Reduction of Carbon Impurities in Aluminum Nitride from Time-Resolved Chemical Vapor Deposition Using Trimethylaluminum

Abstract

Aluminum nitride (AlN) is a semiconductor with a wide range of applications from light-emitting diodes to high-frequency transistors. Electronic grade AlN is routinely deposited at 1000 °C by chemical vapor deposition (CVD) using trimethylaluminum (TMA) and NH3, while low-temperature CVD routes to high-quality AlN are scarce and suffer from high levels of carbon impurities in the film. We report on an atomic layer deposition-like CVD approach with time-resolved precursor supply where readsorption of methyl groups from the AlN surface is suppressed by the addition of an extra pulse, H2, N2, or Ar, between the TMA and NH3 pulses. The suppressed readsorption allowed deposition of AlN films with a carbon content of 1 at. % at 480 °C. Kinetic and quantum-chemical modeling suggests that the extra pulse between TMA and NH3 prevents readsorption of desorbing methyl groups terminating the AlN surface after the TMA pulse.

Amorphous AlN films grown by ALD from trimethylaluminum and monomethylhydrazine

“…Crystallinity generally increases with the deposition temperature, however according to the literature most of the AlN films grown both at relatively low and high temperatures are crystalline. [18][19][20][21][22][23][24][25] This fact indicates that the major contributing factor leading to a decrease in the crystallinity is apparently not the deposition temperature but the chemical structure of MMH. Namely, the suppression in crystallinity is likely resulting from the presence of methyl groups in the MMH molecules, which upon reaction at the surface occupy more space than NH 3 or N 2 H 4 , thereby disturbing the order and suppressing the crystallite growth.…”

“…Amorphous AlN films are of particular interest due to their improved mechanical, electrical and optical properties compared to those of the crystalline phase of AlN. [14][15][16][17] However, most AlN films grown by ALD are of crystalline nature [18][19][20][21][22][23][24][25] hence obtaining amorphous AlN films by ALD is an actual problem. AlCl 3 with NH 3 is a common precursor combination that has often been used for depositing AlN.…”

Surface ligand removal in atomic layer deposition of GaN using triethylgallium

“…This made the ALD process into an ABC-type pulsed ALD process with TEG as A-pulse, the additional gas as the B-pulse and the NH 3 /Ar plasma as C-pulse, similar to a previous study on ALD of aluminum nitride. 10 For each set of experiments, the A-pulse was 0.3 s TEG exposure and the C-pulse was a 30 s NH 3 plasma exposure using a mixture of 50 SCCM NH 3 and 100 SCCM Ar with 2800 W plasma power. The N 2 purge was 10 s after the TEG and 6 s after the NH 3 plasma.…”

Atomic Layer Deposition of AlN on Graphene

“…[ 23 ] ALD of AlN has been reported using trimethylaluminum (Al(CH 3 ) 3 ) (TMA) and NH 3 in a thermal process or N 2 or NH 3 plasmas. [ 24,25 ] MOCVD of 2D AlN and the effect of hydrogenation have been reported using TMA and NH 3 on three‐layer graphene and Si substrates. [ 8 ]…”