Patent ID: 12196802

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the invention will be described. Although the drawings shown in the present embodiment show the specific embodiment of the invention, the drawings are for the purpose of understanding the invention, and are in no way to be used for limiting interpretation of the invention.

In a semiconductor inspection device according to the present embodiment, an electrical characteristic of a device or a material constituting the device is evaluated by an optical inspection. Therefore, a mechanism is provided for controlling an electric charge in a sample to be inspected and changing an electrical state of the sample. Since an optical characteristic of the sample also changes when the electrical state of the sample changes, it is possible to detect an abnormality in the electrical characteristic of the device or the material by grasping a change in the optical characteristic when the electrical state of the sample is changed. Specifically, in order to change the electrical state of the sample, the sample is irradiated with an electron beam.

Here, the term “electrical state” is used to broadly refer to a state of a sample, such as a potential, charge, or an electronic state, brought about by fluctuations in the electric charge in the sample due to irradiation on the sample with the electron beam. For example, when a semiconductor film made of Si or the like is irradiated with an electron beam, an electronic state of the semiconductor film changes. Since a semiconductor with a change in an electronic state also has a change in an optical characteristic, for example, a change in the electronic state of the semiconductor can be estimated based on a change in optical reflectance. A field of view for an optical inspection does not need to be made of a uniform material, and may include a device structure made of different materials. For example, when a plug (conductor) disposed in an insulating film is irradiated with an electron beam, the plug is charged and a potential of the plug generates an electric field around the plug (nm to μm), so that it is possible to inspect the electrical characteristic based on the optical characteristic of the sample in this range.

FIG.1shows a schematic configuration of a semiconductor inspection device1according to the present embodiment. The semiconductor inspection device1includes an electron beam device10, a computer30, and an input and output device40including a display, a keyboard, operation buttons, and the like.

The electron beam device10is provided with a lens barrel10A which embeds an electron optical system which generates an electron beam to be emitted to a sample23to be inspected in a sample chamber10B in which the sample23is accommodated, and a control unit11is disposed outside the lens barrel10A and sample chamber10B. In the lens barrel10A, an electron source12, a blanker15which pulses an electron beam, an aperture13which adjusts a current amount of electron beam irradiation, a deflector14which controls a trajectory of the electron beam, an objective lens16which focuses the electron beam on a sample surface, and the like are accommodated. These are examples of optical elements constituting the electron optical system, and the electron optical system also includes a condenser lens, a beam separator, and the like.

In the lens barrel10A, an electron detector25which detects a secondary electron emitted from the sample23by electron beam irradiation and outputs a detection signal based on the secondary electron is accommodated. The detection signal from the electron detector25is used for generation of a scanning electron microscopy (SEM) image, measurement of a size of the sample23, measurement of the electrical characteristic, and the like. Although the electron detector25which detects the secondary electron is shown here, an electron detector which detects a reflection electron (backscattered electron (BSE)) may be provided, or both of the electron detectors may be provided.

A stage21, the sample23, and the like are accommodated in the sample chamber10B. The sample23is placed on the stage21. The sample23is, for example, a semiconductor wafer including a plurality of semiconductor devices, or an individual semiconductor device. The stage21is provided with a stage drive mechanism (not shown), and a stage position is controlled by the control unit11according to an observation field of view.

A light source26, a light adjuster27, and a photodetector29are disposed in the sample chamber10B. The light source26provides light to irradiate the sample23, and includes, for example, a solid-state laser, a semiconductor device such as a light emitting diode (LED) or a laser diode (LD), or a white lamp. The light source26may include a plurality of types of light sources having different wavelengths. The light adjuster27is a functional block which adjusts an optical path of light such that the light emitted from the light source26is emitted to a predetermined region of the sample23. The light adjuster27preferably further has a function of modulating an intensity, polarization, and the like of the light emitted from the light source26. Signal light generated by the light with which the sample23is irradiated is detected by the photodetector29. The signal light to be detected includes reflected light, scattered light, diffracted light, and emitted light. According to the signal light to be detected, a photodetector29suitable for the detection can be used. A detection signal from the photodetector29is used to evaluate an electrical characteristic of the sample23.

The light source26and the light adjuster27constitute an optical system which irradiates the sample23with light for an optical inspection. All or a part of the optical elements constituting the optical system and the photodetector may be disposed outside the sample chamber10B, and light may be emitted to the sample23via a port in the sample chamber10B, or signal light may be detected by the photodetector29disposed outside the sample chamber10B.

