Low-temperature LPCVD of Si nanocrystals from disilane and trisilane (Silcore®) embedded in ALD-alumina for non-volatile memory devices

Non-volatile memory devices are realized using CVD and ALD of all active layers in a cluster tool. The floating gate consists of silicon nanocrystals. A high nanocrystal density was obtained through an enhanced nucleation rate by using disilane (Si2H6) as well as trisilane (Si3H8, known as Silcore®) as precursors for low-pressure chemical vapor deposition (instead of silane). The deposition temperature was 300–325 °C and the deposition pressure ranged between 0.1 and 10 mbar. To prevent oxidation of the nanocrystals, they were encapsulated directly after deposition with a 10-nm thick ALD-grown Al2O3 layer (blocking oxide). The deposition of Si-nanocrystals as a function of substrate temperature, precursor flow rate and total gas pressure was explored. Appreciable retention and endurance were measured on realized Al/TiN/Al2O3/Si-nanocrystal/SiO2/ Si(100) floating-gate capacitor structures.