CN-122017518-A - High-sensitivity heterojunction spectrum detection system and data acquisition method thereof

CN122017518ACN 122017518 ACN122017518 ACN 122017518ACN-122017518-A

Abstract

The application relates to the technical field of photoelectric performance test of semiconductor devices, and discloses a high-sensitivity heterojunction spectrum detection system and a data acquisition method thereof. The digital processing unit adopts a trapezoidal hysteresis scanning strategy, utilizes a transient shielding window and asymmetric residence time to induce charge hysteresis, and performs synchronous demodulation on current response through a parallel channel to extract differential conductance, differential capacitance and second harmonic components and utilizes a rotation matrix to correct phase errors of the system. The upper computer processing unit constructs an augmentation matrix based on multidimensional physical parameters, and inversion calculation of interface state density distribution spectrum is performed by utilizing a mixed regularization algorithm with smoothness and sparseness constraint in combination with a physical kernel function. The method solves the problems of large signal scanning interference and inversion of the disease state in general detection, and realizes high-precision quantitative characterization of interface state defects.

Inventors

ZHANG YING
LI XIANG
LI YOU

Assignees

哈尔滨理工大学

Dates

Publication Date: 20260512
Application Date: 20260202

Claims (10)

1.A high sensitivity heterojunction spectral detection system, the system comprising: the bias control unit is used for applying a scanning voltage signal with a preset time sequence to the heterojunction detector to be detected; The signal acquisition unit is used for acquiring a current response signal of the heterojunction detector under the excitation of the scanning voltage signal; a digital processing unit connected with the bias control unit and the signal acquisition unit and configured to generate control time sequences and perform synchronous demodulation operation on the current response signals to output multidimensional physical parameter data, and The upper computer processing unit is in communication connection with the digital processing unit and is configured to receive the multidimensional physical parameter data and execute a spectrum inversion algorithm to generate an interface state density distribution spectrum; The digital processing unit is configured with parallel multi-channel signal processing logic for extracting a direct current component, a fundamental complex impedance component and a second harmonic component in the current response signal respectively.
2. The high sensitivity heterojunction spectral detection system of claim 1, wherein said digital processing unit implements a trapezoidal hysteresis scan timing control strategy that controls said bias control unit to output discrete step voltages that are discontinuous; In each voltage stepping period, the time sequence comprises a transient shielding window and a data acquisition window, and the duration of the transient shielding window is set to be larger than the time constant of a bias loop so as to shield displacement current impact caused by voltage stepping; The digital processing unit is configured to set asymmetric single step dwell times in the forward and reverse scan phases, inducing a charge hysteresis effect in the heterojunction detector by varying the number of integration periods within the data acquisition window.
3. The high-sensitivity heterojunction spectrum detection system according to claim 1, wherein a first-in first-out FIFO delay queue module is integrated inside the digital processing unit; The FIFO delay queue module is configured between the instruction path of the bias control unit and the packaging path of the multidimensional physical parameter data, and is used for carrying out delay buffering on the voltage control instruction advanced in the time domain, so that the voltage control instruction is aligned with the delayed physical parameter data after demodulation operation in time sequence, and the aligned voltage value and the physical parameter data are synchronously packaged and transmitted to the upper computer processing unit.
4. The high sensitivity heterojunction spectral detection system of claim 1, the multi-channel signal processing logic of the digital processing unit comprising: A DC channel comprising a cascaded integrator-comb filter or a moving average filter for filtering AC components to extract DC averages; a fundamental wave channel including a quadrature demodulator for mixing and integrating the current response signal using an in-phase reference signal and a quadrature reference signal to extract an original in-phase component and an original quadrature component; The harmonic channel comprises a frequency multiplication correlation arithmetic unit, extracts a second harmonic amplitude by using a frequency multiplication reference signal, and calculates the ratio of fundamental wave to harmonic amplitude so as to output a nonlinearity index.
5. The high sensitivity heterojunction spectral detection system of claim 4, wherein the digital processing unit further comprises a phase rotation correction module; The phase rotation correction module is used for carrying out linear transformation on the original in-phase component and the original quadrature component by using a rotation matrix algorithm so as to compensate hardware delay in a signal transmission path and output corrected in-phase component and quadrature component.
6. The high-sensitivity heterojunction spectral detection system of claim 5, wherein the digital processing unit performs physical parameter mapping according to a parallel equivalent circuit model; The digital processing unit maps the corrected in-phase component into differential conductance and the corrected quadrature component into differential capacitance, wherein the differential conductance represents the transport characteristic of carriers, and the differential capacitance represents the width change of a depletion layer and the interface state charge-discharge characteristic.
7. The high-sensitivity heterojunction spectral detection system of claim 1, wherein the upper computer processing unit is configured to perform background noise stripping logic; the logic comprises the steps of carrying out voltage grid alignment and interpolation on multidimensional physical parameter data generated by forward scanning and reverse scanning, calculating a difference value between forward current and reverse current to eliminate common-mode body leakage current, calculating a geometric displacement current component caused by scanning speed difference by utilizing measured differential capacitance data, and subtracting the geometric displacement current component from the difference value, so as to extract an unstable current component from interface state trap charge and discharge.
8. The high-sensitivity heterojunction spectral detection system of claim 1, wherein the upper computer processing unit is configured to construct an augmentation matrix to perform regularized spectral inversion; the upper computer processing unit performs standardization processing on differential conductance, differential capacitance and hysteresis current data, and constructs a weighted augmentation observation vector and an augmentation coefficient matrix according to the signal-to-noise ratio of each physical quantity, wherein the augmentation coefficient matrix comprises a plurality of physical kernel function submatrices generated based on a Shockley-Read-Hall statistical theory and is used for establishing a mapping relation between discrete energy levels and multidimensional physical parameters.
9. The high sensitivity heterojunction spectral detection system of claim 8, wherein the spectral inversion is solved using a hybrid regularized objective function; The objective function comprises a data fidelity term, a smoothness constraint term, a sparse constraint term and an upper computer processing unit, wherein the data fidelity term is used for constraining an inversion result to accord with an experimental observation value, the smoothness constraint term comprises a second-order differential matrix and is used for restraining non-physical vibration caused by noise, the sparse constraint term comprises an L1 norm and is used for representing discrete features of deep level defects, and the upper computer processing unit minimizes the objective function through a convex optimization algorithm to obtain an interface state density distribution spectrum.
10. A data acquisition method of a high-sensitivity heterojunction spectrum detection system, implemented by the high-sensitivity heterojunction spectrum detection system as claimed in any one of claims 1 to 9, characterized by comprising the steps of: Controlling bias voltage to output scanning voltage in discrete steps, sequentially executing transient shielding and steady-state perturbation detection on each voltage step, and setting different residence time in forward scanning and reverse scanning stages to generate hysteresis data; Carrying out multichannel parallel processing on the acquired signals, extracting differential conductance and differential capacitance by using quadrature demodulation, extracting second harmonic by using frequency multiplication correlation, and carrying out phase rotation correction on demodulation data; Mapping the forward and reverse scanning data to a uniform voltage grid, eliminating the body leakage current through differential operation, compensating the geometric displacement current by utilizing differential capacitance, and extracting pure trap current; An augmentation matrix comprising differential conductance, differential capacitance and trap current is constructed, and an interface state density distribution spectrum is calculated by inversion of a regularization algorithm with smooth and sparse constraint in combination with a physical kernel function.

