Abstract:
When defects of a fine pattern are detected, it is difficult to achieve sufficient detection accuracy since conventional optical systems do not have sufficient defect detection sensitivity for small contrast of an optical image in the fine pattern part. To solve this problem, focusing attention on improving the contrast in the fine pattern part, the present invention acquires the image of the sample that has high contrast both in large and fine pattern parts by using an optical system for coaxial bright field epi-illumination, forming the optical image of the sample with various transmission ratio of 0-th order diffracted light that is reflected regularly from the sample, and capturing the image by an image sensor. Further, it is possible to set optical conditioning automatically and in a short time by detecting a plurality of optical images of the sample under various conditions for the transmission ratio of the 0-th order diffracted light, evaluating quality of the detected images, and determining the transmission ratio of the 0-th order diffracted light showing the maximum defect detection sensitivity.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a high resolution optical system for inspection and observation of fine pattern defects, foreign particles and the like that is typically performed in manufacturing process of semiconductors and flat panel displays and also relates to a method and an apparatus for detecting defects by using such optical system.  
           [0002]    As a prior art, Japanese Patent Laid-open No. Hei 8-327554 discloses a technique for improving contrast of an object by changing an impinging angle of illumination depending on optical characteristics of the object to be observed.  
           [0003]    In the above prior art, the impinging (incident) angle of the illumination is changed and determined so that minute unevenness on a surface of the object becomes obvious by improving the contrast of the unevenness. In such method, an optical system for oblique illumination and oblique detection is utilized, wherein the optical system changes a viewing mode of the object from bright field illumination to dark field illumination continuously by changing the impinging angle of the oblique illumination. However, for example, in the dark field illumination mode, it may be difficult to detect certain defects such as residual thin films, if any. Further, when semiconductor devices are inspected, minute unevenness (grains) may be appeared on a surface of metal wiring created in a metallization process. Such grains are not fatal for the semiconductor devices and therefore should not be detected as defects, however in the above prior art, it has been difficult to distinguish such grains from other defects properly to perform more reliable defect detection.  
         SUMMARY OF THE INVENTION  
         [0004]    According to an object of the present invention, it is possible to implement more reliable defect detection that has been difficult to accomplish in the above prior art.  
           [0005]    In particular, a method of the present invention comprises the steps of: obtaining an image signal of a sample by picking up (imaging) the sample through an optical system; adjusting optical conditions of the optical system so as to decrease a difference of contrast or contrast of a pattern in the image signal among segments (points) corresponding to a plurality of regions (positions) on the sample; obtaining the image signal of the sample under the adjusted optical conditions by picking up (imaging) the sample through the optical system having the adjusted optical conditions; and detecting a defect of the sample by processing the image signal.  
           [0006]    Also, a method of the present invention comprises the steps of: obtaining an image signal of a sample by illuminating and picking up (imaging) the sample; adjusting a transmission (detection) ratio of 0-th order diffracted light (regular reflected light) included in reflected light reflected from the sample in according with illumination so as to decrease a difference of contrast or contrast of a pattern in the image signal among segments (points) corresponding to a plurality of regions (positions) of the sample; obtaining the image signal of said sample with the adjusted transmission ratio of the 0-th order diffracted light by picking up the sample under the conditions in that the transmission ratio of the 0-th order diffracted light has been adjusted; and detecting a defect of the sample by processing the image signal.  
           [0007]    Further, a method of the present invention comprises the steps of: illuminating a sample; obtaining a plurality of images having different transmission ratios of 0-th order diffracted light included in entire light generated by the illumination and reflected from the sample by changing the transmission ratio of the 0-th order diffracted light and imaging the sample; determining conditions for the transmission ratio of the 0-th order diffracted light on which defect detection sensitivity is increased by using the plurality of images; setting the transmission ratio of the 0-th order diffracted light included in the entire light reflected from the sample to the determined conditions for the transmission ratio; obtaining the image by imaging the sample under the determined conditions for the transmission ratio; and detecting a defect of the sample by using the image captured under the determined conditions for the transmission ratio.  
