Thermal Field of 6-inch Indium Phosphide Single Crystal Growth by Semi-sealed Czochralski Method

doi:10.15541/jim20220645

Abstract

Abstract:

Indium phosphide (InP) is a kind of important compound semiconductor material, now increasingly used in high frequency electronic devices and infrared optoelectronic devices. Currently, the price of InP devices is much higher than that of GaAs devices, mainly because of its low yield of single crystals and increase of epitaxy, and device process cost due to smaller wafer diameter. Increasing the diameter of InP single crystals is critical to reducing wafer and semiconductor process costs. The main difficulties in preparing large diameter InP single crystals are increasing crystal yield and reducing stress in the crystal. The vertical gradient freeze (VGF) and the liquid encapsulated Czochralski (LEC) methods are commonly used in the industry to prepare InP, while the VGF method has little success in preparing 6-inch InP crystals, and the crystals prepared by the LEC method tend to have higher stress and dislocation density. Here we reported a semi-sealed Czochralski (SSC) method to grow large diameter InP crystals. Numerical simulations were used to analyze the temperature distribution in melt, crystal, boron oxide, and atmosphere in LEC and SSC method, with emphasis on temperature field of the SSC method. As a simulation result, the temperature gradient in the crystal of SSC method is 17.4 K/cm, significantly lower thanthat of 28.7 K/cm in the LEC method. And temperature of atmosphere near the crystal shoulder in the diameter control stage of the SSC method is 504 K higher than that of the LEC method. Then the used thermal field of SSC method was optimized according to the simulation results, and 6-inch (1 inch=2.54 cm) S doped InP single crystals with low defect density and no cracks were prepared by this optimized method, which confirmed that the optimized SSC method is promising for growing large-size InP single crystals.

Key words: indium phosphide, semi-sealed Czochralski, numerical simulation, thermal field

CLC Number:

TQ174

SHI Yanlei, SUN Niefeng, XU Chengyan, WANG Shujie, LIN Peng, MA Chunlei, XU Senfeng, WANG Wei, CHEN Chunmei, FU Lijie, SHAO Huimin, LI Xiaolan, WANG Yang, QIN Jingkai. Thermal Field of 6-inch Indium Phosphide Single Crystal Growth by Semi-sealed Czochralski Method[J]. Journal of Inorganic Materials, 2023, 38(3): 335-342.

Figures/Tables 8

Fig. 1 Schematic of the processes of semi-sealed Czochralski method (a) Seeding and shoulder stage; (b) Diameter-controlling stage; (c) Crystal raised from the melt

Fig. 2 Thermal field distributions in the seeding stages with different methods (a) SSC method; (b) VCZ method; (c) LEC method

Fig. 3 Temperature distribution in the melt at the front of the solid-liquid interface (a) Sampling position in the melt; (b) Temperature distribution in the melt at the front of solid-liquid interface; (c) Schematic of heat flow in VCZ method

Fig. 4 Temperature distribution in the crystal (a) Schematic diagram of the temperature sampling points in the crystal; (b) Temperature distribution in the crystal from the solid-liquid interface to the seed-crystal interface

Fig. 5 Temperature distribution in the melt, B2O3 and atmosphere around the crystal (a) Location of sampling points; (b) Comparison of temperature distributions by using different methods

Table 1 Location, temperature and temperature gradient of each section

Method	Item	Melt	B₂O₃	Gas 1		Gas 2	Gas 3
	Node	Start point	Node 1	Node 2	Node 3	Node 4	End point
	Distance/mm	0.0	11.0	52.0	55.0	70.0	76.0
SSC	Temperature/K	1340.0	1338.1	1221.4	1190.7	1185.8	1148.4
SSC	Temperature gradient/(K·mm^-1)	-0.2	-2.8	-10.2		-0.3	-6.2
LEC	Temperature/K	1344.5	1340.3	1127.6	877.7	808.7	644.4
LEC	Temperature gradient/(K·mm^-1)	-0.4	-5.2	-62.5		-6.9	-16.4

Fig. 6 Digital photographs of 6-inch InP crystal and cutting wafer (a) LEC-grown InP crystal; (b) SSC-grown InP crystal; (c) Cracked cutting wafer of LEC-grown crystal

Fig. 7 Dislocation densities of crystal tails by LEC and SSC methods (a) Crystal dislocation density by LEC method; (b) Crystal dislocation density by SSC method

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