JPH05323109A - Optical reflecting element - Google Patents

Abstract

PURPOSE:To obtain an optical reflecting element which can be made thin and decreases the production cost. CONSTITUTION:The optical reflecting element 11 consists of a silicon substrate 12 having an oxidized layer 13 on the surface formed by heat treatment, metal coating film 14 having high reflectance formed by vapor deposition or the like on the surface of the oxidized layer 13, and oxidation preventing coating 15 formed on the metal film. By using the silicon substrate 12, the rigidity of the element can be maintained even the element is made thin. By forming the oxidized layer 13 on the surface of the silicon substrate 12, the metal film 14 can be formed with higher adhesion by vapor deposition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reflecting element used for reflecting a laser beam and changing its optical path in various optical devices such as an optical pickup.

[0002]

2. Description of the Related Art Conventionally, there is a reflection mirror (mirror) as an optical reflection element for changing the optical path of light used in an optical pickup or the like, and an example thereof is shown in FIG. FIG. 4 is a sectional view showing the structure of a conventional reflection mirror. The mirror 1 shown in FIG. 4 includes a glass substrate 2 formed in a flat plate shape or a triangular prism shape by using a crown type glass material such as so-called K5, BK7, and the like, and formed on the substrate 2 as a dielectric film. For example, a coating 3 made of ZnS (refractive index n1 = 2.35) of a high refractive index member and MgF of a low refractive index member
₂ (refractive index n2 = 1.38). The dielectric film 3 and the dielectric film 4 are formed alternately, and the total thickness d of these two types of film 3 and film 4 is d.
But,

[0003]

## EQU1 ## nd = λ / 4 [where (λ: wavelength), (n: substantial refractive index of dielectric film formed by n1 and n2)].
As described above, when the film is formed, the incident laser light or the like is reflected with a high reflectance, and the course of the incident laser light can be changed according to the incident angle on the reflecting surface.

[0004]

In recent years, there has been a demand for reduction in size and weight of optical equipment. For this reason, in the mirror 1 having the above-described configuration, a flat plate-shaped mirror is often used rather than a triangular prism-shaped mirror, and the substrate 2 is made thin to cope with a reduction in size and weight.

However, since glass is used as the material of the substrate 2, when the thickness of the substrate 2 is reduced in order to reduce the size and weight, the rigidity of the substrate itself due to an external force becomes low, and for example, when it is bonded to another member or the like. Curved (distorted)
However, there is a problem in that there is a problem such as that, and there is a limit to thinning. Also,
When the glass substrate 2 is thinned as described above, a polishing process and the like have not been established, so that this work imposes a time and economical burden and causes a problem that the production cost increases.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide an optical reflection element which can be made thinner and whose production cost is reduced.

[0007]

The constitution of the present invention for achieving the above object is to provide a silicon substrate, an oxide layer formed by heat treating the surface of the substrate, and a light reflection film formed on the oxide layer. And a light-reflecting layer,
It is composed of a metal film and an oxide layer formed on the metal film, or the light reflection layer is composed of a dielectric film formed in multiple layers.

[0008]

In the above construction, by using the silicon substrate as the substrate, the substrate can be made thin and the rigidity can be maintained.
Further, the silicon substrate can be mass-produced because the thinning technique and the polishing technique have been established. Further, by heat-treating the surface of the silicon substrate to form an oxide layer, a metal film or a dielectric film is easily attached to the oxide layer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the optical reflection element according to the present invention. The optical reflection element 11 shown in FIG. 1 uses a silicon substrate (silicon wafer) 12 similar to that used for the substrate of an integrated circuit. This board 12
After being polished to a desired thickness in the same manner as the circuit board, the chips are appropriately cut into fine chips. Also, this substrate 1
The surface of 2 is heat-treated to form an oxide layer 13, that is, a SiO ₂ layer similar to quartz glass.

On the oxide layer 13, for example, 780 nm
Metal film with high reflectance for laser light of near wavelength 1
4 are formed. The metal film 14 is made of aluminum (reflectance 86.3%), silver (reflectance 98.7%), gold (reflectance 97.8%), copper (reflectance 98.1%), or the like. Is formed by an appropriate method such as vacuum deposition. Since the surface of the substrate 12 is heat-treated to form the oxide layer 13, the metal coating 14 that is difficult to be directly attached to the silicon substrate 12 is easily attached. Since the adhesion strength between the oxide layer 13 and the metal film 14 is high, the metal film 14 is affected by environmental changes such as temperature and humidity.
It is possible to form an optical reflection element that does not cause characteristic deterioration due to environmental changes.

