Abstract:
A color filter of a liquid crystal on silicon (LCOS) display device is disclosed, including a substrate including a plurality of pixel regions wherein each pixel region includes a first color dot, a second color dot and a third color dot; and a first color resist, a second color resist and a third color resist disposed in the first color dot, the second color dot and the third color dot on the substrate, wherein each of the first color resist, the second color resist and the third color resist includes at least one opening.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to a liquid crystal on silicon (LCOS) display device and more particularly to a color filter of a liquid crystal on silicon (LCOS) display device. 
     2. Description of the Related Art 
     As technology develops, electronic devices with display panels are widely applied in many fields. Important features that a customer especially looks for in an electronic device include color quality and resolution of the display panel attached thereto. Among different types of display panels, a liquid crystal on silicon (LCOS) display panel has good resolution and therefore is commonly used in many kinds of electronic devices. 
     Liquid crystal on silicon (LCOS) is a “micro-projection” or “micro-display” technology typically applied in projection apparatuses. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors. By way of comparison, LCD projectors use transmissive LCD chips, allowing light to pass through the liquid crystal. In LCOS, liquid crystals are applied directly to the surface of a silicon chip coated with an aluminized layer, with some type of passivation layer, which is highly reflective. 
     LCOS technology can typically produce higher resolution and higher contrast images than standard liquid crystal display and plasma display technologies, which makes it less expensive to implement in such devices as televisions. 
     In order to display colorful images, an LCOS display device usually includes a color filter layer disposed on the side of a silicon substrate. The color filter layer is between the alignment layer and the silicon substrate and includes color dots of different colors for displaying all kinds of colors. However, given conventional technology, transmittance of LCOS display devices is not fully maximized. A new LCOS display device which has high transmittance and meets national television standard committee (NTSC) specifications is required. 
     BRIEF SUMMARY OF INVENTION 
     The invention provides a color filter of a liquid crystal on silicon (LCOS) display device, comprising a substrate comprising a plurality of pixel regions wherein each pixel region comprises a first color dot, a second color dot and a third color dot and a first color resist, a second color resist and a third color resist disposed in the first color dot, the second color dot and the third color dot on the substrate, wherein each of the first color resist, the second color resist and the third color resist comprises at least one opening. 
     The invention provides a method for forming a color filter of a liquid crystal on silicon (LCOS) display device, comprising providing a substrate, forming a first color resist on the substrate, patterning the first color resist to form a first color dot, wherein the first color resist comprises an opening in the first color dot, forming a second color resist on the substrate and the first color resist, patterning the second color resist to form a second color dot, wherein the second color resist comprises an opening in the second color dot, forming a third color resist on the substrate and the first and the second color resists, and patterning the third color resist to form a third color dot, wherein the third color resist comprises an opening in the third color dot. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein, 
         FIG. 1A  shows a plan view of a color filter of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention. 
         FIG. 1B  shows a cross section of a color filter of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention. 
         FIGS. 2A˜2I  show fabrications of a color filter of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     It is understood that specific embodiments are provided as examples to teach the broader inventive concept, and one of ordinary skill in the art can easily apply the teaching of the present disclosure to other methods or apparatus. In addition, it is understood that the methods and device discussed in the present disclosure include some conventional structures and/or processes. Since these structures and processes are well known in the art, they will only be discussed in a general level of detail. Furthermore, reference numbers are repeated throughout the drawings for sake of convenience and example, and such repetition does not indicate any required combination of features or steps throughout the drawings. Moreover, the formation of a first feature over and on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. 
       FIG. 1A  shows a plan view of a color filter  102  of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention.  FIG. 1B  shows a cross section of a color filter  102  of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention. It is noted that  FIGS. 1A and 1B  only show one pixel region  112  for simplicity, and the color filter  102  can comprise a plurality of arranged pixel regions  112 . Referring to  FIGS. 1A and 1B , a color filter  102  is provided, wherein a pixel region  112  of the color filter  102  comprises a first color dot  104 , a second color dot  106  and a third color dot  108  on a substrate  100 , made of material such as silicon. Many other active or passive devices, elements or layers may be formed on the substrate  100 . However, these devices, elements or layers are not shown for simplicity. In an embodiment, the first color is red, the second color is green and the third color is blue. Furthermore, the first, second and third color dots  104 ,  106 ,  108  comprise a first color resist  105 , a second color resist  107  and a third color resist  109 , respectively. In an important feature of the embodiment, each of the first color resist  105 , the second color resist  107  and the third color resist  109  in the first, second and third color dots  104 ,  106 ,  108  comprises an opening  110 , and transmittance of the color filter  102  of the embodiment can be increased due to the openings  110  in the dots. The openings  110  can be regarded as slits, wherein light passes the color filter  102  to generate diffraction and this diffraction can increase transmittance of the color filter  102 . As shown in  FIG. 1A , the openings  110  are rectangular shaped in an embodiment of the invention. The invention, however, is not limited thereto. The openings  110  can be circular shaped, cross shaped or other suitable shapes. It is noted that the color filter  102  of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention has higher transmittance than prior art and meets national television standard committee (NTSC) specifications. 
       FIGS. 2A˜2I  show fabrication of a color filter of a liquid crystal on silicon (LCOS) display device of an embodiment of the invention. Referring to  FIG. 2A , a substrate  202  is provided. In an embodiment of the invention, the substrate  202  is a semiconductor substrate, made up of material such as silicon. Next, a first color resist  204  is coated on the substrate  202 . In an embodiment, the first color is red and the first color resist  204  is a positive resist. Alternatively, the first color can be another color and the first color resist  204  can be a negative resist. Next, referring to  FIG. 2B , an exposure step is performed to the first color resist  204  with light passing through a first mask  206 . Referring to  FIG. 2C , a development step is performed to remove the exposed portions of the first color resist  204  and thus a first color dot  208  comprising an opening  210  is formed. Referring to  FIG. 2D , a second color resist  212  is coated on the substrate  202 . In an embodiment, the second color is green and the second color resist  212  is a positive resist. Alternatively, the second color can be another color and the second color resist  212  can be a negative resist. Next, referring to  FIG. 2E , an exposure step is performed to the second color resist  212  with light passing through a second mask  214 . Referring to  FIG. 2F , a development step is performed to remove the exposed portions of the second color resist  212 , and thus a second color dot  216  comprising an opening  218  is formed neighboring the first color dot  208 . Referring to  FIG. 2G , a third color resist  220  is coated on the substrate  202 . In an embodiment, the third color is blue and the third color resist  220  is a positive resist. Alternatively, the third color can be another color and the third color resist  220  can be a negative resist. Next, referring to  FIG. 2H , an exposure step is performed to the third color resist  220  with light passing through a third mask  222 . Referring to  FIG. 2I , a development step is performed to remove the exposed portions of the third color resist  220 , and thus a third color dot  224  comprising an opening  226  is formed neighboring the second color dot  216 . 
     According to the description above, the color filter of a liquid crystal on silicon (LCOS) display device of embodiments of the invention can provide advantages as follows. First, transmittance of the color filter of a liquid crystal on silicon (LCOS) display device provided by an embodiment of the invention can be increased 15%˜30% and the LCOS display device meets NTSC specifications. Second, process for fabricating the color filter does not have to be changed, wherein only layout of patterns of the mask for defining the color resists have to be modified for the color dots to comprise openings. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. It is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.