Nitrogen-Modified SiC Layer for Wafer Bow Reduction
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Solution Overview
Problem
The production of silicon carbide/silicon heteroepitaxy is hindered by tensile stress at the Si/SiC interface due to lattice mismatch and differential thermal contraction, leading to wafer bow, which compromises the robustness and flatness of the wafer.
Innovation Solution
Introducing nitrogen atoms during the epitaxial growth of the silicon carbide layer generates compressive stress that counteracts the tensile stress, thereby reducing wafer bow by incorporating nitrogen into the crystal lattice during the initial growth phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon carbide epitaxial layer is grown on silicon wafer, then heteroepitaxy structure is formed, but tensile stress is introduced at the interface due to lattice mismatch and thermal contraction
Solution Approach 1:
The patent applies nitrogen atoms during the epitaxial growth process to change the physical-chemical parameters of the SiC layer. The nitrogen incorporation modifies the lattice structure and thermal properties, generating compressive stress that counteracts the tensile stress from lattice mismatch and thermal contraction, thereby resolving the stress problem while maintaining heteroepitaxy formation
Solution Approach 2:
Nitrogen atoms serve as an intermediary substance introduced during growth. These nitrogen atoms mediate the stress state at the Si/SiC interface by incorporating into the SiC lattice and generating compressive stress, effectively counterbalancing the harmful tensile stress without requiring post-growth processing
2Ease of manufacture
If tensile stress is present at the Si/SiC interface, then heteroepitaxy can be formed, but wafer bow occurs which compromises robustness and flatness
Solution Approach 1:
By introducing nitrogen atoms during epitaxial growth, the patent changes the stress state parameter from tensile to compressive. This parameter change directly addresses the wafer bow problem by generating compressive stress that counteracts the tensile stress causing bow, thereby improving flatness while maintaining the heteroepitaxy structure
Solution Approach 2:
The patent applies preliminary anti-action by introducing nitrogen atoms during the growth process itself, rather than after. This preliminary measure generates compressive stress in advance to counteract the tensile stress that would otherwise cause wafer bow, preventing the problem before it manifests
3Stress or pressure
If nitrogen atoms are applied during epitaxial growth, then compressive stress is generated to counteract tensile stress, but process complexity increases
Solution Approach 1:
The patent merges the stress control function with the existing epitaxial growth process. By introducing nitrogen atoms during the standard epitaxial growth, the process combines material deposition with stress engineering in a single step, avoiding the need for separate stress modification steps and minimizing additional process complexity
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 technique effectively reduces wafer bow, enhancing the robustness and flatness of the composite wafer, facilitating further processing and device fabrication by maintaining a compressive stress at the critical interface, allowing for more precise semiconductor device construction.
Implementation Method 1
applying nitrogen atoms during the epitaxial growth of the silicon carbide epitaxial layer on the silicon wafer so as to generate a compressive stress within the composite wafer
Implementation Method 2
the tensile stress introduced at the Si/SiC interface due to the lattice miss-match between the two materials and the faster thermal contraction of SiC while cooling down from the typical growth temperature of 1370° C.
Data Source
AI summary
We describe a method for reducing bow in a composite wafer comprising a silicon wafer and a silicon carbide layer grown on the silicon wafer. The method includes applying nitrogen atoms during the growth process of the silicon carbide layer on the silicon wafer so as to generate a compressive stress within the composite wafer.