Photomask Coating Layer Enhances Contrast
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Solution Overview
Problem
As minimum device pitch falls below 100 nanometers, attenuated phase-shift photomasks experience contrast issues with specific wavelengths of actinic energy, leading to degraded resolution at the edges of patterns.
Innovation Solution
A photomask construction featuring a transparent base with a thin layer of phase-shifting material, such as molybdenum silicide, and a light-attenuating stack comprising materials like chromium and silicon nitride, with a coating layer that enhances contrast by selectively allowing or blocking actinic energy, particularly absorbing the transverse magnetic component to improve pattern resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If attenuated phase-shift photomasks are used for patterning, then the resolution can be improved, but contrast issues occur with specific wavelengths of actinic energy at critical dimensions below 50 nanometers
Solution Approach 1:
The patent changes the optical parameters of the photomask by introducing a coating layer with specific optical properties (refractive index and absorption coefficient) that interact with the actinic energy to enhance contrast. This parameter change allows the system to maintain improved resolution while resolving the contrast issue at sub-50nm critical dimensions
Solution Approach 2:
The patent employs a composite structure combining multiple materials with different optical properties: the phase-shift material (such as molybdenum silicide) and the coating layer (such as chromium or silicon nitride). This composite approach enables simultaneous achievement of phase-shifting for resolution enhancement and contrast improvement through selective absorption of actinic energy
2Length of moving object
If the critical dimension is reduced below 50 nanometers, then the device pitch can be reduced for higher integration, but the contrast and resolution degrade
Solution Approach 1:
The patent modifies the optical interaction parameters by adding a coating layer that absorbs specific components of actinic energy. This changes the effective wavelength and contrast of the illumination, enabling resolution of patterns at reduced device pitches below 50 nanometers that would otherwise be unresolved
Solution Approach 2:
The coating layer acts as an intermediary between the actinic energy and the photoresist, selectively absorbing the transverse magnetic component to enhance contrast. This intermediary enables the system to achieve the required manufacturing precision at smaller device pitches by modifying the optical field before it reaches the photoresist
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 provides improved contrast and resolution at critical dimensions below 50 nanometers by optimizing the interaction of actinic energy with the photomask features, enhancing the patterning process in integrated circuit fabrication.
Implementation Method 1
a coating layer that enhances contrast by selectively allowing or blocking actinic energy, particularly absorbing the transverse magnetic component to improve pattern resolution
Implementation Method 2
The phase-shifting masks can increase the resolution of patterns by creating phase-shifting regions in transparent areas of the photomask. One of these transmission areas transmits light 180° out of phase from the other of the transmission areas. Light diffracted underneath the opaque regions from the phase-shifted regions may be destructively canceled by light that is not phase-shifted
Data Source
AI summary
Some embodiments include methods of forming photomasks. A stack of at least three different materials is formed over a base. Regions of the stack are removed to leave a mask pattern over the base. The mask pattern includes a pair of spaced-apart adjacent segments of the stack. A liner is formed to cover sidewalls of the segments. Some embodiments include photomasks. The photomasks may include a transparent base supporting a pair of spaced-apart adjacent features. The spaced-apart adjacent features may include sidewalls, with inner sidewalls of the spaced-apart features being adjacent one another, and spaced from one another by a gap. A coating layer of from about 5 Angstroms thick to about 50 Angstroms thick may be along the entirety of the sidewalls of the spaced-apart adjacent features. Some embodiments include methods of photolithographically patterning substrates.