SURFACE INSPECTION APPARATUS AND SURFACE INSPECTION METHOD

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the description as set out below with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram of a surface inspection apparatus according to the prior art;

FIG. 2 is a diagram showing an arrangement of dies on a semiconductor wafer;

FIG. 3 is a block diagram of a surface inspection apparatus according to an embodiment of the present invention;

FIG. 4 is a diagram showing an example of an arrangement of standard defects;

FIGS. 5A and 5B show examples of standard defects formed under different exposure conditions;

FIG. 6 is a block diagram showing one configuration example of a manufacturing process management unit shown in FIG. 3;

FIG. 7 is a flowchart illustrating a method for judging the suitability of a process recipe in the manufacturing process management unit shown in FIG. 6; and

FIG. 8 is a flowchart illustrating a method for selecting a process recipe in the manufacturing process management unit shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described in detail below while referring to the attached figures. FIG. 3 is a general block diagram of a surface inspection apparatus according to an embodiment of the present invention. The surface inspection apparatus 1 is an apparatus for detecting a defect appearing on the surface of an actual wafer 2 on which a prescribed pattern such as a circuit pattern has been formed by one or a plurality of successive manufacturing processes.

The surface inspection apparatus 1 detects a defect appearing on the surface of the real wafer 2 by using the same method as that employed in the prior art surface inspection apparatus described earlier with reference to FIGS. 1 and 2, and comprises, like the prior art surface inspection apparatus, a microscope unit 10 as an optical system for acquiring an image by capturing an optical image of the surface of an actual wafer 2 and an image processing unit 20, which inputs the image captured by the microscope unit 10 and detects a defect appearing in the captured image.

The microscope unit 10 and the image processing unit 20 shown in FIG. 3 are the same configuration as the microscope unit 10 and the image processing unit 20 previously described with reference to FIG. 1, and therefore, the same component elements are designated by the same reference numerals, and the description of the same functions will not be repeated hereafter.

The surface inspection apparatus 1 according to the embodiment of the present invention further comprises a manufacturing process management unit 50. When a prescribed standard defect is formed on the surface of the actual wafer 2, as will be described later, the image processing unit 20 detects the standard defect and supplies the result to the manufacturing process management unit 50, which based on the result of the detection, judges the suitability of the process recipe used in the prescribed manufacturing process to form the standard defect or selects the process recipe that can be advantageously used in the manufacturing process.

Here, the image processing unit 20 and the manufacturing process management unit 50 may be implemented using a computer or the like that performs data processing and calculations.

The term “process recipe” used here refers to, for example, in the case of a semiconductor circuit manufacturing process, to a set of items for specifying the modes of wafer processing in the manufacturing process, including specification of setting conditions for semiconductor circuit manufacturing equipment such as exposure equipment, film deposition equipment, etching equipment, cleaning equipment, etc. used in the manufacturing process, as well as specification of the kinds of chemicals and gases used in the above equipment, their mixing ratios, and various other conditions, such as processing time and processing temperatures. In other words, the term includes everything generally referred to as a “recipe” in the manufacturing processes of semiconductor wafers, photomasks, and liquid crystal display panels.

FIG. 4 shows an example of an arrangement of standard defects formed by the above-mentioned prescribed manufacturing process. A plurality of dies 3a, 3b, 3c, 3d, . . . are arranged in a matrix pattern in repeated fashion in X and Y directions. The standard defects 9 may be provided, for example, one for every other die or one for every plurality of dies arranged in a repeated fashion. When the surface inspection apparatus 1 performs a die-to-die comparison between two adjacent dies, if the standard defects 9 are provided as just described, the defect detection unit 24 in the image processing unit 20 can detect the standard defect 9, because the gray level of the image captured from the portion of the standard defect 9 formed in one adjacent die 3a differs from the gray level of the image captured from the corresponding portion in the other adjacent die 3b.

Likewise, when the surface inspection apparatus 1 performs a cell-to-cell comparison between adjacent cells, the standard defects 9 may provide one for every other cell or one for every plurality of cells arranged in a repeated fashion.

