Advancing Semiconductor Processes With Novel Extreme UV Photoresist Materials
                     Advancing Semiconductor 
Processes With  Novel Extreme 
UV Photoresist Materials
Introduction
The ever-growing demand for faster, smaller, and more efficient electronic  
devices has fueled the semiconductor industry relentless pursuit of  
innovation. One crucial technology at the heart of semiconductor  
manufacturing is Extreme Ultraviolet Lithography (EUVL) to achieve  
smaller feature sizes with higher resolution, leading to miniaturized 
devices.  Researchers and companies across the globe are focusing on 
developing  novel Extreme UV (EUV) photoresist materials that support 
EUVL  patterning at nanometer-scale resolutions and improve the 
performances  of semiconductor devices.
Lithography is a crucial step in semiconductor fabrication, where patterns  
are transferred onto wafers to create integrated circuits and other  
microstructures. Traditional lithography relies on deep ultraviolet light, but  
as integrated circuits reach single-digit nanometre scales, EUV lithography  
becomes imperative. EUV light operates at wavelengths around 13.5  
nanometres, enabling the printing of significantly smaller features with  
high precision. EUV photoresists are light-sensitive materials utilized in the  
semiconductor manufacturing process, particularly in advanced  
lithography techniques. These materials must withstand high-energy EUV  
photons and provide high-resolution patterning capabilities. Some  
challenges for developing EUV photoresist materials are that they need to  
be highly sensitive to the short wavelengths, achieving high resolution is  
essential for producing intricate and small-scale patterns under 3nm,  
minimizing line-edge roughness, and outgassing (contamination) creates  
issues for manufacturers in maintaining production.
These innovative materials are often classified as Chemically Amplified  
Photoresists (CARs), Non-Chemical Amplified Resists, Inorganic EUV  
Photoresists, and Hybrid EUV Photoresists depending on their formulations or  
compositions. When exposed to EUV light, they undergo chemical or physical  
changes, enabling the accurate transfer of patterns onto surfaces.
Understanding Extreme UV Photoresist Material
EUV photoresist materials are light-sensitive substances that undergo  
chemical changes when exposed to high-energy EUV photons. EUV 
photons  generate photoacids from a photosensitive compound. This acid 
catalyzes  a deprotection reaction in the resist polymer, making it more 
soluble in  the developer solution. The amplified reaction enhances 
sensitivity and  enables high-resolution patterning. As semiconductor 
nodes advance to  smaller scales, maintaining resolution, sensitivity, and 
pattern fidelity  becomes more complex and challenging. Research is 
ongoing to develop new  materials, mechanisms, and processing 
techniques to address these  challenges and enable further 
miniaturization.
●Chemical Amplified Resist: Chemically amplified photoresists are the  
most commonly used EUV photoresists. They employ a photoacid 
generator  (PAG) that produces acid upon exposure to EUV photons. This 
acid  catalyzes a chemical reaction in the resist, leading to the dissolution 
of the  exposed regions during the development process. CARs are known 
for their  high sensitivity, making them suitable for low-dose EUV exposure 
and  improving throughput during semiconductor manufacturing. They may 
 find applications in optical devices, displays, and advanced packaging.
●Inorganic EUV Photoresists: Inorganic photoresist materials with  
different EUV absorption coefficients and high etching are important to  
solve some existing problems. Therefore, many researchers have begun to  
study the use of inorganic materials in the field of photoresists. These  
materials differ from organic CARs as they are composed of inorganic  
materials, such as metal oxides or metal-containing compounds. They work
by applying the metal oxide system with acrylic acid as the organic ligand  
to EUV lithography. Inorganic photoresists are expected to offer higher  
thermal stability and reduced outgassing than their organic counterparts.  
They may find applications in extreme environments or specialized  
semiconductor processes.
●Non-chemically Amplified Resists: Unlike CARs, non-chemically 
amplified  photoresists do not rely on acid-catalyzed reactions. Instead, 
they directly  undergo a photolytic reaction upon EUV exposure, resulting 
in a change in  solubility. These materials often require higher doses of EUV 
light for  patterning and are being explored for specific applications and 
process  requirements.
●Hybrid EUV Photoresists: Hybrid EUV photoresists combine organic and 
 inorganic elements to leverage the advantages of both material types. 
These  materials work by selecting the resins selected for the purification 
step  after the ligand exchange reaction as polystyrene resins 
functionalized with  tertiary amines, piperidine, and dimethylamine. These 
materials aim to  provide enhanced sensitivity, resolution, and thermal 
stability, addressing  some of the limitations of purely organic or inorganic 
photoresists.
Key Challenges in EUV Photoresist Development
●EUV Sensitivity: Sensitivity is one of the key challenges of EUV  
lithography; developing and optimizing photoresist materials that  
effectively absorb and react with EUV light to produce precise patterns on  
semiconductor wafers is difficult. EUV photons are scarce and expensive,  
necessitating photoresist materials with high sensitivity to achieve an  
adequate throughput of 100 to 120 wafers per hour during  manufacturing.
