Abstract:
The present invention provides a semiconductor inspection method which detects a short circuit failure of adjacent lines having the possibility of a short circuit occurring, which short circuit failure cannot be detected by the conventional semiconductor inspection methods. The semiconductor inspection method comprises steps of: extracting adjacent lines having the possibility of a short circuit occurring between the lines from a layout patter of a semiconductor (step S 101 ), obtaining input logical values such that one of the adjacent lines has a logical value “1” while the other has a logical value “0” (step S 102 ), and monitoring outputs of a logical circuit which receives the input logical values, thereby to compare the outputs with output logical values which are expected when the input logical values are input to the logical circuit (step S 103 ). Therefore, the short circuit failure of the adjacent lines in the logical circuit can be correctly detected in a short time.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a method for inspecting semiconductors of ICs or LSIs, which are constituted by logical circuits. 
   BACKGROUND OF THE INVENTION 
   In recent years, it is getting more difficult to detect failures in LSIs because the scales and complexities of LSIs are increased. As an example of methods for detecting the failures, there is a semiconductor inspection method which detects stuck-at failures from circuit data of a logical circuit. 
   Hereinafter, a description is given of a prior art semiconductor inspection method for detecting stuck-at failures in a logical circuit which comprises a three-input AND gate and a two-input AND gate. 
     FIG. 2  is a diagram illustrating the logical circuit comprising the three-input AND gate and two-input AND gate.  FIG. 3  is a diagram illustrating a layout pattern of the logical circuit shown in FIG.  2 . FIGS.  6 ( a )- 6 ( c ) are truth tables showing input logical values and output logical values corresponding thereto, which are used in the prior art semiconductor inspection method. 
   The logical circuit  200  shown in  FIG. 2  includes a three-input AND gate  210  and a two-input AND gate  211 . Input to the three-input AND gate  210  is performed through input terminals  201 ,  202  and  203 . Input to the two-input AND gate  211  is performed through input terminals  203  and  204 . Outputs from the three-input AND gate  210  and two-input AND gate  211  are performed through output terminals  206  and  207 , respectively. 
   Next, the prior art semiconductor inspection method is described in detail. 
   Initially, in the three-input AND gate  210 , when “1”s are input to the input terminals  201 - 203  as inputs A-C, respectively, as shown in logical column (a) of the truth table in FIG.  6 ( a ), and an output E of the output terminal  206  is monitored, “0” stuck-at failures in the terminals  201 - 203  and  206  are detected. In addition, when “0” is input to the input terminal  201  as the input A and “1”s are input to the input terminals  202  and  203  as the inputs B and C, respectively, as shown in logical column (b) of the truth table, and the output E of the output terminal  206  is monitored, “1” stuck-at failures in the terminals  201  and  206  are detected. Similarly, when “0” is input to the input terminal  202  as the input B and “1”s are input to the input terminals  201  and  203  as the inputs A and C, respectively, as shown in logical column (c) of the truth table, and the output E of the output terminal  206  is monitored, or when “0” is input to the input terminal  203  as the input C and “1”s are input to the input terminals  201  and  202  as the inputs A and B, respectively, as shown in logical column (d) of the truth table, and the output E of the output terminal  206  is monitored, “1” stuck-at failures in the input terminals  202  and  203  are detected. Thus, when the combinations of the input logical values shown in the truth table of FIG.  6 ( a ) are input to the terminals, the stuck-at failures in the terminals  201 - 203  and  206  are detected. Further, the combinations of the input logical values shown in the truth table in FIG.  6 ( a ) have good detection efficiency and failures can be detected with fewer combinations. Accordingly, these combinations are conventionally generally used. 
