FinFET Self-Aligned Contact Etch for Gate-Source Short Prevention
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Solution Overview
Problem
The increasing density of semiconductor devices, particularly in advanced node FinFETs, leads to a higher risk of electrical shorts between gate and source/drain contacts due to their proximity, which adversely affects yield and device performance.
Innovation Solution
A method is developed to form FinFET devices with a reduced risk of electrical shorts by forming a semiconductor fin with source/drain regions and a channel, using an isolation layer and dielectric layers to create cavities that are filled with a selective dielectric material, and forming conductive contacts with a conductive liner and contact layer, ensuring the gate stack is co-planar with the contact layer to prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device density is increased to improve circuit performance, then device performance and circuit speed are improved, but the risk of electrical shorts between adjacent conductive elements increases
Solution Approach 1:
The patent segments the gate contact and source/drain contact structures by introducing a mandrel structure that physically separates them. The mandrel creates distinct regions for gate contacts and source/drain contacts, preventing their merging even as device density increases. This segmentation maintains electrical isolation between adjacent conductive elements while allowing higher device density.
Solution Approach 2:
The mandrel structure serves as an intermediary element between the gate contact and source/drain contact regions. It acts as a physical barrier and spacer that maintains the necessary separation distance, preventing direct electrical contact between the gate and source/drain contacts while allowing both structures to exist in close proximity for high-density device design.
2Quantity of substance
If the distance between gate contacts and source/drain contacts is decreased to increase device density, then device density is improved, but unwanted conduction and leakage between structures increase
Solution Approach 1:
The mandrel structure segments the device into distinct gate contact regions and source/drain contact regions, maintaining physical separation even when overall device density is increased. This segmentation prevents the formation of unwanted conduction paths between adjacent structures.
Solution Approach 2:
The patent applies different structural characteristics to different regions: the mandrel provides rigid structural separation in critical areas where leakage prevention is needed, while allowing flexible device layout in other regions to achieve high density. The local structural quality varies to optimize both density and leakage prevention.
3Ease of manufacture
If a self-aligned contact etch method is used to simplify fabrication, then manufacturing complexity is reduced, but precision in preventing electrical shorts must be maintained
Solution Approach 1:
The mandrel structure is formed in advance before the contact etch process, establishing the separation geometry beforehand. This preliminary action defines the precise locations where contacts should be formed and ensures proper spacing is maintained throughout subsequent self-aligned etching operations, combining fabrication simplicity with manufacturing precision.
Solution Approach 2:
The self-aligned contact etch method uses the mandrel structure itself as the alignment reference for forming contacts. The process is self-aligning because the etch automatically follows the mandrel geometry, eliminating the need for separate alignment steps while maintaining precise contact placement and spacing for preventing electrical shorts.
Data Source
AI summary
A method of fabricating a FinFET device includes a self-aligned contact etch where a source/drain contact module is performed prior to a replacement metal gate (RMG) module. In particular, the method involves forming a sacrificial gate over the channel region of a fin, and an interlayer dielectric over adjacent source/drain regions of the fin. An etch mask is then used to protect source/drain contact regions and enable the removal of the interlayer dielectric from outside of the protected area, e.g., between adjacent fins.