JP6059893B2 - Electron beam automatic length measuring device, parameter automatic setting system for electron beam automatic length measuring device, and parameter automatic setting program - Google Patents

Description

  The present invention relates to an electron beam automatic length measuring device, and more particularly, to an electron beam automatic length measuring device parameter automatic setting system, an electron beam automatic length measuring device including the parameter automatic setting system, and a parameter automatic setting program.

  2. Description of the Related Art Conventionally, in a semiconductor manufacturing process, an electron beam automatic length measuring device has been used for measuring a dimension of an integrated circuit including a circuit wiring width, a gate width, and a contact hole diameter. In recent years, pattern miniaturization has progressed in an etching process and a lithography process. As a result, the number of measuring points by the electron beam automatic length measuring device increases, and the electron beam automatic length measuring device is required to have high throughput and high length measuring accuracy.

  In the semiconductor manufacturing process, when inspecting whether the dimension of the pattern formed on the wafer is far from the design value, the width of the pattern and the interval between the patterns are measured using an automatic electron beam length measuring device. The dimensions of the finished pattern are inspected based on the measurement results. However, in recent years, miniaturization of semiconductor manufacturing apparatuses has progressed, and much effort is required for pattern length measurement and evaluation by an electron beam automatic length measurement apparatus. Therefore, the image of the pattern to be measured by the electron beam automatic length measuring device and its position are registered on the electron beam automatic length measuring device using the wafer that is the actual product, and the recipe includes the sequence until automatic length measurement. (Measurement recipe) is created. Then, a desired pattern is measured according to a recipe registered in advance, and the quality of the product is determined from the result.

  In order to determine the quality of a product, reliability of the measurement result is required. Therefore, the quality of the recipe affects the reproduction accuracy of the measurement result and changes the measurement result. It has been proven that the reproduction accuracy of measurement results varies depending on the quality of the recipe.

  The quality of the recipe varies from operator to operator, that is, depending on the skill of creating the recipe. In particular, since the automatic electron beam length measuring device is not a device that enables absolute dimension measurement, the quality of measurement results generally uses the reproducibility of the measurement results as an index.

  The quality of the recipe varies depending on the setting of the measurement method for the pattern to be measured. When the quality of the recipe is good, the reproduction accuracy of the measurement result is high, and when the quality of the recipe is bad, the reproduction accuracy of the measurement result is low. The desired pattern for length measurement is subjected to pattern observation using an automatic electron beam length measuring device, and an image of the pattern is registered. This registered image is a black-and-white shading that shows the amount of secondary electrons generated from the pattern in multiple steps in the order in which the pattern was irradiated with an electron beam while scanning the pattern in a vacuum. Is an image displaying. The scanning dose of actual scanning irradiation in a vacuum is 256, 384, 512, 768, 1024, 1536, 2048, or 4096, and forms one frame of the image.

  A secondary electron profile is created for the length measurement target pattern shown in the image. In this secondary electron profile, the generated amount of secondary electrons is defined on the vertical axis, and the X direction of the image is defined on the horizontal axis. The secondary electron profile is obtained when the primary electron beam is scanned and irradiated on a desired pattern. This is a plot of the amount of generated electrons. Automatic length measurement is performed using the plotted secondary electron profile. In automatic length measurement, a portion defined as an edge of a pattern to be measured is automatically captured and measured using a secondary electron profile. In order to execute this process, the operator sets parameters relating to automatic length measurement. In this automatic length measurement parameter setting, the location where the edge is defined for each operator, the definition of the quantity of the integration profile used for length measurement, and the like are different, so that variations in length measurement are reflected.

  Patent Document 1 discloses a pattern dimension measuring apparatus. In the measurement apparatus of Patent Document 1, the relationship between the pattern shape and the SEM signal waveform is calculated in advance by SEM simulation, and measurement independent of the target shape is performed using the simulation result. In Patent Document 1, the pattern shape is digitized using parameters, and SEM simulation results of cross-sectional shapes of various patterns are stored as a library. Then, the pattern shape and dimensions are estimated by comparing the cross-sectional shape information stored in the library with the actual SEM waveform.

JP 2009-198339 A JP 2010-276487 A

  In the above-described measurement apparatus disclosed in Patent Document 1, information on a cross-sectional shape of a pattern stored in a library is compared with an actual SEM waveform, and only a cross-sectional shape of the pattern is estimated. Therefore, in Patent Document 1, it cannot be solved that the reproduction accuracy of the measurement result varies due to the variation in the quality of the automatic side length parameter (that is, the measurement recipe).

  In order to solve the above-described problems, the present invention can prevent variations in reproduction accuracy due to the setting of automatic length measurement parameters (measurement recipes) for each operator, and a constant reproduction regardless of which operator sets the automatic length measurement parameters. Provide technology that can satisfy the accuracy.

  In order to solve the above-described problem, in the present invention, when the secondary electron profile obtained from the secondary electron image registered as a model matches the secondary electron profile stored in the library, they are matched. An automatic length measurement parameter corresponding to the secondary electronic profile is acquired, and the acquired automatic length measurement parameter is automatically set as a length measurement parameter used in a measurement target measurement pattern.

  That is, the parameter automatic setting system of the present invention includes a plurality of first secondary electron images, a plurality of first secondary electron profiles created from the plurality of first secondary electron images, and the plurality of the plurality of first secondary electron images. A storage unit that stores a plurality of length measurement parameters used when the first secondary electron image is captured; and a calculation unit that sets a length measurement parameter used for a measurement target measurement pattern. The arithmetic unit creates a second secondary electron profile from a second secondary electron image registered in advance, and matches the second secondary electron profile with the plurality of first secondary electron profiles. A length measurement parameter corresponding to the first secondary electron profile that matches the second secondary electron profile is acquired from the storage unit by executing processing, and used for the length measurement pattern to be measured. The length measurement parameter acquired from the storage unit is set as the length parameter.

  Moreover, according to this invention, the electron beam automatic length measuring apparatus provided with the above-mentioned parameter automatic setting system is provided.

