Abstract:
In a charged particle beam drawing data preparing method of preparing drawing pattern data used in a charged particle beam drawing apparatus that forms a micropattern with a charged particle by converting CAD data, it is verified by using interlayer calculation whether a difference exists between the CAD data and the drawing pattern data. When it is verified that a difference exists between the CAD data and the drawing apparatus pattern data, drawing pattern data that compensates for this difference is generated by using interlayer calculation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pattern data preparing method used in a charged particle beam drawing apparatus that prepares a micropattern with a charged particle beam and, more particularly, to a pattern data preparing method of obtaining highly reliable pattern data. 
     2. Description of the Prior Art 
     Along with the development of LSIs, patterns used in semiconductor devices continue to shrink rapidly in feature size. The charged particle beam drawing method using a charged particle beam is an effective method capable of forming a pattern with a size of 0.25 μm or less which will be needed in the future. As a charged particle beam drawing apparatus, a variable shaping type electron beam drawing apparatus as shown in FIG. 1 is used. According to this apparatus, an electron beam is shaped to have a rectangular spot with a first aperture  3  and a second aperture  6 . A resultant electron beam  50 B is radiated onto a semiconductor wafer  11  coated with a resist, thereby forming a micropattern. 
     Referring to FIG. 1, an electron beam  50  emitted from an electron gun  1  passes through a blanking electrode  2 , the first aperture  3 , a shaping lens  4 , a shaping deflector  5 , the second aperture  6 , a reduction lens  7 , a main deflector  8 , a sub-deflector  9 , and a projection lens  10  to irradiate the semiconductor wafer  11  on a stage. A square opening  3 A is formed in the first aperture  3  to form a rectangular beam  50 A. The rectangular beam  50 A passes through an opening  6 A of the second aperture  6  to have a small-size square beam spot. Shot (one exposure operation) is repeated with this small-size electron beam  50 B to form one latent image pattern in the resist on the semiconductor wafer  11 . 
     A storage unit  15  stores figure data. The figure data is read by a computer  14  and temporarily stored in a figure data memory  17 . The drawing apparatus reads this figure data as required, converts it into a control signal with a controller  16 , and controls the blanking electrode  2 , the shaping deflector  5 , the main deflector  8 , and the sub-deflector  9  to draw a figure. This figure data is obtained by subjecting CAD data to overlapping removal, proximity effect correction, and the like and converting the resultant CAD data into a specific format for the drawing apparatus. Japanese Unexamined Patent Publication No. 7-288224 describes a method that uses interlayer calculation in order to prevent occurrence of deformation of the pattern on the cell boundary when enlargement and reduction are performed while retaining the hierarchical cell structure. Japanese Unexamined Patent Publication No. 4-372155 describes a method of comparing and verifying the LSI layout pattern, outputting the coordinates of different points, and correcting the layout pattern by using an editor. 
     In recent years, as the integration degree of semiconductor devices as objects on which patterns are to be drawn increases, the number of patterns to be drawn becomes very large, and the amount of data handled by the conversion software also increases very much. For this reason, batch processing is widely performed. More specifically, a semiconductor chip is divided, and conversion is performed in units of batch process regions. After conversion for all the regions is ended, obtained data are combined to prepare 1-chip data. When this batch processing is performed, it is difficult to handle a pattern crossing the boundary or boundaries between more than one region. Sometimes pattern losses, generation of a redundant pattern, or positional shifts may occur in the data after conversion. If data having such a defect is directly used for drawing, it produces interconnect disconnections, short-circuits, or the like to lead to a decrease in yield of devices. Therefore, it is important to verify whether converted data is different from the original CAD data. Japanese Unexamined Patent Publication No. 7-288224 provides no means for verifying such defects of the pattern data. According to Japanese Unexamined Patent Publication No. 4-372155, the layout pattern is directly corrected with reference to the coordinates of different points, and the corrected data is converted into drawing data again. Accordingly, a very long process time is required to obtain normal drawing data. Since correction is manually performed by the operator, a new defective portion may be undesirably formed during the course of correction. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the above situation in the prior art, and has as its object to provide a method of preparing charged particle beam drawing data, which can quickly correct any calculation error that occurs when converting CAD data into pattern data without forming a new defective portion, and a recording medium on which a program thereof is recorded. 
