Third Day Poster Session, 17 June 2010 - NanoTR-VI

Poster Session, Thursday, June 17
Theme F686 - N1123
Fabrication of Micro Channels with Angled Sidewall on Silicon by Nd:YAG Laser Ablation
Alperen Acemoglu, 1 Veysel Ozkapici 2,* ,Vural Kara 1 ,Omid Tayafeh 3 ,Huseyin Kizil 4 and Levent Trabzon 1,*
1 Department of Mechanical Engineering, Istanbul Technical University, Gumussuyu, Istanbul 34437, Turkey
2 BNM Fabrika Biyo Nano Mikro Tek. San. Ve Tic. Ekinciler Cad. 7/4 stanbul 34830, Turkey
3 Department of Electronics and Communication Engineering, Istanbul Technical University, Maslak, Istanbul 34469, Turkey
4 Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak, Istanbul 34469, Turkey
Abstract— We present experimental results on microfabrication of micro channels with angled sidewall on silicon surface by Nd:YAG laser.
The purpose is to create V-shaped deep micro channels on silicon surface for producing nano-sharp micro Si-knife. The results can be used to
characterize the behavior of ablation process under different laser parameters to achieve optimal processing conditions for Si-micromicromaching
in MEMS such as V-shaped channels, slots and singulation process of vias.
Micro channels on silicon wafer play an important role in
many MEMS and NEMS applications. There are several
microfabrication processes for creating proper micro channels
on silicon surface. Conventional chemical and mechanical
processes like etching, engraving and sawing have been
successfully applied on to fabrication of micro channels [1, 2].
Although well developed and mature production process, they
are not suitable for all kind of MEMS application. That’s why
laser are widely used to create this kind of channels on
material, laser fabrication process is a non contact process
therefore preferred in our task.
Lasers are a powerful tool for micromachining
applications. A focused laser beam can easily be concentrated
onto a small target of a few micron diameters. The laser
material-interaction in this target area will be controlled by
laser parameters such as wavelength, pulse energy and pulse
duration which determine peak power density [3]. Certain sets
of parameters can cause thermal effects for marking, cutting,
and drilling.
In our work, we have specially chosen to work with
Nd:YAG DPSS laser which has 1064 nm wavelength and 60
W maximum power. There were limited survey on that, most
of the laser on literature was in the UV range with either
femto- or pico-seconds system, which are very expensive. Our
main focus was creating those micro channels by nanosecond
laser with a wavelength of 1064 nm.
One of the important findings in the study is to have U-
shaped channels with laser beam directed on the Si-wafer
perpendicular. This observation is defined as tapering affect
and it depends on the repletion of the laser ablation and depth
of the channel produced in the ablation process [5]. Tapering
affect is around 30°- 40° for 10 – 50 μm deep channels and
they are roughly V-shaped channel as shown in Fig. 2a.
Tapering affect was reduced to 10 °- 15° when channel depth
is in between 51 and 150 μm.
Main aim of this work is to create angled sidewall
production on silicon wafer by laser. Then, we examined laser
beam ablation on Si-wafer by different angles with laser beam.
By means of adjustable wedge, the Si is oriented as 30°-45°-
60° degree with respect to incoming laser in order to see
sidewall affect and channel-wall angles. The channel-wall
angles should be 30°-45°-60° degrees after inclined Si-wafer
ablation by laser if there is no tapering effect. We measured
channel-wall angles by profilometer on each Si wafer ablated
by a different angle. We found that the channel-wall angles are
38°-42°, 29°-34° and 19°-22° for ideally expected sidewall
angel 60°, 45° and 30°, respectively. The difference between
measured and expected angles is due to tapering effect in Si
laser ablation.
(a)
(b)
Figure 1: (a) Schematic drawings of angled channels set up (b) Angled
micro channel fabrication setup.
We first studied ablation effect of perpendicular laser
beam on silicon surface. We observe and measure the effect of
laser on scribed or grooved channels by profilometre by
changing laser ablation velocity, frequency, power and
repetition. It is been showed that 40 – 100 μm wide and 5- 250
μm deep groves can easily been produced by laser. There were
big debris or (HAZ) around the channel due to thermal affect
of laser. As our expectation and previous literature info,
ablation affect of laser increased by power, frequency,
repetition increments and velocity decrements [3]. The degree
of ablation does not linearly depend on the aforementioned
parameters; the relationship is very complex and well
explained [4].
Figure 2: (a) Optical microscope picture of micro channels produced by laser
(b) Profilometre result graph of sidewall angel of laser ablated micro channel.
This work was partially supported by TUBITAK under Grant No. 8080090
*Corresponding authors: levent.trabzon@itu.edu.tr and
veysel.ozkapici@bnmfabric.com
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6th Nanoscience and Nanotechnology Conference, zmir, 2010 694