  Furthermore, according to the present invention, there is provided a program for causing an information processing apparatus including a storage unit and a calculation unit to execute processing for automatically setting a length measurement parameter used for a length measurement pattern to be measured. The storage unit includes a plurality of first secondary electron images, a plurality of first secondary electron profiles obtained from the plurality of first secondary electron images, and the plurality of first secondary electron images. A plurality of length measurement parameters used when the image is captured. The program includes processing for creating a second secondary electron profile from a second secondary electron image registered in advance in the arithmetic unit, the second secondary electron profile, and the plurality of first 2 A process of executing a matching process with a secondary electron profile to obtain a length measurement parameter corresponding to the first secondary electron profile that matches the second secondary electron profile from the storage unit; And a process of setting a length measurement parameter acquired from the storage unit as a length measurement parameter used in the length measurement pattern.

  According to the present invention, it is possible to prevent variation in reproduction accuracy due to setting of an automatic length measurement parameter for each operator, and a certain reproduction accuracy can be satisfied regardless of which operator sets the automatic length measurement parameter.

  Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Further, problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a schematic block diagram of the electron beam automatic length measuring apparatus which concerns on this invention. It is a figure which shows the structure of the automatic setting system of the length measurement parameter which concerns on this invention. It is a figure which shows an example of the library which concerns on this invention. It is a flowchart which shows the outline | summary of the process performed in the electron beam automatic length measuring apparatus which concerns on this invention. It is a flowchart which shows the outline | summary of the process performed in the automatic setting system of the length measurement parameter which concerns on this invention. It is a flowchart which shows the outline | summary of the registration process performed in the automatic setting system of the length measurement parameter which concerns on this invention. It is a figure which shows the area | region used for the matching of a secondary electron profile in case a side length pattern is Line. It is a figure which shows an example of a secondary electron profile. It is a figure which shows an example of the setting screen of the length measurement parameter for electron beam automatic length measurement apparatuses. It is a figure which shows another example of the setting screen of the length measurement parameter for electron beam automatic length measurement apparatuses. It is a figure which shows the relationship between the parameter set in FIG. 9, and the edge on the secondary electron profile extracted by the parameter. It is a figure which shows the relationship between the parameter set in FIG. 10, and the edge on the secondary electron profile extracted by the parameter.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The accompanying drawings show specific embodiments in accordance with the principle of the present invention, but these are for the understanding of the present invention, and are never used to limit the interpretation of the present invention. is not.

<Configuration of electron beam automatic measuring device>
FIG. 1 is a schematic configuration diagram of an electron beam automatic length measuring apparatus of the present invention. The electron beam length measuring apparatus 100 includes a cathode 101, first and second anodes 102 and 103, a condenser lens 104, a deflection coil 105, an objective lens 108, a holder 110, a stage 111, and a secondary. An electron detector 112 and a controller 113 are provided.

  The cathode 101 is a sufficiently thin electrode having a tip of 1 μm or less. When a high voltage is applied to the cathode 101 in a high vacuum, electrons are generated. The generated electrons drift out like an atmosphere and are extracted by the first anode 102. Since the extracted electrons are diverged, the electrons are converged by the second anode 103. Then, the electrons are further converged by the condenser lens 104. The converged electrons are called primary electrons 106.

  The sample 109 is held by a holder 110 on the stage 111. The primary electrons 106 pass through the deflection coil 105 and irradiate the sample 109, and the deflection coil 105 scans the sample 109 in the X direction and the Y direction (in the plane perpendicular to FIG. 2). Further, when the sample 109 is irradiated with the primary electrons 106, the objective lens 108 is focused.

  Then, electrons that are protruded from the surface of the sample 109 at the location irradiated with the primary electrons 106 from a depth within 10 nm are generated as secondary electrons 107. The secondary electrons 107 are attracted to the tip of the secondary electron detector 112 applied to 10 kV and detected. The secondary electron detector 112 converts the detected secondary electrons into light and amplifies them, converts them again into electrons, converts the electrons into electric signals, and sends them to the controller 113.

  The controller 113 outputs an image displaying black and white shades indicating the amount of generation of secondary electrons in multiple steps for each time and position at which the transmitted electrical signal is detected. The controller 113 incorporates software for automatically measuring a pattern from the image. In the following, the threshold method is used as the edge detection method for the automatic length measurement pattern, but it is not necessarily limited to the threshold method, and includes other methods such as a linear approximation method. .

  The controller 113 includes a length measurement parameter automatic setting system 120 according to the present invention. The length measurement parameter automatic setting system 120 may be incorporated in the controller 113 or may be configured by another information processing apparatus connected to the controller 113.

  The length measurement parameter automatic setting system 120 includes an information processing apparatus such as a computer. The automatic setting system 120 includes a display unit 121 for displaying data, an input unit (for example, a keyboard and a pointing device) 122 for performing an operation such as selecting a menu for the displayed data, A calculation unit 123 that executes processing, control processing, and the like, and a storage unit (for example, a memory and a hard disk) 124 for storing data are provided. In addition, the calculation unit 123 includes a setting processing unit 125 and a registration processing unit 126.

  Note that the processing of the automatic setting system 120 described below may be realized as a function of a program executed on a computer. That is, the processing described below may be stored in the storage unit 124 as a program code, and the calculation unit 123 may execute each program code to implement the present invention. Further, the processing described below may be realized as a hardware configuration.

<Configuration of automatic length measurement parameter setting system>
Currently, the sequence until the pattern is automatically measured in the electron beam automatic length measuring apparatus 100 is set by the operator. Therefore, the inventor of the present invention provides a secondary electron image (first secondary electron image) obtained by capturing a pattern measured in advance, and a secondary electron profile (first image) obtained from the image. There is provided a technique of associating three secondary electron profiles) and automatic length measurement parameters set for measuring the pattern thereof, and storing them as library data (Library Data). The library data also includes information about the image such as the magnification at the time of pattern measurement, the integration frame at the time of acquiring the secondary electron image, the acceleration voltage of the primary electron, and the information on the amount of current of the primary electron. save.
That is, the automatic side length parameter (measurement recipe) accumulated as library data in the present invention includes the parameters shown in the description of FIG. 9 and FIG. 10, the magnification at the time of pattern measurement, and the integration at the time of acquisition of the secondary electron image. It also includes information at the time of acquiring a secondary electron image, such as a frame, an acceleration voltage of primary electrons, and an amount of current of primary electrons.

