GaN Wafer Transfer Bonding for Low-Defect Device Manufacturing
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Solution Overview
Problem
The manufacturing of high-quality gallium nitride (GaN) semiconductor devices is hindered by the high cost and limited availability of native GaN substrates, and heteroepitaxial growth on foreign substrates results in unacceptable crystalline defects, especially in power electronic devices.
Innovation Solution
A method involving selective etching and bonding processes transfers arrays of GaN-based electronic devices from donor wafers to larger carrier wafers, allowing for high-throughput, low-cost production of high-density semiconductor devices using a wafer-level transfer process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heteroepitaxial growth is used on foreign substrates (sapphire, SiC, Si), then manufacturing cost is reduced and substrate availability is improved, but crystalline defect density increases making devices unacceptable for high current density applications
Solution Approach 1:
The patent segments the substrate and device layers into separate components. Native GaN substrates are grown separately with low defect density, then device layers are epitaxially grown on these substrates. The completed devices are then singulated and mounted on foreign substrates (sapphire, SiC, Si) for final packaging. This segmentation allows each component to be optimized independently - substrates for low defects, foreign substrates for cost and availability.
Solution Approach 2:
The patent uses native GaN substrates as intermediary carriers during the manufacturing process. These substrates serve as temporary platforms for growing high-quality epitaxial layers, which are then transferred to the final foreign substrates. The intermediary substrate enables the transition from high-quality growth conditions to cost-effective final mounting without directly compromising device quality.
2Manufacturing precision
If native GaN substrates are used for epitaxial growth, then crystal quality and defect density are improved, but substrate cost increases and wafer diameter is limited to small sizes
Solution Approach 1:
The patent separates the high-quality crystal growth function from the final mounting function. Native GaN substrates are used only for the critical epitaxial growth stage where high crystal quality is needed. After devices are fabricated on these substrates, they are singulated and mounted on inexpensive foreign substrates. This segmentation allows native substrates to be used minimally and efficiently only where high crystal quality is essential.
Solution Approach 2:
The patent treats native GaN substrates as disposable intermediate carriers rather than permanent mounting platforms. These expensive substrates are used temporarily during manufacturing to achieve high crystal quality, then discarded after the devices are transferred to permanent foreign substrates. This approach justifies the high substrate cost by limiting their use to the critical growth phase only.
3Reliability
If native GaN substrates are used, then strain-related defects are reduced, but substrate availability and scalability are worsened due to limited wafer sizes
Solution Approach 1:
The patent segments the substrate function into two distinct roles: native GaN substrates provide strain-matched growth conditions for defect-free epitaxial layers, while foreign substrates provide scalable mounting platforms. By separating these functions, the patent achieves both low strain-related defects and high scalability, as foreign substrates like Si and SiC are available in large wafer diameters for mass production.
Solution Approach 2:
The patent creates a copy of the device structure on foreign substrates after initial fabrication on native substrates. The devices are singulated from their native substrate carriers and remounted on foreign substrates, effectively copying the device architecture to a more scalable platform. This copying process preserves the low defect density achieved during growth while enabling production on larger wafer sizes.
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 enables the production of high-quality GaN semiconductor devices on larger, more affordable carrier wafers, overcoming the limitations of small native GaN substrates and reducing fabrication costs while maintaining device performance.
Implementation Method 1
The sacrificial region is configured to be selectively removed to allow transfer of at least a portion of the plurality of electronic devices to the carrier wafer
Implementation Method 2
bonding regions overlying a first portion of the plurality of electronic devices... bonding processes transfers arrays of GaN-based electronic devices from donor wafers to larger carrier wafers
Data Source
AI summary
Electronic devices are formed on donor substrates and transferred to carrier substrates by forming bonding regions on the electronic devices and bonding the bonding regions to a carrier substrate. The transfer process may include forming anchors and removing sacrificial regions.