New Process Simulation Procedure for High-Rate Plasma Jet Machining

Abstract

Surface figuring using chemically reactive plasma jet machining (PJM) is a promising non-conventional technology for deterministic ultra-precision machining of optical components. Based on chemical reactions between plasma generated radicals and the surface atoms this technology is capable to fabricate complex shaped free form surfaces. Since the material removal rate during PJM depends strongly on the surface temperature which itself is influenced by the jet heat flux to the surface, the arising nonlinear effects on the etch result have to be regarded. Conventionally applied dwell time calculation algorithms do not consider those effects leading to significant machining errors in some cases. In order to improve the machining procedure with respect to deterministic material removal yielding predictable results a process simulation model has been developed. This model considers spatio-temporal variations of surface temperature and temperature dependent material removal and is able to predict the final workpiece topography after machining.

Etch Mechanism and Temperature Regimes of an Atmospheric Pressure Chlorine-Based Plasma Jet Process

“…The jet was repeatedly scanned on a linear path over the surface at a fixed working distance between nozzle and sample of 2.8 mm, resulting in groove structures with depths in the order of magnitude of 1 μm. Previous studies showed that heat flux from the plasma can significantly influence etch rates at higher microwave powers (>200 W), leading to an etch rate dependence on scan velocity . The microwave power of 9.6 W used here was comparably low and the heat flux from the plasma jet was found to be negligible.…”

“…Previous studies showed that heat flux from the plasma can significantly influence etch rates at higher microwave powers (>200 W), leading to an etch rate dependence on scan velocity. [8] The microwave power of 9.6 W used here was comparably low and the heat flux from the plasma jet was found to be negligible.…”

“…The groove cross section profiles exhibit a U-shape with steep sidewalls indicating an anisotropic etching trend rather than a fully isotropic etching that would result in a Gaussian-like profile, which occurs, e.g., in plasma jet etching using CF 4 as precursor gas. [8] The SEM micrograph of the groove etched with no oxygen in Figure 7(d) shows that sidewalls are covered by layers. XPS spectra have been recorded at the center of the etch grove and at the rim, respectively.…”

Calorimetric Probes for Energy Flux Measurements in Process Plasmas

“…Due to the small size and strong spatial inhomogeneities, the interpretation of the measurements is quite difficult. However, if a quantitative description cannot be given, at least the maximum substrate temperature [41], the temperature distribution across the substrate [101,102] or the ratios of the different contributions [40,41] are interesting and important characteristics.…”

Development of array-type atmospheric-pressure RF plasma generator with electric on–off control for high-throughput numerically controlled processes

“…1 In the case of a next-generation silicon-on-insulator (SOI) wafer, the thickness distribution of the top thin silicon layer should have a peak-to-valley (P-V) value of less than 1.0 nm over the entire surface of a 450-mm wafer. 2 Deterministic processing methods, such as ion beam figuring (IBF), 3,4 numerically controlled (NC) elastic emission machining (EEM), 5 plasma jet machining (PJM), 6,7 electrical discharge machining (EDM), 8,9 NC plasma chemical vaporization machining (PCVM), [10][11][12] local wet etching (LWE), 13 NC sacrificial oxidation, 14,15 and others, have been developed to achieve such accuracy. Although the processing mechanisms of these machining methods differ, they all consist of two components: a processing head that can process small areas, ranging in diameter from approximately the sub-millimeter range to several millimeters and an X-Y table system that enables the processing head to scan the whole area of a workpiece at a controlled feed speed.…”