Patent Application
20250046569
The present disclosure relates to an inspection device and a film quality inspection method using the same.
PTL 1 discloses a SEM equipped with ultraviolet light for discharge. It is known that charge on an insulating film can be removed by irradiation with the ultraviolet light. PTL 2 discloses a SEM equipped with a charge control electrode that controls an electric field on a sample. It is known that a charge amount of the sample charged by electron beam irradiation can be controlled by controlling a voltage of the charge control electrode.
In a semiconductor device, a film quality of a semiconductor film or an insulating film is important. For example, performance of a transistor greatly depends on properties of a gate insulating film and properties of an interface between the gate insulating film and a layer in contact therewith. If there is a defect in the insulating film or the interface, charge accumulates in the defect due to application of an electric field when driving the device, which adversely affects a device operation. In order to inspect the film quality such as the defect that becomes a problem during the device operation, it is effective to apply an electric field to the film to be inspected in the same manner as during the device operation and measure a change in characteristics thereof.
After the device is completed, the film quality can be inspected by electrical characteristic inspection in which the device is actually operated. However, the post-completion inspection cannot prevent defects from occurring during a mass production process. In development of a semiconductor manufacturing process, a film quality can be measured under application of an electric field by manufacturing electrodes that sandwich a film to be inspected and applying a voltage between the electrodes, but manufacturing the electrodes for this purpose is time-consuming and costly.
Accordingly, in the mass production process of the semiconductor device or in the development of the semiconductor manufacturing process, it is desired to inspect the film quality of the deposited semiconductor film, insulating film, or the like in a non-contact manner. Here, the film quality refers to material characteristics that the film exhibits depending on charge, a strain, a defect, a state of a base, a state of an interface, or the like of the deposited material. The film to be inspected in the invention includes a wide range of films formed in the manufacturing process of the semiconductor device, regardless of a manufacturing method and a material of the film. This also applies to, for example, a film obtained by performing processing such as annealing after deposition, a film (thermal oxide film) obtained by thermally oxidizing a semiconductor substrate, and a film formed by ion implantation on a semiconductor substrate. The material includes both an inorganic material and an organic material.
According to an aspect of the invention, there is provided an inspection device for inspecting a film quality of a film formed on a sample, and the inspection device includes: a charged particle source configured to irradiate the sample with a charged particle beam; a first light source configured to irradiate the sample with first light; a photodetection system configured to detect signal light generated when the sample is irradiated with the first light; a charge control electrode configured to control an electric field on the sample or a second light source configured to irradiate the sample with second light; a control device configured to modulate an electronic state of the sample using the charged particle source and the charge control electrode or the second light source; and a computer configured to estimate the film quality of the film formed on the sample based on a detection signal of the signal light modulated according to the modulated electronic state of the sample, the detection signal being output from the photodetection system.
According to another aspect of the invention, there is provided a film quality inspection method for inspecting a film quality of a film formed on a sample, and the film quality inspection method includes: irradiating the sample with a charged particle beam to charge the sample; irradiating the sample with probe light in a state in which an electronic state of the sample is modulated; detecting signal light generated when the sample is irradiated with the probe light; and estimating the film quality of the film formed on the sample based on a detection signal of the signal light modulated according to the modulated electronic state of the sample.
The film quality of the deposited semiconductor, insulating film, or the like can be inspected in a non-contact manner. Other problems and novel features will become apparent from description of the present specification and the accompanying drawings.
Hereinafter, embodiments of the invention will be described. The drawings shown in the present embodiment show specific examples of the invention, and these are provided for understanding the invention, and are not to be used for limitedly interpreting the invention.
In an inspection device according to the present embodiment, a film quality is evaluated by optical inspection. That is, as specific examples will be described later, material characteristics of a film are detected as optical characteristics of the film, and information on the film quality is obtained from the detected optical characteristics. In the present embodiment, in the optical inspection, an electronic state of a sample to be inspected is modulated and controlled by controlling charge on the film to be inspected and/or controlling an internal electric field by light irradiation.
In the following embodiments, a purpose of controlling an electric field intensity on the film to be inspected is roughly divided into two. The first is to optimize conditions for the optical inspection. For example, by executing the optical inspection under the electric field intensity at which a maximum signal light intensity is obtained, the inspection can be executed at a high SNR, and a throughput of the inspection can be improved. The second is to inspect the film quality depending on the electric field. As for the material characteristics depending on the electric field intensity, information on the film quality can be obtained by changing the applied electric field intensity and detecting a change in a detection signal. Details will be described later.
