Patent ID: 8257602

Claim:
A method of etching a sample via an etching system having an etching gas source, a main chamber where etching of a sample occurs, a first expansion chamber, a second expansion chamber, a flow controller, means for connecting each expansion chamber to the flow controller and to the source of etching gas, and a pressure controller for setting a pressure of the etching gas in the main chamber to a setpoint pressure, the method comprising: (a) controlling the means for connecting to charge the first expansion chamber with a suitable amount of etching gas from the etching gas source to sustain a constant flow of etching gas to the main chamber, and once charged is isolated therefrom; (b) controlling the means for connecting to connect the charged first expansion chamber to the main chamber via the flow controller, whereupon the charge of etching gas in the first expansion chamber flows to the main chamber via the flow controller such that the pressure of etching gas inside the first expansion chamber decreases while the pressure in the main chamber is at the setpoint pressure; (c) while etching gas in the first expansion chamber is flowing to the main chamber via the flow controller, controlling the means for connecting such that the second expansion chamber is charged with a suitable amount of etching gas from the etching gas source to sustain a constant flow of etching gas to the main chamber, and once charged is isolated therefrom; (d) following step (c), controlling the means for connecting to isolate the first expansion chamber from the main chamber and to connect the second expansion chamber to the main chamber via the flow controller before a pressure of the etching gas in the first expansion chamber decreases below a level sufficient to sustain a constant flow of etching gas to the main chamber at the setpoint pressure; (e) following step (d), while etching gas in the second expansion chamber is flowing to the main chamber via the flow controller, controlling the means for connecting such that the first expansion chamber is charged with a suitable amount of etching gas from the etching gas source to sustain a constant flow of etching gas to the main chamber, and once charged is isolated therefrom; and (f) following step (e), controlling the means for connecting to isolate the second expansion chamber from the main chamber and to connect the first expansion chamber to the main chamber via the flow controller before a pressure of the etching gas in the second expansion chamber decreases below a level sufficient to sustain a constant flow of etching gas to the main chamber at the setpoint pressure.