Photomask Blank Silicon Interlayer Pattern Accuracy
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Solution Overview
Problem
The existing photomask blanks face challenges in forming accurate fine patterns due to degradation of the chemical amplification resist at the interface with chromium-containing films, leading to deviations in pattern size and shape during etching, and require multiple etching steps with different gases, resulting in increased cycle time and defect management issues.
Innovation Solution
A photomask blank configuration where a silicon compound film is stacked between a chromium-containing film and a transition metal film, allowing for etching with fluorine and oxygen-containing chlorine, ensuring accurate pattern formation and reducing size deviations by using the same etching conditions for both films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a chemical amplification resist is provided directly on a film containing chromium, then the resist can be used for pattern formation, but the cross-sectional shape of the resist is degraded at the interface due to acid coordination with chromium lone pairs
Solution Approach 1:
A silicon compound film is introduced as an intermediary layer between the chromium-containing film and the chemical amplification resist. This intermediate film prevents direct contact between the acid in the resist and the chromium compound, thereby preventing acid deactivation while still allowing the resist to function properly for pattern formation.
Solution Approach 2:
The interface between the chromium-containing film and the resist is segmented by introducing a silicon compound film in between. This segmentation separates the harmful interaction zone, allowing the resist to maintain its cross-sectional shape while still being able to form accurate patterns.
2Ease of manufacture
If different etching gases are used for chromium-containing film and silicon compound film, then each film can be etched selectively, but the number of etching steps increases and cycle time is extended
Solution Approach 1:
The etching parameters (gas composition, power, pressure) are optimized to enable a single oxygen-containing chlorine-based gas to etch both the chromium-containing film and the silicon compound film at appropriate rates, eliminating the need for separate etching steps with different gases.
Solution Approach 2:
A single oxygen-containing chlorine-based etching gas is used to perform the etching function for both the chromium-containing film and the silicon compound film, making the etching process universal and reducing the total number of steps required.
3Manufacturing precision
If isotropic etching is used for chromium-containing film, then the film can be etched uniformly, but the pattern size deviates from the mask pattern due to lateral etching
Solution Approach 1:
The etching process transitions from a static isotropic etching mode to a dynamic anisotropic etching mode by adjusting process parameters (increasing ion energy, reducing pressure), enabling directional etching that maintains vertical profile while achieving uniform removal.
Solution Approach 2:
The etching parameters are changed to achieve anisotropic etching characteristics, including increasing ion bombardment energy and adjusting gas flow rates, which enables the etch front to proceed primarily in the vertical direction rather than laterally, thus preserving pattern dimensions.
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 enables proper formation of photomask patterns with reduced size deviations and cycle time, improving defect management and achieving accurate pattern transfer for the half-pitch 45 nm generation and beyond.
Implementation Method 1
A typical chemical amplification resist uses what is called a photoacid generator that generates an acid by means of light or an electron beam
Implementation Method 2
A negative resist is a resist a portion of which is subjected to a crosslinking reaction with an acid generated by irradiation with light or an electron beam
Implementation Method 3
The acid generated acts as a catalyst to cause a chain reaction by, for example, starting or promoting the next reaction
Implementation Method 4
the light blocking film is not substantially etched by the dry etching using fluorine and is etchable by the dry etching using oxygen-containing chlorine
Data Source
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Figure 9~12
AI summary
According to one embodiment, a photomask blank wherein a second film (14) is stacked on a first film (13), the first film containing chromium and which is not substantially etched by the dry etching using fluorine and which is etchable by the dry etching using oxygen-containing chlorine, and the second film containing no chromium and which is etchable by dry etching using fluorine and dry etching using oxygen-containing chlorine.