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Demonstration Setup

 Demonstration Setup


  The layout of a small IC is used as a demonstration to familiarize a new
  user with LASI. The circuit is a simple opamp, but not necessarily a good
  one. It is mainly designed to show drawing techniques.

  When you loaded the drawing files either from a self-extracting
  executable or from a ZIP file, you created a subdirectory on your hard
  disk called \LASI4\DEMO. This is the drawing directory for the
  demonstration IC.

  You need to leave this tutorial and go to your computer's DOS command
  level and perform the setup steps listed below. If you have a printer
  print this information for reference, or just try to remember it. You
  will be able to come back to this tutorial later. Click "Quit" or press
  ESC twice to exit.


  To set up the demonstration do the following:

  1. If you have not already done so, you must add the directory "\LASI4"
     to your computer's PATH entries. Adding this to the PATH allows LASI
     programs to be called from any directory.

  2. Make the drawing directory \LASI4\DEMO the default directory by typing
     "cd \lasi4\demo" on DOS's command line. When running LASI, you always
     work on a drawing while logged into the drawing's directory.

  3. Type "tlc } . ." on the DOS command line. (Be SURE you type the RIGHT
     brace character or you will try to translate backwards.) This will run
     the TLC.EXE program and convert the drawing cell files into a form
     (called internal) that LASI can use. Answer "y" to the "replace
     question" that TLC will ask. You should see a few files with .BP4 and
     .CL4 extension generated.

  4. With your mouse operational, now simply type "lasi". LASI will start
     and after checking a few details come up in System Mode.

  5. Go to Cell Mode on the basic NPN transistor in the drawing by clicking
     your RIGHT mouse bottom on the LIST command and then clicking the LEFT
     mouse button on the name "NPN1" in the listing.

  6. Test out the LASI help system by pressing F1. The Help and Information
     screen should pop up. This an information reader that can be called at
     any time while running LASI to explain any procedures or commands.
     Exit LHI by clicking "Back", "Quit" or by pressing ESC.

  7. Return to this tutorial by pressing F2. The drawing is arranged so
     that F2 calls the command "DOS, LHI \LASI4\DEMO\DEMO.HLP", which
     starts this program again from a drawing context. In fact, typing the
     command "lhi \lasi4\demo\demo.hlp" will run this tutorial from DOS.
     Read the topic Help on Help under General Information in the LASI help
     system for more information on LHI command line arguments.

Basic Transistor Cells

 Introduction

  The opamp is made from bipolar transistors based on a simple bipolar IC
  process. There are only 8 masking layers used, which are in the usual
  terminology:

        1  N-type Buried Island  (green)
        2  P-type Isolation  (yellow)
        3  N-type Sinker  (cyan)
        4  P-type Base  (red)
        5  P-type Resistor  (orange)
        6  N-type Emitter  (blue)
        7  Contact  (white)
        8  Metallization  (magenta)

  Additionally, layout text is on layer 32 and the schematic is on layers
  30 and 31.

  There are different types of NPN and PNP transistors, some resistors and
  miscellaneous bits and pieces. These are all made as rank 1 cells.

 Going to a Cell

  1. If you are not there already, enter Cell Mode with the NPN1 transistor
     by clicking your RIGHT mouse button on the LIST command and then click
     the LEFT mouse button on the name "NPN1" in the listing. The cell
     should appear.

    The cell is made from "basic objects": boxes, polygons and text.

    If the transistor does not show completely in the display window click
    the FIT command with the RIGHT mouse button.

    The demonstration drawing is set up so that pressing F3 will call the
    VIEW command and will make the correct layers visible.

  2. Use the commands ZOOM, XPND and the pan arrows to examine the cell
     more closely.

  3. There are two menus of commands that can be flipped by clicking the
     RIGHT mouse button while the mouse cursor is to the LEFT of the menu
     area on the screen. The commands are always selected by clicking the
     RIGHT button on a menu. The LEFT mouse button is always used to make
     cursor points or windows to input graphical information. Flip the
     menus to see the different commands, and if you are curious, place the
     mouse cursor on a command name and press F1. You will jump to the help
     information for that command.

 The Grid Systems

  When you work with LASI you will discover that your mouse cursor jumps
  between two grid systems: the unit grid and the working grid. This may
  seem confusing, but its purpose is to control the placement of drawing
  objects to certain discrete positions. As we know, IC layouts are not
  really drawings, but are precisely placed items.

  You use the SET command to program working grid sizes, and then click the
  WGRD command to step through them. The number and size is up to you. This
  demonstration is set up for 3 convenient sizes of 1um, 5um and 25um. The
  working grid is indicated at the bottom of the display.

  The DGRD and GRID commands set a display dot grid size and turn it on and
  off. The dot grid is a drawing aid and has no control over object
  placement.


  Hint: Pressing A or ALT keys flips the grid types.

