Nitrogen-Rich Protective Layer for Epitaxial Selectivity
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Solution Overview
Problem
The challenge in CMOS fabrication at technology nodes below 22 nm is the low selectivity in forming strained epi films, leading to epi loss and defects due to the similarity in growth rates on pre-determined regions and protective layers, which affects device yield and production throughput.
Innovation Solution
A method involving the use of nitrogen-rich protective layers with a high nitrogen-to-silicon atomic ratio, formed through processes like LPCVD or PECVD, to reduce silicon dangling bonds and enhance selectivity between epi film growth on designated regions and protective layers, thereby preventing unwanted epi film formation on protective layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional protective layers are used during epi formation, then the protective layer provides basic protection, but the epi film grows at similar rates on both pre-determined regions and protective layers, resulting in low formation selectivity and epi loss
Solution Approach 1:
The protective layer is designed with non-uniform nitrogen concentration, creating regions of high nitrogen content that specifically inhibit epi film growth. This local variation in composition provides high formation selectivity without requiring uniform modification throughout the entire protective layer structure.
Solution Approach 2:
The nitrogen-to-silicon atomic ratio is optimized within specific ranges (0.5-2.0, preferably 0.8-1.5) to control epi film formation. By adjusting this compositional parameter, the protective layer achieves optimal inhibition of epi growth while maintaining processability and device performance.
2Manufacturing precision
If the epi formation rate is reduced to increase formation selectivity, then epi film formation selectivity improves, but the throughput of IC production decreases
Solution Approach 1:
The protective layer is pre-modified with nitrogen-rich regions before the epi formation process. This preliminary modification creates a surface that inherently resists epi film growth, eliminating the need to reduce epi formation rate and allowing high-speed epi processes to proceed with high selectivity.
Solution Approach 2:
Nitrogen acts as an intermediary element that modifies the protective layer's surface properties to inhibit epi film formation. The nitrogen-rich regions serve as a mediator between the protective layer and the epi film, preventing unwanted growth without affecting the overall epi process speed on pre-determined regions.
3Manufacturing precision
If nitrogen-rich protective layers with high nitrogen-to-silicon atomic ratio are used, then epi film formation selectivity is enhanced and unwanted epi growth is prevented, but the process complexity increases due to additional process parameters
Solution Approach 1:
The nitrogen-to-silicon atomic ratio is controlled within specific ranges (0.5-2.0, preferably 0.8-1.5) to achieve optimal epi film formation selectivity. This parameter optimization provides a systematic approach to managing process complexity while ensuring high manufacturing precision.
Solution Approach 2:
The nitrogen-rich protective layer self-regulates epi film formation through its compositional properties. The high nitrogen content automatically inhibits epi growth on protective layer regions without requiring additional control mechanisms or complex process monitoring, simplifying the overall fabrication 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 achieves high epi film formation selectivity, reducing defects and epi loss, and maintains production throughput by limiting epi film growth on protective layers, thus improving the yield and performance of CMOS devices.
Implementation Method 1
reduce silicon dangling bonds and enhance selectivity between epi film growth on designated regions and protective layers
Implementation Method 2
formed through processes like LPCVD or PECVD
Data Source
AI summary
A method for fabricating an integrated device is disclosed. The disclosed method provides improved formation selectivity of epitaxial films over a pre-determined region designed for forming an epi film and a protective layer preferred not to form an epi, polycrystalline, or amorphous film thereon during an epi film formation process. In an embodiment, the improved formation selectivity is achieved by providing a nitrogen-rich protective layer to decrease the amount of growth epi, polycrystalline, or amorphous film thereon.