Patent Publication Number: US-2005139874-A1

Title: Test patterns for semiconductor devices and methods of fabricating the same

Description:
FIELD OF THE DISCLOSURE  
      The present disclosure relates generally to semiconductor fabrication and, more particularly, to test patterns for semiconductor devices and methods of fabricating the same in which a distance between p-well and n-well patterns can be adjusted within one mask set to evaluate a well-isolation characteristic.  
     BACKGROUND  
      Generally, the sizes of n-well and p-well mask patterns are adjusted in a sizing method when fabricating a mask for evaluating a well-isolation characteristic. However, it is difficult to set a reference appropriate for deciding how to apply a mask sizing.  
      A prior art test pattern for performing a well-isolation characteristic evaluation requires multiple modifications to the ion implantation conditions and multiple evaluations to obtain an optimized well-isolation characteristic of an appropriate size. These processes require many efforts and waste much time.  
       FIG. 1  is a combined diagram illustrating the layout and cross-section of a prior art well-isolation evaluating test pattern. A cross-sectional diagram of a semiconductor device is provided below the mask pattern.  
      Referring to  FIG. 1 , the illustrated test pattern includes an n-well mask  17  and a p-well mask  18 .  
      An n-well  13 , a p-well  14 , and shallow trench isolation (STI) layers  12  are formed in the semiconductor device illustrated in  FIG. 1 . A p+ moat region  15  and an n+ moat region  16  are formed in the n-well  13  and the p-well  14 , respectively.  
      The prior art well mask of  FIG. 1  is used to form the n-well  13  and the p-well  14  after completing the formation of the STI layers  12  in the semiconductor substrate  11 .  
      In fabricating an n-well mask  17  and a p-well mask  18 , a sizing is used to increase/decrease a size by a prescribed value so that a fixed distance d 1  lies between the n-well  13  and the p-well  14 . In the illustrated example, the reference letter A in the layout indicates a well mask prior to applying the sizing and the reference letter A′ indicates the well mask after applying the sizing.  
      However, the well-isolation characteristic evaluation must be done with a fixed value. Further, a new test pattern should be fabricated for another well-isolation characteristic evaluation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a combined diagram illustrating the layout and cross-section of a prior art well-isolation characteristic evaluation test pattern.  
       FIG. 2  is a combined diagram illustrating the layout and cross-section of an example well-isolation characteristic evaluation test pattern constructed in accordance with the teachings of the present invention. 
    
    
     DETAILED DESCRIPTION  
       FIG. 2  is a combined diagram illustrating the layout and cross-section of an example well-isolation characteristic evaluation test pattern constructed in accordance with the teachings of the present invention. A cross-sectional diagram of an example semiconductor device is also included in  FIG. 2 .  
      Referring to  FIG. 2 , an n-well  23 , a p-well  24 , and shallow trench isolation (STI) layers  22  are formed in a semiconductor substrate  21  of the illustrated semiconductor device. A p+ moat region  25  and an n+ moat region  26  are formed in the n-well  23  and the p-well  24 , respectively.  
      A well test mask constructed in accordance with the teachings of the present invention is used to form the n-well  23  and the p-well  24  after the formation of the STI layers  22  on the semiconductor substrate  21  is completed.  
      In forming the illustrated test pattern, a dummy layer  29  having a specific width d 2  is inserted into the well-isolation evaluation test pattern. Later, in fabricating the mask, the interval d 2  of the dummy layer  29  is cut out to leave a prescribed interval between the n-well mask  27  and the p-well mask  28 .  
      In the example test pattern of  FIG. 2 , the dummy layer  29  having the specific width is inserted between the n-well mask  27  and the p-well mask  28 . The dummy layer  29  is cut out to leave a prescribed interval d 2  in-between the masks  27 ,  28 . As a result, in carrying out ion implantation for forming the n-well  23  or the p-well  24 , ions are not implanted via the interval d 2 . However, dopant diffusion in the n-well  23  or the p-well  24  forms a junction therein. As a result, a condition for securing an isolation characteristic between the n+ and p+ moat regions  25 ,  26  is achieved.  
      The optimal interval is set by evaluating the well-isolation characteristic using the above-configured mask test pattern, thereby saving time and cost.  
      Moreover, the above-described test pattern enables one mask set to be fabricated with multiple intervals of difference widths d 2 , thereby facilitating the finding of the optimal interval condition, (i.e., the optimal mask sizing factor), by evaluating the well-isolation characteristics for the various test patterns having the different intervals d 2 .  
      In view of the foregoing, persons of ordinary skill in the art will appreciate that test patterns having different intervals between the n-well and p-well masks can be fabricated in one mask set without fabricating an additional mask. As a result, the well mask sizing factor having the optimal well-isolation characteristic may be found in one fabrication process.  
      Accordingly, the fabrication time for a semiconductor device is reduced due to the ready availability of the well mask sizing factor having the optimal well-isolation characteristic.  
      From the foregoing, persons of ordinary skill in the art will also appreciate that test patterns and fabricating methods have been provided in which one well mask set is used to provide multiple intervals to evaluate a well-isolation characteristic and by which an optimal sizing factor can be found in an early stage of development.  
      A disclosed example test pattern includes: an n-well test mask and a p-well test mask for evaluating an isolation characteristic between an n-well and p-well formed on a semiconductor substrate. The test pattern also includes a dummy layer inserted between the n-well test mask and the p-well test mask.  
      Preferably, the dummy layer is cut by tooling in fabricating a next mask to leave a set-up interval between the n-well test mask and the p-well test mask.  
      Preferably, the dummy layer has multiple intervals of different widths on one mask set.  
      A disclosed example method of fabricating a test pattern for a semiconductor device includes: forming an n-well test mask and a p-well test mask for evaluating an isolation characteristic between an n-well and a p-well formed on a semiconductor substrate; inserting a dummy layer between the n-well test mask and the p-well test mask; and cutting the dummy layer to leave a setup interval between the n-well test mask and the p-well test mask.  
      Preferably, the dummy layer has multiple intervals of different widths on one mask set.  
      From the foregoing, persons of ordinary skill in the art will appreciate that, in order to secure an optimal condition by evaluating a well-isolation characteristic without using multiple mask sets, a dummy layer is inserted between an n-well mask and a p-well mask to forcibly form an interval between an n-well and a p-well by removing the dummy layer in subsequently fabricating a mask test pattern. The well-isolation characteristic is then evaluated using the mask test pattern to set an optimal interval. As a result, time and costs can be saved in fabricating a semiconductor device.  
      It is noted that this patent claims priority from Korean Application No. P2003-0096993, which was filed on Dec. 24, 2003, and which is hereby incorporated by reference in its entirety.  
      Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.