Low pressure chemical vapor deposited borosilicate glasses for materials integration applications.

摘要

This thesis work investigated the growth and characterization of borosilicate glasses (BSGs), (SiO₂)_1−x(B₂O ₃)_x, for materials integration applications. In particular, BSG layers deposited by low-pressure chemical vapor deposition (LPCVD) were used in wafer bonding and compliant substrate applications.; A reaction model for BSG film growth from tetraethylorthosilicate (TEOS) and trimethylborate (TMB) was developed that predicts the growth rate and composition of BSG films up to x = 0.70. The BSG reaction model includes a strongly adsorbed TEOS-derived intermediate that forms SiO₂ and a direct surface reaction of TMB, in O₂, to form B₂O ₃. The BSG film morphology, critical to wafer bonding, was found to have a root-mean-square roughness of ∼0.5 nm, however, the specific morphology depended on reactor conditions. The BSG film can be planarized by thermal annealing between 550–725°C in a waterfree environment.; Room temperature wafer bonding of GaAs to BSG/GaAs followed by thermal annealing and thermocompression bonding were investigated. For room temperature bonding, the surfaces were treated with a pre-bonding treatment of O ₂ plasma exposure and H₂O rinsing to make the surfaces hydrophilic. The chemical role of this pre-bonding treatment was investigated by Fourier transform infrared (FTIR) spectroscopy. The O₂ plasma sputter etched the BSG surface, resulting in the presentation of a fresh surface for bonding. The H₂O rinse added H₂O/OH groups, however, the selective removal of B₂O₃ was measured. The bonding chemistry of various GaAs-to-oxide/GaAs bonded samples was investigated using multiple internal transmission (MIT) FTIR, providing a detailed bond-chemistry model. The initial bond is formed from surface absorbed H₂O/OH species. After annealing at temperatures up to 600°C, a covalent bond between BSG and As(V)-O-related and Ga-O-related oxides is formed.; BSG layers were used to develop a compliant substrate, consisting of 10 nm of GaAs on a BSG layer, for lattice-mismatched epitaxial growth. A process of wafer bonding and aqueous-based etching was used to fabricate the compliant substrate. Lattice-mismatched In_xGa_1−xAs films grown on compliant substrates exhibit smoother surfaces and narrower strain distributions in the X-ray diffraction spectra than films grown on conventional substrates. The mechanism for compliant behavior is demonstrated to be a result of modified dislocation introduction compared to conventional substrates.