Inspection apparatus and film quality inspection method

Abstract

In the present invention, film qualities of deposited semiconductor film, insulating film, and the like are inspected in a non-contact manner. This inspection device (1) for inspecting the film quality of a film formed on a sample (16) has: a charged particle source (12) for irradiating the sample with a charged particle beam (13); a first light source (21) for irradiating the sample with first light (26); a photodetection system for detecting signal light (28) generated when the sample is irradiated with the first light; a charge control electrode (17) for controlling an electric field on the sample, or a second light source (22) for irradiating the sample with second light (27); a control device (30) for modulating the sample's electronic state by using the charged particle source as well as the charge control electrode or the second light source; and a computer (31) for estimating the film quality of the film formed on the sample on the basis of a detection signal of signal light which has been modulated in accordance with the sample's modulated electronic state, the detection signal being output from the photodetection system.

Description

Inspection device and film quality inspection method

[0001] The present disclosure relates to an inspection device and a film quality inspection method using the same.

[0002] Patent Document 1 describes an SEM equipped with an ultraviolet light for static elimination. It is known that charge on an insulating film can be removed by irradiating it with ultraviolet light. Patent Document 2 describes an SEM equipped with a charge control electrode that controls the electric field on the sample. It is known that the amount of charge on a sample that is charged by electron beam irradiation can be controlled by controlling the voltage of the charge control electrode.

[0003] JP 2000-357483 A JP 2006-338881 A

[0004] DE Aspnes, “Third-Derivative Modulation Spectroscopy with Low-Field Electroreflectance” Surface Science 37 (1973) 418-442

[0005] In semiconductor devices, the quality of the semiconductor film and insulating film is important. For example, the performance of a transistor is greatly influenced by the properties of the gate insulating film and the properties of the interface between the gate insulating film and the adjacent layer. If defects exist in the insulating film or interface, charge accumulates in the defects when an electric field is applied during device operation, adversely affecting device operation. To inspect film quality that can cause problems during device operation, such as defects, it is effective to apply an electric field to the film under inspection, just as during device operation, and measure the change in its characteristics.

[0006] After a device is completed, its film quality can be inspected by an electrical property test that actually operates the device. However, inspections after completion cannot prevent defects from being built into the mass production process. Furthermore, in the development of semiconductor manufacturing processes, it is possible to measure film quality under an applied electric field by fabricating electrodes that sandwich the film to be inspected and applying a voltage between the electrodes, but fabricating the electrodes for this purpose is time-consuming and costly.

[0007] Therefore, in the mass production of semiconductor devices or in the development of semiconductor manufacturing processes, it is desirable to be able to inspect the quality of deposited semiconductor films, insulating films, and other films without contact. Here, "film quality" refers to the material properties exhibited by the deposited material, such as charges, distortions, and defects, or the state of the underlying substrate and interface. Furthermore, the films to be inspected in this invention broadly include films formed during the semiconductor device manufacturing process, regardless of the film manufacturing method or material. For example, films that have been processed by annealing or other processes after deposition, films obtained by thermally oxidizing a semiconductor substrate (thermal oxide films), and films formed by ion implantation into a semiconductor substrate are also subject to inspection. Furthermore, the term "material" includes both inorganic and organic materials.

[0008] An inspection device according to one aspect of the present invention is an inspection device for inspecting the quality of a film formed on a sample, and includes a charged particle source that irradiates the sample with a charged particle beam, a first light source that irradiates the sample with first light, an optical detection system that detects signal light generated when the first light is irradiated on the sample, a charge control electrode that controls the electric field on the sample or a second light source that irradiates the sample with second light, a control device that modulates the electronic state of the sample using the charged particle source, the charge control electrode, or the second light source, and a computer that estimates the quality of the film formed on the sample based on a detection signal of the signal light modulated in accordance with the modulation of the electronic state of the sample and output from the optical detection system.

[0009] A film quality inspection method according to one aspect of the present invention is a film quality inspection method for inspecting the film quality of a film formed on a sample, which involves irradiating the sample with a charged particle beam to charge the sample, modulating the electronic state of the sample, irradiating the sample with probe light, detecting signal light generated by irradiating the sample with the probe light, and estimating the film quality of the film formed on the sample based on the detection signal of the signal light modulated in accordance with the modulation of the electronic state of the sample.

