JP2009117691A - Shape measuring method and shape measuring apparatus - Google Patents

Abstract

A shape measuring method and a shape measuring apparatus capable of improving productivity by improving measurement reliability and enabling more accurate measurement.
A diffraction signal is acquired from a measurement coordinate position, and detection data is stored in a detected diffraction signal storage unit (50). A predetermined library is selected from the library storage unit 43 (51). Next, the calculation unit 44 performs first waveform matching between the acquired detected diffraction signal and the library (52). Next, detection diffraction signals are acquired again (54), library selection (55), and second waveform matching are executed (57). Next, a difference is calculated between the result of the first waveform matching and the result of the second waveform matching, and it is determined whether or not this value satisfies the spec value (58).
[Selection] Figure 2

Description

  The present invention relates to a shape measuring method and a shape measuring apparatus for measuring a dimension or three-dimensional shape of a fine pattern in a semiconductor manufacturing process.

  In the inspection process of fine patterns in the semiconductor manufacturing process, attention is focused on a method for optically monitoring the shape. As a representative method, there is a technique called Scatterometry. This technique performs matching between a diffraction signal obtained by irradiating a pattern with light and a library that is a collection of virtual diffraction signals that are simulated and calculated by predicting the shape change of the pattern measured in advance. This is a method for estimating the shape of a pattern (see, for example, Patent Document 1).

  This measurement method not only has high throughput and high accuracy, but also has many advantages such as less damage to the pattern compared to the measurement method using an electron beam. However, it is necessary to create a library before performing the measurement, which requires labor and time. Further, in such a method of calculating an answer by matching with a library, when the number of parameters increases, a plurality of solution candidates exist, and there is a problem that rarely shows an incorrect result. Hereinafter, an explanation will be given using an actual example.

  FIG. 14 shows a result of measuring five points (site 1 to site 5) in the wafer by the technique described above. The cross-sectional structure of the measurement pattern is the structure shown in FIG. 3, and the library used for the measurement has the structure shown in FIG. As shown in FIG. 3, the measurement pattern is formed of a resist 21. As shown in FIG. 4, for the resist 21, three variable parameters (resist middle CD, resist height, resist side wall angle) are set. As for the lower layer film, three variable parameters are set for the antireflection film, the lower layer film A, and the lower layer film C. It should be noted that whether the parameter is variable or fixed can be arbitrarily set, but in general, a parameter that is sensitive to process changes is often variable.

  Looking at the measurement results in FIG. 14, only the bottom CD (Bottom CD (defined here as the line width of 10% from the bottom of the resist height)) value of Site 4 is the other value. It can be seen that it is smaller than the result of the site. In general, the line width management provides a spec (predetermined range of allowable values) and determines whether or not the value is satisfied. In this product, the bottom CD spec is 55 nm ± 5 nm. Therefore, the site 4 is determined to be spec out (out of spec). As a result, the wafer is reworked and a pattern is formed again, and the same measurement is repeated.

  However, there is a high possibility that the measurement result of this site 4 is caused by the fact that the actual dimension is not correctly measured for the following reason. Focus on the behavior of the lower layer film B. Only the site 4 shows a large value by skipping the value of the lower layer film B. This cannot be explained in the range of process variations. That is, at the time of measuring the site 4, it is highly possible that the change in the waveform of the bottom CD and the lower layer film B is misread and an incorrect value is shown as a result. By the way, if the same measurement is repeated at the same site 4 with the measurement point slightly shifted (defined as site 4 '), the value of the bottom CD now satisfies the specifications, and the value of the lower layer B is also different from that of the other sites. Similar values are shown.

  As a result, it can be seen that the measurement of the site 4 performed first was inaccurate. Until now, there was a method to judge whether or not the measurement was performed correctly based on the degree of coincidence when comparing the diffraction signals, but this is clearly effective when the measurement is strange, It was impossible to find such a subtle measurement error.

Therefore, if a wrong measurement result is trusted as it is and rework is executed, a large loss may occur. On the other hand, there is a possibility that a sample that is out of spec is determined to be spec-in (within spec), and in this case, a larger loss is caused. As described above, conventionally, there is a problem in that productivity is reduced due to occurrence of erroneous measurement.
JP 2005-534192 A

  As described above, with the conventional technology, productivity may be reduced due to the occurrence of erroneous measurement.In addition, by improving measurement reliability and enabling more accurate measurement, productivity can be improved. It has been desired to develop a shape measuring method and a shape measuring apparatus that can be improved.

