Gate Cap Spacer Structure for Parasitic Capacitance Reduction
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Solution Overview
Problem
The existing gate contact structures in semiconductor devices often result in parasitic gate-to-contact capacitors due to the positioning of gate contacts above isolation regions, leading to delayed switching speed and area penalties, as they create electrical shorts with source/drain structures.
Innovation Solution
The implementation of a sacrificial gate cap spacer structure that allows for self-aligned gate and source/drain contacts, where the gate cap layer has a reduced width compared to the gate structure, and an upper spacer contacts the sidewall surfaces of the gate cap layer and the inner surface of the first sidewall spacer, enabling more efficient electrical connections without shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CB gate contact is positioned above the isolation region to avoid electrical shorts, then electrical short prevention is improved, but area penalty increases and switching speed decreases due to parasitic capacitance
Solution Approach 1:
The patent introduces a vertical gate cap layer positioned above the gate structure, creating a three-dimensional configuration. This vertical dimension allows the gate contact to be positioned above the isolation region while the gate cap extends over the channel region, effectively reducing parasitic capacitance without increasing lateral device area.
Solution Approach 2:
The gate cap structure acts as an intermediary element between the gate contact and the channel region. It provides a conductive path that reduces the parasitic capacitance effect while maintaining proper electrical isolation, serving as a mediator that resolves the conflict between contact positioning and capacitance reduction.
2Reliability
If the CB gate contact is positioned above the isolation region, then electrical short prevention is improved, but switching speed decreases due to parasitic gate-to-contact capacitor
Solution Approach 1:
By adding the vertical gate cap dimension, the patent reduces the effective parasitic capacitance between the gate contact and channel. The gate cap's vertical positioning allows it to overlap with the channel region, creating a more efficient electrical path that reduces capacitive effects and improves switching speed while maintaining contact above the isolation region.
Solution Approach 2:
The patent changes the geometric parameters of the gate structure by adding a vertical cap layer with specific width and height dimensions. This parameter modification reduces the parasitic capacitance value, directly improving switching speed while maintaining the contact's position above the isolation region for reliability.
3Reliability
If a gate cap layer with reduced width is implemented, then parasitic capacitance is reduced, but manufacturing complexity increases
Solution Approach 1:
The gate structure is segmented into two distinct parts: the horizontal gate structure at the device level and the vertical gate cap layer above it. This segmentation allows each part to be optimized independently - the gate structure for channel control and the gate cap for parasitic capacitance reduction - while simplifying the overall manufacturing process through self-aligned formation.
Solution Approach 2:
The gate cap layer is formed as a preliminary structure before final contact formation. By pre-positioning the gate cap with the appropriate reduced width, the patent simplifies subsequent manufacturing steps and ensures proper parasitic capacitance reduction without requiring complex post-processing adjustments.
Data Source
AI summary
A device is disclosed that includes an active layer, a gate structure positioned above a channel region of the active layer and a first sidewall spacer positioned adjacent the gate structure. The device also includes a gate cap layer positioned above the gate structure and an upper spacer that contacts sidewall surfaces of the gate cap layer, a portion of an upper surface of the gate structure and an inner surface of the first sidewall spacer.