Charged particle beam system

Abstract

To achieve both throughput improvement and measurement accuracy in semiconductor pattern measurement processing.SOLUTION: A charged particle beam system comprises: a charged particle beam apparatus including a charged particle source which emits a charged particle beam, a stage on which a sample is mounted, a first deflector configured to deflect the charged particle beam, a second deflector configured to deflect signal particles emitted from the sample, a detector configured to detect the signal particles, and a position detection device configured to detect the position of the sample or the stage; and a computer system which controls the operation of the charged particle beam apparatus. The computer system executes output control of the second deflector on the basis of position information detected by the position detection device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a charged particle beam system.

Background Art

[0002] As a general form of a charged particle beam apparatus, a scanning electron microscope can be mentioned. In a scanning electron microscope, a beam of primary electrons emitted from an electron source is converged or deflected by an electromagnetic field and two-dimensionally scanned over a sample. At the location irradiated with the primary electrons on the sample, secondary electrons carrying information of the sample are generated. These secondary electrons are detected by a detector and converted into an electrical signal, and then an image is generated in synchronization with the scanning position.

[0003] Since the beam of primary electrons can be converged to a small size by using a scanning electron microscope, an image with high resolution can be obtained as compared with an optical microscope. Therefore, a scanning electron microscope is applied to a semiconductor measurement apparatus for measuring the dimensions of circuit patterns on a semiconductor wafer in a semiconductor manufacturing process.

[0004] The integration degree of semiconductor products has been continuously improving, and further higher precision is required for circuit patterns. Therefore, higher precision in measurement is also required for semiconductor measurement apparatuses. In recent years, the demand for full-surface inspection of semiconductor wafers has been increasing, and improvement in throughput is also required for semiconductor measurement apparatuses. From the above, in semiconductor measurement apparatuses, the coexistence of higher precision and higher throughput is strongly required.

[0005] A semiconductor measurement apparatus is configured to be able to irradiate primary electrons at an arbitrary position on a semiconductor wafer by placing the semiconductor wafer on a stage configured to be movable. Further, the semiconductor measurement apparatus is provided with a configuration capable of changing the irradiation position on the sample by deflecting the primary electrons with a primary electron deflector. By using these in combination, measurement is performed at a specified position on the semiconductor wafer.

[0006] For example, Patent Document 1 discloses a method for improving throughput by shortening the static time of a stage. In this method, information on the state of the stage is input to a position control unit to calculate the deviation from the irradiation target position of the primary electrons. Based on this information, by adjusting the deflection amount of the primary electron deflector, the time variation of the stage position can be compensated for by deflection, and the primary electrons can be irradiated onto the irradiation target position.

[0007] Further, Patent Document 2 discloses a method for canceling variations in the information incident on a detector due to the fact that when primary electrons are deflected by a primary electron deflector, secondary electrons are also affected by the deflection action of the primary electron deflector and the information incident on the detector fluctuates, by causing a secondary electron deflector to output in response to the output of the primary electron deflector.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] As described above, in a semiconductor measuring apparatus, it is required to achieve both high throughput and high precision.

[0010] However, when applying the technology of Patent Document 1, although throughput improvement can be expected, it is difficult to achieve high definition. That is, when measuring the dimensions of a semiconductor pattern, secondary electrons also receive the deflection action of the primary electron deflector, and the trajectory of the secondary electrons incident on the detector changes. This causes fluctuations in the detection rate of the detector, changes the detection signal, i.e., the image, and deteriorates the measurement accuracy.

[0011] On the one hand, according to the technology of Patent Document 2, in the irradiation position movement operation by a normal primary electron deflector, the influence of secondary electrons by the primary electron deflector can be canceled by applying a secondary electron deflector output corresponding to the output of the primary electron deflector.

[0012] However, in the technology according to Patent Document 2, since the information of the stage is fed back to the primary electron deflector, high-speed operation cannot be realized by performing control such that the output of the secondary electron deflector is based on the output of the primary electron deflector.

[0013] Furthermore, the secondary electron deflector is a deflector that has the function of making the primary electrons travel straight and deflecting only the secondary electrons, but the influence on the primary electrons cannot be completely zero due to processing tolerances, assembly tolerances, etc. For this reason, when the output of the secondary electron deflector is varied during the two-dimensional scanning of the primary electrons on the sample, the measurement accuracy deteriorates because the primary electrons are affected by the secondary electron deflector and the primary electron irradiation position is slightly shifted.

[0014] In view of such a situation, the present disclosure proposes a technology that achieves both an improvement in throughput and measurement accuracy in semiconductor pattern measurement processing.

Means for Solving the Problems

[0015] In order to solve the above problems, the present disclosure provides a charged particle beam system including a charged particle source that emits a charged particle beam, a stage on which a sample is placed, a first deflector configured to deflect the charged particle beam, a second deflector configured to deflect signal particles emitted from the sample, a detector configured to detect the signal particles, and a position detection device configured to detect the position of the sample or the stage, and a computer system that controls the operation of the charged particle beam device, wherein the computer system executes output control of the second deflector based on the position information detected by the position detection device.

[0016] Further features related to the present disclosure will become apparent from the description herein and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by elements and combinations of various elements and the aspects of the following detailed description and the appended claims. It should be understood that the description herein is merely exemplary and is not intended to limit the scope or application of the claims of the present disclosure in any way.

