Papers by Author: Hai Bin Pan

Abstract: Inspection and measurement for the sheet resistance and resistivity play a pivotal role in the semiconductor industry. In this study, a high-accuracy measurement system for sheet resistance of thin films was designed based on dual-measurement with four-point probe method. The measurement system was composed of a special switching circuit, a digital output module, Keithley 2400 SourceMeter, and a computer running LabVIEW. The special switching circuit designed based on the multiplexer played an important role in current probes and voltage probes automatic switching under the control of virtual instrumentation software LabVIEW and National instruments digital output module hardware NI 9401. Keithley 2400 SourceMeter controlled by LabVIEW was used for two-times high-precision voltage measurement. Van der Pauw correction factor were calculated based on the results of the two-times voltage measurement. Then the sheet resistance of thin films was calculated by LabVIEW softwares powerful computing. The experimental results show that the designed and developed system can meet the needs of fast on-line measurement of thin films sheet resistance with a wide range, and moreover, the accuracy of measurements and the level of automatization have been dramatically improved compared to the conventional measurement system.

Abstract: We report on a novel method for measurement of the strain in microcantilever, and a contactless measurement system for strain in microcantilever is designed and implemented based on position sensitive detector (PSD) using optical lever method. To verify the validity and accuracy of the results from measurement, a finite element model of the uniform strength microcantilever has been developed to simulate mechanical behavior in microcantilever based on finite element method (FEM). The results show that results obtained from FEM and measurement based on PSD show excellent agreement. This work has provided a novel and more effective method for measurement of the strain in microcantilever.

Abstract: With the socio-economic development and increasingly higher buildings, public concern is growing over high-rise fire evacuation issues. Considering the shortcomings of the existing escape device and methods, such as difficult speed adjustment, high demand for escaping skill, difficult unification of speediness and security, poor recycling etc, an integrated speed limited escape method is proposed by analyzing kinetics of high-rise evacuation. On one hand, the escape acceleration is limited by using centrifugal mechanism, on the other, according to the building height and people's weight, the landing speed of people is restricted by controlling the break height and braking force of brakes. The developed escape machine use the micro-controller to monitor the height and speed real-timely, control the brake automatically and start rope recycling mechanism after the landing, which achieves quick and safe escape. The experiment shows that when heavy object weighing around 75kg drops from a height of 14. 6m, the maximum speed reaches 3m/s, the landing speed is less than 0.5m/s and the falling time is within 7.5s, which achieves better escaping effect.

Abstract: Doppler speed radar is a high precision velocity measuring instrument based on Doppler Effect, which has widely applications in measuring moving target’s velocity. In this paper, a novel design of Doppler signal processing system was presented to perform projectile’s speed measurement tasks. The system architecture is based on an Altera Cyclone II chip and designed as a System-on-a-Programmable-Chip (SOPC) with the help of an embedded Nios II software processor. And the SOPC system integrates CPU, memory, I/O interface and some other reconfigured modules required in system. According to the proposed scheme, the peripheral circuits were designed in this system, such as signal condition, A/D conversion and auto gain control (AGC) circuit. We also proposed to use spectral analysis method based on windowed FFT to deal with the measured target’s Doppler signal. Further, the signal source of simulating targets was used to testify the system feasibility. In addition, future work can include the further study on frequency estimation algorithms or comparisons of the proposed architecture with traditional design.

Abstract: In this paper a twin-island structure in piezoresistive pressure sensor based on MEMS technology has been presented, and a finite element mechanical model has been developed to simulate the static mechanical behavior of this twin-island structure sensor chip, especially the stress distributions in diaphragm of the sensor chip, which has a vital significance on piezoresistive pressure sensors’ sensitivity. The possible impacts of twin-island’s location and twin-island’s width on the stress distributions, as well as the maximum value of compressive stress and tensile stress, have been investigated based on numerical simulation with Finite Element Method (FEM). The simulation results show that twin-island’s location has great effect on the stress distributions in sensor chips’ diaphragms and the sensitivity of piezoresistive pressure sensors, compared with the twin-island’s width.

Abstract: Boron-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited by plasma enhanced chemical vapor deposition (PECVD). Microstructures of these films were characterized and analyzed by Raman spectrum and atomic force microscopy (AFM). Thickness and resistivity of these films was measured by high-resolution profilometer and four-point probe respectively. The impact of annealing on boron-doped nc-Si:H thin films’ resistivity and the relationship between resistivity and microstructure were investigated. The results show that annealing and the annealing temperature have great impact on resistivity of nc-Si:H thin films as a result of microstructures changing after annealing. Resistivity of nc-Si:H thin films decreases after annealing, but it rises with the increasing annealing temperature in the range of 250°C to 400°C.