Non-destructive, In-line Characterization of Shallow Junction Processes
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Non-destructive, In-line Characterization of Shallow Junction Processes G. Jonathan Kluth, Laurie Bechtler*, Peter Borden*, and Jian Mi* Advanced Micro Devices, Inc. Sunnyvale, CA 94088 *Boxer Cross Inc., 978 Hamilton Court, Menlo Park, CA 94025 ABSTRACT This paper describes the application of a novel optical metrology tool to in-line monitoring of shallow junction processes in a production setting. Recent results demonstrate the sensitivity of junction depth to implant dose and energy, as well as to annealing temperature and time. Results are also presented on monitoring of amorphizing implants and low dose implants. The in-line measurement has been performed on both bare wafers and product wafers. Measurements are compared with results obtained by destructive techniques such as SIMS and SRP. These results demonstrate that the optical method has the capability to provide in-line control of shallow junction processes. MRS ID #36341 INTRODUCTION Formation of shallow junctions necessary for 0.18 µm devices and beyond pose stringent requirements not only for process equipment, but also for metrology equipment. New processes for shallow junction formation, such as amorphization and ultra-low energy implants, create new demands not well met with current metrology. The need exists for a tool that can be used as an in-line monitor of the amorphization implants and low energy implants that will be an integral part of future processes. As described previously [1], a newly developed optical metrology tool is capable of measuring the active doping depth of shallow implants. Because the measurement is non-destructive and can be performed on patterned wafers with high throughput, the tool is well suited for in-line monitoring of shallow junction processes. This paper describes the application of this tool to monitoring of shallow junction processes in a production environment. EXPERIMENT In-line measurements were obtained using the carrier illumination™ (CI) technique that has been described previously [1]. CI uses a laser with photon energy above the bandgap to bias the diode structure created by the annealed doped layer. Under quasi-static conditions, a steep gradient in the excess carrier profile, and, therefore, index of refraction, occurs at the edge of the doped region. Light from a second laser with photon energy at the band edge is reflected from this gradient, providing a signal that varies with the depth of the active carrier profile. A BX-10 platform (from Boxer Cross Inc) is used to make the CI measurements. This system includes an automatic wafer handler and pattern recognition system, enabling measurements on wafers passing through standard process flows. The system reports junction depth of the activated profile at a concentration of 1E18 cm-3. The BX-10 was installed in an 8” fab running 0.18 µm logic processes. The tool was used to monitor shallow junction processes immediately after implant, as well as after anneal, on both bare and patterned wafers.
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Table I shows a summary of the measurements that w
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