Tin-Modified Chromium Hard Mask for Photomask Etching
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Solution Overview
Problem
Conventional photomask blanks face challenges in achieving high-precision patterning and sufficient etching resistance when the resist film is thinned, particularly with chromium-containing materials, which limits the miniaturization and precision of photomask patterns in semiconductor manufacturing.
Innovation Solution
A photomask blank with a hard mask film made of a chromium-containing material including tin, integrated with an inorganic material film etched by fluorine-containing dry etching, such as molybdenum, tantalum, hafnium, niobium, tungsten, or silicon, to enhance etching rate and resistance during chlorine-containing dry etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resist film is thinned to achieve finer patterning, then the pattern precision is improved, but the etching resistance deteriorates causing pattern distortion
Solution Approach 1:
A hard mask film made of chromium-containing material is introduced as an intermediary layer between the resist film and the light-shielding film. This hard mask film serves as a protective mediator that maintains etching resistance while allowing high-precision pattern transfer, solving the contradiction between thin resist film requirements and sufficient etching resistance
Solution Approach 2:
The patent employs a composite structure combining a chromium-containing hard mask film with a light-shielding film containing silicon and transition metal. This composite material approach provides both the etching resistance needed for thin resist films and the optical properties required for photomask functionality
2Manufacturing precision
If the resist film is made thinner to reduce aspect ratio, then pattern transfer is improved, but damage from etching process increases
Solution Approach 1:
The hard mask film is formed beforehand as a protective cushioning layer between the resist film and the light-shielding film. This pre-established protective layer absorbs the harmful effects of the etching process, preventing direct damage to the thin resist film while enabling high-precision pattern transfer
3Reliability
If conventional chromium-containing material is used as hard mask film, then etching resistance is maintained, but etching rate is insufficient
Solution Approach 1:
The patent modifies the composition parameters of the chromium-containing hard mask film by adding specific elements (such as Mo, Ta, Hf, Nb, W, or Si) to enhance the etching rate. This parameter change allows the hard mask film to maintain etching resistance while achieving sufficient etching rate for high-precision patterning
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 configuration significantly increases the etching rate during chlorine-containing dry etching while maintaining high etching resistance during fluorine-containing dry etching, allowing for high-precision pattern transfer even with a thin resist film, reducing the burden on the photoresist and ensuring reliable pattern formation.
Implementation Method 1
an inorganic material film configured to be etched by fluorine-containing dry etching
Implementation Method 2
forming a hard mask pattern by subjecting the hard mask film to chlorine-containing dry etching
Data Source
AI summary
A light-shielding film 2 is formed on a transparent substrate 1. A hard mask film 3 is formed on this light-shielding film 2. The entire hard mask film 3 is made of a chromium-containing material including tin. The film made a chromium-containing material including tin can cause a significant increase in the etching rate at the time of chlorine-containing dry etching. Furthermore, comparing with a film made of a chromium-containing material in which part of chromium is replaced with a light element, the above film has an equal or higher level of etching resistance to fluorine-dry etching. Thus, burden on a photoresist at the time of etching the chromium-containing material film can be reduced. Therefore, high-precision pattern transfer can be performed even in the case that the resist film is thinned.