Multi-Station RF Power Balancing for Wafer Bow Control
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Solution Overview
Problem
Wafer bow in multiple plasma processing stations impairs RF power application, leading to inefficiencies in film deposition due to increased capacitance and impedance variations across stations, affecting plasma density and ion bombardment.
Innovation Solution
A combiner and distributor system that splits non-50 ohm source signals, uses active tunable elements for RF power balancing, and incorporates shunt inductors to manage plasma sheath capacitance and resonant frequency shifts, allowing for selective power delivery and impedance matching across multiple stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple plasma processing stations share a common RF power source, then device complexity is reduced, but impedance variations and power distribution instability occur due to wafer bow effects
Solution Approach 1:
The patent divides the RF power distribution system into multiple independent impedance matching networks, one for each plasma processing station. Each matching network independently matches the impedance of its associated station to the common RF power source, thereby isolating impedance variations at one station from affecting other stations. This segmentation resolves the contradiction by maintaining simple common power source architecture while ensuring stable power distribution to each station despite wafer bow-induced impedance changes.
2Manufacturing precision
If wafer bow increases with more deposited layers, then film thickness and deposition quality improve, but capacitance increases impeding RF power application
Solution Approach 1:
The patent employs dynamically adjustable impedance matching networks with variable capacitors and inductors at each plasma processing station. These dynamic elements can be tuned in real-time to compensate for changes in station impedance caused by wafer bow. As more layers are deposited and wafer bow increases, the matching network adjusts its parameters to maintain optimal RF power transfer, thereby resolving the contradiction between achieving high deposition quality and maintaining power application efficiency.
3Manufacturing precision
If active tunable elements are used for RF power balancing, then power distribution uniformity improves, but device complexity and control requirements increase
Solution Approach 1:
The patent incorporates feedback control mechanisms where the state of each impedance matching network is monitored and adjusted based on measured power distribution across stations. The controller receives information about power levels and impedance conditions at each station and automatically adjusts the tunable elements to achieve uniform power distribution. This feedback approach resolves the contradiction by automating the balancing process, making the increased device complexity manageable while achieving the goal of uniform power distribution.
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 system effectively controls wafer bow, stabilizes low-frequency power, and maintains consistent RF delivery, enhancing the uniformity of film deposition and reducing the impact of wafer bow on processing outcomes.
Implementation Method 1
A shunt inductor is coupled in parallel to one of the plasma processing stations to increase an amount of current to the one of the plasma processing stations
Implementation Method 2
manage plasma sheath capacitance and resonant frequency shifts
Implementation Method 3
radio frequency (RF) power is supplied to produce plasma that enables the deposition
Implementation Method 4
a plasma enhanced chemical vapor deposition (PECVD) reactor may be used to deposit insulation films
Data Source
AI summary
A system for controlling of wafer bow in plasma processing stations is described. The system includes a circuit that provides a low frequency RF signal and another circuit that provides a high frequency RF signal. The system includes an output circuit and the stations. The output circuit combines the low frequency RF signal and the high frequency RF signal to generate a plurality of combined RF signals for the stations. Amount of low frequency power delivered to one of the stations depends on wafer bow, such as non-flatness of a wafer. A bowed wafer decreases low frequency power delivered to the station in a multi-station chamber with a common RF source. A shunt inductor is coupled in parallel to each of the stations to increase an amount of current to the station with a bowed wafer. Hence, station power becomes less sensitive to wafer bow to minimize wafer bowing.