Flip chip assembled MEMS inductors

High performance suspended MEMS inductors produced using a flip chip assembly approach are described. An inductor structure is fabricated on a carrier and then flip chip assembled onto a substrate to form a suspended inductor for RF-IC applications with significant improvement in Q-factor and frequency of operation over the conventional IC inductors. A spiral MEMS inductor has been successfully produced on a silicon substrate with an air gap of 26 /spl mu/m between the inductor structure and the substrate. The inductance of the device was measured to be /spl sim/2 nH and a maximum Q-factor of 19 at /spl sim/2.5 GHz was obtained after pad/connector de-embedding.     

双层悬空结构射频微电感制作研究

利用MEMS工艺制作了一种双层悬空结构的圆形射频微电感,研究了双层结构微电感中微带线宽度对其性能的影响。研究表明,双层悬空结构的圆形射频微电感不仅具有较大的电感量,而且其Q值也较高;双层微电感的Q值随微带线宽度的增大而升高,而电感量则随微带线宽度的增大而降低。对于微带线宽度为60μm的双层微电感,在频率2～4GHz时,其电感量可达到5nH左右,Q值达到20。     

新型悬空结构射频微电感的制作与测试

利用MEMS(Micro Electro-Mechanical System:微机电系统)工艺中的牺牲层技术制作了一种新型悬空结构微电感,在此悬空结构中,微电感的线圈制作在与衬底平行的平面上,线圈与衬底之间有立柱支撑;此新型微电感的制作工艺流程简单,与集成电路工艺相兼容,且其高频性能较好。并对此结构微电感的性能进行了测试,测试频率范围在0.05~10 GHz之间,结果表明:当悬空结构微电感的悬空高度为20 靘,工作频率在3~5 GHz范围内时,其电感量达到4 nH,其Q值最大可达到22。     

A deep submicron CMOS process compatible suspending high-Q inductor

A novel high-Q on-chip inductor structure called suspending inductor is developed to improve the characteristics of the conventional on-chip spiral inductor. The suspending inductor employs the air gap and is supported by a set of novel metal pillars to suppress the capacitance from the metal layer to the substrate. The measured maximum quality factor of the suspending inductor is improved from 4.8 to 6.3 in comparison to the conventional spiral inductor. Furthermore, the frequency at maximum quality factor is raised from 1.5-2 GHz     

Packaging-compatible high Q microinductors and microfilters forwireless applications

To meet requirements in mobile communication and microwave integrated circuits, miniaturization of the inductive components that many of these systems require is of key importance. At present, active circuitry is used which simulates inductor performance and which has high Q-factor and inductance; however, such circuitry has higher power consumption and higher potential for noise injection than passive inductive components. An alternate approach is to fabricate integrated inductors, in which lithographic techniques are used to pattern an inductor directly on a substrate or a chip. However, integrated inductors can suffer from low Q-factor and high parasitic effects due to substrate proximity. To expand the range of applicability of integrated microinductors at high frequency, their electrical characteristics, especially quality factor, should be improved. In this work, integrated spiral microinductors suspended (approximately 60 μm) above the substrate using surface micromachining techniques to reduce the undesirable effect of substrate proximity on the inductor performance are investigated. The fabricated inductors have inductances ranging from 15-40 nH and Q-factors ranging from 40-50 at frequencies of 0.9-2.5 GHz. Microfilters based on these inductors are also investigated by combining these inductors with integrated polymer filled composite capacitors     

Fabrication and performance of novel RF spiral inductors on silicon

This paper presents and discusses the fabrication and the performance of RF circular spiral inductors on silicon. The substrate materials underneath the inductor coil are removed by wet etching process. In the fabrication process, fine polishing of the photoresist is used to simplify the processes and ensure the seed layer and the pillars contact perfectly, and dry etching technique is used to remove the seed layer. The results show that Q-factor of the novel inductor is greatly improved by removing the silicon underneath the inductor coil. The spiral inductor for line width of 50 μm has a peak Q-factor of 17 at frequency of 1 GHz. The inductance is about 3.2 nH in the frequency range of 0.05-3 GHz and the resonance frequency of the inductors is about 6 GHz. If the strip is widened to 80 μm, the peak Q-factor of the inductor reduces to about 10 and the inductance is 1.5 nH in the same frequency range.     

RF inductors with suspended and copper coated thick crystalline silicon spirals for monolithic MEMS LC circuits

This letter presents a novel radio frequency (RF) inductor in a monolithic inductor-capacitor circuit developed by using micro-electromechanical systems (MEMS) fabrication technology. The inductor consists of 40-/spl mu/m-thick single crystalline silicon spiral with copper surface coating as the conductor, which is suspended on a glass substrate. The fabricated inductor exhibits a self-resonance frequency higher than 15GHz, with the quality factor more than 35 and inductance over 5nH at 11.3GHz. Simulations based on a compact equivalent circuit model with parameters extracted using a characteristic-function approach have also been carried out for the inductor, and good agreement with measurements is obtained.     