Advantages of the Invention

[0017] According to the technology of the present disclosure, it is possible to prevent the deterioration of measurement accuracy that occurs when throughput is improved, and to achieve both high throughput and high-precision measurement.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

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Figure 5

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Figure 7

Figure 8

[0019] The present embodiment is a charged particle beam system that acquires information on a sample by detecting signal charged particles generated at the charged particle beam irradiation position on the sample. The charged particle beam system scans the electron beam of a probe converged on the sample two-dimensionally, detects secondary electrons generated from the sample, and obtains a sample image by mapping the signal intensity for each scanning position (scanning electron microscope system). Hereinafter, embodiments according to the present disclosure will be described.

[0020] (1) First Embodiment <Configuration Example of Charged Particle Beam System> FIG. 1 is a diagram showing a schematic configuration example of a charged particle beam system 100 in which a charged particle beam apparatus according to a first embodiment is used as a scanning electron microscope.

[0021] The charged particle beam system 100 includes a computer system 50 and a scanning electron microscope 51. The computer system 50 includes an overall control unit 52, a signal processing unit 53, a deflector control processing unit 54, an input / output unit 55, and a storage unit 56. The scanning electron microscope 51 includes an electron source 1, a condenser lens 21, an upper primary electron deflector 22, a lower primary electron deflector 23, an upper scanning deflector 24, a lower scanning deflector 25, a subsequent acceleration electrode 26, an objective lens 27, a lower secondary electron deflector 31, an upper secondary electron deflector 32, a secondary electron aperture 33, an upper detector 34, a lower detector 35, a stage 42, a stage carrier 43, and a position detector 44.

[0022] In the scanning electron microscope 51, primary electrons 11 are generated from the electron source 1. The primary electrons 11 are focused by the condenser lens 21 and deflected by the upper scanning deflector 24 and the lower scanning deflector 25 to two-dimensionally scan the sample 41. The deflected primary electrons 11 are accelerated by the subsequent acceleration electrode 26 and then focused onto the sample 41 by the objective lens 27.

[0023] Secondary electrons are generated from the irradiation position of the primary electrons 11 on the sample 41. This secondary electrons contain surface information of the sample 41 and the like. Therefore, by irradiating the primary electrons 11 at an arbitrary position on the sample 41 and detecting the information of the secondary electrons, the information on the surface of the sample 41 can be obtained.

[0024] Among the generated secondary electrons, the high elevation angle secondary electrons 12 with an elevation angle close to 90° pass through the secondary electron aperture 33 and are deflected by the upper secondary electron deflector 32 and converted into an electrical signal by the upper detector 34. On the other hand, the low elevation angle secondary electrons 13 with a smaller elevation angle than this collide with the secondary electron aperture 33. Then, tertiary electrons 14 are generated from the secondary electron aperture 33 and detected by the lower detector 35 and converted into an electrical signal.

[0025] The electrical signals from the upper detector 34 and the lower detector 35 are sent to the signal processing unit 53. The signal processing unit 53 integrates the signal intensity in synchronization with the two-dimensional scan and generates an image mapping each signal intensity. The image is output to the input / output unit 55 via the overall control unit 52.

[0026] The sample 41 is placed on a stage 42 that can operate in two dimensions. This is for irradiating the primary electrons 11 at arbitrary coordinates on the sample 41. The position of the stage 42 is measured in real time by the position detection laser 45 of the laser interferometer of the position detection unit 44 installed on the stage carrier 43. The position detection method in the position detection unit 44 is not limited to the laser interferometer as described above, and the same effect can be obtained with a linear scale. By operating the stage 42, irradiation of the primary electrons 11 at arbitrary coordinates is realized.

[0027] Furthermore, control can be performed to irradiate the primary electrons 11 at the target position by deflecting the primary electrons 11 with the upper-stage primary electron deflector 22 and the lower-stage primary electron deflector 23. The upper-stage primary electron deflector 22 and the lower-stage primary electron deflector 23 may be electrostatic deflectors or electromagnetic deflectors. Also, the upper-stage scanning deflector 24 and the upper-stage primary electron deflector 22, and the lower-stage scanning deflector 25 and the lower-stage primary electron deflector 23 can be controlled as one deflector, respectively.

[0028] Generally, the stage operation can move over a wide range but has poor alignment accuracy, while the primary electron deflection control has a narrow movement range but high alignment accuracy. Therefore, in order to irradiate the primary electrons 11 at the target position coordinates on the sample specified by the user (hereinafter also referred to as the operator), combined control of both of these is performed. At this time, in order to prevent the primary electron irradiation position from fluctuating due to the vibration or drift of the stage 42, the stage position information obtained from the position detector 44 is input to the deflector control processing unit 54. The deflector control processing unit 54 calculates the primary electron deflection amount so that the primary electron irradiation position on the sample 41 does not change, and controls the upper-stage primary electron deflector 22 and the lower-stage primary electron deflector 23. This control can be similarly performed for the upper-stage scanning deflector 24 and the lower-stage scanning deflector 25.

[0029] <Reasons for the change in the detection rate of secondary electrons> FIG. 2 is a schematic diagram showing an example of the trajectories (changes) of the high-elevation secondary electrons 12 and the low-elevation secondary electrons 13 when the primary electron irradiation position is controlled using the upper-stage primary electron deflector 22 and the lower-stage primary electron deflector 23, and an example of correcting the change in the trajectory using the lower-stage secondary electron deflector 31.

