Infrared study of Si surfaces and buried interfaces

Abstract

Multiple internal reflection and transmission IR spectra of hydrophobic and hydrophilic Si wafers, Si wafers with thermally grown SiO 2 layers, and Si wafers bonded at high and room temperature were investigated. It was found that the surface of the as-prepared hydrophobic wafer is terminated by hydrogen and water molecules, while the IR spectra of hydrophilic wafer demonstrate only the presence of water molecules at the surface. IR spectra of Si wafers covered by a thermally grown SiO 2 layer exhibit a number of the strong absorption bands assigned to combinational phonon bands in SiO 2 . The wafer bonding leads to the appearance of siloxane and hydroxyl groups at the buried interface whose absorption bands were observed in IR spectra. A rearrangement of atoms at the buried interface takes place after annealing of Si bonded wafers. IR spectra of room temperature bonds show a large number of water molecules and presence of the hydrogen in the oxide layer at the interface.

Chemical investigations of GaAs wafer bonded interfaces

“…Previous reports indicate that these groups are present during the formation of hydrophilic Si-to-Si and Si-to-SiO 2 /Si bonds. [8][9][10] Table I is a compilation of the integrated intensities for this spectral region for all samples as well as the measured room temperature bond strength, as measured by the blade insertion test. 25 The values in the table show that the oxide-bonded samples have a larger concentration of H 2 O/OH groups than the GaAs-to-GaAs bonded samples.…”

“…7 The bonding chemistry of hydrophilic Si wafers as well as Si-to-SiO 2 /Si has been well studied by infrared spectroscopy. [8][9][10] Room temperature bonding of hydrophilic Si and SiO 2 layers has been shown to be a result of surface absorbed H 2 O/OH groups. [8][9][10] During thermal annealing, these interfacial species react and are removed from the bonded interface as the bond strengthens.…”

“…[8][9][10] Room temperature bonding of hydrophilic Si and SiO 2 layers has been shown to be a result of surface absorbed H 2 O/OH groups. [8][9][10] During thermal annealing, these interfacial species react and are removed from the bonded interface as the bond strengthens. The chemical pathway for the evolution of the H and O species has been elucidated in great detail and follows a well accepted mechanism for the Si materials system.…”

“…The chemical pathway for the evolution of the H and O species has been elucidated in great detail and follows a well accepted mechanism for the Si materials system. [8][9][10] The chemistry of GaAs bonded to oxide layers, however, has not been studied. In the present investigation, the bonding chemistry of GaAs to SiO 2 and GaAs to (SiO 2 ) 0.7 (B 2 O 3 ) 0.3 was investigated using infrared spectroscopy.…”

Characterization of low-temperature wafer bonding by infrared spectroscopy

“…Recently, significant progress has been achieved in understanding and optimizing Si-Si bonding processes, especially at high temperatures. [2][3][4][5][6][7][8] The variety of chemical pretreatments used leads to different bond strengths and causes changes in the IR response of the bonds due to absorption of IR light by chemical species at the buried interfaces. Characterization and quality control of lowtemperature bonds are of great importance for silicon-oninsulator-related microelectronic devices, sensors, and actuators.…”