SiNx Layer Composition Control for Elastic Wave Device IMD
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Solution Overview
Problem
Elastic wave devices with semiconductor substrates and silicon nitride films suffer from degraded intermodulation distortion (IMD) characteristics and self-destruction issues when the composition of silicon nitride is not optimized.
Innovation Solution
The elastic wave device includes a semiconductor substrate with a SiNx layer having a composition ratio of x between 1.34 and 1.66, a piezoelectric film, and an interdigital transducer electrode, with an optional low-acoustic-velocity film and insulating film to reduce IMD degradation and prevent silicon nitride self-destruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high-acoustic-velocity film composed of silicon nitride is used on a semiconductor substrate, then the acoustic wave propagation characteristics are improved, but the intermodulation distortion characteristics are degraded and the silicon nitride film is self-destroyed
Solution Approach 1:
The patent changes the compositional parameters of the silicon nitride film by controlling the ratio of silicon to nitrogen (represented by x in SiNx where 1.34 ≤ x ≤ 1.66). This parameter optimization allows the film to maintain high acoustic velocity while preventing self-destruction and improving IMD characteristics, resolving the contradiction between speed and reliability
Solution Approach 2:
The patent uses a composite structure consisting of multiple layers including the optimized silicon nitride film, piezoelectric film, and optional low-acoustic-velocity film. This composite approach allows each layer to contribute specific properties, maintaining high acoustic velocity while the overall structure provides improved reliability and reduced self-destruction
2Reliability
If the silicon nitride composition is optimized to prevent self-destruction, then the film stability is improved, but the acoustic velocity may be reduced
Solution Approach 1:
The patent identifies and controls the critical compositional parameter x in SiNx within the specific range of 1.34 to 1.66. This precise parameter control achieves the optimal balance where the film maintains high acoustic velocity (close to that of bulk silicon nitride) while simultaneously achieving sufficient stability to prevent self-destruction
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 effectively confines elastic wave energy, reduces IMD characteristics degradation, and prevents silicon nitride self-destruction, enhancing the performance and reliability of the elastic wave device.
Implementation Method 1
a piezoelectric film stacked directly or indirectly on the SiNx layer, the piezoelectric film including a pair of main surfaces facing away from each other
Implementation Method 2
a low-acoustic-velocity film and a piezoelectric film that are stacked on a SiNx layer defining and functioning as a high-acoustic-velocity film
Data Source
AI summary
An elastic wave device includes a SiNx layer stacked directly or indirectly on a supporting substrate made of a semiconductor material, a piezoelectric film stacked on directly or indirectly the SiNx layer, and an interdigital transducer electrode stacked directly or indirectly on at least one main surface of the piezoelectric film. In the SiNx layer, x is about 1.34 or more and about 1.66 or less.