I read the article write by B. Schwartz and H. Robbins with purpose to find the
best process to smooth the wafer suface.
  After few experiments  to my  surprise   I found out that this composition
(that isn't written in the article):
                                                 98% HNO3 ( 70%) and 2 % HF (
48.5%)
  gives a more smooth surface than the compositions in the article.

  I choose this composition because of it the slowly etching rate - 0.6 micron /
minute
  But the surface  smooth result is not enough  for me . I still  see the micro
rounds holes on the surface.

  Do you have any better proccess ? Thank you