Integrated LIDAR Semiconductor Substrates With TSV CTE Matching
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Solution Overview
Problem
The mismatch in coefficient of thermal expansion (CTE) between III-V semiconductor materials and silicon substrates in LIDAR sensor systems leads to mechanical stress and defects, such as cracks and delamination, under thermal cycling conditions, affecting the reliability and yield of the bonding interface.
Innovation Solution
Incorporating an array of conductive through-silicon vias (TSVs) in the silicon substrate to adjust the composite CTE of the silicon substrate to match that of the III-V semiconductor substrate, reducing mechanical stress and improving the bonding interface reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If III-V semiconductor substrate is bonded to silicon substrate, then optical device functionality is achieved, but mechanical stress and defects occur due to CTE mismatch
Solution Approach 1:
The patent modifies the physical parameters of the silicon substrate by incorporating through-silicon vias (TSVs) filled with materials having different CTE values. This changes the effective CTE of the silicon substrate to better match the III-V semiconductor substrate, thereby reducing thermal stress at the bonding interface during thermal cycling.
Solution Approach 2:
The patent creates a composite structure by integrating TSVs within the silicon substrate. The TSVs are filled with materials such as copper, tungsten, or other metals that have higher CTE values than silicon, forming a composite material system whose effective CTE can be tuned to match the III-V semiconductor substrate.
2Reliability
If through-silicon vias are added to adjust CTE, then mechanical stress is reduced, but device complexity increases
Solution Approach 1:
The patent divides the silicon substrate into regions with and without TSVs, or uses an array of discrete TSVs at specific locations. This segmentation allows the CTE adjustment function to be localized to areas where it is most needed, rather than requiring uniform modification throughout the entire substrate.
Solution Approach 2:
The TSVs act as intermediary elements between the silicon substrate and the III-V semiconductor substrate. These vias serve as a bridge that compensates for the CTE mismatch, absorbing thermal expansion differences and protecting the bonding interface from stress.
3Productivity
If CTE mismatch is tuned to reduce stress, then bonding interface yield improves, but manufacturing process complexity increases
Solution Approach 1:
The patent incorporates TSVs into the silicon substrate before bonding to the III-V semiconductor substrate. This preliminary action allows the CTE-matching structure to be pre-formed and integrated, simplifying the bonding process itself and ensuring stress compensation is already in place before the critical bonding operation.
Solution Approach 2:
The patent applies TSVs selectively in specific regions of the silicon substrate, particularly in areas where thermal stress is most critical or where the III-V substrate is bonded. This local application of CTE adjustment provides targeted stress relief without requiring modification of the entire substrate, reducing manufacturing complexity.
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 solution effectively reduces mechanical stress and enhances the reliability and yield of the LIDAR sensor systems by tuning the CTE mismatch, leading to improved thermal management and reduced defects.
Implementation Method 1
an array of conductive through-silicon vias (TSVs) in the silicon substrate to adjust the composite CTE of the silicon substrate
Implementation Method 2
The mismatch in coefficient of thermal expansion (CTE) between III-V semiconductor materials and silicon substrates in LIDAR sensor systems leads to mechanical stress and defects
Data Source
AI summary
A light detection and ranging (LIDAR) sensor system includes a circuit module. The circuit module includes a silicon substrate having a first thermal feature. The circuit module includes a III-V semiconductor substrate coupled to the silicon substrate, the III-V semiconductor substrate having a second thermal feature. The circuit board includes an optical device coupled to the III-V semiconductor substrate, the optical device configured to output a transmit beam. The circuit module further includes a plurality of vias disposed in a particular portion of the silicon substrate, where the particular portion corresponds to the III-V semiconductor substrate, at least one of the plurality of vias having a third thermal feature. The LIDAR system further includes a scanner configured to direct the transmit beam to an environment of the vehicle.