Division of Micro/Nano Devices and Systems

1. Introduction
The research fields in Micro-Nano Devices System Research Division include new type micro-nano devices and system consisted of these devices. The research scope includes New devices and system, new technique and technology, new material and architecture, new concepts and principles.

There are two research directions in recent years. One is new microelectronics devices and systems; the other is nano-electronics. The research division undertake national high-tech development research project (863) 、National Basic research (973)and key project of National Natural Science Foundation (NSF) in recent years. These projects have passed the national appraisals acceptance examinations.

The new integrated sensors (silicon integrated micro-motor、silicon micro-phone 、 silicon integrated micro-pump、Biochips 、 SiGe devices and GMR devices have been developed. Besides, infra-speed annealing equipment and GeSi UHVCVD equipment have reached the world advanced level in recent years.

2. Staff

Director:

Prof. Wei Chen

Tel: 86-10-62772608

Fax: 86-10-62771130

Email: weichen@tsinghua.edu.cn

Vice-director:

Associate Prof. Zheyao Wang

Tel: 86-10-62789151 ext.322

Fax: 86-10-62771130

Email: Z. Wang @tsinghua.edu.cn

Assitant Prof. Huajun Fang

Tel: 86-10-62789147 ext.310

Fax: 86-10-62771130

Email: hjfang@tsinghua.edu.cn

There are 1 academician of Chinese Academy of Sciences, 6 professors, 9 associate professors, 4 lecturers, 3 post-doctors, and 10 technicians. There are 53 graduate students in the division, including 31 PhD candidates and 22 MS candidates.

3. Research Field

The scope of research in the division includes new devices and structures, new materials and technologies, new concepts and theories, new models and simulation methods, and other related aspects of micro and nano electronic devices and systems.

There are a mature 1.0-micron fabrication processing line and many advanced micro and nano fabrication tools for micro and nano electronic devices and systems in the Devices Research Division.

Present research fields are:

1.2.1 MEMS and Smart Sensors

•  Integrated micro sensors and actuators

•  RF MEMS devices

•  Silicon micro acoustic devices and system

•  MOEMS devices

•  Micro fluid system

•  Micro fuel Cell

•  GMR magnetic sensors

•  MEMS process and technology

1.2.2 Nano Science and Technology

•  Si-based nano-structure material, multilayer-magnetic structure and related devices

•  Ge QD's Infrared detectors

•  Solid Implantation of quantum computation: superconductive quantum computer

•  Current-driven spin magnetic switch with nano-structure

•  NEMS

•  Nano fabrication technology

1.2.3 Nonvolatile Memories

•  FeRAM/FRAM

•  MRAM

•  RRAM

1.2.4 Micro Devices for Bio and Chemical Applications

•  Microfluidic systems

•  Silicon based and non-silicon based Bio chips

1.2.5 Fuzzy Controller technology

•  Fuzzy logic controller with multiple variables and multiple rules (MVMRFLC)

•  Programmable fuzzy logic controller (PFLC)

•  Fuzzy-neural network control technology

1.2.6 New Materials for Micro and Nano Electronic Applications

•  Ferroelectric and Piezoelectric films

•  Magnetoelectronic and Spintronic Materials

•  Poly Silicon

•  GeSi

1.2.7 Packaging and Assembly

•  Lead free bumping methods, both by electroplating and stencil printing, have been developed. A low temperature bumping method with adhesive has been developed and applied on the flip chip bonding of a process temperature sensitive detector. Through-Silicon-Via (TSV) was in research for 3D packaging.

•  Research on related process and design methology was performed. Fluxless solder bonding technology for MEMS packaging was developed.

•  Other achievement including package design and failure analysis for high reliability application devices.

1.2.8 Integrated magnetoelectronics & spintronics

•  Novel magnetoelectronics & spintronics materials

•  Multilayer nano film and spintronics devices

•  Novel non-volatile memories, such as MRAM and RRAM

•  Spin control

2.Research Achievements in 2007

2.1 MEMS and Smart Sensors

2.1.1 Micro Acoustic Devices

•  High quality integrated silicon microphone and microspeaker have been developed based on ferroelectric thin films.

•  Silicon micro acoustic devices for ultrasonic applications have been fabricated.

