Magnetron Sputtering Plasma Steering for Uniform Edge Film Thickness
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Solution Overview
Problem
Magnetron sputtering techniques face challenges in achieving uniform film thickness, particularly at the periphery of substrates, leading to reduced effectiveness in manufacturing bulk acoustic wave devices due to substantial drop-offs in AlN film thickness, resulting in a loss of usable substrate area.
Innovation Solution
A method and apparatus utilizing a secondary magnetic field produced by an electromagnet or permanent magnet to steer ions away from the substrate's peripheral portion, expanding the plasma and reducing sputter etching, thereby maintaining uniform film thickness across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pulsed DC magnetron sputtering is used, then the deposition process is simple and fast, but the film thickness becomes non-uniform with marked drop-off at the radially outermost part of the substrate
Solution Approach 1:
A secondary magnetic field is introduced as an intermediary element between the plasma and the substrate. This secondary magnetic field, generated by electromagnets positioned around the chamber periphery, acts as a mediator to steer plasma expansion and redirect ions away from the substrate periphery, thereby achieving uniform film thickness without modifying the fundamental magnetron sputtering process
Solution Approach 2:
The invention changes the magnetic field parameters by superimposing a secondary magnetic field on the primary magnetron field. By adjusting the strength and configuration of the secondary magnetic field through controllable electromagnets, the plasma distribution and ion bombardment patterns are modified to achieve uniform deposition across the entire substrate surface
2Manufacturing precision
If the radially outermost 15 mm of the wafer is excluded due to thickness drop-off, then film uniformity is maintained, but 28% of the available silicon substrate area is lost
Solution Approach 1:
The secondary magnetic field serves as an intermediary that redistributes plasma and ions uniformly across the entire substrate surface, eliminating the need to exclude the peripheral 15 mm region. This enables 100% substrate utilization while maintaining the required <1% thickness non-uniformity specification
Solution Approach 2:
The invention achieves homogeneous film thickness distribution across the entire substrate by using the secondary magnetic field to create uniform plasma expansion and ion bombardment patterns. This homogenization allows the previously problematic peripheral regions to contribute fully to production without compromising film quality
3Manufacturing precision
If plasma is expanded towards chamber walls using secondary magnetic field, then ion bombardment at substrate periphery is reduced, but the apparatus complexity increases due to additional electromagnets
Solution Approach 1:
The electromagnets serving as secondary magnetic field sources are designed to perform multiple functions: they generate the secondary magnetic field for plasma steering, provide structural support for chamber assembly, and can potentially serve as mounting positions for other process control components. This multi-functionality reduces the need for separate dedicated components
Solution Approach 2:
The electromagnets are designed with controllable parameters including adjustable current strength and configurable positioning. This parametric flexibility allows optimization of the secondary magnetic field to achieve uniform deposition while minimizing the number of electromagnets required and simplifying their integration into the existing chamber structure
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 effectively maintains uniform film thickness across the substrate, reducing non-uniformity and enabling the use of the entire substrate area for manufacturing bulk acoustic wave devices by minimizing ion bombardment at the edge regions.
Implementation Method 1
a secondary magnetic field is produced within the chamber which causes a plasma produced by the pulsed DC magnetron device to expand towards one or more walls of the chamber
Implementation Method 2
a plasma produced by the pulsed DC magnetron device
Implementation Method 3
Magnetron sputtering is a well known example of PVD (Physical Vapour Deposition)
Implementation Method 4
a sputtering material is sputtered from a target
Implementation Method 5
Magnetron sputtering is a well known example of PVD (Physical Vapour Deposition)
Data Source
AI summary
A method is for depositing a dielectric material on to a substrate in a chamber by pulsed DC magnetron sputtering with a pulsed DC magnetron device which produces one or more primary magnetic fields. In the method, a sputtering material is sputtered from a target, wherein the target and the substrate are separated by a gap in the range 2.5 to 10 cm and a secondary magnetic field is produced within the chamber which causes a plasma produced by the pulsed DC magnetron device to expand towards one or more walls of the chamber.