  The present invention has been made in response to the above-described conventional circumstances, and improves the reliability of measurement and enables measurement with higher accuracy, thereby improving the productivity. And it aims at providing a shape measuring device.

  One aspect of the shape measuring method of the present invention is a shape measuring method for measuring a dimension or three-dimensional shape of a fine pattern of a semiconductor device formed on a substrate, wherein light is applied to the fine pattern at a predetermined measurement location on the substrate. A first waveform matching step of performing waveform matching between a detected diffraction signal detected by irradiation and a library which is a collection of virtual diffraction signals to obtain at least one parameter of the measurement location; and A second waveform matching step for performing waveform matching by changing at least one of the detected diffraction signal and the library in a waveform matching step to obtain at least one parameter of the measurement location; and the first waveform matching step. And at least one parameter determined by the second waveform matching step , Characterized in that these differences are anda determination step of determining the whether the range of a preset tolerance.

  One aspect of the shape measuring apparatus of the present invention is a shape measuring apparatus that measures the size or three-dimensional shape of a fine pattern of a semiconductor device formed on a substrate, and is configured to receive incident light under a predetermined condition with respect to the fine pattern. , A detector that detects a diffraction signal from the fine pattern, a library storage unit that stores a plurality of libraries as a collection of virtual diffraction signals, and a detection diffraction signal detected by the detector A detection diffraction signal storage unit, a detection diffraction signal in the detection diffraction signal storage unit, and a waveform matching of the library in the library storage unit to obtain at least one parameter, and a calculation unit on the substrate. At the measurement location, the waveform matching by the calculation unit is performed a plurality of times by changing at least one of the detected diffraction signal and the library. A control unit that compares the parameters obtained as a result of the plurality of waveform matching operations and controls to determine whether or not the difference is within a preset allowable value range. It is characterized by.

  According to the present invention, it is possible to provide a shape measuring method and a shape measuring device capable of improving productivity by improving measurement reliability and enabling more accurate measurement.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a shape measuring apparatus according to the present embodiment. In FIG. 1, an optical system 30 surrounded by a solid line obliquely enters incident light 33 from a light source 31 that emits white light, for example, on a measurement target 37 formed on a semiconductor substrate via a deflector 32. Reflected light 34 is generated from the measurement object 37, and this reflected light 34 is detected by the detector 36 via the analyzer 35. The incident light 33 from the light source 31 can be adjusted by the light source adjustment mechanism 45.

  In FIG. 1, a processing unit 40 surrounded by a broken line is constituted by a personal computer or the like. The processing unit 40 includes a control unit 41 that comprehensively controls the processing unit 40, a detected diffraction signal storage unit 42, a library storage unit 43, and a calculation unit 44 that performs operations such as waveform matching described later. ing. Note that it is necessary to set a library in the library storage unit 43 before performing the measurement. The creation of the library will be described later. In addition, information necessary for measurement is input in advance to the control unit 41 in the form of a recipe.

  Next, the flow up to the measurement will be described with reference to FIG. First, a recipe including all information necessary for measurement is input to the control unit 41, and measurement is started using this recipe. Here, the information necessary for the measurement particularly refers to measurement coordinates, light irradiation angle, library information used, matching information, specification values, and the like.

  When the measurement is started, the diffraction signal is acquired from the measurement coordinate position according to the instruction of the recipe in the control unit 41, and the detection data is stored in the detected diffraction signal storage unit 42 (50). A predetermined library is selected from the library storage unit 43 (51). Thereafter, the calculation unit 44 performs waveform matching between the acquired detected diffraction signal and the library (52). Thus, the first waveform matching process is completed.

  Next, the second waveform matching process is performed. In the second waveform matching step, the step to be executed differs depending on whether the detection diffraction signal acquisition is necessary or not (53). In this embodiment, a case where a detection diffraction signal is acquired again will be described. In this case, the detected diffraction signal is acquired according to the instruction of the recipe in the control unit 41 (54), library selection (55) and matching are executed (57), and the second waveform matching process is completed.

