Abstract
In this paper, theoretical models of the critical indentation depth and critical force on brittle materials using cleavage strength and contact theory are proposed. A Berkovich indenter is adopted for nanoindentation tests on a 4H-SiC single crystal sample to evaluate its mechanical behaviors. The stages of brittle material deformation (elastic, plastic, and brittle) can be characterized by the load versus indentation depth curves through the nanoindentation test. The curve of the elastic deformation stage follows the Hertz contact theory, and plastic deformation occurs at an indentation depth of up to 10 nm. The mechanism of 4H-SiC single crystal cracking is discussed, and the critical indentation depth and critical force for the plastic–brittle transition are obtained through the occurrence of the pop-in point. This shows that the theoretical results have good coherence with the test results. Both the values of the elastic modulus and hardness decrease as the crack length increases. In order to obtain more accurate mechanical property values in the nanoindentation test for brittle materials such as SiC, GaN, and sapphire, an appropriate load that avoids surface cracks should be adopted.
Highlights
With the rapid development of the modern semiconductor industry, silicon-based semiconductors are quickly approaching their limit according to Moore’s Law [1], and an important direction for the semiconductor industry will be in looking for a substitute for silicon
Pang et al [24] conducted indentation experiments on 6H-silicon carbide (SiC) single crystal, and the results showed that classical crystal plasticity theory can be reliably applied in predicting the plastic deformation of ceramic at small scales
The nanoindentation tests were conducted on 4H-SiC single crystal samples with a Berkovich indenter in a nanomechanical test system
Summary
With the rapid development of the modern semiconductor industry, silicon-based semiconductors are quickly approaching their limit according to Moore’s Law [1], and an important direction for the semiconductor industry will be in looking for a substitute for silicon. Nanoindentation testing refers to a technology using a diamond indenter (Berkovich, cone, pyramid, and sphere), for which the mechanical properties are given, to determine another material’s mechanical properties by means of indentation It is a process of driving an indenter into the material surface and investigating the mechanical behavior (hardness H, modulus E, creep compliance C, etc.) of the material based on the response of the indenter [15,16]. Matsumoto et al [20] clarified the mechanical properties of 4H-SiC single crystal by means of nanoindentation with a Berkovich indenter, and studied the deformation process. The changing law of elasticity modulus and hardness with the increase of the indentation depth is discussed These provide important technical parameters for the plastic region process of 4H-SiC single crystal
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