ECE 730 Topic 30 - Spring 2017

ECE 730 Topic 30 - Advanced VLSI Devices

Instructor

Professor Lan Wei

Course description

The nano era has seen modern VLSI technologies become increasingly sensitive to structural details and fabrication techniques. While "technology scaling" continues as the strongest driver for technology advancement, it has evolved from traditional Dennard Scaling into a multi-dimensional concept that combines new materials, novel structures and different physical principles. Accordingly, this course will cover topics such as: advanced VLSI devices design; future challenges of VLSI devices; the implications for device electrical performance caused by fabrication technique, physical models for nanometer scale structures, control of electrical characteristics (threshold voltage, short channel effects, ballistic transport) in small structures; and alternative device structures for VLSI in the nano era.

Expected background knowledge: solid state physics and devices (ECE 630, or equivalent). Students should be familiar with the physical principles and operation of p-n junctions, MOS capacitors and long-channel MOSFETs.

Course objective

• At the end of the course, you will be able to:
  • Make projections about CMOS device scaling and how it affects circuit/system performance
  • Recognize the relevant device physics that underlies CMOS device design
  • Go to a conference or read a journal article about CMOS devices and use the knowledge obtained in this course to understand the material
  • Design a state-of-the-art MOSFET and project its performance
  • Use device modeling (TCAD) tools and interpret results from device modeling
• Develop an intuitive feel in addition to solving equations
• Obtain necessary skills to explore the research space of state-of-the-art VLSI technology

Grading policy

The Course grade will be based on the total numerical score on the following:

• Homework: 15%
• Project: 35%
• Final: 50%

Exams are mandatory unless they are excused, ahead of time, for a documented illness. Students who do not take the exam(s) and are not excused will receive a score of zero for the exam(s).

Homework

• Given on Thursday, hand in by following Thursday in class (or equivalent time).
• No credit for late submission.

Course material

• Textbook:
  • Y. Taur & T. H. Ning, “Fundamentals of Modern VLSI Devices,” 2nd edition, Cambridge University Press
    – ISBN-13: 9780521832946 (Hardcopy, 2nd edition)
    – Roughly, I will cover Chapters 1 – 5 and 10
• Course notes:
  • Available on-line (course website)

Course outline

• Overview of the semiconductor industry (~0.5 week)
• MOSFET – MOS capacitor, MOSFET long channel behavior (a short review) (~1week)
• Si MOSFET device scaling, non-scaling factors (~1 week)
• Reading the ITRS, industry trend (~0.5 week)
• Device modeling (~1 week)
  • TCAD tools, fundamentals of numerical device simulation, interpretation of device simulation results and tricks of the trade
• MOSFET electrostatics (~2.5 weeks)
  • Short-channel MOSFET
  • Channel length, scale length theory, minimum channel length
  • PDSOI, FDSOI, ultra-thin body SOI, double-gate, FinFET, multi-gate FET, gate-all-around (nanowire) FET
  • Threshold voltage, quantum effects
  • Non-uniform channel doping, halo, super-halo
• MOSFET electrodynamics (~2.5 weeks)
  • Carrier mobility, velocity saturation
  • Scattering theory, ballistic transport
  • Virtual source model
  • Strain effects, alternative channel materials (Ge, III-V)
• High field effects (~1 week)
  • Impact ionization and breakdown, band-to-band tunneling, tunneling into gate dielectrics, hot carriers, dielectric degradation mechanisms
• Parasitic elements (~0.5 week)
  • Series resistance, parasitic capacitance
  • Interconnect R and C, interconnect scaling
• CMOS performance factors (~1 week)
  • CMOS circuit elements, propagation delay, delay metrics, power dissipation
  • Device pitch scaling
  • Device design tradeoff, energy-delay optimization