Abstract:
A photosensitive structure and method of fabricating the same. A substrate with at least an insulator layer formed thereon is provided. The insulator layer comprises a plurality of photoreceiving regions, and a plurality of conductive patterns are formed thereon without covering the photoreceiving regions. A dielectric layer is formed on the insulator and the conductive patterns, and polished by CMP.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a semiconductor device fabrication, and more particularly to a method for forming a photosensitive device with color filter.  
         [0003]     2. Description of the Related Art  
         [0004]     FIGS.  1  are schematic representations of structures in the final stages of formation of a photosensitive device using conventional technology. Referring to  FIG. 1A , a planarized inter-metal dielectric layer  100  with a photoreceiving region  130  therein is formed on a substrate (not shown). A metal layer  114  is deposited and defined to expose the photoreceiving region  130  on the inter-metal dielectric layer  100 , and a protective layer  150  is formed thereon.  
         [0005]     Referring to  FIG. 1B , a thick planar film  152 , for example spin-on glass, is coated on a protective layer  150  for planarization. The planar film  152  and protective layer  150  are transparent for enhancing light sensitivity of the photosensitive device. A color filter process, comprising coating R, G, and B filters, development, etching and top coating, is then performed to form color filter  112 . Next, another protective layer  120  is coated thereon to cover the color filter  112  and planar film  152 .  
         [0006]     The coated planar film  152  described cannot effectively fill in some concave areas of the photosensitive device to produce a flat surface over the entire wafer surface. Additionally, the planar film  152  must achieve a thick thickness, about 2 μm, to produce a flat surface. Shrinkage, however, may be generated, affecting flatness of the surface of the planar layer  152 . The uneven layer  152  under the color filter  112  may diminish color performance of the device. Due to the unevenly coated dielectric layer  152 , a yellow strip may occur in the step height regions, for example the regions near the bonding pads or the scribe lines.  
       SUMMARY OF THE INVENTION  
       [0007]     Embodiments of the invention achieve technical advantages by providing a chemical mechanical polishing (CMP) process in the fabrication of a photosensitive device.  
         [0008]     In accordance with an embodiment of the invention, a method for fabricating a photosensitive device comprises the following steps. A substrate with at least an insulator layer formed thereon is provided. The insulator layer comprises a plurality of photoreceiving regions, and a plurality of conductive patterns are formed thereon without covering the photoreceiving regions. A dielectric layer is formed on the insulator and the conductive patterns, and polished by CMP thereof.  
         [0009]     In accordance with an embodiment of the invention, a photosensitive device comprises the following elements, at least an insulator layer comprising a plurality of photoreceiving regions is disposed on a substrate, a plurality of conductive patterns are disposed on the insulator layer without covering the photoreceiving regions, a dielectric layer with a flat surface is disposed on the conductive patterns and the insulator layer, wherein the dielectric layer has a thickness of 2000 Å˜4000 Å on the conductive patterns.  
         [0010]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Embodiments of the present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0012]      FIGS. 1A  to  1 B are schematic representations of structures in the final stages during the formation of the photosensitive device using conventional technology;  
         [0013]      FIGS. 2A  to  2 D illustrate the fabrication method of a photosensitive device of an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      FIGS. 2A  to  2 D illustrate the fabrication method of a photosensitive device of an embodiment of the invention. Referring to  FIG. 2A , a substrate, useful in forming a layered semiconductor device, is shown wherein an insulator layer  200  thereof comprises a photoreceiving region  202 . This insulator layer  200  is the final inter-metal dielectric layer formed in photosensitive device. The photoreceiving region  202  is a light-receiving region and will have a converter (not shown in the figures) to transfer light into current. Hence, the material of this insulator layer  200  is transparent and can be made from any typical and well-known dielectric material used in sensor device, but is preferably silicon oxide.  
         [0015]     A conductive layer (not shown) is deposited on the partially fabricated device. The material of this layer can be A 1  and formed using any known technique such as reactive sputtering process (with or without collimation) wherein sputtering is carried out in an Ar+N2 atmosphere using an A 1  target. The thickness of this conductive layer can be in the range of about 8000 Å to about 10000 Å. The conductive layer is patterned to expose the described photoreceiving region  202 . The patterned conductive layer refers to conductive patterns  204  described later in this specification. The conductive patterns  204  can comprise conductive lines in cell regions, bonding pads or test pads with large step height in the periphery regions or scribe lines.  
         [0016]     Referring to  FIG. 2B , a dielectric layer  206  is formed on the insulator layer  200  and the conductive patterns  204 . In this embodiment, the dielectric layer  206  is formed of transparent materials, for example silicon oxide or silicon oxynitride, thus the device is photosensitive. The dielectric layer  206  can be deposited by any deposition method, such as chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), or high density plasma enhanced chemical vapor deposition (HDP). Preferably, the dielectric layer  206  comprises a first dielectric layer deposited by HDP to 1000 Å˜2000 Å and a second dielectric layer deposited by PECVD to 7000 Å˜10000 Å, thus increasing the gap filling. The thickness of the deposited dielectric layer  206  depends on the step height of the underlying conductive patterns  204 , in which a gap between two conductive patterns  204  must be filled. The dielectric layer  206  formed of silicon oxide can further comprise a silicon nitride layer deposited thereon to protect the underlying photosensitive device.  
         [0017]     Referring to  FIG. 2C , the dielectric layer  206  is polished to have a uniformly flat surface  208  over the entire wafer surface. In a preferred embodiment, the dielectric layer  206  is polished by chemical mechanical polishing (CMP). Dielectric layer  206 , formed of silicon oxide, can be polished using fumed silica as slurry. In addition, the dielectric layer  206  comprising a silicon nitride layer thereon, colloidal silica can be used as slurry during polishing. The polished dielectric layer  206  preferably has a flat surface higher than the conductive pattern in a range between 2000 Å to 4000 Å.  
         [0018]     Referring to  FIG. 2D , a color filter process is performed using photo resist to form R, G and B color filter layers ( 210 R,  210 G and  210 B) respectively, and a upper planar layer  212  is coated thereon. A micro lens  214  is formed on the upper planar layer  212  by coating and defining an organic thin film, and a protective layer  216  is formed thereon.  
         [0019]      FIG. 2D  illustrates a photosensitive device of the embodiment. As shown in  FIG. 2D , an insulator layer  200  comprising a plurality of photoreceiving regions  202  is formed on a substrate (not shown). A plurality of conductive patterns  204  is disposed on the insulator layer  200  without covering the photoreceiving regions  202 . A dielectric layer  206  with a flat surface is disposed on the insulator layer  200  and the conductive patterns  204 , and surface of the dielectric layer  206  is higher than the conductive patterns  204  in the range between 2000 Å to 4000 Å. The dielectric layer  206  is formed of transparent materials, such as silicon oxide or silicon oxynitride, thus the device is photosensitive. A color filter layer  210 , an upper dielectric layer  212 , a micro lens  214 , and a protective layer  216  are disposed on the dielectric layer  206  in order.  
         [0020]     Consequently, the dielectric layer  206  planarized by CMP is flatter than the planar layer formed by a conventional coating method. Specifically, due to the flat dielectric layer  206  achieved by CMP, yellow strips occurring in the conventional technology are ameliorated. Further, since the dielectric layer is planarized by CMP instead of coating a very thick film, better sensitivity and transmittance of photosensitive devices can be achieved.  
         [0021]     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. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of thee appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.