Rotating Magnet Assembly for PVD Thickness Uniformity
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Solution Overview
Problem
The challenge in manufacturing bulk acoustic wave (BAW) devices is achieving precise and uniform thickness of piezoelectric layers during pulsed DC physical vapor deposition, which is crucial for frequency stability but often results in short-range thickness variations, making post-deposition trimming difficult and costly.
Innovation Solution
A magnet assembly with a radially varying magnetic field is used during pulsed DC physical vapor deposition to steer ions and improve thickness uniformity, comprising a plurality of magnets arranged in various configurations around an axis of rotation, allowing for tailored magnetic field strength along the radial direction to control ion distribution and film stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a narrow ion beam is used to correct local short range thickness variations, then thickness uniformity is improved, but the scan speed must be reduced and accelerations increase making trimming difficult
Solution Approach 1:
The magnetic field is applied during the deposition process itself to prevent short range thickness variations from occurring in the first place, rather than correcting them afterward through trimming. This preliminary action eliminates the need for complex post-deposition corrections.
Solution Approach 2:
The patent replaces the mechanical ion beam scanning system with a magnetic field-based ion steering system. Instead of physically moving a narrow ion beam across the wafer surface, magnetic fields are used to steer ions during deposition, achieving uniformity control without the mechanical complexity and speed limitations of beam scanning.
2Manufacturing precision
If the ion beam etch rate is lowered to accommodate scan speed limitations, then thickness precision is improved, but system throughput decreases and device cost increases
Solution Approach 1:
The magnetic field control is implemented during the deposition process to achieve thickness precision upfront, eliminating the need for subsequent slow trimming operations. This maintains high deposition rates and system throughput while achieving the required precision.
Solution Approach 2:
The patent changes the control parameter from post-deposition etching rate to in-situ magnetic field strength during deposition. By adjusting magnetic field parameters during the deposition process, both precision and throughput are maintained without the trade-off inherent in lowering etch rates.
3Ease of manufacture
If standard deposition techniques are used, then manufacturing simplicity is maintained, but short range thickness variations occur making post-deposition trimming necessary
Solution Approach 1:
The patent merges the deposition process with real-time magnetic field-based ion steering control. By combining these functions into a single integrated process, the system achieves both thickness uniformity and manufacturing simplicity without requiring separate trimming operations.
Solution Approach 2:
The patent replaces mechanical beam scanning and post-deposition trimming with a magnetic field-based ion steering system operated during deposition. This substitution maintains manufacturing simplicity while achieving superior thickness uniformity.
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 significantly reduces short-range thickness variations, enabling easier correction and achieving ±0.1% thickness control, thus improving the manufacturing efficiency and cost-effectiveness of BAW devices by maintaining within-wafer stress control and reducing the complexity of ion beam trimming.
Implementation Method 1
a magnetic field generating arrangement for generating a magnetic field proximate the substrate
Implementation Method 2
magnet assembly with a radially varying magnetic field is used during pulsed DC physical vapor deposition to steer ions
Implementation Method 3
pulsed DC physical vapour deposition
Implementation Method 4
a plasma generating arrangement for generating a plasma within the chamber
Data Source
AI summary
A magnet assembly is disclosed for steering ions used in the formation of a material layer upon a substrate during a pulsed DC physical vapour deposition process. Apparatus and methods are also disclosed incorporating the assembly for controlling thickness variation in a material layer formed via pulsed DC physical vapour deposition. The magnet assembly comprises a magnetic field generating arrangement for generating a magnetic field proximate the substrate and means for rotating the ion steering magnetic field generating arrangement about an axis of rotation, relative to the substrate. The magnetic field generating arrangement comprises a plurality of magnets configured to an array which extends around the axis of rotation, wherein the array of magnets are configured to generate a varying magnetic field strength along a radial direction relative to the axis of rotation.