Abstract:
A method for fabricating a color filter structure includes: providing a base layer; forming a first colored layer on the base layer; patterning the first colored layer to form a pair of first colored patterns, a first opening between the first colored patterns, and a second opening adjacent to the first colored patterns; forming a first dielectric layer on the first colored patterns and the base layer exposed by the first and second openings; forming a second colored layer on the first colored patterns and the first dielectric layer; patterning the second colored layer to form a second colored pattern in the first opening; forming a second dielectric layer on the first dielectric layer and the second colored pattern; forming a third colored layer on the second dielectric layer; and patterning the third colored layer to form a third colored pattern in the second opening.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to image sensing devices, and more particularly to a color filter structure having improved resolution and reduced cross-talk issues for an image sensing device. 
         [0003]    2. Description of the Related Art 
         [0004]    Image sensors are necessary components in many optoelectronic devices, including digital cameras, cellular phones, and toys. Conventional image sensors include both charge coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors. An image sensor typically includes a plane array of pixel cells, wherein each pixel cell comprises a photogate, photoconductor or a photodiode having a doped region for accumulating a photo-generated charge. 
         [0005]    In addition, a periodic pattern of different colors is superimposed over the plane array of pixel cells. This periodic pattern of different colors is known as a color filter array (CFA). The periodic pattern of different colors is typically made of I-line photosensitive materials such as dye-type photosensitive materials or pigment-type photosensitive materials, such that formation of the periodic pattern of different colors is typically achieved by photolithography processes. The pigment-type photosensitive materials, however, show poor resolution performance in the photolithography processes when compared with the dye-type photosensitive materials. The dye-type photosensitive materials, however, show poor chemical duration in the photolithography processes when compared with the pigment-type photosensitive materials. Therefore, accurate definition of the periodic pattern in the color filter array, however, is problematic and becomes more critical as a size thereof is further reduced to, for example, a sub-micron size. Moreover, the resolution limitation of I-line photolithography tools for performing the photolithography processes to the I-line photosensitive materials of the color filter array is also limited as a size thereof is further reduced to, for example, a sub-micron size. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    Therefore, a method for fabricating a color filter structure having improved resolution and alignment accuracy for an image sensing device is provided. 
         [0007]    An exemplary method for fabricating a color filter structure comprises: providing a base layer; forming a first colored layer on the base layer; patterning the first colored layer to form a pair of first colored patterns on the base layer, a first opening between the pair of first colored patterns, and a second opening adjacent to the pair of the first colored patterns; forming a first dielectric layer on the pair of the first colored patterns and the base layer exposed by the first and second openings; forming a second colored layer on the pair of first colored patterns and the first dielectric layer; patterning the second colored layer to form a second colored pattern in the first opening; forming a second dielectric layer on the first dielectric layer and the second colored pattern; forming a third colored layer on the second dielectric layer; and patterning the third colored layer to form a third colored pattern in the second opening. 
         [0008]    Another exemplary method for fabricating a color filter structure comprises: (a) forming a dielectric layer; (b) forming a colored layer over the dielectric layer; (c) forming a hard mask pattern over the colored layer; (d) patterning the colored layer by the hard mask pattern to form a colored pattern; (e) removing the hard mask pattern; (f) repeating steps (a)-(e); and repeating steps (a)-(e). 
         [0009]    A color filter structure with improved resolution and alignment accuracy for an image sensor is also provided. An exemplary color filter structure comprises: a pair of first colored patterns; a second colored pattern between the pair of first colored patterns; a third colored pattern adjacent to the pair of first colored patterns; a first dielectric layer on the pair the first colored patterns; and a second dielectric layer on the first dielectric layer and the second colored pattern. 
         [0010]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0012]      FIGS. 1-4  are schematic cross sections showing a method for fabricating an image sensing device according to an embodiment of the invention; 
           [0013]      FIGS. 5-9  are schematic cross sections showing a method for fabricating an image sensing device according to another embodiment of the invention; 
           [0014]      FIGS. 10-11  are schematic cross sections showing a method for fabricating an image sensing device according to yet another embodiment of the invention; and 
           [0015]      FIG. 12  is a schematic cross section showing an image sensing device according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
         [0017]      FIGS. 1-4  are schematic cross sections showing an exemplary method for fabricating an image sensing device. 
