Vertical Breakdown ESD Structure for Precise BV Control
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Solution Overview
Problem
Current ESD devices face challenges in accurately adjusting and locating the breakdown voltage (BV) within semiconductor devices, leading to insufficient protection against electrostatic discharge due to hot spots and increased current density, which can result in irreparable damage to integrated circuits.
Innovation Solution
The solution involves a vertical location of the breakdown area within a p-n junction, allowing for finer adjustment of the BV by controlling the spacing between adjacent openings in the mask used to form the N-type buried layer, enabling precise modulation of the BV and reducing voltage overshoot during fast ESD events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the breakdown voltage (BV) is adjusted by lateral spacing between doped layers, then the BV can be modified, but the current density concentrates at the closest spacing creating hot spots that reduce protection reliability
Solution Approach 1:
The patent transitions from lateral spacing adjustment to vertical depth control of the breakdown region. By forming the breakdown region at a specific depth below the surface (in the drift region) rather than at the lateral interface between doped layers, the current density is distributed over a larger volume, eliminating hot spots while maintaining precise BV adjustment capability through control of the breakdown region depth and characteristics
Solution Approach 2:
The patent creates a localized breakdown region with specific properties (depth, doping concentration, volume) within the drift region. This localized region is formed at a controlled distance from the surface, allowing precise control of where breakdown occurs and how current is distributed, thereby achieving both accurate BV adjustment and reliable protection without hot spot formation
2Adaptability or versatility
If lateral spacing between doped layers is used to adjust BV, then BV modulation is achieved, but the hot spot location prevents sufficient current stress distribution
Solution Approach 1:
The invention moves the breakdown region from the lateral plane to the vertical dimension, positioning it at a specific depth in the drift region. This allows BV modulation through control of vertical parameters (depth, doping profile) while the resulting current flow distributes stress more uniformly through the bulk material, achieving both adaptability and stability
3Reliability
If conventional ESD devices are used, then basic ESD protection is provided, but voltage overshoot occurs during fast ESD events reducing protection effectiveness
Solution Approach 1:
The patent pre-forms a breakdown region with optimized characteristics (depth, doping concentration, volume) in the drift region before ESD events occur. This preliminary structuring ensures that when fast ESD events occur, the breakdown happens at the predetermined location with controlled voltage characteristics, preventing voltage overshoot and providing immediate effective protection without requiring additional response time
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 provides improved ESD protection with reduced voltage overshoot and increased reliability by allowing for precise adjustment of the BV, ensuring better protection of integrated circuits against electrostatic discharge.
Implementation Method 1
an N-type buried layer in the P-type substrate... a P-type deep well... forming a p-n junction with a vertical location of the breakdown area within the p-n junction
Data Source
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Figure 5
AI summary
Semiconductor device and methods for making the devices includes a buried layer of a first conductivity in a substrate in which a distance between two adjacent ends can be selected to achieve a desired breakdown voltage. A deep well having a first doping concentration of a second conductivity type is implanted in an epitaxial layer above the two adjacent ends of the buried layer. A patterned doped region is formed in the deep well and extending into the epitaxial layer above and separated a distance from the two adjacent ends of the buried lay. The patterned doped region has a second doping concentration of the second conductivity type that is greater than the first doping concentration.