COAG Etch Stop Layers for Compact Self-Aligned Gate Contacts
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Solution Overview
Problem
The scaling of multi-gate transistors to smaller dimensions poses challenges in semiconductor fabrication, particularly in forming gate contacts over active regions without increasing transistor size or risking short circuits, due to constraints in current fabrication processes.
Innovation Solution
The implementation of contact over active gate (COAG) structures with etch stop layers allows for self-aligned gate contact formation over active gate regions, eliminating the need for additional gate contact layers and reducing layout space by recessing contact metals and introducing a trench insulating layer, thereby improving via contact selectivity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication processes are used for scaling multi-gate transistors, then existing process infrastructure can be maintained, but manufacturing precision and reliability deteriorate at 10 nanometer node and smaller dimensions
Solution Approach 1:
The fabrication process is segmented into distinct stages with specialized etch stop layers for different materials (silicon nitride, silicon oxide, titanium nitride, cobalt). Each etch stop layer is selectively removed to expose specific underlying structures, enabling precise control over contact formation at each stage rather than requiring a single complex monolithic process
Solution Approach 2:
Etch stop layers serve as intermediary structures between the gate electrode and the contact formation process. These intermediate layers (titanium nitride, cobalt, silicon oxide) mediate the selective exposure of gate regions, allowing precise contact placement without directly modifying the gate electrode itself
2Ease of manufacture
If gate contact layers are extended to reach inactive gate regions, then contact formation becomes easier, but layout area increases
Solution Approach 1:
The etch stop layers are positioned and configured to automatically guide the contact formation process to the correct locations. The selective etching of these self-aligned layers provides inherent registration, eliminating the need for extended gate contact layers to reach inactive regions while maintaining ease of contact formation
Solution Approach 2:
Instead of extending contacts horizontally to reach inactive gate regions, the solution uses vertical dimensionality through stacked etch stop layers. The contacts form through vertical etching sequences that selectively remove layers to expose gate regions, converting a horizontal layout problem into a vertical process sequence
3Reliability
If contact metals are recessed and trench insulating layers are introduced, then via contact selectivity improves, but fabrication process complexity increases
Solution Approach 1:
Different etch stop layers are introduced at specific locations with distinct etch selectivities. The titanium nitride layer provides one level of selectivity, while the cobalt and silicon oxide layers provide additional selective etching stages. This localized differentiation of material properties enables precise via contact formation without requiring complex overall process changes
Solution Approach 2:
The fabrication process utilizes changes in etch selectivity parameters by introducing multiple etch stop layers with different chemical compositions and etch rates. Each layer responds differently to specific etchants, enabling selective exposure of underlying structures through controlled parameter changes in the etching process rather than increasing mechanical or geometric complexity
Data Source
AI summary
Contact over active gate (COAG) structures with etch stop layers, and methods of fabricating contact over active gate (COAG) structures using etch stop layers, are described. In an example, an integrated circuit structure includes a plurality of gate structures above substrate, each of the gate structures including a gate insulating layer thereon. A plurality of conductive trench contact structures is alternating with the plurality of gate structures, each of the conductive trench contact structures including a trench insulating layer thereon. A first dielectric etch stop layer is directly on and continuous over the trench insulating layers and the gate insulating layers. A second dielectric etch stop layer is directly on and continuous over the first dielectric etch stop layer, the second dielectric etch stop layer distinct from the first dielectric etch stop layer. An interlayer dielectric material is on the second dielectric etch stop layer.