JPH0274902A - Diffraction grating forming device - Google Patents

Abstract

PURPOSE:To eliminate the need for resetting a sample even if the quantity of the reflected light on one surface of the sample is insufficient by irradiating both sides faces of the sample with laser light and adjusting the inclination angle of the sample with the side face with which the strong reflected light is obtd. CONSTITUTION:The laser beam emitted from an He-Ne laser light source 1 is split by a half mirror 18 to the reflected light and the transmitted light. The reflected light is turned back by a mirror 21 and a half mirror 22 and is made incident on the side face of the sample while a shutter 20 is held open. The reflected light from the side face passes the half mirror 22 and an aperture 23 and is made incident on a photodetector 24. On the other hand, the laser beam transmitted through the half mirror 18 is reflected by a half mirror 14 and is made incident on the side face on the opposite side of the sample if a shutter 19 is held open. The reflected light therefrom passes the half mirror 14 and an aperture 17 and is made incident on a photodetector 15. The detection is switched to the detection with the other side face without resetting the sample if the quantity of the reflected light from the one side face is weak. The detection of the reflected light and the adjustment of the inclination are thus executed with the stronger quantity of the reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a diffraction grating production device, and more particularly to a device for producing a diffraction grating on a sample by interference of laser light.

[Conventional technology]

In recent years, as a method for manufacturing a two-distribution feedback semiconductor laser,
A method of creating a diffraction grating by irradiating interference fringes of laser light onto a semiconductor has been adopted and has been made into an apparatus. An example of the general configuration of this type of device is shown in FIG.

In FIG. 3, reference numeral 1 denotes a laser light source, and the laser light emitted from it is reflected by a mirror 2.3 and enters a beam splitter 4. Typically, the beam splitter 4 reflects 50% of the laser beam.

It is designed to transmit 50 inches. The reflected light is reflected by the mirror 5, once focused by the lens 8 at the position of the bin ho 9, and then collimated by the lens 10 again. Here, the pinhole 9 works as a spatial filter to clean the mode of the laser beam, and this collimated beam is reflected by the mirror 11 and is placed on the sample 12.
is irradiated. On the other hand, the transmitted light is reflected by the mirror 6.7, collimated by the lens in the same way as above, and then
The sample 12 is irradiated by the mirror 11. These two beams interfere on the sample, creating interference fringes.

In this figure, the interference fringes occur in a direction perpendicular to the plane of the paper.

Δ Also, the period l of this interference fringe is given by J = λ/[2 parts φS stone θ] where the incident angle θ of the Rede light, the rotation angle φ of the sample, and the wavelength λ of the laser light are as shown in Fig. 4. It will be done.

How to actually create a diffraction grating using this device.

A sample coated with photoresist is set in advance, irradiated with laser light, and then developed.

By etching! 7 will be done. Typically, an Ar laser, a He-Cd laser, or the like is used as a radar light source, and the period of one diffraction grating is around 2000X depending on the desired oscillation wavelength of the semiconductor laser. The period can be changed by changing the incident angle θ and at the same time changing the position of the sample.

By the way, what is important when using this type of device is that the diffraction grating 12a is aligned with respect to the reference plane of the sample as shown in FIG.
need to be created in parallel. Normally, in the case of a sample for a semiconductor laser, this reference plane is a so-called valve opening plane, and in FIG. 5, the valve opening planes 12b and 12c are both sides of the sample. Therefore, in this type of device, a mechanism is provided to make the valve opening plane vertical.

As shown in FIG. 3, the H@-Ne laser light source 1
3, a half mirror 14, a photodetector 15, and an indicator 16. The He--Ne laser beam is reflected by the half mirror 14 and enters the interfold surface of the sample 12.

Of this incident light, the beam reflected by the valve opening surface passes through the half mirror 14 and enters the photodetector 15.

Detector.

The output of 15 is input to an indicator 16 to indicate a value corresponding to one amount of reflected light. If the detector 15 is an ordinary photodiode, it is necessary to limit the beam with an aperture 17 or the like. With this method, when the indicator swings to the maximum,
The optical axis of the He-Ne laser beam is adjusted so that the valve opening plane is perpendicular.

When a split detector is used as a detector, the indicator is configured to swing in positive and negative directions around the zero point, and the optical axis is adjusted so that the valve opening plane is vertical at the zero point. Therefore, the sample set on the sample stage (not shown) must first be tilted using a tilt adjustment mechanism (not shown) so that the indicator is at the maximum or zero point, and the valve opening plane is vertical. It will be adjusted so that

[Problem to be solved by the invention]

In the conventional diffraction grating production apparatus described above, it is possible to vertically adjust the valve opening plane by shining a He-Ne laser beam on one side of the sample and detecting the reflected light. is coated with photoresist, and since this resist is also adhered to the side surfaces, the two reflected light amounts vary, and in extreme cases, detection becomes impossible. In such a case, the sample is usually rotated 180 degrees and set again, and the reflected light is detected using the valve opening surface on the opposite side as the measurement surface.

In this way, the conventional device is configured so that the He4 laser beam for detecting the valve opening surface hits one side of the sample, so if the amount of reflected light is insufficient on one side, the valve opening surface on the opposite side becomes the measurement surface. The sample has to be reset to ensure that the sample is correct, which is not only a problem in that the operation is complicated, but also there is a risk of dropping the sample or damaging the resist when resetting.

