Bidirectional Semiconductor Fabrication Using Handle Wafers
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Solution Overview
Problem
Conventional semiconductor device fabrication methods are complex and costly due to their inability to accommodate multiple electrodes on both sides of a wafer, limiting the fabrication of bidirectional devices like B-TRANs and IGBTs.
Innovation Solution
The method involves using high-temperature-resistant and medium-temperature-resistant handle wafers to facilitate dopant diffusion on both sides of the semiconductor device, allowing for the formation of multiple leads on each surface through a series of high-temperature and medium-temperature processing steps, with protective layers and sequential handle wafer attachment to ensure symmetric and efficient fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fabrication methods are used, then manufacturing simplicity is maintained, but the ability to fabricate multiple electrodes on both sides of the wafer is lost
Solution Approach 1:
The fabrication process is segmented into distinct temperature zones (high-temperature-resistant and medium-temperature-resistant handle wafers) that allow independent processing of different device regions. This segmentation enables multiple electrodes to be fabricated on both sides without requiring complete process redesign.
Solution Approach 2:
Handle wafers serve as intermediary substrates that support the semiconductor device during fabrication. These handle wafers with different temperature resistances act as mediators enabling dopant diffusion and electrode formation on both sides of the device simultaneously, reducing overall process complexity.
2Manufacturing precision
If high-temperature processing is performed on thin wafers, then dopant diffusion is achieved, but the thin wafers may be damaged
Solution Approach 1:
Thin wafers are mounted on handle wafers before high-temperature processing. The handle wafers with appropriate temperature resistance serve as protective cushions that prevent damage to the thin device wafers during high-temperature dopant diffusion while still allowing precise control of dopant diffusion depths.
3Productivity
If multiple handles are used for bidirectional fabrication, then fabrication efficiency is improved, but process complexity increases
Solution Approach 1:
Multiple fabrication operations are merged into a single coordinated process using handle wafers with different temperature resistances. The high-temperature-resistant and medium-temperature-resistant handle wafers work together in a unified fabrication sequence, enabling simultaneous dopant diffusion and electrode formation on both sides of the device, which improves productivity despite the apparent increase in process steps.
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 simplifies the fabrication of two-sided semiconductor devices, enables efficient formation of multiple active regions and electrodes on both sides, and allows for the processing of thin wafers without damage, resulting in vertically-symmetric devices with acceptably similar dopant diffusion depths.
Implementation Method 1
comprising a single long dopant diffusion step that can be used to drive-in dopants on both sides of a device
Implementation Method 2
High-temperature-resistant and medium-temperature-resistant handle wafers facilitate fabrication
Data Source
AI summary
Methods and systems for double-sided semiconductor device fabrication. Devices having multiple leads on each surface can be fabricated using a high-temperature-resistant handle wafer and a medium-temperature-resistant handle wafer. Dopants can be introduced on both sides shortly before a single long high-temperature diffusion step diffuses all dopants to approximately equal depths on both sides. All high-temperature processing occurs with no handle wafer or with a high-temperature handle wafer attached. Once a medium-temperature handle wafer is attached, no high-temperature processing steps occur. High temperatures can be considered to be those which can result in damage to the device in the presence of aluminum-based metallizations.