           [0008]    Still further, a method of the present invention comprises the steps of: illuminating a sample with polarized light; obtaining an image of the sample by imaging the illuminated sample; adjusting polarization conditions of light generated by the illumination and reflected from the sample based upon contrast information about the image of the sample; obtaining the image of the sample by imaging the sample under the adjusted polarization conditions of the reflected light; and detecting a defect of the sample by using the image.  
           [0009]    According to the present invention, it is possible to obtain a high resolution image. Further, it is also possible to set optical conditioning automatically in a short time.  
           [0010]    These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a graph showing a relationship between a transmission ratio of 0-th order diffracted light and contrast of an image;  
         [0012]    [0012]FIG. 2 is a top plan view showing appearance of a wafer for memory merged logic products;  
         [0013]    [0013]FIG. 3 is a top plan view with a distribution diagram of light quantity showing an example of a detected image by conventional bright field illumination;  
         [0014]    [0014]FIG. 4 is a top plan view with a distribution diagram of light quantity showing an example of a detected image when a transmission ratio of 0-th order diffracted light is reduced;  
         [0015]    [0015]FIG. 5 is a front view showing a general configuration of an inspection apparatus according to the present invention;  
         [0016]    [0016]FIG. 6 is a flow chart showing a procedure for conditioning the detection ratio of the 0-th order diffracted light;  
         [0017]    [0017]FIG. 7 is a top plan view showing an example of a region for obtaining an image for conditioning;  
         [0018]    [0018]FIG. 8 is a table showing an example of an image evaluation result;  
         [0019]    [0019]FIG. 9 is a block diagram showing a general configuration of an image processing section according to the present invention;  
         [0020]    [0020]FIG. 10 is a diagram showing an operation of secondary differential; and  
         [0021]    [0021]FIG. 11 is a table showing an example of a relationship between evaluation values and descriptions of these values. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    An embodiment of the present invention is shown in FIG. 5. A sample (a wafer)  1  contained in a wafer  41  is transported to a Z-stage  10 , a θ-stage  11 , an X-stage  12  and a Y-stage  13  by a wafer transporting robot  40 . The wafer  1  that has been transported to any one of the stages is moved into a field of view of a sub-optical system  20  having low magnification for detection in an entire chip area to detect an image of the entire chip area. Then, the chip image being divided into a peripheral circuit  2   a   1 , a logic part  2   a   2 , a memory part  2   a   3  and the like, is captured by a camera  21  in the sub-optical system  20 . This image is transferred to an image processing section  30 . This image is stored in a data server  31 . The system is configured so that this image may be shown on a display of an operating computer  35  in this inspection apparatus. Therefore, the operating computer  35  can select a region (a peripheral circuit part  2   a   1 , a logic part  2   a   2 , a memory part  2   a   3  and the like) to acquire an image for conditioning the transmission ratio (Ib/Ia) of the 0-th order diffracted light, on the display. The sub-optical system  20  for detection in an entire chip area is provided a polarizing conditions adjusting section  201  which comprises a PBS and a half wave plate or a quarter wave plate, and an objective lens  2 .  
         [0023]    However, in an actual inspection, an image is detected while a surface of the wafer  1  is scanned in a field of view of an optical system  15  for visual inspection. Then, this image data detected by the image sensor  154  also transfers to the image processing section  30 , and then candidate defects are sought by comparatively checking with images of adjacent chips. An inspection result is stored in the data server  31  and read when the result is reviewed. It is noted that mechanical operating sections such as the stages and the like (a drive motor  156 ) are controlled by a mechanical controller  32 .  
         [0024]    The optical system  15  using in the actual inspection is formed by coaxial bright field epi-illumination system. Then, the optical system  15  is provided an objective lens  151 , a half wave plate or a quarter wave plate  152 , a drive motor  156  for adjusting minute rotation of the wave plate  152 , a belt for transferring an rotation output of the drive motor to the minute rotation of the wave plate  152 , a PBS (polarizing beam splitter)  153 , an image sensor  154  for imaging each region and a light source  155 . The light source  155  is formed by a laser source such as a semiconductor laser, an argon laser, a YAG-SHG laser or an exima laser, or a discharge tube such as a xenon lamp, or a mercury lamp, or a filament light source such as a halogen lamp. The image sensor  154  is formed by a TDI image sensor or a CCD image sensor. The PBS  153  converts by reflecting a light outputted from the light source  155  to a linear polarized light. Further, the wave plate  152  converts the linear polarized light to an elliptically polarized light. Therefore, the elliptically polarized light is irradiated by focusing through the objective lens  151  on the region of the wafer  1 .  