Description

High-sensitivity heterojunction spectrum detection system and data acquisition method thereof Technical Field The invention relates to the technical field of photoelectric performance test of semiconductor devices, in particular to a high-sensitivity heterojunction spectrum detection system and a data acquisition method thereof. Background The performance of heterojunction devices depends to a large extent on the quality of the heterojunction. The dangling bonds at the interface, lattice mismatch or interface state traps introduced by impurities can become recombination centers of carriers, so that dark current is remarkably increased and the photoelectric conversion efficiency of the device is reduced. Therefore, the accurate characterization of interface state density and its energy level distribution is a key element in optimizing device processes. Common electrical characterization methods include capacitance-voltage measurement, admittance spectroscopy, and deep level transient spectroscopy techniques. The method mainly calculates the physical parameters of the trap by detecting the capacitance and conductivity change of the device under bias or temperature excitation. However, the prior art has limitations in performing high sensitivity detection for high impedance heterojunction devices. Conventional voltage scanning methods typically employ either continuous linear scanning or simple step scanning. The continuous scanning can cause aliasing of displacement current and trap charge-discharge current, and is difficult to distinguish, while the simple step scanning lacks accurate time sequence control, and the transient impact at the moment of voltage switching can submerge weak steady-state response signals, so that the signal-to-noise ratio of measured data is reduced. In addition, the charge-discharge process of the deep level defect is often accompanied by obvious hysteresis effect, and the dynamics characteristic of the unbalanced state is difficult to capture by a conventional unidirectional or symmetrical scanning mode, so that the deep level defect is missed. At the signal processing level, the response current caused by interface states is typically submerged in large bulk leakage currents and background noise. Traditional analog phase-locked amplifiers or measuring devices based on simple digital integration are susceptible to readout circuit transmission delay and anti-aliasing filter phase shift when processing broadband weak signals. Such phase errors can lead to confusion in the calculation of the capacitive component (stored charge) and the conductive component (lost charge), such that the final resolved differential capacitance and differential conductance values are distorted and cannot truly reflect the physical impedance characteristics of the device. At the data inversion level, the density distribution of the microcosmic interface states is deduced from the measured macroscopic physical quantity, and the method belongs to the solving process of the first-class Friedel-crafts integral equation mathematically. This is a typical pathological inversion problem, in which small noise in the measured data is amplified sharply during the direct inversion process, resulting in non-physical sharp oscillations in the calculated energy spectrum. The existing simplification algorithm usually adopts a depletion layer approximation or differentiation method, and although the calculation is simple, the coupling relation between the smoothing effect of the kernel function and the multiple physical fields is ignored, and only single capacitance or conductance data is often used for analysis, so that nonlinear information contained in current hysteresis and higher harmonics is wasted, and the stability of a solution is difficult to maintain while the energy level resolution is ensured. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a high-sensitivity heterojunction spectrum detection system and a data acquisition method thereof, which solve the problems of weak signal acquisition caused by scanning transient impact interference, impedance parameter mapping distortion caused by hardware transmission phase errors and single information utilization caused by solving the pathological state by a traditional inversion algorithm in the existing heterojunction interface state detection. The first aspect of the invention provides a high-sensitivity heterojunction spectrum detection system, which comprises a bias voltage control unit, a signal acquisition unit, a digital processing unit and an upper computer processing unit. The bias control unit is connected with the heterojunction detector to be detected and used for applying a scanning voltage signal with a preset time sequence, the signal acquisition unit is used for acquiring a current response signal of the detector under voltage excitation, the digital processing unit generates a control time sequence and executes