Patent ID: 7855150

Claim:
A method for anisotropically etching structures into a substrate positioned in an etching chamber, comprising: providing an etching mask on a silicon substrate positioned in the etching chamber; and providing the etching chamber at least intermittently with an etching gas and at least intermittently with a passivation gas; wherein the passivation gas is supplied to the etching chamber in cycles each having a time period between 0.05 second and 1 second; wherein the etching gas and the passivation gas are used alternately during separate etching steps and passivation steps that are controlled independently of one another, the passivation gas being supplied to the etching chamber substantially only during the passivation steps, and the etching gas being supplied to the etching chamber substantially only during the etching steps; and the duration of the passivation steps is set to be shorter than the duration of the etching steps by a factor of 10 to 30; wherein a passivation gas line is provided upstream from the etching chamber, a buffer tank is located along the passivation gas line upstream from the etching chamber, a passivation gas valve is located downstream from the buffer tank and upstream from the etching chamber, and an etching gas line is provided upstream from the etching chamber; wherein the passivation gas line and the etching gas line one of: a) connect directly into the etching chamber; and b) connect directly into a common feed line upstream from the etching chamber, wherein the common feed line feeds into the etching chamber; wherein all of the passivation gas supplied to the etching chamber passes through the passivation gas line and the buffer tank; and wherein during the etching steps, the buffer tank is filled with passivation gas, and during the passivation steps, the buffer tank is emptied and the passivation gas formerly in the buffer tank flows into the etching chamber.