Method of treating a microelectronic substrate using dilute TMAH

A method for treating a microelectronic substrate, comprising:

• receiving a microelectronic substrate into a process chamber, the microelectronic substrate comprising a layer, feature or structure of polysilicon;
• applying a treatment solution to the microelectronic substrate to etch the polysilicon, the treatment solution comprising a mixture of a dilution solution and tetramethylammonium hydroxide (TMAH) and having a first oxygen concentration of less than 1% by weight;
• prior to or during applying the treatment solution, exposing the treatment solution or an environment in the process chamber to a nitrogen-containing gas comprising a second oxygen concentration of less than 20% by weight and a nitrogen concentration of the nitrogen-containing gas greater than the second oxygen concentration, wherein the first and second oxygen concentrations are controlled to achieve a target etch selectivity of the polysilicon, or a target etch uniformity across the layer, feature or structure of polysilicon, or both by the treatment solution.