Layered Passivation Structure for Semiconductor Reliability
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Solution Overview
Problem
Thick passivation layers in power semiconductor devices are prone to cracking under thermal cycling, reducing the reliability of the semiconductor device due to internal stress and adhesion issues between silicon nitride and metal wiring layers.
Innovation Solution
A layered passivation structure comprising a first silicon nitride layer, a silicon oxide layer with added nitrogen, and an organic polymer layer, where the silicon oxide layer is continuously formed over the metal wiring layer, and the organic layer covers the end sections of the silicon oxide and nitride layers, reducing peeling and cracking by enhancing adhesion and barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick passivation layer is formed to provide high insulation and mechanical protection, then the insulating property and mechanical strength are improved, but the layer is prone to peeling and cracking due to internal stress and adhesion issues
Solution Approach 1:
The passivation layer is divided into multiple sub-layers (first silicon nitride layer, silicon oxide layer, second silicon nitride layer, organic layer) with different material properties and functions. Each layer has optimized thickness and characteristics, allowing the overall structure to achieve both mechanical strength and adhesion without excessive stress concentration in any single layer.
Solution Approach 2:
The patent uses a composite structure combining different materials (silicon nitride, silicon oxide, organic polymer) with complementary properties. The silicon nitride provides density and barrier properties, silicon oxide provides stress relief and adhesion, and the organic layer provides flexibility and environmental protection, creating a composite passivation system that overcomes the limitations of single-material thick films.
2Object-affected harmful factors
If a thick silicon nitride film is formed to provide high barrier properties, then the ability to block impurities and moisture is improved, but the film develops internal stress that causes peeling and makes thick film formation difficult
Solution Approach 1:
The barrier function is segmented across multiple layers. The first silicon nitride layer provides the primary barrier against impurities and moisture, while the second silicon nitride layer reinforces this barrier property. The intermediate silicon oxide layer manages stress, enabling the overall structure to achieve high barrier performance without the manufacturing difficulties of a single thick silicon nitride film.
Solution Approach 2:
The silicon oxide layer acts as an intermediary between the silicon nitride layers and the metal wiring layer. It provides a transition zone that reduces internal stress accumulation, allowing thick silicon nitride layers to be formed without peeling while maintaining their impurity-blocking capability.
3Strength
If the passivation layer is made thick to protect the semiconductor element, then mechanical protection is improved, but cracking occurs under thermal cycling due to internal stress
Solution Approach 1:
The thick passivation structure is segmented into multiple layers with different thermal expansion characteristics and mechanical properties. This segmentation allows each layer to accommodate thermal stress independently, preventing crack propagation through the entire thickness during thermal cycling while maintaining overall mechanical protection.
Solution Approach 2:
The patent changes the physical and chemical parameters of different layers (composition, thickness, density) to optimize thermal stress distribution. The silicon oxide layer specifically has parameters tuned to provide stress relief during thermal cycling, while the organic layer adds flexibility that further accommodates thermal expansion differences, preventing cracking under thermal stress.
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 provides a highly reliable semiconductor device with a thick passivation layer that suppresses peeling and cracking, maintaining mechanical protection and insulation while preventing moisture and impurity penetration.
Implementation Method 1
both be formed by a PCVD (plasma CVD) method or the like
Implementation Method 2
an organic film that is formed on the very top surface of the passivation layer made of a polymer material such as a polyimide or the like is formed by coating or the like
Data Source
AI summary
Provided is a highly reliable semiconductor device that uses a thick passivation layer. The protective film is formed so as to cover mostly the entire surface of a semiconductor substrate, and is open only in an area of part that is above a metal wiring layer (connection area). The passivation layer includes starting from the bottom side, a first silicon nitride film that includes silicon nitride (Si3N4), a silicon oxide film that includes silicon oxide (SiO2), and an organic film (organic layer) that includes a polyimide. The silicon oxide film and organic film are formed so as to cover the electrode layer (metal wiring layer) except the top of the insulation layer and the connection area, however, the first silicon nitride film is formed only on the insulation layer and not formed on the electrode layer.