KR20030027446A - Optical modulator and manufacturing method for thereof - Google Patents

Abstract

PURPOSE: An optical modulator and a method for manufacturing the same are provided to disperse stress concentrated on post parts due to a mechanical driving of ribbons by adding insulating organic patterns, thereby securing the stability of the mechanical driving. CONSTITUTION: An insulating layer(2) is deposited on a silicon substrate(1). A lower electrode(3) is formed at the center of the insulating layer by depositing and patterning tungsten. Amorphous silicon is deposited and is patterned to form sacrificial layer patterns. A plurality of bridge type ribbons(4) are formed by depositing and patterning aluminum. Both ends of each ribbon contact with the insulating layer and a center part is separated from the lower electrode at a regular interval. A bridge reinforcing film(5), which is insulating organic matter, is formed on a post part which is an area between both ends and the center part.

Description

Optical modulator and its manufacturing method {OPTICAL MODULATOR AND MANUFACTURING METHOD FOR THEREOF}

The present invention relates to an optical modulator and a method for manufacturing the same, and more particularly, to an optical modulator and a method for manufacturing the optical modulator suitable for improving the mechanical stability of the optical modulator by reinforcing a thin film bridge for mechanical driving in response to application of a voltage. will be.

One-dimensional optical modulators used in conventional displays are diffracted by modulating the incident light, a representative example of which is GLV (GRATING LIGHT VALVE) of SLM (SILICON LIGHT MACHINE) of the United States. This GLV is a reflection type and has excellent speed and contrast characteristics, and is emerging as a modulator for the next display.

Hereinafter, with reference to the accompanying drawings will be described in detail the structure and operation characteristics of the GLV.

FIG. 1 is a perspective view of the GLV, in which an insulating layer 2 is positioned on an upper portion of the substrate 1, and a lower electrode (which is a high-temperature metal film such as tungsten) is formed on an upper portion of the insulating layer 2. 3) is located, a plurality of ribbons 4 in the form of bridges, which are spaced apart from the lower electrode 3 by a predetermined distance, and whose both ends are bonded to the insulating layer 2.

In addition, the plurality of ribbons 4 have a high light reflectivity and use a conductive material that can serve as an upper electrode for the lower electrode 3, and examples thereof include aluminum.

When a voltage is applied to the ribbon 4 at the alternating position among the lower electrodes 3 and the plurality of ribbons 4, the ribbon 4 to which the voltage is applied is only bent toward the substrate 1 side, The ribbon 4 to which no voltage is applied is fixed, so that the separation distance of the ribbon 4 from the substrate 1 can be changed.

As such, the upper surface of a part of the ribbon 4 is not coplanar with the upper surface of the other ribbon 4, thereby forming a grating for light incident from the outside, and using diffraction by the grating. It is possible to modulate the light.

That is, if no voltage is applied to the ribbon 4 to which voltage can be applied, the upper surfaces of all the ribbons 4 are all coplanar, which is the same effect as the mirror surface. To reflect light incident perpendicularly to the upper surface of the ribbon 4 as it is.

In addition, when a voltage is applied to the ribbon 4 configured to apply a voltage among the plurality of ribbons 4, the ribbon 4 to which the voltage is applied is bent toward the substrate 1 as described above. The upper surface of (4) shows a lattice structure, which diffracts the light irradiated vertically.

FIG. 2 is a right side view of FIG. 1, in which the distance between the ribbon 4 to which the voltage is applied is reduced from the substrate 1 in the air gap region 3 between the ribbon 4 and the substrate 1. It can be seen that it is mechanically driven.

FIG. 3A is a schematic diagram of reflecting the incident light as it is when no voltage is applied to all the ribbons 4, and FIG. 3B is a voltage applied to some of the ribbons 4 to form a lattice-like surface. As a schematic diagram of a process for diffraction, light can be modulated by using a change in the reflecting surface according to whether or not a voltage is applied as shown in the drawing.

In the operation of the GLV, the distance from which the ribbon 4 to which the voltage is applied is lowered to the substrate 1 side must be 1/4 of the wavelength of the irradiated light to obtain an optimal diffraction efficiency.

4 is a plan view and a side view of the projection apparatus using the GLV, and as shown therein, a prism that reflects light of the light source 41 toward the GLV 42 side and blocks light that is not diffracted in the GLV 42 ( 43); And a lens 44 for focusing the light diffracted by the GLV 32 and displaying it on the screen 45.

