In one aspect, a highly scalable diffusion-couple apparatus includes a transfer chamber configured to load a wafer into a process chamber. The process chamber is configured to receive the wafer substrate from the transfer chamber. The process chamber comprises a chamber for growth of a diffusion material on the wafer. A heatable bottom substrate disk includes a first heating mechanism. The heatable bottom substrate disk is fixed and heatable to a specified temperature. The wafer is placed on the heatable bottom substrate disk. A heatable top substrate disk comprising a second heating mechanism. The heatable top substrate disk is configured to move up and down along an x axis and an x prime axis to apply a mechanical pressure to the wafer on the heatable bottom substrate disk. While the heatable top substrate disk applies the mechanical pressure a chamber pressure is maintained at a specified low value. The first heating mechanism and the second heating mechanism can be independently tuned to any value in the working range.