   Similarly, also in the two-input AND gate  211 , when input logical values as shown in logical column (e) of the truth table in FIG.  6 ( b ) are input to the input terminals  203  and  204  and an output F of the output terminal  207  is monitored, the “0” stuck-at failures in the terminals  203 ,  204  and  207  are detected. In addition, when input logical values as shown in logical columns (f) and (g) of the truth table in FIG.  6 ( b ) are input to the input terminals  203  and  204  and the respective outputs F of the output terminal  207  are monitored, the “1” stuck-at failures in the terminals  203 ,  204  and  207  are detected. Therefore, in the logical circuit  200  shown in  FIG. 2 , when input logical values as shown in logical columns (h)-(k) of the truth table in FIG.  6 ( c ), which is obtained by combining the logical columns (a)-(d) of the truth table in FIG.  6 ( a ) as necessary combinations for detecting the stuck-at failures in the three-input AND gate  210  and the logical columns (e)-(g) of the truth table in FIG.  6 ( b ) as necessary combinations for detecting the stuck-at failures in the two-input AND gate  211 , are input to the input terminals  201 - 204  as the inputs A-D, and the outputs E and F of the output terminals  206  and  207  are monitored, the “0” stuck-at failure and “1” stuck-at failure in the terminals  201 - 204 ,  206  and  207  are detected. 
   Here, in a case where the logical circuit  200  shown in  FIG. 2  has a layout pattern as shown in  FIG. 3  on a semiconductor, when the input logical values shown in logical columns (h)-(k) of the truth table in FIG.  6 ( c ) given by the prior art semiconductor inspection method for detecting the stuck-at failure are input to the input terminals  201 - 204 , the “0” stuck-at failure and “1” stuck-at failure in the terminals  201 - 204 ,  206  and  207  can be detected. However, in this case, since the logical values output from the output terminals  206  and  207  are the same, even when the output terminals  206  and  207  are short-circuited, the short circuit of the terminals cannot be detected. As described above, in the prior art semiconductor inspection method, there are some cases where short circuit failures cannot be detected and failures in LSIs or the like cannot be detected. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a semiconductor inspection method for detecting short circuit failures occurring between adjacent lines. 
   Other objects and advantages of the present invention will become apparent from the detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the spirit and scope of the invention will be apparent to those of skill in the art from the detailed description. 
   A semiconductor inspection method according to a 1st aspect of the present invention comprises steps of: extracting adjacent lines which have a possibility of a short circuit occurring between the lines from a layout pattern of a semiconductor; obtaining input logical values such that one of the adjacent lines has a logical value “1” while the other has a logical value “0”; and monitoring an output of a logical circuit which receives the input logical values, and comparing the monitored output with an output logical value which is expected when the input logical values are input to the logical circuit. Therefore, the short circuit failure between the adjacent lines, which cannot be detected by the prior art semiconductor inspection method, can be detected correctly. Further, the minimum combination of the input logical values is utilized, whereby the short circuit failure can be detected in a shorter time. 
   A semiconductor inspection method according to a 2nd aspect of the present invention comprises steps of: extracting lines, a distance between said lines being equal to or less than a threshold, from layout data of a semiconductor as adjacent lines; obtaining input logical values such that one of the adjacent lines has a logical value “1” while the other has a logical value “0”; and monitoring an output of a logical circuit which receives the input logical values, and comparing the monitored output with an output logical value which is expected when the input logical values are input to the logical circuit. Therefore, the same effects as those described in the 1st aspect can be obtained. 
   According to a 3rd aspect of the present invention, there is provided a computer-readable recording medium which records a program for making a computer execute steps of: extracting adjacent lines which have a possibility of a short circuit occurring between the lines from a layout pattern of a semiconductor; obtaining input logical values such that one of the adjacent lines has a logical value “1” while the other has a logical value “0”; and monitoring an output of a logical circuit which receives the input logical values, and comparing the monitored output with an output logical value which is expected when the input logical values are input to the logical circuit. Therefore, the same effects as those described in the 1st aspect can be obtained. 
   According to a 4th aspect of the present invention, there is provided a computer-readable recording medium which records a program for making a computer execute steps of: extracting lines, a distance between said lines being equal to or less than a threshold, from layout data of a semiconductor as adjacent lines; obtaining input logical values such that one of the adjacent lines has a logical value “1” while the other has a logical value “0”; and monitoring an output of a logical circuit which receives the input logical values, and comparing the monitored output with an output logical value which is expected when the input logical values are input to the logical circuit. Therefore, the same effects as those described in the 1st aspect can be obtained. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a flowchart showing a semiconductor inspection method according to a first embodiment of the present invention. 
       FIG. 2  is a diagram illustrating a logic circuit comprising a three-input AND gate and a two-input AND gate as an example of an inspection target. 
       FIG. 3  is a diagram illustrating a layout pattern of the logical circuit. 
