HV LDMOS Transistor with Oxygen Implant for Leakage Reduction
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Solution Overview
Problem
High voltage semiconductor devices face challenges with substrate leakage and breakdown voltage thresholds, particularly in MOSFETs like HV LDMOS and IGBTs, where standard fabrication processes lead to decreased voltage performance, and the use of silicon-on-insulator substrates is expensive and difficult to implement for mass-manufacturing.
Innovation Solution
A high voltage lateral diffusion metal oxide semiconductor (HV LDMOS) transistor design featuring an implanted oxygen layer and a dual-well structure with a deep trench isolation, where the drain region is separated from the insulating pocket, allowing for reduced substrate leakage and increased breakdown voltage without the need for expensive SOI substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard MOS fabrication process flows with multiple implantations are used to prevent punch-through and reduce resistance, then voltage performance is maintained, but substrate leakage increases and breakdown voltage decreases
Solution Approach 1:
An insulating pocket is introduced as an intermediary structure between the drain region and the substrate. This insulating pocket acts as a mediator that blocks the harmful substrate leakage current path while allowing the device to maintain its voltage performance through standard fabrication processes.
Solution Approach 2:
The substrate region beneath the drain is segmented into distinct zones: a drain region, an insulating pocket region, and a substrate region. This segmentation isolates the high-field drain region from the substrate, preventing leakage current while maintaining electrical functionality.
2Object-generated harmful factors
If silicon-on-insulator (SOI) substrates are used to reduce substrate leakage, then substrate leakage is reduced, but manufacturing cost increases and breakdown voltage threshold decreases
Solution Approach 1:
Instead of using expensive full SOI substrates, the invention employs a localized insulating pocket formed through standard fabrication processes. This approach uses inexpensive materials and processes to achieve the same leakage reduction effect, making it suitable for mass production.
Solution Approach 2:
The insulating property is applied locally only where needed (beneath the drain region) rather than throughout the entire substrate. This localized approach reduces manufacturing cost and material usage while maintaining the breakdown voltage threshold.
3Reliability
If partial SOI substrates are used to improve breakdown voltage threshold, then breakdown voltage threshold is improved, but manufacturing difficulty and cost increase
Solution Approach 1:
The invention extracts the essential function of SOI substrates (providing an insulating layer to reduce leakage and improve breakdown voltage) and implements it through a simplified structure that can be formed using standard fabrication processes, eliminating the need for complex partial SOI substrate manufacturing.
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
The solution achieves low substrate leakage and high breakdown voltage thresholds, enhancing switching speed and reducing the likelihood of latch-up, while being cost-effective and suitable for mass-manufacturing.
Implementation Method 1
A portion of the lightly doped semiconductor substrate includes an implanted oxygen layer below a top surface of the lightly doped semiconductor substrate
Data Source
AI summary
A method of making a high voltage metal-oxide-semiconductor laterally diffused device (HV LDMOS), particularly an insulated gate bipolar junction transistor (IGBT), is disclosed. The device includes a semiconductor substrate, a gate structure formed on the substrate, a source and a drain formed in the substrate on either side of the gate structure, a first doped well formed in the substrate, and a second doped well formed in the first well. The gate, source, second doped well, a portion of the first well, and a portion of the drain structure are surrounded by a deep trench isolation feature and an implanted oxygen layer in the silicon substrate.