Charged particle beam apparatus

A computing unit generates a to-be-used-in-computation netlist on the basis of a to-be-used-in-calculation device model corresponding to a correction sample, estimates a first application result, on the basis of the to-be-used-in-computation netlist and an optical condition, when a charged particle beam is applied to the correction sample under the optical condition, compares the first application result and a second application result based on a detection signal when the charged particle beam is applied to the correction sample under the optical condition, and corrects the optical condition when the first application result and the second application result differ from each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a charged particle beam apparatus.

2. Description of the Related Art

Charged particle beam apparatuses such as electron microscopes and ion microscopes are used in observation of various samples having a fine structure. For example, for the purpose of process control on a manufacturing process of semiconductor devices, a scanning electron microscope that is one of the charged particle beam apparatuses is used in measurement of dimensions of a semiconductor device pattern formed on a semiconductor wafer serving as a sample, defect inspection of the semiconductor device pattern, or the like.

A method known as one of the sample analysis methods using an electron microscope is to form a potential contrast image from secondary electrons obtained through application of an electron beam to a sample and evaluate electrical resistance of an element formed on the sample on the basis of analysis of the potential contrast image.

For example, JP 2003-100823 A discloses a method for identifying a defect by calculating an electrical resistance value from a potential contrast. JP 2008-130582 A discloses a method for predicting characteristics of a defect in an electric resistance value or the like by creating, as an equivalent circuit, a netlist that describes information on electrical characteristics and connectivity of circuit elements from a potential contrast.

SUMMARY OF THE INVENTION

For inspection and measurement of semiconductor devices, it is required that a defect in electrical characteristics of the devices in a manufacturing process be detected. However, with the techniques disclosed in JP 2003-100823 A and JP 2008-130582 A, it is difficult to estimate the electrical characteristics with consideration given to interactions between a plurality of the devices using design data and inspection measurement data. Further, when the electrical characteristics are estimated using a plurality of apparatuses, an error may occur in the estimation result between apparatuses.

Therefore, an object of the present invention is to reduce an error in charged particle beam application result of a sample between apparatuses.

The following is a brief description of the summary of a primary aspect of the invention disclosed herein.

A charged particle beam apparatus according to a primary aspect of the present invention includes a database configured to store a to-be-used-in-calculation device model for use in estimation of a circuit of a sample or correction sample and an optical condition under which a charged particle beam is applied to the sample or the correction sample, a charged particle beam optical system configured to control the charged particle beam applied to the sample or the correction sample under the optical condition, a detector configured to detect secondary electrons emitted from the sample or the correction sample excited by the application of the charged particle beam and output a detection signal based on the secondary electrons, and a computing unit configured to generate a to-be-used-in-computation netlist on the basis of the to-be-used-in-calculation device model corresponding to the correction sample, estimate, on the basis of the to-be-used-in-computation netlist and the optical condition, a first application result when the charged particle beam is applied to the correction sample under the optical condition, compare the first application result with a second application result based on the detection signal when the charged particle beam is applied to the correction sample under the optical condition, and correct the optical condition when the first application result and the second application result differ from each other.

The following is a brief description of an effect obtained by the primary aspect of the invention disclosed herein.

That is, according to the primary aspect of the present invention, it is possible to reduce an error, between apparatuses, in result of charged particle beam application to a sample.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Each of the embodiments described below is an example for practicing the present invention and is not intended to limit the technical scope of the present invention. Note that, in the embodiments, components having the same function are denoted by the same reference numerals, and repeated description of such components will be omitted unless particularly necessary.

First Embodiment

<Structure of Charged Particle Beam Apparatus>

FIG. 1is a schematic diagram showing an example of a structure of a charged particle beam apparatus according to a first embodiment of the present invention.FIG. 2is a block diagram showing an example of the structure of the charged particle beam apparatus according to the first embodiment of the present invention. As shown inFIGS. 1and2, a charged particle beam apparatus1includes a charged particle beam apparatus main body10, a computer30, and an input and output part50.

<Charged Particle Beam Apparatus Main Body>

The charged particle beam apparatus main body10has a structure where a lens barrel10A is mounted on a sample chamber10B in which a sample23to be inspected is held, and a controller11is disposed outside the lens barrel10A and the sample chamber10B. In the lens barrel10A, an electron source (charged particle source)12that emits an electron beam (charged particle beam), a pulsed electron generator19that pulses the electron beam, a diaphragm13that regulates an application current of the electron beam thus emitted, a deflector14that controls an application direction of the electron beam, an objective lens18that causes the electron beam to converge, and the like are held. Although not shown, in the lens barrel10A, a condenser lens is provided. Note that, unless the electron beam is pulsed, the pulsed electron generator19need not be provided.

In the lens barrel10A, a detector25that detects secondary electrons emitted from the sample23or correction sample24excited by the application of the electron beam, and outputs a detection signal based on the secondary electrons and the like are further held. The detection signal is used in generation of a scanning electron microscopy (SEM) image, measurement of the size of the sample23or correction sample24, measurement of electrical characteristics, and correction of an optical condition under which the electron beam is applied to the sample23or the correction sample24.

In the sample chamber10B, a stage21, the sample23, the correction sample24, and the like are held. The sample23and the correction sample24are mounted on the stage21. Examples of the sample23include a semiconductor wafer including a plurality of semiconductor devices, and an individual semiconductor device. The stage21is provided with a stage drive mechanism (not shown) and is movable within the sample chamber10B under the control of the controller11.

The correction sample24is a sample for use in correction of the optical condition in a plurality of charged particle beam apparatuses. Specifically, in the plurality of charged particle beam apparatuses, even when the charged particle beam is applied to the same sample under the same optical condition, application results may be different from each other. Such a difference in application result between the plurality of apparatuses may be referred to as “machine difference”. In order to reduce such a machine difference, the optical condition is corrected using a correction sample whose to-be-used-in-calculation device model (to be described in detail later) representing a circuit configuration, electrical characteristics, or the like is known.

