Reverse-Blocking IGBT Wafer Bonding for 1200V Reverse Current Blocking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing reverse-blocking insulated-gate bipolar transistors (IGBTs) face challenges in efficiently blocking reverse current, requiring thick and expensive junction termination structures, and have limitations in optimizing voltage levels, particularly for 1200V applications, due to the use of soft punch through structures and boron separation diffusion processes.
Innovation Solution
A method involving wafer bonding of silicon substrates with different dopant properties to form separation diffusion regions and a contact diffusion layer, allowing for the formation of a backside metallization layer, which enables the creation of a reverse-blocking IGBT capable of blocking high voltages with reduced thickness and cost, using aluminum separation diffusion to bring the collector junction up to the surface for termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If soft punch through structure with collector side buffer diffusion is used, then manufacturing is simplified, but reverse voltage blocking capability is lost
Solution Approach 1:
The device is divided into two separate silicon wafers: a first wafer containing the MOS structure and drift region, and a second wafer containing the collector junction. This segmentation allows each wafer to be optimized independently - the first wafer can use simple soft punch through structure while the second wafer provides the necessary reverse voltage blocking capability through its P-type collector junction.
Solution Approach 2:
An aluminum separation diffusion layer is introduced as an intermediary between the N-type drift region and the P-type collector junction. This separation layer facilitates the formation of a deep collector junction that can block reverse voltage while maintaining manufacturing simplicity through standard diffusion processes.
2Reliability
If non-punch through structure is used, then reverse voltage blocking capability is improved, but device thickness increases and optimization for predetermined voltage becomes difficult
Solution Approach 1:
The invention changes the doping parameters of the collector junction in the second wafer to achieve the desired reverse voltage blocking capability. By controlling the P-type doping concentration and using deep diffusion processes, the collector junction can be optimized for specific voltage ratings (e.g., 1200V) without requiring excessive device thickness.
3Reliability
If backside junction termination structures are added, then reverse voltage blocking capability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The complex junction termination structures are extracted from the main device structure and implemented separately in the second wafer. The P-type collector junction is formed independently in the second wafer before bonding, which simplifies the overall manufacturing process compared to adding termination structures to an existing IGBT structure.
4Reliability
If boron separation diffusion is used, then reverse voltage blocking capability is improved, but drive time becomes very long
Solution Approach 1:
The invention changes the dopant material from boron to aluminum for the separation diffusion layer. Aluminum diffusion can be achieved with shorter drive times compared to boron, thereby reducing the overall manufacturing cycle time while still achieving the necessary deep collector junction for reverse voltage blocking.
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 allows for the efficient manufacturing of reverse-blocking IGBTs that can reliably block 1200V with lower losses and costs, providing a flexible and optimized structure for reverse voltage blocking without the need for expensive epitaxial layers or deep collector layers.
Implementation Method 1
bonding the first and second silicon wafer substrates
Implementation Method 2
diffusing one or more particles from the second silicon wafer substrate into the first silicon wafer substrate to form a diffusion region
Implementation Method 3
forming one or more separation diffusion regions in the first silicon wafer substrate
Data Source
AI summary
Methods for making reverse-blocking insulated gate bipolar transistors and associated structures. A first and a second silicon wafer substrates are provided and bonded. One or more separation diffusion regions are formed in the first silicon wafer substrate. One or more front side metal-oxide semiconductor (MOS) structures are formed on a top surface of the first silicon wafer substrate. The second silicon wafer substrate layer is removed. A contact diffusion layer is formed on a bottom surface of the first silicon wafer substrate. A backside metallization layer is formed on a bottom surface of the contact diffusion layer.