Inspection measurement system and sample inspection measurement method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HITACHI HIGH TECH CORP
- Filing Date
- 2025-01-28
- Publication Date
- 2026-08-06
Smart Images
Figure JP2025002643_06082026_PF_FP_ABST
Abstract
Description
Inspection and measurement system and sample inspection and measurement method
[0001] The present invention relates to an inspection and measurement system and a sample inspection and measurement method.
[0002] In semiconductor device manufacturing, in-line inspection and measurement technologies are crucial for non-contact inspection and measurement of devices formed on silicon wafers during the manufacturing process, with the aim of improving yield. One such in-line inspection and measurement tool is the scanning electron microscope (SEM). By scanning a focused electron beam over a sample and imaging the spatial distribution of generated secondary electrons, the dimensions and shape of nanoscale patterns can be inspected and measured. Furthermore, the Voltage Contrast (VC) method is known, which inspects the electrical properties of a pattern, such as conductivity or non-conductivity, to the silicon wafer from the amount of detected secondary electrons. Patent Document 1 also describes a VC method that calculates more detailed electrical properties and morphological properties in the cross-sectional direction of a sample from the transient response of the secondary electron detection signal.
[0003] Japanese Patent Publication No. 2016-100153
[0004] In the VC method, two main models are used to calculate the electrical properties of a sample from the amount of secondary electrons detected and its transient response when the sample is charged with an electron beam. The first model is used to calculate the sample potential from the detected signal, taking into account the configuration of the apparatus and the detector conditions. The second model is used to calculate the electrical properties from the sample potential using an equivalent circuit representing the electrical properties within the sample and electron beam irradiation conditions. In order to calculate the electrical properties with high accuracy, these two models must faithfully represent the measurement conditions.
[0005] The first model assumes that changes in the detection signal are solely due to changes in the sample potential. However, this assumption is often invalid. For example, if the sample contains a large capacitance component, the electron beam irradiation time must be extended to charge the sample, and contamination such as carbon accumulates on the sample during electron beam irradiation. This contamination affects the amount of secondary electrons emitted from the sample and, therefore, the detection signal intensity. In other words, the transient response waveform of the detection signal includes factors other than changes in the sample potential and does not satisfy the assumption of the first model. Even when the capacitance component is not large, similar problems arise when measuring materials that are prone to contamination or samples in a state prone to contamination. Furthermore, not limited to contamination, the amount of secondary electrons that reach and are detected by the detector may differ depending on the state and shape of the sample. The transient response waveform is also affected by the detector's response characteristics and their changes over time. Thus, the transient response waveform of the detector is not determined solely by the sample potential.
[0006] The first model relies solely on the sample potential as the factor in the detection signal. If the detection signal is influenced by factors other than the sample potential, it leads to errors in the calculated electrical characteristics. On the other hand, most of these phenomena that disrupt the model's assumptions depend on the individual sample being tested, making it difficult to include them in the model beforehand.
[0007] An inspection and measurement system according to one embodiment of the present invention comprises a charged particle beam apparatus including a primary beam generator that irradiates a sample with a pulsed primary beam, a detection system including a charged particle detector that detects charged particles emitted as a result of the pulsed primary beam irradiating the sample and outputs a detection signal waveform, and a computer that calculates the electrical and / or material properties of the sample based on the detection signal waveform from the detection system, wherein the computer acquires a first transient response waveform, which is a detection signal waveform output from the detection system when a pulsed primary beam under predetermined irradiation conditions is irradiated at a reference acquisition position on the sample, and a second transient response waveform, which is a detection signal waveform output from the detection system when a pulsed primary beam under predetermined irradiation conditions is irradiated at a measurement point on the sample, generates a third transient response waveform by correcting the second transient response waveform based on the first transient response waveform, and uses a model to determine the sample potential waveform at the measurement point from the third transient response waveform, The second transient response waveform is a detection signal waveform output by a charged particle detector that is sensitive to the sample potential or by a charged particle detector with detection conditions set to be sensitive to the sample potential, while the first transient response waveform is a detection signal waveform output by a charged particle detector that is not sensitive to the sample potential or by a charged particle detector with detection conditions set to be insensitive to the sample potential.
[0008] This makes it possible to calculate the electrical and / or material properties of a sample with greater accuracy. Other challenges and novel features will become apparent from the description and accompanying drawings herein.
[0009] This is a schematic diagram of the inspection and measurement system of Example 1. This is an example of the hardware configuration of the control device. This is a flowchart for calculating the electrical characteristic parameter values of the sample. This is a schematic diagram of the charged particle beam apparatus of Example 1. This is an example of the sample configuration. This is an example of the sample configuration. This is an example of the sample configuration. This is a flowchart for calculating the electrical characteristic parameter values of the sample. This is a schematic diagram showing an example of a transient response waveform. This is a schematic diagram of a calibration curve. This is a schematic diagram showing an example of an equivalent circuit model and corresponding examples of sample potential response characteristic models and corrected measurement point waveforms. This is an example of a settings / analysis screen. This is an example of a settings / analysis screen. This is an example of a settings / analysis screen. This is an example of a settings / analysis screen. This is a schematic diagram of the inspection and measurement system of Example 2. This is a schematic diagram of the charged particle beam apparatus of Example 2. This is a schematic diagram of the charged particle beam apparatus of Example 2 (modified version).
[0010] The following describes an embodiment with reference to the drawings.
[0011] Figure 1A is a schematic diagram of the inspection and measurement system. The inspection and measurement system comprises a charged particle beam apparatus 100 and a control device 200 that controls the charged particle beam apparatus 100. The charged particle beam apparatus 100 mainly comprises a primary beam generator 110 that generates a primary beam to irradiate the sample and a charged particle detector 120 that detects charged particles emitted as a result of the irradiation of the sample with the primary beam. An input device 211 and a display device 212 are connected to the control device 200. The user can control the charged particle beam apparatus 100 through a GUI (Graphical User Interface) in which instructions are entered using the input device 211 from the screen displayed on the display device 212. The charged particle beam apparatus 100 may also be controllable from a terminal that is connected to the control device 200 via a network.
