Substrate Alignment via Through-Substrate Optical Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor lithography alignment methods are complex and expensive, particularly for dual-side alignment, as they require specialized equipment and coatings, and struggle with achieving precise positioning of alignment marks on substrates with varying topography.
Innovation Solution
A method and apparatus that utilize a reflective alignment feature on a substrate with a partially transparent layer, allowing light to be directed through the substrate and reflected back for detection by an optical detector made of similar material, enabling precise alignment with a signal-to-noise ratio sufficient for ±0.5 micrometer accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment methods using IR-reflective coatings and specialized stages are used, then alignment precision can be achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention extracts and eliminates the unnecessary IR-reflective coating from the alignment system. By viewing alignment marks directly through the substrate without requiring reflective coatings, the method removes a complex and expensive component while maintaining alignment precision through direct optical detection of marks on the substrate surface.
Solution Approach 2:
The substrate itself is made multi-functional by using it both as the device under test and as the optical window for viewing alignment marks. The substrate's natural transparency at specific wavelengths allows it to serve dual purposes: protecting the device structure and enabling direct optical access to alignment features without requiring specialized stages or coatings.
2Measurement precision
If dual-side alignment is achieved through direct backside viewing, then alignment accuracy improves, but the method becomes complex requiring specialized equipment
Solution Approach 1:
Instead of bringing the optical system to the backside of the substrate through complex mechanical arrangements, the invention inverts the approach by bringing light from the frontside through the substrate to view alignment marks on the backside. This eliminates the need for movable chucks or complex optical path arrangements while achieving the same alignment accuracy.
3Adaptability or versatility
If alignment light passes through the reticle and wafer simultaneously, then dual-side alignment is achieved, but the method becomes complex
Solution Approach 1:
The alignment process is segmented into separate operational phases: first aligning and exposing the frontside, then repositioning the substrate to align and expose the backside. This segmentation allows each alignment operation to be performed independently through the substrate using simple optical paths, avoiding the complexity of simultaneous dual-side viewing while maintaining full dual-side alignment capability.
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 simplifies and cost-reduces substrate alignment by using a silicon-based detector and light of specific wavelengths to achieve precise alignment without the need for specialized chucks or coatings, improving image contrast and reducing mechanical complexity.
Implementation Method 1
the alignment feature reflects light directed thereto and is intercepted by an optical detector
Implementation Method 2
The material has at least partial transparency to light of a selected wavelength
Data Source
AI summary
Methods and apparatuses are provided for positioning a substrate having a target that may be located on either the front-side or the backside of the substrate. The optical detector that views the target contains a signal-generating material that is substantially identical to the substrate material.