Trench Power MOSFET Layout With Simultaneous Gate-Source Etching
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Solution Overview
Problem
The existing manufacturing methods for trench type power devices face limitations in photoetching technology, particularly in aligning gate and source trenches, which restricts integration level and increases on-resistance, making it challenging to improve the device's efficiency and integration density.
Innovation Solution
A manufacturing method that simultaneously forms gate and source trenches using a multi-layer mask structure, employing dry etching and thermal oxidation to achieve precise trench dimensions, followed by polysilicon deposition and impurity doping, allowing for improved integration and reduced on-resistance without additional masks, thereby overcoming photoetching technology limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gate trenches and source trenches are manufactured sequentially using conventional photoetching technology, then the manufacturing process is simpler, but the alignment precision between gate trenches and source trenches deteriorates, limiting integration level and increasing on-resistance
Solution Approach 1:
The patent combines the formation of gate trenches and source trenches into a single simultaneous etching process. The multi-layer mask structure (comprising first photoresist, first insulator mask, second photoresist, and second insulator mask) enables both trench types to be defined and etched in one step, eliminating alignment errors from sequential processing while maintaining manageable process complexity through systematic mask design.
Solution Approach 2:
The patent introduces a multi-layer mask structure as an intermediary element to achieve precise simultaneous patterning. The multiple insulator mask layers (silicon dioxide, silicon nitride) serve as intermediate protective and defining layers that enable precise trench positioning without requiring complex direct photoetching alignment, thus improving alignment precision while keeping the manufacturing process systematic.
2Reliability
If the distance between adjacent gate trenches is reduced to lower on-resistance, then the device efficiency improves, but the photoetching alignment requirements become more stringent, limiting further integration level improvements
Solution Approach 1:
By merging the patterning of gate trenches and source trenches into a single simultaneous etching step using the multi-layer mask, the patent eliminates cumulative alignment errors that would normally worsen with reduced trench spacing. This allows adjacent gate trenches to be placed closer together (reducing on-resistance) without the alignment precision deteriorating, as both trench types are defined in one process step.
3Manufacturing precision
If additional masks are used to improve trench positioning precision, then the alignment precision improves, but the manufacturing cost and process complexity increase
Solution Approach 1:
The patent merges multiple mask functions into a single integrated multi-layer mask structure. Rather than using separate masks for gate trenches and source trenches (which would increase process steps), the invention combines both patterning functions into one simultaneous etching process using the multi-layer mask, achieving high positioning precision without proportionally increasing manufacturing complexity.
Solution Approach 2:
The multi-layer mask structure serves multiple functions simultaneously: it defines both gate trench and source trench positions, provides protective layers during etching, and enables selective etching through its layered design. This multi-functionality achieves high trench positioning precision without requiring a proportional increase in the number of separate masks or process steps.
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 enhances the integration level and reduces on-resistance of trench type power devices, improving their efficiency and cost-effectiveness by breaking through the limitations of photoetching technology and allowing for more precise trench positioning and denser cellular structures.
Implementation Method 1
step S1, performing chemical vapor deposition on an upper surface of a silicon substrate with one or more epitaxial layers
Implementation Method 2
the photoresist is spin-coated through a photoetching technology
Implementation Method 3
forming the pattern of the circuit on each of the one or more epitaxial layers through the dry etching
Implementation Method 4
performing rounding and plasma damage repair on the cellular gate trench, the source trench, and the gate interconnection trench through a thermal oxidation method, growing an oxide layer on each of side walls
Implementation Method 5
growing the silicon nitride thin film through low-pressure chemical vapor deposition
Implementation Method 6
etching the silicon nitride thin film through hot phosphoric acid
Implementation Method 7
doping the pentavalent elements in a deposition process of the polysilicon or doping the trivalent elements through ion implantation after the gate is formed
Data Source
AI summary
A trench type power device and a manufacturing method of the trench type power device are provided, which relate to a technical field of manufacturing power semiconductor devices. The manufacturing method includes steps of preparing a cellular structure, preparing contact holes and tungsten bolts, performing etching to form a circuit, and depositing a passivation layer and etching the passivation layer, which overcomes limitation on relative positions of the gate trench and source trench from technology capability of photoetching machines, so as to further improve the integration level. Moreover, simultaneously manufacturing the gate trench and the source trench overcomes difficulties of the photoetching technology and reduces cellular density and on-resistance, so as to improve efficiency of the trench type power device. And, there is no other mask additionally added.