Patent 7582220 was granted and assigned to Tokyo Electron on September, 2009 by the United States Patent and Trademark Office.
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.