Gate Cut-Fill Structure for Protecting FinFET Epitaxy Regions
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Solution Overview
Problem
In the semiconductor industry, particularly for FinFET devices, the challenge lies in effectively cutting gate structures without damaging epitaxy source/drain regions, as existing etching processes can lead to misalignment and damage due to the differential etching rates of conductive and dielectric materials.
Innovation Solution
An etching process combining anisotropic and isotropic etching techniques is employed to create cut openings in gate structures, where the isotropic etching preferentially removes conductive materials over dielectric layers, thereby maintaining a greater distance from epitaxy source/drain regions and reducing the risk of damage, while allowing sufficient etching of gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching processes are used to cut gate structures, then the etching process can be completed, but the epitaxy source/drain regions may be damaged due to misalignment and differential etching rates
Solution Approach 1:
A mandrel structure is introduced as an intermediary element to define the cut opening position. The mandrel serves as a physical barrier that prevents the etching process from extending into the epitaxy source/drain regions, thereby protecting them from damage while enabling precise gate structure cutting. The mandrel is positioned between the gate structure and the epitaxy regions, acting as a mediator that controls the etching boundary.
Solution Approach 2:
The mandrel structure is formed prior to the etching process to pre-establish the boundaries of the cut opening. By performing this preliminary structuring step, the patent ensures that when the etching process subsequently removes conductive materials, the epitaxy source/drain regions are already protected by the pre-positioned mandrel, preventing misalignment-related damage.
2Area of moving object
If the cut opening width is reduced to increase pattern density, then higher device density is achieved, but the risk of damaging epitaxy source/drain regions increases
Solution Approach 1:
The mandrel structure acts as a protective intermediary that decouples the cut opening width from the distance to epitaxy regions. By introducing this intermediate element, the patent enables reduced cut opening widths for higher pattern density while the mandrel maintains a sufficient protective distance from the epitaxy source/drain regions, preventing damage even as features scale down.
Solution Approach 2:
The patent applies different structural qualities to different regions: the mandrel provides a robust, protective structure in critical areas near epitaxy regions, while allowing the cut opening to be narrow in active gate areas. This local differentiation of structural properties enables high pattern density in gate regions while maintaining protection in sensitive epitaxy regions.
3Reliability
If the distance between cut opening and epitaxy source/drain regions is increased to prevent damage, then epitaxy region protection is improved, but the process window for forming conductive features is reduced
Solution Approach 1:
The mandrel serves as a flexible intermediary that can be positioned at optimal distances from epitaxy regions to provide protection. This intermediate structure allows the patent to maintain adequate protection distances while still allowing sufficient space for conductive feature formation, effectively mediating between the conflicting requirements of protection and process flexibility.
Solution Approach 2:
The patent segments the structure into distinct functional zones: the mandrel region for protection, the cut opening region for gate isolation, and the epitaxy region for device formation. This segmentation allows each zone to be optimized independently - the mandrel can be positioned to provide protection while maintaining appropriate spacing for conductive feature formation in the epitaxy region.
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 enhances the yield of gate cut processes by reducing the risk of epitaxy source/drain region damage and increases the process window for forming conductive features, allowing for higher pattern density and improved device performance.
Implementation Method 1
An etching process is performed using a mask to form a cut opening in a gate structure... The etching process can include an anisotropic etching and an isotropic etching
Data Source
AI summary
Methods of cutting gate structures, and structures formed, are described. In an embodiment, a structure includes first and second gate structures over an active area, and a gate cut-fill structure. The first and second gate structures extend parallel. The active area includes a source/drain region disposed laterally between the first and second gate structures. The gate cut-fill structure has first and second primary portions and an intermediate portion. The first and second primary portions abut the first and second gate structures, respectively. The intermediate portion extends laterally between the first and second primary portions. First and second widths of the first and second primary portions along longitudinal midlines of the first and second gate structures, respectively, are each greater than a third width of the intermediate portion midway between the first and second gate structures and parallel to the longitudinal midline of the first gate structure.