|
Issue Browser

Volume 36, Issue 7, Jul 2015

    SEMICONDUCTOR PHYSICS

  • Electric and magnetic optical polaron in quantum dot——Part 1: strong coupling

    A. J. Fotue, N. Issofa, M. Tiotsop, S. C. Kenfack, M. P. Tabue Djemmo, H. Fotsin, L. C. Fai

    J. Semicond.  2015, 36(7): 072001

    doi: 10.1088/1674-4926/36/7/072001

    Abstract Full Text PDF Get Citation

    We investigated the influence of electric field and magnetic field on the ground state energy of polaron in spherical semiconductor quantum dot (QD) using a modified Lee Low Pines (LLP) method. The numerical results show the increase of the ground state energy with the increase of the electric field and the decreasing with the magnetic field. The modulation of the electric field, magnetic field and the confinement lengths lead to the control of the decoherence of the system.

  • Optimized geometry and electronic structure of three-dimensional β-graphyne

    Yang Pei, Haibin Wu, Jingmin Liu

    J. Semicond.  2015, 36(7): 072002

    doi: 10.1088/1674-4926/36/7/072002

    Abstract Full Text PDF Get Citation

    β-graphyne, a carbon allotrope, is a gapless semiconductor with hexagonal lattice symmetry, just like graphene. We calculated the optimized structure and electronic structures of some possible three-dimensional β-graphyne stacking arrangements by means of the first-principles frozen-core projector augmented-wave method implemented in the Vienna ab initio simulation package. The optimized lattice constant a of the three-dimensional β-graphyne turns out to be 9.46 Å, which is slightly smaller than its two-dimensional counterpart. The binding energy is about 90% of that of graphite, which suggests that three-dimensional β-graphyne will be stable when it is synthesized. The band structure is calculated via the hybrid functional. We found that the most stable three-dimensional stacking arrangement is an indirect band gap semiconductor with an energy gap of 0.1 eV.

  • Scattering mechanism of hole in (001), (101), (111) biaxially-strained Si and Si1-xGex materials

    Lixia Zhao, Chao Yang, He Zhu, Jianjun Song

    J. Semicond.  2015, 36(7): 072003

    doi: 10.1088/1674-4926/36/7/072003

    Abstract Full Text PDF Get Citation

    Based on Fermi's golden rule and the theory of Boltzmann collision term approximation, the hole scattering mechanism related to stress and orientation in Si-based strained materials was studied in-depth. The results show that: (1) the total hole scattering rates in Si-based strained materials decrease obviously under strain; (2) the turn is Si/(111)Si1-xGex > Si/(101)Si1-xGex > Si1-xGex/(111)Si > Si1-xGex/(101)Si > Si/(001)Si1-xGex > Si1-xGex/(001)Si when Ge fraction is about 0.2; (3) the decreasing total hole scattering rates of in strained materials with the increasing stress is mainly caused the decreasing acoustic phonon scattering rate under strain. The theoretical conclusions obtained could provide important references for researching the hole mobility and the understanding of Si-based materials or other physical strained materials.

  • SEMICONDUCTOR MATERIALS

  • Growth-temperature-dependent optical and acetone detection properties of ZnO thin films

    P. S. Shewale, Y. S. Yu

    J. Semicond.  2015, 36(7): 073001

    doi: 10.1088/1674-4926/36/7/073001

    Abstract Full Text PDF Get Citation

    Zinc oxide (ZnO) thin films were prepared onto glass substrates at moderately low growth temperature by two-stage spray pyrolysis technique. The effects of growth temperature on structural, optical and acetone detection properties were investigated with X-ray diffractometry, a UV-visible spectrophotometer, photoluminescence (PL) spectroscopy and a homemade gas sensor testing unit, respectively. All the films are polycrystalline with a hexagonal wurtzite phase and exhibit a preferential orientation along [002] direction. The film crystallinity is gradually enhanced with an increase in growth temperature. The optical measurements show that all the films are physically highly transparent with a transmittance greater than 82% in the visible range. The band gap of the film is observed to exhibit a slight red shift with an increasing growth temperature. The PL studies on the films show UV/violet PL band at ~ 395 nm. Among all the films investigated, the film deposited at 250 ℃ demonstrates a maximum sensitivity of 13% towards 20 ppm of acetone vapors at 300 ℃ operating temperature.