  FIG. 2 is a diagram showing the configuration of a length measurement parameter automatic setting system for an electron beam automatic length measurement device. The length measurement parameter automatic setting system 201 registers a secondary electron profile (second secondary electron) of a secondary electron image (second secondary electron image) registered as a model when a desired length measurement pattern is registered. Profile) and a secondary electron profile stored as a library in advance are matched. Here, the image registered as a model is a secondary electronic image having the same pattern as the pattern to be measured, and is a secondary electronic image having a pattern at a position different from the actual measurement target. The secondary electronic image of this model is registered in advance before the processing of the automatic setting system 201.

  The length measurement parameter automatic setting system 201 includes a library 220. The library 220 is stored in the storage unit 124 as a database. The length measurement parameter automatic setting system 201 creates a secondary electronic profile 211 from the secondary electronic image 210 registered as a model. The length measurement parameter automatic setting system 201 executes a matching process between the secondary electron profile 211 obtained from the secondary electron image 210 and the secondary electron profile 221 stored in the library 220 acquired in the past in advance. .

  FIG. 8 shows an example of the secondary electron profiles 211 and 221. FIG. 8 shows a profile of a two-dimensional graph in which the vertical axis represents the generation amount of secondary electrons and the horizontal axis represents the generation position of secondary electrons in the scanning direction of the primary electrons. The vertical axis in FIG. 8 corresponds to the black-and-white shading of the secondary electron image expressed by the gradation by dividing the generation amount of secondary electrons into multi-steps. The past secondary electronic profile 221 is stored in the library 220 in association with the automatic length measurement parameter 222 set at the time of measurement.

  The length measurement parameter automatic setting system 201 extracts a secondary electron profile 221 that matches the secondary electron profile 211 obtained from the secondary electron image 210 registered as a model from the library 220, and extracts the extracted secondary electron profile 221. An automatic length measurement parameter 222 corresponding to the electronic profile 221 is acquired. Then, the length measurement parameter automatic setting system 201 sets the automatic length measurement parameter 222 acquired from the library 220 as the length measurement parameter used for the length measurement pattern to be measured. As a result, a parameter that matches the measurement pattern to be measured this time is automatically set from the automatic measurement parameter 222 that has been accumulated in the past, and the variation in reproduction accuracy due to the setting of the automatic measurement parameter for each operator is reduced. Can be prevented.

<Library configuration>
FIG. 3 is a diagram showing an example of the library 220 of the present embodiment. The library 220 includes a Library Data directory 301, and a profile directory 302, an images directory 303, and an amp directory 304 are created in the Library Data directory 301. The images directory 303 stores a plurality of secondary electronic images captured during length measurement performed in the past. The profile directory 302 stores a plurality of secondary electron profiles obtained from a plurality of secondary electron images. The amp directory 304 stores a plurality of automatic side length parameters. Data stored in the profile directory 302, the images directory 303, and the amp directory 304 are associated with each other. For example, as shown in FIG. 3, if the file name of the images directory 303 is img20120101000001, the file name of the profile directory 302 is pro20120101000001, and the file name of the amp directory 304 is amp20120101000001, which is an 8-digit date below the directory name. And 6 digits. This association method is an example, and other association methods may be used. By associating each piece of data in this way, it becomes possible to handle each piece of data in association with each other, such as a process for acquiring an automatic length measurement parameter corresponding to the secondary electron profile.

<Auto side length parameter setting screen>
FIG. 9 shows a length measurement parameter setting screen for the electron beam automatic length measurement device displayed on the display unit 121, and shows a line (Line) length measurement parameter setting screen. The automatic length measurement parameter setting screen 322 includes a length measurement type selection button 323, a length measurement target pattern setting button 324, and a cursor type selection unit 325. The length measurement type selection button 323 incorporates a line width measurement, a line width variation measurement, a line edge variation measurement, a hole diameter measurement, and the like in order to enable measurement of various patterns. This is for selecting the type of side director.

  The length measurement target pattern setting button 324 includes Line, Space, Pitch (Left), Pitch (Right), Top, Slope (Left), and Slope (Right), and corresponds to the pattern to be measured. . The cursor type selection unit 325 is used to select whether two left and right boxes are used as a cursor for searching for a pattern edge, or a cursor integrated in a lump is used.

  The automatic length measurement parameter setting screen 322 includes a profile processing method selection button 326 and a plurality of parameter setting boxes 327, 328, 329, 330, 331. In FIG. 9, “Threshold (threshold method)” is selected as the profile processing method.

  The parameter setting box 327 is a box for setting a distance between cursors as a range for performing measurement, and the parameter setting box 329 is a box for setting a peak search range. The parameter setting box 330 is a box for setting a range used for measurement. The parameter setting box 328 is a box for setting profile processing intensity, and the parameter setting box 331 is a box for setting a threshold value for defining an edge.

  FIG. 11 shows the relationship between the parameters set in FIG. 9 and the edges on the secondary electron profile extracted by the parameters. The distance between the cursors (parameter setting box 327), the profile processing intensity (parameter setting box 328), and the peak search range (parameter setting box 329) for the secondary electron image 530 for a certain side length pattern. Is set. As shown in FIG. 11, a secondary electron profile 532 obtained by integrating the peak search range (parameter setting box 329) and the range set in the parameter setting box 330 is created and set in the parameter setting box 331. The threshold position is detected as an edge 533.

  FIG. 10 shows a length measurement parameter setting screen for the electron beam automatic length measurement apparatus displayed on the display unit 121, and shows a hall measurement parameter setting screen. The automatic length measurement parameter setting screen 332 is a setting screen when the length measurement type selection button 323 is set to Diameter (Hole). The automatic length measurement parameter setting screen 332 includes a profile processing method selection button 326 and a plurality of parameter setting boxes 333, 334, 335, 336, 337.

  The parameter setting box 333 is a box for setting the number of holes, and the parameter setting box 334 is a box for setting the diameter (nm) of the holes. The parameter setting box 335 is a box for setting a Hole edge detection range (pixel). The parameter setting box 336 is a box for setting a fan-shaped angle as a signal area for creating a profile. The parameter setting box 337 is a box for setting a threshold value for defining an edge.

