Dual-Mode Plasma Etching for High Aspect Ratio Dielectric Features
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Solution Overview
Problem
Current etching processes face challenges in forming high aspect ratio features due to redeposition of by-products, leading to irregular profiles, corner erosion, and critical dimension loss, which can result in device failure and low yield.
Innovation Solution
The method involves a dual-mode plasma etching process with different gas flow rates and process parameters to manage sidewall and bottom protection, allowing for controlled etching and passivation to achieve high aspect ratio features with precise profile control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If traditional anisotropic etching is used to form high aspect ratio features, then etching depth increases, but redeposition of by-products blocks the feature opening and limits further etching
Solution Approach 1:
The etching process is segmented into multiple cycles, each consisting of an etching step followed by a passivation step. This segmentation allows the process to alternate between removing material and protecting surfaces, preventing redeposition from blocking the feature opening while enabling continued etching to achieve high aspect ratios.
Solution Approach 2:
The etching process employs periodic alternation between etching mode and passivation mode. During etching mode, reactive ions remove dielectric material; during passivation mode, the same process conditions promote formation of a protective layer on sidewalls and bottoms. This periodic action resolves the contradiction by temporarily suppressing redeposition harm during passivation phases.
2Length of stationary object
If etching continues to increase aspect ratio, then feature depth increases, but irregular redeposition alters etchant flow path causing profile distortion
Solution Approach 1:
By segmenting the etching process into repeated etching-passivation cycles, the process prevents irregular redeposition from accumulating and distorting the profile. Each passivation step resets the surface condition, ensuring uniform etchant flow paths are maintained throughout the depth of the feature.
Solution Approach 2:
The passivation step enables the sidewalls and bottom surfaces to self-protect by forming a protective layer that prevents irregular redeposition. This self-service mechanism maintains uniform etchant flow paths and prevents profile distortion as etching depth increases.
3Length of stationary object
If etching process is used to form high aspect ratio features, then feature depth increases, but corner erosion and CD loss occur resulting in device failure
Solution Approach 1:
The segmented etching-passivation cycle provides periodic protection during the etching process. The passivation step forms a protective layer on corners and sidewalls that prevents erosion, while the etching step advances the feature depth. This segmentation maintains critical dimensions and prevents device failure.
Solution Approach 2:
The passivation step performs preliminary protection of corners and sidewalls before the next etching step begins. By pre-forming the protective layer, the process prevents corner erosion and CD loss that would otherwise occur during subsequent etching, ensuring device reliability.
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 enables the formation of features with high aspect ratios while maintaining accurate dimensions and preventing device failure by ensuring proper passivation and etching control throughout the process.
Implementation Method 1
performing a plasma process to etch a dielectric layer disposed on a substrate during a first mode to form features in the dielectric layer
Implementation Method 2
supplying an etching gas mixture during a first mode to etch a portion of a dielectric layer disposed on a substrate
Implementation Method 3
forming a passivation protection in the dielectric layer while etching the dielectric layer through openings defined in a patterned mask layer
Data Source
AI summary
Methods for forming high aspect ratio features using an etch process are provided. In one embodiment, a method for etching a dielectric layer to form features in the dielectric layer includes (a) supplying an etching gas mixture during a first mode to etch a portion of a dielectric layer disposed on a substrate while forming a passivation protection in the dielectric layer, wherein the dielectric layer is etched through openings defined in a patterned mask layer disposed on the dielectric layer, (b) supplying an etching gas mixture during a second mode to continue forming the passivation protection in the dielectric layer without etching the dielectric layer, and repeatedly performing (a) and (b) to form features in the dielectric layer until a surface of the substrate is exposed.