Abstract:
A metrology recipe generator is offered which is capable of automatically creating a metrology recipe without halting the operation of the production line. The metrology recipe is used to carry out SEM-based dimensional metrology for evaluating patterns transferred onto wafers according to CAD data. The generator has a CAD alignment-specifying portion for specifying alignment in CAD according to CAD data and a CAD metrology position-specifying portion for specifying both the coordinates of positions on the wafers on which metrology measurements are made and a metrology type. The metrology recipe is created according to data from the CAD alignment-specifying portion and from the CAD metrology position-specifying portion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a waferless metrology recipe generator and a generating method for managing the finish of patterns transferred onto wafers.  
           [0003]    2. Description of the Related Art  
           [0004]    When there arises the need to inspect whether patterns formed on wafers have intended geometries in semiconductor fabrication steps, metrology SEMs have been heretofore used. Lengths such as pattern widths and pattern spacings are measured by these tools. The finished pattern geometries are evaluated based on the results of the metrology measurements. In recent years, however, miniaturization has progressed in semiconductor fabrication equipment and so a large amount of labor has been required to observe and evaluate patterns by metrology SEMs. Accordingly, the observation and evaluation have been conducted as follows. A pattern position to be measured by a metrology SEM is placed in position on the metrology SEM using a wafer that will become a finished product in practice. Recipe information for automation is created. A desired SEM image is obtained according to the created recipe information, for the observation and evaluation.  
           [0005]    In this way, in the past, a worker obtains low- and high-magnification images at given checkpoints on a fabricated wafer within a clean room at a wafer fabrication site. A metrology location is determined from the images, and a recipe is created. Therefore, during fabrication of the recipe, the equipment is temporarily placed out of in-line operation. The recipe is created manually. Consequently, the efficiency of automation has been deteriorated in the fabrication sequence.  
           [0006]    Furthermore, the observed subject on a wafer is placed in position at a wafer fabrication site. Therefore, limitations are placed on the measured locations. This presents another problem that pattern geometries cannot be sufficiently measured.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an advantage of the present invention to provide a waferless metrology recipe generator capable of automatically creating a metrology recipe for evaluating the geometries of transferred patterns formed on fabricated wafers without halting the operation of the manufacturing line.  
           [0008]    The present invention provides a waferless metrology recipe generator for creating a metrology recipe used to implement SEM-based dimensional metrology that evaluates transferred patterns formed on wafers according to CAD data. The recipe generator has alignment-specifying means for specifying alignment in CAD based on the CAD data, coordinate-specifying means for specifying the coordinates of positions on a wafer where metrology measurements should be performed, metrology type-specifying means for specifying a metrology type for each specified coordinate, and recipe creation means for creating the metrology recipe in response to the alignment-specifying means, coordinate-specifying means, and metrology type-specifying means.  
           [0009]    In the present invention, a recipe for specifying an observational position where the geometry of a pattern transferred onto a semiconductor wafer is observed using an electron microscope is automatically created using CAD data. This makes it unnecessary to halt the operation of the production equipment. Consequently, full automation and efficient operation of production are enabled. Furthermore, metrology locations can be specified in CAD data. Hence, measurements can be optimized. Yield management can be run optimally. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a schematic view of an automated metrology SEM system according to one embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a detailed block diagram of a metrology recipe creation portion shown in FIG. 1;  
         [0012]    [0012]FIG. 3 is a detailed block diagram of a metrology SEM portion shown in FIG. 1; and  
         [0013]    [0013]FIG. 4 is a flowchart illustrating the operation of the automated metrology SEM system shown in FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    An embodiment of the present invention is hereinafter described in detail with reference to the drawings.  
         [0015]    [0015]FIG. 1 is a schematic view showing the configuration of an automated metrology SEM system according to the invention. FIG. 2 is a detailed block diagram of the metrology recipe creation portion of FIG. 1. FIG. 3 is a detailed block diagram of the metrology SEM portion of FIG. 1.  