As the correction sample24, a test element group (TEG) including a plurality of elements having different electric characteristics can be used. Alternatively, an antenna TEG or time dependent dielectric breakdown (TDDB) TEG can be used as the correction sample24. Further alternatively, a TEG or the like for use in evaluation of leakage current of a p-n junction can be used as the correction sample24. The correction sample24may be provided separately from the sample23as shown inFIG. 1. Further, the correction sample24may be formed on a wafer prepared in advance for use in apparatus maintenance and transported as the sample23into the apparatus.

FIGS. 3A and 3Bare diagrams showing an example of the correction sample.FIGS. 3A and 3Bshow a correction sample including a plurality of elements.FIG. 3Ais a diagram schematically showing circuits (equivalent circuits) of a plurality of elements24a,24b, secondary electrons emitted by the application of the electron beam, and the like.FIG. 3Bshows cross-sectional views of the plurality of elements24a,24b. The circuit of the element24ais an RC parallel circuit in which a resistor having a resistance value R1and a capacitor having a capacitance value Cl are connected in parallel. On the other hand, the circuit of the element24bis an RC parallel circuit in which a resistor having a resistance value R2and a capacitor having a capacitance value C2are connected in parallel. Note that P1, P2denote electrodes, for example.

As shown inFIG. 3B, the element24ais larger than the element24bin region where an insulation film located below a conductive film serving as the electrode becomes thinner. Accordingly, the element24ais larger than the element24bin range of the electrode. When a plurality of elements are provided, the correction sample may include a plurality of elements that are similar in circuit structure but different in size.

The controller11is a functional block responsible for controlling components of the charged particle beam apparatus main body10. The controller11controls the operation of each component such as the electron source12, the pulsed electron generator19, the diaphragm13, the deflector14, and the objective lens18under, for example, an optical condition input from the computer30and the like. As described above, the controller11, the electron source12, the pulsed electron generator19, the diaphragm13, the deflector14, the objective lens18, and the like constitute a charged particle beam optical system BS that controls the electron beam.

Further, the controller11moves the sample23to a predetermined position by controlling the stage drive mechanism under, for example, the optical condition input from the computer30and the like. Further, the controller11controls a power supply or control signal supply to the detector25to control a process of detecting the secondary electrons performed by the detector25.

The controller11is implemented with a program executed by a processor such as a CPU. Further, the controller11may be configured by, for example, a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

As shown inFIG. 1, the computer30includes a computing unit31and a storage device41. The computing unit31is a functional block responsible for estimating a circuit (or equivalent circuit) of the sample23or correction sample24. As shown inFIG. 2, for example, the computing unit31includes a to-be-used-in-computation netlist generator32, an electron beam application result estimation computing unit33, a comparator34, and an optical condition correcting unit35. The to-be-used-in-computation netlist generator32generates a to-be-used-in-computation netlist corresponding to the sample23or correction sample24on the basis of the to-be-used-in-calculation device model (to be described later) and the optical condition. Further, the to-be-used-in-computation netlist generator32also updates the to-be-used-in-computation netlist on the basis of a comparison result from the comparator34.

The electron beam application result estimation computing unit33estimates an electron beam application result on the basis of the to-be-used-in-computation netlist generated by the to-be-used-in-computation netlist generator32. The comparator34compares the electron beam application result estimated by the electron beam application result estimation computing unit33(first application result) with an actually measured electron beam application result (second application result).

The optical condition correcting unit35corrects the optical condition on the basis of the comparison result between the first application result and the second application result from the comparator34. The optical condition correcting unit35corrects, for example, the optical condition stored in an optical condition storage section43. That is, the optical condition correction is made on the optical condition related to the last electron beam application.

In addition to these processes, the computing unit31performs a process of displaying the estimated electron beam application result, the measured electron beam application result, and a netlist identified for the sample23(hereinafter, also referred to as “estimated netlist”), a process of generating an inspection image (SEM image or the like) of the sample23on the basis of the detection signal, measuring the size of the sample23, and measuring the electrical characteristics of the sample23, and the like.

The computing unit31may be implemented with a program executed by a processor such as a CPU, as in the controller11, or alternatively, may be configured by an FPGA, an ASIC, or the like.

The storage device41includes a database42, an optical condition storage section43, a to-be-used-in-computation netlist storage section44, an electron beam application result storage section45, and an estimated application result storage section46. The database42stores to-be-used-in-calculation device models (for example, DM1and DM2) and optical conditions (for example, LC1and LC2) used in generation of the to-be-used-in-computation netlist. Note that the to-be-used-in-calculation device model includes a model representing a defect in a sample.

A user may operate the input and output part50to register the to-be-used-in-calculation device models and the optical conditions, or alternatively, the computer30may be connected to an external device to receive the to-be-used-in-calculation device models from the external device. The database42stores the to-be-used-in-calculation device models and the optical conditions, for example, in the form of a look up table (LUT).

FIG. 4is a diagram showing an example of the to-be-used-in-calculation device model stored in the database. A unique ID42a(for example, DM1and DM2) is assigned to each of to-be-used-in-calculation device models, and each of the to-be-used-in-calculation device models is identified by the ID42a. The database42stores the to-be-used-in-calculation device model for use in inspection of the sample23and the to-be-used-in-calculation device model corresponding to the correction sample24.

Each of the to-be-used-in-calculation device models includes pieces of information such as a model42b, a mathematical expression42c, a parameter type42d, a parameter value42e, and other data42f. Note that, in each of the to-be-used-in-calculation device models, only some of the pieces of information may be defined.

