JPH08195357A - Laser irradiating device - Google Patents

Abstract

PURPOSE: To provide uniform effect, such as an annealing effect, of laser irradiation to semiconductor. CONSTITUTION: The radiation energy of an excimer laser is measured, and the excimer laser is so controlled as to radiate laser beams of constant energy. Laser beams emitted from an optical system 4 and reflected by a mirror 9 are made to irradiate a specimen 11. At this point, a beam profiler is disposed just after the mirror 9 to measure the energy of laser beams. An energy attenuator arranged between a mirror 8 and the optical system 4 is actuated and controlled so as to irradiate the specimen 11 with laser beams constant in energy basing on the measured value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a laser device used for manufacturing a semiconductor device, for example. In particular, the present invention is a semiconductor material which is partially or wholly composed of an amorphous component, or a substantially intrinsic polycrystalline semiconductor material, and further, which is damaged by ion irradiation, ion implantation, ion doping, or the like. The present invention relates to the configuration of a laser device used for the purpose of improving the crystallinity of a semiconductor material or recovering the crystallinity by irradiating the semiconductor material whose crystallinity is significantly impaired with laser light.

[0002]

2. Description of the Related Art In recent years, much research has been conducted on lowering the temperature of semiconductor device processes. The big reason is
This is because it becomes necessary to form a semiconductor element on an insulating substrate such as glass. In addition, there are demands for miniaturization of elements and multilayering of elements.

[0003] In a semiconductor process, an amorphous component contained in a semiconductor material or an amorphous semiconductor material is crystallized, or a semiconductor material whose crystallinity is lowered due to irradiation of ions although it is originally crystalline. It may be necessary to recover the crystallinity of (3) or to improve the crystallinity, although it is crystalline. Conventionally, thermal annealing has been used for this purpose. 600 ° C. when using silicon as the semiconductor material
Therefore, by performing annealing at a temperature of 1 to 1100 ° C. for 0.1 to 48 hours or more, amorphous crystallization, recovery of crystallinity, improvement of crystallinity and the like have been performed.

[0004] In such thermal annealing, in general, the higher the temperature, the shorter the processing time may be, but at a temperature of 500 ° C or lower, there is almost no effect. Therefore, from the viewpoint of lowering the process temperature, it has been necessary to replace the step conventionally performed by thermal annealing with another means.

The laser light irradiation technique is drawing attention as the ultimate low temperature process. That is, the laser light can be applied to only the places where high energy comparable to thermal annealing is required, and it is not necessary to expose the entire substrate to high temperature. Regarding the irradiation of laser light,
Two methods were roughly proposed.

The first method uses a continuous wave laser such as an argon ion laser and irradiates a semiconductor material with a spot-like beam. This is a method of crystallizing the semiconductor material by melting the semiconductor material and then slowly solidifying it due to the difference in energy distribution inside the beam and the movement of the beam. Second
Is a method of crystallizing a semiconductor material by irradiating the semiconductor material with a high-energy laser pulse using a pulsed laser such as an excimer laser to instantaneously melt and solidify the semiconductor material.

[0007]

The problem of the first method is that the processing takes a long time. This is because the maximum energy of the continuous wave laser is limited and the size of the beam spot is at most mm. On the other hand, in the second method, the maximum energy of the laser is very large, and therefore, mass productivity can be further improved by using a large spot of several cm ² or more. However, with a commonly used square or rectangular shaped beam, it is necessary to move the beam up, down, left and right in order to process one large area substrate.
There was still room for improvement in terms of mass productivity.

In this regard, the beam is deformed linearly,
This can be greatly improved by making the width of the beam longer than the substrate to be processed and scanning this beam. What remains to be improved is the uniformity of the laser irradiation effect. A pulsed laser that oscillates by discharging a gas represented by an excimer laser has a property that energy varies to some extent for each pulse. Further, the pulsed laser has a characteristic that the degree of fluctuation of the energy changes depending on the energy output. In particular, when the laser is irradiated in an energy region where stable oscillation is difficult, it is difficult to perform laser processing with uniform energy over the entire surface of the substrate.

Another problem of using the pulse oscillation type laser is that the gas required for laser oscillation deteriorates and the laser energy decreases as the laser is used for a long time. In this regard, increasing the laser power also increases the laser energy, so there seems to be no problem. However, in practice, changing the laser output makes the laser energy unstable for a while, so this method is not very preferable.

[0010]

In the present invention, these problems are solved by using an energy attenuator represented by a neutral density filter and an energy measuring instrument represented by a beam profiler in combination. That is, the present invention relates to a method of irradiating an object by adjusting the laser intensity to an optimum energy by irradiating the laser with an output that is as stable as possible and using an energy attenuator in combination.

In the case of the present invention, the energy attenuation device preferably has a continuously variable energy attenuation rate, but may have a discontinuously variable energy attenuation rate. That is, according to the outline of the present invention, the laser energy is set higher than the optimum energy, and the optimum energy is adjusted by using the energy attenuator. At this time, the laser oscillates in an energy range in which it can oscillate as stably as possible. And
If the laser continues to oscillate for a long time, the laser energy will decrease. It is the gist of the present invention to compensate for this decrease by adjusting the energy attenuator. That is, the energy that is finally reduced is attenuated by the energy attenuator in the first stage, and the attenuation rate is gradually reduced in the stage where the laser light irradiation is continued, so that the laser light is always kept at a constant energy. It is characterized by irradiating. Therefore, it is preferable that the energy attenuator is continuously variable.

