Indentation testing of silicon micropillars from cryogenic dry etching

Silicon micropillars find diverse applications, requiring precise mechanical properties for effective design. To ensure functionality under pressure or vibration, mechanical characteristics must match the application needs. A standardized method for characterizing micropillar properties is crucial, despite challenges due to their small size. This study focuses on cryogenically dry-etched micropillars, employing instrumented indentation testing (IIT). Deviations of around 40% in both indentation modulus (E_IT) and hardness (H_IT) were observed compared to bulk crystal. A correction formula, considering compressibility, reduced E_IT deviation to 20%. The study identifies systematic deviations, examining factors such as anisotropic properties, indenter type, and surface roughness. Three single-crystal silicon samples (Si, Si, Si) were used, revealing the impact of crystal orientation and indenter type on measurements. Surface roughness, generated through cryogenic dry etching, was studied, with corrections proposed to minimize its influence. The correction method successfully reduced roughness impact on E_IT to below 10%. Surface inclination contributed the most to standard uncertainty (2%), followed by sample rotation (1.7%), and roughness (0.2%) when known.