[0010] It becomes possible to inspect, without contact, the quality of a film formed such as a semiconductor or insulating film. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0011] 1 is a schematic diagram of an inspection apparatus according to a first embodiment. FIG. 1 is an example of a control sequence for controlling the electronic state of a sample. FIG. 2 is an example of a control sequence for controlling the electronic state of a sample. FIG. 3 is an example of a control sequence for controlling the electronic state of a sample. FIG. 4 is an example of a detection signal spectrum. FIG. 5 is an example of a detection signal spectrum. FIG. 6 is an example of a data structure of a database for estimating film quality. FIG. 7 is a control flow for film quality inspection that can be estimated from the electric field dependency of a detection signal. FIG. 8 is a diagram showing a change in intensity of a detection signal when the applied voltage of a charge control electrode is swept. FIG. 9 is an example of a data structure of a database for estimating film quality obtained from the electric field dependency of a detection signal. FIG. 10 is an example of a display of results of a film quality inspection. FIG. 11 is an example of a setting and measurement screen (setting tab). FIG. 12 is an example of a setting and measurement screen (measurement tab). FIG. 13 is an example of a result output screen. FIG. 14 is a schematic diagram of an inspection apparatus according to a first modification. FIG. 15 is a diagram showing the relationship between the amount of signal electrons detected and the energy filter voltage. FIG. 16 is a schematic diagram of an inspection apparatus according to a second modification. FIG. 17 is a schematic diagram of an inspection apparatus according to a second embodiment. FIG. 18 is a schematic diagram of an inspection apparatus according to a third embodiment. FIG. 19 is a schematic diagram of an inspection apparatus according to a fourth embodiment.

[0012] Hereinafter, examples of the present invention will be described. The drawings shown in the examples show specific examples of the present invention, but these are for understanding the present invention and are not to be used to interpret the present invention in a limiting manner.

[0013] In the inspection device of this embodiment, film quality is evaluated by optical inspection. That is, as will be described later in detail, the material properties of the film are detected as the optical properties of the film, and information about the film quality is obtained from the detected optical properties. In this embodiment, during optical inspection, the electronic state of the sample to be inspected is modulated and controlled by controlling the charge of the film to be inspected and / or controlling the internal electric field by light irradiation.

[0014] In the following examples, the purpose of controlling the electric field strength on the film to be inspected can be broadly divided into two. The first is to optimize the conditions for optical inspection. For example, by performing optical inspection under an electric field strength that provides the maximum signal light intensity, inspection can be performed with a high SNR, thereby improving inspection throughput. The second is to inspect film quality that is dependent on the electric field. For material properties that are dependent on the electric field strength, information about film quality can be obtained by changing the applied electric field strength and detecting changes in the detection signal. Details will be described later.

[0015] In the following, an example will be disclosed in which the inspection target is an insulating film formed on a semiconductor wafer and its interface, but the application of this technology is not limited to this. Film quality measurement under an electric field is also effective for, for example, semiconductor films, organic films, and their interfaces.

[0016] 1 shows a schematic configuration of an inspection apparatus 1 of Example 1. The inspection apparatus 1 mainly comprises a charged particle beam device that controls the electronic state of an inspection target sample in a sample, a light irradiation system that irradiates the sample with probe light, a light detection system that detects signal light generated by irradiating the sample with the probe light, and a control system that controls these.

[0017] (Charged Particle Beam Device) The charged particle beam device includes a sample chamber 10 and a lens barrel 11, the interiors of which are maintained in a vacuum by an exhaust mechanism (not shown). The sample chamber 10 accommodates a sample 16 such as a semiconductor wafer. The lens barrel 11 accommodates a charged particle source 12 that generates a charged particle beam 13 to irradiate the sample 16, and a blanker 14 that chops the charged particle source 12. The charged particle source 12 may be any device capable of generating the charged particle beam 13 for charging the sample 16, such as an electron gun, a flood gun, or an ion source. The charged particle beam device may also include charged particle optical components such as lenses and deflectors that constitute a charged particle optical system for guiding the charged particle beam 13 to the sample 16.

[0018] A charge control electrode 17 is provided near the sample 16, which controls the amount of charge on the sample 16 by controlling the electric field on the sample 16. The electric field directly above the sample 16 is controlled by applying a voltage to the charge control electrode 17. The electric field applied to the charge control electrode 17 repels or pushes back secondary charged particles generated when the charged particle beam 13 is irradiated onto the sample 16, thereby controlling the charged state of the sample 16. The charge control electrode 17 is disposed at a position, for example, several to 30 mm away from the sample 16. For this reason, it is desirable to configure the charge control electrode 17 using a metal mesh or an electrode plate with holes so as not to obstruct irradiation of the charged particle beam 13 or the probe light 26 and pump light 27, which will be described later, onto the sample 16.

[0019] Furthermore, the use of ultraviolet light, as disclosed in Patent Document 1, can quickly remove charge from the sample 16. On the other hand, it is known that light with a wavelength longer than ultraviolet light can control the electric field (interfacial electric field) inside the sample without changing the charged state. For this reason, the configuration example shown in FIG. 1 includes a second light source 22 that irradiates the sample 16 with light (referred to as pump light (second light) 27). Irradiating the sample with pump light 27 can control the electronic state of the test sample, and the controlled electronic state can be further varied by selecting the wavelength of the pump light 27. Specifically, the use of ultraviolet light can remove charge from the sample and control the interfacial electric field, while the use of light with a wavelength longer than ultraviolet light can control the interfacial electric field. The second light source 22 can be configured similarly to the first light source 21, described below.

