Its a Small Wireless World'

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Its a Small Wireless World.

• Engineering 1202
• TEAM E0108
• Adam Harris
• Patrice Harrington
• Chris Sides
• Joshua Huff
• Kile Blair
• Peter Rached
• Brendan Oldham

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Agenda

• Problem Statement and Constraints
• Research
• Wavelength Calculations
• Antenna Design
• Conductor Comparison/ Decision
• Cost Analysis
• Global, Societal and Contemporary Issues
• The Fabrication Process
• Clean Room Safety and Attire
• Dealing with a Silicon wafer
• Photolithography
• Finished Product
• Proposed Alternative Solutions
• Questions Answers

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Problem Statement

We were required, as a freshman engineering
team, to research and design a planar antenna for
use inside a miniature communications device that
is the size of a modern day watch. The design
made is to fit specific and well defined criteria
such as size range (size ranging from 5mm 5mm
to 20mm 20mm), and unique frequency band
(2400-2497 MHz), which is specific for the
Bluetooth/Wi-Fi model.
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Design Constraints

• Design area must be larger than 5mm x 5mm but
  smaller than 20mm x 20mm
• Antenna must be set for frequencies
• 824-894 MHz (cellular), 1850-1990 MHz (pcs),
  or 2400-2497 MHz (Bluetooth/Wifi)
• Cost, Reliability, and Manufacturability should
  also be taken into account

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Research
Wireless systems were researched as part of the
Project to further the teams understanding of
the subject matter. The research revealed that
cell phones are nothing more than complex two way
radios sending and receiving on separate
bandwidths Bluetooth and Wi-Fi are on the
unlicensed bandwidth (2400-2497 MHz) and are used
for wireless data communications. Bluetooth
transmits with a 10 m range, while Wi-Fi
transmits within a 100 m range.
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Antenna Type Decision

• We have chosen the Bluetooth
• and Wi-Fi model because
• - It is a newer technology
• - It has a higher frequency
• (higher frequency ? smaller antenna)
• - More money is to be made (hopefully)
• in a more recent technology.

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Calculations

• c speed of light in meters/second.
• W Wavelength in meters.
• P time or period is seconds.
• f frequency in Hertz.
• c W/P, f 1/P ? c Wf ? W c/f
• W c/f (3.0108) / (2448106) .120144 m 12
  cm
• Since we have decided to use a quarter
  wavelength instead of a full wavelength for the
  length of the antenna, our design would have the
  length of
• Length ¼ Wavelength ¼ 12 cm 3.0 cm.

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Design Alternatives
As part of the design process the team had to
decide on not only the antenna shape and size but
also the type of conductor to be used.
The two major designs for the antenna were the
Square Nautilus design and the Octagonal design.
The Square Nautilus design was chosen due to its
simplicity and compact size
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Design Decided
The final design made using AutoCad.
All measurements are in millimeters.
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Conductor Decision Matrix
Copper was our choice for conductor material.
Scale 1 (poor) 10 (excellent)
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Cost Analysis Sheet
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Global, Societal and Contemporary issues

• Maintenance and Security
• Changing the workplace
• Saving money

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FabricationThe Microelectronics Clean Room
Kile getting gowned up for the clean room.
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The Attire

• Shoe covers
• Face mask
• Hood (hair cover)
• Tyvek Coveralls
• Gloves

Josh wearing his coveralls, putting on a facemask.
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The Silicon (Si) Wafer

• Started with an Si wafer
• 4 inches in diameter
• Cleaned the wafer using
  H2SO4, H2O2, and HF

Visual of the silicon wafer.
Chris (left) and Adam (right) cleaning the Si
wafer.
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Oxidizing the Silicon

• Silicon is a semiconductor
• SiO2 was formed on the Silicon wafer in
  the Oxidation/Diffusion furnace

Si wafer with the layer of SiO2 surrounding
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Applying the conductor
The chosen conductor (Cu) was added using the
Varian vacuum thin film system
Copper applied to silicon dioxide layer.
Adam (left) and Kile (right) operating the Varian
system.
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Photo-litho-WHAT!?
Definition from ECE lab website Photolithography
The transfer of a pattern or image from one
medium (mask) to another (wafer) using light. It
is considered microphotolithography if the images
have features in the micrometer range.
Basically it is the process the team used to put
the design on the antenna.
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PhotolithographySpin coating

• Place wafer in high speed spin processor
• Apply Photoresist to the wafer.
• Spin at 4000 RPM for 1 minute.
• Soft bake on hotplate for 1 minute.

Operating the spin processor.
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PhotolithographyExposure
Place the wafer in the mask printer, cover with
the mask, and expose to UV light for 10
seconds. The photo resist reacts with the UV
light and the exposed portions of Photoresist
become a soluble acid.
WARNING NEVER LOOK INTO UV LIGHT DIRECTLY! The
wafer being exposed to UV light.
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Exposure (contd)
Before being exposed the Photoresist is insoluble.
Once exposed the Photoresist becomes a soluble
acid.
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PhotolithographyDevelopment

• Place the wafer into the spray developer
• Make sure the vacuum on the wafer is good before
  starting the process

The soluble gets washed away during development.
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Etching
Photolithography etch is a method of etching away
the conductor unprotected by the Photoresist.
(see below)
Brendan etching a wafer.
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Dicing
The wafer is placed on the MicroAutomation Wafer
dicing saw. The saw has a small diamond blade
that cuts the antennas out. The saw can be
operated manually or can be set to cut
measurements on a wafer.
Kile dicing a wafer, and monitoring the cut on
the screen.
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The Finished Product
Adams Reflection in the diced wafer.
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Proposed Alternative Solutions

• Use professional mask for better dimensions and
  quality.
• Redesign and test different antenna designs to
  achieve optimal performance and capacity.
• Use a clean room that allows us to process
  better, bigger wafers with lower contamination
  and at a faster pace.

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QAThank You For Your Time.Any Questions?
Team E0108 and TA