JPH0673346B2 - Laser annealing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laser beam annealing apparatus, and more particularly to a wafer laser annealing apparatus used for manufacturing a semiconductor integrated circuit.

(Prior Art) Conventionally, there is an annealing technique using a laser beam as a means for recovering the crystallinity of a silicon wafer used for manufacturing a semiconductor integrated circuit. As a method for further promoting the effect of this laser annealing, a sample is used. There is a method of irradiating a laser beam while heating. A laser annealing apparatus using such a method is already on the market.

FIG. 1 is a block diagram showing a general configuration example of the above-mentioned device. The laser beam emitted from the laser light source 1 is shaped into a desired shape by the beam shaping optical system 2, then guided to the scanning optical system 3, and focused on the sample 6. The beam shaping optical system 2 includes reflection mirrors 21, 22, 24 and a beam expander 23, and expands and shapes the laser beam. The scanning optical system 3 is fixed on a moving table (not shown) that can move in the XY directions, and can scan the sample 6 in the XY directions. Inside it, a reflection mirror 33,
The optical system 32 that reflects the laser beam from the reflection mirror 24 and transmits the observation light from the sample, and the objective lens 31.
The sample 6 is held on a stage 7 in which a heating device 8 is incorporated, and this heating device is controlled to an arbitrary temperature by a temperature controller 9. Heating temperature is generally room temperature to 700
The temperature is appropriately selected in the range of about ℃ according to the purpose, but in the high temperature range, the radiant heat from the sample surface causes the scanning optical system 3
The air between the objective lens 31 and the sample surface is heated and fluctuates, and the optical paths of the laser beam and the observation light reflected from the sample 6 change irregularly. For example, it looks like Kagerou stands on a hot summer day.

In the conventional apparatus, due to the change in the optical path of the laser beam due to the fluctuation of air as described above, the trajectory of the laser beam on the sample surface becomes meandering, and the screen of the TV monitor 5 that displays the processed surface of the sample by the observation optical system It always looks fluctuating, making it difficult to correctly observe the sample surface condition. Second
In the figure, 10 indicates the locus of the laser beam on the sample surface in a normal and desirable annealing state, and when the above-mentioned air fluctuation occurs, the locus is shown in FIG.
Will be 10. Further, when the laser beam is scanned with the scanning interval further reduced, an overlapping portion 11 may occur between adjacent trajectories as shown in FIG. Irradiation of such a serpentine irregular laser beam does not realize uniform crystallinity, which deteriorates the characteristics of the silicon wafer,
As a result, the yield of the semiconductor integrated circuit may be deteriorated.

(Object of the invention) The object of the present invention is to eliminate the above-mentioned drawbacks of the conventional device,
It is an object of the present invention to provide a laser annealing device capable of irradiating a laser beam that is not meandering.

(Structure of the Invention) The present invention includes a laser light source, an optical system that shapes the light flux of a laser beam emitted from the laser light source, and a scanning optical system that collects the shaped laser beam and scans the sample.
In a laser annealing device having an optical system for observing a sample surface and a stage for holding the sample while heating it, a transparent heat shield plate is provided between the scanning optical system and the sample surface, and It is characterized by having a mechanism for cooling the shield plate.

(Example) Next, the Example of this invention is described in detail with reference to drawings.

FIG. 5 is a block diagram showing an embodiment of the present invention.

In the figure, a laser light source 1, a beam shaping optical system 2, a scanning optical system 3, an observation optical system 4, a TV monitor 5 and a temperature controller 9 have the same structure as the conventional laser annealing device shown in FIG. Is as described above.

In the present embodiment, a heat shield plate 12 such as a glass plate is installed between the scanning optical system 3 and the sample 6 to prevent direct heat radiation from the sample surface, and the nozzle 13 is provided on the glass plate. Install and heat the air or nitrogen gas 15 heat shield plate
I am trying to spray it on 12. However, in order to reduce the energy loss of the laser beam, a heat shield
No. 12 has a sufficient transmittance for the laser beam and must not have any scratches or bubbles inside. Further, since this heat shield plate receives a considerable amount of heat radiation from the sample surface, it must have sufficient strength against heat. A quartz plate is suitable as the heat shield plate 12 for the reasons described above. The heat shield plate 12 may be heated by itself as described above, and the nozzle may prevent it.
It is a cooling mechanism consisting of 13. This mechanism has the function of air-cooling the heat shield plate 12 by blowing air or nitrogen gas 15 from the nozzle to the heat shield plate 12, but it is better to use a gas that has been cooled in advance to further enhance this effect. Of course. The flow rate of the gas is appropriately adjusted by the flow rate adjusting valve 14 depending on the temperature near the heat shield plate.

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent the heat radiation from the heated sample surface and remove the fluctuation of the air. Therefore, it is possible to prevent the conventional meandering of the laser beam. ,
The annealing effect of the silicon wafer can be enhanced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a general configuration example of a conventional laser annealing device, FIG. 2 is a diagram showing a locus of a laser beam in a normal annealing state, and FIGS. 3 and 4 are inside an optical path of the laser beam. FIG. 5 is a diagram showing a trajectory of a laser beam when air fluctuations occur in FIG. 5, and FIG. 5 is a block diagram showing an embodiment of the present invention. 1 ... Laser light source, 2 ... Beam shaping optical system, 3 ... Scanning optical system, 31 ... Objective lens, 4 ... Observation optical system, 5 ...
… TV monitor, 6… Sample, 7… Stage, 8… Heating device, 9… Temperature controller, 10… Laser beam locus, 11… Laser beam overlap, 12… Heat shield plate , 13 ... Blowing nozzle, 14 ... Flow rate adjusting valve.

Claims (1)

[Claims] 1. A laser light source, an optical system for shaping a light beam of a laser beam emitted from the laser light source, a scanning optical system for focusing the shaped laser beam and scanning the sample, and observing the sample surface. In a laser annealing device having an optical system for performing and holding a sample while heating and holding the sample, a transparent heat shield plate disposed between the scanning optical system and the sample surface, and the heat shield plate. A laser annealing device having a cooling mechanism.