基于SOI的硅微谐振式压力传感器芯片制作

采用SOI硅片,基于MEMS技术,设计并加工了一种新型三明治结构的硅微谐振式压力传感器,根据传感器敏感单元的结构设计,制定了相应的制备工艺步骤,并且针对湿法深刻蚀过程中谐振子的刻蚀保护等问题,提出了一种基于氮化硅、氧化硅和氮化硅三层薄膜的保护工艺,实验表明,在采用三层薄膜保护工艺下进行湿法刻蚀10 h后,谐振子被完全释放,三层薄膜保护工艺对要求采用湿法刻蚀镂空释放可动结构具有较高的实用价值。最后对加工完成的谐振式压力传感器进行了初步的性能测试,结果表明,在标准大气压力下谐振子的固有频率为9.932 kHz,品质因数为34。     

Detection of the boundary-layer separation point based on the flexible sensor arrays

Microelectromechanical systems plays an important role for studying gaseous or liquid fluid flows experimentally due to the dimensions of the device on the μm-scale. For aerodynamic applications, the detection of the location of the separation point of the boundary layer is very important, which is used for active flow control and smart skin adaptive control system. This paper presents the design and integration methods of a flexible polymide substrate micro thermal sensor array, sensor array driver circuit, dynamic data acquisition circuit, and criterion algorithm of the boundary layer separation point. The above algorithms were used to analyze the NACA0012 wind tunnel test data at flow conditions of the velocity 40 m/s and AOA 16°. The result demonstrated the above system can fulfill the dynamic and real-time of the adaptive control system.     

Investigations on electric properties and domain structures of Nd-doped 0.70Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 relaxor ferroelectric ceramics with high piezoelectric properties

Although rare earth neodymium (Nd) doping is common in Pb(Mg1/3Nb2/3)O₃–PbTiO₃ (PMN–PT) single crystals, it is rarely reported in PMN–PT ceramics. To explore the effect of Nd doping on PMN–PT ceramics, PMN–30PT:xNd³⁺ (x = 0%, 1%, 2%, and 3%) relaxor ferroelectric ceramics were fabricated using a solid-state method via two-step sintering. An enhanced piezoelectric charge coefficient (d₃₃) of ∼870 pC/N and a high piezoelectric strain coefficient (d₃₃*) of ∼1025 pm/V were achieved for x = 2%. Through Rayleigh analysis of polarization–electric field (P–E) hysteresis loops under small electric fields, it was found that the dielectric property was mainly influenced by the intrinsic contribution (local lattice distortion). Furthermore, by investigating domain configurations, high piezoelectric properties were found to be associated with the domain size reduction and local structural heterogeneity. The results indicate that the PMN–30PT:xNd³⁺ ceramics is a promising material for electronic devices, and that rare earth Nd doping is an efficient strategy for improving the electronic performance of Pb-based relaxor ferroelectrics.     

Concrete–ice abrasion mechanics

The mechanisms of abrasion of concrete by ice are investigated by review of lab and field studies, wear theory, fracture-, contact- and poromechanics. Experience indicates that ice abrasion does not require freeze/thaw cycles. Three distinct mechanisms may contribute to abrasion damage of concrete: (1) asperities of ice sliding on concrete can create tensile stresses sufficient to initiate cracks (with fatigue from repeated contacts playing an important role); (2) debris released from the surface of the concrete can act as sharp abrasive particles that enhance the damage as the ice drags them along the surface; and (3) water forced into surface defects can create pressure that propagates cracks. Topics for further research and recommendations for minimizing abrasion are suggested.     

Microstructures and properties of Bi10Ag high temperature solder doped with Cu element

High temperature Bi10Ag solders with different amounts of Cu were used to investigate the impacts of Cu on the microstructures, melting characteristics, wettability and shear strength of the Bi-10Ag-xCu (x = 0, 0.5, 1, and 2 wt%) solders. A metastable Cu-rich phase was formed due to the addition of Cu. The Cu has negligible effect on the solidus but it can decrease about 6 °C on the liquidus. Doped with 0.5 wt% of Cu, the solders showed the largest melting range in the DSC curves and improved wettability on Cu substrates. When the Cu addition excesses to 0.5 wt%, it will induce negative effects on wettability of the solders on the substrate. Moreover, the addition of Cu has no significant influence on the strength of the Bi10Ag lap solder joints. The Bi-10Ag-0.5Cu solder joint has higher shear strength than that of Pb5Sn.     