         [0025]    The high order diffracted light be generated from the edge of pattern of the region is condensed by the objective lens  151  and is converted to the ellipse polarized light by the wave plate  152 . On the result, the high order diffracted light is transmitted through the PBS  153  and is detected as image by the image sensor  154 . On the other hand, the 0-th order diffracted light (regular reflected light) be generated from the pattern of the region is condensed by the objective lens  151  and is converted to the linear polarized light by the wave plate  152 . The PBS  153  splits the 0-th order diffracted light into the transmission light and the reflection light. Therefore, the transmission ratio (Ib/Ia) of the 0-th order diffracted light through the PBS  153  can adjust by varying the elliptically polarized condition in accordance with controlling the minute rotation angle of the wave plate  152 .  
         [0026]    Ib is an intensity of the 0-th order diffracted light transmitted through the PBS  153 .  
         [0027]    Ia is an intensity of the 0-th order diffracted light inputted to the PBS  153 .  
         [0028]    On case of the other embodiment, the wave plate is removed and a half mirror is provided instead of the PBS  153 . Further, a spatial filter (not shown) is provided on a Fourier transform plane of the surface of the wafer  1  or in the neighborhood of the Fourier transform plane in the optical system  15 . The spatial filter shields the 0-th order diffracted light and transmits the high-order (not less than 1-th order) diffracted light. So, a plurality of spatial filters in which each of shielding portions has different size, are prepared. The adjustment of the transmission ratio (Ib/Ia) of the 0-th order diffracted light can perform by changing some spatial filter into different spatial filter.  
         [0029]    According to above mention, the minute rotation adjustment of the wave plate  152  or the change of the spatial filters can adjust the transmission ratio (Ib/Ia) of the 0-th order diffracted light (an optical condition of the optical system  15 ) so as to decrease a difference of contrasts (amplitude M of intensity) or contrasts of a pattern in the image signals detected by the image sensor  154  ( 25 ) among points (segments) corresponding to a plurality of regions (a peripheral circuit part  2   a   1 , a logic part  2   a   2 , a memory part  2   a   3  and the like in a chip) of the wafer  1 .  
         [0030]    The optical system  15  comprises a polarizing conditions adjusting section  152 ,  153  for adjusting polarizing conditions of both illuminating light for the wafer  1  and reflecting light from the wafer  1 , which acts as elements for adjusting contrast M (amplitude of intensity) of the detected image.  
         [0031]    [0031]FIG. 1 shows a relationship between the transmission ratio (Ib/Ia) of 0-th order diffracted light and pattern contrast of a detected image. When the transmission (detection) ratio of the 0-th order light is 100%, the image is the same as the one that is detected in a typical bright field detection manner. As the transmission ratio of the 0-th order light decreases by adjusting polarizing conditions using the polarizing conditions adjusting section  152 ,  153 , amplitude of higher order diffracted light approaches amplitude of the 0-th order diffracted light, which initially results in improved contrast. However, as the transmission ratio of the 0-th order diffracted light further decreases, contrast will be reduced. It is because the amplitude of the higher order diffracted light becomes too high, and as a result of which the contrast (modulation) generated by interference between the 0-th order light and the higher order diffracted light decreases.  
         [0032]    [0032]FIG. 2 shows appearance of a wafer to be inspected. On the wafer  1 , a similar pattern is formed in every die (chip)  2 . For example, in semiconductor products in which memory and logic circuits are combined, each die region is divided into a peripheral circuit part  2   a   1 , a logic part  2   a   2 , a memory part  2   a   3  and the like. A width and a density of the pattern formed in each region usually varies. Here, assume the pattern width and pattern density of each region (part) as follows: (i) the peripheral circuit part  2   a   1  has a large pattern width and a low pattern density; (ii) the logic part  2   a   2  has a fine pattern width but a relatively low pattern density; and (iii) the memory part  2   a   3  has a fine pattern width and a high pattern density.  
