Methods for VFET cell placement and cell architecture
A cell architecture and a method for placing a plurality of cells to form the cell architecture are provided. The cell architecture includes at least a 1 st cell and a 2 nd cell placed next to each other in a cell width direction, wherein the 1 st cell includes a one-fin connector which is formed around a fin among a plurality of fins of the 1 st cell, and connects a vertical field-effect transistor (VFET) of the 1 st cell to a power rail of the 1 st cell, wherein a 2 nd cell includes a connector connected to a power rail of the 2 nd cell, wherein the fin of the 1 st cell and the connector of the 2 nd cell are placed next to each other in the cell width direction in the cell architecture, and wherein the one-fin connector of the 1 st cell and the connector of the 2 nd cell are merged.
1 . A method for cell placement in a cell layout to form a cell architecture comprising a plurality of vertical field-effect transistors (VFETs), the method comprising:
placing, in the cell layout, a 1 st cell comprising a one-fin connector which connects a VFET to a power rail of the 1 st cell, and is formed around one fin of the 1 st cell;
determining characteristics of a 2 nd cell to be placed next to the 1 st cell with respect to an at least one-fin connector which connects at least one VFET to a power rail of the 2 nd cell, and is formed around at least one fin of the 2 nd cell; and
based on a result of the determining, performing:
a first operation in which the 2 nd cell is placed next to the 1 st cell in the cell layout, and the one-fin connector of the 1 st cell is merged with the at least one-fin connector of the 2 nd cell,
a second operation in which the 1 st cell is replaced with a 3 rd cell which is configured to perform a same logic function or operation of the 1 st cell, and comprises an at least two-fin connector connecting at least one VFET of the 3 rd cell to a power rail of the 3 rd cell and formed around at least two fins of the 3 rd cell, or
a third operation in which a fill cell is placed next to the 1 st cell, and a connector connected to a power rail of the fill cell is merged with the one-fin connector of the 1 st cell.
2 . The method of claim 1 wherein the 1 st cell, the 2 nd cell and the 3 rd cell are configured to perform a same logical function or operation.
3 . The method of claim 1 , wherein at least one of the 1 st cell, the 2 nd cell and the 3 rd cell is configured to perform a logic function or operation different from a logic functions or operation of the other one or two of the 1 st cell, the 2 nd cell and the 3 rd cell.
4 . The method of claim 1 , wherein the 1 st cell, the 2 nd cell and the 3 rd cell are selected from a cell library comprising a plurality of cells.
5 . The method of claim 1 , wherein one of the 1 st cell and the 2 nd cell, and the 3 rd cell constitutes one of a NAND3 circuit, or-and-inverter 211 (OAI211) circuit, and and-or-inverter 12 (AOI21) circuit.
6 . The method of claim 1 , wherein, in the fill cell, the connector is formed around the only fin of the fill cell.
7 . The method of claim 6 , wherein the connector of the fill cell comprises a bottom S/D region of a dummy VFET configured not to receive a gate input signal.
8 . The method of claim 1 , wherein the first operation is performed based on a result of the determining is positive, and one of the second and third operations is performed based on the result of the determining is negative.
9 . The method of claim 8 , wherein, in the 2 nd cell, the at least one-fin connector comprises one of an at least one-fin bottom S/D region of the at least one VFET, and an at least one-fin top S/D contact structure formed on at least one top S/D region of the at least one VFET and connected to a power rail of the 2 nd cell as the at least one-fin connector of the 2 nd cell,
wherein, based on a result of the determining is negative, the third operation is performed, and
wherein the method further comprises placing the 2 nd cell next to the fill cell so that the 2 nd cell, the fill cell, and the 1 st cell are arranged in a row in the cell layout in a cell width direction to form the cell architecture.
10 . The method of claim 9 , wherein, in the fill cell, the connector is formed around the only fin of the fill cell, and
wherein, in the 2 nd cell, the one of the at least one-fin bottom S/D region and the at least one-fin top S/D contact structure is formed around at least one fin of the 2 nd cell which is not placed next to the only fin of the fill cell.
11 . The method of claim 1 , wherein the characteristics of the 2 nd cell comprises a location of the at least one fin around which the at least one-fin connector of the 2 nd cell is formed.
12 . The method of claim 11 , wherein the determining comprises determining whether, when the 2 nd cell is placed next to the 1 st cell in the cell layout in a cell width direction to form the cell architecture, the at least one fin of the 2 nd cell is placed next to the one fin of the 1 st cell to enable the one-fin connector of the 1 st cell to be merged with the at least one-fin connector of the 2 nd cell.
13 . The method of claim 12 , wherein the at least two-fin connector of the 3 rd cell is not merged with the at least one-fin connector of the 2 nd cell in the cell architecture.
14 . The method of claim 12 , wherein, in the 2 nd cell, the at least one-fin connector comprises one of an at least one-fin bottom S/D region of the at least one VFET, and an at least one-fin top S/D contact structure formed on at least one top S/D region of the at least one VFET and connected to a power rail of the 2 nd cell as the at least one-fin connector of the 2 nd cell.
15 . The method of claim 1 , wherein the cell architecture comprises a plurality of cells comprising the 1 st cell and the 2 nd cell, and
wherein the method further comprises:
determining, in each of the plurality of cells, a location of at least one fin around which at least one-fin connector is connected to a power rail;
placing 1 st cells, comprising the 1 st cell, each of which comprises a one-fin connector connected to a power rail of each of the 1 st cells and formed around a single left-most single fin provided for at least one VFET, at even positions of the cell layout in a cell width direction;
placing 2 nd cells, comprising the 2 nd cell, each of which comprises at least one-fin connector connected to a power rail of each of the 2 nd cells and formed around at least one right-most fin provided for at least one VFET, at odd positions of the cell layout in the cell width direction so that each of the 2 st cells is placed between two neighboring 1 st cells of the 1 st cells; and
merging the one-fin connector of each of the 1 st cells with the at least one-fin connector of the each of the 2 nd cells which is placed next to the each of the 1 st cells.
16 . The method of claim 15 , wherein the at least one-fin connector of each of the 2 nd cells comprises one of an at least one-fin bottom S/D region of the at least one VFET and an at least one-fin top S/D contact structure formed on at least one top S/D region of the at least one VFET.
17 . The method of claim 15 , further comprising:
placing, next to one of 2 nd cells, other fill cell comprising a connector connected to a power rail of the other fill cell; and
merging the connector of the other fill cell with the connector of the one of the 2 nd cells.
18 . The method of claim 17 , wherein the connector of the other fill cell is formed around the only fin of the fill cell.
19 . The method of claim 18 , wherein the other fill cell comprises a dummy VFET which is formed on the only fin, comprises a bottom S/D region and a top S/D region on which a top S/D contact structure is formed, and configured not to receive a gate input signal, and
wherein one of the bottom S/D region and the top S/D contact structure of the other fill cell is connected to the power rail of the other fill cell.