Abstract:
A structure of a micro electro mechanical system and a manufacturing method are provided, the structure and manufacturing method is adapted for an optical interference display cell. The structure of the optical interference display cell includes a first electrode, a second electrode and posts. The second electrode comprises a conductive layer covered by a material layer and is arranged about parallel with the first electrode. The support is located between the first plate and the second plate and a cavity is formed. In the release etch process of manufacturing the structure, the material layer protects the conductive layer from the damage by an etching reagent. The material layer also protects the conductive layer from the damage from the oxygen and moisture in the air.

Description:
RELATED APPLICATION  
       [0001]     This application is a continuation of U.S. application Ser. No. 10/810,660, filed Mar. 29, 2004, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a structure of an optical interference display cell and the manufacturing method thereof, and more particularly, to the structure of a movable electrode in an optical interference display cell and the manufacturing method.  
       BACKGROUND OF THE INVENTION  
       [0003]     In a micro electro mechanical system (MEMS), the development of a sacrificial layer technique has become a key factor for manufacturing a suspended structure, such as a cantilever, a beam, a membrane, a channel, a cavity, a joint or hinge, a link, a crank, a gear or a rack, to name a few. A structure release etching process is adapted for removing a sacrificial layer, so a structure of a structure release in a micro electro mechanical system has a critical influence on the process of removing the sacrificial layer.  
         [0004]     A conventional structure release etching process is first introduced with an optical interference display cell as an example. The optical interference display cell, a kind of a micro electro mechanical system, is used to fabricate a planar display. Planar displays are popular for portable displays and displays with space limits because they are light and small in size. To date, planar displays in addition to liquid crystal displays (LCD), organic electro-luminescent displays (OLED), plasma display panels (PDP), a mode of optical interference displays is another option for planar displays.  
         [0005]     U.S. Pat. No. 5,835,255 discloses an array of display units of visible light that can be used in a planar display. Please refer to  FIG. 1 , which depicts a cross-sectional view of a display unit in the prior art. Every optical interference display unit  100  comprises two walls,  102  and  104 . Posts  106  support these two walls  102  and  104 , and a cavity  108  is subsequently formed. The distance between these two walls  102  and  104 , that is, the length of the cavity  108 , is D. One of the walls  102  and  104  is a hemi-transmissible/hemi-reflective layer with an absorption rate that partially absorbs visible light, and the other is a light reflective layer that is deformable when voltage is applied. When the incident light passes through the wall  102  or  104  and arrives in the cavity  108 , in all visible light spectra, only the visible light with the wavelength corresponding to the formula 1.1 can generate a constructive interference and can be emitted, that is, 
 
2D=Nλ  (1.1) 
 
         [0006]     , where N is a natural number.  
         [0007]     When the length D of cavity  108  is equal to half of the wavelength times any natural number, a constructive interference is generated and a sharp light wave is emitted. In the meantime, if the observer follows the direction of the incident light, a reflected light with wavelength λ 1  can be observed. Therefore, the display unit  100  is “open”.  
         [0008]      FIG. 2  depicts a cross-sectional view of a display unit in the prior art after applying a voltage. As shown in  FIG. 2 , while driven by the voltage, the wall  104  is deformed and falls down towards the wall  102  due to the attraction of static electricity. At this time, the distance between wall  102  and  104 , that is, the length of the cavity  108  is not exactly zero, but is d, which can be zero. If we use d instead of D in formula 1.1, only the visible light with a wavelength satisfying formula 1.1, which is λ 2 , can generate a constructive interference, and be reflected by the wall  104 , and pass through the wall  102 . Because wall  102  has a high light absorption rate for light with wavelength λ 2 , all the incident light in the visible light spectrum is filtered out and an observer who follows the direction of the incident light cannot observe any reflected light in the visible light spectrum. The display unit  100  is now “closed”.  
         [0009]      FIG. 3A  to  FIG. 3B  illustrate a method for manufacturing a conventional display cell. Referring to  FIG. 3A , a first electrode  110  and a sacrificial layer  111  are formed in sequence on a transparent substrate  109 , and opening  112 , which is suitable for forming a supporter therein, is formed in the first electrode  110  and the sacrificial layer  111 . Then, a supporter  106  is formed in the opening  112 . Next, an electrode  114  is formed on the sacrificial layer  111  and the supporter  106 , Subsequently, referring to  FIG. 3B , the sacrificial layer  111  shown in  FIG. 3A  is removed by a release etching process to form a cavity  116 , which is located in the position of the sacrificial layer  111 , and the length D of the cavity  116  is the thickness of the sacrificial layer  111 .  