Hereinafter, an embodiment will be disclosed in which an object to be inspected is an insulating film formed on a semiconductor wafer and an interface thereof, but application of the present technology is not limited thereto. Film quality measurement under an electric field is also effective in, for example, a semiconductor film, an organic film, or an interface thereof.
The charged particle beam device includes a sample chamber 10 and a lens barrel 11, the inside of which is maintained in a vacuum atmosphere by an exhaust mechanism (not shown). A sample 16 such as a semiconductor wafer is accommodated in the sample chamber 10. 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. Here, an electron gun, a flood gun, an ion source, or the like can be used as the charged particle source 12 as long as the charged particle source 12 can generate the charged particle beam 13 for charging the sample 16. A charged particle optical component such as a lens or a deflector constituting a charged particle optical system that guides the charged particle beam 13 to the sample 16 may be provided.
A charge control electrode 17 that controls a charge amount of the sample 16 by controlling an electric field on the sample 16 is provided in the vicinity of the sample 16. The electric field immediately above the sample 16 is controlled by applying a voltage to the charge control electrode 17. A charged state of the sample 16 is controlled by the electric field applied to the charge control electrode 17 moving secondary charged particles generated when the sample 16 is irradiated with the charged particle beam 13 away from or back to the sample 16. The charge control electrode 17 is disposed at a position about several to 30 mm away from the sample 16, for example. For this reason, it is desirable to use an electrode plate having a metal mesh or holes so as not to interfere with irradiating the sample 16 with the charged particle beam 13, or probe light 26 or pump light 27 to be described later.
Further, charge on the sample 16 can be quickly removed by using ultraviolet light as disclosed in PTL 1. On the other hand, in a case of light having a longer wavelength than the ultraviolet light, it is known that the electric field (interface electric field) inside the sample can be controlled without changing the charged state. Therefore, in a configuration example in
The inspection device 1 includes the first light source 21 that irradiates the sample 16 with probe light (first light) 26 in order to execute optical inspection on a film to be inspected formed on the sample 16. A white light source such as a xenon lamp, a laser, an LED, or the like can be used as the first light source 21. The white light source can also be used monochromatically through a monochromator. Although not shown, the light irradiation system includes optical components such as a lens or a mirror constituting an optical system that guides the probe light 26 to the sample 16, and a polarizer that controls polarization of the probe light 26.
In the example in
Signal light 28 is generated by irradiating the sample 16 with the probe light 26. The signal light 28 includes reflected light, scattered light (including Raman scattered light), emitted light, and diffracted light. The photodetection system detects the signal light 28, and includes an optical filter 23, a photodetection system 24, and a signal processing device 25. The optical filter 23 is a filter that removes light other than the signal light 28, and the photodetection system 24 detects the signal light 28 by receiving light transmitted through a viewport 15b via the optical filter 23. A power meter, a photodiode, a spectrometer, or the like can be used as the photodetection system 24 according to the signal light 28 to be detected. The signal processing device 25 processes a detection signal from the photodetection system obtained under an electric field condition inside the plurality of samples. The signal processing device 25 is, for example, a lock-in amplifier, and extracts a modulation intensity, a phase, and the like of the detection signal from the photodetection system 24.
The signal light 28 detected by the photodetection system 24 is determined according to a film quality that is inspected for the film to be inspected. For example, information such as an interface electric field, a defect, and a strain can be obtained by detecting the reflected light, information such as a vibration level, a stress, and a strain can be obtained by detecting the scattered light (including the Raman scattered light), information such as a defect and a light emission efficiency can be obtained by detecting the emitted light, and information such as structural periodicity and a refractive index can be obtained by detecting the diffracted light.
The control device 30 controls components of the inspection device 1. The control device 30 controls operations of the charged particle beam device, the light irradiation system, and the photodetection system based on inspection conditions input from a computer 31, for example. The control device 30 is implemented by a program executed by a processor such as a CPU. For example, a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC) may be used.
The computer 31 sets conditions for inspection and measurement by the inspection device 1 and estimates the film quality based on the detection signal from the photodetection system. The computer 31 stores various databases and conversion formulas necessary for setting the conditions and estimating the film quality.
