Non-Interleaving Well Pickup Layout to Reduce IC Latch-Up
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Solution Overview
Problem
The scaling down of semiconductor integrated circuit (IC) technology has led to smaller P-well and N-well pickup regions, causing issues such as latch-up due to implant aperture effects and inter-well implant dose compensation, which degrade device performance and reliability.
Innovation Solution
Reconfiguring the N-well and P-well pickup regions into larger continuous regions, eliminating the interleaving configuration that causes these issues, thereby reducing inter-well implant dose compensation and alleviating the implant aperture effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the P-well and N-well pickup regions are scaled down to increase functional density, then the number of interconnected devices per chip area increases, but implant aperture effects and inter-well implant dose compensation occur causing latch-up and device failures
Solution Approach 1:
The pickup regions are segmented into interdigitated fingers alternating between P-well and N-well types. This segmentation allows each finger to be individually optimized while maintaining overall compactness, resolving the contradiction by enabling high functional density through efficient space utilization without causing implant aperture effects that would occur with fully scaled-down continuous regions
Solution Approach 2:
Different regions of the pickup structure are given different properties - the interdigitated fingers have alternating P-well and N-well doping characteristics, while the overall structure maintains continuous substrate connection. This local differentiation allows each zone to perform its specific function optimally while preventing the inter-well implant dose compensation that leads to latch-up
2Area of stationary object
If the P-well and N-well pickup regions are made smaller, then chip area is reduced and production efficiency increases, but the smaller sizes lead to implant aperture effects and inter-well implant dose compensation
Solution Approach 1:
The pickup regions are arranged in an interdigitated pattern extending in one dimension (creating fingers) while maintaining compactness in the perpendicular dimension. This dimensional transformation allows the structure to achieve high functional density without reducing the effective implantation area in any single direction, thereby avoiding implant aperture effects while maintaining small overall chip area
Solution Approach 2:
Multiple P-well and N-well fingers are merged into a continuous interdigitated structure that shares common substrate connections. This merging ensures uniform implant dose distribution across the entire pickup region while maintaining the compact interdigitated geometry, preventing inter-well implant dose compensation issues
3Productivity
If interleaving P-well and N-well pickup regions are used, then space utilization is maximized and device density increases, but latch-up occurs due to implant aperture effects and inter-well implant dose compensation
Solution Approach 1:
The interleaved pickup regions are segmented into discrete fingers with alternating P-well and N-well doping. This segmentation maintains the space-efficient interleaved arrangement while creating distinct zones that prevent the formation of continuous parasitic paths, thereby eliminating latch-up conditions that would occur in fully continuous interleaved structures
Solution Approach 2:
The interdigitated finger structure acts as an intermediary between the P-well and N-well regions, providing controlled interfaces that prevent direct interaction causing latch-up. The segmented fingers with alternating doping types create buffer zones that interrupt potential parasitic thyristor paths while maintaining the compact interleaved geometry for high device density
Data Source
AI summary
A semiconductor device includes a first region, a second region, a third region, and a fourth region. The first region includes a first portion of an N-well and a plurality of P-type transistors formed over the first portion of the N-well. The first region extends in a first direction. The second region includes a first portion of a P-well and a plurality of N-type transistors formed over the first portion of the P-well. The second region extends in the first direction. The third region includes a second portion of the P-well. The fourth region includes a second portion of the N-well. The first region and the second region are disposed between the third region and the fourth region.