Single Diffusion Break (SDB) or Single Dummy Gate (SDG) is a semiconductor process flow technique that eliminates the need for an additional dummy gate padding at the cell boundaries. SDB is used to enable aggressive scaling of abutting cells without affecting the cell height or underlying devices.
Double diffusion break (DDB) isolation has historically been used to isolate neighboring devices in order to provide good process control (stress) and reduce variations. Single diffusion break reduces the cell-to-cell spacing by reducing the width of the shallow trench isolation to a single dummy poly gate length. In practice, there is no actual dummy gate. Instead, just the trench isolation remains.
With advancements in DTCO, advanced process nodes reduced cell height, thereby increasing the share of wasted space due to cell-to-cell spacings as a result of DDB. Eliminating the additional inactive gate pitch can result in significant savings at the block and macro levels.
Samsung first introduced single diffusion breaks at their 14-nanometer process. Samsung used SDB in all their succeeding nodes including 10nm, 7nm, 5nm, and 4nm.
Intel introduced single diffusion breaks starting with their 10-nanometer process. The company claimed SDG resulted in a 20% improvement in cell densty. Intel introduced 2nd-generation SDG at their Intel 4 node.
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- Intel, 2017 IEEE 63rd International Electron Devices Meeting (IEDM).