 Getting Objects

  1. You will find that the transistor is mostly drawn with box objects.
     First use the GET and FGET commands by making a cursor window that
     crosses a box side. Notice that the command and the points are
     indicated at the top of the screen and that the cursor turns into a
     dotted rectangle. When you use GET, a side of the box turns bright
     white. This is called "active". Using FGET (full get) makes the entire
     box object active.

  2. Click the IDEN or SHOW commands if you want information on an object.
     SHOW is like IDEN except that it gives more information on a new
     screen. To exit a SHOW screen press ESC.

  3. The base of the transistor is made from a poly(gon) object. To "get" a
     poly object think of it as a series of vertices and make a cursor
     rectangle around one or more vertices. A diamond symbol will appear at
     an active vertex, and a segment line will turn bright white if
     adjacent vertices are active. GET makes a single vertex active. FGET
     makes an entire poly or path active. Use the IDEN and SHOW commands
     again on the poly.

  4. Try the PUT and FPUT commands. The "put" commands are the inverse of
     any "get" commands.


  Hint:  You can start a command over again by reclicking the command or by
    pressing ESC.

 Moving Objects

  1. Now try the MOV command. First make one or more box sides active with
     GET and then click the MOV command. Notice that the mouse cursor now
     jumps in discrete working grid distances and requires two input
     points. Notice also that the cursor turns into a dotted vector to
     indicate the movement.

  2. Click the APUT (all put) command to make boxes inactive again.

  3. Make a vertex active on the base poly. Try MOV again and notice that
     vertices move discretely in any direction.

  4. Click APUT again to make all objects inactive.

 Adding Objects

  1. You can now try the ADD command. To do so, first set the type of
     object using the OBJ command. You only have a choice of "b" (box) or
     "p" (path) in this case. (Later cellnames will be OK.)  Make your
     boxes by clicking at diagonally opposite corners. The boxes will be on
     the layer indicated at the bottom of the screen. Notice that boxes
     will be "snapped" into the working grid indicated at the bottom of the
     screen.

  2. Use the LAYR and CLYR command to set and change the layer of boxes.
     For CLYR to work a box must have all four sides active.

    You can use boxes for parts of a transistor (isolation, contacts etc.)
    that would normally be rectangular.

  3. Make polys by setting the object to "p" and clicking the cursor at
     different points to add vertices. You will produce a sequence of line
     segments with the last vertex active and marked by an "x". By adding
     the last vertex at the same point as the first vertex, you produce a
     closed polygon. Notice like boxes that the vertices are set at working
     grid points.

  4. Try the WDTH and CWTH commands to set and change a poly's width.
     Setting width greater than zero makes a poly into a "path".

    In general, the term "path" refers to both poly and paths; a poly just
    has zero width.

  5. There are special commands ARC, PREV, PBEG, PEND, CUT and JOIN that
     act on paths only. You can try these if you wish after you have
     determined their function by consulting LHI (Put the cursor on the
     command and press F1).

    You would use closed polygons to make non-rectangular areas in a
    transistor. (In this case, a base area with clipped corners, or PNP
    emitters and collectors as you will find in the PNP1 cell)

  6. Now add some text. Choose the TEXT command and click a reference
     point, and then type in some characters terminated by ENTER. Text is a
     form of path, and the LAYR, CLYR, WDTH and CWTH work on it. Width for
     text is the same as character height. Text is like a one vertex path,
     you "get" text by its reference point, which is always in the lower
     left corner of the character string.

 More Commands

  1. You should try the CPY, ROT and FLP commands on the boxes, paths and
     text that you have made. These commands save time when symmetries
     occur in a drawing.

    CPY will copy individual active vertices, so you can copy pieces of
    paths. Boxes copy only if they have all sides active.

    ROT will rotate boxes paths and text. Boxes and text rotate in 90 deg
    increments. Paths rotate to any angle.

    FLP flips boxes, paths and text around a horizontal or vertical axis.

  2. You can also try the WMOV and QMOV commands. These are composite
     commands that combine the actions of "getting" and "moving". The
     action of these commands on boxes, paths and text is the same except
     that the WMOV command requires that the cursor window completely
     enclose a box side. (WMOV also acts on whole cells as you will see
     later.)

  3. There are two commands, VIEW and OPEN that restrict the layers which
     are shown on the display and limit the action of commands on different
     layers. These accept a series of individual layer numbers, or an
     inclusive notation using a "-". Layers that are not VIEWed are never
     OPENed.

  4. There are additional commands like AGET, WGET, STEP, SMSH, PSIZ and
     OVSZ that act on basic objects. These are more rarely used and you
     will find their purpose once you have worked with LASI for a while.

 Cleaning Up

  1. You should use the DEL command to delete all of the boxes that you
     have added yourself. To delete a box you must have all sides active.
     Remember that the FGET command "gets" all four sides.