         [0018]    In  FIG. 1 , a substantially fabricated image sensing structure is first provided, including a semiconductor substrate  100 , an active layer  102  with a plurality of photo-sensing elements  104  formed therein over the substrate  100 , and a passivation layer  106  with a plurality of light shielding metals  108  formed therein formed over the active layer  102 . The photo-sensing elements  104  can be, for example, photodiodes or CMOS sensing elements, and are separately formed in the active layer  102 , and the light shielding metals  108  formed in the passivation layer  106  are formed over the active layer  102  at a place not covering the photo-sensing elements  104  to define light-shielding areas for shielding the area of the pixel except for the area of the photo-sensing elements  104 . 
         [0019]    Next, a dielectric layer  110  is formed over the passivation layer  106 . The dielectric layer  110  may be formed with a thickness less than 50 Å and may comprise materials such as silicon oxide. The dielectric layer  110  is a light transmitting layer and may have a refraction index (N) of about 1.4-1.6, and is formed by a deposition process such as chemical vapor deposition (CVD) process under a temperature not greater 200° C. Next, a colored layer  112  is formed over the dielectric layer  110 . The colored layer  112  may comprise non-photosensitive type color resists, and may be formed by, for example, spin coating. The colored layer  112  may have a thickness of about 5000-10000 Å. Next, a plurality of hard mask patterns  114  is separately formed over the colored layer  112 . The hard mask patterns  114  may comprise photosensitive materials other than I-line photosensitive materials, and are formed by a photolithography process (not shown), thereby forming the plurality of hard mask patterns  114  over the dielectric layer  110 . As shown in  FIG. 1 , the hard mask patterns  114  are formed with rectangular shapes. Next, a patterning process  116  such as dry etching process is performed to the colored layer  112 , using the hard mask patterns  114  as an etching mask. 
         [0000]    In  FIG. 2 , after the patterning process  116 , a plurality of colored patterns  112   a  are separately formed over the dielectric layer  110 , and the underlying passivation layer  106  is protected by the dielectric layer  110  and not etched during the patterning process  116 . The colored patterns  112   a  are respectively formed over one of the photo-sensing elements  104 , and every two of the colored patterns  112   a  can be divided into a sub-group. Therefore, each sub-group of the colored patterns  112  may have an opening  118  formed between the colored patterns  112   a  therein, and an opening  120  is formed between two adjacent sub-groups of the colored patterns  112   a . Next, a dielectric layer  122  is formed over the colored patterns  112   a  and the dielectric layer  110 . The dielectric layer  122  may be formed with a thickness less than 50 Å and may comprise materials such as silicon oxide. The dielectric layer  122  is a light transmitting layer and may have a refraction index (N) of about 1.4-1.6, and is formed by a deposition process such as chemical vapor deposition (CVD) process under a temperature not greater 200° C. Next, a colored layer  124  is formed over the dielectric layer  122 . The colored layer  124  may comprise non-photosensitive type color resists, and may be formed by, for example, spin coating. The colored layer  124  may have a thickness of about 5000-10000_Å. Next, a plurality of hard mask patterns  126  is separately formed over the colored layer  124 . The hard mask patterns  126  may comprise photosensitive materials other than I-line photosensitive materials, and can be formed by a photolithography process (not shown), thereby forming the plurality of hard mask patterns  126  over the colored layer  124 . The hard mask patterns  126  are formed with rectangular shapes. As shown in  FIG. 2 , the hard mask patterns  126  are respectively formed at a place substantially over the openings  118 . Next, a patterning process  128  such as dry etching process is performed to the colored layer  124 , using the hard mask patterns  126  as an etching mask. 
         [0020]    In  FIG. 3 , after the patterning process  128 , a plurality of colored patterns  124   a  are separately formed over the dielectric layer  122  and respectively formed in one of the openings  118 . The colored patterns are also respectively formed over one of the photo-sensing elements  104  thereunder. The underlying colored patterns  112   a  are not etched and are protected by the dielectric layer  122  during the patterning process  128 . Next, a dielectric layer  130  is formed over the dielectric layer  122 , covering the colored patterns  124   a . The dielectric layer  130  may be formed with a thickness less than 50 Å and may comprise materials such as silicon oxide. The dielectric layer  130  is a light transmitting layer and may have a refraction index (N) of about 1.4-1.6, and is formed by a deposition process such as chemical vapor deposition (CVD) process under a temperature not greater 200° C. Next, a colored layer  132  is formed over the dielectric layer  130 . The colored layer  132  may comprise non-photosensitive type color resists, and may be formed by, for example, spin coating. The colored layer  132  may have a thickness of about 5000-10000 Å. Next, a plurality of hard mask patterns  134  is separately formed over the colored layer  132 . The hard mask patterns  134  may comprise photosensitive materials other than I-line photosensitive materials and can be formed by a photolithography process (not shown), thereby forming the plurality of hard mask patterns  134  over the colored layer  132 . As shown in  FIG. 3 , the hard mask patterns  134  are respectively formed at a place substantially over the openings  120  and are formed of rectangular shapes. Next, a patterning process  136  such as dry etching process is performed to the colored layer  132 , using the hard mask patterns  134  as an etching mask. 