[0030] As described in the above problem, since the deflection control in the primary electron deflector affects the trajectory of the secondary electrons, the detection rate at the detector changes. The secondary electrons generated at the primary electron irradiation position are also affected by the deflection actions of the upper-stage primary electron deflector 22 and the lower-stage primary electron deflector 23. For example, when the high-elevation secondary electrons 12 collide with the secondary electron aperture 33 and the low-elevation secondary electrons 13 pass through the secondary electron aperture 33, the information on the secondary electrons detected by the upper detector 34 and the lower detector 35 changes.

[0031] In this regard, the correction of this trajectory (the changed trajectory) can be performed by the lower secondary electron deflector 31 provided between the upper primary electron deflector 22 and the secondary electron aperture 33. The lower secondary electron deflector 31 is a Wien filter, which is a deflector that allows the primary electrons 11 to travel straight and deflects only the secondary electrons. Due to the action of the lower secondary electron deflector 31, the trajectories of the high elevation secondary electrons 12 and the low elevation secondary electrons 13 can be deflected as shown by the dashed lines. This can prevent the detection rates of the secondary electrons detected by the upper detector 34 and the lower detector 35 from changing.

[0032] <Output adjustment method of the lower secondary electron deflector 31> Here, one form of the output adjustment method of the lower secondary electron deflector 31 with respect to the output of the primary electron deflector to prevent changes in the detection rate will be described.

[0033] (Example of detected image) FIG. 3 is a diagram showing examples of an upper detector image 61 obtained by the upper detector 34 and a lower detector image 62 obtained by the lower detector 35.

[0034] In the two-dimensional scanning of the primary electrons 11 by the upper scanning deflector 24 and the lower scanning deflector 25, changes in the detection rate at the detector due to the output of the deflector as described above also occur. At the center of the image, a white dot silhouette 63 and a black dot silhouette 64 reflecting the shape of the secondary electron aperture 33 can be seen. Since the secondary electron aperture 33 is usually made axially symmetric with respect to the optical axis, the silhouette is shown as a circle, but this is not always the case depending on the shape of the secondary electron aperture 33. The variation in the detection rate during this two-dimensional scanning is constant and does not vary with time regardless of the drift of the stage, etc., so it has no effect on the measurement accuracy.

[0035] When the irradiation position of the primary electron 11 is moved (when the field of view is moved), the change in the trajectory of the secondary electrons caused by the outputs of the upper primary electron deflector 22 and the lower primary electron deflector 23 can be measured by the displacement amounts of the positions of the white dot silhouette 63 and the black dot silhouette 64. Also, regarding the change in the trajectory of the secondary electrons by the lower secondary electron deflector 31, it can be measured by the displacement amounts of the positions of the white dot silhouette 63 and the black dot silhouette 64.

[0036] (Displacement vector of the lower detected image) FIG. 4 is a schematic diagram showing an example of the black dot silhouette 64-2 seen in the lower detector image 62 when the lower secondary electron deflector 31 is output (voltage is applied and current flows), the black dot silhouette 64-1 before the output, and the black dot silhouette position displacement vector 65.

[0037] The black dot silhouette position displacement vector 65 represents the position displacement of the black dot silhouette 64 before and after the output of the lower secondary electron deflector 31, and is a vector quantity that depends on the output of the lower secondary electron deflector 31. Also, the movement of the black dot silhouette 64 is similarly observed when the primary electron irradiation position is moved (when the field of view is moved).

[0038] (Relational expression between the primary electron irradiation position movement amount and the output of the lower secondary electron deflector 31) (i) In adjusting the output of the lower secondary electron deflector 31, the relationship between the black dot silhouette position displacement vector 65 with respect to the output of the lower secondary electron deflector 31 is obtained to determine the coefficient A in Equation 1. As a result of investigations by the inventors, when measuring the values of the black dot silhouette position displacement vectors corresponding to each output value while changing the output of the lower secondary electron deflector 31, it was found that they are in a linear relationship. Therefore, the coefficient A can be determined as the slope of the linear relationship.

[0039] [Equation 1] Black dot silhouette position displacement vector = Coefficient A × Lower secondary electron deflector output ··· Equation 1

[0040] (ii) Further, the relationship between the displacement vector 65 of the black dot silhouette position with respect to the primary electron irradiation position movement amount is obtained to determine the coefficient B in Equation 2. Similarly, as a result of the inventors' studies, it was found that the relationship between the primary electron irradiation position movement amount (the variation amount from the initial irradiation position (field of view) = the variation amount of the position detection information) and the value of the displacement vector of the black dot silhouette position corresponding to the field of view movement amount is also a linear relationship. Therefore, the coefficient B can also be obtained as the slope of this linear relationship. Note that the primary electron irradiation position movement amount is a value for tracking the drift and vibration of the stage 42.

[0041] [Equation 2] Displacement vector of black dot silhouette position = Coefficient B × Primary electron irradiation position movement amount ··· Equation 2

[0042] (iii) From the above Equations 1 and 2, relational expressions of the primary electron irradiation position movement amount and the output of the lower secondary electron deflector 31 as shown in Equations 3 and 4 are obtained.

