Compact Focusing and Leveling Device Using Double Reflection
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Solution Overview
Problem
Conventional focusing and leveling devices are complex, bulky, costly, and difficult to construct due to their intricate structure and separate 4F systems on opposing sides of the substrate.
Innovation Solution
A compact focusing and leveling device is designed with a projection-side 4F system that includes an illumination unit, a projection-side mark plate, a deflection prism, a beam splitter, and a detection unit, where the probe beam is reflected twice at the substrate surface, allowing for calculation of defocus and tilt using a signal processing unit, thereby eliminating the need for a separate detection-side 4F system and simplifying the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional device uses two separate 4F systems arranged on opposing sides of the substrate for projection and detection, then the measurement function is achieved, but the structure becomes complicated and bulky
Solution Approach 1:
The patent combines the projection-side 4F system and detection-side 4F system into a single integrated optical path. The beam splitter divides the optical path such that the projection objective and detection objective share common optical components (illumination unit, projection-side mark plate, beam splitter), reducing the number of separate systems from two to one while maintaining both projection and detection functions
Solution Approach 2:
The projection-side mark plate serves dual functions: it acts as a mark for focus detection (by reflecting light back through the projection objective) and as a reference for alignment. The beam splitter also serves multiple functions by directing light to different paths for projection and detection simultaneously
2Measurement precision
If a conventional device incorporates two 4F systems on opposing sides of the substrate, then projection and detection functions are separated, but the device footprint increases
Solution Approach 1:
The patent merges the projection and detection optical paths into a compact configuration where both functions operate within the same physical space. The beam splitter enables the optical path to fold back on itself, allowing the detection path to overlap with the projection path rather than extending in a separate direction, thereby reducing the overall device footprint
3Reliability
If a conventional device uses separate projection and detection 4F systems, then the functions are independent, but construction becomes difficult and costly
Solution Approach 1:
The patent integrates multiple functions into shared optical components, reducing the total number of components that need to be manufactured and assembled. The beam splitter and projection-side mark plate serve multiple purposes, eliminating the need for separate dedicated components for each function, thereby simplifying construction and reducing manufacturing costs
Solution Approach 2:
The projection objective and detection objective are designed to work within a unified optical system where the same optical components serve both projection and detection functions. This multi-functionality reduces the complexity of alignment and calibration during construction, making the device easier to manufacture while maintaining measurement reliability
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 device achieves a simpler structure, reduced fabrication costs, and enhanced compactness while doubling the measuring accuracy for defocus and tilt due to the multiplexed 4F system and double reflection of the probe beam at the substrate surface.
Implementation Method 1
the deflection prism configured to deflect the probe beam that has been reflected by the surface of the substrate for a first time so that it is again incident on the surface of the substrate and reflected thereby for a second time
Implementation Method 2
the beam splitter configured to direct the probe beam that has travelled through the projection-side imaging group onto the detection unit
Data Source
AI summary
A focusing and leveling device calculates an amount of defocus and/or tilt of a substrate and includes an illumination unit, projection-side mark plate with projection-side slit mark, projection-side imaging group, deflection prism, beam splitter, detection unit and signal processing unit. A light beam emitted from the illumination unit passes through the projection-side mark plate and is trimmed into a probe beam directed by the projection-side imaging group onto a substrate surface. The prism deflects the probe beam reflected by the surface of the substrate for a first time so that it is incident on the substrate surface and reflected for a second time onto the projection-side imaging group. The beam splitter directs the probe beam that travelled through the projection-side imaging group onto the detection unit. The signal processing unit calculates the amount of defocus and/or tilt based on a measurement spot detected by the detection unit.