JPS62299806A - Periodic uneven pattern forming device - Google Patents

Abstract

PURPOSE:To obtain a high-accuracy diffraction grating having a irregular pattern whose depth is controlled with high accuracy by detecting the ratio of the intensity of monitor light detected by a 1st photodetector ad the intensity of diffracted light detected by a 2nd photodetector. CONSTITUTION:A substrate 11 is irradiated with laser light at an angle theta of incidence from a laser light source 14 through half-mirrors 21 and 22, the diffracted light from the substrate is projected on a reference mark 24 formed on a screen 23, and a photodetector 15 detects light projected by a laser light source 14 as the monitor light. Further, a substrate holder 17 is lowered by a pulse stage 17 to dip the substrate 11 in an etchant 12, the light from the light source 14 is projected on a substrate 11A where the irregular pattern is formed at the angle theta of incidence through a half-mirror 21, and its diffracted light is detected by a photodetector 16. The diffracted light is compared with the monitor light detected by the photodetector 15 to accurately detect the depth of the irregular pattern. Consequently, etching condition such as etching time is determined based on the detection information to accurately control the depth size of the irregular pattern.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Summary) Distributed feedback semiconductor laser (Distributed F
This is a device that accurately forms a diffraction grating constituting an eedback laser (hereinafter referred to as DFB laser), and when a semi-dedicated substrate on which a periodic uneven pattern is formed by chemical etching is irradiated with laser light, the substrate By controlling the etching conditions by utilizing the phenomenon that the intensity of the diffracted light of the laser beam that is diffracted by the laser beam differs depending on the depth of the uneven pattern, we can create an uneven pattern to form a diffraction grating with good reproducibility and high precision. Forming device.

[Industrial application field]

The present invention relates to an apparatus for forming a periodic uneven pattern on a substrate.

DFB laser elements that can obtain single wavelength oscillation using a diffraction grating have recently been used as light sources for large-capacity optical communications.

[Conventional technology]

Conventionally, when forming a diffraction grating constituting such an FB laser element, a resist film 2 with a predetermined pattern is formed on an InP substrate 1 as shown in FIG. By chemically etching 1 with an etching solution, a periodic uneven pattern with a depth P is formed on the substrate 11- as shown in FIG. 4, and this periodic uneven pattern is used to form a diffraction grating. There is.

[Problem that the invention seeks to solve]

When a periodic pattern of concavo-convex shapes is formed on a substrate by etching in this manner, the depth l of the concavo-convex pattern is controlled by controlling the amount of etching by changing the etching time.

However, with this method, there are many cases where the resist film pattern is not formed with the specified pinch, and the etching speed varies depending on the concentration and temperature of the etching solution.
Therefore, a problem arises in that the depth of the concavo-convex pattern cannot be precisely controlled to a predetermined dimension.

The present invention eliminates the above-mentioned problems and utilizes the phenomenon that when a laser beam is irradiated onto a substrate having an uneven shape, the intensity of the diffracted light diffracted from the substrate differs depending on the difference in the depth dimension of the uneven pattern. The present invention aims to provide a device for controlling the depth of a concavo-convex pattern.

[Means for solving problems]

As shown in FIG. 1, the periodic uneven pattern forming apparatus of the present invention includes a substrate 11 on which a periodic uneven pattern is to be formed, a container 13 containing an etching solution 12 for the substrate, and irradiation of the substrate 11. a first photodetector 15 that detects the intensity of the monitor light of the laser beam irradiated onto the substrate 11 before the substrate 11 is inserted into the etching solution 12; a second photodetector 16 that detects the intensity of the diffracted light introduced into the etching solution 12 and irradiated onto the substrate 11 on which a periodic uneven pattern is formed; By detecting the ratio of the intensity of the monitor light detected by the detector 15 and the intensity of the diffracted light detected by the second photodetector 16, the convex surface of the periodic concavo-convex pattern formed on the substrate is detected. and control the depth of the four parts.

[Effect]

The periodic uneven pattern forming apparatus of the present invention detects the ratio of the intensity of the monitor light emitted from the laser light source and the intensity of the diffracted light of the laser beam that irradiates the substrate on which the uneven pattern is being etched. By doing so, the depth of the uneven pattern is detected with high accuracy, and the depth of the uneven pattern is accurately controlled based on this detection information.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an apparatus configuration diagram showing an embodiment of the periodic uneven pattern forming apparatus of the present invention.

As shown in the figure, in the apparatus of the present invention, a substrate 1 on which a periodic uneven pattern is to be formed is placed in a substrate holder 17 made of Teflon, and the jig 17 is placed inside a container 13 containing an etching solution 12. It is installed in

In addition, the etching liquid 12 inside the container 13 is disposed at the bottom of the container 13.
A stirring device 18 such as an ultrasonic vibration device is installed to stir the water.