     In order to achieve the above object, according to the first aspect of the present invention, there is provided a charged particle beam drawing data preparing method of preparing drawing pattern data used in a charged particle beam drawing apparatus that forms a micropattern with a charged particle by converting CAD data, the method comprising the steps of verifying, by using interlayer calculation, whether a difference exists between the CAD data and the drawing pattern data, and when it is verified in the verifying step that a difference exists between the CAD data and the drawing apparatus pattern data, generating drawing pattern data that compensates for this difference by using interlayer calculation. 
     According to the second aspect of the present invention, there is provided a charged particle beam drawing data preparing method of preparing pattern data used in a charged particle beam drawing apparatus that forms a micropattern with a charged particle, wherein when a difference exists between original CAD data and drawing apparatus pattern data, pattern data that compensates for this difference is generated by using interlayer calculation. 
     According to the third aspect of the present invention, there is provided a charged particle beam drawing data preparing method according to the second aspect, comprising, as means for generating the compensation pattern data, the steps of performing an exclusive logical sum operation (eor) between the original CAD data and the drawing apparatus pattern data having pattern loss, and outputting, as drawing pattern data, both the drawing apparatus pattern data having the pattern loss and pattern data obtained by the exclusive logical sum operation. 
     According to the fourth aspect of the present invention, there is provided a charged particle beam drawing data preparing method according to the second aspect, comprising, as means for generating the compensation pattern data, the steps of performing an exclusive logical sum operation (eor) between the original CAD data and the drawing apparatus pattern data having a pattern shift, performing a logical product operation (and) between the original CAD data and pattern data obtained by the exclusive logical sum operation, performing a logical difference operation (sub) between the drawing apparatus pattern data having the pattern shift and the pattern data obtained by the exclusive logical sum operation, and outputting, as drawing pattern data, both the pattern data obtained by the logical difference operation and the pattern data obtained by the logical product operation. 
     According to the fifth aspect of the present invention, there is provided a charged particle beam drawing data preparing method according to the second aspect, comprising, as means for generating the compensation pattern data, the steps of performing an exclusive logical sum operation (eor) between the original pattern data and the drawing apparatus pattern data having a redundant pattern, performing a logical difference operation (sub) between the redundant pattern and the pattern data obtained by the exclusive logical sum operation, and outputting, as drawing pattern data, the pattern data obtained by the logical difference operation. 
     According to the sixth aspect of the present invention, there is provided a charged particle beam drawing data preparing method according to the second aspect, comprising, as means for generating the compensation pattern data, the steps of performing an exclusive logical sum operation (eor) between the original CAD data and drawing apparatus pattern data having pattern losses, pattern shifts, and redundant patterns, performing a logical product operation (and) between the original cad data and pattern data obtained by the exclusive logical sum operation, performing a logical difference operation (sub) between the drawing apparatus pattern data having pattern losses, pattern shifts, and redundant patterns, and the pattern data obtained by the exclusive logical sum operation, and determining whether the number of figures of the pattern data obtained by the logical product operation is 0, wherein if the number of figures of the pattern data obtained by the logical product operation is 0, the pattern data obtained by the logical difference operation is output as the drawing data; otherwise, both the pattern data obtained by the logical difference operation and the pattern data obtained by the logical product operation are output as the drawing data. 
     According to the seventh aspect of the present invention, there is provided a machine-readable recording medium, on which is recorded a program of preparing charged particle beam drawing data, used in a charged particle beam drawing apparatus that forms a micropattern with a charged particle by converting CAD data with a computer, the program serving to cause the computer to execute the steps of verifying, by using interlayer calculation, whether a difference exists between the CAD data and the drawing data, and when it is verified in the verifying step that a difference exists between the CAD data and the drawing data, generating drawing pattern data that compensates for the difference by using interlayer calculation. 