●Resolution and LER: As feature sizes reduce, maintaining high 
resolution  without excessive line-edge roughness (LER) becomes 
problematic. An  important potential source of LER for EUV resists is photon 
shot noise due
to the high photon energy. The LER challenge involves minimizing  
irregularities or roughness along the edges of the developed photoresist  
lines that form the transistor features. Excessive LER can lead to variations 
 in transistor performance and reduced chip yield. The manufacturers need 
 to optimize the photoresist formulation and process conditions to achieve  
an LER of 2 nm but a sensitivity of only 70 mJ/cm and smoother, more  
precise edges on the transistor features.
●Outgassing: The outgassing problem in EUV lithography refers to  
releasing volatile organic compounds (VOCs) or other materials from the  
photoresist during exposure to EUV light. These outgassed materials  
potentially contaminate the surrounding environment, including the optics  
and mirrors used in the EUV lithography equipment. Contamination  
reduces equipment performance and production yield, alongside increasing 
 maintenance requirements. Controlling and minimizing outgassing is  
critical to maintaining the reliability and efficiency of the entire EUV  
lithography process.
●Thermal Stability: EUV exposure generates considerable heat, 
demanding  stable photoresist materials under high-energy conditions. 
Many  applications demand coatings with excellent thermal stability. Most  
commercially available removers rapidly dissolve resist layers after thermal 
 loads of up to 130°C.
Promising Advancements in Novel EUV Photoresist Materials
●High Sensitivity, Low Dose Materials: Researchers are exploring  
innovative chemically amplified photoresists that react strongly to EUV  
photons even at lower doses, improving throughput to 100 wafers per  
hour and reducing manufacturing costs.
●Improved Resolution and LER Control: Novel materials such as 
chemically  amplified and inorganic resists are designed to mitigate LER 
while  maintaining high-resolution patterning capabilities. Advanced 
chemical
atomic resist compositions and unique polymer structures play a vital role  
in achieving higher sensitivity to EUV light, improving contrast, and  
reducing LER below 2nm.
●Reduced Outgassing: The development of low-outgassing photoresists  
ensures cleaner EUV exposure, resulting in a higher yield and improved  
semiconductor device reliability. Reducing outgassing is crucial to  
maintaining the cleanliness and integrity of the EUV lithography process,  
which is highly sensitive to contaminants. Semiconductor manufacturers  
collaborate closely with material suppliers and equipment manufacturers  
to ensure that the photoresists and other materials used in the EUV  
lithography process meet stringent outgassing requirements and 
contribute  to producing high-quality semiconductor devices.
●Thermal Stability Solutions: To tackle the thermal challenges of EUV  
lithography, researchers are bringing engineering materials with enhanced  
thermal stability, allowing for more prolonged exposure times without  
compromising performance.
Collaboration and Future Prospects
Developing and optimizing novel EUV photoresist materials requires  
collaboration between semiconductor manufacturers, material suppliers,  
and research institutions. The semiconductor industry’s pursuit of next-  
generation devices relies on the continual advancement and refinement of  
EUV lithography technology.
The successful implementation of novel EUV photoresist materials will  
unlock numerous possibilities for semiconductor technology. Smaller and  
more powerful devices will revolutionize various sectors, including data  
centers, healthcare, automotive, and artificial intelligence. The impact is  
not only limited to traditional computing, allowing semiconductor  
manufacturers to produce chips with smaller feature sizes. This leads to  
higher transistor density, improved performance, and lower power
consumption in electronic devices. It also enhances the capabilities of  
semiconductor devices, enabling the production of advanced processors,  
memory devices, and sensors that drive technological innovation in various 
 industries.
Conclusion
Novel Extreme UV photoresist materials represent a crucial stepping-stone  
in the relentless drive to enhance semiconductor technology. The ability to  
print ever smaller and more precise features on semiconductor wafers is  
vital to meeting the demands of the digital age. Collaborative research and 
 development in this field promise a bright future for the semiconductor  
industry, ensuring the continuous evolution of electronic devices that  
empower and enrich our lives.
Developing novel EUV photoresist materials requires collaboration among  
material scientists, chemists, physicists, and engineers. Material suppliers,  
semiconductor manufacturers, and research institutions work in tandem  to 
design, characterize, and test these materials under demanding EUV  
exposure conditions.
The field of EUV lithography and photoresist development is continuously  
evolving. Researchers are exploring a wide range of material innovations,  
including inorganic resists, nanostructured materials, and hybrid polymers.  
As the semiconductor industry strives for even greater levels of  
miniaturization and performance, the pursuit of novel EUV photoresist  
materials remains an active area of research and innovation.
Learn more about how we can empower your organization in the dynamic  
world of Semiconductors by emailing us at [email protected].
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