Butted Contact Structure With Leveling Pad
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Solution Overview
Problem
Conventional butted contacts in semiconductor devices often have non-vertical profiles due to the etching loading effect, leading to increased contact resistance and a higher risk of open circuits, especially when the overlapping portion with the source region is reduced or disappears.
Innovation Solution
A contact pad is introduced between the butted contact and the source/drain region, with its top surface leveled with the gate extension, reducing the recessing distance and increasing the contact area, thereby decreasing contact resistance and the likelihood of open circuits. This is achieved through a method involving replacement gate processes, including forming a dummy gate, depositing an inter-layer dielectric layer, and planarizing it to create openings for metal filling, which forms both the metal gate and the contact pad.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional butted contacts are formed without additional contact pads, then the layout area is minimized, but the contact resistance increases and open circuit risk rises due to non-vertical profiles and reduced overlapping portions
Solution Approach 1:
A contact pad is introduced as an intermediary element between the butted contact and the source/drain region. This contact pad serves as a mediator that increases the overlapping area and improves electrical connection reliability without significantly increasing the overall layout area. The contact pad compensates for the non-vertical profile effects and ensures adequate contact area even when the butted contact geometry is constrained.
2Area of stationary object
If the overlapping portion of the butted contact with the source region is reduced to minimize layout area, then the layout density increases, but the contact resistance increases and open circuit failure occurs
Solution Approach 1:
The contact pad acts as an intermediary that decouples the relationship between butted contact geometry and actual electrical contact area. By introducing this intermediate structure, the design can maintain smaller overlapping portions for layout density while the contact pad ensures sufficient electrical connection area, effectively resolving the conflict between layout area minimization and contact overlap precision.
3Reliability
If contact pads are added to reduce contact resistance and open circuit risk, then contact reliability improves, but the layout area and device complexity increase
Solution Approach 1:
The contact pad formation is merged with the existing gate formation process in replacement gate architectures. The same metal deposition and planarization steps that create the gate also form the contact pad, eliminating the need for separate process steps. This merging approach improves contact reliability while minimizing the increase in device complexity and manufacturing process complexity.
4Ease of manufacture
If conventional etching processes are used to form butted contacts, then the manufacturing process is simple, but the etching loading effect causes non-vertical profiles that increase contact resistance
Solution Approach 1:
The contact pad serves as an intermediary structure that compensates for the non-vertical profile caused by simple etching processes. Rather than requiring complex etching control, the contact pad provides an additional overlapping area that ensures adequate electrical connection even when the butted contact profile is not perfectly vertical, thus maintaining ease of manufacture while improving contact profile precision.
Data Source
AI summary
A semiconductor structure and a method of forming the same using replacement gate processes are provided. The semiconductor structure includes a butted contact coupling a source/drain region, or a silicide on the source/drain region, of a first transistor and a gate extension. The semiconductor structure further includes a contact pad over the source/drain region of the first transistor and electrically coupled to the source/drain region. The addition of the contact pad reduces the contact resistance and the possibility that an open circuit is formed between the butted contact and the source/drain region. The contact pad preferably has a top surface substantially leveled with a top surface of the gate extension.