Memory Macro Well Isolation Using Cut Metal Gates
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Solution Overview
Problem
As semiconductor devices scale down, leakage current between oppositely doped wells increases, leading to latch-up issues in memory devices due to dopant diffusion, which existing technologies fail to adequately address in advanced process nodes.
Innovation Solution
The implementation of well isolation features formed through a cut metal gate process, where metal gate trenches are etched along every well boundary in well pick-up and middle strap areas, filled with an isolation material to separate adjacent oppositely doped wells, effectively reducing leakage and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometry is scaled down to increase functional density, then production efficiency increases and costs decrease, but leakage current between adjacent wells increases and latch-up issues worsen
Solution Approach 1:
The patent applies segmentation by dividing the continuous well structure into isolated segments using cut metal gates. The cut metal gate structure physically segments the n-well and p-well regions, creating isolated zones that prevent dopant diffusion between adjacent wells. This segmentation approach allows continued scaling while maintaining well isolation and preventing latch-up conditions.
Solution Approach 2:
The patent introduces an intermediary structure (the cut metal gate with isolation material) between adjacent n-wells and p-wells. This intermediary barrier acts as a mediator that blocks the harmful interaction (dopant diffusion) between oppositely doped wells, thereby preventing leakage current and latch-up while allowing the device to maintain scaled dimensions.
2Productivity
If device geometry is scaled down, then functional density increases, but well pick-up resistance increases due to dopant diffusion
Solution Approach 1:
The cut metal gate structure segments the well regions, creating isolated zones that prevent dopant diffusion. This segmentation maintains sharp dopant profiles and prevents contamination between n-well and p-well regions, thereby maintaining low well pick-up resistance even as device dimensions are scaled down and functional density increases.
3Productivity
If advanced process nodes are used to scale down geometry, then manufacturing efficiency improves, but leakage between adjacent wells increases
Solution Approach 1:
The cut metal gate structure serves as an intermediary barrier that actively blocks the harmful leakage current between adjacent wells. The isolation material within the cut metal gate creates a physical and electrical barrier that prevents dopant diffusion and leakage paths, enabling advanced process nodes to be used without suffering from increased leakage.
Solution Approach 2:
The patent extracts or removes the continuous conductive path between adjacent wells by introducing the cut metal gate structure. This extraction of the harmful leakage path allows the device to benefit from advanced process node scaling while eliminating the dopant diffusion and leakage problems that would otherwise occur.
Data Source
AI summary
A semiconductor device includes a memory macro having a middle strap area between edges of the memory macro and memory bit areas on both sides of the middle strap area. The memory macro includes n-type wells and p-type wells arranged alternately along a first direction with well boundaries between the adjacent n-type and p-type wells. The n-type and the p-type wells extend lengthwise along a second direction and extend continuously through the middle strap area and the memory bit areas. The memory macro includes a first dielectric layer disposed at the well boundaries in the middle strap area and the memory bit areas. From a top view, the first dielectric layer extends along the second direction and fully separates the n-type wells from the p-type wells in the middle strap area. From a cross-sectional view, the first dielectric layer vertically extends into the n-type or the p-type wells.