[0043] [Equation 3] Output of lower secondary electron deflector = Coefficient C × Primary electron irradiation position movement amount ··· Equation 3

[0044] [Equation 4] Coefficient C = Coefficient A^(-1) × Coefficient B ··· Equation 4

[0045] The output of the lower secondary electron deflector 31, the movement amount of the primary electron irradiation position, and the displacement vector of the black dot silhouette position are vector quantities of two components. Also, the coefficient A, the coefficient B, and the coefficient C may be scalar quantities or two-dimensional matrices. Note that the coefficient A, the coefficient B, and the coefficient C are experimentally or by simulation obtained as adjustment parameters for each device in advance (for example, before shipment), stored in the storage unit 56, and can be read out and used. Also, the coefficient A, the coefficient B, and the coefficient C can be obtained again for each measurement. However, the control equations shown in the above equations 1, 2, 3, and 4 are merely examples, and can also be polynomials including components of the second order and higher orders of each equation for higher precision control. Also, it may be a control equation that changes the coefficient A, the coefficient B, and the coefficient C according to the output range of the lower secondary electron deflector 31 and the range of the movement amount of the primary electron irradiation position.

[0046] (iv) When performing primary electron deflection control in accordance with the vibration or drift of the stage position (in order to keep the primary electron irradiation position on the sample constant), the primary electron deflector output varies at a certain period (for example, when vibrating) based on the information from the position detection unit 44. Therefore, this secondary electron orbit control also needs to vary the output in conjunction with the primary electron deflector output. In that case, the above coefficient C is input in advance from the storage unit 56 to the deflector control processing unit 54. Then, the output of the lower two-electron deflector is calculated using the information from the position detection unit 44. The lower secondary electron deflector 31 is output in conjunction with the primary electron deflector output from this calculated value.

[0047] (v) Regarding controlling the primary electron deflector using image position shift information (hereinafter also referred to as "movement amount information" or "field of view movement amount") without using the information of the position detection unit 44 In addition, the upper primary electron deflector 22 and the lower primary electron deflector 23 can also be controlled based on the image misalignment information. The overall control unit 52 calculates the amount of deviation from the target position of the image integrated by the signal processing unit 53, inputs it to the deflector control processing unit 54, and calculates the outputs of the upper primary electron deflector 22 and the lower primary electron deflector 23 that compensate for the deviation amount based on this information. As the deviation amount, either the relative deviation amount from the position when reaching the target position and starting imaging can be used, or the deviation amount from the model image at the target position stored in the storage unit 56 can be used. Also, the calculation formula at this time can be calculated by simulation, or the one stored in the storage unit 56 as an adjustment parameter in advance can be read out.

[0048] (vi) Regarding the use of Wien filter type deflectors When the upper secondary electron deflector 32 and the lower secondary electron deflector 31 are configured as Wien filter type deflectors, ideally, secondary electron deflection can be achieved without affecting the primary electrons 11. However, in reality, it is difficult to completely zero the deflection influence of the primary electrons 11 due to the influence of machining tolerances and assembly tolerances. For this reason, when the outputs of the upper secondary electron deflector 32 and / or the lower secondary electron deflector 31 are varied during two-dimensional scanning, the irradiation position of the primary electrons 11 may change slightly, and the measurement accuracy of the image may deteriorate. In such a case, by operating according to the following operation flow, the influence of the secondary electron deflector on the primary electrons 11 can be prevented and controlled.

[0049] (Control operation of the lower secondary electron deflector 31 when the drift and vibration amounts of the stage 42 are small) FIG. 5 is a flowchart for explaining the control operation of the lower secondary electron deflector 31. In this control operation, the lower secondary electron deflector 31 is controlled between scanning frames (the time between frames). Here, the scanning frame refers to the image unit obtained by one two-dimensional scan. Also, "when the drift and vibration amounts of the stage 42 are small" means, for example, when the drift amount and the vibration amount are smaller than a predetermined threshold value.

[0050] (i) Step 101 The overall control unit 52 acquires information on the imaging mode (M) and the number of scanning frames (Ntot: the number of frames acquired (integrated)) input (specified) by the user from the input / output unit 55. Here, the imaging mode means, for example, the time (imaging speed) required to capture a single-frame image. Also, the number of scanning frames (Ntot) means the desired number of frames to be finally integrated. For example, the user can specify Ntot = 256.

[0051] (ii) Step 102 The overall control unit 52 reads out the number of scanning frames (Nse) between secondary electron deflector controls stored in the storage unit 56 associated with the specified imaging mode. Here, the number of scanning frames (Nse) between secondary electron deflector controls means a value indicating how many frames out of the number of scanning frames (Ntot) a secondary electron deflection output (here, the lower secondary electron deflection output) is given. For example, when the number of scanning frames between secondary electron deflector controls corresponding to the specified imaging mode is Nse = 4, a secondary electron deflection output is given every time 4 frames are acquired. Also, if Nse = 1, a secondary electron deflection output is given every time 1 frame is acquired. That is, the secondary electron deflection output control is executed at predetermined time intervals, although it may be longer or shorter depending on the imaging mode. This is also the same in the secondary electron deflection output control according to FIG. 6 described later. That is, in the case of FIG. 6, the secondary electron deflection output control is executed every predetermined waiting time (specified time) regardless of the scanning period of the primary electrons (the time required to scan a single frame with the primary electrons).

[0052] (iii) Step 103 The overall control unit 52 controls the deflector control processing unit 54, the upper detector 34, the lower detector 35, and the signal processing unit 53 so as to repeat the processing from Step 104 to Step 110 until the number of acquired frames reaches the number of scanning frames (Ntot).

[0053] (iv) Step 104 The overall control unit 52 controls the deflector control processing unit 54, the upper detector 34, the lower detector 35, and the signal processing unit 53 so as to execute the processing from step 105 to step 107 Nse times. That is, every time a scanning frame for Nse is acquired, the processing for giving the lower secondary electron deflection output (from step 108 to step 110) is executed.