  Next, a difference is calculated between the result of the first waveform matching process and the result of the second waveform matching process. This calculated value is compared with a spec value preset in a recipe in the control unit 41, and it is determined whether or not the spec value is satisfied (58).

  If the specification value is satisfied as a result of the above determination, the measurement at the measurement point ends there, and the result of the first waveform matching process or the second waveform is determined according to the recipe instruction in the control unit 41. The result of the waveform matching process or the average value of these results is taken as the result. On the other hand, when the specification is not satisfied, the process proceeds to the third waveform matching step again, and diffraction signal acquisition (54) and library selection (55) are performed again, and matching is executed (57). The result of the third waveform matching process is compared with the results of the first and second waveform matching processes described above, and the spec determination is made in the same manner (58), and basically measured until the spec determination is satisfied. Will continue.

  Hereinafter, an actual example will be described. As shown in FIG. 3, the measurement pattern applied in the present embodiment is formed of a resist 21, and an antireflection film 23, a lower layer film A24, a lower layer film B25, a lower layer film C26, a lower layer film D27, and a lower layer film are formed thereunder. Each film of E28 is present. An arrow 22 shown in FIG. 3 indicates the bottom CD of the resist 21 that is a parameter used for actual management. In consideration of this structure, it is necessary to prepare a library in advance. Here, as described above, the library refers to a collection of a plurality of predicted virtual diffraction signals obtained by predicting a change in diffraction signals accompanying a shape change in advance by simulation.

  FIG. 4 shows library parameters used in this embodiment. There are nine parameters, of which six parameters are variable, and three parameters are fixed values (one with 1 step is a fixed value). Of course, it is possible to set all of them as variable parameters, but in many cases, fixed parameters are set in consideration of the size of the library. In addition, it is important that the range of the variable parameter sufficiently covers the range in which the actual measurement object varies. It is possible to shift to the execution of measurement by inputting the library created in this manner to the library storage unit 43.

  The measurement is then performed. A recipe in the control unit 41 is started, and first, a diffraction signal is acquired. All necessary information such as the coordinate position or the incident angle of light measured at this time is included in the recipe. The acquired detection diffraction signal is temporarily stored in the detection diffraction signal storage unit 42. Then, the operation unit 44 executes waveform matching between the library in the library storage unit 43 and the detected diffraction signal stored in the detected diffraction signal storage unit 42, and the first waveform matching step is performed. At this time, which library is selected is also input to the recipe.

  An example of the result obtained by the above waveform matching is shown in FIG. In the example shown in FIG. 5, all the results of the variable parameters are displayed, bottom CD = 55.26094 nm, height = 132.6824 nm, side wall angle = 89.81015 degrees, antireflection film = 90.37878 nm. Amorphous silicon = 38.81566 nm and nitride film = 23.7364 nm. However, the bottom CD is the only parameter used for actual management.

  Next, the second waveform matching process is executed. In the case of the present embodiment, the detection diffraction signal is acquired again based on the information input to the recipe in order to execute acquisition of the detection diffraction signal anew. At this time, in this embodiment, as shown in FIG. 6, the detection diffraction signal is acquired at the second measurement location 62 shifted to the right by 1 μm from the first measurement location 61. In this embodiment, the shift amount is set to 1 μm. However, if the measurement target has a sufficient area, it is not necessary to stick to 1 μm, and even if it is sufficiently larger or smaller than 1 μm, there is a problem. There is no.

  Thereafter, a library is selected. In the present embodiment, the same library as that of the first waveform matching is adopted and matching is executed. This completes the second waveform matching process. An example of the result obtained by this is shown in FIG. In the example shown in FIG. 7, all the results of the variable parameters are displayed, bottom CD = 42.15739 nm, height = 133.472 nm, sidewall angle = 89.30516 degrees, antireflection film = 89.30516 nm. Amorphous silicon = 39.65079 nm and nitride film = 163.9193 nm.

  Next, the difference between the first waveform matching result and the second waveform matching result is calculated. The difference of the bottom CD is 13.1 nm. Since this greatly exceeds the preset specification value of 1 nm, it is estimated that the first waveform matching or the second waveform matching is not correctly executed. This is also inferred from the fact that the measurement result of the nitride film is greatly different from 23.7364 nm in the first waveform matching and 163.9193 nm in the second waveform matching. Here, the spec value should be set from the repeatability of the apparatus and the ability of the process, and in this example, it was set to 1 nm.

