What Happens to Repeatable Low TCE Copper with Annealing

1. Introduction Since the Copper resistivity is second lowest next to the Silver, the Copper electrodeposits have been very intensively used in the wiring for the semiconductor and the printed circuit board (PCB). The Copper problem is the thermal coefficient of expansion(TCE). The TCE of Silicon is 2x10-6(1/K) and the TCE of Copper is 18x10-6(1/K). If the composite of the Silicon and the Copper warpage, protrusion or delamination occurs. This discussion is focused on the low TCE Copper with repeatable annealing. 2. Results 1) Figure 1 shows the TCE comparison with our repeatable low TCE Copper and the conventional Copper. X-axis is the expansion length and y-axis is the temperature. For the conventional Copper, the TCE is 18x10-6(1/K) and the expansion length is linear with the temperature. However, for our repeatable low TCE Copper, the TCE is 6x10-6(1/K) and 1/3 of the conventional Copper. The TCE of 6x10-6(1/K) repeats three times. This TCE of 6x10-6(1/K) starts after two times pre-annealing. 2) Also we have run 200 cycles of -40℃ to 200℃ heat cycle test and measured the TCE and the resistivity. These TCE and the resistivity have been measured after 50,100,150 and 200 cycles. The TCE up to 300℃ for 50, 100 and 150 cycles show constant value and the TCE is lower with 200 cycles. The resistivities of 50,100,150 and 200 cycles become even lower than as deposit of zero cycle. The repeatable low TCE mechanism will be discussed at the meeting. Reference V. Q. Dinh and K. Kondo, ECS J.Solid State Sci. Technol., 6, P566-P569 (2017) Figure 1