Multi-Frequency Bias Control for Perpendicular Etching
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Solution Overview
Problem
Existing plasma processing methods struggle to achieve high selectivity and perpendicular processing when etching gate electrodes with metal and high-k materials, often resulting in underlayer penetration, footings, and defective shape profiles in MOSFET and FIN-FET structures.
Innovation Solution
A plasma processing apparatus and method utilizing a vacuum reactor with a bias supplying mechanism for multiple frequencies, an IEDF control mechanism, and plasma impedance monitoring to independently control ion energy distribution and detect plasma status, allowing for precise control of ion energy and etching conditions to prevent underlayer penetration and footings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-frequency bias is used for etching metal gate/high-k gate electrode, then the etching process is simple, but underlayer penetration and footings occur causing poor manufacturing precision
Solution Approach 1:
The bias frequency is segmented into multiple frequency components (e.g., 13.56 MHz and 400 kHz) that can be independently controlled. This allows separate optimization of different etching aspects: high frequency for anisotropic etching and low frequency for ion energy control, thereby achieving precise etching profiles without underlayer penetration or footings
Solution Approach 2:
The bias system transitions from static single-frequency control to dynamic multi-frequency control where the amplitude and phase of each frequency component can be independently adjusted. This dynamic control enables real-time optimization of ion energy distribution and etching rate to achieve precise manufacturing results
2Productivity
If high ion energy is used to improve etching rate, then productivity increases, but underlayer penetration occurs reducing manufacturing precision
Solution Approach 1:
The ion energy distribution is controlled by changing the low frequency bias component (e.g., 400 kHz). By adjusting the amplitude and phase of this low frequency component, the average ion energy and energy distribution width are optimized to achieve high etching rate while preventing underlayer penetration through precise energy control
3Shape
If conventional plasma processing is used for metal gate/high-k gate electrode, then the process is straightforward, but perpendicular processing cannot be achieved resulting in poor shape
Solution Approach 1:
The plasma processing parameters are segmented into multiple controllable frequency components. The high frequency component (13.56 MHz) provides the plasma chemistry for anisotropic etching, while the low frequency component (400 kHz) controls ion directionality. This segmentation enables independent optimization of etching anisotropy and ion angular distribution to achieve perpendicular profiles
Solution Approach 2:
The bias signal is composed of multiple frequency components superimposed together. This composite bias waveform combines the benefits of high frequency (plasma generation and chemistry control) and low frequency (ion energy and direction control) to achieve the complex requirement of perpendicular etching profiles
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 solution enables stable perpendicular processing and improved underlayer selectivity, reducing defects such as footings and underlayer penetration, and maintaining high etching precision for metal and high-k gate electrodes.
Implementation Method 1
plasma is generated from reactive gases via electromagnetic waves
Implementation Method 2
supplying bias power of multiple frequencies for forming a bias potential in the lower electrode
Implementation Method 3
independently changing the energy of ions being incident on the wafer and IEDF
Implementation Method 4
ion assisted reaction is caused by the generated ions and neutral radicals
Data Source
AI summary
The invention provides a plasma processing apparatus and a dry etching method for etching a multilayered film structure having steps with high accuracy. The plasma processing apparatus comprises a vacuum reactor, a lower electrode placed within a processing chamber of the vacuum reactor and having a wafer to be etched mounted on the upper surface thereof, bias supplying units and for supplying high frequency power for forming a bias potential to the lower electrode, a gas supply means for feeding reactive gas into the processing chamber, an electric field supplying means through for supplying a magnetic field for generating plasma in the processing chamber, and a control unit for controlling the distribution of ion energy in the plasma being incident on the wafer via the high frequency power.