Inspection system integrates motion and vision
Innovative microelectronics companies use a hybrid of materials to design the next-generation of devices that are smaller, faster, and cheaper to manufacture.
Innovative microelectronics companies use a hybrid of materials to design the next-generation of devices that are smaller, faster, and cheaper to manufacture. They have created a need to migrate from semiautomated operator-assisted inspection equipment to fully automated vision-inspection and alignment systems with precision in the submicron range.
To address the critical requirements of MEMS (microelectromechanical systems) and MEOMs (microelectroopticalmechanical systems) inspection, NanoVia LP (Londonderry, NH) has developed a high-speed critical-dimension inspection and alignment system for volume component manufacturing. The NV60 critical dimension and alignment (CDI&A) system incorporates microscopy techniques with vision and motion-control technology to achieve measurements up to 200 data points/s.
Data are captured using a dual-camera setup and can be configured with Pulnix America (Sunnyvaale, CA) RS-170 NTSC cameras or Camera Link digital megapixel cameras for applications requiring high resolution. The pixel resolution of the camera directly determines the resolution of the motion system. The dual fixed-magnification camera setup offers both micro- and macroviews within the same scope. This allows rapid placement of components in assembling systems.
To enhance the contrast of the microscope image, a polarized illuminating beam is split into two components by a patent-pending hybrid-Nomarski prism. These two rays intersect each other at the back focal plane of the microscope objective (MO), illuminating the sample with two orthogonally polarized parallel rays. After reflection from the sample and passing through the MO, both rays meet again at the back focal plane of the MO and are recombined after passing through the Nomarski prism. Images produced are then due to the interference of polarized light reflected from two closely separated points of the same object and the contrast of the captured image is enhanced.
The host computer manages the data routing and distributed intelligence. Depending upon the exact system design, image data from the cameras are sent to either a Matrox Imaging (Dorval, Quebec, Canada) or Data Translation (Marlboro, MA) frame grabber. The image data in the frame grabber are calibrated (pixels/micron) with respect to space relative to motion per pixel. A position is established with respect to both field of motion and field of view. The code for these calculations is written in Visual C with canned dynamic link libraries from Matrox's MIL library or Data Translation's Foundry software packages. The positioning information is sent to a database and read into the Delta Tau Data Systems (Chatsworth, CA) multiaxis PMAC motion controllers. The controllers can perform interpolation along several axes. NanoVia has formed a technical alliance with Axis New England (Woburn, MA), a distributor of Delta Tau and Data Translation products, to jointly develop the complex motion algorithm for the system.
~Joe Delfino,Contributing Editor