Pulsed RF Bias Control for High-Aspect-Ratio Plasma Etching
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is to reliably produce high aspect ratio features with atomic precision, particularly at technology nodes advancing towards 2 nanometers, where ion energy control in plasma-assisted etching processes is difficult, leading to inconsistent results and microloading effects.
Innovation Solution
A plasma processing system and method that synchronizes and controls the delivery of an RF bias signal and a pulsed voltage waveform to electrodes within a plasma processing chamber, using a voltage waveform generator and an RF generator to manage asymmetric voltage pulses and RF power levels across distinct process sequence intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sinusoidal RF waveforms are used to excite the plasma, then the plasma can be formed and maintained, but the ion energy control becomes inconsistent and unreliable
Solution Approach 1:
The patent applies periodic pulsed RF biasing instead of continuous sinusoidal RF waveforms. The RF bias is applied in periodic pulses with controlled duration and amplitude, allowing precise control of ion energy by adjusting pulse parameters. This periodic action enables reliable ion energy control while maintaining plasma stability, resolving the contradiction between reliability and operational ease.
Solution Approach 2:
The patent introduces dynamic control of RF bias parameters including pulse width, amplitude, and duty cycle. By dynamically adjusting these parameters during the etching process, the system can precisely control ion energy distribution and adapt to different process requirements, achieving both reliability and operational flexibility.
2Quantity of substance
If high RF power is used to maintain plasma, then plasma density is sufficient, but ion energy distribution becomes uncontrolled
Solution Approach 1:
The patent segments the continuous RF power delivery into discrete pulsed intervals. By separating the plasma maintenance function (continuous low-power RF) from the ion acceleration function (pulsed high-power RF bias), the system can maintain sufficient plasma density while precisely controlling ion energy distribution through the pulsed bias component.
Solution Approach 2:
The patent changes the temporal parameters of RF power delivery by introducing pulsed operation with variable duty cycles and pulse widths. This parameter change allows independent control of plasma density (through average power) and ion energy distribution (through peak pulse power and duration), resolving the contradiction between quantity and precision.
3Stability of the object's composition
If continuous RF biasing is applied, then plasma sheath is maintained, but microloading effects increase
Solution Approach 1:
The patent uses periodic pulsed RF biasing instead of continuous biasing. During the pulse-off periods, the plasma sheath relaxes and reconfigures, allowing more uniform reactive species distribution across the substrate surface. This periodic action reduces microloading effects while maintaining sheath stability during the pulse-on periods, achieving both sheath stability and etch uniformity.
Solution Approach 2:
The patent maintains continuous plasma presence through low-power continuous RF while applying high-power bias pulses intermittently. This ensures the plasma sheath remains stable and reactive species are continuously generated, while the intermittent pulsing prevents excessive localized etching that causes microloading, thus maintaining both sheath stability and etch uniformity.
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 improves the control of plasma characteristics and ion energy distribution, minimizing microloading effects and achieving greater precision in forming high-aspect ratio features, thereby enhancing the reliability and consistency of semiconductor device fabrication.
Implementation Method 1
a plasma is formed over the substrate by use of a radio frequency (RF) generator that is coupled to an electrode disposed on or within the plasma processing chamber
Implementation Method 2
ions are accelerated from the plasma towards the substrate across a plasma sheath
Implementation Method 3
a plasma is formed over the substrate by use of a radio frequency (RF) generator that is coupled to an electrode disposed on or within the plasma processing chamber
Data Source
AI summary
Embodiments of the present disclosure generally relate to a system used in a semiconductor device manufacturing process. More specifically, embodiments provided herein generally include apparatus and methods for synchronizing and controlling the delivery of an RF bias signal and a pulsed voltage waveform to one or more electrodes within a plasma processing chamber. The apparatus and methods disclosed herein can be useful to at least minimize or eliminate a microloading effect created while processing small dimension features that have differing densities across various regions of a substrate. The plasma processing methods and apparatus described herein are configured to improve the control of various characteristics of the generated plasma and control an ion energy distribution (IED) of the plasma generated ions that interact with a surface of a substrate during plasma processing. The ability to synchronize and control waveform characteristics of a voltage waveform bias established on a substrate during processing allows for an improved control of the generated plasma and process of forming, for example, high-aspect ratio features in the surface of the substrate by a reactive ion etching process. As a result, greater precision for plasma processing can be achieved, which is described herein in more detail.