[0054] (v) Step 105 The deflector control processing unit 54 scans (scans) the sample 41 with primary electrons to generate secondary electrons.

[0055] (vi) Steps 106 and 107 The upper detector 34 and the lower detector 35 acquire the signal of the generated secondary electrons (for one frame) and input it to the signal processing unit 53. When the processing from step 105 to step 107 is repeated Nse times and an image for Nse frames is acquired, the processing proceeds to step 108.

[0056] (vii) Step 108 The overall control unit 52 inputs the stage position information acquired from the position detection unit 44 to the deflector control processing unit 54. The stage position information corresponds to the primary electron irradiation position movement amount described above and is information indicating the position shift amount from the first irradiation position or the previous irradiation position.

[0057] (viii) Step 109 Based on the above formula 3, the overall control unit 52 calculates the lower secondary electron deflector output using the stage position information as the primary electron irradiation position movement amount, and transfers the information of the calculated lower secondary electron deflector output to the signal processing unit 53.

[0058] (ix) Step 110 The signal processing unit 53 outputs the value of the lower secondary electron deflector output to the deflector control processing unit 54. The deflector control processing unit 54 operates the lower secondary electron deflector 31 (applies a voltage and passes a current) based on the value of the lower secondary electron deflector output. When the process is repeated until the total number of scanning frames reaches Ntot or more, the process proceeds to step 111.

[0059] (x) Step 111 The signal processing unit 53 integrates the image signals of the frames corresponding to the number of scanning frames Ntot, and transfers the integrated value to the overall control unit 52. The overall control unit 52 outputs (displays on the screen) the integrated value of the image signals from the input / output unit 55.

[0060] Note that the number of scanning frames (Nse) between secondary electron deflector controls is to be selected according to the required time per scanning frame (imaging mode) and the magnitude of the drift and vibration of the stage 42. The smaller the time interval of the secondary electron deflector output, the smaller the variation in the detection rate at the detector can be made. However, since the influence on the image due to the secondary electron deflector output can be reduced when the time interval is larger, this is determined by these trade - offs. When the drift and vibration of the stage 42 are large, the detection rate variation becomes large as the amount of primary electron irradiation position movement increases, so it is necessary to narrow the time interval. The required time per scanning frame can be determined for each imaging mode, and the magnitude of the drift and vibration of the stage 42 is determined by the configuration of the apparatus. Therefore, it is appropriate to set the number of scanning frames Nse between secondary electron deflector controls for each imaging mode. Of course, it may be configured to input the number of scanning frames Nse between secondary electron deflector controls as a parameter specified by the user, or it may be operated with the same number of scanning frames Nse between secondary electron deflector controls under all conditions without making it a setting parameter for each imaging mode.

[0061] In this embodiment, the control flow of the secondary electron deflector has been described. Here, the correction control of the field of view deviation in the primary electron deflector due to the stage position deviation is performed independently of this. However, when the measurement accuracy deteriorates due to the output variation of the primary electron deflector during the scanning frame due to problems such as the responsiveness of the primary electron deflector, by setting the output calculation in step 109 and the output destination in step 110 of this flow to the primary electron deflector, it is also possible to correct the field of view movement between scanning frames and suppress the deterioration of the measurement accuracy.

[0062] On the other hand, when the drift or vibration of the stage 42 is large and the detection rate variation cannot be corrected even in one operation of the scanning frame, it is necessary to narrow the time interval of the secondary electron deflector output and vary the secondary electron deflector output also during two-dimensional scanning. In that case, it can be controlled by the operation flowchart shown in FIG. 6.

[0063] (Control operation of the lower secondary electron deflector 31 when the drift or vibration amount of the stage 42 is large) FIG. 6 is a flowchart for explaining the control operation of the lower secondary electron deflector 31 when the drift or vibration amount of the stage 42 is large. Here, the phrase "when the drift or vibration amount of the stage 42 is large" means, for example, when the drift amount or vibration amount is equal to or greater than the above-mentioned threshold value determined in advance. Also, whether to execute the control operation of FIG. 5 or FIG. 6 can be determined by the overall control unit 52 by comparing the separately measured drift amount or vibration amount, or the drift amount or vibration amount specific to the stage set in advance (for example, stored in the storage unit 56 as a set value) with the above-mentioned threshold value. Alternatively, the overall control unit 52 may determine whether to perform the process of FIG. 5 or the process of FIG. 6 in association with the above-mentioned imaging mode (since the drift amount is small if the imaging speed is high). Further, the control operation of FIG. 6 may be executed when the overall control unit 52 determines that the drift amount or vibration amount of the stage 42 cannot be corrected after first executing the control operation of FIG. 5.

[0064] (i) Step 201 The overall control unit 52 acquires information on the imaging mode (M) input (designated) by the user from the input / output unit 55. Here, the imaging mode means, as described above, for example, the time (imaging speed) required to capture one frame image.

[0065] (ii) Step 202 The overall control unit 52 reads out the secondary electron deflector control waiting time (Tse) stored in the memory unit 56 in association with the designated imaging mode. Note that the secondary electron deflector control waiting time (Tse) can be determined for each imaging mode, or it may be set to the same value under all conditions.

