Plasma Immersion Ion Implantation

1. Plasma Immersion Ion Implantation Chris Seymore

2. A couple of things you should be able to answer at the conclusion� What is my name? What does PIII stand for? What are the benefits of Plasma Immersion Ion Implantation versus conventional beam implantation? What are the benefits of using a pulsed negative bias voltage on the substrate?

3. Overview Why do Ion Implantation? Differences between Ion Beam Implantation versus Immersion Discuss types of plasmas used in this process Some Applications to Ion Implantation

4. Ion Implantation Accelerate Ions at high energies to implant them into a substrate Pulsed Bias voltages range from 1-100kV yielding energies on the order of keV-MeV Lower energies needed for semi-conductor processes Higher energies needed for metallurgy processes Ion Implantation Depth around 100nm Pulsed Voltages prevent arcing and allows the ions in the ion sheath to be refreshed i.e. Nitrogen ions at a bias voltage of 50kV, results in 25keV/atom yielding implantation of about 30nm Deeper implantation can be accomplished by hybrid processes such as Thermal Diffusion

5. Ion Implantation Early developments between 1960-1985 Semi-Conductors Used for doping Equipment Manufacturers Improves material wear, friction and corrosion properties Preferred to coating No delaminating Doesn�t increase item�s size Doesn�t require high processing temperatures Great, but not always cost effective

6. Ion Beam vs Immersion The focusing magnets serve to obtain an ion beam of a single ion species only The pulses bias prevents arcing as well as allowing the ions to �replenish� themselves within the sheath The focusing magnets serve to obtain an ion beam of a single ion species only The pulses bias prevents arcing as well as allowing the ions to �replenish� themselves within the sheath

7. A Complete System� (see book)

8. What types of Plasma can I use to accomplish Ion Implantation through Immersion? Large Volume Ionization Systems Glow Discharge, Filament Discharge or Inductive Coupled Sources Localized Plasma Systems Magnetrons or Arc Discharges Macroscopically at rest or Large Volume Streams (diameter around 40cm)

9. More on the types of Plasmas Noncondensable (gaseous) plasmas Condensable (metal) plasmas (more used for deposition coatings) Or combinations of the above Typically want Low Pressures to ensure collisionless implants (.75-7.5 mTorr)

10. What types of Plasma can I use to accomplish Ion Implantation through Immersion? Most 1980-1990s used a Thermionic filament discharge to make the plasma Pulsed Glow dicharges is one of the simplest RF Plasmas (Capacitively and Inductively Coupled) are widely used as macroscopically stationary gas plasmas

11. Thermionic Discharges Electron emission from a �hot� cathode (1100-2000 C) Plasma Densities around 10^15-10^18 m^-3 Benefits Simple to fabricate Easily produce high plasma densities Drawbacks Finite lifetime of cathodes due to evaporation Possible contamination of substrate by this material Chemical reactions of the plasma gas with this cathode material

12. Pulsed Glow Discharge Pulse generator serves dual purpose Generating the plasma Accelerating the ions across the sheath Benefits Any electrode geometry and any gas Surface treatments <100cm^2 up to >10m^2 Eliminating a lot of components Disadvantages Plasma generation and Implantation parameters are coupled, limiting versatility of the process High pressures leads to arcing vs. uniform discharge Limits the Pressure, PRF and Ion current density achievable

13. RF Capacitively Coupled Plasmas Low Density (electron density around 10^14 to 10^16 m^-3) Benefits Simple, low pressure operation, uniformity and relatively low equipment cost Disadvantages Not suited for complex geometric workpieces

14. Capacitively Coupled Plasma Generator

15. RF Inductively Coupled Plasmas High Density (10^16-10^18 m^-3) Benefits Good for workpieces with complex geometries Simple Plasma Generation Source Drawbacks Not compatible with some gas chemistries such as hydrocarbons

16. Inductively Coupled Plasma Generator

17. Semiconductor Applications Shallow Junction Formation Sub 100nm p+/n junctions for MOS transistors Flat-Panel Displays Source and Drain doping of amorphous silicon thin-film transistors (TFTs) Silicon-On-Insulator Fabrication SIMOX (separation by implantation of oxygen) Provides superior isolation between adjacent devices in an integrated circuit

18. Conclusion Little about what Ion Implantation is Compared Ion Beam technique to the Immersion Looked at the types of plasmas that can be utilized by a PIII system Glanced at a few applications to this technology

19. Answers What is my name? Chris Seymore What does PIII stand for? Plasma Immersion Ion Implantation What are the benefits of Plasma Immersion Ion Implantation versus conventional beam implantation? Simpler design, better/faster performance Why are the benefits of using a pulsed negative bias voltage on the substrate? Prevents arcing and allows for recovery of ions in the sheath