Semiconductor material interface state characterization system

Abstract

The invention provides a semiconductor material interface state characterization system, which comprises an incident light path unit used for changing the position of an incident light beam focus relative to a sample along a Z axis; the emergent light path unit is used for enabling the second harmonic signal to pass through; and the FROG detection module is used for synthesizing the second harmonic signal into an FROG trace diagram, identifying an interface signal observation area according to a change curve of the FROG trace diagram along with the Z position, and reconstructing intensity information and phase information of a time domain electric field of the second harmonic signal according to the FROG trace diagram. According to the embodiment, the FROG detection module can identify an interface signal observation area according to a change curve of the spectral intensity of the second harmonic signal along with the Z position in the FROG trace diagram, and the FROG detection module reconstructs intensity information and phase information of a time domain electric field of the second harmonic signal according to the FROG trace diagram. And real-time observation of the second harmonic signal carrying the interface state information is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material characterization, in particular to a semiconductor material interface state characterization system. BACKGROUND

[0002] The performance of semiconductor devices is highly dependent on the quality of its interface. Interface states, as traps or scattering centers for charge carriers, seriously restrict the development of high-performance devices.

[0003] As a second-order nonlinear optical effect, the second harmonic generation (SHG) characterization technique is extremely sensitive to the breaking of structural symmetry. It not only occurs in the interior of non-centrosymmetric bulk materials, but also occurs in the surface and interface due to the termination of atomic arrangement, adsorption or strain leading to the breaking of symmetry.

[0004] However, the related SHG characterization technique uses a high numerical aperture microscope to perform two-dimensional surface scanning on the sample, and images through the spatial distribution of SHG intensity, which has the following technical problems: 1. Unable to distinguish between bulk and interface signals: the traditional SHG technique lacks spatial resolution in the depth direction. Strong SHG signals from bulk materials completely overwhelm weak interface signals, resulting in the loss of interface-specific information; 2. Incomplete information dimension: the existing technology only measures the SHG intensity, and loses the phase containing key information of the microscopic physical environment of the interface; 3. Weak dynamic characterization capability: it is difficult to track the ultrafast dynamic evolution process of the interface state under external excitation in real time. SUMMARY

[0005] The summary section is used to introduce the concepts in a brief form, which will be described in detail in the specific embodiments section. The summary section of the present disclosure is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0006] Some embodiments of the present application provide a semiconductor material interface state characterization system to solve the technical problems mentioned in the background section.

[0007] Some embodiments of the present application provide a semiconductor material interface state characterization system, comprising: An incident light path unit for regulating the polarization direction of the light beam, filtering out stray light, and changing the position of the incident light beam focal point relative to the sample along the Z axis; An exit light path unit for collimating and filtering the light beam emitted by the sample, so that the second harmonic signal passes through; The FROG detection module is configured to synthesize the second harmonic signal into a FROG trace diagram, identify an interface signal observation area according to a curve of the FROG trace diagram changing with a Z position, and reconstruct intensity information and phase information of a time-domain electric field of the second harmonic signal according to the FROG trace diagram.

[0008] Optionally, the incident light path unit comprises, in sequence along a light beam incident direction, a laser, a half-wave plate, a polarizer, a half-wave plate, two fast mirrors, a fundamental frequency filter, and an incident objective lens. The laser is configured to generate a fundamental frequency light beam; the half-wave plate is configured to change a polarization direction of the incident light beam; the polarizer is configured to convert the fundamental frequency light beam into polarized light; the two fast mirrors are configured to guide the light beam; the fundamental frequency filter is configured to filter stray light; and the incident objective lens is configured to focus the incident light beam that meets a test condition onto the sample to generate a second harmonic wave.

[0009] Optionally, the incident light path unit further comprises a five-axis adjusting frame, and the incident objective lens is mounted on the five-axis adjusting frame, and the five-axis adjusting frame is configured to move the incident objective lens along a Z axis.