[0020] (Light Irradiation System) The inspection device 1 includes a first light source 21 that irradiates the sample 16 with probe light (first light) 26 to perform optical inspection of a film to be inspected formed on the sample 16. The first light source 21 can be a white light source such as a xenon lamp, a laser, an LED, or the like. The white light source can also be used after being converted to monochromatic light through a monochromator. Although not shown, the light irradiation system includes optical components such as lenses and mirrors that constitute an optical system for guiding the probe light 26 to the sample 16, and a polarizer for controlling the polarization of the probe light 26.

[0021] 1, the first light source 21 is disposed outside the sample chamber 10, and the probe light 26 is introduced into the sample chamber 10 through a viewport 15a provided in the sample chamber 10. In this example, the pump light 27 is also introduced into the sample chamber 10 through the viewport 15a, but the probe light 26 and the pump light 27 may be introduced into the sample chamber 10 through different viewports.

[0022] (Optical Detection System) When the probe light 26 illuminates the sample 16, signal light 28 is generated. The signal light 28 includes reflected light, scattered light (including Raman scattered light), luminescence, and diffracted light. The optical detection system detects the signal light 28 and includes an optical filter 23, an optical detection system 24, and a signal processing device 25. The optical filter 23 is a filter that removes light other than the signal light 28. The optical detection system 24 detects the signal light 28 by receiving light transmitted through the viewport 15b via the optical filter 23. The optical detection system 24 can be a power meter, a photodiode, a spectrometer, or the like, depending on the signal light 28 to be detected. The signal processing device 25 processes the detection signals of the optical detection system obtained under multiple electric field conditions inside the sample. The signal processing device 25 is, for example, a lock-in amplifier, and extracts the modulation intensity, phase, etc. of the detection signal from the optical detection system 24.

[0023] The signal light 28 detected by the light detection system 24 is determined depending on the film quality to be inspected for the film to be inspected. For example, by detecting reflected light, information such as interfacial electric field, defects, and strain can be obtained; by detecting scattered light (including Raman scattered light), information such as vibrational level, stress, and strain can be obtained; by detecting emitted light, information such as defects and luminous efficiency can be obtained; and by detecting diffracted light, information such as structural periodicity and refractive index can be obtained.

[0024] (Control System) The control device 30 controls the components of the inspection device 1. The control device 30 controls the operation of the charged particle beam device, the light irradiation system, and the light detection system, for example, based on inspection conditions input from a computer 31. The control device 30 is realized by a program executed by a processor such as a CPU. Alternatively, the control device 30 may be configured by, for example, a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0025] The setting of conditions for inspection and measurement by the inspection device 1 and the estimation of film quality based on detection signals from the optical detection system are performed by a computer 31. The computer 31 stores various databases or conversion formulas required for setting conditions and estimating film quality.

[0026] The inspection and measurement condition settings include the setting of the following parameters. These parameters are set by the user via the GUI of the computer 31. The conditions for the charged particle beam 13 that charges the sample include the acceleration voltage, current amount, irradiation area, irradiation position, and irradiation period using a blanker. The conditions for the charge control electrode 17 that controls the amount of charge on the sample include the voltage value and its application period. The conditions for the pump light 27 that controls the sample's charge removal or internal electric field include wavelength, intensity, polarization, and irradiation period. The conditions for the probe light 26 include wavelength, intensity, polarization, and other conditions. The conditions for the detector of the light detection system 24 include gain, etc.

[0027] It is also possible to configure the computer 31 to execute the functions of the control device 30 .

[0028] 2A to 2C show examples of control sequences for modulating the electronic state of a sample. Each example is a control sequence for controlling the electronic state of a sample 16 using three sources of influence: the charged particle beam 13, the charge control electrode 17, and the pump light 27. In FIG. 2A, the conditions of the charged particle beam 13 and the charge control electrode 17 are fixed, and the conditions of the pump light 27 are modulated. While the modulation parameter may be wavelength or polarization, it is intensity here. When the intensity of the pump light 27 is ON, the charge on the sample 16 is removed or the electric field inside the sample is controlled depending on the wavelength of the pump light 27. In FIG. 2B, the conditions of the charged particle beam 13 and the pump light 27 are fixed, and the conditions of the charge control electrode 17 are modulated. In FIG. 2C, the conditions of the charge control electrode 17 and the pump light 27 are fixed, and the conditions of the charged particle beam 13 are modulated. To modulate the electronic state of the sample 16, it is sufficient to modulate some parameter for at least one of the three sources of influence. When multiple action sources are modulated, the modulation patterns of the multiple action sources may be the same or different. Furthermore, if the wavelength of the pump light 27 is short and used to neutralize the film to be inspected, and only the presence or absence of charge on the sample needs to be controlled, the charge control electrode 17 can be eliminated. Furthermore, as in the control sequences of Figures 2B and 2C, if the charge amount on the sample is modulated using the charged particle beam 13 and the charge control electrode 17, the second light source 22 can be eliminated. However, even in such a case, if it is desired to control the electric field inside the sample (interface electric field), it is effective to provide a second light source 22 capable of irradiating light with a wavelength longer than ultraviolet light, and if it is desired to reset the charge amount on the sample for each modulation, it is effective to provide a second light source 22 capable of irradiating ultraviolet light.