         [0010]     In a micro electro mechanical process, a micro suspended structure is fabricated by using a sacrificial layer. A suspended movable microstructure is fabricated by a selective etching between a device structure layer and the sacrificial layer to remove the sacrificial layer and leave the structure layer, and this process is called a structure release etching. The difference between the structure release etching process and an IC process is that in the structure release etching process, the selective etching is an isotropic etching, so that an undercut or an under etching is formed in the structure layer for smooth separation of the structure layer and the substrate.  
         [0011]     No matter the wet structure release process or the dry structure release process is used, the choices of the material of the sacrificial layer and the micro suspended structure should be restricted, that is, the material used should have high etching-selectivity in the etching process or else the goal of removing the sacrificial layer without etching the micro suspended structure can not be achieved. Therefore, it is impossible to use the same material in both sacrificial layer and the micro suspended structure in the present process.  
         [0012]     In the process of the optical interference display cell, some materials, such as molybdenum, are very suitable to form the sacrificial layer and the movable electrodes. However, in the structure and the process of the conventional optical interference display cell, molybdenum cannot be the material of forming both sacrificial layer and the micro suspended structure at the same time. Thus results in enormous limits in choosing the materials.  
         [0013]     Furthermore, the aforementioned movable electrode is generally a membrane that is usually metal. The thickness of the movable electrode is so small that the quality of the metal membrane is easily worsen because of the oxidation caused by the contact with air or moisture. Thus would affect the optical interference display cell. Accordingly, how to provide a new structure and the manufacturing method thereof of an optical interference display cell to broaden the choices of process materials and to protect the movable electrode from the oxidation caused by the air or moisture has become a very important issue.  
       SUMMARY OF THE INVENTION  
       [0014]     Hence, an object of the present invention is to provide a structure of a micro electro mechanical system, suitable in an optical interference display cell, wherein the materials of the sacrificial layer and the suspended movable micro structure are not needed to restrict in the materials with high etching selectivity.  
         [0015]     An alternative objective of the present invention is to provide a structure of a micro electro mechanical system, suitable in an optical interference display cell, wherein a protection layer is added between the sacrificial layer and the suspended movable micro structure and the materials of forming the protection layer and the sacrificial layer have high etching selectivity.  
         [0016]     Another objective of the present invention is to provide a structure of a micro electro mechanical system, suitable in an optical interference display cell, wherein the materials of the sacrificial layer and the suspended movable microstructure are the same.  
         [0017]     Still another objective of the present invention is to provide a structure of a micro electro mechanical system, suitable in an optical interference display cell, wherein the materials of the sacrificial layer and the suspended movable microstructure can be the materials with not-high etching selectivity.  
         [0018]     Still another objective of the present invention is to provide a structure of a micro electro mechanical system, suitable in an optical interference display cell, wherein a protection layer covers the suspended movable microstructure and the materials of forming the protection layer and the sacrificial layer have high etching selectivity and will protect the suspended movable microstructure from the etching of the air and moisture.  
         [0019]     Still another objective of the present invention is to provide a structure of a micro electro mechanical system suitable in an optical interference display cell and suitable to manufacture the structure of a micro electro mechanical system with the aforementioned protection layer.  
         [0020]     According to the aforementioned objectives, in one preferred embodiment of the present invention, an optical interference display cell is taken as an example to explain how the present invention is used on the structure of a micro electro mechanical system. An optical interference display cell comprises a first electrode and a second electrode, and there are a supporter and a sacrificial layer therein, wherein the second electrode is movable. There is a protection layer between the second electrode and the sacrificial layer. The materials used in the sacrificial layer and the protection layer have high etching selectivity. There are no limits in choosing the materials used in the sacrificial layer and the second electrode, but the material of the second electrode needs to be a conductor.  
