RC-IGBT Diode Structure With Deep Anode for Lower Recovery Loss
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Solution Overview
Problem
The existing reverse-conducting insulated gate bipolar transistors (RC-IGBTs) face issues with recovery loss and degradation of forward drop voltage (VF) due to shallow anode layers, which can lead to increased electric field intensity and damage to the trench oxide film, and also have a high-cost process for forming the free-wheeling diode (FWD) within the IGBT region, necessitating a solution to reduce these losses and improve power density.
Innovation Solution
The semiconductor device incorporates a deep anode layer with its bottom surface located deeper than the trench bottom, reducing the forward drop voltage (VF) and allowing for easier control of a lifetime killer introduction without damaging the trench oxide film, while maintaining a cost-effective process by forming the FWD in a region where the IGBT has a high-cost process, thus enhancing the power density and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the anode layer is formed shallower than the trench bottom to reduce manufacturing complexity, then the manufacturing process is simpler, but the electric field intensity at the trench bottom increases causing breakdown resistance degradation and reliability issues
Solution Approach 1:
The patent transitions from a two-dimensional planar anode layer to a three-dimensional deep anode structure that extends below the trench bottom. This vertical dimensionality change allows the anode to reach deeper into the drift layer, reducing electric field intensity at the trench bottom while maintaining manufacturing feasibility through controlled epitaxial growth or ion implantation processes.
Solution Approach 2:
The patent changes the depth parameter of the anode layer from shallow (above trench bottom) to deep (below trench bottom). This parameter modification fundamentally alters the electric field distribution, reducing peak field intensity at the trench bottom and improving breakdown resistance without requiring complex manufacturing processes.
2Loss of energy
If a lifetime killer is introduced under the anode layer to suppress recovery loss and forward drop voltage degradation, then the diode performance is improved, but the trench oxide film may be damaged due to increased electric field intensity
Solution Approach 1:
The patent performs preliminary action by forming the deep anode layer before introducing the lifetime killer. This sequence ensures that the electric field is already distributed more favorably by the deep anode structure, preventing excessive field intensity that would damage the trench oxide film during subsequent lifetime killer introduction processes.
Solution Approach 2:
The patent modifies the depth parameter of the anode layer to extend below the trench bottom, which changes the electric field distribution pattern. This parameter change reduces peak field intensity, allowing lifetime killer introduction without damaging the trench oxide film while still achieving suppression of recovery loss and forward drop voltage degradation.
3Adaptability or versatility
If the free-wheeling diode is formed in the IGBT region with high-cost process to achieve integration, then the device integration is improved, but the manufacturing cost increases
Solution Approach 1:
The patent segments the semiconductor device into distinct IGBT regions and diode regions with different structural characteristics. The diode is formed in a dedicated region with optimized doping and structure, allowing it to be manufactured with appropriate process complexity for that specific function rather than forcing high-cost IGBT processes onto the entire device.
Solution Approach 2:
The patent applies local quality by giving the diode region its own optimized structure and doping profile, different from the IGBT region. This allows each region to be manufactured with the appropriate process complexity - the diode region can use simpler, lower-cost processes optimized for diode formation, while the IGBT region uses the necessary high-cost processes for its complex structure.
Data Source
AI summary
A semiconductor device according to the present disclosure includes a semiconductor substrate having a first surface and a second surface opposite to the first surface, and a diode formed in the semiconductor substrate. The diode includes a drift layer of a first conductivity type on a side provided with the first surface, an anode layer of a second conductivity type opposite in conductivity type to the first conductivity type on the drift layer, and a trench. A bottom surface of the anode layer is located in a region deeper than a bottom surface of the trench with reference to the first surface.