[0029] The optical detection system detects the signal light 28 and outputs a detection signal, which is sampled according to a sampling trigger. The sampling trigger is synchronized with the modulation of the electronic state of the sample. As a result, the intensity S of the signal light 28 when the modulated action source is in the first state (in the example of FIG. 2A, the intensity of the pump light 27 is OFF) is Ａ The intensity S of the signal light 28 when the action source is in the second state (in the example of FIG. 2A, the intensity of the pump light 27 is ON) is Ｂ can be obtained, and the intensity S Ａ and strength S Ｂ2A to 2C are all for creating two types of electronic states, the first state and the second state, but it is also possible to create three or more types of electronic states by modulating multiple action sources with different modulation patterns.

[0030] Here, the sampling trigger can take various forms depending on the configuration of the optical detection system, and is not limited to a specific form. For example, assume that the second light source 22 modulates the pump light 27 in synchronization with a synchronization signal from the control device 30, and the optical detection system continuously outputs a detection signal from the signal processing device 25. In this case, the computer 31 can receive a synchronization signal from the control device 30 and sample the detection signal from the signal processing device 25 using a sampling trigger synchronized with the synchronization signal. Alternatively, in the optical detection system, the optical detection system 24 may be configured to continuously output a detection signal, and the signal processing device 25 may receive a synchronization signal from the control device 30 and sample the detection signal from the optical detection system 24 using a sampling trigger synchronized with the synchronization signal, thereby performing signal processing. Furthermore, in the optical detection system, the optical detection system 24 may be configured to receive a synchronization signal from the control device 30 and detect the signal light 28 using a sampling trigger synchronized with the synchronization signal. This configuration is preferable when the detector of the optical detection system 24 is a spectrometer.

[0031] The signal processing of the signal processing device 25 in the optical detection system will be described. For example, assume that the detector in the optical detection system 24 is a power meter and the signal light 28 is the reflected light of the probe light 26. If the control sequence of FIG. 2A is applied, the signal intensity S of the signal light 28 in the first state will be Ａ , the signal intensity S of the signal light 28 in the second state Ｂ The signal processing device 25 normalizes the difference between the signal intensities acquired in the two electronic states and outputs the normalized difference as a detection signal. In this case, the detection signal is expressed as (Equation 1) and represents the rate of change of reflectance.

[0032]

[0033] When a lock-in amplifier is used as the signal processing device 25, the amplitude ΔR０ , and the phase θ are output, and in this case, the detection signal is expressed as (Equation 2).

[0034]

[0035] When the detection signal ΔR / R is detected while changing the wavelength of the probe light 26, a spectrum like that shown in FIG. 3A or 3B is obtained. The horizontal axis represents the wavelength or energy of the reflected light. Here, FIG. 3A shows the case where the voltage of the charge control electrode 17 is set to 0 V, and FIG. 3B shows the case where the voltage of the charge control electrode 17 is set to +3 V. By adjusting the voltage of the charge control electrode 17, i.e., the amount of charge on the sample 16, a detection signal with a higher SNR is obtained. Note that a similar spectrum can also be obtained by using a white light source for the probe light 26 and a spectrometer as the detector of the light detection system 24.

[0036] The computer 31 estimates the film quality, for example, the strain and dopant concentration of the semiconductor at the interface between the insulating film and the semiconductor, from the intensity and shape of the detection signal spectrum as shown in Figure 3A or 3B. The obtained detection signal spectrum has a relationship expressed by, for example, (Equation 3) (Non-Patent Document 1).

[0037]

[0038] In (Equation 3), A is intensity, θ is phase, E is energy, E ＣＰ is the critical point energy, Γ is the broadening factor, and n is a coefficient that depends on the material of the film to be inspected. Equation 3 is fitted to the obtained detection signal spectrum. By fitting, the fit parameters (A, θ, E ＣＰ , Γ) can be calculated. Meanwhile, the computer 31 stores film quality information for various combinations of fit parameters as a database. An example of the database is shown in FIG.

[0039] FIG. 4 shows an example of the data structure of a database 41 for estimating film quality. In the database 41, fit parameters (A, θ, E ＣＰ, Γ) are registered. The computer 31 estimates the strain of the film to be inspected by comparing the fit parameters calculated from (Equation 3) with the database 41. The database 41 may register film quality information as a function with the fit parameters as arguments, and is not limited to this registration format. This example uses a model formula and database 41 such as (Equation 3) when measuring the strain using the signal light 28 as reflected light of the probe light 26. For example, if the signal light 28 is scattered light or luminescent light, or if the measurement target is something other than strain, a model formula or database appropriate for that purpose may be used.

[0040] The computer 31 stores the relationship between the parameters obtained from the detection signals and the film quality in this way as a database, and estimates film quality information from the parameters detected from the signal light 28. The computer 31 is provided with a database corresponding to the detection signals from the optical detection system used in the film quality inspection performed by the inspection device 1 and analytical expressions, and estimates the film quality using the database corresponding to the inspection to be performed.

