Bisphenol Undercoat Material for 193 nm Lithography
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Solution Overview
Problem
Current undercoat materials for lithography processes, particularly in bilayer and tri-layer resist processes, face challenges in achieving high transparency, etching resistance, and antireflective effects, especially at shorter wavelengths like 193 nm, while maintaining sufficient etching resistance and minimizing substrate reflection.
Innovation Solution
A bisphenol compound with a large carbon group is used to form an undercoat layer that provides high transparency, improved etching resistance, and an antireflective effect, combined with a novolac resin and optional additives like organic solvents, crosslinkers, and acid generators, to enhance the material's properties for use in high-energy radiation lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional undercoat materials are used to achieve high etching resistance, then etching resistance is improved, but transparency and antireflective effect deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the undercoat material by introducing a bisphenol compound with specific structural features (large carbon groups at positions 2 and 2') to simultaneously achieve high etching resistance and improved transparency. This parameter change allows the material to reduce substrate reflection while maintaining etching resistance.
Solution Approach 2:
The patent uses a composite undercoat material system comprising a bisphenol compound combined with novolac resin and other additives. This composite formulation integrates the high etching resistance of the bisphenol compound with the desirable optical properties of the novolac resin, achieving both etching resistance and antireflective effect.
2Object-affected harmful factors
If undercoat layer thickness is increased to improve antireflective effect, then substrate reflection is reduced, but manufacturing complexity and process time increase
Solution Approach 1:
The patent changes the optical parameters (refractive index and extinction coefficient) of the undercoat material through the use of the bisphenol compound, enabling achieving the desired antireflective effect at thinner film thicknesses. This parameter optimization reduces the required layer thickness while maintaining effective reflection control.
3Reliability
If conventional undercoat materials are used to achieve high etching resistance, then etching resistance is improved, but transparency at shorter wavelengths deteriorates
Solution Approach 1:
The patent optimizes the optical parameters of the undercoat material specifically for short wavelength applications (193 nm) by incorporating the bisphenol compound with appropriate optical constants (n=1.5-1.7, k=0.05-0.15 at 193 nm). This parameter optimization achieves high transparency at 193 nm while maintaining high etching resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The bisphenol-based undercoat material achieves significant reductions in substrate reflection, maintains high etching resistance, and ensures a satisfactory antireflective effect, even at thinner film thicknesses, effectively supporting the patterning process with improved resist profile and reduced etching rates.
Implementation Method 1
the undercoat layer must also have the function of an antireflective coating. Specifically, the reflectance from the undercoat layer back into the resist film must be reduced to below 1%
Implementation Method 2
The undercoat layer of the bilayer resist process is formed of a hydrocarbon compound which can be etched with oxygen gas, and must have high etching resistance since it serves as a mask when the underlying substrate is subsequently etched
Data Source
AI summary
A material comprising a specific bisphenol compound of formula (1) is useful in forming a photoresist undercoat wherein R1 and R2 are H, alkyl, aryl or alkenyl, R3 and R4 are H, alkyl, alkenyl, aryl, acetal, acyl or glycidyl, R5 and R6 are alkyl having a ring structure, or R5 and R6 bond together to form a ring. The undercoat-forming material has an extinction coefficient sufficient to provide an antireflective effect at a thickness of at least 200 nm, and a high etching resistance as demonstrated by slow etching rates with CF4/CHF3 and Cl2/BCl3 gases for substrate processing.