5.2a Poly Resistor

1
5.2a Poly Resistor

• Value of resistor is from Problem 5.11K?
• Sheet resistance of poly25?/
• Thus number of squares in poly resistor1K?/25?/
• 40
• Therefore L/W40.
• Minimum feature size (2l)2mm
• Thus if we assume width of poly resistor to be
  2mm then length of the resistor is 80mm.

2
Steps in Layout of Resistor

• Since the minimum dimension in question 5.2 is
  2mm. Therefore we should use the technology file
  corresponding to l1mm

3
Resistor Layout
There are 5 long sections of length 17l and width
2l Thus the number of squares is (5x17)/242 Also
the edges contribute another 4 squares There is
additional resistance due to current crowding at
the corners and also the poly contact regions add
additional resistance.
4

• W/L of nfet was 90
• Since L is 2l2mm, W180mm (90x2l)
• Remember to account for Ld (lateral diffusion) in
  L of NMOS

5
Extraction

• Once layout is drawn, DRC cleared and saved, it
  is ready to be extracted
• Go to tools and click on extract
• The window shown will appear. In the definition
  file tab, choose the appropriate technology file
  from the folder it is present by browsing.
• Then hit run, the extracted output file can be
  opened with notepad.

6
Extracted file
The extracted file will look as such
This is the information required from extracted
file to be used in spice Note L2.5mm to account
for lateral diffusion mentioned in q.5.2
7
Pspice

• First draw the circuit.
• Choose MbreakN part and place it.
• Goto edit and click on model
• Choose the Edit instance model (text)
• Add the model parameters as below and click ok
• .model NMOD NMOS (
• LEVEL1,
• VTO1
• GAMMA0.2
• KP20U)
• Also double click on part and change the
  attributes according to extracted Ledit file
• Other parameters and other level models can also
  be added for more complex simulations
• Finish the circuit by adding the dc source

8
Analysis

• Choose dc sweep analysis
• Click on the this tab and choose the voltage
  source to be swept and its range
• Here the input voltage name is V3 and it was
  initialized to 0V

9
DC Sweep response
10
VIL,VIH determination
The blue curve represents dVout/dVin, the markers
point to where the slope is -1 VIL1.5V,
VIH3.09V