No abstract

No abstract

The bonding chemistry of various GaAs-to-oxide/GaAs bonded samples was investigated using multiple internal transmission Fourier transform infrared spectroscopy for thermally annealed and thermocompression annealed samples. The oxides used in these investigations included a native GaAs oxide as well as two compositions of borosilicate glass ͑BSG͒ deposited by low-pressure chemical vapor deposition ͑LPCVD͒. For the thermally annealed samples, the hydrogen-bonded H 2 O/OH groups on the hydrophilic surface form a room temperature bond without the application of pressure. Chemical changes at the wafer-bonded interface occur in two temperature regions. For anneals between 200 and 400°C for 1 h in N 2 , the H 2 O/OH groups react and evolve H that becomes absorbed within the oxide. The LPCVD BSG oxide was chemically unaltered during anneals in this temperature range, however, the GaAs native oxide underwent chemical modification. Initially, the GaAs oxide consisted of As͑III͒-O and Ga-O related oxides. The As͑III͒-O oxides react to form free As and Ga-O during annealing between 200 and 400°C. For anneals between 500 and 600°C, the reaction of H 2 O/OH groups continue and the H becomes infrared inactive, most likely forming H 2 voids at the bonded interface. In addition, As͑V͒-O related oxides were observed during thermal annealing in this temperature range. No detectable chemical changes in the BSG were observed over the temperature range investigated. Samples that were annealed under an estimated 1-10 MPa of pressure had similar chemical changes to thermally annealed samples.

No abstract

In 0.44 Ga 0.56 As ͑3% mismatch͒ films 3 m thick were grown simultaneously on a conventional GaAs substrate, glass-bonded GaAs compliant substrates employing glasses of different viscosity, and a twist-bonded GaAs compliant substrate. High-resolution triple-crystal x-ray diffraction measurements of the breadth of the strain distribution in the films and atomic force microscopy measurements of the film's surface morphology were performed. The films grown on the glass-bonded compliant substrates exhibited a strain distribution whose breadth was narrowed by almost a factor of 2 and a surface roughness that decreased by a factor of 4 compared to the film simultaneously grown on the conventional substrate. These improvements in the film's structural quality were observed to be independent of the viscosity of the glass-bonding media over the range of viscosity investigated and were not observed to occur for the film grown on the twist-bonded substrate. © 1999 American Institute of Physics. ͓S0003-6951͑99͒01637-X͔ Limits on the structural quality of an epitaxial film which is lattice mismatched to the substrate precludes many potential device applications of heteroepitaxial semiconductor structures. Thin mismatched films retain a pseudomorphic strain so as to match the lattice constant of the much thicker substrate in the plane of the interface. Relaxation of a mismatched film grown beyond some critical thickness, 1 h c , which decreases with increasing mismatch, occurs at the expense of the film's structural quality. The film is eventually fully relaxed to its bulk lattice constant as it is grown beyond h c through the generation of an increasing number of misfit dislocations at the film/substrate interface and the subsequent propagation of threading dislocations into the film. 2 The concept of a compliant substrate has been proposed as a method for modifying the relaxation behavior of the heterostructure. 3 An ideal compliant substrate consists of a thin ''template'' layer mechanically decoupled from a thicker ''handle'' wafer. Calculations 3-6 of the strain partitioning in such a system predict enhanced relaxation without structural degradation of a mismatched film grown to a thickness well beyond the conventional h c on a template whose thickness is less than or approximately equal to h c .Experimentally realized compliant substrates have not had template layers that are completely decoupled from the handle wafer. Two approaches to fabricating macroscopic compliant substrates have predominated. The first utilized a metal 7 or glass 8-11 media to join the template and handle. The second approach employed twist-bonded ͑TB͒ substrates, 12,13 in which the template was directly bonded to the handle with an intentional azimuthal angular misorientation . The exact influence of the critical template/handle interface on film relaxation is uncertain at present. In glassbonded substrates, the ability of the glass to flow under a shear strain has been proposed as a means to allow strain relaxation. 9,14 This mechanism depends ...