Intra-Cell Dummy Transistor Repurposing for Hold-Slack Mitigation
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Solution Overview
Problem
Existing methods for mitigating hold-slack violations in semiconductor devices, particularly in the context of advanced technology nodes with smaller time scales (less than about 5 psec), are ineffective, leading to increased cell footprints and performance issues due to the use of isolation dummy gates and cell padding techniques.
Innovation Solution
The method involves repurposing disconnected dummy transistors within a circuit design as connected passive devices, specifically converting shorted or capacitor-configured transistors to mitigate hold-slack violations without enlarging the cell footprint, known as the DD2CP method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation dummy gates and cell padding techniques are used to mitigate hold-slack violations, then timing reliability is improved, but cell footprint increases
Solution Approach 1:
The patent recovers and repurposes dummy transistors that were previously discarded as non-functional elements. By converting these dummy transistors into functional delay elements through selective connection to circuit nodes, the solution eliminates the need for additional isolation dummy gates and cell padding, thereby maintaining timing reliability without increasing cell footprint
Solution Approach 2:
The patent makes dummy transistors multi-functional by enabling them to serve both as placeholders during manufacturing and as active delay elements for timing correction. This universal usage allows the same transistor structures to fulfill multiple purposes, eliminating the need for separate dedicated delay elements that would increase footprint
2Reliability
If isolation dummy gates and cell padding techniques are used to mitigate hold-slack violations, then timing uncertainty is reduced, but device complexity increases
Solution Approach 1:
The patent recovers previously discarded dummy transistors and transforms them into functional delay elements. This approach reduces device complexity by eliminating the need for additional isolation dummy gates and cell padding structures, while simultaneously reducing timing uncertainty through controlled delay insertion
Solution Approach 2:
The patent changes the functional state of dummy transistors from non-conductive to conductive by modifying their connection parameters. By selectively connecting dummy transistor terminals to specific circuit nodes, the solution adjusts timing parameters without adding structural complexity
3Ease of manufacture
If conventional methods are used in advanced technology nodes with smaller time scales, then manufacturing processes are maintained, but hold-slack violations increase
Solution Approach 1:
The patent changes the operational parameters of existing dummy transistors by modifying their connectivity rather than their physical structure. This parameter-based approach maintains compatibility with standard manufacturing processes while achieving the required timing performance for advanced technology nodes with sub-5 picosecond scales
Solution Approach 2:
The patent enables dummy transistors to self-serve dual purposes: maintaining manufacturing simplicity while automatically providing timing correction functionality. The same structures that facilitate easy manufacture also become the mechanism for hold-slack mitigation
Data Source
AI summary
In some embodiments, a method of generating a cell in a layout diagram includes: selecting a cell from a library of standard cells, components of the cell defining an active circuit; identifying a dummy device within the cell that is disconnected from the active circuit within the cell; and connecting the dummy device to a target node of the active circuit.