The projection apparatus using the GLV 42 separates the light diffracted from the GLV 42 and the light of the light source 41 which is directly reflected, and displays only the diffracted light. Accurate separation of light improves contrast.

When no voltage is applied to the ribbon 4 of the GLV 42 and the surface of the GLV 42 is flat like a mirror surface, the light of the light source 41 to be irradiated is vertically reflected, which is referred to as zero-order light. When the voltage is applied to a part of the ribbon 4 to generate a step on the reflective surface of the GLV 42 and the diffracted light is ± 1st order light, the prism is located at a portion where the 0th order light and ± 1st order light do not overlap. Position 43 so that only ± 1st order light can reach the lens 44, and the light focused through the lens 44 is displayed on the screen 45. As shown in FIG.

However, in the conventional optical modulator such as a shopping mall, the bridge ribbon 4 is mechanically driven up and down, so that stress STRESS is concentrated on the bridge post which is in contact with the insulating film 2, and thus the mechanical configuration is weak. There is a structural problem.

As described above, the conventional optical modulator modulates light by using a bridge-type ribbon mechanically up and down by an electric field. As a result, there is a problem that the reliability of the operation is deteriorated, such as a change in the separation distance between the substrate and the ribbon due to the repeated operation.

It is an object of the present invention to provide a mechanically stable optical modulator and a method of manufacturing the same by dispersing stress concentrated in a post according to vertical displacement of a ribbon.

1 is a perspective view of a conventional optical modulator.

2 is a right side view of FIG. 1;

3A and 3B are schematic diagrams of reflected light depending on whether voltage is applied.

4 is a block diagram of a display device using FIG. 1;

5 is a side view of the present invention optical modulator.

** Description of symbols for the main parts of the drawing **

1: substrate 2: insulation layer

3: lower electrode 4: ribbon

5: bridge reinforcement film

The above object is an insulating film forming step of forming an insulating film by depositing a nitride film or an oxide film on the silicon substrate; A lower electrode forming step of depositing and patterning a metal on the insulating film to form a lower electrode positioned on the center of the insulating film; A sacrificial layer forming step of depositing a sacrificial layer on an upper surface of the structure and patterning the sacrificial layer pattern on a portion of an insulating layer positioned on an upper portion of the lower electrode and a periphery of the lower electrode; A ribbon forming step of depositing and patterning a metal on the top of the structure to form a plurality of ribbons having a central portion located on the sacrificial layer and having both ends contacting the insulating layer on the side of the sacrificial layer; Forming a bridge reinforcement film formed by coating and patterning an insulating organic material on the upper surface of the structure to form a bridge reinforcement film positioned on the insulating film around the upper and both sides of the ribbon; Through a manufacturing process comprising a step of removing the sacrificial layer selectively, a substrate, an insulating film on the substrate, a lower electrode located on the center of the insulating film, the central portion of the lower electrode A plurality of bridge-shaped ribbons which are positioned to be spaced apart from each other by a predetermined distance and fixed on an insulating film on both sides of the upper electrode, and a post portion which is an area between the both ends and the central part fixed to the insulating film of the ribbon It is achieved by manufacturing an optical modulator composed of a bridge reinforcement film located in the, in detail with reference to the accompanying drawings, the present invention as follows.

Fig. 5 is a side view of the optical modulator of the present invention, as shown therein; An insulating layer (2) positioned on the upper side of the substrate (1); A lower electrode 3 positioned at an upper portion of the insulating layer 2; A bridge-shaped ribbon (4) having both ends in contact with the insulating layer (2) at a predetermined distance from the lower electrode (3), the center portion of which is spaced apart from the lower electrode (3) by a predetermined distance; It consists of a bridge reinforcement film 5 located in the upper part of the area | region which contacts the insulating layer 2 of the said ribbon 4.

Hereinafter, the structural features and the manufacturing method of the optical modulator of the present invention as described above will be described in more detail.

First, the insulating layer 2 is deposited on the silicon substrate 1 by using a low pressure chemical vapor deposition (LPCVD) method or a thin film deposition method.

Next, tungsten is deposited on the upper surface of the insulating layer 2 and patterned through a photolithography process to form a lower electrode 3 positioned at the center of the insulating layer 2.

The reason for depositing tungsten is that tungsten exhibits stable shape and physical properties without changing its properties even at a later high temperature process. Deposit.

Next, an amorphous silicon to be used as a sacrificial layer is deposited on the upper surface of the structure and patterned to form one of the insulating layer 3 on the upper part of the lower electrode 3 and on the periphery of the lower electrode 3. Form an amorphous silicon pattern located in the flotation.

