Abstract:
A method and system for making a photographic mask. The method includes determining a first contact area, processing information associated with the first contact area, and determining whether a first optical compensation should be applied to the first contact area based on at least information associated with the first contact area. Additionally, the method includes if the first optical compensation should be applied to the first contact area, applying the first optical compensation to the first contact area, processing information associated with first optical compensation, determining a first distance between the first optical compensation and a second optical compensation or a second contact area, processing information associated with the first distance, and adjusting the first optical compensation based on at least information associated with the first distance.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This application claims priority to Chinese Patent Application No. 200510030306.2, filed Sep. 28, 2005, commonly assigned, incorporated by reference herein for all purposes. 
   BACKGROUND OF THE INVENTION 
   The present invention is directed to integrated circuits and their processing for the manufacture of semiconductor devices. More particularly, the invention provides a method and system for optical pattern compensation for the manufacture of integrated circuits. Merely by way of example, the invention has been applied to photolithographic masks for the manufacture of integrated circuits. But it would be recognized that the invention has a much broader range of applicability. 
   Integrated circuits or “ICs” have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Current ICs provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of ICs. Semiconductor devices are now being fabricated with features less than a quarter of a micron across. 
   Increasing circuit density has not only improved the complexity and performance of ICs but has also provided lower cost parts to the consumer. An IC fabrication facility can cost hundreds of millions, or even billions, of dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of ICs on it. Therefore, by making the individual devices of an IC smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as each process used in IC fabrication has a limit. That is to say, a given process typically only works down to a certain feature size, and then either the process or the device layout needs to be changed. An example of such a limit is photographical masks used for the manufacture of integrated circuits in a cost effective and efficient way. 
   Fabrication of custom integrated circuits using chip foundry services has evolved over the years. Fabless chip companies often design the custom integrated circuits. Such custom integrated circuits require a set of custom masks commonly called “reticles” to be manufactured. A chip foundry company called Semiconductor International Manufacturing Company (SMIC) of Shanghai, China is an example of a chip company that performs foundry services. Although fabless chip companies and foundry services have increased through the years, many limitations still exist. For example, photolithography is limited by optical diffraction and other effects. These and other limitations are described throughout the present specification and more particularly below. 
   From the above, it is seen that an improved technique for processing semiconductor devices is desired. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is directed to integrated circuits and their processing for the manufacture of semiconductor devices. More particularly, the invention provides a method and system for optical pattern compensation for the manufacture of integrated circuits. Merely by way of example, the invention has been applied to photolithographic masks for the manufacture of integrated circuits. But it would be recognized that the invention has a much broader range of applicability. 
   In a specific embodiment, the invention provides a method for making a photographic mask. The method includes determining a first contact area, processing information associated with the first contact area, and determining whether a first optical compensation should be applied to the first contact area based on at least information associated with the first contact area. Additionally, the method includes if the first optical compensation should be applied to the first contact area, applying the first optical compensation to the first contact area, processing information associated with first optical compensation, determining a first distance between the first optical compensation and a second optical compensation or a second contact area, processing information associated with the first distance, and adjusting the first optical compensation based on at least information associated with the first distance. The processing information associated with the first contact area includes determining a plurality of distances from a first plurality of boundaries of the first contact area to a second plurality of boundaries of a conductive area, processing information associated with the plurality of distances, determining a plurality of areas associated with the plurality of distances respectively, and processing information associated with the plurality of areas. The determining whether a first optical compensation should be applied to the first contact area is performed based on at least information associated with the plurality of distances and the plurality of areas. 
   In another specific embodiment of the present invention, a method for making a photographic mask includes determining a first conductive area and a first extended area, processing information associated with the first conductive area and the first extended area, determining a second conductive area based on at least information associated with the first conductive area and the first extended area, determining a second extended area based on at least information associated with the first conductive area and the first extended area, processing information associated with the second conductive area and the second extended area, and determining whether a first optical pattern compensation should be applied to the second conductive area. Additionally, the method includes if the first optical pattern compensation should be applied to the second conductive area, applying the first optical compensation to the second conductive area, processing information associated with first optical compensation, determining a first distance between the first optical compensation and a second optical compensation or a third conductive area, processing information associated with the first distance, and adjusting the first optical compensation based on at least information associated with the first distance. The first extended area includes a first active area and a protective area. The protective area surrounds the first active area and is free from being a part of a photolithographic mask. The determining whether a first optical pattern compensation should be applied to the second conductive area is performed based on at least information associated with the second conductive area and the second extended area. 
