Wafer alignment mark scheme

Abstract

A wafer alignment apparatus includes a light source, a light detection device, and a rotation device configured to rotate a wafer. The light source is configured to provide light directed to a backside of the wafer. The light detection device is configured to detect reflected light intensity from the backside of the wafer to find a position of at least one wafer alignment mark formed on the back side of the wafer.

What is claimed is: 
     
         1 . A wafer alignment apparatus, comprising:
 a light source;   a light detection device; and   a rotation device configured to rotate a wafer,   wherein the light source is configured to provide light directed to a backside of the wafer, the light detection device is configured to detect reflected light intensity from the backside of the wafer to find a position of at least one wafer alignment mark formed on the back side of the wafer.   
     
     
         2 . The wafer alignment apparatus of  claim 1 , wherein the position of the at least one wafer alignment mark is found by recognizing reduced light intensity detected by the light detection device. 
     
     
         3 . The wafer alignment apparatus of  claim 1 , wherein the wafer is rotated for a specified angle depending on a number of the at least one alignment mark. 
     
     
         4 . The wafer alignment apparatus of  claim 3 , wherein the specified angle is given as 360° divided by the number of the at least one wafer alignment mark. 
     
     
         5 . The wafer alignment apparatus of  claim 3 , wherein the number of the at least one alignment mark is four and the specified angle is 90°. 
     
     
         6 . The wafer alignment apparatus of  claim 1 , wherein each of the at least one wafer alignment mark includes at least one recess. 
     
     
         7 . The wafer alignment apparatus of  claim 6 , wherein the at least one recess has a depth ranging from 100 nm to 200 nm. 
     
     
         8 . The wafer alignment apparatus of  claim 6 , wherein a number of the at least one recess is from one to a number of the at least one wafer alignment mark. 
     
     
         9 . The wafer alignment apparatus of  claim 1 , wherein each of the at least one wafer alignment mark comprises multiple recesses. 
     
     
         10 . The wafer alignment apparatus of  claim 1 , wherein positions of multiple wafer alignment marks of the at least one wafer alignment mark are evenly distributed along an edge of the wafer. 
     
     
         11 . The wafer alignment apparatus of  claim 1 , wherein the light detection device is a charge-coupled device (CCD) sensor. 
     
     
         12 . A method, comprising:
 transmitting light from a light source to a backside of a wafer;   rotating the wafer for a specified angle;   detecting reflected light from the backside of the wafer by a light detection device; and   finding a position of at least one wafer alignment mark formed on the backside of the wafer.   
     
     
         13 . The method of  claim 12 , wherein finding the position of the at least one wafer alignment mark comprises recognizing reduced light intensity detected by the light detection device. 
     
     
         14 . The method of  claim 12 , wherein the wafer is rotated for a specified angle depending on a number of the at least one alignment mark. 
     
     
         15 . The method of  claim 14 , wherein the specified angle is given as 360° divided by the number of the at least one wafer alignment mark. 
     
     
         16 . The method of  claim 14 , wherein the number of the at least one alignment mark is four and the specified angle is 90°. 
     
     
         17 . The method of  claim 12 , wherein each of the at least one wafer alignment mark comprises multiple recesses. 
     
     
         18 . The method of  claim 12 , wherein positions of multiple wafer alignment marks of the at least one wafer alignment mark are evenly distributed along an edge of the wafer. 
     
     
         19 . The method of  claim 12 , wherein the light detection device is a charge-coupled device (CCD) sensor. 
     
     
         20 . A wafer, comprising:
 a front side for integrated circuit formation;   a back side; and   at least one wafer alignment mark formed on the back side,   wherein the at least one wafer alignment mark is configured to change a light intensity reflected from the back side in order to find a position of the at least one wafer alignment mark.