Multi-Station RF Power Balancing for Wafer Bow Control
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Solution Overview
Problem
In plasma processing systems, wafer bow caused by film stress and thickness variations leads to impedance issues, limiting RF power delivery and affecting process consistency across multiple stations, especially in PECVD reactors where multiple layers are deposited, resulting in uneven power distribution and reduced process efficiency.
Innovation Solution
A combiner and distributor system that splits non-50 ohm source signals to multiple substrate stations with active tunable elements, allowing for selective power diversion, RF in-situ balancing, and impedance matching, using shunt inductors to stabilize low-frequency power and manage plasma sheath capacitance, enabling continuous multi-layer processing without turning off RF power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple layers are deposited on the wafer in a PECVD reactor, then the film thickness and material properties are improved, but wafer bow increases creating capacitance that impedes power application
Solution Approach 1:
The patent divides the single PECVD reactor into multiple stations (first station, second station, third station) that can process wafers simultaneously or sequentially. Each station has its own RF power supply and plasma generation capability, allowing the deposition process to be segmented across multiple locations. This segmentation prevents excessive wafer bow by distributing the processing load and enabling intermediate handling or resetting of wafer orientation between stations.
Solution Approach 2:
The patent implements a dynamic wafer handling system where the wafer carrier can rotate or reorient the wafer between different stations. The wafer may be deposited at one station, then reoriented by 90 degrees or 180 degrees before being processed at another station. This dynamic reorientation changes which edge of the wafer is affected by bow, allowing continuous processing despite the presence of wafer bow from previous deposition layers.
2Productivity
If wafer bow creates capacitance, then RF power delivery is impeded, but continuous processing is required for efficiency
Solution Approach 1:
The patent introduces an intermediary wafer carrier system that physically connects multiple stations and enables wafer transfer between them. This carrier acts as a mediator that allows continuous processing by moving wafers between stations without breaking vacuum or stopping the overall process. The carrier system manages the impedance and power delivery issues by providing controlled electrical connections and isolation between stations.
Solution Approach 2:
The patent combines multiple PECVD stations into a single integrated system that shares common vacuum infrastructure, control systems, and wafer handling mechanisms. By merging multiple processing locations into one coordinated system, the patent enables continuous processing where wafers can move between stations without atmospheric exposure, maintaining productivity while managing RF power delivery through coordinated control of multiple plasma sources.
3Reliability
If RF power is turned off between processing steps, then wafer bow control is simplified, but process efficiency is reduced
Solution Approach 1:
The patent maintains continuous RF power delivery and plasma generation across multiple stations without turning off the power between processing steps. Each station operates independently with its own RF power supply, allowing the useful action of plasma deposition to continue uninterrupted as wafers move between stations. This continuity eliminates idle time and maintains process efficiency while still controlling wafer bow through the multi-station architecture.
Solution Approach 2:
The patent uses dynamic control of individual station RF power supplies to manage wafer bow in real-time. Each station's RF power can be independently adjusted based on the wafer's current state and orientation. This dynamic power control allows the system to maintain optimal deposition conditions at each station while compensating for wafer bow effects, achieving both reliability and productivity simultaneously.
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, ensures consistent RF power delivery, and improves station-to-station matching, maintaining process efficiency and surface flatness, even with high film stress and thickness variations, by actively compensating for impedance changes and maintaining power stability across multiple stations.
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
Implementation Method 3
radio frequency (RF) power is supplied to produce plasma that enables the deposition
Implementation Method 4
radio frequency (RF) power is supplied to produce plasma
Implementation Method 5
low frequency impedance matching network... high frequency impedance matching network
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.