Plasma Etching Bias Pulses for Round High-Aspect-Ratio Holes
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Solution Overview
Problem
Conventional etching methods face challenges in maintaining the roundness of holes with high aspect ratios in organic material layers, as improving roundness often leads to bowing issues on the side walls, making it difficult to control the cross-sectional shape uniformly.
Innovation Solution
A plasma processing method involving a substrate support with a power supply that applies bias RF power in a low-frequency pulse form, with a duty ratio of 20% to 60% and an OFF time of 10 msec or longer, to control the etching cycle, thereby improving roundness and suppressing bowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional continuous bias power is applied during etching, then etching speed is maintained, but roundness of high aspect ratio holes deteriorates
Solution Approach 1:
The patent applies periodic pulsed bias power instead of continuous power during etching. The bias power is supplied in pulses with a duty ratio of 10% to 50% (preferably 20% to 40%) and a frequency of 1 Hz to 100 Hz (preferably 10 Hz to 50 Hz). During the ON period, ions are accelerated to etch the organic material layer; during the OFF period, ion acceleration stops allowing polymer relaxation and side wall protection. This periodic action maintains both roundness (by preventing side wall bowing) and etching speed (by ensuring sufficient etching occurs during ON periods).
Solution Approach 2:
The patent dynamically adjusts the bias power supply conditions by introducing time-varying pulsed power with specific duty ratios and frequencies. This dynamic control allows the etching process to adapt between aggressive etching (high duty ratio) and side wall protection (low duty ratio), achieving optimal roundness while maintaining productivity. The dynamic parameter adjustment enables real-time optimization of the etching profile.
2Manufacturing precision
If bias power is increased to improve etching uniformity, then cross-sectional shape control improves, but side wall bowing occurs
Solution Approach 1:
By using pulsed bias power with duty ratios of 10% to 50%, the patent creates periodic cycles of ion acceleration (etching phase) and ion cessation (relaxation phase). During the OFF period, polymer deposits on side walls and existing structures relax, preventing excessive ion bombardment that causes bowing. During the ON period, uniform ion acceleration ensures consistent etching across the cross-section. This periodic modulation eliminates side wall bowing while maintaining cross-sectional uniformity.
Solution Approach 2:
The patent changes the temporal parameters of bias power supply by introducing pulse width, frequency, and duty ratio controls. Instead of continuous high power that causes bowing, the system uses intermittent power with optimized parameters (duty ratio 10-50%, frequency 1-100 Hz). This parameter transformation converts a harmful continuous process into a beneficial pulsed process that achieves uniform cross-sectional shapes without side wall deformation.
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 effectively enhances the roundness of holes while minimizing bowing, achieving a roundness ratio of 0.90 or more and a bowing CD value of 40 nm or less, by optimizing the pulse frequency and duty ratio of the RF power.
Implementation Method 1
generating plasma in the processing chamber
Implementation Method 2
a power supply that supplies a bias power to at least the substrate support... supplying a bias power to the substrate support in a low-frequency pulse form
Data Source
AI summary
A method for etching a substrate includes: (a) providing a substrate processing apparatus including a processing chamber that forms a processing space, a substrate support provided inside the processing chamber to hold a substrate, and a power supply that supplies a bias power to at least the substrate support; (b) providing the substrate on the substrate support, the substrate including an underlying layer and an organic material layer on the underlying layer; (c) generating plasma in the processing chamber; and (d) repeating a predetermined cycle including an ON time during which the bias power is supplied to the substrate support and an OFF time during which the bias power is not supplied to the substrate support. The OFF time is 10 msec or longer.