ELECTROPLATING CURRENT SUPPLY

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ELECTROPLATING CURRENT SUPPLY

• Steven Tin
• McNair Scholar
• Mentor Dr. Norman Tien
• Department of Electrical Engineering
• University of California, Davis

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INTRODUCTION

• Electroplating plays an important role in
  microfabrication of integrated circuits (IC) and
  microelectromechanical systems (MEMS).
• The requirement for the electroplating
• Good uniformity
• Low Stress

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• Power supply is of great importance in the
  electroplating process.
• DC power supply is widely used in academic
  research laboratories.
• Advantages of DC power supply
• Inexpensive
• Easy to use
• Disadvantages of DC power supply
• Lack of uniformity
• Uncontrollable stress

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• DC pulse is preferred to DC power supply in
  advanced microfabrication.
• Advantages
• Uniformity and stress is controllable.
• Disadvantages
• Current DC pulse power supplies are usually
  designed for industrial applications.
• Expensive. The prices ranges from 5,000 to
  20,000.

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• Therefore, a cost effective DC pulse power supply
  is desirable for academic research on
  microfabrication.
• Requirements
• To provide constant DC current and DC pulse
  current
• To provide tunable frequency and duty cycle
• Low cost
• Easy to use

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CURRENT SOURCE CIRCUIT

• The circuit can be divided into three parts
• Square wave with tunable frequency and duty cycle
• To adjust the magnitude of the output current
• The circuit that provides constant current

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CIRCUIT FOR SQUARE WAVE

• This circuit outputs a triangle wave whose
  voltage varies from Vcc/3 to 2Vcc/3..
• The frequency of the wave varies from 7HZ to
  3KHZ by changing the value of R2.

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TRIANGLE WAVE OUTPUT
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CIRCUIT FOR SQUARE WAVE

• By changing the value of R4, the voltage at node
  7 varies from Vcc/3 to 2Vcc/3
• The duty cycle of the wave can change from 0 to
  100

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DUTY CYCLE
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SQUARE WAVE OUTPUT
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VOLTAGE MAGNITUDE

• A voltage buffer is added to separate the
  circuits
• Two variable resistors are used to change the
  output voltage of this circuit
• Negative voltage is applied to opamp

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NEGATIVE VOLTAGE
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CONSTANT CURRENT CIRCUIT

• The circuit maintains a constant current through
  RL. The current I Vin / Rsense.
• Ic Ie, the current flows through Rsense is about
  equal to the current through Rload

Negative Voltage
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THE OVERALL CIRCUIT
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CURRENT SOURCE
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FUTURE RESEARCH

• We will use the current source to do
  electroplating
• Current mode and Magnitude
• Frequency and Duty cycle
• Temperature

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ACKNOWLEDGEMENTS

• Dr. Norman Tien
• Dr. Ellen Robert
• Andy Liu
• Ray Shiraishi
• McNair staff
• Dr. Tiens research group

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REFERENCES

• 1 F. A. Lowenheim, "Modern electroplating,"
  Electrochemical Society, 1974
• 2 R.C.Dorf, and J. A. Svoboda, Introduction To
  Electric Circuits" John Wiley Sons, 2001
• 3 D. A. Johns, and K Martin, "Analog integrated
  circuit design," John Wiley Sons, 1997
• 4 www.ecircuitcenter.com/Circuit/curr_src1.htm
• 5 www.smoke.com.cu/neg-volt-gen.html
• 6www.elecdesign.com/Articles/index.cfm/ArticalID
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