System and Method to Align and Measure Alignment Patterns on Multiple Layers

Abstract

A system and method are used to increase alignment accuracy of feature patterns through detection of alignment patterns on both a surface layer and at least one below surface layers of an object. A first frequency of light, such as visible light, is used to detect alignment patterns on the surface layer and a second frequency of light, such as infrared light, is used to detect patterns one layer below the surface. For example, reflected light of a first frequency and transmitted light of a second frequency are co-focused onto detector after impinging on respective alignment patterns. The co-focused light is then used to determine proper alignment of the object for subsequent pattern features. This substantially increases accuracy of alignment of pattern features between layers, as compared to conventional systems.

1 . A system, comprising:
 an alignment system including first and second light sources and a detector that generates a measured signal therefrom;   an object, including,
 a first layer including a first alignment pattern, and 
 a second layer including a second alignment pattern, the second layer being below the first layer; and 
   a focusing system that co-focuses on the detector light from the first and second light sources after each has impinged on the respective the first and second alignment patterns,   whereby the object is aligned based on the measured signal and wherein the measured signal is generated from the co-focused light from the first and second alignment patterns.   
   
   
       2 . The system of  claim 1 , wherein the focusing system comprises:
 an optical system positioned between the object and the detector, wherein the optical system performs the co-focusing the light from the at least the first and second light sources onto the detector.   
   
   
       3 . The system of  claim 2 , wherein the focusing system further comprises:
 a positioning system that receives the measured signal from the alignment system and that moves at least one of the object and the detector relative to the optical system based on the measured signal, such that the light from the at least first and second light sources are co-focused on the detector.   
   
   
       4 . The system of  claim 2 , wherein the optical system comprises an optical element including at least first, second, and third lenses. 
   
   
       5 . The system of  claim 4 , wherein:
 the first lens comprises R 1 =−64 to −65 mm, R 2 =−71 to −72 mm, thickness≦1.5 to 1.6 mm, diameter,=22.0 mm, and a glass type is SF20 (Schott);   the second lens comprises R 1 =−71 to −72 mm, R 2 =15 to 16 mm, thickness≦1 to 2 mm, diameter=22.0 mm, and a glass type is N-PSK3(Schott); and   the third lens comprises R 1 =15 to 16 mm, R 2 =−35 to −36 mm, thickness=10 to 11 mm, diameter=22.0 mm, and a glass type is N-PK51 (Schott).   
   
   
       6 . The system of  claim 5 , wherein:
 the first lens comprises R 1 =−64.795 mm, R 2 =−71.20 mm, thickness=1.518 mm, diameter,=22.0 mm, and a glass type is SF20 (Schott);   the second lens comprises R 1 =−71.20 mm, R 2 =15.469 mm, thickness=1.5 mm, diameter=22.0 mm, and a glass type is N-PSK3 (Schott); and   the third lens comprises R 1 =15.469 mm, R 2 =−35.382 mm, thickness≦10.083 mm, diameter=22.0 mm, and a glass type is N-PK51 (Schott).   
   
   
       7 . The system of  claim 2 , wherein the optical system comprises an optical element including at least first and second lenses. 
   
   
       8 . The system of  claim 7 , wherein:
 the first lens comprises R 1 =−26 to −27 mm, R 2 =infinity, thickness≦3 mm, diameter=12 to 13 mm, and a glass type is BK7 (Schott);   the second lens comprises R 1 =infinity, R 2 =−59 to −60 mm, thickness≦5 mm, diameter=12 to 13 mm, and a glass type is F2 (Schott).   
   
   
       9 . The system of  claim 8 , wherein:
 the first lens comprises R 1 =−26.697 mm, R 2 =infinity, thickness≦3 mm, diameter=12.7 mm, and a glass type is BK7 (Schott);   the second lens comprises R 1 =infinity, R 2 =−59.03 mm, thickness≦5 mm, diameter=12.7 mm, and a glass type is F2 (Schott).   
   
   
       10 . The system of  claim 1 , wherein:
 the first light source is configured to generate visible light that is used to detect a position of the first alignment pattern; and   the second light source is configured to generate infrared light that is used to detect a position of the second alignment pattern.   
   
   
       11 . The system of  claim 10 , wherein:
 the visible light is reflected from the first alignment pattern before being focused onto the detector using the focusing system; and   the infrared light is transmitted through the second alignment pattern before being focused onto the detector using the focusing system.   
   
   
       12 . The system of  claim 1 , wherein:
 the light from the first light source is generated from a first side of the object; and   the light from the second light source is generated from a second side of the object, opposite the first side.   
   
   
       13 . A method, comprising:
 (a) generating at least a first light beam and a second light beam;   (b) impinging the first light beam onto a first alignment pattern on a first layer of an object;   (c) focusing the impinged first light beam onto a detector;   (d) impinging the second light beam onto a second alignment pattern on a second layer of the object, the second layer of the object being below the first layer of the object;   (e) focusing the impinged second light beam onto the detector;   (f) generating an alignment signal based on the detected first and second alignment patterns; and   (g) aligning the object to receive a subsequent portion of a feature pattern based on step (f).   
   
   
       14 . The method of  claim 13 , wherein the first and second light beams are focused onto the detector substantially simultaneously. 
   
   
       15 . The method of  claim 13 , wherein first light beam is visible light and the second light beam is infrared light. 
   
   
       16 . The method of  claim 15 , wherein:
 the visible light beam is reflected from the first alignment pattern before being focused onto the detector; and   the infrared light beam is transmitted through the second alignment pattern before being focused onto the detector.   
   
   
       17 . The method of  claim 13 , wherein:
 the first light beam is generated from a first side of the object; and   the second light beam is generated from a second side of the object, opposite the first side.   
   
   
       18 . A flat panel display formed using the method of  claim 13 . 
   
   
       19 . An integrated circuit formed using the method of  claim 13 . 
   
   
       20 . A system, comprising:
 means for generating at least a first light beam and a second light beam;   means for impinging the first light beam onto a first alignment pattern on a first layer of an object;   means for focusing the impinged first light beam onto a detector;   means for impinging the second light beam onto a second alignment pattern on a second layer of the object, the second layer of the object being below the first layer of the object;   means for focusing the impinged second light beam onto the detector;   means for generating an alignment signal based on the detected first and second alignment patterns; and   means for aligning the object to receive a subsequent portion of a feature pattern based on the alignment signal.