Electrical signal measuring device and electrical signal measuring method

Abstract

An electrical signal measurement device (2A) is provided with: a signal conversion unit (30) for intensity-modulating measurement light on the basis of a time-waveform electrical signal to be measured, and outputting the signal as an optical signal corresponding to the electrical signal; a waveform measurement unit (40) that measures the time waveform of the optical signal; and a waveform analysis unit (52) that finds the time waveform of the electrical signal on the basis of the measurement result of the optical signal. The waveform measurement unit (40) includes a streak tube (42) including a photoelectric surface to which an optical signal is input, a scanning electrode, and a fluorescent surface, an imaging element (44) that captures a fluorescent image generated on the fluorescent surface and outputs a waveform image, and an input optical system (41) that inputs the optical signal to the photoelectric surface, and the waveform analysis unit (52) obtains a temporal waveform of an electric signal on the basis of the waveform image. The input optical system (41) inputs the optical signal into the photoelectric surface as a linear optical image extending in a direction intersecting the scanning direction. Therefore, the electric signal measuring device and the measuring method can measure the time waveform of the electric signal at high speed.

Description

Technical Field

[0001] This disclosure relates to an electrical signal measuring device and a method for measuring the time waveform of an electrical signal. Background Technology

[0002] An oscilloscope is used as a device for measuring the time waveform of electrical signals. Currently, the measurement bandwidth of oscilloscopes has increased, with some commercially available boasting bandwidths exceeding 100 GHz. Furthermore, for measuring the time waveform of weak electrical signals, if a high-speed accumulation function (fluorescent mode) is used to increase the number of accumulations per unit time, an input bandwidth of around 20 GHz and an accumulation speed of up to 20 kHz are considered. Existing technical documents Patent documents

[0003] Patent Document 1: International Publication No. 2022 / 064798 Patent Document 2: International Publication No. 2007 / 136681 Patent Document 3: European Patent Application Publication No. 0197196 Patent Document 4: European Patent Application Publication No. 0344986 Summary of the Invention

[0004] [The problem the invention aims to solve] In the inspection of semiconductor devices, the aforementioned oscilloscope is used to measure the time waveform of electrical signals. As methods for inspecting the operating state of semiconductor devices, methods such as EOP (Electro Optical Probing), EOFM (Electro Optical Frequency Mapping), LVP (Laser Voltage Probing), and LVI (Laser Voltage Imaging) are known (for example, see Patent Documents 1 and 2).

[0005] In EOP (Electronic Operating Procedure), a semiconductor device whose state changes over time due to the application of a voltage pattern with a specified period is illuminated from the back side with a probe light of a specified wavelength, and the time change in the intensity of the reflected light is measured to check the operating state of the semiconductor device. Furthermore, in EOFM (Electronic Operating Frequency), a spectrum analyzer is used to perform frequency analysis on the reflected light from the semiconductor device, and the parts operating at a specified frequency are imaged.

[0006] In the semiconductor inspection methods described above, such as EOP and EOFM, an oscilloscope is used to measure the time waveform of the electrical signal output by the photodetector that detects the reflected light. On the other hand, the performance of LSIs continues to improve, and in the inspection of such semiconductor devices, it is sometimes necessary to measure jitter of 10 ps units, for example. However, with existing oscilloscopes, it is difficult to measure the time waveform of the electrical signal corresponding to the time change of the intensity of such high-speed reflected light with sufficient accuracy.

[0007] Furthermore, in the aforementioned inspection methods, the intensity of reflected light from semiconductor devices sometimes exhibits only slight temporal variations due to the application of a voltage pattern. In such cases, to measure these weak intensity variations with a sufficient signal-to-noise ratio (S / N), it is considered to accumulate or average the time waveform of the electrical signal output from the photodetector multiple times. However, high-speed accumulation of electrical signals is difficult to achieve in existing oscilloscopes. This problem of measuring the time waveform of such high-speed electrical signals also arises in the measurement of electrical signals outside of semiconductor inspection.

[0008] The purpose of this implementation is to provide an electrical signal measuring device and method capable of high-speed measurement of the time waveform of electrical signals. [Methods used to solve problems]

[0009] For high-speed measurement of the time waveform of electrical signals, a structure of a stripe oscilloscope is considered, which converts the electrical signal into an optical signal and uses a stripe camera to measure the optical signal (for example, see Patent Documents 3 and 4). However, after conducting detailed research on such a structure using a stripe camera, the inventors of this application discovered problems such as an upper limit on the input light density of the photoelectric surface of the stripe tube, or degradation of the photoelectric surface when performing cumulative measurement of the time waveform of the optical signal, and thus achieved the present invention.

[0010] The implementation method is an electrical signal measuring device. The electrical signal measuring device includes: (1) a signal conversion unit, which has: a measurement light source that supplies measurement light of a predetermined wavelength, and an optical modulator that modulates the intensity of the measurement light based on an electrical signal input as a measurement object with a time waveform, and outputs the measurement light modulated by the optical modulator as an optical signal having a time waveform corresponding to the time waveform of the electrical signal; (2) a waveform measurement unit that measures the time waveform of the optical signal output from the signal conversion unit; and (3) a waveform analysis unit that determines the time waveform of the electrical signal based on the measurement result of the time waveform of the optical signal by the waveform measurement unit; (4) the waveform measurement unit includes: a stripe tube, which includes: a stripe tube that generates a stripe tube based on the input of the optical signal. The photoelectric surface that generates electrons, the scanning electrode that scans electrons from the photoelectric surface in a specified scanning direction within a scanning period set according to the time waveform of the electrical signal, and the fluorescent surface that inputs electrons scanned by the scanning electrode and generates a fluorescent image representing the time waveform of the light signal; the imaging element that captures the fluorescent image generated on the fluorescent surface of the stripe tube and outputs a waveform image; and the input optical system that inputs the light signal into the photoelectric surface; (5) the waveform analysis unit calculates the time waveform of the electrical signal based on the waveform image output by the imaging element, and (6) the input optical system of the waveform measurement unit inputs the light signal as a linear optical image extending in a direction intersecting the scanning direction into the photoelectric surface.

[0011] The implementation method is an electrical signal measurement method. The electrical signal measurement method includes: (1) a signal conversion step, in which an optical modulator is used to intensity-modulate a measurement light of a specified wavelength based on an electrical signal input as a measurement object with a time waveform, and the measurement light modulated by the optical modulator is output as an optical signal having a time waveform corresponding to the time waveform of the electrical signal; (2) a waveform measurement step, in which the time waveform of the optical signal output in the signal conversion step is measured; and (3) a waveform analysis step, in which the time waveform of the electrical signal is determined based on the measurement result of the time waveform of the optical signal in the waveform measurement step; and (4) in the waveform measurement step, a stripe tube is used to photograph the fluorescent surface of the stripe tube. The generated fluorescence image and output waveform image, the stripe tube includes: a photoelectric surface that generates electrons according to the input of the light signal, a scanning electrode that scans the electrons from the photoelectric surface in a specified scanning direction within a scanning period set according to the time waveform of the electrical signal, and a fluorescence surface that inputs the electrons scanned by the scanning electrode and generates a fluorescence image representing the time waveform of the light signal; (5) in the waveform analysis step, the time waveform of the electrical signal is determined based on the waveform image output in the waveform measurement step, and (6) in the waveform measurement step, the light signal is input to the photoelectric surface as a linear optical image extending in a direction intersecting the scanning direction.

[0012] In the aforementioned electrical signal measuring apparatus and method, an electrical signal input as a time waveform measurement object is converted into an optical signal of a predetermined wavelength using an optical modulator. Furthermore, the time waveform of the optical signal is measured by a waveform measuring unit including a stripe tube, and the time waveform of the electrical signal is determined based on the obtained waveform image.

[0013] With this structure, after converting the electrical signal into an optical signal, waveform measurement is performed using a streak camera containing a streak tube, thereby enabling high-speed measurement of the time waveform of the electrical signal. Furthermore, in the above structure, by appropriately setting the wavelength of the measurement light used to generate the optical signal, waveform measurement of the optical signal using the streak tube can be preferably performed, while the time waveform of the electrical signal can be measured with good accuracy.

[0014] Furthermore, in the above structure, the input optical system provided in the front section of the stripe tube in the waveform measurement unit is configured to input the optical signal as a linear optical image extending in a direction intersecting the scanning direction in the stripe tube into the photoelectric surface. Therefore, compared to the case where the optical signal is input as a dot-shaped optical image into the photoelectric surface, the input light density can be reduced and degradation of the photoelectric surface can be suppressed, and the measurement of electrical signals using the stripe tube is preferably performed. [The effects of the invention]

[0015] According to the embodiment of the electrical signal measuring device and electrical signal measuring method, the time waveform of an electrical signal can be measured at high speed. Attached Figure Description

[0016] Figure 1 This is a block diagram that schematically illustrates the structure of one embodiment of an electrical signal measuring device, namely a semiconductor inspection device, as an example of its application. Figure 2 This is a block diagram illustrating an example of the specific structure of the voltage application section, the inspection optical system, and the optical measurement section. Figure 3 This is a block diagram that schematically shows the structure of the first embodiment of an electrical signal measuring device including a signal conversion unit and a waveform measurement unit. Figure 4 This is a diagram showing an example of the structure of an optical modulator in a signal conversion section. Figure 5 This is a diagram illustrating an example of the structure of a stripe tube in a waveform measurement section. Figure 6 This is a side view showing an example of the structure of the waveform measurement unit. Figure 7 Here are (a) top views and (b) side views showing an example of the structure of the input optical system in the waveform measurement section. Figure 8In the diagram, (a) is an optical image showing the light signal incident on the photoelectric surface of the stripe tube, and (b) is a scan of the electron image on the fluorescent surface. Figure 9 This is a diagram showing an example of a fluorescence image generated on a fluorescent surface, corresponding to an optical image of the light signal from the photoelectric surface of the input stripe tube. Figure 10 The diagram shows an example of: (a) a waveform image obtained when the generation of the optical signal in the signal conversion unit is ON, and (b) a basic image obtained when the generation of the optical signal is OFF. Figure 11 It is the measurement result displayed on the oscilloscope showing the electrical signal, and Figure 3 A graph showing the measurement results from the electrical signal measuring device. Figure 12 This is a graph showing the relationship between (a) the intensity of reflected light, (b) the intensity of electrical signals, and (c) the intensity of optical signals. Figure 13 These are (a) top views and (b) side views of a first modified example showing the structure of the input optical system of the waveform measurement unit. Figure 14 These are (a) top views and (b) side views of a second modified example showing the structure of the input optical system of the waveform measurement unit. Figure 15 These are (a) top views and (b) side views of a third modified example showing the structure of the input optical system of the waveform measurement unit. Figure 16 This is a diagram showing the structure of the second embodiment of the electrical signal measuring device. Figure 17 This is a schematic diagram illustrating the main scan and retrace scan in a stripe tube. Figure 18 This is a diagram illustrating an example of the setting of the measurement period and the phase of the scan cycle in a stripe tube. Figure 19 This is a diagram showing the structure of the third embodiment of the electrical signal measuring device. Figure 20 It is shown Figure 19 The diagram shows the input of two types of optical signals to the photoelectric surface in the structure shown. Figure 21 This is a diagram showing the structure of the fourth embodiment of the electrical signal measuring device. Detailed Implementation

[0017] The following, along with the accompanying Figure 1This section provides a detailed description of the implementation methods for electrical signal measuring devices and methods. Furthermore, in the description of the accompanying drawings, identical elements are labeled with the same symbols, and repeated descriptions are omitted. Additionally, the scale of the accompanying drawings may not be consistent with the description.