  FIG. 12 shows the relationship between the parameters set in FIG. 10 and the edges on the secondary electron profile extracted by the parameters. A Hole diameter (parameter setting box 334) and a Hole edge detection range (parameter setting box 335) are set for the secondary electron image 531 for a certain side length pattern. As shown in FIG. 12, a secondary electron profile 340 obtained by integrating the peak search range (parameter setting box 335) and the range set in the parameter setting box 336 is created and set in the parameter setting box 337. The threshold position is detected as an edge 338.

  The automatic side length parameter described with reference to FIGS. 9 and 10 is an example of the automatic side length parameter stored in the amp directory 304 of the library 220. Therefore, the length measurement parameter automatic setting system 201 acquires the automatic side length parameter from the library 220 after the matching processing, and automatically sets it in the automatic length measurement parameter setting screens 322 and 332 of FIGS.

<Processing in an electron beam automatic length measuring device>
Next, processing performed in the electron beam automatic length measuring apparatus having the above-described configuration will be described. FIG. 4 is a flowchart showing an outline of processing performed in the electron beam automatic length measuring apparatus.

  First, in step S001, a sample wafer is loaded onto the holder 110 on the stage 111. Next, in step S002, sample wafer alignment information (wafer rotation, alignment between chips, etc.) is set. Next, in step S003, the measurement chip is registered. Note that step S003 is developed based on the measurement information of one chip without any problem even before and after the order of registration of the measurement method (S006).

  Next, in step S004, the coordinates of the measurement point on the chip are registered. Here, the coordinates of the measurement point that is actually measured and the coordinates of the model imaged in the next step S005 are registered.

  Thereafter, in step S005, a measurement pattern model is registered. Here, the image registered as a model is a secondary electronic image having the same pattern as the pattern to be measured, and is a secondary electronic image having a pattern at a position different from the actual measurement target. A secondary electron image of this model is captured and registered in step S005.

  Next, in step S006, a measurement method for the measurement pattern is registered. Specifically, an automatic side length parameter for the measurement pattern is set. Here, detailed steps of step S006 will be described later.

  Next, when there are a plurality of measurement points in step S007, the process returns to step S003 to register the measurement method for the measurement points. Then, the sequence from step S003 to S006 is sequentially repeated until registration for measurement points is completed.

  Next, after the registration for the measurement points is completed, in step S008, in order to confirm whether or not the measurement sequence using the automatic side length parameter set in step S006 can be executed without any problem, To implement. If there is no problem in the measurement sequence using the automatic side length parameter in step S009, the process ends.

  However, if a problem occurs during the test run, the process proceeds from step S009 to step S010. In step S010, it is determined whether an error during execution of the test run is an error due to an automatic side length parameter. In step S010, for example, a secondary electron image of the measurement pattern is displayed, but if there is an error in which measurement pattern measurement cannot be performed, the process proceeds to step S011, and the process returns to step S003 to change the automatic side length parameter. On the other hand, if the secondary electron image of the measurement pattern is not displayed in step S010, the process proceeds to step S012, and it is determined that the coordinate of the measurement point needs to be changed. In this case, the process returns to step S003, and steps S003 to S008 are repeatedly executed. In step S008, a test run is executed, and if there is no problem in the measurement sequence using the automatic side length parameter, the process ends.

<Setting process in automatic length measurement parameter setting system>
Conventionally, the automatic side length parameter setting (corresponding to step S006 in FIG. 4) has been performed manually by an operator. Therefore, there is a variation in quality for each operator who creates automatic side length parameters (measurement recipes), and this variation has been a factor in reducing the measurement reproducibility when measured using an electron beam length measuring device. . A feature of the present invention is that automatic length parameter setting is automatically performed in the length measurement parameter automatic setting system 201 described above.

  FIG. 5 is a flowchart showing an outline of processing performed in the length measurement parameter automatic setting system, and shows processing executed in step S006 of FIG. The subject of the following processing is the setting processing unit 125 of the calculation unit 123.

  First, in step S101, a secondary electron profile is created (extracted) from a secondary electron image of a pattern registered as a model. Here, as described above, when a secondary electron image is irradiated while scanning an electron beam with respect to the pattern in a vacuum, the amount of secondary electrons generated from the pattern in the order of positions irradiated to the pattern. Is an image displaying black-and-white shades showing the multi-tone.

  Next, in step S102, matching processing between the secondary electronic profile of the model and the secondary electronic profile stored in the profile directory 302 of the library 220 is executed. Here, the matching of the secondary electron profile is performed for the regions 701 to 709 shown in FIG. FIG. 7 will be described later.

  Next, in step S103, with respect to the secondary electron profile of the model and the secondary electron profiles stored in the profile directory 302 of the library 220, the slopes and minimum values for each of the regions 701 to 709 shown in FIG. , And calculate the highest value. Then, for the slope, the minimum value, and the maximum value, the percentage of the secondary electronic profile value stored in the profile directory 302 is matched with the secondary electronic profile value of the model. Hereinafter, this value is referred to as the degree of coincidence. For example, if the value of the secondary electronic profile of the model is 100 and the value of the secondary electronic profile stored in the profile directory 302 is 80, the degree of coincidence is 80%. Between the secondary electronic profile of the model and the secondary electronic profile stored in the profile directory 302, the slope, the minimum value, and the maximum value coincidence of each region of the regions 701 to 709 are calculated and calculated. Find the average value of the degree of coincidence.

  Next, in step S104, it is determined whether the average value of the degree of coincidence obtained in step S103 is 80% or more. If there is a secondary electronic profile with an average matching degree of 80% or more among the secondary electronic profiles stored in the profile directory 302, the process proceeds to step S105. If there is no secondary electron profile having an average value of coincidence of 80% or more, the process proceeds to step S106.

  Next, in step S105, a secondary electron profile corresponding to the highest degree of coincidence is extracted from secondary electron profiles having an average degree of coincidence of 80% or more, and automatic length measurement parameters corresponding to the secondary electron profile are extracted. Is obtained from the amp directory 304 of the library 220. Thereafter, the process proceeds to step S108.

