Gas Modulated Cyclical Etch Process for High Rate Feature Shaping
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Solution Overview
Problem
Existing semiconductor etching processes face challenges in achieving precise control over etch feature profiles, leading to sidewall damage, striation, bowing, roughness, and the formation of silicon shards due to high bias directional etching, which affects etch rate and feature quality.
Innovation Solution
A method involving a gas modulated cyclical etch process in a plasma processing chamber, where each cycle includes a deposition phase with a high bias for anisotropic deposition and an etch phase with a lower bias for isotropic etching, allowing selective deposition on tops and sidewalls while preventing deposition at the bottoms of etch features, followed by a pressure ramping strategy to optimize etch rates and feature shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high bias directional etching is used to achieve precise control over etch feature profiles, then etch rate is improved, but sidewall damage, striation, bowing, roughness, and silicon shard formation occur
Solution Approach 1:
The etching process is divided into multiple cycles, each containing a deposition phase followed by an etching phase. This segmentation allows the process to alternate between protecting the substrate and removing material, thereby achieving high etch rates while minimizing sidewall damage through the protective deposition layers.
Solution Approach 2:
A deposition phase is performed before each etching phase to deposit a protective layer on the substrate surface. This preliminary action prepares the substrate by creating a protective barrier that prevents damage during the subsequent high-bias etching step, while still allowing the etch to proceed efficiently at the exposed areas.
2Shape
If high bias is applied during etching to achieve anisotropic etching, then directional control is improved, but feature quality deteriorates due to sidewall damage and defects
Solution Approach 1:
The process employs periodic alternation between deposition phases (with high bias for anisotropic deposition) and etching phases (with lower bias for isotropic etching). This periodic action maintains directional control during deposition while reducing sidewall damage during etching, thereby improving overall feature quality without sacrificing shape control.
Solution Approach 2:
The bias parameter is dynamically changed between phases: high bias is applied during deposition to achieve anisotropic directional control, then reduced during the etching phase to minimize sidewall damage. This parameter modulation allows the process to achieve both directional control and high feature quality.
3Productivity
If isotropic etching is used to efficiently etch feature bottoms, then etch rate is improved, but directional control is lost causing potential sidewall damage
Solution Approach 1:
The etching process is segmented into alternating deposition and etching phases. During the etching phase, isotropic etching is used to efficiently remove material from feature bottoms at high rates. The subsequent deposition phase then restores directional control by anisotropically depositing material, preventing the loss of shape control that would occur from continuous isotropic etching.
Solution Approach 2:
The deposition phase acts as an intermediary between etching steps. It provides a protective layer that enables the use of isotropic etching chemistry during the etch phase while maintaining overall process control. The alternating phases mediate between the conflicting requirements of high etch rate and directional control.
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 increases etch rates, reduces sidewall damage, and improves feature shape by using a directional anisotropic deposition phase to protect sidewalls and tops, allowing a non-directional etch to efficiently etch the bottoms of features without causing defects.
Implementation Method 1
forming a plasma from the etch gas in the plasma processing chamber
Implementation Method 2
providing a second bias during the etch phase
Data Source
AI summary
A method for etching features into an etch layer in a plasma processing chamber, comprising a plurality of cycles is provided. Each cycle comprises a deposition phase and an etching phase. The deposition phase comprises providing a flow of deposition gas, forming a plasma from the deposition gas in the plasma processing chamber, providing a first bias during the deposition phase to provide an anisotropic deposition, and stopping the flow of the deposition gas into the plasma processing chamber. The etching phase, comprises providing a flow of an etch gas, forming a plasma from the etch gas in the plasma processing chamber, providing a second bias during the etch phase, wherein the first bias is greater than the second bias, and stopping the flow of the etch gas into the plasma processing chamber.