Atomic‐Layer‐Deposited Al2O3 as Effective Barrier against the Diffusion of Hydrogen from SiNx:H Layers into Crystalline Silicon during Rapid Thermal Annealing. Issue 12 (2nd October 2020)

• Record Type: Journal Article
• Authors: Helmich, Lailah; Walter, Dominic C.; Bredemeier, Dennis; Schmidt, Jan
• Is Part Of: Physica status solidi. Volume 14:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-10-02
• Subjects: aluminum oxide -- defects -- diffusion -- hydrogen -- silicon; Solid state physics -- Periodicals; 530.4105
• DOI: 10.1002/pssr.202000367
• Languages: English
• ISSNs: 1862-6254

Abstract

Abstract : Stacks of hydrogen‐lean aluminum oxide, deposited via plasma‐assisted atomic‐layer‐deposition, and hydrogen‐rich plasma‐enhanced chemical vapor‐deposited silicon nitride (SiN x ) are applied to boron‐doped float‐zone silicon wafers. A rapid thermal annealing (RTA) step is performed in an infrared conveyor‐belt furnace at different set‐peak temperatures. The hydrogen content diffused into the crystalline silicon during the RTA step is quantified by measurements of the silicon resistivity increase due to hydrogen passivation of boron dopant atoms. These experiments indicate that there exists a temperature‐dependent maximum in the introduced hydrogen content. The exact position of this maximum depends on the composition of the SiN x layer. The highest total hydrogen content, exceeding 10 15 cm −3, is introduced into the silicon bulk from silicon‐rich SiN x layers with a refractive index of 2.3 (at λ = 633 nm) at an RTA peak temperature of 800 °C, omitting the Al2 O3 interlayer. Adding an Al2 O3 interlayer with a thickness of 20 nm reduces the hydrogen content by a factor of four, demonstrating that Al2 O3 acts as a highly effective hydrogen diffusion barrier. Measuring the hydrogen content in the silicon bulk as a function of Al2 O3 thickness at different RTA peak temperatures provides the hydrogen diffusion length in Al2 O3 as a function of measured temperature. Abstract : This article shows that atomic‐layer‐deposited Al2 O3 (ALD‐Al2 O3 ) layers are effective diffusion barriers against in‐diffusion of hydrogen from a hydrogen‐rich plasma‐enhanced chemical vapor deposited SiN x :H (PECVD‐SiN x :H) source layer into the bulk of crystalline silicon during a high‐temperature rapid thermal annealing (RTA) step. It is demonstrated that only a few nanometer thick layer is required for an effective suppression of hydrogen in‐diffusion.