MEC3010 Micro and Nanotechnologies
Micro and Nanotechnologies
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MEC3010
Micro and Nanotechnologies:
Fabrication and applications
In the last two lectures we have seen examples of sensors and microfluidic devices. Here we
will explore how to combine these, as integration of sensors and/or actuators with microfluidic
systems is necessary to provide interaction between analyte and solid‐state devices.
Polymer‐based microfluidic systems offer the possibility to integrate complementary metal‐
oxide‐semiconductor (CMOS) devices at low temperatures because less aggressive bonding
approaches are usually used and a variety of polymer fabrication methods can be chosen such
as poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS), and SU‐8.
3Advanced Lithography Question – Exam like question
For instance, in Workshop 5 we analysed the fabrication of a giant magnetoresistance (GMR)
device, such as the one in Figure 1 (left). Normally a complex microfluidic system such as the
one in Figure 1 (right) with 4 distinct layers would be used.
Figure 1
Peng Z. et al., 2006 Journal of Microelectromechanical Systems 15(3)
4Advanced Lithography Question – Exam like question
Question 1. Here you are going to design the integration of a SU‐8 microfluidic system on top
of this sensor to form the structure in Figure 2. The SU‐8 microfluidic system consist of 2 layers
of this UV‐curable negative photoresist and all the dimensions are larger than 10 microns, as
depicted here:
If you have access only to SU‐8 2050 and 2025, using the datasheet provided (click here),
design the detailed fabrication steps including all the parameters for each of the layers in figure
2.
Figure 2
5Advanced Lithography Question – Exam like question
Question 2. Would it be possible to use a similar fabrication approach, as in question 1, if the
system has 2 additional layers such as in Figure 3?
Figure 3
6Advanced Lithography Question – Exam like question
Question 3. Mobile devices such as laptops and camcorders present a challenge when
considering their continuously increasing electric energy demand. Miniaturized solid oxide fuel
cells (micro‐SOFC) have drawn increasing attention as potential electrochemical energy
conversion devices. Of advantage are the high specific energy and high energy density, fuel
flexibility as well as fast start‐up times.
Two main micro‐SOFC designs can be found in the literature. The first one consists of a
cathode‐electrode‐electrolyte assembly (CEA) deposited on the same side of the substrate. Yet
nowadays most of the research groups focus on the second arrangement with one electrode
on each side of the silicon substrate (see the Figure below).
7Advanced Process flow design – Difficult exam like question
The key component of the micro‐SOFC is an electrolyte layer that for instance could be made of
yttria‐stabilized zirconia (YSZ), a refractory ceramic with ion‐conducting properties that makes
it perfect for fuel cells development. The YSZ membranes have between tens and few hundred
microns.
Design a process flow to mass manufacture these devices.
Remember than Al is not compatible with KoH etching.
Figure 4
8Advanced Metrology Question – Exam like question
Question 4. What methods will you use to make sure that the thickness of each of the layers in
the device is accurate to the requirements?
9Advanced Process flow design – Difficult exam like question
Question 5. Figure 5 shows the SEM images of two Au diffractive x‐ray Fresnel zone plane that
can be used as a lens. Lenses for high energy light sources, such as x‐ray or Extreme UV, cannot
be manufactured by standard methods and often only diffractive or reflective elements can be
used. Furthermore, to reduce absorption and the loss of intensity any layers that the light must
transmit through must be manufactured with the highest possible quality, and be as thin as
possible.
Advanced Process flow design – Difficult exam like question
Design the process flow to fabricate one of these Fresnel zone plates considering that only a
very small number of them is needed. A schematic is presented in Figure 6.
Note: If required, make sure to include the fabrication of any adhesions layers.
Hint: Remember that Au and photoresist (PMMA) have very low adhesion.