Field Plate Insulating Stack for Moisture-Resistant Semiconductors
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Solution Overview
Problem
The reliability of semiconductor devices with field plate portions is compromised due to moisture exposure, which can lead to deterioration of the polycrystalline silicon field plate portions, and existing solutions face challenges in balancing moisture barrier properties with stress management and manufacturing complexity.
Innovation Solution
A semiconductor device design featuring a field plate portion made of polycrystalline silicon, covered by an insulating film composed of a stacked film of one or more silicon nitride films and one or more silicon oxide films, which acts as a moisture barrier while minimizing stress and manufacturing complications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer insulating film is used to cover the field plate portion, then the manufacturing process is simple, but the moisture barrier property is insufficient
Solution Approach 1:
The patent employs a stacked film structure comprising a first insulating film (silicon oxide) and a second insulating film (silicon nitride) to achieve superior moisture barrier properties compared to single-layer films. The silicon nitride layer provides enhanced moisture resistance while the silicon oxide layer offers good interface characteristics with the field plate portion, creating a composite barrier that effectively prevents moisture ingress.
Solution Approach 2:
The insulating film is divided into multiple functional layers: the first insulating film (silicon oxide) provides a stable interface with the field plate portion and baseline insulation, while the second insulating film (silicon nitride) provides enhanced moisture barrier properties. This segmentation allows each layer to optimize its specific function, achieving overall superior moisture protection.
2Reliability
If a thick insulating film is used to improve moisture barrier, then moisture protection is enhanced, but stress on the semiconductor substrate increases
Solution Approach 1:
The stacked film structure with silicon oxide and silicon nitride layers provides effective moisture barrier properties without requiring excessive film thickness. The silicon nitride layer has lower stress characteristics compared to other high-barrier materials, allowing adequate moisture protection while minimizing stress on the underlying semiconductor substrate and field plate portion.
Solution Approach 2:
The patent optimizes the thickness parameters of each insulating film layer to achieve the right balance between moisture barrier performance and stress management. The first insulating film has a thickness of 50-200 nm and the second insulating film has a thickness of 50-200 nm, providing sufficient moisture protection while keeping individual layer stresses within acceptable limits.
3Stress or pressure
If the field plate portion is made thinner to reduce stress, then stress is reduced, but the field plate effectiveness decreases
Solution Approach 1:
The combination of silicon oxide and silicon nitride insulating films provides enhanced moisture barrier properties that compensate for the reduced field plate thickness. This allows the field plate portion to be made thinner (reducing stress) while the composite insulating film structure maintains adequate moisture protection, effectively decoupling the trade-off between thickness and protection.
4Ease of manufacture
If polycrystalline silicon is used for the field plate portion, then manufacturing is simplified, but moisture reaction causes deterioration
Solution Approach 1:
The stacked film structure of silicon oxide and silicon nitride provides a robust moisture barrier that protects the polycrystalline silicon field plate portion from moisture ingress. The silicon nitride layer acts as a diffusion barrier, preventing moisture from reaching and reacting with the polycrystalline silicon, thereby maintaining both manufacturing simplicity and moisture resistance.
Solution Approach 2:
The insulating films, particularly the silicon nitride layer, serve as an intermediary barrier between the moisture environment and the polycrystalline silicon field plate portion. This intermediate layer prevents direct interaction between moisture and the polycrystalline silicon, protecting it from deterioration while allowing the field plate to maintain its desirable electrical and manufacturing characteristics.
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 design effectively prevents moisture from reaching the field plate portion, enhancing the reliability of the semiconductor device by suppressing reaction with moisture and reducing stress-related issues, thus improving the device's durability and manufacturing feasibility.
Implementation Method 1
an insulating film composed of a stacked film of one or more silicon nitride films and one or more silicon oxide films, which acts as a moisture barrier while minimizing stress
Data Source
AI summary
An insulating film is formed on a main surface of a semiconductor substrate constituting a semiconductor device so as to cover a field plate portion, a metal pattern thicker than the field plate portion is formed on the insulating film, and a protective film is formed on the insulating film so as to cover the metal pattern. The field plate portion is made of polycrystalline silicon, and the insulating film is composed of a stacked film of one or more silicon nitride films and one or more silicon oxide films.