The model42bis information that defines a circuit of the device. Information defining a circuit such as an RC parallel circuit is registered as the model42b. This circuit may be a model representing an accurate circuit configuration or a model representing an equivalent circuit. Alternatively, a waveform model of the device or the like may be registered as the model42b. The mathematical expression42cincludes information that defines electrical characteristics or the like of the device that cannot be expressed by the circuit. The mathematical expression42cmay be an expression that represents a time-series change in electrical characteristics or the like. The parameter type42dis information that defines a type of circuit element included in the device, such as resistance (R) or capacitance (C). The parameter value42eis associated with each element of the parameter type42dand is information that defines a value of the circuit element associated with the parameter type42d. For example, when the resistance (R) and the capacitance (C) are registered as the parameter types, their respective parameter values are a resistance value and a capacitance value. The other data42fincludes information such as a shape of the device or physical properties of the device.

FIG. 5is a diagram showing the optical condition stored in the database. A unique ID42g(for example, LC1and LC2) is assigned to each of the optical conditions, and each of the optical conditions is identified by the ID42g. Each of the optical conditions includes pieces of information such as application energy42h, an application current42i, a scan condition42j, a parameter value42k, and other data42l. Note that, in each of the optical conditions, only some of the pieces of information may be defined. Note that a reference optical condition for use in correction of the optical condition applied to the correction sample24may be separately stored in the database.

The application energy42his information that defines energy of the charged electron beam applied to the sample. The application energy includes, for example, an electron accelerating voltage or retarding voltage. Herein, the retarding voltage refers to a voltage that decelerates the electron beam (charged particle beam) immediately before the sample by applying the voltage to the sample. The application current42iis information that defines the current of the electron beam. The application current may also be referred to as a probe current.

The scan condition42jis information that defines an electron beam application method. The scan condition42jincludes, for example, pieces of information such as a scan speed (scanning speed) and a scanning interval. The parameter value42kis information that defines a parameter associated with the application of the electron beam. The parameter value42kincludes, for example, pieces of information such as a magnification, an aperture angle, and a working distance. The other data421includes the other pieces of information associated with a corresponding optical condition. Further, the other data421may include an electron beam pulse conversion condition (modulation condition). The electron beam pulse conversion condition includes, for example, a pulse width, a duty cycle, a frequency, any pattern in which the pulse width and the duty cycle change with time, and the like.

Note that the optical condition may be referred to as an electron optical condition, for example.

The optical condition storage section43stores a selected electron beam optical condition or an optical condition corrected by the optical condition correcting unit35. Note that the optical condition stored in the optical condition storage section43may be the above-described reference optical condition or an optical condition that results from correcting the reference optical condition.

The to-be-used-in-computation netlist storage section44stores the to-be-used-in-computation netlist generated by the to-be-used-in-computation netlist generator32. The electron beam application result storage section45stores the electron beam application result of the sample23actually measured on the basis of the detection signal output from the detector25. The electron beam application result stored in the electron beam application result storage section45may be the detection signal output from the detector25, the SEM image manipulate on the basis of the detection signal, or the like. The estimated application result storage section46stores the electron beam application result of the sample23or correction sample24estimated by the electron beam application result estimation computing unit33.

The storage device41is configured by, for example, a non-volatile memory such as a flash memory. Further, some of the storage sections included in the storage device41may be configured by a volatile memory such as a dynamic random access memory (DRAM) or a static random access memory (SRAM). Each of the storage sections included in the storage device41may be provided as a separate device, or alternatively, as a separate storage area defined in one storage device.

<Input and Output Part>

The input and output part50is a functional block responsible for operations on the charged particle beam apparatus1, selection of the to-be-used-in-calculation device model or optical condition, display of the electron beam application result and estimated application result of the sample23, and the estimated netlist, and the like. The input and output part50includes a display60of, for example, a touch screen type. On the display60, for example, an operation panel of the charged particle beam apparatus1, a selection section51for use in selection of the to-be-used-in-calculation device model or optical condition, an estimated netlist52, an estimated application result53, an electron beam application result54, and the like are displayed.

Next, an optical condition correction method will be described. According to the present embodiment, the optical condition is corrected using the correction sample24.FIG. 6is a flowchart showing an example of the optical condition correction method according to the first embodiment of the present invention. InFIG. 6, the optical condition is corrected in steps S10to S120.

Once the optical condition correction process is initiated, the user selects a to-be-used-in-calculation device model (step S10).FIG. 7is a diagram showing an example of a to-be-used-in-calculation device model selection screen. On the to-be-used-in-calculation device model selection screen61shown inFIG. 7, for example, a list61aof the to-be-used-in-calculation device models registered in the database42and a selection determination button61eare displayed. The list61aincludes an ID display field61bof each of the registered to-be-used-in-calculation device model, a to-be-used-in-calculation device model selection field61c, and a details display field61dof a corresponding to-be-used-in-calculation device model.

Herein, from the to-be-used-in-calculation device model selection screen61displayed on the display60, a to-be-used-in-calculation device model for the correction sample is selected. Specifically, the user checks a check box corresponding to a to-be-used-in-calculation device model to be selected, and then touches the selection determination button61eto finalize the selection of the to-be-used-in-calculation device model.FIG. 7shows a case where a to-be-used-in-calculation device model for the correction sample assigned the ID “DMC1” is selected. The to-be-used-in-calculation device model thus selected is sent to the to-be-used-in-computation netlist generator32shown inFIG. 2.

In step S10, an optical condition is also selected.FIG. 8is a diagram showing an example of an optical condition selection screen. On the optical condition selection screen62shown inFIG. 8, for example, a list62aof the optical conditions registered in the database42and a selection determination button62eare displayed. The list62aincludes an ID display field62bof each of the registered optical condition, an optical condition selection field62c, and a details display field62dof a corresponding optical condition.

The user selects a desired optical condition from the optical condition selection screen62displayed on the display60. More specifically, the user checks a checkbox corresponding an optical condition to be selected, and then touches the selection determination button62eto finalize the selection of the optical condition.FIG. 8shows a case where an optical condition assigned the ID “LC2” is selected. Note that the reference optical condition described above may be selected as the optical condition. The optical condition thus selected is stored in the optical condition storage section43shown inFIG. 2.

