GAA Semiconductor Device Source/Drain Formation
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving accurate optical critical dimension (OCD) measurements during the fabrication of Gate All-Around (GAA) devices due to variations in the source/drain epitaxial growth process, which can lead to inaccurate control of process parameters and gate height, and potential nanosheet crashing during the wire release process.
Innovation Solution
The method involves forming source/drain regions as homogenous blocks of silicon prior to forming fins, providing support for nanostructures during the wire release process and allowing for accurate in-line OCD monitoring, thereby preventing nanosheet crashing and maintaining process uniformity without additional costs or noise from source/drain epi process variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If source/drain regions are formed through epitaxial growth process, then source/drain regions can be formed with semiconductor material, but measurement precision of OCD is degraded due to process variations
Solution Approach 1:
The patent forms source/drain regions as homogenous blocks of silicon prior to forming fins and nanostructures. This preliminary formation establishes stable reference structures before subsequent processing steps, enabling accurate OCD measurements to be taken on these pre-formed regions rather than on subsequently grown epitaxial layers that introduce variability.
2Measurement precision
If source/drain regions are formed prior to fin formation, then OCD measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The homogenous source/drain blocks formed prior to fin creation serve multiple functions: they provide stable reference structures for OCD measurements, act as support structures during wire release to prevent nanosheet crashing, and define the final source/drain regions. This multi-functionality justifies the additional process step.
3Reliability
If wire release process is performed on fins with epitaxial source/drain, then nanosheet crashing occurs, but forming support structures beforehand increases process steps
Solution Approach 1:
The patent forms homogenous source/drain blocks before the wire release process to provide structural support and cushioning during the release operation. These pre-formed blocks prevent nanosheet crashing by providing a stable foundation, thereby protecting the delicate wire release process from failures that would occur with epitaxially grown source/drain regions.
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 highly accurate critical dimension measurements and controlled process parameters, improving the robustness of OCD models in manufacturing processes like MPG and RPG loops, ensuring uniformity and reducing noise from source/drain epi process variations.
Implementation Method 1
etching a first opening into the multi-layer stack and exposing the substrate through the first opening; etching a fin from the multi-layer stack
Implementation Method 2
forming a first source/drain region in the first opening; depositing the second semiconductor material in the first opening
Implementation Method 3
removing the first layer and the third layer from the fin
Data Source
AI summary
Gate-all-around (GAA) devices and methods of manufacturing such devices are described herein. A method includes forming a multi-layer structure over a substrate and forming a plurality of source/drain regions in the multi-layer structure. Fins are then patterned into the multi-layer structure through adjacent source/drain regions. A wire release process is performed to remove materials of one or more of the layers in the multi-layer stack. The remaining layers of the multi-layer stack form a stack of nanostructures connecting adjacent source/drain regions of the fins.