[0010] Optionally, the incident light path unit further comprises a laser displacement sensor and a microscope arranged above the sample stage, wherein the sample stage is configured to prevent the sample, the laser displacement sensor is configured to detect a distance from a sample surface, and the microscope is configured to provide a visual optical image of the sample surface.

[0011] Optionally, the sample stage is a four-dimensional sample stage configured to move the sample in X, Y, and Z directions and rotate the sample around the Z axis.

[0012] Optionally, the emergent light path unit comprises, in sequence along a light beam reflection direction, a detection objective lens, two fast mirrors, a polarimeter, and a frequency doubling filter. The detection objective lens is configured to change the emergent light beam reflected by the sample into parallel light; the two fast mirrors are configured to guide the light beam; the polarimeter is configured to analyze a polarization direction of the emergent light beam; and the frequency doubling filter is configured to filter the fundamental frequency light and stray light, and only allow the second harmonic signal to pass through.

[0013] Optionally, the emergent light path unit further comprises a five-dimensional adjusting frame, and the detection objective lens is mounted on the five-dimensional adjusting frame, and the five-dimensional adjusting frame is configured to adjust a position of the detection objective lens to achieve collimation of the emergent light beam.

[0014] Optionally, the FROG detection module comprises a beam splitter, a plurality of fast mirrors, an SHG crystal, and a spectrometer. The beam splitter and the plurality of fast mirrors are configured to split the second harmonic signal into an original signal pulse and a delay time signal pulse. The SHG crystal is configured to generate a frequency signal from the two signal pulses. The spectrometer is configured to detect the frequency signal. ; the spectrometer is used to generate a spectral map varying with delay time τ, i.e. a FROG trace map .

[0015] Optionally, the FROG detection module further comprises a processing terminal, which is used to control the movement of the plurality of fast mirrors to adjust the delay time τ.

[0016] Optionally, the processing terminal is based on the FROG trace map reconstructs the time-domain electric field of the second harmonic signal using an iterative phase retrieval algorithm , the time-domain electric field includes intensity information and phase information .

[0017] The above embodiments of the present application have the following beneficial effects: By changing the position of the focus of the incident light beam relative to the sample along the Z axis, the FROG detection module can identify the bulk signal dominant region, the bulk-interface signal mixed region and the optimal interface signal observation region according to the curve of the spectral intensity of the second harmonic signal in the FROG trace map varying with the Z position, thereby determining the interface signal observation region.

[0018] In the non-centrosymmetric structure inside the sample material, the intramolecular charge distribution is asymmetric, generating a bulk signal; at the interface of the sample, the atomic arrangement is disordered or the adsorbed molecules destroy the symmetry, generating an interface signal, and the time-domain waveforms and phase characteristics of the SHG pulses generated by the two are inherently different. The FROG detection module can capture this difference to provide a basis for signal discrimination. In the optimal interface signal observation region, the pump light is used to vertically irradiate the sample to excite the carriers at the interface, change the electric field at the interface, set the observation time point within a period of time after excitation, collect the FROG trace map at each point, perform inversion through the recovery algorithm, extract the intensity information and phase information of the interface electric field, and realize real-time observation of the second harmonic signal carrying the interface state information. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0020] Figure 1 Structure diagram of an embodiment of the semiconductor material interface state characterization system of the present application; Figure 2Structure diagram of an embodiment of the FROG detection module of the present application.

