Pressure Purge Etch Method for 3D Structures
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Solution Overview
Problem
Current substrate processing systems face challenges in selectively etching one film material relative to another, particularly in 3D structures like NAND flash memory, where etch byproducts such as fluorine are trapped, leading to defects and device failures, and traditional wet etching methods are limited by selectivity, cost, and efficiency.
Innovation Solution
A method involving a selective dry etch process with controlled pressure variations and remote plasma use, where the processing chamber pressure is set to a first predetermined range and then reduced by a factor of at least 4 for purging, allowing efficient removal of etch byproducts and preventing damage to 3D structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching with hot phosphoric acid is used to selectively etch SiN film, then selectivity to SiO2 and polysilicon is improved, but etch rate becomes slow and pattern collapse occurs due to surface tension
Solution Approach 1:
The patent replaces wet chemical etching with a dry plasma etching process using fluorocarbon-based gases. This substitution eliminates liquid-phase surface tension effects that cause pattern collapse while maintaining selective etching of SiN relative to SiO2 and polysilicon through controlled plasma chemistry and pressure conditions.
Solution Approach 2:
The patent employs pressure modulation during the etching process, transitioning from higher pressure (1-10 Torr) for selective etching to lower pressure (0.1-1 Torr) for byproduct removal. This parameter change optimizes both etch selectivity and rate while preventing pattern collapse through controlled gas flow dynamics.
2Productivity
If conventional dry etching is used for etching 3D structures, then etch rate is improved, but etch byproducts such as fluorine are trapped in the 3D structures leading to defects
Solution Approach 1:
The patent implements a periodic pressure modulation cycle during dry etching, alternating between higher pressure phases for selective etching and lower pressure phases for byproduct removal. This periodic action maintains high etch rates while preventing accumulation of harmful fluorine byproducts in 3D structures, thereby reducing defects and improving device reliability.
3Manufacturing precision
If hot phosphoric acid wet etching is used, then selectivity is improved, but cost increases due to expensive wet chemicals and chemical waste management
Solution Approach 1:
The patent replaces wet chemical etching with dry plasma etching using fluorocarbon-based gases. This substitution eliminates the need for expensive wet chemicals and complex waste management infrastructure, reducing operational costs while maintaining high etch selectivity through controlled plasma processes.
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 efficiency, reduces fluorine in 3D structures, prevents pattern collapse, and decreases the cost of ownership by effectively removing etch byproducts, thereby improving the throughput and reliability of the etching process.
Implementation Method 1
Inductively coupled plasma is generated in the upper chamber region by supplying power to the inductive coil
Implementation Method 2
Different gas mixtures may be introduced into the processing chamber and plasma may be used to activate chemical reactions
Implementation Method 3
plasma may be used to activate chemical reactions
Implementation Method 4
lowering pressure in the processing chamber to a second predetermined pressure that is less than the first predetermined pressure by a factor greater than or equal to 4
Data Source
AI summary
A method for etching a substrate and removing byproducts includes a) setting process parameters of a processing chamber for a selective dry etch process; b) setting process pressure of the processing chamber to a first predetermined pressure in a range from 1 Torr to 10 Torr for the selective dry etch process; c) selectively etching a first film material of a substrate relative to a second film material of the substrate in the processing chamber during a first period; d) lowering pressure in the processing chamber to a second predetermined pressure that is less than the first predetermined pressure by a factor greater than or equal to 4; and e) purging the processing chamber at the second predetermined pressure for a second period.