The control unit11controls components of the electron beam device10. The control unit11performs operation control over the electron source12, the blanker15, the aperture13, the deflector14, the objective lens16, and the like based on observation conditions input from the computer30. The control unit11is implemented by a program executed by a processor such as a CPU. For example, the control unit11may include a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

An inspection by the semiconductor inspection device1, setting of measurement conditions and processing of detection signals obtained by the electron detector25and the photodetector29of the electron beam device10are executed by the computer30. The computer30includes a calculation unit31and a storage unit32. The storage unit32stores various databases required for condition setting and processing. The calculation unit31controls the electron beam device10via the control unit11while referring to user input data and databases input from the input and output device40, processes a detection signal, and displays a result on the input and output device40.

FIG.2shows a wafer (semiconductor sample)50as an example of a sample to be inspected. The wafer50is divided into mesh-shaped chip sections51of the same magnitude so that a large number of chips can be manufactured all at once, and each chip section is formed with the same pattern. After a previous process of forming elements such as transistors and wirings on the wafer50is completed, the wafer50is separated into chips for each chip section. Patterns of various materials constituting the semiconductor device are formed on the wafer50.FIG.2shows a pattern of one memory array52when the chip is a DRAM memory chip. The memory array52includes a region53in which capacitors are integrated, a region54in which word lines are integrated, and a region55in which bit lines are integrated. Each region is formed with a pattern formed by materials (insulators, semiconductors, conductors, and the like) for the region. The semiconductor inspection device1optically inspects, for each region, an electrical characteristic of a pattern or a semiconductor film formed in the region (first measurement mode).

InFIG.2, the wafer on which the memory chip is formed is shown as the sample to be inspected, but the sample to be inspected is not limited thereto. As long as the chip has a region in which a pattern made of the same material is formed, the chip may be, for example, a sensor chip or a test pattern (test element group) for inspection. Alternatively, the chip may be a wafer (or a part of the wafer) on which a uniform film having no pattern formed thereon is formed. Since a semiconductor device usually includes a stacked film having a plurality of different materials, when the wafer is inspected in an inline manner, depending on a removal process, materials for regions may be different, and further, materials for the same region may be different even in the same chip section. Depending on an inspection purpose, a region and an inspection specification for each region are determined.

FIG.3shows a state in which the region55is irradiated with an electron beam61and light62for an optical inspection (first measurement mode). In the optical inspection, since the electron beam61is emitted in order to change an electrical state of the sample, a spot diameter is large so as to be substantially equal to a spot diameter (1 μm to 1 mm) of the emitted light62. Generated signal light63is detected by the photodetector29.

An example of the inspection specification of the optical inspection will be described with reference toFIG.4. As described above, the signal light includes reflected light, scattered light, diffracted light, emitted light, and the like, and is selected according to the electrical state to be detected. The scattered light may be generated with a wavelength different from a wavelength of light from the light source, such as Raman scattered light. The wavelength of the light from the light source is not limited. In the optical inspection, presence or absence of an abnormality in an electrical characteristic of the pattern in the field of view is determined by comparing a detection signal from the photodetector when an electron beam is not emitted with a detection signal from the photodetector when an electron beam is emitted. The electrical characteristic is typically resistance, capacitance, a defect, and a carrier density, but is not limited thereto.

When a photodiode or a monochromator is used as the photodetector29, an intensity of signal light having a specific wavelength can be detected (a first stage (uppermost stage) inFIG.4). Here, an example is shown that in a case where signal light with an intensity of 010 mW is detected in a state without electron beam irradiation, it is determined that there is no abnormality when signal light with an intensity of 003 mW is detected, and it is determined that there is an abnormality when signal light with an intensity of 009 mW is detected in a state with electron beam irradiation. For example, in a case where the region constitutes a capacitor and an electric charge charged by the electron beam irradiation is lost due to a shape defect, when there is a defect, a signal light intensity in a state without the electron beam irradiation and a signal intensity in a state with the electron beam irradiation are substantially similar, and when there is no defect, a signal light intensity in a state without the electron beam irradiation and a signal intensity in a state with the electron beam irradiation are different depending on charge of the electric charge. Therefore, it is possible to perform abnormality detection based on the signal light intensity.

Signal light used for measurement, parameters to be detected by the photodetector (in addition to the intensity, a spectrum, an intensity distribution and the like described below), and abnormality determination methods based on the parameters are different depending on a material for a region to be inspected and an inspection specification determined according to the electrical characteristic to be detected.

