Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an OPC process, and more particularly, to an OPC method for a dual damascene structure. 
     2. Description of the Prior Art 
     In semiconductor manufacturing processes, in order to transfer an integrated circuit layout onto a semiconductor wafer, the integrated circuit layout is first designed and formed as a photo-mask pattern. The photo-mask pattern is then proportionally transferred to a photoresist layer positioned on the semiconductor wafer. 
     In recent years, with the increasing miniaturization of semiconductor devices, the design rule of line width and space between lines or devices becomes finer. However, the width is subject to optical characteristics. To obtain fine-sized devices in the exposure, the interval between transparent regions in a mask is scaled down with device size. When the light passes through the mask, diffraction occurs and reduces resolution. Moreover, when light passes through the transparent regions of a mask having different interval sizes, the light through the regions having small interval sizes is influenced by the transparent regions having large interval sizes and results in deformation of the transfer pattern. Currently, a technical called “optical proximity correction (OPC)” is developed. The OPC method is to imitate the feature that light passes through the photo-mask and to further compensate the pattern of the mask to form the desired pattern after the exposure process. 
     In the conventional arts, the “dual damascene” process is wildly used to form a metal interconnection system which is consisted of metal lines and plugs. However, the OPC method used for forming the masks of the metal interconnection system is not well studied. 
     SUMMARY OF THE INVENTION 
     The present invention therefore provides a method of fabricating an OPC method for a dual damascene structure. 
     Accordingly to one embodiment, an OPC process is provided. The method comprising receiving a first pattern corresponding to a first structure of a semiconductor structure, and a second pattern corresponding to a second structure of the semiconductor structure. Next, a first OPC process is performed for the first pattern to obtain a revised first pattern, wherein the revised first pattern has a first shift regarding to the first pattern. A second OPC process is performed for the second pattern to obtain a revised second pattern, wherein the second OPC process comprises moving the second pattern according to the first shift. 
     In the present invention, it is featured that the first structure and the second structure are two related structure and an additional aligning process is performed during the second OPC process by moving the second pattern toward a second distance, which is based on a first distance of the first pattern in the first OPC. By doing this, the connection between the first structure and the second structure can be ensured. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a flow chart of the method of an optical proximity correction according to one embodiment of the present invention. 
         FIG. 2  to  FIG. 6  shows schematic diagrams of the method of an OPC method according to one embodiment of the present invention. 
         FIG. 7  to  FIG. 10  show schematic diagrams of the method of fabricating a semiconductor structure according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details, as well as accompanying drawings, are given to provide a thorough understanding of the invention. It will, however, be apparent to one skilled in the art that the invention may be practiced without these specific details. 
     Please refer to  FIG. 1 , which shows a flow chart of the method of an optical proximity correction according to one embodiment of the present invention. Please also see  FIG. 2  to  FIG. 6 , which shows schematic diagrams of the method of an OPC method according to one embodiment of the present invention. 
     As shown in  FIG. 1  and  FIG. 2 , a layout  300  of an integrated circuit is imported into a computer (step  500 ). In one embodiment, the layout  300  may be in the form of GDSII or OASIS™ or some other format for describing various shapes, sizes, and relationships of elements of a semiconductor chip and can be imported into a database to be included with other information about the integrated circuit. The term “computer” in the present invention refers to any programmable apparatus that can execute any computer program instructions including multiple programs or threads. The multiple programs or threads may be processed approximately simultaneously to enhance utilization of the processor and to facilitate substantially simultaneous functions. As depicted in  FIG. 2 , the layout  300  includes a plurality of first patterns  302  and a plurality of second patterns  304 . Each first pattern  302  is related to a first structure (not shown) which is to be formed in a semiconductor substrate (not shown), each second pattern  304  is related to a second structure (not shown) which is be to formed on the substrate, above or below the first structure. The first structure and the second structure are two strongly related structures and the positions thereof should be controlled precisely. For example, the first structure may be a metal line in a metal interconnection system and the second pattern may be a via plug, wherein the metal line of the first structure and the via plug of the second structure are fabricated by a dual damascene process. Thus, the alignment of the first structure and the second structure is important. Alternatively, the first structure and the second structure can be any semiconductor structures, for example, the first structure is a source/drain region of a transistor and the second structure is a contact plug. It is noted that the first structure and the second structure do not require to be two adjacent layers, that is, there can be one or more than one layer with other semiconductor structures disposed between the first structure and the second structure. 
