Download some control questions

Control questions (physics basics, pn-junction)
• What does “direct bandgap” and “indirect bandgap” semiconductor
mean?
• What is the Fermi-level? How does it shift due to doping?
• What is the mass-action law?
• How does the majority carrier concentration change with
temperature? How doe the minority concentration change? Why?
• What does “drift current” mean? What does “diffusion current” mean?
• Which carriers are “faster” in silicon? By what factor (roughly)?
• What does the “diffusion length” mean?
• What is the metallurgical pn-junction?
• How to calculate the “diffusion potential” of a pn-junction?
• On which side of the pn-junction is the depletion layer wider?
• How does the ideal diode equation look like? What does the saturation
current depend on? How does it change with temperature?
10/20/2015
Microelectronics Control questions 1 / A. Poppe
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Control questions (pn-junctions)
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What does “drift current” mean? What does “diffusion current” mean?
Which carriers are “faster” in silicon? By what factor (roughly)?
What does the “diffusion length” mean?
What is the metallurgical pn-junction?
How to calculate the “diffusion potential” of a pn-junction?
On which side of the pn-junction is the depletion layer wider?
How does the ideal diode equation look like? What does the saturation
current depend on? How does it change with temperature?
• How much needs the forward voltage to be increased if we want to
achieve a 10-fold increase in the forward current?
• List some secondary effects of in real diodes!
• What is the space charge capacitance? What is the diffusion
capacitance? Which is larger, when and why?
10/20/2015
Microelectronics Control questions 1 / A. Poppe
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Control questions (bip tr, FETs)
• List the major steps of a bipolar process optimized for preparing
npn-BJTs. Provide cross-sectional views for the steps and indicate
when a mask is needed.
• List the major steps of the simplest self-aligned poly-Si gate nMOS
process. Provide cross-sectional views for the steps and indicate
when a mask is needed.
• List the major steps of the simplest metal gate nMOS process.
Provide cross-sectional views for the steps and indicate when a mask
is needed.
• Draw the cross-sectional view and the top view of an npn BJT with
buried layer
• Draw the cross-sectional view and the top view of poly-Si gate nMOS
transistor
10/20/2015
Microelectronics Control questions 1 / A. Poppe
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Control questions (processes)
• Draw the cross-sectional view and the top view of a poly-Si gate
n-well CMOS inverter
• What is the available set of circuit elements with the basic npn
bipolar process?
• Explain the meaning of R!
• What are the basic requirements for realizing nearly identical
components in an IC?
• How can we make capacitors in a bipolar process?
• How can we make resistors in a bipolar process?
• What does common centroid placement mean?
• What are the dummy components and why are they needed?
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Microelectronics Control questions 1 / A. Poppe
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Control questions (continued)
• How to realized components with weighted values such as R, 2R, 4R
etc?
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How one can realize pnp transistors in an npn bipolar process?
How one can realize a resistor in a MOS process?
Where and why one should use symmetrical layouts?
Explain what is the thermal feedback? How one can reduce the
negative effects of thermal feedback?
10/20/2015
Microelectronics Control questions 1 / A. Poppe
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