Each standard defect 9 is formed in an unused portion within a die or near a die so that, if it is formed on the actual wafer, the wafer will not be rendered defective. If the standard defect 9 is to be used for judging the acceptability of the detection sensitivity of the surface inspection apparatus 1 or for checking the condition of the apparatus, it is desirable that the standard defect 9 be formed so as to have the minimum feature size that the surface inspection apparatus 1 can detect.

The pattern formed on the wafer 2 differs depending on the process recipe used in the manufacturing process for the formation of the pattern. Therefore, if the standard defect 9 is formed so as to have the minimum feature size that the manufacturing process can form on the wafer 2, the standard defect 9 is not formed on the wafer 2 unless the process recipe is appropriate.

FIGS. 5A and 5B show examples of patterns that occur when the standard defect 9 is formed by varying the exposure conditions in the photolithography process as one example of an item prescribed in the process recipe. Here, FIG. 5A shows the pattern formed under optimum exposure conditions, and FIG. 5B shows the pattern formed when the amount of exposure was insufficient.

As shown in FIG. 5A, in a case where the standard defect 9 having the same shape as a short pattern is formed within a parallel line pattern 70 having a line width of the minimum dimension that can be formed by the manufacturing process, the dimension of the standard defect 9 is also the minimum dimension that can be formed by the manufacturing process.

If this pattern is formed in underexposed conditions, then as shown in FIG. 5B the parallel line pattern is not resolved, and the standard defect 9 formed therein is not resolved either, and as a result, the standard defect 9 cannot be detected by the surface inspection.

Accordingly, by forming the standard defect 9 using the same manufacturing process as that used for forming the pattern on the real wafer 2 to be inspected, and by checking whether the standard defect 9 can be detected by the surface inspection, it is possible to determine the suitability of the process recipe used in the manufacturing process for forming the pattern on the surface of the real wafer 2.

Turning back to FIG. 3, when the image of the surface of the actual wafer 2 with the standard defect 9 formed thereon is captured by the microscope unit 10, and the captured image is input to the signal processing unit 20, the signal processing unit 20, which comprises the signal storing unit 21, difference detection unit 22, detection threshold value calculation unit 23, and defect detection unit 24, detects defects appearing on the surface of the wafer 2, including the standard defect 9, and outputs the defect information for each detected defect, as in the surface inspection method previously described with reference to FIGS. 1 and 2.

The manufacturing process management unit 50 receives each defect information from the defect detection unit 24, and selects the defect information concerning the standard defect 9 from among the thus received defect information in order to check the result of the detection of the standard defect 9 accomplished by the image processing unit 20. At this time, the manufacturing process management unit 50 compares the received defect information with standard defect data, i.e., the known information concerning the standard defect 9 formed on the surface of the actual wafer 2, and determines whether the received defect information is the defect information concerning the standard defect 9.

Standard defect data may include die designation information designating the die in which the standard defect 9 is provided and defect position information indicating the position within the die at which the standard defect 9 is provided. Standard defect data may further include standard defect mode information, such as the size of the standard defect 9, and the gray level value that the pixel in the portion of the standard defect 9 shows when the image is captured under optical conditions optimum for the surface inspection.

Standard defect data may further include, for example, the gray level difference that occurs between the portion containing the standard defect 9 and other portions within the captured image (i.e., the gray level difference between the inspection image and the reference image for the portion of the standard defect 9) when an image comparison similar to the one performed in the surface inspection method previously described with reference to FIGS. 1 and 2 is performed using the image captured under optical conditions optimum for the surface inspection.

If the standard defect data includes data concerning more than one standard defect 9, identifier information for identifying each individual standard defect 9 may be included.

The standard defect data may be generated externally to the surface inspection apparatus 1 based on the design data used when forming the standard defect 9 on the actual wafer 2, or as will be described later, some of the earlier listed items of the standard defect data (position information, size, gray level value, gray level difference, etc.) may be generated by a standard defect data generating unit 52 in the manufacturing process management unit 50 to be described later with reference to FIG. 6.

