Stepped Conductive Layer Wiring Substrate for MIM Capacitor Stress Relief
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Solution Overview
Problem
MIM capacitors face reliability issues due to stress generated by thermal expansion differences between conductive and insulating layers, leading to peeling or cracking of the insulating layer, which deteriorates performance and power efficiency, especially when thickened for reduced transmission resistance.
Innovation Solution
A wiring substrate design with a stepped structure in the conductive layer, where the first part has a thicker thickness and the second part is thinner, alleviates stress on the insulating layer by creating a step that reduces stress distribution, using a substrate with an insulating surface and specific thicknesses for the conductive and insulating layers to enhance adhesion and prevent dielectric breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the conductive layer is thickened to reduce transmission resistance, then the transmission resistance decreases, but the stress on the insulating layer increases causing peeling or cracking
Solution Approach 1:
The conductive layer is segmented into multiple thickness regions: a first conductive layer with first thickness and a second conductive layer with second thickness (different from the first thickness). This segmentation allows the wiring to achieve low transmission resistance through the thicker first conductive layer while the thinner second conductive layer reduces stress on the insulating layer, preventing peeling or cracking.
Solution Approach 2:
Different regions of the conductive layer are assigned different thicknesses to serve different functions. The first conductive layer (thicker) is positioned to provide low transmission resistance for signal transmission, while the second conductive layer (thinner) is positioned to reduce stress on the insulating layer. This local differentiation of quality resolves the contradiction between low resistance and high reliability.
2Reliability
If the insulating layer is made elastic to relieve stress, then stress relief is achieved, but the organic material has high dielectric loss affecting power efficiency
Solution Approach 1:
The patent extracts the stress relief function from the insulating layer material properties and transfers it to the conductive layer structure. Instead of making the insulating layer elastic (which would increase dielectric loss), the conductive layer is designed with varying thickness to inherently reduce stress on the insulating layer. This separates the stress relief function from the insulating layer, allowing it to maintain low dielectric loss while still achieving stress relief through the stepped conductive layer structure.
Solution Approach 2:
The stepped conductive layer structure acts as an intermediary that mediates between the thermal expansion of the conductive layer and the insulating layer. By introducing the thickness variation in the conductive layer, it serves as a buffer that reduces the direct stress transmission to the insulating layer, eliminating the need for the insulating layer to be elastic while still achieving stress relief.
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 stepped structure effectively reduces stress on the insulating layer, improving the reliability and power efficiency of the capacitor by minimizing dielectric breakdown and enhancing adhesion, thus maintaining signal quality and reducing thermal noise.
Implementation Method 1
The conductive layer and the insulating layer have different thermal expansion coefficient. Therefore, stress is generated by expansion and contraction according to the thermal history
Data Source
AI summary
A wiring substrate of the present disclosure includes a substrate, a first conductive layer, a first insulating layer, and a second conductive layer. The substrate has an insulating surface. The first conductive layer is disposed on the substrate and includes a first part and a second part. The first part has a first thickness. The second part has a second thickness thinner than the first thickness and is adjacent to the first part. The first insulating layer is disposed on the first part and apart from the second part. The first insulating layer is disposed between the second conducting layer and the first part.