[0066] (iii) Step 203 The overall control unit 52 controls the deflector control processing unit 54, the upper detector 34, the lower detector 35, and the signal processing unit 53 so as to repeat the processing from step 204 to step 207 until imaging is completed. Although not shown in FIG. 6, it is assumed that the processing of scanning the sample with primary electrons and acquiring secondary electrons by the detector (frame image acquisition processing) is being executed independently of the control operation of the lower secondary electron deflector 31.

[0067] (iv) Step 204 After an imaging start instruction is input, the overall control unit 52 waits without performing the imaging operation for a specified time (secondary electron deflector control waiting time Tse). This makes it possible to stabilize the image output and acquire an image with sufficient image quality. Note that since the specified time is not equal to the frame scanning time, secondary electron deflection output control may be executed even during the scanning operation.

[0068] (v) Step 205 The overall control unit 52 inputs the stage position information acquired from the position detection unit 44 to the deflector control processing unit 54.

[0069] (vi) Step 206 Based on the above formula 3, the overall control unit 52 calculates the lower secondary electron deflector output using the stage position information as the primary electron irradiation position movement amount, and transfers the information on the calculated lower secondary electron deflector output to the signal processing unit 53.

[0070] (vii) Step 207 The signal processing unit 53 outputs the value of the lower secondary electron deflector output to the deflector control processing unit 54. The deflector control processing unit 54 operates the lower secondary electron deflector 31 (applies a voltage and passes a current) based on the value of the lower secondary electron deflector output. The processes from step 204 to step 207 are repeated until imaging is completed. When imaging is completed, the process proceeds to step 208.

[0071] (viii) Step 208 The signal processing unit 53 integrates the captured image signals and transfers the integrated value to the overall control unit 52. The overall control unit 52 outputs the integrated value of the image signals from the input / output unit 55 (displays on the screen).

[0072] (2) Second Embodiment <Configuration Example of Charged Particle Beam System> FIG. 7 is a diagram showing a schematic configuration example of a charged particle beam system 100 in which the charged particle beam apparatus according to the second embodiment is used as a scanning electron microscope.

[0073] The charged particle beam system 100 in FIG. 7 includes a computer system 50 and a scanning electron microscope 51, similar to the charged particle beam system 100 according to the first embodiment. The computer system 50 has the same configuration as in the case of the first embodiment. Further, the scanning electron microscope 51 according to the second embodiment does not include the position detection unit 44 as compared with that according to the first embodiment, but has a configuration in which an energy filter 36 is added.

[0074] In the charged particle beam apparatus (scanning electron microscope 51) according to the second embodiment, since the position detection unit is not included as described above, the output of the lower secondary electron deflector 31 is set based on image information instead of stage position information. Hereinafter, the calculation of the output of the lower secondary electron deflector 31 based on image information will be described.

[0075] <Calculation of Lower Secondary Electron Deflector Output Based on Image Information> The black dot silhouette 64 of the lower detector image 62 shown in FIG. 4 moves depending on the primary electron deflector output. Therefore, immediately before, the black dot silhouette position displacement vector 65 is calculated by image processing from the lower detector image 62 in the scanning frame. Then, the overall control unit 52 calculates the output of the lower secondary electron deflector 31 based on the information of the calculated black dot silhouette position displacement vector 65 and the above formula 1.

[0076] Also, at the time of imaging, the overall control unit 52 acquires the silhouette position information from the image integrated by the signal processing unit 53, calculates the black dot silhouette position displacement vector 65, and inputs it to the deflector control processing unit 54. The deflector control processing unit 54 calculates the output of the lower secondary electron deflector corresponding to the black dot silhouette position displacement vector 65 based on the information of formula 1 and the coefficient A read from the storage unit 56, and outputs it to the lower secondary electron deflector 31 (applies a voltage and passes a current).

[0077] Here, a method using the position information of the black dot silhouette 64 seen in the lower detector image 62 has been described, but the same method can also be used to control the position information of the white dot silhouette 63 seen in the upper detector image 61.

[0078] <Control of the incident angle of high elevation secondary electrons> So far, a method for suppressing the detection rate variation of a plurality of detectors (upper detector 34 and lower detector 35) has been described, but control can also be performed to make the incident angle of the high elevation secondary electrons 12 incident on the upper detector 34 and the energy filter 36 constant.

[0079] As shown in FIG. 7, when an energy filter 36 is provided between the upper detector 34 and the upper secondary electron deflector 32, the energy of the high elevation secondary electrons 12 can be discriminated and detected. However, at this time, if the incident angle of the high elevation secondary electrons 12 incident on the energy filter 36 changes, the threshold value of the high elevation secondary electrons shaken off by the energy filter 36 fluctuates, the accuracy of the filter deteriorates, and thus the measurement accuracy deteriorates.

[0080] Therefore, by controlling the output of the lower secondary electron deflector 31 according to the primary electron irradiation position movement amount, fluctuations in the incident angle of the high elevation angle secondary electrons 12 to the energy filter 36 are suppressed.

[0081] FIG. 8 is an example of the trajectory of the high elevation angle secondary electrons 12 when the primary electron irradiation position is controlled by the upper primary electron deflector 22 and the lower primary electron deflector 23, and a schematic diagram of the lower secondary electron deflector 31 for correcting the same. In FIG. 8, the trajectory before deflection by the lower secondary electron deflector 31 is represented by a solid line, and the trajectory after deflection is represented by a broken line. In the solid line trajectory, since the high elevation angle secondary electrons do not enter the energy filter 36 vertically, the accuracy in the energy filter 36 deteriorates. On the other hand, in the broken line trajectory after deflection, since the high elevation angle secondary electrons incident on the energy filter 36 become vertical, it can be seen that the measurement accuracy can be maintained even when the primary electron irradiation position changes.

