Method of etching substrates having a low thermal conductivity

A method of etching a substrate having a low thermal conductivity and which is sensitive to temperature to a high degree of etch rate uniformity, in a vacuum reactor at a pressure ranging from about 100 to 10.sup.-3 mbar by electrically or optically energized particles, using a process gas supplying said particles, said vacuum reactor comprising a process chamber, means for introducing said process gas into said process chamber, means for connecting a vacuum pump to said process chamber, and electrode mounted in said process chamber, a counterelectrode in said process chamber, a substrate holder associated with said electrode for supporting a substrate to be etched and an energy source for applying RF energy to one of said electrode and said counterelectrode, said method comprising:

• maintaining the substrate at a predetermined distance from said electrode surface, said predetermined distance being at least about 0.2 mm from said electrode surface, and wherein the heat reflected from said electrode to the substrate is absorbed by a layer disposed on said electrode surface.