Die-to-Wafer Alignment Marks for Photonic Coupling Accuracy
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Solution Overview
Problem
Accurate alignment between a source die and a target wafer is crucial for efficient light coupling in silicon photonics systems, but existing methods struggle to measure and correct misalignments effectively, leading to degraded coupling efficiency and low yields.
Innovation Solution
A method involving the formation of alignment marks and pillars on both the source die and target wafer, using a single etching operation to ensure precise alignment, followed by image acquisition and analysis to measure offsets and misalignments, allowing for correction of translational and angular misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks are formed separately from waveguide facets, then alignment measurement is possible, but manufacturing complexity and misalignment risk increase
Solution Approach 1:
The patent combines the formation of alignment marks and waveguide facets into a single etching operation. The alignment marks are formed at the same time as the waveguide facets using the same etching process, eliminating separate alignment mark fabrication steps. This merging reduces manufacturing complexity while maintaining the ability to measure alignment between source die and target wafer through the integrated marks.
2Manufacturing precision
If multiple etching operations are used to form alignment marks and waveguide facets, then feature precision can be optimized independently, but cumulative misalignment and process complexity increase
Solution Approach 1:
The patent merges the etching operations for alignment marks and waveguide facets into a single simultaneous process. This eliminates cumulative misalignment that would occur from multiple sequential etching steps, as both features are created in the same process window with the same reference frame, thereby improving alignment accuracy while maintaining feature precision.
3Difficulty of detecting and measuring
If alignment marks are placed far from waveguide facets, then measurement access is improved, but coupling efficiency may be compromised
Solution Approach 1:
The patent implements different types of alignment marks at different locations: edge-aligned marks positioned away from facets for easy measurement access, and corner-aligned marks positioned near facets for verifying critical coupling alignment. This local differentiation allows measurement marks to be accessible while ensuring coupling-critical alignment is also verified, maintaining both measurement ease and coupling efficiency.
4Reliability
If comprehensive alignment verification is performed, then assembly quality improves, but inspection time and complexity increase
Solution Approach 1:
The patent segments alignment verification into two distinct measurement systems: edge-aligned marks for measuring translational misalignment (x-y shifts) and corner-aligned marks for measuring angular misalignment (rotational errors). This segmentation allows independent optimization of each measurement type and enables selective inspection based on which alignment errors are most critical for a given assembly, reducing overall inspection time while maintaining comprehensive quality verification.
Data Source
AI summary
A system and method for alignment. In some embodiments, the method includes measuring a first offset, the first offset being an offset along a first direction between a first alignment mark and a second alignment mark, the first alignment mark being an alignment mark on a first edge of a source die, the second alignment mark being an alignment mark on a target wafer, and the first direction being substantially parallel to the first edge of the source die.