Long Slender Piezo-Resistive Silicon Microprobes for Fast Measurements of Roughness and Mechanical Properties inside Micro-Holes with Diameters below 100 µm

Abstract

During the past decade, piezo-resistive cantilever type silicon microprobes for high-speed roughness measurements inside high-aspect-ratio microstructures, like injection nozzles or critical gas nozzles have been developed. This article summarizes their metrological properties for fast roughness and shape measurements including noise, damping, tip form, tip wear, and probing forces and presents the first results on the measurement of mechanical surface parameters. Due to the small mass of the cantilever microprobes, roughness measurements at very high traverse speeds up to 15 mm/s are possible. At these high scanning speeds, considerable wear of the integrated silicon tips was observed in the past. In this paper, a new tip-testing artefact with rectangular grooves of different width was used to measure this wear and to measure the tip shape, which is needed for morphological filtering of the measured profiles and, thus, for accurate form measurements. To reduce tip wear, the integrated silicon tips were replaced by low-wear spherical diamond tips of a 2 µm radius. Currently, a compact microprobe device with an integrated feed-unit is being developed for high-speed roughness measurements on manufacturing machines. First measurements on sinusoidal artefacts were carried out successfully. Moreover, the first measurements of the elastic modulus of a polymer surface applying the contact resonance measurement principle are presented, which indicates the high potential of these microprobes for simultaneous high-speed roughness and mechanical parameter measurements.

Review: Cantilever-Based Sensors for High Speed Atomic Force Microscopy

“…For biological applications, the microcantilever biosensors should be sensitive, fast, and flexible for identification of biomolecules and high-throughput screening in the pharmaceutical industries [ 52 ]. They have also been applied in the study of biosample stiffness measurements [ 53 ], surface morphological and mechanical analysis [ 54 ], and viscosity–density sensing in liquid media.…”

Cantilever Sensors

“…From the collected papers in this special issue, several important sensing fields have been demonstrated, i.e., biosample stiffness measurements [1], surface topography and mechanical properties analysis by fast scanning and contact resonance measurements [2], viscosity–density sensing in liquid media [3], vibration monitoring in remote and harsh environments [4], low-voltage electrostatic activation of resonant cantilever devices [5], atomic force microscopy (AFM) in vacuum [6], and high-sensitive, fast-responding quartz-tuning-force AFM [7]. The rather large cantilevers considered in this special issue, with dimensions typically in the hundreds-of-micron to several-millimeter range, are manufactured using both well-established semiconductor planar-technology-based micromachining [2,3,5,6] as well as unconventional fabrication methods using emerging materials [1,4,7]. Primary physical parameters (e.g., force, acceleration, stiffness, density, and viscosity) to be sensed by quasistatic cantilever deflection [1,2,4] or its operation in a resonant mode [2,3,5,6,7] are converted into cantilever deflection and stress/strain induced in the cantilever spring.…”

“…The rather large cantilevers considered in this special issue, with dimensions typically in the hundreds-of-micron to several-millimeter range, are manufactured using both well-established semiconductor planar-technology-based micromachining [2,3,5,6] as well as unconventional fabrication methods using emerging materials [1,4,7]. Primary physical parameters (e.g., force, acceleration, stiffness, density, and viscosity) to be sensed by quasistatic cantilever deflection [1,2,4] or its operation in a resonant mode [2,3,5,6,7] are converted into cantilever deflection and stress/strain induced in the cantilever spring. Electrical output signals are then generated from these intermediate mechanical parameters by optical [4] or capacitive [5] detection of cantilever bending.…”

“…Electrical output signals are then generated from these intermediate mechanical parameters by optical [4] or capacitive [5] detection of cantilever bending. Alternatively, stress/strain generated in the cantilever spring can be read out using a piezoresistive strain gauge [2] or by piezoelectric transduction [3,6,7].…”

“…Long, slender piezoresistive silicon cantilevers were used as surface-scanning microprobes for fast measurement of roughness and mechanical properties of high-aspect-ratio microstructures, e.g., inside micro holes of critical flow Venturi nozzles and diesel injection nozzles [2]. After surface scanning at high traverse speeds up to 15 mm/s, wear of integrated silicon tips was observed and measured using a tip-testing artifact.…”