Automated Wafer Metrology Tool from DWFritz Automation

This sophisticated, flexible wafer metrology system combines a Micro-Epsilon profilometer with a high-performance, high-resolution vision system and laser interferometers to detect and measure laser-cut features on one side of a wafers relative to features on the other side of the wafer.

Bowed wafers enter the system at two cassette tilt stations. Wafer handling is via a robot fitted with an edge grip end effector. Wafers are oriented on a notch finder, with wafer ID captured by a Cognex OCR camera. Wafers are then inspected at a custom wafer pocket mounted on an open-frame X-Y stage assembly. The wafer on the table is inspected on both the top and bottom by opposing 1392 X 1040 pixel vision cameras. The top and bottom inspections can be referenced to top or bottom fiducials.

Unique three-dimensional features are inspected by the profilometer, providing final resolutions of less than 0.1 micron. The wafer handling and inspection process are fully automated and wafers are automatically tracked throughout the system. In addition, the entire process can be visually monitored with custom touch-sensitive screens at the user interface.

Wafer bowing causes measurement errors as the wafer is scanned. A unique custom self-calibration tool and algorithm finds very small angular errors in the cameras and the machine uses this information to compensate for the induced errors, to achieve the error budget.

The system is mounted on vibration isolated granite supported by a welded steel base for superior stability. All pneumatic, computer, and control hardware is contained within the base structure. This tool is designed for use in a clean room environment and features on-board temperature, humidity and barometric pressure monitoring and weather compensation routines.