JP3093411B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an optical scanning device capable of two-dimensional scanning using a cantilever.

[0002]

2. Description of the Related Art Conventionally, a two-dimensional optical scanning apparatus generally uses a combination of a vibrating plane mirror (a so-called galvanometer mirror) and a rotating polyhedron (a so-called polygon mirror), or a combination of two vibrating plane mirrors, and scans in each mirror direction. Are arranged so as to be orthogonal to each other. This example is shown in FIG. In FIG. 8, light emitted from a laser light source 24 is subjected to relatively high-speed horizontal scanning by a rotating polyhedron 25, and this light is further subjected to relatively low-speed vertical scanning by a vibrating plane mirror 26. And the vibrating plane mirror 2
The light from 7 is condensed by a lens 28, the luminescent spot moves two-dimensionally on a screen 29, and a raster scan is performed.

[0003]

However, in the above-described optical scanning device, the size of the vibrating plane mirror and the rotating polyhedral mirror is relatively large, so that there is a disadvantage that the size of the device becomes large. In addition, in order to perform accurate two-dimensional scanning, each element must be arranged in a strict positional relationship, and optical adjustment when assembling the apparatus is very complicated. SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-dimensional optical scanning apparatus which solves the above-mentioned disadvantages of the conventional example and has a compact configuration and easy optical adjustment.

[0004]

A feature of the present invention is that, first, a plurality of actuators formed on a semiconductor substrate have light emitting elements in contact with the actuators, and the actuators are independent of each other. A light scanning device that scans light emitted from a plurality of the light emitting elements by driving the light emitting device, and secondly, the actuator has a cantilever (cantilever) shape. Thirdly, an optical scanning device is characterized in that the actuator is driven by a piezoelectric effect.

The components of the present invention have been described above, and the details and operation thereof will be described below. The purpose of the present invention is
An object of the present invention is to provide a two-dimensional optical scanning device which solves the drawbacks of the conventional example and has a compact configuration and easy optical adjustment.

An actuator manufactured by using a semiconductor process technology is applied to the actuator used in the present invention. As the form of the actuator, various forms such as a cantilever (a cantilever), a doubly supported beam, a membrane, a hinge, and a motor can be considered. As the driving method of each actuator,
Bimorphs and unimorphs using the piezoelectric effect, electrostatic drive using the counter electrode, bimetals and shape memory alloys using heat, those using gels that change in volume due to an electric field, etc., those that are displaced by gas pressure, etc. There is. Above all, the piezoelectric bimorph cantilever has a simple optical adjustment and can be displaced in two axial directions, as described in detail in Example 1, in order to arrange a light emitting element on the cantilever and perform two-dimensional optical scanning. This is advantageous in that

In the present invention, as the light emitting element disposed in contact with the actuator, a light source such as a light emitting diode, a semiconductor laser, an electron beam, and a white light source can be considered. Above all, semiconductor lasers have great utility in applications such as measurement to laser beam printers and interference measurement. As a structure of a semiconductor laser having good luminous efficiency and temperature characteristics, there is a structure employing a multiple quantum well structure.
Since laser light emitted from a semiconductor laser generally diffuses, it needs to be condensed. In particular, a micro collimator lens is necessary to condense a semiconductor laser manufactured on a micro cantilever. An example of manufacturing such a microcollimator lens is one using photolithographic technology ("Fabrication").
of active Integrated Opt
ical Micro-Encoder "1991 I
EEE Micro Electro Mechani
calSystems Workshop, Proce
edings pp 233-238).

The present invention provides a novel optical scanning device combining these actuators and light emitting elements. Further, it is also possible to improve the scanning speed on the screen by manufacturing a plurality of the optical scanning devices of the present invention on the same semiconductor substrate and operating them independently. Hereinafter, the optical scanning device of the present invention will be described in detail with reference to examples.

[0009]

Embodiment 1 The embodiment 1 shows a cantilever type optical scanning device according to the present invention. FIG. 1 is a longitudinal sectional view of the cantilever type optical scanning device according to the first embodiment. FIG. 2 is a cross-sectional view of the cantilever type optical scanning device according to the first embodiment. FIGS. 3, 4, 5, 6, and 7 are views showing the manufacturing process of the cantilever type optical scanning device according to the first embodiment. Hereinafter, the manufacturing process will be described in detail with reference to these drawings.

