Stress Simulation, Thermal Bonding, and Growth of 2-Inch Aluminum Nitride Single Crystals

doi:10.16553/j.cnki.issn1000-985x.2026.0031

Abstract

Abstract: This paper，focusing on the stress regulation，thermal bonding process，and high-quality thick-crystal growth of 2-inch aluminum nitride （AlN） single crystals，performed systematic computational simulations and single-crystal growth experiments. It reveals the mechanism of cooling-induced thermal stress imposed on AlN single crystals by different substrate materials，and elucidates the intrinsic correlation between the properties of metal substrates and the residual stress of the crystals，providing theoretical support for the substrate selection in AlN single-crystal growth. Moreover，relying on simulation technology，an innovative low-stress thermal bonding process for 2-inch AlN is achieved，addressing the stress-induced cracking problem encountered during the high-temperature thermal bonding of AlN seed crystals. Meanwhile，by integrating simulation with structural optimization design，the thick-growth technology is successfully broken through，and a 2-inch high-quality AlN single crystal with a thickness of 10.8 mm is fabricated. The full width at half maximum （FWHM） of the （002） high-resolution X-ray diffraction （HRXRD） rocking curve of the wafer is as low as 51.67″.

Key words: AlN single crystal; stress control; finite element analysis; thermal expansion coefficient; physical vapor transport; thermal bonding

CLC Number:

O782

GAO Fei, XIN Qian, WANG Yingmin, CHENG Hongjuan, WANG Zenghua. Stress Simulation, Thermal Bonding, and Growth of 2-Inch Aluminum Nitride Single Crystals[J]. Journal of Synthetic Crystals, 2026, 55(6): 878-885.

Figures/Tables 4

Fig.1 Thermal stress simulation of different substrates. Temperature dependence of thermal expansion coefficients （a） and thermal contraction （ΔL/L0） curves （b） for W，Re，Ta，TaC，and AlN；（c） stress distribution of AlN boule with different substrates after cooling；（d） radial stress versus boule radius；（e） axial stress versus boule thickness

Fig.2 Thermal bonding and stress simulation of AlN seed. （a） Schematic diagram of thermal bonding of AlN seed onto W substrate；（b） meshing of the computational model； residual stress distribution of AlN seed undergoing one-step （c） and stepwise cooling processes （d）；（e） crack-free thermal bonded AlN seed

Fig.3 Thermal stress simulation of AlN single crystal. （a） Cooling thermal stress distribution of AlN boule on W substrate with different diameters；（b） axial stress versus boule thickness；（c） radial stress versus boule radius；（d） radial stress distribution at different thickness positions of ?50 mm AlN

Fig.4 Growth structure and result of 2-inch AlN single crystal. （a） Schematic diagram of the PVT device and optimized thermal distribution for growing 2-inch AlN single crystal； as grown 2-inch AlN single crystal （b） and wafers （c）；（d） crossed polarizer image；（e） AFM image； HRXRD （002） rocking curve （f） and Raman Mapping （g） for 2-inch AlN wafer

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