Plasma Etching Method Modulating High Frequency Bias Power
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Solution Overview
Problem
Conventional plasma etching methods often result in twisting of holes or grooves during deep etching processes due to uneven deposition of etching byproducts on the inner surfaces, which leads to unsatisfactory etching of sidewalls.
Innovation Solution
A plasma etching method involving a processing gas with fluorocarbon, applying dual frequency powers where the first high frequency power (27 MHz to 100 MHz) excites plasma and the second high frequency power (400 kHz to 13.56 MHz) attracts ions, with cyclic ON/OFF switching of the second power during the first process and continuous application during the second process, ensuring uniform deposition and protection of inner surfaces from ion etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma etching method with continuous ion attraction is used, then etching speed is improved, but hole twisting occurs due to uneven deposit formation
Solution Approach 1:
The patent applies periodic ON/OFF switching of the second high frequency power (ion attraction power) during plasma etching. By cyclically switching the ion attraction between ON and OFF states, the method enables periodic deposition of etching byproducts on the hole inner surface, which prevents hole twisting while maintaining etching speed through the alternating etching-deposition cycles
Solution Approach 2:
The patent changes the operational parameters by introducing dual frequency high frequency powers with different functions. The first high frequency power (27-100 MHz) excites plasma for etching, while the second high frequency power (400 kHz-13.56 MHz) controls ion attraction to the substrate. By independently controlling these parameters and switching the second power cyclically, the method achieves uniform deposit formation that prevents hole twisting
2Productivity
If fluorocarbon processing gas is used for etching, then etching capability is improved, but uneven deposit formation causes sidewall etching and hole twisting
Solution Approach 1:
The periodic switching of the second high frequency power creates alternating phases of etching and deposit formation. During ON phases, ions are attracted to the substrate for etching; during OFF phases, etching byproducts deposit uniformly on the sidewalls. This periodic action ensures that fluorocarbon-based etching capability is maintained while preventing uneven sidewall etching and hole twisting through regular deposit formation
Solution Approach 2:
The patent modifies the plasma process parameters by applying dual frequency high frequency powers. The specific frequency ranges (first: 27-100 MHz, second: 400 kHz-13.56 MHz) and their cyclic switching control the balance between etching reactions and deposit formation. This parameter control ensures uniform fluorocarbon deposit distribution on sidewalls, preventing the twisting problem
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 effectively suppresses the twisting of holes or grooves by uniformly forming deposits from the top to the bottom of the etched features, thereby preventing ion etching of the sidewalls and stabilizing the plasma.
Implementation Method 1
applying a first high frequency power (having a frequency appropriately selected within a range from 27 MHz to 100 MHz) for excitation of the processing gas into plasma
Implementation Method 2
a second high frequency power (having a frequency appropriately selected within a range from 400 kHz to 13.56 MHz) for attraction of ions to the processing target object
Implementation Method 3
deposits, which are originated from the processing gas and stuck to an inner surface of a hole or a groove formed by the etching
Data Source
AI summary
A plasma etching method includes a first process of applying, while applying a first high frequency power to a lower electrode, a second high frequency power to the lower electrode while switching the second high frequency power ON and OFF cyclically; and a second process of applying, while applying the first high frequency power to the lower electrode, the second high frequency power to the lower electrode while maintaining the second high frequency power ON continuously. The first process and the second process are alternately performed. If the deposits are formed on a bottom portion of an inner surface of the hole formed by the etching, the inner surface of the hole is protected by the deposits from the ions introduced into the hole. Therefore, the etching of the inner surface of the hole can be suppressed, and, thus, the twisting of the hole can also be suppressed.