Segmented N-well Tap for High Voltage Breakdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor structures, particularly CMOS devices, face limitations in breakdown voltage, leading to junction breakdown when biased at high voltages, necessitating an increase in breakdown voltage without increasing silicon area usage.
Innovation Solution
The p-n junction is repositioned to be under the active area of the tap, with a more heavily doped region serving as an ohmic contact and a lightly doped region providing isolation, decoupling breakdown voltage from the isolation area, allowing for optimization of implantation for increased n-channel isolation without affecting the N-well breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the N-well tap is formed close to the edge of the well, then the silicon area usage is minimized, but the breakdown voltage decreases causing junction breakdown at high voltages
Solution Approach 1:
The tap structure is segmented into multiple regions with different doping concentrations (heavily doped N+ region and lightly doped N- region). This segmentation allows the heavily doped region to provide low resistance contact while the lightly doped region extends the depletion region and increases breakdown voltage, resolving the contradiction between area efficiency and high voltage capability
Solution Approach 2:
Different regions of the tap are assigned different doping qualities - the region closer to the well edge uses heavy doping for low resistance, while the region extending toward the isolation area uses light doping for high breakdown voltage. This local quality differentiation allows simultaneous optimization of both area usage and breakdown voltage
2Loss of energy
If the tap is heavily doped to reduce resistance, then the contact resistance decreases, but the breakdown voltage at the p-n junction interface with isolation area decreases
Solution Approach 1:
The tap is divided into a heavily doped N+ region for low resistance contact and a lightly doped N- region for high breakdown voltage. This segmentation allows each region to optimize its doping level for its specific function, eliminating the need to choose between low resistance and high breakdown voltage
Solution Approach 2:
The doping concentration varies locally within the tap structure - heavy doping near the contact point minimizes resistance, while light doping near the isolation area interface maximizes breakdown voltage. This local quality gradient resolves the contradiction between resistance loss and reliability
3Area of stationary object
If the isolation area is positioned closer to the tap, then the device area is reduced, but the p-n junction breaks down at the interface under high voltage bias
Solution Approach 1:
The tap structure segments the current path through different doping regions, allowing the isolation area to be positioned closer to the tap while maintaining high breakdown voltage. The lightly doped N- region acts as a buffer that prevents premature breakdown at the isolation area interface
Solution Approach 2:
The solution moves the breakdown voltage enhancement from the lateral dimension (distance to isolation area) to the vertical dimension (doping concentration gradient within the tap). This allows area reduction while maintaining reliability through controlled doping profiles rather than increased spacing
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 increases breakdown voltage while maintaining the same silicon area usage as prior art devices, optimizing n-channel isolation and preventing junction breakdown at higher voltages.
Implementation Method 1
A p-type isolation area can be formed in the semiconductor material that forms the bottom surface of a trench between two taps. The isolation area can provide isolation between neighboring n-channel devices.
Implementation Method 2
a more heavily doped region serving as an ohmic contact
Implementation Method 3
When a voltage is applied to the N-well contact that is greater than the designed breakdown voltage for the device, the p-n junction breaks down at the interface of the p-n junction with the isolation area.
Data Source
AI summary
Apparatuses and methods are disclosed. One such apparatus includes a well having a first type of conductivity formed within a semiconductor structure having a second type of conductivity. A boundary of the well intersects an active area of a tap to the well.