Effect of the SiO2 interlayer properties with solid-source hydrogenation on passivated contact performance and surface passivation

Abstract

We investigate how SiOx oxide interlayers prepared by different techniques (chemical, thermal) in combination with hydrogen released from an ALD Al2O3 source layer govern passivation in 1) passivated contacts based on doped poly-Si layers and tunneling SiO2, and 2) wafer surface passivation by Al2O3. Profiles of O and H in these structures with engineered, buried SiOx interlayers were measured by Time-of-Flight SIMS (TOF-SIMS) at nanometer resolution. Passivated contacts perform best with thermally oxidized SiOx, while chemical SiOx causes poly-Si film blistering and performance degradation. ALD Al2O3 acts as passivating H source, significantly improving B-doped and intrinsic poly-Si contacts for IBC cells. Fast-diffusing hydrogen from the Al2O3 source layer appears to penetrate Si wafer thickness, improving the passivation of structures at the opposite side. In contrast to the passivated contacts, chemical SiOx interlayer promotes wafer surface passivation by ALD Al2O3, while similarly thin thermal SiO2 suppresses passivation and built-in charge.