         [0021]     In the process of removing the sacrificial layer through a structure release etch process, the etching plasma has high selectivity in the sacrificial layer and the protection layer, so only the sacrificial layer will be removed. Hence, there are no limits in choosing the materials used in the sacrificial layer and the second electrode.  
         [0022]     According to the aforementioned objectives of the present invention, in another preferred embodiment of the present invention, another optical interference display cell is taken as an example that a protection layer is used to cover a suspended movable micro structure (a movable electrode). The materials of forming the protection layer and the sacrificial layer have high etching selectivity and will protect the suspended movable microstructure from the etching of the air and moisture. An optical interference display cell comprises a first electrode and a second electrode, and there are a supporter and a sacrificial layer therein, wherein the second electrode is movable. A protection layer covers the second electrode. The materials used in the sacrificial layer and the protection layer have high etching selectivity. There are no limits in choosing the materials used in the sacrificial layer and the second electrode, but the material of the second electrode needs to be a conductor.  
         [0023]     In the process of removing the sacrificial layer through a structure release etch process, the etching plasma has high selectivity in the sacrificial layer and the protection layer, so only the sacrificial layer will be removed. Hence, there are no limits in choosing the materials used in the sacrificial layer and the second electrode. Besides, the protection layer covers the second electrode and keeps it from exposing to the air, and further avoids the second electrode from the damage of the oxygen and moisture in the air.  
         [0024]     According to the structure of a micro electro mechanical system and the manufacturing method thereof disclosed in the present invention, the choosing of the materials used in the protection layer between the second electrode and the sacrificial layer are not restricted in the materials of high etching selectivity, and the protection layer covering or wrapping the second electrode will protect the second electrode from the damage of the oxygen and moisture in the air. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, where:  
         [0026]      FIG. 1  illustrates a cross-sectional view of a conventional display cell;  
         [0027]      FIG. 2  illustrates a cross-sectional view of a conventional display cell after a voltage is applied;  
         [0028]      FIG. 3A  to  FIG. 3B  illustrates a method for manufacturing a conventional display cell;  
         [0029]      FIG. 4A  to  FIG. 4C  illustrates a method for manufacturing an optical interference display cell structure in accordance with the first embodiment of the present invention;  
         [0030]      FIG. 5A  to  FIG. 5D  illustrates a method for manufacturing an optical interference display cell structure in accordance with the second embodiment of the present invention; and  
         [0031]      FIG. 6A  to  FIG. 6D  illustrates a method for manufacturing an optical interference display cell structure in accordance with the third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]     In order to make the illustration of a structure of a micro electro mechanical system and a method for manufacturing the same provided in the present invention more clear, an embodiment of the present invention herein takes an optical interference display cell structure and a manufacturing method thereof for example, to illustrate how to apply the structure of the structure release and the method for manufacturing the same disclosed in the present invention, and to further explain advantages of the present invention according to the disclosure of the embodiment.  
       The First Embodiment  
       [0033]      FIG. 4A  to  FIG. 4C  illustrates a method for manufacturing an optical interference display cell structure in accordance with an embodiment of the present invention. Please referring to  FIG. 4A , a first electrode  402  and a sacrificial layer  406  are formed on a transparent substrate  401  in sequence. The material of the sacrificial layer  406  can be transparent material, such as dielectric material, or opaque material, such as metal material. The opening  408 , suitable for forming a supporter therein, is formed in the first electrode  402  and the sacrificial layer  406  by a photolithography process.  
         [0034]     Then, a material layer  410  is formed on the sacrificial layer  406  to fill up the opening  408 . The material layer  410  is suitable for forming the supporter, and the material layer  410  is generally made of photosensitive materials such as photoresists, or non-photosensitive polymer materials such as polyester, polyamide etc. If non-photosensitive materials are used for forming the material layer  410 , a photolithographic etching process is required to define supporters in the material layer  410 . In this embodiment, the photosensitive materials are used for forming the material layer  410 , so merely a photolithography process is required for patterning the material layer  410 . In the embodiment, the materials suitable for forming the material layer  410  comprise positive photoresists, negative photoresists, and all kinds of polymers, such as acrylic resins, epoxy resins etc.  