  • Magnetic polarization of a Mn-doped semiconductor nanostructure controlled by an external bias

    P. Paradeo

    J. Semicond.  2015, 36(7): 073002

    doi: 10.1088/1674-4926/36/7/073002

    Abstract Full Text PDF Get Citation

    The interplay between the electric and magnetic properties in a double quantum well heterostructure doped by magnetic ions is theoretically investigated. In this material, the magnetism is mediated by the hole gas. The total magnetic polarization of the system is controllable by an external applied bias. The device has two equilibrium states (symmetric and antisymmetric configurations). In the stable configuration (anti-ferromagnetic type), the particle spin distribution is reversed in the adjacent wells. The stability of the system is investigated by simulating the interaction of the hole gas with the light. By using an ab initio method, we estimate the switching time of the device.

  • Photocatalytic degradation of RhB and TNT and photocatalytic water splitting with CZTS microparticles

    S. S. Shinde

    J. Semicond.  2015, 36(7): 073003

    doi: 10.1088/1674-4926/36/7/073003

    Abstract Full Text PDF Get Citation

    Cu2ZnSnS4 (CZTS) is a main candidate material for solar energy conversion through both photovoltaics and photocatalysis based on environmentally friendly elements and with a direct band gap of 1.5 eV. We report the synthesis of quasi Cu2ZnSnS4 microparticles with unprecedented narrow size distributions. The structural, morphological and core level analysis has been carried out by XRD, SEM and XPS techniques. These microparticles have shown excellent photocatalytic activity toward degradation of Rhodamine B dye (RhB) and TNT under visible light. The extent of mineralization has been analyzed by COD and TOC values. Photocatalytic water splitting for H2 generation has also been reported.

  • Temperature sensor based on composite film of vanadium complex (VO2(3-fl)) and CNT

    Kh. S. Karimov, M. Mahroof-Tahir, M. Saleem, M. Tariq Saeed Chani, A. Khan Niaz

    J. Semicond.  2015, 36(7): 073004

    doi: 10.1088/1674-4926/36/7/073004

    Abstract Full Text PDF Get Citation

    A vanadium complex (VO2(3-fl)) and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VO2(3-fl) and CNT composite was coated as a temperature-sensing material on the top of the pre-patterned Ag electrodes. The temperature-sensing principle of the sensor was based on the conductivity change of the coated sensing element upon heating or cooling processes. DC and AC (100 Hz) resistances of the temperature sensor decreased quasi-linearly with increasing the temperature in the range of 25-80 ℃. The overall resistance of the sensor decreases by 1.8-2.1 and 1.9-2.0 times at DC and AC voltage, respectively. The resistance temperature coefficients of the sensor were in the range of -(0.9-1.3)% and -(1.1-1.3)% at DC and AC voltage, respectively. The properties of the sensor studied in this work, make it beneficial to be used in the instruments for environmental monitoring of temperature.

  • Effect of Ge-GeO2 co-doping on non-ohmic behaviour of TiO2-V2O5-Y2O3 varistor ceramics

    Kunyong Kang, Guoyou Gan, Jikang Yan, Jianhong Yi, Jiamin Zhang, Jinghong Du, Wenchao Zhao, Xuequan Rong

    J. Semicond.  2015, 36(7): 073005

    doi: 10.1088/1674-4926/36/7/073005

    Abstract Full Text PDF Get Citation

    An investigation was made into the effect of doping with the elemental crystal Ge or/and GeO2 on the TiO2-V2O5-Y2O3 varistor ceramics. The result shows that as the doping contents of V2O5 and Y2O3 are 0.5 mol%, respectively, co-doping with 0.3 mol% Ge and 0.9 mol% GeO2 makes the highest α value (α = 12.8), the lowest breakdown voltage V1mA (V1mA = 15.8 V/mm) and the highest grain boundary barrier ΦB (ΦB = 1.48 eV), which is remarkably superior to the TiO2-V2O5-Y2O3 varistor ceramics undoped with Ge and GeO2 and mono-doped with Ge or GeO2. The TiO2-V2O5-Y2O3-Ge-GeO2 ceramic has the prospect of becoming a novel varistor ceramic with excellent electrical properties.

