Development of a Measuring System for Shape and Dimension Determination of Micro-components

摘要

This study seeks to develop a system for measuring the three-dimensional (3D) shape and dimensions of micro-components using a micro-probe (nose radius: <1 μm). Recent developments in high-precision manufacturing technologies have resulted in an increased need for micro-shape evaluation technologies. However, numerous factors have been reported that affect the reliability of micro-component measurements and the degree of uncertainty has increased or decreased dramatically as the size of micro-components has decreased. In particular, the effect of surface profile characteristics such as surface roughness has increased. In addition, establishing datum on micro-components is considerably difficult. It is therefore important to acquire a variety of data, such as surface roughness, shape and size relating to a workpiece after the datum has been established.By detecting the proximity of the probe to the measured sample, and by using the tunneling effect, our measurement system can measure micro-shape without contact. Using a precision PZT stage, the positioning accuracy of the system is 10 nm within a 500×500×500 μm cube. The response speed of the PZT stage, which is controlled by a computer, is not sufficient to avoid collision of the measurement object with the probe. In order to avoid such collisions, the probe employs what we refer to as a Probe Over-travel Protection System to affect rapid probe control. This protection system is driven by 10-μm stroke piezoelectric actuators, and is controlled directly by a simple electronic circuit.Using the current measurement system and a titanium probe, micro-components can be measured to an accuracy of 64 nm, at a rate of three measurement points per second. In addition, our system employs a three-dimensional (3D) optical measurement system that uses the Shape from Focus (SFF) method to assist withprobe positioning. If a workpiece with asperities ranging from several μm to tens of |xm were to be examined, then it is important that the measurement system has visual-assist capability to facilitate precise positioning of the probe at a specific point.In general, two or more cameras are required to produce a 3D picture through image processing. However, the SFF method can be used to generate a 3D figure using data collected by a microscope fitted with a CCD (charge-coupled device) camera. Using this optical system, it is possible to obtain an approximate 3D representation of the target, which can then be used to optimize the path of the probe. An import facet of the visual-assist system is that it reduces measurement time by more than 50%.In this research, we describe the configuration of the measurement system in detail, and then we verify the validity of this measurement system using several measurement examples.