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					                                   CMOS Layout/Verification with LASI

Contents

PART A: DOWNLOADING, INSTALLING, AND STARTING LASI .................................................. 1
    1 INSTALLING LASI (FROM LASI HELP) ................................................................................................... 1
    2 UNINSTALLING LASI .............................................................................................................................. 2
PART B: BACKGROUND INFORMATION ........................................................................................... 2




Part A: Downloading, Installing, and Starting LASI
This section replicates what was on Homework 4The LASI software (for Windows only) is
available at http://cmosedu.com. You will be downloading the LASI 7 version.
LASI (LAyout System for Individuals, pronounced "LAZY") was written by Dr. David E.
Boyce.
The basic download steps are as follows.
     Create two folders: C:\Lasi7 and C:\Lasi7\Zips
     Download the LASI installation file (Lasi7xxx.exe) to C:\Lasi7 from the LASI Home Site
      (http://members.aol.com/lasicad/) or at (http://cmosedu.com/cmos1/winlasi/lasi7017.exe).
     Download the following design files into the C:\Lasi7\Zips folder:
           mosis.zip Contains the setups for the MOSIS Scalable CMOS design rules (SCMOS)
           2uchip.zip An (old) chip design using the MOSIS design rules. See also here for
            additional examples. Optional.
           clib2.zip Mississippi State's standard cell library in SCMOS. Recommended
           clib2s.zip Mississippi State’s library redrawn to be compatible with the MOSIS
            submicron design rules. Optional
           clib.chm (~1,800k) clib documentation (optional but very useful).
The following instructions will be found in the LASI Help menu once the software is installed.
They are basically reproduced here to get you started.



1 Installing LASI (From LASI Help)
The following information outlines the installation procedures for installing LASI on most any
PC. If you are reading this, you probably have done most of the installation already. The
information is given here so that you can verify that installation has been done correctly.
LASI should install and run on any of the Windows operating systems. You should also have the
Internet Explorer 4.0 or higher as part of your operating system. The Internet Explorer addon
contains an HTML reader named HH.EXE which is used to read the LASI help files. Early
versions of Windows 95 and NT 4.0 may not have this program without the Explorer.
LASI will be ready to run with just the basic installation. When you are more familiar with
LASI's workings you can do more advanced things.
If you downloaded from the Internet, LASI should be in a single Zip file LASI7XXX.ZIP. Where
the "XXX" indicates the version number. We now supply the download as a Zip because many
ISP block executables because of viruses and a Zip gives an extra degree of protection.
    Unzip LASI7XXX.EXE from LASI7XXX.ZIP and run this executable from any folder. LASI
    should be installed.
       The \LASI7 folder and its subfolders should be created.
       The system and any extra files should be decompressed into these folders.
       Start Menu items should also be created under the "Programs" item "Lasi 7".
Note: LASI7XXX.EXE incorporates a file length check which reduces tampering with
LASI7XXX.EXE, possibly by a virus. If the file length is wrong, an failure message will appear.
You can continue the installation by holding down the CTRL key, but expect errors.

2 Uninstalling LASI
All LASI system files go into the \LASI7 folder and its subfolders. Drawings and shortcuts to
drawings can be placed almost anywhere.
For this reason there is no particular Uninstall program. To remove LASI remove files in this
order:
       If a shortcut link to a drawing exists, delete it
       If a drawing folder exists, delete it.
       If "Lasi 7" is in the Start Menu, delete the "Lasi 7" menu item.
       To remove LASI system files just delete the \Lasi7 folder.
LASI does nothing to the Windows registry, other than the usual Windows system bookkeeping,
so you should not have any strange behavior caused by registry information errors.
Tip: It is usually easier to delete all drawing folders if the are under one master folder, instead of
scattering them all over your hard drive.



