Adjustable Middle Coil for ICP Plasma Density Profile Control
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Solution Overview
Problem
Inductively coupled plasma reactors face challenges in achieving uniform plasma density distribution across semiconductor substrates due to variations in process gases, leading to non-uniformities that require customized RF coil designs for each process, which can result in suboptimal substrate processing.
Innovation Solution
The implementation of an adjustable middle coil within the plasma processing system, coupled with an impedance match circuit that measures current and voltage to calculate plasma density, allowing real-time adjustments to the resonant frequency of the middle coil to achieve desired plasma profiles, thereby compensating for gas-induced non-uniformities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If customized RF coil designs are used for each process gas, then plasma uniformity across substrate surface is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent implements a dynamically adjustable middle coil with variable resonant frequency capability. The middle coil's resonant frequency can be tuned in real-time to match different process gas requirements, replacing the need for multiple fixed customized coils. This dynamic adjustment mechanism allows a single coil structure to adapt to various process conditions, thereby maintaining plasma uniformity without increasing device complexity
Solution Approach 2:
The middle coil is designed to serve multiple functions: it can operate at different resonant frequencies to accommodate various process gases, and it works in conjunction with the inner and outer coils to provide versatile plasma control. This multi-functional design eliminates the need for process-specific customized coils, reducing both device complexity and manufacturing costs while maintaining plasma uniformity
2Manufacturing precision
If multiple RF coils are used to improve plasma uniformity, then plasma profile control is improved, but system complexity and power delivery control difficulty increase
Solution Approach 1:
The patent incorporates an impedance match circuit that measures current and voltage from the inner and outer coils to calculate plasma density in real-time. This feedback information is used to dynamically adjust the middle coil's resonant frequency, creating a closed-loop control system. The feedback mechanism enables automatic optimization of plasma uniformity without requiring complex manual control of multiple coils
Solution Approach 2:
The middle coil acts as an intermediary element between the inner and outer coils. By positioning the middle coil between the other two coils and adjusting its resonant frequency, it mediates the plasma distribution pattern to achieve uniformity. This intermediary approach simplifies the control mechanism compared to independently managing multiple coils, as the middle coil's frequency adjustment directly influences the overall plasma profile
3Manufacturing precision
If real-time plasma density measurement and adjustment is implemented, then plasma profile uniformity is improved, but measurement and control system complexity increases
Solution Approach 1:
The impedance match circuit serves a dual function: it matches the impedance of the RF coils to the power source and simultaneously measures the current and voltage to calculate plasma density. This integrated feedback approach provides real-time plasma density information without requiring separate complex measurement systems. The calculated plasma density is then used to adjust the middle coil's resonant frequency, creating a simple yet effective closed-loop control system that improves plasma 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 enables real-time measurement and adjustment of plasma density, improving uniformity across the substrate surface by dynamically tuning the plasma profile to match desired specifications, thus enhancing processing efficiency and reducing substrate damage from ion bombardment.
Implementation Method 1
An impedance match circuit is coupled to the inner coil and the outer coil... Current and voltage for an inner coil and an outer coil are measured using the impedance match circuit
Implementation Method 2
The plasma profile density is adjusted using an adjustable middle coil, in response to the calculated plasma density... The plasma density by changing the resonant frequency of an adjustable middle coil
Implementation Method 3
An inductively coupled RF plasma reactor typically has inductive coil antenna wound around the reactor chamber and connected to a plasma source RF power supply
Data Source
AI summary
Apparatuses and methods are provided that, in some embodiments use an adjustable middle coil to tune plasma density in a plasma processing system. For example, in one embodiment, a plasma processing apparatus includes an impedance match circuit coupled to an Rf power source. The impedance match circuit measures voltage and current at an inner and an outer coil. The match circuit calculates plasma density from the measured voltage and/or current. An adjustable middle coil located between the inner and outer coils is adjusted and/or replaced to tune the plasma density radial profile.