Photolithography Mask Repair Using Alternative Structures
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Solution Overview
Problem
Current photolithography mask repair techniques using charged particle beams often introduce unintended damage and imperfections, especially with shorter wavelengths, affecting the substrate and the aerial image quality, as they struggle to precisely replicate the original structure and optical properties of binary intensity and phase-shift masks.
Innovation Solution
The system employs a charged particle beam system that utilizes diverse structures and techniques, including ion and electron beam processing, and laser use, to create alternative structures that replicate the desired aerial image rather than the original mask design, leveraging implanted ions and sacrificial layers to achieve the necessary optical functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct replacement with original mask material is used, then the repair is straightforward, but the optical fidelity is limited due to practical considerations
Solution Approach 1:
The patent changes the material parameter from native mask material to carbon-based deposition material, and adjusts the height parameter of the deposited material to mimic the desired optical properties, thereby achieving both ease of repair and improved optical fidelity
Solution Approach 2:
The patent uses composite material approach by combining carbon-based deposition material with the existing mask structure, creating a repaired region that achieves the desired optical properties through material composition rather than exact material replication
2Quantity of substance
If FIB-induced deposition is used to fabricate repair structures, then material can be deposited, but the process is complicated and difficult to control on the nanometer scale
Solution Approach 1:
The patent replaces the complex FIB-induced gas phase deposition process with a simpler material transfer process using a movable manipulator that physically transports material, substituting a complex chemical/physical deposition mechanism with a more controllable mechanical transfer approach
3Manufacturing precision
If ion beam is used to remove extra material, then opaque defects can be repaired, but the ion beam damages the mask surface and implants ions into the substrate
Solution Approach 1:
The patent introduces an intermediary material layer that is selectively removed along with the defect, protecting the underlying substrate from ion beam damage while still allowing defect removal. The sacrificial layer acts as a buffer between the ion beam and the critical substrate
Solution Approach 2:
The patent converts the harmful ion implantation effect into a beneficial etching mechanism by using the implanted ions to facilitate selective removal of the sacrificial layer, thereby transforming the harmful ion beam interaction into a useful material removal process
4Length of moving object
If shorter wavelengths are used in photolithography, then smaller structures can be produced, but imperfections in the substrate have a greater effect on the aerial image
Solution Approach 1:
The patent applies local quality by creating a repaired region with specific optical properties that match the surrounding native structure. The repair is localized to the defect area while maintaining the same optical characteristics as the original mask, ensuring uniform aerial image quality across the entire mask including repaired regions
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 repair process by reducing substrate damage, improving resolution and repeatability, and achieving optical fidelity close to defect-free conditions, making it suitable for smaller feature sizes in photolithography.
Implementation Method 1
the substitution of a void with the original mask material... by focused ion beam (FIB) induced deposition
Implementation Method 2
the defect can be repaired by removing the extra material using charged particle beam, for example, a focused beam of gallium ions
Implementation Method 3
including ion and electron beam processing, and laser use
Data Source
AI summary
Masks can be repaired by creating a structure that is different from the original design, but that produces the same aerial image. For example, missing opaque material can be replaced by implanting gallium atoms to reduce transmission and quartz can be etched to an appropriate depth to produce the proper phase. In another aspect, a laser or other means can be used to remove an area of a mask around a defect, and then mask structures, either the intended design structures or alternate structures that produce the same aerial image, can be constructed using charged particle beam deposition and etching. For example, an electron beam can be used to deposit quartz to alter the phase of transmitted light. An electron beam can also be used with a gas to etch quartz to remove a layer including implanted gallium atoms. Gallium staining can also be reduced or eliminated by providing a sacrificial layer that can be removed, along with the implanted gallium atoms, using, for example, a broad ion beam. In another aspect, a charged particle beam can be programmed to etch a defect using three-dimensional information derived from two charged particle beams images of the defect from different angle.