Further, the substrate holder 17 can be moved vertically by the pulse stage 19, and can also be freely moved horizontally at a predetermined angle.

Further, in the horizontal direction with respect to the container I3, a helium-cadmium (lie-Cd) laser light source 14 for irradiating the substrate 11 and half mirrors 21 and 22 for branching the laser light emitted from the laser light source 14 are provided. A part of the light branched by this half mirror 21 reaches the substrate 11 immersed in the etching liquid 12 and is diffracted by the substrate 2, and then the diffracted light is transmitted to the second photodetector 16. be introduced.

Further, a part of the light branched by the half mirror 2I reaches the half mirror 22 and is branched, and a part of the light is introduced into the first photodetector I5 as monitor light, and is further transmitted to the half mirror 22.
A part of the light branched at 2 irradiates the substrate 11 that is not immersed in the etching solution 12 and reaches the screen 23 .

The operation of forming a periodic uneven pattern on a substrate using the apparatus of the present invention will be described.

First, the substrate 1 on which the uneven pattern is to be formed on the substrate holder 17
1, and this substrate holder 17 is mounted on a pulse stage 19.
to be installed.

Next, before the substrate 11 is immersed in the etching solution 12, a half mirror 21,
22 is used to irradiate a laser beam at an incident angle θ, and the diffracted light from the substrate is reflected onto the reference mark 2 formed on the screen 23.
Copy onto 4J-.

When the laser beam is not projected on the screen 23,
Move the pulse stage 19 so that it can be photographed.

This is done by etching the substrate 11 with an etching solution 12.
This is to allow the diffracted light to reach the photodetector 16 when the substrate 11 is irradiated with laser light when the substrate 11 is immersed in water.

At the same time, the photodetector 15 detects the light emitted from the laser light source 14 as monitor light.

Further, the substrate holder 17 is lowered by the pulse stage 19, and the substrate 11 is immersed in the etching liquid 12. Next, the light emitted from the light source 14 is irradiated onto the substrate 11A on which the concavo-convex pattern is formed through the half mirror 21 at an incident angle θ, and the diffracted light is detected by the photodetector 16.

Since the intensity of the diffracted light detected by the photodetector 16 differs depending on the depth of the uneven pattern, this light is compared with the monitor light detected by the photodetector 15 to detect the depth of the uneven pattern. If the etching conditions such as etching time are determined based on this detected information, the depth of the uneven pattern can be controlled with high accuracy.

If a diffraction grating constituting a laser element is formed using such an apparatus of the present invention, a highly reliable diffraction grating in which the depth of the concavo-convex pattern is controlled to a predetermined value can be obtained.

〔Effect of the invention〕

As described above, according to the apparatus of the present invention, it is possible to obtain a highly reliable diffraction grating in which the depth of the concavo-convex pattern is controlled with high precision.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a diagram showing the configuration of an apparatus according to an embodiment of the present invention, Fig. 3 is a sectional view for explaining a conventional method of manufacturing a diffraction grating, and Fig. 4 is a diagram of the conventional method of manufacturing a diffraction grating. FIG. 2 is a cross-sectional view of a substrate on which a concavo-convex pattern is formed by the method. In the figure, 11.11^ is a substrate, 12 is an etching solution, 13 is a container, 14 is a laser light source, 15 is a first photodetector, 16 is a second photodetector, 17 is a substrate holder, 1 day is a stirring device, 1
9 is a pulse stage, 21.22 is a half mirror 123
indicates a screen, and 24 indicates a mark. Easy 8 Fando Rizu Figure 1 μ brown column 1f 4r Sokatsu Kago Rikihira 0b Me tun Taiyo m Figure 3 Name Warehouse A Taiyo 7. Irregularity Iv7-shi left behind J

Claims (1)

[Claims] A substrate (11) on which a periodic uneven pattern is to be formed, and a container (1) containing an etching solution (12) for the substrate (11).
3) and a laser light source (14) that irradiates the substrate (11).
), a first photodetector (15) that detects the intensity of a monitor light of a laser beam irradiated to the substrate (11) before the substrate (11) is inserted into the etching solution (12); , the substrate (11) is introduced into an etching solution (12), and the substrate (11) has a periodic uneven pattern formed thereon.
a second photodetector (16) that detects the intensity of the diffracted light that has been irradiated and diffracted by the first photodetector (15); Periodicity characterized by controlling the depth of the periodic uneven pattern formed on the substrate (11) by detecting the intensity ratio of the diffracted light detected by the second photodetector (16). A device for forming uneven patterns.