[0018] Below, we will first describe the structure of a semiconductor inspection apparatus, using one specific application of the electrical signal measuring device as an example. Then, we will explain the structure and operation of the electrical signal measuring device used in the semiconductor inspection apparatus. Furthermore, the application of the electrical signal measuring device described later is not specifically limited to semiconductor inspection, but can be widely used for measuring the time waveform of electrical signals from various structures.

[0019] Figure 1 This is a block diagram schematically illustrating the structure of one embodiment of the semiconductor inspection apparatus. The semiconductor inspection apparatus 1A of this embodiment is a device for inspecting a semiconductor device D by irradiating it with probe light. It is configured to include a semiconductor inspection unit 10, a light measurement unit 20, a probe light source 21, an electrical signal measurement device 2A, a control device 50, an input unit 53, a display unit 54, and a scan control unit 55. Furthermore, the semiconductor inspection apparatus 1A also includes a second light measurement unit 61, a second waveform measurement unit 62, and a frequency resolution unit 63.

[0020] Furthermore, in the following figures, the double lines shown between the various parts of the device represent the transmission paths of light such as probe light, reflected light, measurement light, and optical signals. Optical fibers, such as single-mode optical fibers, are preferably used as these transmission paths. Alternatively, depending on the transmission conditions, spatial transmission paths utilizing lenses or mirrors may also be used. Additionally, the single lines and arrow lines shown between the various parts of the device represent the transmission paths of electrical signals, synchronization signals, trigger signals, control signals, etc., or the optical paths of probe light and reflected light relative to the semiconductor device D.

[0021] become Figure 1 The semiconductor device D of the device under test (DUT) of the semiconductor inspection apparatus 1A shown can be any semiconductor device, such as integrated circuit (IC) with a PN junction such as a transistor, or logic device, memory device, or analog device of large scale integrated circuit (LSI).

[0022] Furthermore, as semiconductor device D, mixed-signal devices combining the above-mentioned components, or power semiconductor devices (power devices) such as high-current / high-voltage MOS transistors, bipolar transistors, and IGBTs can also be used. Furthermore, the inspection of semiconductor device D performed by semiconductor inspection apparatus 1A uses methods such as EOP and EOFM, including verifying the operating status of each part of the device and identifying the location of the fault. Furthermore, the various parts of semiconductor device D that are subject to inspection can include, for example, transistors, diodes, capacitors, and wiring that are subject to applied voltage.

[0023] The semiconductor inspection unit 10 is configured to include an inspection optical system 11 and a voltage application unit 12. The inspection optical system 11 illuminates the semiconductor device D to be inspected with a first wavelength of probe light supplied from the probe light source 21 via the light measurement unit 20. In addition, the inspection optical system 11 outputs the reflected light from the probe light reflected by the semiconductor device D to the light measurement unit 20.

[0024] The probe light irradiation of the semiconductor device D is typically performed from the back side of the device, such as the Si substrate side. Therefore, light with a wavelength that is transparent to silicon is used as the probe light. In this case, the first wavelength of the probe light is preferably set in the wavelength range of 1050 nm or more and 5000 nm or less. Specifically, light with a wavelength of 1.3 μm can be used as such a probe light.

[0025] The probe light supplied by the self-probe light source 21 can be either coherent or incoherent. Specifically, the probe light source 21 can be, for example, a laser light source, an SLD (Super Luminescent Diode), an ASE (Amplified Spontaneous Emission) light source, an LED (Light Emitting Diode), etc.

[0026] The voltage application unit 12 applies a voltage to the semiconductor device D, and a test pattern that repeats over time within a predetermined test cycle. During this time, the state of each part of the semiconductor device D, to which the test pattern is applied, changes over time within the test cycle of voltage variation. The optical measurement unit 20 supplies probe light output from the probe light source 21 to the inspection optical system 11, and also inputs reflected light from the semiconductor device D output from the inspection optical system 11. The intensity of the reflected light from the semiconductor device D changes over time within the test cycle according to the time-varying state of the semiconductor device D.

[0027] Figure 2This is a block diagram illustrating an example of the specific structure of the voltage application unit 12, the inspection optical system 11, and the optical measurement unit 20. In this structural example, the voltage application unit 12 is configured as a test head 12a having a semiconductor LSI tester and a test plate 12b. The test head 12a mounts the semiconductor device D via the test plate 12b, and repeatedly applies a test pattern containing a predetermined operating pulse signal to the semiconductor device D during the aforementioned test cycle, thereby driving the semiconductor device D.

[0028] The test head 12a includes, for example, a pulse generator for generating operating pulse signals to drive transistors and the like contained in the semiconductor device D, a test section for inputting the operating pulse signals to the semiconductor device D, and a power supply. Furthermore, the test board 12b is a semiconductor substrate on which the semiconductor device D is mounted. The test board 12b includes peripheral chips, circuits, and terminals required for the operation of the semiconductor device D.

[0029] The inspection optical system 11 is configured to include a stage 14, a scanning optical system 15, an imaging optical system 16, and an objective lens 17. Furthermore, the scanning optical system 15, the imaging optical system 16, and the objective lens 17 are disposed within a dark box 13 while being mounted on the stage 14. The objective lens 17 is positioned between the imaging optical system 16 and the semiconductor device D. In this structural example, multiple objectives are provided as the objective lens 17, which can be switched by a turret 18. For example, a low-magnification (e.g., 5x) objective lens and a high-magnification (e.g., 50x) objective lens may be provided as the multiple objectives 17.

[0030] The scanning optical system 15 guides the probe light from the self-probe light source 21, input via the light measurement unit 20 and the optical fiber, to the imaging optical system 16. To reduce light reflection, the output end of the probe light from the optical fiber is preferably of the APC (Automatic Power Control) type. The scanning optical system 15 is configured, for example, as an optical scanner having optical scanning elements including a galvano mirror, a MEMS mirror, etc., and scans and sets the illumination position of the probe light on the semiconductor device D based on the control of the scanning control unit 55.

[0031] The imaging optics system 16 guides the probe light input from the self-scanning optics system 15 along a predetermined optical path to the objective lens 17. The objective lens 17 focuses the probe light onto a predetermined illumination position in the semiconductor device D. Furthermore, the reflected light (return light) generated by illuminating the semiconductor device D with the probe light is input to the light measurement unit 20 via the objective lens 17, the imaging optics system 16, the scanning optics system 15, and the optical fiber. The wavelength of this reflected light is the same as the probe light, being the first wavelength. Additionally, if necessary, a solid-state lens may be provided between the objective lens 17 and the semiconductor device D.

[0032] In the reflected light from semiconductor device D, the reflectivity and absorptivity of the probe light undergo subtle changes (on the order of tens of ppm / V) due to the electric field or heat generated at the measurement point where the probe light is irradiated, and the resulting changes in carrier density. This results in a slight time-varying intensity of the reflected light. By measuring this time-varying intensity of the reflected light, semiconductor device D can be inspected.

[0033] The optical measurement unit 20 is configured to include an optical coupler 22, an optical amplifier 23, an optical splitter 24, a photodetector 25, and an AC amplifier 26. The optical coupler 22 is optically coupled to the probe light source 21, the optical amplifier 23, and the scanning optical system 15 via an optical fiber, outputting probe light input from the probe light source 21 to the scanning optical system 15, and outputting reflected light from the semiconductor device D input from the scanning optical system 15 to the optical amplifier 23. Furthermore, an FC adapter for APC is used, for example, to connect the optical coupler 22 and the scanning optical system 15.

[0034] Specifically, the optical coupler 22 can be, for example, a PBS-type optical coupler or a circulator-type optical coupler. When the optical coupler 22 is a PBS-type optical coupler, a λ / 4 wavelength plate can also be provided in the scanning optical system 15. Furthermore, when the optical coupler 22 is a circulator-type optical coupler, a λ / 2 wavelength plate can also be provided in the scanning optical system 15. Alternatively, a Faraday rotator can be provided in the scanning optical system 15 instead of the aforementioned wavelength plate. Furthermore, an optical splitter can also be used as the optical coupler 22.

[0035] Optical amplifier 23 amplifies the intensity of the reflected light from semiconductor device D, input from optical coupler 22, within the range of gain desaturation and the range of desaturation of the subsequent photodetector 25, and outputs the amplified reflected light to optical splitter 24. Specifically, optical amplifier 23 can be, for example, a semiconductor optical amplifier, fiber optic amplifier, solid-state optical amplifier (SOA), tapered optical amplifier, booster optical amplifier, etc. Furthermore, optical amplifiers using crystals, gases, liquids, etc., as amplification media can also be used as optical amplifier 23.

[0036] Optical splitter 24 is optically coupled to photodetector 25, second optical measurement unit 61, and optical amplifier 23 via optical fiber, outputting reflected light from optical amplifier 23 to photodetector 25 and second optical measurement unit 61 at a predetermined branching ratio. Specifically, optical splitter 24 can be, for example, a 90:10 optical splitter. In this case, the light from optical amplifier 23 is branched in optical splitter 24 relative to photodetector 25 and second optical measurement unit 61 at a branching ratio of 90:10. Furthermore, the connection between optical splitter 24 and second optical measurement unit 61 uses, for example, an FC connector.

[0037] The photodetector 25 detects the amplified reflected light input from the light splitter 24 and outputs an electrical signal (detection signal) representing the detection result. The electrical signal output from the photodetector 25 has a time waveform corresponding to the time change of the intensity of the reflected light from the semiconductor device D. As the photodetector 25, a PIN photodiode (PIN-PD) capable of high-speed detection is preferably used.

[0038] When a high-speed optical sensor such as a PIN-PD is used as the photodetector 25, the input is essentially a single-mode optical fiber. Therefore, the input optical fiber, optical coupler, etc., are preferably all composed of single-mode optical fibers. However, this light guiding system can also be composed of an optical system that combines a semi-reflective mirror, a polarizing beam splitter, a collimator, etc. In addition to a PIN-PD, other photodiodes such as avalanche photodiodes (APDs) and photoelectron multipliers can also be used as the photodetector 25.

[0039] AC amplifier 26 amplifies the AC component of the detection signal input from photodetector 25 and outputs the amplified signal to electrical signal measuring device 2A. Through signal amplification by AC amplifier 26, the time-varying intensity component of the detection signal is extracted. Furthermore, the offset level of the electrical signal input to electrical signal measuring device 2A is appropriately adjusted and set. The operation of resetting this offset will be described later.

[0040] Refer again Figure 1 The electrical signal measuring device 2A is configured to include a signal conversion unit 30 and a waveform measuring unit 40. The signal conversion unit 30 converts the electrical signal input from the AC amplifier 26 of the optical measuring unit 20, which is the object of measurement, into an optical signal for signal waveform measurement, and outputs the converted optical signal to the waveform measuring unit 40. The waveform measuring unit 40 measures the time waveform of the optical signal input from the signal conversion unit 30 and outputs the measurement result to the control device 50. The structure of the electrical signal measuring device 2A will be described in detail below.