       FIG. 4  is a flowchart showing the semiconductor inspection method according to the first embodiment in detail. 
     FIGS.  5 ( a )- 5 ( d ) are truth tables showing input logical values and output logical values for the semiconductor inspection method according to the first embodiment. 
     FIGS.  6 ( a )- 6 ( c ) are truth tables showing input logical values and output logical values for a prior art semiconductor inspection method. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   [Embodiment 1] 
   Hereinafter, a semiconductor inspection method according to a first embodiment of the present invention will be described with reference to the drawings. 
     FIG. 1  is a flowchart showing the semiconductor inspection method according to the first embodiment. Also in this first embodiment, the description is given with reference to the logical circuit  200  shown in  FIGS. 2 and 3 , which is referred to in the description of the prior art. Since the logical circuit  200  shown in  FIG. 2  is already described as the prior art, this is not described here. 
   The semiconductor inspection method of the first embodiment is described with reference to FIG.  1 . 
   Initially, in step S 101 , combinations of lines having possibilities of short circuits occurring between the lines are extracted from the layout pattern of the logical circuit. 
   Next, in step S 102 , input logical values are derived such that the lines of each extracted combination receive logical values “1” and “0”, respectively, and then correct output logical values which are expected from the derived input logical values are obtained. Here, the correct output logical values which are expected from the input logical values are output logical values obtained when the logical circuit has no failure. 
   Then, in step S 103 , outputs of the logical circuit which receives the input logical values which are obtained in step S 102  are monitored, and the monitored outputs are compared with the correct output logical values expected from the input logical values. As a result of this comparison, the short circuit failure between the lines is detected. 
     FIG. 4  is a flowchart showing the semiconductor inspection method in detail, in accordance with the flowchart of FIG.  1 . 
   Initially, in step S 201 , combinations of lines which are adjacent to each other and within a predetermined distance are extracted from the layout pattern of the logical circuit as the combinations of lines having possibilities of short circuits occurring between the lines. The process of step S 201  corresponds to the process of step S 101  in the flowchart of FIG.  1 . 
   In step S 202 , one combination is selected from the combinations of lines extracted in step S 201 , and the logical value “0” is set for one of lines of the selected combination and the logical value “1” is set for the other of the lines. 
   In step S 203 , input values for other input terminals are set such that when the combination of lines selected in step S 202  includes the short circuit failure, the output of the logical circuit is changed by the inputs to the input terminals which are set in step S 202 , compared with an output in a case including no short circuit failure. 
   In step  5204 , correct output logical values expected from the input logical values which are set in steps S 202  and S 203  are obtained. 
   In step S 205 , the combination of the lines selected in step S 202  is excluded from the combinations of lines having the possibilities of short circuit failures occurring, which are extracted in step S 201 . 
   In step S 206 , it is decided whether or not any unselected combinations of lines having the possibilities of the short circuit failures occurring remain. When combinations remain, the processes from step S 202  are repeatedly performed. When no combination remains, it proceeds to step S 207 . These processes of steps S 202 -S 206  correspond to the process of step S 102  of flowchart in FIG.  1 . 
   In step S 207 , the outputs of the logical circuit which receives the input logical values obtained by the processes of steps S 202 -S 206  are monitored, and the monitored outputs are compared with the correct output logical values which are expected from the input logical values. The process of step S 207  corresponds to the process of step S 103  of the flowchart in FIG.  1 . 
   Next, this semiconductor inspection method of the first embodiment is described using a specific example. 
   In this specific example, the logical circuit as shown in  FIG. 2  is utilized and this logical circuit has the layout pattern as shown in FIG.  3 . FIGS.  5 ( a )- 5 ( d ) are truth tables when the logical values “1” and “0” are input to lines extracted as the lines having the possibility of shorting. 
   Initially, combination of a line  251  and a line  254 , combination of the line  251  and a line  253 , combination of a line  252  and the line  253 , and combination of a line  256  and a line  257  are extracted from the layout pattern shown in  FIG. 3 , as the combinations of lines having possibilities of the short circuit failures occurring, because the lines of each combination are adjacent lines and close to each other (step S 201 ). 