Setting the conditions for inspection and measurement includes setting parameters as follows. These parameters are set by a user through a GUI of the computer 31. Conditions for the charged particle beam 13 that charges the sample include an acceleration voltage, a current amount, an irradiation area, an irradiation position, an irradiation cycle by a blanker, and the like. Conditions for the charge control electrode 17 that controls the charge amount of the sample include a voltage value, an application cycle thereof, and the like. Conditions for the pump light 27 for controlling discharge or an internal electric field of the sample include a wavelength, an intensity, polarization, an irradiation cycle, and the like. Conditions for the probe light 26 include a wavelength, an intensity, polarization, and the like. Conditions for a detector of the photodetection system 24 include a gain and the like.
Functions of the control device 30 may be executed by the computer 31.
Sampling of the detection signal output from the photodetection system by detecting the signal light 28 is performed according to a sampling trigger. The sampling trigger is synchronized with the modulation of the electronic state of the sample. Accordingly, it is possible to obtain an intensity SA of the signal light 28 when the modulated action source is in a first state (the intensity of the pump light 27 is OFF in the example in
Here, the sampling trigger has various aspects depending on a configuration of the photodetection system, and is not limited to a specific aspect. For example, the second light source 22 modulates the pump light 27 in synchronization with a synchronization signal from the control device and 30, the photodetection system continuously outputs the detection signal from the signal processing device 25. In this case, the computer 31 can receive the synchronization signal from the control device 30 and sample the detection signal from signal processing device 25 using the sampling trigger synchronized with the synchronization signal. Alternatively, in the photodetection system, the photodetection system 24 may continuously output the detection signal, and the signal processing device 25 may execute signal processing by receiving the synchronization signal from the control device 30 and sampling the detection signal from the photodetection system 24 using the sampling trigger synchronized with the synchronization signal. Further, in the photodetection system, the photodetection system 24 may receive the synchronization signal from the control device 30 and detect the signal light 28 using the sampling trigger synchronized with the synchronization signal. This configuration may be adopted when the detector of the photodetection system 24 is a spectrometer.
The signal processing by the signal processing device 25 in the photodetection system will be described. For example, the detector of the photodetection system 24 is a power meter and the signal light 28 is reflected light of the probe light 26. Assuming that the control sequence in
When a lock-in amplifier is used as the signal processing device 25, an amplitude ΔR0 and a phase θ are output, and in this case, the detection signal is expressed as (Math. 2).
When a detection signal ΔR/R is detected while changing the wavelength of the probe light 26, a spectrum as shown in
As shown in
In (Math. 3), A is an intensity, θ is a phase, E is energy, ECP is critical point energy, Γ is a broadening factor, and n is a coefficient depending on the material of the film to be inspected. (Math. 3) is fitted to the obtained detection signal spectrum. Fit parameters (A, θ, ECP, Γ) included in (Math. 3) are obtained by fitting. On the other hand, the computer 31 stores, as a database, film quality information on various combinations of fit parameters.
The computer 31 stores, as a database, a relationship between the parameter obtained from the detection signal in this way and the film quality, and estimates the film quality information based on the parameter detected from the signal light 28. The computer 31 includes a database corresponding to the detection signal from the photodetection system and an analysis formula used for film quality inspection executed by the inspection device 1, and estimates the film quality using the database corresponding to the inspection to be executed.
Next, a control flow when the film quality is obtained from electric field dependency of the detection signal will be described. The film quality such as a defect or a mobile charge amount can be estimated based on how the detection signal changes (electric field dependency of the detection signal) when the electric field applied to the sample is changed.
First, a variable parameter is selected and a range there of is set (S01). Here, the variable parameter is a voltage applied to the charge control electrode 17. Subsequently, a control sequence for film quality measurement is set. As described above, the control sequence in
As an example of the control flow,
By selecting a control sequence tab included in a setting tab 72, the control sequences in
The user opens the laser modulation tab 73 and sets conditions for modulating the electronic state of the wafer by an electron beam condition setting section 75, a charge control electrode condition setting section 76, and a laser condition setting section 77. Further, in this example, in order to estimate the film quality based on the electric field dependency of the detection signal, the applied voltage is set to be swept in the charge control electrode condition setting section 76. In this case, a sweep range setting section 78 is displayed, and the user sets a range in which the applied voltage is swept. When the above setting is completed, a save button 79 is pressed to save the set contents.