2.1.2 RF MEMS Devices

•  Novel type of Multi resonant frequency RF-MEMS Switch has been realized.

•  High Q Inductor with optimized layout structure has been obtained

•  MEMS VCO with long life time has been realized

•  LC filter with lumped L and C for high Microwave application is realized.

•  100nm Mechanical Structure with traditional 2 micro IC process has been realized.

2.1.3 Integrated Sensors

•  A novel uncooled infrared detector is developed.

•  High quality silicon micro accelerometers have been fabricated.

2.1.4 Silicon-based micro direct methanol fuel cells (μDMFC)

•  A silicon-based μDMFC stack which consists of two μDMFC cells in electrically parallel connection was developed. The μDMFC stack has an open circuit voltage of 0.47V and the maximum power density of 12.71 mW/cm2, 39.3% higher than the power density generated by a μDMFC cell at room temperature, while the volume of the μDMFC stack was only 23% large than that of the single cell.

•  A μDMFC with microblocks in anode structure, which could improve the fuel flow and increase the fuel utilization efficiency to enhance the fuel cell performance, was developed. The μDMFC with microblocks has an open circuit voltage of 0.45V and the maximum power density of 8.08mW/cm2, which is much higher than that of the regular μDMFC at value of 3.87mW/cm2 at room temperature.

•  Porous silicon-based proton exchange membranes (PEMs) compatible with MEMS technology by using the combination of the nanoporous silicon membranes and Nafion were investigated. The proton conductivities of the porous silicon-based PEMs are 0.01~0.07s/cm comparable to Nafion(0.05~0.08s/cm).

2.1.5 Biochips for protein and disease detection

•  Multiple microcantilever arrays are used as the biosensor and detection method to construct a biochip for detection of diseases and proteins.

•  Stress-optimization method has been developed to improve the sensitivity.

•  DEP based protein transportation has been developed.

2.1.6 3-D MEMS Technology:

•  Base on positive thick photoresist process, the microstructures patterned using negative thick photoresist with high-aspect-ratio more than 10:1 and vertical sidewalls above 86? have been done, which contribute to the integrity of 3-D MEMS technology.

•  The high performance 3-D MEMS inductor has been achieved, and its 80μm high bridge-microstructure is stand for the advantage of the 3-D MEMS technology.

2.1.7 Ferroelectric Random Access Memory (FeRAM)

•  The PZT、SBT、BNT ferroelectric films with high quality based on Si have been fabricated by using the methods such as Sol-Gel, sputtering. The PZT ferroelectric thin films with 100-200nm on 5” silicon was obtained, the uniformity < ± 3%.

•  The available etching technology of ferroelectric thin films and electrode materials have been obtained using RIE 、 IBE and ICP.

•  A capacitor model suitable for Hspice simulation has been put forward, it can satisfy the need of circuit simulation for FeRAM.

2.2 Nano Electronics and Quantum Devices

2.2.1 Fabrication of semiconductor nanostructures

•  Fabricate high density uniform self-assembled Ge islands on Si substrates by UHV/CVD and establish the optimized process and growth model.

•  Investigate quantum effects in small-size MOSFET systematically.

•  Fabricate self-ordered stacked Ge quantum dots structures by UHV/CVD.

•  Establish nano-fabrication processes with SPM primarily and use it for Si, ferromagnetic and ferroelectric nanowires.

2.2.2 Development of Si-based quantum devices and opto-electronic devices

•  The Ge QD's Infrared detectors have been demonstrated and their responsivity reaches 0.54A /W.

•  The scheme of Ge quantum dot memory realized with vertical Si/SiGe resonant tunneling structure has been proposed.

•  Attached the pattern generator to SEM has been finished which accuracy of process is less than 0.1 um.

•  Si-based and ferromagnetic nano-wires have been demonstrated by AFM.

•  The design of structure and technology of superconducting computer has been completed and the sample starts to fabricate.

2.2.3 Investigation of Quantum Effects and Quantum Transportation, Establishment of Device Models

•  Establish the device model of RTD based on NEGF method.

•  Abstract the parameters of RTD and calculate the sub-bands in quantum well.

