Epitaxial Layer Defect Reduction in Source Drain Regions
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Solution Overview
Problem
Existing methods for forming epitaxial source and drain regions in semiconductor devices, such as MOSFETs, face challenges in reducing defects and achieving uniformity, particularly due to native oxide layer formation and residual particles that interfere with the growth of high-quality silicon-containing layers.
Innovation Solution
The implementation of an asymmetric cyclic deposition and etch (CDE) process, which includes controlled removal of native oxide layers, pre-deposition cleaning, and initial CDE unit cycles with a lower etch-to-deposition ratio to minimize particle defects and enhance epitaxial layer quality, is employed. This process integrates native oxide removal and deposition steps within an integrated processing system to prevent reformation and improve surface cleanliness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods are used to form epitaxial source and drain regions, then the formation process is simple, but particle defects and non-uniformity increase due to native oxide layer interference
Solution Approach 1:
The deposition process is divided into multiple sequential stages: native oxide removal, pre-deposition cleaning, initial deposition with low etch-to-deposition ratio, and subsequent deposition cycles. This segmentation allows each stage to address specific defects systematically, improving epitaxial layer uniformity while managing process complexity through structured progression.
Solution Approach 2:
Native oxide layers are removed and surfaces are cleaned before epitaxial deposition begins. Pre-deposition cleaning steps are performed to eliminate particles and contaminants in advance. These preliminary actions prevent defect formation during the main deposition process, thereby improving manufacturing precision.
2Reliability
If native oxide layers are not removed, then the process is simpler, but particle defects increase and epitaxial layer quality deteriorates
Solution Approach 1:
Native oxide removal is performed as a preliminary step before epitaxial deposition. This advance action eliminates the harmful oxide layer that would otherwise cause particle defects and reliability issues, while the subsequent streamlined deposition process maintains manufacturing efficiency.
Solution Approach 2:
The native oxide layer, which is normally harmful and causes defects, is deliberately removed to create a clean surface. The removal process itself becomes beneficial by preventing particle formation and improving epitaxial layer quality, thereby enhancing device reliability.
3Manufacturing precision
If etch-to-deposition ratio is high in all CDE cycles, then material removal is efficient, but particle defects increase and surface cleanliness deteriorates
Solution Approach 1:
Different etch-to-deposition ratios are applied to different stages of the CDE process. Initial cycles use a lower ratio to prioritize surface cleanliness and particle reduction, while subsequent cycles can use higher ratios for efficient material removal. This localized quality approach optimizes both surface cleanliness and deposition efficiency at appropriate process stages.
Solution Approach 2:
The CDE process employs periodic cycles with varying etch-to-deposition ratios. Early cycles feature lower ratios for surface preparation and particle elimination, followed by cycles with higher ratios for bulk material deposition. This periodic variation in process parameters achieves both surface cleanliness and overall deposition efficiency.
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
The approach significantly reduces particle defects and enhances the quality of the epitaxial silicon-containing layers, leading to improved performance and reliability of semiconductor devices by ensuring a cleaner substrate surface and optimized growth conditions.
Implementation Method 1
performing an asymmetric cyclic deposition and etching (CDE) process to form an epitaxial layer in the recesses
Implementation Method 2
performing an asymmetric cyclic deposition and etching (CDE) process to form an epitaxial layer
Data Source
AI summary
The embodiments of mechanisms for forming source/drain (S/D) regions of field effect transistors (FETs) described enable forming an epitaxially grown silicon-containing layer with reduced number of particles on surface of recesses. The described mechanisms also reduce the effect of the residual particles on the epitaxial growth. The mechanisms include controlled etch of a native oxide layer on the surfaces of recesses to reduce creation of particles, and pre-CDE etch to remove particles from surface. The mechanisms also include reduced etch/deposition ratio(s) of initial CDE unit cycle(s) of CDE process to reduce the effect of residual particles on the formation of the epitaxially grown silicon-containing layer. With the application of one or more of the mechanisms, the quality of the epitaxial layer is improved.