   In yet another specific embodiment of the present invention, a method for making a photographic mask includes determining a first contact area and at least one neighboring contact area, processing information associated with the first contact area and the at least one neighboring contact area, classifying the first contact area into one of a plurality of categories, and applying a first optical pattern compensation to the first contact area based on at least information associated with the first contact area and the at least one neighboring contact area. The classifying the first contact area is performed based on at least information associated with at least a first distance between the first contact area and the at least one neighboring contact area. 
   Many benefits are achieved by way of the present invention over conventional techniques. For example, the present technique provides an easy to use process that relies upon conventional technology. The present invention has numerous advantages over conventional techniques. Certain embodiments of the present invention selectively apply optical pattern compensations and reduce the database volume for mask design. Some embodiments of the present invention automatically check the spacing between various mask areas and adjust optical pattern compensations accordingly. The computation requirement for detecting design rule violations is reduced. Certain embodiments of the present invention consider relationship between different layers to select areas for optical pattern compensation. For example, the layers include a metal layer and a via layer, or an active layer and a polysilicon layer. Some embodiments of the present invention provides different optical pattern compensations to different types of contact hole areas. Certain embodiments of the present invention reduce mask conversion and writing time. Additionally, the method provides a process that is compatible with conventional process technology without substantial modifications to conventional equipment and processes. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below. 
   Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified diagram of a method for optical pattern compensation according to an embodiment of the present invention; 
       FIG. 2  is a simplified diagram for contact areas and metal areas according to an embodiment of the present invention; 
       FIG. 3  is a simplified diagram for the process  120  according to an embodiment of the present invention; 
       FIG. 4  is a simplified diagram for the process  120  according to an embodiment of the present invention; 
       FIGS. 5 and 6  are simplified diagrams for applying optical pattern compensation according to an embodiment of the present invention; 
       FIGS. 7 and 8  are simplified diagrams for determining spacing according to an embodiment of the present invention; 
       FIGS. 9 and 10  are simplified diagrams for adjusting optical pattern compensation according to an embodiment of the present invention; 
       FIG. 11  shows a simplified diagram for a photolithographic mask with optical pattern compensation according to an embodiment of the present invention; 
       FIG. 12  is a simplified diagram of a method for optical pattern compensation according to another embodiment of the present invention; 
       FIG. 13  is a simplified diagram for polysilicon areas and extended areas according to an embodiment of the present invention; 
       FIGS. 14 and 15  are simplified diagrams for determining extended areas without polysilicon areas below threshold; 
       FIG. 16  is a simplified diagram for determining extended areas overlapping with polysilicon areas according to an embodiment of the present invention; 
       FIG. 17  is a simplified diagram for determining polysilicon areas for optical pattern compensation according to an embodiment of the present invention; 
       FIG. 18  is a simplified diagram for applying optical pattern compensation according to an embodiment of the present invention; 
       FIG. 19  is a simplified diagram for determining spacing according to an embodiment of the present invention; 
       FIG. 20  is a simplified diagram for adjusting optical pattern compensation according to an embodiment of the present invention; 
       FIG. 21  is a simplified diagram for a photolithographic mask with optical pattern compensation according to another embodiment of the present invention; 
       FIG. 22  is a simplified diagram of a method for optical pattern compensation according to yet another embodiment of the present invention; 
       FIG. 23  is a simplified diagram for contact hole areas according to an embodiment of the present invention; 
       FIG. 24  is a simplified diagram for determining spacing below threshold according to an embodiment of the present invention; 
       FIG. 25  is a simplified diagram for determining contact hole areas not associated with spacing below threshold according to an embodiment of the present invention; 
       FIGS. 26 and 27  are simplified diagrams for classifying contact hole areas associated with spacing below threshold according to an embodiment of the present invention; 
       FIG. 28  is a simplified diagram for applying optical pattern compensation according to an embodiment of the present invention; 
       FIG. 29  is a simplified diagram for a photolithographic mask with optical pattern compensation according to yet another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is directed to integrated circuits and their processing for the manufacture of semiconductor devices. More particularly, the invention provides a method and system for optical pattern compensation for the manufacture of integrated circuits. Merely by way of example, the invention has been applied to photolithographic masks for the manufacture of integrated circuits. But it would be recognized that the invention has a much broader range of applicability. 