Then, aluminum is deposited on the upper surface of the structure, and patterned, so that both ends contact the insulating layer 2 located on the lower side of the amorphous silicon, and a metal pattern in which the center passes through the amorphous silicon is formed in each pixel. Each ribbon 6 is formed so as to be spaced apart from each other by six.

Subsequently, SU-8 is applied to the upper surface of the structure by a spin coating method, and then patterned to form an area between the ribbon 4 positioned on the upper side of the amorphous silicon as the sacrificial layer and the upper side of the insulating layer 2. That is, the bridge reinforcement film 5 which is located in the post (POST) part of the bridge-shaped ribbon 4 is formed.

At this time, SU-8 used as the bridge reinforcement film 5 is excellent in mechanical properties as an insulating organic material. In addition, by forming the bridge reinforcement film 5 on the upper side of the post portion of the ribbon 4 in this way, it is possible to disperse the stress concentrated in the post portion during the mechanical movement of the ribbon (4).

Then, the amorphous silicon is removed using XeF ₂ gas which can selectively remove only the amorphous silicon, thereby forming the bridged ribbon 4.

That is, a voltage is applied to a specific one or a plurality of ribbons 4 of the tungsten lower electrode 3 and the plurality of ribbons, and between the lower electrode and the ribbon to which the voltage is applied according to the application of the voltage. When the previous position occurs, the ribbon to which the voltage is applied is bent to the substrate 1 side.

At this time, the bending of the ribbon 4 causes a stress to act on posts that are both end portions of the ribbon 4 supporting the central portion of the ribbon 4. Such stress is dispersed by the bridge reinforcement film 5, and the stress acting on the post of the ribbon is reduced by the dispersion of such stress.

As described above, the present invention increases the stability to the mechanical movement of the ribbon 4 by dispersing the stress acting on the post.

As described above, the optical modulator of the present invention and a manufacturing method thereof add an insulating organic pattern to a post portion of a ribbon which modulates light through mechanical driving by application of a voltage, and concentrates on the post by mechanical driving of the ribbon. By dispersing the stress to be applied, there is an effect of ensuring the stability of the mechanical drive and improving the reliability of the operation.

Claims (8)

A substrate, an insulating film positioned on the substrate, a lower electrode positioned on the center of the insulating film, and a central portion thereof positioned to be spaced apart from the upper side of the lower electrode by a predetermined distance; And a bridge reinforcement film positioned at a post portion, which is a region between both end portions and a center portion fixed to the insulating film of the ribbon, and a bridge-shaped ribbon fixed on the insulating film located at the optical fiber modulator. 2. The optical modulator of claim 1, wherein the bridge reinforcement film is positioned at the same level or higher than the top surface of the center portion of the ribbon. The optical modulator according to claim 1, wherein the bridge reinforcement film is an insulating organic material, and preferably SU-8. An insulating film forming step of forming an insulating film by depositing a nitride film or an oxide film on the silicon substrate; A lower electrode forming step of depositing and patterning a metal on the insulating film to form a lower electrode positioned on the center of the insulating film; A sacrificial layer forming step of depositing a sacrificial layer on an upper surface of the structure and patterning the sacrificial layer pattern on a portion of an insulating layer positioned on an upper portion of the lower electrode and a periphery of the lower electrode; A ribbon forming step of depositing and patterning a metal on the top of the structure to form a plurality of ribbons having a central portion located on the sacrificial layer and having both ends contacting the insulating layer on the side of the sacrificial layer; Forming a bridge reinforcement film formed by coating and patterning an insulating organic material on the upper surface of the structure to form a bridge reinforcement film positioned on the insulating film around the upper and both sides of the ribbon; And a sacrificial layer removing step of selectively removing the sacrificial layer. The method of claim 4, wherein the bridge reinforcing film is formed by coating SU-8 by spin coating and then patterning the SU-8. The method of claim 4, wherein the lower electrode is formed by depositing tungsten by sputtering or a possible deposition method, and patterning the same by a photolithography process. 5. The method of claim 4, wherein the ribbon is formed by depositing and patterning a metal having high light reflectivity and good electrical conductivity, and preferably using aluminum. The method of claim 4, wherein the sacrificial layer uses amorphous silicon, and the sacrificial layer removing step selectively removes the amorphous silicon sacrificial layer using XeF ₂ gas as an etching gas.