Optical-gradient antireflective coatings for 157-nm optical lithography applications

Area of Science:

• Materials Science
• Optical Engineering
• Semiconductor Manufacturing

Background:

• Advanced lithography requires precise control over light reflection to achieve smaller feature sizes.
• Traditional bottom antireflective coatings (BARCs) face challenges in meeting the stringent requirements of sub-70-nm lithography.
• Minimizing substrate reflectance is crucial for improving lithographic performance and process latitude.

Purpose of the Study:

• To develop a novel optical-gradient bottom antireflective coating (BARC) film.
• To investigate a simple and effective method for preparing the optical-gradient BARC.
• To evaluate the performance and suitability of the developed BARC for sub-70-nm lithography.

Main Methods:

• Preparation of silicon nitride films treated with oxygen plasma to create an optical gradient.
• Gradual variation of oxygen composition and optical constants within the silicon nitride film.
• Characterization of reflectance, thickness tolerance, and thermal stability of the optical-gradient BARC.

Main Results:

• Achieved reflectance below 1% on various highly reflective substrates.
• Demonstrated high thickness-controlled tolerance for the optical-gradient film.
• Confirmed high thermal stability during postexposure bake procedures.

Conclusions:

• The optical-gradient BARC film is easily prepared via oxygen plasma treatment of silicon nitride.
• The developed BARC exhibits excellent optical properties and thermal stability.
• This optical-gradient BARC is suitable for ArF and F2 excimer laser lithography in sub-70-nm applications.