SiC Body Diode Contact Structure for Lower Forward Voltage
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices have a high forward voltage (VF) of the built-in diode, which limits the ability to pass large current quickly during screening, leading to heat generation and extended screening times.
Innovation Solution
The method involves forming a NiAl silicide film in contact with the p+-type contact regions, rather than the conventional Ni silicide film, which reduces contact resistance and VF of the body diode. This is achieved through a high-temperature sintering process that facilitates thermal diffusion of Al into the Ni film, forming a NiAl silicide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Ni silicide film is formed in contact with p+-type contact regions, then the manufacturing process is simple, but the contact resistance and forward voltage (VF) of the body diode are high
Solution Approach 1:
The patent applies composite materials by forming a multi-layer structure consisting of a Ni silicide film layer and a NiAl silicide film layer in contact with the p+-type contact regions. This composite structure combines the advantages of both materials: the Ni silicide provides good basic contact properties while the NiAl silicide reduces contact resistance and forward voltage, thereby resolving the contradiction between manufacturing simplicity and electrical performance.
Solution Approach 2:
The patent changes the material composition parameter by introducing aluminum into the silicide structure. The NiAl silicide film has different chemical composition and electrical properties compared to pure Ni silicide, with lower contact resistance and forward voltage. This parameter change allows improved electrical performance while maintaining a relatively simple manufacturing process through selective sintering.
2Reliability
If a NiAl silicide film is formed through high-temperature sintering, then contact resistance and forward voltage are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by first forming both the Ni silicide film and NiAl silicide film layers before selective sintering. The aluminum layer is prepared in advance, and then both layers are sintered simultaneously at high temperature to form the NiAl silicide. This preliminary preparation simplifies the overall process compared to forming the NiAl silicide through multiple separate steps.
Solution Approach 2:
The patent merges two separate film formation processes into a single sintering step. By depositing both the Ni silicide and Al layers sequentially and then performing one high-temperature sintering operation, the process combines multiple operations into fewer steps, reducing process complexity while achieving the desired NiAl silicide formation.
3Productivity
If large current is passed through the device during screening, then screening speed increases, but heat generation increases due to high forward voltage
Solution Approach 1:
The patent converts the harmful effect of high forward voltage into a beneficial outcome by using the NiAl silicide film to reduce the forward voltage in the first place. The lower contact resistance and forward voltage of the NiAl silicide reduce power loss and heat generation during current passage, enabling faster screening without excessive heat buildup.
Solution Approach 2:
The patent changes the electrical parameters of the contact regions by forming NiAl silicide, which has lower contact resistance and forward voltage compared to Ni silicide. This parameter change allows larger currents to be passed during screening with reduced heat generation, thereby improving screening speed while controlling thermal effects.
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 reduced contact resistance and VF of the body diode allow for faster and more efficient screening, enabling larger currents to be passed with reduced heat generation and shorter screening times.
Implementation Method 1
sintering the lower Ni film by a heat treatment and thereby forming a Ni silicide film
Implementation Method 2
a high-temperature sintering process that facilitates thermal diffusion of Al into the Ni film
Implementation Method 3
a high-temperature sintering process that facilitates thermal diffusion of Al into the Ni film, forming a NiAl silicide layer
Implementation Method 4
forming a NiAl silicide film in contact with the p+-type contact regions, rather than the conventional Ni silicide film
Data Source
AI summary
On a silicon carbide semiconductor substrate of a first conductivity type, a first semiconductor layer of the first conductivity type, a second semiconductor layer of a second conductivity type, first semiconductor regions of the first conductivity type, second semiconductor regions of the second conductivity type, a gate insulating film, gate electrodes, an interlayer insulating film, first electrodes, and a second electrode are formed. Each of the first electrodes are formed by depositing a lower Ni film, an Al film, and an upper Ni film and etching the films to be apart from the interlayer insulating film; sintering the lower Ni film by a heat treatment and thereby forming a Ni silicide film; depositing a Ti film, a TiN film, and an AlSi film; and etching the AlSi film.