[0012]

【Example】

[Embodiment 1] First, the apparatus will be described. FIG. 1 shows a conceptual diagram of a laser annealing apparatus used in this embodiment.
Reference numeral 1 is the main body of the laser annealing apparatus. The laser light is oscillated by the oscillator 2. The laser light oscillated by the oscillator 2 is a KrF excimer laser (wavelength 248 nm, pulse width 25 ns). Of course, other excimer lasers or lasers of other types can be used.

The laser light oscillated by the oscillator 2 is amplified by the amplifier 3 via the total reflection mirrors 5 and 6, and is further introduced into the optical system 4 via the total reflection mirrors 7 and 8.
Although not shown in FIG. 1, an energy attenuator is inserted between 8 and 4. The structure of this machine is shown in FIG.

The apparatus shown in FIG. 3 is a system in which one filter is oriented substantially in the direction of the laser beam and the energy transmittance is changed by changing the angle.

The beam of laser light immediately before entering the optical system is a rectangle of about 3 × 2 cm ² , but the optical system 4 allows a long and narrow beam (line of 8 to 30 cm and width of 0 to 0.5 mm). Beam). The energy of the laser beam that has passed through this optical system 4 is 1000 mJ / shot at the maximum.

The reason why the laser beam is processed into such an elongated beam is to improve the workability. That is, the linear beam exits the optical system 4, passes through the total reflection mirror 9, and is irradiated on the sample 11. However, since the width of the beam is longer than the width of the sample, the sample should be moved in one direction. Thus, the entire sample can be irradiated with laser light. Therefore, the sample stage and the driving device 10 have a simple structure and are easy to maintain. In addition, the positioning operation (alignment) when setting the sample is easy.

Stage 1 of the sample irradiated with laser light
0 is controlled by a computer and is designed to move in a direction substantially perpendicular to the linear laser beam.

The optical path inside the optical system 4 is shown in FIG. The laser light incident on the optical system 4 passes through the cylindrical concave lens A, the cylindrical convex lens B, and the lateral fly-eye lenses C and D, so that the laser light changes from the Gaussian distribution type to the rectangular distribution. Further, the light passes through the cylindrical convex lenses E and F, and the mirror G (see FIG.
Then, it is focused by the cylindrical lens H via the mirror 9) and is irradiated onto the sample.

Mirror G (corresponding to mirror 9 in FIG. 1) is designed to allow a small amount of laser energy to be transmitted, and a beam profiler is placed behind mirror G to
Laser energy can be measured in real time even when the sample is irradiated with laser. Since the linear laser has a large area, the energy is measured by scanning the beam profiler inside the linear laser. (See FIG. 4) By doing so, the energy distribution in the linear laser can also be measured.

In these devices, when the energy of the linear laser deviates from the set energy by a certain ratio or more during laser irradiation, a signal is automatically sent from the beam splitter to the energy attenuator, and the laser energy is changed to the set energy. It is designed to be fixed.

[Embodiment 2] While making the mirror G shown in FIG. 1 transparent by the method of Embodiment 1 has the advantage that the energy of laser irradiation can be measured in real time,
It has the drawback of losing laser energy. Therefore, in the present embodiment, a device arrangement for solving the above-mentioned drawback will be described. However, with the apparatus arrangement of this embodiment, the energy of the linear laser beam cannot be measured in real time during sample irradiation.

The laser-irradiated portion of the apparatus used in this embodiment is shown in FIG. The mirror G in FIG. 1 corresponds to the mirror P in FIG. The mirror P is a total reflection mirror, and below it is a 4% reflection mirror Q. The energy returned by the mirror Q enters the beam profiler R. The size of the mirror Q is smaller than that of the mirror P. This is because the beam profiler has a small area that can be measured at one time. The mirror Q is interlocked with the beam profiler R so that it can slide along the linear laser in a wider range than that of the linear laser. The mirror Q and the beam profiler R are slid to the outside of the linear laser during laser irradiation. Here, if the irradiation target is narrower than the width of the linear laser, it is possible to measure the energy during laser irradiation by placing the mirror Q at the end of the linear laser that does not affect the irradiation. Becomes

[0023]

The laser irradiation technique of the present invention makes it possible to perform laser processing while keeping laser energy as constant as possible. As a result, it can be expected that the reproducibility of the laser processing step is improved and the variation in products that have undergone the laser processing step is significantly reduced. The present invention, in particular,
It can be effectively used for all laser processing processes used for semiconductor device processes. This is because the above process has a narrow laser energy margin, and a slight difference in energy greatly affects the characteristics.
As described above, the present invention is considered to be industrially useful.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a laser annealing apparatus.

FIG. 2 is a diagram showing an optical system.

FIG. 3 is a diagram showing a neutral density filter.

FIG. 4 is a diagram showing a state in which the energy of a linear laser is measured.

FIG. 5 is a diagram showing a schematic configuration of a laser irradiation device.

[Explanation of symbols]

 1 Laser irradiation apparatus 2 Laser light oscillator 3 Laser light amplifier 4 Optical system 5, 6, 8, 9 Total reflection mirror 10 Stage 11 Sample

Claims (6)

[Claims] 1. A laser irradiation apparatus comprising an excimer laser provided with an energy measuring device. 2. An excimer laser equipped with an energy attenuating device, which is a laser irradiation device. 3. A laser irradiation device according to claim 2, wherein the energy attenuation device has a variable energy attenuation rate. 4. A laser irradiating device comprising an excimer laser provided with an energy measuring device and an energy attenuating device. 5. A laser irradiation apparatus comprising an excimer laser equipped with an energy measuring device and an energy attenuating device having a variable energy attenuating rate. 6. A laser irradiating device, wherein the energy measuring device according to claim 5 and the energy attenuating device are interlocked with each other, and laser irradiation can be performed while keeping the laser energy at a certain value.