Note that, in step S10, when the selection determination button61eis touched to finalize the selection of the to-be-used-in-calculation device model, the optical condition selection screen62may be displayed after the to-be-used-in-calculation device model selection screen61is deleted. Further, when the selection of the to-be-used-in-calculation device model is finalized, the optical condition selection screen62may be displayed superimposed on the to-be-used-in-calculation device model selection screen61. The optical condition selection screen62may be provided with a button that causes the to-be-used-in-calculation device model selection screen61to be displayed again.

Further, in the optical condition selection, the electron beam pulse conversion condition may also be selected, as necessary. Further, the electron beam pulse conversion condition may be used together with the optical condition, or the electron beam pulse conversion condition alone may be set as the optical condition. Note that the optical condition may be selected and stored in the optical condition storage section43before step S40to be described later.

In step S20, a to-be-used-in-computation netlist is generated on the basis of the to-be-used-in-calculation device model selected by the user. For example, the to-be-used-in-computation netlist generator32combines any of the model42b, the parameter type42d, the shape of the device, or the physical properties of the device and the parameter value42eincluded in the selected to-be-used-in-calculation device model to generate the to-be-used-in-computation netlist. Note that the to-be-used-in-computation netlist generation method is not limited to the above method.

In step S30, the to-be-used-in-computation netlist generated in step S20is stored in the to-be-used-in-computation netlist storage section44. Note that step S20and step S30are separately shown inFIG. 6, but the process of step S30may be executed in step S20.

In step S40, an electron beam application result is estimated. The electron beam application result estimation computing unit33estimates the electron beam application result of the correction sample24on the basis of the to-be-used-in-computation netlist stored in the to-be-used-in-computation netlist storage section44and the optical condition stored in the optical condition storage section43. The electron beam application result to be estimated here corresponds to an application result in step S80, that is, for example, the detection signal (signal waveform) output from the detector25, an electrical charge, the inspection image, brightness of the inspection image, brightness of each pixel of the inspection image, or the like.

In step S50, the electron beam application result estimated in step S40is stored in the estimated application result storage section46.

In step S60, the optical condition is set. Note that, inFIG. 6, the optical condition is selected and set before the estimation of the electron beam application result in step S40. Therefore, no particular process is executed in step S60of a first time. That is, in step S60, the optical condition corrected in step S120to be described later is stored and set.

In step S70, the electron beam is applied to the correction sample24under the optical condition selected in step S10or the like. The optical condition stored in the optical condition storage section43is sent to the controller11of the charged particle beam apparatus main body10. The controller11controls each component of the charged particle beam optical system BS to apply the electron beam to the correction sample24under the optical condition thus received. When the electron beam is applied to the correction sample24, the secondary electrons are emitted from the correction sample24. When detecting the secondary electrons emitted from the correction sample24, the detector25outputs a predetermined detection signal in accordance with the number of the secondary electrons, energy, or the like to the computer30(computing unit31).

In step S80, an actual electron beam application result of the correction sample24is stored. The computing unit31may store, for example, the detection signal (signal waveform) output from the detector25in the electron beam application result storage section45as the electron beam application result. Further, the computing unit31may generate an inspection image (SEM image or the like) on the basis of the detection signal and store the inspection image in the electron beam application result storage section45as the electron beam application result. Further, the computing unit31may measure an electrical charge carried by the correction sample24on the basis of the detection signal and store the electrical charge thus measured in the electron beam application result storage section45. Further, the computing unit31may detect brightness of the inspection image or brightness of each pixel of the inspection image and store the brightness thus detected in the electron beam application result storage section45.

In step S90, the actual electron beam application result of the correction sample24and the estimated electron beam application result are compared. The comparator34compares the actual electron beam application result and the estimated electron beam application result for each item of the electron beam application result. The comparator34compares the detection signals for each electron beam application region or each pixel of the inspection image, for example. The comparator34also compares, for example, the electrical charge, the inspection image, the brightness of the inspection image, the brightness of each pixel of the inspection image, and the like. The comparator34, for example, digitizes these application results and calculates a difference between the actual electron beam application result and the estimated electron beam application result for each item to generate a comparison result. Note that the comparator34may compare all of these items, or may compare only some of the items.

In step S100, a determination is made as to whether the actual electron beam application result of the correction sample24and the estimated electron beam application result coincide with each other on the basis of the comparison result calculated in step S90. For example, when a value of the comparison result is “0”, the comparator34determines that these application results coincide with each other. On the other hand, when the value of the comparison result is not “0”, the comparator34determines that these comparison results differs from each other. Note that, in practice, these application results rarely coincide with each other; therefore, it is necessary to take a measurement error within a predetermined range into account.

This allows the comparator34to determine that the application results coincide with each other when the value of the comparison result is equal to or less than a predetermined threshold. The predetermined threshold is defined for each item. Note that when the comparison is made for a plurality of items, the comparator34may determine that these application results coincide with each other only when the comparison results for all the items are equal to or less than the respective thresholds, or alternatively, may determine that these application results coincide with each other when the comparison results for at least a predetermined number of items are equal to or less than the respective thresholds.

When the comparator34determines in step S100that these electron beam application results differ from each other (No), the process of step S110is executed.

In step S110, the optical condition is corrected. The comparator34sends, for example, the comparison result to the optical condition correcting unit35, and the optical condition correcting unit35corrects the optical condition. The optical condition correcting unit35reads, for example, the optical condition stored in the optical condition storage section43, and corrects the optical condition thus read on the basis of the comparison result.

For example, the optical condition correcting unit35corrects the optical condition by changing a condition of each item of the set optical condition within a predetermined range in accordance with the comparison result. Further, the optical condition correcting unit35may predetermine an item whose condition is changeable from among the items of the optical condition and correct the optical condition by changing the condition only of the changeable item. This allows the user to easily grasp an influence on the comparison result between the electron beam application results before and after correction and to thereby correct the optical condition in a short time.