[0041] The control device 50 is configured to include an inspection control unit 51 and a waveform analysis unit 52. The inspection control unit 51 controls and executes the inspection of the semiconductor device D in the semiconductor inspection device 1A and the measurement of the time waveform of the electrical signal in the electrical signal measurement device 2A by controlling the operation of various parts of the device, including the semiconductor inspection unit 10, the light measurement unit 20, the detection light source 21, the scanning control unit 55, and the electrical signal measurement device 2A. The waveform analysis unit 52 calculates the time waveform of the electrical signal based on the measurement result of the time waveform of the light signal input from the waveform measurement unit 40 of the electrical signal measurement device 2A. In the case of the semiconductor inspection device 1A described above, the electrical signal for calculating the time waveform is an electrical signal generated in the light measurement unit 20 based on the time change of the intensity of the reflected light.

[0042] In addition, Figure 1 In the structure shown, the control device 50 is provided with an input section (input device) 53 and a display section (display device) 54. The input section 53 is composed of, for example, a keyboard or mouse, and is used to input information required for semiconductor inspection in the semiconductor inspection device 1A, electrical signal measurement in the electrical signal measurement device 2A, and waveform analysis. The display section 54 is composed of, for example, a liquid crystal display, and is used to display the inspection results of the semiconductor device D and the results of waveform analysis of the electrical signals.

[0043] The control device 50 can be specifically configured as a computer, for example, having a CPU as a processing unit and ROM, RAM, and external memory devices as memory units. In this case, the computer functions as an inspection control device (measurement control device) and a waveform analysis device. Furthermore, the inspection control unit (measurement control unit) 51 and the waveform analysis unit 52 can be configured as different computers or as a single computer.

[0044] exist Figure 1 In the semiconductor inspection apparatus 1A shown, the second optical measurement unit 61, the second waveform measurement unit 62, and the frequency analysis unit 63 are device components that perform EOP and EOFM using the same methods as conventional inspection apparatuses. The second optical measurement unit 61 is configured, for example, as a photodetector including an avalanche photodiode and an amplifier. The second waveform measurement unit 62 is configured, for example, using a digitizing board or a digital oscilloscope. The frequency analysis unit 63 is configured, for example, using a spectrum analyzer for EOFM image acquisition or a lock-in amplifier.

[0045] In this structure, the electrical signal measuring device 2A functions as a high-speed digitization unit, and the second waveform measuring unit 62 functions as a low-speed digitization unit. Furthermore, a sinusoidal synchronization signal and a rectangular trigger signal are output from the voltage application unit 12 of the semiconductor inspection unit 10, and these synchronization signals and trigger signals are supplied to various parts of the device, such as the electrical signal measuring device 2A, the second waveform measuring unit 62, and the frequency analysis unit 63, as needed. Additionally, the synchronization signal is not limited to the aforementioned sinusoidal signal; for example, it can also be a rectangular wave signal.

[0046] Then, Figure 1 The structure and operation of the electrical signal measuring device 2A used in the semiconductor inspection apparatus 1A shown will be explained.

[0047] Figure 3 This is a block diagram schematically illustrating the structure of a first embodiment of an electrical signal measuring device including a signal conversion unit 30 and a waveform measurement unit 40. The electrical signal measuring device 2A of this embodiment is configured as a stripe oscilloscope using a stripe camera (see, for example, Patent Documents 3 and 4). Furthermore, as... Figure 3 As shown, the electrical signal measuring device 2A includes a waveform analysis unit (waveform analysis device) 52 of the control device 50, as needed.

[0048] In addition, Figure 3 In the diagram, the electrical signal measuring device 2A includes an optical measuring unit 20, a test head 12a, and a delay generator (DG) 19 connected to the test head 12a. For convenience, these are also presented as an electrical signal supply unit 80. Within the electrical signal supply unit 80, the optical measuring unit 20 functions as an electrical signal output unit 81, the test head 12a functions as a synchronization signal output unit 82, and the delay generator 19 functions as a trigger signal output unit 83. The delay generator 19 adjusts the delay time and pulse width of the signal supplied from the test head 12a and outputs it as a trigger signal.

[0049] Furthermore, as described above, the application of the electrical signal measuring device 2A in this embodiment is not limited to the semiconductor inspection device 1A, but can be applied to the measurement of the time waveform of electrical signals in various structures. In this case, the electrical signal output unit 81, the synchronization signal output unit 82, and the trigger signal output unit 83 in the electrical signal supply unit 80 are appropriately configured according to the specific measurement object. Furthermore, the synchronization signal output unit 82 and the trigger signal output unit 83 may also be configured so that they are not provided if not needed.

[0050] The signal conversion unit 30 is configured to include a measurement light source 31, an optical attenuator 32, and an optical modulator 33. The measurement light source 31 supplies measurement light of a predetermined wavelength. Furthermore, in the case of the semiconductor inspection apparatus 1A as described above, the measurement light source 31 supplies measurement light of a second wavelength different from the first wavelength of the probe light used in semiconductor inspection. This measurement light is continuous light that serves as the source of the optical signal input to the waveform measurement unit 40. As the measurement light, light of a wavelength that can be modulated by the optical modulator 33 and whose waveform can be measured by the stripe tube 42 in the waveform measurement unit 40 (described later) is used.

[0051] In this case, considering factors such as the sensitivity distribution of the photoelectric surface used in the stripe tube 42, the specified wavelength of the measurement light is preferably set in the wavelength range of 115 nm or more and 1600 nm or less. Furthermore, to obtain sufficient sensitivity, it is preferable to set it in the wavelength range of 200 nm or more and less than 1050 nm. Specifically, light with a wavelength of, for example, 850 nm or 780 nm can be used as such measurement light. In addition, to suppress the degradation of time resolution caused by dispersion within the optical fiber, it is preferable to use narrow-band light as the measurement light.

[0052] The measurement light source 31 can be, for example, a laser light source, an SLD (Super Luminescent Diode), or an LED (Light Emitting Diode). The measurement light source 31 used in practice is preferably selected according to the type of modulator used as the light modulator 33. The measurement light output from the measurement light source 31 is attenuated and adjusted in intensity (light quantity) in the light attenuator 32, and then input as continuous light into the light modulator 33.

[0053] The electrical signal from the optical measurement unit 20 is input to the optical modulator 33 as a modulation control signal. Based on the electrical signal input from the optical measurement unit 20, the optical modulator 33 modulates the intensity of the measurement light supplied from the measurement light source 31, and outputs the modulated measurement light as an optical signal with a time waveform corresponding to the time waveform of the electrical signal. As the optical modulator 33, an optical modulator configured to perform analog light intensity modulation is used.

[0054] As the optical modulator 33, specific types such as EO (Electro-Optic) modulators, AO (Acousto-Optic) modulators, MO (Magneto-Optic) modulators, and Pockels cells can be used. However, since Pockels cells require voltages in the hundreds of volts, they present problems in modulation of weak electrical signals. Furthermore, the bandwidth of AO modulators is limited to the hundreds of MHz range. Additionally, MO modulators require relatively large magnetic fields (currents).

[0055] Taking these aspects into consideration, an EO modulator is preferably used as the optical modulator 33. This allows for the preferred realization of intensity modulation of the measurement light by a high-speed electrical signal. Furthermore, when using an EO modulator, AO modulator, or MO modulator as the optical modulator 33, a laser light source is preferably used as the measurement light source 31. Moreover, when using a Boehringer cell as the optical modulator 33, an SLD or LED is preferably used as the measurement light source 31.

[0056] Figure 4 This diagram illustrates an example of the structure of the optical modulator 33 in the signal conversion unit 30. In this example, the optical modulator 33 includes an EO crystal 330, optical waveguides 331-334 formed on the crystal 330, an RF electrode 335, a bias electrode 336, and ground electrodes 337a-337d, and is configured as an EO modulator capable of optical intensity modulation. Specifically, lithium niobate (LiNbO3) can be used as the EO crystal 330, for example.

[0057] exist Figure 4 In the structure shown, an input waveguide 331 is arranged on the left side of the rectangular EO crystal 330, and an output waveguide 334 is arranged on the right side. The input waveguide 331 branches into a first branch waveguide 332 and a second branch waveguide 333 via a 50:50 optical coupler. Furthermore, these first and second branch waveguides 332 and 333 are again coupled to the output waveguide 334 via a 50:50 optical coupler.

[0058] The measurement light from the input optical waveguide 331, which is the source of the measurement light from the measurement light source 31, is branched by the input-side optical coupler to the first and second branch optical waveguides 332 and 333. Furthermore, the branched light, guided separately by the first and second branch optical waveguides 332 and 333, interferes when combined at the output-side optical coupler, and is output from the output optical waveguide 334 as interference light with a specified intensity. The interference light output from this output optical waveguide 334 becomes the optical signal of the measurement target input waveform measurement unit 40, which is a time waveform.

[0059] Between the first and second branch waveguides 332 and 333, an RF electrode 335 is provided on its input side, and a bias electrode 336 is provided on its output side. A ground electrode 337a is provided across the first branch waveguide 332, and a ground electrode 337b is provided across the second branch waveguide 333, relative to the RF electrode 335. Furthermore, a ground electrode 337c is provided across the first branch waveguide 332, and a ground electrode 337d is provided across the second branch waveguide 333, relative to the bias electrode 336.

[0060] In the above structure, the region between the electrodes, indicated by the shaded lines in the figure, is where an electric field is applied to the optical waveguide by applying a voltage to the RF electrode 335 or the bias electrode 336. When an electric field is applied to the EO crystal 330, the refractive index changes within the optical waveguide formed in the region where the electric field is applied. Consequently, the optical path difference between the first and second branch optical waveguides 332 and 333 changes, and the intensity of the interference light output from the output optical waveguide 334 changes.

[0061] An electrical signal from the light measurement unit 20 is applied to the RF electrode 335 on the input side of the EO crystal 330 for intensity modulation of the measured light. The light modulator 33 then converts the electrical signal into an optical signal. Furthermore, a phase adjustment for light interference is applied to the voltage of the bias electrode 336, for example, offset adjustment during the signal conversion from electrical to optical signal, as described later.

[0062] As described above, in the optical modulator 33 using an EO modulator, the polarization direction of the modulated light has been determined. Furthermore, it needs to have an interference distance longer than the interferometer in the optical modulator 33; therefore, laser light is preferably used as the measurement light to be modulated. In particular, when the Z-direction in the crystal is the up-down direction as shown in the figure, if the directions of the electric field applied to the Z-axis are opposite, the change in refractive index is opposite, thus allowing for higher voltage and faster light modulation. Alternatively, a thin-film EO modulator utilizing a photonic integrated circuit (PIC) can also be used as the optical modulator 33.

[0063] Refer again Figure 3 The waveform measurement unit 40 includes an input optical system 41, a stripe tube 42, an output optical system (imaging optical system) 43, an imaging element 44, and a synchronization unit 45, and is configured as a stripe camera. Furthermore, a rectangular wave trigger signal from the delay generator 19 (trigger signal output unit 83) is input to the waveform measurement unit 40, which includes the stripe tube 42. Additionally, a sine wave or similar synchronization signal from the test head 12a (synchronization signal output unit 82) is input via the synchronization unit (synchronization circuit) 45.

[0064] The structure of the streak camera, which includes the waveform measurement unit 40 with the streak tube 42, will be described. Figure 5 This is a perspective view showing an example of the structure of the striped tube 42. Furthermore, Figure 6This is a side view showing an example of the structure of the waveform measurement unit 40 including the stripe tube 42. In this structural example, the stripe tube 42 is configured to have a peripheral tube 420, a photoelectric surface 421, an accelerating electrode 422, a vertical scanning electrode 423, a horizontal scanning electrode 424, a microchannel plate (MCP) 425, and a fluorescent surface 426. Alternatively, the stripe tube 42 may be configured without the MCP 425.

