International Business Machines Corporation

Ieng Ong

Pierre B Mollier

Gerard Boudon

Anthony Gus Aipperspach

Pascal R Tannhof

Nghia Van Phan

Allan Harvey Dansky

Steven John Zier

Jean-Paul J Nuez

Robert M Hornung

Adrian Zuckerman

Eric Gouze

Biagio Pluchino

Martine Bonneau

Franck Wallart

Jean-Marc Piccino

Multi-emitter BICMOS logic circuit family with superior performance

A CMOS FET master slice integrated circuit (20) of the gate-array type implemented in a semiconductor logic chip, comprises a plurality of core cells (CELL1, CELL2, . . . ) arranged adjacent one another on a repetitive basis in a row direction to form horizontal stripe shaped functional gate region (21) of a determined height (H). Each core cell (e.g., CELL1) is comprised of four different sized devices: one small and one large NFET (N1.1, N2.1), thus one small and one larger PFET (P1.1, P2.1), that are disposed in a column direction. The NFETs have separate gate electrodes (GN1.1, GN2.1) to define individual devices, while the PFETs have preferably a common gate electrode (GP1) to define a single device. The relative size of NFETs and PFETs have been optimized to provide the required functionality to the latches and to ensure the balanced rise and fall delays in a maximum of basic logic circuits of the chip. As a result, the use of such core cells, allows that complex logic functions, such as latches, can be implemented in gate arrays that have a density and performance comparable with standard cell circuits. In addition, the use of these core cells also permits optimization of other basic logic circuits (INV, NOR, . . . ) that are used in critical logic paths and clock distribution trees, where balanced delays are highly desirable.

Gate array cell having FETs of different and optimized sizes

According to the present invention, a CMOS interface circuit (C2) similar to a latch made by two CMOS cross coupled inverters (INV1, INV2) is placed directly on the output node (14) of conventional BICMOS logic circuit (11) operating alone in a partial swing mode. This latch is made of four FETs P5, P6, N8, N9 cross-coupled in a conventional way with the feedback loop connected to said output node (14). The partial voltage swing (VBE to VH-VBE) naturally given by the output bipolar transistors (T1, T2) mounted in a push pull configuration is reinforced to full swing (GND to VH) by the latch at the end of each transition. The state of the output node if forced by the latch because of the high driving capability due to the presence of said output bipolar transistors (T1, T2). As a result, the improved BICMOS logic circuit (D2) has an output signal (S) that ranges within the desired full swing voltage at the output terminal (15). It is a characteristic of this embodiment that the structure of CMOS interface (C2) is always independent of the logic function implemented in the conventional BICMOS logic circuit (11). More generally, the CMOS interface circuit may have various physical implementations, however, it is always comprised of CMOS FETs and it becomes active at least in one of the GND to VBE or (VH-BE) to VH range.

BICMOS logic circuit with full swing operation

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Ieng Ong