Pulsed chemical vapor deposition for crystalline aluminum nitride thin films and buffer layers on silicon and silicon carbide

Low temperature aluminum nitride (AlN) deposition has applications ranging from serving as a heat spreading material to serving as a buffer layer for III-V semiconductors on silicon or silicon carbide (SiC) for radio frequency, power, and microLED devices. While crystalline AlN is traditionally deposited at high temperature (>800 °C), in the present study AlN is deposited on Si(100), Si(111), and 4H-SiC substrates by two modest temperature processes using a metal precursor with high thermal stability, tris(dimethylamido) aluminum (III), and a highly reactive nitrogen source, anhydrous hydrazine. A 580 °C pulsed chemical vapor deposition (CVD) process is compared to a more complex 400 °C atomic layer annealing process, in which the same precursors are utilized with periodic ion bombardment to induce film crystallinity. Films deposited by both processes template preferential c-axis orientation in subsequently sputtered AlN on unheated substrates. Both templating techniques demonstrate equivalent enhancements in crystallinity of the sputtered AlN relative to a non-templated sputtered film by x-ray diffraction and transmission electron microscopy studies. On 4H-SiC substrates, a comparison of sputtering directly and templating with the 580 °C pulsed CVD process reveals epitaxial deposition by the 580 °C pulsed CVD process which extends into the low temperature sputtered AlN.