         [0035]     Please referring to  FIG. 4B , supporters  412  are defined by patterning the material layer  410  through a photolithography process. Next, a material layer  414  is formed on the sacrificial layer  406  and the supporters  412 . Then, a conductor layer  404  is formed on the material layer  414 . The materials used in the material layer  414  and the sacrificial layer  406  have high etching selectivity. While the sacrificial layer  406  uses metal material, the material layer  414  uses dielectric material, such as silicon oxide, silicon nitride, or transparent conductor material, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (IO), or macromolecule polymer. While the sacrificial layer  406  uses silicon material, such as poly-silicon or amorphous silicon, the material layer  414  uses metal silicon oxide, or macromolecule polymer.  
         [0036]     Please refer to  FIG. 4C . The conductor layer  404  and the material layer  414  not yet covered by a photoresist layer (not shown in the drawing) is etched through a photolithography process and the second electrode  405  of every optical interference display cell is defined, wherein the second electrode  405  is movable. Finally, the sacrificial layer is removed through a structure release etch process, and a cavity  416  is formed. The material layer  414  is a protection layer. While the material of the material layer  414  is conductor material, it can also be the conductor part of the second electrode  405 .  
         [0037]     The optical interference display cell manufactured through the aforementioned process is illustrated in  FIG. 4C . An optical interference display cell  400 , which can be a color-changeable pixel unit, comprises a first electrode  402  and a second electrode  405 , wherein the first electrode  402  and the second electrode  405  are set approximately in parallel. The first electrode  402  and the second electrode  405  are chosen from the group consisting of narrowband mirrors, broadband mirrors, non-metal mirrors, metal mirrors and any arbitrary combination thereof.  
         [0038]     The supporters  412  support the first electrode  402  and the second electrode  405 , and a cavity  416  is formed therein. The second electrode  405  comprises the conductor layer  404  and the material layer  414 . The length of the cavity in the conventional optical interference display cell is the thick of the sacrificial layer, and the sacrificial layer is removed through a structure release process and then the cavity  416  is formed. In the embodiment, the material layer  414  of the second electrode  405  can protect the conductor layer  404  in the structure release process from the injury of the etching reagent. Therefore, when choosing the materials for the sacrificial layer and the second electrode, there is no need to restrict the material within the material with high etching selectivity. Hence, the chosen in materials is broader.  
       The Second Embodiment  
       [0039]      FIG. 5A  to  FIG. 5D  illustrate a method for manufacturing an optical interference display cell structure in accordance with an alternative embodiment of the present invention. Please referring to  FIG. 5A , a first electrode  502  and a sacrificial layer  506  are formed on a transparent substrate  501  in sequence. The material of the sacrificial layer  506  can be transparent material, such as dielectric material, or opaque material, such as metal material. The opening  508 , suitable for forming a supporter therein, is formed in the first electrode  502  and the sacrificial layer  506  by a photolithography process.  
         [0040]     Then, a material layer  510  is formed on the sacrificial layer  506  to fill up the opening  508 . The material layer  510  is suitable for forming the supporter, and the material layer is generally made of photosensitive materials such as photoresists, or non-photosensitive polymer materials such as polyester, polyamide etc. If non-photosensitive materials are used for forming the material layer, a photolithographic etching process is required to define supporters in the material layer  510 . In this embodiment, the photosensitive materials are used for forming the material layer  510 , so merely a photolithography process is required for patterning the material layer  510 . In the embodiment, the materials suitable for forming the material layer  510  comprise positive photoresists, negative photoresists, and all kinds of polymers, such as acrylic resins, epoxy resins etc.  
         [0041]     Please referring to  FIG. 5B , supporters  512  are defined by patterning the material layer  510  through a photolithography process. Next, a material layer  514  is formed on the sacrificial layer  506  and the supporters  512 . Then, a conductor layer  504  is formed on the material layer  514 . The materials used in the material layer  514  and the sacrificial layer  506  have high etching selectivity. While the sacrificial layer  506  uses metal material, the material layer  514  uses dielectric material, such as silicon oxide, silicon nitride, or transparent conductor material, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (IO), or macromolecule polymer. While the sacrificial layer  506  uses silicon material, such as poly-silicon or amorphous silicon, the material layer  514  uses metal silicon oxide, or macromolecule polymer.  