  Next, the third waveform matching process is performed. In the present embodiment, the diffraction signal is acquired by changing the coordinates as in the second waveform matching step. That is, as shown in FIG. 6, the third measurement location 63 is obtained by shifting the coordinate position by 1 μm further to the right. Next, matching by the library is executed, and third waveform matching is executed. An example of the result is shown in FIG. In the example shown in FIG. 8, all the results of the variable parameters are displayed, bottom CD = 55.37311 nm, height = 132.4951 nm, sidewall angle = 87.35832 degrees, antireflection film = 91.11919 nm. Amorphous silicon = 38.04964 nm and nitride film = 27.13452 nm.

Next, the difference between the measurement results by the first and third, second and third waveform matching is obtained. Each (first result)-(third result) =-0.113 nm
(Second result) − (third result) = − 13.216 nm
It turns out that the difference between the first and third results satisfies the specification of 1 nm. That is, the second measurement was shown to be unreliable.

  In the present embodiment, the first measurement result is adopted as the final measurement result. Here, there is no problem even if the third result is adopted, or there is no problem if the average value of the first and third results is used. In this example, the specification value was satisfied in the third measurement, but basically the measurement is repeated until the specification value is satisfied. Alternatively, when an upper limit of repetition is provided and the upper limit number is reached, it is necessary to review the conditions to be measured.

  Further, in this embodiment, the specification is made for the value of the bottom CD, and the determination is made. Of course, the specification may be judged in the same manner using other variable parameters, or the specifications may be provided for a plurality of parameters. It is clear that judgment is also effective. As described above, in the present embodiment, by performing the matching a plurality of times, it is possible to confirm the reliability of the measurement and to realize a highly accurate measurement.

  Next, a second embodiment will be described. In the second embodiment, since the measurement is performed using the shape measuring apparatus shown in FIG. 1 described above, a duplicate description is omitted. In the second embodiment, the recipe input to the control unit 41 includes an incident angle of incident light 33 incident obliquely on the measurement object 37 formed on the semiconductor substrate from the light source 31 via the deflector 32. Information is included, and the light source adjustment mechanism 45 sets the incident angle in accordance with an instruction from the recipe in the control unit 41.

  With reference to FIG. 2, the process of 2nd Embodiment is demonstrated. First, a recipe including all information necessary for measurement is input to the control unit 41, and measurement is started using this recipe. Here, the information necessary for the measurement particularly refers to measurement coordinates, light irradiation angle, library information used, matching information, specification values, and the like.

  When the measurement is started, the diffraction signal is acquired from the measurement coordinate position according to the instruction of the recipe in the control unit 41, and the detection data is stored in the detected diffraction signal storage unit 42 (50). A predetermined library is selected from the library storage unit 43 (51). Thereafter, the calculation unit 44 performs waveform matching between the acquired detected diffraction signal and the library (52). Thus, the first waveform matching process is completed. The steps so far are the same as those in the first embodiment.

  Next, the second waveform matching process is performed. Even in the case of the second embodiment, the acquisition of the diffraction signal is repeated, but at this time, the acquisition of the diffraction signal is executed at the same coordinate position on the semiconductor substrate as in the first waveform matching step, provided that the incident angle of light is Different from the first waveform matching step. The adjustment of the incident angle is executed by the light source adjustment mechanism 45 in accordance with recipe information input to the control unit 41. In this second embodiment, the diffraction signal is acquired at 76 degrees for the first measurement in the first waveform matching process and at 77 degrees for the second measurement in the second waveform matching process (54).

  Thereafter, a library is selected from the library storage unit 43 (55), matching is executed (57), and the second waveform matching process is completed. The library used at this time was prepared in consideration of incidence at an incident angle of 77 degrees.

  Next, a difference is calculated between the result of the first waveform matching process and the result of the second waveform matching process. The calculated value is compared with a spec value preset in the recipe in the control unit 41, and it is determined whether or not the spec value is satisfied (58).

