Tokyo Electron ALD of AlN Thin Films Report Unprecedented Uniformity on Large Batch 200 mm Tool

In the rapidly evolving world of semiconductor technology, achieving high uniformity in thin films is important for enhancing production yield and device performance. In a study led by Partha Mukhopadhyay and his team at Tokzo Electron has made significant strides in this domain, using ALD of aluminum nitride (AlN) thin films on a 200 mm large batch furnace platform. AlN is particularly relevant for gallium nitride (GaN)-based power industry, where AlN's wide bandgap, high dielectric constant, and superior thermal conductivity make it an ideal choice for various applications, including UV LEDs, transistors, and micro-electromechanical systems.

The study's focus lies in its ability to maintain extraordinary uniformity across large batches of 200 mm wafers, achieving a thickness variation of less than 0.5 Å. This level of uniformity was obtained by optimizing the ALD process in a reactor capable of handling over 100 wafers, marking a significant achievement in high-volume production environments. The research examined the effects of deposition temperatures, film thicknesses, and different substrate types, including Si, quartz, and GaN/Si(111), on the material and optical properties of the AlN films.

One of the key findings was the identification of an optimal narrow temperature window between 300°C and 350°C for the deposition process, with 350°C being the sweet spot. The study also delved into the nuanced challenges of nucleation on different substrates, revealing that substrate-inhibited growth and a non-linear deposition rate are pivotal factors to consider. This understanding is crucial for maintaining uniformity in extremely thin films, which are sensitive to the underlying substrate's crystal orientation.

From a compositional standpoint, the development showcased the high purity of the AlN films, with negligible carbon and oxygen contamination. This purity is essential for the semiconductor industry, particularly for applications where chemical stability is critical. The study's rigorous material analysis, which included techniques like XPS and TEM, provided in-depth insights into the AlN films' structural and compositional integrity.

Optically, the AlN films demonstrated a bandgap of 5.8 eV, a key attribute for their use in optoelectronic applications. The research also highlighted the refractive index's dependence on film thickness and deposition temperature, offering valuable data for the design and optimization of optical devices.

In summary, this study represents a significant progress in ALD of AlN thin films, combining high throughput with exceptional film uniformity and quality. 

Source: Nucleation of highly uniform AlN thin films by high volume batch ALD on 200 mm platform | Journal of Vacuum Science & Technology A | AIP Publishing