Method of stripping a nitride layer from a wafer and wet etching apparatus using the same

A method of stripping a nitride layer from a semiconductor wafer using a wet etching apparatus comprising a process bath containing a stripping solution, a filter, an electrical in-line heater having at least two heating parts connected in parallel, and a circulating pump for circulating said stripping solution from said process bath through said filter to said in-line heater and back to said process bath, said method comprising the steps of:

• placing said wafer in a process bath containing a stripping solution;
• etching said nitride layer on said wafer with said stripping solution;
• filtering said stripping solution through said filter to remove nitride particles contained in said stripping solution, to produce a filtered stripping solution;
• heating said filtered stripping solution to a temperature sufficient to etch said nitride layer by branching said filtered stripping solution through said at least two parallel, connected heating parts to produce a heated stripping solution;
• and
• returning said heated stripping solution to said process bath.