  If the specification value is satisfied as a result of the above determination, the measurement at the measurement point ends there, and the result of the first waveform matching process or the second waveform is determined according to the recipe instruction in the control unit 41. The result of the waveform matching process or the average value of these results is taken as the result. On the other hand, when the specification is not satisfied, the process proceeds to the third waveform matching step again, and diffraction signal acquisition (54) and library selection (55) are performed again, and matching is executed (57). The result of the third waveform matching process is compared with the results of the first and second waveform matching processes described above, the spec determination is made in the same manner, and the measurement is basically continued until the spec determination is satisfied. It will be.

  Hereinafter, an actual example will be described. The measurement pattern applied in the second embodiment has the structure shown in FIG. 3 as in the first embodiment. First, the detection diffraction signal is acquired by starting the recipe in the control unit 41. All necessary information such as the coordinate position or the incident angle of light measured at this time is included in the recipe. In the second embodiment, the incident angle θ of light shown in FIG. 1 is set to 76 degrees. The acquired detection diffraction signal is temporarily stored in the detection diffraction signal storage unit 42. Then, the operation unit 44 executes waveform matching between the library in the library storage unit 43 and the detected diffraction signal stored in the detected diffraction signal storage unit 42, and the first waveform matching step is performed.

  By the above waveform matching, the result as shown in FIG. 5 is obtained. In the example shown in FIG. 5, all the results of the variable parameters are displayed. However, the parameter actually used for management in the second embodiment is only the bottom CD (the line width at a position 10% from the bottom of the resist height).

  Next, the second waveform matching process is executed. In the case of the second embodiment, the detection diffraction signal is acquired again based on the information input to the recipe in order to execute acquisition of the detection diffraction signal anew. At that time, the incident angle of light is changed. In the case of the second embodiment, the incident angle θ of light is set to 77 degrees. As for the measurement coordinates, in the case of the second embodiment, the measurement was performed at the same position as the first measurement. However, the measurement coordinates need not be the same place, and may be shifted to the left and right as in the first embodiment. There is no problem.

  Thereafter, a library in the library storage unit 43 is selected based on the recipe information in the control unit 41. Of course, this library is produced in consideration of the incident angle of light being 77 degrees. Next, waveform matching of the detected diffraction signal is executed by the selected library, and the second waveform matching process is completed. An example of the result obtained by this is shown in FIG. In the example shown in FIG. 9, all the results of the variable parameters are displayed, bottom CD = 54.6233 nm, height = 131.3727 nm, side wall angle = 88.254489 degrees, antireflection film = 91.425 nm Amorphous silicon = 38.0594 nm and nitride film = 27.556224 nm.

  Next, the difference between the first waveform matching result and the second waveform matching result is calculated. The difference of the bottom CD is 0.64 nm. Since this satisfies the preset specification value of 1 nm, it is estimated that the first waveform matching and the second waveform matching are correctly executed.

  In the second embodiment, the first measurement result is the first measurement result. Here, there is no problem even if the second result is adopted, or there is no problem if the average value of the first and second results is used. Which one to select may be set in the recipe in advance. In the above example, the specification value is satisfied in the second measurement, but basically the measurement is repeated until the specification value is satisfied. Alternatively, when an upper limit of repetition is provided and the upper limit number is reached, it is necessary to review the conditions to be measured.

  In the second embodiment described above, by performing measurement while changing the incident angle, it is possible to perform matching multiple times with different combinations without shifting the measurement location at all, and confirming the reliability of the measurement. This makes it possible to achieve highly accurate measurement.

  Next, a third embodiment will be described. In the third embodiment, since the measurement is performed using the shape measuring apparatus shown in FIG. 1 described above, a duplicate description is omitted.

  With reference to FIG. 2, the process of 3rd Embodiment is demonstrated. First, a recipe including all information necessary for measurement is input to the control unit 41, and measurement is started using this recipe. Here, the information necessary for the measurement particularly refers to measurement coordinates, light irradiation angle, library information used, matching information, specification values, and the like.

  When the measurement is started, the diffraction signal is acquired from the measurement coordinate position according to the instruction of the recipe in the control unit 41, and the detection data is stored in the detected diffraction signal storage unit 42 (50). A predetermined library is selected from the library storage unit 43 (51). Thereafter, the calculation unit 44 performs waveform matching between the acquired detected diffraction signal and the library (52). Thus, the first waveform matching process is completed.