[0012] The control device 200 is implemented by an information processing device (computer) whose main components include a processor (Central Processing Unit: CPU) 201, memory 202, storage device 203, input interface (I / F) 204, output I / F 205, communication I / F 206, and bus 207, as shown in Figure 1B. The processor 201 functions as a functional unit that provides predetermined functions by executing processing according to a program loaded into the memory 202. The storage device 203 stores data and programs used by the functional unit. The input I / F 204 is connected to an input device 211 such as a keyboard, pointing device, or operation panel, and the output I / F 205 is connected to a display device 212. The communication I / F 206 enables communication with terminals and other information processing devices via a network. These are connected to each other via the bus 207.
[0013] In the following explanation, when describing processing by a program, the program or functional components may be described as the main focus. However, the main hardware component is the processor, or the information processing device (computer) that includes such a processor. The information processing device, using resources such as memory and communication interfaces as appropriate, executes processing according to the program read into memory. Figure 1A shows an example of a CPU as the processor, but a GPU (Graphical Processing Unit) or the like may also be used. Furthermore, the processing to realize the function is not limited to software program processing; it can also be implemented with dedicated circuits. Applicable dedicated circuits include FPGAs (Field Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits).
[0014] The inspection and measurement system of this embodiment irradiates a pulsed primary beam (pulsed primary beam) onto predetermined measurement points on a sample, and calculates predetermined electrical characteristic parameter values from the transient response characteristics of the amount of charged particles emitted due to irradiation with the pulsed primary beam. By calculating the electrical and material characteristic values of the sample at the measurement points from the electrical characteristic parameter values, the quality of the structure and materials formed on the sample can be inspected. Figure 1C shows the calculation flow of the electrical characteristic parameter values of a sample performed by the control device 200 using the charged particle beam apparatus 100.
[0015] First, a pulsed primary beam is irradiated onto the measurement point on the sample, and a detection signal waveform corresponding to the amount of charged particles emitted is obtained (S01). Next, the detection signal waveform is converted into a sample potential waveform using a charged particle emission model (S02). Subsequently, electrical characteristic parameter values are calculated from the sample potential waveform using a sample potential response characteristic model (S03). From the electrical characteristic parameter values, electrical characteristics of the sample such as resistance, capacitance, leakage current, flat band voltage, threshold voltage, etc., or material characteristics of the sample such as dielectric constant, dielectric strength, semiconductor dope concentration, work function, trap charge amount, interface state, etc., are calculated. The calculated electrical characteristic values or material characteristic values of the sample include these values themselves, or signal values and converted values that reflect these values. In this embodiment, in order to improve the accuracy of the conversion from the detection signal waveform to the sample potential waveform by the secondary electron emission model in step S02, a detection signal waveform with reduced error factors is obtained in step S01.
[0016] Figure 2 is a schematic diagram of the charged particle beam apparatus 100 of Example 1. The charged particle beam apparatus 100 includes a stage 130 on which the sample 131 is placed, a primary beam optical system including a primary beam generator 110 that irradiates the sample 131 with a primary beam 113, and a detection system including a charged particle detector 120 that detects charged particles 123 emitted from the sample 131. Although not shown in Figure 2, the primary beam optical system and the detection system include optical elements such as lenses and deflectors for controlling the trajectories of the primary beam 113 and the charged particles 123. Furthermore, it may also include a light irradiation system for irradiating the sample 131 with light to remove charge from the sample 131 and control the sample potential.
[0017] In this embodiment, the primary beam 113 only needs to be capable of emitting charged particles 123 from the sample 131 and irradiating the sample intermittently to investigate its transient response characteristics. A charged particle beam such as electrons or ions, or electromagnetic waves such as light or X-rays can be used. Below, an example in which the primary beam 113 is an electron beam will be described.
[0018] The primary beam generator 110 comprises an electron source 111 and a blanker 112. The electron source 111 generates an electron beam as the primary beam. The blanker 112 gates the electron beam and pulses it. In the example in Figure 1C, the electron beam is pulsed by controlling the direction of electron beam propagation with a deflector 112a to control whether or not it passes through the aperture 112b. Note that the configuration of the primary beam generator 110 that generates the electron beam is not limited to this example. For example, if a photo-excited electron source is used as the electron source 111, it is possible to emit a pulsed electron beam by irradiating the photocathode with pulsed excitation light.
[0019] The charged particle detector 120 comprises an energy filter 121 and a detector 122. The energy filter 121 is configured as a mesh or perforated electrode placed on the trajectory of the charged particles 123. The transmittance of the charged particles 123 through the energy filter 121 can be adjusted according to the voltage applied to the electrode. When a voltage of a certain value is applied to the electrode, whether or not the charged particles can pass through the energy filter 121 depends on the energy of the charged particles 123 emitted from the sample 131. That is, the amount of charged particles 123 that pass through the energy filter 121 changes in accordance with the energy distribution of the charged particles 123 before the energy filter is applied. The detector 122 detects the charged particles 123 that have passed through the energy filter 121 and converts them into a voltage signal (detection signal) of an intensity corresponding to the amount of detected charged particles 123. The detector 122 is a secondary electron detector such as an ET (Everhart-Thornley) detector.
[0020] The control device 200 controls the overall operation of the charged particle beam device 100. Here, in order to calculate the electrical characteristic parameters of the sample 131, it controls these according to the conditions set in the primary beam optical system and the detection system, and receives the detection signal from the detector 122, and the operation of calculating the electrical characteristics and material characteristics of the sample will be described.
