Modules and Sub-assemblies

Triptar designs and manufactures optical modules and sub-assemblies for OEMs. Here are the stories behind three such products.

Up-Down Microscope for a Wafer Alignment System

The client needed a vision guidance system for a next-generation bond aligner with sub-micron accuracy and the capability to handle 300 millimeter silicon wafers. Older models in the product line handled smaller wafers with larger features and 2 micron alignment accuracy. The new model's much larger size presented unprecedented challenges for rigidity and stability in the opto-mechanical performance specifications. The optical systems had to be long and slender. Some of the requirements were:

• Image quality good enough for nanometer assessment of the position of fiducials in the fields of view (accuracy and repeatability).
• Alignment of upwards looking and downwards looking fields of view to within 70 microns.
• Thin, bridge-like form factor to fit onto the bond aligner's gantry and between two wafers.
• High mechanical stiffness to avoid problematic sagging across a 1-meter length.
• Tip-tilt-and-role adjustability with no more than micro-radian creep over several days.
• Negligible heating from internal illumination.

The solution was to put two independent imaging systems inside of a single rectangular tube. To get the length needed to span the distance between mounting points on the gantry and minimize the weight and sag, several intricately carved bars of T7075-T6 aluminum were attached end to end. Coaxial illumination was provided by widening the tubes at the ends near the camera mounting points. Kinematic stages at both ends attached the optical systems to the gantry's mounting points.

The prototypes performed flawlessly. Modifications were implemented to simplify manufacturing and improve initial alignment procedures. Production started at three pairs of systems per year.