Effect of Substrate Holder Design on Stress and Uniformity of Large-Area Polycrystalline Diamond Films Grown by Microwave Plasma-Assisted CVD

Vadim Sedov,Andrey Sinogeykin,Maxim Zanaveskin,Vitaly Konov,Mikhail Shevchenko,Evgeny Zavedeev,Alexey Popovich,Artem Martyanov,Alexandr Altakhov,Victor Ralchenko,Sergey Savin

doi:10.3390/coatings10100939

Abstract

In this work, the substrate holders of three principal geometries (flat, pocket, and pedestal) were designed based on E-field simulations. They were fabricated and then tested in microwave plasma-assisted chemical vapor deposition process with the purpose of the homogeneous growth of 100-μm-thick, low-stress polycrystalline diamond film over 2-inch Si substrates with a thickness of 0.35 mm. The effectiveness of each holder design was estimated by the criteria of the PCD film quality, its homogeneity, stress, and the curvature of the resulting “diamond-on-Si” plates. The structure and phase composition of the synthesized samples were studied with scanning electron microscopy and Raman spectroscopy, the curvature was measured using white light interferometry, and the thermal conductivity was measured using the laser flash technique. The proposed pedestal design of the substrate holder could reduce the stress of the thick PCD film down to 1.1–1.4 GPa, which resulted in an extremely low value of displacement for the resulting “diamond-on-Si” plate of Δh = 50 μm. The obtained results may be used for the improvement of already existing, and the design of the novel-type, MPCVD reactors aimed at the growth of large-area thick homogeneous PCD layers and plates for electronic applications.

Highlights

IntroductionDiamond has a record-high thermal conductivity of up to 24 W/cm·K at room temperature, reaching maximum values of up to 285 W/cm·K at temperatures near 63 K [1]
Among all known materials, diamond has a record-high thermal conductivity of up to 24 W/cm·K at room temperature, reaching maximum values of up to 285 W/cm·K at temperatures near 63 K [1].This makes diamond the material of choice for thermal management applications [2–6]
We found that the heights (h as shown in Figure 1) of the protective ring in pocket geometry (Figure 2b) should not exceed 2–3 mm, as in deeper pockets the sample itself becomes screened from the plasma by the protective ring

Summary

Introduction

Diamond has a record-high thermal conductivity of up to 24 W/cm·K at room temperature, reaching maximum values of up to 285 W/cm·K at temperatures near 63 K [1]. This makes diamond the material of choice for thermal management applications [2–6]. Solving thermal management problems is especially important for modern electronic devices, operating in extreme regimes, which makes diamond a highly used “cutting-edge” material in electronics [7–10]. A great prospect to combine GaN devices with diamond thermal management layers may be achieved by the means of layer bonding or the direct growth of diamond layers on GaN heterostructures [13–15]

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Results

Discussion

Conclusion