Semiconductor Edge Termination Shielding External Charge
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Solution Overview
Problem
The existing semiconductor devices have insufficient shielding of external charges due to the significant thickness difference between the first and second field plates, which affects the reliability of the breakdown voltage.
Innovation Solution
A semiconductor device structure is implemented where the first field plates, made of polysilicon, and second field plates, made of aluminum alloy, are arranged with an insulating film in between, with the barrier metal film having the same ring width as the first field plates, and the second field plates being thicker and spaced farther apart, enhancing charge shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the second field plate is made significantly thicker than the first field plate to simplify patterning, then the ease of manufacture is improved, but the shielding effect against external charges deteriorates
Solution Approach 1:
The field plate structure is divided into multiple segments (first field plate and second field plate) with different thicknesses and materials. The first field plate uses thin polysilicon for fine patterning, while the second field plate uses thick aluminum alloy for easy patterning. This segmentation allows each part to be optimized for its specific function without compromising the overall shielding effect.
Solution Approach 2:
The field plate structure employs composite materials with different properties - polysilicon for the first field plate and aluminum alloy for the second field plate. This composite approach combines the advantages of both materials: polysilicon's fine patternability and aluminum's ease of manufacture, while achieving both fine patterning and effective charge shielding.
2Ease of manufacture
If the gap between second field plates is increased to facilitate patterning of thick aluminum alloy film, then the ease of manufacture is improved, but the charge shielding effectiveness deteriorates
Solution Approach 1:
The field plate is segmented into first and second field plates with different spacing requirements. The first field plates can be closely spaced for fine pattern control, while the second field plates have larger spacing for easy patterning. The combined structure maintains shielding effectiveness despite the larger gaps between second field plates.
Solution Approach 2:
The first field plate acts as an intermediary between the semiconductor substrate and the second field plate. It provides fine pattern control and enhances the overall shielding effect, compensating for the larger gaps between the second field plates. This intermediary structure enables both ease of manufacture and effective charge shielding.
3Device complexity
If a thick aluminum alloy film is used for the second field plate to simplify the formation process, then the device complexity is reduced, but the ability to shield external charges deteriorates
Solution Approach 1:
The field plate structure uses composite materials - thin polysilicon for the first field plate and thick aluminum alloy for the second field plate. This composite approach reduces device complexity by using materials with suitable properties for their respective functions, while the combined structure maintains effective charge shielding and breakdown voltage reliability.
Solution Approach 2:
The field plate is segmented into functional parts with different thicknesses and materials. The first field plate (thin polysilicon) provides fine pattern control, while the second field plate (thick aluminum) provides ease of manufacture. This segmentation resolves the contradiction between simplified formation process and effective charge shielding.
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 configuration effectively reduces the electric field intensity and improves the reliability of the breakdown voltage by increasing the gap between equipotential lines and enhancing charge shielding, even with thicker second field plates.
Implementation Method 1
The field plate has a function of reducing a high electric field which is likely to be generated in the edge termination region. Specifically, the field plate makes it easier for a depletion layer, which is mainly spread from the main pn junction to the drift layer with an increase in the reverse voltage when the reverse bias is applied to the main pn junction, to be spread in the edge termination region than at the center of the bottom of the semiconductor. Therefore, the gap between the equipotential lines increases and a high electric field generated in the edge termination region is reduced.
Implementation Method 2
In addition, the field plate has a function of shielding an external charge (for example, a free ion) which is generated in the vicinity of the front surface of the substrate in the edge termination region due to, for example, a molding resin to suppress a change in the electric field in the vicinity of the interface between the molding resin and the front surface of the semiconductor substrate.
Data Source
AI summary
An edge termination region (100) which surrounds an active region (101) includes an electric field reduction mechanism including guard rings (2), first field plates (4) which come into contact with the guard rings (2), and second field plates (7) which are provided on the first field plates (4), with an interlayer insulating film (5) interposed therebetween. The second field plate (7) is thicker than the first field plate (4). A gap between the second field plates (7) is greater than a gap between the first field plates (4). A barrier metal film (6) is provided between the second field plate (7) and the interlayer insulating film (5) so as come into conductive contact with the second field plate (7). A gap between the barrier metal films (6) is equal to the gap between the first field plates (4). Therefore, even in a structure including the first and second field plates (4, 7), it is possible to improve the effect of shielding an external charge.