     FIG. 1  is a simplified diagram of a method for optical pattern compensation according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The method  100  includes the following processes:
         1. Process  110  for determining contact areas;   2. Process  120  for determining contact areas for optical pattern compensation;   3. Process  130  for applying optical pattern compensation;   4. Process  140  for determining spacing;   5. Process  150  for adjusting optical pattern compensation.       
   The above sequence of processes provides a method according to an embodiment of the present invention. Other alternatives can also be provided where processes are added, one or more processes are removed, or one or more processes are provided in a different sequence without departing from the scope of the claims herein. Future details of the present invention can be found throughout the present specification and more particularly below. 
   At the process  110 , contact areas are located.  FIG. 2  is a simplified diagram for contact areas and metal areas according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. A photolithographic mask  200  includes contact areas  210 ,  212  and  214 , and a metal area  220 . For example, the contact areas  210 ,  212  and  214  are the areas of a metal area  220  exposed to contact holes or vias. The metal area  220  may form part of metal 1 layer, metal 2 layer, metal 3 layer, metal 4 layer, metal 5 layer, or other metal layer. 
   At the process  120 , contact areas for optical pattern compensation are selected.  FIG. 3  is a simplified diagram for the process  120  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The process  120  includes the following processes:
         1. Process  310  for determining widths below threshold;   2. Process  320  for determining areas below threshold;   3. Process  330  for determining widths below threshold without areas below threshold;   4. Process  340  for selecting contact areas for optical pattern compensation.       

   At the process  310 , widths below a width threshold are determined. The widths are measured from the edges of contact areas to the outer edges of the metal area. At the process  320 , areas associated with the widths below the width threshold are identified. Among them, the areas that are smaller than an area threshold are identified. At the process  330 , the widths below the width threshold that are not associated with any area below the area threshold are identified. At the process  340 , contact areas for optical pattern compensation are selected. These contact areas should have at least 3 sides in contact with the widths below the width threshold that are not associated with any area below the area threshold. 
     FIG. 4  is a simplified diagram for the process  120  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. Areas  410 ,  412 ,  414 ,  416 ,  418 ,  420 ,  422  and  424  each have a width small than a width threshold. The width is measured from an edge of the contact area  210 ,  212  or  214  to an outer edge of the metal area  220 . For example, the area  410  has a width smaller than the width threshold, and the width is measured from an edge  430  to an edge  432 . Among the areas  410 ,  412 ,  414 ,  416 ,  418 ,  420 ,  422  and  424 , the area  420  has an area smaller than an area threshold. Other areas  410 ,  412 ,  414 ,  416 ,  418 ,  422  and  424  are associated with the widths below the width threshold that are not associated with an area below the area threshold. Among the contact areas  210 ,  212  and  214 , the contact area  214  has at least 3 sides in contact with the areas  410 ,  412  and  414  associated with the widths smaller than the width threshold. The contact area  214  is selected for optical pattern compensation. 
   At the process  130 , an optical pattern compensation is applied.  FIGS. 5 and 6  are simplified diagrams for the process  130  according to an embodiment of the present invention. These diagrams are merely examples, which should not unduly limit the scope of the claims herein. The photolithographic mask  500  includes an optical pattern compensation  510  surrounding the area  214  previously selected for optical pattern compensation. The optical pattern compensation  510  provides a protective layer with a certain width around the contact area  220 . The optical pattern compensation  510  is merged with the metal area to form a mask area. 