  Next, the second waveform matching process is performed. In the case of the third embodiment, it is not necessary to newly acquire the diffraction signal (53). Instead, matching is performed using a library different from the library used in the first waveform matching step. Which library is used is selected based on recipe information in the control unit 41 (56), waveform matching is executed (57), and the second waveform matching process is completed.

  Next, a difference is calculated between the result of the first waveform matching process and the result of the second waveform matching process. This calculated value is compared with a spec value preset in a recipe in the control unit 41, and it is determined whether or not the spec value is satisfied (58).

  As a result of the above determination, if the specification value is satisfied, the measurement at the measurement point is ended, and the result of the first waveform matching process or the second waveform matching process is performed according to the recipe instruction in the control unit 41. Or the average of these results. On the other hand, if the specification is not satisfied, the process proceeds to the third waveform matching step again, and diffraction signal acquisition (54) and library selection (55) are performed again, and waveform matching is executed (56). . The result of the third waveform matching process is compared with the results of the first and second waveform matching processes described above, the spec determination is made in the same manner, and the measurement is basically continued until the spec determination is satisfied. It will be.

  Hereinafter, an actual example will be described. The measurement pattern applied in the third embodiment has the structure shown in FIG. 3 as in the first embodiment. First, the detection diffraction signal is acquired by starting the recipe in the control unit 41. All necessary information such as the coordinate position or the incident angle of light measured at this time is included in the recipe. The acquired detection diffraction signal is temporarily stored in the detection diffraction signal storage unit 42. Then, the operation unit 44 executes waveform matching between the library in the library storage unit 43 and the detected diffraction signal stored in the detected diffraction signal storage unit 42, and the first waveform matching step is performed. The parameter information of the library selected here is shown in FIG. 4 described above.

  By the above waveform matching, the result as shown in FIG. 5 is obtained. In the example shown in FIG. 5, all the results of the variable parameters are displayed. However, the parameter used for actual management in the third embodiment is only the bottom CD (the line width at 10% from the bottom of the resist height).

  Next, the second waveform matching process is executed. In the case of the third embodiment, since the diffraction signal acquired in the first waveform matching process is used, it is not necessary to acquire the diffraction signal again. Instead, a library different from the library used in the first waveform matching process is selected. Information on the library selected here is shown in FIG. Of course, this library also needs to be prepared in advance, like the library used in the first waveform matching process. The only difference between the libraries used in the first waveform matching step and the second waveform matching step is the parameter range of the lower layer film C. Here, the change is made by only one parameter, but there is no problem even if a plurality of parameters are different, and the same effect can be obtained by changing other parameters such as the step size.

  Thereafter, waveform matching is executed using this library, and the second waveform matching process is completed. An example of the result obtained by this is shown in FIG. In the example shown in FIG. 11, all the results of the variable parameters are displayed, bottom CD = 55.57976 nm, height = 132.169 nm, sidewall angle = 89.68176 degrees, antireflection film = 91.20994 nm. Amorphous silicon = 38.98743 nm and nitride film = 23.889133 nm.

  Next, the difference between the first waveform matching result and the second waveform matching result is calculated. The difference of the bottom CD is 0.32 nm. Since this satisfies the preset specification value of 1 nm, it is estimated that the first waveform matching and the second waveform matching are correctly executed.

  In the third embodiment, the first measurement result is adopted as the final measurement result. Here, there is no problem even if the second result is adopted, or there is no problem if the average value of the first and second results is used. In the above example, the specification value is satisfied in the second measurement, but basically the measurement is repeated until the specification value is satisfied. Alternatively, when an upper limit of repetition is provided and the upper limit number is reached, it is necessary to review the conditions to be measured.

  In the third embodiment, by preparing a plurality of libraries in advance, it is possible to execute waveform matching with different combinations in a short time, a plurality of times, and it is possible to check the reliability of the measurement with high accuracy. Measurement can be realized.

  Next, a fourth embodiment will be described. In the fourth embodiment, since the measurement is performed using the shape measuring apparatus shown in FIG. 1 described above, a duplicate description is omitted.

  With reference to FIG. 2, the process of 4th Embodiment is demonstrated. First, a recipe including all information necessary for measurement is input to the control unit 41, and measurement is started using this recipe. Here, the information necessary for the measurement particularly refers to measurement coordinates, light irradiation angle, library information used, matching information, specification values, and the like.