When a spectrometer is used as the photodetector29, a spectrum of the signal light can be detected (second and third stages inFIG.4). In the second stage, an example in which an abnormality is detected by a change in a peak intensity of the spectrum is shown. Presence or absence of an abnormality can be detected by comparing a peak intensity of a spectrum71ain the state without electron beam irradiation with a peak intensity of a spectrum71b(71c) in the state with electron beam irradiation. In the third stage, an example in which an abnormality is detected by a shift amount of the spectrum is shown. Presence or absence of an abnormality can be detected by a shift amount between a spectrum72ain the state without electron beam irradiation and a spectrum72b(72c) in the state with electron beam irradiation.

When a multi-pixel optical sensor such as a CCD or a CMOS sensor is used as the photodetector29, the intensity distribution of the signal light can be detected (a fourth stage (lowermost stage) inFIG.4). In the fourth stage, an example in which an abnormality is detected by the intensity distribution of the signal light is shown. In this example, the intensity distribution of the signal light in which diffracted light appears on both sides of zero-order light in an x direction is observed. Presence or absence of an abnormality can be detected based on a characteristic of a two-dimensional pattern of the intensity distribution of the signal light, such as a magnitude of the diffracted light or a distance between the zero-order light and the diffracted light. The intensity distribution of the signal light to be detected may be an optical microscope image of the sample. In this case, a sample surface may be projected onto the multi-pixel optical sensor by an optical lens.

Instead of comparing a detection signal from the photodetector when the electron beam is not emitted with a detection signal from the photodetector when the electron beam is emitted, a difference between the detection signal when the electron beam is not emitted and the detection signal when the electron beam is emitted may be detected, and presence or absence of an abnormality may be determined based on a magnitude of the difference.

FIG.5shows a time chart of electron beam irradiation, light irradiation, and signal light detection in an optical inspection. An electron beam irradiation trigger81is a control signal from the control unit11to the blanker15, and indicates an irradiation period of the electron beam to the sample23. A cycle of the electron beam irradiation trigger81is on the order of Hz to MHz. A light irradiation trigger82is a control signal from the control unit11to the light source26or to the light adjuster27, and indicates an irradiation period of light to the sample23. In this example, irradiation light is continuous light. A signal light measurement trigger83is a control signal from the control unit11to the photodetector29, and indicates a detection period of signal light. The signal light measurement trigger83and the electron beam irradiation trigger81are synchronized with each other. It is possible to perform measurement in a state with electron beam irradiation by a signal light measurement trigger83awhich is ON during a period in which the electron beam irradiation trigger81is ON, and to perform measurement in a state without electron beam irradiation by a signal light measurement trigger83bwhich is ON during a period in which the electron beam irradiation trigger81is OFF. In order to improve an SN ratio of the measurement, it is effective to measure a measurement value a plurality of times and take an average value thereof. When the difference between a state in which the electron beam is not emitted and a state in which the electron beam is emitted is taken, accuracy can be improved by performing lock-in detection using a lock-in amplifier.

FIG.6shows a display example of a result of the optical inspection. The optical inspection is performed on a user-designated region in a user-designated chip section51on the wafer50. The optical inspection may be performed on all chip sections on the wafer50. When an electrical characteristic or an optical characteristic of a pattern in the region where the optical inspection is performed is out of an allowable range set by the user, it is determined that there is an abnormality, and is displayed as a wafer heat map90based on coordinates of a chip section determined to have the abnormality and a degree of deviation from the allowable range (abnormality degree) of the chip section. In the wafer heat map90, a chip section92is displayed in a wafer91, and a chip section determined to have the abnormality is displayed with a color corresponding to the abnormality degree, so that the chip section determined to have the abnormality and the abnormality degree thereof are displayed so as to be visually recognizable to the user. The user executes SEM measurement (second measurement mode) using an electron beam on the chip section determined to have the abnormality. In the SEM measurement, the user sets a specification of the SEM measurement by the electron beam based on the abnormality degree thereof.