[0065] Additionally, in the following figures, such as Figure 5 As shown in the diagram, with respect to the structure of the stripe tube 42, the input optical system 41, and the output optical system 43, the direction of propagation of the light signal and electrons is defined as the z-axis direction, the scanning direction of electrons in the stripe tube 42, which is orthogonal to the z-axis direction, is defined as the y-axis direction, and the direction orthogonal to both the z-axis and y-axis directions is defined as the x-axis direction. Furthermore, Figure 6 This is a side view of the structure of the waveform measurement unit 40 as viewed from the x-axis direction.

[0066] exist Figure 5 In the structure shown, a photoelectric surface 421 is provided on the input side of the peripheral tube 420, which extends relative to the z-axis direction, and a fluorescent surface 426 is provided on the output side opposite to the photoelectric surface 421. An optical signal from the signal conversion unit 30 is incident on the photoelectric surface 421 via the input optical system 41, forming an optical image P1 on the photoelectric surface 421. The photoelectric surface 421 generates electrons (photoelectrons) according to the input optical signal. The number of electrons generated on the photoelectric surface 421 corresponds to the intensity of the optical signal at each moment. Electrons emitted from the photoelectric surface 421 are accelerated in the z-axis direction by the accelerating electrode 422 within the peripheral tube 420.

[0067] Within the peripheral tube 420 between the photoelectric surface 421 and the phosphor surface 426, the aforementioned vertical scanning electrode 423, horizontal scanning electrode 424, and MCP 425 are sequentially arranged from the side of the photoelectric surface 421. The vertical scanning electrode 423, by applying a scanning voltage of a predetermined pattern, scans electrons from the photoelectric surface 421 in a predetermined scanning direction (y-axis direction) within a scanning cycle set according to the test cycle in the semiconductor inspection unit 10. The electrons scanned by the scanning electrode 423 are multiplied by the MCP 425 and incident on the phosphor surface 426. The size of the phosphor surface 426 is, for example, φ18mm.

[0068] Furthermore, at this time, the electron image P2 formed on the fluorescent surface 426 is scanned by the scanning electrode 423 and moves along the y-axis direction over time. Thus, on the fluorescent surface 426, with the y-axis direction as the time axis, a fluorescent image representing the time waveform of the light signal input to the photoelectric surface 421 is generated. Additionally, in Figure 5For ease of illustration, the movement of the electron image P2 along the y-axis on the incident surface of the MCP425 is schematically shown. Furthermore, the horizontal scanning electrode 424 is used when it is necessary to scan and move the electron image P2 in the x-axis direction, which is orthogonal to the normal scanning direction.

[0069] The fluorescence image produced on the fluorescent surface 426 of the striped tube 42, such as Figure 6 As shown, the image is input to the imaging element 44 via the output optical system 43. The imaging element 44 captures the fluorescence image generated on the phosphor surface 426 and outputs a waveform image as a 2D image. The imaging element 44 is a 2D imaging element such as a CMOS imaging element or a CCD imaging element; specifically, for example, a CMOS camera with 2048×2048 pixels and a pixel size of 6.5μm×6.5μm is used. Furthermore, in Figure 6 In the structure shown, the output optical system 43 consists of lenses 430 and 431.

[0070] The waveform image acquired in the imaging element 44, like the fluorescence image on the phosphor surface 426, becomes an image representing the time waveform of the light signal input to the waveform measurement unit 40, with the y-axis as the time axis. The waveform analysis unit 52 of the control device 50 (see reference...) Figure 3 Based on the waveform image output by the self-image sensor 44, the time waveform of the electrical signal corresponding to the time waveform of the optical signal is obtained. This time waveform of the electrical signal corresponds to the time change in the intensity of the reflected light from the semiconductor device D in the semiconductor inspection unit 10. Therefore, by referring to the time waveform of the electrical signal obtained by the waveform analysis unit 52, the semiconductor device D can be inspected.

[0071] Furthermore, to accurately measure the minute temporal changes in the intensity of reflected light in the semiconductor inspection section 10, the configuration can be such that the optical signal from the signal conversion section 30 is repeatedly input into the waveform measurement section 40 over multiple cycles, and a fluorescence image of the time waveform of the optical signal accumulated over multiple test cycles is generated on the fluorescent surface 426 of the stripe tube 42. In this case, the waveform image acquired by the imaging element 44 also becomes a waveform image of the time waveform of the optical signal accumulated over multiple cycles. This accumulation of the time waveform of the optical signal can also be appropriately used in structures other than semiconductor inspection, such as when the electrical signal of the object being measured is a weak signal and the time waveform repeats within a specified period.

[0072] In order to preferably perform the measurement of the time waveform of the electrical signal and the inspection of the semiconductor device D as described above, the stripe camera of the waveform measurement unit 40 controls the measurement operation of the time waveform of the optical signal based on the synchronization signal or trigger signal supplied by the voltage application unit 12. Specifically, the waveform measurement unit 40 has two measurement modes for measuring the time waveform of the optical signal: single scan mode and synchronous scan mode.

[0073] In single-scan mode, the waveform measurement unit 40 performs single-shot measurements synchronously with a rectangular wave trigger signal from the test head 12a or the delay generator 19. In this case, the scan voltage applied to the scan electrode 423 becomes, for example, a voltage pattern that changes linearly. Furthermore, the test cycle for voltage application in the semiconductor tester can be freely determined at this time. In addition, in single-scan mode, single-shot measurements can be repeated multiple times, and the time waveform can be accumulated.

[0074] In synchronous scan mode, the waveform measurement unit 40 measures the time waveform accumulated over multiple cycles in sync with a sinusoidal synchronization signal from the test head 12a. In this case, the scan voltage applied to the scan electrode 423 is controlled by the synchronization unit 45 and, like the synchronization signal, becomes a sinusoidal voltage pattern. In this mode, for example, a high time accuracy of 800 fs or less can be achieved. However, at this time, the test cycle in the semiconductor tester is limited to an integer multiple of the period of the synchronization signal.

[0075] The input conditions for the optical signal to the photoelectric surface 421 of the stripe tube 42 and the structure of the input optical system 41 provided at the front end of the stripe tube 42 will be described. In the above structure, the noise floor for measurement is determined by the shot noise based on the amount of optical signal input to the stripe tube 42. In this case, it is preferable to increase the amount of light to reduce the proportion of shot noise, but the photoelectric surface 421 has an upper limit with respect to the input light density. Furthermore, when performing multiple cumulative measurements of the time waveform of the optical signal, the resulting degradation of the photoelectric surface becomes a problem.

[0076] Considering this aspect, in order to reduce the input light density to the photoelectric surface and suppress its degradation, the input optical system 41 preferably inputs the light signal as a linear optical image extending in a direction intersecting the scanning direction (y-axis direction) in the stripe tube 42 to the photoelectric surface 421. Thus, as... Figure 5 Compared to the case where the light signal is input as a point-like optical image P1, the input light density can be reduced. Furthermore, the image formation direction of the linear optical image in this case is preferably set to a direction orthogonal to the scanning direction (x-axis direction).

[0077] Figure 7 This is a diagram illustrating an example of the structure of the input optical system 41 in the waveform measurement unit 40. Figure 7 middle, Figure 7 (a) shows a top view viewed from the y-axis direction. Figure 7 (b) shows a side view as viewed from the x-axis direction. Furthermore, Figure 7 The lens structure in the input optical system 41 shown is similar to... Figure 6 The lens structure shown in the figure is the same as the one described above.

[0078] Figure 6 and Figure 7 The input optical system 41 shown is composed of a cylindrical lens 410, a lens 411, and a lens 412, sequentially from the input side of the optical signal from the signal conversion unit 30 (the fiber optic end of the output optical signal). Thus, by using a cylindrical lens 410 in the input optical system 41, such as... Figure 7 As shown in the diagram, a linear optical image can be formed on the photoelectric surface 421, such that the light diffuses.

[0079] Figure 8 This is a schematic diagram illustrating the optical and electronic images formed in the stripe tube 42. Figure 8 middle, Figure 8 (a) is an optical image P3 showing the light signal incident on the photoelectric surface 421 of the stripe tube 42. Figure 8 (b) is a diagram showing a scan of the electron image P4 on the fluorescent surface 426. Furthermore, Figure 8 The optical image P3 and electronic image P4 shown are used in Figure 7 It is formed in the structure of the input optical system 41 shown.

[0080] like Figure 8 As shown in (a), the optical signal is input to the photoelectric surface 421 as a linear optical image P3 extending in the x-axis direction. Furthermore, as... Figure 8 As shown in (b), a linear electronic image P4 corresponding to the optical image P3 and extending in the x-axis direction is formed on the fluorescent surface 426. By scanning the electronic image P4 in the y-axis direction, a fluorescent image showing the time waveform of the light signal is generated.

[0081] Figure 9 This is an example of a fluorescence image generated on the phosphor surface 426 corresponding to a linear optical image of the light signal from the photoelectric surface 421 of the input stripe tube 42. Here, scanning of electrons by the scanning electrode 423 is not performed; instead, the fluorescence image corresponding to the linear electron image is measured directly. Furthermore, with... Figure 9 The linear optical image on the photoelectric surface 421 corresponding to the fluorescent image shown has a length of approximately 5 mm in the x-axis direction and a width of approximately 15 μm in the y-axis direction.

[0082] also, Figure 10 This illustrates an example of an image obtained by the imaging element 44 capturing a fluorescent image generated on the fluorescent surface 426 during a typical measurement in which the scanning electrode 423 scans electrons. Figure 10 middle, Figure 10 Image (a) shows a waveform image obtained when the generation of optical signal in the signal conversion unit 30 is turned on (ON). Figure 10 (b) shows the base image (background image) obtained with the light signal generation off. Figure 10 The fluorescence image obtained by measuring the scan line electron image in waveform image (a).

[0083] Depend on Figure 3 The electrical signal measurement method performed by the electrical signal measuring device 2A shown includes a signal conversion step, a waveform measurement step, and a waveform analysis step. In the signal conversion step, in the signal conversion unit 30, based on the electrical signal input as the measurement object as a time waveform, the measurement light is intensity modulated by the optical modulator 33, and the modulated measurement light is output as an optical signal having a time waveform corresponding to the time waveform of the electrical signal.

[0084] In the waveform measurement step, the waveform measurement unit 40 uses a stripe tube 42 and an imaging element 44 to measure the time waveform of the optical signal output from the signal conversion unit 30, and outputs the obtained waveform image. Meanwhile, the input optical system 41 inputs the optical signal as a linear optical image extending in a direction intersecting the scanning direction of electrons in the stripe tube 42 to the photoelectric surface 421. In the waveform analysis step, the waveform analysis unit 52 of the control device 50 calculates the time waveform of the electrical signal based on the waveform image output from the waveform measurement unit 40.

[0085] The effects of the electrical signal measuring device 2A according to the above embodiments and the electrical signal measuring method performed thereon will be explained.

[0086] exist Figures 3-8 In the electrical signal measuring device 2A and the electrical signal measuring method shown, the electrical signal input as a measurement object with a time waveform is converted into an optical signal of a predetermined wavelength by the optical modulator 33. Furthermore, the time waveform of the optical signal is measured by the waveform measuring unit 40, which includes the stripe tube 42, and the time waveform of the electrical signal is determined based on the waveform image acquired by the imaging element 44.