  • Chemical and electrical properties of (NH4)2S passivated GaSb surface

    Dongyan Tao, Yu Cheng, Jingming Liu, Jie Su, Tong Liu, Fengyun Yang, Fenghua Wang, Kewei Cao, Zhiyuan Dong, Youwen Zhao

    J. Semicond.  2015, 36(7): 073006

    doi: 10.1088/1674-4926/36/7/073006

    Abstract Full Text PDF Get Citation

    The surface chemical properties of gallium antimonide (GaSb) after ammonium sulfide ((NH4)2S) solution passivation have been studied by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (TOF-SIMS) and I-V measurement. An advantage of neutral (NH4)2S + S solution over pure (NH4)2S solution and alkaline (NH4)2S + S solution has been found in the ability to passivate the GaSb surface by contrast and comparison. It has been found that alkaline (NH4)2S + S solution passivation effectively removes oxides of the GaSb surface and forms sulfide products to improve device performance. TOF-SIMS complementally demonstrates that pure (NH4)2S passivation did form sulfide products, which are too soluble to really exist. The lowest roughness determined using a 3D optical profilometer and the highest improved SBD quality proved that neutral (NH4)2S + S solution passivation worked much better in improving the surface properties of GaSb.

  • SEMICONDUCTOR DEVICES

  • Dopingless impact ionization MOS (DL-IMOS)——a remedy for complex process flow

    Sangeeta Singh, P. N. Kondekar

    J. Semicond.  2015, 36(7): 074001

    doi: 10.1088/1674-4926/36/7/074001

    Abstract Full Text PDF Get Citation

    We propose a unique approach for realizing dopingless impact ionization MOS (DL-IMOS) based on the charge plasma concept as a remedy for complex process flow. It uses work-function engineering of electrodes to form charge plasma as surrogate doping. This charge plasma induces a uniform p-region in the source side and an n-region in the drain side on intrinsic silicon film with a thickness less than the intrinsic Debye length. DL-IMOS offers a simple fabrication process flow as it avoids the need of ion implantation, photo masking and complicated thermal budget via annealing devices. The lower thermal budget is required for DL-IMOS fabrication enables its fabrication on single crystal silicon-on-glass substrate realized by wafer scale epitaxial transfer. It is highly immune to process variations, doping control issues and random dopant fluctuations, while retaining the inherent advantages of conventional IMOS. To epitomize the fabrication process flow for the proposed device a virtual fabrication flow is also proposed here. Extensive device simulation of the major device performance metrics such as subthreshold slope, threshold voltage, drain induced current enhancement, and breakdown voltage have been done for a wide range of electrodes work-function. To evaluate the potential applications of the proposed device at circuit level, its mixed mode simulations are also carried out.

  • Numerical simulation of the effect of the free carrier motilities on light-soaked a-Si:H p-i-n solar cell

    L. Ayat, A. F. Bouhdjar, AF. Meftah, N. Sengouga

    J. Semicond.  2015, 36(7): 074002

    doi: 10.1088/1674-4926/36/7/074002

    Abstract Full Text PDF Get Citation

    Using a previous model, which was developed to describe the light-induced creation of the defect density in the a-Si:H gap states, we present in this work a computer simulation of the a-Si:H p-i-n solar cell behavior under continuous illumination. We have considered the simple case of a monochromatic light beam nonuniformly absorbed. As a consequence of this light-absorption profile, the increase of the dangling bond density is assumed to be inhomogeneous over the intrinsic layer (i-layer). We investigate the internal variable profiles during illumination to understand in more detail the changes resulting from the light-induced degradation effect. Changes in the cell external parameters including the open circuit voltage, Voc, the short circuit current density, Jsc, the fill factor, FF, and the maximum power density, Pmax, are also presented. This shows, in addition, the free carrier mobility influence. The obtained results show that Voc seems to be the less affected parameter by the light-induced increase of the dangling bond density. Moreover, its degradation is very weak-sensitive to the free carrier mobility. Finally, the free hole mobility effect is found to be more important than that of electrons in the improvement of the solar cell performance.

