High-Resistance Silicon Target for Low-Defect Photomask Sputtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the fabrication of photomask blanks for semiconductor processing, silicon-based materials used in sputtering processes often generate particles during film formation, leading to defects in the photomask, particularly when the pattern size is 45 nm or less, necessitating a method to reduce particle defects effectively.
Innovation Solution
A silicon target material with a specific resistance of 20 Ω·cm or more at room temperature is used for DC sputtering, which improves discharge characteristics and reduces particle defects, employing n-type conductivity and single-crystalline silicon targets like those grown by the FZ method, and forming films in atmospheres with reactive gases like oxygen and nitrogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sputtering target of stand-alone silicon is used for forming a silicon-based material film, then the film can be formed with good light-shielding characteristics, but particles are generated during sputtering because the electrical conductivity of the target material is low, leading to particle defects on the optical film
Solution Approach 1:
The patent changes the electrical conductivity parameter of the silicon target material by adding impurities (phosphorus, arsenic, or antimony) to transform the intrinsic semiconductor into an n-type semiconductor with higher conductivity. This parameter change resolves the contradiction by enabling stable sputtering discharge (reducing particles) while maintaining the silicon-based material's excellent light-shielding properties.
Solution Approach 2:
The patent creates a composite target material by combining silicon with small amounts of donor impurities (phosphorus, arsenic, or antimony). This composite structure maintains the base silicon properties for light-shielding while the added impurities provide the necessary electrical conductivity to prevent particle generation during sputtering.
2Manufacturing precision
If the conductivity of the silicon target is increased by adding donor impurities or acceptor impurities, then particle generation is suppressed, but the purity of the silicon-based material film may be compromised
Solution Approach 1:
The patent applies local quality by adding impurities only in specific, controlled amounts (0.01-5% by atomic ratio) rather than uniformly throughout the material. This localized addition of impurities provides sufficient conductivity improvement to suppress particles while minimizing the impact on overall material purity and film quality.
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
This approach results in a low-defect, high-quality silicon-containing film suitable for light-shielding or phase shift films in photomask blanks, reducing particle defects and enhancing the accuracy and reliability of the photomask fabrication process.
Implementation Method 1
forming a silicon-containing film by DC sputtering
Implementation Method 2
DC sputtering in which a specific resistance of the silicon target material is 20 Ω·cm or more at room temperature
Data Source
AI summary
Provided is a silicon target material in which particles are not easily generated during a sputtering process and to form a low-defect (high quality) silicon-containing film. A silicon target material having a specific resistance of 20 Ω·cm or more at room temperature is used for forming a silicon-containing film. The silicon target material may be polycrystalline or noncrystalline. However, when the silicon target material is single-crystalline, a more stable discharge state can be obtained. Also, a single-crystal silicon in which crystals are grown by an FZ method is a preferable material as a highly-pure silicon target material because its content of oxygen is low. Further, a target material having n-type conductivity and containing donor impurities is preferable to obtain stable discharge characteristics. Only a single or a plurality of silicon target materials according to the present invention may be used for sputtering film formation of the silicon-containing film.