Reduction of watermarks in HF treatments of semiconducting substrates

A process for reducing or suppressing the appearance of watermarks in a hydrophobic surface of a semiconductor substrate prepared as a base substrate for epitaxial growth, which process comprises:

• cleaning the hydrophobic surface of the semiconductor substrate with an aqueous solution containing hydrofluoric acid (HF) and hydrochloric acid (HCl), wherein the HF is present in the solution at a concentration in the range of 0.5% <[HF] by weight<49% and the HCl is present at a concentration in the range of 0.01% <[HCl] by weight<38% with the HCl present in the solution at a concentration by weight that is less than that of the HF;
• and
• final rinsing the cleaned hydrophobic surface of the semiconductor substrate with deionised water while subjecting the hydrophobic surface of the semiconductor substrate to megasonic waves for a time sufficient to reduce or suppress watermarks that could otherwise occur on the hydrophobic surface if the megasonic waves were not applied;
• wherein the megasonic waves are applied at a power in the range of at least 100 Watts and at most 1200 Watts, at a frequency of at least 1 kHz and at most 10 MHz and for a time in the range of at least 1 second and at most 5 minutes.