Plasma process induced radiation effects in CMOS technology

Typical semiconductor processing plasma contains various energetic entities that may cause radiation damage to the CMOS devices and circuits exposed to the plasma. The most vulnerable parts of a CMOS circuit that are susceptible to radiation damage are gate dielectrics and field isolation dielectrics. The most notable radiation damage in these dielectrics includes a buildup of dielectric charge, an increase of interface traps (as well as border traps), and an increase of bulk neutral traps. In terms of MOS device properties, these radiation effects translate into a shift in the threshold voltage, a reduction in the transconductance, a decrease in the subthreshold slope, and a degradation of the reliability. Much of the radiation damage may be removed by a thermal anneal if sufficient thermal budget is allowed. A relatively low temperature RF plasma annealing process has been discussed, and the annealing mechanism has been described in terms of recombination-enhanced defect reactions. It is interesting to note that ostensibly the same plasma that causes radiation damage may be used to anneal out the damage by adjusting a few processing parameters.