U-Shape RESURF MOSFET Drift Region Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RESURF MOSFET devices face challenges in miniaturization due to long RESURF length and high conduction resistance, requiring costly additional masks and lengthy development times for optimizing charge density and drift region depth.
Innovation Solution
A MOSFET device with a recessed-FOX structure and U-shaped drift region, where the depth and width of the drift region are controlled through the layout width, allowing for a longer RESURF length and smaller cell pitch without increasing costs, achieved by adjusting the mask opening width during semiconductor processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a long RESURF length is used to achieve high breakdown voltage, then breakdown voltage is improved, but cell pitch increases and miniaturization is hindered
Solution Approach 1:
The patent transforms the traditional linear RESURF structure into a three-dimensional U-shaped drift region configuration. By extending the drift region vertically to form a U-shape under the FOX structure, the RESURF length is increased in the vertical dimension while maintaining a compact horizontal footprint, thus achieving high breakdown voltage without increasing cell pitch.
Solution Approach 2:
The U-shaped drift region is nested within the FOX structure, with the drift region forming a U-shape that fits underneath the FOX isolation structure. This nesting arrangement allows the drift region to utilize the vertical space under the FOX, effectively increasing the RESURF length while keeping the overall device footprint small.
2Strength
If a long drift region is used to achieve high breakdown voltage, then breakdown voltage is improved, but conduction resistance increases
Solution Approach 1:
The drift region is formed with a U-shaped curved configuration instead of a straight linear path. This curvature allows the drift region to fold back on itself, increasing the effective RESURF length and breakdown voltage capability while maintaining a compact horizontal span that reduces the conduction path length and associated resistance.
3Manufacturing precision
If additional masks are used to control charge density and drift region depth, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The drift region depth and charge density are controlled through self-aligned processes where the FOX structure itself serves as the defining mask. The U-shaped drift region is formed by doping through openings created by the FOX structure, eliminating the need for separate dedicated masks for depth control. The process uses the existing FOX structure to define the drift region geometry, making the system self-defining and self-controlled.
Solution Approach 2:
The FOX structure serves multiple functions: it provides electrical isolation, defines the drift region boundaries, controls the drift region depth through its thickness, and establishes the U-shape geometry. This multi-functionality eliminates the need for separate structures or masks dedicated to each of these functions, reducing overall device complexity.
Data Source
AI summary
The present technology discloses a U-shape RESURF MOSFET device. Wherein the MOSFET device comprises a drain having a drain contact region and a drift region, a source, a body, a gate and a recessed-FOX structure. Wherein the recessed-FOX structure is between the gate and the drift region vertically and between the body and the drain contact region laterally, and wherein the recessed-FOX structure is configured to make the drift region into a U shape. The present technology further discloses the depth of the drift region is controlled by adjusting a layout width.