   At the process  140 , spacing between outer edges of mask areas is determined. For example, a distance between an outer edge of an optical pattern compensation and an outer edge of another optical pattern compensation is determined. As another example, a distance between an outer edge of an optical pattern compensation and an outer edge of the metal area is determined. If a distance is below a spacing threshold, the outer edge of the optical pattern compensation that is associated with the distance below the spacing threshold is selected.  FIGS. 7 and 8  are simplified diagrams for the process  140  according to an embodiment of the present invention. These diagram are merely examples, which should not unduly limit the scope of the claims herein. A distance  730  is measured from an outer edge  720  of the optical pattern compensation  510  to an outer edge  722  of another optical pattern compensation  710 . If the distance  730  is smaller than a spacing threshold, the outer edges  720  and  722  are selected. 
   At the process  150 , an optical pattern compensation is adjusted if an distance associated with the optical pattern compensation is smaller than a spacing threshold. An outer edge previously selected and associated with the distance below the spacing threshold is adjusted so that the distance increases to meet or exceed the spacing threshold.  FIGS. 9 and 10  are simplified diagrams for the process  150  according to an embodiment of the present invention. These diagram are merely examples, which should not unduly limit the scope of the claims herein. The outer edges  720  and  722  are adjusted towards outer edges  1010  and  1012  of the contact areas  220  and  1020  respectively. For example, the adjusted outer edges coincide with the edges  1010  and  1012  respectively. In another example, only one or neither of the adjusted outer edges coincides with the edges  1010  and  1012  respectively. 
   As discussed above and further emphasized here,  FIG. 1  is merely an example, which should not unduly limit the scope of the claims herein. An addition process for making an photolithography mask can also be performed. The photolithographic mask includes a metal area and an optical pattern compensation. For example, the photolithographic mask includes the metal area  220  and the optical pattern compensation  510 . As another example,  FIG. 11  shows a simplified diagram for a photolithographic mask with optical pattern compensation according to an embodiment of the present invention. These diagram are merely examples, which should not unduly limit the scope of the claims herein. 
     FIG. 12  is a simplified diagram of a method for optical pattern compensation according to another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The method  1200  includes the following processes:
         1. Process  1210  for determining polysilicon areas and extended areas;   2. Process  1220  for determining extended areas without polysilicon areas below threshold;   3. Process  1230  for determining extended areas overlapping with polysilicon areas;   4. Process  1240  for determining polysilicon areas for optical pattern compensation;   5. Process  1250  for applying optical pattern compensation;   6. Process  1260  for determining spacing;   7. Process  1270  for adjusting optical pattern compensation.       
   The above sequence of processes provides a method according to an embodiment of the present invention. Other alternatives can also be provided where processes are added, one or more processes are removed, or one or more processes are provided in a different sequence without departing from the scope of the claims herein. Future details of the present invention can be found throughout the present specification and more particularly below. 
   At the process  1210 , polysilicon areas and extended areas are determined.  FIG. 13  is a simplified diagram for polysilicon areas and extended areas according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. A photolithographic mask  1300  includes polysilicon areas  1310  and  1320 , and active areas  1330  and  1340 . Extended areas  1350  and  1360  include the active areas  1330  and  1340  respectively and additional layers surrounding the active areas  1330  and  1340  respectively. For example, the extended area  1350  includes an additional layer surrounding the polysilicon layer  1330 . The polysilicon areas  1310  and  1320  each intersect the areas  1330 ,  1340 ,  1350  and  1360 . 
   At the process  1220 , extended areas without polysilicon areas below threshold are determined.  FIGS. 14 and 15  are simplified diagrams for the process  1220  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. As shown in  FIG. 14 , parts of extended areas excluding polysilicon areas are determined. For example, the extended areas without polysilicon areas include areas  1410 ,  1420 ,  1430 ,  1440 ,  1450  and  1460 . As shown in  FIG. 15 , the areas  1410 ,  1420 ,  1430 ,  1440 ,  1450  and  1460  are compared with an area threshold. Among them, the areas  1410 ,  1420 ,  1440  and  1450  are smaller than the area threshold, and they are the extended areas without polysilicon areas below threshold. 