Design and modeling of a micromachined high-Q tunable capacitor with large tuning range and a vertical planar spiral inductor

In wireless communication systems, passive elements including tunable capacitors and inductors often need high quality factor (Q-factor). In this paper, we present the design and modeling of a novel high Q-factor tunable capacitor with large tuning range and a high Q-factor vertical planar spiral inductor implemented in microelectromechanical system (MEMS) technology. Different from conventional two-parallel-plate tunable capacitors, the novel tunable capacitor consists of one suspended top plate and two fixed bottom plates. One of the two fixed plates and the top plate form a variable capacitor, while the other fixed plate and the top plate are used to provide electrostatic actuation for capacitance tuning. For the fabricated prototype tunable capacitors, a maximum controllable tuning range of 69.8% has been achieved, exceeding the theoretical tuning range limit (50%) of conventional two-parallel-plate tunable capacitors. This tunable capacitor also exhibits a very low return loss of less than 0.6 dB in the frequency range from 45 MHz to 10 GHz. The high Q-factor planar coil inductor is first fabricated on a silicon substrate and then assembled to the vertical position by using a novel three-dimensional microstructure assembly technique called plastic deformation magnetic assembly (PDMA). Inductors of different dimensions are fabricated and tested. The S-parameters of the inductors before and after PDMA are measured and compared, demonstrating superior performance due to reduced substrate loss and parasitics. The new vertical planar spiral inductor also has the advantage of occupying much smaller silicon areas than the conventional planar spiral inductors.     

Air Cavity Incorporation to LTCC Spiral Inductor for High Q-factor and SRF

We have devised a new LTCC spiral inductor incorporating an air cavity underneath for high Q-factor and high self-resonant frequency (SRF). The air cavity employed under the spiral reduces the shunt capacitance of the inductor, and results in high Q-factor and SRF of the embedded inductors. The optimized spiral inductor with the embedded air cavity shows a maximum Q of 51 and SRF of 9.1 GHz, while conventional spiral inductor has a maximum Q of 43 and SRF of 8 GHz with effective inductance of 2.7 nH.     

Surface micromachined solenoid on-Si and on-glass inductors for RFapplications

RF performance of surface micromachined solenoid on-chip inductors fabricated on a standard silicon substrate (10 Ω·cm) has been investigated and the results are compared with the same inductors on glass. The solenoid inductor on Si with a 15-μm thick insulating layer achieves peak quality (Q-) factor of 16.7 at 2.4 GHz with inductance of 2.67 nH. This peak Q-factor is about two-thirds of that of the same inductor fabricated on glass. The highest performance has been obtained from the narrowest-pitched on-glass inductor, which shows inductance of 2.3 nH, peak Q-factor of 25.1 at 8.4 GHz, and spatial inductance density of 30 nH/mm². Both on-Si and on-glass inductors have been modeled by lumped circuits, and the geometrical dependence of the inductance and Q-factor have been investigated as well     

Experimental analysis of the effect of metal thickness on the quality factor in integrated spiral inductors for RF ICs

The effect of metal thickness on the quality (Q-) factor of the integrated spiral inductor is investigated in this paper. The inductors with metal thicknesses of 5/spl sim/22.5 /spl mu/m were fabricated on the standard silicon substrate of 1/spl sim/30 /spl Omega//spl middot/cm in resistivity by using thick-metal surface micromachining technology. The fabricated inductors were measured at GHz ranges to extract their major parameters (Q-factor, inductance, and resistance). From the experimental analysis assisted by FEM simulation, we first reported that the metal thickness' effect on the Q-factor strongly depends on the innermost turn diameter of the spiral inductor, so that it is possible to improve Q-factors further by increasing the metal thickness beyond 10 /spl mu/m.     

表面镀铜悬浮厚单晶硅螺线MEMS电感

报道了一种由悬浮在玻璃衬底上的表面镀铜平面单晶硅螺线构成的新型MEMS电感,可消除衬底损耗及减小电阻损耗.采用一种硅玻璃键合-深刻蚀成型释放工艺并结合无电镀技术制作该电感,形成厚约40μm的硅螺线,在硅螺线表面镀有高保形厚铜镀层,在铜镀层表面镀有起钝化保护作用的薄镍镀层.该电感的自谐振频率超过15GHz,在11.3GHz下,品质因子达到约40,电感值超过5nH.基于该电感的简化等效电路模型,采用一种特征函数法进行了参数提取,模拟结果与测量结果符合得很好.     

High-performance inductors integrated on porous silicon

To study the substrate effect on inductor performance, several types of spiral inductors were fabricated on porous silicon (PS), p/sup -/ and p/sup +/ silicon substrate. /spl pi/-network analysis results show that the use of PS effectively reduces the shunt conductance and capacitance. The analysis further shows that the use of PS significantly reduces the eddy current portion of series resistance of inductor, leading to slower increase of the apparent series resistance with increasing frequency. Higher Q-factor and resonant frequency (f/sub r/) result from the reduced shunt conductance, shunt capacitance, and frequency dependence of series resistance. Inductors fabricated on PS regions are subjected to a much less stringent set of constraints than those on bulk Si substrate, allowing for much higher inductance to be achieved without severe sacrifice in Q-factor and f/sub r/. Similarly, much higher Q-factor can be obtained for reasonable inductance and f/sub r/.     