First, on the n-type GaAs substrate 1, n-type GaAs is 1 μm as the buffer layer 2, n-type AlGaAs is 2 μm as the cladding layer 3, and n-type Al0.4Ga is formed.
0.6 μm as 2 μm, non-doped GaAs as the active layer 4
s100Å and Al0.2Ga0.8As30Å were repeated four times, and finally GaAs100Å was laminated to form an active region 4 having a multiple quantum well structure. Next, as the cladding layer 5, P
Type Al0.4Ga0.8As 15 μm, cap layer 6
Was formed by a 0.5 μm molecular beam epitaxy method.

Subsequently, as shown in order to limit the current injection area, after etching to about 0.4 μm before the active layer 4, a polyimide 7 is formed by spin coating, and only the edge crest is etched to form an injection area. . Next, a Cr-Au ohmic electrode was formed as the wiring electrode 8. After performing a heat treatment for diffusion, the GaAs substrate is etched to form the resonance surfaces 22 and 23. The etching was performed by a reactive ion beam etching (RIBE) method using Cl ₂ gas. Here, the cavity length (the interval between the resonance surfaces 22 and 23) is 300 μm. The semiconductor laser 9 was manufactured by the above method (FIG. 3).

Next, silicon nitride 11 is applied to both surfaces of a silicon substrate 10 (thickness: 525 μm) having a crystal orientation (100) plane as a principal surface by LPCVD to a thickness of 2000 °.
After the film formation, the two-layer piezoelectric members 13 and 14 and the three electrode layers 15, 16 and 17 which are the bimorph driving portion 12 are formed. The piezoelectric layer is formed using zinc oxide by an AC sputtering method, and a pattern is formed by wet etching with an aqueous acetic acid solution. The lower electrode layer 15 is made of 1000% gold obtained by sublimating 30% chromium. Chromium and gold are deposited by resistance heating deposition, and chromium
Pattern formation is performed by wet etching with an aqueous solution of cerium ammonium and perchloric acid, and an aqueous solution of gold with iodine and potassium iodide. For the middle electrode layer 16 and the upper electrode layer 17, 1000 ° of gold is used. Gold is deposited by an evaporation method using resistance heating, and a pattern is formed using an aqueous solution of iodine and potassium iodide. Each of the electrodes has an extraction portion connected to a driving amplifier circuit. Lower electrode 1
5.15 ′ and the upper electrode 17 ・ 17 ′ are each divided into two at the center line in the longitudinal direction of the cantilever, and cantilever beams (cantilever) having a total of five drive electrodes and can be driven in at least two axial directions. ). After that, plasma CV
A silicon nitride film 18 was formed by the method D to form an insulating layer.

Further, a microcollimator lens 19 is formed at the tip of the cantilever. Laser light 20
Oscillates at an oscillation wavelength of 780 nm in the active layer, and emits an elliptical beam having a beam diameter of about 2 μm, a divergence angle of θ // = 20 °, and θ⊥ = 30 ° into the air. The distance between the resonance surface 22 and the microcollimator lens 19 is 10 to 60 μ
m, more preferably 28 μm. The micro-collimator lens 19 is made of SiO _{2 by} sputtering.
And two movable targets of Si—O—N and were formed so as to have a gradient refractive index gradient in the film thickness direction. After that, normal reactive ion beam etching (RIBE)
The micro collimator lens 19 was formed by (FIG. 4). The laser beam 20 can be converted into linear light by the microcollimator lens 19.

Next, GaAs is formed using an epoxy-based adhesive.
The substrate 1 and the silicon substrate 10 were joined as shown in FIG. Thereafter, the GaAs substrate 1 is cut by lapping to a thickness indicated by a dotted line in FIG. 5, an Au-Ge electrode is deposited as an n-type ohmic electrode 21, and a plasma C is formed as an insulating layer 31.
A silicon nitride film was formed by a VD method, gold of 1000 ° was obtained by sublimating 20 ° of chromium as a wiring electrode 32, and wiring was performed by wire bonding 33 (FIG. 6).

