Strain accommodation of 3C–SiC grown on hydrogen-implanted Si (0 0 1) substrate

Abstract

The hydrogen-implanted Si substrate has been used for the fabrication of the “compliant substrate”, which can accommodate the mismatch strain during the heteroepitaxy. The compliance of the substrate can be modulated by the energy and dose of implanted hydrogen. In addition, the defects caused by implantation act as the gettering center for the internal gettering of the harmful metallic impurities. Compared with SiC films growth on substrate without implantation, all the measurements indicated that the mismatch strains in the SiC films grown on this substrate have been released and the crystalline qualities have been improved. It is a practical technique used for the compliant substrate fabrication and compatible with the semiconductor industry.

Introduction

The ever increasing demands to integrate diverse electronic and optoelectronic devices have imposed great challenges on the heteroepitaxy. The lack of suitable substrates has severely limited the choice of epitaxial materials available for device design. Interest in the growth, microstructure, and electronic properties of SiC thin films has increased markedly over the past 10 years driven by potential applications including high-power, high-frequency, high-temperature, and radiation-hard transistors as well as substrate for light-emitting GaN films [1]. It is highly desirable to fabricate high quality of 3C–SiC on Si substrate, which have several advantages, such as low cost, large size, good electrical conduction, high crystalline perfection, etc. The main obstacle for the fabrication of high quality of 3C–SiC on Si substrate is the lattice mismatch (as large as 20%) and the difference in thermal expansion coefficients (8%).

Compliant substrates [2] have been proposed to overcome the large differences in lattice constant and thermal expansion coefficient. Various types [3] of compliant substrates have been developed since the introduction of the concept, which include free standing [4], oxide bonded [5], borosilicate-glass bonded [6], direct twist bonded [7], modulated bonding strength [8] compliant substrates, and substrates with oxidized underlying Al(Ga)As layers [9]. Most of the attempts, however, will introduce the contamination during the fabrication of compliant substrate and the process is complex and time consuming, which will degenerate the electronical and optical properties of the epilayers.

The physics and chemistry of hydrogen implanted in silicon has been studied in the past three decades. Hydrogen profoundly alters the electrical characteristics of the resultant device by diffusing into active region and passivating the dopant. High concentrations of H in Si are able to produce platelets and gas bubbles inside the crystalline lattice [10], [11], [12]. Efficient and healthy strain relaxation of pseudomorphic SiGe/Si heterostructures have been obtained by H⁺ implantation [13], which indicated that the mechanical behavior of the bulk Si have been altered. Implantation of H⁺ can produce a “weak bonding” belt in the thick substrate, which can lead to the thin top layer “decoupled” from the thick part. It is feasible to fabricate a “compliant substrate” by implantation of certain dose of H⁺, which is compatible to the process of the semiconductor industry. In this work, compliant substrates have been obtained by hydrogen implantation. Subsequent 3C–SiC film growth indicated that the mismatch between the epilayer and substrate has been accommodated by this compliant substrate.