[0021] First, using FIGS. 3A to 3C, a configuration example of the sample inspected by the inspection and measurement system is shown. The inspection target is a material or structure formed on the silicon wafer 310 serving as a base, and the inspection and measurement system measures the material characteristics or electrical characteristics thereof. The figure shows a state where an electron beam 113 is irradiated on the measurement point set on the sample. The samples 301 to 303 shown in FIGS. 3A to 3C are all examples of semiconductor devices having a silicon wafer 310 as a base, but the base may be a conductor, and other semiconductors or metals may also be used. Further, the base may not be flat and may have some structure.
[0022] The inspection target of the sample 301 shown in FIG. 3A is the insulating film 311 formed on the silicon wafer 310. When the electron beam 113 is irradiated on the insulating film 311, the response characteristics of the secondary electrons (charged particles 123) detected by the detector 122 reflect the material characteristics such as the resistance value, breakdown voltage, trap amount of the insulating film 311, and the doping concentration of the semiconductor adjacent to the insulating film 311 (in this example, the underlying silicon wafer 310).
[0023] Figures 3B and 3C show examples where the object to be inspected is a structure formed on a silicon wafer 310. Sample 302 has an electrode 312 formed on an insulating film 311 or an electrode 313 embedded in the insulating film 311. Sample 303 has a semiconductor element (e.g., a FinFET) 315 formed beneath an insulating film 314, and a gate electrode 316 connected to the gate of the semiconductor element 315 is connected to a wiring 317 on the sample surface. In this case, when the electron beam 113 is irradiated onto the electrode 312 or wiring 317, the response characteristics of the secondary electrons (charged particles 123) detected by the detector 122 reflect the electrical characteristics such as resistance, capacitance, and leakage current between the electrode 312 or wiring 317 and the silicon wafer 310. These electrical characteristics further reflect the material properties of one or more materials constituting the structure.
[0024] Figure 4 shows the flowchart for calculating the electrical characteristic parameter values of a sample. The flowchart in Figure 4 corresponds to the flowchart in Figure 1, specifically, step S01 corresponds to steps S11 to S16, and steps S02 to S03 correspond to step S17. Figures 8A to D show examples of the setting and analysis screen, which is a GUI for calculating the electrical characteristic parameter values. The setting and analysis screen 400 includes a measurement conditions tab 411, a reference tab 421, a correction tab 431, and an analysis tab 441, and allows setting conditions and executing processes corresponding to each tab. In addition, a setting file selection unit 401 is provided, and conditions can be set by selecting and loading a setting file that has been pre-stored with processing conditions, etc. The calculation flowchart in Figure 4 will be explained with reference to Figures 8A to D as appropriate.
[0025] First, measurement conditions are set (S11). The setting of the measurement conditions is performed using the measurement condition tab 411 shown in FIG. 8A. Here, an example including the irradiation conditions and the irradiation position (measurement point position) of the pulsed electron beam is shown as the measurement conditions. This is just an example. For example, when discharging the sample 131, the conditions can also be set in this step, and a condition setting section for discharging can be provided in the measurement condition tab 411. The electron beam condition setting section 412 includes, for example, the acceleration voltage, current, irradiation time (pulse width), and integration count of the electron beam emitted by the primary beam generator 110 as setting conditions. The detection signal waveform may be obtained by irradiating a single pulsed electron beam, but the SNR can be improved by measuring the detection signal waveform the number of times specified by the "integration count" and taking the average. The measurement coordinate setting section 413 designates the position (measurement point) on the sample 131 irradiated with the pulsed electron beam using two-dimensional coordinates. By pressing the Save button 414, the set measurement conditions are saved.
[0026] Next, a first charged particle detection condition (reference condition) is set for the charged particle detector 120 (S12). The reference condition is set using the reference tab 421 shown in Figure 8B. Here, an example is shown in which the reference condition includes the detector condition for detecting charged particles and the position (reference acquisition position) where the pulsed electron beam is irradiated to measure the reference waveform (first transient response waveform). This is just one example, and other conditions may be included as reference conditions. The detector condition setting unit 422 includes, for example, the selection of the detector from which to acquire the reference waveform when the charged particle beam apparatus 100 has multiple detectors, and the voltage of the energy filter 121 as setting conditions. The reference acquisition coordinate setting unit 423 specifies, for each measurement point set as a measurement condition, the position on the sample 131 irradiated with the pulsed electron beam to acquire the reference waveform using two-dimensional coordinates. In this example, the reference acquisition position is set near the measurement point. For example, it is desirable that the reference acquisition position and the measurement point to be corrected are within the same chip of the chips arranged on the silicon wafer 310. When the reference waveform has a distribution on the wafer, using a reference waveform acquired near the measurement point allows for more accurate correction. On the other hand, it is also possible to set reference acquisition positions corresponding to multiple measurement points. For example, if the structure of the sample being inspected can be considered uniform, it is possible to reduce the number of reference acquisition positions and shorten the measurement time.
[0027] When the Start button 425 is pressed, a pulsed electron beam is irradiated to the reference acquisition position with the irradiation conditions set in the measurement condition setting (S11), and the charged particle detector 120, for which the reference conditions have been set, acquires a reference waveform (first transient response waveform) for each measurement point (S13). The acquired reference waveform R can be displayed on the reference waveform display unit 424 of the reference tab 421. The reference waveform R for each measurement point can be visually checked, and if there are no problems, the reference waveform data is saved by pressing the Save button 426.
[0028] Next, a second charged particle detection condition is set for the charged particle detector 120 (S14). The second charged particle detection condition is set in the detector condition setting unit 415 of the measurement condition tab 411 shown in Figure 8A. In Embodiment 1, it is assumed that the reference waveform and the measurement point waveform are acquired by the same charged particle detector, so the detector condition is set to the voltage of the energy filter 121 of the charged particle detector 120. By pressing the Start button 416, measurement is started according to the set measurement condition. The pulsed electron beam is irradiated onto the measurement point with the irradiation conditions set in the measurement condition setting (S11), and the measurement point waveform (second transient response waveform) for each measurement point is acquired by the charged particle detector 120 with the detector conditions set in the second charged particle detection condition setting (S14) (S15).