  When the measurement is started, the diffraction signal is acquired from the measurement coordinate position according to the instruction of the recipe in the control unit 41, and the detection data is stored in the detected diffraction signal storage unit 42 (50). A predetermined library is selected from the library storage unit 43 (51). Thereafter, the calculation unit 44 performs waveform matching between the acquired detected diffraction signal and the library (52). Thus, the first waveform matching process is completed.

  Next, the second waveform matching process is executed. In the case of the fourth embodiment, it is not necessary to newly acquire the diffraction signal (53). Further, it is not necessary to change the library, and the library used in the first waveform matching process is used as it is (select the same library (56)). However, the matching is executed by changing the applicable wavelength region. For example, in the first waveform matching step, waveform matching is performed using the region of 250 nm to 750 nm (52), and in the second waveform matching step, the waveform matching step is performed using the region of 300 nm to 700 nm (57). . Information on these wavelength regions is selected based on information input to the recipe, and the second waveform matching process is completed.

  Next, a difference is calculated between the result of the first waveform matching process and the result of the second waveform matching process. This calculated value is compared with a spec value preset in a recipe in the control unit 41, and it is determined whether or not the spec value is satisfied (58).

  As a result of the above determination, if the specification value is satisfied, the measurement at the measurement point is ended, and the result of the first waveform matching process or the second waveform matching process is performed according to the recipe instruction in the control unit 41. Or the average of these results. On the other hand, if the specification is not satisfied, the process proceeds to the third waveform matching step again, and diffraction signal acquisition (54) and library selection (55) are performed again, and waveform matching is executed (56). . The result of the third waveform matching process is compared with the results of the first and second waveform matching processes described above, the spec determination is made in the same manner, and the measurement is basically continued until the spec determination is satisfied. It will be.

  Hereinafter, an actual example will be described. The measurement pattern applied in the fourth embodiment has the structure shown in FIG. 3 as in the first embodiment. First, the detection diffraction signal is acquired by starting the recipe in the control unit 41. All necessary information such as the coordinate position or the incident angle of light measured at this time is included in the recipe. The acquired detection diffraction signal is temporarily stored in the detection diffraction signal storage unit 42. Then, the operation unit 44 executes waveform matching between the library in the library storage unit 43 and the detected diffraction signal stored in the detected diffraction signal storage unit 42, and the first waveform matching step is performed.

  The matching here is performed using the detected diffraction signal, but strictly speaking, it can be performed by various methods. In the case of the fourth embodiment, as shown in FIG. 12, the information (71) of the intensity ratio of the vertical axis light at the horizontal axis wavelength and the information (72) of the vertical axis phase difference at the horizontal axis wavelength are obtained. To perform matching by waveform. At this time, it is possible to select a wavelength region. In this measurement, waveform matching is executed using information (73) within a range of 250 nm to 750 nm.

  By the above waveform matching, the result as shown in FIG. 5 is obtained. In the example shown in FIG. 5, all the results of the variable parameters are displayed. However, the parameter actually used in the management in the fourth embodiment is only the bottom CD (the line width at 10% from the bottom of the resist height).

  Next, the second waveform matching process is executed. In the case of the fourth embodiment, since the diffraction signal acquired in the first waveform matching process is used, it is not necessary to acquire the diffraction signal again, but the wavelength region for executing the matching is different from that of the first waveform matching process. Set as follows. For example, as shown in FIG. 12, the horizontal axis wavelength (76) and the vertical axis light intensity ratio information (74) and the vertical axis phase difference information (75) with the wavelength range of 300 nm to 700 nm (76) as shown in FIG. The waveform matching is executed using the two pieces of information.

  Thus, the second waveform matching process is completed. An example of the result obtained by this is shown in FIG. In the example shown in FIG. 13, all the results of the variable parameters are displayed, bottom CD = 54.67694 nm, height = 131.6368 nm, sidewall angle = 89.13165 degrees, antireflection film = 91.15607 nm. Amorphous silicon = 38.69052 nm and nitride film = 24.2445 nm.

  Next, the difference between the first waveform matching result and the second waveform matching result is calculated. The difference of the bottom CD is 0.58 nm. Since this satisfies the preset specification value of 1 nm, it is estimated that the first waveform matching and the second waveform matching are correctly executed.

