Angled Light Guide Fabrication via Oblique Exposure
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Solution Overview
Problem
Current methods for manufacturing optical systems, such as light guides, face challenges in creating angled portions with precise control over the dose profile, which is crucial for guiding light efficiently, especially in applications like LIDAR systems.
Innovation Solution
The described methods involve double exposure techniques using photoresist materials like SU-8, where the first exposure is performed at a near-normal angle and the second at an oblique angle, and the use of 'blur mask' approaches with multiple photomasks to achieve a controllable dose profile, allowing for the formation of angled portions with reflective coatings for optimal light guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single exposure methods are used, then the manufacturing process is simple, but the dose profile control precision is insufficient for creating accurate angled portions
Solution Approach 1:
The exposure process is divided into multiple sequential exposure steps, where each exposure applies a specific dose profile to different regions of the photoresist. This segmentation allows precise control over the dose distribution to create angled portions with accurate geometries, resolving the contradiction between manufacturing precision and process complexity by breaking down the complex dosing requirement into manageable sequential steps.
Solution Approach 2:
The patent employs periodic exposure actions with varying parameters (angle, dose, duration) to build up the desired dose profile in the photoresist. By applying exposures in periodic cycles with different characteristics, the method achieves precise dose control for angled features while maintaining a systematic and controllable process framework.
2Manufacturing precision
If multiple photomasks are used for blur mask approach, then the dose profile control is improved, but the manufacturing time and process steps increase
Solution Approach 1:
Multiple photomasks are merged and aligned on the same substrate, allowing simultaneous definition of multiple features and dose regions. This merging approach enables the creation of complex dose profiles that would require multiple sequential mask changes, thereby reducing manufacturing cycle time while maintaining precise angled portion geometry through the coordinated action of multiple masks.
Solution Approach 2:
The photomasks are prepared and positioned in advance on the substrate before the exposure process begins. This preliminary arrangement of multiple masks eliminates the need for time-consuming mask changes during exposure, allowing the exposure system to directly apply the intended dose profile in a single operation, thus reducing manufacturing cycle time while achieving precise geometric control.
3Reliability
If oblique angle exposure is used, then the angled portions are formed with better light guidance, but the photoresist development control becomes more difficult
Solution Approach 1:
The patent systematically varies exposure parameters including angle, dose, and duration to create a tailored dose profile that compensates for the challenges of oblique angle exposure. By carefully controlling these parameters, the method achieves the desired angled portion geometries that provide excellent light guidance while maintaining manageable photoresist development characteristics through optimized dose distribution.
Solution Approach 2:
The exposure process incorporates feedback control where the dose profile is adjusted based on the desired final geometry and the known characteristics of the photoresist material. This feedback approach allows optimization of the exposure parameters to achieve both good light guidance efficiency and ease of development, by predicting and compensating for development behavior during the exposure planning stage.
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
These techniques enable the fabrication of optical elements with precise angled portions that enhance light guidance and reflection, improving the performance of optical systems, particularly in compact LIDAR systems by providing accurate point cloud data and object information.
Implementation Method 1
causing a light source to illuminate the photoresist material through the first mask. The light source is positioned at a first angle. The first angle includes a non-normal angle with respect to a plane parallel to the substrate
Implementation Method 2
depositing a reflective material through the second mask onto the angled portion
Implementation Method 3
Such light guiding devices may transmit light from an input facet to an output facet via total or partial internal reflection
Data Source
AI summary
Systems and methods described herein relate to the manufacture of optical elements and optical systems. An example method includes overlaying a first mask on a photoresist material and a substrate, and causing a light source to illuminate the photoresist material through the first mask during a first exposure so as to define a first feature. During the first exposure, the light source is positioned at a non-normal angle with respect to a plane parallel to the substrate. The method includes developing the photoresist material so as to retain an elongate portion of the photoresist material on the substrate. A first end of the elongate portion includes an angled portion that is sloped at an angle with respect to a long axis of the elongate portion. The method also includes depositing a reflective material through a second mask onto the angled portion.