High-quality SGOI by annealing near the alloy melting point

#The present invention relates to a method of fabricating a semiconductor substrate material, and more particularly to a method of fabricating a low-defect, substantially relaxed SiGe-on-insulator (SGOI) substrate material. In one embodiment, a method is provided that can form a low-defect, substantially relaxed SGOI substrate in which surface pitting and crosshatching have been substantially reduced. The low-defect, substantially relaxed SiGe-on-insulator substrate material of the present invention can be used as a lattice mismatched template for creating a strained Si layer thereon by subsequent Si epitaxial overgrowth. Such a substrate material is desired for the enhanced charge carrier transport properties within a strained Si layer and is a candidate for future high performance complementary metal oxide semiconductor (CMOS) applications. The present invention is also directed to a SiGe-on-insulator substrate material as well as structures which include at least the substrate material.

#In the semiconductor industry, there has recently been a high-level of activity using strained Si-based heterostructures to achieve high mobility structures for CMOS applications. Traditionally, the prior art method to implement this has been to grow strained Si layers on thick (on the order of from about 1 to about 5 micrometers) relaxed SiGe buffer layers.

#Despite the high channel electron mobilities reported for prior art heterostructures, the use of thick SiGe buffer layers has several noticeable disadvantages associated therewith. First, thick SiGe buffer layers are not typically easy to integrate with existing Si-based CMOS technology. Second, the defect densities, including threading dislocations (TDs) and misfit dislocations, are from about 105 to about 108 defects/cm2 which are still too high for realistic VSLI (very large scale integration) applications. Thirdly, the nature of the prior art structure precludes selective growth of the SiGe buffer layer so that circuits employing devices with strained Si, unstrained Si and SiGe materials are difficult, and in some instances, nearly impossible to integrate.

#FIGS. 1A-1E are pictorial representations (through cross-sectional views) showing the basic processing steps that are employed in the present invention in fabricating a thin, high-quality, substantially relaxed SiGe-on-insulator substrate material wherein the initial substrate includes an unpatterned diffusion barrier region.

#FIGS. 2A-E are pictorial representations (through cross-sectional views) showing the basic processing steps that are employed in an alternative embodiment of the present invention in fabricating a thin, high-quality, substantially relaxed SiGe-on-insulator substrate material wherein the initial substrate includes a patterned diffusion barrier region.

#FIGS. 3A-3B are pictorial representations (through cross-sectional views) showing an alternative embodiment of the present invention wherein a Si cap layer is formed atop a Ge or SiGe layer which is formed on an unpatterned (3A) or patterned (3B) substrate.

#The present invention, which provides a method of fabricating thin, high-quality, substantially relaxed SiGe-on-insulator substrate materials which can then serve as a lattice mismatched template for subsequent overgrowth of epitaxial Si, will now be described in greater detail by referring to the drawings that accompany the present application. In the accompanying drawings, like and/or corresponding elements are referred to by like reference numerals.

#The present application provides a direct approach to the formation of low-defect, substantially relaxed SiGe-on-insulator substrate materials whereby the heating step of the present invention is performed at a temperature approaching the melting point of the SiGe alloy, while high enough to retard SF formation. The result of the controlled heating step, which is performed at or near the melting point of the final relaxed SiGe alloy layer, is a reduction in the residual defect density compared to similar layers that are annealed at lower temperatures.

#Reference is first made to FIGS. 1A and 2A, which show initial substrate materials that can be employed in the present invention. Specifically, the initial substrate materials illustrated in FIGS. 1A and 2A each comprise a Si-containing semiconductor substrate 10, a barrier layer 12 which is resistant to Ge diffusion (hereinafter “barrier layer”) present atop a surface of the Si-containing semiconductor substrate 10 and a first single crystal Si layer 14 having misfit and TD densities of less than about 1×104 defects/cm2 present atop the barrier layer 12. In the drawings, reference numeral 17 denotes the interface between the barrier layer 12 and the first single crystal Si layer 14.