Semiconductor RESURF Isolation Structure Corner Impurity Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor devices with a double RESURF structure, the breakdown voltage varies between straight and corner portions due to differences in depletion layer spreading, leading to reduced peak breakdown voltage and increased vulnerability to process variations.
Innovation Solution
A semiconductor device with a high voltage isolation structure featuring a RESURF region with a high concentration and low concentration area, where the total net amount of impurities in both regions is optimized to meet specific charge conditions, and ion implantation is performed simultaneously for both regions with a mask blocking a portion of the corner area to match the dose for maximum breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the total net amount of impurities in the RESURF region is uniformly optimized for maximum breakdown voltage, then the peak breakdown voltage is maximized, but the structure becomes vulnerable to process variations and the breakdown voltage varies between straight and corner portions
Solution Approach 1:
The patent applies local quality by differentiating the impurity concentration between straight portions and corner portions of the RESURF region. The straight portions have a first total net amount of impurities optimized for maximum breakdown voltage, while corner portions have a second total net amount of impurities that is more conservative. This local differentiation ensures that corner portions, which are more susceptible to process variations, have sufficient breakdown voltage margin while straight portions achieve peak performance.
2Ease of manufacture
If ion implantation is performed simultaneously for both straight and corner portions with uniform dose, then manufacturing complexity is reduced, but the breakdown voltage cannot be optimized for both regions due to different depletion layer spreading
Solution Approach 1:
The patent implements local quality through selective mask placement during ion implantation. Masks are positioned to block ion implantation in corner portions while allowing implantation in straight portions, or to apply different doses to different regions. This enables simultaneous ion implantation processing for both straight and corner portions while achieving different impurity concentrations tailored to each region's specific requirements.
Solution Approach 2:
The patent segments the RESURF region into straight portions and corner portions with distinct impurity concentration requirements. By dividing the region into these functional segments and applying different impurity amounts to each, the patent achieves optimized breakdown voltage for both regions while maintaining a relatively simple simultaneous ion implantation process.
3Strength
If the total net amount of impurities in corner portions is increased to match straight portions, then peak breakdown voltage is maximized, but the device becomes more sensitive to process variations
Solution Approach 1:
The patent applies beforehand cushioning by setting the impurity concentration in corner portions at a level that provides a safety margin against process variations. The second total net amount of impurities in corner portions is chosen to ensure sufficient breakdown voltage even when process variations occur, cushioning the device against potential failures while the straight portions operate at peak performance.
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 approach enhances the peak breakdown voltage and reduces the impact of process variations, maintaining higher breakdown voltage stability across the device.
Implementation Method 1
a first region of the first conductivity type which has an annular shape in a plan view is formed in the well region... using the implantation of first-conductivity-type impurity ions
Implementation Method 2
a first region of the first conductivity type which has an annular shape in a plan view is formed in the well region... and a heat treatment is performed
Data Source
AI summary
A semiconductor device includes a high voltage isolation structure having a double RESURF structure. The high voltage isolation structure separates a low potential region from a high potential region. The high voltage isolation structure has an annular strip shape in a plan view and includes a straight portion and a corner portion which is connected to the straight portion. In the high voltage isolation structure, a p-type RESURF region is formed in a surface layer of a front surface of a substrate in an n-type well region along the outer circumference of the n-type well region. In the corner portion, the total amount of impurities per unit area in the RESURF region is less than that in the straight portion.