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The rapid development of integration density at present integrated circuits has caused a serious demand for high resolution thermal imaging for defect analysis. As conventional methods have reached their physical limits far above the feature size scanning thermal microscopy (SThM) has moved into the focus of this application. Although, this method is well-known for years its industrial application is still hindered by the insufficient availability of dedicated probes.
Commercially available probes for scanning thermal microscopy as well as those realized by several scientific groups suffer either from poor lateral resolution or inadequate stability under commonly used measurement conditions. Furthermore the fabrication scheme is often extremely complex and, thus, either not applicable for mass production or it is very expensive.
Hence we have developed a fabrication process suitable for mass production to realize different types of silicon probes for SThM with the potential of an outstanding spatial resolution of less than 50nm and a high temperature sensitivity.
We have worked out a sophisticated technique to realize a Schottky-junction or a thin film thermocouple with a height that could be controlled in a range of 30-50nm onto the tip apex of a scanning probe microscopy (SPM) probe. In contrast to all other methods of implementing a nano-junction on the very end of a tip our technique enables a high precision definition of the contact in the sub 50nm range and due to its semi-automation a high throughput of machined probes.
The manufacturing process also includes a progressive shadow mask concept which allows depositing a wide scope of different metals onto pronounced topographies with a position accuracy and a structure integrity of better than 5µm. In such a way it is also possible to post-process finished SPM-probes.
Furthermore we have systematically benchmarked different metals, various metal combinations and Schottky-junctions to determine their characteristics.
Based on the new high throughput manufacturing process and the investigated metals we have realized first thermal probes with a nano-contact on the tip apex and demonstrated their capability using a test bench.
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