[0021] Explanation of reference numerals: 1, laser; 2, half-wave plate; 3, polarizer; 4, half-wave plate; 5, fast mirror; 6, fundamental filter; 7, five-axis adjustment frame; 8, incident objective lens; 9, laser displacement sensor and microscope; 10, sample stage; 11, sample; 12, detection objective lens; 13, five-axis adjustment frame; 14, fast mirror; 15, analyzer; 16, frequency doubling filter; 17, FROG detection module; 18, second harmonic signal; 19, fast mirror; 20, beam splitter; 21, fast mirror; 22, second fast mirror; 23, delay time signal pulse; 24, original signal pulse; 25, focusing lens; 26, SHG crystal; 27, focusing lens; 28, sum frequency signal; 29, spectrometer; 30, processing terminal. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be described below in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] Please see Figure 1 , Figure 1 This is a schematic diagram of an embodiment of the semiconductor material interface state characterization system of the present invention. Figure 1 As shown, the semiconductor material interface state characterization system of the present invention includes an incident optical path unit, a sample stage, an exit optical path unit, and a FROG detection module. The incident optical path unit is used to change the position of the focal point of the incident beam relative to the sample along the Z-axis. The exit optical path unit is used to allow the second harmonic signal to pass through. The FROG detection module is used to synthesize the second harmonic signal into a FROG trace map, identify the interface signal observation area based on the curve of the FROG trace map changing with the Z-position, and reconstruct the intensity and phase information of the time-domain electric field of the second harmonic signal based on the FROG trace map, thereby realizing real-time observation of the second harmonic signal carrying interface state information.

[0027] The incident optical path unit, along the beam incident direction, sequentially includes a laser 1, a half-wave plate 2, a polarizer 3, a half-wave plate 4, two fast-reflecting mirrors 5, a fundamental frequency filter 6, a five-axis adjustment frame 7, and an incident objective lens 8. The laser 1 generates the fundamental frequency beam as the incident beam. Half-wave plates 2 and 4 change the polarization direction of the incident beam. The polarizer 3 converts the incident beam into polarized light, enhancing its polarization characteristics. Optionally, the polarizer 3 can be a Glan-Thompson polarizer. The two fast-reflecting mirrors 5 guide the beam. The fundamental frequency filter 6 filters out stray light, etc. The incident objective lens 8 focuses the incident beam meeting the test conditions onto the sample 11 to generate a second harmonic.

[0028] The aforementioned incident objective 8 is mounted on a five-axis adjustment mount 7, which can adjust the displacement of the incident beam in the horizontal X and Y directions, the vertical Z direction, and the pitch around the X and Y directions. The Z-scan technique is realized by controlling the five-axis adjusting frame 7 to move the incident objective lens 8 along the Z axis, so as to change the position of the focus of the incident light beam relative to the sample 11.

[0029] Specifically, when the incident objective lens 8 moves forward and backward along the Z axis, the overlapping area of the effective area and the sample 11 is different, resulting in changes in the second harmonic intensity and phase. By analyzing the curve of the change of the spectral intensity of the second harmonic signal in the FROG trace diagram formed by the FROG detection module 17 with the Z position, the body signal dominant area, the body-interface signal mixed area and the optimal interface signal observation area can be identified.

[0030] The above-mentioned effective area refers to the fact that when the focus of the incident light beam reaches a certain intensity, the second harmonic can be effectively excited, and therefore, according to whether the intensity of the focus reaches the polarization intensity, the effective area and the ineffective area are distinguished.

[0031] In an optional manner of some embodiments, the incident light path unit can further include a laser displacement sensor and a microscope 9 arranged above the sample stage 10. The laser displacement sensor is used to detect the distance from the sample surface, and the microscope is used to provide a visual optical image of the sample surface, so as to monitor and accurately position the sample surface in real time.

[0032] The above-mentioned sample stage 10 can be a four-dimensional sample stage, which is used to move the sample 11 in the X, Y and Z directions and rotate the sample around the Z axis, so as to facilitate detection of multiple regions of the sample 11.