     As is apparent from the respective aspects described above, according to the present invention, when converting CAD data into the drawing apparatus pattern data, even if a calculation error occurs, pattern data that compensates for the error can be automatically generated by using interlayer calculation. Therefore, the error can be corrected quickly. Since the original CAD data is not manipulated, no new defective portion will be formed. As a result, disconnections and short-circuits of the semiconductor devices can be prevented, thereby improving the yield. 
     Although the present invention has been described by way of an electron beam direct drawing apparatus, the present invention can also be applied to an optical exposure reticle drawing apparatus, i.e., a so-called a mask drawing apparatus. The charged particle beam is not limited to the electron beam, but the present invention can also be applied to a drawing apparatus which uses an ion beam as a charged particle beam. 
     The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principles of the present invention are shown by way of illustrative examples. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing the arrangement of a conventional charged particle beam drawing apparatus; 
     FIG. 2 is a flow chart showing a method of preparing charged particle beam drawing data according to the first embodiment of the present invention; 
     FIG. 3 is a diagram explaining the data preparing method according to the first embodiment shown in FIG. 2; 
     FIG. 4 is a flow chart showing a method of preparing charged particle beam drawing data according to the second embodiment of the present invention; 
     FIG. 5 is a diagram explaining the data preparing method according to the second embodiment shown in FIG. 4; 
     FIG. 6 is a flow chart showing a method of preparing charged particle beam drawing data according to the third embodiment of the present invention; 
     FIG. 7 is a diagram explaining the data preparing method according to the third embodiment shown in FIG. 6; 
     FIG. 8 is a flow chart showing a method of preparing charged particle beam drawing data according to the fourth embodiment of the present invention; and 
     FIG. 9 is a diagram explaining the data preparing method according to the fourth embodiment shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described in detail with reference to the several preferred embodiments shown, in the accompanying drawings. 
     FIG. 2 is a flow chart showing a method of preparing charged particle beam drawing data according to the first embodiment of the present invention. This flow chart shows the process of verifying whether drawing pattern data is different from the original CAD data and, if an abnormality is found, generating data that compensates for the abnormality. The arrangement of a charged particle beam drawing apparatus to which the method of preparing charged particle beam drawing data according to the present invention is identical to the conventional one shown in FIG.  1 . Accordingly, in all the following embodiments, illustration of this apparatus will be omitted. The method of preparing charged particle beam drawing data according to the present invention is executed by a computer  14  of FIG.  1 . 
     In this embodiment, drawing pattern data obtained by converting CAD data 00 is referred to as EB data 0. First, the exclusive logical sum (eor) between CAD data 00 and EB data 0 is calculated to obtain eor data (step  19 ). Whether the number of figures of eor data is 0 is checked (step  20 ). If YES in step  20 , it is determined that EB data 0 is normal, and EB data 0 is output as the drawing data (step  21 ). 
     If NO in step  20 , it is determined that EB data 0 has an abnormality, and the flow advances to a compensation data generation step. The eor data is added to EB data 0 to generate compensation data (drawing data) (step  22 ), and the processing operation is ended. 
     FIG. 3 is a view explaining a case wherein pattern loss occurs when converting the CAD data into the drawing pattern data. In this case, when the CAD data  18  is converted into drawing data by applying the method of preparing charged particle beam drawing data described above, EB data  19   a  (EB data 0) is generated. In step  19 , the exclusive logical sum between the CAD data  18  and the EB data  19   a  is calculated. As the result of this exclusive logical sum operation, a FIG. 20 a  of a portion where pattern loss has occurred is extracted as eor data. In step  22 , both the EB data  19   a  and the eor data  20   a  are output as drawing data. Drawing data  25   a  which is not different from the CAD data  18  can be obtained, and the pattern loss defect can be compensated for. 
