Columnar grains and twins in high-purity sputter-deposited copper

Abstract

Columnar grains were normal to the substrate in thick, high-purity copper deposits made by high-rate (80–110 Å/sec) sputter deposition. The grains contained a high density of stacking faults and twin boundaries parallel to the substrate. The columnar grains for a deposit made at 6 °C, 80 Å/sec, and with a −75 V substrate to anode bias were uniformly about 700 Å in diameter, but a deposit made at 100 °C, 110 Å/sec, and with a −20 V bias had a few large grains with diameters up to 13 000 Å and many smaller grains with diameters of about 2500 Å. Deposits made at 100 °C did not recrystallize, but deposits made at −196 °C and at about 10 °C recrystallized at room temperature. Recrystallized regions had annealing twins that were 1000–10 000 Å across. The deposits had (111) crystallographic planes parallel to the substrate before recrystallization, but after recrystallization (100) planes were parallel to the substrate. Chemical analyses for impurity elements in the sputtering target material and a deposit showed four elements not detected in the target material were detectable in the deposit. Krypton gas pickup in the deposits during sputtering was estimated to be less than 5 ppm.