[0041] Next, a control flow for determining film quality from the electric field dependence of the detection signal will be described. Film quality, such as defects and the amount of mobile charge, can be estimated from how the detection signal changes when the electric field applied to the sample is changed (the electric field dependence of the detection signal). Figure 5 shows a control flow for film quality inspection that can be estimated from the electric field dependence of the detection signal. An example will be described in which the control sequence of Figure 2A is applied to estimate the amount of mobile charge of the film to be inspected.

[0042] First, a variable parameter is selected and its range is set (S01). In this example, the variable parameter is the applied voltage to the charge control electrode 17. Next, a control sequence for film quality measurement is set. As described above, the control sequence of FIG. 2A is set (S02). The control sequence is executed and the signal light 28 is measured while changing the variable parameter (S03 to S06). After obtaining a detection signal within the set range of the variable parameter, a feature quantity indicating the variable parameter dependency of the detection signal is calculated (S07). The computer 31 stores film quality information for the feature quantity indicating the variable parameter dependency of the detection signal as a database. This database is referenced to estimate the film quality of the film to be inspected (S08).

[0043] As an example of the control flow, FIG. 6 shows the change in intensity of the detection signal (ΔR / R) when the voltage applied to the charge control electrode 17 is swept in the forward direction (from negative to positive) and the reverse direction (from positive to negative). The horizontal axis represents the surface potential V of the sample 16. ｓ The surface potential V ｓ is the applied voltage V of the charge control electrode 17 ｃｃ Since the relationship shown in (Equation 4) holds, the applied voltage V ｃｃ (Equation 4) can be calculated by converting from Equation 4. Equation 4 is calculated in advance by simulation or the like.

[0044]

[0045] FIG. 7 shows an example of the data structure of a database 51 for estimating film quality from the electric field dependence of the detection signal. Database 51 stores the mobile charge amount of the film for each combination of feature quantities (V1, V2, ΔV) that indicate the electric field strength dependence of the detection signal. Computer 31 estimates the mobile charge amount of the film under test by comparing the feature quantities (here, voltages V1, V2, and hysteresis that result in a specific reflectance) obtained from the measurement results shown in FIG. 6 with database 51. Using a database corresponding to the target film quality allows estimation of film quality, such as the fixed charge amount, flat band voltage, and, as described above, the charge contained in the material, strain, defects, and interface state. Furthermore, database 51 may store film quality information as a function using feature quantities as arguments, and the registration format is not limited to this.

[0046] FIG. 8 shows an example of the display of the results of optical inspection by the inspection device 1. Optical inspection is performed, for example, on chip sections specified by the user on a semiconductor wafer. Optical inspection may also be performed on all chip sections. The film quality of each chip section that has undergone optical inspection is displayed as a wafer heat map 60. In the wafer heat map 60, chip sections 62 are displayed within a wafer 61, and if the inspected film quality is defective, for example, the chip section with a higher defect density is displayed in a darker color. This allows the user to visually recognize the film quality of each chip section.

[0047] 9A shows an example of a setting and measurement screen 70, which is a GUI (Graphical User Interface) for performing film quality measurements using the inspection device 1 and displaying the results. The setting and measurement screen 70 is provided with a setting file selection section 71, which makes it possible to call up setting files saved in the computer 31 in past measurements. For example, when inspecting the same wafer for different film qualities, the user's workload can be reduced by utilizing the past setting contents.

[0048] 2A to 2C or other control sequences can be selected by selecting the control sequence tab included in the setting tab 72. Here, the laser modulation tab 73 is selected, and in this case, the control sequence for modulating the pump light shown in Fig. 2A is selected, as shown in sequence diagram 74. In this device, an electron beam is used as the charged particle beam, and laser light is used as the pump light.

[0049] The user opens the laser modulation tab 73 and sets the conditions for modulating the electronic state of the wafer in the electron beam condition setting section 75, the charge control electrode condition setting section 76, and the laser condition setting section 77. Furthermore, in this example, in order to estimate the film quality from the electric field dependency of the detection signal, the charge control electrode condition setting section 76 is set to sweep the applied voltage. In this case, a sweep range setting section 78 is displayed, and the user sets the range over which the applied voltage is to be swept. When the above settings are complete, the user presses the save button 79 to save the settings.

[0050] Once the condition settings are complete, the user opens the measurement tab 81, as shown in FIG. 9B. The user specifies the chip sections to be optically inspected in the inspection chip section setting section 82 and presses the inspection execution button 83. This causes optical inspection to be performed on the specified chip sections under the conditions set in the setting tab 72. Once optical inspection of all specified chip sections is complete, a wafer heat map is displayed in the wafer heat map display section 84 to simply show the inspection results to the user. The user checks the inspection results and presses the save button 85 to save the optical inspection results.

