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On these pages I give an overview of hardware requirements and the different processes. I mention some problems the development process engineer faces and need to resolve; the solution might not be 100% process and might be recommendations for new methods, or hardware re-design. Communication between the plasma modelers, the hardware designers, and the process engineer will lead to reasonable causes of problems and eventually solutions. A good process is 75% hardware and 25% process; it is the cleverness of the process engineer to find that robust process, meeting the specifications of the integration scheme.
The process development engineer need not be a plasma physicist, but need to have a sense for some plasma properties. In general, the fundamentals of physics and chemistry of plasma are well documented in the literature and on the world-wide-web. I list below some of the plasma properties, and the interested reader will find adequate explanation in references cited on the Etch page:
- Electron Density versus Characteristic Electron Energy
- Electron Energy Distribution Function (EEDF): N(E) vs Energy
- Collision cross-section versus electron energies
- Electron Temperature and Ion Temperature (The neutrals temperature in the plasma is comparable to the ion temperature.)
- Electron impact events: Dissociation - Ionization - Excitation
- Recombination
- The rate of ionization, dissociation or excitation per unit volume as result of electron collisions with neutral gas atoms or molecules
- Plasma potential is positive with respect to all surfaces whether grounded powered
- DC bias is the voltage shift at the powered electrode (with respect to ground). This bias depends on: Pressure, RF Power, magnetic field, and whether the gas is electronegative or electropositive
- Capacitively coupled plasma generates medium-density plasma, while inductively coupled plasma generates high-density plasma. The choice of high plasma density or medium plasma density depends on the process.
A handy plasma reference booklet is the "NRL Plasma Formulary" published by the US Naval Research Lab; it is described as "the mini-Bible of plasma physicists for the past 25 years. It is an eclectic compilation of mathematical and scientific formulas, and contains physical parameters pertinent to a variety of plasma regimes, ranging from laboratory devices to astrophysical objects".
The development process engineer need to be familiar with plasma diagnostic equipment and fault detection and classification systems. Some of the providers for these technologies are: Scientific Systems, Straatum, and Pivotal Systems.
You can learn more about advances in plasma physics by following the big names in the field. These people are the recipients of the "James Clerk Maxwell Prize in Plasma Physics" ; you can look up their publications and patents, and in some cases their lecture notes.
This site was last updated 07/11/10
© 2009 Stephen Hyatt
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