JP3418863B2 - Optical switch manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to an optical communication system, for example.
Optical switches used in systemsMade ofAbout the manufacturing method
You. [0002] 2. Description of the Related Art An example of a conventional structure of this type of optical switch is shown below.
As shown in FIG. Movable on the substrate 11 in parallel with the surface of the substrate
An electrode 12 is arranged. The movable electrode 12 is rectangular in this example
And the two opposite sides form a frame as shown in the figure.
The support structure 13 is connected to and supported by the support structure 13.
The other ends of the support structures 13 are respectively connected to the fixing portions 14.
And the fixing portion 14 has a structure installed on the substrate 11.
I have. The movable electrode 12 is a flexible supporting structure.
13 to support the substrate surface
The movable electrode 12 can be displaced in the vertical direction.
Is mounted with a micro mirror 15. On the other hand, the substrate 11
In the portion facing the movable electrode 12 and the support structure 13
Is such that the through hole 16 opens in a square shape as shown in the figure.
The fixed electrode is formed in the through hole 16.
A conductive substrate 17 is provided. The conductive substrate 17 has a shape matching the through hole 16.
And is bonded from the back side of the substrate 11
To be integrated with the substrate 11. The guide located in the through hole 16
The upper surface of the conductive substrate 17, that is, the fixed electrode surface is the surface of the substrate 11.
Is located at a position lower by a predetermined amount, thereby
The structure is such that a required displacement amount of the pole 12 can be secured. [0005] The optical switch 18 having the above structure
In, the movable electrode 12 is driven by electrostatic attraction
The movable electrode 1 is displaced in a direction perpendicular to the surface of the substrate.
2 and the micromirror 15 standing upright on the substrate surface
Displacement in the vertical direction allows the
Can switch the optical path of the incoming light beam
It has become. In FIG. 4A, reference numerals 21a to 21c denote, for example, this light.
2 shows an optical fiber disposed around the switch 18;
Reference numeral 2 denotes incident light incident on the optical switch 18, 23a and 23
b indicates the emitted light. Micro mirror 15 is inserted in the optical path
Incident light 22 is reflected by the micro mirror 15
Outgoing light 23a is incident on the optical fiber 21b.
You. On the other hand, when the micro mirror 15 is not inserted into the optical path
Indicates that the incident light 22 proceeds as it is to become the output light 23b,
The light enters the optical fiber 21c. FIG. 5 shows the optical switch 18 shown in FIG.
The manufacturing method is shown in the order of the steps.
Will be described. (1) Prepare the substrate 11. In this example, as the substrate 11,
Is a silicon substrate. (2) SiO on the substrate 11_TwoA protective film 24 is formed. (3) Protective film on the part where the fixing part 14 is formed
24 is removed. (4) As a material constituting a movable body such as the movable electrode 12,
A polycrystalline silicon film 25 is formed. (5) The polycrystalline silicon film 25 is etched and
Forming a moving electrode 12, a support structure 13, and a fixing portion 14;
You. (6) SiO_TwoProtective film 26 is formed on both front and back surfaces.
Film. (7) The movable electrode 12 and the support structure 1 on the back surface of the substrate 11
The protective film 26 at the position corresponding to No. 3 is removed. (8) The substrate 11 is etched with a KOH solution and penetrated.
A hole 16 is formed. (9) The protective films 24 and 26 are removed. (10) A fixed electrode on which required processing has been performed is configured.
Bonding the conductive substrate 17 to be formed from the back surface of the substrate 11
You. This conductive substrate 17 is also a silicon substrate in this example.
It is. Hereinafter, although not shown in the figure, a microphone is placed on the movable electrode 12.
The optical switch 18 is completed by installing the mirror 15. [0011] However, as described above,
Formed through hole 16 by etching from the back of substrate 11
Then, when the conductive substrate 17 is bonded from the back surface of the substrate 11,
In such a structure, the substrate 11 has a frame shape, so that its strength and
It is necessary to secure the required frame width considering the bonding area
4A, the device area surrounded by a broken line 18a in FIG.