[0029] Subsequently, a corrected measurement point waveform (third transient response waveform) is generated by correcting the measurement point waveform (second transient response waveform) based on the reference waveform (first transient response waveform) (S16). The relationship between these three transient response waveforms will be explained using Figure 5. Figure 5 schematically shows examples of three transient response waveforms for a certain measurement point, with time on the horizontal axis and the detected signal intensity S on the vertical axis.
[0030] waveform f １ (t) is the reference waveform (first transient response waveform). A key feature of the detector conditions set for the charged particle detector 120 when acquiring the reference waveform is that the detector conditions are insensitive to the energy of the charged particles 123. That is, the voltage V applied to the energy filter 121 is set so that the charged particles 123 reaching the charged particle detector 120 are detected by the detector 122 regardless of their energy. ＥＦ Set the voltage V. ＥＦ It is sufficient to set it to ≥ 0V (including the case where there is no voltage applied to the energy filter 121 (OFF)). In this case, waveform f １ (t) reflects almost all of the charged particles emitted from the measurement point (reference acquisition position) that reached the charged particle detector 120. That is, waveform f １(t) reflects the amount of charged particles that changes due to contamination or the like.
[0031] Waveform f ２ (t) is a measurement point waveform (second transient response waveform). The detector conditions set for the charged particle detector 120 when acquiring the measurement point waveform are characterized in that they are detector conditions sensitive to the energy of the charged particles 123. When the detector 122 is a secondary electron detector, since secondary electrons are defined as electrons having an energy lower than 50 eV for convenience, for example, the voltage V ＥＦ applied to the energy filter 121 is set in the range of -20 V ≤ V ＥＦ < 0 V. In this case, the energy filter 121 forms an energy barrier for the charged particles reaching the charged particle detector 120, and only the charged particles exceeding the energy barrier are detected by the detector 122. In this case, the waveform f ２ (t) reflects the amount of charged particles emitted from the measurement point and reaching the charged particle detector 120 and the energy of the charged particles. The energy of the charged particles reflects the sample potential that changes due to charging or the like.
[0032] Waveform f ３ (t) is a corrected measurement point waveform (third transient response waveform). In this example, f ３ (t) = f ２ (t) / f １ (t) is calculated as. As will be described later, the model for converting the detection signal intensity S into the sample potential V is created on the premise that, for example, during the period when the pulsed electron beam is irradiated, the amount of charged particles reaching the charged particle detector 120 changes only due to the sample potential. Therefore, if the change in the amount of charged particles due to factors other than the sample potential cannot be ignored, the conversion accuracy deteriorates. To prevent the deterioration of accuracy, the waveform f ３ (t) suppresses the change in the amount of charged particles due to factors other than the sample potential of the waveform f ２ (t), and the waveform f ２ (t) has a different curve slope and detection signal intensity.
[0033] Furthermore, the correction formula for obtaining the corrected measurement point waveform (third transient response waveform) is not limited to the division described above. It depends on the properties of factors other than the sample potential that cause a change in the detected signal intensity S with respect to the transient response waveform.
[0034] For example, suppose the error factor to be removed is BSE (backscattered electrons) reaching the detector 122. BSE has energy corresponding to the energy of the primary beam and is not sensitive to the voltage of the energy filter 121. Also, the amount of BSE emitted from the measurement point differs depending on the state of the sample (contamination, uneven shape, composition). To obtain a corrected measurement point waveform that removes BSE, for example, the following detector condition settings and corrections can be performed.
[0035] First, the voltage V applied to the energy filter 121 is a detector condition set for the charged particle detector 120 when acquiring the reference waveform. ＥＦ Regarding V ＥＦ Set to ≤ -20V. In this case, secondary electrons will not be detected by detector 122, and waveform f １ (t) reflects the amount of BSE emitted from the measurement point (reference acquisition position) and reaching the charged particle detector 120.
[0036] BSE is waveform f ２ Because it acts as an offset for (t), f ３ (t) = f ２ (t)-f １ (t) represents the waveform f ３ (t) is calculated. This allows us to obtain a transient response waveform that excludes the error factor caused by BSE.
[0037] Correction of the measurement point waveform is performed using the correction tab 431 shown in Figure 8C. The measurement point selection unit 432 is used to select the measurement point for which waveform correction is to be performed, and the correction formula to correct the measurement point waveform is selected in the correction formula selection unit 433. The user selects the correction formula based on the measurement target and the factors causing the measurement error. Pressing the Start button 436 executes the correction of the measurement point waveform. The measurement point waveform display unit 434 and the corrected measurement point waveform display unit 435 each display the measurement point waveform M １ (f ２(t) and corrected measurement point waveform M ２ (f ３ (t)) is displayed. By pressing the Save button 437, the correction method for each measurement point and the waveform data for the corrected measurement point are saved.
[0038] Next, electrical characteristic parameters are calculated from the corrected measurement point waveform (third transient response waveform) (S17). This step includes converting the corrected measurement point waveform to a sample potential waveform (S02) and calculating electrical characteristic parameter values from the sample potential waveform (S03).
