Plasma Etching Method for High Aspect Ratio Contact Holes
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Solution Overview
Problem
Conventional plasma etching methods face challenges in forming high aspect ratio contact holes in semiconductor devices while preventing bowing and maintaining vertical sidewall shapes.
Innovation Solution
A plasma etching method involving a two-step process using gases with varying C/F ratios, where the first process uses a gas with a higher C/F ratio for deposition and the second process uses a gas with a lower C/F ratio to control residual mask amounts and suppress bowing, ensuring a vertical sidewall shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a plasma etching method using a single processing gas is employed to form high aspect ratio contact holes, then the etching depth can be increased, but the sidewall shape becomes non-vertical and bowing occurs
Solution Approach 1:
The plasma etching process is divided into multiple steps, each using a different processing gas with specific C/F ratio characteristics. The first step uses a gas with higher C/F ratio for initial etching, and subsequent steps use gases with lower C/F ratios to correct sidewall shape and reduce bowing, achieving both deep etching and vertical sidewalls
Solution Approach 2:
The C/F ratio of the processing gas is systematically changed throughout the etching process. By adjusting the carbon to fluorine ratio in different etching steps, the patent controls the deposition and etching behavior to maintain vertical sidewalls while achieving high aspect ratio contact holes
2Productivity
If a processing gas with high deposition property is used to etch the substrate, then the etching rate increases, but excessive deposition occurs on the mask layer causing bowing
Solution Approach 1:
The patent changes the C/F ratio parameter of the processing gas between different etching steps. The first step uses a gas with higher C/F ratio for efficient etching, while subsequent steps use gases with lower C/F ratios to minimize deposition on the mask layer and prevent bowing, thus controlling both etching rate and deposition
3Shape
If a processing gas with low deposition property is used to etch the substrate, then mask layer protection is improved, but the etching rate decreases making high aspect ratio formation difficult
Solution Approach 1:
The etching process is segmented into multiple steps with different gas compositions. Early steps use gases optimized for high etching rates, while later steps use gases with lower deposition properties to protect the mask layer and refine the sidewall shape, combining the benefits of both high productivity and mask protection
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 method effectively forms high aspect ratio contact holes with reduced bowing and maintains vertical sidewall integrity by adjusting the C/F ratios of the etching gases, enhancing etching selectivity and preventing excessive deposition.
Implementation Method 1
a plasma etching process using a processing gas including a first processing gas containing carbon (C) and fluorine (F)
Implementation Method 2
etching the substrate by using plasma of a gas having a low deposition property
Implementation Method 3
a process of forming a protection film by using plasma of a gas having a high deposition property
Data Source
AI summary
A plasma etching method includes a preparation process for performing a plasma etching process using a processing gas including a first processing gas containing carbon (C) and fluorine (F), a ratio (C/F) of the first processing gas having a first value, and obtaining a residual amount of the mask layer corresponding to a variation point where a variation amount of the bowing CD is increased; a first plasma etching process using the processing gas including the first processing gas until a residual amount of the mask layer reaches the variation point; and a second plasma etching process performed after the first plasma etching process. The second plasma etching process is performed by using a processing gas including at least a second processing gas containing carbon (C) and fluorine (F), and a ratio (C/F) of the second processing gas is smaller than the first value.