Trench Transistor Doping via Variable Mesa Width
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Solution Overview
Problem
Existing methods for producing trench transistors face challenges in creating semiconductor zones of the same conduction type as the source zone outside the cell array, such as channel stoppers, due to limitations in dopant atom diffusion and geometry of the trench structure.
Innovation Solution
A method involving coordinated first and second diffusion processes to introduce dopant atoms of different conduction types into the mesa and component regions, where the second conduction type dopants indiffuse further vertically and not as far as the first type, forming a semiconductor region with net doping matching the source zone, utilizing the geometry and interface effects of the trench structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dopant atoms are implanted and indiffused to produce body and source zones in mesa regions, then the transistor structure is formed, but it becomes difficult to produce semiconductor zones of the same conduction type as the source zone outside the cell array
Solution Approach 1:
The patent applies local quality by making the mesa region width variable across different spatial locations. The mesa width is reduced in the cell array region compared to the edge region, creating locally different diffusion conditions. This allows dopant atoms to indiffuse to different depths in different regions during the same thermal process, enabling the formation of both transistor structures in mesa regions and channel stop zones in edge regions with the same conduction type
Solution Approach 2:
The patent introduces a lateral dimension variation in mesa width to control vertical dopant diffusion depth. By changing the mesa width in the lateral direction (narrower in cell array, wider in edge region), the patent achieves different vertical diffusion depths for dopant atoms. This dimensional approach allows the second dopant type to indiffuse further vertically in edge regions while being constrained in mesa regions, solving the contradiction between forming transistors and channel stop zones
2Reliability
If the second dopant atoms indiffuse further than the first dopant atoms vertically, then channel stop zones can be formed, but the dopant atoms must not indiffuse as far as the first type in mesa regions to maintain the pn junction
Solution Approach 1:
The patent uses local quality by creating spatially varying mesa widths that locally control dopant diffusion behavior. In edge regions with wider mesas, second dopant atoms can indiffuse deeper to form channel stop zones. In cell array regions with narrower mesas, the same second dopant atoms are constrained from indiffusing as deeply, preserving the pn junction between source and body zones. This local geometric variation enables differentiated doping outcomes from a single diffusion process
Solution Approach 2:
The patent changes the geometric parameter of mesa width to control dopant diffusion depth. By reducing mesa width in cell array regions and maintaining larger width in edge regions, the patent creates different diffusion resistance conditions. This parameter change allows precise control over where second dopant atoms indiffuse vertically, enabling reliable channel stop zone formation in edge regions while maintaining proper junction depth in transistor regions
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 method effectively produces semiconductor zones with the same conduction type as the source zone, enabling the creation of channel stop zones and other component zones outside the cell array, enhancing the integration density and performance of trench transistors.
Implementation Method 1
carrying out a first diffusion method, by which dopant atoms of a first conduction type are introduced via the first side into the mesa region and into a component region lying outside the cell region, with the dopant atoms forming the body zone in the mesa region
Implementation Method 2
the dopant atoms of the second conduction type indiffuse further than the dopant atoms of the first conduction type in the vertical direction in the component region
Data Source
AI summary
A method for producing an integrated circuit including a semiconductor and in one embodiment a trench transistor structure, is disclosed. A first diffusion method is carried out. A second diffusion method is carried out, by which dopant atoms of a second conduction type are introduced via a first side into a mesa region and into a component region, which form a source zone in the mesa region, the diffusion methods being coordinated with one another in such a way that the dopant atoms of a second conduction type indiffuse further than the dopant atoms of a first conduction type from the first diffusion method, in the vertical direction in the component region and indiffuse not as far as the dopant atoms of the first conduction type in the vertical direction in the mesa region.