Impact of doping and silicon substrate resistivity on the blistering of atomic-layer-deposited aluminium oxide

• Published in: Applied surface science 2020-08, Vol.522, p.146400, Article 146400
• Main Authors: Ott, Jennifer, Pasanen, Toni P., Gädda, Akiko, Garín, Moisés, Rosta, Kawa, Vähänissi, Ville, Savin, Hele
• Format: Article
• Language: English
• Subjects: Aluminium oxide; Blistering; Doping; Silicon; Surface passivation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.146400

(left) Photograph of a high-resistivity n-type Si wafer coated with 50 nm of ALD-grown aluminium oxide, with clearly reduced blistering in the 2 × 2 cm2 areas implanted with boron. (right) Comparison of blister properties in areas with diffused emitter and surrounding areas. [Display omitted] •The impact of doping in silicon on blistering of Al2O3 thin films is investigated.•Diffusion and implantation of the silicon substrate significantly reduce blistering.•Blistering is affected even by doping during crystal growth.•Increasing substrate resistivity promotes fewer, but larger blisters. Aluminium oxide (Al2O3) thin films grown at low temperatures using atomic layer deposition (ALD) are known to often suffer from local delamination sites, referred to as “blisters”, after post-deposition annealing during device processing. In this work, we report our observation that doping of the silicon substrate has an effect on blister formation. The introduction of a highly doped layer by diffusion or implantation is found to significantly reduce blistering, compared to the non-doped regions in the immediate vicinity. Similar behavior is observed for both phosphorus and boron doping. Further investigation of this phenomenon using substrates with different resistivities reveals that even when introduced already during silicon crystal growth, doping affects the blistering of aluminium oxide films. Changes in several properties of silicon affected by doping, most importantly surface terminating groups, native oxide growth, and passivation of defects with hydrogen, are discussed as potential reasons behind the observed effect on blistering.