Dependence Of Silicon Fracture Strength And Surface Morphology On Deep Reactive Ion Etching Parameters

Abstract

The development of a high power-density micro-gas turbine engine is currently underway at MIT. The initial goal is to produce the components by deep reactive ion etching (DRIE) single crystal silicon. The capability of the silicon structures to withstand the very high stress levels within the engine limits the performance of the device. This capability is determined by the material strength and by the achievable fillet radii at the root of turbine blades and other etched features rotating at high speeds. These factors are strongly dependent on the DRIE parameters. Etching conditions that yield large fillet radii and good surface quality are desirable from a mechanical standpoint. In order to identify optimal DRIE conditions, a mechanical testing program has been implemented. The designed experiment involves a matrix of 55 silicon wafers with radiused hub flexure specimens etched under different DRIE conditions. The resulting fracture strengths were determined through mechanical testing, while SEM analysis was used to characterize the corresponding fillet radii. The test results will provide the basis for process optimization of micro-turbomachinery fabrication and play an important role in the overall engine redesign.

Effect of process parameters on the surface morphology and mechanical performance of silicon structures after deep reactive ion etching (DRIE)

“…As shown in Fig. 8, the fracture strength was determined by finite element analysis with the fracture load as input [14], [26].…”

Characterisation of a small viscous flow turbine

“…The development of these components was largely made feasible because of the rapid advancement of micromachining techniques that initially migrated from the semiconductor industry [14,15]. Thus, it is now possible to economically produce gas turbines with rotors in the millimetre size range, with flow path dimensions in sub-millimetre scales, or even microns through application of micro-electro-mechanical systems (MEMS) fabrication techniques [16][17][18][19]. MEMS fabrication techniques, because of their low cost of batch production, have been shown to be suitable for manufacturing rotors with 2D planer structures applicable for micro-turbo-machinery.…”

Suppression of Premature Fracture of Silicon under Three‐Point Bending: Role of Nanoscale Localized Deformation of Metallic Multilayered Coating

“…For example, single crystal (SC) silicon (Si) microcomponents fabricated by different etching ''recipes'' in the same deep reactive ion etch chamber may have scattered strengths varying by nearly an order of magnitude. [3][4][5] To enhance the working reliability of the whole MEMS device it is of great significance to effectively prevent brittle rupture in the mechanical microcomponents. [6] Owing to the confinement of the layer thickness and the heterogeneous layer interface, nanoscale metallic multilayers possess higher strength and relatively finer toughness than conventional brittle materials.…”