Further, the optical condition correcting unit35may correct the optical condition on the basis of a comparison result between the electron beam application results for each of the plurality of items. This makes it possible to increase accuracy in correction of the optical condition. Further, the optical condition correcting unit35may correct the optical condition on the basis of the electron beam application result for each of the plurality of elements. This makes it possible to increase accuracy in correction of the optical condition.

The optical condition thus corrected is stored in the optical condition storage section43(step S60). Under the corrected optical condition, the electron beam is applied to the correction sample24again (step S70), and the actual electron beam application result of the correction sample24is stored again (step S80). Then, the electron beam application result estimated using the optical condition before correction and the actual electron beam application result under the optical condition after correction are compared again (step S90). The processes of steps S60to S110are repeatedly executed until the estimated electron beam application result and the actual electron beam application result coincide with each other.

As described above, according to the present embodiment, the electron beam application result is estimated using the optical condition before correction. In other words, assuming that the estimated result based on the optical condition before correction is correct, the optical condition for the apparatus is corrected.

To put it simply, it is conceivable that the electron beam application result estimated on the basis of the to-be-used-in-computation netlist based on the to-be-used-in-calculation device model and the optical condition before correction will be the same even with any apparatus. On the other hand, even when the electron beam is applied to the correction sample24under the same optical condition, an error may occur in the electron beam application result between apparatuses. Therefore, correcting the optical condition on the basis of the estimated result considered to be invariable between apparatuses so as to cause the actual electron beam application result to coincide with the estimated result makes it is possible to reduce the machine difference between a plurality of apparatuses.

On the other hand, in step S100, when the comparator34determines that these electron beam application results coincide with each other (Yes), the process of step S120is executed. In step S120, the optical condition stored in the database42is updated. For example, when receiving, from the comparator34, the comparison result indicating that the actual electron beam application result of the correction sample24and the estimated electron beam application result coincide with each other, the optical condition correcting unit35determines that the correction of the optical condition has been completed, and then sends the optical condition after correction stored in the optical condition storage section43to the database42to store the optical condition in the database42with the optical condition after correction associated with the optical condition before correction.

Alternatively, the optical condition correcting unit35(another block of the computing unit31) may compare the optical conditions before and after correction, calculate an optical condition correction coefficient for each item, and store the optical condition correction coefficient in the database42with the optical condition correction coefficient associated with the optical condition before correction stored in the database42. In this case, the optical condition correction coefficient thus calculated may be stored as the other data421of a corresponding optical condition, for example. Then, when the updated optical condition is used, the value of each item of the optical condition is converted into a value based on the optical condition correction coefficient.

According to the present embodiment, the optical condition correction process may be executed on each optical condition stored in the database42.

When the optical condition has been corrected, the updated optical condition and the optical condition correction coefficient may be displayed on the display60. Note that processes such as the generation of the to-be-used-in-computation netlist, the measurement through the application of the electron beam, and the estimation of the electron beam application result have been described in order with reference toFIG. 6, but these processes may be executed in parallel. For example, the measurement of the actual electron beam application result through the application of the electron beam may be executed at the same time as the generation of the to-be-used-in-computation netlist and the estimation of the electron beam application result.

Further, artificial intelligence (AI) based on a method such as machine learning or deep learning may be applied to processes such as the estimation of the electron beam application result in step S40, the correction of the optical condition in step S110, and the like.

<Circuit Estimation Method for Sample>

Next, a circuit estimation method for the sample23will be described. Herein, it is assumed that the correction process on each optical condition has already been completed. In the circuit estimation for the sample23, a step having the same process as the optical condition correction is provided. Therefore, some description of the circuit estimation will be omitted below as appropriate.FIG. 9is a flowchart showing an example of the circuit estimation method for the sample. InFIG. 9, the circuit estimation for the sample is made in steps S210to S330.

Once the circuit estimation process is initiated, a to-be-used-in-calculation device model is selected (step S210). The process of step S210is the same as step S10shown inFIG. 6. The to-be-used-in-calculation device model is selected, for example, through the above-described to-be-used-in-calculation device model selection screen61shown inFIG. 7. The to-be-used-in-calculation device model thus selected is sent to the to-be-used-in-computation netlist generator32shown inFIG. 2.

In step S220, the to-be-used-in-computation netlist generator32generates a to-be-used-in-computation netlist on the basis of the to-be-used-in-calculation device model selected by the user. The process of step S220is the same as step S20shown inFIG. 6.

In step S230, an optical condition is selected. The process of step S230is the same as step S10shown inFIG. 6. The optical condition is selected, for example, through the above-described optical condition selection screen62shown inFIG. 8. The optical condition thus selected is stored in the optical condition storage section43shown inFIG. 2. Further, the optical condition may be set together with the electron beam pulse conversion condition, as necessary.

In step S240, the electron beam is applied to the sample23under the optical condition selected in step S230. The process of step S240is the same as step S70shown inFIG. 6. When detecting the secondary electrons emitted from the sample23, the detector25outputs a predetermined detection signal in accordance with the number of the secondary electrons, energy, or the like to the computer30(computing unit31).

In step S250, an actual electron beam application result of the sample23is stored. The process of step S250is the same as step S80shown inFIG. 6. The electron beam application result corresponds to, for example, the detection signal, the electrical charge, the inspection image, the brightness of the inspection image, the brightness of each pixel, or the like.

In step S260, the to-be-used-in-computation netlist generated in step S220is stored in the to-be-used-in-computation netlist storage section44. Note that step S220and step S260are separately shown inFIG. 9, but the process of step S260may be executed in step S220.

In step S270, an electron beam application result is estimated. The process of step S270is the same as step S40shown inFIG. 6.

In step S280, the electron beam application result estimated in step S270is stored in the estimated application result storage section46. The process of step S280is the same as step S50shown inFIG. 6.

In step S290, the actual electron beam application result and the estimated electron beam application result are compared. The process of step S290is the same as step S90shown inFIG. 6.

