Quasi-atomic layer etching of silicon nitride

Abstract

Atomic layer etching (ALE) is a promising technique that can solve the challenges associated with continuous or pulsed plasma processes—trade-offs between selectivity, profile, and aspect ratio dependent etching. Compared to silicon, oxide, and other materials, atomic layer etching of silicon nitride has not been extensively reported. In this paper, the authors demonstrate the self-limited etching of silicon nitride in a commercial plasma etch chamber. The process discussed in this paper consists of two sequential steps—surface modification in hydrogen plasma followed by the removal of modified layers in fluorinated plasma. In addition to the ALE characteristics, the authors also demonstrate that the process is anisotropic and the selectivity to oxide is >100. Although the saturated etch rate of one monolayer per cycle could not be attained, self-limited etching of silicon nitride still enables us to incorporate the benefits of atomic layer etching such as an absence of isodense bias and an extremely high selectivity to oxide into practical etch applications.

Atomic layer etching of gallium nitride (0001)

“…In order to confirm ALE, we performed a synergy test, 4,24 with the initial ALE parameters shown in Fig. 1.…”

Utilizing surface modification in plasma‐enhanced cyclic etching of tantalum nitride to surpass lithographic limits

“…Sub‐surface modification of films such as Si 3 N 4 and indium‐doped tin oxide (ITO) by low atomic weight ions such as H + has been discussed in literature . This modification typically occurs in the absence of pronounced physical sputtering and drastically affects subsequent etch behavior of the film by chemical or physical processes.…”

“…Overall, ALE processes offer a significantly higher degree of tunability over traditional continuous‐wave (CW) plasma etching, due to the fact that parameters such as gas flows, pressure, and bias power can be adjusted on a step‐specific basis rather than as a global setting for the length of the process. ALE has been studied for a variety of blanket films ranging from semiconductors to dielectrics to metals, however, the number of papers in the literature that have discussed its applications to patterned profiles is significantly fewer …”

Plasma etch challenges for next-generation semiconductor manufacturing

“…In one recent study, Sherpa and co-workers have developed a novel all-dry process solution for the precision etching of silicon nitride. 6 The new frontier of semiconductor device fabrication will rely on collaboration between the computational and experimental communities to facilitate our understanding of the fundamental material properties and interactions at the atomic/near-atomic scale. This approach will enable the formation of ever-decreasing device dimensions with high fidelity and electrical reliability.…”