The OSU Nanoscale Patterning Laboratory - Diary

May 2006 Highlights of OSU Nanoscale Patterning Lab:

Transparent Substrates:

Successfully patterned and Ti/Au lift-off of dose arrays for large gratings on glass using copolymer resist process (not bilayer resist). Doses required for this process are low for PMMA based resist, 150-200 uC/cm² at 50kV. We were able to produce gratings using a bilayer process, but the gratings actually looked nicer with just the copolymer.

Recently, liftoff using optimized dose from dose array of Ti/Au on glass is showing issues. It appears much of the gold is removed during the liftoff. This was not the case in the dose array studies. Some pattern remains, but it is too thin to be diffractive. AFM studies will be performed in early June to determine the thickness of remaining metal. If possible, EDX will also be performed to determine if the remaining pattern is composed of Ti or Ti/Au. I plan on repeating the process with Ti/Au as the control, thick Ti, thick Cr, and Cr/Au to determine if the adhesion of Au to Ti is the issue.

Gratings were also created using the copolymer process and by depositing MgF2 onto glass. The deposition and liftoff process were determined (Physics lab equipment). The user needs to transfer this process to their specific thin film. Currently, we are working to optimize the draw size and dose on the required thin film. We'll be running another dose array in early June to determine the dose shift required by their film.

T-Gate Processing:

Began dose and draw size arrays for T-gate at 100kV. User has a trilayer process with a foot and side-lobe exposure. Dose array was performed on Si substrate. Awaiting SEM results.

Dots/Circles:

First pattern of dots was imaged with Sirion SEM. Results are good down to 25 nm. These were patterned in single layer 950K PMMA, approximately 90 nm in thickness.

More recent dot patterns (4 different patterns) are hanging the tool. These are dose arrays only, so only part of the pattern is being exposed. Leica (Vistec) is working on the problem. Suggestions from other Leica tool owners are to use a single dot exposure (make the beam the size of the required dot size). This would be a good solution if we can guarantee no stigmation in the beam throughout the exposure. For many patterns, this approach is sufficient. For others, however, we need to reproducibly create the same pattern over a large area. I believe that we need to use a smaller beam and draw the dots using an address grid that is smaller than the dot itself. I hope to hear some information from Leica at the Users' group meeting on Friday/Saturday June2/3rd.

Upcoming in June:

Continued work on gratings on transparent substrate, using liftoff technique 4" mask plates arrive in early June
Begin mask process development on both EBR9 (positive) and SAL601H (negative)
Espacer anticharging layer sample arrives courtesy of Showa Denko
Begin characterization of Espacer on our process
Lay out process development study for Nanoimprint Lithography masters, will develop master process over the summer. This will be specific to MicroMD's EVG NIL tool.

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Last updated June 19, 2006.