JPH0498205A - Light input device and its production - Google Patents

Abstract

PURPOSE:To offer a practically effective light input device and its production method without using resin by forming a thin film layer consisting of at least two layers formed on a substrate having a hole, forming peripheral structure on the thin film layer and providing at least one layer in the thin film layer with tensile stress. CONSTITUTION:The thin film 11 is formed on the upper surface of a silicone substrate 10. A silicon, substrate having face orientation (1,0,0) is used. An optically transparent thin film having passivation property against an etching solution and tensile stress as its internal stress is used as the thin film 11. Then, a transparent buffer layer 12 having tensile stress as its internal stress, a waveguide layer 13 and a loading layer 14 are formed on the thin film 11. A grating 15 is formed on the surface of the layer 14 by an electron beam plotting method or a photolithographic method. On the other hand, a mask film 16 forming a hole part is formed on the lower face of the substrate 10 and a hole 17 is formed by etching. Since the thin film has passivation property, the etching is ended at a portion arriving at the thin film 11. Thus, input light 18 can be inputted to the waveguide layer 13 through the grating 15 as waveguide light 19 without using resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical input device for manually applying light into a thin film and a method for manufacturing the same, and is useful for use in, for example, a thin film optical head.

Conventional technology As a conventional optical input device, for example, Japanese Patent Application Laid-Open No. 186568
There is one shown in the thin film optical head of the publication.

Figure 3 shows a schematic diagram. 100 is a silicon substrate, on which a photodetector 101 is formed, and a hole 102 for light input is formed in the center of the substrate. Both sides of the silicon substrate 100 and the holes 102 are covered with a resin 103, and a grating 104 having an uneven shape is formed on the resin. A grating 105 is formed. A buffer layer 106 and a waveguide layer 107 are formed on the surface of the resin 103. A waveguide layer 108 is formed.

Input light 109 enters the silicon substrate 100 from below.
The resin 103 passes through the holes 102 and the grating 104
reach. The light that has reached the grating 104 is input into the waveguide layer 107 by the grating, and the waveguide light 11
0, and the direction propagates toward the outer periphery.

When the guided light reaches the waveguide layer 108, the grating 105
The light is radiated out of the waveguide layer, becomes radiation light 111, and reaches the optical disk reflective surface 112. Optical disk reflective surface 112
The signal light from the grating 1 becomes the feedback light 113.
05 into the waveguide layer, propagates to the inner circumference of the waveguide layer 108, is radiated from the end face of the waveguide layer, and reaches the photodetector 101. This allows the signal on the optical disc to be detected.

Optical input device and six companies Used in such thin-film optical heads, etc., this device has the function of inputting light into a waveguide layer using a grating.

In particular, in optical disk devices, since the optical disk is on the grating side, it is difficult to input light from the grating side, and it is necessary to input light from the bottom surface of the substrate to the waveguide layer on the top surface of the substrate through a hole. An unused optical input device will be explained using FIG. 4. SiO2 is deposited on a silicon substrate 200 by sputtering.
A buffer layer 201 made of a film and a waveguide layer 202 made of a Coning 7059 film are formed. A grating 203 is formed on the Corning 7059 film by electron beam lithography or photolithography.

Further, a mask film 204 having a hollow pattern is formed on the lower surface of the silicon substrate.
A hole for light input is formed in the silicon substrate by etching the hole portion with a BHF etching solution.

Problems to be Solved by the Invention However, the structure using resin as shown in FIG. 3 has the following problems. When air bubbles are mixed in the resin and light is input into the thin film, the light is scattered by the air bubbles in the resin, making it difficult to achieve good input characteristics.

In addition, since the heat resistance temperature of the resin 103 is about 100 degrees, it is not possible to form a thin film at high temperatures.As a result, the adhesion between the thin film and the resin 103 decreases, causing the thin film to peel off. When curing resin 10
3, the surface shape of the resin in the holes, that is, the surface of the grating 104, becomes concave due to curing shrinkage, and as a result, the human power characteristics deteriorate.还 Had the following problems: 5i02 film 201 created by sputtering method, Conning 7059 film 202
The problem was that wrinkles were generated due to internal stress, the shape of the surface of the grating 203 provided at the top of the hole was deformed, and the input characteristics were deteriorated.At this time, the BHF etching solution also etched the SiO2 film. There is also the problem that the input characteristics deteriorate further as a result of the change in the thickness of the LSiQ2 film. , BHF
Since the silicon substrate is etched isotropically by the etching solution, the hole size W tends to change due to subtle differences in etching time, making it difficult to guarantee the accuracy of hole processing. If a pinhole 205 exists above, etching may proceed around this point and even reach the buffer layer 201 . in this case,
The destruction of the photodetector (not shown) formed on the silicon substrate 200 has become a serious problem in practice, and the present invention has been designed to take this into account. The purpose of this invention is to provide a device and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention comprises a substrate having holes, a thin film layer formed on the substrate and consisting of at least two layers, and a periodic structure formed on the thin film layer, and the thin film. At least one layer of the optical input device has tensile stress.

Further, in the thin film formed on the substrate, the first layer counting from the substrate is a silicon nitride film or a silicon oxynitride film.

Another object of the present invention is to provide an optical input device in which the tensile stress thin film is a silicon dioxide film, a silicon nitride film, or a silicon oxynitride film.

