Poly-filled Trenches for Semiconductor ON-Resistance and Thermal Management
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Solution Overview
Problem
Semiconductor devices face limitations such as high ON-resistance, breakdown voltage, heat dissipation, substrate leakage current, and energy handling capabilities, particularly in lateral and vertical devices, which are challenging to address with existing technologies.
Innovation Solution
The implementation of poly-filled trenches in semiconductor devices, which reduce series resistance and minority carrier injection, allowing for improved heat removal and reduced device area, by using polycrystalline semiconductor materials in N-channel lateral and NPN vertical devices on silicon or SOI substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional semiconductor device structures are used, then device area is reduced, but ON-resistance and heat dissipation capability deteriorate
Solution Approach 1:
The device structure is segmented by introducing trenches that divide the semiconductor layer into distinct regions. These trenches are filled with conductive material to create low-resistance pathways, effectively segmenting the current flow paths and reducing overall ON-resistance while maintaining compact device area.
Solution Approach 2:
The trenches filled with conductive material act as intermediaries between the source/drain regions and the substrate. These intermediary structures provide low-resistance current pathways and improved thermal conduction, bridging the gap between high-current-density regions and the substrate while reducing both ON-resistance and improving heat dissipation.
2Area of moving object
If device area is reduced to improve integration, then heat removal capability deteriorates
Solution Approach 1:
The solution moves from two-dimensional planar heat dissipation to three-dimensional heat removal by introducing vertical trenches. These trenches extend downward toward the substrate, creating additional thermal conduction pathways in the vertical dimension, thereby improving heat removal capability without increasing the lateral device footprint.
Solution Approach 2:
The conductive filler material in the trenches serves as a thermal intermediary, providing high-thermal-conductivity pathways from the heat-generating regions down to the substrate. This intermediary structure efficiently conducts heat away from the active device regions, improving heat removal capability while maintaining small device area.
3Reliability
If series resistance is reduced to improve performance, then device complexity increases
Solution Approach 1:
The electrical parameter of the trench filler material is changed to be highly conductive, transforming the trench from a passive structural element into an active low-resistance current pathway. By changing the material parameter (filling with conductive material rather than leaving empty or filling with insulator), series resistance is reduced without requiring complex additional structures.
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 significantly reduces minority carrier injection, decreases device size by up to 70%, and enhances thermal coupling, thereby improving the performance and cost-effectiveness of semiconductor devices.
Implementation Method 1
enhances thermal coupling, thereby improving the performance
Implementation Method 2
reduce series resistance and minority carrier injection
Data Source
AI summary
Structure and method are provided for semiconductor devices. The devices include trenches filled with highly doped polycrystalline semiconductor, extending from the surface into the body of the device for, among other things: (i) reducing substrate current injection, (ii) reducing ON-resistance and/or (iii) reducing thermal impedance to the substrate. For isolated LDMOS devices, the resistance between the lateral isolation wall (tied to the source) and the buried layer is reduced, thereby reducing substrate injection current. When placed in the drain of a lateral device or in the collector of a vertical device, the poly-filled trench effectively enlarges the drain or collector region, thereby lowering the ON-resistance. For devices formed on an oxide isolation layer, the poly-filled trench desirably penetrates this isolation layer thereby improving thermal conduction from the active regions to the substrate. The poly filled trenches are conveniently formed by etch and refill. Significant area savings are also achieved.