  On the other hand, if there is no secondary electron profile with an average value of coincidence of 80% or more, in step S106, the display unit 121 says “Can set up to a third candidate with a high degree of coincidence? Display a message. Here, when the operator selects “No”, the automatic length measurement parameter is manually set. If the operator selects “Yes”, the process proceeds to step S107.

  In step S107, three secondary electronic profiles are extracted from the secondary electronic profiles stored in the profile directory 302 in descending order of the average value of the matching degree, and automatic length measurement parameters corresponding to the respective secondary electronic profiles are extracted. Obtained from the amp directory 304 of the library 220. Thereafter, the process proceeds to step S108.

  Next, in step S108, the acquired automatic length measurement parameter is automatically registered anew. Thereafter, in step S109, when the automatic length measurement parameters up to the third candidate are acquired in step S107, the automatic length measurement parameters for the third candidate are registered. Even if the secondary electron profile corresponding to the highest matching degree is acquired in step S105, three secondary electron profiles are extracted in descending order of the average degree of matching, and automatic measurement up to the third candidate is performed. A long parameter may be registered.

  Next, in step S110, a test run is performed. The controller 113 has a built-in function for confirming variations in measured values. In the test run, a value (3σ) indicating variation in the measured value is calculated by the above function. Here, σ is a standard deviation. In step S111, the automatic length measurement parameter having the smallest measurement value variation (3σ) among the first to third candidates is automatically registered. As a result, it is possible to set a more appropriate automatic length measurement parameter in consideration of variations in measurement values.

<Area used for secondary electron profile matching>
FIG. 7 shows a region used for secondary electron profile matching when the side length pattern is Line.

  The secondary electronic profile of the model and the secondary electronic profiles stored in the profile directory 302 of the library 220 are each divided into a first area to a ninth area 701 to 709, and Index is assigned to each area. Assigned. Therefore, matching the secondary electronic profile of the model with the secondary electronic profile stored in the profile directory 302 of the library 220 uses this Index to calculate the slope, minimum value, and maximum value of the same region. Can be performed.

  The first region 701 indicates a region from the lowest left portion to the lowest right portion of the secondary electron profile (region from the lowest portion outside the left protruding portion to the lowest portion outside the right protruding portion). It is a Bottom CD. The second region 702 is a Peak CD that indicates a region from the leftmost highest portion to the rightmost highest portion (region from the highest portion of the left protruding portion to the highest portion of the right protruding portion) of the secondary electron profile. It is. A third region 703 indicates a region from the lowest left portion to the highest left portion of the secondary electron profile (region from the lowest portion outside the left protruding portion to the highest portion of the left protruding portion). Footing (L).

  The fourth region 704 is a region from the highest part on the left side of the secondary electron profile to the part where the slope is zero on the left side (the slope is zero on the inside of the left part of the protruding part on the left side. Top Rounding (L) indicating a region up to a part). The fifth region 705 is a region from the portion where the inclination is 0 on the right side of the secondary electron profile to the highest portion on the right side (the portion protruding rightward from the portion where the inclination is 0 inside the protruding portion on the right side) Top Rounding (R) indicating the region up to the highest part of the image). A sixth region 706 indicates a region from the highest right part to the lowest right part of the secondary electron profile (an area from the highest part of the right protruding part to the lowest part outside the right protruding part). Footing (R).

  Further, the seventh region 707 is a region from the lowest left portion of the secondary electron profile to a portion where the inclination is zero on the left side (inclination is from the lowest portion outside the left protruding portion to the inside of the left protruding portion. This is a White Band (L) indicating a region up to a portion where becomes zero. The eighth region 708 is a region from a portion where the slope is 0 on the left side of the secondary electron profile to a portion where the slope is 0 on the right side (from a portion where the slope is 0 inside the protruding portion on the left side. It is a Top CD showing a region up to a portion where the inclination becomes 0 inside the protruding portion on the right side. The ninth region 709 is a region from the portion where the inclination is 0 on the right side to the lowest right side of the secondary electron profile (the portion protruding right from the portion where the inclination is 0 inside the protruding portion on the right side) This is a White Band (R) indicating the area up to the lowest part outside the area.

  The secondary electron profile is divided into the first to ninth regions 701 to 709 described above, and the degree of coincidence is calculated in each region, so that the model secondary electron profile and the profile directory 302 of the library 220 are calculated. It is possible to perform the matching process with the secondary electron profile stored in the computer with high accuracy.

<Registration process in length measurement parameter automatic setting system>
As described above, the length measurement parameter automatic setting system 201 extracts the secondary electron profile that matches the secondary electron profile of the model from the library 220 and automatically measures the length corresponding to the extracted secondary electron profile 221. The parameter 222 is set. Therefore, hereinafter, a process of registering the secondary electronic profile 211 and the automatic length measurement parameter 222 corresponding to the secondary electronic profile 211 in the library 220 in advance will be described. Registration in the library 220 is performed on data when measurement was performed in the past. As data when the measurement is performed in the past, there are data performed during the development process and data performed in the inspection after the manufacture.

  FIG. 6 is a flowchart showing an outline of a registration process performed in the length measurement parameter automatic setting system. The subject of the following processing is the registration processing unit 126 of the calculation unit 123 of the length measurement parameter automatic setting system 120.

  First, in step S201, a profile directory 302, an images directory 303, and an amp directory 304 are created in the Library Data directory 301 of the library 220. Next, in step S202, data stored in the profile directory 302, the images directory 303, and the amp directory 304 in the library 220 are associated with each other. As described above, for example, there is a method of associating an 8-digit date below the directory name with a 6-digit number.

  Next, in step S203, only data in which both the automatic length measurement parameter at the time of measurement and the secondary electron image image are stored is extracted from the data when the measurement has been performed in the past. This is because when there is no automatic length measurement parameter, it cannot be used in the length measurement parameter automatic setting system 120, and when there is no secondary electron image, a secondary electron profile for matching cannot be created.

  Next, in step S204, automatic side length parameters from past measurement recipes are organized and stored in the amp directory 304 in the library 220. In step S205, the secondary electronic images are organized and stored in the images directory 303 in the library 220.

