Photomask Capping Layer for Haze Defect Suppression
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Solution Overview
Problem
The semiconductor industry faces challenges with haze defects and haze-related crystal growth defects on photomasks during high-energy exposure in UV and EUV lithography processes, leading to increased production cycle time and costs due to the need for repeated chemical cleaning.
Innovation Solution
A self-passivated hydrogenic capping layer is formed on photomasks by modifying the capping layer to react with ionic residues, suppressing haze defect growth through hydrogenic bonding, using materials like metal oxides, nitrides, or oxynitrides deposited on low thermal expansion substrates and opaque layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase shift mask is used to improve lithography resolution, then lithography resolution is improved, but haze defects and crystal growth defects occur on the photomask
Solution Approach 1:
A capping layer is introduced as an intermediary between the photomask substrate and the environment. This capping layer contains hydrogenic compounds that react with incoming ionic residues during lithography exposure, forming a protective barrier that prevents ion interaction and suppresses haze defect formation while allowing the phase shift mask to maintain its resolution-enhancing function
2Object-affected harmful factors
If repeated chemical cleaning processes are performed to remove haze defects, then haze defects are reduced, but production cycle time increases
Solution Approach 1:
The capping layer is applied in advance to the photomask before lithography exposure. This preliminary protective layer prevents haze defect formation during the exposure process by neutralizing ionic residues, thereby eliminating the need for subsequent repeated chemical cleaning operations and reducing production cycle time
3Object-affected harmful factors
If repeated chemical cleaning processes are performed to remove haze defects, then haze defects are reduced, but production cost increases
Solution Approach 1:
The capping layer is applied in advance to the photomask before lithography exposure. This preliminary protective layer prevents haze defect formation during the exposure process by neutralizing ionic residues, thereby eliminating the need for subsequent repeated chemical cleaning operations and reducing production cycle time
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 solution effectively reduces haze defects on photomasks, decreasing production costs and cycle time by forming a stable hydrogenic layer that absorbs hydrogen ions and suppresses ion interaction, thereby enhancing the reliability and efficiency of advanced lithography processes.
Implementation Method 1
A self-passivated hydrogenic capping layer is formed on photomasks by modifying the capping layer to react with ionic residues, suppressing haze defect growth through hydrogenic bonding
Data Source
AI summary
A photomask includes a low thermal expansion material (LTEM) substrate, a patterned opaque layer over the LTEM substrate, and a patterned capping layer over the opaque layer. The patterned capping layer includes a transition metal material for suppressing haze growth, such as metal oxide, metal nitride, or metal oxynitride. The material in the capping layer reacts with a hydrogenic compound from a lithography environment to for an atomic level hydrogen passivation layer. The passivation layer has superior ability to suppress photo-induced haze defect growth on the photomask surface, to improve production cycle time and reduce the production cost.