The present invention is an attempt to solve the above-mentioned problems of the conventional apparatus, and provides a diffraction grating producing apparatus that does not require re-centering the sample when the amount of reflected light on one side is insufficient.

[Means to solve the problem]

The diffraction grating producing apparatus of the present invention is characterized in that both sides of the sample are irradiated with laser light, and the inclination angle of the sample can be adjusted using the side from which strong reflected light is obtained.

〔Example〕

Next, eight aspects of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

Reference numeral 1 denotes a laser light source, and the laser light emitted from the source is reflected by mirrors 2 and 3 and enters a beam splitter 4. The laser beam reflected by the beam splitter 4 passes through the mirror 5
The light is turned back by the lens 8, focused once at the position of the pinhole 9, and then collimated again by the lens 10. This collimated beam is reflected by a mirror 11 and irradiated onto a sample 12 coated with resist.

On the other hand, the laser beam that has passed through the beam splinter 4 is reflected by the mirror 6.7 and is reflected by the lens 1 in the same way as above.
After being collimated at zero, the sample 12 is irradiated.

These two beams interfere on the sample, producing interference fringes. The direction of this interference fringe must be parallel to the reference plane of the sample. In the case of a sample for a normal distributed feedback semiconductor laser, a side surface called the arm opening plane serves as a reference plane, and it is necessary to create interference fringes parallel to this arm opening plane. In this device, the interference fringes are formed in a direction perpendicular to the plane of the paper, so the arm opening plane must be aligned in the direction perpendicular to the plane of the paper.

For this reason, in the present invention, the tilt angle of the sample can be adjusted by shining a He--Ne laser beam onto the side surface of the sample and detecting the reflected light. An optical system for this purpose will be explained below.

The laser beam emitted from the H6-Ne laser light source is split into a reflected light and a transmitted light by a half mirror 18, and when the shutter 20 is open, the two reflected lights are reflected by a mirror 21. The light is reflected by the half mirror 22 and enters the side surface of the sample. The reflected light from this side surface passes through the nof mirror 22 and passes through the aperture 23 .

The light is made incident on the photodetector 24.

On the other hand, when the shutter 19 is open, the laser beam that has passed through the top mirror 18 passes through the lever and the top mirror 14.
The reflected light from here is reflected by the sample and enters the reflective side of the sample.

Transparent through half mirror 14 a/<? - After passing through the channel 17, the light enters the photodetector 15.

Shutters 20 and 19 can be turned on at any time by commands from the console.
N and OFF, and in synchronization with this, the indicator 16 displays the output of the corresponding photodetector. In this way, when the amount of reflected light from one side is weak, detection can be immediately switched to the other side, and reflected light detection and tilt adjustment can be performed using whichever side has the stronger amount of reflected light.

Here, the He-Ne laser has a power of about 2 mW and a beam diameter of about 1 node, but the thickness of the semiconductor sample is 0.5 mW.
Since it is thin at about 51 mm, and the reflectance is reduced due to the adhesion of resist, it is better to use a highly sensitive detector such as a pin photodiode. Furthermore, it goes without saying that the detection accuracy of the inclination angle will be higher if the distance between the sample and the detector is increased. Further, it has been experimentally confirmed that if the opening width of the aperture is about 0.5 to 1 m when the above-mentioned distance is about 1 m, the detection sensitivity will not decrease so much.

FIG. 2 is a block diagram of a second embodiment of the invention. In this embodiment, the optical path of the He-Ne laser beam is
The structure is such that the light is incident on both sides of the sample. According to this, since the number of half mirrors is one less than that of the first embodiment, He-
Ne laser light? It is possible to reduce war loss1
This has the advantage that reflected light detection can be increased to s7. The other configurations are similar to the first embodiment.

〔Effect of the invention〕

As explained above, the present invention is configured so that both sides of a sample can be irradiated with a laser beam, and the reflected light from there can be detected at will with a photodetector. If the light is weak, you can switch to detecting the reflected light from the other side without having to reset the sample. This not only allows you to easily and quickly adjust the tilt angle of the sample, but also allows you to easily and quickly adjust the sample tilt angle without having to set the sample again. This has the effect of eliminating the risk of dropping the sample or leaving islands on the resist when redoing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a block diagram showing a second embodiment, and FIG. 3 is a block diagram showing a general configuration example of a conventional device. FIG. 4 is a diagram showing the relationship between the period of interference fringes and the incident beam angle, and FIG. 5 is a diagram showing the relationship between the diffraction grating and the arm opening plane. Explanation of symbols: 1...Laser light source, 2.3...Mirror. 4... Beam splitter, 5, 6.7... Mirror,
8゜10...Lens, 9...Pinhole, 11...
・Movable mirror, 12-...sample, 13...He-Ne
Laser light source, 14°18.22...half mirror, 1
5... Photodetector, 16... Indicator, 17.
...Aperture, 19°20...Shutter, 23...
・Aperture, 24...Photodetector. Figure 2

Claims (1)

[Claims] 1. A device that uses laser light to create a diffraction grating on a sample, which is characterized by irradiating both sides of the sample with laser light so that the tilt angle of the sample can be adjusted using the side that receives strong reflected light. Diffraction grating creation device.