Creating an Inverter Layout using L-EditTo launch L-Edit in one of the LAB PCs, go to START > PROGRAMS > ELECTRICAL > TANNER > L-EDIT

The following window will open up.

Create a new layout file by going to File > New. The following dialog box will appear.

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

1 of 9 1/10/2011 4:03 PM

Under the Copy TDB setup from file area, use the browse button to locate the mamin08.tdb file (usually P:\Tanner\L-Edit 11.0\samples\tech\mosis\mamin08.tdb on the lab PCs)

Go to Setup > Design. Leave everything on the dialog box as it is. This dialog box shows the relationship between lambda and microns, specifies the gridsettings and shows the type of technology being use.

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

2 of 9 1/10/2011 4:03 PM

Now that we have setup the technology, we will layout a simple CMOS inverter with PMOS sized W=12 lambda, L = 2 lambda and NMOS sized W=6lambda, L=2 lambda.

In Tanner, in order to layout either an NMOS or a PMOS, a series of layers must be laid out. Here are the requirements:

PMOS: First layout a n-well (n-substrate). Then put a layer of P-select. On area designated P-select, add an appropriate sized Active layer. Nowput a layer of Poly for gate.

NMOS: First layout a p-well (p-substrate). Then put a layer of N-select. On area designated N-select, add an appropriate sized Active layer. Nowput a layer of Poly for gate.

While each layer must be added, there is no need to layout a p-well or p-substrate when laying out an NMOS. The empty grid of L-edit represents a

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

3 of 9 1/10/2011 4:03 PM

p-well or p-substrate.

The substrate/bulk needs to be connected to Vdd for PMOS and Gnd for NMOS. For PMOS, place a small N-select (NOT P-select) on the n-wellsubstrate, add a small Active layer. From this active layer put a contact to a Metal 1 layer that connects to VDD. For NMOS, on the p-wellsubstrate (i.e. just the background grid) place a small P-select, followed by an Active layer. From this active layer put a contact to a Metal 1 layerthat connects to Gnd.

Now using the shape tool from the top bar and the layer-pallet from the side-bar, and the requirements mentioned above draw a PMOS. Similarly draw theNMOS (remember you do not need to draw the P-well). Before you go any further, it is important to note that your design is not correct until you connectyour substrate.

Check your layout using a the design rule check function. Click the DRC button on the top toolbar. It is a good idea to run DRC at each stage of yourdesign so that you can fix any error along the way.

Once you have your NMOS and PMOS done, layout an inverter as shown below: Use the design rules (from Digital Integrated Circuits: A DesignPerspective - color leaflet between pages 10 and 11) to properly space the objects.

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

4 of 9 1/10/2011 4:03 PM

Notice how compact the above inverter design is. The goal is to create a minimum physical implementation of all the layout designs, and to use minimalwires, transistors, contacts, etc. Not doing so will decrease circuit speed and performance as well as increase circuit size.

Label the Input, Output ports and the Power ports using button on the top-toolbar. On the final design run DRC. If there is a Design Rule Violation, adialog box will open pointing out what the error is. If you click on the error message, it will show exactly where on the design the problem resides.

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

5 of 9 1/10/2011 4:03 PM

Fix any DRC error before proceeding. Keep in mind that passing the DRC test does not guarantee that your design will work as you expect. A DRCPass just means that there are NO DESIGN RULE violations.

Now that we have a complete error free design, it is time to extract the SPICE netlist for the layout. Click on the button on the toolbar. Browse to thecorrect Extract Definition File (for this tutorial we used mamin08 technology. so use the mamin08.ext extract definition file usually located at P:\Tanner\L-Edit 11.0\samples\tech\mosis\mamin08.ext)

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

6 of 9 1/10/2011 4:03 PM

Click on the output tab on the Extract dialog box. Uncheck everything except: Write terminal names for subcircuits, and Write nodes and devices asNames. Also make sure the SPICE include statement textbox is empty.

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

7 of 9 1/10/2011 4:03 PM

Click Run. You might get an error message similar to:

Ignore all warning messages related to Capacitances.

The SPICE netlist is now generated from your layout. Again this netlist needs some further work before you can run any kind of analysis on it. Read the

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

8 of 9 1/10/2011 4:03 PM

tutorial on Simulating your inverter with SmartSpice to figure out what to do next.

Some quick tricks:

To resize an object, select the object with the left mouse button, hold the ALT key and use the left mouse button to drag a side of the object.

To move an object, select the object with the left mouse button, hold the ALT key and use the left mouse button to drag the object.

To duplicate an object, select the object with the left mouse button, hold the CTRL key and use the left mouse button to place the copied/duplicated objectat the right place.

Last Updated:Kundan

02/02/2005 10:53 AM

L-Edit Tutorial http://scale.engin.brown.edu/classes/EN1600S08/tutorials/ledit_tutorial.htm

9 of 9 1/10/2011 4:03 PM