INFLUENCE OF THE COLLECTOR RESISTANCE ON THE PERFORMANCE OF ACCUMULATION CHANNEL DRIVEN BIPOLAR-TRANSISTOR

In this paper, the physical mechanism limiting the maximum controllabl e current density (J(mcc)) and safe operating area (SOA) of the accumu lation channel driven bipolar transistor (ACBT) is identified and anal yzed for the first time. According to our analysis, the hole current f lowing into the P+ collector at the shallow trench creates a bias oppo sing the built-in potential of the P+ collector/N-drift junction due t o a finite resistance associated with the contact to the diffused P+ c ollector region. This lowers the potential barrier established in the narrow mesa region tin between the self-aligned trenches) by the built -in potential of the P+ collector/N-drift junction and the control gat e potential and promotes electron injection from the N+ emitter into t he N-drift region over the potential barrier. At the onset of electron injection over the potential barrier, gate control over the base driv e of the vertical wide base PNP transistor in the ACBT is lost. This h ypothesis has been verified through numerical simulations and confirme d by experimental measurements which indicated an increase of over 300 % in J(mcc) due to a reduction in the contact resistance to the P+ col lector region after a post metallization anneal of the fabricated ACBT designs. Based upon these observations, a new ACBT structure with a S chottky collector junction is proposed. It is demonstrated that the pr oposed ACBT structure has a higher J(mcc) and wider SOA in comparison to the ACBT structure with P+ collector region. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.