FIG.7shows a state in which the region55is irradiated with an electron beam101and light102for the SEM measurement (second measurement mode). If only dimension measurement and shape evaluation for a pattern in the region55are performed, irradiation of the light102is unnecessary, but if the SEM measurement is performed in a state where an electrical state is controlled, such as a charging state in the pattern of the region55, the light102is emitted to an observation field of view as shown inFIG.7. In the SEM measurement, a spot diameter of the electron beam101is narrowed down to a small size, and the observation field of view is two-dimensionally scanned. A spot diameter of the light102is set to a size including the observation field of view two-dimensionally scanned by the electron beam101. A signal electron103generated by irradiation of the electron beam101is detected by the electron detector25, and an SEM image is formed based on a detection signal of the electron detector25. An electron beam condition (probe size, acceleration voltage, probe current, and the like) and a light condition (wavelength, polarization, intensity, and the like) in the SEM measurement are determined according to the abnormality degree detected in the optical inspection. For example, in a case where the electrical characteristic detected by the optical inspection is resistance, it is possible to optimize the obtained SEM image by reducing the probe current and reducing charging in a case where a high resistance abnormality is detected.

Thus, since electron beam conditions and light conditions to be used in the first measurement mode and the second measurement mode are different, the semiconductor inspection device performs measurement by switching to the corresponding conditions. In a configuration ofFIG.1, the electron source12is shared as an electron source for the optical inspection and an electron source for the SEM measurement, but an electron source for the optical inspection or a lens barrel including the electron source may be separately provided.

FIG.8shows a measurement flow in which an abnormality in the electrical characteristic of the sample is detected by the optical inspection (first measurement mode) by the semiconductor inspection device1, and the SEM measurement (second measurement mode) is performed on the region where the abnormality is detected.

First, calibration setting is performed (S01). As shown inFIG.3, in the optical inspection (first measurement mode), it is necessary to adjust irradiation positions of the light and the electron beam. Therefore, calibration is performed so that the light and the electron beam are emitted at any position on the wafer in a correct positional relation.FIG.9shows an example of an inspection and measurement calibration screen210which is a graphical user interface (GUI) for performing calibration setting. The inspection and measurement calibration screen210is provided with a setting file selection portion211, and can call calibration data stored in the storage unit32in past measurement. For example, a work load of the user can be reduced by utilizing past calibration data in a case where an inspection is performed on the same wafer with different electrical characteristics to be detected or in a case where the inspection is performed on the same wafer with different inspection regions.

The user selects several chip sections on the wafer for calibration. A chip section for calibration may be directly designated in a calibration coordinate list212, or may be designated on a wafer map213displayed on the screen. By pressing a calibration execution button220to execute alignment of the wafer, it is possible to irradiate any position on the wafer with light and an electron beam.

Subsequently, the user sets a region to be inspected in the chip section to be inspected. An SEM image of the chip section is displayed in an electron beam irradiation position image214, and the user adjusts an observation field of view so that an inspection region215is at a center of the SEM image. There are a plurality of electron beam irradiation methods, and a method selection is made from a selection frame223.FIG.9shows an example in which a method of fixed point irradiation of the sample with the electron beam shown inFIG.3is selected, but a scanning method or the like as described in a modification to be described later can be selected. By inputting a coordinate name of the inspection region215ato an input frame221and pressing a selection button216, an irradiation position is determined, and coordinates of the irradiation position are registered. The user can register a plurality of electron beam irradiation positions by displaying another region in the electron beam irradiation position image214. Similarly, with respect to setting of light irradiation position, a light irradiation position image217, which is an SEM image of the chip section, is displayed, and the light irradiation position is registered by inputting a coordinate name of an inspection region215bto an input frame222, and then pressing a selection button218. InFIG.3, the light and the electron beam are set to the same irradiation position, but it is also possible to inspect the electrical characteristic of the device by emitting the light and the electron beam to different positions as in a modification described later. Therefore, an electron beam irradiation position and a light irradiation position can be set independently. A method for setting the irradiation position shown inFIG.9is an example. For example, a low-magnification SEM image or an optical microscope image may be displayed in the electron beam irradiation position image214or the light irradiation position image217, and one or more irradiation positions may be designated on the SEM image or the optical microscope image. When the above setting is completed, a save button219is pressed to save set contents in the storage unit32.

Subsequently, the electron beam condition and the light condition of the optical inspection (first measurement mode) are set (S02).FIG.10Ashows an example of an inspection and measurement setting screen230which is a GUI for performing condition setting. Similarly to the inspection and measurement calibration screen210, a setting file selection portion231is provided, and inspection and measurement condition data stored in the storage unit32in past measurement can be called. The user sets an irradiation condition (first irradiation condition) in a light condition parameter column233and an electron beam condition parameter column234of an inspection parameter column232.