  Next, in step S206, it is determined whether the pattern shape of the measurement pattern of the secondary electronic image to be registered has changed by 10% or more in the secondary electronic image to be registered. As will be described in detail below, in the case of a secondary electron image during the development process, the pattern shape may change between a plurality of images. Here, in the case of a Line (line) pattern, the determination condition may be whether the length of the line width has changed by 10% or more, or the length of the pattern interval has changed by 10% or more. it can. In the case of Hole, whether the diameter, the distance from the center to the edge, or the like has changed by 10% can be used as the determination condition. If the pattern shape has not changed by 10% or more, the process proceeds to step S207.

  On the other hand, if the pattern shape has changed by 10% or more, the process proceeds to step S210. The fact that the pattern shape has changed by 10% or more means that the pattern shape has changed in the development process for the purpose of narrowing down the optimum production conditions like a wafer for new process development. Here, secondary electron images of a plurality of measurement points are acquired in order to deal with samples created by changing the production conditions with chips on the entire wafer surface. In the case of a pattern in which the creation conditions have changed for chips on the entire surface of the wafer, it is difficult for the operator to determine which chip image is best registered. Therefore, optimization of automatic length measurement parameters corresponding to changes in shape and dimensions leads to shortening of new process development.

  In step S210, for example, secondary electronic images stored at the time of measurement are extracted from 60% of a plurality of measurement points registered in one measurement recipe. Note that this image extraction may be performed at random. In addition, when a plurality of automatic length measurement parameters are registered in one measurement recipe, a plurality of images having the same automatic length measurement parameter in the same pattern among a plurality of measurement points registered in one measurement recipe. You may make it extract.

  Next, in step S211, the display positions of the plurality of extracted image patterns are aligned, and a plurality of images are added and averaged. Thereby, an image obtained by averaging a plurality of images can be created. For example, as in the measurement device described in Patent Document 2, in the case of a Line pattern, an image of a pattern with an averaged line width can be obtained by averaging an image with a large line width or a thin image. In step S212, a secondary electron profile is created from the image created in step S211. Note that when an averaged image is created from a plurality of images, it is important to select which automatic length measurement parameter. For example, as the automatic length measurement parameter, an automatic length measurement parameter corresponding to an image having a secondary electron profile that most closely matches the secondary electron profile of the averaged image among a plurality of images is employed. For the degree of coincidence between the secondary electron profiles, the same processing as described above can be used. The automatic length measurement parameter is stored in the amp directory 304. Thereby, even when an averaged image is created, appropriate parameters can be stored in the library 220.

  Next, in step S208, the secondary electron profile created in step S207 or S212 is divided into first to ninth regions 701 to 709 as shown in FIG. 7, and an index is assigned to each region. In step S209, the secondary electronic profiles are organized and stored in the profile directory 302.

<Summary>
The length measurement parameter automatic setting system 120 according to the present embodiment captures a plurality of secondary electron images, a plurality of secondary electron profiles created from the plurality of secondary electron images, and a plurality of secondary electron images. A storage unit 124 that stores a plurality of automatic length measurement parameters used in the above, and a calculation unit 123 that sets automatic length measurement parameters used for the length measurement pattern to be measured. The setting processing unit 125 of the calculation unit 123 creates a secondary electronic profile from a secondary electron image (model) registered in advance, and stores the secondary electronic profile of the model and the secondary 220 stored in the library 220 of the storage unit 124. A matching process with the electronic profile is executed, and automatic length measurement parameters corresponding to the secondary electron profile that matches the model's secondary electron profile are acquired from the library 220 of the storage unit 124, and used for the length measurement pattern to be measured. The automatic length measurement parameter acquired from the library 220 of the storage unit 124 is set as the automatic length measurement parameter.
According to this configuration, it is possible to prevent variation in reproduction accuracy due to the setting of the automatic length measurement parameter for each operator, and it is possible to satisfy a certain reproduction accuracy regardless of which operator sets the automatic length measurement parameter. Further, by applying the present invention, it is possible to minimize the variation in measurement reproducibility by each operator without functions such as standardization and unification of measurement recipe creation.

Further, according to the automatic setting system 120 of this embodiment, the secondary electron profile is a two-dimensional graph including the first to ninth regions 701 to 709, respectively, and the setting processing unit 125 of the calculation unit 123. As a matching process, the minimum value, the maximum value, and the slope are calculated for each of the plurality of regions 701 to 709, and the secondary electron profile of the model and the secondary electron profile stored in the library 220 of the storage unit 124 are calculated. The degree of coincidence with is calculated.
According to this configuration, matching between the secondary electron profile of the model and the secondary electron profile stored in the library 220 of the storage unit 124 is calculated by calculating the degree of coincidence for each characteristic region of the secondary electron profile. Can be performed with high accuracy.

Further, according to the automatic setting system 120 of the present embodiment, the setting processing unit 125 of the calculation unit 123 calculates the average value of the degree of coincidence, and the secondary value is greater than a predetermined numerical value (80%). When the electronic profile exists, the length measurement parameter corresponding to the secondary electronic profile having the highest degree of matching is acquired from the library 220 of the storage unit 124 (step S105). Thereby, when the degree of coincidence is high to some extent, the secondary electron profile having the highest degree of coincidence can be selected and the length measurement parameter can be set.
Further, the setting processing unit 125 of the calculation unit 123 acquires secondary electronic profiles up to the third candidate in order of matching degree when there is no secondary electronic profile in which the average value of the matching degree is greater than a predetermined numerical value. The length measurement parameters corresponding to the secondary electron profiles up to are acquired from the library 220 of the storage unit 124, and one length measurement parameter is acquired from among the third candidates. Thereby, when the degree of coincidence is not high, a more appropriate length measurement parameter can be set by selecting one length measurement parameter from a plurality of candidates.

