Magnetron Erosion Prediction and Dynamic Height Compensation
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Solution Overview
Problem
In plasma sputtering, the uniformity of target erosion and plasma stability are compromised due to the peripheral scanning of small magnetrons, leading to non-uniform sputtering and potential contamination, with existing methods failing to accurately predict target end-of-life and compensate for erosion-induced changes in magnetic field strength.
Innovation Solution
Calculating a predicted erosion profile to determine target end-of-life and dynamically adjusting the magnetron's vertical position to maintain consistent plasma conditions by monitoring electrical signals and using a universal magnetron motion mechanism for complex scan patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If peripheral scanning of small magnetron is used to increase power density and ionization fraction, then sputtering rate into high aspect-ratio holes is improved, but target erosion uniformity deteriorates
Solution Approach 1:
The magnetron is made dynamically movable through a scanning mechanism that translates it in complex paths across the target surface. This dynamic positioning allows concentration of power density at specific locations for high aspect-ratio hole filling while periodically scanning to other areas to maintain uniform target erosion, thus resolving the contradiction between productivity and erosion uniformity
Solution Approach 2:
The target surface is segmented into different functional zones: a primary sputtering zone for high aspect-ratio hole deposition and secondary scanning zones for erosion control. The scanning mechanism segments the magnetron's operation into focused deposition cycles and distributed erosion cycles, allowing simultaneous optimization of both productivity and erosion uniformity
2Quantity of substance
If peripheral scanning of small magnetron is used to concentrate power density, then plasma density is improved, but plasma stability deteriorates due to erosion-induced magnetic field changes
Solution Approach 1:
A feedback control system monitors plasma parameters and magnetron position, and adjusts the scanning pattern and speed in real-time to compensate for target erosion. This feedback mechanism maintains consistent magnetic field conditions at the sputtering surface, ensuring plasma stability while preserving high plasma density through concentrated power delivery
Solution Approach 2:
The system performs preliminary scanning of the magnetron across the target surface before intensive sputtering begins. This preliminary action pre-distributes erosion and establishes stable magnetic field conditions, preventing plasma instability that would otherwise occur during prolonged focused sputtering operations
3Productivity
If magnetron is fixed at peripheral position for most of sputter deposition, then deposition efficiency is improved, but target contamination increases due to redeposited material flaking
Solution Approach 1:
The magnetron scanning follows a periodic pattern that alternates between prolonged residence at the peripheral deposition zone (for high deposition efficiency) and periodic excursions to central and intermediate zones (to prevent redeposited material buildup and flaking). This periodic scanning eliminates target contamination while maintaining overall deposition efficiency
Solution Approach 2:
The scanning mechanism periodically moves the magnetron to zones where redeposited material accumulates, effectively 'discarding' this problematic material through controlled sputtering. This prevents flaking and contamination while the majority of the scanning time is spent in optimal deposition zones, recovering high deposition efficiency
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 plasma conditions and extends target life by accurately predicting end-of-life and compensating for erosion, reducing defects and contamination in sputtered layers.
Implementation Method 1
project a magnetic field B in front of the target layer 16. The magnetic field traps electrons of the plasma and hence increases the density of the plasma to thereby increase the sputtering rate
Implementation Method 2
The positively charged argon ions are attracted to the negatively biased target at high energy and sputter target atoms from it
Implementation Method 3
When a negative DC bias of several hundred volts is applied to target while the chamber walls or shields remain grounded, the argon is excited into a plasma
Data Source
AI summary
When a magnetron is scanned about the back of a target in a selected complex path having radial components, the erosion profile has a form depending upon the selection of paths. A radial erosion rate profile for a given magnetron is measured. Periodically during scanning, an erosion profile is calculated from the measured erosion rate profile, the time the magnetron spends at different radii, and the target power. The calculated erosion profile may be used to indicate when erosion has become excessive at any location prompting target replacement or to adjust the height of the magnetron above the target for repeated scans. In another aspect of the invention, the magnetron height is dynamically adjusted during a scan to compensate for erosion. The compensation may be based on the calculated erosion profile or on feedback control of the present value of the target voltage for a constant-power target supply.