Scan Flip-Flop Clock Layout for Lower Routing Congestion
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Solution Overview
Problem
The increasing complexity and integration density of semiconductor devices lead to significant challenges in testing, particularly in reducing congestion, resistance, and capacitance of metal lines, which hinders efficient scan testing and integration.
Innovation Solution
A scan flip-flop design incorporating a multiplexer, latches, an output buffer, and a clock buffer arranged in a parallel structure with cross-coupled clock lines, reducing layout congestion and improving integration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If components are arranged in a conventional sequential layout, then ease of manufacture is maintained, but layout congestion and metal line resistance increase
Solution Approach 1:
The patent transitions from a conventional one-dimensional sequential arrangement to a two-dimensional parallel arrangement. The first latch, second latch, and clock buffer are positioned side-by-side in parallel rather than in sequence, allowing clock lines to be routed more efficiently and reducing metal line congestion and resistance while maintaining manufacturing feasibility.
2Productivity
If integration density is increased, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent combines the clock buffer with the latch circuits in a unified parallel structure. The clock buffer is positioned adjacent to both the first and second latches, allowing shared clock signal distribution. This merging reduces the overall device area and improves integration density while the modular parallel design keeps the circuit complexity manageable.
3Ease of operation
If clock lines are routed conventionally, then ease of operation is maintained, but metal line capacitance and resistance increase
Solution Approach 1:
The clock lines are routed in a parallel configuration rather than sequentially. The first clock line connects the clock buffer to the first latch, and the second clock line connects the clock buffer to the second latch, both in parallel. This dimensional change in routing reduces the total length of metal lines, thereby reducing both resistance and capacitance while maintaining ease of signal routing.
Data Source
AI summary
A scan flip-flop includes a multiplexer, a first latch, a second latch, an output buffer and a clock buffer. The multiplexer selects one of a data input signal and a scan input signal based on an operation mode. The first latch latches an output of the multiplexer. The second latch latches an output of the first latch. The output buffer generates an output signal based on an output of the second latch. The clock buffer generates a first clock signal and a second clock signal that control operation of the first latch and the second latch. The first latch, the second latch, and the clock buffer are sequentially arranged along a first direction. A first clock line supplying the first clock signal and a second clock line supplying the second clock signal have a cross couple connection.