Molybdenum Etching Cycles for Vertical Sidewall Control
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Solution Overview
Problem
Current dry etching methods for metallic molybdenum in semiconductor manufacturing lack effective control over etch profile, etch rate, and selectivity, leading to issues like undercut, line-edge roughness, and defects in high-density interconnects, particularly at sub-5 nm nodes.
Innovation Solution
A cyclic etching process is employed, alternating between depositing an etch protection layer and etching the metallic molybdenum layer using plasma-excited gases, with optimized process parameters for each step to achieve improved vertical sidewall profiles and reduced undercut, incorporating techniques like gas pulsing and atomic layer deposition for enhanced control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching methods are used for metallic molybdenum, then the etching process can be performed, but the etch profile control, etch rate control, and etch selectivity are insufficient, leading to undercut and line-edge roughness
Solution Approach 1:
The etching process is segmented into multiple cycles, where each cycle consists of a deposition step forming an etch protection layer followed by an etching step. This segmentation allows independent optimization of sidewall protection and etch rate, achieving vertical profiles without excessive process complexity
Solution Approach 2:
The patent employs periodic cyclic processing where deposition and etching steps are alternated multiple times. This periodic action enables continuous refinement of the etch profile, maintaining vertical sidewalls while controlling undercut and line-edge roughness through repeated protection-etch cycles
2Manufacturing precision
If conventional dry etching methods are used for metallic molybdenum, then the etching process can be performed, but undercut and line-edge roughness occur
Solution Approach 1:
An etch protection layer is deposited on the sidewalls before the main etching process begins. This preliminary action of sidewall passivation prevents undercut formation and line-edge roughness during subsequent etching steps, ensuring vertical sidewall profiles
Solution Approach 2:
The etch protection layer acts as an intermediary between the plasma etching gas and the molybdenum sidewalls. This intermediate layer selectively protects sidewalls from lateral etching while allowing vertical etch progression, eliminating undercut and roughness issues
3Manufacturing precision
If cyclic etching process with alternating deposition and etching steps is used, then etch profile control and sidewall verticality are improved, but process time increases
Solution Approach 1:
The patent optimizes process parameters including gas composition, pressure, and power settings for both deposition and etching steps. By carefully tuning these parameters, the process achieves vertical sidewalls and controlled etch rates while minimizing the number of cycles required, thus reducing overall process time
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
The cyclic etching process provides a wider process window, reducing undercut and line-edge roughness, achieving smooth vertical sidewalls and minimizing defects, thus enabling robust manufacturing of high-density molybdenum interconnects with improved etch rate and selectivity.
Implementation Method 1
exposing the substrate to a plasma-excited deposition gas that forms an etch protection layer on a sidewall of the recessed feature
Implementation Method 2
exposing the substrate to a plasma-excited etching gas that etches the metallic molybdenum layer according to the etch mask
Data Source
AI summary
A substrate processing method including: providing a substrate containing an etch mask over a metallic molybdenum layer in a recessed feature; exposing the substrate to a plasma-excited deposition gas that forms an etch protection layer on a sidewall of the recessed feature; and exposing the substrate to a plasma-excited etching gas that etches the metallic molybdenum layer according to the etch mask, where the exposing steps are alternatingly performed a plurality of times.