Rotating Magnet Arrays for Sputtering Flux Alignment
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Solution Overview
Problem
Magnetron sputtering apparatuses face a rotational shift issue where deposited films tend to shift from their intended location on the substrate, affecting alignment marks in lithography, especially as feature sizes decrease and film thickness increases.
Innovation Solution
The introduction of one or more magnet arrays that create symmetric or asymmetric plasma discharge paths to balance the movement of charged particles, offsetting the rotational shift by moving ions in opposite directions on these paths, either through symmetric or asymmetric magnet configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional asymmetric magnet array is used for magnetron sputtering, then the sputtering process can be maintained, but rotational shift of deposition flux occurs on the substrate
Solution Approach 1:
The patent applies asymmetry by using an asymmetric magnet array configuration where the magnet array is positioned at a specific offset distance from the center of the target. This asymmetric positioning creates an asymmetric magnetic field distribution that generates a rotational force on the plasma discharge path, causing the deposition flux to rotate and align with the substrate features. The asymmetric configuration is specifically designed to counteract the rotational shift by introducing a controlled rotational component to the deposition process.
2Productivity
If the target radius is increased to accommodate larger wafers, then productivity is improved, but rotational shift increases with radius
Solution Approach 1:
The patent changes the parameter of magnet array positioning by introducing an offset distance from the target center. This parameter change creates a rotational moment that compensates for the increased rotational shift associated with larger target radii. By adjusting the offset distance, the system can maintain alignment accuracy across different target sizes and wafer dimensions, enabling scalable processing while preserving precision.
3Manufacturing precision
If magnet array rotation speed is increased to improve film uniformity, then deposition quality is improved, but rotational shift dynamics become more complex
Solution Approach 1:
The patent employs periodic rotation of the magnet array at controlled speeds to achieve uniform film deposition. The periodic motion of the asymmetric magnet array creates a time-averaged symmetric deposition pattern, ensuring uniformity across the substrate. By maintaining specific rotation speeds, the system balances the benefits of uniformity improvement with the management of rotational shift dynamics, avoiding excessive complexity in control while achieving desired film quality.
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 solution effectively reduces rotational shifting of deposition flux, allowing for more precise film deposition and alignment, as illustrated by reduced vector plots showing minimal movement of deposition flux on the substrate.
Implementation Method 1
A magnetic field is superposed on the cathode with the target 120 in a sputtering chamber filled with Ar (argon) gas
Implementation Method 2
Planar magnetron sputtering uses a magnetic field to confine the motion of secondary electrons to near the target surface
Implementation Method 3
Physical vapor deposition (PVD) has been widely used in forming films on a wafer surface during fabrication of integrated circuits
Implementation Method 4
Ar ions generated in the glow discharge are accelerated at the cathode and sputter the target 120, resulting in the deposition of thin films on the substrate 112
Implementation Method 5
PVD involves physical vaporization of atoms from a target surface using bombarding energetic particles that are usually ions of a gaseous material accelerated in an electric field
Implementation Method 6
Ar ions generated in the glow discharge are accelerated at the cathode
Data Source
AI summary
In one embodiment, a magnetron sputtering apparatus includes one or more magnet arrays for moving ions or charged particles on at least two plasma discharge paths on a target. Charged particles on one of the plasma discharge paths are moved in one direction, while charged particles on the other plasma discharge path are moved in the opposite direction to reduce rotational shifting of deposition flux on the patterned substrates. The plasma discharge paths may be formed by two symmetric magnet arrays or a single asymmetric magnet array rotated from behind the target.