The entire optical switch 18 becomes large with respect to the area,
A silicon substrate was used as 11 and its anisotropic etchin
When the through hole 16 is formed by the
Since the opening area on the back surface of the substrate 11 becomes large,
Larger, which limits optical switch miniaturization
Was to be done. [0012] Also, due to such bonding,
The lowering of the manufacturing accuracy is inevitable, and the upper surface of the conductive substrate 17
The accuracy of the position, that is, the position of the fixed electrode surface, is not good.
It had become a thing. In addition, a series of film formation and etchin
Bonding process (adhesion process) is required separately from the
Process, the process is complicated, and the
Was to be taken. An object of the present invention is to address these conventional problems.
In view of the above, miniaturization can be achieved, with high accuracy and simplicity.
Structure of optical switch that can be manufactured and method of manufacturing the same
Is to provide a law. [0014] [Means for Solving the Problems]ThisAccording to the invention ofManufactured
Optical switchLocated on the board, parallel to the board surface
And can be displaced in the vertical direction with respect to the substrate surface.
Micro mirror is mounted on the movable electrode
Drive the poles to displace the micromirror
An optical switch that switches the optical path of the emitted light beam
Above, the substrate is made of a conductive material, and the surface of the substrate is etched.
A recess is formed by the etching process, and the bottom surface of the recess is
It is a fixed electrode surface that faces the movable electrode in parallel. [0015]AndThe above substrate is a silicon substrate,
The moving electrode is formed by a polycrystalline silicon film. Claim
1The invention is directed to a bottom surface of a concave portion formed on a surface of a conductive substrate.
Is the fixed electrode surface, and it is possible to face parallel to the fixed electrode surface.
The moving electrode is fixed on the conductive substrate via the fixed part and the support structure.
Placed, the movable electrode is driven, and perpendicular to the fixed electrode surface
The microphone mounted on the movable electrode
The optical path of the incident light beam is
A method of manufacturing an optical switch having a structure to be performed,
The conductive substrate is a silicon substrate.
A polycrystalline silicon film is provided on the surface, and movable electrodes, support structures and
And the fixing part is SiO_Two After protection with a coating,
Using a KOH solution with the con film as an etchant entry path
By etching the silicon substrate from the movable electrode side
The recess is formed. [0016] Embodiments of the present invention will be described with reference to the drawings.
An example will be described with reference to FIG. FIG.Made
BuiltLight switchHFIG. 4 corresponds to FIG.
Are given the same reference numerals. In this example, the substrate 11
Is formed of a conductive material, and the surface of the substrate 11 is etched.
The recess 31 is formed by the chining process.
Forms a fixed electrode surface whose bottom faces parallel to the movable electrode 12
That is, the substrate 11 itself forms a fixed electrode.
It is assumed that FIG. 2 shows the optical switch 32 shown in FIG.
FIG. 2 shows a manufacturing method in the order of steps, with reference to FIG.
A method for manufacturing the optical switch 32 will be described. (1) A substrate 11 made of a conductive material is prepared. This substrate 1
1 is a silicon substrate. (2) A polycrystalline silicon film 33 is formed on the substrate 11. (3) SiO_TwoA protective film 34 is formed. (4) The portion of the protective film 34 where the fixing portion 14 is to be formed is removed.
You. (5) A polycrystalline silicon film 35 is formed. (6) The polycrystalline silicon film 35 is etched and
Forming a moving electrode 12, a support structure 13, and a fixing portion 14;
You. At this time, the movable electrode 12 has a plurality of through holes 36.
Are provided in a matrix as shown in FIG. 1A. (7) SiO_TwoA protective film 37 is formed on the entire front and back.
Film. (8) SiO on the front side (movable electrode 12 side)_TwoProtective film 34,
37 is patterned into each through hole 36 of the movable electrode 12.
The corresponding portion reaches the polycrystalline silicon film 33 on the substrate 11.
A through hole 38 is formed. In addition, the movable electrode 12 and the support
The outer shape of protective film 34, 37 (larger
Patterning and fixing to slightly increase
Putter so that the required amount is larger than the outer shape of part 14
To synchronize. (9) The substrate 11 is etched with a KOH solution.
Ching. The KOH solution passes through each through hole 38 and is polycrystalline.
Reaches the silicon film 33 and has isotropic etching properties
This polycrystalline silicon film 33 serves as an etching solution (KOH solution).
Liquid 11), the substrate 11
And is subjected to anisotropic etching to form a recess 31.