However, when the actual wafer 2 is used for the first time on which the standard defect 9 has been formed, it is preferable that at least the position information of the standard defect 9 be supplied externally to the surface inspection apparatus 1. For this purpose, the surface inspection apparatus 1 includes a data input unit 4 for inputting at least a portion of the standard defect data concerning the standard defect 9 to the manufacturing process management unit 50.

The data input unit 4 may be constructed from any one of input devices selected, for example, from the group consisting of a user interface such as a keyboard, mouse, touch panel, etc., that an operator uses to input data, a removable media reading device such as a flexible disk drive, a CD-ROM drive, or a memory reading device for reading data provided in the form of a removable medium such as a flexible disk, a CD-ROM, or a memory card, and an interface device for inputting the data.

The manufacturing process management unit 50, based on the result of the detection of the standard defect 9, determines the suitability of the process recipe used in the prescribed manufacturing process for the formation of the standard defect 9, and outputs recipe suitability information indicating whether or not the process recipe is suitable. The surface inspection apparatus 1 includes a data output unit 5 for outputting the recipe suitability information outside the surface inspection apparatus 1.

The data output unit 5 may be constructed from any one of output devices selected, for example, from the group consisting of a display device such as a CRT or a liquid crystal display panel on which the data to be output is displayed, a printer for printing the data on paper, a removable media writing device such as a flexible disk drive, a CD-ROM drive, or a memory writing device for storing the data to be output and for writing the data to a removable medium such as a flexible disk, a CD-ROM, or a memory card, and an interface device for outputting the data.

The defect information output from the image processing unit 20 is also output outside the surface inspection apparatus 1 via the data output unit 5.

The manufacturing process management unit 50 also has the function of selecting, based on the result of the detection of the standard defect 9, the process recipe that can be advantageously used in the same manufacturing process as that used for the formation of the standard defect 9.

When the manufacturing process management unit 50 selects the advantageous process recipe in this way, a plurality of standard defects 9 are formed in advance on the wafer 2 by changing the process recipe. Or when the process recipe to be changed is one that concerns processing conditions, such as etching and that has to be set for each individual wafer, a plurality of wafers 2 are processed by changing the process recipe, and a plurality of standard defects are formed.

On the other hand, information concerning the process recipes respectively used for the formation of the plurality of standard defects 9 (hereinafter referred to as the “process recipe information”) is input to the manufacturing process management unit 50 via the data input unit 4. The process recipe information may itself be the values that specify the earlier listed modes of wafer processing in the manufacturing process or may be an identifier for identifying each individual process recipe.

Process recipe information may be included in the standard defect data relating to the standard defect formed by using the corresponding recipe. Alternatively, the process recipe information may be input separately from the standard defect data. In this case, an identifier may be assigned to each process recipe information, and the identifier of the process recipe information used when forming the corresponding standard defect may be included in the standard defect data.

Based on the result of the detection of each of the plurality of standard defects 9 formed by changing the process recipe, the manufacturing process management unit 50 selects the process recipe that can be used advantageously, and outputs the process recipe information for the selected process recipe. The process recipe information is output outside the surface inspection apparatus 1 via the data output unit 5.

The configuration and operation of the manufacturing process management unit 50 will be described below.

FIG. 6 is a block diagram showing one configuration example of the manufacturing process management unit 50 shown in FIG. 3. The manufacturing process management unit 50 includes a standard defect data storing unit 51 which stores the standard defect data input from the input unit 4 as information concerning the standard defect 9 formed on the real wafer 2. The manufacturing process management unit 50 may further include a standard defect data generating unit 52 for generating some of the earlier listed items of the standard defect data (position information, size, gray level value, gray level difference, etc.) within the manufacturing process management unit 50.

