Epitaxial Source/Drain Growth With Protected Dummy Gate Ends
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Solution Overview
Problem
Existing processes for forming multi-gate devices often result in mushroom-like structures due to epitaxial growth on exposed portions of dummy gate stacks, leading to shorts and defects when the dummy gate stacks are replaced with metal gate structures.
Innovation Solution
A method is introduced where a gate spacer is deposited over dummy gate stacks, and patterned photoresist layers are used to prevent semiconductor material deposition on terminal end portions during source/drain feature formation, ensuring the gate spacers remain intact and preventing unwanted epitaxial growth, which is then followed by the replacement of dummy gate stacks with functional gate structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate spacer is deposited over dummy gate stack before source/drain recesses are formed, then gate control is improved, but mushroom-like structures form on exposed portions causing shorts
Solution Approach 1:
The patent applies preliminary action by forming a protective coating layer on the dummy gate stack before the epitaxial deposition process. This protective layer prevents semiconductor material from depositing on the dummy gate stack during source/drain feature formation, thereby preventing mushroom-like structures from forming while maintaining proper gate control.
2Productivity
If epitaxial deposition is performed on exposed dummy gate stack portions, then source/drain features are formed, but mushroom-like structures are created that cause shorts
Solution Approach 1:
The patent introduces an intermediary protective coating layer that acts as a barrier between the epitaxial deposition process and the dummy gate stack. This coating layer allows the epitaxial deposition to proceed efficiently for source/drain feature formation while preventing unwanted deposition on the dummy gate stack, thus eliminating mushroom-like structures and ensuring device reliability.
3Ease of manufacture
If dummy gate stack is replaced with metal gate structure, then functional gate is achieved, but existing mushroom-like structures become metal features causing shorts
Solution Approach 1:
The patent applies preliminary action by removing the protective coating layer after the epitaxial deposition is complete but before the dummy gate stack is replaced with the metal gate structure. This ensures that no mushroom-like structures remain on the dummy gate stack that could become problematic metal features after replacement, while maintaining ease of manufacture through a straightforward process sequence.
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 prevents the formation of mushroom-like structures, reducing defects and shorts, and allows for the successful replacement of dummy gate stacks with functional gates, enhancing the reliability and performance of multi-gate devices.
Implementation Method 1
depositing a gate spacer layer over the workpiece
Implementation Method 2
epitaxially forming source/drain features over the recessed source/drain regions
Data Source
AI summary
Semiconductor structures and methods are provided. A method according to the present disclosure includes providing a workpiece that includes a plurality of active regions including channel regions and source/drain regions, and a plurality of dummy gate stacks intersecting the plurality of active regions at the channel regions, the plurality of dummy gate stacks including a device portion and a terminal end portion. The method further includes depositing a gate spacer layer over the workpiece, anisotropically etching the workpiece to recess the source/drain regions and to form a gate spacer from the gate spacer layer, forming a patterned photoresist layer over the workpiece to expose the device portion and the recessed source/drain regions while the terminal end portion is covered, and after the forming of the patterned photoresist layer, epitaxially forming source/drain features over the recessed source/drain regions.