Plasma Etching Apparatus High Aspect Ratio Charge Neutralization
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Solution Overview
Problem
The miniaturization of semiconductor devices requires High Aspect Ratio Contact (HARC) etching, but conventional plasma etching methods face challenges in maintaining etching rate and profile accuracy due to positive ion accumulation and charge distortion in high aspect ratio holes, leading to reduced etching efficiency.
Innovation Solution
A plasma etching method using a capacitively coupled parallel plate apparatus with alternating RF power and minus DC voltage conditions to generate and extinguish plasma, allowing positive ions to etch under plasma-on conditions and neutralizing them with negative ions during plasma-off conditions to prevent charge accumulation and maintain etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used for high aspect ratio holes, then etching can proceed, but positive ions accumulate at the bottom causing charge distortion and profile distortion
Solution Approach 1:
The patent applies periodic pulsing of the RF power to alternately generate and extinguish plasma. During plasma generation periods, positive ions etch the target film. During plasma extinction periods, negative ions are introduced to neutralize accumulated positive ions in high aspect ratio holes. This periodic action prevents charge distortion and maintains profile accuracy throughout the etching process.
2Productivity
If continuous plasma is used for etching, then high etching rate is maintained, but positive ion accumulation causes repulsive force bending ion travel direction
Solution Approach 1:
The RF power is pulsed periodically to create alternating plasma generation and extinction phases. During plasma generation, etching proceeds at high rate with positive ions accelerating toward the substrate. During plasma extinction, negative ions neutralize accumulated positive charges, eliminating repulsive forces that would bend ion trajectories. This maintains both high etching rate and directional accuracy.
3Manufacturing precision
If high aspect ratio etching is performed, then miniaturization requirements are met, but less positive ions reach the bottom reducing etching rate
Solution Approach 1:
The patent converts the harmful accumulation of positive ions into a beneficial process by periodically introducing negative ions during plasma extinction phases. This neutralization prevents charge buildup that would otherwise repel positive ions and reduce etching rate. The periodic plasma extinction and negative ion introduction maintains consistent etching rate throughout high aspect ratio hole formation.
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 high aspect ratio hole etching with improved etching rate and profile accuracy by controlling ion direction and neutralizing positive ions, thus preventing charge distortion and maintaining efficient etching as the aspect ratio increases.
Implementation Method 1
an RF power is applied to at least one of the electrodes to form an RF electric field between the electrodes, thereby generating a plasma of the processing gas
Implementation Method 2
negative ions are produced and supplied into the hole by the DC voltage to neutralize positive ions in the hole
Implementation Method 3
positive ions act as dominant ions... an RF power for ion attraction having a relatively low frequency
Data Source
AI summary
A plasma etching method for forming a hole in an etching target film by a plasma processing apparatus is provided. The apparatus includes an RF power supply for applying RF power for plasma generation to at least one of upper and lower electrodes, and a DC power supply for applying minus DC voltage to the upper electrode. A first condition that plasma is generated by turning on the RF power supply and minus DC voltage is applied to the upper electrode and a second condition that the plasma is extinguished by turning off the RF power supply and minus DC voltage is applied to the upper electrode are alternately repeated. Etching is performed by positive ions in the plasma under the first condition and negative ions are supplied into the hole by the DC voltage to neutralize positive ions in the hole under the second condition.