[0087] According to this structure, the time waveform of the electrical signal can be measured at high speed by using a streak camera containing a streak tube 42 to measure the waveform after the electrical signal is converted into an optical signal. Furthermore, in the above structure, by appropriately setting the wavelength of the measurement light used to generate the optical signal, waveform measurement of the optical signal using the streak tube 42 can be preferably performed, while the time waveform of the electrical signal can be measured with good accuracy.

[0088] Furthermore, in the above structure, the input optical system 41 provided in the front section of the stripe tube 42 in the waveform measurement unit 40 is configured such that the optical signal is input to the photoelectric surface 421 as a linear optical image extending in a direction intersecting the scanning direction of the electrons in the stripe tube 42. Therefore, compared to the case where the optical signal is input to the photoelectric surface 421 as a dot-shaped optical image, the input light density can be reduced and the degradation of the photoelectric surface 421 can be suppressed, preferably performing the measurement of the electrical signal using the stripe tube 42.

[0089] Figure 11 This is a graph showing the measurement results of the time waveform of the electrical signal. Figure 11 In the chart, the horizontal axis represents time (ps), and the vertical axis represents signal strength (au). Furthermore, in Figure 11 In the diagram, chart G1 shows the measurement results of electrical signals measured with a 20GHz oscilloscope, and chart G2 shows the results of measurements taken with a 20GHz oscilloscope. Figure 3 The measurement results of the electrical signal measuring device 2A with the structure shown are as follows.

[0090] Here, pulsed laser light from a femtosecond laser was detected using a PIN-PD in the 40 GHz band, and the output electrical signal was measured. The laser wavelength was 1550 nm, the repetition rate was 100 MHz, and the pulse width was less than 100 fs. Furthermore, in the measurement results shown in Figure G1, a Tektronix DPO72004C oscilloscope in the 20 GHz band was used.

[0091] Regarding the measurement results of graph G2, the cumulative velocity in the stripe camera of waveform measurement unit 40 is 50MHz, the frame rate is 60Hz, and the cumulative time is 1.6 seconds (100 frames with an exposure time of 10ms). The cumulative time of the base image used for subtraction described later is also 1.6 seconds. Figure 11 As shown in the graphs, in the structure of the above embodiment, in the measurement of weak signals, high-speed accumulation that cannot be achieved in an oscilloscope is performed, and time waveforms are preferably obtained. Furthermore, the FWHM of the measured waveform is 31.85 ps in graph G1 and 19.21 ps in graph G2.

[0092] In the measurement device 2A and measurement method of the above embodiments, the electrical signal may also be configured such that its time waveform repeats within a specified period (e.g., the test period in semiconductor inspection). Furthermore, in the waveform measurement unit 40, the fluorescent surface 426 of the stripe tube 42 generates a fluorescence image of the time waveform of the light signal accumulated over a specified period of multiple cycles.

[0093] In this case, after converting the electrical signal into an optical signal, waveform measurement is performed using the stripe tube 42. While generating a fluorescence image using the fluorescent surface 426 and acquiring the waveform image using the imaging element 44, the time waveform of the optical signal is accumulated. This allows for high-speed, optical accumulation of the time waveform of the electrical signal multiple times. Furthermore, the number of accumulations of the time waveform of the optical signal in this case is preferably appropriately set according to the conditions of the object being measured, i.e., the electrical signal. For example, in the case of synchronous scanning at 40MHz using a stripe camera, the number of accumulations per second is determined by factors such as the test cycle, within a maximum range of 40 million times / second.

[0094] In the measuring apparatus 2A and measuring method of the above embodiments, regarding the setting of the wavelength of the measuring light, as described above, the specified wavelength of the measuring light is preferably set in the wavelength range of 115 nm or more and 1600 nm or less. By setting the wavelength of the measuring light used to generate the optical signal as described above, it is preferable to perform waveform measurement of the optical signal in which the measuring light is intensity modulated by an electrical signal using the stripe tube 42, and the time waveform of the electrical signal can be measured with good accuracy.

[0095] In the measuring device 2A and measuring method of the above embodiments, the waveform analysis unit 52 may also be configured to correct the waveform image obtained when the generation of the light signal in the signal conversion unit 30 is turned on, based on a base image obtained when the generation of the light signal is turned off. In this way, by correcting the waveform image based on the base image and using the corrected waveform image to determine the time waveform of the electrical signal, the time waveform of the electrical signal can be measured with even higher accuracy.

[0096] The acquisition of this basic image and the resulting basic correction of the waveform image can be used, for example, to correct deviations in the measurement efficiency of the position of the fluorescent surface 426 of the stripe tube 42 or the imaging element 44 (gain correction). Furthermore, the basic correction described above is also effective for correcting time-related drift in the measurement characteristics of the electrical signal measuring device 2A.

[0097] For example, the EO modulator used in the optical modulator 33 of the signal conversion unit 30 has a characteristic drift caused by heat, and even after gain correction, the offset sometimes shifts. In this case, it is preferable to implement heat dissipation measures for the optical modulator 33 and to correct the characteristic drift caused by time in the waveform image acquired by the waveform measurement unit 40.

[0098] When the electrical signal measuring device 2A is applied to the semiconductor inspection device 1A, the inspection device 1A and inspection method described in the above embodiments may also be configured such that: the optical measuring unit 20 has an optical amplifier 23 that amplifies and outputs the reflected light output from the self-inspection optical system 11, and a photodetector 25 detects the reflected light amplified by the optical amplifier 23. Furthermore, the photodetector 25 of the optical measuring unit 20 may also be configured as a PIN-PD.

[0099] Based on these structures, the optical measurement unit 20 can measure the reflected light from the semiconductor device D and output electrical signals at high speed and with good accuracy. That is, during the inspection of the semiconductor device D, the amount of probe light needs to be set to a level that does not damage the semiconductor device D, and the amount of reflected light is also reduced. For example, when using a solid-state lens that achieves an NA of 1 or higher, the upper limit of the amount of probe light is on the order of several mW, and the upper limit of the amount of reflected light from the semiconductor device D is on the order of 0.1 mW.

[0100] Therefore, when directly detecting reflected light with the photodetector 25, an APD (Optical Photodetector) can be used as the photodetector 25, for example. However, the capacitance of the APD is relatively large, making it difficult to adequately handle high-speed signal measurements. In contrast, by providing an optical amplifier 23 such as an SOA (Optical Photodetector Amplifier) ​​in front of the photodetector 25, a high-speed optical sensor such as a PIN-PD can be used as the photodetector 25. Combined with waveform measurement using a streak camera, high-speed signal measurement can preferably be achieved.

[0101] In the inspection apparatus 1A and inspection method of the above embodiments, the optical measurement unit 20 in the electrical signal supply unit 80 that generates and outputs an electrical signal of the object to be measured may also be configured to have an amplification element such as an AC amplifier 26 that amplifies the AC component of the detection signal output from the photodetector 25 and outputs it as an electrical signal.

[0102] According to this structure, the AC amplifier 26 at the rear end of the photodetector 25 removes the DC component of the detection signal and performs an offset reset that amplifies only the AC component. This allows the extraction of the time-varying intensity component of the detection signal, and appropriately adjusts and sets the offset level of the electrical signal before conversion to a light signal in the signal conversion unit 30. Furthermore, in addition to the AC amplifier 26, other components that remove the DC component or extract the AC component can be used as amplification elements for extracting and amplifying the AC component of the detection signal.

[0103] Here, the relationship between the time variation of the intensity of reflected light, the time waveform of the electrical signal, the time waveform of the optical signal, and the setting of the signal offset level in the semiconductor inspection apparatus 1A described above will be explained. Figure 12 It is a graph showing the relationship between (a) the intensity of reflected light from semiconductor device D, (b) the intensity of electrical signal generated in optical measurement unit 20, and (c) the intensity of optical signal generated in signal conversion unit 30.

[0104] For example, when irradiated with probe light at a wavelength of 1.3 μm, the intensity of the reflected light from semiconductor device D is, as described above, to the level of 0.1 mW. At this time, in Figure 12 In the intensity of the reflected light shown in (a), with the intensity level (DC component) A0 of the reflected light set to 1, the shot noise level in 1σ is 2.25% at a frequency band of 100 GHz. In contrast, the signal level (AC component) A1 of the time variation of the intensity of the reflected light used for semiconductor inspection is very small, ranging from 0.001% to 0.01%.

[0105] The signal level of the electrical signal generated by the optical measurement unit 20, which includes the optical amplifier 23, the photodetector 25, and the AC amplifier 26, relative to the reflected light, is, for example, Figure 12 As shown in (b), the detection signal output from the photodetector 25 contains both DC and AC components, just like the intensity of the reflected light. However, by removing the DC component of the detection signal in the AC amplifier 26 and amplifying only the AC component, the signal level corresponding to the intensity level A0 of the reflected light is approximately zero. Furthermore, the shot noise level is around 300 mV in 1σ. On the other hand, the signal level B1 corresponding to the signal level A1 of the time-varying intensity of the reflected light is around 0.15 mV to 1.5 mV.

[0106] Furthermore, the signal level of the optical signal generated by intensity modulation of the measured light in the optical modulator 33 based on this electrical signal is, for example, as follows: Figure 12 As shown in (c). Figure 12In (c), curve C5 shows the sinusoidal relationship between the voltage (vertical axis) of the electrical signal applied to the EO modulator constituting the optical modulator 33 and the intensity (horizontal axis) of the generated optical signal.

[0107] like Figure 12 As shown in (c), during the signal conversion from an electrical signal to an optical signal in the optical modulator 33, in order to maximize the sensitivity to voltage changes in the electrical signal and ensure good linearity of the signal conversion, it is preferable to apply a bias voltage that is offset as indicated by the signal level C0, such that the amount of transmitted light when the voltage of the electrical signal is zero is a predetermined amount, for example, 50% of the maximum transmitted light. In this case, the intensity variation range C2 of the converted optical signal can be sufficiently expanded relative to the voltage variation range C1 of the electrical signal.

[0108] Furthermore, by adjusting the offset in the optical measurement unit 20 and the signal conversion unit 30, the measurement of the time variation of the intensity of reflected light and the accumulation of the time waveform can be performed with good accuracy. Additionally, regarding the maximum value of the light signal intensity, considering the upper limit of the incident light density on the photoelectric surface, it is preferable to appropriately set it to be the same as or below the upper limit value using the optical attenuator 32 or the like.

[0109] also, Figure 12 While this method is based on semiconductor inspection using probe light, the same principles can be applied to measurements of electrical signals other than those used in semiconductor inspection, such as offset reset of the electrical signal of the object being measured, offset adjustment during signal conversion from electrical to optical signals, and the correspondence between the voltage variation range of the electrical signal and the intensity variation range of the optical signal. For example, the electrical signal input to the signal conversion unit 30, which is the object being measured, can be configured such that an amplification element or similar component for offset reset of the electrical signal is provided at the front end of the signal conversion unit 30.

[0110] Regarding the setting of the cumulative number of times the time waveform is accumulated in signal measurement using the electrical signal measuring device 2A, the example of applying the electrical signal measuring device 2A to the semiconductor inspection device 1A will be explained. As described above, the shot noise level in the reflected light measurement is 2.25% at a frequency band of 100 GHz, and 0.225% at a frequency band of 1 GHz. Furthermore, the signal level is 0.001% to 0.01%.