On the metal coating 14, an antioxidant coating 1
5 is formed. This antioxidant film 15 is made of SiO.
₂ (silicon oxide) is formed by vapor deposition by an appropriate method such as vacuum vapor deposition as in the above. This antioxidant film 1
5 is preferably formed into a film having a thickness of (λ / 2).
By forming the film with this thickness, there is no phase difference between the incident light such as laser light having a predetermined wavelength λ and the reflected light reflected by the metal film 14, and the interference between the incident light and the reflected light does not occur.

FIG. 2 is a schematic sectional view showing the structure of an optical reflecting element according to another embodiment of the present invention. The optical reflection element 21 shown in FIG. 2 uses the same silicon substrate 12 as that used in the substrate of the integrated circuit as shown in FIG.
The surface is heat-treated to form an oxide layer 13.

On the oxide layer 13, a dielectric film similar to that formed on the surface of a normal glass mirror is formed. This dielectric film is, for example, Zn of a high refractive index member.
S (refractive index 2.35) coating 3 and low refractive index member MgF ₂
(Refractive index 1.38) The film 4 and the film 4 are formed alternately. Total n of these two types of film thickness
d is the same as the conventional example

[0014]

## EQU1 ## It is formed to conform to nd = λ / 4. In this way, when the film is formed, the incident laser light or the like is reflected with a high reflectance.

According to each embodiment having the above-mentioned structure, the silicon substrate 12 for which the thinning technique and the polishing technique are established.
By using, it is possible to reduce the thickness and reduce the production cost. Further, by forming an oxide layer on the surface of the silicon substrate, the metal film and the dielectric film can be attached with high adhesion strength.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in each of the above-described embodiments, the oxide layer 13 formed by heat-treating the surface of the substrate 12 and the metal film 14 formed on the oxide layer 13.
Alternatively, although it has been described that the reflecting member is composed of the dielectric films 3 and 4, the reflectance of silicon (Si) (30%)
As long as it is an optical device that can be used to some extent, the silicon substrate 12 having an oxide layer formed on its surface may be used as it is as an optical reflection element.

Further, since silicon has a higher rigidity than glass, it can be made extremely thin while maintaining surface accuracy, but when it is used as a mirror of an optical system of equipment, it needs to be fixed. An adhesive is generally used for fixing, but if the plate thickness is made too thin, adhesive distortion becomes a problem. For this reason, in order to use it as a thin film substrate and eliminate the distortion due to adhesion, a silicon substrate is formed in a U-shaped cross section as shown in FIG. Then, the optical reflection element 16 may be configured to be adhesively fixed. Then, such a U-shaped process can be easily performed by an anisotropic etching method or the like.

Further, a so-called polygon mirror may be applied as a structure in which the above-mentioned mirrors are provided on multiple surfaces. In this case, the thin plate-like optical reflection element shown in FIG. 1 or 2 may be adhered to the polygonal surface of the polygon mirror, or a silicon substrate having a polygonal surface may be formed and the polygonal surface of the silicon substrate You may oxidize and may form a metal film or a dielectric film on the surface of an oxide layer.

[0019]

According to the present invention described in detail above, it is possible to provide an optical reflection element which can be made thinner and whose production cost can be reduced. In particular, by heat-treating the surface of the silicon substrate to form an oxide layer, the metal film or the dielectric film easily adheres to the silicon substrate.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of an optical reflecting element according to an embodiment of the optical reflecting element of the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of an optical reflecting element according to another embodiment of the optical reflecting element of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of a method for fixing an optical reflecting element according to an embodiment of the optical reflecting element of the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a mirror as an example of a conventional optical reflection element.

[Explanation of symbols]

 11, 16, 21 Optical reflection element 12 Silicon substrate 13 Oxide layer 14 Metal film 15 Antioxidation film

Claims (3)

[Claims] 1. An optical reflection element comprising a silicon substrate, an oxide layer formed by heat-treating the surface of the substrate, and a light reflection layer formed on the oxide layer. 2. The optical reflection element according to claim 1, wherein the light reflection layer is a metal film and an oxide layer formed on the metal film. 3. The optical reflection element according to claim 1, wherein the light reflection layer is a dielectric film formed in multiple layers.