Variable Stripe Width Diluted Drift Layer for MFLHVT
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Solution Overview
Problem
Multi-finger lateral high voltage transistors (MFLHVTs) face a reduced drain-to-source breakdown voltage (BVDSS) due to significant curvature-induced electric field crowding at the fingertip drift region, particularly in the highest junction curvature portions, which limits their performance compared to racetrack layouts.
Innovation Solution
A calculation-based diluted buried drift layer (DBDL) design with a monotonically increasing overdesign dimension for dilution stripe width along the fingertip drift region is implemented, relieving electric field crowding and enhancing the BVDSS of MFLHVTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional diluted buried drift layer design is used in multi-finger lateral high voltage transistors, then the device complexity and manufacturing process remain simple, but the drain-to-source breakdown voltage is reduced due to curvature-induced electric field crowding at the fingertip drift region
Solution Approach 1:
The patent applies local quality by implementing a non-uniform diluted buried drift layer design where the dilution stripe width varies across different regions of the drift layer. Specifically, the dilution stripe width is increased at the fingertip drift region where curvature-induced electric field crowding occurs, while maintaining standard dimensions in other regions. This localized modification targets the specific problem area without unnecessarily complicating the entire device structure.
Solution Approach 2:
The patent employs parameter changes by modifying the geometric parameters of the diluted buried drift layer, specifically the dilution stripe width and spacing. By adjusting these parameters to be non-uniform across the drift layer, the design optimizes the electric field distribution to reduce crowding effects at the fingertip region while maintaining overall device performance and managing complexity.
2Reliability
If the dilution stripe width is increased uniformly across the entire drift layer to reduce electric field crowding, then the breakdown voltage improves, but the device area and manufacturing cost increase
Solution Approach 1:
The patent implements local quality by concentrating the increased dilution stripe width specifically in the fingertip drift region where electric field crowding is most severe, rather than uniformly increasing it across the entire drift layer. This localized approach reduces the overall device area requirement while still achieving the necessary breakdown voltage improvement.
Solution Approach 2:
The patent converts the harmful effect of curvature-induced electric field crowding into a beneficial design feature by strategically placing wider dilution stripes at the fingertip region. This transforms the problem area into a targeted optimization zone, improving breakdown voltage without requiring uniform area expansion across the entire device.
3Reliability
If a non-uniform diluted buried drift layer design with variable dilution stripe widths is implemented, then electric field crowding is reduced and breakdown voltage improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by implementing variable dilution stripe widths only in specific critical regions (fingertip drift region) while maintaining standard uniform dimensions in other areas. This approach limits the scope of manufacturing precision challenges to localized zones rather than requiring high precision across the entire drift layer.
Solution Approach 2:
The patent employs preliminary action by designing the non-uniform diluted buried drift layer configuration into the fabrication process from the beginning, using appropriate masking and implantation techniques that pre-establish the variable stripe width pattern. This proactive design approach integrates the complexity into the manufacturing flow rather than requiring post-processing adjustments, thereby managing precision requirements more effectively.
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 DBDL design improves the BVDSS of MFLHVTs by reducing electric field crowding, allowing for higher voltage operation with reduced area requirements, thereby decreasing the cost and increasing the efficiency of integrated circuits.
Implementation Method 1
a masked implant that enables implanting dilution stripes separated by masked (non-implanted) stripes
Implementation Method 2
One or more high temperature annealing processes follow which results in dopant from the implanted stripes diffusing into the non-implanted stripes
Implementation Method 3
A RESURF region may be for example a buried semiconductor region (or layer) with an opposite conductivity type from the adjacent semiconductor region (or layer). RESURF structures are described in Apples, et.al., 'Thin Layer High Voltage Devices' Philips J, Res. 35 1-13, 1980.
Data Source
AI summary
A multi-finger lateral high voltage transistors (MFLHVT) includes a substrate doped a first dopant type, a well doped a second dopant type, and a buried drift layer (BDL) doped first type having a diluted BDL portion (DBDL) including dilution stripes. A semiconductor surface doped the second type is on the BDL. Dielectric isolation regions have gaps defining a first active area in a first gap region (first MOAT) and a second active area in a second gap region (second MOAT). A drain includes drain fingers in the second MOAT interdigitated with source fingers in the first MOAT each doped second type. The DBDL is within a fingertip drift region associated drain fingertips and/or source fingertips between the first and second MOAT. A gate stack is on the semiconductor surface between source and drain. The dilution stripes have stripe widths that increase monotonically with a drift length at their respective positions.