Pulsed Ion Beam Anisotropic Etching Control
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Solution Overview
Problem
Reactive ion etching processes face challenges in controlling isotropic etching and process-induced damage due to random radical trajectories, leading to undercutting, scalloping, and composition changes in complex semiconductor structures.
Innovation Solution
A pulsed ion beam etching method is employed, where a plasma chamber generates a pulsed ion beam with distinct ON and OFF portions, and RF power levels, synchronized with the ion beam pulses, to control the etching process, reducing isotropic etching by managing the transit time of etchant species and adjusting the separation between the plasma chamber and substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reactive radicals are used for etching, then etching speed is improved, but isotropic etching occurs causing undercutting and scalloping
Solution Approach 1:
The patent employs pulsed plasma generation where the plasma is turned on and off in periodic cycles. During the on-phase, reactive radicals are generated for etching. During the off-phase, radical flux is reduced while ion bombardment continues to provide anisotropic directionality. This periodic control allows the system to achieve both high etching speed and precise pattern transfer by separating the functions of radical-driven material removal and ion-driven directional control.
2Productivity
If continuous plasma is used for etching, then etching efficiency is improved, but process-induced damage and composition change increase
Solution Approach 1:
The patent implements pulsed plasma operation where continuous plasma is replaced by periodic plasma pulses. During the on-phase, etching occurs with high efficiency. During the off-phase, the plasma is extinguished or significantly reduced, allowing the substrate to be relieved from continuous radical exposure and ion bombardment. This periodic action maintains etching efficiency while reducing cumulative process-induced damage and composition changes in the substrate materials.
3Manufacturing precision
If ion beam extraction is used to achieve anisotropic etching, then directional control is improved, but radical flux control becomes difficult
Solution Approach 1:
The patent uses pulsed plasma generation coupled with synchronized pulsed ion beam extraction. During the on-phase, both radicals and ions are generated and extracted. During the off-phase, plasma generation is reduced or stopped while ion extraction may continue at reduced levels or be synchronized to match the plasma pulses. This periodic synchronization provides natural temporal control over radical flux while maintaining ion-driven anisotropic etching, simplifying the control mechanism compared to independent continuous control of both species.
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 enhances anisotropic etching, minimizing isotropic etching and process-induced damage, resulting in improved pattern transfer and reduced composition changes in semiconductor materials.
Implementation Method 1
generating a plasma in a plasma chamber, the plasma comprising an etchant species
Implementation Method 2
extracting a pulsed ion beam from the plasma chamber and directing the pulsed ion beam to a substrate
Implementation Method 3
trajectories of the ions may follow electric fields that extend to a substrate
Implementation Method 4
Reactive ion beam etching (RIBE), chemically assisted ion beam etching (CAIBE) and other plasma dry etching methods use a combination of energetic ions like Ar+, Cl+ and CF3+ and reactive neutrals species like radicals Cl, F, and CF3 or excited state species like Cl* or F* to remove solid substrate material as volatile gas phase molecular species
Implementation Method 5
solid silicon, Si(s) may be converted into gas phase silicon tetrafluoride, SiF4(g) by reaction with a combination of fluorine ions, F+, and fluorine atoms, F
Data Source
AI summary
A method may include generating a plasma in a plasma chamber, the plasma comprising an etchant species and extracting a pulsed ion beam from the plasma chamber and directing the pulsed ion beam to a substrate, where the pulsed ion beam comprises an ON portion and an OFF portion. During the OFF portion the substrate may not be biased with respect to the plasma chamber, and the duration of the OFF portion may be less than a transit time of the etchant species from the plasma chamber to the substrate.