Silicon-Doped Boron Nitride Hard Mask for Epitaxy Control
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Solution Overview
Problem
The challenge in integrated circuit fabrication lies in maintaining consistent spacing and preventing damage to underlying layers when patterning and removing hard masks over epitaxially grown semiconductor material in MOS transistors, particularly due to issues with etch selectivity and epitaxial growth inhibition.
Innovation Solution
A silicon-doped boron nitride (SixBN) hard mask with 1-30 atomic percent silicon is used, allowing for selective etching and epitaxial growth in source/drain regions of one polarity MOS transistor while inhibiting growth on the other, and left in place to form spacers, ensuring consistent spacing and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hard mask is used to block epitaxial growth in opposite polarity MOS transistor, then epitaxial growth control is achieved, but removing the hard mask without damaging underlying layers becomes problematic
Solution Approach 1:
The patent modifies the chemical composition of the hard mask by doping boron nitride with silicon (1-30 atomic percent), which fundamentally changes the etch selectivity parameters. This parameter change enables selective removal of the hard mask from source/drain regions while preserving the underlying epitaxial semiconductor material and other sensitive layers.
Solution Approach 2:
The patent uses a composite material system consisting of silicon-doped boron nitride hard mask combined with specific etch chemistries. The silicon doping creates a composite structure within the hard mask that provides both the blocking function during epitaxial growth and the selective removability afterward, resolving the contradiction between mask effectiveness and safe removal.
2Reliability
If silicon-doped boron nitride hard mask is used, then etch selectivity is enhanced, but epitaxial growth inhibition on hard mask may occur
Solution Approach 1:
The patent optimizes the silicon doping concentration parameter within a specific range (1-30 atomic percent) to balance two competing requirements: achieving sufficient etch selectivity for hard mask removal while preventing unwanted epitaxial growth inhibition. This parameter optimization resolves the contradiction by finding the optimal doping level that satisfies both conditions.
Solution Approach 2:
The patent applies local quality modification by doping the boron nitride hard mask with silicon at controlled concentrations. This creates a material with locally enhanced etch selectivity properties in the source/drain regions where the hard mask needs to be removed, while the overall hard mask structure maintains its protective function during epitaxial growth in other 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 enhances etch selectivity, maintains consistent spacing between epitaxial semiconductor material, and provides better stress management in the channel region of MOS transistors, improving the overall fabrication process.
Implementation Method 1
A hard mask of silicon-doped boron nitride (SixBN) with at least 1 atomic percent silicon is formed over the first polarity MOS transistor and the second polarity MOS transistor. The hard mask is removed from source/drain regions of the first polarity MOS transistor and left in place over the second polarity MOS transistor.
Implementation Method 2
Semiconductor material is epitaxially grown at the source/drain regions of the first polarity MOS transistor while the hard mask is in place.
Implementation Method 3
A hard mask of silicon-doped boron nitride (SixBN) with at least 1 atomic percent silicon is formed over the first polarity MOS transistor and the second polarity MOS transistor. Having at least 1 atomic percent silicon in the SixBN hard mask provides better etch selectivity to underlying materials such as silicon and silicon dioxide compared to silicon-free boron nitride.
Data Source
AI summary
An integrated circuit is formed to include a first polarity MOS transistor and a second, opposite, polarity MOS transistor. A hard mask of silicon-doped boron nitride (SixBN) with 1 atomic percent to 30 atomic percent silicon is formed over the first polarity MOS transistor and the second polarity MOS transistor. The hard mask is removed from source/drain regions of the first polarity MOS transistor and left in place over the second polarity MOS transistor. Semiconductor material is epitaxially grown at the source/drain regions of the first polarity MOS transistor while the hard mask is in place. Subsequently, the hard mask is removed from the second polarity MOS transistor.