When the condition setting is completed, the user opens a measurement tab 81 as shown in
The user can confirm details of the inspection result from a result output screen 90 shown in
An inspection device 1b in
In the present modification, the energy of the signal electrons 100 is discriminated using the energy filter 101, but the sample surface voltage Vs can also be measured by detecting the electron energy with a spectrometer or the like that spectrally detects the signal electrons according to the energy.
Hereinafter, other configuration examples of the inspection device 1 will be described as Embodiments 2 to 4. The same components as those in Embodiment 1 are denoted by the same reference numerals, and redundant description thereof will be omitted.
In Embodiment 1, since the sample 16 is disposed in a vacuum atmosphere and vacuum pumping takes time, which reduces a throughput of inspection and measurement. Embodiment 2 is a configuration example in which the sample 16 is disposed in the atmosphere.
In a configuration of an inspection device 2 shown in
In Embodiment 3, photoelectrons generated by irradiating a metal electrode with excitation light are used as charged particles. An inspection device 3 according to Embodiment 3 uses an electron beam source having a simple configuration as a charged particle beam source, and can modulate a 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.
A third light source 131 and a fourth light source 132 are light sources that generate light having a wavelength less than 400 nm, and outputs thereof 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 light from the light sources is introduced into the sample chamber 10 via a viewport 15c provided in the sample chamber 10.
The charge control electrode 17 is irradiated with first excitation light (third light) 133 from the third light source 131. First photoelectrons 135 are generated from a location irradiated with the first excitation light 133. When a potential of the charge control electrode 17 is negative compared to that of the sample 16, the first photoelectrons 135 receive a force toward the sample and the sample 16 is irradiated with the first photoelectrons 135. Accordingly, the sample 16 is negatively charged.
On the other hand, the sample 16 is irradiated with second excitation light (fourth light) 134 from the fourth light source 132. Second photoelectrons 136 are generated from a location irradiated with the second excitation light 134. When the potential of the charge control electrode 17 is positive compared to that of the sample 16, the second photoelectrons 136 receive a force toward the charge control electrode and move away from the sample 16. Accordingly, the sample 16 is positively charged.
In this way, the potential of the sample 16 can be modulated and controlled by the first photoelectrons 135 and the second photoelectrons 136 generated by the first excitation light 133 and the second excitation light 134. The third light source 131 and the fourth light source 132 may be one light source, and in this case, an optical path of the excitation light is controlled by the control device 30 such that the charge control electrode 17 or the sample 16 is irradiated with the excitation light. Alternatively, both the charge control electrode 17 and the sample 16 may be simultaneously irradiated with the excitation light. In order to avoid absorption of short-wavelength light in the atmosphere, the third light source and the fourth light source may be disposed in a vacuum.
In the configuration of the inspection device 1 shown in
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 such that an optical axis thereof is along a direction perpendicular to a film to be inspected formed on the sample. Since the probe light 26 and the pump light 27 are focused on the sample 16 by the optical lens 141, measurement can be performed with high spatial resolution. The charged particle source 12 is disposed obliquely 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 the sample 16 is obliquely irradiated with the charged particle beam 13. Further, since a distance between the optical lens 141 and the sample 16 is shortened, the optical lens 141 also functions as a charge control electrode. That is, a transparent conductive film 17b is deposited on the optical lens 141, and a voltage can be applied by the control device 30 while transmitting the probe light 26, the pump light 27, and the signal light 28. As a material of the transparent conductive film 17b, ITO, ITZO, or the like may be used, or a metal thin film made of aluminum, gold, or the like may be used. Instead of depositing the film on the optical lens 141, the charge control electrode may be a transparent electrode and may be disposed below the optical lens 141 separately from the optical lens 141. The probe light 26 and the pump light 27 are integrated on the same optical path using a dichroic mirror 142 having different transmission-reflection characteristics depending on a wavelength of the light. The signal light 28 propagates in a reverse direction along the optical path of the probe light 26, is reflected by a beam splitter 143, passes through the optical filter 23, and is detected by the photodetection system 24. In this way, in the inspection device 4, the probe light 26 is focused on the sample 16 by the optical lens 141, whereby the film quality measurement can be performed with high space resolution. Since the optical lens 141 is disposed in the vicinity of the sample 16, there is also an advantage of improving a detection rate for scattered light and emitted light from the sample 16.
The invention has been described above by way of embodiments and modifications. The embodiments and modifications described above can be variously modified without departing from the gist of the invention, and can also be used in combination.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/003391 | 1/28/2022 | WO |