[0111] At this point, for example, to obtain a time waveform with an S / N ratio of 10 or higher, at a signal level of 0.001% in a 1 GHz band, the required number of iterations is 2250 squared, approximately 5 million. Furthermore, if the band is increased by 10, the required number of iterations is simply increased by 10; for example, for a 10 GHz band, the required number of iterations is 50 million, and for a 40 GHz band, the required number of iterations is 200 million.

[0112] If the signal strength relative to the noise is high, the required number of accumulations is small; for example, if the S / N ratio is 10, the required number of accumulations is 1 / 100. Alternatively, as a method to improve the S / N ratio, increasing the light intensity can be considered to change the ratio of shot noise to signal. However, as mentioned above, the intensity of the probe light must be set to a level that does not damage the semiconductor device D. Therefore, increasing the signal strength in this way is sometimes difficult. Considering practical conditions in semiconductor inspection, the number of accumulations for the time waveform in reflected light measurement is preferably set in, for example, a range of more than 1 million and less than 1 billion.

[0113] A specific example of a method for measuring the time waveform of an electrical signal using an electrical signal measuring device 2A will be described. First, the waveform of the electrical signal to be measured is measured using a conventional oscilloscope or the like, and its time waveform is obtained. Furthermore, the measurement range for waveform measurement using the electrical signal measuring device 2A with a streak camera is set.

[0114] Next, the display unit 54 displays the time waveform of the electrical signal acquired by an oscilloscope or the like, and sets and selects the actual measurement period (measurement start time and duration) within the waveform to be measured. Then, during the set measurement period, the electrical signal measuring device 2A performs the measurement, and the waveform analysis unit 52 calculates the time waveform of the electrical signal, displaying the measurement result on the display unit 54. Furthermore, if there are multiple measurement periods to be measured, the phase can be changed as needed, and the same measurement can be repeated multiple times. Additionally, waveform image acquisition and basic image acquisition can be performed alternately, and basic corrections such as drift correction can be performed as described above.

[0115] The structure of the input optical system 41 in the streak camera of the waveform measurement unit 40 will be further explained. As described above, the input optical system 41 preferably inputs the light signal as a linear optical image to the photoelectric surface 421. As an example of a specific structure for this purpose, in Figure 7 The diagram shows the structure of an input optical system 41 composed of cylindrical lens 410, lens 411, and lens 412, but the structure of the input optical system 41 is not limited to... Figure 7 In addition to the structure, various other structures can also be used.

[0116] Figure 13 These are (a) a top view and (b) a side view showing a first modified example of the structure of the input optical system 41 in the waveform measurement unit 40. In this first modified example, the input optical system 41 is composed of a lens 413 and a cylindrical lens 414 sequentially from the input side of the optical signal. With this structure, [the system]... Figure 7 Similarly, a linear optical image can also be formed on the photoelectric surface 421.

[0117] Furthermore, the cylindrical lens 410 is positioned at the front end of the lens structure in the input optical system 41. Figure 7 The structure, and the cylindrical lens 414 are positioned at the rear. Figure 13 In the structure, the cylindrical lenses are arranged in different directions. Furthermore, in... Figure 13 In the structure shown, the cylindrical lens 414 in the rear section also serves as an imaging lens.

[0118] Figure 14 These are (a) a top view and (b) a side view showing a second modified example of the structure of the input optical system 41 in the waveform measurement unit 40. In this second modified example, the input optical system 41 is composed of a lens 413, a cylindrical lens 414, a lens 415, and a lens 416, sequentially arranged from the input side of the optical signal. Figure 14 The structure is for Figure 13 The structure is supplemented with a relay optical system consisting of lenses 415 and 416.

[0119] Figure 15 These are (a) a top view and (b) a side view of a third modified example showing the structure of the input optical system 41 in the waveform measurement unit 40. The input optical system 41 in the third modified example is composed of a lens 417, a Powell lens 418, and a lens 419, sequentially from the input side of the optical signal. A Powell lens is a lens that expands parallel light in a fan shape; by combining it with a conventional lens or a cylindrical lens, it can form a fine and uniform linear optical image.

[0120] In addition, Figure 15 In the structure shown, the rear lens 419 can also be replaced with a combination of two cylindrical lenses with different orientations and orthogonal axes. In this case, the imaging position of the light can be easily adjusted. Furthermore, in the formation of linear optical images, in addition to the cylindrical lenses and Powell lenses mentioned above, a combination of deformable prisms and slits can also be used, for example.

[0121] Generally, the input optical system 41 of the waveform measurement unit 40 preferably includes at least one of a cylindrical lens, a Powell lens, and a pair of deformable prisms. In the input optical system 41, by using the above-described optical elements, a linear optical image of a light signal extending in a direction intersecting the scanning direction (preferably a direction orthogonal to the scanning direction) can preferably be formed.

[0122] The structure and operation of the aforementioned electrical signal measuring device using a stripe camera structure will be further explained.

[0123] Figure 16 This is a block diagram schematically illustrating the structure of a second embodiment of an electrical signal measuring device including a signal conversion unit 30 and a waveform measurement unit 40. In the structure of the electrical signal measuring device 2B of this embodiment, the waveform measurement unit 40 and... Figure 3 The structures shown are the same, but the structure of the signal conversion unit 30 is different. Additionally, in Figure 16 In the figure, the waveform analysis unit 52 of the control device 50, which is part of the electrical signal measuring device 2B, is omitted.

[0124] The signal conversion unit 30 is configured to include a measurement light source 31, an optical attenuator 32, a conversion control optical modulator 34, and an optical modulator 33. The structures of the measurement light source 31, the optical attenuator 32, and the optical modulator 33 are similar to... Figure 3 The structures shown are the same.

[0125] A conversion control optical modulator 34 is disposed between the optical attenuator 32 and the optical modulator 33. Based on measurement conditions such as the test cycle in the semiconductor inspection unit 10, it controls the on / off state of the signal conversion operation from electrical signal to optical signal in the signal conversion unit 30. Specifically, the conversion control optical modulator 34 controls the on / off state of the signal conversion operation by switching the passage / non-passage of the measurement light from the optical attenuator 32 based on a trigger signal input from the self-delay generator 19 or a control signal input from the inspection control unit 51 of the self-control device 50.

[0126] Thus, by providing a conversion control optical modulator 34 separately from the optical modulator 33 used for signal conversion in the signal conversion unit 30, various measurement controls can be performed according to the specific measurement conditions in the semiconductor inspection apparatus 1A. Furthermore, as with the optical modulator 33, the conversion control optical modulator 34 can be an EO modulator, an AO modulator, an MO modulator, a Bokel cell, etc., but an EO modulator is particularly preferred.

[0127] As a control of the signal conversion operation using the optical modulator 34 for conversion control, control corresponding to the main scan and retrace in the stripe tube 42 of the waveform measurement unit 40 can be performed, for example. Figure 17 This diagram schematically illustrates the main scan and retrace scan in the stripe tube 42. In the stripe tube 42, for example in synchronous scan mode, electrons are scanned by a sinusoidal scan voltage, but in this case, the main scan in the original scan direction and the retrace scan in the opposite direction are alternately repeated.

[0128] In this case, such as Figure 17 As shown, the main scan electronic image P5 and the retrace scan electronic image P6 are alternately input into the fluorescent surface 426. However, if the retrace scan electronic image pattern is superimposed on the main scan electronic image pattern during measurement, the time waveform that is the target cannot be accurately measured.

[0129] In contrast, Figure 16In the structure shown, the conversion control optical modulator 34 provided in the signal conversion unit 30 can be controlled in the following way: during the period corresponding to the main scan in the stripe tube 42, the signal conversion operation is turned on, and during the period corresponding to the retrace scan, the signal conversion operation is turned off. Therefore, only the electronic image pattern of the main scan can be selectively measured.

[0130] Furthermore, in addition to the structure described above using the conversion control optical modulator 34 of the signal conversion unit 30, various other structures can be used for the measurement control related to the main scan and retrace scan in the stripe tube 42. For example, the following structure can be used: by controlling the horizontal scanning electrode 424 in the stripe tube 42 (refer to...) Figure 5 A voltage is applied to a specified pattern, thereby shifting the electronic image to a position outside the fluorescent surface 426 during the retrace period.

[0131] Alternatively, the following structures can be used: modulating and controlling the high voltage applied to the stripe tube 42, and modulating and controlling the voltage applied to the MCP425. Alternatively, instead of the MCP425, an image intensifier can be provided between the stripe tube 42 and the output optical system 43, and the on / off state of the image intensifier can be controlled according to the main scan and retrace scan.

[0132] However, in these structures, during the retracement period when no time waveform measurement is performed, the optical image of the optical signal is also incident on the photoelectric surface 421, thus causing degradation of the photoelectric surface 421. In contrast, since the signal conversion operation is controlled by the conversion control optical modulator 34 of the signal conversion unit 30 as described above, the optical image of the optical signal is not incident on the photoelectric surface 421 during the retracement period, thus suppressing degradation of the photoelectric surface 421. Furthermore, regarding the placement of the conversion control optical modulator 34, in... Figure 16 It can be configured in the front section of the optical modulator 33, but it can also be configured in the rear section of the optical modulator 33.

[0133] Furthermore, in addition to controlling the measurement period and measurement conditions of the time waveform of the electrical signal in the electrical signal measuring device 2B, the phase during waveform measurement can also be controlled by the optical modulator 34 for conversion control. Specifically, for example, it can be configured such that the stripe tube 42 in the waveform measuring unit 40 adjusts the phase of the scanning period according to the period of the time waveform of the electrical signal to be measured. With this structure, various measurement controls can be performed according to specific measurement conditions.

[0134] Figure 18 This is a diagram illustrating an example of the phase setting for the measurement period and scan cycle in a stripe tube. Figure 18The following are shown in sequence from top to bottom: (a) the synchronization signal supplied from the test head 12a, (b) the trigger signal supplied from the test head 12a or the delay generator 19, (c) the measurement period T1 set in the time waveform of the electrical signal (the time change of the intensity of the reflected light) as the period for waveform measurement, (d) the scanning voltage pattern in the stripe tube 42, and (e) the control signal pattern supplied to the optical modulator 34 for conversion control.

[0135] exist Figure 18 In the example shown, such as Figure 18 As shown in (c), within each test cycle of the semiconductor inspection unit 10, a measurement period (measurement time window) T1 is set for inspecting the semiconductor device D. Furthermore, based on this measurement period T1, as... Figure 18 As shown in (e), the control signal pattern for the conversion control optical modulator 34 is determined, thereby controlling the on / off of the signal conversion operation.

[0136] Furthermore, in the striped tube 42, such as Figure 18 As shown in (d), the timing of the electronic scan is delayed by a time T2 from the synchronization signal, such that the measurement period T1 of the time waveform is included within the main scan period, thereby adjusting the phase of the scan cycle. In this way, the measurement period of the time waveform is set by the conversion control optical modulator 34 of the signal conversion unit 30, and the phase of the electronic scan cycle is set and adjusted in the stripe tube 42, thereby performing waveform measurement under desired conditions. Furthermore, the aforementioned phase adjustment can be performed, for example, using the phase delay function of the stripe camera. Alternatively, a phase delay device can be provided on the synchronization line connecting the test head 12a of the electrical signal supply unit 80 and the waveform measurement unit 40 to perform the aforementioned phase adjustment.

