Search

Defective pixels always exist in an uncooled infrared focal plane array (IR FPA), and have a significant impact on image quality. To fundamentally reduce defective pixels and improve IR FPA’s reliability, failure analysis (FA) is critically needed. In this work, a self-test (ST) method is proposed to detect the structural failures of uncooled IR FPA. Based on the lumped thermal parameters of a pixel, a structural failures model is presented, and an electrical circuit is designed. The insufficient released, normal released, over released and contaminated IR FPAs are measured. The measured results show that their lumped thermal parameters have a clear differentiation, which not only experimentally verifies the validity of this method, but also shows that it is an effective method for nondestructive analysis of structural failures.

On approach towards the end of technology roadmap, a revolutionary approach towards the nanowire transistors is favorable due to the full control of carrier transport. The transistor design moves toward vertically or laterally stacked Gate-All-Around (GAA) where Si or SiGe can be used as channel material. This study presents a novel isotropic inductively coupled plasma (ICP) dry etching of Si1−xGex (0.10 ≤ x ≤ 0.28) in SiGe/Si multilayer structures (MLSs) with high selectivity to Si, SiO2, Si3N4 and SiON which can be applied in advanced 3D transistors and Micro-Electro-Mechanical System (MEMS) in future. The profile of SiGe etching for different thicknesses, compositions and locations in MLSs using dry or wet etch have been studied. A special care has been spent for layer quality of Si, strain relaxation of SiGe layers as well as residual contamination during the etching. In difference with dry etching methods (downstream remote plasma), the conventional ICP source in situ is used where CF4/O2/He gas mixture was used as the etching gas to obtain higher selectivity. Based on the reliability of ICP technique a range of etching rate 25–50 nm/min can be obtained for accurate isotropic etching of Si1−xGex, to form cavity in advanced 3D transistor processes in future.

Diode based micro-Pirani vacuum sensors attract considerable attention because they do not require special materials and are compatible with complementary metal oxide semiconductors (CMOS). However, their complex heating structure makes it difficult to reduce the sensor size. This paper reports a novel compact micro-Pirani vacuum sensor based on series diodes. The self-heating effect of the series diodes helps simplify the structural design by avoiding a dedicated heating structure. Moreover, the small size of the series diodes ensures high temperature coefficient. The proposed design reduces the sensor size without sacrificing the performance. In fact, simulation results indicate that the series diodes help enhance the device performance. A sensor was fabricated by a CMOS compatible process. The sensor size was reduced significantly to 35 μm × 35 μm. The sensor is sensitive to the vacuum pressure range from 10−1 Pa to 104 Pa when driven by a constant current as small as 10 μA, and the power consumption is low at 50 μW.

Thermopile sensors have a wide range of applications in consumer and industry. Seebeck coefficient is a basic thermal parameter of thermopile sensors. Extracting the Seebeck coefficient of both materials and thermocouple in thermopile sensors is of great importance. In this work, an on-chip test structure is designed. It consists of a substrate, a framework, supporting legs and a sensitive region which has a resistor serving as both heater and temperature detector. A set of on-chip test structures are fabricated along with a thermopile sensor. Its measurement results are analyzed and compared with apparatus measurement results. These results are consistent with each other, and the validity of structure is verified.

The stress stability in plasma-enhanced chemical vapor deposition (PECVD) silicon dioxide (SiO2) films is a key factor of device performance. In this study, the PECVD SiO2 films are annealed at 400–1000 °C in a nitrogen (N2) or oxygen (O2) ambience for 2 h. The influences of annealing parameters on the stress state and stress stability in PECVD SiO2 films are investigated. The bonding nature and surface morphology of the films are also studied to analyze the physical mechanism involved. It is demonstrated that the stress stability is first deteriorated and then improved with increasing annealing temperature. In addition, O2 ambience is more appropriate to improve stress stability than N2, and the stress in PECVD SiO2 film can be stabilized when it is annealed at 1000 °C in O2 ambience. These results should be able to provide important insights into the design of device fabrication processes.

The stress state of low-pressure chemical vapor deposition (LPCVD) silicon dioxide (SiO2) films fluctuates upon aging due to the ambient moisture. The related variation of the SiO2 films is a key factor of device reliability. In this study, ion implantation is introduced to improve film stress stability. The stress state modified by ion implantation is discussed in detail and an analytical model is presented. The evolution of the stress in as-deposited and P+-, As+-, and B+-implanted LPCVD SiO2 films upon aging is investigated, and the bonding nature of the films is also studied to provide insight into the physical mechanisms involved. It is demonstrated that low implantation energy slightly modifies the stress in films. In addition, P+ ion is the most appropriate impurity ion to improve film stress stability, and the stress in P+-implanted LPCVD SiO2 film can be stabilized with a low tensile stress of 67 MPa when the film is implanted at 15 keV with a dose of 1 × 1015 cm− 2.

We propose a novel Fabry–Perot interferometer (FPI) sensor for simultaneous measurement of refractive index (RI) and temperature based on Fresnel reflection and the thermo-optic effect of silica. The sensor head consists of a short section of multimode photonic crystal fiber (MPCF) and a conventional single mode fiber (SMF), where two thin films are formed by collapsing the air holes of MPCF with a commercialized fusion splicer. Experimental results show that such a device has a linear RI sensitivity of ~21.52 dB/RIU (RI unit) and a linear optical path difference (OPD) temperature sensitivity of ~25 nm/°C. In addition, a high RI resolution of about ~1.7×10 −5 is obtained by using the Fourier transformation to decompose the spectral response in different spatial frequencies. Low-cost, easy fabrication and high resolution make it appropriate for practical applications.

A novel and simple refractive index tip sensor based on filling-free Fabry–Perot interferometer is realized by simply splicing a section of endlessly single-mode photonic crystal fiber to a conventional single-mode fiber. The temperature and refractive index characteristics of the proposed device are investigated. Experimental results show that the device can provide temperature-independent measurement of refractive index with a fringe–contrast-sensitivity of ~52.4 dB/RIU. Meanwhile, it can also be used as a temperature sensor with a wavelength–temperature-sensitivity of ~7 pm/°C. In addition, we also propose that using a spectrum differential integration method to improve the performance of the device as compared to the method of measuring the fringe contrast.

An optical readout focal plane array (FPA) usually has a differently tilted reflector/absorber at the initial state due to the micromachining technique. The angular deviation of the reflector/absorber has a strong impact on the optical sensitivity non-uniformity, which is a key factor which affects the imaging uniformity. In this study, a theoretical analysis has been developed, and it is found that the stress matching in SiO2-Aluminum (Al) bilayer leg could make a contribution towards reducing the optical sensitivity non-uniformity. Ion implantation of phosphorus (P) has been utilized to control the stress in SiO2 film. By controlling the implantation energy and dose, the stress and stress stability are modified. The optical readout FPA has been successfully fabricated with the stress-control technique based on P+ implantation. It is demonstrated that the gray response non-uniformity of optical readout FPA has decreased from 25.69% to 10.7%.

An optical readout focal plane array (FPA) usually has a bent cantilever due to the micro-machining techniques. This bent morphology has a strong negative impact on optical sensitivity, which is a key factor that affects the imaging performance. In this study, an optical readout FPA with a stiffener-supported pixel is presented in order to reduce the deformation. The theoretical analysis has been developed to optimize the structure. Based on this, an FPA with a stiffener-supported pixel is fabricated. It is demonstrated that the curvature radius and optical sensitivity can increase by 5 times and 5.74 times respectively with respect to that without a stiffener. Better thermal imaging has been achieved.