Pcells

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Parameterized Cells (pcells)

Parameterized cells (pcells) are basically layout macros; when the you instantiate a pcell you fill in various parameters, and the layout of the instance changes to reflect these values. Where you get the pcells from depends on the type of design library you have:


  • If your library was created with the "Attach to existing tech file" option, get pcells from the technology library to which your library is attached by entering its name in the "Create Instance" form. The technology libraries that come with the CDK have names similar to NCSU_TechLib_tsmc03.
  • If your library was created with the "Compile tech file" option (i.e., your design library is its own technology library), the pcells are in your design library in a category called layout_macros, and these should be used.

As of now, the following pcells are defined:

Contacts:

ntap Nwell ohmic
ptap Psubstrate ohmic
m1_n metal1 - N-diffusion
m1_p metal1 - P-diffusion
m1_poly metal1 - poly
m1_elec metal1 - elec (poly 2)
m2_m1 metal2 - metal1
m3_m2 metal3 - metal2
m4_m3 metal4 - metal3
m5_m4 metal5 - metal4
m6_m5 metal6 - metal5

Capacitors:

cap thin-oxide (linear) capacitor


Devices:

nmos N-mosfet
pmos P-mosfet
nmos_hv high-voltage N-mosfet
pmos_hv high-voltage P-mosfet

When compiling a technology library, all pcells whose required layers exist in that technology are created.

Contacts are parameterized by row and column. Contacts are placed with minimum spacing.

The thin-ox capacitor is parameterized by total capacitance desired, height and width. The user can also specify the number of rows of contacts to the active and poly capacitor plates.

For the transistors, the user specifies both width and length (which are subject to being on a half-lambda grid, and also to minimum values). Additionally, the user can optionally define one of two cases:

  1. multiple devices in parallel (i.e., with a column of contacts between devices) by setting the m (for "multiplier") parameter
  2. multiple devices in series by setting the fingers parameter (adjacent devices have minimum spacing)

The two are mutually exclusive.

The pcell SKILL code is in local/skill/pcells.

--Slipa 12:02, 27 February 2006 (EST)