Phase II year
2014
(last award dollars: 2017)
Phase II Amount
$1,740,068
This project targets the development of a commercially viable silicon-nitride (SiN) Atomic Layer Deposition (ALD) process for gallium nitride (GaN) Monolithic Microwave Integrated Circuits (MMICs) applications. In particular, this project will provide a higher quality substitution for commonly used PEVCD SiN passivation layers. These better passivation layers will enable the development and manufacturing of GaN MMICs with ground-breaking impact on performance, power efficiency, size and cost of many military systems, as well as commercial products. Previously, a large scale survey was used to evaluate multiple possible ALD processes and ALD process conditions. Following the selection of the most promising process, the focus of this project now shifts to process integration, reduced cost and the commercialization of SiN ALD equipment.
Benefit: GaN had its beginnings in Defense industry R&D funding and is being used or designed into many high power, wideband applications such as electronic warfare (EW), improvised explosive device (IED) jamming, communications and AESA radar. Due to their performance and energy efficiency advantages, GaN components are expected to capture a growing share of the RF and power components markets that are currently dominated by GaAs and SiC technologies. In particular, migration of military MMICs, CATV, satellite and wireless base stations to GaN is anticipated in the next decade. MMICs performance is currently limited by the relatively low, 0.4 MV/cm electric-field-strength of GaAs. Short Source-Drain separation best suits microwave amplifiers and switches. Therefore, GaAs based MMICs are limited to low voltage and power. In contrast, wider bandgap GaN can handle about 10x stronger electric fields. For example, 5 MV/cm (Wurtzite and Zinc Blende crystals). GaN can handle 5-10 times higher operation voltage and 10-20 times higher power densities. For MMICs, the order-of-magnitude higher field-strength enables both smaller transistors and higher operation voltage. For example, 2x smaller transistors and operation at 4x higher voltage. Smaller size transistors have smaller parasitic capacitance and related wider operating frequency bandwidth. Both wider bandwidth and higher operation voltage substantially boost the power efficiency to typically >60%, compared to the typical GaAs based MMICs efficiency of 20-30%. Likewise, higher operation voltage reduces the current per given power which is better suited to power efficiency characteristics of DC power supplies. These higher performance, reduced size and higher power efficiency characteristics could also benefit many commercial products such as base station wireless, power inverter systems, cable TV and satellite communication systems. There are also several applications in silicon based manufacturing. Those include transistor gate spacers, etch stop layers, Low-K liners, barrier layers of tunneling magnetoresistance junctions and trench isolation guard rings. The continuous scale down of semiconductor devices high temperature CVD SiN process is becoming a severe limitation with adverse impact on the quality of many different components. The industry is frantically working to reduce the temperature of CVD processes and ALD processes. However, so far there was very little progress toward a CVD solution and no progress towards an ALD solution. Ultimately, the industry is seeking a multi generation solution that will reduce the process temperature down to below 400 C and at the same time improve the conformality of the films. That spells SiN ALD.
Keywords: gallium nitride, GaAs, Silicon Nitride, GaN, ALD, SiN, HPA, MMIC