  • Hydrolysis preparation of the compact TiO2 layer using metastable TiCl4 isopropanol/water solution for inorganic-organic hybrid heterojunction perovskite solar cells

    Xiaoyan Dai, Chengwu Shi, Yanru Zhang, Ni Wu

    J. Semicond.  2015, 36(7): 074003

    doi: 10.1088/1674-4926/36/7/074003

    Abstract Full Text PDF Get Citation

    A hydrolysis process was applied to prepare the compact TiO2 layer using the fresh metastable TiCl4 isopropanol/water solution as the precursor solution for the preparation of the inorganic-organic hybrid heterojunction perovskite solar cells. The optimal compact TiO2 layer prepared from the aqueous solution of 2 mol· L-1 TiCl4 diluted in isopropanol at 1 : 3 by volume as precursor solution was uniform and with a film thickness of 126 nm. The corresponding perovskite solar cell gave a photovoltaic conversion efficiency of 10.61%.

  • A new method for calculation of majority carrier compensation in photovoltaics

    Rumin Zhang, Peng Liu, Dijun Liu, Guobin Su

    J. Semicond.  2015, 36(7): 074004

    doi: 10.1088/1674-4926/36/7/074004

    Abstract Full Text PDF Get Citation

    In thin film solar cells, the semiconductor materials usually contain multiple impurity/defect states as donor or acceptor dopants. The local charge neutrality (LCN) condition determines the equilibrium Fermi (EF) level and concentration of electrons and holes. However, the equation of LCN is a transcendental equation of EF. It is impossible to find its analytical solution and we can only solve it by graphic or numerical method. A simple approximate graphic method (GM) used for estimation of majority carrier compensation of semiconductors with multiple donors and acceptors was proposed by Chin. By introducing the concept of ranking the dopants and the wrapping step function, dopants concentration and Fermi level could be obtained easily. In this paper, we analyze the graphic method and propose a new numeric graphic method (NGM) based on GM. In addition, comparison of NGM with NM and analytics of the accuracy of GM are presented. With numerical calculation, some procedures of GM extending the application of GM are improved.

  • Mechanism of the self-changing parameters and characteristics in AlGaN/GaN high-electron mobility transistors after a step voltage stress

    Lei Shi, Shiwei Feng, Kun Liu, Yamin Zhang

    J. Semicond.  2015, 36(7): 074005

    doi: 10.1088/1674-4926/36/7/074005

    Abstract Full Text PDF Get Citation

    The phenomenon of self-changing on the device parameters and characteristics after a step voltage stress was applied to the gate is studied in AlGaN/GaN high electron mobility transistors. The device was measured every 5 min after the stress was removed. The large-signal parasitic source (drain) resistance, transfer characteristics, threshold voltage, drain-source current, gate-source (drain) reverse current-voltage characteristics changed spontaneously after the removal of the stress. The time constant of the self-changing was about 25-27 min. The gate-source (drain) capacitance-voltage characteristics were constant during this process. Electrons were trapped by the surface states and traps in the AlGaN barrier layer when the device was under stress. The traps in the AlGaN barrier layer then released electrons in less than 10 s. The surface states released electrons continuously during the entire measurement stage, leading to the self-changing of mearsurement result.

  • Optimized power simulation of AlGaN/GaN HEMT for continuous wave and pulse applications

    Pongthavornkamol Tiwat, Lei Pang, Xinhua Wang, Sen Huang, Guoguo Liu, Tingting Yuan, Xinyu Liu

    J. Semicond.  2015, 36(7): 074006

    doi: 10.1088/1674-4926/36/7/074006

    Abstract Full Text PDF Get Citation

    An optimized modeling method of 8 × 100 μm AlGaN/GaN-based high electron mobility transistor (HEMT) for accurate continuous wave (CW) and pulsed power simulations is proposed. Since the self-heating effect can occur during the continuous operation, the power gain from the continuous operation significantly decreases when compared to a pulsed power operation. This paper extracts power performances of different device models from different quiescent biases of pulsed current-voltage (I-V) measurements and compared them in order to determine the most suitable device model for CW and pulse RF microwave power amplifier design. The simulated output power and gain results of the models at Vgs = -3.5 V, Vds = 30 V with a frequency of 9.6 GHz are presented.

  • Influence of field plate on surface-state-related lag characteristics of AlGaN/GaN HEMT

    Yong Lei, Hai Lu

    J. Semicond.  2015, 36(7): 074007

    doi: 10.1088/1674-4926/36/7/074007

    Abstract Full Text PDF Get Citation

    The relationship between AlGaN/GaN HEMT gate field plate (FP) and surface-state-related gate lag phenomena is investigated by two-dimensional numerical transient simulations to study the mechanism of the influence of FPs on current collapse. The simulations reveal that adding a field plate has a noticeable impact on the extent of current collapse while it has no influence on lapsed time. The FP is found to suppress current collapse through reducing the ionization probability of surface states by enhancing free hole accumulation next to the AlGaN surface between gate and drain.

