Plasma Etching Pulse Control for Reduced Hole Bowing
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Solution Overview
Problem
In semiconductor device manufacturing, dry etching techniques often result in 'bowing' of holes, where the sidewall width increases relative to the bottom width, leading to potential connection of adjacent holes and suboptimal aspect ratios, which complicates the formation of structures with large aspect ratios.
Innovation Solution
A plasma etching apparatus and method utilizing a capacitively coupled parallel plate configuration with a control device that generates periodic pulse signals for high-frequency power supplies, where the first high-frequency power is supplied for plasma formation and the second high-frequency power is used for ion attraction, with controlled duty ratios to stabilize plasma and improve hole shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous high frequency power is supplied for plasma etching, then etching speed is improved, but hole shape deteriorates with increased bowing
Solution Approach 1:
The patent applies periodic pulsed power supply to the plasma etching process, where high frequency power is supplied in periodic pulses rather than continuously. This periodic action allows the plasma to be generated and maintained while providing intervals that prevent excessive ion bombardment and heating at the hole bottom, thereby maintaining straight hole shapes with reduced bowing while still achieving high etching speeds through the cumulative effect of the pulsed plasma exposure.
2Manufacturing precision
If high frequency bias power is increased for ion attraction, then etching anisotropy is improved, but charge-up damage increases
Solution Approach 1:
The patent utilizes periodic pulsed power supply where the high frequency bias power is applied in periodic intervals rather than continuously. This periodic application provides sufficient ion attraction during the power-on periods to achieve the required etching anisotropy, while the power-off intervals allow the substrate charge to dissipate, thereby preventing charge-up damage. The periodic cycling balances the competing requirements of ion attraction strength and charge accumulation prevention.
3Stability of the object's composition
If pulse width of high frequency power is increased, then plasma stability is improved, but hole shape deteriorates with increased bowing
Solution Approach 1:
The patent employs periodic pulsed power supply with optimized pulse widths and duty cycles. The periodic nature of the power supply maintains plasma stability through repeated ignition and sustenance cycles, while the controlled pulse duration and off-periods prevent excessive energy accumulation at the hole bottom. This periodic modulation allows the plasma to remain stable and reactive throughout the etching process without causing the bowing that would result from continuous or excessively long pulsed power application.
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
The approach effectively reduces bowing in hole shapes, enhancing the aspect ratio and preventing adjacent hole connections, thereby improving the precision and quality of semiconductor device structures.
Implementation Method 1
The first high frequency power supply is configured to supply a first high frequency power into the processing vessel to form a processing gas supplied into the processing vessel into plasma
Implementation Method 2
The second high frequency power supply is configured to supply a second high frequency power having a frequency lower than a frequency of the first high frequency power to the stage
Data Source
AI summary
A plasma etching apparatus includes a processing vessel, a stage, a gas supply, a first high frequency power supply, a second high frequency power supply and a control device. The stage is provided and configured to place thereon a substrate. The gas supply is configured to supply a processing gas. The first high frequency power supply is configured to supply a first high frequency power. The second high frequency power supply is configured to supply a second high frequency power to the stage. The control device controls a supply and a stop of the supply of each of the first and the second high frequency powers at every preset cycle. The first and the second high frequency powers are supplied exclusively. A ratio of a supply time with respect to a single cycle of the first high frequency power is lower than that of the second high frequency power.