In step S300, a determination is made as to whether the actual electron beam application result and the estimated electron beam application result coincide with each other on the basis of the comparison result calculated in step S290. The process of step S300is the same as step S100shown inFIG. 6. When the comparator34determines in step S200that these electron beam application results differ from each other (No), the process of step S310is executed.

In step S310, the to-be-used-in-computation netlist is updated. The comparator34sends the comparison result to the to-be-used-in-computation netlist generator32, and the to-be-used-in-computation netlist generator32updates the to-be-used-in-computation netlist, for example. The to-be-used-in-computation netlist generator32changes, on the basis of the comparison result, a parameter value used in generation of the last to-be-used-in-computation netlist, and generates a to-be-used-in-computation netlist using the parameter value thus changed, for example. As described above, the to-be-used-in-computation netlist generator32updates the to-be-used-in-computation netlist. At this time, the to-be-used-in-computation netlist generator32may change the parameter value on the basis of the comparison results for a plurality of items. Further, the to-be-used-in-computation netlist generator32may preset a parameter whose parameter value is variable and update the to-be-used-in-computation netlist while changing the parameter value of only such a variable parameter.

The to-be-used-in-computation netlist thus updated is stored in the to-be-used-in-computation netlist storage section44(step S260). The electron beam application result is estimated again using the updated to-be-used-in-computation netlist and the optical condition (step S270), and the estimated electron beam application result is stored in the estimated application result storage section46(step S280). Then, the electron beam application result estimated using the updated to-be-used-in-computation netlist and the actual electron beam application result are compared again (step S290).

The processes of steps S260to S310are repeatedly executed until the estimated electron beam application result and the actual electron beam application result coincide with each other. Note that the to-be-used-in-computation netlist may be updated in the to-be-used-in-computation netlist storage section44. In this case, the processes of steps S270to S310are repeatedly executed until the estimated electron beam application result and the actual electron beam application result coincide with each other.

On the other hand, in step S300, when the comparator34determines that these electron beam application results coincide with each other (Yes), the process of step S320is executed. In step S320, the computing unit31(comparator34) determines that the to-be-used-in-computation netlist stored in the to-be-used-in-computation netlist storage section44can be identified as a netlist describing the circuit of the sample23, and stores this to-be-used-in-computation netlist in the estimated netlist storage section47as an estimated netlist. Further, in addition to the estimated netlist, a correspondence table that associates a position of a plug electrode in the inspection image with each node in the estimated netlist may be stored in the estimated netlist storage section47.

In step S330, the estimation result and measurement result are output to the input and output part50. For example, the estimated netlist stored in the estimated netlist storage section47, the estimated electron beam application result stored in the estimated application result storage section46, the actual electron beam application result stored in the electron beam application result storage section45are output to the input and output part50and displayed on the display60.

FIG. 10is a diagram showing an example of a result display screen after circuit estimation. As shown inFIG. 10, a to-be-used-in-calculation device model designation section71, an estimated result display section72, an estimated electron beam application result display section73, and an electron beam application result display section74are each displayed as a result display screen70.

In the to-be-used-in-calculation device model designation section71, details of the selected to-be-used-in-calculation device model, the selected optical condition, and the like are displayed. For example, the user can confirm the details of the selected to-be-used-in-calculation device model and optical condition by touching the to-be-used-in-calculation device model designation section71. In the estimated result display section72, each parameter value used in generation of the estimated netlist is displayed. Further, in the estimated result display section72, information on whether the parameter is variable may be displayed together with the parameter value. Note that the optical condition correction result or the optical condition correction coefficient may be displayed on the estimated result display section72or the like.

In the estimated electron beam application result display section73, the estimated electron beam application result is displayed. In the estimated electron beam application result display section73, a graph in which the horizontal axis represents the electron beam application condition (optical condition), and the vertical axis represents the brightness (brightness) is displayed. Specifically, in the estimated electron beam application result display section73, electron beam application results estimated for a plurality of nodes (plug electrodes) are displayed. Note that, in the estimated electron beam application result display section73, not only the estimated result using the estimated netlist but also the estimated result using the to-be-used-in-computation netlist before being identified may be displayed.

In the electron beam application result display section74, the actually measured electron beam application result is displayed. In the electron beam application result display section74, a graph in which the horizontal axis represents the electron beam application condition and the vertical axis represents the brightness is displayed in the same manner. In the electron beam application result display section74, electron beam application results for a plurality of nodes are displayed.

Note that the graphs displayed in the estimated electron beam application result display section73and the electron beam application result display section74can be configured as desired. For example, a graph in which the vertical axis represents the amount of detected secondary electrons may be displayed. Further, in each of the estimated electron beam application result display section73and the electron beam application result display section74, the waveform of the detection signal, the inspection image, and the like may be displayed.

Further, the estimated electron beam application result display section73and the electron beam application result display section74may be combined such that the estimated result and the measured result are displayed together.

FIGS. 11A to 11Care diagrams showing another example of the result display screen after circuit estimation. In the result display screen70, not only the sections shown inFIG. 10, but also images shown inFIGS. 11A to 11Cmay be displayed, for example.FIG. 11Ais an image representing an inspection image in which coordinates of plug electrodes are additionally illustrated.FIG. 11Bis an estimated netlist.FIG. 11Cis a correspondence table that associates each of the positions of the plug electrode in the inspection image with a corresponding node in the estimated netlist. Further, a circuit diagram based on the estimated netlist may be displayed in the result display screen70.

Note that processes such as the generation of the to-be-used-in-computation netlist, the measurement through the application of the electron beam, and the estimation of the electron beam application result have been described in order with reference toFIG. 9, but these processes may be executed in parallel. For example, the measurement through application of the electron beam may be executed at the same time as the generation of the to-be-used-in-computation netlist and the estimation of the electron beam application result.

Further, AI based on a method such as machine learning or deep learning may be applied to processes such as the estimation of the electron beam application result in step S270, the update on the to-be-used-in-computation netlist in step S310, and the like.