  In the fourth embodiment, the first measurement result is adopted as the final measurement result. Here, there is no problem even if the second result is adopted, or there is no problem if the average value of the first and second results is used. In the above example, the specification value is satisfied in the second measurement, but basically the measurement is repeated until the specification value is satisfied. Alternatively, when an upper limit of repetition is provided and the upper limit number is reached, it is necessary to review the conditions to be measured.

  In the fourth embodiment, waveform matching with different combinations can be executed a plurality of times in a shorter time, and the reliability of the measurement can be confirmed, thereby realizing highly accurate measurement. .

The figure which shows schematic structure of the shape measuring apparatus which concerns on embodiment of this invention. The flowchart which shows the process of the shape measuring method which concerns on embodiment of this invention. The figure which shows the cross-sectional schematic structure of a measurement pattern. The figure which shows the example of the parameter of the library used in embodiment of this invention. The figure which shows the example of the measurement result of the 1st waveform matching process in embodiment of this invention. The figure for demonstrating the position which acquired the diffraction signal in 1st Embodiment of this invention. The figure which shows the example of the measurement result of the 2nd waveform matching process in 1st Embodiment of this invention. The figure which shows the example of the measurement result of the 3rd waveform matching process in 1st Embodiment of this invention. The figure which shows the example of the measurement result of the 2nd waveform matching process in 2nd Embodiment of this invention. The figure which shows the example of the parameter of the library used in the 2nd waveform matching process of 3rd Embodiment of this invention. The figure which shows the example of the measurement result of the 2nd waveform matching process in 3rd Embodiment of this invention. The figure for demonstrating the waveform matching in 4th Embodiment of this invention. The figure which shows the example of the measurement result of a 2nd waveform matching process in 4th Embodiment of this invention. The figure for demonstrating the measuring method in a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Optical system, 31 ... Light source, 32 ... Deflector, 33 ... Incident light, 34 ... Reflected light, 35 ... Analyzer, 36 ... Detector, 37 ... Measurement object, 40 ... Processing unit 41... Control unit 42... Detection diffraction signal storage unit 43 43 Library storage unit 44 Calculation unit 45 Light source adjustment mechanism

Claims (5)

In a shape measuring method for measuring the size or three-dimensional shape of a fine pattern of a semiconductor device formed on a substrate,
Waveform matching is performed between a detected diffraction signal detected by irradiating the fine pattern at a predetermined measurement location on the substrate with a library that is a collection of virtual diffraction signals, and at least one parameter of the measurement location A first waveform matching step for obtaining
A second waveform matching step for performing waveform matching by changing at least one of the detected diffraction signal and the library in the first waveform matching step, and obtaining at least one parameter of the measurement location;
At least one or more parameters obtained by the first waveform matching step and the second waveform matching step are compared with each other, and it is determined whether or not the difference is within a preset allowable value range. A determination process;
A shape measuring method comprising: The shape measuring method according to claim 1,
In the second waveform matching step, a detected diffraction signal detected by irradiating light on the fine pattern under conditions different from those in the first waveform matching step is used. The shape measuring method according to claim 1,
In the second waveform matching step, waveform matching is performed using the library different from the first waveform matching step. The shape measuring method according to claim 1,
In the second waveform matching step, waveform matching is performed in a wavelength region different from that of the first waveform matching step. A shape measuring device for measuring the size or three-dimensional shape of a fine pattern of a semiconductor device formed on a substrate,
A light source that makes incident light incident on the fine pattern under a predetermined condition;
A detector for detecting a diffraction signal from the fine pattern;
A library storage unit that stores a plurality of libraries that are collections of virtual diffraction signals;
A detected diffraction signal storage unit for storing a detected diffraction signal detected by the detector;
A calculation unit that performs waveform matching between the detected diffraction signal in the detected diffraction signal storage unit and the library in the library storage unit, and obtains at least one parameter;
At one measurement location on the substrate, the waveform matching by the calculation unit was performed a plurality of times by changing at least one of the detected diffraction signal and the library, and the result of the plurality of waveform matching was obtained. A control unit that compares the parameters and controls to determine whether these differences are within a preset tolerance range;
A shape measuring apparatus comprising:

Images