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.
Highlights
Aluminum nitride (AlN) is a widely used semiconductor material in several electronic devices[1] because of its direct wide band gap of 6.2 eV.[2]
A high-temperature thermal atomic layer deposition (ALD)-like chemical vapor deposition (CVD) approach with time-resolved precursor supply for AlN was explored by adding an extra pulse of H2, N2, or Ar between the TMA and NH3 pulses to investigate if that could change the surface chemistry and lower the carbon content in the film
The surface chemistry and the role of the extra pulse between TMA and NH3 were investigated with quantum chemical and kinetic modeling
Summary
Aluminum nitride (AlN) is a widely used semiconductor material in several electronic devices[1] because of its direct wide band gap of 6.2 eV.[2] A conventional method for depositing epitaxial films of AlN is chemical vapor deposition (CVD) using trimethylaluminum (TMA), Al2(CH3)[6], and ammonia, NH3, at temperatures, typically, above 1000 °C.3. An alternative low-temperature deposition route is atomic layer deposition (ALD), which is a time-resolved form of CVD where the Al and N precursors are pulsed into the deposition chamber sequentially, separated by inert gas pulses This gas pulsing makes the process solely depend on surface chemical reactions and omits gas-phase chemical reactions, which typically need high temperatures. Plasma processes can lead to crystalline and conformal AlN films at temperatures 375 °C is needed.[5,6]
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