Plasma processing method and plasma processing apparatus
Provided are a plasma processing method and a plasma processing apparatus which may form a protective film on the surface of an etching stop layer and suppress clogging of openings of holes when etching an oxide layer are provided. The plasma processing method forms a plurality of holes having different depths in multi-layered films that include an oxide layer, a plurality of etching stop layers made of tungsten, and a mask layer. The plasma processing method includes an etching process in which a processing gas is supplied to generate plasma such that etching is performed from the top surface of the oxide layer to the plurality of etching stop layers so as to form hole having different depths in the oxide layer. Here, the processing gas includes a fluorocarbon-based gas, a rare gas, oxygen, and nitrogen.
1. A plasma processing method comprising:
providing a plasma processing apparatus that includes a processing container which defines a processing space and a gas supply unit configured to supply a processing gas into the processing space;
supplying the processing gas including a fluorocarbon-based gas, a rare gas, an oxygen gas, and a nitrogen gas into the processing container to generate plasma; and
etching multi-layered films which include an oxide layer and a plurality of etching stop layers, the etching stop layers being made of tungsten and disposed below a top surface of the oxide layer in a laminating direction as well as at different positions in the laminating direction, from the top surface of the oxide layer to the plurality of etching stop layers so as to simultaneously form a plurality of holes having different depths in the oxide layer,
wherein each of a flow rate of the oxygen gas and a flow rate of the nitrogen gas is controlled to satisfy a condition of Y=−5X+b where X is the flow rate of the oxygen gas, Y is the flow rate of the nitrogen gas, and b is a flow rate between 300 sccm and 375 sccm.
2. The plasma processing method of claim 1 , wherein flow rates of the oxygen and the nitrogen are set in such a manner that the plurality of etching stop layers except the etching stop layer which is a bottom of the deepest hole are suppressed from being etched and openings of the plurality of holes are also suppressed from being clogged until the etching is performed from the top surface of the oxide layer to the surface of the etching stop layer which forms the bottom of the deepest hole.
3. The plasma processing method of claim 1 , wherein the numerical value b satisfies 325 sccm≦b≦350 sccm and the flow rate of the nitrogen Y is 50 sccm≦Y≦100 sccm.
4. The plasma processing method of claim 1 , wherein in the multi-layered films, the plurality of etching stop layers are disposed such that the depth of the deepest hole is twice or more than the depth of the shallowest hole.
5. The method of claim 1 , wherein the rare gas is an Ar gas.