Low-energy (2-5 keV) argon damage in silicon

The damage caused by low-energy argon bombardment of silicon has been investigated by Rutherford back-scattering and transmission electron microscopy. At the doses required for sputter cleaning, gas bubbles are formed even at argon energies as low as 2 keV. The bubbles, and the argon they contain, cannot be annealed out below 1100 degrees C, although a significant amount of gas is trapped more weakly in other sites and is released at lower temperatures. The stability of the bubbles is explained in terms of the knock-in of oxygen from the native oxide during bombardment. The formation of bubbles cannot be avoided unless the angle of incidence of the argon is almost glancing.