         [0021]    In  FIG. 4 , after the patterning process  136 , a plurality of colored patterns  132   a  are separately formed over the dielectric layer  130  and respectively formed in one of the openings  120 . The colored patterns  132   a  are also respectively formed over one of the photo-sensing elements  104  thereunder. The underlying colored patterns  124   a  and the dielectric layer  122  are not etched and are protected by the dielectric layer  130  during the patterning process  136 . Next, a spacer layer  130  is formed over the dielectric layer  130 , covering the colored patterns  132   a . The spacer layer  130  may be formed with a thickness of about 1000-6000 Å and may comprise materials such as silicon oxide. After formation of the spacer layer  138 , a planar top surface for sequential processing is provided, and a plurality of microlenses  140  is formed over the spacer layer  130 . Each of the microlenses substantially and vertically aligns to one of the colored patterns  112   a / 124   a / 132   a  and one of the photo-sensing elements  104  thereunder. 
         [0022]    In the above embodiment, the colored layers  112 ,  124 , and  132 , and the colored patterns  112   a ,  124   a  and  132   a  are formed of non-photosensitive type color resists and may be pigment-type color resists or dye-type color resists. The colored layers  112 ,  124 , and  132 , and the colored patterns  112   a ,  124   a  and  132   a  are formed of different colors, and may comprise different colors selected from a group consisting of green, blue and red, or from a group consisting of cyan, magenta and yellow, thereby forming an overall color mosaic matrix. The colored patterns  112   a ,  124   a  and  132   a  are patterned by the hard mask patterns  114 ,  126 , and  134  made of photosensitive materials rather than I-line photosensitive materials, such that improved resolution and alignment accuracy thereof can be achieved when compared with the directing patterning of the colored layers made of the conventional I-line photoresists. In one embodiment, the patterning processes  116 ,  128  and  136  can be, for example, a dry etching process using O 2  as an etching gas, such that undesired organic residue issues after patterning of the colored layers  112 ,  124  and  132  can be thus eliminated. In this embodiment, combination of the colored patterns  112   a ,  124   a  and  132   a , and the dielectric layers  122  and  130  provides a color filtering structure for an image sensing device, and the color filter structure is formed with improved resolution and alignment accuracy. 
         [0023]      FIGS. 5-9  are schematic cross sections showing another exemplary method for fabricating an image sensing device which is modified from the embodiment illustrated in  FIGS. 1-4 . 
         [0024]    In  FIG. 5 , a substantially fabricated image sensing structure is first provided, including a semiconductor substrate  200 , an active layer  202  with a plurality of photo-sensing elements  204  formed therein over the substrate  200 , and a passivation layer  206  with a plurality of light shielding metals  208  formed therein formed over the active layer  202 . The photo-sensing elements  204  can be, for example, photodiodes or CMOS sensing elements, and are separately formed in the active layer  202 , and the light shielding metals  208  formed in the passivation layer  206  formed over the active layer  202  at a place not covering the photo-sensing elements  204  therein to define light-shielding areas for shielding the area of the pixel except for the area of the photo-sensing elements  204 . 
