IN-SITU ANALYSIS OF PARTICLE CONTAMINATION IN MAGNETRON SPUTTERING PROCESSES

Defects caused by particulate contamination are an important concern i n the fabrication of thin film products. Often, magnetron sputtering p rocesses are used for this purpose. Particle contamination can cause e lectrical shorting, pin holes, problems with photolithography, adhesio n failure, as well as visual and cosmetic defects. Particle contaminat ion generated during thin film processing can be detected using laser light scattering, a powerful diagnostic technique that provides real-t ime, in situ imaging of particles > 0.3 mu m in diameter. Using this t echnique, the causes, sources and influences on particles in plasma an d non-plasma processes may be independently evaluated and corrected. S everal studies employing laser light scattering have demonstrated both homogeneous and heterogeneous causes of particle contamination. In th is paper, we demonstrate that the mechanisms for particle generation, transport and trapping during magnetron sputter deposition are differe nt from the mechanisms reported in previously studied plasma etch proc esses. During magnetron sputter deposition, one source of particle con tamination is linked to portions of the sputtering target surface expo sed to weaker plasma density. In this region, film redeposition is fol lowed by filament or nodule growth and enhanced trapping that increase s filament growth. Eventually, the filaments effectively 'short-circui t' the sheath, causing high currents to flow through these features. T his, in turn, causes heating failure of the filament fracturing and ej ecting the filaments into the plasma and onto the substrate. Evidence of this effect has been observed in semiconductor (IC) fabrication and storage disk manufacturing. Discovery of this mechanism in both techn ologies suggests that this mechanism may be universal to many sputteri ng processes. (C) 1998 Elsevier Science S.A.