Further, according to the automatic setting system 120 of the present embodiment, the registration unit 123 registers the past secondary electronic image and the length measurement parameter that have been captured at the time of length measurement performed in the past in the library 220 of the storage unit 124. The processing unit 126 includes a registration unit 126. The registration processing unit 126 creates a secondary electronic profile from the past secondary electronic image, and creates the secondary secondary profile created from the past secondary electronic image and the length measurement parameter, and the past secondary electronic image. The electronic profile is stored in the library 220 of the storage unit 124.
According to this configuration, the secondary electron image and the measurement parameter information captured at the time of length measurement performed in the past can also be stored in the library 220 of the storage unit 124, thereby matching with the model's secondary electron profile. This increases the secondary electron profile, and it is possible to search for a more matched secondary electron profile. As a result, it is possible to obtain a more appropriate automatic length measurement parameter as the automatic length measurement parameter used in the measurement target length measurement pattern.

  Further, according to the automatic setting system 120 of the present embodiment, the registration processing unit 126 applies the past secondary electronic image pattern to the secondary electronic image pattern stored in the library 220 of the storage unit 124. It is determined whether or not the ratio has changed to a predetermined ratio (10%) or more. If the ratio has not changed to a predetermined ratio or more, a secondary electron profile is created from the pattern of the past secondary electron image. Further, when the registration processing unit 126 changes to a predetermined ratio or more, the registration processing unit 126 acquires a plurality of past secondary electronic images, creates an averaged image of the plurality of past secondary electronic images, and calculates the average A secondary electron profile is created from the digitized image. According to this configuration, since an average image can be obtained from a plurality of images, automatic length measurement corresponding to a secondary electron image having a change in shape and dimensions, such as a secondary electron image taken in the development process, is possible. Parameter optimization can be performed.

  In addition, this invention is not limited to embodiment mentioned above, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. In addition, a part of the configuration of an embodiment may be replaced with the configuration of another embodiment, and the configuration of another embodiment may be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  In the above-described embodiment, the region used for the matching process in the Line pattern has been described with reference to FIG. 7, but the same region may also be used in the Hole pattern. For example, as shown in FIG. 12, in the case of the Hole pattern, the portion where the generation amount of secondary electrons protrudes is one, but the region from the lowest part to the highest part of the part, or from the highest part to the lowest part. You may divide | segment into some area | regions, such as an area | region. Then, the degree of coincidence may be calculated by calculating an inclination, a minimum value, a maximum value, and the like for the divided areas.

  In the above-described embodiment, in the matching process, the inclination, the minimum value, and the maximum value are calculated for each of the regions 701 to 709 shown in FIG. In order to execute the matching process, it is not always necessary to calculate all of them, and it is sufficient to calculate at least one numerical value of the slope, the minimum value, and the maximum value.

  In the above-described embodiment, the threshold value of the average value of the matching degree is set to 80% in the matching process. However, the threshold value is not limited to this, and the operator may arbitrarily set the threshold value.

  In the above-described embodiment, the pattern shape of the measurement pattern of the secondary electronic image to be registered changes by 10% or more with respect to the secondary electronic image already stored in the images directory 303 in step S206 of FIG. However, the present invention is not limited to this. The pattern shape change rate may be arbitrarily set by the operator.

  In the embodiment described above, in step S210 in FIG. 6, images stored at the time of measurement are extracted for 60% of the measurement points registered in one measurement recipe. However, the present invention is not limited to this. Not. The number of images to be extracted may be arbitrarily set by the operator. In consideration of the subsequent averaging process, at least two images may be extracted.

  As described above, the length measurement parameter automatic setting system 120 can be realized by hardware by designing a part or all of them, for example, by an integrated circuit. Further, the automatic setting system 120 of the present invention may be realized by a program code of software that realizes the functions of the embodiment. In this case, a storage medium in which the program code is recorded is provided to the information processing apparatus, and the information processing apparatus (or CPU) reads the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the program code itself and the storage medium storing the program code constitute the present invention. As a storage medium for supplying such program code, for example, a flexible disk, CD-ROM, DVD-ROM, hard disk, optical disk, magneto-optical disk, CD-R, magnetic tape, nonvolatile memory card, ROM Etc. are used.

  Further, based on the instruction of the program code, an OS (operating system) operating on the information processing apparatus performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. It may be. Furthermore, by distributing the program code of the software that realizes the functions of the embodiments via a network, the program code is stored in a storage device of an information processing device or a storage medium such as a CD-RW or CD-R, and is used when used. The CPU of the information processing apparatus may read and execute the program code stored in the storage device or the storage medium.

  Finally, it should be understood that the processes and techniques described herein are not inherently related to any particular apparatus, and can be implemented by any suitable combination of components. Further, various types of devices for general purpose can be used in accordance with the teachings described herein. It may prove useful to build a dedicated device to perform the method steps described herein. Although the present invention has been described with reference to specific examples, these are in all respects illustrative rather than restrictive. Those skilled in the art will appreciate that there are numerous combinations of hardware, software, and firmware that are suitable for practicing the present invention. For example, the program code for realizing the functions described in the present embodiment can be implemented by a wide range of programs or script languages such as assembler, C / C ++, perl, Shell, PHP, Java (registered trademark).

  Further, the control lines and information lines in the drawings are those that are considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. All the components may be connected to each other.

100 Electron Beam Automatic Measuring Device 101 Cathode 102, 103 Anode 104 Condenser Lens 105 Deflection Coil 106 Primary Electron 107 Secondary Electron 108 Objective Lens 109 Sample 110 Holder 111 Stage 112 Secondary Electron Detector 113 Controller 120 Automatic Setting System 121 Display Unit 123 arithmetic unit 124 storage unit 125 setting processing unit 126 registration processing unit 220 library 301 Library Data directory 302 profile directory 303 images directory 304 amp directory

Claims (13)