[0033] The exit light path unit includes, in sequence along the light beam reflection direction, a detection objective lens 12, a five-dimensional adjusting frame 13, two fast mirrors 14, a polarizer 15 and a frequency doubling filter 16. The detection objective lens 12 changes the exit light beam reflected by the sample 11 into parallel light. The detection objective lens 12 is installed on the five-dimensional adjusting frame 13, and the collimation of the exit light beam is realized by adjusting the position of the detection objective lens 12 by using the five-dimensional adjusting frame 13. The two fast mirrors 14 are used for light beam guiding, and the polarizer 15 is used for analyzing the polarization direction of the exit light beam. The frequency doubling filter 16 is used to filter the fundamental frequency light and stray light, and only the second harmonic signal 18 is allowed to pass. Finally, the second harmonic signal 18 carrying the defect information is received by the FROG detection module 17.

[0034] FROG technology (Frequency-Resolved Optical Gating) is a complete ultra-short pulse characterization technology. The FROG detection module 17 synthesizes the above-mentioned second harmonic signal 18 into a FROG trace diagram, and interface state defect information is obtained by analyzing and processing the FROG trace diagram.

[0035] The FROG detection module 17 includes a beam splitter 20, multiple fast-reflecting mirrors, an SHG crystal 26, a spectrometer 29, and a processing terminal 30. The beam splitter 20 and multiple fast-reflecting mirrors are used to split the second harmonic signal 18 into original signal pulses 24. ) and delayed time signal pulse 23 ( ), and then passes through SHG crystal 26. SHG crystal 26 is used to generate a sum-frequency signal 28 from the two signal pulses ( Spectrometer 29 is used to generate a spectrum as a function of delay time τ, i.e., a FROG trace plot. The processing terminal 30 is used to control the delay time. And according to the FROG trace map The time-domain electric field of the second harmonic signal is reconstructed, thereby enabling real-time observation of the second harmonic signal carrying interface state information.

[0036] Specifically, the outgoing optical path carrying the second harmonic signal 18 passes through the fast-reflecting mirror 19 and then enters the beam splitter 20. The second harmonic signal 18 is split into two paths. One path passes through the fast-reflecting mirror 22, then through the focusing lens 25, and enters the SHG crystal 26, which is the original signal pulse 24. The other path passes through the fast-reflecting mirror 21 for a delay of time τ, then through the focusing lens 25, and enters the SHG crystal 26, which is the delayed signal pulse 23.

[0037] The two signal pulses mentioned above are mixed in the SHG crystal 26 to generate a sum-frequency signal 28, wherein: The sum-frequency signal 28 is received by the spectrometer 29 after passing through the focusing lens 27. The spectrometer 29 processes the sum-frequency signal 28 to obtain the sum-frequency signal over a delay time. The changing spectrum, i.e., the FROG trace plot. And transmit it to the processing terminal 30.

[0038] Delay time The change is achieved through the processing terminal 30. The two fast-reflecting mirrors 21 can be mounted on a mobile platform, which is communicatively connected to the processing terminal 30. The mobile platform controls the rotation of the lead screw via a motor, causing the sliders carrying the two fast-reflecting mirrors 21 to reciprocate, changing the distance between the fast-reflecting mirrors 21 and the beam splitter 20, thereby adjusting the delay time τ. As an example, the mobile platform can be a linear lead screw module.

[0039] Finally, the processing terminal 30 is based on the FROG trace map. The time-domain electric field of the second harmonic signal can be reconstructed using an iterative phase retrieval algorithm. Including intensity information With phase information .

[0040] In the system, FROG is used to identify the second harmonic pulse. In the non-centrosymmetric structure inside the sample material, the asymmetric intramolecular charge distribution generates the bulk signal; at the sample interface, the disorder of atomic arrangement or the adsorbed molecules destroy the symmetry, generating the interface signal, and the time-domain waveforms and phase characteristics of the SHG pulses generated by the two are inherently different.

[0041] FROG can capture this difference and provide the basis for signal differentiation. In the optimal interface signal observation area, the sample is vertically irradiated by the pump light, the carriers at the interface are excited, the electric field at the interface is changed, the observation time points are set in a period of time after excitation, the FROG trace diagram is collected at each point, the inversion is carried out through the recovery algorithm, and the intensity information of the interface electric field is extracted and phase information In this way, the real-time observation of the SHG signal carrying the interface state information is realized.

