Research on increasing silicon etch rate in deep wet etching with tetramethyl ammonium hydroxide etchant

Abstract

The etching characteristics of Si (1 0 0) in silicon deep wet etching with tetramethyl ammonium hydroxide solution, containing silicic acid and ammonium persulfate, were studied in this article. The phenomena associated with the addition of ammonium persulfate at intervals in tetramethyl ammonium hydroxide solution were analyzed, and the mechanism of interplay between ammonium persulfate and silicic acid for increasing etch rate was proposed. The influence of these phenomena on the etch rate and roughness of Si (1 0 0) was discussed. The addition of ammonium persulfate at a periodic interval of time to a tetramethyl ammonium hydroxide solution, especially at the temperature of 80 °C, resulted in remarkable ascending of silicon etch rate. The etch rate of Si (1 0 0) in tetramethyl ammonium hydroxide solution with adding ammonium persulfate at intervals was superior to the etch rate in tetramethyl ammonium hydroxide solution without adding ammonium persulfate at intervals. The highest etch rate of Si (1 0 0) (0.83 µm/min), calculated with the help of profiler, was achieved after etching in tetramethyl ammonium hydroxide solution with adding ammonium persulfate at an interval of 120 min. This method appears to be a good candidate in applications where high and stable etch rate is required in long-time etching.