Selective SiN Lateral Recess via Remote Plasma Etching
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Solution Overview
Problem
Conventional etching techniques face challenges in laterally etching silicon nitride in high aspect ratio trenches of 3D NAND structures, leading to uneven etching profiles and deformation of structures due to inadequate diffusion of precursors and excessive etching by wet processes.
Innovation Solution
A dry etching method involving a remote plasma system where fluorine-containing and oxygen-containing precursors are used to generate plasma effluents that laterally etch silicon nitride while maintaining silicon oxide layers, with controlled flow-rate ratios and temperatures to ensure uniform etching across the trench, forming a fluorinated oxide that allows precise etching of silicon nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet HF etching is used to laterally etch silicon nitride, then the etching speed is fast, but the structure deforms and the etching uniformity is poor
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a dry etching process with specific gas compositions (CF4, O2, and CHF3) instead of wet HF etching. This parameter change enables controlled lateral etching of silicon nitride with uniform cell sizes (varying by less than 3 nm) while avoiding the deformation issues associated with wet etching, thus resolving the contradiction between etching speed and etching uniformity.
2Manufacturing precision
If conventional dry etching is used to penetrate high aspect ratio trenches, then the trench can be accessed, but the precursor diffusion is inadequate leading to uneven etching profiles
Solution Approach 1:
The patent introduces an intermediary mechanism by forming a fluorinated oxide layer on the silicon nitride surface before lateral etching. This fluorinated oxide layer acts as a mediator that enhances precursor diffusion and enables uniform etching profiles in high aspect ratio trenches (greater than 100:1). The fluorinated oxide is subsequently removed, leaving uniformly etched silicon nitride lateral regions.
3Manufacturing precision
If local plasma is used to etch constrained trenches, then the trench penetration is improved, but substrate damage occurs due to electric arcs
Solution Approach 1:
The patent extracts the plasma generation from direct contact with the substrate by using a remote plasma source. The plasma is generated in a separate region and the reactive species are transported to the substrate surface, eliminating the harmful electric arcs that cause substrate damage while maintaining effective trench penetration and etching capability.
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 finely controlled lateral etching of silicon nitride layers with minimal deformation, ensuring uniform cell sizes throughout the vertical stack and reducing the risk of crosstalk between memory cells, while being performed in a single chamber to enhance processing efficiency.
Implementation Method 1
forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor
Implementation Method 2
Fluorine within the fluorinated oxide may diffuse through the oxidized portion of the silicon nitride to laterally etch the silicon nitride
Implementation Method 3
oxidizing a portion of the silicon nitride to produce a fluorinated oxide
Data Source
AI summary
Exemplary methods for laterally etching silicon nitride may include flowing a fluorine-containing precursor and an oxygen-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor. The methods may also include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region, and the substrate may include a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide. The methods may also include laterally etching the layers of silicon nitride from sidewalls of the trench while substantially maintaining the layers of silicon oxide. The layers of silicon nitride may be laterally etched less than 10 nm from the sidewalls of the trench.