Bidirectional Semiconductor Fabrication with 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 production 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 device, allowing for the formation of multiple leads on each surface through a series of sequential processing steps that include high-temperature and medium-temperature processing, with protective layers and handle wafer attachments to ensure symmetric and efficient fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fabrication methods are used, then devices can be manufactured with standard single-sided lead configuration, but multiple electrodes on both wafer surfaces cannot be accommodated
Solution Approach 1:
The fabrication process is segmented into distinct temperature zones (high-temperature zone for dopant diffusion, medium-temperature zone for subsequent processing). Handle wafers are selectively attached to specific regions and temperature zones, allowing independent optimization of each processing stage while accommodating multiple electrodes on both surfaces.
Solution Approach 2:
Handle wafers serve as intermediary substrates that temporarily support the device wafer during fabrication. These handle wafers are attached at specific temperature zones and can be selectively removed later, enabling complex multi-electrode configurations without requiring the final device structure to withstand all processing temperatures.
2Adaptability or versatility
If multiple electrodes are formed on both wafer surfaces, then bidirectional devices can be fabricated, but fabrication complexity and cost increase
Solution Approach 1:
The patent creates equipotential processing conditions by establishing symmetric dopant diffusion depths on both wafer surfaces through the high-temperature zone treatment. This equipotential approach to dopant distribution simplifies the overall fabrication complexity despite the increased device functionality, as both surfaces undergo equivalent thermal processing.
Solution Approach 2:
The fabrication process utilizes parameter changes in temperature zones to control dopant diffusion. By varying the temperature parameter across different zones (high-temperature for diffusion, medium-temperature for subsequent steps), the process achieves bidirectional device fabrication with controlled dopant depths while managing fabrication complexity through systematic parameter management.
3Volume of moving object
If thin wafers are processed, then device miniaturization is achieved, but wafer damage risk increases
Solution Approach 1:
Handle wafers are attached to thin device wafers before high-temperature processing in advance. This preliminary attachment provides mechanical support and protection to the thin wafer structure during subsequent high-temperature dopant diffusion and other processing steps, preventing wafer damage while enabling miniaturization.
Solution Approach 2:
The handle wafer attachment serves as a cushioning support structure that absorbs thermal stress and mechanical stress during processing. This beforehand cushioning protects thin wafers from damage during high-temperature dopant diffusion and handling, maintaining wafer structural integrity throughout the fabrication process.
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.