Interposer-Based Wafer Testing for Vertical Optical Coupling
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Solution Overview
Problem
Current wafer level testing methods for adiabatic couplers in optical components are wavelength dependent and require dicing of wafers, which increases time and cost and may result in improperly functioning components due to improper wafer processing.
Innovation Solution
A system and method for wafer level testing of adiabatic couplers that involves forming cavities in the BEOL layer of the wafer to expose the adiabatic couplers, and using an interposer with waveguides and a redirecting element to adiabatically couple optical signals into and out of the adiabatic couplers without dicing the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dicing is performed to enable testing of adiabatic couplers, then testing access is improved, but manufacturing time and cost increase
Solution Approach 1:
The wafer structure is segmented by forming individual cavities in the BEOL layer for each IC, allowing the interposer to access specific adiabatic couplers without dicing the entire wafer. This localized access approach enables testing of individual components while maintaining wafer integrity.
Solution Approach 2:
An interposer is introduced as an intermediary component between the optical source and the adiabatic couplers. The interposer contains waveguides that extend into cavities formed in the BEOL layer, providing optical access to the couplers without requiring wafer dicing.
2Ease of operation
If dicing is performed to enable testing of adiabatic couplers, then testing access is improved, but cost increases
Solution Approach 1:
The wafer structure is segmented by forming individual cavities in the BEOL layer for each IC, allowing the interposer to access specific adiabatic couplers without dicing the entire wafer. This localized access approach enables testing of individual components while maintaining wafer integrity.
Solution Approach 2:
An interposer is introduced as an intermediary component between the optical source and the adiabatic couplers. The interposer contains waveguides that extend into cavities formed in the BEOL layer, providing optical access to the couplers without requiring wafer dicing.
3Adaptability or versatility
If conventional coupling methods are used, then testing can be performed, but wavelength dependence limits versatility
Solution Approach 1:
The patent replaces conventional grating couplers (which are wavelength-dependent) with adiabatic couplers that use total internal reflection. This substitution eliminates wavelength dependence and enables broadband operation across multiple wavelengths.
Solution Approach 2:
The coupling mechanism is changed from grating-based (wavelength-dependent) to adiabatic mode conversion (wavelength-independent). The adiabatic coupler uses gradual mode transformation based on refractive index differences, which operates effectively across a broad wavelength range.
4Reliability
If wafer processing is performed improperly during dicing, then component functionality is compromised, but dicing is required for conventional testing
Solution Approach 1:
An interposer is introduced as an intermediary component between the optical source and the adiabatic couplers. The interposer contains waveguides that extend into cavities formed in the BEOL layer, providing optical access to the couplers without requiring wafer dicing.
Solution Approach 2:
The patent transitions from edge-based coupling (requiring wafer dicing) to vertical coupling through cavities in the BEOL layer. This dimensional change allows optical access from the top surface of the wafer, eliminating the need for edge access and dicing operations.
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
Enables efficient and cost-effective wafer level testing of adiabatic couplers by allowing vertical coupling of optical signals, reducing the need for dicing and minimizing the risk of improper wafer processing.
Implementation Method 1
The at least one waveguide may be configured to adiabatically couple at least one optical signal out of the multiple ICs
Implementation Method 2
The redirecting element may be configured to receive the at least one optical signal from the at least one waveguide. The redirecting element may also be configured to vertically redirect the at least one optical signal towards the transparent layer
Implementation Method 3
The transparent layer may be configured to permit optical signals to pass through
Data Source
AI summary
A system may include a wafer that includes ICs and defines cavities. Each cavity may be formed in a BEOL layer of the wafer and proximate a different IC. The system may also include an interposer that includes a transparent layer configured to permit optical signals to pass through. The interposer may also include at least one waveguide located proximate the transparent layer. The at least one waveguide may be configured to adiabatically couple at least one optical signal out of the multiple ICs. Further, the interposer may include a redirecting element optically coupled to the at least one the waveguide. The redirecting element may be located proximate the transparent layer and may be configured to receive the at least one optical signal from the at least one waveguide. The redirecting element may also be configured to vertically redirect the at least one optical signal towards the transparent layer.