         [0033]    [0033]FIG. 3 shows an example of an image obtained from the die region by conventional bright field detection. Considering distribution of detected light quantity (intensity) in a range A-A of the detected image, it can be found that the peripheral circuit part  2   a   1  having the large pattern width and the low density shows high pattern modulation M 1 . The memory part  2   a   3  having the fine pattern width and the high density is generally detected darkly and has low modulation M 3 . Such generally dark detection of the memory part  2   a   3  results from reduction of ratios of the 0-th order light and the higher order diffracted light captured by an objective lens. In a defect inspection, a difference between images of adjacent dies is firstly acquired by difference image calculating section  64 , and then points having values beyond a threshold are determined as defects by defect determining section  65 . Therefore, inspection sensitivity is reduced in a region (part) having low modulation of the detected image. Thus, in order to have uniform defect detection sensitivity, it is desirable that the modulation (contrast) is equal in the entire die region irrespective of the pattern width and the pattern density.  
         [0034]    [0034]FIG. 4 shows a detected image when the transmission ratio of the 0-th order light is set to approximately 40%. Considering the fact that the low contrast (modulation) in the memory part  2   a   3  results from a reduced converging ratio of the higher order diffracted light by the objective lens  151  (2), it is possible to detect the amplitude of the 0-th order light and the higher order diffracted light equally and to improve the modulation M 31  due to interference by reducing the 0-th order light. Further, with the reduced 0-th order diffracted light, the peripheral circuit part  2   a   1  having a large pattern width shows a lower intensity (brightness) level as compared to the one before the reduction of the 0-th order light. Thus, it is possible to improve the contrast in regions having a fine pattern width by reducing the 0-th order light, though at this time it is necessary to increase an illumination light quantity as the detection ratio of the light quantity decreases as a result of the reduced 0-th order light. Accordingly, the inspection sensitivity in the parts having a fine pattern can be improved.  
         [0035]    Further, when a wafer having embedded memory is inspected, the memory part is inspected by cell-by-cell comparison, while the other parts are inspected by die-by-die comparison. These inspection procedures may be either performed in two steps separately, or performed simultaneously in a combined inspection method. In view of inspection performance, the combined inspection method may be advantageous because it can be performed in a short time. Still further, the modulation in the cell part due to reduction of the 0-th order light is increased, whereby also the inspection sensitivity can be improved.  
         [0036]    Since every wafer to be inspected varies in a pattern width and a pattern density, it is necessary to condition the detection ratio of the 0-th order diffracted light (regular reflected light) for the defect inspection in advance. FIG. 6 shows a flowchart of such inspection. A wafer to be inspected is loaded on the stage  10 - 13  into an inspection apparatus (S 61 ). Then information about a die arrangement in the wafer is registered to the operating computer  35  or the data server  31  (S 62 ). Then, coordinates of an inspection area in a die are registered to the operating computer  35  or the data server  31  (S 63 ). Then, a region to acquire an image for conditioning the transmission (detection) ratio of the 0-th order diffracted light is selected on the display of the operating computer  35  (S 64 ).  
         [0037]    Initial optical conditions are set for half wave (½ λ) plate or quarter wave (¼ λ) plate  152  in the optical system  15  through the mechanical controller  32  by the operating computer  35  (S 65 ). Then the image of the conditioning region is acquired while a surface of the wafer  1  is scanned in a field of view of an optical system  15  for visual inspection (S 66 ). Then, contrast (modulation) of the acquired image is evaluated by the image processing section  30  (S 67 ). Then, images with varying transmission ratio of the 0-th order diffracted light by controlling the rotation of half wave plate or quarter wave plate  152  are acquired by the optical system  15  and evaluated by the image processing section  30 . After the evaluation of the images has been completed, image evaluation values determined for each transmission ratio of the 0-th order diffracted light are listed on a display (S 68 ).  
