Sacrificial Gate Isolation for Reduced Pitch Semiconductor Devices
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in achieving effective device isolation with reduced area usage, particularly at advanced nodes, due to limitations in lithographic dimensions and the need for efficient inter-device spacing.
Innovation Solution
The method involves forming self-aligned isolation structures by leveraging pre-existing sacrificial gate architectures, allowing for controlled epitaxial growth and maintaining contact with adjacent active regions on dissimilar electrical nets without skipping the contacted poly pitch, thereby reducing area requirements and improving device isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shallow trench isolation (STI) is used to provide device isolation, then effective isolation between adjacent devices is achieved, but the trench width and device-to-device spacing (pitch) are limited by lithographic dimensions, increasing area usage
Solution Approach 1:
A sacrificial gate structure is introduced as an intermediary element to define the isolation region. The sacrificial gate is formed between adjacent active regions, and its removal creates a precise isolation trench without requiring direct lithographic definition of the trench boundaries, thereby overcoming lithographic dimension limits
Solution Approach 2:
The sacrificial gate structure is formed in advance before the isolation trench is created. This preliminary structure serves as a template that guides subsequent etching and material removal processes, enabling precise isolation formation with reduced pitch
2Area of stationary object
If device density is increased to improve chip real estate utilization, then area efficiency is improved, but effective device isolation becomes more difficult to achieve with traditional methods
Solution Approach 1:
The sacrificial gate acts as a mediator that enables precise definition of isolation regions at reduced pitches. By using this intermediate structure, the patent achieves both high device density and effective isolation, as the sacrificial gate provides a reliable template for trench formation regardless of the reduced spacing between devices
3Area of moving object
If lithographic dimensions are reduced to enable smaller device features, then device areal dimensions decrease, but the constraints on trench width and device spacing increase due to lithographic limitations
Solution Approach 1:
The sacrificial gate structure serves as an intermediary that decouples the trench definition from direct lithographic constraints. The sacrificial gate can be formed with relaxed lithographic requirements, and its presence enables subsequent formation of isolation trenches with dimensions smaller than what could be directly lithographically defined
Solution Approach 2:
The sacrificial gate is formed preliminarily with larger, more manufacturable dimensions, and then used as a template to guide the formation of smaller isolation features. This preliminary action with relaxed constraints enables subsequent creation of smaller features without direct lithographic limitations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the formation of semiconductor devices with smaller areal dimensions and effective device isolation, overcoming the limitations of traditional methods by allowing for more dense device placement and efficient use of chip real estate.
Implementation Method 1
forming self-aligned isolation structures by leveraging pre-existing sacrificial gate architectures
Implementation Method 2
achieving controlled epitaxial growth while maintaining the ability to contact adjacent active regions
Data Source
AI summary
A fin cut process cuts semiconductor fins after forming sacrificial gate structures that overlie portions of the fins. Selected gate structures are removed to form openings and exposed portions of the fins within the openings are etched. An isolation dielectric layer is deposited into the openings and between end portions of the cut fins. The process enables a single sacrificial gate structure to define the spacing between two active regions on dissimilar electrical nets.