     FIG. 4 is a flow chart showing a method of preparing charged particle beam drawing data according to the second embodiment of the present invention. This flow chart shows the process of verifying whether drawing pattern data is different from the original CAD data and, if an abnormality is found, generating data that compensates for the abnormality. In this embodiment, drawing pattern data obtained by converting CAD data 00 is referred to as EB data 0. First, the exclusive logical sum (eor) between CAD data 00 and EB data 0 is calculated to obtain eor data (step  19 ). Whether the number of figures of eor data is 0 is checked (step  20 ). If YES in step  20 , it is determined that EB data 0 is normal, and EB data 0 is output as the drawing data (step  21 ). If NO in step  20 , it is determined that EB data 0 has an abnormality, and the flow advances to step  22  for generating compensation data. 
     In step  22 , the logical product (and) between the CAD data and the eor data is calculated to extract patch data including only patterns that should exist. Subsequently, the logical difference (sub) between EB data 0 and the eor data to generate EB data 1 is calculated (step  23 ). The patch data described above is added to EB data 1. The sum is output as the drawing data (step  24 ), and the processing operation is ended. 
     FIG. 5 is a view explaining a case wherein a positional shift has occurred when converting the CAD data into the drawing pattern data. In this case, when CAD data  18  is converted into drawing data by applying the method of preparing charged particle beam drawing data described above, EB data  19   b  (EB data 0) is generated. In step  19 , the exclusive logical sum between the CAD data  18  and the EB data  19   b  is calculated. As the result of this exclusive logical sum operation, a pattern  20   b  that should originally exist and a pattern  20   d  that should not exist are extracted. 
     Furthermore, the logical product (and) between the CAD data and the eor data (step  22 ) is calculated to extract only the pattern  20   b  (patch pattern) which should exist. Subsequently, the logical difference (sub) between the EB data  19   b , and the eor data  20   b  and  20   d  is calculated to generate EB data  23   b  (step  23 ). Data as the sum of the EB data  23   b  and the patch data  20   b  is output as the drawing data to obtain drawing data  25   b  which is not different from the CAD data (step  24 ). As a result, drawing data which is not different from the CAD data can be obtained, and the positional shift defect can be compensated for. 
     FIG. 6 is a flow chart showing a method of preparing charged particle beam drawing data according to the third embodiment of the present invention. This flow chart shows the process of verifying whether drawing pattern data is different from the original CAD data and, if an abnormality has occurred, generating data that compensates for the abnormality. In this embodiment, drawing pattern data obtained by converting CAD data 00 is referred to as EB data 0. 
     First, the exclusive logical sum (eor) is calculated between CAD data 00 and EB data 0 to obtain eor data (step  19 ). Whether the number of figures of the eor data is 0 is checked (step  20 ). If YES in step  20 , it is determined that EB data 0 is normal, EB data 0 is output as the drawing data (step  21 ), and the processing operation is ended. If NO in step  20 , it is determined that EB data 0 has an abnormality, and the flow advances to step  22  for generating compensation data. In step  22 , the logical difference between EB data 0 and the eor data is calculated to generate EB data 1. EB data 1 is output as the drawing data (step  23 ), and the processing operation is ended. 
     FIG. 7 is a view explaining a case wherein a redundant pattern is generated when converting the CAD data into the drawing pattern data. In this case, when CAD data  18  is converted into the drawing data by applying the method of preparing charged particle beam drawing data described above, EB data  19   c  (EB data 0) is generated. In step  19 , the exclusive logical sum between the CAD data  18  and the EB data  19   c  is calculated. As the result of this exclusive logical sum operation, an abnormally generated pattern  20   c  is extracted as eor data. Subsequently, the logical difference (sub) between the EB data  19   c  and the eor data  20   c  (step  22 ) is calculated to generate EB data  23   c.  The EB data  23   c  is a pattern which is not different from the CAD pattern. The EB data  23   c  is directly output as the drawing data (step  23 ). Hence, the redundant pattern generation defect can be compensated for. 
