Hydrogen and processing damage in CMOS device reliability: defect passivation and depassivation during plasma exposures and subsequent annealing

Formation of aluminum nitride thin films as gate dielectrics on Si (100)

“…One example of this is the permeation of dielectrics by hydrogen during plasma exposure [12]. Such hydrogen permeation can increase [13] or decrease the dielectric defect density. The latter possibility is exploited in plasma-based hydrogenation of polysilicon [14].…”

Plasma processing damage in etching and deposition

“…One example of this is permeation of dielectrics and semiconductors by hydrogen during plasma exposures [4]. This hydrogen permeation can, in some cases, increase dielectric/semiconductor defect densities [5], while in other cases it can decrease them. The latter possibility is exploited in plasma-based hydrogenation of polysilicon [6].…”

“…If passivation occurs, it may be undone in another plasma-based step (because of current flow stressing) or thermal processing step. It may also be undone by stress during device operation [1,5]. n"*" polysilicon liO,…”

“…Inadvertent bonding disruption in dielectrics and semiconductors due to plasma particle and/or photon fluxes can occur during etching or deposition, as noted in Table L Such damage can cause gap states in semiconductors that affect lifetimes and band bending [1,4]; it can cause fixed charge and traps in dielectrics [1][2][3]5].…”

“…As noted in Table 2, the impact of permeation can depend very much on process flow and on layout. For example, inadvertent hydrogen permeation resulting in passivation of defects can be a problem if it causes the presence of damage to go unobserved [2], or if subsequent thermal or plasma processing can modify the state of this hydrogen, resulting in depassivation and even enhanced damage [5]. Layout can affect the state of this hydrogen because hydrogen-passivated defects can be reactivated by electrical stressing currents produced in subsequent processing or in device operation.…”