The manufacturing process management unit 50 further includes a process recipe evaluation information generating unit 53, which takes as an input defect information output from the defect detection unit 24, and based on this defect information creates prescribed process recipe evaluation information, which differs depending on the process recipe used in the manufacturing process for the formation of the standard defect 9.

The process recipe evaluation information may be generated as information that indicates, for example, the detection or non-detection of the standard defect 9. In this case, the process recipe evaluation information generating unit 53 may determine whether or not the standard defect 9 has been detected, by referring to the standard defect data stored in the standard defect data storing unit 51, and thereby checking whether or not the defect detected at the known position of the standard defect 9 indicated by the standard defect data is included in the input defect information.

Further, the process recipe evaluation information may be generated as information that indicates the number of standard defects detected, for example, within a prescribed range. In this case, the process recipe evaluation information generating unit 53 may obtain the number of detected standard defects 9 by determining the detection or non-detection for each standard defect 9 in the same manner as described above. Alternatively, the defect information concerning the standard defect 9 detected within the prescribed range may itself be generated as the process recipe evaluation information.

Further, the process recipe evaluation information may be generated as information that indicates the size of the detected standard defect 9. In this case, the process recipe evaluation information generating unit 53 extracts defect information concerning the detected standard defect 9 from the input defect information by using, for example, the position information included in the standard defect data stored in the standard defect data storing unit 51, and acquires the defect size included in the defect information.

The manufacturing process management unit 50 further includes a process recipe suitability judging unit 54 which, based on the process recipe evaluation information output from the process recipe evaluation information generating unit 53, judges in accordance with prescribed criteria the suitability of the process recipe used in the manufacturing process for the formation of the standard defect 9, and a recipe suitability information generating unit 55, which generates recipe suitability information indicating the result of the judgment made by the process recipe suitability judging unit 54, and supplies the information to the data output unit 5.

The process recipe suitability judging unit 54 judges the suitability of the process recipe based, for example, on the result of the determination made as to the detection or non-detection of the standard defect 9, which is indicated by the process recipe evaluation information. In others words, if the standard defect 9 is detected, it is determined that a pattern about the same size (for example, line width, etc.) as the standard defect 9 can be formed using the same process recipe, but if the standard defect is not detected, it is determined that a pattern of this size cannot be formed using the same process recipe.

FIG. 7 is a flowchart illustrating a method for judging the suitability of the process recipe in the manufacturing process management unit 50 shown in FIG. 6.

In step S1, when the image of the surface of the actual wafer 2 with the standard defect 9 formed thereon is captured by the microscope unit 10, and the captured image is input to the signal processing unit 20, the defect detection unit 24 in the signal processing unit 20 detects a defect appearing on the surface of the wafer 2, and outputs its defect information. The defect information thus output is input to the process recipe evaluation information generating unit 53 in the manufacturing process management unit 50.

In step S2, the process recipe evaluation information generating unit 53 compares the position information of the defect included in the input defect information with the position information of the standard defect stored in the standard defect data storing unit 51, determines whether the standard defect 9 has been detected by the image processing unit 20, generates the process recipe evaluation information indicating the detection or non-detection of the standard defect 9, and supplies the evaluation information to the process recipe suitability judging unit 54.

If the process recipe evaluation information indicates that the standard defect 9 has been detected, the process recipe suitability judging unit 54 determines that the process recipe used for the formation of the standard defect 9 is suitable (step S3). However, if the information indicates a non-detection, it is determined that the process recipe used for the formation of the standard defect 9 is unsuitable (step S4). In step S5, the recipe suitability information generating unit 55 generates recipe suitability information indicating the result of the judgment made by the process recipe suitability judging unit 54, and supplies the information to the data output unit 5.

Here, in step S2, the process recipe evaluation information generating unit 53 may retrieve the defect size of the detected defect from the defect information concerning the detected standard defect 9, and generate the process recipe evaluation information by including the defect size therein.