     FIG. 8 is a flow chart showing a method of preparing charged particle beam drawing data according to the fourth embodiment of the present invention. This flow chart shows the process of verifying whether drawing pattern data is different from the original CAD data and, if an abnormality has occurred, generating data that compensates for the abnormality. In this embodiment, drawing pattern data obtained by converting CAD data 00 is referred to as EB data 0. 
     First, the exclusive logical sum (eor) between CAD data 00 and EB data 0 is calculated to obtain eor data (step  19 ). Whether the number of figures of eor data is 0 is checked (step  20 ). If YES in step  20 , it is determined that EB data 0 is normal, EB data 0 is output as the drawing data (step  21 ), and the processing operation is ended. If NO in step  20 , it is determined that EB data 0 has an abnormality, and the flow advances to step  22  for generating compensation data. 
     The logical product (and) between CAD data 00 and the eor data is calculated to generate patch data (step  22 ). Subsequently, the logical difference (sub) between EB data 0 and the eor data is calculated to generate EB data 1 (step  23 ). In order to discriminate each defective mode, whether the number of figures of the patch data is 0 is checked (step  24 ). If YES in step  24 , it is determined that this is mode  3  (generation of a redundant pattern), and EB data 1 is adopted as the drawing data (step  25 ). If NO in step  24 , it is determined that this is mode  1  (pattern loss) or mode  2  (positional shift), and data as the sum of EB data 1 and patch data is output as the drawing data (step  26 ). 
     FIG. 9 is a view explaining a case wherein all of the defects described in the first to third embodiments of the present invention described above are included in EB data 0. In other words, in this case, a pattern loss, a positional shift, and generation of a redundant pattern have occurred. In such a case, when the CAD data  18  is converted into the drawing data by employing the method of creating charged particle beam drawing data described above, EB data  19   a  to  19   c  (EB data 0) is generated. In step  19 , the exclusive logical sum between the CAD data  18  and the EB data  19   a  to  19   c  is calculated. As the result of the exclusive logical sum operation, at least one of a pattern loss, a positional shift, and generation of a redundant pattern generates eor data. In other words, when a pattern loss occurs, eor data  20   a  is generated. When a positional shift occurs, error data  20   b  and  20   d  are generated. When a redundant pattern is generated, eor data  20   c  is generated. 
     Thereafter, the logical product (and) between the CAD data  18  and the eor data ( 20   a  to  20   d ) is calculated (step  22 ). As a result, in a pattern having a defect of mode  1  (loss), patch data  22   a  similar to the eor data is generated. In a pattern having a defect of mode  2  (shift), a pattern  20   b  that should originally exist is extracted. In a pattern having a defect of mode  3  (generation), no common portion is present between the CAD data  18  and the eor data  20   c , and nothing remains accordingly. 
     The logical difference (sub) between EB data 0 ( 19   a  to  19   c ) and the eor data ( 20   a  to  20   d ) is calculated (step  23 ). As a result, in a pattern having a defect of mode  1  (loss), a pattern ( 23   a ) identical to EB data 0 ( 19   a ) is generated. In a pattern having a defect of mode  2  (shift), a pattern  23   b  obtained by subtracting the pattern  20   b , that should originally exist, from the CAD data  18  is generated. In a pattern having a defect of mode  3  (generation), a pattern  23   c  which is not different from the CAD data is generated. In order to discriminate each defective mode, whether the number of figures of the patch data is 0 is checked (step  24 ). 
     If YES in step  24 , it is determined that this is mode  3  (generation), and the EB data  23   c  is adopted as the drawing data (step  25 ). If NO in step  24 , it is determined that this is mode  1  or mode  2 , and data  25   a  as the sum of the EB data  23   a  and the patch data  22   a , or data  25   b  as the sum of the EB data  23   b  and the patch data  20   b , is adopted as the drawing data (step  26 ). 
     With the above steps, for EB data having defects of mode  1  to mode  3 , pattern data that compensates for these defects can be generated. A decrease in yield caused by data errors occurring during data conversion can thus be prevented.