[0039] Step S02 will now be explained. The detection signal intensity S can be converted to the sample potential at the measurement point. This is because the energy distribution of secondary electrons emitted from the measurement point changes depending on the sample potential, and the charged particle detector 120 is sensitive to the energy of secondary electrons. For example, if the sample is positively charged, the amount of secondary electrons reaching the charged particle detector 120 decreases as the energy-poor secondary electrons are pulled back into the sample. As a result, the detection signal intensity output from the charged particle detector 120 decreases in accordance with the decrease in the amount of secondary electrons. Secondary electrons are also pulled back by the energy filter, and the amount detected by the charged particle detector 122 decreases. The calibration curve is a model created assuming that the conversion from sample potential V to detection signal intensity S is determined by the characteristics of the charged particle beam apparatus 100 and the detector 122. The calibration curve includes the action of the energy filter, so the voltage V applied to the energy filter 121 is ＥＦ It depends on [something]. Figure 6 is a schematic diagram of the calibration curve that defines the relationship between the detected signal intensity S and the sample potential V, V = g(S). In general, strictly speaking, a calibration curve refers to a model between the energy of secondary electrons emitted from the measurement point and the detected signal intensity, but since the sample potential V can be linearly converted from the energy of secondary electrons, for the sake of simplicity, the relationship between the detected signal intensity S and the sample potential V is referred to as the calibration curve here.
[0040] The control device 200 pre-creates and saves a calibration curve for the pulsed electron beam irradiation conditions set in step S11. The calibration curve can be stored in the form of a table or a conversion formula.
[0041] Here, the calibration curve assumes that the change in detection signal intensity S is due solely to the change in secondary electron energy. Therefore, as mentioned above, if the amount of secondary electrons emitted from the measurement point fluctuates during the measurement period due to contamination or other factors, i.e., based on factors other than the sample potential, then an error will occur in the sample potential V determined based on the calibration curve. In Example 1, by using a corrected measurement point waveform obtained by correcting the measurement point waveform with a reference waveform, it becomes possible to determine the sample potential V while reducing the influence of factors other than the sample potential V.
[0042] The calibration curve can be described as a model in which the relationship between the detected signal intensity S and the sample potential V depends on the instrument characteristics. However, it may not always be appropriate to determine the sample potential V from the detected signal intensity S using only this model. For example, if charging occurs due to the electron beam, disturbances in the electric field near the sample, such as at potential saddle points, may affect the detection of secondary electrons by the charged particle detector 120. In this case, the effects of these potential saddle points can be calculated through physical simulation, and the sample potential V can be determined from the corrected measurement point waveform using a conversion model, conversion table, or relational formula that takes these effects into account. On the other hand, if the trajectory of the secondary electrons to the charged particle detector 120 does not change significantly even with charging, it is acceptable to determine the sample potential V using the calibration curve.
[0043] Step S03 will now be explained. To calculate the electrical and material properties of a sample from the sample potential waveform, an equivalent circuit model is required between the measurement point and the silicon wafer (base) 310. A netlist or similar document containing equivalent information may also be used. The equivalent circuit model connects the measurement point and the silicon wafer 310 with one or more elements (capacitors, resistors, diodes, etc.) that represent electrical properties. In the equivalent circuit model, the electron beam acts as a current source. The current source is a function of the electric field generated by the charging near the irradiation region, such as the electron beam current, the secondary electron emission characteristics of the material irradiated by the electron beam, and the potential saddle point. The effects of the electron beam current, the secondary electron emission characteristics of the material, and the potential saddle point are set values or known information, and by using them in combination with the equivalent circuit model, the sample potential response characteristics during pulsed electron beam irradiation can be calculated.
[0044] Specifically, the characteristic values of the elements constituting the equivalent circuit are determined by fitting a sample potential response characteristic model, derived from an equivalent circuit model, which uses the sample potential as the objective variable and electrical characteristic parameters as explanatory variables, to the sample potential waveform obtained from the corrected measurement point waveform measured at the measurement point. In this embodiment, by correcting for the influence of factors other than the sample potential from the transient response waveform of the measurement point, a more accurate sample potential waveform can be obtained, and as a result, the electrical characteristic parameter values included in the sample potential response characteristic model can be determined with higher accuracy. Consequently, the electrical and material properties of the sample calculated from the electrical characteristic parameter values can also be determined with similarly high accuracy.
[0045] Figure 7 shows three examples of equivalent circuit models, along with corresponding sample potential response identification models and examples of corrected measurement point waveforms (schematic diagrams).
[0046] [Example 1] The equivalent circuit model 501 corresponds to the sample 301 shown in Figure 3A, and is an equivalent circuit model representing the relationship between the electron beam 113 irradiation position and the silicon wafer 310. The current generated by the electron beam 113 irradiated onto the insulating film 311 flows into the silicon wafer 310. The insulating film 311 can be represented by the resistive and capacitive components connecting the electron beam irradiation position and the silicon wafer 310. The sample potential response characteristic model 502 derived from this equivalent circuit model is h１ The result is an exponential waveform represented as (t). The sample potential waveform converted from the corrected measurement point waveform 503 generated in step S16 is model h １ By fitting (t), Model h １ The electrical characteristic parameters A, B, and τ included in (t) can be determined. The resistance value R is determined by the parameter value B and the current I of the current source, and the time constant τ is the product of the resistance value R and the capacitance value C. Therefore, the electrical characteristic values, resistance value R and capacitance value C, can be calculated from the fitted electrical characteristic parameter values.
