Uniform Growth of Two-inch MPCVD Optical Grade Diamond Film

doi:10.15541/jim20230202

Abstract

Abstract:

The uniform growth of large-size optical grade diamond films has been one of the hot spots and difficulties in the field of microwave plasma chemical vapor deposition (MPCVD) diamond research, in which the structure and position of the deposition platform are crucial to the uniformity of diamond films and the long-term stability of thick film growth. Here, the effect of deposition platform height on the electric field uniformity, plasma state and temperature uniformity on the substrate surface was investigated by COMSOL simulation combined with experiments to optimize the process parameters for the uniform growth of optical grade diamond films. The 2-inch diamond film with thickness of 337 μm and inhomogeneity <11% was obtained at the optimal deposition platform height of 2 mm. The full width of the Raman half-peak from the center to the edge of the film is in the range of 3-4 cm^-1, and the maximum transmittance is 69%-70% in the visible light band and 70% in the infrared light at 10.6 μm. This indicates that thickness and quality of the diamond film are relatively uniform, thus the uniform deposition of 2-inch optical grade diamond film is achieved. Above results show that the deposition platform height has a great influence on the electric field distribution and plasma state on the substrate surface, and the electric field uniformity on the substrate surface is significantly improved with the increase of the deposition height, but the influence on the temperature uniformity is smaller.

Key words: optical grade diamond film, temperature uniformity, infrared transmittance, deposition platform height, COMSOL simulation

CLC Number:

O484

CHAN Siyi, TU Juping, HUANG Ke, SHAO Siwu, YANG Zhiliang, LIU Peng, LIU Jinlong, CHEN Liangxian, WEI Junjun, AN Kang, ZHENG Yuting, LI Chengming. Uniform Growth of Two-inch MPCVD Optical Grade Diamond Film[J]. Journal of Inorganic Materials, 2023, 38(12): 1413-1419.

Figures/Tables 10

Fig. 1 Schematic diagram of substrate placement for different deposition platform heights (a) 2 mm; (b) 0 mm; (c) -2 mm

Table 1 Experimental parameters

Nucleation					Growth
Power/ kW	Pressure/ kPa	Gas: CH₄/H₂	Time/ min	Temperature/ ℃	Power/ kW	Pressure/ kPa	Gas: CH₄/O₂/H₂	Temperature/ ℃	Height/ mm
4.7	21	35/500	40	880	4.7-4.9	21-22	25/5/500	870-880	2

Fig. 2 Electric field simulations above the substrate for different deposition platform heights (a) 2 mm; (b) 1 mm; (c) 0 mm; (d) -1 mm; (e) -2 mm

Fig. 3 Electric field inhomogeneity (a) and electric field intensity distributions (b) above the substrate at different deposition platform heights 1 inch=25.4 mm

Fig. 4 Shape diagrams of the plasma spheres at different deposition platform heights (a) 2 mm; (b) 1 mm; (c) 0 mm; (d) -1 mm; (e) -2 mm

Fig. 5 Optical emission spectra (a), relative C2, Hα, Hβ, CH emission intensities and variations in IC2/IHα, ICH/IHα, IHβ/IHα ratio (b) at different deposition platform heights

Fig. 6 Uniformity of temperature distributions at different deposition platform heights (a) 2 mm; (b) 0 mm; (c) -2 mm

Fig. 7 Photographs of deposited state of the sample (a), polished state on both sides (b), and thickness distribution of the deposited state (c)

Fig. 8 XRD pattern (a) and Raman spectra (b) of the diamond films

Fig. 9 UV-Vis transmission spectra (a) and IR transmission spectra (b) of the diamond film Colorful figures are available on website

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