JPS59165428A - Manufacture of diffraction grating - Google Patents

Abstract

PURPOSE:To form a periodic structure on the surface of a semiconductor without deteriorating composition and crystal of semiconductor as a diffraction grating by irradiating the surface of semiconductor within the photo chemical etchant with a linearly polarized single laser light. CONSTITUTION:When a semiconductor base plate 2 within a photo chemical etchant 3 is irradiated with a linearly polarized single laser light, a diffraction grating pattern is formed on the surface of substrate on the basis of the incident light and interference of surface magnetic wave induced by such incident light. The intensive field area of semiconductor surface is more quickly etched than the weak field area and a pattern consisting of concaved and convexed areas is formed in the same interval as that of diffraction grating pattern. Depth and shape of concaved groove are determined by an output of laser light, irradiation time, etchant and a kind of semiconductor. When wavelength of laser light and angle of receiving the light at the semiconductor substrate are changed, an interval of irregular areas also changes and thereby an interval of diffraction grating can be adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a diffraction grating on a semiconductor surface.

Diffraction gratings are used to obtain spectra by diffracting light, and up until now, they have been made by moving the grating material at regular intervals using a high-precision feeding mechanism and carving fine grooves with a diamond cutting tool. Recently, a holographic diffraction grating that utilizes laser light diffraction and interference and thread trick roughy has been developed, and is used for distributed feedback (DFB) lasers, grating lenses, and coupling between lasers and waveguides, and will be used in optical integrated circuits in the future. will contribute to the manufacturing and development of

However, this method of manufacturing a diffraction grating using photolithography requires a process of creating a mask using photoresist, and it is necessary to remove this photoresist mask after creating the diffraction grating.

Applying photoresist to the semiconductor surface as a grating material, baking, etching, and removing the photoresist as described above will affect the composition, crystallinity, etc. of the semiconductor surface. It is difficult to achieve quality crystallization.

The method of manufacturing a diffraction grating using photolithography as described in Part B is not economical because it requires many processes, and there are also problems with the resulting product.

Furthermore, it is known that when a semiconductor acid or dielectric is irradiated with a strong laser beam (laser annealing), periodic damage is formed on the irradiated surface. In other words, for a linearly polarized single laser beam oscillated by a YAG laser or the like, if the wavelength of the laser beam is λ and the angle of incidence of the laser beam on the substrate surface is θ, then the electric field of the laser beam is parallel to the laser incidence plane. If P
- In the case of polarized light, two types of fringes with different periods given by A±=λ/(1±sinθ) are observed in the direction substantially perpendicular to the electric field direction of the laser beam, while on the other hand, when the electric field of the laser beam In the case of perpendicular to the laser incidence plane, that is, in the case of S-polarized light, the period of damage is given by Ao=λ/, osθ.

As mentioned above, the method of creating a periodic structure using a powerful laser beam that melts the semiconductor surface is impractical because the composition and crystallinity of the semiconductor are impaired. Furthermore, in the case of compound semiconductors such as gallium arsenide and indium phosphide, the vapor pressures of their constituent elements vary considerably, so irradiation with powerful laser light evaporates elements with high vapor pressure, while elements with low vapor pressure evaporate on the surface. In the case of a gallium arsenide compound semiconductor, for example, the arsenic evaporates and only gallium remains, so a completely outer periodic structure cannot be obtained.

An object of the present invention is to provide a method for forming a periodic structure as described above on a semiconductor surface without impairing the composition and crystallinity of the semiconductor to form a diffraction grating.

In order to achieve the above object, the method for manufacturing a diffraction grating according to the present invention includes irradiating a semiconductor surface in a photochemical etching solution with a single linearly polarized laser beam to form a large number of uneven stripes parallel to the semiconductor surface. It is characterized by

The present invention will be explained with reference to the accompanying drawings. By irradiating a single straight laser beam onto a semiconductor substrate 2 in a photochemical etching solution 3, the incident light is induced onto the substrate surface and the semiconductor surface is thereby induced. A diffraction grating pattern is formed based on the interference of surface electromagnetic waves, and areas of the semiconductor surface where the electric field is strong are etched faster than areas where the electric field is weak. will be formed. The depth and shape of the grooves to be formed are determined by the output of the laser beam, irradiation time, etching liquid, type of semiconductor, etc., but the depth of the grooves is 0.0.
The distance between the grooves of the uneven grooves to be formed is λ/n in the case of normal incidence, where n is the refractive index of the etching liquid and λ is the wavelength of the laser light. It can be controlled by changing the wavelength of light. Furthermore, if the angle at which the semiconductor substrate receives the irradiated laser light is changed, the interval between the formed uneven stripes will also be changed, and the interval between the diffraction gratings can be adjusted.

