Semiconductor Fabrication Solutions
Halocarbon science leverages a legacy of knowledge and expertise in organofluorine chemistry to develop unique solutions that help our partners drive advances in the electronics industry by enabling semiconductor miniaturization and enhancing semiconductor design.
Photoresist Monomer Precursors
Photoresist Monomers
Engineering Thermoplastic Fluorinated Monomer Precursors
In 1965 Gordon Moore, one of the co-founders of Intel predicted that the number of transistors per integrated circuit would double every year. After 50+ years, Moore’s seminal observation has been shown to still be true, serving as a map that sets the direction for the modern digital revolution. Implicit in Moore’s law is the demand for ancillary technologies to keep pace with ever-increasing circuit density. These technologies include the methods and raw materials required to produce microprocessors with increasingly infinitesimal feature sizes.
Over the past three to four decades, semiconductors have been designed and manufactured using photolithography. These processes involve the use of lasers of ever-decreasing wavelengths of light to etch circuits. Most modern processes use a broad range of radiation-sensitive polymeric films, reactive gasses, and other chemicals in combination with physical equipment to create semiconductor highly-miniaturized microprocessors. The figure below describes the latest evolution of the photolithography process at a high-level, depicting the use of photoresist materials (photo-responsive polymeric coatings), photomasks (a patterning plate), and incident light to create circuit patterns ultimately used in a microprocessor design. In traditional photolithography, imaging is performed under an inert gas atmosphere whereas immersion photolithography utilizes a water layer in contact with the substrate as a final lens element. Fluorinated materials are required to control the surface interactions with the water layer, thus enabling finer features through immersion photolithography.
For over a decade Halocarbon scientists and engineers have been partnering with leading manufacturers of the raw materials used in advanced photolithography processes. Halocarbon offers a broad range of high-purity electronics grade monomers, monomer pre-cursors, and other specialty fluorochemicals for use in this process. Our key technologies leverage our expertise in producing hexafluoroisopropyl (HFIP) derivatives, which have been demonstrated to provide unique value to the semiconductor fabrication industry.
The Advantages of Hexafluoroisopropyl Chemistry
In order to keep pace with Moore’s Law, and to achieve better resolutions in photolithography, the chip manufacturing industry has employed light sources of progressively shorter wavelengths of light. This trend has required the industry to adopt new physical and consumable technologies. The transitions from 248 nm to 193 nm, and then again recently to EUV poses major challenges, requiring not only investments in new laser technologies but also the type of polymers used in compatible photoresist coatings. The constituent materials of the 248 nm photoresist coatings were not transparent to the lower wavelengths of light, rendering them unusable in the new lithographic methods. Fluorinated materials are inherently transparent at 193 nm, making them ideally suited for use in the monomers and monomer precursors of modern photoresist coatings. Interestingly, as the industry introduces EUV technology at 13.5 nm, the number of incident photons has dramatically reduced while the photoresist film thicknesses have also decreased. EUV thus demands materials with higher absorption efficiency to utilize the limited available patterning light. Fluorinated compounds provide the necessary enhanced absorption at EUV wavelengths with as much as a four-fold increased absorption as compared to carbon based materials. Halocarbon Electronics Solutions provides a broad range of customizable monomers and monomer precursors with exceptional optical transparency control at the relevant wavelengths of light to the semiconductor industry.
In order to increase the resolution of the laser beam used in the creation of smaller and smaller feature sizes, some chip manufacturers have begun to employ immersion lithography. This technique involves replacing the air gap between the final lens element and the photoresist layer with a liquid that has a refractive index greater than that of air (~1.0). The most commonly used liquid used in this technique is water (refractive index ~ 1.44). However, this improvement bares some degree of risk, as the physical and chemical interactions occurring between water and the photoresist can lead to defects in patterning and slowing of the photolithography process. For example, the photoresist layer can absorb water, leading to swelling and/or deleterious transmission and absorption of the impinging light. To abate the ingress of water into the photoresist, some chip manufacturers have employed the use of a hydrophobic topcoat or sought to improve the hydrophobicity of the photoresist coating itself. Halocarbon manufactures novel high-quality, high-purity HFIP-based monomers (and monomer precursors) that can provide very high water contact angles (a measure of hydrophobicity). By increasing the water contact angles (both advancing and receding) bubble defects are reduced, water ingress is eliminated, and high scanning speeds are enabled. These materials when incorporated into photoresists and top-coats have been demonstrated to provide superior hydrophobicity and exceptional patterning control.
The HFIP based monomers and monomer precursors developed and manufactured by Halocarbon allow for control over hydrophobicity and hydrophilicity. A key part in the photolithography process is the clean removal of the photoresist layer from the surface of a patterned wafer. This stage of the process, known in the industry as the development step, involves the dissolution of the patterned portions of the photoresist using aqueous base (most commonly tetramethylammonium hydroxide, or TMAH). The acidity of the alcohol group in HFIP-based materials can be used to modulate the overall solubility of the photoresist layer at different pHs of aqueous alkalinity. This pH-triggered solubility switching allows a photoresist layer to function as a hydrophobic coating within an acidic to neutral pH-range, and as a hydrophilic and aqueous-soluble material at the alkaline pH-range, ensuring high-fidelity across both the patterning and development stages of the photolithography process.
