Preserving Channel Strain in FinFET Fin Cuts
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Solution Overview
Problem
In semiconductor structures, particularly in FinFETs, early fin cuts result in significant strain loss, which affects carrier mobility and on-current performance, and existing methods fail to effectively preserve channel strain during the fin cutting process.
Innovation Solution
The method involves forming fin cuts later in the process, after gate and epitaxial source/drain formation, to minimize strain loss, using a fin cut mask to determine the portion of the fin to be removed, and depositing an oxide to replace the removed fin portion, thereby preserving channel strain and reducing spacer etching and pulldown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fin cuts are performed early in the process, then manufacturing progress is made, but channel strain is significantly lost affecting carrier mobility and on-current performance
Solution Approach 1:
The patent applies preliminary action by performing the fin cut operation at a later stage in the manufacturing process, specifically after gate and source/drain formation, rather than early in the process. This timing allows the fin structure to maintain its strain characteristics longer during fabrication, preserving channel strain and improving carrier mobility while still enabling subsequent manufacturing steps to proceed.
2Reliability
If fin cuts are performed later in the process, then channel strain is preserved increasing drive current, but process complexity increases
Solution Approach 1:
The patent merges the fin cut operation with the gate patterning process by using the gate patterning hard mask and spacers as the etch mask for the fin cut. This integration eliminates the need for a separate dedicated fin cut mask and process step, thereby preserving channel strain while avoiding additional process complexity. The combined approach uses existing process elements to achieve both strain preservation and manufacturing efficiency.
3Device complexity
If fin cuts are performed early, then process steps are reduced, but spacer etching and pulldown increase
Solution Approach 1:
The patent performs the fin cut operation after the spacers have been formed, allowing the spacers to serve as protective structures during the etching process. This preliminary formation of spacers before fin cutting prevents excessive spacer etching and pulldown that would occur if fins were cut earlier, thereby improving manufacturing precision while maintaining a streamlined process.
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 results in increased drive current by 1-10% with no additional leakage current, enables better control over fin cuts, and reduces end capacitance by maintaining longer fin lengths and allowing for single diffusion breaks, while preventing gate shorting and preserving materials used for gate patterning.
Implementation Method 1
depositing an oxide to replace the portion of said at least one fin removed during the fin cut
Data Source
AI summary
A method of forming a semiconductor structure includes forming a fin cut mask over a region in a fin field-effect transistor (finFET) structure. The finFET structure includes one or more fins and one or more gates and source/drain regions formed over the one or more fins in active regions of the finFET structure. The method also includes performing a fin cut by removing a portion of at least one fin. The portion of the at least one fin is determined by an exposed area of the fin cut mask. The exposed area of the fin cut mask includes at least a portion of the at least one fin between a first dummy gate and a second dummy gate formed over the at least one fin. The method further includes removing the fin cut mask and depositing an oxide to replace the portion of the at least one fin removed during the fin cut.