You. Note that the polycrystalline silicon film located below the fixing portion 14
As described above, reference numeral 33 denotes a large amount of protective films 34 and 37 as described above.
Is present and remains without being etched. (10) The protective films 34 and 37 are removed. Hereinafter, although not shown in the figure, a microphone is placed on the movable electrode 12.
The optical switch 32 is completed by installing the mirror 15. By adopting the above manufacturing method,
Then, the movable electrode 12, the support structure 13, and the like were formed as films.
Thereafter, the substrate 11 is etched from the side where they are formed.
The required depth to allow the movable electrode 12 to be displaced.
Having the concave portion 31 and the concave portion 3
The bottom surface of 1 is a fixed electrode surface. Therefore, the conventional optical switch
Bonding process required in the method for manufacturing the h18
Is unnecessary, and it can be manufactured with high accuracy and ease.
It will be. Further, as in the prior art, the through hole 16 is formed in the substrate 11.
Need not be provided, that is, the substrate 11 has a frame shape
Therefore, the area that was conventionally required to secure the frame width is
It becomes unnecessary, and a small optical switch 32 can be obtained.
it can. FIG. 3 shows a 2 × 2 matrix optical switch.
The size of the conventional one and the one according to the present invention.
It is the conceptual diagram which was compared. In the conventional device shown in FIG.
Through hole by anisotropic etching on substrate 11 having a thickness of 00 μm
When 16 is formed, penetrate 1 mm square on the substrate surface
In order to form the hole 16, about 1.6 mm
Etching window 16a must be formed.
From the strength of the substrate 11 to be formed, the bonding area, etc., at least the width
W ₁, W_TwoIs required about 1 mm, which is clear from the figure.
Thus, the area loss of this frame portion is extremely large. On the other hand, according to the present invention shown in FIG.
The optical switch structure does not require the frame portion as described above,
The distance between adjacent switch elements is very short (for example, 1
0 μm or less).
It has a suitable structure. [0026] As described above, according to the first aspect of the present invention,
YoThe optical switch manufactured, The conventional optical switch shown in FIG.
The frame-shaped region of the substrate 11 is switched by a switch element
No need to install around the area, so optical switch
Can be downsized. In addition, the optical path
Can be made shorter, so that
Performance can be improved. In addition, as in the case of the conventional optical switch 18,
Because it does not use a laminated structure, for example,
Of the fixed electrode surface due to
Can solve problems such as the effects of stress, and
Since the bonding is not required, the manufacturing process can be simplified.
Can be. The claim1According to the invention of
Fixed electrode surface on the surface, that is, the side facing the movable electrode 12 etc.
And enables the required displacement of the movable electrode 12
The recess 31 can be formed easily and satisfactorily.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an optical switch manufactured according to the invention of claim 1;
H is a plan view, and B is a CC cross-sectional view. FIG. 2 is a manufacturing process diagram for explaining the embodiment of the invention of claim 1 ; FIG. 3 is a diagram for comparing the size of a conventional device and that of the present invention when a 2 × 2 matrix optical switch is configured. FIG. 4A is a plan view showing a conventional optical switch, and FIG. FIG. 5 is a manufacturing process diagram for explaining the manufacturing method of the optical switch of FIG. 4;

Claims (1)

(57) Claims 1. A bottom surface of a concave portion formed on the surface of a silicon substrate is a fixed electrode surface, and a movable electrode made of first polycrystalline silicon is opposed in parallel to the fixed electrode surface. Is disposed on the silicon substrate via a fixed portion and a support structure integrated with the movable electrode, and the movable electrode is driven to be displaced in a direction perpendicular to the fixed electrode surface, whereby the movable A method for manufacturing an optical switch in which a micromirror mounted on an electrode is displaced to switch an optical path of an incident light beam, wherein a second polycrystalline silicon film is formed on the silicon substrate. ,
Formation of multiple through-holes protected by SiO ₂ coating thereon
The movable electrode, the support structure, and the fixed
Parts were fabricated, after which, by etching the silicon substrate from the movable electrode side by a KOH solution, the
The above-mentioned second polycrystalline silicon other than the lower part of the fixing part is isotropic.
Etch and further anisotropically etch the silicon substrate
Method of manufacturing an optical switch, characterized in that by grayed forming the recess.