         [0016]    The automated metrology SEM system, generally indicated by reference numeral  1 , is described by referring to FIGS.  1 - 3 . The SEM system  1  is an instrument for evaluating the geometries of actual patterns by measuring the widths or spacing of these transferred patterns formed on wafers according to given CAD data. The SEM system  1  is made up of a CAD server  2  for storing the CAD data, a metrology recipe creation portion  3  for reading desired CAD data from the CAD server  2  and automatically creating a recipe according to the CAD data to specify observation positions on the wafers, and a metrology SEM portion  4  for taking desired SEM images of wafer surfaces according to the metrology recipe created by the metrology recipe creation portion  3  and performing metrology measurements of the specified locations.  
         [0017]    The metrology recipe creation portion  3  is now described. This portion  3  has a storage portion  31  for storing various kinds of data. The storage portion  31  has a first memory  31 A for storing alignment data indicating the correspondence in coordinates between each wafer and CAD data, a second memory  31 B for storing data about the coordinates of observed points on the wafer, thirdmemories  31 C for storing data about metrology points, fourth memories  31 D for storing data about images of the wafer derived by the metrology SEM portion  4  as described later, and a fifth memory  31 E for storing matching data Δx, y for making a matching between the coordinates of a transferred pattern on the surface of the wafer and the coordinates of a transferred pattern in the CAD data.  
         [0018]    Indicated by numeral  32  is a recipe creation portion having a CAD metrology position-specifying portion  32 A for producing instruction data D 32 A for indicating metrology positions according to CAD data, a CAD alignment-specifying portion  32 B for producing data D 32 B for specifying alignment mark positions on the wafer (not shown) according to the CAD data, and a metrology information portion  32 C for preparing information for metrology in response to the instruction data D 32 A.  
         [0019]    The metrology information data D 32 C from the metrology information portion  32 C is sent to a recipe converter portion  32 D, where the data is converted into a given format. Then, the data is sent as recipe data D 32 D to the creation portion  32 E. Indicated by symbol  32 F is a recipe editor portion that edits the recipe data D 32 D sent to the creation portion  32 E from the recipe converter portion  32 D and performs editing processing such that the recipe data assumes an appropriate form. Metrology recipe data D 32 E prepared by the creation portion  32 E in this way and indicating a metrology recipe is sent to the metrology SEM portion  4 .  
         [0020]    The metrology recipe creation portion  32  further includes a CAD matching portion  33 , which in turn has a CAD matching engine  33 A for making a matching between the transferred pattern formed on the wafer and a transferred pattern contained in the, CAD data D 2  from the CAD server  2 . The CAD matching portion  33  also has a communication function for exchanging data with the metrology SEM portion  4 . The CAD matching portion  33  has a function of accepting SEM image data D 4  about the wafer obtained by the metrology SEM portion  4  as described later and storing the data in the fourth memories  31 D and a function of storing matching data Δx, y obtained by the CAD matching engine  33 A in the fifth memory  31 E. If necessary, the CAD matching portion  33  can send the matching data Δx, y to the metrology SEM portion  4 .  
         [0021]    The metrology SEM portion  4  has a scheduler  41  for receiving the metrology recipe data D 32 E and determining an observation order for efficiently carrying out positioning into a plurality of observed points, an SEM image taking portion  42  for taking SEM images of the specified observed points according to schedule data D 41  from the scheduler  41 , and an image processing board  43  for performing processing to remove noise from the SEM image data D 42  taken by the SEM image taken portion  42 .  
         [0022]    The SEM image data D 4  which is output from the image processing board  43  and from which a clear image having only a small amount of noise can be obtained is stored in an image memory  44 . If desired, the SEM image data D 4  can be read from the metrology recipe creation portion  3 .  
         [0023]    Indicated by  45  is a wafer processing portion for loading, aligning, and unloading wafers according to instructions from the scheduler  41 .  