[0047] [Example 2] The equivalent circuit model 511 corresponds to the sample 302 shown in Figure 3B, and is an equivalent circuit model of a MOS (Metal-Oxide-Semiconductor) structure in which a thin insulating film 311 of the order of nm is sandwiched between the electrode 312 and the silicon wafer (n-type) 310. The equivalent circuit model of the MOS structure is an equivalent circuit model that includes a capacitive component and a resistive component that represents leakage that increases sharply when the voltage rises. This equivalent circuit model shows that the resistance is high when the voltage is low and decreases sharply as the voltage increases. Thus, since the leakage current of the insulating film 311 is not proportional to the voltage, it is represented as a nonlinear resistance. The sample potential response characteristic model 512 derived from this equivalent circuit model is given by time t ２ This results in a model with two linear regions having inflection points at time t. ２ Slope A of the region before １ This indicates the rate at which the MOS structure is charged by the electron beam, and reflects the capacitance value C. ２ In the later region, an equilibrium state is reached when the increased leakage current, corresponding to the increased voltage, balances the current injected by the electron beam. That is, at time t ２ The latter region reflects the resistance value R when the voltage increases. Therefore, the sample potential waveform converted from the corrected measurement point waveform 513 generated in step S16 is model h ２ By fitting to (t), time t ２ The slope A1 of the region before time t ２ Steady-state value B in the region after this point ２This determines the electrical characteristics. From these, it is possible to calculate the resistance value R, which is an electrical characteristic value, or the leakage amount or capacitance value C that reflects it, from the fitted electrical characteristic parameter values.
[0048] [Example 3] Equivalent circuit model 521 also corresponds to the MOS structure of sample 302 shown in Figure 3B, but it is an equivalent circuit model when the silicon wafer 310 is composed of p-type silicon. When the electrode 312 is positively charged by the electron beam, a depletion layer without carriers is generated in the p-type silicon. The depletion layer has a capacitance component, and its capacitance value depends on the voltage applied to the depletion layer. That is, the depletion capacitance representing the depletion layer is a nonlinear capacitance. Therefore, the MOS structure in Example 3 is represented as an equivalent circuit model in which the capacitance due to the insulating film 311 and the nonlinear capacitance due to the depletion layer are connected in series. Note that the resistance component is assumed to be sufficiently large and is omitted from the equivalent circuit model. The sample potential response characteristic model 522 derived from this equivalent circuit model is model h ３ The result is a complex waveform shown by (t). The sample potential waveform converted from the corrected measurement point waveform 523 generated in step S16 is model h ３ By fitting to (t), two capacitance components are determined. The nonlinear capacitance is determined by the dielectric constant and doping concentration of the semiconductor constituting the depletion layer. Therefore, these material properties can be determined from the fitted electrical characteristic parameter values. In addition, the sample potential dependence graph of the capacitance component measured by capacitance-voltage measurement (C-V measurement), as well as the flat band voltage Vfb and charge density extracted therefrom, can be measured.
[0049] In Examples 1-3 shown above, the equivalent circuit model is constructed using resistive and capacitive components. However, other elements, such as diodes, photodiodes, and transistors, may also be used in the equivalent circuit model. As shown in Figure 3C, the equivalent circuit model becomes more complex when semiconductor elements are included. The equivalent circuit model may use one or more types of elements. Multiple elements may be arranged in parallel or in series.
[0050] The characteristic values of the elements included in the equivalent circuit model are themselves the electrical characteristics of the sample. Furthermore, electrical characteristics are determined by their shape and one or more material properties. For example, in the case of a MOS structure as shown in Figure 3B, its electrical characteristics can be expressed as capacitance. Capacitance is determined by the area of the electrode 312, the thickness of the insulating film 311, and the dielectric constant. Therefore, if the capacitance value, the area of the electrode 312, and the thickness of the insulating film 311 are known, the dielectric constant, which is a material property of the insulating film 311, can be calculated. The relationship between the electrical characteristics of an element and the material properties of the materials constituting that element is not generalizable as it depends on the element, but the relationship between elements with electrical characteristics and material properties is publicly known. That is, if the electrical characteristics and the shape of the element are known, material properties such as withstand voltage, dielectric constant, and dope concentration can be calculated.
[0051] The electrical and / or material properties of the sample are analyzed using the analysis tab 441 shown in Figure 8D. The equivalent circuit model display unit 442 displays the equivalent circuit model used for the analysis, and the waveform display unit 443 displays the sample potential waveform 444 and the sample potential response characteristic model 445 fitted to the sample potential waveform. The analysis results 446 displays the analysis results for each measurement point. In this example, an example where the resistance value R and capacitance value C were calculated as electrical characteristics is displayed. Pressing the Start button 447 executes the analysis. Pressing the Save button 448 saves the analysis results.
[0052] In Example 1, the reference waveform and the measurement point waveform were acquired using a single charged particle detector by changing the detector conditions. In this configuration, if two waveforms are acquired in two separate steps at the same coordinates, contamination from the first measurement may alter the state of the sample, potentially affecting the second measurement. In Example 1, an example was shown where the measurement point and the reference acquisition position were at different coordinates to acquire each waveform. However, if the reference waveform depends on the irradiation position of the primary beam, this can lead to a deterioration in correction accuracy. Thus, to improve correction accuracy, it is desirable to acquire the reference waveform and the measurement point waveform simultaneously at the same location. Furthermore, simultaneous acquisition allows for a reduction in measurement time.
[0053] Figure 9 shows a schematic configuration diagram of the inspection and measurement system of Example 2. The detection system of the charged particle beam apparatus 100b, which constitutes the inspection and measurement system, is equipped with two charged particle detectors. The first charged particle detector 120 acquires the measurement point waveform, and the second charged particle detector 600 acquires the reference waveform.
[0054] Figure 10 is a schematic diagram of the charged particle beam apparatus 100b of Example 2. Components similar to those in Example 1 are denoted by the same reference numerals, and redundant explanations are omitted. The charged particle beam apparatus 100b includes a first charged particle detector 120 for acquiring measurement point waveforms, as well as a second charged particle detector 600 for acquiring reference waveforms. The optical system of the charged particle beam apparatus 100b includes an annular reflector 602, and the detector 603 of the second charged particle detector 600 detects charged particles 124 emitted from the sample 131 and reflected by the reflector 602.