         [0042]     Please refer to  FIG. 5C . The conductor layer  504  and the material layer  514  not yet covered by a photoresist layer (not shown in the drawing) is etched through a photolithography process and the second electrode  505  of every optical interference display cell is defined, wherein the second electrode  505  is movable. Next, a material layer  518  is formed to cover the second electrode  504 . The material forming the material layer  518  is selected from the group comprising silicon material, dielectric material, transparent conductor, macromolecule polymer or metal oxide, wherein the silicon material can be poly-silicon or amorphous silicon, such as silicon oxide, silicon nitride, silicon oxynitride or transparent conductor material, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (IO), or macromolecule polymer, such as paraffin or macromolecule material which can be coated by vapor. The material layer  514  and  518  are protection layers. While the materials of the material layer  514  and  518  are conductor material, they can also be the conductor parts of the second electrode  505 .  
         [0043]     Please refer to  FIG. 5D . Through a photolithography process, the material layer  518  is patterned and part of the material layer  518  on the supporters  512  is removed. It is to achieve the goal that the sacrificial layer  506  as shown in  FIG. 5C  can be laterally etching through the openings by the etching reagent in the following structure release etch process. Finally, the sacrificial layer is removed through the structure release etch process, and a cavity  516  is formed.  
         [0044]     The optical interference display cell manufactured through the aforementioned process is illustrated in  FIG. 5C . An optical interference display cell  500 , which can be a color-changeable pixel unit, comprises a first electrode  502  and a second electrode  505 , wherein the first electrode  502  and the second electrode SOS are set approximately in parallel. The first electrode  502  and the second electrode SOS are chosen from the group consisting of narrowband mirrors, broadband mirrors, non-metal mirrors, metal mirrors and any arbitrary combination thereof.  
         [0045]     The supporters  512  support the first electrode  502  and the second electrode  505  and a cavity  516  is formed therein. The second electrode  505  comprises the conductor layer  504 , the material layer  514  and the material layer  518 , wherein the material layer  514  and the material layer  518  cover the conductor layer  504 . The length of the cavity in the conventional optical interference display cell is the thick of the sacrificial layer, and the sacrificial layer is removed through a structure release process and then the cavity  516  is formed. In this embodiment, the material layer  518  and the material layer  514  of the conductor layer  504  of the second electrode  505  can protect the conductor layer  504  in the structure release process from the injury of the etching reagent. Therefore, when choosing the materials for the sacrificial layer and the second electrode, there is no need to restrict the material within the material with high etching selectivity. Hence, the chosen in materials is broader. Besides, the material layer  514  and the material layer  518  will further protect the conductor layer  504  from the oxidation and etching of the oxygen and the moisture in the air.  
       The Third Embodiment  
       [0046]      FIG. 6A  to  FIG. 6D  illustrate a method for manufacturing an optical interference display cell structure in accordance with another embodiment of the present invention. Please referring to  FIG. 6A , a first electrode  602  and a sacrificial layer  606  are formed on a transparent substrate  601  in sequence. The material of the sacrificial layer  606  can be transparent material, such as dielectric material, or opaque material, such as metal material. The opening  608 , suitable for forming a supporter therein, is formed in the first electrode  602  and the sacrificial layer  606  by a photolithography process.  
         [0047]     Then, a material layer  610  is formed on the sacrificial layer  606  to fill up the opening  608 . The material layer  610  is suitable for forming the supporter, and the material layer is generally made of photosensitive materials such as photoresists, or non-photosensitive polymer materials such as polyester, polyamide etc. If non-photosensitive materials are used for forming the material layer, a photolithographic etching process is required to define supporters in the material layer  610 . In this embodiment, the photosensitive materials are used for forming the material layer  610 , so merely a photolithography process is required for patterning the material layer  610 . In the embodiment, the materials suitable for forming the material layer  610  comprise positive photoresists, negative photoresists, and all kinds of polymers, such as acrylic resins, epoxy resins etc.  
