This subject aims to develop the students knowledge of cleanroom fabrication techniques and how to manufacture semiconductor devices. The student will also understand the structure and operation of devices such as a MOSFET and CMOS inverter, and be able to explain how device structure can affect device performance.
1. Semiconductor materials properties
Energy Bands in Semiconductors, insulators and metals. E-k diagrams for direct and indirect band gaps. Fermi function. Donors and acceptors in semiconductors. Carrier concentration equations. Conduction in semiconductors. Electron and hole mobility and drift velocities. Four point probe.
2. The pn junction
Diffusion; diffusion in solids, Fick's Law, constant surface concentration, diffusion from finite source, junction formation, redistribution diffusion, lateral diffusion, junction depth, sheet resistance, profile measurement, basic diffusion systems. Quantative treatment of the built-in voltage, width of the depletion regions, maximum electric field in a p-n junction. Capacitance of the p-n junction. LEDs, photodiodes.
3. Ion Implantation
Ion implantation system, dose control, distribution profiles, lattice damage, channeling, annealing of implanted impurities, masking, applications and future trends
4. The MOS Structure
The MOSFET gate stage as a MOS capacitor, Energy-Band diagrams for the n- channel and p-channel MOS capacitor, band bending, Threshold Voltage, Flat-Band Voltage. Calculation of depletion width and capacitance, C-V characteristics.
5. The MOSFET
Operation of the MOSFET transistor. Characteristics of the device. Calculation of the threshold voltage of the MOSFET taking the work function difference between gate & semiconductor and oxide charges into consideration. Ion implantation for adjusting the threshold voltage. The MOSFET as the CMOS inverter. MOSFET latch up. The self aligned process for fabrication of MOSFET. Isolation structures in CMOS
| Module Content & Assessment | |
|---|---|
| Assessment Breakdown | % |
| Other Assessment(s) | 40 |
| Formal Examination | 60 |