Effective cooling of substrates with low thermal conductivity under conditions of gas-jet MPCVD diamond synthesis

The paper presents the results of an experimental study of heating molybdenum and silicon substrates under the conditions of gas-jet deposition of diamond structures using the precursor gases of a microwave discharge to activate. A cooled substrate holder using a metal melt to improve heat removal by reducing the thermal resistance between the substrate and the substrate holder has been developed. The use of the melt allowed lowering the temperature of the silicon substrate under the conditions of gas-jet deposition to a level that ensures the preservation of its structure. The developed substrate holders were used to carry out gas-jet synthesis of diamond structures on molybdenum and silicon substrates.

Особенности согласования нижнего электрода с высокочастотным генератором смещения при реактивно-ионном травлении массивных подложек

This paper presents theoretical and experimental results on reactive ion etching of massive substrates in freon-14 with RF bias at the lower electrode. A hypothesis is proposed according to which a large-sized substrate violates the matching of the lower electrode with the RF generator by adding an additional reactive component to the impedance of the lower electrode. A numerical simulation of reactive ion etching with substrates of various sizes in a CF4 environment is performed . The simulation results showed a significant increase in the reactive component of RF power at the lower electrode if the substrate area exceeds 50% of the area of the lower electrode, which is consistent with the proposed hypothesis. It has been experimentally shown that the etching of massive substrates violates the matching of the lower electrode with the RF generator. A special design of the substrate holder for massive substrates has been developed. It is shown that such a substrate holder significantly improves the matching of the RF generator with the lower electrode, especially when adding 0.3-0.9 l/h argon to the plasma-forming mixture.

Влияние металлических масок на согласование нижнего электрода с высокочастотным генератором смещения при реактивно-ионном травлении массивных подложек

The effect of metal masks on the matching of the lower electrode with a high-frequency bias generator during selective reactive-ion etching through the mask of massive substrates in freon-14 has been studied theoretically and experimentally. It is shown that masks with a substrate coating above 30% lead to an increase in the reactive power component at distances from the center close to the substrate radius. The absence of influence on the specific reactive power of the thickness and material of the masks is established. It is experimentally shown that masks with any practically significant coating coefficient of the substrate, connected to the lower electrode through the substrate holder, improve the matching, reducing the power reflection coefficient.

High-temperature etching of SiC in SF6/O2 inductively coupled plasma

In this work, we demonstrate an effective way of deep (30 µm depth), highly oriented (90° sidewall angle) structures formation with sub-nanometer surface roughness (Rms = 0.7 nm) in silicon carbide (SiC). These structures were obtained by dry etching in SF6/O2 inductively coupled plasma (ICP) at increased substrate holder temperatures. It was shown that change in the temperature of the substrate holder in the range from 100 to 300 °C leads to a sharp decrease in the root mean square roughness from 153 to 0.7 nm. Along with this, it has been established that the etching rate of SiC also depends on the temperature of the substrate holder and reaches its maximum (1.28 µm/min) at temperatures close to 150 °C. Further temperature increase to 300 °C does not lead to the etching rate rising. The comparison of the results of the thermally stimulated process and the etching with a water-cooled substrate holder (15 °C) is carried out. Plasma optical emission spectroscopy was carried out at different temperatures of the substrate holder.

Design and construction of a compact rotary substrate heater for deposition systems

We have designed and constructed a compact rotary substrate heater for the temperature range of 25 °C to 700 °C. The heater can be implemented in any deposition system where crystalline samples are needed. Its main function is to provide heat treatment in situ during film growth. The temperature is monitored and controlled by a temperature controller coupled to a type-K thermocouple. A heater case was designed to host a resistive element and at the same time allow the substrate holder to freely rotate. Rotation is crucial not only for film homogeneity during deposition but also for the elimination of temperature gradients on the substrate holder. To tolerate oxidizing and corrosive environments, the instrument was made of stainless steel, which also works as a “coolant”, taking advantage of heat dissipation. The instrument performs well for long periods of time with stable temperatures. We hope that this project is useful for laboratories wishing to have a compact rotary heater that meets the requirements for crystal growth and film homogeneity.

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

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.