The SEBL facilty consists of 2 electron-beam-lithography
- The VS26 was developed at IBM to for in-house research.
It has a 50kV acceleration voltage and an approximate beam
diameter (for low currents) of 12 nm. The pattern generator
can deflect the beam at 750 kHz and writes field sizes between
75 and 500 microns. The fields are addressed by a 14 bit
D/A so the step size varies from about 4 to 30 nm, depending
on the field size. This tool has written isolated lines
as fine as 30 nm and gratings with a pitch of <100nm
(i.e. 50 nm lines and 50 nm spaces).
- The Raith 150 is a commercial tool based on a Leo SEM
column. It has an acceleration voltage variable from 1-30kV
and an approximate beam diameter (for low currents) of 3
nm. The pattern generator can deflect the beam at effective
speeds of about 1 MHz and can write field sizes between
50 and 300 microns. The step size on this tool is fixed
at 2nm. This tool has written isolated lines as fine as
17 nm and gratings with a pitch of <70 nm (i.e. 35 nm
lines and 35 nm spaces).
Jobs written on the VS26 tool are run by the facility manager,
Mark K. Mondol. See more information below on how to submit
jobs for this tool. Time is charged at a rate of $75/hour
for job setup and run times- after a free initial consultation.
The Raith 150 is a user-run tool. To become a qualified
user of the Raith 150 approximately 10 hours of training will
be required. Training sessions for this tool will be setup
depending on demand and will run over about 2 weeks. After
completing training, users will be allowed to run their own
jobs at an hourly cost of $75. Training will cost $750 (i.e.
10 hours times $75).
First time e-beam lithography users are encouraged to start
working with Mark K. Mondol on the
VS26. As specific needs occur, work may be transferred to
the Raith 150 tool.
What you need to know
There are many and varied parameters that need to be considered
before writing a pattern with e-beam lithography. Here is
a short list:
Substrate- thickness , diameter, conductivity, flatness.
Resist type neede - positive (PMMA) or negative (HSQ)*.
Pattern transfer- how will the pattern be transferred into/onto
the substrate, does it need to be transferred? How thick does
the resist need to be?
What are the finest and grossest features in your pattern?
E-beam lithography produces big patterns by stitching together
smaller fields, what sort of stitching errors (between fields)
can you tolerate?
What are the tolerances of your pattern; i.e. if you want
100 nm wide lines will you accept 110 nm lines or even 150
Are your patterns amenable to “Manhattan geometries”?
VS26 can write only rectangles on an orthogonal grid. The
Raith 150 can write polygons on an orthogonal grid. VS26 also
allows certain types of true circles to be written.
What is the total written area of your pattern? A grating
consisting of 100 lines that are 100 microns long about 50
nm wide and spaced 1 micron apart takes about 30 seconds to
write. A grating of 100 lines that are 100 microns long about
500nm wide and spaced 1 micron apart takes about 3 minutes
to write. It is sometimes possible to increase beam current
and field sizes to write large areas faster, but for reasonable
resolution consider that it takes about 6 minutes to write
10,000 square microns. These numbers refer to PMMA as a resist.
HSQ will take longer to expose.
What format is the pattern in, or do you still need to generate
the pattern data?
Do you want to align the pattern to some pre-existing pattern?
Will you want to align subsequent e-beam patterns to previous
ones? Will you want to do an optical alignment to the e-beam
How many times might you want to write the pattern? How often
will you want to change the pattern you write?
* Positive resists get developed away in exposed areas, negative
resists leave resist behind in exposed areas.