Plasma Etching Cycle Pressure Variation for Self-Limited Reaction Layer
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Solution Overview
Problem
Existing cycle etching methods struggle to achieve high-accuracy isotropic etching for three-dimensional semiconductor devices with sufficient etching amounts per cycle, as they fail to form a self-limited reaction layer and are prone to deposit accumulation, leading to unstable mass production processes.
Innovation Solution
A plasma processing method involving an adsorption step with higher pressure and lower radio frequency power, followed by a desorption step with lower pressure and higher radio frequency power, using the same plasma generation space to form and remove the reaction layer with reactive and rare gases, respectively, while maintaining plasma generation between steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a reactive gas is supplied to form a reaction layer in the adsorption step, then the reaction layer thickness increases, but the etching amount per cycle becomes insufficient
Solution Approach 1:
The patent changes the pressure parameter between adsorption and desorption steps. The adsorption step is performed at a higher pressure (0.1-10 Pa) to form a sufficient reaction layer thickness, while the desorption step is performed at a lower pressure (0.01-1 Pa) to enable effective removal by metastable rare gas. This pressure parameter change resolves the contradiction by allowing thick reaction layer formation without sacrificing etching efficiency.
2Device complexity
If the adsorption and desorption steps are performed at the same pressure, then the process is simplified, but the reaction layer cannot be effectively formed and removed
Solution Approach 1:
The patent introduces pressure as a control parameter that changes between steps. The adsorption step uses higher pressure (0.1-10 Pa) to maximize reaction layer formation, while the desorption step uses lower pressure (0.01-1 Pa) to optimize metastable rare gas interaction and layer removal. This dynamic pressure control achieves precise etching while maintaining manageable process complexity through systematic parameter variation.
3Quantity of substance
If carbon-containing gas is used to form the reaction layer, then the reaction layer thickness increases, but deposit accumulates in the chamber
Solution Approach 1:
The patent extracts and removes deposits from the chamber interior surfaces during the desorption step. By performing the desorption step at lower pressure with metastable rare gas, the process effectively cleans carbon-containing deposits from chamber walls while maintaining the reaction layer formation capability during the adsorption step. This separates the harmful deposit accumulation effect from the useful reaction layer formation function.
Solution Approach 2:
The patent uses periodic alternation between adsorption (high pressure, reaction layer formation) and desorption (low pressure, deposit removal) steps. This periodic action allows the system to accumulate the necessary reaction layer thickness during adsorption phases while systematically removing harmful deposits during desorption phases, preventing uncontrolled deposit accumulation.
4Productivity
If the process time per cycle is reduced to increase productivity, then the etching amount decreases, but mass production efficiency increases
Solution Approach 1:
The patent optimizes the balance between process time and etching amount by changing pressure parameters. The adsorption step at higher pressure (0.1-10 Pa) forms the reaction layer more quickly, while the desorption step at lower pressure (0.01-1 Pa) efficiently removes it. This parameter optimization achieves several nm to several tens of nm etching per cycle within a reasonable time frame, suitable for mass production of semiconductor devices.
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 method enables a self-limited etching process with increased reaction layer thickness per cycle, preventing deposit adhesion and reducing process time, thus enhancing mass productivity and stability.
Implementation Method 1
an adsorption step of forming a reaction layer on an etching target film by plasma generated using a reactive gas
Implementation Method 2
forming a reaction layer on an etching target film by plasma generated using a reactive gas
Implementation Method 3
a desorption step of removing the reaction layer by plasma generated using a rare gas
Implementation Method 4
removing the reaction layer by plasma generated using a rare gas
Data Source
AI summary
The invention provides a plasma processing method capable of constructing a self-limited process excellent in mass productivity in a cycle etching method in which an adsorption step of forming a reaction layer on a surface of an etching target wafer and a desorption step of removing the formed reaction layer using a rare gas in a metastable state are repeated. The plasma processing method includes: an adsorption step of forming a reaction layer on an etching target film by plasma generated using a reactive gas; and a desorption step of removing the reaction layer using the rare gas in the metastable state generated by the plasma. The adsorption step and the desorption step are repeated, and a pressure of the adsorption step is higher than a pressure of the desorption step.