Then, when judging the suitability of the process recipe, the process recipe suitability judging unit 54 may compare the defect size included in the process recipe evaluation information with the size of the standard defect 9 included in the standard defect data, and if the difference is within a prescribed range, it is determined that the standard defect 9 is correctly formed on the wafer 5, and therefore the process recipe used for the formation of the standard defect 9 is suitable. However, it is determined that the process recipe is unsuitable if the difference is outside the prescribed range.

Turning back to FIG. 6, the manufacturing process management unit 50 further includes a standard defect selecting unit 56, a process recipe information storing unit 57, and a process recipe selecting unit 58.

In the case where a plurality of standard defects 9 are formed on the wafer 2 by changing the process recipe, each of these standard defects 9 is detected by the defect detection unit 24, by checking, for example, which of the plurality of standard defects 9 is detected, an advantageous process recipe can be determined for the manufacturing process used for the formation of the detected standard defect 9.

In view of this, the standard defect selecting unit 56 selects, from among the plurality of standard defects 9 formed by changing the process recipe, the standard defect for which the process recipe evaluation information acquired by the process recipe evaluation information acquiring unit 53 satisfies a prescribed condition.

On the other hand, the process recipe information storing unit 57 stores the process recipe information received via the data input unit 4 for the respective process recipes used for the formation of the plurality of standard defects 9.

Here, it is understood that each process recipe information contains an identifier for uniquely identifying each individual process recipe information, and that the standard defect data stored in the standard defect data storing unit 51 contains the identifier of the process recipe information corresponding to the process recipe used for the formation of the standard defect 9.

Process recipe information may be stored in the standard defect data storing unit 51 by including it in the standard defect data concerning the standard defect formed by using the corresponding recipe.

The process recipe selecting unit 58 retrieves from the process recipe information storing unit 57 the process recipe information corresponding to the process recipe used for the formation of the standard defect 9 selected by the standard defect selecting unit 56, and supplies to the data output unit 5 the process recipe information indicating the process recipe that can be advantageously used in the same manufacturing process as that used for the formation of the standard defect 9.

FIG. 8 is a flowchart illustrating a method for selecting the process recipe in the manufacturing process management unit 50 shown in FIG. 6.

In this method, defect information concerning the plurality of standard defects 9 formed by changing the process recipe is successively stored by repeating the routine of steps S11 to S14.

First in step S11, the defect detection unit 24 detects a defect on the surface of the actual wafer 2, generates its defect information, and supplies it to the process recipe evaluation information generating unit 53. In step S12, the process recipe evaluation information generating unit 53 determines whether the received defect information is one that concerns the standard defect 9. If the received defect information is not one that concerns the standard defect 9, the process returns to step S11 to wait for an input of defect information. In step S13, the process recipe evaluation information generating unit 53 stores the defect information of the standard defect 9 in a storage means not shown.

Then, in step S14, the process recipe evaluation information generating unit 53 determines whether the defect detection unit 24 has detected all the standard defects 9 formed by changing the process recipe. The process recipe evaluation information generating unit 53 can determine whether all the standard defects 9 have been detected or not, for example, by referring to the position information carried in the received defect information and thereby checking if the defect position indicated by the defect information is the position to be inspected by the defect detection unit 24 at a later time than the position of the standard defect 9.

If there is any standard defect 9 for which the defect information is not received, the process returns to step S11 repeating steps S11 to S14, and when defect information has been received for all the standard defects 9, the process proceeds to step S15.

In step S15, the process recipe evaluation information generating unit 53 creates process recipe evaluation information based on the standard defects 9 whose information has been stored in step S13, and supplies the evaluation information to the standard defect selecting unit 56. In step S16, the standard defect selecting unit 56 selects from among the standard defects the standard defect for which the process recipe information satisfies a prescribed condition.

Then, in step S17, the process recipe selecting unit 58 selects, from among the process recipe information stored in the process recipe information storing unit 57, the process recipe information corresponding to the standard defect 9 selected by the standard defect selecting unit 56, and supplies the selected information to the data output unit 5.

