Back-illuminated type imaging device and fabrication method thereof

Abstract

Light is illuminated from a back-surface side of a silicon substrate 4. A back-illuminated type imaging device 100 reads out, from a front-surface side of the silicon substrate 4, charges that are generated in the silicon substrate 4 in response to the illuminated light, so as to perform imaging. The back-illuminated type imaging device 100 includes pad portions 17 formed on the back surface of the semiconductor substrate 4, and a plurality of pillars 9 that are formed in the semiconductor substrate 4, are made of a conductive material and electrically connect wiring portions 12 formed on the front surface of the semiconductor substrate 4 and the pad portions 17 to each other.

1 . A back-illuminated type imaging device comprising:
 a semiconductor substrate including a front surface and a back surface, wherein light is illuminated from the back-surface side of the semiconductor substrate, and charges that are generated in response to the light are read out from the front-surface side of the semiconductor substrate to perform imaging;   a plurality of pad portions formed on the back surface of the semiconductor substrate;   a plurality of wiring portions formed on the front surface of the semiconductor substrate; and   a plurality of contact wiring portions that are formed in the semiconductor substrate and electrically connect the wiring portions formed on the front surface of the semiconductor substrate and the pad portions.   
   
   
       2 . The back-illuminated type imaging device according to  claim 1 , wherein
 each contact wiring portion is configured by a pillar made of a conductive material, the pillar extending from the front surface of the semiconductor substrate in a direction perpendicular to the front surface of the semiconductor substrate, the pillar reaching the back surface of the semiconductor substrate, and   the pad portions are connected to one ends of the pillars, and   the wiring portions are connected to the other ends of the pillars.   
   
   
       3 . The back-illuminated type imaging device according to  claim 2 , wherein the plurality of pillars are arranged two-dimensionally, when viewed in plan view. 
   
   
       4 . The back-illuminated type imaging device according to  claim 2 , wherein portions of the plurality of pillars at which the pillars have a maximum width have 2 μm or less in length. 
   
   
       5 . The back-illuminated type imaging device according to  claim 1 , further comprising:
 an alignment mark that is formed in the semiconductor substrate and is used to align components on the front-surface side of the semiconductor substrate with components on the back-surface side, wherein   the alignment mark is formed by a pattern of a plurality of pillars that are made of a conductive material and extend in a direction perpendicular to the front surface of the semiconductor substrate.   
   
   
       6 . The back-illuminated type imaging device according to  claim 5 , wherein the plurality of pillars, which form the alignment mark, are arranged two-dimensionally. 
   
   
       7 . The back-illuminated type imaging device according to  claim 5 , wherein the pattern of the plurality of pillars, which form the alignment mark, is symmetric. 
   
   
       8 . The back-illuminated type imaging device according to  claim 5 , wherein portions of the plurality of pillars at which the pillars have a maximum width have 2 μm or less in length. 
   
   
       9 . The back-illuminated type imaging device according to  claim 5 , wherein each of the pillars, which form the alignment mark, extends from the front surface of the semiconductor substrate and reaches the back surface of the semiconductor substrate. 
   
   
       10 . The back-illuminated type imaging device according to  claim 1 , further comprising:
 a supporting substrate bonded to the front surface of the semiconductor substrate via an inorganic adhesive layer.   
   
   
       11 . The back-illuminated type imaging device according to  claim 10 , wherein the supporting substrate is made of the same material as the semiconductor substrate. 
   
   
       12 . The back-illuminated type imaging device according to  claim 1 , further comprising:
 a film that is made of the same material as the pad portions and is formed above the back surface of the semiconductor substrate, wherein   the film includes at least one of (i) a light shielding film for shielding a part of pixel portions formed in the semiconductor substrate from light and (ii) a light shielding film for shielding a boundary between the pixel portions from light.   
   