         [0024]    The metrology SEM portion  4  further includes a metrology measurement portion  46  that is supplied with metrology point data D 31 C indicating metrology points from the third memories  31 C of the metrology recipe creation portion  3 . Furthermore, matching data Δx, y is supplied to the metrology measurement portion  46  from the fifth memory  31 E. The metrology measurement portion  46  is so designed that it can perform image viewer function  46   a  for the taken image, metrology function  46   b  for measuring pattern linewidths and line spacing, reporting function  46   c  for delivering the results of metrology measurements as reports, and type backup function  46   d . Thus, given metrology measurements are made on the metrology points according to the metrology point data D 31 C. In this kind of metrology SEM system, the structure of the metrology measurement portion  46  having the aforementioned functions for metrology measurements is known per se. Therefore, the structure and operation of the metrology measurement portion  46  will not be described in further detail.  
         [0025]    The operation of the automated metrology SEM system  1  is next described by referring to FIG. 4. In FIG. 4, steps S 1 -S 6  illustrate the operation of the metrology recipe creation portion  3 . Steps S 11 -S 18  illustrate the operation of the metrology SEM portion  4 .  
         [0026]    When the operation of the automated SEM system  1  is started, CAD data about a pattern to be transferred onto a wafer and to be observed is first read from the CAD server  2  and entered, in step S 1 . In step S 2 , the entered CAD data is sent to the CAD alignment-specifying portion  32 B, where an alignment is specified in the CAD data.  
         [0027]    The program then enters step S 3 , where metrology coordinates are specified. In step S 4 , a metrology type used here is specified. The processing steps in steps S 3  and S 4  are executed by the CAD metrology position-specifying portion  32 A. In step S 5 , a decision is made as to whether there is, a next metrology point. If there is, the result of the decision is YES. In steps S 3  and S 4 , metrology coordinates of the next metrology point are specified and a metrology type is specified. After designation of coordinates and metrology types of all metrology points is completed, the result of the decision of step S 5  is NO. The program then enters step S 6 , where a metrology recipe is output by the metrology information portion  32 C, recipe converter portion  32 D, metrology recipe creation portion  32 E, and recipe editor portion  32 F. Metrology recipe data  32 E is sent to the metrology SEM portion  4 .  
         [0028]    The operation of the metrology SEM portion  4  that has received the metrology recipe data D 32 E is next described.  
         [0029]    In step S 11 , a wafer (not shown) is loaded. In step S 12 , the wafer is aligned according to alignment specifications made in S 2 . In next steps S 13 -S 15 , low-, moderate-, and high-magnification matchings are respectively made about one observation point. In step S 16 , a decision is made as to whether there is a next observation point specified in the metrology recipe. If there is, the result of the decision in step S 16  is YES. Steps S 13 -S 15  are carried out for the next observation point. When matchings about all the observation points are completed in this way, the result of the decision in step S 16  is NO. The program then proceeds to step S 17 .  
         [0030]    In step S 17 , the wafer is unloaded. In step S 18 , a decision is made as to whether there is a next wafer. If there is, the result of the decision in step S 18  is YES. The program goes back to step S 11  and steps S 11 -S 17  are carried out for the next wafer. When taking of desired SEM images of all wafers is completed in this way, the result of the decision in step S 18  is NO. The operation of the automated metrology SEM system  1  ends.  
         [0031]    In this way, a metrology recipe is automatically created according to CAD data. SEM images are automatically taken according to this recipe. Therefore, equipment downtime that would normally be required to create a recipe is dispensed with. This achieves fully automated operation of production steps. As a result, production can be run efficiently. The fabrication costs can be curtailed.  
         [0032]    Furthermore, since metrology locations can be specified in CAD data, optimum pattern positions and geometries can be defined as metrology locations. Therefore, sufficient metrology measurements of pattern geometries can be accomplished. In addition, yield management can be run optimally.  
         [0033]    According to the present invention, a metrology recipe can be automatically created according to CAD data. SEM images are automatically taken according to this recipe. Therefore, equipment downtime that would normally be required to create a recipe is dispensed with. In consequence, fully automated operation of production steps can be attained. As a result, production can be run efficiently. The production costs can be reduced. In addition, metrology locations can be specified in CAD data. Therefore, optimum pattern positions and geometries can be defined as metrology locations. Hence, sufficient metrology measurements of pattern geometries can be accomplished. Additionally, yield management can be run optimally.