SiC Dry Etching Research Articles

Micro-trench free 4H-SiC etching with improved SiC/SiO2 selectivity using inductively coupled SF6/O2/Ar plasma

SiC dry etching process for formation of a trenched-gate structure in trench metal-oxide-semiconductor field-effect-transistors employing bottom protection p-well (BPW) has been investigated. SF6/O2/Ar based inductively-coupled-plasma reactive-ion-etching were utilized with various variations in process parameters, such as bias power, ICP power, kind of gas species, working pressure and temperature. The effects of process parameters on trench profiles were analyzed by a cross-sectional scanning electron microscope and profilometer to suppress micro trenches at a bottom corner of the trench and improve SiC/SiO2 etch selectivity. We successfully demonstrated the micro-trench free SiC trench structure with high SiC/SiO2 etch selectivity of 3.7 at bias power of 1 kW, ICP power of 4 kW, SF6/O2/Ar flows of 6/6/8 sccm, working pressure of 15 mTorr and temperature of 20 °C.

Dry etching of SiC using Ar/F2 plasma and XeF2 plasma

We investigated the SiC dry etching process using Ar/F2 plasma and XeF2 plasma. We carried out optical observation of Ar/F2 plasma and XeF2 plasma. The dominant etching species were different between Ar/F2 plasma and XeF2 plasma. The etching rates of SiC were approximately 100 nm/min at 25 sccm and 200 W for Ar/F2 plasma and 45 nm/min at 2.5 sccm and 100 W for XeF2 plasma. Vertical etching profiles and a smooth etched surface were obtained. The average roughness of the etched bottom surface was 1 nm, which satisfied the requirements for optical device fabrication. We believe that the proposed etching process using F2 of zero-global-warming-potential gases is very simple and useful for fabricating optical devices and micro-electromechanical systems (MEMSs).

Development of Silicon Carbide Dry Etcher Using Chlorine Trifluoride Gas

A SiC dry etching reactor using chlorine trifluoride (ClF3) gas was designed and evaluated with the help of numerical calculations and experimental results. The etching rate was about 16 μm/min when the ClF3 gas concentration, the total flow rate and the SiC substrate temperature were 90%, 0.3 slm and 500 °C, respectively. The gas stream above the substrate surface was concluded to significantly affect the etching rate profile.

Reduction of Fluoride Species and Surface Roughness by H<sub>2</sub> Gas Addition in SiC Dry Etching

We study for the effects of additional gas such as oxygen (O2) and hydrogen (H2) into SF6. When H2 gas was added to SF6, surface fluoride atomic concentration and surface roughness were lower than the other additional gases. Surface fluoride atomic concentration under this experiment was reduced from 28 at % to 6 at % by the H2 addition. In post-processing, the fluoride atomic concentration was succeeded in a large reduction by processing H2, O2 plasma and high temperature hydrogen annealing. In hydrogen annealing, surface fluoride atomic concentration could be suppressed to less than 3 at %. This is new result succeeded in reduction of surface fluoride species greatly by hydrogen processing.

Dry etching of SiC in inductively coupled Cl2/Ar plasma

Inductively coupled Cl2/Ar plasma etching of 4H–SiC has been studied. The SiC etch rate has been investigated as a function of average ion energy, Ar concentration in the gas mixtures, inductively coupled plasma power, work pressure and substrate temperature. The etch mechanism has been investigated by correlating the ion current density and relative atomic chlorine content to the etch rate under various etch conditions. For the first time, it has been found that the etch rate of SiC increases by about 50% at lower substrate temperatures (−80°C) than at high substrate temperatures (150°C) with the highest SiC etch rate of 230 nm min−1 being achieved at a substrate temperature of −80°C.

Inductively coupled plasma reactive ion etching of SiC single crystals using NF3-based gas mixtures

Inductively coupled plasma reactive ion etching of SiC single crystals using NF3-based gas mixtures was investigated. Mesas with smooth surfaces and vertical sidewalls were obtained, with a maximum etch rate of about 400 nm/min. Effects of CH4 and O2 addition to the NF3 gas and the crystalline quality of substrates were studied during the SiC dry etching using various masks. Selectivity of the photoresist (PR) mask improved from about 0.2 to about 0.4 by the addition of 30% CH4 during the RIE, although the etch rate decreased by 50–70%. Results also indicated that the substrate quality does not significantly affect the etch results.

Low Bias Dry Etching of Sic and Sicn in ICP NF3 Discharges

ABSTRACTA parametric study of the etching characteristics of 6H p+ and n+ SiC and thin film SiC0.8N0.2 in Inductively Coupled Plasma NF3/O2 and NF3/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF3 percentage and rf chuck power reaching 3500Å·min−1 for SiC and 7500 Å·min−1 for SiCN. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tinoxide( ITO) masks display relatively good etch selectivity over SiC(maximum of 70:1) while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF3/O2 discharges, while extensive surface degradation occurs for SiCN under high NF3:O2 conditions. The high ion flux available in the ICP tool allows etching even at very low dc self-biases, ≤ −10V, leading to very low damage pattern transfer.

Dry Etching of SiC for Advanced Device Applications

AbstractIn this paper we review and compare most of the published results on dry etching of silicon carbide using various techniques. The vast majority of reports have used RIE methods due to the wide availability of such reactors. Recently, alternative methods of magnetron enhanced RIE (MIE) and electron cyclotron resonance (ECR) plasmas have been demonstrated. MIE has resulted in extremely high etch rates and ECR etching has resulted in smooth, residue-free surfaces with an ability to control the etched profiles.