Superjunction Semiconductor Layout for Low On-Resistance Breakdown Control
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Solution Overview
Problem
Existing semiconductor devices face challenges in simultaneously achieving high breakdown voltage and low on-resistance due to limitations in pitch and impurity concentration in parallel pn structures, leading to decreased breakdown voltage when attempting to reduce on-resistance.
Innovation Solution
The semiconductor device incorporates a semiconductor substrate with a superjunction region and an electric field relaxation region featuring openings and connection regions, where the second conductivity type column regions have lower impurity concentrations and are arranged to avoid overlapping with openings, allowing for uniform depletion and reduced on-resistance while maintaining high breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pitch and impurity concentration in parallel pn structures are increased to reduce on-resistance, then on-resistance decreases, but breakdown voltage decreases
Solution Approach 1:
The semiconductor substrate is divided into multiple alternating column regions of first conductivity type and second conductivity type arranged in a stripe pattern. This segmentation creates multiple parallel current paths while maintaining controlled depletion regions, allowing current to flow through multiple channels which reduces overall on-resistance without requiring increased impurity concentration in individual regions that would compromise breakdown voltage.
Solution Approach 2:
Different regions of the semiconductor substrate are assigned different impurity concentrations and conductivity types. The column regions have higher impurity concentration to reduce resistance, while the intervening regions have lower impurity concentration to maintain breakdown voltage. This local differentiation allows each region to optimize for its specific function within the overall structure.
2Reliability
If the pitch in parallel pn structures is decreased to maintain breakdown voltage, then breakdown voltage is maintained, but on-resistance increases
Solution Approach 1:
The invention transitions from a two-dimensional planar arrangement to a three-dimensional vertical stripe structure with alternating conductivity types. This dimensional change allows current to flow through multiple vertical paths simultaneously, increasing the effective conduction area without increasing the lateral pitch, thereby maintaining breakdown voltage while reducing on-resistance through enhanced current distribution in the vertical dimension.
Solution Approach 2:
The substrate is segmented into multiple alternating column regions that create multiple parallel conduction paths. This segmentation increases the number of current channels available for conduction without requiring larger pitch between structures, allowing reduced on-resistance while maintaining the breakdown characteristics through controlled depletion in the intervening regions.
3Loss of energy
If impurity concentration is increased to reduce on-resistance, then on-resistance decreases, but depletion uniformity deteriorates
Solution Approach 1:
The invention implements spatially varying impurity concentrations with high concentration in column regions for low resistance and low concentration in intervening regions for uniform depletion control. This local quality differentiation allows each region to be optimized for its specific role: column regions provide conductive paths while intervening regions ensure uniform electric field distribution and controlled depletion during off-state operation.
Solution Approach 2:
The segmented alternating stripe structure creates distinct functional zones with different impurity concentrations. This segmentation isolates the high impurity concentration regions to specific column structures, preventing the depletion uniformity issues that would arise from uniformly high impurity concentration across the entire substrate, while still achieving low on-resistance through the cumulative effect of multiple parallel conductive paths.
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 ensures a high breakdown voltage and reduces on-resistance by facilitating uniform depletion and unobstructed current flow, with finely divided connection regions and strategically placed openings in the electric field relaxation region.
Implementation Method 1
a second conductivity type electric field relaxation region disposed below the first conductivity type upper region to be connected to the upper electrode
Implementation Method 2
a superjunction region disposed below the electric field relaxation region, and a plurality of first conductivity type connection regions. The superjunction region has a plurality of second conductivity type column regions and a plurality of first conductivity type column regions
Data Source
AI summary
A semiconductor substrate has a first conductivity type upper region, a second conductivity type electric field relaxation region, a superjunction region, and first conductivity type connection regions. A second conductivity type column region and a first conductivity type column region of the superjunction region extend linearly along a first direction and are alternately arranged in a second direction. The electric field relaxation region has openings in a dispersed manner. The first conductivity type connection regions are respectively disposed in the openings to connect the first conductivity type upper region to the corresponding first conductivity type column region. A concentration of second conductivity type impurity in the second conductivity type column region is lower than that of the electric field relaxation region. When the semiconductor substrate is viewed from the upper side, the second conductivity type column regions do not overlap with the openings.