Confocal microscopy for probe-mark characterization
A sidebar for "Probe-mark inspection," from our May 2007 issue.
A. Edward Robinson, Hyphenated Systems -- Test & Measurement World, 4/30/2007 12:54:00 PM
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Process inspection equipment used to inspect probe marks is designed to handle high throughput while capturing process excursions with high probability. Once excursions are detected, the first questions are: What do probe marks in the anomalous areas look like? And how do they compare with the normal process?
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 with timely data so they can correct the problems. The tool should supply the data required for production meetings as well as images that represent the data to management and remote customers. The tool should allow automated review and give engineers the option of full manual control to drill down to a solution.
| a) |  |
| b) |  |
| These images generated by Hyphenated Systems’ advanced confocal profiling systems provide the same height information available from scanning-electron microscope (SEM) cross-section measurements. a) This probe mark is relatively shallow, with the deepest portion less than 500 nm below the pad level. b) This mark is deeper and clearly shows a breakthrough to a barrier layer and the underlying dielectric around 1 mm beneath the pad surface. Courtesy of Hyphenated 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 hit the deepest part of the features, a process that generally delays results for days, with the work in progress sitting in limbo, begging questions at every production meeting.
In a matter of seconds, advanced confocal profiling systems provide the same height information that is available from the most careful scanning electron microscope (SEM) cross-section measurement (figure). Cross sectioning is carried out on the data rather than on the sample, so that the untouched wafer can be returned to the process unharmed and lot disposition promptly determined. Analysis may be performed under automated recipe control, interactively under recipe guidance, or manually, allowing the engineer to quickly drill down to the root cause.—A. Edward Robinson, PhD., VP applications and product development, Hyphenated Systems, Burlingame, CA. eddy@hyphenated-systems.com.
Go to "Probe-mark inspection"