The condition setting of the optical inspection in steps S01and S02is ended, and the optical inspection (first measurement) is performed according to the set condition (S03).FIG.10Bshows an example of an operation screen (inspection and measurement screen)240for executing the optical inspection. An inspection and measurement screen240ashown inFIG.10Bshows a state in which a first tab241including an operation screen and a result display screen of the optical inspection is opened. An upper half of the first tab241is an operation screen, and the user designates a chip section to be inspected in an inspection chip section designation portion242. It is also possible to designate all chip sections on the wafer. Thereafter, by pressing an inspection execution button243, an optical inspection is executed on the designated chip section.

In the optical inspection, presence or absence of an abnormality in the designated chip section is determined, and an abnormality degree is calculated for at least coordinates (chip section) determined to be abnormal (S04). For example, a relation between the optical characteristic to be measured and an electrical characteristic of a measurement region may be stored in the storage unit32as a database and used for abnormality determination. For example, an amount of spectrum shift and a magnitude of a resistance value or a magnitude of a defect density are stored in a database, and the electrical characteristic such as a resistance value and a defect are obtained based on a measured amount of spectrum shift to determine the presence or absence of abnormality. Alternatively, the presence or absence of abnormality may be directly determined based on an optical characteristic of a semiconductor material such as a measured band gap and refractive index. A lower half of the first tab241on the inspection and measurement screen240ashown inFIG.10Bis the result display screen. An inspection result of the chip section designated by the inspection chip section designation portion242is displayed on an inspection result display portion244. This example shows an example in which electrical characteristic values are calculated and displayed regardless of whether the chip section is normal or abnormal. A wafer heat map245shown inFIG.6is also displayed. After checking a result of the optical inspection, the user presses a save button246to save the result of the optical inspection in the storage unit32.

The user sets the electron beam condition and the light condition in second measurement based on the abnormality degree (S05). In the condition setting, the user sets an irradiation condition (second irradiation condition) in an electron beam condition parameter column236and a light condition parameter column237of a measurement parameter column235in the inspection and measurement setting screen230(FIG.10A). The semiconductor inspection device1stores default values of measurement parameters to be set according to the abnormality degree or the electrical characteristic detected in the optical inspection in the storage unit32as a database in advance. An example of the database is shown inFIG.11. With a material for the region and under an acceleration voltage to be emitted, an electron beam current amount (probe current amount) used in the second measurement is stored according to the electrical characteristic (resistance value and the like) of the region calculated in the first measurement. The database may include a light condition used for a second measurement condition. The user can easily set appropriate parameters by referring to such a database.

The computer30switches a device condition of the electron beam device10to an electron beam condition and a light condition of SEM measurement (second measurement mode) set by the user (S06), and executes the SEM measurement on the chip section determined to have an abnormality in the optical inspection (S07). The user performs a detailed analysis on the abnormality detected in the optical inspection based on an SEM image.FIG.10Cshows an example of an operation screen (inspection and measurement screen)240for executing the SEM measurement. An inspection and measurement screen240bshown inFIG.10Cshows a state in which a second tab251including an operation screen and a result display screen of the SEM measurement is opened. An upper half of the second tab251is an operation screen, and the user calls result data of the optical inspection stored in the storage unit32from a result file selection portion252. Accordingly, an inspection result display portion253and the wafer heat map254corresponding to the inspection result display portion244and the wafer heat map245in the first tab241(FIG.10B) are displayed. By pressing a measurement execution button255, the SEM measurement is executed for the chip section determined to have an abnormality, and an SEM measurement result is displayed in a lower half of the second tab251on the inspection and measurement screen240b. The result display screen includes a measurement result display portion256. An optical inspection result of the same chip section as that in the inspection result display portion253is displayed in the measurement result display portion256. An SEM image257acquired by the SEM measurement is displayed by pointing a record in which an abnormality is detected in the optical inspection with a pointer. The SEM image257shown inFIG.10Cis an image of a region in which capacitors of a DRAM memory array shown inFIG.2are integrated. A dimension of a pattern is measured based on the SEM image of the chip section determined to have an abnormality in the optical inspection, it is determined that the abnormality is caused by a shape, and the SEM image and the measured dimension are stored as a measurement result. Alternatively, an SEM image is acquired by irradiation with light, it is determined based on a luminance value of the SEM image that the abnormality is caused by some kind of electrical characteristic, and an electrical characteristic value is stored as the measurement result. The SEM measurement result is stored in the storage unit32when a save button258is pressed.