         [0048]     Please referring to  FIG. 6B , supporters  612  are defined by patterning the material layer  610  through a photolithography process. Next, a material layer  614  is formed on the sacrificial layer  606  and the supporters  612 . Then, a conductor layer  604  and a material layer  616  are formed in order on the material layer  614 . The materials used in the material layer  614  and the material layer  616  and the material used in the sacrificial layer  606  have high etching selectivity. While the sacrificial layer  506  uses metal material, the material layer  614  and the material layer  616  use dielectric material, such as silicon oxide, silicon nitride, silicon oxynitride, or transparent conductor material, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (IO), or macromolecule polymer, such as paraffin or macromolecule material which can be coated by vapor. While the sacrificial layer  606  uses silicon material, such as poly-silicon or amorphous silicon, the material layer  614  and the material layer  616  use metal silicon oxide, or macromolecule polymer.  
         [0049]     Please refer to  FIG. 6C . The conductor layer  604 , the material layer  614  and the material layer  616  not yet covered by a photoresist layer (not shown in the drawing) are etched through a photolithography process and the second electrode  605  of every optical interference display cell is defined, wherein the second electrode  605  is movable. Next, a material layer  618  is formed to cover the conductor layer  604 , the material layer  614  and the material layer  616 . The material forming the material layer  618  is selected from the group comprising silicon material, dielectric material, transparent conductor, macromolecule polymer or metal oxide, wherein the silicon material can be poly-silicon or amorphous silicon, such as silicon oxide, silicon nitride, silicon oxynitride or transparent conductor material, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (IO), or macromolecule polymer, such as paraffin or macromolecule material which can be coated by vapor.  
         [0050]     Please refer to  FIG. 6D . The material layer  618  is etched through a self-aligned etching process. The spacer  618   a  is formed on the sidewalls of the second electrode  604 , and the sacrificial layer  606  under the material layer  614  is exposed. Finally, the sacrificial layer is removed through the structure release etch process, and a cavity  616  is formed. The material layer  614 , the material layer  616  and the spacer  618   a  are protection layers. While the materials of the material layer  614 , the material layer  616  and the spacer  618   a  are conductor materials, they can also be the conductor parts of the second electrode  605 .  
         [0051]     The optical interference display cell manufactured through the aforementioned process is illustrated in  FIG. 6C . An optical interference display cell  600 , which can be a color-changeable pixel unit, comprises a first electrode  602  and a second electrode  605 , wherein the first electrode  602  and the second electrode  605  are set approximately in parallel. The first electrode  602  and the second electrode  605  are chosen from the group consisting of narrowband mirrors, broadband mirrors, non-metal mirrors, metal mirrors and any arbitrary combination thereof.  
         [0052]     The supporters  612  support the first electrode  602  and the second electrode  605  and a cavity  620  is formed therein. The second electrode  605  comprises the conductor layer  604 , the material layer  614 , the material layer  616  and the spacer  618   a , wherein the conductor layer  604  is covered by the material layer  614 , the material layer  616  and the spacer  618   a . The length of the cavity in the conventional optical interference display cell is the thick of the sacrificial layer, and the sacrificial layer is removed through a structure release process and then the cavity  620  is formed. In this embodiment, the material layer  618 , the material layer  614  and the spacer  618   a  of the conductor layer  604  and the side walls can protect the conductor layer  604  of the second electrode  605  in the structure release process from the injury of the etching reagent. Therefore, when choosing the materials for the sacrificial layer and the second electrode, there is no need to restrict the material within the material with high etching selectivity. Hence, the chosen in materials is broader. Besides, the material layer  614 , the material layer  618  and the spacer  618   a  will further protect the conductor layer  604  from the oxidation and etching of the oxygen and the moisture in the air.  
         [0053]     The manufacturing method of the optical interference display cell disclosed in the third embodiment has another advantage that only one mask is needed to produce the second electrode. The decrease of one mask not only accelerates the process but also decreases the cost.  
         [0054]     The thick of the material layer used to protect the suspended movable microstructure disclosed in the present invention is decided according to the demands. There are also no limits in the thick of the material layer used to protect the suspended movable microstructure in the two embodiments. It depends on the size of the optical interference display cell. Generally speaking, the thick of the material layer in the embodiments of the present invention is about several angstroms to 2000 angstrom, preferably about 200 angstrom to 1000 angstrom.  
         [0055]     As is understood by a person skilled in the art, the foregoing embodiments of the present invention are illustrative of the present invention rather than limiting of the present invention. The structure of a micro electro mechanical system and the method for manufacturing the same disclosed in the present invention can be applied in various micro electro mechanical structure systems. It is intended that various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.