Digital Micromirror Autofocus for Lithography Depth of Focus
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Solution Overview
Problem
The existing photolithography processes for creating patterns on large area substrates, such as those used in LCD and OLED manufacturing, face challenges due to the limited resolution of digital micromirror devices (DMDs), requiring multiple pattern generators that increase costs and complexity in alignment and reliability.
Innovation Solution
An autofocus system that uses a single light beam and a diffractive optical element to split the beam into multiple beams, which are reflected off a substrate to position sensors, allowing individual adjustment of DMDs to account for surface height and tilt variations, thereby improving focus and alignment precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple pattern generators are used to achieve desired throughput, then productivity is improved, but device complexity and alignment difficulty increase
Solution Approach 1:
The patent divides the substrate processing into multiple regions, each processed by a separate projection unit with its own DMD. By implementing individual autofocus systems for each DMD, the patent enables independent optimization of each segment, allowing parallel processing that maintains high throughput while reducing the complexity of managing a single large-scale system
Solution Approach 2:
The patent implements dynamic autofocus adjustment for each DMD based on measured substrate surface height and tilt variations. This dynamic adaptation allows each projection unit to automatically compensate for substrate variations, enabling reliable operation of multiple units without increasing alignment difficulty
2Productivity
If multiple pattern generators are used to achieve desired throughput, then productivity is improved, but reliability deteriorates
Solution Approach 1:
The patent implements feedback control by measuring the position of split light spots on the substrate surface and using this information to individually adjust each DMD's focus and tilt. This closed-loop feedback system ensures that each projection unit maintains optimal performance independently, improving overall system reliability even as the number of units increases
Solution Approach 2:
The patent performs preliminary autofocus measurement and adjustment for each DMD before pattern exposure. By pre-compensating for substrate variations, the system ensures reliable operation of multiple projection units from the start, preventing alignment and focus issues that would otherwise reduce reliability
3Manufacturing precision
If DMD size is increased to improve resolution, then manufacturing precision is improved, but the DMD becomes too large for the projection lens field size
Solution Approach 1:
The patent uses optical splitting to create multiple virtual image fields from a single DMD by dividing the light beam into multiple paths. This effectively projects multiple reduced-scale patterns simultaneously, achieving high resolution without requiring a physically large DMD that would exceed the projection lens field size
4Manufacturing precision
If individual DMD adjustment is implemented to compensate for substrate variations, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal autofocus system that uses the same optical components (beam splitter, position sensor) to simultaneously measure and control focus and tilt for multiple DMDs. This multi-functional approach achieves high manufacturing precision while minimizing the addition of complex dedicated components for each adjustment function
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 solution enables precise and cost-effective pattern creation on substrates by individually adjusting DMDs to compensate for substrate variations, enhancing the depth of field and focus, and reducing the need for multiple pattern generators, thus improving throughput and reducing production costs.
Implementation Method 1
a diffractive optical element configured to split the single light beam into two or more split beams
Implementation Method 2
The two or more split beams are directed to a beam splitter. The two or more split beams are then reflected off the surface of a substrate
Implementation Method 3
The two or more split beams are then reflected off the surface of a substrate to at least one position sensor. The position sensor is configured to measure the position of each of the two or more split beams
Data Source
AI summary
The present disclosure generally relates to lithography devices comprising an autofocus system. The autofocus system is configured to individually focus and adjust a plurality of digital micromirror devices. The autofocus system comprises a single light beam and a diffractive optical element configured to split the single light beam into two or more split beams. The two or more split beams are directed to a beam splitter. The two or more split beams are then reflected off the surface of a substrate to at least one position sensor. The position sensor is configured to measure the position of each of the two or more split beams. At least one digital micromirror device is then individually adjusted based on the measured position to adjust the focus of the at least one digital micromirror device with respect to surface height and tilt variations of the substrate.