FinFET Isolation Depth Variation for Void-Free Stressor Regrowth
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Solution Overview
Problem
In FinFET devices, the closeness of fins during regrowth leads to void formation between re-grown source/drain regions, reducing stress and performance due to insufficient space for contact etch stop layers, which limits the stress applied to the channel region.
Innovation Solution
A FinFET structure with inter-fin and intra-fin isolation regions of differing heights, allowing for a continuous source/drain region and improved stress application by forming isolation regions of varying depths to accommodate stressor growth, thereby avoiding voids and enhancing channel stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fins are placed close together during regrowth to improve device density, then device integration is improved, but voids form between re-grown source/drain regions reducing stress application
Solution Approach 1:
The patent transitions from a planar isolation structure to a three-dimensional stepped isolation structure with multiple depth levels. The first isolation region extends to a first depth while the second isolation region extends to a second depth greater than the first depth, creating vertical differentiation that allows source/drain regions to be regrown without forming voids between closely spaced fins.
Solution Approach 2:
The patent applies different isolation depths at different locations: the first isolation region between adjacent fins extends to a first depth, while the second isolation region outside the fins extends to a second depth. This localized differentiation in isolation depth allows for proper stress application in the channel region while maintaining close fin spacing for high device integration.
2Ease of manufacture
If isolation regions are made uniform in depth, then manufacturing is simplified, but voids form and stress control is reduced
Solution Approach 1:
The isolation structure is segmented into two distinct depth levels: a first isolation region at a first depth and a second isolation region at a second depth. This segmentation allows each isolation region to serve its specific function - the first isolation region provides base isolation between fins while the second isolation region provides additional isolation and stress control outside the fin regions, eliminating void formation.
3Reliability
If source/drain regions are regrown with stressor material, then carrier mobility is improved, but voids form reducing the effective stress applied to the channel
Solution Approach 1:
The patent performs preliminary action by forming the stepped isolation structure with two depth levels before regrowing the source/drain regions. The first isolation region and second isolation region are established at different depths prior to regrowth, which prevents void formation during the regrowth process and ensures continuous stress application to the channel region.
Data Source
AI summary
A system and method for manufacturing multiple-gate semiconductor devices is disclosed. An embodiment comprises multiple fins, wherein intra-fin isolation regions extend into the substrate less than inter-fin isolation regions. Regions of the multiple fins not covered by the gate stack are removed and source/drain regions are formed from the substrate so as to avoid the formation of voids between the fins in the source/drain region.