Isolation Pillar Gate Structures for 7nm FinFET Epi Merge Prevention
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Solution Overview
Problem
The 7 nanometer technology node in semiconductor device manufacturing faces challenges with high gate budget requirements and high aspect ratios during trenching/cutting, as well as 'epi merge' issues due to decreased and unequal spacing between fins, which affect device performance.
Innovation Solution
The method involves forming isolation pillars by creating trenches in shallow trench isolation regions and filling them with an isolation material, extending below the upper surface of the shallow trench isolations, and using epitaxial diamond junctions to separate fins, thereby reducing gate budget and aspect ratios while preventing epi merge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a larger gate budget is used to combat gate height loss, then gate height is improved, but aspect ratio increases
Solution Approach 1:
The isolation pillars are formed before the dummy gate is formed, which is a preliminary action that establishes the isolation structure early in the process. This preliminary formation of isolation pillars allows for better control of the subsequent gate formation process, reducing gate height loss without requiring an increased gate budget, thereby avoiding high aspect ratios in trenches.
Solution Approach 2:
The patent changes the sequence of process steps, specifically forming isolation pillars before dummy gates, which alters the parameters of gate height loss and trench aspect ratio. This parameter change in process sequencing achieves reduced gate height loss without increasing the gate budget, thus resolving the contradiction between gate height and aspect ratio.
2Quantity of substance
If fins are placed closer together to increase density, then device density is improved, but epi merge occurs
Solution Approach 1:
The isolation pillars serve as intermediary structures between adjacent fins. These pillars physically separate the fins and prevent the epitaxial films from merging during subsequent processing steps. The intermediary isolation pillars maintain the desired fin spacing and prevent epi merge while allowing high device density.
Solution Approach 2:
The patent segments the space between fins by introducing isolation pillars that divide the continuous region between adjacent fins into separate isolated regions. This segmentation prevents the merging of epitaxial structures by creating physical barriers, thereby maintaining fin separation even at high densities.
3Ease of manufacture
If equal spacing between fins is maintained, then manufacturing simplicity is improved, but gate budget increases
Solution Approach 1:
The isolation pillars are formed in a preliminary step before dummy gate formation, establishing uniform spacing references early in the process. This preliminary structuring enables subsequent steps to maintain spacing uniformity without requiring increased gate budget, as the isolation pillars serve as fixed reference points for alignment.
Data Source
AI summary
A method of forming isolation pillars for a gate structure, the method including: providing a preliminary structure including a substrate having a plurality of fins thereon, an STI formed between adjacent fins, an upper surface of the STIs extending higher than an upper surface of the fins, and a hardmask over the upper surface of the fins and between adjacent STIs; forming a first trench in a first selected STI and between adjacent fins in a gate region, and forming a second trench in a second selected STI and between adjacent fins in a TS region; and filling the first and second trenches with an isolation fill thereby forming a first isolation pillar in the gate region and a second isolation pillar in the TS region, the first and second isolation pillars extending below the upper surface of the STIs.