Controlled Spalling of Single Crystal 4H-SiC Bulk Substrates

TL;DR

This paper presents innovative methods for controlled spalling of high-quality 4H-SiC films from bulk substrates, enabling substrate reuse and quantum applications, with demonstrated spin coherence in the spalled films.

Contribution

It introduces novel stressor layer control techniques for spalling 4H-SiC, achieving high fracture toughness and enabling substrate reuse and quantum device integration.

Findings

Successful controlled spalling of 4H-SiC films

Demonstration of substrate re-use and film bonding

Achieved spin coherence with T2 of 79.7 μs in spalled films

Abstract

We detail several scientific and engineering innovations which enable the controlled spalling of 10 - 50 micron thick films of single crystal 4H silicon carbide (4H-SiC) from bulk substrates. 4H-SiC's properties, including high thermal conductivity and a wide bandgap, make it an ideal candidate for high-temperature, high-voltage power electronic devices. Moreover, 4H-SiC has been shown to be an excellent host of solid-state atomic defect qubits for quantum computing and quantum networking. Because 4H-SiC single crystal substrates are expensive (due to long growth times and limited yield), techniques for removal and transfer of bulk-quality films in the tens-of-microns thickness range are highly desirable to allow for substrate reuse and integration of the separated films. In this work we utilize novel approaches for stressor layer thickness control and spalling crack initiation to demonstrate controlled spalling of 4H-SiC, the highest fracture toughness material spalled to date. Additionally, we demonstrate substrate re-use, bonding of the spalled films to carrier substrates, and explore the spin coherence of the spalled films. In preliminary studies we are able to achieve coherent spin control of neutral divacancy ($VV^{0}$) qubit ensembles and measure a quasi-bulk spin $T_{2}$ of 79.7 $\mu$s in such spalled films.