Trench Field Plate Oxide Formation for Gate Insulation Reliability
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Solution Overview
Problem
The existing manufacturing methods for semiconductor devices with trench gate structures face issues with insulation resistance between the gate electrode and the field plate electrode, and between the lead-out part and the semiconductor substrate, leading to potential leak currents and reduced reliability.
Innovation Solution
The proposed manufacturing method involves forming a silicon oxide film on the upper surface of the field plate electrode through thermal oxidation, followed by selective retraction of the field plate electrode and careful etching processes to ensure the insulation films are properly positioned and thick enough to maintain insulation withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If anisotropic etching is performed on the conductive film to form the gate electrode, then the gate electrode can be formed at the top of the trench, but conductive film residue remains on the side of the lead-out part, reducing insulation resistance
Solution Approach 1:
The patent segments the etching process into two distinct stages: first forming the gate electrode with initial anisotropic etching, then performing a second anisotropic etching to remove conductive film residue from the lead-out part side. This segmentation allows each etching step to target specific areas, ensuring complete removal of residue that would otherwise compromise insulation resistance.
Solution Approach 2:
The patent applies preliminary protective measures by forming an insulating film covering the lead-out part before the first anisotropic etching, and then selectively removing this protective film after etching. This preliminary action prevents conductive film contamination on the lead-out part during the gate electrode formation process, ensuring maintained insulation resistance.
2Ease of operation
If the field plate electrode is formed extending to the top of the trench, then electrical connection to the source electrode is enabled, but conductive film residue on the side of the lead-out part causes insulation problems
Solution Approach 1:
The patent segments the field plate electrode into two functional regions: the main body extending to the top of the trench for electrical connection, and the lead-out part where the insulating film is selectively removed. This segmentation allows the field plate to maintain both its electrical connection function and its insulation property at the lead-out interface with the semiconductor substrate.
Solution Approach 2:
The patent extracts the insulating film specifically from the lead-out part region after the field plate electrode is formed. This selective extraction removes the insulating barrier only where electrical connection is needed, while preserving the insulating film elsewhere to maintain proper insulation between the lead-out part and the semiconductor substrate.
3Reliability
If thermal oxidation is performed to form silicon oxide film on the field plate electrode, then insulation resistance is improved, but additional manufacturing steps are required
Solution Approach 1:
The patent merges the silicon oxide film formation step with the existing gate electrode formation process. The thermal oxidation is performed on the field plate electrode while it is exposed during the trench filling process, combining insulation enhancement with the necessary structural formation steps rather than adding a completely separate process.
Solution Approach 2:
The patent performs thermal oxidation as a preliminary action before completing the trench filling with conductive films. This timing allows the silicon oxide film to be formed on the field plate electrode surface while maximizing its protective effect, and the oxidation process is integrated into the sequence of operations already required for trench formation.
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 method effectively improves the insulation resistance between the gate electrode and the field plate electrode, as well as between the lead-out part and the semiconductor substrate, thereby enhancing the reliability of the semiconductor device by preventing leak currents and ensuring consistent performance.
Implementation Method 1
forming a first silicon oxide film on the upper surface of the field plate electrode by thermal oxidation
Data Source
AI summary
The reliability of the semiconductor device is improved. A field plate electrode FP is formed inside the trench TR via an insulating film IF1. The other part of the field plate electrode FP is selectively retracted toward the bottom of the trench TR so that a part of the field plate electrode FP remains as a lead-out part FPa. A silicon oxide film OX1 is formed on the upper surface of the field plate electrode FP by thermal oxidation. The insulating film IF1 located on the upper surface TS of the semiconductor substrate SUB and the silicon oxide film OX1 are removed, and the insulating film IF1 is retracted so that its upper surface position is lower than the upper surface position of the field plate electrode FP.