[0082] An example of the adjustment of this control will be described. The overall control unit 52 obtains a detection signal from the signal processing unit 53 before moving the primary electron irradiation position in a state where the energy filter 36 is operating, and then moves the primary electron irradiation position (field of view). Similarly, the overall control unit 52 obtains a detection signal from the signal processing unit 53 when moving the primary electron irradiation position. Then, the overall control unit 52 compares the images before and after the movement of the primary electron irradiation position (field of view). Furthermore, thereafter, the overall control unit 52 repeats the same detection while outputting the lower secondary electron deflector 31, and obtains the lower secondary electron deflector output that most closely matches the image before moving the irradiation position. Thereby, control is performed by obtaining the relational expression of the optimal lower secondary electron deflector output with respect to the primary electron irradiation position. In addition to this method, it is also possible to calculate the optimal output value by simulation to obtain the output formula. Note that since this control process is the same as the process described in the flowcharts of FIGS. 5 and 6, detailed description is omitted.

[0083] (3) Summary (i) In the first and second embodiments, the lower secondary electron deflector 31 is controlled to improve the detection rate of the detectors (the upper detector 34 and the lower detector 35) and to suppress the energy filter incident angle variation of the high elevation angle secondary electrons 12. Needless to say, the same control is possible for the upper secondary electron deflector 32 as well.

[0084] (ii) In one aspect of the present disclosure, in a charged particle beam system 100 including a computer system 50 and a scanning electron microscope (charged particle beam device) 51, the computer system 50 performs output control of a second deflector (the lower secondary electron deflector 31 and / or the upper secondary electron deflector) based on position information (field movement amount) detected by a position detection device (position detection unit 44). Here, the output of the second deflector can be calculated by multiplying the primary electron irradiation position movement amount based on the position information (stage position deviation amount) by a predetermined parameter (see the above equations 3 and 4). By performing the deflection output control of the secondary electrons together with the deflection control of the primary electrons based on the position information in this way, it becomes possible to improve the throughput and also improve the measurement accuracy (achieving both throughput improvement and measurement accuracy improvement).

[0085] Also, the deflection output control of secondary electrons can be selectively executed during the period (scanning period interval) between the two-dimensional scanning periods by the charged particle beam (primary electrons). That is, each time a two-dimensional scan of the sample to be measured is completed, an image is acquired while determining whether or not to perform the deflection output control of secondary electrons. For example, the deflection output control of secondary electrons may be executed every time a single-frame image is acquired, or the deflection output control of secondary electrons may be executed every time a plurality of frame images are acquired. However, when the drift amount or vibration amount of the stage is larger than a predetermined threshold value (when the scanning speed is slower than a predetermined speed), the deflection output control of secondary electrons may be executed at predetermined time intervals (designated times) regardless of the scanning period interval (even during scanning). By doing so, the deflection output control of secondary electrons can be executed at an appropriate frequency according to the imaging mode (high or low scanning speed), so that the measurement accuracy can be improved without reducing the throughput.

[0086] (iii) In another aspect of the present disclosure, in the charged particle beam system 100, the computer system 50 calculates position information (field movement amount) from an image based on the signal detected by the detector, and based on the amount of positional deviation indicated by the position information, after the end of one two-dimensional scanning period by the charged particle beam, at least one of the output controls of the first deflector (upper primary electron deflector 22 and / or lower primary electron deflector 23) or the second deflector (lower secondary electron deflector 31 and / or upper secondary electron deflector) is selectively executed. Here, "selectively" is as agreed above. Since the amount of positional deviation can be detected from the deviation amount of the acquired image without using the position detection unit 44 in this way, the number of components of the apparatus can be reduced and the apparatus manufacturing cost can be suppressed. Also, as described above, based on the position information (field movement amount), the deflection control of secondary electrons is performed together with the deflection control of primary electrons, so that it becomes possible to improve the throughput and the measurement accuracy at the same time (both improvement of throughput and improvement of measurement accuracy).

[0087] (iv) The functions of this embodiment can also be realized by software program codes. In this case, a storage medium storing the program codes is provided to a system or device, and a computer (or CPU or MPU) of the system or device reads out the program codes stored in the storage medium. In this case, the program codes themselves read out from the storage medium realize the functions of the above-described embodiment, and the program codes themselves and the storage medium storing them constitute the present disclosure. As the storage medium for supplying such program codes, 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.

[0088] Also, based on the instructions of the program codes, an OS (operating system) running on a computer, etc. may perform part or all of the actual processing so that the functions of the above-described embodiment are realized by the processing. Further, after the program codes read out from the storage medium are written into the memory on the computer, based on the instructions of the program codes, a CPU of the computer, etc. may perform part or all of the actual processing so that the functions of the above-described embodiment are realized by the processing.

[0089] Furthermore, by distributing the software program codes for realizing the functions of the embodiment via a network, they are stored in a storage means such as a hard disk or memory of a system or device or a storage medium such as a CD-RW or CD-R, and at the time of use, a computer (or CPU or MPU) of the system or device reads out and executes the program codes stored in the storage means or the storage medium.