隔层不交叠多层电感分析与设计

提出了一种隔层不重叠的新型结构片上螺旋电感,其实现工艺与标准CMOS多层布线技术兼容.结合螺旋电感的集总模型,利用电磁场仿真软件HFSS进行了该器件的模拟仿真,与相同结构参数和工艺参数的传统不隔层交叠多层电感相比,提出的新型电感在品质因子、自谐振频率、3dB带宽等性能参数上明显改善,其中电感品质因子提高3.5％,带宽增...     

Micromachined high-Q inductors in a 0.18-μm copper interconnectlow-k dielectric CMOS process

On-chip spiral micromachined inductors fabricated in a 0.18-μm digital CMOS process with 6-level copper interconnect and low-K dielectric are described. A post-CMOS maskless micromachining process compatible with the CMOS materials and design rules has been developed to create inductors suspended above the substrate with the inter-turn dielectric removed. Such inductors have higher quality factors as substrate losses are eliminated by silicon removal and increased self-resonant frequency due to reduction of inter-turn and substrate parasitic capacitances. Quality factors up to 12 were obtained for a 3.2-nH micromachined inductor at 7.5 GHz. Improvements of up to 180% in maximum quality factor, along with 40%-70% increase in self-resonant frequency were seen over conventional inductors. The effects of micromachining on inductor performance was modeled using a physics-based model with predictive capability. The model was verified by measurements at various stages of the post-CMOS processing. Micromachined inductor quality factor is limited by series resistance up to a predicted metal thickness of between 6-10 μm     

一种硅衬底镂空结构的圆形射频微电感

利用MEMS工艺以及硅的湿法刻蚀工艺制作了一种硅衬底镂空结构的圆形射频微电感，并研究了硅衬底背面减薄对射频微电感性能的影响，结果表明：微电感硅衬底经过局部刻蚀减薄后其自谐振频率上升，电感量的频率稳定性提高，而其最大Q值下降。     

On the design of RF spiral inductors on silicon

This review of design principles for implementation of a spiral inductor in a silicon integrated circuit fabrication process summarizes prior art in this field. In addition, a fast and physics-based inductor model is exploited to put the results contributed by many different groups in various technologies and achieved over the past eight years into perspective. Inductors are compared not only by their maximum quality factors (Q/sub max/), but also by taking the frequency at Q/sub max/, the inductance value (L), the self-resonance frequency (f/sub SR/), and the coil area into account. It is further explained that the spiral coil structure on a lossy silicon substrate can operate in three different modes, depending at first order on the silicon doping concentration. Ranging from high to low substrate resistivity, inductor-mode, resonator-mode, and eddy-current regimes are defined by characteristic changes of Q/sub max/, L, and f/sub SR/. The advantages and disadvantages of patterned or blanket resistive ground shields between the inductor coil and substrate and the effect of a substrate contact on the inductor are also addressed in this paper. Exploring optimum inductor designs under various constraints leverages the speed of the model. Finally, in view of the continuously increasing operating frequencies in advancing to new generations of RF systems, the range of feasible inductance values for given quality factors are predicted on the basis of optimum technological features.     

采用MEMS技术制作的螺线管电感

采用微机电系统技术制作了螺线管电感.为了获得高电感量和Q值,采用UV-LIGA、干法刻蚀、抛光和电镀技术,研制的电感大小为1500μm×900μm×70μm,线圈匝数为41匝,宽度为20μm,线圈之间的间隙为20μm,高深宽比为3.5:1.测试结果表明电感量最大值为6.17nH,Q值约为6.     

Experimental Characterization of On-Chip Single and Double-Coupling Spiral Inductors

Experimental investigations on on-chip single and double-coupling square spiral inductors on silicon substrate are performed. For each pair of double-coupling inductors, they have the same edge distance, but with different turn numbers. Based on the measured S-parameters using de-embedding procedure, the inductance and Q-factor of the single square inductor are examined at first, and good agreement is obtained in the extracted inductance, compared to the predicted values using a closed-form series inductance equation. While for double-coupling spiral inductors, the smaller the product of two turn numbers, the weaker coupling will be, and in particular at low frequencies.     

硅微机械悬浮结构电感的设计与制作工艺研究

本文系统分析了影响平面螺旋电感Q值的主要因素,并制作出一种应用于射频通信的硅微机械悬浮结构电感.在考虑趋肤效应、涡流损耗等高频电磁场效应对电感Q值的影响后,获得了微机械电感的简化电学模型,得到了具有较高Q值电感的优化结构.在制作硅微机械电感的工艺过程中,采用多孔硅作为牺牲层材料,将螺旋结构铝线圈制作在二氧化硅薄膜上,在使用添加了硅粉和过硫酸铵的TMAH溶液释放牺牲层之后,得到设计值为4nH的悬浮结构微机械平面螺旋电感.实验结果证明,整个工艺流程可靠,并与CMOS工艺兼容.