Kissan Mistry

University of Waterloo | UWaterloo · Department of Mechanical and Mechatronics Engineering

I am trying to pattern a spin coated PEDOT:PSS layer (CLEVIOS PH 1000 + ethylene glycol + dodecylbenzenesulfonic acid + 3-glycidyloxypropyl trimethoxysilane) by utilizing Orthogonal OSCoR 4020 photoresist as an etch mask. I use a plasma asher, running a descum process (50 W, 100mTorr, T=25C, 10 SCCM O2 flow) but it tends to etch away the photoresist faster than the PEDOT:PSS layer.

Has anyone encountered similar issue? Any tips to get get around this?

I am trying to obtain the response and recovery times for my gas sensor device. It appears the the response/recovery times are primarily dependant on the flow rate of the gas I inject into the chamber, as well as its volume. In other words, I can saturated the chamber much quicker using a higher flow rate and thus my sensor would respond quicker to the gas.

In literature the response and recovery times are always reported independant of these factors. How can I be sure that the response/recovery times i measured are not limited by the flow rate of the gas or the volume of the chamber?

As researchers I think it's important to acknowledge that despite being "peer reviewed" many flaws still exist in materials science research.

For example, X-ray Photoelectron Spectroscopy (XPS) characterization seems to be highly subjective to the user doing the analysis. Another user doing the analysis on the same data would not achieve the same result!

I have successfully released MEMS cantilevers with a photoresist sacrificial layer, using a dry plasma ashing technique. However, this process tends to damage the metal contact pads and result in curved beams. To rectify this issue, I have attempted to perform a wet release process with critical point drying. The die is placed in a remover PG bath (heated 90C, for 3 hours). Then it is placed in IPA and followed by critical point drying. When the process is done, all the cantilevers on the die are cracked at the anchor point and no photoresist is removed.

What can be the possible reason for the cracking?

appreciate any responses.

I've created a simple cantilever MEMS structure with very thin aluminum contact pads. Through the release process of the MEMS structure, the contact pads have become damaged and therefore do not bond with wirebonds. Are there any options i have to re-deposit more metal (increase the thickness) on the metal contact pads, without affecting the rest of the structure?

i have few chips that have already been released and few chips that havent been released yet.

help is appreciated! thank you.

There are so many different sensing methods (transistor, optical, MEMS..etc) and so many different sensing materials that can vary in size and volume used that I find it difficult to compare my sensor results to that reported in literature.

The sensitivities reported in literature use different calculation methods. Some report change in signal (R2-R1), others report the relative change in signal, some report the change in signal with respect to a concentration ppm.. etc. There seems to be no consistiency in reporting these results despite there being many review papers in the field of chemical gas sensing.

Is there a general consensus on how to report sensor sensitivities and results? There seems to be a well defined standard in reporting solar cell results but not gas sensors.

the optical fiber is composed of silica, is there a measurement i can do to determine its exact refractive index?