RF Power Balancing in Multi-Station Semiconductor Reactors
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Solution Overview
Problem
In semiconductor device fabrication, multiple processing stations sharing an RF power source face challenges in maintaining uniformity and repeatability due to small variations in power delivery, leading to unacceptable variations in deposition and etch rates across wafers.
Innovation Solution
A method and apparatus for fine-tuning dynamic impedances at each station during plasma operation by measuring RF parameters, comparing them to set points, and adjusting the RF power using variable capacitors or inductors to ensure equal power distribution across stations, thereby achieving high wafer-to-wafer repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single RF power source is shared among multiple processing stations with symmetric design and high impedance delivery circuit, then power distribution is simplified and cost is reduced, but small variations in characteristics result in different power levels at each station causing process variation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the impedance characteristics (capacitance and inductance values) of each station's RF circuit. Variable capacitors and inductors are used to fine-tune the RF power delivery to each station, changing the electrical parameters to compensate for variations and achieve uniform power distribution across all stations sharing the common RF source.
Solution Approach 2:
The patent implements feedback control by measuring the actual RF power or impedance at each station and using this information to adjust the variable capacitors and inductors. The system continuously monitors the RF parameters and modifies the impedance settings to maintain equal power distribution, creating a closed-loop control system that compensates for variations in real-time.
2Reliability
If RF power is distributed equally to all stations, then wafer-to-wafer repeatability is improved, but the system cannot accommodate processes requiring different power levels for different stations
Solution Approach 1:
The patent applies dynamics by making the RF power distribution adjustable rather than fixed. The variable capacitors and inductors allow the system to dynamically change the power split ratio between stations. The control system can switch between equal power distribution mode (for repeatability) and unequal power distribution mode (for versatile processing), adapting to different process requirements in real-time.
Solution Approach 2:
The patent implements universality by designing a single RF power distribution system that can perform multiple functions: it can distribute power equally to all stations for high repeatability applications, or distribute power in specified unequal ratios for processes requiring different power levels at different stations. The variable impedance components enable one system to serve multiple operational modes and process types.
3Manufacturing precision
If impedance matching components are added to each station for fine-tuning, then power balance precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by using variable capacitors and inductors that can be electronically adjusted to change the impedance parameters of each station. Rather than adding complex active control circuits, the invention modifies the passive electrical parameters (capacitance and inductance values) to achieve precise power balancing, providing fine-tuning capability through relatively simple passive components.
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
This approach ensures consistent RF power delivery across multiple stations, minimizing process variation and enhancing wafer-to-wafer uniformity and repeatability, even in parallel or mixed processing scenarios, by dynamically adjusting impedance to maintain specified power ratios.
Implementation Method 1
The adjusting may include changing capacitances on one or more capacitors associated with a particular station or varying an inductance on an inductor associated with a particular station
Implementation Method 2
The adjusting may include changing capacitances on one or more capacitors associated with a particular station or varying an inductance on an inductor associated with a particular station
Implementation Method 3
generating a total RF power, distributing the total RF power to the stations
Implementation Method 4
A method of plasma-assisted semiconductor deposition process in multiple stations sharing an RF power source includes providing a substrate at each station, generating a total RF power
Data Source
AI summary
Apparatus and methods to minimize wafer-to-wafer process variation in RF-based semiconductor processing reactors with shared RF source for multiple processing areas. RF sensors associated with each processing area sends signal to the RF balance controller. The controller modifies station impedance using power adjustment mechanisms. As a result, station to station distribution of a selected RF parameter (e.g., load power) may match the station set points. Closed loop control maintains balance despite changing conditions.