   At the process  1230 , extended areas overlapping with polysilicon areas are determined.  FIG. 16  is a simplified diagram for the process  1230  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The extended areas overlapping with polysilicon areas are areas  1610 ,  1620 ,  1630  and  1640 . These areas  1610 ,  1620 ,  1630  and  1640  are parts of the extended areas  1350  and  1360  overlapping with the polysilicon areas  1310  and  1320 . For example, the area  1610  overlaps with the polysilicon area  1310  and the extended area  1350 . 
   At the process  1240 , polysilicon areas for optical pattern compensation are determined. The polysilicon areas for optical pattern compensation are the extended areas without polysilicon areas below threshold that in contact with only one of the extended area overlapping with polysilicon areas.  FIG. 17  is a simplified diagram for the process  1240  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The polysilicon areas for optical pattern compensation include the areas  1410  and  1440 . For example, the area  1410  is in contact with the area  1610 , not the areas  1620 ,  1630  and  1640 . The area  1420  touches both the areas  1610  and  1620 , and the area  1420  is not a polysilicon area for optical pattern compensation. 
   At the process  1250 , an optical pattern compensation is applied.  FIG. 18  is a simplified diagram for the process  1250  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The photolithographic mask  1800  includes optical pattern compensations  1810  and  1820  surrounding the areas  1810  and  1820  selected for optical pattern compensation. For example, the optical pattern compensation  1810  provides a protective layer with a certain width around the area  1410 . The optical pattern compensations  1810  and  1820  are merged with the areas  1410  and  1440  respectively to form mask areas. 
   At the process  1260 , spacing between outer edges of mask areas is determined. For example, a distance between an outer edge of an optical pattern compensation and an outer edge of another optical pattern compensation is determined. As another example, a distance between an outer edge of an optical pattern compensation and an outer edge of the poly area is determined. If a distance is below a spacing threshold, the outer edge of the optical pattern compensation that is associated with the distance below the spacing threshold is selected.  FIG. 19  is a simplified diagram for the process  1260  according to an embodiment of the present invention. These diagram are merely examples, which should not unduly limit the scope of the claims herein. A distance  1910  is measured from an outer edge  1920  of the optical pattern compensation  1810  to an outer edge  1930  of another optical pattern compensation  1820 . If the distance  1910  is smaller than a spacing threshold, the outer edges  1920  and  1930  are selected. 
   At the process  1270 , an optical pattern compensation is adjusted if an distance associated with the optical pattern compensation is smaller than a spacing threshold. An outer edge previously selected and associated with the distance below the spacing threshold is adjusted so that the distance increases to meet or exceed the spacing threshold.  FIG. 20  is a simplified diagram for the process  1270  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The outer edges  1920  and  1930  are adjusted towards outer edges  2010  and  2020  of the polysilicon areas  1310  and  1320  respectively. For example, the adjusted outer edges coincide with the edges  2010  and  2020  respectively. In another example, only one or neither of the adjusted outer edges coincides with the edges  1310  and  1320  respectively. 
   As discussed above and further emphasized here,  FIG. 12  is merely an example, which should not unduly limit the scope of the claims herein. An addition process for making an photolithography mask can also be performed. The photolithographic mask includes a polysilicon area and an optical pattern compensation. For example, the photolithographic mask includes the polysilicon area  1310  and the optical pattern compensation  1810 . As another example,  FIG. 21  is a simplified diagram for a photolithographic mask with optical pattern compensation according to another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. 
     FIG. 22  is a simplified diagram of a method for optical pattern compensation according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The method  2200  includes the following processes:
         1. Process  2210  for determining contact hole areas;   2. Process  2220  for determining spacing below threshold;   3. Process  2230  for determining contact hole areas not associated with spacing below threshold;   4. Process  2240  for classifying contact hole areas associated with spacing below threshold;   5. Process  2250  for applying optical pattern compensation.       
   The above sequence of processes provides a method according to an embodiment of the present invention. Other alternatives can also be provided where processes are added, one or more processes are removed, or one or more processes are provided in a different sequence without departing from the scope of the claims herein. Future details of the present invention can be found throughout the present specification and more particularly below. 
