Plasma Etching Selectivity via In Situ Polymer Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Plasma etching methods in semiconductor fabrication result in uneven etching due to the nature of the process, leading to reduced selectivity, as portions closer to the top of recesses are etched faster than those closer to the bottom, affecting the uniformity and effectiveness of layer removal.
Innovation Solution
A plasma treatment method using a treatment gas comprising a first component for forming a protective polymer and a second component for etching, allowing for selective etching of isolating layers by protecting top portions with a polymer layer while etching the bottom portions, with adjustable ratios and gases like C4F6, CH4, CF4, and SF6 to control the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching is used to remove semiconductor layers and/or dielectric layers, then high etch rates and good uniformity of etch depth are achieved, but when layers are arranged within recesses, portions closer to the top are etched faster than portions closer to the bottom, resulting in uneven etching and reduced selectivity
Solution Approach 1:
The patent applies local quality by introducing a protective polymer layer selectively on specific surfaces (external surface and upper sidewalls) while leaving other surfaces (bottom and lower sidewalls) exposed to plasma etching. This creates spatially varying etching characteristics: protected areas maintain their original morphology while exposed areas undergo controlled removal, resolving the uniformity issue in recessed structures
Solution Approach 2:
The protective polymer acts as an intermediary substance that mediates between the plasma etching process and the isolating layer. It selectively shields certain regions from plasma exposure while allowing plasma to access and etch other regions, thereby controlling the non-uniform etching behavior inherent in plasma processes
2Productivity
If plasma etching is used to selectively remove layers in recesses, then high etch rates are achieved, but selectivity is reduced due to uneven etching
Solution Approach 1:
By creating spatially differentiated protection (polymer on external surface and upper sidewalls, no polymer on bottom and lower sidewalls), the method achieves selective etching where only specific regions are removed. This local quality approach maintains high etch rates in exposed areas while preserving protected areas, thereby improving selectivity without sacrificing productivity
Solution Approach 2:
The protective polymer layer is formed preliminarily before plasma etching occurs. This preliminary protection step establishes which regions will be etched and which will be preserved, enabling selective removal of the isolating layer from specific surfaces while maintaining the integrity of other regions
3Productivity
If conventional plasma etching is used, then layer removal is achieved, but multiple steps including etch masks are required, increasing process complexity
Solution Approach 1:
The method employs self-service by using the treatment gas itself to simultaneously form the protective polymer layer and enable selective etching. The polymer forms in situ during the plasma treatment process based on the geometry of the structure, eliminating the need for separate mask application and removal steps, thereby reducing process complexity while maintaining layer removal 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
Enables selective and controlled etching of semiconductor layers, maintaining uniformity and improving etch selectivity by protecting desired areas from plasma exposure, reducing complexity and cost by eliminating the need for etch masks, and achieving efficient electrical isolation.
Implementation Method 1
a layer of a protective polymer or a protective polymer layer will start forming on at least portions of the isolating layer present on the external surface of the semiconductor structure and on at least portions of the isolating layer present on upper portions of sidewalls of the opening. The protective polymer being formed due to the first component of the treatment gas
Implementation Method 2
plasma etching methods such as Reactive Ion Etching, RIE, or Deep RIE has attracted significant interest in recent years
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A plasma treatment method (400) for etching a portion (112) of an isolating layer (106) present on a surface (110) of an opening in a semiconductor structure (100) is provided. The method (400) comprising: providing (402) a semiconductor structure (100) comprising an opening (102) in an external surface (104), wherein the external surface (104) of the semiconductor structure (100) and surfaces (108,110, 114) defining the opening (102) are at least partially covered by the isolating layer (106), introducing (404) a treatment gas to the semiconductor structure (100) and the isolating layer (106), the treatment gas comprising a first component providing forming of a protective polymer during plasma treatment and second component providing etching of the isolating layer (106) during plasma treatment, and treating (406) the semiconductor structure (100) and the isolating layer (106) by inducing a plasma in the treatment gas, such that a protective polymer layer (118) is formed on at least portions (1 06a) of the isolating layer (106) present on the external surface (104) of the semiconductor structure (100) and on at least portions (1 06b) of the isolating layer (106) present on upper portions of sidewalls (114) of the opening (102), thereby protecting the portions (106a, 1 06b) of the isolating layer (106) where the protective polymer layer (118) is being formed, from the plasma, wherein portions (112) of the isolating layer (106) being exposed to the plasma are etched.