Patent attributes
In an etching method for etching an etching target film formed on a substrate placed inside an airtight processing chamber 104 by inducing a processing gas into the processing chamber 104, the processing gas contains CF4, N2 and Ar and the etching target film is constituted of an upper organic polysiloxane film and a lower inorganic SiO2 film. The flow rate ratio of CF4 and N2 in the processing gas is essentially set within a range of 1≦(N2 flow rate/CF4 flow rate)≦4. If (N2 flow rate/CF4 flow rate) is less than 1, an etching stop occurs and, as a result, deep etching is not achieved. If, on the other hand, (N2 flow rate/CF4 flow rate) is larger than 4, bowing tends to occur and, thus, a good etching shape is not achieved. Accordingly, the flow rate ratio of CF4 and N2 in the processing gas should be set essentially within a range of 1≦(N2 flow rate/CF4 flow rate)≦4, to ensure that improvements in both the selection ratio and the etching shape are achieved.