When a plurality of first secondary electron images, a plurality of first secondary electron profiles created from the plurality of first secondary electron images, and the plurality of first secondary electron images are captured. Library data including a plurality of first length measurement parameters used in the above and a second secondary electron image obtained by imaging another position having the same pattern as the length measurement pattern to be measured are stored. A storage unit to
An arithmetic unit for setting a measurement parameter used for measured pattern of the measurement target,
With
The computing unit is
Create a second secondary electron profile from the second secondary electron images,
A matching process between the second secondary electron profile and the plurality of first secondary electron profiles is executed to correspond to the first secondary electron profile that matches the second secondary electron profile Obtaining the first length measurement parameter from the storage unit;
An automatic parameter setting system, wherein the first length measurement parameter acquired from the storage unit is set as a length measurement parameter used for the length measurement pattern to be measured. In the parameter automatic setting system according to claim 1,
Each of the first secondary electron profile and the second secondary electron profile is a two-dimensional graph including a plurality of regions,
The arithmetic unit calculates, as the matching process, at least one numerical value of a minimum value, a maximum value, and a slope for each of the plurality of regions, and the at least one numerical value in the first secondary electron profile A parameter automatic setting system, wherein a degree of coincidence with the at least one numerical value in the second secondary electron profile is calculated. In the parameter automatic setting system according to claim 2,
The computing unit is
Calculate the average value of the degree of coincidence,
When the first secondary electron profile having an average value of coincidence greater than a predetermined value exists, the first length measurement parameter corresponding to the first secondary electron profile having the largest coincidence is obtained. A parameter automatic setting system obtained from the storage unit. In the parameter automatic setting system according to claim 2,
The computing unit is
Calculate the average value of the degree of coincidence,
When the first secondary electron profile having an average value of the matching degree larger than a predetermined numerical value does not exist, a plurality of first secondary electron profiles are obtained in order of the matching degree;
Acquiring the plurality of first measuring parameters corresponding to the plurality of first secondary electron profile from the storage unit,
A parameter automatic setting system, wherein one length measurement parameter is acquired from the plurality of first length measurement parameters. In the parameter automatic setting system according to claim 4,
The computing unit is
Run the test run with the plurality of first measuring parameters, calculates a value indicating the variation of the measured values for each of the plurality of first measurement parameters,
A parameter automatic setting system characterized by acquiring a length measurement parameter having the smallest value indicating the variation among the plurality of first length measurement parameters. In the parameter automatic setting system according to claim 2,
The measurement target measurement pattern is a line pattern,
In each of the first secondary electron profile and the second secondary electron profile, the vertical axis represents the generation amount of secondary electrons, and the horizontal axis represents the generation position of secondary electrons in the scanning direction of the primary electrons. A two-dimensional graph
The plurality of regions are
A first region indicating a region from a minimum portion outside the left protruding portion to a minimum portion outside the right protruding portion;
A second region indicating a region from the highest portion of the left protruding portion to the highest portion of the right protruding portion;
A third region indicating a region from the lowest portion outside the left protruding portion to the highest portion of the left protruding portion;
A fourth region showing a region from the highest portion of the left protruding portion to a portion where the inclination is 0 inside the protruding portion on the left side;
A fifth region indicating a region from the portion where the inclination is 0 inside the protruding portion on the right side to the highest portion of the protruding portion on the right side;
A sixth region indicating a region from the highest portion of the right protruding portion to the lowest portion outside the right protruding portion;
A seventh region indicating a region from the lowest portion outside the protruding portion on the left side to the portion where the inclination is 0 inside the protruding portion on the left side;
An eighth region indicating a region from a portion where the inclination is 0 inside the protruding portion on the left side to a portion where the inclination is 0 inside the protruding portion on the right side;
A ninth region indicating the region from the portion where the slope is 0 inside the protruding portion on the right side to the lowest portion outside the protruding portion on the right side;
An automatic parameter setting system comprising: In the parameter automatic setting system according to claim 1,
The automatic parameter setting, wherein the first secondary electron image, the first secondary electron profile, and the first length measurement parameter are stored in the storage unit in association with each other. system. In the parameter automatic setting system according to claim 1,
A plurality of third secondary electron images captured at the time of length measurement performed in the past by the storage unit, and a plurality of third length measurements used when the third secondary electron image is captured. Stores the parameters,
The arithmetic unit is provided with a registration processing unit,
The registration processing unit
Create a third secondary electron profile from the third secondary electron images,
Secondary electrons created from the third secondary electron image using the third secondary electron image as the first secondary electron image and the third length measurement parameter as the first length measurement parameter. A parameter automatic setting system , wherein a profile is stored in the storage unit as the first secondary electronic profile . In the parameter automatic setting system according to claim 8,
The registration processing unit, the measurement pattern of the third secondary electron image, for the measurement patterns to the first secondary electron image image captured to determine whether the changes to the predetermined ratio or more,
The parameter automatic setting system, wherein the registration processing unit creates a secondary electron profile from a pattern of the third secondary electron image when the registration processing unit does not change to the predetermined ratio or more. In the parameter automatic setting system according to claim 9,
The registration processing unit, if changed to the predetermined ratio or more, to create an averaged image from the plurality of third secondary electron image, creating a secondary electron profile from the averaged images A parameter automatic setting system. In the parameter automatic setting system according to claim 10,
The registration processing unit acquires the third measurement parameter corresponding to the third secondary electron images to be most secondary electrons profile that matches the secondary electron profile created from the averaged image,
The registration processing unit uses the averaged image as the first secondary electron image and the secondary electron profile created from the averaged image as the first secondary electron profile . A parameter automatic setting system , wherein a length measurement parameter is stored in the storage unit as the first length measurement parameter .   An electron beam automatic length measuring device comprising the parameter automatic setting system according to any one of claims 1 to 11. A program for causing an information processing apparatus including a storage unit and a calculation unit to execute processing for automatically setting a length measurement parameter used for a length measurement pattern to be measured,
The storage unit
When a plurality of first secondary electron images, a plurality of first secondary electron profiles obtained from the plurality of first secondary electron images, and the plurality of first secondary electron images are captured. Library data including a plurality of first measurement parameters used ;
Storing a second secondary electron image obtained by imaging another position having the same pattern as the length measurement pattern to be measured ;
In the calculation unit,
A process of creating a second secondary electron profile from the second secondary electron images,
A matching process between the second secondary electron profile and the plurality of first secondary electron profiles is executed to correspond to the first secondary electron profile that matches the second secondary electron profile Processing for obtaining the first length measurement parameter from the storage unit;
A process for setting the first length measurement parameter acquired from the storage unit as a length measurement parameter used for the length measurement pattern to be measured;
A program for running

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