Trenched Power MOSFET Insulating Separation Layer
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Solution Overview
Problem
The manufacturing process of trenched power MOSFETs with shielding electrodes often results in holes or slits in the gate trench, which can lead to leakage currents and poor electrical properties due to the difficulty in controlling the depth of etching the dielectric layer, affecting the gate/drain capacitance and breakdown voltage.
Innovation Solution
A trenched power semiconductor element is designed with an insulating separation layer that seals holes and spaces the gate electrode apart from them, preventing electrical property degradation, even if holes exist in the trench structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dielectric layer is etched away to form shielding electrode structure, then the gate/drain capacitance is reduced and breakdown voltage is increased, but the depth of etching is difficult to control causing holes or slits in the gate trench
Solution Approach 1:
A new gate dielectric layer is deposited on the side wall at the upper portion of the gate trench before etching the dielectric layer away, serving as a pre-formed protective layer that prevents etching from penetrating too deeply and forming holes or slits
Solution Approach 2:
The newly deposited gate dielectric layer acts as a cushioning protective layer during the etching process, absorbing the etching action and preventing it from reaching the metal silicide layer, thus avoiding the formation of harmful holes or slits
2Ease of manufacture
If holes or slits are formed in the gate trench during etching, then the manufacturing process is simplified, but leakage currents occur between gate and source causing poor electrical properties
Solution Approach 1:
The gate dielectric layer is deposited in advance on the side wall before etching, creating a protective barrier that prevents holes or slits from forming during the etching process, thereby maintaining good electrical properties
Solution Approach 2:
The etching process that would normally create harmful holes is transformed into a beneficial process by the presence of the protective gate dielectric layer, which allows the etching to proceed safely without compromising the integrity of the gate trench
Data Source
AI summary
A trenched power semiconductor element, a trenched-gate structure thereof being in an element trench of an epitaxial layer and including at least a shielding electrode, a shielding dielectric layer, a gate electrode, an insulating separation layer, and a gate insulating layer. The shielding electrode is disposed at the bottom of the element trench, the shielding dielectric layer is disposed at a lower portion of the element trench, surrounding the shielding electrode to separate the shielding electrode from the epitaxial layer, wherein the top portion of the shielding dielectric layer includes a hole. The gate electrode is disposed above the shielding electrode, being separated from the hole at a predetermined distance through the insulating separation layer. The insulating separation layer is disposed between the shielding dielectric layer and the gate electrode layer to seal the hole.