Photomask Overlay Correction via Laser Thermal Modification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The semiconductor industry faces challenges in maintaining the precision and performance of photomasks due to variations in critical dimensions and overlay errors, which can lead to defective masks and increased production costs, especially with the use of intense radiation and cleaning processes that degrade photomask quality.
Innovation Solution
A method and apparatus using laser-based thermal modification to adjust the overlay of photomasks by heating the substrate and thin films, allowing for localized or global changes in the photomask's material properties to improve performance and extend its lifespan while minimizing surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If photomasks are subjected to intense radiation and cleaning processes during production use, then the photomasks can be reused multiple times, but the critical dimensions and overlay precision deteriorate, leading to defective masks
Solution Approach 1:
The patent applies laser irradiation to induce thermal effects that modify the physical and chemical parameters of the photomask surface and thin films. By controlling the laser parameters (wavelength, power, pulse duration), the treatment alters surface properties such as adhesion, roughness, and stress distribution, thereby restoring overlay precision without requiring replacement of the photomask
Solution Approach 2:
The laser treatment utilizes thermal expansion and subsequent cooling contraction of the photomask substrate and thin films. The rapid heating and cooling cycles induce controlled thermal stress that releases accumulated stress from fabrication and usage, restoring the dimensional stability and overlay accuracy of critical features
2Reliability
If conventional cleaning processes are used to maintain photomask performance, then surface contamination is removed, but the cleaning processes themselves cause degradation of the photomask materials and reduce mask lifetime
Solution Approach 1:
The patent replaces conventional mechanical and chemical cleaning processes with laser-based thermal treatment. Instead of using solvents, ultrasonic vibration, or abrasive materials that can damage the photomask, the laser induces thermal effects that volatilize contaminants and restore surface properties through controlled heating and cooling cycles
Solution Approach 2:
The laser treatment converts the harmful thermal exposure that degrades photomasks during normal use into a beneficial restorative process. By applying controlled laser irradiation with specific parameters, the same thermal energy that causes degradation under uncontrolled conditions is used to volatilize contaminants, relieve stress, and restore the photomask surface to its original performance state
3Productivity
If photomasks with varying material properties and film stresses are used, then production can proceed with available masks, but the mask-to-mask variability leads to variations in critical dimensions and overlay
Solution Approach 1:
The laser treatment modifies the physical and chemical parameters of the photomask materials through controlled thermal exposure. This changes the stress state, crystalline structure, and surface properties of the thin films and substrate, thereby standardizing the performance characteristics across masks that were originally manufactured with varying properties
Solution Approach 2:
The laser treatment enables photomasks to self-correct their dimensional and stress-related variations through controlled thermal exposure. The photomask materials undergo stress relief and reorganization during the laser treatment, allowing the masks to self-adjust to standardized performance levels without requiring external mechanical adjustment or re-fabrication
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 enhances the precision and longevity of photomasks, reduces production delays and costs by correcting overlay errors and extending the usable life of photomasks, and improves the overall yield and quality of semiconductor wafers.
Implementation Method 1
A method and apparatus using laser-based thermal modification to adjust the overlay of photomasks by heating the substrate and thin films
Implementation Method 2
The properties of photomasks, such as dimensional properties and material properties, for example, may vary within ranges resulting from tolerances applied during the manufacturing process. For example, the optical performance characteristics of partially absorbing films may depend on the material composition of the film and a thickness of the film
Data Source
AI summary
A photomask includes at least one feature disposed thereon. The at least one feature has an associated design location, where a distance between a location of the at least one feature and the associated design location defines a positional error of the at least one feature. A method for improving a performance characteristic of the photomask includes directing electromagnetic radiation toward the photomask, the electromagnetic radiation having a wavelength that substantially coincides with a high absorption coefficient of the photomask; generating a thermal energy increase in the photomask through incidence of the electromagnetic radiation thereon; and decreasing the positional error as a result of the generating the thermal energy increase in the photomask.