Electrostatic Faraday Shield for ICP Dielectric Window
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Solution Overview
Problem
In inductively coupled plasma (ICP) processing chambers, dielectric windows suffer from localized sputter damage and non-uniform contamination due to capacitive coupling, leading to defects on production wafers and worsening over time as the window coating accumulates damage.
Innovation Solution
An electrostatic shield with radially spoked petals, connected to a segmented annulus and powered at equal potential locations, is used to distribute energy uniformly and reduce capacitive coupling, combined with a specific window conditioning gas chemistry to recondition the dielectric window surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inductively coupled power is provided through a dielectric window, then plasma processing can be performed, but localized sputter damage and non-uniform contamination accumulate on the window surface over time
Solution Approach 1:
An electrostatic shield is introduced as an intermediary component between the inductive coil and the dielectric window. The shield distributes the capacitive coupling more uniformly across the window surface, preventing localized sputter damage while still allowing inductively coupled plasma processing to occur. This mediator structure protects the window from direct concentrated ion bombardment.
Solution Approach 2:
The patent modifies the electrical parameters at the window surface by applying a controlled electrostatic field through the shield. This changes the distribution of ion bombardment energy from localized high-intensity spots to a more uniform lower-intensity distribution, preventing accumulation of sputter damage and contamination.
2Productivity
If the dielectric window is used continuously for plasma processing, then production efficiency is maintained, but particle contamination on wafers increases due to window degradation
Solution Approach 1:
The electrostatic shield serves as a protective intermediary that prevents direct ion bombardment of the dielectric window, reducing the generation of particulate contamination. By distributing the energy load uniformly, the shield prevents window degradation that would otherwise shed particles onto the wafers during continuous processing.
Solution Approach 2:
The electrostatic shield is positioned in advance between the coil and window to preemptively distribute the capacitive coupling energy before it can cause localized damage. This preliminary protective action prevents the formation of contaminated spots on the window that would generate particles during subsequent wafer processing.
3Power
If high power is applied to the dielectric window, then plasma processing efficiency increases, but capacitive coupling causes localized sputter damage
Solution Approach 1:
The electrostatic shield acts as a mediator that decouples the high power application from localized window damage. It redistributes the capacitive coupling energy uniformly across the window surface, allowing high power processing while preventing concentrated ion bombardment that causes sputter damage.
Solution Approach 2:
The shield creates a more uniform potential distribution across the dielectric window surface, eliminating the localized high-field regions that cause concentrated sputter damage. This equipotentializing effect allows high power to be applied without creating hot spots of ion bombardment.
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 effectively reduces particle contamination on wafers by minimizing localized sputtering and uniformly cleaning the window surface, maintaining performance over extended periods.
Implementation Method 1
dielectric windows suffer from localized sputter damage and non-uniform contamination due to capacitive coupling
Implementation Method 2
Inductively coupled power is provided to the plasma processing chamber through a floating electrostatic shield and a dielectric window
Implementation Method 3
localized sputter damage
Implementation Method 4
Inductively coupled power is provided to the plasma processing chamber
Data Source
AI summary
Disclosed herein are various embodiments, including an electrostatic screen for use in a plasma processing chamber with a plurality of electrical leads. A plurality of petal groups is provided with each petal group comprising a substantially-flat structure, wherein each petal group is electrically connected to at least one electrical lead of the plurality of electrical leads and wherein each petal group is insulated from any other petal group, wherein the plurality of petal groups form a radial symmetry around a vertical axis. Each substantially flat structure comprises a sector of a conductive annulus and a plurality of conductive petals, each connected to the sector of the conductive annulus, wherein the at least one electrical lead is connected to substantially equal potential locations in each petal group.