MEMS版图抽取及系统级模型自动构建技术

研究了一种抽取版图信息构建系统级模型的技术,即从标准版图文件中提取结构的几何信息和拓扑信息,将其转换对应于系统级中的参数化元件库,并按原始版图拓扑互连,从而生成基于saber仿真平台的系统级模型文件,实现了MEMS工艺级到系统级的数据传递,使用C 编程语言开发了相应的转换接口。通过典型器件——微加速度计和微变形镜的多种结构验证了转换方法的可行性。     

An investigation into material-induced surface roughness in ultra-precision milling

This paper presents a theoretical and experimental investigation into the effect of the workpiece material on surface roughness in the ultra-precision milling process. The influences of material swelling and tool-tip vibration on surface generation in ultra-precision raster milling are studied. A new method is proposed to characterize material-induced surface roughness on the raster-milled surface. A new parameter is defined to characterize the extent of surface roughness profile distortion induced by the materials being cut. An experiment is conducted to compare the proposed method with surface roughness parameters and power spectrum density analysis method by machining three different workpiece materials. The results show that the presence of elastic recovery improves the surface finish in ultra-precision raster milling and that, among the three materials being cut in the experiment, aluminum bronze has the greatest influence on surface finish due to its highest elastic recovery rate and hardness. The results also show that, in the case of faster feed rates, the proposed method more efficiently characterizes material-induced surface roughness.     

4H-SiC肖特基微型同位素电池(英文)

半导体同位素电池由于其寿命长、集成性优良、环境适应性强等特点成为解决MEMS能源问题的理想手段。利用4H-SiC材料的宽禁带特性,制造了4H-SiC肖特基同位素电池。对电池的耗尽层厚度以及掺杂浓度进行了优化设计,对肖特基金属进行了选择。使用4mCi/cm2的63Ni作为同位素电池的放射源对制造的同位素电池进行了测试。测试结果表明,该同位素电池可以获得31.3nW/cm2的功率密度、0.5V的开路电压、3.13×10-8A/cm2的短路电流密度和1.3%的转换效率。将电池的输出特性和硅基的平板型、3D结构电池输出特性进行了比较,证明4H-SiC肖特基同位素电池能够获得较高的功率密度。电池的性能可通过提升势垒高度、提高工艺质量、更换同位素等方式得到提高。     

Notching效应在MEMS单步干法制造工艺中的应用

研究了一种基于深反应离子刻蚀（DRIE）中notching效应的MEMS单步干法制造工艺.首先,基于DRIE刻蚀SOI硅片时notching现象产生的机理,设计了多种不同线宽的槽结构,验证notching效应的发生条件.实验结果表明,对于所采用的具有30μm器件层的SOI硅片,发生notching现象的临界槽宽为12μm,而notching释放的极限结构宽度同样为12μm.其次,为实现大面积结构的notching释放,研究了正方形、矩形、三角形及六边形等4种典型释放孔结构的干法释放效果.实验结果表明,六边形释放孔不但能够快速有效地释放结构,同时还能降低notch-ing效应的磨损,有利于惯性MEMS器件的加工.最后,设计了一种Z轴微机械陀螺结构以验证提出的设计及工艺.加工及测试结果表明,所提出的单步干法制造工艺完全满足微机械陀螺设计加工要求,工艺简单、成品率高,所测试的陀螺在常压下即可达到122的品质因数.     

Modulation method for measuring thermal impedance components of semiconductor devices

The paper describes the modulation method of measuring the thermal impedance of semiconductor devices as well as its implementation. In contrast to the standard method (JESD51-1 standard) which requires heating the device under test by the stepped power, the modulation method uses heating power modulated harmonically. A pulse sequence of heating current, with the pulse length varying harmonically, is passed through the device under test. The p-n junction temperature is measured through a temperature-sensitive parameter, namely a forward voltage drop on the p-n junction between heating pulses at low measuring current. First harmonic of the p-n junction temperature oscillation is determined by the discrete Fourier transform, which allows to determine thermal impedance absolute value and phase at modulation frequency of heating power. An analysis of the dependence of thermal impedance on modulation frequency allows to determine thermal impedance components corresponding to the structural elements of the device under test. Numerical simulation shows that the thermal resistance components on the Foster's network may be determined at the modulation frequencies corresponding to the first derivative minima of the thermal impedance of the real part of frequency dependence. The main characteristics of the device that implements the method are described.