This Small Business Innovation Research (SBIR) Phase I project addresses the metrology needs of next-generation manufacturing of precision components by developing a surface measuring microscope with extended vertical range/slope capability that can operate under extreme vibration conditions. The aims of this Phase I project are to develop a breadboard system capable of making high spatial resolution measurements without the need for vibration isolation, to develop and demonstrate an extended range measurement technique that will enable the measurement of any type of surface, and to evaluate the performance of this prototype in terms of repeatability, precision and accuracy. The Phase II goal is to develop a prototype instrument that will be mounted on computer-controlled machining equipment used in the manufacturing of precision components such as large optics and x-ray telescope mirrors. The proposed instrument will enable the manufacture of complex surfaces and provide a flexible research tool to study a wide variety of surface phenomenon.
The broader impact/commercial potential of this project extends to industries such as micro electro-mechanical structures (MEMS), flat panel displays, bio-medical devices, data storage, solar, semiconductor, and automotive. Surface finish/roughness is critical to the performance of precision machined components in all these industries. For example, in the manufacture of large mirrors for astronomy and aspheric mirrors for x-ray optics, surface roughness is critical to the final imaging performance due to limitations caused by light scattering. In applications such as medical implants and precision automotive components, longevity is critically affected by surface finish owing to friction and wear. Additionally, the measurement of nanostructures is important in the fields of hard disk drive components, MEMS, flat-panel displays, and semiconductor chips to provide feedback to improve fabrication processes and tools. Instruments that directly measure surface roughness in-situ in the presence of vibration, and over a large area, are not readily available. The proposed instrument will allow rapid measurement over a large scale in manufacturing environments enabling quick optimization of the fabrication process, minimization of productions costs, and development of new surface fabrication processes.
The Aims of this SBIR Phase I project were to 1) design and develop a breadboard interference microscope objective suitable to be used with a breadboard dynamic interferometric microscope over a large range of magnifications, 2) develop and demonstrate an extended range multiple wavelength technique usable in shop environments that would extend the vertical measurement range of interferometric optical profilers while still obtaining data quickly enough to essentially freeze effects due to vibration, and 3) evaluate the performance of 1) and 2). We successfully completed each of the aims of this Phase I project and demonstrated "proof of principle" for this novel measurement technology over a wide variety of applications. Measurements from our breadboard system demonstrated the desired vertical range, resolution, and vibration immunity that were the primary goals of this research. We compared our results with a commercial optical profilometer system and believe that our breadboard measurements actually show better accuracy and spatial resolution, while at the same time were made in the presence of significant vibration. In evaluating the performance of this system, we demonstrated that the noise floor was comparable to that of commercial interferometric optical profilers when operating using a single wavelength while be able to make successful measurements in non-ideal environments. The multiple wavelength performance was consistent with single wavelength measurements in terms of fractions of the equivalent wavelength. We demonstrated feasibility for in-situ optical manufacturing by measuring bare glass surfaces at various states of fine grinding and polishing as well as measuring ground machined surfaces, and studying scratches in a roughened silicon wafer [Fig. 1]. We demonstrated the flexibility of this technique by measuring through glass windows causing dispersion that commercial interference microscopes are unable to handle, and by measuring critical dimensions of complex and extended objects such as the mirrors in a DMD MEMS device used in DLP (digital light projector)[Fig. 2]. This technology has the potential to enable measurements in manufacturing environments where measurements previously could not be made. The broader impact of this research is that it will help provide better monitoring of surface finish and critical dimension measurement for improving manufacturing capability in markets such as data storage components, LCD display panels, solar panels, semiconductor wafers and chips, micro electro-mechanical structures, machined and lapped surfaces, bio-optical devices, and textures of paints and papers.
