Plasma Etching Cycle for Uniform Dense and Sparse Patterns
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Solution Overview
Problem
Conventional etching methods struggle to achieve uniform etching on both dense and sparse pattern portions in a single wafer, often resulting in tapered shapes due to varying etching rates and reaction product accumulation.
Innovation Solution
A plasma processing method involving alternating reactive ion etching (RIE) and radical etching steps, where the duration of each step is controlled to achieve independent etching control over dense and sparse pattern portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reactive ion etching (RIE) is used to achieve vertical etching shapes in dense pattern portions, then the etching rate in sparse pattern portions becomes excessively high causing tapered shapes, but using lower etching rate conditions to suppress sparse portion etching results in insufficient verticalness in dense portions
Solution Approach 1:
The etching process is segmented into multiple alternating steps: reactive ion etching (RIE) steps for anisotropic etching to achieve vertical shapes, and radical etching steps for isotropic etching to remove reaction products. Each step type is repeated a predetermined number of times, allowing independent control of etching characteristics for different pattern densities.
Solution Approach 2:
The method employs periodic alternation between RIE and radical etching steps. The RIE step duration is set shorter than the radical etching step duration, creating a cyclic process that periodically switches between anisotropic and isotropic etching modes to balance verticalness and reaction product removal.
2Productivity
If high etching rate conditions are used to improve productivity, then sparse pattern portions develop tapered shapes due to excessive etching, but low etching rate conditions are needed to achieve uniform etching across dense and sparse portions
Solution Approach 1:
The etching process is segmented into multiple alternating steps: reactive ion etching (RIE) steps for anisotropic etching to achieve vertical shapes, and radical etching steps for isotropic etching to remove reaction products. Each step type is repeated a predetermined number of times, allowing independent control of etching characteristics for different pattern densities.
Solution Approach 2:
The method changes etching parameters dynamically by alternating between different etching modes. The RIE step uses parameters optimized for anisotropic etching (vertical shapes), while the radical etching step uses parameters optimized for isotropic etching (reaction product removal), with each step duration independently controlled to achieve overall process optimization.
3Manufacturing precision
If long RIE step duration is used to achieve vertical shapes, then reaction products accumulate excessively causing tapered shapes, but short RIE step duration reduces verticalness in dense pattern portions
Solution Approach 1:
The etching process is segmented into multiple alternating steps: reactive ion etching (RIE) steps for anisotropic etching to achieve vertical shapes, and radical etching steps for isotropic etching to remove reaction products. Each step type is repeated a predetermined number of times, allowing independent control of etching characteristics for different pattern densities.
Solution Approach 2:
The radical etching step acts as an intermediary process between RIE steps. It periodically removes reaction products that accumulate during RIE steps, preventing excessive accumulation that would cause tapered shapes, while allowing the RIE steps to maintain vertical etching characteristics.
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 uniform etching of both dense and sparse pattern portions by independently controlling the etching shapes, ensuring consistent taper angles through precise control of RIE time ratios.
Implementation Method 1
performing reactive ion etching using gas resulting in a tapered shape
Implementation Method 2
ion-based anisotropic etching
Implementation Method 3
radical-based isotropic etching of non-cumulative gas on the substrate
Data Source
AI summary
To independently control etching shapes of sparse and dense pattern portions in a single wafer and enable uniform etching processing regardless of whether the pattern is dense or sparse, a plasma processing method is characterized by including a first step of performing reactive ion etching using gas resulting in a tapered shape, and a second step of performing radical etching, characterized in that the first step and the second step are alternately repeated for a predetermined number of times, and a time of the first step is shorter than a time of the second step.