Assignment_Quiz 3 Topic Oxidation
1. A one-hour dry oxidation at 1100 C is followed by a 5-hour wet oxidation at 1100 C.
(a) Calculate the oxide thickness after each step for a wafer. (b) Find the final oxide thickness
graphically.
2. A square window is etched through 200 nm of oxide prior to a second oxidation. Second
oxidation grows 300 nm of oxide in the thick oxide region. Make a scale drawing of the cross
section of the wafer after the second oxidation. What are the colors of the various regions
under vertical illumination by white light?
3. A silicon wafer has 400 nm of oxide on its surface. How long will it take to grow an additional
1 um Of oxide in wet oxygen at 11000 C? Compare graphical and mathematical results. What
is the color of the final oxide under vertical illumination by white light?
4. How much oxide is needed to mask a 4-hr boron diffusion at 11500 C? A 1 -hr. phosphorus
diffusion at 10500 C?
5. The n-well in a <100> CMOS process is formed with a 20-hour phosphorus diffusion at 12000
C. How much oxide is required as a barrier layer for this diffusion?
6. Yellow light has a wavelength of approximately 0.57 um. Calculate the thicknesses of silicon
dioxide that will appear yellow under vertical illumination by white light. Consider Oxide
thicknesses less than 1.5 um. Compare with the color chart.
7. A bare and undeveloped <100> silicon sample is oxidised for 1 hour at 11000 C in dry O2. It is
then covered and has the oxide removed over half the wafer. Next it is re-oxidised in wet O2
at 10000 C for 30 minutes. Use SUPREM to determine the thickness in the two regions. How
high are the steps on the surface and step in the substrate?
8. Suppose we want to perform wet-dry-wet oxidation sequence on a <100> wafer at 30 minutes
in wet O2, 10 minutes in dry O2 and 39 minutes in wet O2. If the silicon substarate is doped
with phosphorous at a level of 1012 cm-3. Write a SUPREM listing to determine the final
oxidation thickness and the phosphorous doping profile in the oxide and silicon layers.