  • High performance AlGaN/GaN HEMTs with AlN/SiNx passivation

    Xin Tan, Yuanjie Lü, Guodong Gu, Li Wang, Shaobo Dun, Xubo Song, Hongyu Guo, Jiayun Yin, Shujun Cai, Zhihong Feng

    J. Semicond.  2015, 36(7): 074008

    doi: 10.1088/1674-4926/36/7/074008

    Abstract Full Text PDF Get Citation

    AlGaN/GaN high electron-mobility transistors (HEMTs) with 5 nm AlN passivation by plasma enhanced atomic layer deposition (PEALD) were fabricated, covered by 50 nm SiNx which was grown by plasma enhanced chemical vapor deposition (PECVD). With PEALD AlN passivation, current collapse was suppressed more effectively and the devices show better subthreshold characteristics. Moreover, the insertion of AlN increased the RF transconductance, which lead to a higher cut-off frequency. Temperature dependence of DC characteristics demonstrated that the degradations of drain current and maximum transconductance at elevated temperatures for the AlN/SiNx passivated devices were much smaller compared with the devices with SiNx passivation, indicating that PEALD AlN passivation can improve the high temperature operation of the AlGaN/GaN HEMTs.

  • Fabrication of ridge waveguide of 808 nm GaAs-based laser diodes by wet chemical etching

    Xiang Li, Degang Zhao, Desheng Jiang, Ping Chen, Zongshun Liu, Jianjun Zhu, Ming Shi, Danmei Zhao, Wei Liu, Shuming Zhang, Hui Yang

    J. Semicond.  2015, 36(7): 074009

    doi: 10.1088/1674-4926/36/7/074009

    Abstract Full Text PDF Get Citation

    The fabrication of ridge waveguide of 808 nm GaAs-based laser diodes by wet chemical etching is investigated. The etching behavior of GaAs, InGaP and AlGaInP in various solutions is evaluated. As a result, the etching solutions simultaneously corroding InGaP and AlGaInP layers are searched successfully. Effects of etching time and the concentration of mixtures on etching depth and the geometrical shape of ridge are analyzed. It is found that under proper conditions, appropriate etching depth and smooth surfaces can be obtained and the steep degree of pattern can be accepted, especially for wide ridge waveguide laser diodes.

  • Frequency stability of an RF oscillator with an MEMS-based encapsulated resonator

    Bohua Peng, Wei Luo, Jicong Zhao, Quan Yuan, Jinling Yang, Fuhua Yang

    J. Semicond.  2015, 36(7): 074010

    doi: 10.1088/1674-4926/36/7/074010

    Abstract Full Text PDF Get Citation

    This paper presents a high-Q RF MEMS oscillator consisting of a micro-disk resonator and low noise feedback circuits. The oscillator has high frequency stability and low phase noise. The two-port resonator was hermetically encapsulated using low-cost Sn-rich Au-Sn solder bonding, which significantly improves the frequency stability. A low noise oscillator circuit was designed with a two-stage amplifying architecture which effectively improves both the frequency stability and phase noise performance. The measured phase noise is -96 dBc/Hz at 1 kHz offset and -128 dBc/Hz at far-from-carrier offsets. Moreover, the medium-term frequency stability and Allan deviation of the oscillator are ± 4 ppm and 10 ppb, respectively. The oscillator is a promising component in future wireless communication application.

  • SEMICONDUCTOR INTEGRATED CIRCUITS

  • A 0.75 dB NF LNA in GaAs pHEMT utilizing gate-drain capacitance and gradual inductor

    Shuo Wang, Xinnian Zheng, Hao Yang, Haiying Zhang

    J. Semicond.  2015, 36(7): 075001

    doi: 10.1088/1674-4926/36/7/075001

    Abstract Full Text PDF Get Citation

    A two-stage monolithic microwave integrated circuit (MMIC) low noise amplifier (LNA) fabricated in 0.5 μm GaAs pHEMT is presented. The Miller effect introduced by the parasitic gate-drain capacitance is utilized to decrease the value of the input inductor. Additionally, the input on-chip inductor is a novel high Q gradual structure. The noise figure is reduced with these two methods. With good input and output matching, the LNA achieves a noise figure of 0.75 dB and a small signal gain of 32.7 dB over 698-806 MHz. The input 1 dB compression point is -21.8 dBm and the input third order interception point is -10 dBm.