Semiconductors used as lattice materials include group III semiconductors such as 5ZIGo and group III-III compound semiconductors, which have particularly high electron mobility and are composed of elements with different vapor pressures that are used in opto-electronic device materials. Diffraction gratings can be easily formed even for gallium arsenide, which is

As the photochemical etching solution, a solution having a composition normally used for photochemical etching of semiconductors can be used, and the solution is selected as appropriate depending on the semiconductor used as the grating material.

Further, as the laser to be used, a laser that oscillates a single linearly polarized laser beam, such as a YAG laser, a helium neon laser, an argon laser, a krypton laser, etc., can be used.

As mentioned above, a semiconductor substrate is immersed in a photochemical etching solution, and a linearly polarized single laser beam with an output of about 0.1 to 100 frames is irradiated onto the immersed substrate for 3 to 10 minutes. A diffraction grating having an uneven height of about 0.1 to 0.2 μm is formed at intervals of λ/n.

FIG. 2 shows a method of forming a plurality of diffraction gratings with locally different spacing or directions on a semiconductor substrate, in which a photochemical etching solution 3 is contained in a container, and the semiconductor substrate is mounted on a rotating support shaft! It is supported so that it can move up and down and rotate in the etching solution 3. A transparent window 6 is provided on one side of the container, and a 1/2 wavelength plate 7 is rotatably provided outside the window 6.

The laser beam l from the laser is adjusted to a specific size by a lens g, passes through a wavelength plate and a window 6, and irradiates the semiconductor substrate in the etching solution 3. The semiconductor substrate is positioned in advance by driving the rotation support shaft S so that the position where the diffraction grating is to be formed is irradiated with the above laser beam, and is fixed for a predetermined period of time. Once formed, the laser beam irradiation is stopped, the semiconductor substrate is moved, and the next position where the diffraction grating is to be formed is irradiated with the laser beam. At this time, the interval between the formed diffraction gratings can be controlled by changing the angle at which the semiconductor substrate receives the laser beam.

Furthermore, when the wave plate 7 provided with the outside pressure of the window A is rotated by 45 degrees, the direction of the diffraction grating formed on the semiconductor substrate is changed by 90 degrees.
That will change. Therefore, by rotating the wave plate, the direction in which the diffraction grating is formed can be set arbitrarily, and it is possible to easily form multiple diffraction gratings with different dimensions, intervals, and directions at any position within one semiconductor substrate. Even when forming a diffraction grating on a compound semiconductor containing an arsenic component that easily evaporates, such as gallium arsenide, it is manufactured by irradiating a very weak laser beam in a solution, so it is difficult to evaporate the arsenic. It is possible to obtain a semiconductor in which a diffraction grating is formed in which the component ratio does not change.

As is clear from the above description, the present invention makes it possible to form diffraction gratings with different spacing and directions at arbitrary positions on the semiconductor surface without using a mask, and makes a significant contribution to the construction of optical integrated circuits. Become.

Next, embodiments of this invention will be described. Hp 804'&
Photochemical solution JCGaAt (5 mn x 3 sw) with a composition of 1:1:50 Ox:H,
), and the upper part is exposed to laser light from a YAG laser (
As a result of irradiation with a wavelength of 55 μm for 10 minutes at an output of 1 cm, uneven lines with a height of 0.02 μm were formed on the entire semiconductor surface at equal intervals of Q, 4 PL, and the formed uneven lines were diffracted. It could be used as a grid.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of the method for manufacturing a diffraction grating according to the present invention, and FIG. 2 is a sectional view showing another example of the method for manufacturing a diffraction grating according to the invention. In the figure, / indicates a laser beam, - indicates a semiconductor substrate, and 3 indicates a photochemical etching solution. Patent applicant: Makoto Nagaishiita, Institute of Industrial Technology

Claims (2)

[Claims] (1) A method for manufacturing a diffraction grating, which comprises irradiating a semiconductor surface in a photochemical etching solution with a single linearly polarized laser beam to form a large number of uneven lines parallel to the semiconductor surface. (2) Claim 1 in which the semiconductor is gallium arsenide
Method for manufacturing the diffraction grating described in Section 1.