Although the inspection of the electrical characteristic of the semiconductor device and the material by the semiconductor inspection device according to the present embodiment and a detailed inspection in the case where the abnormality in the electrical characteristic is detected have been described above, executable inspection and measurement are not limited to the above description. Hereinafter, modifications thereof will be described.

(First Modification)

In an example ofFIG.3, the electron beam and the light are emitted at the same irradiation position. In a first modification, an example in which electron beam and light are emitted at different irradiation positions will be described.FIG.12Ashows an example of a circuit of a device to be inspected. A circuit A132, a circuit B134, and a circuit C136have an external terminal131, an external terminal133, and an external terminal135, respectively. The circuit A132is coupled to the circuit B134, and the circuit B134is coupled to the circuit C136, thereby creating a relation of interdependence between the circuits.FIG.12Bshows a layout of a device on which the circuits inFIG.12Aare mounted.FIG.12Bshows a region A131ain which a plug (group) corresponding to the external terminal131is formed, a region B133ain which a plug (group) corresponding to the external terminal133is formed, and a region C135ain which a plug (group) corresponding to the external terminal135is formed. The circuits A to C are formed in layers positioned below layers shown inFIG.12B.

In the optical inspection (first measurement mode) of such a device, as shown inFIG.12B, the region131ais irradiated with an electron beam137, the region133ais irradiated with light138, and generated signal light139is detected. By charging the plug (group) in the region131ain this manner, an electrical state of the circuit B134is indirectly changed, and an electrical characteristic of circuit B134is measured in this state. Accordingly, dependency of the electrical characteristic of the circuit B134on the circuit A132can be grasped.

In this case, in the calibration setting step (S01, seeFIG.8), as shown inFIG.13, the electron beam irradiation position and the light irradiation position are set at different positions.FIG.13shows an example in which a plurality of electron beam irradiation positions are set (irradiation position coordinates of the electron beam and the light in each chip set in an electron beam condition and light condition setting step (S02) in the first measurement are indicated in parentheses), specifically, the electrical characteristic is measured by directly or indirectly changing the electrical state of the circuit B134by irradiating the regions A to C with electron beams. Thus, by registering a plurality of electron beam irradiation positions on the inspection and measurement calibration screen210inFIG.9, a plurality of types of inspections can be performed in each chip. Similarly, a plurality of light irradiation positions are registered, and a plurality of inspections in which the light irradiation positions are changed in the chip can be performed.

(Second Modification)

In the time chart shown inFIG.5, an example has been described in which a timing of the electron beam irradiation and the signal light detection is set to a predetermined constant cycle, and a magnitude of an electrical characteristic detected at the timing is measured in the optical inspection (first measurement mode). However, not only the magnitude of the electrical characteristic at a certain timing, but also a response characteristic of the electrical characteristic of the device, such as an electric charge retention capability of a capacitor, may be desired to be inspected. In such a case, the response characteristic of the electrical characteristic of the device can be measured by varying timings of the electron beam irradiation and the signal light detection.

A time chart inFIG.14Ais similar as the time chart inFIG.5, and a cycle of an electron beam irradiation trigger141, and a cycle of a signal light measurement trigger143awhich is ON during a period in which the electron beam irradiation trigger141is ON and a signal light measurement trigger143bwhich is ON during a period in which the electron beam irradiation trigger141is OFF are both T. In the optical inspection (first measurement), a difference between detection signals in a state with electron beam irradiation and in a state without electron beam irradiation is detected while the cycle T is modulated.

FIG.14Bshows a change in a detection signal difference depending on the cycle T. For example, in a cycle Ti in which the detection signal difference greatly changes, it can be determined that the electric charge charged in the device (capacitor) due to the electron beam irradiation in the above example is lost. Thus, the electrical characteristic measured in the optical inspection (first measurement) can include the response characteristic of the electrical characteristic.

FIG.15Ais another time chart of the second modification. In this example, the light source26is pulsed light, and a light irradiation trigger152and a signal light measurement trigger153which control light emission of the light source26are synchronized with an electron beam irradiation trigger151. It is possible to perform measurement in a state with electron beam irradiation by a light irradiation trigger152aand a signal light measurement trigger153awhich are ON during a period in which the electron beam irradiation trigger151is ON, and to perform measurement in a state without electron beam irradiation by a light irradiation trigger152band a signal light measurement trigger153bwhich are ON during a period in which the electron beam irradiation trigger151is OFF. In this example, a difference between the detection signals in the state with electron beam irradiation and the state without electron beam irradiation is detected while the delay time T between a timing at which the electron beam irradiation trigger151changes from ON to OFF and a timing at which the signal light measurement trigger153bchanges from ON to OFF is modulated.FIG.15Bshows a change in the detection signal difference depending on the delay time T. Similar toFIG.14B, the response characteristic of the electrical characteristic can be measured.

