SiC Device Electrode Pad Geometry for Field Relaxation
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face challenges in achieving both electric field relaxation in static off-state and dynamic switching while maintaining high withstand voltage, as the extension of the depletion layer from the terminal end well region is delayed, leading to potential element failures due to electric field concentration at the outer peripheral end of the electrode pad.
Innovation Solution
The silicon carbide semiconductor device incorporates a first conductivity-type silicon carbide substrate with a field insulation film, a Schottky electrode, an electrode pad covering the Schottky electrode, and a surface protective film, where the protruding width of the electrode pad is optimized to reduce the electric field strength at the outer peripheral end, ensuring it remains below the dielectric breakdown strength of the insulation materials, thereby minimizing electric field concentration and enhancing withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer peripheral end of the electrode pad protrudes to the outer peripheral side on the field insulation film, then the etching residue at the outer peripheral end of the Schottky electrode is covered and failures are suppressed, but the electric field around the outer peripheral end of the electrode pad is increased at the time of switching and dielectric breakdown occurs
Solution Approach 1:
The invention changes the geometric parameter of the electrode pad by defining a controlled protruding width (L1) that extends beyond the field insulation film. This parameter optimization allows the electrode pad to cover etching residues while limiting the electric field concentration to prevent dielectric breakdown of the surface protective film during switching operations.
2Reliability
If the protruding width of the electrode pad is increased, then the coverage of etching residue is improved, but the electric field concentration at the outer peripheral end increases and causes dielectric breakdown
Solution Approach 1:
The invention optimizes the protruding width parameter (L1) of the electrode pad to achieve the right balance. The electrode pad extends beyond the field insulation film to cover etching residues, but the protruding width is controlled to prevent excessive electric field concentration that would cause dielectric breakdown during switching.
3Speed
If the depletion layer extension from terminal end well region is delayed during switching, then the electric field relaxation effect is insufficient, but increasing the P type dose amount increases the electric field in static off-state and lowers withstand voltage
Solution Approach 1:
The invention applies different P type impurity concentrations in different regions: a first concentration in the terminal end well region and a second, different concentration in the guard ring region. This local differentiation allows optimization of depletion layer extension during switching while maintaining adequate withstand voltage in the static off-state.
Solution Approach 2:
The invention changes the P type impurity concentration parameter by introducing two distinct concentration levels in different regions. The first P type impurity concentration in the terminal end well region and the second P type impurity concentration in the guard ring region are optimized to balance switching performance and withstand voltage characteristics.
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 density around the outer peripheral end of the electrode pad during switching and suppresses the increase in electric field in the off-state, thereby enhancing the element's withstand voltage and reliability.
Implementation Method 1
the electric field at the time of being applied with reverse voltage by a depletion layer, which is formed by a PN junction of the silicon carbide semiconductor layer and the guard ring region, is relaxed
Implementation Method 2
In a Schottky barrier diode composed of SiC (SiC-SBD)
Data Source
AI summary
An object of the present invention is to provide a silicon carbide semiconductor device with which the electric field at the time of switching is relaxed and the element withstand voltage can be enhanced. The distance between the outer peripheral end of a second surface electrode and the inner peripheral end of a field insulation film is smaller than the distance between an outer peripheral end of the second surface electrode and an inner peripheral end of the field insulation film in the case where the electric field strength applied to the outer peripheral lower end of the second surface electrode is calculated so as to become equal to the smallest dielectric breakdown strength among the dielectric breakdown strength of the field insulation film and the dielectric breakdown strength of the surface protective film at the time of switching when the value of dV/dt is greater than or equal to 10 kV/μs.