[0051] The user can check the details of the inspection results from the result output screen 90 shown in FIG. 9C . A result file selection section 91 on the result output screen 90 allows the user to call up a result data file for detailed display. In this example, a wafer heat map display section 92, which displays the same wafer heat map as the setting / measurement screen 70, and a histogram display section 93 are provided. The histogram displayed in the histogram display section 93 indicates the frequency of appearance (number of chip sections) of shading indicating defect density in the wafer heat map displayed in the wafer heat map display section 92. Furthermore, by specifying one of the chip sections displayed in the wafer heat map display section 92, detailed measurement results for an individual chip section can be displayed. In this example, the inspection chip section measurement result display section 94 displays the measurement results of the detection signal for a specific chip section and estimated film quality information.

[0052] (Modification 1) Fig. 10A shows a modification of the inspection device 1 shown in Fig. 1. In the first embodiment, when the applied voltage of the charge control electrode 17 is swept, the sample surface potential V ｓ Using (Equation 4), the applied voltage V of the charge control electrode 17 is calculated. ｃｃ However, depending on the measurement conditions, the value obtained from (Equation 4) and the true sample surface potential V ｓ There is a risk of error occurring between

[0053] The inspection device 1b in FIG. 10A detects the sample surface potential V ｓThe inspection device 1b is provided with an energy filter 101 and a signal electron detector 102 as mechanisms for actually measuring the potential V. Here, the signal electron detector 102 is a detector that detects signal electrons 100 generated when the charged particle beam 13 is irradiated onto the sample 16, and the detected signal electrons 100 may be secondary electrons or reflected electrons (backscattered electrons). A negative voltage is applied to the energy filter 101 by the control device 30, and only signal electrons that can overcome the electric field barrier generated by the negative voltage are detected by the signal electron detector 102. In other words, the amount of signal electrons detected by the signal electron detector 102 depends on the voltage of the energy filter 101. Using this feature, the computer 31 in the inspection device 1b calculates the sample surface potential V from the energy of the signal electrons 100. ｓ Calculate.

[0054] 10B shows the relationship between the amount of detected signal electrons and the energy filter voltage. The signal electron spectrum can be obtained by detecting the amount of detected signal electrons while changing the negative voltage applied to the energy filter 101. The amount of shift is proportional to the sample surface potential V ｓ The sample surface potential V ｓ This is because the force that pulls the signal electrons 100 back toward the sample varies depending on the voltage. If the signal electron spectrum 103 is the signal electron spectrum when the sample 16 is uncharged, the signal electron spectra 104 and 105 are the signal electron spectra when the sample 16 is positively charged and negatively charged, respectively. Therefore, for example, the voltage at which the differential value of the signal electron spectrum is maximum is defined as the sample surface potential V ｓ When the potential is defined as V, the potential when the electrode is uncharged, positively charged, or negatively charged is V ０ , V １ , V ２ As a result, the sample surface potential V ｓ The signal electron spectrum 103 can be obtained by measuring the sample 16 in a state where the charge on the sample 16 is removed by using a pump light 27 with a short wavelength such as ultraviolet light.

[0055] In this modified example, the energy of the signal electrons 100 is discriminated using the energy filter 101. However, the sample surface potential V ｓ It is possible to measure.

[0056] (Modification 2) Fig. 11 shows a modification of the inspection apparatus 1 shown in Fig. 1. In the modification 2, similarly to the modification 1, the sample surface potential V ｓ The inspection device 1c is capable of measuring the sample surface potential V ｓ The sample 16 is moved to the position of the surface electrometer 110 provided in the sample chamber 10, and the sample surface potential V ｓ Measure.

[0057] Hereinafter, other configuration examples of the inspection device 1 will be described as Examples 2 to 4. The same components as those in Example 1 are given the same reference numerals, and duplicated descriptions will be omitted.

[0058] In Example 1, the sample 16 is placed in a vacuum atmosphere, which takes time to evacuate, thereby reducing the throughput of inspection and measurement. Example 2 is an example of a configuration in which the sample 16 is placed in the atmosphere.

[0059] 12 , the charged particle source 12 is disposed in a lens barrel 11 that is kept in a vacuum atmosphere, and the lens barrel 11 is provided with a partition wall 120 for maintaining the interior of the lens barrel 11 in a vacuum atmosphere. The charged particle beam 13 emitted from the charged particle source 12 passes through the partition wall 120 and is emitted into the atmosphere, where it is irradiated onto the sample 16. Furthermore, if the charged particle source 12 is an electrode that generates ions by corona discharge in the atmosphere, the lens barrel 11 and the partition wall 120 for maintaining the charged particle source in a vacuum atmosphere can be eliminated.

[0060] In Example 3, photoelectrons generated by irradiating a metal electrode with excitation light are used as the charged particles. The inspection device 3 of Example 3 uses an electron beam source with a simple configuration as the charged particle beam source, and can modulate the charge amount of the sample 16 by exchanging photoelectrons generated by irradiating the sample 16 and / or the charge control electrode 17 with short wavelength light.