         [0038]    The series of varying transmission ratios of the 0-th order diffracted light is narrowed down to a plurality of transmission ratios having relatively higher evaluation values (S 69 ). Then, a test inspection is performed with sensitivity including false defects by using the optical system  15  (S 70 ). And defects to be detected are classified as true or false defects by the image processing section  30  (S 71 ). Images of the true and false defects parts are detected for each of the plurality of narrowed-down detection ratios of the 0-th order diffracted light by the optical system  15  and difference images for each detection ratio are computed by the image processing section  30  (S 72 ). Then, the maximum contrast difference of the false defects part Nmax is determined for each transmission ratio of the 0-th order diffracted light by the image processing section  30  (S 73 ). Further, for each transmission ratio of the 0-th order light, when an inspection threshold is determined by adding a constant a to the Nmax, the number of the detectable true defects is calculated by the image processing section  30  (S 74 ). The transmission ratio of the 0-th order diffracted light with which the maximum number of the true defects can be detected is set as a condition of the actual inspection for the region selected by step S 64  (S 75 ). Then, setting the inspection threshold to [Nmax+α], the test inspection is performed for the particular region (S 76 ), and then, if desirable sensitivity is satisfied (S 77 ), the conditioning procedure is completed (S 78 ). Hereinafter, the actual inspection will be performed with the conditioned sensitivity under the conditions in that the transmission ratio of the 0-th order diffracted light has been adjusted for each of a peripheral circuit part  2   a   1 , a logic part  2   a   2 , a memory part  2   a   3  and the like in a die (chip).  
         [0039]    [0039]FIG. 7 shows a schematic diagram of an image region that is acquired for conditioning the transmission ratio of the 0-th order diffracted light. If the pattern width and the pattern density in the die can be divided into a plurality of segments, it is desirable that each of the segments includes regions that correspond to every pattern width and pattern density that may be observed in the die. However, if there is no preliminary information used for the segmentation, it may be contemplated to set a central field of the die as a default segment, and the like. Alternatively, the image that has been acquired by the optical system for detection in an entire chip area  20  may be used to determine the image-acquiring region.  
         [0040]    [0040]FIG. 8 shows an example of summed differential values of the images acquired for each transmission (detection) ratio of the 0-th order diffracted light. In this calculation result, it is noted that about 40% of the transmission ratio of the 0-th order diffracted light shows the highest summed differential value and therefore such transmission ratio is advantageous for a defect inspection. Considering these summed differential values, various conditions for the transmission ratio of the 0-th order light listed in FIG. 8 are narrowed down to two conditions, i.e. 40% and 60%, and then the image of the true and false defects parts shown in FIG. 6 is acquired to determine the conditions of the transmission ratio of the 0-th order light for the actual inspection.  
         [0041]    [0041]FIG. 9 shows a block diagram of the image processing section  30 . An image of a wafer  1  is magnified and projected on an image sensor  25  ( 154 ) by an objective lens  2  ( 151 ). An output signal of the image sensor  25  ( 154 ) is converted into a digital signal in an A/D converting section  60 . The detection digital signal is, on one hand, sent to an image evaluating section  61  for evaluation of image quality. On the other hand, the detection digital signal is stored in a delay memory  62  temporarily and is formed as a reference digital signal for comparing between images of adjacent chips or cells. Each of the detection digital signal and the reference digital signal is performed relative alignment of the images in an image alignment section  63 . Then, a difference image between the detection digital signal and the reference digital signal is calculated in a difference image calculating section  64 , and then a feature amount of the difference is sent to a defect determining section  65 . In the defect determining section  65 , coordinates of the feature amount that exceeds the inspection threshold is determined. The position of such coordinates is considered as a candidate defect, and the coordinates, feature amount and so on are stored in the defect storing section  66 . Data in the defect storing section  66  is sent to a data server  70  and stored in a hard disk.  
         [0042]    [0042]FIG. 10 shows an operation of secondary differential that is one of evaluation values for conditioning the transmission ratio of the 0-th order diffracted light in the step S 67  of evaluating the image quality as shown in FIG. 6. By way of example, assume that a light quantity of a pixel for which the secondary differential is to be calculated is I (x, y). Difference values between I (x, y) and adjacent eight pixels are calculated respectively, and summation of absolute values of these eight difference values is considered as the secondary differential of I (x, y). The evaluation value is acquired by performing the above operation for each pixel of the detected image and summing the secondary differential values for each of pixels.  
         [0043]    [0043]FIG. 11 shows a list of evaluation values to narrow down the transmission ratio of the 0-th order diffracted light in the step S 66  of listing the image quality evaluation values for each transmission ratio of 0-th order diffracted light as shown in FIG. 6. A differential value is acquired by performing secondary differentiation of detected images for each transmission ratio of the 0-th order diffracted light and then summing the secondary differential values. This operation is performed as described in FIG. 10.  