  • Novel pre-equalization transimpedance amplifier for 10 Gb/s optical interconnects

    Qiwei Song, Luhong Mao, Sheng Xie, Yuzhuo Kang

    J. Semicond.  2015, 36(7): 075002

    doi: 10.1088/1674-4926/36/7/075002

    Abstract Full Text PDF Get Citation

    This paper presents a modified regulated cascode (RGC) transimpedance amplifier (TIA) with a novel pre-equalized technique. The pre-equalized circuit employed the broadband series inductive π-network and Gm-boosting technique. The introduction of this technique compensates the transferred signal at the input port of the TIA without an increase in power dissipation. Furthermore, a novel miller capacitance degeneration method is designed in the gain stage for further bandwidth improvement. The TIA is realized in UMC 0.18 μm CMOS technology and tested with an on-chip 0.3 pF capacitor to emulate a photodetector (PD). The measured transimpedance gain amounts to 57 dBΩ with a -3 dB bandwidth of about 8.2 GHz and consumes only 22 mW power from a single 1.8 V supply.

  • LTE turbo decoder design

    Le Yang, Tianchun Ye, Bin Wu, Ruiqi Zhang

    J. Semicond.  2015, 36(7): 075003

    doi: 10.1088/1674-4926/36/7/075003

    Abstract Full Text PDF Get Citation

    This paper presents a turbo decoder supporting all 188 block sizes in 3GPP long term evolution (LTE) standard which can be employed in the LTE micro-eNodB system. The design allows 1, 2, 4, 8 or 16 soft-in/soft-out (SISO) decoders to concurrently process each block size, and the number of iterations can be adjusted. This article proposes an improved SISO algorithm and interleaving design, calculated forward state matrix and backward state matrix alternately, and the branch transition probability can be used in the Turbo decode process directly just after one clock delay. The structure enables a decoder processing radix-2 algorithm with high speed, instead of radix-4 as the conventional decoder. Moreover, the paper details an interleaver/de-interleaver, which is combined by two operational steps. One is column address mapping and the other is intra-row permutation. Decoder realizes interleaving by loading data from memories whose address is generated by column mapping and then lets data passing through inter-row permutation. For de-interleaving, the system can adopt reverse operation.

  • A CMOS analog front-end chip for amperometric electrochemical sensors

    Zhichao Li, Yuntao Liu, Min Chen, Jingbo Xiao, Jie Chen

    J. Semicond.  2015, 36(7): 075004

    doi: 10.1088/1674-4926/36/7/075004

    Abstract Full Text PDF Get Citation

    This paper reports a complimentary metal-oxide-semiconductor (CMOS) analog front-end chip for amperometric electrochemical sensors. The chip includes a digital configuration circuit, which can communicate with an external microcontroller by employing an I2C interface bus, and thus is highly programmable. Digital correlative double samples technique and an incremental sigma-delta analog to digital converter (Σ-Δ ADC) are employed to achieve a new proposed system architecture with double samples. The chip has been fabricated in a standard 0.18-μm CMOS process with high-precision and high-linearity performance occupying an area of 1.3 × 1.9 mm2. Sample solutions with various phosphate concentrations have been detected with a step concentration of 0.01 mg/L.

  • Design of a reliable PUF circuit based on R-2R ladder digital-to-analog convertor

    Pengjun Wang, Xuelong Zhang, Yuejun Zhang, Jianrui Li

    J. Semicond.  2015, 36(7): 075005

    doi: 10.1088/1674-4926/36/7/075005

    Abstract Full Text PDF Get Citation

    A novel physical unclonable functions (PUF) circuit is proposed, which relies on non-linear characteristic of analog voltage generated by R-2R ladder DAC. After amplifying the deviation signal, the robustness of the DAC-PUF circuit has increased significantly. The DAC-PUF circuit is designed in TSMC 65 nm CMOS technology and the layout occupies 86.06 × 63.56 μm2. Monte Carlo simulation results show that the reliability of the DAC-PUF circuit is above 98% over a comprehensive range of environmental variation, such as temperature and supply voltage.