[0090] Note that the processes and techniques described herein are not inherently related to any specific device and can also be implemented by an appropriate combination of components. Furthermore, a dedicated device may be constructed to execute the steps of the methods described herein. Also, various technical elements can be formed by appropriately combining the multiple components disclosed in this embodiment. For example, some components may be deleted from all the components shown in the embodiment. Although the present disclosure has been described in relation to specific examples, these are for ease of understanding rather than for limitation. Those of ordinary skill in the art will readily appreciate that there are numerous combinations of hardware, software, and firmware suitable for implementing the technology of the present disclosure. For example, the described software can implement the technology of the present disclosure in a wide range of programming or scripting languages such as assembler, C / C++, perl, Shell, PHP, Java (registered trademark), etc.

[0091] Furthermore, in the above-described embodiments, the control lines and information lines show those considered necessary for explanation, and not necessarily all control lines and information lines are shown on the product. All components may be interconnected.

[0092] In addition, those of ordinary skill in the art will clearly understand other implementations of the present disclosure from the consideration of the specification and embodiments of the present disclosure disclosed herein. The description content and specific examples in the specification are merely typical, and the scope and spirit of the present disclosure are shown in the subsequent claims.

Description of Reference Numerals

[0093] 1 Electron source, 11 Primary electron, 12 High elevation secondary electron, 13 Low elevation secondary electron, 14 Tertiary electron, 21 Condenser lens, 22 Upper primary electron deflector, 23 Lower primary electron deflector, 24 Upper scanning deflector, 25 Lower scanning deflector, 26 Rear acceleration electrode, 27 Objective lens, 31 Lower secondary electron deflector, 32 Upper secondary electron deflector, 33 Secondary electron aperture, 34 Upper detector, 35 Lower detector, 36 Energy filter, 41 Specimen, 42 Stage, 43 Stage carrier, 44 Position detection unit, 45 Position detection laser, 51 Scanning electron microscope, 52 Overall control unit, 53 Signal processing unit, 54 Deflector control processing unit, 55 Input / output unit, 56 Memory unit, 61 Upper detector image, 62 Lower detector image, 63 White dot silhouette, 64 Black dot silhouette, 65 Black dot silhouette position displacement vector

Claims

1. A charged particle source that emits a charged particle beam, A stage for placing a sample, A first deflector configured to deflect the charged particle beam, A second deflector configured to deflect signal particles emitted from the sample, A detector configured to detect the signal particles, A charged particle beam apparatus including a position detection device configured to detect the position of the sample or the stage, and A computer system for controlling the operation of the charged particle beam apparatus, The computer system executes output control of the second deflector based on position information detected by the position detection device. A charged particle beam system.

2. In Claim 1, The computer system calculates the output of the second deflector by multiplying a predetermined parameter by the amount of field movement by the first deflector. A charged particle beam system.

3. In Claim 1, The computer system selectively executes output control of the second deflector after the end of one two-dimensional scanning period by the charged particle beam. A charged particle beam system.

4. In Claim 1, The computer system executes output control of the second deflector at predetermined time intervals. A charged particle beam system.

5. In Claim 4, The computer system executes output control of the second deflector at intervals of two-dimensional scanning periods by the charged particle beam for a predetermined number of frames associated with the input imaging mode. A charged particle beam system.

6. In Claim 5, The computer system executes output control of the second deflector between a scanning process for a first predetermined number of frames and a scanning process for a second predetermined number of frames following the scanning process for the first predetermined number of frames. A charged particle beam system.

7. In Claim 4, When the computer system scans and images the sample with the charged particle beam, it executes output control of the second deflector at designated times associated with the input imaging mode. A charged particle beam system.

8. In Claim 1, The position detection device is a laser interferometer having an irradiation source that irradiates the sample or the stage with a laser, and a reflected light detector configured to detect the reflected light of the laser. A charged particle beam system.

9. A charged particle source that emits a charged particle beam, A stage for installing a sample, A first deflector configured to deflect the charged particle beam, A second deflector configured to deflect signal particles emitted from the sample, A charged particle beam apparatus including a detector configured to detect the signal particles, A computer system for controlling the operation of the charged particle beam apparatus, The computer system, Calculates the position information of the sample or the stage from an image based on the signal detected by the detector, A charged particle beam system that selectively executes output control of at least one of the first deflector or the second deflector after the end of a two-dimensional scanning period by the charged particle beam based on the position information of the sample or the stage.

10. In claim 9, The computer system executes output control of at least one of the first deflector or the second deflector based on the position information after the end of the one two-dimensional scanning period and before the start of the next two-dimensional scanning period. A charged particle beam system.

11. A charged particle source that emits a charged particle beam, A stage for installing a sample, A first deflector configured to deflect the charged particle beam, A second deflector configured to deflect signal particles emitted from the sample, A detector configured to detect the signal particles, A charged particle beam apparatus including a position detection device configured to detect the position of the sample or the stage, A computer system for controlling the operation of the charged particle beam apparatus, The computer system selectively executes output control of at least one of the first deflector or the second deflector after the end of a two-dimensional scanning period by the charged particle beam based on the position information detected by the position detection device. A charged particle beam system.

12. In claim 11, The computer system executes output control of at least one of the first deflector or the second deflector based on the position information after the end of the one two-dimensional scanning period and before the start of the next two-dimensional scanning period. A charged particle beam system.

13. In claim 11, The charged particle beam system, wherein the position detection device is a laser interferometer having an irradiation source that irradiates a laser to the sample or the stage, and a reflected light detector configured to detect reflected light of the laser.

Images