2.3 Packaging and Assembly

Electronic Packaging

•  Fabrication of wafer-level lead-free bump

•  Through-wafer-interconnection for 3D integration

•  Thermal resistance measurement of package

2.4 Fuzzy Controller and Fuzzy Neural Network

2.4.1 A daptive Fuzzy Logic Controller

•  A novel multiplication computation circuit named multi-access multiplier is proposed and designed. A novel normalization circuit has been designed. It can calculate the normalized activation degree of activated fuzzy logic rules. Using this normalization circuit, a novel center of gravity defuzzification function circuit block is realized.

•  Subunits fabricated in SMIC 0.18um mixed signal process hspice simulation of function approximation experiment was made, showing that the circuit can realize the designed capability.

•  A circuit of a single input single output Adaptive fuzzy logic controller is presented. The key cell based on the simplified BP learning algorithm is designed for on chip learning of the fuzzy logic controller. Combining the designed fuzzy logic controller and the learning circuit cell, an adaptive fuzzy logic controller is completed, which can tune the rule base parameters automatically with the help of a direction signal.

•  A CMOS analog circuits for neuron-fuzzy network, including Gaussian-like membership function circuit, minimization circuit, and a centroid algorithm defuzzier circuit without using division, is proposed and designed. A two-input/one-output neuro-fuzzy network composed of these circuits is implemented and testified for non-linear function approximating. All the circuits have been fabricated in SMIC 0.18- m m CMOS technology. Experiment results show that all the proposed circuits provide characteristics of high operation capacity, high speed, and simple structures.

2.4.2 Smart Sensors

•  The signal collection circuits and its fuzzy control scheme of GMR sensor are proposed, which is used to collect the signal successfully. The noise reducing research is under progress.

•  The theory and design of temperature sensors in CMOS technology is presented. The temperature sensitivity simulated using CSMC 0.6μm process is -1.15μA/ ℃ over the temperature range -40℃ to 125℃ , and measured is -0.99μA/ ℃ . The power dissipation of which is 1.15mW at a 5V voltage supply.

•  The design of subthreshold low power temperature sensor in CMOS technology is presented. Simulated with the CSMC 0.6μm technology, the circuit can work well over the temperature range from -50oC to 150oC. For the amplifier feedback, it has high power supply rejection ratio under VDD from 2V to 6V. The measurement result proves the simulation, and the temperature sensitivity is 0.77V/oC, the power dissipation is only 16μA.

•  A new CMOS voltage reference is proposed. For the bias current is generated by the MOSFET's subthreshold characteristic, the power dissipation is only 50μW. This voltage source is fabricated with SMIC 0.18μm technology, the measurement demonstrates the temperature coefficient is only 25ppm/℃, within the range of temperature between 18℃ to 108℃ . It can work well when VDD is above 1.4 V. PSRR is -57 dB.

2.4.3 Research of Software and Hardware Implementation of Cellular Neural Network

•  Test the experimental Cellular Neural Network (CNN) chip that was manufactured in SMIC. The cell circuit fulfills the expected requirement, but the overall function of CNN system can not work properly. After analysis, the failure reason was found, and there is a need for a new design of the layout of the CNN system with 4 × 4 cells.

•  The application research of CNN for use in defuzzy module in fuzzy controller. The modeling and application research of CNN with hexagonal structure. Change the CNN structure algorithm in order to implement with hardware.

2.5 Microfluidic Systems

•  Fabricated the microfluidic systems based ITO-microelectrode array and PI-dielectric layer;

•  Fabricated silicon-based super-hydrophobic array

•  Fabricated  an electrowetting-based biofluidics actuation for preventing   biomolecular adsor-ption;

•  realized the fundamental operations based on digital microfluidics (the droplet  transportation,  division, creation, and mergence);

•  Designed the channel-configuration EWOD-based microfluidics;

•  Studied the curing and wettability of PDMS films with different proportions.

•  Demonstrated a cylindrical variable-focus liquid lens based on EWOD.

•  Designed and fabricated an experimental equipment of photoanodic electrochemical etching of Si substrate.

•  Presented a novel self-centered variable-focus liquid lens based on EWOD, and demonstrated a prototype of our new structure.

2.6 Micro Optical Devices

•  A Si-based novel Fabry-Perot microcavity electroluminescence device that can emit blue-green light at room temperature has been designed and fabricated.

•  A novel ferroelectric-based optical switch has been proposed.

