Electrostatic Shield Tuning for Plasma Uniformity
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Solution Overview
Problem
Plasma processing tools face challenges in achieving high plasma uniformity and precise control over plasma profile, density, and ion energy, particularly in sustaining stable plasmas across various process gases and conditions, and in efficiently removing difficult-to-remove materials like photoresists and hard surface layers during etching processes.
Innovation Solution
A plasma processing apparatus with an inductive coupled plasma source and an electrostatic shield connected through tunable reactive impedance circuits, allowing for adjustment of RF voltage to control plasma potential, enabling isotropic and anisotropic etching processes by varying the impedance to achieve desired ion bombardment energies and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an electrostatic shield is introduced to control plasma potential, then plasma uniformity and ion energy control are improved, but device complexity increases due to additional tunable reactive impedance circuits
Solution Approach 1:
An electrostatic shield is introduced as an intermediary component between the inductive coupling element and the plasma chamber. This shield, when connected to ground through a tunable reactive impedance circuit, mediates the control of plasma potential and ion energy, enabling precise control of plasma uniformity without directly modifying the plasma generation mechanism
Solution Approach 2:
The patent employs parameter changes by tuning the reactive impedance circuit connected to the electrostatic shield. By adjusting the impedance parameters (inductive or capacitive reactance), the plasma potential and ion energy can be dynamically controlled, achieving high plasma uniformity and enabling different etching modes (isotropic or anisotropic) as needed
2Power
If RF voltage of the electrostatic shield is increased to improve ion energy control, then etching capability is improved, but energy consumption increases
Solution Approach 1:
The patent utilizes parameter changes by adjusting the reactive impedance circuit connected to the electrostatic shield. By tuning the impedance between inductive and capacitive reactance, the RF voltage on the shield can be optimized to achieve the required ion energy for etching while minimizing energy consumption. The system can adapt impedance parameters to match process requirements, avoiding excessive energy input
3Adaptability or versatility
If tunable reactive impedance circuit is used to adjust plasma potential, then plasma control flexibility is improved, but manufacturing complexity increases
Solution Approach 1:
The electrostatic shield with tunable reactive impedance circuit serves multiple functions: it controls plasma potential, regulates ion energy, enables both isotropic and anisotropic etching modes, and can adapt to different process gases and conditions. This multi-functional design provides universal plasma control flexibility while consolidating what could otherwise require multiple separate components
Solution Approach 2:
The tunable reactive impedance circuit acts as an intermediary control mechanism that simplifies the overall system architecture. Instead of requiring multiple independent control systems for different plasma parameters, a single tunable impedance circuit mediates the control of plasma potential and ion energy, making the system more manageable despite the added component
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 apparatus provides flexible control over plasma conditions, enabling efficient etching and deposition processes with high ion energy uniformity, effectively handling difficult-to-remove materials and achieving isotropic or directional etching as needed.
Implementation Method 1
exciting with RF energy an inductive coupling element to initiate ignition of a plasma induced in the process gas
Implementation Method 2
The electrostatic shield can have a stray capacitance to a ground reference
Implementation Method 3
adjusting a first tunable reactive impedance circuit coupled between the electrostatic shield and a ground reference to a condition of inductive reactance
Data Source
AI summary
Plasma processing apparatus and associated methods are provided. In one example, a method can include admitting a process gas into a plasma chamber. The method can include exciting with RF energy an inductive coupling element to initiate ignition of a plasma induced in the process gas. The method can include adjusting an RF voltage of an electrostatic shield located between the inductive coupling element and the plasma chamber. The electrostatic shield can have a stray capacitance to a ground reference. The method can include conducting an ion-assisted etching process on the workpiece based at least in part on the RF voltage of the electrostatic shield.