Next, the silicon nitride 11 on the back surface of the silicon substrate 10 was patterned into the shape of the etching opening on the back surface of the substrate. Patterning is performed by reactive ion etching (R
Etching was performed using CF ₄ gas according to the IE method. Thereafter, the surface of the substrate is not exposed to the etchant, and 11
Potassium hydroxide aqueous solution (KOH: H ₂ O heated to 0 ° C.
= 1: 2, weight ratio) to etch silicon 2
After forming a 0 μm Si membrane, reactive ion etching (RIE) using CF ₄ , O ₂ plasma
The silicon membrane and the surface silicon nitride film 11 were etched from the back surface of the substrate 1 to form a cantilever type (FIG. 7).

The cantilever length of the cantilever type optical scanning device manufactured by the above method is 1000 μm, and the cantilever width is 100 μm. When the middle electrode 16 was set to 0 potential and a sine wave of a voltage of 50 V and a frequency of 200 Hz was applied to the lower electrodes 15 and 15 ′ and the upper electrodes 17 and 17 ′,
The cantilever is perpendicular to the substrate surface (hereinafter referred to as X direction)
At the maximum tip deflection angle θ _X = 30 °. Further, the middle electrode 16 is set to 0 potential, and a sine wave of a voltage of 50 V and a frequency of 200 Hz is applied to the lower electrode 15 and the upper electrode 17 ′.
When a sine wave whose phase is shifted by 180 ° from the above at a voltage of 50 V and a frequency of 200 Hz is applied to the upper electrode 17, the cantilever has a maximum tip deflection angle θ _Y = 3 in a direction parallel to the substrate surface (hereinafter referred to as Y direction). Vibrated at °. By combining the two movements in the X and Y directions, the tip of the cantilever could be vibrated independently in the XY directions.

By applying a voltage between the wiring electrode 8 and the n-type ohmic electrode 21 by the vibration, the laser beam 20 emitted from the semiconductor laser 9 is scanned in the X and Y directions, and the bright spot generated on the screen is detected. I was able to scan. When the distance between the light source and the screen is 500 mm, the scan area on the screen is 350 mm × 5.
It was 0 mm.

Of course, the semiconductor laser used in the first embodiment may be of a surface emitting type (FIG. 10). In this case, since the laser beam is emitted perpendicular to the length direction of the cantilever, the cantilever must be vibrated in the X direction and the cantilever must be vibrated in the twisting direction (Z direction). In this case, the middle electrode 16 is set to 0 potential, and the lower electrode 1
By shifting the phase of the voltage applied to 5 and the upper electrode 17 from the phase of the voltage applied to the lower electrode 15 ′ and the upper electrode 17 ′ by 180 °, the cantilever is twisted (Z direction).
Can be driven. As the light emitting element, a light source such as a light emitting diode, an electron beam, and a white light source can be used in addition to the semiconductor laser.

Also, as shown in FIGS. 7 and 10, a plurality of optical scanning devices can be manufactured on the same semiconductor substrate and operated independently of each other to improve the scanning speed on the screen. If the optical scanning devices shown in FIG. 10 are arranged in a 10 × 10 array on a semiconductor substrate and the scanning area of one optical scanning device is reduced to 1/100, the scanning speed on the screen is reduced to 1 ×. 1 when
00 times.

Reference numeral 31 denotes a silicon nitride film provided on the wiring electrode 8, 32 denotes a wiring electrode provided on the silicon nitride film 31, and 33 denotes an n-type ohmic electrode 21 and a wiring electrode 3.
This is wire bonding that connects the two.

In the first embodiment, the piezoelectric bimorph structure is used. However, when the scanning direction is one direction, the piezoelectric unimorph structure, the electrostatic drive type, the bimetal, the shape memory alloy or the like is used for one-dimensional light. A scanning device can be manufactured. Further, as a form of the actuator, besides a cantilever (cantilever), a double-supported beam, a membrane, a hinge, or the like can be applied. It is also possible to form a form capable of two-dimensional scanning by combining a plurality of these actuators.

The second embodiment is an example of a cantilever type optical scanning device having a monolithic structure. FIG. 9 shows the second embodiment.
1 is a vertical sectional view of a cantilever type optical scanning device according to the present invention. The feature of the second embodiment resides in that a semiconductor laser is manufactured below the bimorph cantilever by using anisotropic etching of GaAs.

