Cr-N Strain-Gauge-Type Precision Displacement Sensor for Measuring Positions of Micro Stage

Abstract

A strain-gauge-type precision displacement sensor, which is developed for a usage of micro-XY stage, is described in this paper. A thin-film strain-gauge element, which is made by Cr-N alloy, is directly fabricated on the base of the strain gauge. The direct fabrication and using the Cr-N element are expected to achieve higher sensitivity for displacement detection and better stability against the change of ambient temperature. In this study, several designs of the thin-film strain gauge, including both of two-gauge-type and four-gauge-type, are prepared to compare sensor performances such as sensitivity, stability and so on. The designed patterns of the strain-gauge element are directly fabricated on zirconia plates by using photolithography processes. The fabricated strain gauges are then evaluated as precision displacement sensors. At first, stability of the fabricated Cr-N strain-gauge-type displacement sensor was confirmed by comparing with the one made by a conventional strain gauge. Resolution of the fabricated Cr-N strain-gauge-type displacement sensors was then evaluated by comparing with a commercially-available laser displacement sensor, while giving sub-micrometer-order deformation to the strain-gauge-type displacement sensor. Details of the design, fabrication and evaluation results of the Cr-N strain-gauge-type displacement sensor are described.

C021 Development of Cr-N strain-gauge-type displacement sensor for positioning of micro-XY stage

“…Table 2 summarizes the specifications of the newlydeveloped sensor and the previous one. Both the sensitivity and resolution of the newly developed sensor is twice better than that of the previous one [7]. The measuring range of the newly developed sensor was also enlarged ten times higher than that of the previous one.…”

“…Some parameters of the leaf spring are shown in Table 1. In our previous research [7], the thickness of the zirconia plate was 0.1 mm; which corresponded to the spring constant of 157 N/m, and would allow the stage to have a stroke of only ±0.1 mm. In order to achieve further larger stroke, in this paper, the thickness of the zirconia plate is designed to be 0.03 mm, which corresponds to the spring constant of 4.24 N/m, so that a stroke of larger than ±1 mm can be achieved.…”

“…To overcome disadvantages of conventional strain gauges, the Research Institute for Electromagnetic Materials developed a Cr-N thin-film as the strain gauge material [6]. In our previous research, a Cr-N strain-gauge-type displacement sensor is proposed for precision positioning of the micro-XY stage [7]. The Cr-N thin film is sputtered directly on one side of a zirconia plate to form a full Wheatstone bridge circuit with four active strain gauges.…”