Part B: Background Information
The Part summarizes some general information that will be helpful as you complete the circuit
layouts.. For this purpose, I recommend that you set up your design folder (placed in c:\Lasi7) as
follows.
       In c:\Lasi7 create a folder called “MyCircuit”
       Copy all the files in c:\Lasi7\Edulib into your “MyCircuit” folder.
       Create a shortcut (right click on the desktop screen of your computer, select “New”, and
        select “Shortcut”). Set the “Target” to be C:\Lasi7\Lasi7.exe. Set the “Start in” folder
        to be C:\Lasi7\MyCircuit. Name the shortcut “MyCircuit”.
   A shortcut icon should appear on your desktop.
   Double click the “MyCircuit” desktop shortcut icon. The LASI7 window should appear
    with a text box asking for a “Cellname”. Enter the name “MyFirstTry”. Click “OK”.
    Another window appears asking for the “New Cell Rank”. Select “1” and then click
    “OK”. A blank LASI window should appear. A complex design would be hierarchically
    organized (bottom-to-top) in increasing ranks. Rank 1 is the lowest level of the design,
    where you create the basic logic cells that you will be using. Having created the Rank 1
    cells, you will find them included in your “MyCircuit” folder. If you were to save the
    Rank 1 circuit design and then exit LASI7, you can restart LASI7 by clicking on the
    desktop icon to MyCircuit. You can then enter a different name for the “Cellname” and
    select rank 2. You are now able to enter your Rank 1 circuit designs as components to be
    interconnected in your higher level Rank 2 circuit cell. Saving it, you can then move to
    Rank 3 cells using the Rank 2 and Rank 1 cells as elements.
   Follow the instructions in the LASI tutorial linked on the homework’s Webpage to set up
    and see the grid. The spacing between dots is lambda and the gate length is typically 2
    times lambda. Design rules are given as multiples of lambda.
   In the lower left hand corner of the LASI7 display, you will see “Wgrd” and “Dgrd” set
    to some value in “lam” (lambda). On the right side of your screen, under “Menu 1” (If
    the menu says “Menu 2”, simply click on it to switch to “Menu 1”), you will see about
    half way down buttons for “Wgrd” and “Dgrd”. Click on the “Wgrd” button until the
    bottom left side of your screen says “Wgrd = 1 lam. Then click on the “Dgrd” button
    until the bottom left side of your screen says “Dgrd = 1 lam.”
   Next, click on the “Layr” button about a third of the way down in “Menu 1”. A window
    showing small labeled boxes (with different color patterns will appear). These represent
    various physical layers defined by masks during the fabrication of the CMOS circuits.
    You will not be using all of them.
        o   To draw boxes representing the area taken up by a transistor (NMOS or PMOS),
            you will be selecting and using the “ACTV” layer (“Active layer”).
        o   Once you draw a rectangle representing the “active layer, you will need to
            specify whether this is the active area for an NMOS transistor or for a PMOS
            transistor. For NMOS transistors, you will use the “NSEL” (N select) layer,
            drawn around and at least two lambda outside the ACTV layer. For PMOS, use
            the “PSEL” layer (also around and at least two lambda outside the ACTV layer.
        o   To draw the polysilicon regions that overlay the gate region, you will be selecting
            the “Poly1” layer.
        o   The create contact holes for contact of the metal layer to source/drain regions, the
            polysilicon gate layer, or the Well layer, use the “CONT” (contact) layer.
        o   You can assume that you are using a P-type substrate, the type required for
            simple fabrication of NMOS transistors (which require a P-Type substrate).
            However, when defining PMOS transistors, you will need to use an N-Type Well
            implanted in the P-Type substrate where the PMOS transistors are located. For
            this purpose, around each PMOS transistor you will need to add the layer
            “NWEL” (N-type well). This N-type well serves as a localized “substrate” for
            the PMOS transistors and must be connected to Vdd for the PMOS transistors to
            operate correctly. You will therefore need to made a metal connection, through a
            contact hole, to the NWEL region, connecting that metal also to the Vdd power
            line.
   You will need to play with the above when creating your circuit since there are
    requirements related to minimum size of some of the regions and minimum distances
    from the edge of one region to another. For example, contact holes MUST BE
    PRECISELY 2 lambda by 2 lambda in size. These are the infamous DESIGN
    RULES.
   The hardest problem you will encounter is in understanding what the design rules are.
    When you downloaded the LASI7 software, one of the .zip files was “Mosis_rules”.
    Unzip this and a folder C:\Lasi7\Mosis_rules will appear. This is a set of pictures (drawn
    using LASI) showing all the detailed rules. I will put together an overview of the design
    rules that will be applying to your design. If you are looking at the information in the
    “Mosis_rules” folder, the rules that apply are the “SCMOS” rules. For now, go into the
    C:\Lasi7\Mosis_rules” directory and look at the files there. One will be called
    “Allmosis”. Double click on “Allmosis” and Lasi7 will start. The first window will give
    the cell name as “Allmosis”. Leave this name unchanged and click “OK”. Next, click
    “Fit” (appears at the top right of the Lasi7 window) and you will see the overall
    collection of pieces. Click on “Zoom” at the top right of the Lasi window and then draw
    a box around the square with some stuff inside that appears at the left top side of the
    “cell”. This will expand it so that it fills the screen. The caption for this window is “26.
    METALS (SUBM and DEEP)”. This is “Rule 26”, which will be checked when you run
    the design rule check later.

    The rules are organized by number starting at the lower left of the overall “MOSIS_rules”
    window, increasing to the right and then moving to the next row above. Find rule “1.
    Well” at the bottom left of the overall “Mosis_rules” window and zoom in on it. You
    will find four distinct rules. 1.1 is for the minimum width (10 lambda for SCMOS). 1.2
    is the minimum spacing between wells at different potentials. 1.3 is the minimum
    distance between two wells at the same potential (e.g., two N-wells or two P-wells). 1.4
    is the minimum spacing between wells of different types. You can “see” what these
    mean by looking at the picture shown
   When you run the design rule checker, it will locate all design rule violations and report
    the “rule number” of each. The rule number will correspond to the rule numbers
    discussed above.
                                               Figure A
After you have completed some of your drawing, it is useful to check whether the design rules
have been satisfied. Click on the “System” menu item at the top left of the Lasi7 window. A new
window entitled “System Mode” appears. Click on the button for “LasiDrc” (Lasi Design rule
Check). A small window appears with Help, Run, Map, Setup, and Go pull-down menus.
Click on the “Setup” pull-down menu and the “DRC Setup” window appears, with the name of
the cell. NOTE: The design rule check will be done on THE LAST SAVED VERSION OF
THE CIRCUIT, not the version that is displayed if not saved. The DRC File Name when I
run this was set to “Mosis-deep.drc”. The “Check Start” was set at “1” (i.e., checking starts at
rule 1) and the “Finish” was set at “115” (i.e., in steps through the rules until it reaches rule 115).
You should change settings as needed to match those in the Figure A above.
I set “Enable SCPY”, “Enable PAUSE”, “Erase Old PCX File”, and “Erase Old Report File.”
The DRC report file name (has a “.rpt” extension) was “LasiDrc.rpt”.
After filling in the “DRC Setup” information, click “OK” and then click the “Go” button on the
small “LasiDrc7” window. The design rule checks are now being performed. The checking will
halt for a while whenever it finds that the design rule being checked has been violated. Be patient
until the final window appears giving the total number of design rule checks violated.

				
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