     Please refer back to  FIG. 2 . In this embodiment, the first patterns  302 A,  302 B,  302 C are stripe patterns that stretch along a first direction  400 . The second patterns  304 A,  304 B,  304 C are rectangle patterns, and each of which is located correspondingly to each of the first patterns  302 A,  302 B,  302 C, respectively. Preferably, boundaries of each second pattern  304 A,  304 B,  304 C completely coincide with boundaries of each first patterns  302 A,  302 B,  302 C along the first direction  400 . In another embodiment, the width (projection along the second direction  402 ) of the each second pattern  304 A,  304 B,  304 C can be equal or smaller than those of each first patterns  302 A,  302 B,  302 C. In addition, the gap G 1  between the first pattern  302 A and  302 B is different from the gap G 2  between the first pattern  302 B and the  302 C. Preferably, the first gap G 1  is smaller than the second gap G 2 , and more preferably, the first gap G 1  is smaller than a tolerance value that the semiconductor manufacturing system can afford. 
     Next, as shown in  FIG. 1  and  FIG. 3 , a first OPC process is performed for the first pattern  302  (step  502 ). The first OPC process comprises considering the parameters of the manufacturing process for forming the first pattern, including development, exposure, or etching or the like. After the first OPC process, a revised first pattern  302 ′ is formed. The revised first pattern  302 ′ may comprise different contour with respect to the original first pattern  302 . For example, the revised first pattern  302 ′ includes round corner, as shown in  FIG. 3 . In the present embodiment, since the first gap G 1  is beyond a tolerance value of the semiconductor manufacturing system, after the first OPC process, the first pattern  302 B has been moved toward the first pattern  302 C by a first distance D 1 . Thus, both the third gap G 3  and the fourth gap G 4  are greater than the tolerance value and therefore can be formed without unwanted defects. The process window for forming structures with the revised first pattern  302 ′ can therefore be enlarged. 
     As shown in  FIG. 4 , a second OPC process is performed for the second pattern (step  504 ). The second OPC process comprises considering the parameters of the manufacturing process for forming the second pattern  304 , including development, exposure, or etching or the like. After the second OPC process, a revised second pattern  304 ′ is formed. The revised second pattern  304 ′ may comprise different contour with respect to the original second pattern  304 . For example, the second pattern  302 ′ includes round corner, as shown in  FIG. 4 . However, since the second pattern  304  is originally a rectangle shape, instead of line stripe like the first pattern  302 , the computer would regard that the first gap G 1  between the revised second pattern  304 A′ and  304 B′ is still within the tolerance value, and would not move the position of the second pattern  304 B′. Thus, by comparing the two revised patterns after the first OPC process and the second OPC process, as shown in  FIG. 5 , the revised second pattern  304 B′ does not well correspond to the revised first pattern  302 B′. 
     Since the first structure of first pattern  302  and the second structure of the second pattern  304  are two related structures, the relative positions thereof should be well considered. As such, as shown in  FIG. 1  and  FIG. 6 , after adjusting the contour of the second pattern  304 , the second OPC process further includes an aligning process to move the revised second pattern  304 ′. The aligning process considers the final position of the first revised pattern  302 ′ to make sure the relative position of the first structure and the second structure can still be remained. In one embodiment, as shown in  FIG. 6 , the revised second pattern  304 B′ is moved toward the revised second pattern  304 C′ by a second distance D 2 , thereby forming another revised second pattern  304 B″. The second distance D 2  can be equal or smaller than the first distance D 1 , depending on the design. Preferably, the second distance D 2  is substantially equal to the first distance, thus the revised second pattern  304 B″ can completely coincide with the revised first pattern  302 B′ and a maximum overlapping region of the revised second pattern  304 B″ and the revised first pattern  302 B′ can be obtained. 
