Hydrogen Mitigation in SiN Passivation via Segmented Barrier Layers
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Solution Overview
Problem
Hydrogen present in Chemical Vapor Deposition (CVD) Silicon Nitride (SiN) passivation structures in semiconductor devices becomes mobile at elevated temperatures, affecting device performance by introducing mobile charges and altering device characteristics.
Innovation Solution
A Silicon Nitride passivation structure comprising Hydrogen-free SiN layers, a Hydrogen barrier layer with repeating sequences of different oxide layers formed by Atomic Layer Deposition, and a Plasma Enhanced CVD SiN layer, which reduces Hydrogen migration and its effects on device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CVD SiN is used for passivation, then ease of deposition and encapsulation properties are improved, but Hydrogen contamination and device performance degradation occur
Solution Approach 1:
The passivation structure is divided into multiple functional layers: a Hydrogen-free SiN layer deposited by sputtering serves as the primary passivation layer, while a separate CVD SiN layer is added as an environmental barrier layer. This segmentation allows each layer to perform its specific function without contaminating the other, eliminating Hydrogen from the device interface while maintaining the deposition advantages of CVD processes.
Solution Approach 2:
The harmful Hydrogen is extracted from the passivation structure by using a different deposition method (sputtering) for the layer in direct contact with the device. This removes the source of Hydrogen contamination from the critical interface, while still allowing CVD SiN to be used in non-critical applications where ease of deposition is prioritized.
2Reliability
If CVD SiN passivation is used, then good encapsulation properties are achieved, but mobile charges are introduced at elevated temperatures
Solution Approach 1:
The encapsulation function is segmented between two layers: the sputtered Hydrogen-free SiN layer provides stable encapsulation without generating mobile charges, while the CVD SiN environmental barrier layer provides additional protection against external contaminants. This segmentation preserves encapsulation reliability while eliminating the harmful mobile charge effect.
Solution Approach 2:
The Hydrogen-free SiN layer acts as an intermediary barrier between the device and the CVD SiN layer. This intermediate layer prevents Hydrogen from migrating into the device while still allowing the CVD layer to provide its encapsulation benefits, thus mediating between the need for good encapsulation and the avoidance of mobile charges.
3Device complexity
If single-layer CVD SiN is used, then process simplicity is maintained, but device characteristics are altered by Hydrogen
Solution Approach 1:
The passivation process is segmented into two deposition steps with different methods, but this is offset by using standard, well-established sputtering and CVD processes that are already integrated into existing manufacturing workflows. The segmentation improves device characteristics while maintaining reasonable process simplicity through the use of conventional techniques.
Solution Approach 2:
The passivation structure uses a composite of two different SiN layers deposited by different methods. This composite structure combines the Hydrogen-free properties of sputtered SiN with the low permittivity and good encapsulation properties of CVD SiN, achieving superior device characteristics while maintaining compatibility with existing manufacturing processes.
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 proposed passivation structure effectively eliminates or mitigates the adverse effects of Hydrogen, improving device characteristics by reducing parasitic capacitance and minimizing trapping, thereby enhancing the performance of semiconductor devices like MESFETs, HEMTs, and MOSFETs.
Implementation Method 1
a Hydrogen barrier layer on, and preferably directly on, a surface of the one or more Hydrogen-free SiN layers opposite the semiconductor body. The Hydrogen barrier layer includes a repeating sequence of different oxide layers. Preferably, the Hydrogen barrier layer includes stoichiometric monolayers of different compositions formed by Atomic Layer Deposition (ALD).
Implementation Method 2
a Chemical Vapor Deposition (CVD) SiN layer on, and preferably directly on, a surface of the Hydrogen barrier layer opposite the one or more Hydrogen-free SiN layers. The CVD SiN layer is preferably a Plasma Enhanced CVD (PECVD) SiN layer.
Implementation Method 3
the one or more Hydrogen-free SiN layers include a first Hydrogen-free SiN layer on, and preferably directly on, the surface of the semiconductor body and a second Hydrogen-free SiN layer on, and preferably directly on, a surface of the first Hydrogen-free SiN layer opposite the semiconductor body. In one embodiment, the first and second Hydrogen-free SiN layers are sputter-deposited SiN layers.
Data Source
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AI summary
Embodiments of a Silicon Nitride (SiN) passivation structure for a semiconductor device and methods of fabrication thereof are disclosed. In general, a semiconductor device includes a semiconductor body and a SiN passivation structure over a surface of the semiconductor body. In one embodiment, the SiN passivation structure includes one or more Hydrogen-free SiN layers on, and preferably directly on, the surface of the semiconductor body, a Hydrogen barrier layer on, and preferably directly on, a surface of the one or more Hydrogen-free SiN layers opposite the semiconductor body, and a Chemical Vapor Deposition SiN layer on, and preferably directly on, a surface of the Hydrogen barrier layer opposite the one or more Hydrogen-free SiN layers. The Hydrogen barrier layer preferably includes one or more oxide layers of the same or different compositions. Further, in one embodiment, the Hydrogen barrier layer is formed by Atomic Layer Deposition.