Semiconductor Isolation Structure Recessing for Gate Spacer Alignment
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Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in optimizing the structure and profile of isolation structures and gate spacers to enhance device performance and prevent short circuits between source/drain and gate regions.
Innovation Solution
A method involving recessing processes to form specific profiles on isolation structures and the subsequent formation of gate spacers that extend to these recessed areas, ensuring proper alignment and preventing short circuits, while also allowing for improved carrier mobility through strained epitaxy structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures and gate spacers are formed with conventional processes, then manufacturing simplicity is maintained, but device performance and short circuit prevention are compromised
Solution Approach 1:
The patent applies preliminary action by performing a recessing process on the isolation structure before forming the gate spacer. This preliminary recessing creates a stepped profile that ensures the gate spacer extends sufficiently over the source/drain region without requiring complex subsequent adjustments, thereby preventing short circuits while maintaining manufacturing feasibility
Solution Approach 2:
The isolation structure is segmented into multiple levels through the recessing process, creating a stepped profile with different heights. This segmentation allows the gate spacer to be formed at different elevations, ensuring proper electrical isolation and preventing short circuits between the gate and source/drain regions
2Reliability
If gate spacers are formed to extend further over source/drain regions, then short circuit prevention is improved, but manufacturing precision requirements increase
Solution Approach 1:
The recessing process is performed as a preliminary action before gate spacer formation, creating a stepped profile that naturally guides the gate spacer to extend the required distance over the source/drain region. This preliminary structuring reduces the precision requirements for subsequent gate spacer formation by providing clear physical boundaries and alignment references
Solution Approach 2:
The recessed isolation structure acts as an intermediary element that mediates between the source/drain region and the gate spacer. This intermediate stepped structure provides a physical platform that ensures proper gate spacer positioning and extension, reducing the direct precision requirements between the source/drain and gate spacer
Data Source
AI summary
A semiconductor device includes a substrate; at least one source/drain feature at least partially disposed in the substrate; an isolation structure disposed on the substrate and includes a first portion; a gate structure disposed on the first portion of the isolation structure and adjacent to the source/drain feature; and at least one gate spacer disposed on a sidewall of the gate structure, in which a top surface of the first portion of the isolation structure is in contact with the gate structure and is higher than a bottommost surface of the gate spacer.