Parameterized Cell Tutorial - How to Create a Pcell

Parameterized Cells ( Pcell ) are a powerful tool to create Cadence layout designs. This Tutorial gives step by step instructions of how to create a Pcell for comb drive fingers and how to instantiate this finger Pcell to create a comb drive. In a later tutorial, we will also use this Pcell to create a mesh for metal membrane designs. This tutorial assume you have set up and started Cadence properly. This tutorial is process independent. However if you choose to skip steps, pre-created tutorial Pcells exists in hp_cds (MOSIS HP 0.5um process).

Part I. Initialize Pcell environment
Part II. Draw basic geometry
Part III. Define parameters
Part IV. Compile Pcell
Next: How to instantiate this Pcell

Part I. Initialize Pcell environment

1. Let's start with a new "pcell_demo" layout in a new "demo_lib" library. Please refer to Layout Edit Help on how to create a new library and how to create a new layout.
2. In layout window, click on Tools => Pcell
   
   
   
3. A new menu Pcell will show up on the top menu bar.
   
   
   
   The Pcell menu indicates this is a Pcell layout instead of a regular layout.

Part II. Draw basic geometry:

1. To draw basic geometry is the same way to draw a regular layout. In this case, we start with a finger that is 2um wide and 8um long.
2. Draw 8um by 2um rectangle (with Metal3 for hp_cds; for other process, choose the proposed structure layer)

Part III. Define parameters

1. First, define "finger_length" parameter. Click on Pcell => Stretch => Stretch in X ...
   
   

 

2. In the layout window, click once to define the starting point of the stretch line; drag the stretch line; and then double click to define ending point of the stretch line.



3. A Stretch in X window will pop up:
   
   
   
   Type in finger_length as the parameter name; keep the default dimension as 8 (same as the length of rectangle we drew); then click OK.
   Red circle indicates user input.
   
4. Next, let's define "fingers" parameter (number of fingers that needs to be repeated in y direction). Click Pcell => Repetition => Repeat in Y ...
   
   
   


5. Click once on each shape that need to be repeated (in this case, just the rectangle); then double click anywhere to end selection of repetition
   
   
   


6. Repeat in Y window pops up:
   
   
   
   Type in step_distance as the parameter name for Stepping Distance; Type in fingers as the parameter name for Number of Repetitions; click OK.
   Red circle indicates user input.
   
7. Now you have successfully defined a Stretch in X, and a Repetition in Y.

Part IV. Compile Pcell

1. The last step of designing a Pcell layout is to compile it. To compile a Pcell, click on Pcell => Compile => To Pcell
   
   
   
2. A Compile To Pcell window pops up, just click on OK.
   
   
   
3. Now your Pcell is done. Don't forget to save your design by clicking Design => Save

After you complete your Pcell, the next step is to instantiate this Pcell in a layout to create a comb drive.

Created September 17, 2001 by Kai He at khe@ece.cmu.edu