Method and apparatus for low energy electron enhanced etching of substrates in an AC or DC plasma environment
An apparatus for low-damage, anisotropic etching of substrates having the substrate mounted upon a mechanical support located within an ac or dc plasma reactor. The mechanical support is independent of the plasma reactor generating apparatus and capable of being electrically biased. The substrate is subjected to a plasma of low-energy electrons and a species reactive with the substrate. An additional structure capable of being electrically biased can be placed within the plasma to control further the extraction or retardation of particles from the plasma.
1. An apparatus for low-damage anisotropic low energy electron enhanced etching of a substrate, comprising:
a plasma reactor;
plasma creation means at least partially disposed within the plasma reactor for creating a plasma having positively charged ions and electrons;
a substrate holder disposed within the plasma reactor for receiving a substrate, wherein the substrate holder is isolated from the plasma creation means;
electron etcher means for etching material from the substrate with electrons from the plasma, wherein the electron etching means is in electrical communication with the substrate holder; and
charged particle controller means, disposed proximal to the substrate holder, for controlling the flux of charged particles directed from the plasma onto a substrate disposed on the substrate holder, the flux having sufficient energy for the electrons to etch material from the substrate.
2. The apparatus of claim 1 , wherein the charged particle controller means is adapted to control the energy of charged particles being impacted onto the substrate.
3. The apparatus of claim 1 , further including:
a charged particle blocking means for preventing charged particles in the plasma from reaching the substrate unless the charged particles pass through the charged particle controller means.
4. The apparatus of claim 1 , further comprising:
a pulse waveform power source adapted to electrically bias the charged particle controller means to direct the electrons from the plasma towards the substrate.
5. The apparatus of claim 4 , wherein said pulse waveform power source is further adapted to periodically bias the charged particle controller means to direct ions from the plasma towards the substrate to electrically neutralize the substrate.
6. The apparatus of claim 4 , wherein said pulse waveform power source is adapted to cycle between a positive electrical potential and a negative electrical potential, and wherein the positive potential is such that electrons having kinetic energy less than 100 electron-volts are attracted to the substrate and etch material therefrom.
7. The apparatus of claim 6 , wherein a waveform of a pulse wave supplied by the pulse waveform power source is defined by a period having a first predetermined interval at the positive electrical potential and a second predetermined interval at the negative electrical potential, wherein during the first interval electrons are directed to the substrate, and wherein the second interval is of duration such that a sufficient number of ions are directed to the substrate to substantially neutralize the accumulated electrons on the substrate.
8. The apparatus of claim 6 , wherein a waveform of a pulse wave supplied by the pulse waveform power source is defined by a period having a first predetermined interval at the positive electrical potential and a second predetermined interval at the negative electrical potential, wherein during the first interval electrons are directed to the substrate to etch the material from the substrate, and wherein the second interval is of duration such that a sufficient number of ions are directed to the substrate to substantially neutralize the accumulated electrons on the substrate.