Outline for Lab 3:

· Finish a partially complete inverter layout (nwell & metal drawn).

o Why would you do this in the real world?

o Your job is to fill in the rest, stay within the template.

o Don’t forget pins, and use appropriate direction types (didn’t do this last time). All pins should be on METAL1 layer. The labels in the original layout are not pins – they are just notes for you, and should be deleted.

o Don’t forget NWELL and Substrate contacts.

o Net names in the “Bulk node connection” for the NMOS and PMOS instances must match the actual net names for the bulk connections.

· Create a schematic view for the inverter – directly analogous to the layout view.

o Schematic editing is a lot like layout editing, but with symbols instead of shapes.

· Hierarchy works the same way, same basic keystrokes (instantiate, move, copy, Escape), but a few are different (Save).

o NMOS/PMOS instances have mostly the same parameters

· Watch out for “Bulk node connection”

o Create pins in the schematic that match pin names in your layout. Also make sure the input/output directions match the layout.

o “Check and Save” makes sure you don’t have any drawing errors.

· Use Layout XL to check correspondence between schematic and layout views

· (Optional) Crosscheck layout and schematic with LVS.

Tutorial moved to:

http://inst.eecs.berkeley.edu/~ee141/lab3/tutorial.pdf, or

http://inst.eecs.berkeley.edu/~ee141/lab3/tutorial.doc

Corrections:

· Don’t create any new NWELL shapes – stay inside the bounds of the existing NWELL rectangle.


Help creating your new library and Inv1 layout cell:

· Copy ~ee141/cds.lib into your new directory for this lab before starting Cadence.

· Start Cadence from your new directory (with the command “icfb &”)
à Should see NCSU_Techlib, NCSU_Analog_Parts, and basic in the library manager

· Create a new library called “Inverter”
à don’t need to specify a path – it creates a subdirectory under the directory you launched Cadence from.

· Close your new (blank) Inv1 layout before copying files over

General Cadence Tips

· Save often! (F2 key)

· Run DRC frequently – maybe even after every shape or two. Uncheck the “Echo Commands” option for faster run times.

· Use WindowàClose command to close a window – don’t just hit the “X” button.

Help with Pins:

· Pins consist of a label (for your benefit only) and a shape (which indicates connectivity to Cadence). Don’t forget to put the shape on the correct layer.

· When creating pins, use type “shape”/”rectangle”, and make sure the “Display Pin Name” is turned on. “Display Pin Name Options…” to chose different text sizes.

· Set “I/O” type to input/output for VIN & VOUT, and inputOutput for supplies.

Things to check if you have viewing/selection problems in cadence

· OptionsàDisplay…àX/Y Snap Spacing should be 0.06 each

· OptionsàLayout Editor… à Gravity On should be unchecked

· Check the LSW – make sure all layers are visible (AV) and selectable (AS). Also, make sure you chose the right layer before drawing any shapes/pins.

· Use Crtl+f and Shift+f to hide/show subcell details

· “f” to fit the entire display to the window – helps if you get “lost”

· click & drag with right mouse button for fast zooming.

Useful editing/selection/measurement commands:

· Press “esc” a few times if it is stuck in the middle of a command and you are confused, finished with the command, or just want to back out.

· Ctrl+d will deselect everything. This is often useful right before starting a command to make sure you haven’t accidentally selected something you don’t want.

· “k” allows to draw rulers, useful for measuring and alignment. “K” will erase them.