Transfer Die Isolation Structure for Low-Capacitance Bond Pads
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Solution Overview
Problem
Conventional micro-transfer printing (MTP) techniques are unable to create high-speed photonic devices due to large parasitic capacitance in the bond pad, which is not easily reduced for devices suitable for MTP.
Innovation Solution
A transfer die is designed with an optoelectronic device featuring a low-capacitance bond pad by incorporating a non-conductive isolation region and isolation trench in the semiconductor stack, separating the bond pad from the waveguide region, thereby reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional MTP techniques are used with standard bond pad design, then the device structure is simple and easy to manufacture, but large parasitic capacitance prevents high-speed operation
Solution Approach 1:
The bond pad region is segmented from the waveguide region by introducing an isolation trench and non-conductive isolation region. This spatial segmentation electrically isolates the bond pad, reducing parasitic capacitance and enabling high-speed operation while maintaining manufacturing feasibility through standard semiconductor processing techniques
Solution Approach 2:
A non-conductive isolation layer (such as silicon dioxide or silicon nitride) is introduced as an intermediary material between the bond pad and the substrate/waveguide region. This intermediary provides electrical isolation and reduces parasitic capacitance without significantly complicating the manufacturing process, as it can be deposited using standard PECVD or LPCVD techniques
2Object-affected harmful factors
If isolation trench is etched deeply to reduce parasitic capacitance, then parasitic capacitance is reduced, but manufacturing complexity and difficulty increase
Solution Approach 1:
The isolation trench is etched to a depth that provides sufficient electrical isolation (extending through the active layers to the substrate or a deep isolation layer), which is adequate to reduce parasitic capacitance to acceptable levels. The trench does not need to extend through the entire wafer thickness, balancing isolation effectiveness with manufacturing simplicity and cost
Solution Approach 2:
The non-conductive isolation layer is deposited and patterned before final device assembly and transfer printing. This preliminary isolation structure is built into the device during standard semiconductor fabrication, ensuring low parasitic capacitance is achieved before the device is transferred to its final substrate, avoiding the need for complex post-processing modifications
Data Source
AI summary
A method of manufacturing a transfer die for use in a transfer print process. The manufactured transfer die comprises a semiconductor device suitable for bonding to a silicon-on-insulator wafer. The method comprises the steps of providing a non-conductive isolation region in a semiconductor stack, the semiconductor stack comprising a sacrificial layer above a substrate; and etching an isolation trench into the semiconductor stack from an upper surface thereof, such that the isolation trench extends only to a region of the semiconductor stack above the sacrificial layer. The isolation trench and the non-conductive isolation region together separate a bond pad from a waveguide region in the optoelectronic device.