Rotating Magnet Array for Pulsed DC PVD Thickness Control
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Solution Overview
Problem
The manufacturing of bulk acoustic wave (BAW) devices faces challenges in achieving precise and uniform thickness of piezoelectric layers during pulsed DC physical vapor deposition, leading to frequency shifts and yield loss due to short-range thickness variations, which are difficult to correct with existing ion beam trimming methods.
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 controlled ion steering and stress management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a continuously rotating array of permanent magnets is used to control film stress during deposition, then within-wafer stress uniformity is improved, but short-range thickness variations (SRTV) are not sufficiently reduced
Solution Approach 1:
The patent employs a continuously rotating array of permanent magnets during deposition to dynamically control ion steering and film stress. The rotation creates time-varying magnetic field patterns that average out local variations, achieving uniform stress distribution across the wafer while minimizing short-range thickness variations.
Solution Approach 2:
The patent changes the temporal and spatial parameters of the magnetic field by using a rotating array configuration. The rotation speed, magnetic field strength, and array geometry are optimized to produce the desired stress control and thickness uniformity, transforming a static field problem into a dynamic solution.
2Manufacturing precision
If ion beam trimming is used to correct thickness variations, then frequency shift is reduced, but throughput decreases and device cost increases
Solution Approach 1:
The patent applies preliminary action by controlling film stress and deposition conditions during the main deposition process to pre-establish uniform thickness distribution. This preventive approach reduces the need for subsequent trimming operations, thereby maintaining high throughput while achieving the required thickness accuracy.
Solution Approach 2:
The patent converts the typically harmful effect of ion bombardment during deposition into a beneficial tool for stress control and thickness uniformity. By carefully managing ion flux through magnetic field control, the deposition process itself achieves the precision previously requiring separate trimming steps.
3Manufacturing precision
If a narrow ion beam is used to correct local short-range thickness variations, then thickness uniformity is improved, but the accelerations required to accommodate the velocity profile make trimming difficult
Solution Approach 1:
The patent replaces the mechanical complexity of high-speed beam scanning and acceleration control with a magnetic field-based solution. The rotating magnetic array passively steers ions to achieve uniform deposition without requiring complex mechanical scanning systems or high accelerations.
4Manufacturing precision
If the ion beam etch rate is lowered to accommodate scan speed limitations, then short-range thickness variations are corrected, but system throughput is affected and device cost increases
Solution Approach 1:
The patent maintains continuous useful action by performing thickness uniformity control during the deposition process itself rather than requiring separate, slower trimming operations. The rotating magnetic field continuously steers ions to achieve uniform deposition throughout the entire wafer surface in a single continuous process.
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 solution significantly reduces short-range ripple in the magnetic field components, enabling better within-wafer stress control and achieving thickness uniformity within ±0.1% (±10 Å) across the wafer, facilitating easier correction and improving device performance and manufacturing efficiency.
Implementation Method 1
a magnetic field generating arrangement for generating a magnetic field proximate the substrate
Implementation Method 2
magnet assembly for steering ions used in the formation of a material layer upon a substrate during a pulsed DC physical vapour deposition process
Implementation Method 3
a plasma generating arrangement for generating a plasma within the chamber
Implementation Method 4
pulsed DC physical vapour deposition
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.