Plasma Etch Technological Advantages

Plasma Etch Electrostatic Shielding

GENERAL
The plasma process generates high energy plasma fields at the edges of the electrodes, which causes accelerated etching at these edges. These localized high energy plasma fields are caused by the plasma reacting with the vacuum chamber walls.
The overall effect is higher etch rates at the electrode edges, with a gradual reduction in the etch rate as it approaches the center of the electrode. This can be viewed as a target or bull's eye effect, which results in severe process non-uniformity.
If unchecked, this non-uniformity will cause parts positioned at the periphery of the electrode to etch more severely than those positioned at the center of the electrode. To obtain uniform etch rates the high energy edge effects must be minimized or eliminated.

DESCRIPTION
In Plasma Etch systems, all vacuum chamber internal surfaces are electrostatically shielded to eliminate plasma reactions with the chamber walls. (See diagram below.) These electrostatic shields are a patented feature, unique to the Plasma Etch product line.

ADVANTAGES
• Plasma activity is uniform across the electrode surface, thereby creating a uniform etch profile.
• Results are controllable and repeatable.
• Surface treatment of individual parts is independent of location and orientation on the electrodes.
• Some plasma equipment manufacturers attempt to minimize the bull's eye effect by distancing the electrodes from the vacuum chamber walls. This somewhat improves the uniformity of etch, but does not eliminate the problem. It has the added negative effect of increasing the internal volume of the vacuum chamber and thereby increases the pumpdown time of the vacuum chamber.