by a heating device (hot chuck) 22. 26
is an X-stage (X-direction moving mechanism) that performs high-speed reciprocating motion, on which an X-stage (Y-direction moving mechanism) 24 is attached, a rotating device 28 is placed on top of it, and the heating device 22 is connected to the rotating device 28. Get on top. In other words, the X stage is the lowest stage and is attached to the pedestal 32.

The wafer 20 is, for example, 400 wafers as shown in FIG.
A silicon substrate Si with a thickness of μm, whose surface is pj3! It consists of silicon dioxide S) 102 with a thickness of about 1.0 μm formed by oxidation, and polycrystalline silicon poli-3i formed by CVD method thereon. Laser device 1
0 is an argon gas laser, and as shown in FIG.
Equipped with.

The laser beam 30 emitted from the laser device 10 has a diameter of about 2n, is guided by mirrors 12, 14, and 16 as shown in the figure, is focused by a lens 18 to a diameter of 20 to 100 μm, and is directed onto the wafer 20.
is projected on. When the laser beam is projected onto the wafer, the polycrystalline silicon in the uppermost layer of the wafer, which has already been heated to about 500°C by the heating device 22, immediately melts, causing
The polycrystalline silicon layer is scanned by movement in the X and Y directions by the X stages 26 and 24, as shown in FIG. 3 (C1), and is melted and solidified over the entire surface, thereby becoming a single crystal.

In this figure 3 (C), 1, 2.・・・・・・ is the first time, 2
The area that is melted and solidified by the X-direction movement of the second time is shown (however, this is for illustration purposes only), and these are within the diameter of the laser beam! ``It is a narrow band-like area with equal width. Since this is a full-surface filling process, these band-shaped areas overlap by δ. The arrow indicates the direction of movement, and as shown in the figure, the movement in the X direction is a reciprocating movement, and each time the direction is reversed, it skips in the Y direction by the width of the strip area minus δ.

The heating device 22, as shown in FIG. rotates the X-X stage so that the movement in the X and Y directions is aligned with the X and Y directions of the processing area on the wafer.In this case, the movement of the X-X stage rotates the center of the heating device 22. The heating device 22 is aligned with the rotation axis of the device 28, and the lock fixing the heating device 22 to the X stage is removed, and the heating device 22 is fixed to the pedestal 32. 2
2 rotates the rotating device 28 after preventing it from rotating with respect to the pedestal 32. In other words, the entire surface of the process 20 is not laser annealed, but only the necessary portions are laser annealed. For example, the scribe lines of the wafer are not laser annealed because they do not need to be laser annealed. Also, some integrated circuits include a mixture of bulk FETs and SOI FETs, and in such integrated circuits, laser annealing is performed on the SOI FET section, while the bulk FET section
I don't have a club. In other words, laser annealing is selective, and in order to perform this reliably, align the scanning direction with the side of the area to be processed as shown in Figure 3 Ca+, and if it looks like the dotted line X', rotate the wafer and It is necessary to do as follows. The rotating device 28 performs this.

[Problem that the invention seeks to solve]

As shown in Figure 2, this laser recrystallization device has an X
The stage is followed by the X stage, the next is the rotation device, and the top stage is the heating device, and the wafer is attached to the heating device. Although it is natural that the top stage is the heating device, the reason why the X stage is the lowest stage is due to its weight. In other words, the X stage performs reciprocating motion in the X direction, and in order to perform filling-in processing in an extremely narrow band-like area, it must be capable of high-speed reciprocating motion, which requires the use of a large motor, etc. First, the amount of M is large. In this respect, the X stage only needs to perform a minute skip every time the direction is reversed as described above, so it may be slow and lightweight, but it must be highly accurate. That is, the third
The width of the narrow strip area 1゜2 in Figure (C) is 30
μm, the smaller the overlap distance δ, the higher the processing capacity, so δ = 5
If it is .mu.m, then the positioning accuracy must be about 1 .mu.m. Thus, the X stage has the characteristics of high speed, but the accuracy does not need to be very high, and the X stage has high accuracy, but the speed does not need to be very high. A specific example is as follows.

Table 1 Heating device Precision Y stage High speed X stage Self weight
18Kg 2.0Kg
4.0 Kg ellipse / 1μm
20 μm speed / 2 w/ sec 400 vn/
sec load capacity / 20 Kg
100 Kg accuracy is specifically determined by the pinch of the feed screw shaft, and high precision ones have small pinches. The drive motors for both the X and Y stages are panel motors.

The high-speed stage is large and heavy, so place it at the bottom.
Conventional equipment places a lightweight, precision stage on top of that, but in this way, the acceleration during the forward and backward movement of the high-speed stage is 1 to 10 m/s2, and the impact is 20 kg.
Reach X10m/52=20ON. This causes deviations in the optical system, changes in the optical axis due to vibration, and fluctuations in laser output. For example, in the case of a gas laser, the oscillation mirror 10b,
10c is positioned by holding it down with a spring and pushing it with a micrometer from the opposite side. Since it is movable in the optical axis direction, if the above-mentioned impact has a component in the optical axis direction, the mirror position will change. , the laser output will change.

The present invention aims to improve these points and enable stable and uniform laser annealing.

[Means for solving problems]

In the present invention, as shown in FIG. 1, an X stage 26 is placed directly below the heating device 22, a Y stage is placed below it, and a rotating device is provided at the lowest stage.

[Effect]

In this way, the load on the high-speed stage 26 is reduced,
The impact caused by acceleration and deceleration is reduced, and the influence on the laser device and optical system is reduced.

〔Example〕

If the high-speed stage is placed on top, the load on the high-speed stage will be small and its mechanical strength will be low, but the precision stage placed below will have a heavy load, so it will need to be more robust and larger. Next, a numerical example is given.

Table 2 Heating device High speed X stage Precision Y stage Self weight
18Kg 4.0Kg
4.0 Kg Ellipticity 720μm1μm Speed / 400B/s 2cm/S Load Capacity /
100Kg 100KgThe overall weight of the device increases in this way, but the load on the high-speed X stage is 18Kg only for the heating device, and assuming the acceleration between forward and backward movements is 10m/s2, the impact is 18KgX10=18
It turns on and reduces the energy consumption by 10% compared to the conventional device.

Furthermore, when the rotation device 28 is at the lowest stage, by aligning the rotation center with the optical axis of the lens 18, the wafer 2
0 can be rotated around the optical axis, as shown in Fig. 3(a).
It is possible to easily perform operations such as aligning the scanning direction with the side of the processing area of l.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reduce the impact caused by acceleration and deceleration of the high-speed stage, which is effective in improving optical axis changes, stabilizing laser output, etc.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the device of the present invention, FIG. 2 is an explanatory diagram of the conventional device, and FIG. 3 is an explanatory diagram of each part. In FIG. 1, 30 is a laser beam, 20 is a wafer, 22 is a heating device, 26 is a χ stage, 24 is a Y stage, and 28 is a rotation device.

Claims (1)

[Claims] A device (22) for supporting and heating a wafer (20) onto which a laser beam (30) is projected, an X stage (26) for reciprocating the heating device at high speed in the X direction, and A laser annealing apparatus that is equipped with a Y stage (24) that moves precisely in the Y direction orthogonal to the Y-direction, and a rotation device (28) that rotates the laser annealing apparatus, which single-crystallizes polycrystalline silicon on the wafer surface by projecting the laser beam. A laser annealing device characterized in that an X stage is placed directly below a heating device, a Y stage is placed below that, and a rotation device is placed at the bottom.