The manufacturing method is as follows. First, 2,000 silicon nitride is used as mask layers 29 and 30 on the back surface of the n-type GaAs substrate 1.
Å A film was formed. Next, n-type Ga
On an As substrate 1, a buffer layer 2, a clad layer 3, an active layer 4, a clad layer 5, a cap layer 6, a polyimide 7, and a wiring electrode 8 were formed. Next, a bimorph structure was formed in the same manner as in Example 1. Further, anisotropic etching of GaAs is performed. The etchant is a mixture of sulfuric acid, hydrogen peroxide, and water. After etching the substrate 1 halfway using the mask layers 29 and 30 as a mask, the mask layer 30 was removed, and the substrate 1 was further etched with the same etchant to produce a resonance surface. Then, unnecessary polyimide was etched by reactive ion etching using oxygen plasma. Next, Au-Ge is used as the n-type ohmic electrode 21.
Electrodes were deposited, and the wiring was taken out by wire bonding. Further, a microcollimator lens 19 was manufactured from the back surface of the substrate 1 in the same manner as in Example 1.
Finally, the silicon nitride 7 around the bimorph structure was removed to obtain a cantilever type.

The cantilever type optical scanning device manufactured by the above method has a cantilever length of 1000 μm and a cantilever width of 100 μm. Vibration was performed in the same manner as in Example 1 with the maximum tip deflection angle θ _X = 30 ° in the X direction and the maximum tip deflection angle θ _Y = 3 ° in the Y direction. By combining the two movements in the X and Y directions, the tip of the cantilever could be vibrated independently in the XY directions. Further, the laser beam 20 emitted from the semiconductor laser 9 by this vibration was scanned in the X and Y directions to scan a bright spot generated on the screen. When the distance between the light source and the screen was 500 mm, the scan area on the screen was 350 mm × 50 mm.

It goes without saying that the semiconductor laser used in the second embodiment may be of a surface emitting type (FIG. 11). In this case, the cantilever can be vibrated in the X direction and the cantilever can be vibrated in the torsion direction (Z direction) as in the first embodiment. In addition to a semiconductor laser, a light source such as a light emitting diode, an electron beam, or a white light source can be used as the light emitting element. Also, as shown in FIG. 11, it is possible to improve the scanning speed on the screen by fabricating a plurality of optical scanning devices on the same semiconductor substrate and operating them independently, as in the first embodiment.

[0026]

As described above, according to the present invention, a plurality of actuators each having a light-emitting element formed on a semiconductor substrate are driven to change the light-emitting direction of the light-emitting element. The optical scanning device was able to be provided.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of an optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the optical scanning device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a manufacturing process of the optical scanning device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a manufacturing process of the optical scanning device according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a manufacturing process of the optical scanning device according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a manufacturing process of the optical scanning device according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a manufacturing process of the optical scanning device according to the first embodiment of the present invention.

FIG. 8 is a schematic diagram showing a configuration of a conventional optical scanning device.

FIG. 9 is a longitudinal sectional view of an optical scanning device according to a second embodiment of the present invention.

FIG. 10 is a longitudinal sectional view of an optical scanning device according to a first embodiment of the present invention, which is different from that of FIG. 1;

FIG. 11 is a longitudinal sectional view of an optical scanning device according to a second embodiment of the present invention, which is different from that of FIG. 9;

[Explanation of symbols]

 Reference Signs List 8 wiring electrode 13 piezoelectric layer 14 piezoelectric layer 15 bimorph lower electrode 16 bimorph middle electrode 17 bimorph upper electrode 18 silicon nitride film 19 microcollimator lens 20 laser light 21 n-type ohmic electrode 22 resonance surface 23 resonance surface 31 silicon nitride Film 32 wiring electrode 33 wire bonding

Claims (3)

(57) [Claims] A plurality of actuators formed on a semiconductor substrate have light emitting elements in contact with the actuators, and scan light emitted from the light emitting elements by driving the actuators independently of each other. Optical scanning device characterized by the following. 2. The optical scanning device according to claim 1, wherein the actuator has a cantilever (cantilever) shape. 3. The optical scanning device according to claim 1, wherein the actuator is driven by a piezoelectric effect.