(Third Modification)

In the flowchart ofFIG.8, an example is described in which the electron beam condition and the light condition of the optical inspection (first measurement mode) are set by the user directly inputting a value on the inspection and measurement setting screen230. An optimum condition for the optical inspection varies depending on a structure and material of the sample. Therefore, in a third modification, in order to set the electron beam condition and the light condition of the optical inspection, preliminary measurement is performed on a region where the optical inspection is to be performed, and the electron beam condition and the light condition of the optical inspection are set based on a result of the preliminary measurement.

The preliminary measurement is SEM measurement similar to the second measurement in the present embodiment, and light irradiation may or may not be performed at the same time. For example, a dimension of the device can be calculated by the preliminary measurement, an amount of electric charge required for charging the device can be calculated, and an electron beam current amount in the first measurement can be calculated. Alternatively, a cycle of the electron beam irradiation in the first measurement can be calculated based on a time constant of the device calculated from the result of the preliminary measurement. Alternatively, an acceleration voltage of an electron beam in the first measurement can be calculated by determining whether the electric charge required for charging is positive or negative based on a charging state of the device calculated based on the result of the preliminary measurement.

(Fourth Modification)

In the irradiation of the sample with the electron beam and the light in the optical inspection (first measurement mode) shown inFIG.3, the irradiation spot diameter of the electron beam61on the sample is substantially equal to the spot diameter of the emitted light62. However, in this case, a region to be irradiated with the electron beam61cannot be freely determined. For example, when it is desired to irradiate the region55inFIG.3with an electron beam in a focusing way, it is difficult to form an irradiation spot of the electron beam61having a shape corresponding to the region55. In a fourth modification, a method for irradiating any region on the sample with the electron beam61without being restricted by the spot diameter will be described. An electron beam irradiation method and a light irradiation method in an optical inspection in the fourth modification will be described with reference toFIG.16. The irradiation method in the present modification is executed by selecting the scanning method in the selection frame223for selecting the electron beam irradiation method in the inspection and measurement calibration screen210shown inFIG.9.

FIG.16shows, as an example, a state in which the region133a(circuit B134) is irradiated with the electron beam137and the light138, and the region133ais optically inspected with respect to the device shown inFIGS.12A and12B. By selecting the scanning method for electron beam irradiation, a spot diameter of the electron beam137on the sample is made smaller than a spot diameter of the light138, and a region set in the electron beam irradiation position image214is two-dimensionally scanned with the electron beam137by the deflector14. By setting the electron beam irradiation position in the region133aand scanning the region with the electron beam, an irradiation region of the electron beam137can be set regardless of the spot diameter of the electron beam137.

Further, a region to be irradiated with the electron beam61may be freely set in the electron beam irradiation position image214on the inspection and measurement calibration screen210, and any region scanning method for scanning the set region with the electron beam61may be selectable from the selection frame223. A characteristic of the any region scanning method is that the region to be irradiated with the electron beam61can have any shape designated by the user. Scanning of the electron beam61is performed during a period in which the electron beam irradiation trigger81is ON inFIG.5. As described above, an electron beam irradiation region in the optical inspection (first measurement mode) can be freely set. In combination with the first modification, the scanning method may be applied for electron beam irradiation to an electron beam irradiation region different from a light irradiation region.

(Fifth Modification)

In the optical inspection (first measurement mode) in the embodiment, inspection of the entire light irradiation region is performed. In other words, the electrical characteristic inspected in the first measurement mode of the embodiment is an average characteristic in the entire light irradiation region. In contrast, in a fifth modification, an optical inspection with excellent spatial resolution is implemented by detecting distribution of electrical characteristics in the light irradiation region. The scanning method described in the fourth modification or any region scanning method is applied to the electron beam irradiation method in the present modification.

