Magnetron Sputtering Grid Layout for Uniform Film Stress
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Solution Overview
Problem
The build-up of film stresses during the manufacturing process of MEMS devices leads to out-of-plane deformation, warping, buckling, and cracking of freestanding structures, which negatively impact device performance and yield, particularly in RF devices, due to unpredictable resonant properties and stress-induced frequency shifts.
Innovation Solution
A magnetron sputtering apparatus with a thermally conductive grid positioned between the substrate support and target, featuring a low aspect ratio and specific cell geometry, which filters high-energy species and thermalizes plasma to reduce within-wafer stress uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional magnetron sputtering is used to deposit material, then deposition efficiency is maintained, but within-wafer stress uniformity deteriorates leading to out-of-plane deformation and warping
Solution Approach 1:
A thermally conductive grid is introduced as an intermediary component between the target and substrate support. The grid comprises an array of pins arranged in a regular pattern, which act as intermediate structures to scatter and thermalize the plasma flux. This intermediary structure redistributes the plasma energy uniformly across the wafer surface, reducing within-wafer stress variations while maintaining the overall deposition process simplicity.
Solution Approach 2:
The patent modifies the physical parameters of the deposition system by introducing a grid with specific geometric parameters (pin diameter, pin spacing, grid density) and thermal properties. By changing these parameters, the plasma transport and energy distribution are altered, resulting in improved within-wafer stress uniformity without fundamentally changing the magnetron sputtering process.
2Productivity
If high plasma flux is used to increase deposition rate, then productivity improves, but film stress variations increase causing warping and buckling
Solution Approach 1:
The thermally conductive grid serves as a mediator that decouples the relationship between plasma flux intensity and stress uniformity. By introducing this intermediate structure, high plasma flux can be maintained for high deposition rates while the grid scatters and thermalizes the plasma, ensuring uniform energy distribution and stress uniformity across the wafer surface.
Solution Approach 2:
The patent utilizes thermal conduction (analogous to thermal expansion principles) through the thermally conductive grid to redistribute heat and plasma energy. The grid conducts thermal energy from high-flux regions to lower-flux regions, equalizing the thermal and kinetic energy distribution across the substrate, thereby maintaining stress uniformity even at high deposition rates.
3Productivity
If plasma flux is increased to improve deposition efficiency, then manufacturing speed increases, but out-of-plane deformation and cracking worsen
Solution Approach 1:
The thermally conductive grid acts as a protective intermediary that allows high deposition efficiency while protecting the film structure from stress-induced deformation and cracking. The grid scatters and thermalizes the plasma flux, preventing localized high-energy impacts that would cause stress concentrations and structural failures.
Solution Approach 2:
The grid provides beforehand cushioning by pre-distributing and thermalizing the plasma flux before it reaches the substrate. This preliminary energy distribution prevents the formation of high-stress regions that would lead to deformation and cracking, cushioning the film against structural failures before they occur.
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 apparatus significantly reduces within-wafer stress range to less than 180 MPa, enhancing mechanical reliability and performance of deposited films by minimizing stress variations and maintaining uniformity across the substrate.
Implementation Method 1
a plasma production device configured to produce a plasma within the chamber suitable for sputtering material from the target onto the substrate
Implementation Method 2
a thermally conductive grid comprising a plurality of cells, in which each cell comprises an aperture... the grid is disposed between the substrate support and the target... thermalizes plasma to reduce within-wafer stress uniformity
Implementation Method 3
a magnetron sputtering apparatus for depositing material onto a substrate... sputtering material from the target onto the substrate
Data Source
AI summary
A magnetron sputtering apparatus for depositing material onto a substrate, comprises: a chamber comprising a substrate support and a target; a plasma production device configured to produce a plasma within the chamber suitable for sputtering material from the target onto the substrate; and a thermally conductive grid comprising a plurality of cells. Each cell comprises an aperture and the ratio of the height of the cells to the width of the apertures is less than 1.0. The grid is disposed between the substrate support and the target and is substantially parallel to the target. The upper surface of the substrate support is positioned at a distance of 75 mm or less from the lower surface of the target.