<Main Effects of the Present Embodiment>

According to the present embodiment, the optical condition is corrected on the basis of a comparison between the estimated electron beam application result of the correction sample24and the electron beam application result when the electron beam is actually applied to the correction sample24. This configuration makes it possible to reduce an error in the electron beam application result of the sample23or correction sample24between apparatuses, that is, the machine difference.

Further, according to the present embodiment, the computing unit31corrects the optical condition by changing a condition of each item of the optical condition within a predetermined range in accordance with the comparison result between the first application result and the second application result. This configuration makes it possible to suitably correct the optical condition and to thereby shorten a time required until the optical condition is updated.

Further, according to the present embodiment, the computing unit31predetermines a changeable item from among the items of the optical condition, and corrects the optical condition by changing only the condition of the changeable item. This configuration makes it possible to reduce the number of items whose conditions are changeable and to thereby shorten a time required until the optical condition is updated. This configuration further makes it possible to determine the optical condition that affects a difference between the electron beam application results and to thereby efficiently correct and update the optical condition.

Further, according to the present embodiment, the correction sample24includes a plurality of elements, and the computing unit31corrects, for each of the plurality of elements, the optical condition on the basis of the first application result and the second application result. This configuration makes it possible to obtain more information for use in correction of the optical condition and to thereby increase accuracy in correction of the optical condition.

Further, according to the present embodiment, the computing unit31corrects a plurality of optical conditions. This configuration makes a plurality of optimized optical conditions available. Further, it is possible to measure the sample23in more detail.

Further, according to the present embodiment, the computing unit31stores, when the first application result and the second application result coincide with each other, the optical condition after correction in the database42with the optical condition after correction associated with the optical condition before correction stored in the database42. This configuration makes the optical conditions before and after correction available.

Further, according to the present embodiment, the computing unit31compares the optical condition before correction and the optical condition after correction to calculate an optical condition correction coefficient for each of the items, and stores the optical condition correction coefficient in the database42with the optical condition correction coefficient associated with the optical condition before correction. This configuration eliminates the need for separately storing the optical condition after correction and thereby makes it possible to reduce the amount of information stored in the database42.

Further, according to the present embodiment, the to-be-used-in-calculation device model includes a model representing a defect in the sample23. This configuration allows measurement of the sample23or correction sample24having a defect structure in the sample23. This makes it possible to easily detect a defect (manufacturing defect) in the sample23and to thereby increase accuracy in circuit estimation.

Further, according to the present embodiment, the to-be-used-in-computation netlist is generated on the basis of the to-be-used-in-calculation device model, and the electron beam application result when the electron beam is applied to the sample is estimated on the basis of the to-be-used-in-computation netlist and the optical condition. Further, the estimated electron beam application result is compared with the electron beam application result when the electron beam is applied to the sample23on the basis of the optical condition.

This configuration eliminates the need of converting an external netlist input from the outside into the to-be-used-in-computation netlist, and thereby allows the electrical characteristics of the sample23to be estimated in a short time, increasing the throughput. The configuration further allows the electrical characteristics and circuit of the sample23to be freely estimated without being affected by the configuration of the external netlist, and thereby allows the electrical characteristics to be estimated with consideration given to interactions between a plurality of devices.

Further, according to the present embodiment, when the estimated electron beam application result and the actual electron beam application result differ from each other, the to-be-used-in-calculation device model is updated. Specifically, the computing unit31updates the to-be-used-in-computation netlist by changing the parameter value included in the to-be-used-in-calculation device model and creating the to-be-used-in-computation netlist again using the changed parameter value. This configuration makes it possible to update the to-be-used-in-computation netlist while suppressing the computation amount and to thereby suppress a load on the computing unit31.

Further, according to the present embodiment, the electron beam application result includes any one of the detection signal, the inspection image based on the detection signal, the brightness of the inspection image, or the brightness of each pixel in the inspection image. This configuration makes it is possible to collate application results with various forms based on the detection signal.

Further, according to the present embodiment, the to-be-used-in-calculation device model includes any one of a model defining a circuit of a device, a mathematical expression defining electrical characteristics of the device, a shape of the device, or physical properties of the device. This configuration makes it possible to estimate the circuit of the sample23from not only the circuit configuration but also the electrical characteristics, the shape, the physical properties, and the like and to thereby increase accuracy in circuit estimation.

Further, according to the present embodiment, the computing unit31generates a correspondence table that associates the position of the plug electrode in the inspection image with each node in the identified to-be-used-in-computation netlist (estimated netlist). This configuration makes the correspondence between the netlist and the inspection image clear.

Further, according to the present embodiment, the electron beam application result is estimated on the basis of the optical condition and the pulse conversion condition. This configuration makes it is possible to increase accuracy in estimation of the electrical characteristics of the sample23with the electron beam that changes in a complicated manner.

Second Embodiment

Next, a second embodiment will be described. According to the present embodiment, as the correction sample24, an external sample23a(seeFIG. 1or the like) whose circuit or electrical characteristics are estimated by another charged particle beam apparatus.

The external sample23ais, for example, a wafer prepared in advance for use in apparatus maintenance. Further, the external sample23amay be, for example, a device of a level that can be shipped as a product, unlike the correction sample24that is primarily configured by a TEG or the like. It is assumed that characteristics such as the circuit or electrical characteristics of the external sample23ahave already been made clear by another charged particle beam apparatus or the like. Then, it is assumed that the database42has already stored a to-be-used-in-calculation device model corresponding to the external sample23a. Therefore, the present embodiment eliminates the need of the correction sample24shown inFIGS. 1 and 2and allows only the external sample23a(sample23) to be placed in the sample chamber10B.

FIG. 12is a flowchart showing an example of the optical condition correction method according to the second embodiment of the present invention.FIG. 12is similar toFIG. 6but is different fromFIG. 6only in that the sample for which the optical condition is corrected is the external sample23arather than the correction sample24. Therefore, the same reference numerals as shown inFIG. 6are applied to each step shown inFIG. 12.