[0055] Unlike the first charged particle detector 120, the second charged particle detector 600 does not have an energy filter 121, and all charged particles that reach the second charged particle detector 600 are detected. In other words, the second charged particle detector 600 is not sensitive to the energy of the charged particles 124. In contrast, the detector conditions of the first charged particle detector 120 are such that they are sensitive to the energy of the charged particles 124. For example, the voltage V applied to the energy filter 121 ＥＦ -20V ≤ V ＥＦ Set within the range of <0V>.
[0056] In Figure 10, an example is shown in which a reflector 602 is installed to enable the second charged particle detector 600 to efficiently detect charged particles, but the installation of the reflector 602 is not mandatory.
[0057] (Modified Version) Figure 11 also shows a charged particle beam apparatus that can simultaneously acquire a reference waveform and a measurement point waveform at the same location, but the configuration of the detection system is different from the charged particle beam apparatus 100b shown in Figure 10.
[0058] Figure 11 is a schematic diagram of the charged particle beam apparatus 100c of Example 2. Components similar to those in Example 1 are denoted by the same reference numerals, and redundant explanations are omitted. Charged particles 123 emitted from the sample 131 are incident on the energy spectrometer 701. The energy spectrometer 701 causes the charged particles 123 to follow different trajectories according to their energy, guiding them to the first charged particle detector 710 and the second charged particle detector 720. The detector 711 of the first charged particle detector 710 and the detector 721 of the second charged particle detector 720 may be different pixels in an array detector. For example, high-energy charged particles 123 are detected by the detector 711, and low-energy charged particles 123 are detected by the detector 721.
[0059] In this detection system configuration, both the first charged particle detector 710 and the second charged particle detector 720 are sensitive to the energy of charged particles. In contrast, the sum of the detection signal intensity of the first charged particle detector 710 and the detection signal intensity of the second charged particle detector 720 reflects the total amount of charged particles that reached the energy spectrometer 701, and therefore is not sensitive to the energy of charged particles. Accordingly, in the detection system configuration of Figure 11, the detection signal waveforms of either or both of the first charged particle detector 710 and the second charged particle detector 720 can be used as the measurement point waveform, and the sum of both detection signal waveforms can be used as the reference waveform. Here, an example with two charged particle detectors is shown, but the same applies when any number of charged particle detectors are provided. That is, the detection signal waveform of any of the multiple charged particle detectors can be used as the measurement point waveform, and the sum of the detection signal waveforms of the multiple charged particle detectors can be used as the reference waveform.
[0060] The above embodiments and modifications are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment or modification with parts of another embodiment or modification, and it is also possible to add parts of other embodiments or modifications to the configuration of one embodiment or modification. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment or modification with other configurations.
[0061] 100, 100b, 100c: Charged particle beam apparatus, 110: Primary beam generator, 111: Electron source, 112: Blanka, 112a: Deflector, 112b: Aperture, 113: Primary beam, 120: Charged particle detector, 121: Energy filter, 122: Detector, 123: Charged particle, 124: Charged particle, 130: Stage, 131: Sample, 200: Control device, 201: Processor, 202: Memory, 203: Storage device, 204: Input I / F, 205: Output I / F ,206: Communication I / F, 207: Bus, 211: Input device, 212: Display device, 301, 302, 303: Sample, 310: Silicon wafer, 311: Insulating film, 312, 313: Electrode, 314: Insulating film, 315: Semiconductor element, 316: Gate electrode, 317: Wiring, 400: Settings / Analysis screen, 401: Setting file selection section, 411: Measurement conditions tab, 412: Electron beam condition setting section, 413: Measurement coordinate setting section, 414: Save button, 415: Start button, 42 1: Reference tab, 422: Detector condition setting unit, 423: Reference acquisition coordinate setting unit, 424: Reference waveform display unit, 425: Start button, 426: Save button, 431: Correction tab, 432: Measurement point selection unit, 433: Correction formula selection unit, 434: Measurement point waveform display unit, 435: Corrected measurement point waveform display unit, 436: Start button, 437: Save button, 441: Analysis tab, 442: Equivalent circuit model display unit, 443: Waveform display unit, 444: Sample electricity Waveform at point 1, 445: Sample potential response characteristic model, 446: Analysis result, 447: Start button, 448: Save button, 501, 511, 521: Equivalent circuit model, 502, 521, 522: Sample potential response characteristic model, 503, 513, 523: Corrected measurement point waveform, 600: Second charged particle detector, 602: Reflector, 603: Detector, 701: Energy spectrometer, 710: First charged particle detector, 711: Detector, 720: Second charged particle detector, 721: Detector.
Claims
1. A charged particle beam apparatus comprising: a primary beam generator that irradiates a sample with a pulsed primary beam; a detection system including a charged particle detector that detects charged particles emitted as a result of the pulsed primary beam irradiating the sample and outputs a detection signal waveform; and a computer that calculates the electrical and / or material properties of the sample based on the detection signal waveform from the detection system, wherein the computer acquires a first transient response waveform which is a detection signal waveform output from the detection system when the pulsed primary beam under predetermined irradiation conditions is irradiated at a reference acquisition position on the sample; a second transient response waveform which is a detection signal waveform output from the detection system when the pulsed primary beam under predetermined irradiation conditions is irradiated at a measurement point on the sample; a third transient response waveform which is obtained by correcting the second transient response waveform based on the first transient response waveform; and a model which determines the sample potential waveform at the measurement point from the third transient response waveform. The inspection and measurement system wherein the second transient response waveform is a detection signal waveform output by a charged particle detector sensitive to the sample potential or a charged particle detector with detection conditions set to be sensitive to the sample potential, and the first transient response waveform is a detection signal waveform output by a charged particle detector insensitive to the sample potential or a charged particle detector with detection conditions set to be insensitive to the sample potential.
2. The inspection and measurement system according to claim 1, wherein the computer corrects the time values of the second transient response waveform based on the values of the first transient response waveform corresponding to the time.