2.7 Magnetoelectronics and Spintronics

•  Si-based GMR materials with high MR ratio(>14%).

•  GMR magnetic microsensors with high sensitivity (1.5mV/ V · Oe ) and large linear scale ( ± 20Oe).

•  Achievement on Novel nonvolatile memory effect based on perovskite oxide and magnetic multilayer thin films

•  Nonvolatile memory design and process.

3.Research Projects in 2007

More than 20 research projects are executed in the division. Below gives introduction for some of the main projects:

(1)New Generation Embedded FeRAM Materials, Device and Compatible Processing for SOC Applications

National Nature Science Foundation (NSF) Key Project

Duration: 2005-2008

Principal: Ren Tian-Ling

Research Content ：

•  FeRAM materials and electrode for SOC applications

•  The compatible processing of ferroelectric cell with CMOS

•  The structure and model of storage cell

•  The design and optimization of the storage array and external circuit

•  SOC integrated technology based on FeRAM

(2)Sensors and Sytems for Automobile Tyre-Pressure-Monitor and Anti-Collision

National Hi-Tech Research and Development Program (863 Project)

Duration: 2007-2009

Principal: Ren Tian-Ling，Liu Li-Tian Liu, Wu Li-Ji

Research Content:

•  Key techonologies for Pressure Sensor, Ultrosonic Sensor and Integrated Systems

(3)Nanocantilever arrays for protein chip and diagnosis applications

NSF

Duration: 2005-2007

Principal: Zheyao Wang

Research Content:

•  Cantilever arrary sensors with high sensitivity

• Detection for biologial molecules

(4) Project: Study on manipulation and control of liquid droplets based on electrowetting-on-dielectric ( EWOD)

NSF

Duration: 2005-2007

Principal: Ruifeng YUE

(5) Nonvolatile memory based on colossal resistive effect produced by non-magnetic stimulation

NSF

Duration: 2005-2007

Principal: Bingjun Qu

Research Content: Novel nonvolatile memory effect based on perovskite oxide and magnetic multilayer thin films, nonvolatile memory process.

(6)Developing a new type of metal lead

Inductry contract

Principal: Cai Jian

(7)Low stress design of Cu based packge

Inductry contract

Principal: Cai Jian

(8)Thermal resistance of ceramic package

Inductry contract

Principal:Wang Shuidi

(9)Research on small power devices package with Ni cap

Inductry contract

Principal:Wang Shuidi

(10)Fluxless solder bonding system with low bonding temperature and higher debonding temperature

International Cooperation

Principal: Cai Jian

(11)Electronic device and packaging

International Cooperation

Principal: Cai Jian

(12) Study of new high speed, low voltage SiGe quantum dots non-volatile memories

Research Project of Ministry of Education

Duration:2005-2007

Principal: Ning Deng

Research Content: Operation mechanism of novel low voltage nonvolatile memory cells

(13) Prototype Development of Microsensor based Stress Test Vehicle

International collaboration with Intel

Duration: 2005-2008

Principal: Zheyao Wang

Research Content: High space resolution stress sensors

(14) Studies on RF MEMS Industrial Applications

Research Project of the Municipal Government of Beijing

Duration: 2005 - 2007

Principal: Zewen Liu

(15) Micro Ultrasonic Transducer for Application in Medical Imaging System

Research Project of the Municipal Government of Beijing

Duration: 2005 - 2007

Principal: Ren Tian-Ling

Research Content: Fabrication of micro-ultrasonic transducers with high performance and miniaturize size based on MEMS techniques and piezoelectric thin films for application in medical imaging systems.

(16)Giant Magnetoresistance (GMR) Biosensor Using Nano Magnetic Particle Tags Applied for Diagnosis

863 Project-Supported by the Ministry of Science and Technology of P. R. China

Duration : 2007-2010

Principal : Bingjun Qu

Research Content: High sensitive magnetic sensing technology based-on GMR effect and its application for biochip; nano magnetic particles with high performance for diagnosis; nano magnetic tags for detection of biomedicine sample.

(17)Read head chip

Industry Cooperation

Duration:2005-2007

Principal: Bingjun Qu

(18)Micromagnetic sensor fabrication

Industry Cooperation

Duration:2005-2006

Principal: Bingjun Qu