Vertical Trench-Gate MOSFET Doping Layout With Fewer Lithography Steps
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Solution Overview
Problem
Current methods for producing semiconductor devices are inefficient, requiring multiple lithography steps and struggling to create small structures, which increases production costs and on-state losses.
Innovation Solution
A method involving a mask with varying thickness sections and a protection layer to form regions of different conductivity types with reduced lithography steps, allowing for precise control of doping profiles and structure sizes, enabling the production of narrow functional portions and insulated gate transistors with improved plasma concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple lithography steps are used to produce semiconductor devices, then manufacturing precision can be improved, but device complexity and production time increase
Solution Approach 1:
The mask is divided into multiple sections with different thicknesses (first section overlapping the trench, second section overlapping the functional portion, third section overlapping both). This segmentation allows different regions to serve different functions during doping, enabling precise control of doping profiles without requiring multiple lithography steps.
Solution Approach 2:
The invention transitions from controlling doping through multiple planar lithography steps to controlling doping through the vertical dimension (mask thickness). The varying thickness of the mask sections creates different doping profiles by allowing or blocking dopant diffusion at different levels, adding a vertical dimension to the doping control process.
2Manufacturing precision
If multiple lithography steps are used, then alignment precision can be improved, but production time and costs increase
Solution Approach 1:
The mask is divided into multiple sections with different thicknesses (first section overlapping the trench, second section overlapping the functional portion, third section overlapping both). This segmentation allows different regions to serve different functions during doping, enabling precise control of doping profiles without requiring multiple lithography steps.
Solution Approach 2:
Multiple doping functions that would traditionally require separate lithography steps are merged into a single lithography step using the multi-section mask. The different thickness sections enable simultaneous formation of different doping regions (first conductivity type near trench, second conductivity type in functional portion) in one operation, reducing production time and eliminating alignment issues between steps.
3Manufacturing precision
If small structure sizes are produced, then device performance can be improved, but manufacturing difficulty increases
Solution Approach 1:
The mask is designed with locally varying thicknesses to provide different functions in different regions. The first section (overlapping trench) has a thickness that allows first-type dopants to reach the functional portion, while the second section (overlapping functional portion) has a different thickness to control second-type dopant diffusion. This local quality variation enables precise control of doping profiles in small structures without increasing overall manufacturing complexity.
Solution Approach 2:
The mask structure is prepared in advance with predetermined thickness variations before the doping process. The first section, second section, and third section are formed with specific thickness relationships that predetermine the doping profiles that will result. This preliminary preparation of the mask eliminates the need for multiple alignment steps during doping, making small structure fabrication more manageable.
4Manufacturing precision
If doping concentrations are increased near trenches, then on-state performance can be improved, but control precision becomes more difficult
Solution Approach 1:
The mask is designed with locally varying thicknesses to provide different functions in different regions. The first section (overlapping trench) has a thickness that allows first-type dopants to reach the functional portion, while the second section (overlapping functional portion) has a different thickness to control second-type dopant diffusion. This local quality variation enables precise control of doping profiles in small structures without increasing overall manufacturing complexity.
Solution Approach 2:
The mask acts as an intermediary structure that mediates the doping process. By varying the mask thickness in different sections, the invention controls how dopants diffuse into the semiconductor body. The mask thickness serves as a mediator that determines the doping concentration and profile without requiring complex in-situ control during the doping process itself, simplifying the control mechanism while achieving precise doping concentrations.
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 reduces the number of lithography steps, allows for the formation of small structural sizes, and enhances on-state performance by minimizing alignment requirements and maintaining high doping concentrations near trenches.
Implementation Method 1
implanting first-type dopants through the top side into the functional portion; implanting second-type dopants through the protection layer and through the top side into the functional portion
Implementation Method 2
a protection layer is deposited onto the mask. The protection layer laterally extends over the trench and the functional portion; at least a part of the first region adjacent to the trench is thereby preserved
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The method comprises a step of providing a semiconductor body with a mask (3) on a top side of the semiconductor body, wherein at least one trench (2) extends from the top side into the semiconductor body. A functional portion (11) is formed laterally adjacent to the trench. In a first section (31) overlapping with the trench, the mask is thicker than in a second section (32) overlapping with the functional portion. A first region (12) of a first conductivity type is formed in the functional portion adjacent to the trench using implanting first-type dopants using an angled implant. Thereafter, protection layer is deposited onto the mask, wherein the protection layer laterally extends over the trenches and the functional portion. A second region of a second conductivity type is formed in the functional portion, between pairs of first regions (12) using implanting second-type dopants through the protection layer. A part of the first region is thereby preserved. The device may either be a vertical trench-gate MOSFET or IGBT.