Stress measurements of Pt/Ti/InP and Pt/Ti/SiO2/InP systems: I n s i t u measurements through sintering and after rapid thermal processing

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Abstract
The stresses induced in an evaporated Pt(75 nm)/Ti(50 nm) bilayer metallization scheme on InP and SiO2 (300 nm)/InP substrates, as well as the stress in a SiO2 layer (300 nm) on an InP substrate, were measured in situ during sintering at temperatures of 25 to 500 °C and after rapid thermal processing (RTP) at temperatures of 400, 450, and 500 °C for 30 s. The as‐deposited highly tensile Pt/Ti bilayer structure on InP (5×109 dyn cm−2) was found to be stress‐free when heated to 400 °C and to have relatively low tensile stress after cooling back to room temperature. The as‐deposited Pt/Ti/SiO2 structure on InP was found to be only moderately tensile stressed (3×109 dyn cm−2) and became more tensile as a result of heating to 500 °C (5×109 dyn cm−2). The high tensile stress was preserved even after cooling back to room temperature. This is mostly due to the tendency of the plasma‐enhanced chemical vapor deposited (PECVD) SiO2 layer to undergo densification and switch its as‐deposited compressive stress (−2.5×109 dyn cm−2) to tensile (2×109 dyn cm−2) when heated to 500 °C. The measured stresses after rapid thermal processing (RTP) revealed no observable difference from the in situ measured stresses. This suggests a negligible influence of the speed of heating and cooling through the RTP on the overall stresses induced in the thin layers. The previously unknown coefficient of thermal expansion and the biaxial elastic moduli of the PECVD SiO2 and the evaporated Ti and Pt thin films were determined by in situ stress measurements of the above‐mentioned structure as well as systems composed of the same thin layers deposited on Si, GaAs, GaP, and InAs substrates.