[0061] The third light source 131 and the fourth light source 132 are light sources that generate light with a wavelength of less than 400 nm, and their outputs are controlled by the control device 30. The third light source 131 and the fourth light source 132 can each be configured similarly to the first light source 21. The third light source 131 and the fourth light source 132 are disposed outside the sample chamber 10, and the light from these light sources is introduced into the sample chamber 10 via a viewport 15c provided in the sample chamber 10.

[0062] The first excitation light (third light) 133 from the third light source 131 is irradiated onto the charge control electrode 17. First photoelectrons 135 are generated from the location irradiated with the first excitation light 133. If the potential of the charge control electrode 17 is more negative than that of the sample 16, the first photoelectrons 135 receive a force in the direction of the sample and are irradiated onto the sample 16. As a result, the sample 16 becomes negatively charged.

[0063] On the other hand, second excitation light (fourth light) 134 from the fourth light source 132 is irradiated onto the sample 16. Second photoelectrons 136 are generated from the location irradiated with the second excitation light 134. If the potential of the charge control electrode 17 is more positive than that of the sample 16, the second photoelectrons 136 are subjected to a force in the direction of the charge control electrode, and move away from the sample 16. Therefore, the sample 16 is positively charged.

[0064] In this way, the potential of the sample 16 can be modulated and controlled by the first photoelectrons 135 and the second photoelectrons 136 caused by the first excitation light 133 and the second excitation light 134. The third light source 131 and the fourth light source 132 can also be combined into one light source, in which case the optical path of the excitation light is controlled by the control device 30 so that the excitation light is irradiated onto the charge control electrode 17 or the sample 16. Alternatively, the excitation light may be configured to be irradiated onto both the charge control electrode 17 and the sample 16 simultaneously. Furthermore, in order to avoid absorption of short-wavelength light in the atmosphere, the third light source and the fourth light source may be placed in a vacuum.

[0065] 1, the arrangement of the charge control electrode 17 and the charged particle source 12 interferes with the probe light (first light) 26 and the pump light (second light) 27, making it impossible to arrange the light irradiation system and the light detection system near the sample 16. This makes it difficult to focus the light on the sample, limiting the spatial resolution of the measurement. In the inspection device 4 of Example 4, in order to obtain high spatial resolution, optical systems such as objective lenses for the probe light and signal light are arranged directly above the sample.

[0066] In the inspection device 4, an optical lens 141 for irradiating the sample 16 with the probe light 26 and the pump light 27 is disposed directly above the sample, with its optical axis aligned perpendicular to the film to be inspected formed on the sample. The optical lens 141 focuses the probe light 26 and the pump light 27 on the sample 16, enabling measurement with high spatial resolution. The charged particle source 12 is disposed diagonally with respect to the optical axis of the optical lens 141, and the charged particle beam 13 passes between the optical lens 141 and the sample 16 and is obliquely irradiated onto the sample 16. Furthermore, to shorten the distance between the optical lens 141 and the sample 16, the optical lens 141 also functions as a charge control electrode. That is, a transparent conductive film 17b is formed on the optical lens 141, which allows the probe light 26, the pump light 27, and the signal light 28 to pass through while allowing a voltage to be applied by the control device 30. The transparent conductive film 17b may be made of ITO, ITZO, or the like, or may be made of a thin metal film such as aluminum or gold. Instead of forming a film on the optical lens 141, the charge control electrode may be a transparent electrode that is disposed separately from the optical lens 141 and below the optical lens 141. The probe light 26 and the pump light 27 are combined on the same optical path using a dichroic mirror 142, which has different transmission and reflection characteristics depending on the wavelength of the light. The signal light 28 propagates in the opposite direction along the optical path of the probe light 26, is reflected by the beam splitter 143, passes through the optical filter 23, and is then detected by the optical detection system 24. In this way, the inspection device 4 can perform film quality measurement with high spatial resolution by focusing the probe light 26 on the sample 16 using the optical lens 141. Furthermore, since the optical lens 141 is disposed near the sample 16, there is also the advantage of improving the detection rate for scattered light and light emitted from the sample 16. Note that FIG. 14 illustrates only typical optical components that constitute the optical system, and general elements such as lenses and mirrors are omitted.

[0067] The present invention has been described above with reference to examples and modifications. The above examples and modifications can be modified in various ways without departing from the spirit of the invention, and these can also be used in combination.

[0068] 1, 2, 3, 4: inspection device, 10: sample chamber, 11: microscope column, 12: charged particle source, 13: charged particle beam, 14: blanker, 15: viewport, 16: sample, 17: charge control electrode, 17b: transparent conductive film, 21: first light source, 22: second light source, 23: optical filter, 24: light detection system, 25: signal processing device, 26: probe light, 27: pump light, 28: signal light, 30: control device, 31: computer, 41, 51: database, 60: wafer heat map, 61: wafer, 62: chip section, 70: setting and measurement screen, 71: setting file selection section, 72: setting tab, 73: laser modulation tab, 74: sequence diagram, 75: electron beam condition setting section, 76: charge control electrode condition setting section, 77: laser condition setting section, 78: sweep range Setting section, 79: save button, 81: measurement tab, 82: inspection chip section setting section, 83: inspection execution button, 84: wafer heat map display section, 85: save button, 90: result output screen, 91: result file selection section, 92: wafer heat map display section, 93: histogram display section, 94: inspection chip section measurement result display section, 100: signal electrons, 101: energy filter, 102: signal electron detector, 103, 104, 105: signal electron spectrum, 110: surface potential meter, 120: partition, 131: third light source, 132: fourth light source, 133: first excitation light, 134: second excitation light, 135: first photoelectrons, 136: second photoelectrons, 141: optical lens, 142: dichroic mirror, 143: beam splitter.