3. An inspection and measurement system according to claim 1, wherein the first transient response waveform and the second transient response waveform are acquired using the same charged particle detector, the charged particle detector is equipped with an energy filter, the energy filter is set to a detection condition in which, when acquiring the first transient response waveform, charged particles that reach the charged particle detector are detected regardless of their energy, and when acquiring the second transient response waveform, the energy filter is set to a detection condition that is sensitive to the energy of charged particles that reach the charged particle detector.
4. The inspection and measurement system according to claim 3, wherein the coordinates of the reference acquisition position are set to be near the measurement point.
5. An inspection and measurement system according to claim 1, wherein the first transient response waveform and the second transient response waveform are acquired using the same charged particle detector, the charged particle detector is equipped with an energy filter, the energy filter is set to a detection condition in which, when acquiring the first transient response waveform, secondary electrons reaching the charged particle detector are substantially undetectable, and when acquiring the second transient response waveform, the energy filter is set to a detection condition sensitive to the energy of secondary electrons reaching the charged particle detector.
6. The inspection and measurement system according to claim 1, wherein the detection system includes first and second charged particle detectors, the first and second charged particle detectors detect charged particles emitted as a result of the pulsed primary beam irradiating the coordinates of the measurement point, the first transient response waveform is acquired using the second charged particle detector, the second transient response waveform is acquired using the first charged particle detector, the first charged particle detector is a charged particle detector sensitive to the sample potential, and the second charged particle detector is a charged particle detector insensitive to the sample potential.
7. The inspection and measurement system according to claim 6, wherein the first charged particle detector is equipped with an energy filter, and the second charged particle detector is not equipped with an energy filter.
8. The inspection and measurement system according to claim 1, wherein the detection system includes an energy spectrometer and a plurality of charged particle detectors that detect charged particles reaching the energy spectrometer according to their energy and output a detection signal waveform, the plurality of charged particle detectors detect charged particles emitted as a result of the pulsed primary beam being irradiated onto the measurement point, and the computer acquires the sum of the detection signal waveforms output from each of the plurality of charged particle detectors as the first transient response waveform, and acquires the detection signal waveform output from any of the plurality of charged particle detectors as the second transient response waveform.
9. The inspection and measurement system according to claim 8, wherein the detection system comprises an array detector, and the plurality of charged particle detectors are configured to detect charged particles in pixels in different regions of the array detector.
10. The inspection and measurement system according to claim 1, wherein the sample potential response characteristic model is a model created based on an equivalent circuit model of the sample, with the sample potential as the objective variable and electrical characteristic parameters as explanatory variables, the computer fits the sample potential waveform to the sample potential response characteristic model to calculate the values of the electrical characteristic parameters, and uses the values of the electrical characteristic parameters to calculate the electrical characteristics and / or material characteristics of the sample.
11. A sample inspection and measurement method for calculating the electrical and / or material properties of a sample using a charged particle beam apparatus comprising a primary beam generator that irradiates a sample with a pulsed primary beam, and a detection system including a charged particle detector that detects charged particles emitted as a result of the pulsed primary beam irradiating the sample with the sample and outputs a detection signal waveform, wherein the method involves acquiring a first transient response waveform which is a detection signal waveform output from the detection system by irradiating a reference acquisition position on the sample with the pulsed primary beam under predetermined irradiation conditions, and a second transient response waveform which is a detection signal waveform output from the detection system by irradiating a measurement point on the sample with the pulsed primary beam under predetermined irradiation conditions, generating a third transient response waveform by correcting the second transient response waveform based on the first transient response waveform, determining the sample potential waveform at the measurement point from the third transient response waveform using a model, and the second transient response waveform being a detection signal waveform output by a charged particle detector sensitive to the sample potential or a charged particle detector with detection conditions set to be sensitive to the sample potential. A sample inspection and measurement method in which the first transient response waveform is a detection signal waveform output by a charged particle detector that is insensitive to the sample potential or a charged particle detector for which detection conditions are set that are insensitive to the sample potential.
12. The sample inspection and measurement method according to claim 11, wherein the first transient response waveform and the second transient response waveform are acquired using the same charged particle detector, the charged particle detector is equipped with an energy filter, the energy filter is set to a detection condition in which it is detected regardless of the energy of the charged particles that reach the charged particle detector when acquiring the first transient response waveform, and is set to a detection condition in which it is sensitive to the energy of the charged particles that reach the charged particle detector when acquiring the second transient response waveform.
13. The sample inspection and measurement method according to claim 11, wherein the detection system includes first and second charged particle detectors, the first and second charged particle detectors detect charged particles emitted as a result of the pulsed primary beam irradiating the coordinates of the measurement point, the first charged particle detector is a charged particle detector sensitive to the sample potential, the second charged particle detector is a charged particle detector insensitive to the sample potential, the first transient response waveform is acquired using the second charged particle detector, and the second transient response waveform is acquired using the first charged particle detector.
14. The sample inspection and measurement method according to claim 11, wherein the detection system includes an energy spectrometer and a plurality of charged particle detectors that detect charged particles that have reached the energy spectrometer according to their energy and output a detection signal waveform, the plurality of charged particle detectors detect charged particles emitted due to the irradiation of the pulsed primary beam on the measurement point, the sum of the detection signal waveforms output from each of the plurality of charged particle detectors is obtained as the first transient response waveform, and the detection signal waveform output from any of the plurality of charged particle detectors is obtained as the second transient response waveform.
15. The sample inspection and measurement method according to claim 11, wherein the sample potential response characteristic model is a model created based on an equivalent circuit model of the sample, with the sample potential as the objective variable and electrical characteristic parameters as explanatory variables, the sample potential waveform is fitted to the sample potential response characteristic model to calculate the values of the electrical characteristic parameters, and the electrical characteristics and / or material characteristics of the sample are calculated using the values of the electrical characteristic parameters.