  2. Delete all the paths that you have added. When deleting paths you may
     delete vertices individually if they are active, or a complete path if
     all vertices are active. Remember, FGET will make all vertices of a
     path active if a single vertex is made active.

  3. Delete any text that you may have added by first making it active.

  Hint 1: If you have made a mess of the transistor while trying commands,
    instead of trying to delete and repair, use the ABRT command. This will
    restore the original version of the cell.

  Hint 2: If you have made a complete disaster of the cell, go back to DOS
    and run the TLC program as was done in step 3 of the Demonstration
    Setup and replace the cell files completely.

  The above hints are not to be taken as cynical. They demonstrate that
  LASI has backups in case you do make errors.

  To exit LASI from Cell Mode, first click SYS and then click QUIT.

 More Cells

  Use the LIST command to go to some of the other cells and see how they
  are made. Remember that the cells are intended to demonstrate drawing,
  not necessarily good device design.

The Main Cell Layout

 Going to the Main Cell

  1. Click the LIST command and choose OPAMP with the LEFT mouse button.
     The overall IC layout should appear. Notice that it is rank 2 and is
     made from the rank 1 cells along with boxes and paths. The transistors
     are set in place and are interconnected using paths on the
     metallization layer.

    This is basically the way that you would layout an IC, although the
    techniques vary with the individual.

  2. Use the FIT, ZOOM, XPND and direction commands to examine the layout.


  The opamp layout is a very simple example. More elaborate ICs may be
  constructed by using subsections (like our opamp), and then assembling
  these subsections into higher rank cells - and so on. This is how LASI
  can handle large if not huge ICs.

 Cell Commands

  1. Try some of the commands that act on cells only. Select the CGET
     command and make a cursor rectangle COMPLETELY AROUND a single
     transistor cell. The cell should redraw in bright white. This is now
     an active cell.

  2. Use the MOV, ROT and FLP commands on the cell. Cells rotate in 90 deg
     increments.

  3. Try the OUTL and FULL commands on a cell by again making a cursor
     window completely around the cell. Outline allows you to draw cells as
     a rectangular outline only. Putting cells in outline can greatly
     improve drawing speed if you have a large complex layout and a slow
     computer.

  4. Also try the CMOV command which moves cells directly. This too is a
     time saver.

  5. There are commands that work on both cells, boxes, paths and text such
     as AGET, WGET and WMOV. These do more things at a time, but are also
     more difficult to use. Try these commands. You will find that they are
     useful for operations like moving a whole section of a drawing.


  Hint: By quickly double clicking the left mouse button while making a
    cursor window in cell commands, you change the sense of the "get". The
    commands then act on cells if there is any overlap of the cell in the
    cursor window at all.

 Adding Cells

  Now you can add a cell. To do so:

  1. Click the OBJ command and make the object the name of a cell such as
     NPN1.

  2. Select ADD and click the LEFT mouse button in some open location to
     input a reference point. Your cell should appear and you can work with
     it just like any other cell.

    Note that the reference point is the 0,0 point in the added cell.

 Deleting Cells

  When you want to eliminate a cell, simply make the cell active and click
  DEL to remove it. Once a cell is gone there is no undo, but cells are
  easy to put back.

  As with lesser objects, you can also use ABRT to restore the original
  drawing, or reload it completely from TLC form.

The Schematic

 The Schematic

  There is a schematic diagram named $OPAMP independently living with the
  IC layout. It is similar to the IC layout except that the cells are
  symbols that are drawn and interconnected using zero width paths or open
  polygons, whichever way you may want to think of them. Different layers
  are used for the schematic and the layout, so that there will be no
  conflict with the layer attributes of color, dashing and filling.

  Notice also that in this example schematic cellnames have "$" as their
  first character so you can easily tell a symbol from a device.

  There are in effect two main cells, one for the IC, and one for the
  schematic. There actually can be as many different cells on a rank as
  memory capacity will allow.

  You may want to use the schematic as a practice for working with open
  polygons. You will find that the techniques are slightly different from
  working with the IC layout.

System Mode

 System Mode

  You do actual drawing in Cell Mode, but you go through System Mode when
  entering and exiting LASI. The commands in System Mode manipulate cells
  as complete entities and perform various organizational tasks.

  Put your mouse cursor on the command name and press F1 to find out what
  the commands do.

  You can try various commands. Their function is pretty straight forward
  and generally requires little explanation. You should be warned however
  that you can completely change some of the fundamental parameters, such
  as scale or cellnames.

  Once you work with LASI for a while this is not so scary.

Summary

 Summary

  You have been introduced to working with LASI. There are many more things
  that you can do using the many commands, and many subtleties in the way
  that the commands work that you will only learn by experience. When help
  is needed press F1. You will soon learn that LASI is really pretty simple
  in the way that it operates.


  Always exit LASI by going to System Mode, first clicking SYS if you are
  in Cell Mode, and then clicking QUIT. This stores the current cell on the
  hard disk, and updates the drawing basic data files.

