Page 149 - Sensors and Control Systems in Manufacturing

110
T w o
Cha p te r

2.11 Confocal Microscopy Sensors
Confocal Microscopy inspection equipment is currently used to inspect
probe marks, which is designed to handle high throughput, while cap-
turing process excursions with high probability. Once excursions are
detected, the data provides probe marks in the anomalous areas.
Efficient defect review, characterization, and root-cause analysis
require a flexible and interactive tool that can provide both lateral
and height measurements, that can revisit and fully describe features
in the areas of interest, and that can provide engineers and scientists
with timely data so they can correct the problems. The tool should
supply the data required for production meetings as well as images
that will represent the data to management and remote customers.
The tool should allow automated review and give engineers the
option of full manual control to devise an effective solution.
2.11.1 Confocal Profiling Characterization Systems
To date, conventional optical review stations and scanning-electron
microscopy have served this purpose, giving engineers good lateral
measurements and pictures of the features but providing only a rough
impression of their volumetric extent. Good depth measurement by
these methods requires skillful cross sectioning to view the deepest
part of the features, a process that generally delays results for long
periods, often for days, with works in progress at a standstill.
In the span of only several seconds, advanced confocal profiling
systems provide the same height information available from the most
careful scanning electron microscope (SEM) cross-section measurement
(Fig. 2.104). Cross-sectioning is carried out on the data rather than on
the sample, so the untouched wafer can be returned to the process
unharmed promptly after determining the disposition. Analysis may be
performed under automated recipe control, interactively under recipe
guidance, or manually, allowing the engineer to reach the root cause.
Images generated by Hyphenated Systems’ advanced confocal
profiling systems provide the same height information available from
scanning-electron microscope (SEM) cross-section measurements
(Fig. 2.105).

FIGURE 2.104 Advanced focal profi ling providing highly accurate heights.