[0137] Figure 19 This is a block diagram schematically illustrating the structure of a third embodiment of an electrical signal measuring device including a signal conversion unit 30 and a waveform measurement unit 40. In the structure of the electrical signal measuring device 2C of this embodiment, the waveform measurement unit 40 and... Figure 3 The structures shown are the same, but the structure of the signal conversion unit 30 is different. Additionally, in Figure 19 The waveform analysis unit 52 of the control device 50, the supply of the synchronization signal from the test head 12a, and the supply of the trigger signal from the delay generator 19 are not shown in the figure.

[0138] The signal conversion unit 30 is configured to include a measurement light source 31, an optical attenuator 32, an optical modulator 33, an optical coupler 35, a first optical delay unit 36a, and a second optical delay unit 36b. The structures of the measurement light source 31, the optical attenuator 32, and the optical modulator 33 are similar to... Figure 3 The structures shown are the same.

[0139] Optical coupler 35 branches the optical signal (modulated measurement light) input from optical modulator 33 and outputs it to first optical delay unit 36a and second optical delay unit 36b. First optical delay unit 36a outputs the optical signal to waveform measurement unit 40 after delaying the optical signal by a first delay time. Second optical delay unit 36b outputs the optical signal to waveform measurement unit 40 after delaying the optical signal by a second delay time. The first and second delay times can be different or the same. Furthermore, one of the first and second delay times can be zero.

[0140] In order to measure their respective time waveforms, the two optical signals from the first and second optical delayers 36a and 36b are preferably input into different regions on the photoelectric surface 421 through the stripe tube 42. Figure 20 It is shown Figure 19 The diagram shows the input of two types of optical signals to the photoelectric surface 421 in the structure shown.

[0141] exist Figure 20 In the structure shown, the optical signal from the first optical retarder 36a is incident as an optical image P7 onto the left-hand region of the photoelectric surface 421 via cylindrical lenses 410a, 411a, and mirror 428. Similarly, the optical signal from the second optical retarder 36b is incident as an optical image P8 onto the right-hand region of the photoelectric surface 421 via cylindrical lenses 410b, 411b, and mirror 428. Therefore, the time waveforms of the optical signals from the first and second optical retarders 36a and 36b can be measured respectively.

[0142] Thus, in the signal conversion unit 30, two optical signals are generated, each having a time waveform corresponding to the time waveform of the electrical signal and with different conversion conditions. In the waveform measurement unit 40, various measurements can be performed by measuring the time waveform of each of these optical signals.

[0143] For example, in Figure 19 The structure shown can also be further configured. Figure 16 The optical modulator 34 in the structure controls the switching operation by turning the signal conversion on / off and makes the delay times in the first and second optical delayers 36a and 36b different, thereby enabling eye pattern observation. Furthermore, regarding the number of optical signals generated in the signal conversion unit 30, in the above structural example, it is set to two types of optical signals, but it can also be configured to generate three or more types of optical signals.

[0144] Figure 21 This is a block diagram schematically illustrating the structure of a fourth embodiment of an electrical signal measuring device including a signal conversion unit 30 and a waveform measurement unit 40. In the structure of the electrical signal measuring device 2D of this embodiment, the waveform measurement unit 40 and... Figure 3The structures shown are the same, but the structure of the signal conversion unit 30 is different. Furthermore, compared to... Figure 19 Similarly, the waveform analysis unit 52 of the control device 50 is omitted from the illustration.

[0145] The signal conversion unit 30 is configured to include a measurement light source 31, an optical attenuator 32, an optical coupler 37, and first and second optical modulators 33a and 33b. The structures of the measurement light source 31 and the optical attenuator 32 are similar to... Figure 3 The structures shown are the same.

[0146] Optical coupler 37 branches the measurement light input from optical attenuator 32 and outputs it to the first optical modulator 33a and the second optical modulator 33b. Electrical signals from optical measurement unit 20 are input to the first and second optical modulators 33a and 33b. The first and second optical modulators 33a and 33b modulate the measurement light intensity based on the electrical signals input from optical measurement unit 20, and output the modulated measurement light as an optical signal with a time waveform corresponding to the time waveform of the electrical signal.

[0147] The two optical signals from the first and second optical modulators 33a and 33b are preferably input into different regions on the photoelectric surface 421 through the stripe tube 42. Furthermore, in this structure, the electrical signals input to the first and second optical modulators 33a and 33b can be different, or optical delayers can be respectively provided for the first and second optical modulators 33a and 33b. With this structure, it is also possible to... Figure 19 Various measurements were performed on the same structure shown.

[0148] The electrical signal measuring device and method are not limited to the above-described embodiments and structural examples, and various variations are possible. For example, the specific structure of the electrical signal measuring device is not limited to... Figure 3 , Figure 16 , Figure 19 , Figure 21 The structure shown can also be used in various other ways. For example, in Figure 19 or Figure 21 The structure shown can also be configured to be further configured. Figure 16 The optical modulator 34 is used for conversion control in the structure.

[0149] Furthermore, the stripe tube 42 of the waveform measurement unit 40 can also be configured such that it is not provided if the horizontal scanning electrode 424 and MCP 425 are not required. Furthermore, regarding... Figure 12 The signal level and offset adjustment settings shown can be adapted to various configurations depending on the structure of the electrical signal supply unit 80 and the electrical signal measuring device. Furthermore, regarding the electrical signal being measured, the example shown above applies the electrical signal measuring device to a semiconductor inspection device, but this configuration is not limited to this one; various electrical signals can be used as the measurement object.

[0150] The electrical signal measuring apparatus of the first embodiment described above comprises: (1) a signal conversion unit having: a measurement light source supplying measurement light of a predetermined wavelength, and an optical modulator that modulates the intensity of the measurement light based on an electrical signal input as a measurement object with a time waveform, and outputs the measurement light modulated by the optical modulator as an optical signal having a time waveform corresponding to the time waveform of the electrical signal; (2) a waveform measurement unit that measures the time waveform of the optical signal output from the signal conversion unit; and (3) a waveform analysis unit that determines the time waveform of the electrical signal based on the measurement result of the time waveform of the optical signal by the waveform measurement unit; and (4) the waveform measurement unit having: a stripe tube, which includes: a stripe tube that measures the time waveform of the optical signal based on the time waveform of the optical signal. The photoelectric surface that generates electrons from the input of the signal, the scanning electrode that scans the electrons from the photoelectric surface in a specified scanning direction within a scanning period set according to the time waveform of the electrical signal, and the fluorescent surface that inputs the electrons scanned by the scanning electrode and generates a fluorescent image representing the time waveform of the light signal; the imaging element that captures the fluorescent image generated on the fluorescent surface of the stripe tube and outputs a waveform image; and the input optical system that inputs the light signal into the photoelectric surface; (5) the waveform analysis unit determines the time waveform of the electrical signal based on the waveform image output from the imaging element, and (6) the input optical system of the waveform measurement unit inputs the light signal as a linear optical image extending in a direction intersecting the scanning direction into the photoelectric surface.

[0151] The electrical signal measurement method of the first embodiment described above includes: (1) a signal conversion step, in which an optical modulator is used to intensity-modulate a measurement light of a predetermined wavelength based on an electrical signal input as a measurement object with a time waveform, and the measurement light modulated by the optical modulator is output as an optical signal having a time waveform corresponding to the time waveform of the electrical signal; (2) a waveform measurement step, in which the time waveform of the optical signal output in the signal conversion step is measured; and (3) a waveform analysis step, in which the time waveform of the electrical signal is determined based on the measurement result of the time waveform of the optical signal in the waveform measurement step; and (4) in the waveform measurement step, a stripe tube is used to photograph the stripe waveform. The fluorescent surface of the strip tube generates a fluorescent image and outputs a waveform image. The strip tube includes: a photoelectric surface that generates electrons according to the input of the light signal, a scanning electrode that scans the electrons from the photoelectric surface in a specified scanning direction within a scanning period set according to the time waveform of the electrical signal, and a fluorescent surface that inputs the electrons scanned by the scanning electrode and generates a fluorescent image representing the time waveform of the light signal. (5) In the waveform analysis step, the time waveform of the electrical signal is determined based on the waveform image output in the waveform measurement step, and (6) In the waveform measurement step, the light signal is input to the photoelectric surface as a linear optical image extending in a direction intersecting the scanning direction.

[0152] In the electrical signal measuring device of the second embodiment, it can also be configured such that, in the structure of the first embodiment, the electrical signal is an electrical signal whose time waveform repeats at a predetermined period, and in the waveform measuring unit, the fluorescent surface of the stripe tube generates a fluorescent image of the time waveform of the light signal accumulated over a predetermined period of multiple periods.

[0153] In the second method of measuring electrical signals, the structure of the first method described above can also be configured such that the electrical signal is an electrical signal whose time waveform repeats at a predetermined period, and in the waveform measurement step, the fluorescent surface of the stripe tube generates a fluorescence image of the time waveform of the light signal accumulated over a predetermined period of multiple periods.

[0154] In the above structure, after the electrical signal is converted into an optical signal, a stripe tube is used to measure the waveform, and the time waveform of the optical signal is accumulated in the fluorescent image generated by the fluorescent surface and the waveform image obtained by the imaging element, so that the time waveform of the electrical signal can be accumulated multiple times at high speed optically.

[0155] In the electrical signal measuring device of the third embodiment, it may also be configured such that, in the structure of the first or second embodiment described above, the input optical system of the waveform measuring unit includes at least one of a cylindrical lens, a Powell lens, and a pair of deformable prisms.

[0156] In the input optical system of the waveform measurement unit, by using the optical components described above, a linear optical image extending in a direction intersecting the scanning direction of the optical signal can preferably be formed.

[0157] In the electrical signal measuring device of the fourth type, it may also be configured such that, in any of the structures of the first to third types described above, the optical modulator of the signal conversion unit is an EO modulator.

[0158] Thus, by using an EO modulator as an optical modulator to modulate the intensity of the measurement light, the conversion of electrical signals to optical signals can preferably be performed.

[0159] In the fifth type of electrical signal measuring device, the signal conversion unit may also be configured such that, in any of the first to fourth types of the above structure, the signal conversion unit has: a conversion control optical modulator that controls the on / off of the signal conversion operation from electrical signal to optical signal according to the time waveform of the electrical signal.

[0160] In the third type of electrical signal measurement method, it can also be configured such that, in the structure of the first or second type described above, a conversion control optical modulator is used in the signal conversion step, which controls the on / off of the signal conversion operation from electrical signal to optical signal according to the time waveform of the electrical signal.

[0161] In this case, the electrical signal measuring device of the sixth embodiment may also be configured such that, in the structure of the fifth embodiment, the optical modulator for conversion control of the signal conversion unit sets the signal conversion operation to on during the period corresponding to the main scan in the stripe tube, and sets the signal conversion operation to off during the period corresponding to the retrace scan.

[0162] Furthermore, in the fourth type of electrical signal measurement method, it can also be configured such that, in the structure of the third type described above, during the signal conversion step, the conversion control optical modulator sets the signal conversion operation to on during the period corresponding to the main scan in the stripe tube, and sets the signal conversion operation to off during the period corresponding to the retrace scan.

[0163] Thus, by providing a separate optical modulator for conversion control from the optical modulator used for signal conversion in the signal conversion section, the on / off state of the signal conversion operation can be controlled according to the main scan and retrace scan in the stripe tube, as described above, and various measurement controls can be performed according to specific measurement conditions. Furthermore, as the optical modulator for conversion control, an EO modulator, for example, can preferably be used, similar to the optical modulator used for signal conversion.