   At the process  2210 , contact hole areas are located.  FIG. 23  is a simplified diagram for contact hole areas according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The contact hole areas include areas  2310 ,  2320 ,  2330 ,  2340 ,  2350 ,  2360 ,  2370 ,  2380  and  2390 . 
   At the process  2220 , spacing below threshold is determined. A distance is measured between an outer edge of a contact hole area and an outer edge of another contact area. The distance is compared with a distance threshold. If the distance is smaller than the distance threshold, the distance is selected.  FIG. 24  is a simplified diagram for the process  2220  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. Areas  2402 ,  2404 ,  2408 ,  2410 ,  2412 ,  2414 ,  2416 ,  2418  and  2420  are associated with distances shorter than the distance threshold. For example, the distance threshold equals 0.7 μm. 
   At the process  2230 , contact hole areas not associated with spacing below threshold are determined.  FIG. 25  is a simplified diagram for the process  2230  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. The contact hole areas  2320 ,  2330 ,  2340 ,  2350 ,  2360 ,  2370 ,  2380  and  2390  are in contact with at least one of the areas  2402 ,  2404 ,  2408 ,  2410 ,  2412 ,  2414 ,  2418  and  2420 , and these contact hole areas are associated with spacing below threshold. For example, the contact hole area  2320  touches the areas  2410  and  2420 . The area  2310  is not in contact with any of the areas  2402 ,  2404 ,  2408 ,  2410 ,  2412 ,  2414 ,  2418  and  2420 , and the area  2310  is a contact hole area not associated with spacing below threshold. 
   At the process  2240 , contact hole areas associated with spacing below threshold is classified. For example, contact hole areas associated with spacing below threshold is classified into three categories A, B and C. The category A refers to the contact hole areas associated with one or two distances below threshold. The category B refers to the contact hole areas associated with three distances below threshold. The category C refers to the contact hole areas associated with four distances below threshold.  FIGS. 26 and 27  are simplified diagrams for the process  2240  according to an embodiment of the present invention. These diagrams are merely examples, which should not unduly limit the scope of the claims herein. As shown in  FIG. 26 , the areas  2320 ,  2330 ,  2340 ,  2370  and  2390  belong to the category A. The areas  2360  and  2380  belong to the category B. The area  2350  belongs to the category C. 
   At the process  2250 , an optical pattern compensation is applied. The optical pattern compensation for various types of contact hole areas may be different.  FIG. 28  is a simplified diagram for the process  2250  according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. Optical pattern compensations of three types are applied, and the three types are labeled as D, E and F. Optical pattern compensations  2810 ,  2820 ,  2830 ,  2840 ,  2870  and  2890  of type D is applied to the contact hole area  2310  not associated with spacing below threshold and the contact hole areas  2320 ,  2330 ,  2340 ,  2370  and  2390  of category A respectively. Optical pattern compensations  2860  and  2880  of type E are applied to the contact hole areas  2360  and  2380  of category B. A optical compensation  2850  of type F is applied to the area  2350  of category C. 
   As discussed above and further emphasized here,  FIG. 22  is merely an example, which should not unduly limit the scope of the claims herein. An addition process for making an photolithography mask can also be performed. The photolithographic mask includes a contact hole area and an optical pattern compensation. For example, the photolithographic mask includes at least the contact hole area  2310  and the optical pattern compensation  2810 . As another example,  FIG. 29  is a simplified diagram for a photolithographic mask with optical pattern compensation according to yet another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. 
   The present invention has numerous advantages over conventional techniques. Certain embodiments of the present invention selectively apply optical pattern compensations and reduce the database volume for mask design. Some embodiments of the present invention automatically check the spacing between various mask areas and adjust optical pattern compensations accordingly. The computation requirement for detecting design rule violations is reduced. Certain embodiments of the present invention consider relationship between different layers to select areas for optical pattern compensation. For example, the layers include a metal layer and a via layer, or an active layer and a polysilicon layer. Some embodiments of the present invention provides different optical pattern compensations to different types of contact hole areas. Certain embodiments of the present invention reduce mask conversion and writing time. 
   It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.