     Finally, as shown in  FIG. 1 , the revised first pattern is output to form a first photo-mask and the revised second pattern is output to form a second photo-mask (step  506 ). By using the first photo-mask and the second photo-mask, the relationship between the first structure and the second structure can therefore be remained. 
     The following context will show one example for forming semiconductor structure with the OPC process shown above. Please see  FIG. 7  to  FIG. 10 , which show schematic diagrams of the method of fabricating a semiconductor structure according to one embodiment of the present invention. As shown in  FIG. 7 , a substrate  600  is provided. The substrate  600  may be a silicon substrate or a dielectric layer on the silicon substrate, but is not limited thereto. A third dielectric layer  606 D are disposed on the substrate  600 . A third structure  606  including a plurality of metal lines is formed in the third dielectric layer  606 D. In one embodiment, the third structure  606  is formed by, for example, forming a plurality of trenches in the third dielectric layer  606 D by using a third photo-mask  706 P having a revised third pattern  706 ′, which are corresponding to the third structure  606 . Thereafter, the trenches are filled with conductive material and a planarization process is performed. The third photo-mask  706 P may be formed by outputting the revised third pattern  706 ′, wherein the revised third pattern  706 ′ is obtained through a third OPC process based on the pattern of the third structure  606 . 
     Next, as shown in  FIG. 8 , a second dielectric layer  604 D and a first dielectric layer  602 D are formed on the third dielectric layer  606 D. A plurality of trenches  601  are formed in the first dielectric layer  602 D by using a first photo-mask  702 P having a revised first pattern  702 ′. The first photo-mask  702 P may be formed by outputting the revised first pattern  702 ′, wherein the revised first pattern  702 ′ is obtained by a first OPC process based on the pattern of the first structure. 
     Another patterning process is performed by using a second photo-mask  704 P having a revised second pattern  704 ′, as shown in  FIG. 9 , to form a plurality of vias  603  in the second dielectric layer  604 D. The second photo-mask  704 P may be formed by outputting the revised second pattern  704 ′, wherein the revised second pattern  704 ′ is obtained by a second OPC process based on the pattern of the second structure. After filling a conductive layer into the trench  601  and the vias  603 , a plurality of dual damascene structures are therefore formed. As shown in  FIG. 9 , the dual damascene structures are comprised of the first structure  602 , in a form of metal line, and the second structure  604 , in a form of via plug. 
     Next, a fourth dielectric layer  608 D with a fourth structure  608  disposed therein are formed on the first dielectric layer  602 D. The fourth structure  608  includes a plurality of via plugs. In one embodiment, the fourth structure  608  is formed by, for example, forming a plurality of vias in the fourth dielectric layer  608 D by using a fourth photo-mask  708 P having a revised fourth pattern  708 ′ corresponding to fourth structure  608 , followed by filling the vias with conductive material and performing a planarization process. The fourth photo-mask  708 P may be formed by outputting the revised fourth pattern  708 ′, wherein the revised fourth pattern  708 ′ is obtained by a fourth OPC process based on the pattern of the fourth structure. 
     In the present embodiment, the revised first pattern  702 ′ on the first photo-mask  702 P and the revised second pattern  704 ′ on the second photo-mask  704 P can be formed by using the OPC method as shown in the flow chart in  FIG. 1 . In one embodiment, the first OPC process for forming the revised first pattern  702 ′ further comprise considering the pattern of the fourth structure  608 . The second OPC process for forming the revised second pattern  704 ′ further comprise considering the third structure  606 . Accordingly, by using the process shown above, the dual damascene structure containing the first structure  602  and the second structure  604  can be precisely formed without short phenomenon. 
     In summary, the present invention provides a method of fabricating a semiconductor structure. The semiconductor structure contains a first structure relating to a first pattern on a first photo-mask, and a second structure relating to a second pattern on a second photo-mask. The first pattern and the second pattern are obtained by a first OPC process and a second OPC process. It is featured that the first structure and the second structure are two related structure and an additional aligning process is performed during the second OPC process by moving the second pattern toward a second distance, which is based on a first distance of the first pattern in the first OPC process. By doing this, the connection between the first structure and the second structure can be insured. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Technology Category: h