It has been a busy couple of weeks but mostly in preparation of events which come and go very quickly. About 3 weeks ago (I have been quite busy and at one point decided to wait to see if I could improve the results prior to posting but the technician was out of town) I saw lines that were 20 nm and less in width, which are seen in Figures . However, I was unable to consistently achieve these line widths and in the end they seem more like happy coincidences than planned results. They reason I say this that the smaller lines appear on a small pattern located within another pattern which does not display the same line widths. I have been using the wheel arrays for some time to try and obtain smaller line widths and they have served their purpose very well up to this point but now I am stuck at 40-45 nm consistently and I thought it might have something to do with a curving line compared to a straight line. The 40-45 nm results are a big improvement over where I began and with each visit I am fine tuning the procedure but I feel that a small something is missing that is necessary for making these lines smaller. I have been in contact with the manufacturer of the e-beam set up being used in Tulsa and he has given many suggestions of why we haven't been getting the finest lines possible and it is his advice which I will be following up on Friday. With the help of a research scientist here at OU I have been using a new pattern which is a set of straight lines which I felt might give an idea if the curve in the lines was what was causing the large line widths. As seen in Figures , the pattern worked very well, which I was a little surprised about since it was my first custom pattern where I input new current dosages and ran it from scratch, but the line widths still hover close to 40 nm at the lowest line dosages used in the dosage array. As the dosage is increased the sharpness of the line is greater but the line widths also increase. This is expected and what we would want to find is a "sweet spot" where the resolution of the line is greatest while also giving the smallest line widths, which is what I'm hoping will occur on Friday when I go to try out the suggestions of the manufacturer. Until I am able to figure out the problem I have been working with AFM to get images of surfactant on the surface of my substrate, but it is more difficult that one initially thinks. It is a very delicate process but I believe that I am slowly getting the hang of it and hope to have some images soon!
On the terraces fore front things are not going as well. I have been trying to contact the research scientist who has been helping me to obtain the pillars via Reactive Ion Etching but I have so far been un-successful. The main problem occurring is that some of the equipment is in need of repair and the technician helping me was gone for a couple weeks for research and had not been able to fix it the last time I spoke with him. So in the mean time I have been working on protocols to use and trying to fine tune the parameters in order to get the cleanest etch with highest aspect ratio. I am hoping that the issues will be resolved soon and I will be able to continue with the project in it's entirety.
All in all I'd say that for a short while everything was working and moving forward and now once again I am at a veritable standstill. However, I am seeing improved imaging of surfactants on silicon which is keeping me busy while I wait for the etching equipment to be fixed, while preparing for the time when 20 nm lines are reached, which I have a feeling is going to be very soon!!
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| Figure 1. Etched 15 nm lines in PMMA on Silicon |
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| Figure 2. Etched 20 nm lines in PMMA on Silicon |
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| Figure 2. Etched 20 nm lines in PMMA on Silicon |
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| Figure 3. Etched 20 nm lines in PMMA on Silicon |
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| Figure 4. Etched 20 nm lines in PMMA on Silicon |
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| Figure 5. 40 nm lines at the lowest current in a custom straight line array |
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| Figure 6. 90 nm lines achieved at highest dosage in straight line array |
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Figure 7. Image showing the entirety of one straight line array which ranges from 1 nC/cm to 8 nC/cm.
Etching in PMMA on Silicon using E-Beam Lithography |
