JPS63109402A - Preparation of optical phase operating plate - Google Patents

Abstract

PURPOSE:To easily obtain an optical phase operating plate excellent in inside uniformity and reproducibility by superposing and stacking plural layers having different etching speeds respectively on a base and etching only the surface side layer having a high etching speed to form the optical phase operating part. CONSTITUTION:Two or more laminated layers having different etching speeds respectively are stacked on the base 1 and then the surface side layer having a high etching speed is etched, so that the phase operation part controlled at its phase operating variable not by etching depth but by layer thickness. Namely, an Si3N4 film 3 is stacked on an SiO2 film 2 stacked on the glass base 1 by using plasma CVD method. Then the Si3N4 film 3 is worked like stripes consisting of W width and P pitch by using photorithography technique and etching technique. When the etching time is optimized, the processing can be comparatively easily controlled so that the Si3N4 film 3 can be completely removed and the SiO2 film 2 is not almost removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for manufacturing an optical phase manipulation plate for spatially precisely controlling an optical phase.

<Prior Art> A phase shifter (phase operation plate) for spatially shifting the phase is an optical component that costs a considerable amount of kg, and is necessary in constructing an optical integrated circuit.

Conventionally, as such a phase shifter, one having a shape as shown in FIG. 2 is generally used.

This phase shifter is manufactured as follows. Here, a case will be described in which the optical phase is spatially inverted by 180'. First, a desired pattern is formed on a glass substrate (201) using ordinary photolithography technology. Here, consider a stripe: a pattern for inverting the phase every W'=5 μm. Next, etching is performed using an etching solution containing a mixture of hydrofluoric acid, ammonium fluoride, and water. At this time, the etching depth: d' is controlled and set so as to satisfy. Thereafter, the resist is removed by organic cleaning to obtain a phase shifter.

<Problems to be solved by the invention> In the conventional phase shifter as described above, control of the phase shift amount depends on the etching depth: d', and the variation in the shift amount corresponds to the variation in d'. do. but,
Improving in-plane uniformity and reproducibility in etching is extremely difficult and requires sophisticated and complicated processes. There is another conventional element that employs a method of changing the refractive index by using ion exchange on a glass substrate, but as in the case of etching described above, it is difficult to control the depth of ion exchange.

<Object of the invention> The present invention aims to solve the above-mentioned problems and provide a manufacturing method that can relatively easily obtain an optical phase operation plate with good in-plane uniformity and reproducibility. The layered structure is deposited on a substrate, and then the layer on the surface side where the etching rate is high is etched, thereby forming a phase manipulation part in which the amount of phase manipulation is controlled not by the etching depth but by the layer thickness. do.

<Embodiment> FIG. 1 is a structural diagram of a phase shifter for explaining one embodiment of the present invention. The method for manufacturing this device will be described below. Glass substrate (1) with a thickness of about 100 to 200 μm
A SiO□ film (2) is deposited thereon using a high frequency sputter deposition method at a single plate temperature of 250°C. This SiO2 film (
2) thickness Si2 is the thickness of the glass substrate (
It is sufficient as long as it is sufficient to protect 1). Here d 2
= 150 OA ToL 7? .

Next, a Si3N4 film (3) is deposited on this SiO2 film (2) using the plasma CVD method. This 513N
The deposition time and deposition conditions are controlled so that the thickness Si3 of the fourth film (3) is satisfied.

Thereafter, the 5iaN4 film (3) is processed into a stripe shape with a width of W and a pitch of 2P using photolithography and etching techniques. At this time, a solution of hydrofluoric acid:ammonium fluoride solution=1:40 is used as an etching agent, and etching is performed at room temperature. For this etching agent, the etching rate of the sputter-deposited fLfcsio□ film (2) is between RE (S i 02) and the etching rate of the Si3N4 film (3) deposited by plasma CVD method: RE (Si3 N4). is RE(SiaN4
) 260 RE (S 102)...(3) There is a relationship. Therefore, by optimizing the etching time, it is relatively easy to control the etching process so that the Si3N* film (3) is removed into the original metal and the SiO2 film (2) is hardly removed. The phase shift amount of the phase shifter manufactured in this way is F.

Si3N4 film (3
), the phase can be inverted by 180° if the above equation (2) is satisfied. The uniformity of the deposited film thickness: d3 by the plasma CVD method is better than the uniformity of the etching depth: d' in the conventional method shown in FIG. 2, and the error in d3 can be reduced by rotating the substrate. It is possible to suppress it to 2-3%. Furthermore, the reproducibility of d3 can be detected by optically (non-destructively) measuring the film deposited by the plasma CVD method before etching. By applying this method, it is possible to control the temperature and obtain good products with a high yield.

The phase shifter manufactured as described above can convert the 1800 phase mode oscillation light of the semiconductor laser array element to the 00 phase mode, and is an important element for obtaining a high output laser. Furthermore, the present invention can be applied not only to phase shifters but also to the production of optical phase manipulation plates such as holograms in which the interaction length between a light wave and a phase manipulation unit must be controlled on the wavelength order, thereby improving yield. be able to.

The present invention is applicable not only to the above embodiments but also to the cases listed below, and similar effects can be expected.

(1) The material composing the optical phase operation plate is SiO2 or Si.
In addition to 3N4, if A 1zOs 9Mg20s, ZrO2゜''a20s r Mg F 2 , T r 02, etc. are used, (2) the film preparation method is ECR plasma C
(3) When using other methods such as VD method, electron beam evaporation method, and resistance heating evaporation method, (4) When the composition of the film deviates from the chemical equilibrium state (for example, SiO2, Si3N,
etc. are SiOx: 0(X(2 and S 13NY: 0<
(If y<4)

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a phase shifter used to explain one embodiment of the present invention. FIG. 2 is a block diagram showing the structure of a conventional phase shifter. 1...Glass substrate 2...SiO2 film 3...
・Si3N4 membrane agent Patent attorney Takeshi Sugiyama (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] 1. After depositing a plurality of layers with different etching rates on a substrate in a superimposed manner, only the layer on the surface side having a higher etching rate is etched to form an optical phase manipulating section. A method for producing an optical phase operation plate characterized by: 2. A method for producing an optical phase shift plate according to claim 1, wherein a layer having a high etching rate is deposited to a thickness corresponding to the amount of optical phase shift. 3. A method for manufacturing an optical phase shift plate according to claim 1, in which a plurality of layers are superimposed, each having an etching rate of about 1:10. 4. The method for manufacturing an optical phase shift plate according to claim 1, wherein the plurality of layers are composed of a SiO_2 layer and a Si_3N_4 layer.