Claims

1. An inspection device for inspecting the quality of a film formed on a sample, comprising: a charged particle source that irradiates the sample with a charged particle beam; a first light source that irradiates the sample with first light; a light detection system that detects signal light generated when the first light is irradiated on the sample; a charge control electrode that controls the electric field on the sample or a second light source that irradiates the sample with second light; a control device that modulates the electronic state of the sample using the charged particle source, the charge control electrode, or the second light source; and a computer that estimates the quality of the film formed on the sample based on a detection signal of the signal light modulated in accordance with the modulation of the electronic state of the sample, which is output from the light detection system.

2. An inspection device according to claim 1, comprising both the charge control electrode and the second light source, and wherein the control device modulates the electronic state of the sample using at least one of the charged particle source, the charge control electrode and the second light source.

3. An inspection device according to claim 2, wherein the optical detection system outputs a detection signal that indicates a change in the signal light due to modulation of the electronic state of the sample.

4. An inspection apparatus according to claim 3, wherein the detection signal is expressed by a model formula including a plurality of fit parameters, the computer has a database that registers film quality information for combinations of the plurality of fit parameters, the computer fits the detection signal to the model formula to calculate the plurality of fit parameters of the detection signal, and the calculated plurality of fit parameters are compared with the database.

5. An inspection apparatus according to claim 3, wherein the control device modulates the second light source while changing the electric field intensity applied to the sample by the charge control electrode.

6. An inspection apparatus according to claim 5, wherein the detection signal has a dependency on the electric field strength applied to the sample, and the computer has a database that registers film quality information for feature quantities that indicate the dependency, calculates the feature quantities that indicate the dependency from the detection signal, and compares the calculated feature quantities that indicate the dependency with the database.

7. An inspection device according to claim 6, further comprising a signal electron detector that detects signal electrons generated when the charged particle beam is irradiated onto the sample, and the computer calculates the surface potential of the sample based on the energy of the signal electrons detected by the signal electron detector.

8. An inspection device according to claim 6, comprising a surface potential meter for measuring the surface potential of the sample.

9. An inspection device according to claim 1, wherein the sample is placed in the atmosphere, the charged particle source is placed in a lens barrel provided with a partition for maintaining the charged particle source in a vacuum atmosphere, and the charged particle beam penetrates the partition and is irradiated onto the sample.

10. An inspection device according to claim 1, wherein the sample and the charged particle source are placed in the atmosphere, and the charged particle source is an electrode that generates ions by corona discharge.

11. An inspection device according to claim 1, wherein the first light is irradiated onto the sample from a direction perpendicular to a film formed on the sample, and the charged particle beam is irradiated onto the sample from an angle oblique to the film formed on the sample.

12. An inspection device according to claim 11, comprising an optical lens that focuses the first light, and a conductive film that serves as the charge control electrode is formed on the surface of the optical lens that faces the sample.

13. An inspection device according to claim 11, further comprising an optical lens that focuses the first light, and the charge control electrode is a transparent electrode that is disposed between the optical lens and the sample.

14. An inspection device for inspecting the quality of a film formed on a sample, comprising: a first light source that irradiates the sample with first light; an optical detection system that detects signal light generated when the sample is irradiated with the first light; a charge control electrode that controls the electric field on the sample; a third light source that irradiates the charge control electrode with third light to generate photoelectrons; a fourth light source that irradiates the sample with fourth light to generate photoelectrons; a control device that controls the voltage applied to the charge control electrode, the third light source, and the fourth light source to modulate the electronic state of the sample; and a computer that estimates the quality of the film formed on the sample based on the detection signal of the signal light modulated in accordance with the modulation of the electronic state of the sample, which is output from the optical detection system.

15. A film quality inspection method for inspecting the quality of a film formed on a sample, comprising: irradiating the sample with a charged particle beam to charge the sample; irradiating the sample with probe light while modulating the electronic state of the sample; detecting signal light generated when the probe light is irradiated on the sample; and estimating the quality of the film formed on the sample based on the detection signal of the signal light modulated in accordance with the modulation of the electronic state of the sample.

16. A film quality inspection method as claimed in claim 15, comprising: irradiating the sample with the probe light while modulating the electronic state of the sample while changing the electric field strength applied to the sample; and estimating the film quality of a film formed on the sample based on the electric field strength dependency of a detection signal of signal light modulated in accordance with the modulation of the electronic state of the sample.

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