A small robust monolithic vacuum-compatible microbalance with automated calibration: achieving high accuracy with a large load capacity

The increasing demand for compact and efficient electronics has led to the miniaturization of components such as microchips, sensors, batteries, and storage devices. As these dimensions decrease, monitoring mass changes becomes essential for controlling the various physical processes involved in manufacturing, including material addition or removal during physico-chemical steps like thin-film micro-fabrication (e.g. depositing, patterning, doping, etching, surface oxidation/nitridation). This need has triggered the development of diverse microbalances. While custom-made setups typically aim for high resolution and large load capacity, they are difficult to construct, fragile, and consume significant space. On the one hand,
quartz sensors, which measure weight changes through resonance frequency, offer high resolution and load capacity in a compact footprint, but for multiple reasons their applicability is limited to the deposition of a thin film directly onto the quartz sensor. On the other hand, commercial microbalances allow loose sample placement but lack vacuum compatibility. To address these limitations, a new robust vacuum-compatible monolithic microbalance has been devised, relying on the design of a dedicated elastic mechanism that achieves a resolution below one microgram for loads exceeding one gram. This balance is manufactured using electrical discharge machining and micromilling, resulting in a small, sturdy device with an automatic
in-situ calibration mechanism. The resulting microbalance is optimized for deposition and etching processes, ensuring accurate measurements in a wide range of challenging vacuum environments. The novelty of the microbalance lies in its unique combination of features: high accuracy (<1 µg), high sensitivity (<0.1 µg), large load capacity (>1 g), a compact footprint (≈ 30 × 30 × 10 cm3), high robustness (≈30 g) due to its built-in mechanical stops, vacuum compatibility, and compatibility with depth profile analyses.