In addition, at least two thin film layers and a periodic structure are formed on the top surface of a silicon substrate with a crystal plane orientation of (1, O, 0), and then etched from the bottom surface of the substrate using a KOH aqueous solution or a pyrocatechol/ethylene/diamine aqueous solution. The first method is to use a manufacturing method in which the holes are formed through the process.

Effect: According to the optical input device having the above structure, an optical input device in which wrinkles do not occur in the grating due to the action of the tensile stress of the thin film layer can be realized.

Furthermore, according to the above manufacturing method, over-etching during etching is effectively prevented by the selected silicon crystal orientation, and a highly reliable optical input device can be manufactured.

Embodiment The structure and manufacturing method of the optical input device of the present invention will be explained using FIG. 1 showing an embodiment.

As shown in FIG. 1(a), a thin film 11 is formed on the upper surface of a silicon substrate 10. As a silicon substrate? Use one with L plane orientation (1,0,0).

Thin film 1111 A thermal CV film that has passivation properties against the etching solution described later, has tensile stress internal stress, and is an optically transparent thin film.
D. Use a silicon nitride film or silicon oxynitride film created by plasma CVD method or the like.

Next, to the top of the thin film 11, a buffer layer 12, a waveguide layer 13, and a loading layer 14, which are transparent and whose internal stress is tensile stress, are formed. For this purpose, for example, a silicon dioxide film is formed as the buffer layer 12, a silicon oxynitride film is formed as the waveguide layer 13, and a silicon nitride film is formed as the loading layer 14 by, for example, a plasma CVD method.

The grating 15 is formed on the loading layer 14 by electron beam lithography or photolithography.

Further, a mask film 16 having holes provided on the bottom surface of the silicon substrate 10 is formed. As a mask film, a silicon dioxide film or a metal film such as Ni, Ti, or Au is used (it does not need to be transparent).

Etching of the silicon substrate 10 is performed from the bottom surface using a KOH aqueous solution or a pyrocatechol/ethylene/diamine aqueous solution.

The etching rate of a KOH aqueous solution or a pyrocatechol/ethylene/diamine aqueous solution on a silicon substrate varies greatly depending on the crystal plane orientation of the silicon substrate.1. ,
(1,0,0) plane and (1,l.

1) The surface etching rate reaches about 400:1. Therefore, if a silicon substrate with plane orientation (1,0,0) is used, the (1,1,1) plane will be oriented at 54.7 degrees, and 5
Etching progresses while forming a slope of 4.7 degrees.

Plasma CVD1'A Silicon nitride film or silicon oxynitride film (Friend KOH aqueous solution or pyrocatechol, ethylene,
Since the diamine aqueous solution has passivating properties, etching ends when the thin film 11 is reached, resulting in the shape shown in FIG. 1(b).

At this time, the thin film 11, buffer layer 12, waveguide layer 13, and loading layer 14 formed on the silicon substrate are under tensile stress. This does not occur and flatness can be maintained.

Therefore, input light 18 can be manually transferred to waveguide layer 13 by daleting 15 to become guided light 19 without using resin.

In addition, it is possible to form a thin film at a temperature of about 300° C. without using a resin, and the adhesion between the thin film and the substrate is improved, which is extremely useful in practice.

In addition, in this embodiment, as shown in FIG.
"Secondly, even if a pinhole 22 exists, the pinhole is extremely small compared to the thickness of the silicon substrate Wx
Etching ends when the (1, 1, l) planes intersect, and holes are not formed all the way to the substrate surface. If is a tensile stress, by adjusting the film thickness, the internal stress of the entire thin film can be made into a tensile stress, and wrinkles can be removed.

As explained in detail, the present invention solves the problems of conventional optical input devices using resin, such as scattering of input light due to bubbles, adhesion of thin films, and deformation of the grating shape. This is extremely useful in practice because it can solve all the problems associated with deterioration of input characteristics.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the optical input device manufacturing method of the present invention together with the structure of the optical input device. Overview of thin film optical head using input device FIG. 4 is a schematic diagram of another conventional optical input device. 10, 23. 100...Silicon substrate 11...
・Thin K 121 1o6-i<tsuyytane 13. 1
07+108... Waveguide # 14... Loading 15,
104゜105...Gratein Hisashi 16. 21.
204...mas'yWL17. 102=iL
18. 101-Human power light 19,110... Waveguide light
22,205...pinho)1. , 24. 101
... Light detection edge 103 ... Resin 111 ... Synchrotron radiation 112 ... Optical disk reflection plate 113 ... Return light

Claims (4)

[Claims] (1) A substrate having a hole through which light is incident, a thin film layer formed on the substrate and consisting of at least two layers, and a periodic structure formed on the thin film layer, Optical input device characterized in that internal stress is tensile stress (2) The optical input device according to claim (1), wherein the first layer of the thin film layer counting from the substrate is a silicon nitride film or a silicon oxynitride film. (3) The optical input device according to claim (1), wherein the tensile stress thin film is a silicon dioxide film, a silicon nitride film, or a silicon oxynitride film. (4) The substrate is silicon with a crystal plane orientation of (1, 0, 0), at least two thin film layers and a periodic structure are formed on the upper surface of the substrate, and then a KOH aqueous solution or pyrocatechol is applied to the lower surface of the substrate. A method for manufacturing an optical input device, comprising forming a hole through which light is incident on the substrate by etching using an ethylene diamine aqueous solution.