   
       13 . A method for fabricating a back-illuminated type imaging device in which light is illuminated from a back-surface side of a semiconductor substrate, and charges that are generated in response to the light are read out from a front-surface side of the semiconductor substrate to perform imaging, the method comprising:
 forming a plurality of first through holes in a plane area, on which pad portions to be formed on the back surface of the semiconductor substrate is to be formed, from the front-surface side of the semiconductor substrate so that the through holes extends from the front surface of the semiconductor substrate and reaches the back surface;   filling the plurality of first through holes with a conductive material to form a plurality of first pillars made of the conductive material;   forming wiring portions on the front surface of the semiconductor substrate so that the wiring portions are connected to the plurality of first pillars; and   after the wiring portions are formed, forming the pad portions on the back surface of the semiconductor substrate so that the pad portions are connected to the plurality of first pillars.   
   
   
       14 . The method for fabricating the back-illuminated type imaging device according to  claim 13 , wherein in the forming of the first through holes, the plurality of first through holes are formed so as to be arranged two-dimensionally, when viewed in plan view. 
   
   
       15 . The method for fabricating the back-illuminated type imaging device according to  claim 13 , wherein in the forming of the first through holes, the plurality of first through holes are formed so that portions of the first through holes at which the through holes have a maximum width have 2 μn or less in length. 
   
   
       16 . The method for fabricating the back-illuminated type imaging device according to  claim 13 , wherein
 in the forming of the first through holes, a plurality of second through holes are formed in a plane area, in which a alignment mark that is used to align components on the front-surface side of the semiconductor substrate with components on the back-surface side are to be formed, so that the second through holes extends from the front surface of the semiconductor substrate and reaches the back surface,   in the filling of the first through holes, the plurality of second through holes are filled with the conductive material to form a plurality of second pillars made of the conductive material, and   the alignment mark is formed by the pattern of the plurality of second pillars.   
   
   
       17 . The method for fabricating the back-illuminated type imaging device according to  claim 16 , wherein in the forming of the first through holes, the plurality of second through holes are formed so as to be arranged two-dimensionally, when viewed in plan view. 
   
   
       18 . The method for fabricating the back-illuminated type imaging device according to  claim 17 , wherein in the forming of the first through holes, a pattern of the plurality of second through hole is formed so as to be symmetric. 
   
   
       19 . The method for fabricating the back-illuminated type imaging device according to  claim 16 , wherein in the forming of the first through holes, the plurality of second through holes are formed so that portions of the second through holes at which the through holes have a maximum width have 2 μm or less in length. 
   
   
       20 . The method for fabricating the back-illuminated type imaging device according to  claim 13 , further comprising
 forming pixel portions in the semiconductor substrate, the pixel portions having charge storage areas for storing therein the charges, wherein   the forming of the pad portions includes
 forming a film of a conductive material having a light shielding property, on the back surface, and 
 removing the conductive material at portions outside at least one of a portion above a plane area in which the pad portions are formed, a portion above a part of the pixel portions, and a portion above a boundary between the pixel portions. 
   
   
   
       21 . The method for fabricating the back-illuminated type imaging device according to  claim 20 , further comprising
 after the pad portions are formed, forming color filters above the pixel portions, so as to correspond to the pixel portions; and   after the pad portions are formed and before the color filters are formed, heating the semiconductor substrate.   
   
   
       22 . The method for fabricating the back-illuminated type imaging device according to  claim 13 , wherein
 the semiconductor substrate is a first semiconductor substrate of a SOT substrate, the SOI substrate comprising the first semiconductor substrate, a second semiconductor substrate, and an oxide film sandwiched between the first and second semiconductor substrates,   the method further comprising:   after the wiring portions are formed, bonding a supporting substrate on the front-surface side of the first semiconductor substrate via an inorganic adhesive film.   
   
   
       23 . The method for fabricating the back-illuminated type imaging device according to  claim 22 , wherein the supporting substrate is made of the same material as the first semiconductor substrate.