Ultra-Thin Super Junction IGBT Structure for Lower Loss and Field Control
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Solution Overview
Problem
Current IGBT technologies face challenges in reducing conduction resistance, switching loss, and improving current conducting capability due to the limitations of silicon thickness and the resulting electric field concentration in the voltage blocking layer.
Innovation Solution
An ultra-thin super junction IGBT is developed with a novel manufacturing method that includes forming a floating P column and an N-type FS isolating layer, thinning the device to alleviate electric field concentration, and optimizing the epitaxial layers to reduce forward conduction voltage drop and switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of the voltage blocking layer is reduced to lower conduction resistance, then conduction loss is reduced, but the device thickness cannot be further thinned due to silicon material limits and electric field concentration
Solution Approach 1:
The voltage blocking layer is segmented into multiple N-type epitaxial layers separated by P-type columns, creating a super junction structure. This segmentation allows the electric field to be distributed across multiple depletion regions, enabling thinner overall device thickness while maintaining sufficient voltage blocking capability and reducing conduction loss.
Solution Approach 2:
The patent employs a composite structure combining P-type columns with N-type epitaxial layers to form super junctions. This composite material approach creates alternating depletion regions that enhance voltage blocking efficiency, allowing the device to achieve lower conduction resistance at reduced thickness compared to conventional single-layer structures.
2Reliability
If deep trench etching and backfilling process is used to form P columns, then super junction structure is achieved, but the trench forms a tapered structure with narrow bottom causing electric field concentration
Solution Approach 1:
The patent applies preliminary action by forming a tapered transition layer at the bottom of the trench before final P-type column formation. This preliminary structural preparation prevents electric field concentration by creating a gradual geometry transition, avoiding the harmful narrow-bottom effect while maintaining voltage blocking capability.
Solution Approach 2:
The patent changes the geometric parameters of the P-type columns by controlling the etching process to create optimized trench profiles. By adjusting etching depth, width, and angle parameters, the structure transitions from a harmful tapered shape to an optimized geometry that distributes electric field uniformly, preventing field concentration while maintaining reliability.
3Reliability
If the P column length is increased to ensure voltage blocking capability, then breakdown voltage is maintained, but the total device thickness increases limiting further reduction in conduction voltage
Solution Approach 1:
The voltage blocking function is segmented across multiple N-type epitaxial layers separated by P-type columns. Each layer-column interface creates a depletion region that contributes to voltage blocking, allowing the total blocking capability to be achieved through distributed segments rather than a single thick layer, thus reducing overall device thickness.
Solution Approach 2:
The patent transitions from a one-dimensional voltage blocking approach (single thick layer) to a two-dimensional super junction structure with alternating P and N regions. This dimensional change creates multiple depletion paths in the lateral direction, achieving equivalent voltage blocking with reduced vertical thickness, thereby enabling lower conduction voltage.
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
The ultra-thin super junction IGBT achieves a thickness reduction of 15 μm, with a breakdown voltage greater than 700V, reduced forward conduction voltage drop by at least 0.1V, and more than 10% reduction in switching loss and thermal resistance, while enhancing current capability.
Implementation Method 1
an N-type FS layer located above the P-type collector region; a P-type collector region located on the metalized collector
Implementation Method 2
a MOS structure located in the second N-type epitaxial layer
Implementation Method 3
The super junction structure formed by PN columns has a similar effect to super junction MOSs in the optimization of the device parameters such as blocking voltage and forward conduction voltage drop, etc. The introduction of PN columns greatly improves the voltage blocking capability of the super junction IGBT by making PN columns deplete each other to generate the transverse electric field in addition to the longitudinal electric field of the Pbody-N-Drift junction
Data Source
AI summary
The present invention discloses an ultra-thin super junction IGBT and a manufacturing method thereof, comprising: a metalized collector; a P-type collector region located on the metalized collector; an N-type FS layer located above the P-type collector region; an N-type FS isolating layer located above the N-type FS layer; a first N-type epitaxial layer located above the N-type FS isolating layer and a second N-type epitaxial layer located above the first N-type epitaxial layer; and a MOS structure located in the second N-type epitaxial layer. According to the present invention, thinning the chip thickness reduces forward conduction voltage drop and switching losses, while reducing thermal resistance and improving current conducting capability.