[0164] In the electrical signal measuring device of the seventh type, it may also be configured such that, in any of the structures of the first to sixth types, the stripe tube in the waveform measuring unit adjusts the phase of the scanning period according to the duration of the time waveform of the electrical signal to be measured.

[0165] In the fifth type of electrical signal measurement method, it can also be configured such that, in any of the first to fourth types of the above structure, in the waveform measurement step, the stripe tube adjusts the phase of the scanning period according to the duration of the time waveform of the electrical signal to be measured.

[0166] Thus, by adjusting the phase structure of the scanning period in the stripe tube of the waveform measurement unit, various measurement controls can be performed according to specific measurement conditions.

[0167] In the electrical signal measuring device of the eighth method, it may also be configured such that, in any of the structures of the first to seventh methods described above, the signal conversion unit generates two or more optical signals as optical signals, each having a time waveform corresponding to the time waveform of the electrical signal and having different conversion conditions.

[0168] In the sixth method of electrical signal measurement, it can also be configured such that, in any of the structures of the first to fifth methods described above, in the signal conversion step, two or more optical signals are generated as optical signals, each having a time waveform corresponding to the time waveform of the electrical signal and having different conversion conditions.

[0169] Thus, in the signal conversion unit, two or more different optical signals are generated. In the waveform measurement unit, by measuring the time waveforms of these optical signals, various measurements can be performed, such as measuring two optical signals with different delay times and observing eye diagrams.

[0170] In the electrical signal measuring device of the ninth embodiment, it may also be configured such that, in any of the structures of the first to eighth embodiments described above, the specified wavelength of the measuring light is set in the wavelength range of 115 nm or more and 1600 nm or less.

[0171] In the electrical signal measurement method of the seventh method, it may also be configured such that, in any of the structures of the first to sixth methods described above, the specified wavelength of the measurement light is set in the wavelength range of 115 nm or more and 1600 nm or less.

[0172] By setting the wavelength of the measurement light used to generate the optical signal as described above, it is preferable to perform waveform measurement of the optical signal in which the measurement light is intensity modulated by an electrical signal using a stripe tube, while measuring the time waveform of the electrical signal with good accuracy.

[0173] In the electrical signal measuring device of the 10th embodiment, it may also be configured such that, in any of the structures of the 1st to 9th embodiments described above, the waveform analysis unit corrects the waveform image obtained by the signal conversion unit when the generation of the optical signal in the signal conversion unit is turned on, based on the base image obtained when the generation of the optical signal is turned off.

[0174] In the electrical signal measurement method of the eighth method, it can also be configured such that, in any of the structures of the first to seventh methods, in the waveform analysis step, the waveform image obtained in the signal conversion step when the generation of the optical signal is turned on is corrected based on the base image obtained when the generation of the optical signal is turned off.

[0175] Thus, by correcting the waveform image based on the base image and using the corrected waveform image to determine the time waveform of the electrical signal, the time waveform of the electrical signal can be measured with even greater accuracy. [Industry availability]

[0176] The implementation method can be used as an electrical signal measuring device and method that can measure the time waveform of electrical signals at high speed. [Symbol Explanation]

[0177] 1A...Semiconductor inspection apparatus; 2A~2D...Electrical signal measuring apparatus; D...Semiconductor device; 10...Semiconductor inspection section; 11...Inspection optical system; 12...Voltage application section; 12a...Tester head; 12b...Test board; 13...Dark box; 14...Stage; 15...Scanning optical system; 16...Imaging optical system; 17...Objective lens; 18...Turret; 19...Delay generator; 20...Optical measurement section; 21...Detection light source; 22...Optical coupler; 23...Optical amplifier; 24...Optical splitter; 25...Photodetector; 26...AC amplifier; 30...Signal conversion unit; 31...Measuring light source; 32...Optical attenuator; 33...Optical modulator; 33a...First optical modulator; 33b...Second optical modulator; 34...Optical modulator for conversion control; 35...Optical coupler; 36a...First optical delay unit; 36b...Second optical delay unit; 37...Optical coupler; 40...Waveform measurement unit; 41...Input optical system; 42...Strip tube; 43...Output optical system; 44...Image sensor; 45...Synchronization unit; 50...Control device; 51...Inspection control unit; 52...Waveform analysis unit; 53...Input unit; 54...Display unit; 55...Scanning control unit; 61...Second optical measurement unit; 62...Second waveform measurement unit; 63...Frequency analysis unit; 330...EO crystal; 331...Input waveguide; 332...First branch waveguide; 333...Second branch waveguide; 334...Output waveguide; 335...RF electrode; 336...Bias electrode; 337a~337d...Ground electrode; 410, 414... Cylindrical lenses; 418... Powell lenses; 411, 412, 413, 415, 416, 417, 419... Lenses; 430, 431... Lenses; 420... Peripheral tube; 421... Photoelectric surface; 422... Accelerating electrode; 423... Vertical scanning electrode; 424... Horizontal scanning electrode; 425... MCP; 426... Phosphor surface; 428... Mirror; 80...Electronic signal supply unit; 81...Electronic signal output unit; 82...Synchronization signal output unit; 83...Trigger signal output unit.

Claims

1. An electrical signal measuring device, wherein, have: The signal conversion unit includes: a measurement light source that supplies measurement light of a predetermined wavelength, and an optical modulator that modulates the intensity of the measurement light based on an electrical signal input as a measurement object with a time waveform, and outputs the measurement light modulated by the optical modulator as an optical signal having a time waveform corresponding to the time waveform of the electrical signal; A waveform measurement unit measures the time waveform of the optical signal output from the signal conversion unit; and The waveform analysis unit calculates the time waveform of the electrical signal based on the measurement results of the time waveform of the optical signal by the waveform measurement unit. The waveform measurement unit has: A stripe tube comprising: a photoelectric surface that generates electrons according to the input of the optical signal; a scanning electrode that scans electrons from the photoelectric surface in a predetermined scanning direction within a scanning period set according to the time waveform of the optical signal; and a fluorescent surface that generates a fluorescent image representing the time waveform of the optical signal by inputting electrons scanned by the scanning electrode. An imaging element that captures the fluorescence image generated on the fluorescent surface of the striped tube and outputs a waveform image; and An input optical system inputs the optical signal into the photoelectric surface. The waveform analysis unit calculates the time waveform of the electrical signal based on the waveform image output from the imaging element, and The input optical system of the waveform measurement unit inputs the optical signal as a linear optical image extending in a direction intersecting the scanning direction to the photoelectric surface.

2. The electrical signal measuring device according to claim 1, wherein, The electrical signal is an electrical signal in which the time waveform repeats at a predetermined period. In the waveform measurement unit, the fluorescent surface of the stripe tube generates a fluorescence image of the time waveform of the optical signal accumulated over a predetermined period of multiple periods.

3. The electrical signal measuring device according to claim 1 or 2, wherein, The input optical system of the waveform measurement unit includes at least one of a cylindrical lens, a Powell lens, and a pair of deformable prisms.

4. The electrical signal measuring device according to any one of claims 1 to 3, wherein, The optical modulator in the signal conversion section is an EO modulator.

5. The electrical signal measuring device according to any one of claims 1 to 4, wherein, The signal conversion unit includes: a conversion control optical modulator that controls the on / off switching of the signal conversion operation from the electrical signal to the optical signal based on the time waveform of the electrical signal.

6. The electrical signal measuring device according to claim 5, wherein, The optical modulator for conversion control in the signal conversion unit sets the signal conversion operation to on during the period corresponding to the main scan in the stripe tube, and sets the signal conversion operation to off during the period corresponding to the retrace scan.

7. The electrical signal measuring device according to any one of claims 1 to 6, wherein, In the waveform measurement unit, the stripe tube adjusts the phase of the scanning period according to the duration of the time waveform of the electrical signal to be measured.

8. The electrical signal measuring device according to any one of claims 1 to 7, wherein, The signal conversion unit generates two or more optical signals, each having a time waveform corresponding to the time waveform of the electrical signal and with different conversion conditions, as the optical signals.

9. The electrical signal measuring device according to any one of claims 1 to 8, wherein, The specified wavelength of the measuring light is set within the wavelength range of 115 nm or higher and 1600 nm or lower.

10. The electrical signal measuring device according to any one of claims 1 to 9, wherein, The waveform analysis unit corrects the waveform image obtained when the optical signal generation in the signal conversion unit is turned on, based on the base image obtained when the optical signal generation is turned off.

11. A method for measuring electrical signals, wherein, have: In the signal conversion step, an optical modulator is used to intensity modulate the measurement light of a specified wavelength based on the electrical signal input as the measurement object as a time waveform. The measurement light modulated by the optical modulator is output as an optical signal having a time waveform corresponding to the time waveform of the electrical signal. The waveform measurement step measures the time waveform of the optical signal output in the signal conversion step. and The waveform analysis step involves determining the time waveform of the electrical signal based on the measurement results of the time waveform of the optical signal obtained in the waveform measurement step. In the waveform measurement step, a stripe tube is used to capture a fluorescence image generated on the fluorescent surface of the stripe tube and output a waveform image. The stripe tube includes: a photoelectric surface that generates electrons according to the input of the optical signal; a scanning electrode that scans electrons from the photoelectric surface in a predetermined scanning direction within a scanning period set according to the time waveform of the electrical signal; and the fluorescent surface that generates the fluorescence image representing the time waveform of the optical signal by inputting electrons scanned by the scanning electrode. In the waveform analysis step, based on the waveform image output in the waveform measurement step, the time waveform of the electrical signal is calculated, and In the waveform measurement step, the optical signal is input into the photoelectric surface as a linear optical image extending in a direction intersecting the scanning direction.

12. The electrical signal measurement method according to claim 11, wherein, The electrical signal is an electrical signal in which the time waveform repeats at a predetermined period; In the waveform measurement step, the fluorescent surface of the stripe tube generates the fluorescence image of the time waveform of the optical signal accumulated over a predetermined period of multiple periods.

13. The electrical signal measurement method according to claim 11 or 12, wherein, In the signal conversion step, a conversion control optical modulator is used to control the on / off of the signal conversion operation from the electrical signal to the optical signal according to the time waveform of the electrical signal.

14. The electrical signal measurement method according to claim 13, wherein, In the signal conversion step, the conversion control optical modulator sets the signal conversion action to on during the period corresponding to the main scan in the stripe tube, and sets the signal conversion action to off during the period corresponding to the retrace scan.

15. The electrical signal measurement method according to any one of claims 11 to 14, wherein, In the waveform measurement step, the stripe tube adjusts the phase of the scan period according to the duration of the time waveform of the electrical signal to be measured.

16. The electrical signal measurement method according to any one of claims 11 to 15, wherein, In the signal conversion step, two or more optical signals are generated, each having a time waveform corresponding to the time waveform of the electrical signal and having different conversion conditions, and are used as the optical signals.

17. The electrical signal measurement method according to any one of claims 11 to 16, wherein, The specified wavelength of the measuring light is set within the wavelength range of 115 nm or higher and 1600 nm or lower.

18. The electrical signal measurement method according to any one of claims 11 to 17, wherein, In the waveform analysis step, the waveform image obtained when the generation of the optical signal in the signal conversion step is turned on is corrected based on the base image obtained when the generation of the optical signal is turned off.

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