Area-Selective Atomic Layer Deposition of SnS₂ Nanosheets for Applications of Back-End-of-Line-Compatible Transistors

Abstract

As semiconductor devices are miniaturized (to dimensions of nanometers), the accurate alignment of each layer on the desired location poses a challenge in the fabrication of multilayer-stacked devices. Area-selective deposition has attracted interest in resolving alignment issues in nanoelectronics. Herein, we demonstrate the area-selective atomic layer deposition (ALD) of SnS2, a promising two-dimensional channel material for the application of back-end-of-line (BEOL)-compatible transistors, on SiO2 (growth area) and Al2O3 (nongrowth area). We employed a super cycle comprising acetylacetone injection as an inhibitor, SnS ALD cycles, and H2S plasma for the area-selective deposition of SnS2. Although SnS ALD possesses good selectivity, the H2S plasma used for the transformation of SnS to SnS2 deteriorated the Al2O3 surface and resulted in nucleation in the nongrowth area. The acetylacetone injection in the super cycle was selectively adsorbed by Al2O3 and protected it from the H2S plasma. The synergistic effects of the selectivity of the SnS ALD process and protection of the Al2O3 surface exhibited excellent selectivity for SnS2. In the super cycle, the increase in the number of SnS cycles enhanced growth incubation on Al2O3 and induced the appearance of the SnS phase on SiO2 as the growth area. By optimizing the super-cycle conditions, ∼7 nm of selective SnS2 deposition was achieved on Al2O3 and SiO2. The proposed strategy will help enhance the area-selective deposition technology for two-dimensional semiconductors in BEOL-compatible transistors.

Two-dimensional materials for future information technology: status and prospects

“…Chen et al reported the direct synthesis of semiconducting PtSe2 layers at 450 • C [1016] and metallic PdSe2 layer at 300 • C [1017] on SOI to fabricate phototransistors, in which the top Si layer and the 2D layers as photoactive channel and the gate bias was applied to the bottom Si layer of the SOI. In addition, other 2D materials such as WSe2 [1018], SnS2 [1019], PdS2 [1020], PdSe2 [1021], and more have also achieved low-temperature growth compatible with BEOL through various methods. It is worth noting that besides the transfer and synthesis processes, other operations for integrating 2D materials with silicon also need to meet BEOL compatibility conditions.…”