   Then, the combination of the lines  251  and  254  is selected first. One of the logical values “0” and “1” is set for the input terminal  201 , and the other of the logical values is set for the input terminal  204  (step S 202 ). In this case, the input terminal  201  is connected to the three-input AND gate  210  of FIG.  2 . Since the output E of the three-input AND gate  210  is affected also by the inputs B and C to the input terminals  202  and  203 , the respective inputs B and C to the input terminals  202  and  203  are set to the logical values “1” such that the output E of the three-input AND gate  210  is changed by the input A to the input terminal  201  (step s 203 ). When these values are set, the value of the output obtained when there is a short circuit failure between the lines  251  and  254  is different from the value in the case including no short circuit failure. 
   Then, the correct output logical values which are expected from the set input logical values are obtained (step S 204 ). FIG.  5 ( a ) shows the truth table which is obtained in this way. As shown in FIG.  5 ( a ), the logical value “0” is set for one of the lines in each of the combination of the lines  251  and  254  and the combination of the lines  256  and  267 , and the logical value “1” is set for the other of the lines. Therefore, when the outputs E and F are monitored through the output terminals  206  and  207 , the short circuit failures between the lines  251  and  254  and the lines  256  and  257  are detected. 
   Then, the combination of the lines whose input logical values are obtained to detect the short circuit failures, i.e., the combination of the lines  251  and  254  and the combination of the lines  256  and  257  are excluded from the combinations of lines having the possibilities of the short circuit failures occurring, extracted in step S 201  (step S 205 ). When any combinations of lines remain (step S 206 ), the processes of steps S 202 -S 205  are repeatedly performed for the remaining combinations. In this case, the combination of the lines  251  and  253  and the combination of the lines  252  and  253  remain. Therefore, the processes of steps S 202 -S 205  are performed similarly to these combinations of the lines, whereby the truth tables as shown in FIGS.  5 ( b ) and  5 ( c ) are obtained. When the truth tables in FIGS.  5 ( a )- 5 ( c ) are integrated with deleting overlapping parts, the truth table as shown in FIG.  5 ( d ) is obtained. 
   Then, the input logical values as shown in logical columns (r)-(u) of the truth table in FIG.  5 ( d ) are input to the input terminals  201 - 204  as the inputs A-D, then the outputs E and F of the output terminals  206  and  207  are monitored, and the monitored outputs E and F are compared with the output logical values of the truth table in FIG.  5 ( d ) (step S 207 ). As a result of the comparison, when the outputs E and F of the output terminals  206  and  207  are equal to the output logical values of the truth table in FIG.  5 ( d ), it is decided that no short circuit failure occurs. On the other hand, when they are not equal, it is decided that the short circuit failure occurs. 
   As described above, according to the semiconductor inspection method of this first embodiment, adjacent lines having the possibilities of short circuits occurring between the lines are extracted from the layout pattern. Then, the truth table concerned with the input logical values and output logical values, which enables to detect the short circuit failures of the adjacent lines is obtained. Then, the outputs of the logical circuit which receives the obtained input logical values are monitored and compared with the output logical values, whereby the short circuit failures in the logical circuit can be detected. 
   In addition, in this embodiment, the truth tables for detecting the short circuit failures between adjacent lines of respective combinations are obtained, and these truth tables are integrated with deleting the overlapping parts. Then, the short circuit failure is detected using this integrated truth table. Therefore, the short circuit failure can be detected in a shorter time. 
   In this first embodiment, the description is given using a simple logical circuit. However, the short circuit failure in a more complex logical circuit can be easily detected using the semiconductor inspection method of the first embodiment. 
   Further, in this first embodiment, the case where the adjacent lines having the possibilities of short circuits occurring between the lines are extracted from the layout pattern of the semiconductor is described. However, lines, a distance between the lines being equal to or less than a threshold, can be extracted as adjacent lines from layout data which are data for creating a layout pattern of a semiconductor. 
   Further, when a recording medium which records a program for implementing the semiconductor inspection method of the first embodiment is supplied to a system or apparatus and a main processor such as a CPU of the system or apparatus reads and executes the program stored in the recording medium, the same effects as those described in the first embodiment can be obtained. 
   Here, as recording media which record the program, floppy discs, hard discs, optical discs, magnetic discs, magneto-optical discs, CD-ROMs, DVD-RAMS, magnetic tapes, punched cards, nonvolatile memory cards, or ROMs can be utilized.