Magic Tutorial : Inverter Layout

bug or comment to pgolani@usc.edu

Execute magic program See Fig 1.
%magic inverter

Show grid on window See Fig 2.
"g" or "box-> :grid"
- "g" : bindkey in magic. Just type "g" while cursor is in the layout window.
- "box-> :grid" : Type ";" or ":" first, then type grid. There are 4 tools in magic (box,wiring,netlist,rsim).
  "box->" means your current tool is box tool. You can switch between tools by typing "spacebar" key.
- Don't type "box->" Just type ":grid".
Draw pmos and nwell See Fig 3.
"box(24,18)-> :paint nwell" "box(10,12)-> :paint pdiff" "box(10,4)-> :paint pdc" "box(10,4)-> :paint pdc" "box(14,2)-> :paint poly"
- "box(24,18)->" : Make a box with height 24 and width 18 by clicking left mouse button at left bottom point and right mouse button at right top point.
  You can check the box size by typing "b" or ":box".
- ":paint" command can be abbreviated as ":pai". So you can type ":pai pdiff".
- Don't type "box(24,18)->" Just type ":paint layer".
- At this moment, you have drawn pmos transistor whose W/L is 10/2.
Increase pmos W from 10 to 12
Sorry!! Your TA should have told you that W of pmos should be 12. So please follow the next steps.
Step 1: Select part of pmos and nwell. See Fig 4.
click lmb(left mouse button) then rmb(right mouse button) to make a box as shown in Fig 4. "a" or "box-> :select" area

Step 2: Stetch selected area to increase W of pmos. See Fig 5.
"E" or ":stretch up 1" "E" or ":stretch up 1"
- Is ":stretch up 2" equivalent to typing "E" twice?? Yes!
- How can you recover pmos with W=10?
- What is the diffrence between "E" and "e" bindkeys? Check Fig 6 to see the result when you type "e" twice instread of "E".
- What are the white dots in Fig 6? Why do these appear?
Draw nmos using copy and wiring tool
Step 1: See Fig 7.
"box(4,12)-> :paint ndiff" "box(4,4)-> :paint ndc"

Step 2: See Fig 8.
put cursor on ndc drawn in step 1. "s" or ":select" put cursor on left bottom where selected ndc will be located. "c" or ":copy"
- Easier and more advanced technique for step 2 is
  put cursor on ndc. "s" ":copy rignt 4"
Step 3: Change to wiring tool by typing "spacebar" key.
- Your command window will display "Switching to "wiring" tool."
- Mouse pointer should switch to arrow type.
Step 4: See Fig 9.
click lmb on bottom of poly at pmos. put cursor at the end point of poly (2 grid below of nmos). click rmb.
- When you click lmb on bottom of poly, click again if it select nwell instead of poly.
Draw via and metal1 See Fig 10.
switch to box tool (type "spacebar" key 3 times) "box(4,4)-> :paint via" "box(4,4)-> :paint m1" "box(4,4)-> :paint via" "box(4,4)-> :paint m1"
- via is a contact between metal1 and metal2.
Draw metal2 See Fig 11.
"box(4,4)-> :paint m2" switch to wiring tool (type "spacebar" key) connect both via by metal2.
Draw Vdd and Ground line
Step 1: See Fig 12.
Draw metal1 connections as shown in Fig 12.

Step 2: See Fig 13.
"box(4,4)-> :paint nwc" "box(4,4)-> :paint pwc"
- nwc (nwell contact) is a contact between Vdd and nwell.
- pwc (pwell contact) is a contact between Ground and p-substrate.
Draw poly contact and metal1 See Fig 14.
switch to wiring tool click lmb on the middle of poly put cursor on any of metal1 click mmb(middle mouse button) to make a poly contact
- clicking middle mouse button make a contact between selected layer (poly) and layer below cursor automatically.
- How can you do the same task within box tool? "box(4,4)-> :paint pc"
- How can you generate via contact between metal1 and metal2 using the same technique?
  click metal1(or metal2) put cursor on metal2(or metal1) click mmb
Finalizing drawing See Fig 15.
Using all techniques you have learned, finalize your layout as shown in Fig 15.
You may use ":move", wiring and contact generation using wiring tool.
Save now
":save"
Delete layer(s)
- Delete selected layers. See Fig 16 and Fig 17.
  put cursor on middle via contact "s" "s" - This will select the whole connection with the via. "d" - This will delete the whole connection. "u" - recover by undoing
- Delete selected layers. See Fig 18 and Fig 19.
  put cursor on middle via contact "s" put cursor on poly contact "S" - This will select poly contact while via is selected. "d" - This will delete via and poly contact. "u" - recover by undoing
- Delete specific layer. See Fig 20 and Fig 21.
  "f" - This will show box around the whole cell. put cursor on poly "Ctrl-d" - This will delete only poly layer inside the box. "u" - recover by undoing
  - "Ctrl-d" is equivalent to ":delete area layer"
  - How can you delete poly only in nmos?
    make a box around nmos (click lmb and rmb around nmos) put cursor on poly "Ctrl-d"
Enlarge the width of inverter
Your inverter turns out that width of cell is too small. Let's enlarge it by 2 lambda on both sides.
- By stretch. See Fig 22 and Fig 23.
  make a box as shown in Fig 22. "a" or ":select area" ":stretch right 2" or "R" twice
- By fill. See Fig 24 and Fig 25.
  make a box as shown in Fig 24. ":fill left 2"
Labeling
Step 1: See Fig 26 and Fig 27.
put cursor on metal1 of input click lmb and rmb at the same point - This will put cross point on metal1. ":label in"

Step 2: See Fig 28.
put cursor on metal1 of Vdd click lmb and rmb at the same point ":label Vdd n m1"
- When two layers are overlapped like Vdd (metal1 and nwell), it is always good practice to specify direction and layer explicitly.
Step 3: See Fig 29.
Complete labeling as shown in Fig 29.
Save
":save"
Practice yourself See Fig 30.
Draw the same nand gate layout shown in Fig 30.

Copyright Joong-Seok "Jay" Moon

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