Surface investigations of the atomic layer growth mechanism in aluminum nitride thin film deposition using dimethylethylamine alane and ammonia.

摘要

Aluminum Nitride (AlN), a wide-bandgap semiconductor, has been shown to be an extremely versatile material in semiconductor applications. Our previous efforts in formulating a Metalorganic Chemical Vapor Deposition (MOCVD) processing strategy to deposit AN using Dimethylethylamine Alane (DMEAA; AlH3:N(CH3)2CH2CH3) and ammonia resulted in high quality film growth at low temperatures (∼600 K). Understanding the surface reactions involved is a key step in successfully optimizing a MOCVD process. In this research, we investigated the surface interactions between DMEAA and ammonia leading to the Atomic Layer Growth (ALG) mode on a Si(100) surface using a combination of surface analysis techniques, including Secondary-Ion Mass Spectrometry (SIMS), Temperature-Programmed SIMS (TPSIMS), X-ray Photoelectron Spectroscopy (XPS), and Temperature-Programmed Desorption (TPD).; The exposure of Si(100) to DMEAA at 310 K resulted in self-limiting adsorption of molecular DMEAA and Dimethylethylamine (DMEA). Based on the stoichiometric information from XPS, the molecularly adsorbed DMEA most likely originated from the exposure of a mixed DMEAA-DMEA gas phase rather than a dissociative adsorption process. The DMEAA molecule is susceptible to thermal decomposition, as the aminealane adduct configuration was no longer observed above 490 K. This can impose an upper temperature limit in developing a processing strategy.; The chemical interaction between ammonia and DMEAA resulted in a displacement of DMEA by ammonia. A new surface intermediate (AlHND2) was detected with both SIMS and XPS. This displacement mechanism was rationalized using Hard-Soft-Acid-Base (HSAB) theory. We were able to observe, in a step-by-step fashion, the atomic layer growth process by monitoring the C:N ratios using XPS. The resulting AlN film contained substantial hydrogen but the hydrogen content may be removed thermally. Atomic layer growth mechanism provides an effective means to grow high quality thin films by specific chemical interactions. Employing this approach, we have shown that the carbon contamination from the organic ligands may be controlled stringently.