Trench-Gate Insulating Film Layout to Suppress IGBT PBTI
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Solution Overview
Problem
The conventional manufacturing method for semiconductor devices with trench-gate IGBTs results in variations in gate insulating film thickness, leading to increased interface states and the formation of hydrogen ions, which cause Positive Bias Temperature Instability (PBTI) and threshold voltage fluctuations, thereby reducing device reliability.
Innovation Solution
A manufacturing method that includes forming a gate insulating film with controlled thickness using wet oxidation and dry oxidation processes, followed by hydrogen annealing, to minimize interface states and hydrogen ion formation, and strategically positioning the boundary between impurity regions to reduce the channel region affected by PBTI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate insulating film with relatively large thickness is formed to reduce damage on the semiconductor substrate during ion implantation, then the substrate damage is reduced, but the interface state increases and hydrogen ions are formed causing PBTI deterioration
Solution Approach 1:
A silicon oxide film is introduced as an intermediary layer between the gate insulating film and the semiconductor substrate. This mediator film absorbs the harmful effects of ion implantation while preventing hydrogen ion formation and interface state generation in the gate insulating film, thus protecting both the substrate and the gate insulating film quality
Solution Approach 2:
The protective function is segmented into two separate layers: the gate insulating film (which maintains electrical properties) and the silicon oxide film (which provides mechanical protection during ion implantation). This segmentation allows each layer to perform its specific function without compromising the other
2Reliability
If the gate insulating film thickness is increased to serve as a through film for ion implantation, then the film provides adequate protection, but the thickness variation increases during formation and dry etching processes
Solution Approach 1:
The protective function is divided between the gate insulating film and a separate silicon oxide film. The gate insulating film can be formed with precise, uniform thickness for electrical performance, while the silicon oxide film provides the necessary protection during ion implantation without compromising the gate insulating film thickness control
3Reliability
If a reoxidation process is performed to form a new silicon oxide film after removing the gate insulating film, then the film provides protection for ion implantation, but the interface state increases and PBTI deteriorates
Solution Approach 1:
The silicon oxide film is formed preliminarily before ion implantation through oxidation of the semiconductor substrate surface, rather than through reoxidation after gate insulating film removal. This preliminary formation avoids the harmful interface states and hydrogen ion generation associated with reoxidation processes
Solution Approach 2:
The silicon oxide film serves as a preliminary intermediary layer that provides protection during ion implantation without requiring subsequent reoxidation processes, thereby avoiding the generation of interface states and hydrogen ions that would deteriorate PBTI
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 method enhances the reliability of semiconductor devices by suppressing PBTI-induced threshold voltage fluctuations, improving the stability and performance of the semiconductor device.
Implementation Method 1
forming a gate insulating film inside the trench and on the semiconductor substrate
Implementation Method 2
the reoxidation process is the thermal oxidation process using oxygen gas, that is, the dry oxidation process
Implementation Method 3
performing a hydrogen annealing process to the semiconductor substrate
Data Source
AI summary
A gate electrode is formed inside a trench via a gate insulating film. The gate insulating film formed on a semiconductor substrate is removed. An insulating film is formed on the semiconductor substrate. A p-type base region is formed in the semiconductor substrate. An n-type emitter region is formed in the base region. Hydrogen annealing process is performed to the semiconductor substrate. A boundary between the base region and the emitter region is located at a position deeper than the insulating film formed between a side surface of the trench and the gate insulating film.