         [0025]    Next, a dielectric layer  210  is formed over the passivation layer  206 . The dielectric layer  210  may be formed with a thickness less than 50 Å and may comprise materials such as silicon oxide. The dielectric layer  210  is a light transmitting layer and may have a refraction index (N) of about 1.4-1.6, and is formed by a deposition process such as chemical vapor deposition (CVD) process under a temperature not greater 200° C. Next, a colored layer  212  is formed over the dielectric layer  210 . The colored layer  212  may comprise non-photosensitive type color resists, and may be formed by, for example, spin coating. The colored layer  212  may have a thickness of about 5000-10000 Å. Next, a plurality of hard mask patterns  214  is separately formed over the colored layer  212 . The hard mask patterns  214  may comprise photosensitive materials other than I-line photosensitive materials and are formed by a photolithography process (not shown), thereby forming the plurality of hard mask patterns  214  over the dielectric layer  210 . The hard mask patterns  214  are formed with rectangular shapes. Next, a thermal process  216  such as a rapid thermal annealing (RTA) process is performed to deform a shape of the hard mask patterns  214 . 
         [0026]    In  FIG. 6 , after the thermal process  216 , a plurality of hard mask patterns  214   a  with semicircular shapes are thus formed, and a patterning process  218  such as a dry etching process is performed to the colored layer  212 , using the hard mask patterns  214   a  as an etching mask. 
         [0027]    In  FIG. 7 , after the patterning process  218 , a plurality of colored patterns  212   a  are separately formed over the dielectric layer  210 , and the underlying passivation layer  206  is protected by the dielectric layer  210  and not etched during the patterning process  218 . The colored patterns  212   a  are respectively formed over one of the photo-sensing elements  204 , and every two of the colored patterns  212   a  can be divided into a sub-group. Therefore, each sub-group of the colored patterns  212  may have an opening  220  formed between the colored patterns  212   a  therein, and an opening  222  is formed between two adjacent sub-groups of the colored patterns  212   a.    
         [0028]    In  FIG. 8 , a dielectric layer  224  is formed over the substrate  200 , covering the colored patterns  212   a  and the dielectric layer  210 . The dielectric layer  224  may be formed with a thickness less than 50 Å and may comprise materials such as silicon oxide. The dielectric layer  224  is a light transmitting layer and may have a refraction index (N) of about 1.4-1.6, and is formed by a deposition process such as chemical vapor deposition (CVD) process under a temperature not greater 200° C. Next, a plurality of colored patterns  226 , a dielectric layer  228 , and a plurality of colored patterns  230  are sequentially formed over the dielectric layer  224  by similarly repeating the processes disclosed in  FIGS. 6-7 . The colored patterns  226  and  230  are also formed with semicircular shapes, and properties and functions of the dielectric layer  228  are the same as that of the dielectric layer  224 . As shown in  FIG. 8 , the colored patterns  226  are formed in the openings  220  (shown in  FIG. 7 ) and the colored patterns  230  are formed in the openings  222  (shown in  FIG. 7 ). 
         [0029]    In  FIG. 9 , a spacer layer  232  is formed over the colored patterns  230  and the dielectric layer  228 , covering the colored patterns  230 . The spacer layer  232  may be formed with a thickness of about 1000-6000 Å and may comprise materials such as silicon oxide. After formation of the spacer layer  232 , a planar top surface for sequential processing is provided, and a plurality of microlenses  234  is formed over the spacer layer  232 . Each of the microlenses  234  substantially and vertically aligns to one of the colored patterns  212   a / 226 / 230  and one of the photo-sensing elements  204  thereunder. 
         [0030]    In this embodiment, the colored layers for forming the colored patterns  212   a ,  226  and  230  are formed of non-photosensitive type color resists and may be pigment-type color resists or dye-type color resists. The colored layers for forming the colored patterns  212   a ,  226  and  230  are formed of different colors, and may comprise different colors selected from a group consisting of green, blue and red, or from a group consisting of cyan, magenta and yellow. The colored patterns  212   a ,  226  and  230  are patterned by the hard mask patterns (e.g.  214   a ) made of photosensitive materials rather than I-line photosensitive materials, such that improved resolution and alignment accuracy thereof can be achieved when compared with directing the patterning of the colored layers made of the conventional I-line photoresists. In one embodiment, the patterning processes (e.g. the patterning process  218 ) can be, for example, a dry etching process using O 2  as an etching gas, such that undesired organic residue issues after patterning of the colored layers for forming the colored patterns  212   a ,  226  and  230  can be thus eliminated. Combination of the colored patterns  212   a ,  226  and  230 , and the dielectric layers  224  and  228  provides a color filtering structure for an image sensing device, and the color filter structure is formed with improved resolution and alignment accuracy. 
         [0031]      FIGS. 10-11  are schematic cross sections showing another exemplary method for fabricating an image sensing device which is modified from the embodiments illustrated in  FIGS. 6-9 . 
