Twisted Pair RF Power Filter for Plasma Uniformity
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Solution Overview
Problem
Existing RF power filters in plasma processing systems cause non-uniformity and inconsistency in plasma processing rates due to varying stray capacitances and capacitor tolerances, leading to undesirable manufacturing yields and the need for costly calibration processes.
Innovation Solution
A filter design with twisted wires and a core member that minimizes stray capacitance differences by securing the cable in place, using a single set of capacitors to form tuned circuits for multiple frequencies, and incorporating positioning mechanisms to maintain consistent wire positions, thereby equalizing impedances and maintaining consistent plasma processing profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate wires are used to connect heating elements, then individual connections are achieved, but stray capacitance variations cause non-uniform plasma processing rates
Solution Approach 1:
The patent combines multiple separate wire connections into a single twisted pair cable assembly. The twisted pair structure integrates multiple conductors into one unified component, ensuring that all heating elements experience identical stray capacitance conditions, thereby eliminating the non-uniformity caused by varying stray capacitances in separate wire configurations.
Solution Approach 2:
The twisted pair cable structure creates homogeneous electrical conditions for all heating elements by ensuring identical stray capacitance for each conductor. The symmetric twisting pattern guarantees that all wires experience the same electromagnetic environment, resulting in uniform plasma processing rates across the wafer surface.
2Ease of manufacture
If wires are allowed to move freely, then installation flexibility is improved, but position variations cause inconsistent plasma processing profiles
Solution Approach 1:
The patent applies preliminary action by pre-assembling the wires into a twisted pair configuration before installation. This pre-configuration ensures that the wires maintain consistent relative positions and stray capacitance characteristics throughout installation and operation, eliminating the need for post-installation calibration while ensuring consistent plasma processing profiles.
Solution Approach 2:
Instead of allowing wires to move freely and then attempting to control their positions, the patent inverts the approach by constraining the wires together in a fixed twisted pair configuration from the outset. This inversion transforms the problem from controlling individual wire positions to maintaining the integrity of the pre-configured twisted pair structure.
3Adaptability or versatility
If multiple capacitors are used for different frequencies, then frequency coverage is improved, but component tolerances cause processing inconsistency
Solution Approach 1:
The patent applies universality by designing a single twisted pair cable structure that serves multiple functions: it provides RF filtering across multiple frequencies (13.56 MHz, 27 MHz, 60 MHz) simultaneously. The twisted pair geometry inherently provides consistent stray capacitance that works effectively for all these frequencies, eliminating the need for multiple discrete capacitors with varying tolerances.
4Manufacturing precision
If calibration processes are implemented, then processing consistency is improved, but cost and complexity increase
Solution Approach 1:
The twisted pair cable structure is self-calibrating in the sense that its symmetric geometry automatically ensures equal stray capacitance for all conductors without requiring external calibration. The structure itself provides the necessary precision through its inherent geometric symmetry, eliminating the need for skill-intensive calibration processes.
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 achieves uniform plasma processing rates and maximized manufacturing yield by reducing stray capacitance variations and eliminating the need for skill-intensive calibration, ensuring consistent profiles across wafers and plasma processing chambers.
Implementation Method 1
A cable is wound around and wound along at least a portion of the core member to form at least a set of inductors having a set of inductances
Implementation Method 2
The set of inductors may be connected to a set of grounded capacitors to form tuned circuits to filter out or block RF power
Implementation Method 3
RF power filter 102 may also minimize or block RF power transmitted from ESC 108 to other components outside of plasma processing chamber body 106
Data Source
AI summary
A filter for filtering radio frequency (RF) power transmitted from an electrostatic chuck (ESC) in a plasma processing system. The plasma processing system may include a heating element disposed at the ESC. The plasma processing system may further include a power supply. The filter may include a core member and a cable wound around and wound along the core member to form a set of inductors. The cable may include a plurality of wires, including a first wire and a second wire, a portion of the first wire and a portion of the second wire being twisted together, a first end of the first wire and a first end of the second wire being connected to the heating element, each of a second end of the first wire and a second end of the second wire being connected to a capacitor and being connected to the power supply.