An optical inspection of the fifth modification will be described with reference to the example inFIG.16. It is assumed that the region133ais irradiated with the light138, the spot diameter of the electron beam137is made smaller than the spot diameter of the light138, and the region133ais scanned. A time chart of the fifth modification is shown inFIG.17. The time chart inFIG.17is similar to the time chart inFIG.5, and an X-direction electron beam scanning signal172and a Y-direction electron beam scanning signal173are added. The electron beam scanning signals172and173are control signals from the control unit11to the deflector14, so that the sample is two-dimensionally scanned with the electron beam137. The X-direction electron beam scanning signal172allows the electron beam137to perform scanning in an X direction, and the Y-direction electron beam scanning signal173allows a scanning position of the electron beam to move in a Y direction orthogonal to the X direction. In the time chart inFIG.17, scanning in the Y direction is continuously performed, while scanning in the X direction is performed during a period in which an electron beam irradiation trigger171is ON, and the region133ais scanned with the electron beam137in a line shape extending in the X direction within the period.

A signal light measurement trigger175and the electron beam irradiation trigger171are synchronized with each other. It is possible to perform measurement in a state with electron beam irradiation by a signal light measurement trigger175awhich is ON during a period in which the electron beam irradiation trigger171is ON, and to perform measurement in a state without electron beam irradiation by a signal light measurement trigger175bwhich is ON during a period in which the electron beam irradiation trigger171is OFF. Since the X-direction electron beam scanning signal172and the Y-direction electron beam scanning signal173indicate a position of the electron beam137emitted on the sample, imaging can be performed by two-dimensionally arranging detection signals from the photodetector in accordance with the electron beam scanning signals172and173. For example, when the detection signal is an intensity of signal light, a value of a pixel is the intensity of the signal light in a state where the scanning position of the electron beam is irradiated with the electron beam137at a timing of the signal light measurement trigger175a. Since a signal light intensity detected at a timing of the signal light measurement trigger175bis an intensity in a state without electron beam irradiation, an influence of the electron beam irradiation can be more easily detected by subtracting a signal intensity detected by the signal light measurement trigger175bas a background from a signal intensity detected by the signal light measurement trigger175a.

An image (schematic diagram) of the region133ainFIG.16obtained in this manner is shown inFIG.18. It is assumed that a region183in which a signal light intensity is significantly higher than a signal light intensity in a surrounding region182is observed in a part of an image181of the region133a. In this case, it can be determined that there is an abnormality in a shape or electrical characteristic of an inspected device or semiconductor film in the region183. Therefore, coordinates of the abnormal region183are stored in the storage unit32as a defective portion. SEM measurement, which is the second measurement mode, is performed for the stored coordinates (region183), and detailed measurement is performed on the electrical characteristic or the shape of the device. A pixel value of the image is not limited to the intensity of the signal light, and may be a numerical value of the amount of spectrum shift or the intensity distribution shown inFIG.4. Alternatively, the pixel value may be a numerical value of an optical characteristic such as a band gap and a refractive index, and an electrical characteristic such as resistance and a defect density. Thus, the spatial resolution in the optical inspection can be improved.

The invention has been described above with reference to the embodiment and the modifications. The embodiment and modifications described above may be modified in various ways without departing from the scope of the invention, and may be used in combination.

REFERENCE SIGNS LIST

1: semiconductor inspection device10: electron beam device10A: lens barrel10B: sample chamber11: control unit12: electron source13: aperture14: deflector15: blanker16: objective lens21: stage23: sample25: electron detector26: light source27: light adjuster29: photodetector30: computer31: calculation unit32: storage unit40: input and output device50: wafer51: chip section52: memory array53to55: region61: electron beam62: light63: signal light71,72: spectrum81,141,151,171: electron beam irradiation trigger82,142,152,174: light irradiation trigger83,143,153,175: signal light measurement trigger90: wafer heat map91: wafer92: chip section101: electron beam102: light103: signal electron131,133,135: external terminal132,134,136: circuit137: electron beam138: light139: signal light172: X-direction electron beam scanning signal173: Y-direction electron beam scanning signal181: image182,183: region210: inspection and measurement calibration screen211,121: setting file selection portion212: calibration coordinate list213: wafer map214: electron beam irradiation position image215: inspection region216,218: selection button217: light irradiation position image219,238,246,258: save button220: calibration execution button221,222: input frame223: selection frame230: inspection and measurement setting screen232: inspection parameter column233,237: light condition parameter column234,236: electron beam condition parameter column235: measurement parameter column240: inspection and measurement screen241: first tab242: inspection chip section designation portion243: inspection execution button244,253: inspection result display portion245,254: wafer heat map251: second tab252: result file selection portion255: measurement execution button256: measurement result display portion257: SEM image