In step S10, the to-be-used-in-calculation device model corresponding to the external sample23ais selected. Note that the method for selecting the to-be-used-in-calculation device model or the optical condition is the same as in the first embodiment. In step S40, the electron beam application result of the external sample23ais estimated. As described above, since the characteristics of the external sample23ahave already been made clear, the subsequent processes are executed on the assumption that an estimated result of the electron beam application result of the external sample23ais correct.

In step S70, the electron beam is applied to the external sample23aunder the selected optical condition. In step S90, the estimated result of the electron beam application result of the external sample23aand the actual electron beam application result are compared. When these electron beam application results differ from each other (No in step S100), the optical condition is corrected (step S110).

<Main Effects of the Present Embodiment>

According to the present embodiment, the following effects can be obtained in addition to the effects of the above-described embodiment. According to the present embodiment, the optical condition is corrected using the external sample23a. This configuration makes it possible to reduce a difference in the electron beam application result between apparatuses without preparing the correction sample24. Further, this configuration eliminates the need for managing the correction sample24.

Third Embodiment

Next, a third embodiment will be described. The correction sample24is usually left in the sample chamber10B, but its electrical characteristics may deteriorate with time. Therefore, in the present embodiment, a method of updating the to-be-used-in-calculation device model in a manner that depends on deterioration of the correction sample24will be described.

FIG. 13is a flowchart showing an example of a process of updating the to-be-used-in-calculation device model according to the third embodiment of the present invention.FIG. 13is similar toFIG. 9. InFIG. 13, the processes of steps S410to S530are executed. First, in step S410, a to-be-used-in-calculation device model corresponding to the correction sample24is selected. Step S410is the same as step S210shown inFIG. 9.

In step S420, an optical condition is selected. Note that it is preferable that the optical condition to be selected have already been corrected. Step S420is the same as step S230shown inFIG. 9. In step S430, the electron beam is applied to the correction sample24under the optical condition selected in step S420. Step S430is the same as step S240shown inFIG. 9. In step S440, an actual electron beam application result (third application result) of the correction sample24is stored. Step S440is the same as step S250shown inFIG. 9.

In step S450, a to-be-used-in-computation netlist is generated on the basis of the to-be-used-in-calculation device model selected in step S410. Step S450is the same as step S220shown inFIG. 9.

In step S460, the to-be-used-in-computation netlist generated in step S450is stored in the to-be-used-in-computation netlist storage section44. Step S460is the same as step S260shown inFIG. 9. In step S470, an electron beam application result is estimated. Step S470is the same as step S270shown inFIG. 9.

In step S480, the electron beam application result estimated in step S470is stored in the estimated application result storage section46. Step S480is the same as step S280shown inFIG. 9. In step S490, the actual electron beam application result and the estimated electron beam application result are compared. The process of step S490is the same as step S290shown inFIG. 9.

In step S500, a determination is made as to whether the actual electron beam application result and the estimated electron beam application result coincide with each other on the basis of the comparison result calculated in step S490. The process of step S500is the same as step S300shown inFIG. 9. When the comparator34determines in step S500that these electron beam application results differ from each other (No), the process of step S510is executed.

In step S510, the to-be-used-in-calculation device model corresponding to the correction sample24is updated. The computing unit31updates the to-be-used-in-calculation device model on the basis of the comparison result from the comparator34. The computing unit31may update the to-be-used-in-calculation device model by changing, for example, a model that defines a circuit of the device, a mathematical expression that defines electrical characteristics of the device, a shape of the device, and physical properties of the device, or alternatively, may update the to-be-used-in-calculation device model by changing the parameter value42eof each parameter type42d. The to-be-used-in-calculation device model may be updated, for example, by the to-be-used-in-computation netlist generator32or through direct access to the database42.

The processes of steps S450to S510are repeatedly executed until the estimated electron beam application result and the actual electron beam application result coincide with each other.

On the other hand, in step S500, when the comparator34determines that these electron beam application results coincide with each other (Yes), the process of step S520is executed. In step S520, the computing unit31(comparator34) determines that the to-be-used-in-computation netlist stored in the to-be-used-in-computation netlist storage section44can be identified as a netlist describing the circuit of the correction sample24and stores this to-be-used-in-computation netlist in the estimated netlist storage section47as an estimated netlist. Further, in addition to the estimated netlist, a correspondence table that associates a position of a plug electrode in the inspection image with each node in the estimated netlist may be stored in the estimated netlist storage section47. The process of step S520is the same as step S320shown inFIG. 9.

Further, in step S520, the to-be-used-in-calculation device model updated in step S510is stored in the database42. At this time, the to-be-used-in-calculation device model before update may remain stored in the database42.

In step S530, the estimation result and measurement result are output to the input and output part50. The process of step S530is the same as step S330shown inFIG. 9. Note that, on the display60, an image representing that the to-be-used-in-calculation device model has been updated may be displayed.

<Main Effects of the Present Embodiment>

According to the present embodiment, after the optical condition is corrected, the first application result is compared with the third application result when the charged particle beam is applied to the correction sample24under the optical condition. When the first application result and the third application result differ from each other, the to-be-used-in-calculation device model corresponding to the correction sample24is updated. This configuration makes it possible to facilitate the update on the to-be-used-in-calculation device model in a manner that depends on a degree of deterioration of the correction sample24. This makes the correction sample24usable for a long period of time.

Note that the present invention is not limited to the above-described embodiments and includes various modifications. Further, some of the components of one embodiment can be replaced with corresponding components of another embodiment, and a component of another embodiment can be added to the components of one embodiment. Further, it is possible to add different components to the components of each embodiment, delete some of the components of each embodiment, and replace some of the components of each embodiment with different components. Note that each member and relative size shown in the drawings have been simplified and idealized for easy understanding of the present invention, and the present invention may have a more complicated shape when being implemented.