Home > Press > Stress-free path to stress-free metallic films paves the way for next-gen circuitry: Optimized sputtering technique helps minimize stress in tungsten thin films
![]() |
(top left) An illustration of the HiPIMS process (top right) The energy distribution of tungsten ions arriving at the substrate over time. At short times, there are a large proportion of ions with high energy. (bottom) Stress-free tungsten films created with the selective pulsed bias technique. (a) Plan view transmission electron microscopy (TEM) image of the film; (b) a higher resolution image; (c) reconstructions of the selected area in (b) based on inverse Fourier transforms, with two regions magnified. CREDIT Tokyo Metropolitan University |
Abstract:
Researchers from Tokyo Metropolitan University have used high power impulse magnetron scattering (HiPIMS) to create thin films of tungsten with unprecedentedly low levels of film stress. By optimizing the timing of a "substrate bias pulse" with microsecond precision, they minimized impurities and defects to form crystalline films with stresses as low as 0.03 GPa, similar to those achieved through annealing. Their work promises efficient pathways for creating metallic films for the electronics industry.
Modern electronics relies on the intricate, nanoscale deposition of thin metallic films onto surfaces. This is easier said than done; unless done right, "film stresses" arising from the microscopic internal structure of the film can cause buckling and curving over time. Getting rid of these stresses usually requires heating or "annealing". Unfortunately, many of the best metals for the job e.g. tungsten have high melting points, meaning that the film needs to be heated to over 1000 degrees Celsius. Not only is this energy intensive, but it severely limits which substrate materials can be used. The race is on to create films out of high melting point metals without these stresses in the first place.
A team led by Associate Professor Tetsuhide Shimizu of Tokyo Metropolitan University have been working with a technique known as high power impulse magnetron scattering (HiPIMS), a sputtering technique. Sputtering involves applying a high voltage across a metallic "target" and a substrate, creating a plasma of charged gas atoms which bombards the metallic target and forms a charged metal vapor; these metal ions fly towards the substrate where they form a film. In the case of HiPIMS, the voltage is pulsed in short, powerful bursts. After each pulse, it is known that there is some separation between the arrival of metal and gas ions at the substrate; a synchronized "substrate bias" pulse can help selectively accelerate the metal ions, creating denser films. Yet despite many efforts, the issue of residual stress remained.
Now, using argon gas and a tungsten target, the team looked at how ions with different energies arrived at the substrate over time in unprecedented detail. Instead of using a bias pulse set off at the same time as the HiPIMS pulse, they used their knowledge of when different ions arrived and introduced a tiny delay, 60 microseconds, to precisely select for the arrival of high energy metal ions. They found that this minimized the amount of gas ending up in the film and efficiently delivered high levels of kinetic energy. The result was a dense crystalline film with large grains and low film stress. By making the bias stronger, the films became more and more stress-free. The efficient delivery of energy to the film meant that they had, in fact, achieved a similar effect to annealing while they deposited the film. By further swapping out argon for krypton, the team realized films with a stress as low as 0.03 GPa, comparable to what can be made with post-annealing.
An efficient pathway to stress-free films will have a significant impact on metallization processes and the manufacture of next-generation circuitry. The technology may be applied to other metals and promises big gains for the electronics industry.
###
This work was supported by the Fund for the Promotion of Joint International Research (No.17KK0136) of the Japan Society for the Promotion of Science (JSPS), the Swedish Research Council (No. VR 2018-04139), and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009-00971).
####
For more information, please click here
Contacts:
Go Totsukawa
81-426-772-728
@TMU_PR
Copyright © Tokyo Metropolitan University
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related Links |
Related News Press |
News and information
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
Night-time radiative warming using the atmosphere November 17th, 2023
A new kind of magnetism November 17th, 2023
Thin films
Understanding the mechanism of non-uniform formation of diamond film on tools: Paving the way to a dry process with less environmental impact March 24th, 2023
New study introduces the best graphite films: The work by Distinguished Professor Feng Ding at UNIST has been published in the October 2022 issue of Nature Nanotechnology November 4th, 2022
Thin-film, high-frequency antenna array offers new flexibility for wireless communications November 5th, 2021
Leibniz Prize winner Professor Dr. Oliver G. Schmidt moves to Chemnitz University of Technology: President Professor Dr. Gerd Strohmeier refers to an 'absolute top transfer' September 10th, 2021
Govt.-Legislation/Regulation/Funding/Policy
Three-pronged approach discerns qualities of quantum spin liquids November 17th, 2023
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
Possible Futures
Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023
Silver nanoparticles: guaranteeing antimicrobial safe-tea November 17th, 2023
Three-pronged approach discerns qualities of quantum spin liquids November 17th, 2023
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
Chip Technology
Charged “molecular beasts” the basis for new compounds: Researchers at Leipzig University use “aggressive” fragments of molecular ions for chemical synthesis November 3rd, 2023
Twisted science: NIST researchers find a new quantum ruler to explore exotic matter October 6th, 2023
Successful morphing of inorganic perovskites without damaging their functional properties October 6th, 2023
Discoveries
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
Night-time radiative warming using the atmosphere November 17th, 2023
A new kind of magnetism November 17th, 2023
Materials/Metamaterials/Magnetoresistance
Porous platinum matrix shows promise as a new actuator material November 17th, 2023
A new kind of magnetism November 17th, 2023
Ferroelectrically modulate the Fermi level of graphene oxide to enhance SERS response November 3rd, 2023
Announcements
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
Night-time radiative warming using the atmosphere November 17th, 2023
A new kind of magnetism November 17th, 2023
Grants/Sponsored Research/Awards/Scholarships/Gifts/Contests/Honors/Records
Three-pronged approach discerns qualities of quantum spin liquids November 17th, 2023
Study on Magnetic Force Microscopy wins 2023 Advances in Magnetism Award: Analysis of finite size effects reveals significant consequences for density measurements November 3rd, 2023
Training quantum computers: physicists win prestigious IBM Award September 8th, 2023
Research partnerships
Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023
Nanoparticle quasicrystal constructed with DNA: The breakthrough opens the way for designing and building more complex structures November 3rd, 2023
Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023
![]() |
||
![]() |
||
The latest news from around the world, FREE | ||
![]() |
![]() |
||
Premium Products | ||
![]() |
||
Only the news you want to read!
Learn More |
||
![]() |
||
Full-service, expert consulting
Learn More |
||
![]() |