Whether or not a given standard defect 9 has been detected can be determined, for example, by checking if the defect information concerning the given standard defect 9 has been stored in step S13. In step S15, the process recipe evaluation information generating unit 53 supplies the defect information of the standard defect 9, stored in step S13, to the standard defect selecting unit 56 as process recipe evaluation information that indicates detection or non-detection of the standard defect.

Then, in step S16, the standard defect selecting unit 56 selects from among the standard defects 9 the standard defect 9 whose defect information has been received from the process recipe evaluation information generating unit 53 as the standard defect that satisfies the prescribed condition “the defect can be detected by the surface inspection apparatus 1,” and supplies it to the process recipe selecting unit 58.

If, for example, there is more than one standard defect 9 for which defect information has been stored in step S13, the standard defect selecting unit 56 in step S16 selects all of the standard defects and supplies them to the process recipe selecting unit 58.

Then, in step S17, the process recipe selecting unit 58 retrieves from among the process recipe information stored in the process recipe information storing unit 57 the process recipe information corresponding to all the standard defects 9 selected by the standard defect selecting unit 56, takes an intermediate value among the thus retrieved process recipe information as representing the most advantageous process recipe information to be used in the manufacturing process, and supplies the process recipe information to the data output unit 5 after setting upper and lower limit values to allow a margin for the process recipe information.

Among the items previously listed as forming the standard defect data, there are items that are difficult to correctly create unless the image of the standard defect 9 is actually captured. For such items, it is advantageous to generate data from the image captured by the surface inspection apparatus 1, rather than externally providing data to the surface inspection apparatus 1 via the data input unit 4. From the defect information of the detected standard defect 9, the standard defect data generating unit 52 generates data for some of the items of the standard defect data to be stored in the standard defect data storing unit 51.

When generating the standard defect data by the standard defect data generating unit 52, first the standard defect 9 generated by a suitable process recipe is formed on the actual wafer 2. Whether or not the recipe used for the formation of the standard defect 9 is suitable can be determined by forming a number of standard defects 9 by changing the process recipe, and by observing the thus formed standard defects using an SEM or the like. Then, the surface of the actual wafer 2 containing the standard defect 9 is inspected. Further, the position information of the standard defect 9 carried in the standard defect data is input via the data input unit 4 and stored in the standard defect data storing unit 51, while the defect information generated during the surface inspection is input to the standard defect data generating unit 52.

From among the defect information thus input, the standard defect data generating unit 52 selects the defect information associated with the standard defect 9 based on the position information of the standard defect 9 stored in the standard defect data storing unit 51. Then, the size of the defect, the gray level value that the pixel in the portion of the standard defect 9 shows, the gray level difference between the inspection image and the reference image for the standard defect 9, etc., are acquired from the selected defect information, and stored in the standard defect data storing unit 51 as the standard defect data concerning the standard defect 9.

According to the present invention, since the inspection for determining the suitability of the process recipe can be performed simultaneously with surface inspection, the inspection (for example, the SEM inspection) separately performed in the prior art for the management of the manufacturing process, such as the determination of the suitability of the process recipe, can be omitted.

Further, in the prior art, when performing the inspection using an SEM for the determination of the suitability of the process recipe, it was possible to inspect only limited specific portions on the wafer surface because of low throughput, but according to the present invention, the entire surface of the wafer can be inspected because the inspection can be performed simultaneously with surface inspection.

The manufacturing process that can form a pattern about the same size as the standard defect, having a prescribed size, can be determined during surface inspection.

The present invention is applicable to a surface inspection apparatus and surface inspection method for detecting a defect appearing on the surface of a sample, based on an image, etc. captured of the surface of the sample. The invention is particularly applicable to a surface inspection apparatus and surface inspection method for detecting a defect in a pattern formed on the surface of a substrate such as a semiconductor wafer, a photomask, a liquid crystal display panel substrate, or a liquid crystal device substrate, based on an image captured of the surface of the substrate.

While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.

SURFACE INSPECTION APPARATUS AND SURFACE INSPECTION METHOD

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