Experimental test for elastic compliance during growth on glass-bonded compliant substrates

Abstract

Highly mismatched films (In 0.44 Ga 0.56 As, 3% mismatch͒ grown well beyond their critical thickness ͑to 3 m͒ on GaAs glass-bonded compliant substrates exhibit surfaces four times smoother and strain distributions twice as narrow as films grown simultaneously on conventional GaAs substrates. The compliant substrates consist of a thin ͑ϳ10 nm͒ GaAs template layer bonded via a borosilicate glass to a mechanical handle wafer. The improvement of highly mismatched films grown well beyond their critical thickness on compliant substrate structures is commonly modeled in terms of an elastic partitioning of strain from the film to the thin ͑ϳ10 nm͒ single-crystal template layer. The present study is a direct test for this mechanism of elastic compliance. A comparison is reported of the strain in 92 nm In 0.09 Ga 0.91 As films and 76 nm In 0.03 Ga 0.97 As films grown simultaneously on conventional GaAs substrates and the compliant substrates responsible for the improved structural quality of In 0.44 Ga 0.56 As films. Elastic partitioning of strain from the mismatched film to the 10 nm template layer prior to the onset of misfit dislocations is not observed for films grown on these glass-bonded compliant substrates. © 2000 American Institute of Physics. ͓S0003-6951͑00͒03318-0͔Modification of the relaxation behavior in latticemismatched films due to growth on a glass-bonded compliant substrate is well documented. 1,3-5 Compliant substrates consist of a thin ͑ϳ10 nm͒ ''template'' layer bonded to a thicker ''handle'' wafer by means of an intermediary glass layer in these studies. Transmission electron microscopy observations have demonstrated a reduced dislocation density of films grown to many times their Matthews-Blakeslee 2 critical thickness h c on glass-bonded compliant substrates. [3][4][5] High-resolution x-ray diffraction ͑HRXD͒ measurements and atomic-force microscopy characterization were carried out on thick ͑3 m͒, highly mismatched ͑3%͒ In 0.45 Ga 0.55 As films grown simultaneously on conventional and the compliant substrates that are the focus of the present study. These measurements demonstrated a ϳ2ϫ reduction in the breadth of the film's strain distribution as determined by triplecrystal diffraction peak widths that decreased from 270Љ on a conventional substrate to 155Љ on the glass-bonded substrate. In addition, there was a ϳ4ϫ decrease in the rms roughness of the films from 42 nm rms on a conventional substrate to 10 nm rms on the glass-bonded substrate. 1 These improvements in the structural quality of the thick, highly mismatched, relaxed films on the glass-bonded substrates occurred for a range in glass viscosity of over five orders of magnitude.A specific mechanism responsible for the changes in relaxation behavior of a mismatched film grown on a glassbonded compliant substrate is uncertain at present and could be specific to the materials system. The present work is a test for a specific mechanism of compliance in substrates fabricated using a materials system that has been shown to modify the relaxati...

Kinetics of strain relaxation in semiconductor films grown on borosilicate glass-bonded substrates

“…The relative thickness of the film and template layers, in conjunction with the mismatch strain, e 0 , determines the residual strain, e x (0,t), in the elastic overlayer. If the thin template layer were mechanically decoupled from the handle wafer, the mismatch strain would partition between the template and film (assuming that the elastic modulii of the film and template are identical) according to the expression: 6,7 e e feq f…”

“…Previous publications have demonstrated that if this thin template layer is mechanically decoupled from the handle wafer such that it can move in the plane of the bonded interface, strain can be partitioned from the film to the template layer before the onset of plastic deformation in the growing film. 6,7 Kinetics of Strain Relaxation in Semiconductor Films Grown on Borosilicate Glass-Bonded Substrates Changes in the strain relaxation of semiconductor films due to growth on a thin epitaxial template bonded via a borosilicate glass to a mechanical handle wafer have been observed. A kinetic analysis of the mechanical decoupling between the film/template heterostructure and the handle wafer is developed in order to estimate and evaluate the contribution of glass viscous deformation to the observed strain relaxation.…”

Process requirements for continued scaling of CMOS—the need and prospects for atomic-level manipulation

“…While it is recognized that a significant reduction in the misfit dislocation density threading into heteroepitaxially grown films has been achieved for a wide range of materials systems, the mechanism for long-range accommodation of the mismatch into the substrate layer is not well understood, and there is considerable dispute about it [85,86]. Much of the work to date has been limited to TEM observations confirming limited misfit dislocation densities, but full characterization of the degree of relaxation in the heteroepitaxially grown layers is frequently lacking.…”

Chemical investigations of GaAs wafer bonded interfaces

“…1 However, GaAs bonded to oxide layers is also being investigated for the integration of GaAs and Si or for the development of structures such as glass-bonded compliant substrates. [2][3][4] For these applications, the native or thermally grown oxide on GaAs is not useful. As a result, oxidebonding media are formed by a variety of other deposition techniques.…”