Avalanche Diode Field Relief Oxide for Breakdown Stability
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Solution Overview
Problem
High-voltage diodes in integrated circuits face reliability issues due to reduced lifetime stability when subjected to repeated breakdown stressing, particularly because the proximity of the breakdown depth to the overlying oxide in existing shallow trench isolation (STI) structures leads to hot carrier charge injection and early failure.
Innovation Solution
The implementation of a shallow N-type well and shallow P-type well diode with a thin field relief oxide structure, which increases the distance between the oxide/substrate interface and the breakdown region, providing greater stability and reliability by reducing hot carrier injection into the oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shallow trench isolation (STI) is used to isolate the SNW from the SPW, then the diode can be formed in an integrated circuit, but the proximity of the breakdown depth to the oxide/substrate interface causes hot carrier charge injection and reduced lifetime stability
Solution Approach 1:
The patent increases the vertical distance between the breakdown region and the oxide/substrate interface by extending the STI structure deeper into the substrate. This dimensional change in the isolation structure effectively moves the harmful oxide interface farther away from the impact ionization zone, reducing hot carrier injection while maintaining lateral isolation functionality.
Solution Approach 2:
The patent introduces a field relief oxide structure as an intermediary layer between the breakdown region and the STI oxide/substrate interface. This intermediate oxide layer acts as a buffer that reduces the direct interaction between hot carriers generated in the breakdown region and the STI oxide, thereby minimizing charge injection and improving reliability.
2Reliability
If the distance between the oxide/substrate interface and the breakdown region is increased, then hot carrier injection is reduced and reliability improves, but the device structure becomes more complex
Solution Approach 1:
The STI structure is designed to serve multiple functions: it provides lateral isolation between the SNW and SPW, acts as a deeper vertical barrier to reduce hot carrier injection, and works in conjunction with the field relief oxide to create a multi-layer isolation system. By making the isolation structure multi-functional, the patent avoids adding separate dedicated components, thus limiting the increase in device complexity.
Solution Approach 2:
The patent modifies the depth parameter of the STI structure and the thickness parameter of the field relief oxide to optimize the distance between the breakdown region and the oxide/substrate interface. By carefully controlling these dimensional parameters, the patent achieves improved reliability while maintaining manufacturability and avoiding excessive structural complexity.
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 configuration enhances the stability and reliability of avalanche diodes, allowing them to operate at higher voltages with reduced drift over time, simplifying circuit design and potentially lowering costs by replacing chains of low-voltage Zener diodes with a single avalanche diode.
Implementation Method 1
the proximity of the breakdown depth to the overlying oxide in existing shallow trench isolation (STI) structures leads to hot carrier charge injection and early failure
Implementation Method 2
an SNW/SPW diode that may operate as an avalanche diode, with a thin field relief oxide structure over the PN junction between the SNW and the SPW
Data Source
AI summary
An integrated circuit includes a shallow P-type well (SPW) below a surface of a semiconductor substrate and a shallow N-type well (SNW) below the surface. The SPW forms an anode of a diode and the SNW forms a cathode of the diode. The SNW is spaced apart from the SPW by a well space region; and a thin field relief oxide structure lies over the well space region.