Sidewall Image Transfer Spacer Etching
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Solution Overview
Problem
Current sidewall image transfer methods face challenges such as corner rounding and material damage due to redeposition of etch by-products and ion bombardment during the etching of silicon nitride spacers and mandrel extraction.
Innovation Solution
A multi-step dry processing method using plasma-excited gases like H2, NF3, O2, and Ar to form and maintain sidewall spacers on silicon raised features without corner rounding and footing, and to selectively remove the mandrel without damaging the underlying material, all within a single processing chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to remove silicon mandrels, then the mandrel can be extracted, but corner residue and material damage occur due to redeposition of etch by-products and ion bombardment
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a two-step plasma process with different gas compositions (H2/Ar followed by NF3/O2/H2/Ar). This parameter change enables selective etching that removes silicon mandrels without the harmful redeposition and ion bombardment effects of conventional single-step etching, thus improving manufacturing precision while reducing material damage
Solution Approach 2:
The patent introduces an intermediary protective layer (such as oxide or nitride) between the silicon mandrel and the etching environment. This intermediary layer prevents direct ion bombardment and redeposition of etch by-products on the underlying material, allowing mandrel removal while protecting against harmful effects
2Manufacturing precision
If conventional spacer etching is used, then sidewall spacers can be formed, but footing and corner rounding occur
Solution Approach 1:
The patent applies parameter changes by using a two-step plasma etching process with specific gas compositions and conditions. The first step (H2/Ar) prepares the surface with minimal damage, while the second step (NF3/O2/H2/Ar) completes the etch with high anisotropy. This prevents footing and corner rounding by controlling the etching parameters to achieve vertical sidewalls with sharp corners
Solution Approach 2:
The patent replaces the conventional single-step mechanical/physical etching process with a chemically-driven two-step plasma process. This substitution uses chemical reactions (H2 dissociation, NF3 fluorination) to achieve the etching, which provides better control over the etch profile and prevents mechanical damage that causes corner rounding and footing
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 method achieves anisotropic etching with high selectivity, avoiding ion bombardment and reducing corner residue and material damage, thus improving the precision and integrity of sidewall image transfer.
Implementation Method 1
exposing the substrate to a plasma-excited first process gas consisting of H2 gas and optionally an inert gas
Implementation Method 2
exposing the substrate to a plasma-excited fourth process gas containing i) NF3, O2, H2, and Ar
Implementation Method 3
depositing a conformal film on the Si raised features
Data Source
AI summary
According to one embodiment, a substrate processing method includes providing a substrate containing Si raised features, depositing a conformal film on the Si raised features, and performing a spacer etch process that removes horizontal portions of the conformal film while substantially leaving vertical portions of the conformal film to form sidewall spacers on the Si raised features, the performing including a) exposing the substrate to a plasma-excited first process gas consisting of H2 gas and optionally an inert gas, and b) exposing the substrate to a plasma-excited second process gas containing i) NF3, O2, H2, and Ar, ii) NF3, O2, and H2, iii) NF3 and O2, iv) NF3, O2, and Ar, v) NF3 and H2, or vi) NF3, H2, and Ar. The method further includes removing the Si raised features while maintaining the sidewall spacers on the substrate. The removing may be performed using steps a) and b).