Investigation of thermal flux to the substrate during sputter deposition of aluminum

The transient and steady state thermal flux at the substrate during the deposition of aluminum film in a direct current magnetron sputter system has been determined by measuring the resistance of a complementary metal–oxide–semiconductor (CMOS) sensor. The sensor is calibrated using ohmic self-heating before the plasma is switched on. The steady state thermal flux at the substrate was measured to vary from 9.6 to 46 mW/cm2 at a substrate-target distance of 10.8 cm depending on the magnetron power (75–300 W) and gas pressure. Plasma radiation and electron bombardment are noted to be the most significant sources of the thermal flux to the substrate, each contributing about 36% and 29%, respectively, of the total thermal flux at the substrate for a magnetron power of 200 W and gas pressure of 5 mTorr. Thermal radiation is also an important factor, along with kinetic energy and condensation energy. Total energy per deposited atom is calculated to be in the range of 28–52 eV depending on the magnetron power and gas pressure, and increases with pressure but decreases with magnetron power. The trend seems to suggest that at higher magnetron powers (>300 W for a 3 in. target), a pressure independent total energy per deposited atom may be obtained.