University of Limerick: EE6641 Semiconductor Technology, Autumn 2009. T. Cummins. Seven Homework Questions (12 marks). Answers to be returned on Mon Nov 23rd 2009. 1. A silicon wafer has substrate doping of 1015 boron atoms per cm3 . It receives a Phosporus ion- implant dose of 7.5 x 1013 ions/cm2 at an implant energy of 200KeV. Calculate the peak concentration, and the resulting junction depth. 2. Consider wet oxidation of a bare (100) wafer (i.e. assume no initial oxide). Estimate the oxide thickness for oxidation times of 10 mins, 30 mins, and 1 hour. For the 1 hour case, calculate the thickness using the Deal-Grove equation and coefficients. 3. Pick a typical CMOS process, and using its physical parameters, show how you would calculate the Threshold Voltage of an N-channel MOS transistor with 2V of back-bias 4. A Sept 2009 listing of almost 400 worldwide currently available semiconductor processes is given on http://www.icknowledge.com/our_products/Processes0908.pdf . Collapse this listing into a single-page spreadsheet of vendor versus features. i.e. Vendors in row headings, and column headings for Wafer Diameter, Technology Node, No Poly layers, No. Metal layers, metal type, and a “Comment” column with any interesting process notes or capability. 5. 1 volt is applied across a piece of pure silicon 100um long with a cross-sectional area of 1um2. Calculate the resulting current flow at room temperature, and at 1250C. 6. The link http://smithsonianchips.si.edu/ice/cd/9712_575.pdf contains a “reverse engineered” analysis of the Analog Devices ADSP21062 DSP processor. (a) What semiconductor process technology is used to fabricate the chip? (b) What is the gate-oxide thickness? (c) Sketch the LOCOS ‘birds-beak’, give it’s dimensions, and explain why it is present. 7. On the chart “Production Sweet-Spot” (below), fill in your estimates for the year 2009, i.e. where you think the “production sweet spots” are for various product categories listed (MPU, DRAM, mix- ed signal, etc). Support your answer with references, vendor names, product announcements, etc.
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