- Dry resist is emerging as a key enabler for next-generation EUV lithography, including high-NA patterning.
- Its advantages include higher resolution, lower scanner dose, improved flexibility, and reduced defects.
- Lam’s Aether® dry resist process helps chipmakers improve EUV patterning performance while supporting lower cost and more sustainable manufacturing.
The Semi 101 series is a beginner’s guide to understanding microchips and the semiconductor industry – from components to processes to players and everything in between.
As chips become smaller and their designs more complex, the processes to create them become more challenging.
- Patterning is one example. Patterning for standard logic, DRAM, and NAND chips is used to create small, intricate features on a wafer through a series of steps that include lithography, deposition, and etching.
- Explore more: How Advanced Patterning Enables Smarter, Smaller Chips (Semi 101)
Next-generation nodes require advanced patterning that uses high numerical-aperture extreme ultraviolet (high-NA EUV) lithography and dry photoresist (“dry resist” for short) to create features that can be as small as a few nanometers wide.
Lam Research’s Aether® dry resist deposition and development process uses a series of Lam tools before and after high-NA EUV to support sub-10-nm patterning.
Key Benefits of Dry Resist
Dry resist is deposited onto a wafer using vapor phase deposition in a vacuum environment. In contrast, wet resist is dispensed in liquid form onto a wafer and then spun using centrifugal force at atmospheric pressure to spread the resist until it thins down and reaches the desired thickness.
Dry resist materials and processes are beneficial to all EUV lithography, not just high-NA, for several reasons:
- Homogeneity: Because smaller molecules of dry resist (about 2.5 Å) are applied in gaseous form, they form a more uniform resist film for higher resolution necessary for finer features, compared to the wet resist spin-on method.
- Flexibility: Substantial changes in dry resist film composition to improve etch performance can be achieved in minutes instead of months, simply by changing the deposition recipe.
- Defectivity and roughness: In addition to increasing resolution, the dry resist film’s compositional homogeneity and purity provide lower roughness and defectivity, all at a lower scanner dose.
- Dose reduction: Dry resist technology has increased sensitivity to EUV photons, compared to chemically amplified resists, thereby reducing the EUV scanner dose required for each wafer exposure.
- Sustainability: Dry resist does not use any acids, bases, solvents, or per- and polyfluoroalkyl substances (PFAS) in any of its process steps.
Lam’s Role in Dry Resist Innovation
Lam Research introduced its groundbreaking dry resist technology in 2020. Most recently, it launched the Aether® dry resist and development process that improves resolution, productivity, and defectivity (yield) of both low- and high-NA EUV lithography processes.
- The bottom line: Dry resist processing not only provides superior circuit pattern images, but also substantially reduces the overall cost of EUV lithography patterning.
Lam Technologies
Lam Research offers dry resist tools suited for EUV lithography:
- Aether® GPX dry resist deposition: Aether GPX offers EUV dry resist deposition for industry-leading lithography performance, providing highest EUV sensitivity and resolution, lowest dose and defectivity, and new 3D engineering capability for greatest extendibility for advanced node patterning.
- Aether® GDX dry resist development: Aether GDX offers uniform and pattern-collapse-free development of all EUV resist patterns, including especially those at the highest feature resolution and density.
- Nimbus®: Nimbus provides a stable and effective underlayer film for the Aether Dry Resist layer that further increases dose reduction benefits for EUV lithography.
- Dry plasma strip systems: These systems, such as the Gamma GxT, G400, and G3D, are used for complete and efficient removal of photoresist and residues without damaging device features.
- Wet clean/spin clean systems: Products like the DV Prime and Da Vinci families and the EOS product family provide effective wet cleaning solutions for the wafer’s backside and bevel areas.
- Plasma bevel clean systems: The Coronus family of products is used for bevel cleaning by a plasma process.
Glossary
Chemically amplified resist (CAR): A type of wet resist that forms an acid during the post-exposure bake that completes the reactions started during photon exposure, significantly reducing the dose required.
Extreme ultraviolet (EUV): 13.5-nm wavelength radiation.
High-NA EUV lithography: Lithography that achieves better resolution through the use of larger EUV scanner mirrors to print smaller features and more densely packed arrays of transistors.
Lithography: Traditionally used as an artistic technique in printmaking, lithography in semiconductor manufacturing uses deep ultraviolet (DUV) and extreme ultraviolet (EUV) radiation to transfer integrated circuit device layer patterns from a reticle onto a photoresist film.
Patterning: The deposition, lithography, and etching processes involved in transferring integrated circuit features, layer by layer, from reticles into target layers on silicon wafers.
Photoresists: Photosensitive materials used to transfer integrated circuit patterns from reticles to target layers on silicon wafers. When exposed to scanner radiation (e.g., deep ultraviolet and EUV), they undergo chemical changes that delineate areas that are either removed during development or remain as a protective mask during subsequent plasma etching or ion implantation steps.
Transistor: A fundamental component in semiconductor devices used to amplify or switch electrical signals and electrical power.