         [0044]    Next, the maximum contrast difference in divided regions is described. A detected image is divided into regions of a predetermined size, the minimum and the maximum contrast value are acquired for each divided region, and then the difference between the minimum and the maximum values is calculated as the maximum contrast difference. The maximum contrast difference values are calculated for all divided regions and absolute values of the maximum contrast difference values are summed. As an example of how to divide a detected image into regions, a region of 3 pixels×3 pixels in X, Y coordinates of the image may be defined as one segment. Since the one segment contains brightness information for 9 pixels, a contrast difference value for the one segment can be acquired by determining a difference between the maximum and the minimum value for such 9 pixels. Considering the fact that the contrast difference value for the one segment corresponds to contrast of the pattern image of such segment, the larger the maximum contrast difference value is, the more advantageous the value is for defect inspection. Therefore, since the larger summation value of the maximum contrast difference values is also more advantageous for defect inspection, it is contemplated to select the inspection conditions for the transmission ratios of the 0-th order diffracted light that have the larger summation value as candidate conditions for actual inspection. Here, it is to be noted that the maximum contrast difference value indicated here does not include variations other than wafer pattern information, such as a sampling error of an image, variations of partial illumination distribution and the like.  
         [0045]    Next, a contrast dispersion value is described. An image is divided into regions of a predetermined size, and dispersion of a contrast value is acquired for the divided region. The dispersion value is acquired for all divided regions and the values for all divided regions are summed. As an example of division into regions, 3×3 pixels may be set to one segment. Here, it is to be noted that this dispersion value indicates variations of contrast in the divided regions, and therefore, the higher the dispersion value is, the more the pattern information should be. Thus, a higher dispersion value is more advantageous for defect inspection. Here, it is to be noted that the contrast variations indicated here does not include variations other than wafer pattern information, such as a sampling error of an image, variations of partial illumination distribution and the like.  
         [0046]    Next, an evaluation method by image Fourier transformation density is described. Two-dimensional Fourier transformation is performed in X and Y directions of an image and then summation of a spectral density value of frequency not less than a predetermined frequency value is defined as an evaluation value. The predetermined frequency value is determined with reference to a pattern pitch, pixel dimensions of the image sensor  154  ( 25 ) that are converted into actual dimensions on a wafer  1  and the like. The high spectral density of frequency not less than the predetermined frequency value means high contrast (modulation) of the image in the fine pattern not larger than the pattern pitch dimensions that correspond to the predetermined frequency. Thus, higher spectral density is more advantageous for defect inspection. Further, it is also possible to use spectral density for the predetermined frequency only as an evaluation value.  
         [0047]    Though the embodiment wherein the polarizing conditions adjusting section  152 ,  153  is used as contrast adjusting means is described in the above description, similar effects may be obtained by using a spatial filter. In this case, in order to change the transmission ratio of the 0-th order diffracted light, a plurality of the spatial filters that correspond to various transmission ratios may be used selectively, or the spatial filter may have variable construction so as to form a suitable pattern that corresponds to various transmission ratios.  
         [0048]    In the above description, a plurality of evaluation values are described, in an actual inspection, a single or more than one evaluation value(s) may be used to narrow down the reduction ratios of the 0-th order diffracted light.  
         [0049]    Further, it is noted that the following optical parameters other than the reduction ratio of the 0-th order light may be used for contrast adjustment:  
         [0050]    (i) illumination σ (setting of an incidence angle range of illumination);  
         [0051]    (ii) a wavelength range of illumination; and  
         [0052]    (iii) the number of apertures NA of the objective lens  151  ( 2 ).  
         [0053]    The evaluation values of the present invention may be also utilized effectively to narrow down these conditions. By using the evaluation values of the present invention, it is possible to set optical conditions that are advantageous in view of inspection sensitivity in a short time.  
         [0054]    As described above, in accordance with the present invention, defect detection sensitivity in the fine pattern part can be improved by improving the contrast of image in the fine pattern part. Each parameter for optical conditions to improve the contrast of image in the fine pattern part can be set in a shorter time, and therefore the amount of time to prepare an inspection recipe can be reduced substantially.  
         [0055]    The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.