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Tips
& tricks on using LEdit for Mask Layouts:
- Standard
Setup: For ease
of use and consistency, try to use the standard setup. Select Setup->Design
to get the Setup Design popup.
- Select
the "Technology" tab. The Technology Name should be "Generic
0.25um Technology". Technnology Units should be checked "Microns"
and the Database Resolution should show 1 internal unit equals 1/1000
microns.
- Select
the "Grid" tab. Under the Mouse Grid, the Cursor Type
should have the "Snapping" box checked. Your Mouse Snap
Grid should be set the same as the address unit value you choose
(usually 0.1 or 0.125 microns.)
- If you are laying out 1X designs for
5X reticles, keep your internal unit at 1/1000 microns, but set
your Mouse Snap Grid to 1/5 of your address unit size (usually,
0.02 or 0.025 microns) since this will scale to 5X. (It's not necessary
and may lead to conversion problems if scale your internal units
by 1/5.)
- Define
Layers: Select
Setup->Layers... to get the Setup Layers popup. On the left side
will be a list of layers that you can choose to use for rendering your
layout. Make sure that the layer(s) you choose to use has a GDSII number
associated with it (under Import/Export.) If there is no associated
GDSII number for a given layer, no data for that layer will be exported.
The GDSII layer ID number is also what is used for specifying which
structures will be written on a mask. For electronic devices, there
is a naming convention which is part of the Technology setup(i.e., "Poly
= 43"). For other applications, the naming convention doesn't need
to be observed -- but each layer must have unique number between 0 and
64.
- Observe
minimum feature spec: Make sure your minimum critical feature (line,
space, or dot) size is no less than the critical dimension (CD) specified
for the grade or type of mask you are ordering. You could get away with
drawing things that are smaller that the specified CD, but they would
not be guaranteed for dimensional control or appearance (for example,
corners will be rounded.)
- Naming
convention: Make
sure to use simple naming conventions for your named structures (file
names, cell names, subroutine names.) Stick to alphanumerics only (no
characters like *&#%$) and do not use spaces (underscores, like
"_" are OK.) The limit is 32 characters -- but if cells from
different files are "instanced", LEdit appends the file name
to the cell name to ensure unique reference pointers, so the final cell
name may exceed this.
- Nifty files for reference:
- ASML image field <1X Digitized
Data Clear-GDSII> or <1X/5X Digitized
Data Dark-GDSII> or <1X/5X DigitizedData
Dark TannerDB>
- Contact mask alignment marks <TannerDB>
or <ZIP>
- Digitized Data Dark & Clear: It is possible to place images
on the same mask with different polarities - in other words, one device
with digitized-data-dark next to one that has digitized-data-clear.
The simplest way to do this is to draw your layout so that there are
only two distinct GDSII layers: one designated for digitized data dark,
and the other, for digitized data clear.
- The digitized data clear layer can be drawn just as you want it to
appear.
- In addition to the digitized data dark features you want, draw large
boxes that cover and protect the digitized data clear structures.
- Your data window should cover your entire write area. The maskwriter
will write one layer and then the other right away.
- For a sketch of this, refer to the Photomask
Basics presentation.
- If you have multiple layers that map to one clear (or dark) layer,
just define the different layers (step 2) to export to your designated
clear or dark GDSII layer number.
- Here's an example in LEdit and
in GDSII formats. The "TopStructure"
cell defines a mask with six structures, three in dark and three in
light. The "Dark" layer exports to GDSII layer number 4, which
is arbitrarily chosen to be dark. The "Clear" layer exports
to GDSII layer number 2.
- Multiple images on a single mask: Devices and device layers
can be arrayed on a single mask; there is generally a data processing
charge for this, depending on how complex the job is. Alternatively,
you can array the images yourself which can save a little money and
not all that much trouble once you've already gone through the task
of mapping out where you want everything. This is one way to array one
device that has multiple layers:
- Starting with your layout, draw an "outline" layer around
your device. This layer can be named anything (the default technology
will have something called "drawn" or "outline"),
but the layer should be defined WITHOUT a GDSII layer number. The purpose
of the outline is to help make sure your device placement in the array
is exact and consistent.
- Copy your layout to other cells. Each cell that you copy to will be
used to define one image in your array. Make sure you use "Copy"
and not "Instance" since layers cannot be separated using
Instance. If you do use Instance, make sure to flatten the cell (which
removes all reference to the Instanced cell.)
- In each of the copied cells, hide the layer you want for your image
and hide the "outline". Delete all the remaining layers. Then
"show" the layers you've just deleted. Now each of your cells
should have only the outline and the layer you want to image.
- In your top structure, array your cells.
- In your layer definition (step 2 above), define your layers to output
to a single GDSII layer number. If you have both digitized dark and
digitized clear data on the same mask, then output to two layers and
make sure you have dark boxes protecting your clear structures.
- Here's an example in LEdit and GDSII
formats. This is one of the layouts used in the EE410 class. The cells,
TopStructure1 (digitized data clear), TopStructure2 (digitized data
dark), and TopStructure3 (digitized data clear) define three different
ASML reticle masks. Each of image is instanced from a cell with a single
layer (plus the outline or "special" layer.) The various layers
(Active, PWell, Poly, Metal1, NSelect, Contact) maps out to either GDSII
layer number 2 (which has been chosen to indicate "digitized data
clear" data) or number 4 (chosen for "dark" data.)
- Text: Select Draw -> Layout Generator -> Layout Text
generator. A box pops up and you can enter this info:
Layout Text String: TEXT YOU WANT TO APPEAR
Layer name: select layer you want text on
Cell name: layout text generator makes a new cell with your text in
it
Text Size: Height of text
- The critical check:
Use LEdit to export your file to GDSII file format. Then, as a sanity
check, re-import your GDSII file into LEdit. Make sure that your imported
GDSII file looks like your original LEdit file. If it doesn't, there
is a good chance there is a problem in one of the areas listed above.
Be aware that unless you specify the technology when you import, the
layer rendering may not be the same as when you exported from LEdit.
- Other
tips and tricks: The
User Guide (loaded on the PC) is the best place to start. Additionally,
there are answer/questions posed by previous labmembers which appear
as PDF files on the machines. If you have questions about how to do
something in LEdit, feel free to contact Process Staff -- if we can't
help you, we can forward your question to Tanner as we have a support
agreement with them.
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