[0042] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A semiconductor material interface state characterization system, characterized in that, include: The incident light path unit is used to control the polarization direction of the beam, filter out stray light, and change the position of the incident beam focus relative to the sample along the Z-axis. The output optical path unit is used to collimate and filter the beam emitted from the sample, allowing the second harmonic signal to pass through; The FROG detection module is used to synthesize the second harmonic signal into a FROG trace map, identify the interface signal observation area based on the curve of the FROG trace map changing with the Z position, and reconstruct the intensity and phase information of the time-domain electric field of the second harmonic signal based on the FROG trace map.

2. The semiconductor material interface state characterization system according to claim 1, characterized in that, The incident optical path unit includes, in sequence along the incident direction of the beam, a laser, a half-wave plate, a polarizer, two fast-reflecting mirrors, a fundamental frequency filter, and an incident objective lens; The laser is used to generate a fundamental frequency beam; the half-wave plate is used to change the polarization direction of the incident beam; and the polarizer is used to convert the fundamental frequency beam into polarized light. Two fast-reflecting mirrors are used for beam guidance; a fundamental frequency filter is used to filter out stray light; and an incident objective is used to focus the incident beam that meets the test conditions onto the sample to generate a second harmonic.

3. The semiconductor material interface state characterization system according to claim 2, characterized in that, The incident optical path unit also includes a five-axis adjustment frame, on which the incident objective lens is mounted. The five-axis adjustment frame is used to move the incident objective lens along the Z-axis.

4. The semiconductor material interface state characterization system according to claim 3, characterized in that, The incident optical path unit also includes a laser displacement sensor and a microscope disposed above the sample stage. The sample stage is used to hold the sample, the laser displacement sensor is used to detect the distance from the sample surface, and the microscope is used to provide a visual optical image of the sample surface.

5. The semiconductor material interface state characterization system according to claim 4, characterized in that, The sample stage is a four-dimensional sample stage, used to move the sample in the X, Y, and Z directions and rotate the sample around the Z-axis.

6. The semiconductor material interface state characterization system according to claim 1, characterized in that, The outgoing optical path unit includes, in sequence along the beam reflection direction, a detection objective, two fast-reflecting mirrors, an analyzer, and a frequency doubling filter; The detection objective lens converts the outgoing beam reflected from the sample into parallel light; two fast-reflecting mirrors are used for beam guidance; the analyzer is used to analyze the polarization direction of the outgoing beam; and the frequency doubling filter is used to filter out the fundamental frequency light and stray light, allowing only the second harmonic signal to pass through.

7. The semiconductor material interface state characterization system according to claim 6, characterized in that, The output optical path unit also includes a five-dimensional adjustment frame, on which the detection objective is mounted. The five-dimensional adjustment frame is used to adjust the position of the detection objective to achieve collimation of the output beam.

8. The semiconductor material interface state characterization system according to claim 1, characterized in that, The FROG detection module includes a beam splitter, multiple fast-reflecting mirrors, an SHG crystal, and a spectrometer; A beam splitter and multiple fast-reflecting mirrors are used to split the second harmonic signal into original signal pulses. and delayed time signal pulse ; SHG crystals are used to generate sum-frequency signals from two signal pulses. The spectrometer is used to generate a spectrum that varies with the delay time τ, i.e., a FROG trace plot. .

9. The semiconductor material interface state characterization system according to claim 8, characterized in that, The FROG detection module also includes a processing terminal for controlling the movement of multiple fast-reflecting mirrors to adjust the delay time τ.

10. The semiconductor material interface state characterization system according to claim 9, characterized in that, The processing terminal is based on FROG trace maps. The time-domain electric field of the second harmonic signal is reconstructed using an iterative phase retrieval algorithm. The time-domain electric field Including intensity information With phase information .

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