Epitaxy and device behaviour of collector-up SiGe HBTs with a partial p-type collector

L.C.M. van den Oever (Corresponding Author), L.K. Nanver, T.L.M. Scholtes, H.W. Van Zeijl, W.D. Van Noort, Q.W. Ren, J.W. Slotboom

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A detailed experimental study has been made of the issues related to base dopant activation and mesa isolation in collector-up SiGe HBTs. It is concluded that to avoid excessive emitter-base diode leakage: (i) the metallurgic emitter-base junction should be moved away from the trenched p+ base doping peak, and (ii) the base contact implant should not be placed in the high n-doped emitter substrate. Both recommendations can be followed by applying an implanted pedestal emitter. To furthermore avoid TED, the base contact implantation is activated by laser annealing. To achieve a good quality collector-base diode, a p-nn+ collector profile is introduced. As a result, the transistor profile is a stack of several doped Si and SiGe layers. This stack is grown by AP/LPCVD dichlorosilane based epitaxy, which was optimised to suppress autodoping and to achieve sharp transitions. Hence the 1150°C prebake was performed at low pressure and high flow, and followed by a 10 nm undoped Si deposition at 700°C. Moreover, 5 nm undoped Si layers were inserted for dopant decoupling. The effect of the p- layer in the collector on the device behaviour was analysed by device simulations. It was found that this p- layer does not significantly affect the DC and high-frequency performance of the device.

Original languageEnglish
Pages (from-to)1899-1904
Number of pages6
JournalSolid-state electronics
Issue number11
Publication statusPublished - Nov 2001
Externally publishedYes


  • Base leakage
  • Laser annealing
  • Si epitaxy
  • SiGe epitaxy
  • SiGe HBT
  • Transient enhanced diffusion

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