  • A current-mode DAC unit circuit with smooth transition

    Yidie Ye, Yinshui Xia

    J. Semicond.  2015, 36(7): 075006

    doi: 10.1088/1674-4926/36/7/075006

    Abstract Full Text PDF Get Citation

    The digital-to-analogue converter (DAC) plays a significant role in modern electronic systems, and current-mode DACs are widely used due to their excellent properties. However, the non-ideal transition at switching instants of the unit circuit will directly affect the performance of the current-mode DAC. The parasitic effects resulting in non-ideal transition are analyzed in this paper. A simple structure unit circuit is proposed to diminish the non-ideal transition. The simulation results show that the parasitic effects are suppressed effectively, and a smoother output transition is achieved. The feasibility of the proposed current-mode DAC unit circuit is verified by the application in a frequency jitter circuit.

  • Design and test of a capacitance detection circuit based on a transimpedance amplifier

    Linfeng Mu, Wendong Zhang, Changde He, Rui Zhang, Jinlong Song, Chenyang Xue

    J. Semicond.  2015, 36(7): 075007

    doi: 10.1088/1674-4926/36/7/075007

    Abstract Full Text PDF Get Citation

    This paper presents a transimpedance amplifier (TIA) capacitance detection circuit aimed at detecting micro-capacitance, which is caused by ultrasonic stimulation applied to the capacitive micro-machined ultrasonic transducer (CMUT). In the capacitance interface, a TIA is adopted to amplify the received signal with a center frequency of 400 kHz, and finally detect ultrasound pressure. The circuit has a strong anti-stray property and this paper also studies the calculation of compensation capacity in detail. To ensure high resolution, noise analysis is conducted. After optimization, the detected minimum ultrasound pressure is 2.1 Pa, which is two orders of magnitude higher than the former. The test results showed that the circuit was sensitive to changes in ultrasound pressure and the distance between the CMUT and stumbling block, which also successfully demonstrates the functionality of the developed TIA of the analog-front-end receiver.

  • SEMICONDUCTOR TECHNOLOGY

  • Mechanism of the development of a weakly alkaline barrier slurry without BTA and oxidizer

    Xiaodong Luan, Yuling Liu, Xinhuan Niu, Juan Wang

    J. Semicond.  2015, 36(7): 076001

    doi: 10.1088/1674-4926/36/7/076001

    Abstract Full Text PDF Get Citation

    Controllable removal rate selectivity with various films (Cu, Ta, SiO2) is a challenging job in barrier CMP. H2O2 as an oxidizer and benzotriazole (BTA) as an inhibitor is considered to be an effective method in barrier CMP. Slurries that contain hydrogen peroxide have a very short shelf life because H2O2 is unstable and easily decomposed. BTA can cause post-CMP challenges, such as organic residue, toxicity and particle adhesion. We have been engaged in studying a weakly alkaline barrier slurry without oxidizer and benzotriazole. Based on these works, the objective of this paper is to discuss the mechanism of the development of the barrier slurry without oxidizer and benzotriazole by studying the effects of the different components (containing colloidal silica, FA/O complexing agent, pH of polishing solution and guanidine nitrate) on removal rate selectivity. The possible related polishing mechanism has also been proposed.

  • Effect of FA/O complexing agents and H2O2 on chemical mechanical polishing of ruthenium in weakly alkaline slurry

    Bo Duan, Weijing An, Jianwei Zhou, Shuai Wang

    J. Semicond.  2015, 36(7): 076002

    doi: 10.1088/1674-4926/36/7/076002

    Abstract Full Text PDF Get Citation

    This paper investigated the effect of FA/O and hydrogen peroxide (H2O2) on ruthenium (Ru) removal rate (RR) and static etching rate (SER). It was revealed that Ru RR and SER first linearly increased then slowly decreaseed with the increasing H2O2 probably due to the formation of uniform Ru oxides on the surface during polishing. Their corrosion behaviors and states of surface oxidation were analyzed. In addition, FA/O could chelate Ru oxides (such as (RuO4)2- and RuO4- changed into soluble amine salts [R(NH3)4] (RuO4)2) and enhance Ru RR. The non-ionic surfactant AD was used to improve the Ru CMP performance. In particular, the addition of AD can lead to significant improvement of the surface roughness.

Search

Advanced Search >>

Issues