Deep Trench Zener Diode Layout for Breakdown Voltage Control
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Solution Overview
Problem
Current semiconductor technologies face challenges in integrating Zener diodes with deep trenches, requiring additional photolithography steps or increased area as device geometries shrink, leading to higher Zener diode breakdown voltages that are undesirable in many applications.
Innovation Solution
The integration of a deep trench diode within a semiconductor device, featuring two or more deep trenches with a silicon dioxide dielectric layer and conductive filler material, surrounded by a deep n-well sheath, allows for controlled breakdown voltage through adjustable n-well dopant concentration between trenches, eliminating the need for extra implant steps and optimizing device layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional Zener diode integration techniques are used, then reliable breakdown for current flow is achieved, but additional photolithography steps and implant processes are required
Solution Approach 1:
The patent merges the Zener diode structure with deep trench isolation structures, combining two separate fabrication processes into one unified approach. The deep trenches serve dual purposes: providing isolation between devices and forming the Zener diode breakdown structure through the n-well region surrounding the trenches.
Solution Approach 2:
The deep trench structure performs multiple functions simultaneously: it provides electrical isolation between adjacent devices, serves as the Zener breakdown structure, and defines the cathode region. This multi-functionality eliminates the need for separate Zener diode fabrication steps.
2Reliability
If traditional Zener diode integration techniques are used, then reliable breakdown for current flow is achieved, but increased device area is required
Solution Approach 1:
By merging the Zener diode active region with the deep trench isolation structure, the patent eliminates wasted space between functional elements. The n-well region surrounding the deep trenches serves as both the breakdown structure and the isolation barrier, maximizing space utilization.
Solution Approach 2:
The patent transitions from a planar Zener diode structure to a three-dimensional structure utilizing deep vertical trenches. This vertical dimension allows the breakdown structure to be formed in the depth direction rather than requiring extended lateral dimensions, significantly reducing the device footprint.
3Manufacturing precision
If deep trench diode structure is implemented, then breakdown voltage control through dopant concentration is achieved, but additional implant steps would normally be required
Solution Approach 1:
The n-well dopant is implanted in advance during the standard CMOS fabrication process, before the deep trench formation. This preliminary doping action establishes the breakdown voltage characteristics without requiring subsequent dedicated implant steps for the Zener diode.
Solution Approach 2:
The deep trench structure and surrounding n-well region self-organize to form the Zener breakdown structure. The n-well dopant concentration, established during standard fabrication, automatically provides the required breakdown voltage control without additional processing interventions.
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 solution enables tailored Zener diode breakdown voltage without additional processing steps, reduces the Zener diode footprint, and allows for modulation of breakdown voltage by adjusting trench spacing, addressing the limitations of existing technologies while maintaining a compact design.
Implementation Method 1
The deep trench diode breakdown voltage is controlled by the concentration of deep n-well dopant in the region between neighboring deep trenches
Implementation Method 2
The deep trench diode is surrounded by a deep n-well sheath which conducts current above the Zener diode breakdown voltage
Data Source
AI summary
A semiconductor device which includes two or more integrated deep trench features configured as a Zener diode. The Zener diode includes a plurality of deep trenches extending into semiconductor material of the substrate and a dielectric deep trench liner that includes a dielectric material. The deep trench further includes a doped sheath contacting the deep trench liner and an electrically conductive deep trench filler material within the deep trench. The doped sheath of adjacent deep trenches overlap and form a region of higher doping concentration which sets the breakdown voltage of the Zener diode. The Zener diode can be used as a triggering diode to limit the voltage on other components in a semiconductor device.