         [0032]    In  FIG. 10 , the processes shown in  FIG. 6-8  are performed and the structure shown in  FIG. 8  is first provided. Next, a dielectric layer  236  is formed over the colored patterns  230  and the dielectric layer  228 . The dielectric layer  236  may be formed with a thickness less than 50 Å and may comprise materials such as silicon oxide. The dielectric layer  236  is a light transmitting layer and may have a refraction index (N) of about 1.4-1.6, and is formed by a deposition process such as chemical vapor deposition (CVD) process under a temperature not greater 200° C. Next, a black matrix layer  238  is formed over the dielectric layer  236 . The black matrix layer  238  may be formed with a thickness of about 5000-10000 Å and may comprise light-blocking materials such non-photosensitive type color resists. The non-photosensitive type color resists of the black matrix layer  238  may be pigment-type color resists or dye-type color resists. Next, a plurality of hard mask patterns  240  are separately formed over the black matrix layer  238 . The hard mask patterns  240  may comprise photosensitive materials other than I-line photosensitive materials and can be formed by a photolithography process (not shown), thereby forming the plurality of hard mask patterns  240  over the black matrix layer  238 . As shown in  FIG. 10 , the hard mask patterns  240  are respectively formed at a place substantially over one of the light-shielding metal  208  and are formed of rectangular shapes. Next, a patterning process  242  such as a dry etching process is performed to the black matrix layer  238 , using the hard mask patterns  240  as an etching mask. 
         [0033]    In  FIG. 11 , after the patterning process  242 , a plurality of light-blocking patterns  238   a  are formed over the dielectric layer  236  at a place substantially aligned to one of the light-shielding metals  208  thereunder. Next, the processes disclosed in  FIG. 9  are performed to form the spacer layer  232  and the microlenses  234 . Each of the microlenses  234  substantially and vertically aligns to one of the colored patterns  212   a / 226 / 230  and one of the photo-sensing elements  204  thereunder. 
         [0034]      FIG. 12  is a schematic cross section showing an exemplary image sensing device formed by a method modified from that illustrated in  FIGS. 10-11 , and the patterning process  242  is a wet etching process performed to the black matrix layer  238  without using the hard mask patterns  240 . As shown, a plurality of light-blocking patterns  238   b  are formed over the dielectric layer  236  at a place substantially aligned to one of the light-shielding metals  208  thereunder. In this embodiment, the light-blocking patterns  238   b  are formed of a tapered shape rather than the substantially rectangular shape of the light-blocking patterns  238   a  shown in  FIG. 11 . 
         [0035]    In the embodiments shown in  FIGS. 5-9 ,  FIGS. 10-11 , and  FIG. 12 , the colored patterns  212   a ,  226  and  230 , and the colored layers for formation of the colored patterns  212   a ,  226  and  230 , are formed of non-photosensitive type color resists and may be pigment-type color resists or dye-type color resists. The colored patterns  212   a ,  226  and  230 , and the colored layers for forming the same are formed of different colors, and may comprise different colors selected from a group consisting of green, blue and red, or from a group consisting of cyan, magenta and yellow, thereby forming an overall color mosaic matrix. The colored patterns  212   a ,  226  and  230  are patterned by the hard mask patterns (e.g. hard mask patterns  214   a  in  FIG. 6 ) made of photosensitive materials rather than I-line photosensitive materials, such that improved resolution and alignment accuracy thereof can be achieved when compared with directing the patterning of the colored layers made of the conventional I-line photoresists. In one embodiment, the patterning processes (e.g the patterning process  218 ) for forming the colored patterns  212   a ,  226  and  230  can be, for example, a dry etching process using O 2  as an etching gas, such that undesired organic residue issues after patterning of the colored layers to form the colored patterns  212   a ,  226  and  230  can be thus eliminated. In this embodiment, combination of the colored patterns  212   a ,  226  and  230 , and the dielectric layers  224  and  228  provides a color filtering structure for an image sensing device, and the color filter structure is formed with improved resolution and alignment accuracy. Moreover, in one embodiment, with the use of the light-blocking patterns (e.g. the light-blocking patterns  238   a  in  FIGS. 11-12 ), cross talk issues between adjacent photo-sensing elements (e.g. the photo-sensing elements  204  shown in  FIGS. 11-12 ) can be thus reduced or even prevented. 
         [0036]    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 the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.