RF Substrate Bias for HIPIMS Sputtering Arc Control
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Solution Overview
Problem
High Power Impulse Magnetron Sputtering (HIPIMS) techniques face issues with arcing on substrates, which causes damage and are ineffective on insulating surfaces, and the use of RF ICP pre-ionization complicates design and reduces deposition rates due to increased target-substrate spacing.
Innovation Solution
The implementation of an RF electrical bias device connected to the substrate, in conjunction with a power supply and capacitors, allows for synchronized pulsing to control current density and inhibit arc formation, reducing arcing and enabling deposition on insulating surfaces with improved deposition rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If DC bias is applied to the workpiece holder to control ion energy, then ion energy control is improved, but arcing occurs on the substrate causing wafer damage
Solution Approach 1:
The patent applies periodic RF bias pulses to the substrate holder instead of continuous DC bias. The RF bias is applied in synchronized pulses during the HIPIMS discharge, creating periodic electric fields that control ion energy while avoiding continuous arcing conditions. This temporal modulation resolves the contradiction by providing ion energy control only when needed while preventing sustained arcing damage.
Solution Approach 2:
The patent replaces the DC electrical bias system with an RF electrical bias system. By using radio frequency alternating current instead of direct current, the system achieves ion energy control through RF-induced plasma effects rather than direct DC field acceleration, thereby preventing DC-related arcing while maintaining ion energy modulation capability.
2Speed
If RF ICP pre-ionization is used to reduce pulse rise time, then ignition speed is improved, but device complexity increases and deposition rate decreases
Solution Approach 1:
The patent combines the RF bias function with the existing substrate holder structure, integrating the electrical bias device into the substrate mounting system. By merging the RF bias electrodes with the substrate holder, the system achieves pre-ionization capability without adding separate complex ICP coil assemblies, thereby reducing device complexity while maintaining fast ignition performance.
Solution Approach 2:
The patent extracts the pre-ionization function from the complex RF ICP coil system and implements it through a simplified RF bias applied directly to the substrate holder. By taking out the essential pre-ionization capability and implementing it through a simpler mechanism, the system achieves fast pulse rise times without the complexity and deposition rate penalties of full ICP pre-ionization systems.
3Speed
If RF ICP pre-ionization is used, then pulse rise time is reduced, but deposition rate decreases due to increased target-substrate spacing
Solution Approach 1:
The patent uses the substrate holder itself as an intermediary element to deliver RF bias directly to the substrate surface. This intermediary approach creates a localized electric field at the substrate without requiring increased target-substrate spacing, thereby achieving fast ignition through RF pre-ionization while maintaining short spacing that preserves high deposition rates.
4Temperature
If DC bias is applied, then ion energy control is achieved, but the method is ineffective on electrically insulating surfaces
Solution Approach 1:
The patent replaces DC bias with RF bias, which can effectively couple to insulating surfaces through dielectric heating and surface charge accumulation mechanisms. The alternating RF field can induce currents and create plasma even on electrically insulating substrates, whereas DC bias cannot establish sustained fields on insulators. This substitution provides both ion energy control and compatibility with insulating surfaces.
Solution Approach 2:
The patent uses periodic RF bias pulses that can charge and discharge insulating surfaces, creating time-varying electric fields that provide ion energy control even on electrically insulating materials. The periodic nature allows charge accumulation during the RF cycle that effectively controls ion bombardment energy without requiring continuous conductive pathways.
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 results in faster ignition of HIPIMS pulses, reduced arcing, and higher deposition rates with better substrate coverage, while allowing for the use of shorter target-substrate distances and lower capacitor capacities, leading to more efficient and reliable sputtering processes.
Implementation Method 1
The electrical bias device 10 can be an RF generator that applies a capacitive RF bias to the substrate 14
Implementation Method 2
The energetic ions for the sputtering process are supplied by a plasma that is induced in the sputtering equipment
Implementation Method 3
The electrons undergo more ionizing collisions with gaseous neutrals near the target surface
Implementation Method 4
Sputtering sources are usually magnetrons that utilize magnetic fields to trap electrons in a closed plasma loop close to the surface of a target
Implementation Method 5
The electrons follow helical paths in a loop around the magnetic field lines
Implementation Method 6
Sputtering is a physical process whereby atoms in a solid target material are ejected into the gas phase due to bombardment of the material by energetic ions
Implementation Method 7
A capacitor can be used to provide the pulsed power
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An apparatus for generating sputtering of a target to produce a coating on a substrate with a current density on a cathode of a magnetron between 0.1 and 10 A/cm2 is provided. The apparatus comprises a power supply that is operably connected to the magnetron and at least one capacitor is operably connected to the power supply. A first switch is also provided. The first switch operably connects the power supply to the magnetron to charge the magnetron and the first switch is configured to charge the magnetron according to a first pulse. An electrical bias device is operably connected to the substrate and configured to apply a substrate bias.