Effect of silicidation on silicon-based thin film resistors in SiGe integrated circuits |
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Authors: | Sang-Heung Lee Seung-Yun Lee Chan Woo Park Dongwoo Suh |
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Affiliation: | (1) IT Convergence & Components Laboratory, Electronics and Telecommunications Research Institute (ETRI), Yuseong-gu, Daejeon, 305-700, Korea |
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Abstract: | The resistance variation of the silicon–germanium (SiGe) thin film resistor caused by the fabrication process of SiGe integrated
circuits (ICs) was investigated. The SiGe resistor and the Si resistor were made of the thin films identical with the p-type SiGe base layer and the n-type Si emitter layer of the SiGe hetero-junction bipolar transistor, respectively. The range of the resistance value of
the SiGe resistor was much larger than that of the Si resistor, and an abnormally high resistance of the SiGe resistor was
often observed. Ti–B precipitates and Ti(Si1−x
Ge
x
)2 protrusions were created as the result of the Ti silicidation of the p-type SiGe layer, whereas no precipitates and protrusions were generated in the case of the n-type Si layer. It was confirmed by scanning electron microscopy that the nonuniform resistance of the SiGe resistor was induced
by the removal of the protrusions and underlying field oxides in the contact window. Resistance uniformity of the SiGe resistor
was much improved by increasing the contact size. The simulation result of the detrimental influence of the resistance change
on ICs indicated that the fabrication process and the structure of the thin film resistor should be optimized for enhancing
IC reliability. |
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Keywords: | |
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