Super Junction MOSFET Structure to Block Substrate Outdiffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing super junction MOSFET manufacturing processes face challenges such as high impurity outdiffusion from high-concentration substrates, leading to non-uniform device performance, increased manufacturing costs, and suboptimal body diode characteristics.
Innovation Solution
The proposed solution involves forming an N-type redundant epitaxial layer and an N-type buffer layer on a low-concentration N-type semiconductor substrate, followed by the formation of a super junction structure with alternately arranged P-type and N-type pillars. This configuration ensures that the outdiffusion of impurities does not affect the super junction structure, allowing for ultra-low specific-on-resistance and improved body diode characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-concentration substrate is adopted to reduce specific on resistance, then specific on resistance is reduced, but impurity outdiffusion occurs causing non-uniform device performance
Solution Approach 1:
The substrate structure is segmented into multiple functional layers: a low-concentration N-type substrate layer and a high-concentration N-type drift region layer. This segmentation allows the high-concentration region to provide low specific on resistance while the low-concentration substrate layer prevents impurity outdiffusion, thus resolving the contradiction between reducing specific on resistance and maintaining device performance uniformity.
Solution Approach 2:
A low-concentration N-type substrate layer acts as an intermediary between the high-concentration drift region and the mechanical support structure. This intermediary layer prevents impurity outdiffusion from affecting the high-concentration region, thereby maintaining device performance uniformity while allowing the drift region to achieve ultra-low specific on resistance.
2Manufacturing precision
If high-concentration substrate is used, then specific on resistance decreases, but manufacturing cost increases due to back protection requirements
Solution Approach 1:
The substrate is segmented into a low-concentration N-type substrate layer and a high-concentration N-type drift region layer. This segmentation eliminates the need for complex back protection structures (oxide film and polysilicon film) because the low-concentration substrate layer inherently prevents impurity outdiffusion, thereby reducing manufacturing cost while maintaining ultra-low specific on resistance.
3Manufacturing precision
If high-concentration substrate is adopted, then specific on resistance is reduced, but production efficiency decreases due to special cleaning management requirements
Solution Approach 1:
The substrate structure is segmented into a low-concentration N-type substrate layer and a high-concentration drift region layer. This segmentation eliminates the need for special cleaning management procedures (such as treating only before liquid change or requiring immediate liquid change after cleaning), as the low-concentration substrate layer prevents impurity outdiffusion issues. Consequently, standard cleaning procedures can be used, improving production efficiency while maintaining ultra-low specific on resistance.
4Manufacturing precision
If trench filling process is used with small pitch or increased P-N depth, then reverse breakdown voltage or specific on resistance requirements are met, but etching and cleaning becomes difficult due to high height-width ratio
Solution Approach 1:
The patent applies partial action by performing multiple sequential P-type epitaxial filling operations instead of a single filling operation. Each filling operation works on a portion of the trench depth, reducing the height-width ratio for each individual filling step. This makes etching and cleaning more manageable while still achieving the required total P-N depth for the specified reverse breakdown voltage.
5Ease of manufacture
If multiple P-type epitaxial fillings are performed to reduce height-width ratio, then etching and cleaning becomes easier, but manufacturing process complexity increases
Solution Approach 1:
The P-type epitaxial filling process is segmented into multiple sequential steps, each filling a portion of the trench depth. This segmentation reduces the height-width ratio for each individual filling operation, making etching and cleaning easier. Although the process sequence is extended, each step uses standard equipment and procedures, managing overall process complexity while significantly improving manufacturability.
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 approach effectively eliminates the adverse effects of impurity outdiffusion, achieving an ultra-low specific-on-resistance and improving the reverse recovery softness of the body diode, thereby enhancing the overall performance and manufacturing efficiency of the super junction MOSFET.
Implementation Method 1
the outdiffusion of substrate impurities will influence the uniformity of device performance
Implementation Method 2
By forming trenches in the N-type epitaxial layer and filling the P-type epitaxial layer in the trenches to form alternately arranged P-N pillars
Implementation Method 3
the part after the P-N pillars is formed through ion implantation after annealing diffusion
Data Source
AI summary
The present application discloses a super junction device, which includes: an N-type redundant epitaxial layer and an N-type buffer layer sequentially formed on an N-type semiconductor substrate; a trench filled super junction structure is formed on the N-type buffer layer; a back structure includes a drain region and a patterned back P-type impurity region; the N-type semiconductor substrate is removed in a back thinning process, and the N-type redundant epitaxial layer is completely or partially removed in the back thinning process; the resistivity of the N-type semiconductor substrate is 0.1-10 times the resistivity of a top epitaxial layer, the resistivity of the N-type redundant epitaxial layer is 0.1-10 times the resistivity of the N-type semiconductor substrate, and the resistivity of the N-type redundant epitaxial layer is lower than the resistivity of the N-type buffer layer. The present application further discloses a method for manufacturing a super junction device.