Super Junction Pillars Under Gate Trenches for Planar MOSFET Uniformity
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Solution Overview
Problem
The integration of super junction MOSFETs in planar devices is challenging due to poor performance and high costs associated with multi-epi and doping processes, which result in poor uniformity and long process times for p-type columns and n-type columns.
Innovation Solution
A semiconductor device with a super junction structure featuring pillars under gate trenches, fabricated using undoped material, which improves performance, uniformity, and reduces process time and cost, allowing for better integration in planar devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-epi and doping processes with masks are used to fabricate p-type columns and n-type columns, then the super junction structure can be formed, but the manufacturing precision deteriorates due to poor uniformity
Solution Approach 1:
The patent changes the doping parameter from requiring multiple separate doping processes to using a single doping process that forms both p-type and n-type columns simultaneously. This is achieved by introducing dopants during the epitaxial growth process, where the dopant distribution is controlled by the patterned sacrificial layer, thereby improving manufacturing precision and uniformity.
Solution Approach 2:
The patent uses a patterned sacrificial layer to segment the epitaxial growth process into regions that will become p-type columns and n-type columns. The sacrificial layer is removed after doping, leaving behind the desired columnar structure with alternating conductivity types, thereby simplifying the overall fabrication process while maintaining precision.
2Productivity
If multi-epi and doping processes with masks are used to fabricate p-type columns and n-type columns, then the super junction structure can be formed, but the productivity deteriorates due to long process time
Solution Approach 1:
The patent merges the epitaxial growth process with the doping process into a single step. By introducing dopants during epitaxial growth and using a patterned sacrificial layer to define the column regions, both the structural formation and doping are accomplished simultaneously, dramatically reducing the total process time and improving productivity.
Solution Approach 2:
The patent performs preliminary patterning of the sacrificial layer before the epitaxial growth and doping process. This pre-established pattern guides the subsequent single-step doping process, eliminating the need for multiple masking steps and reducing overall fabrication time while maintaining precision.
3Ease of manufacture
If multi-epi and doping processes with masks are used to fabricate p-type columns and n-type columns, then the super junction structure can be formed, but the manufacturing cost increases
Solution Approach 1:
The patent combines multiple fabrication steps (epitaxial growth and doping) into a single integrated process. This reduction in the number of process steps directly lowers manufacturing costs by reducing equipment usage, material consumption, and labor requirements, thereby improving ease of manufacture and cost-effectiveness.
Solution Approach 2:
The patent extracts and removes the complex multi-step doping process with multiple masks, replacing it with a single doping step guided by a sacrificial layer pattern. This extraction of unnecessary process complexity simplifies manufacturing and reduces costs while maintaining the required structural precision.
Data Source
AI summary
A super junction structure includes a substrate, wherein the substrate has a first conductivity type. The super junction structure includes an epitaxial layer over the substrate, wherein the epitaxial layer has a second conductivity type opposite the first conductivity type. The super junction structure further includes a bury layer between the epitaxial layer and the substrate, wherein the bury layer has the second conductivity type. The super junction structure further includes a conductive pillar in the epitaxial layer, wherein the conductive pillar has the first conductivity type, sidewalls of the conductive pillar are angled with respect to a top-most surface of the epitaxial layer, a bottom surface of the conductive pillar is rounded, and a top-most surface of the conductive pillar is coplanar with the top-most surface of the epitaxial layer.