Half-through vias suppress substrate modes in ICs
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Solution Overview
Problem
High-frequency integrated circuits face signal attenuation due to substrate signal propagation modes, which require increased power transmission and are challenging to suppress with traditional metal vias, especially as component density and frequency increase, limiting the effectiveness of existing fabrication techniques.
Innovation Solution
The integration of part-way through vias within the substrate, which extend partially from the backside to suppress substrate modes, allowing for reduced signal attenuation without interfering with top-side circuit components, with the number and depth of these vias determined by simulation based on operating frequency and substrate material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of metal vias is increased to suppress substrate modes, then signal propagation is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The via structure is segmented into two types: through-vias that extend completely through the substrate and part-way vias that extend only partially. This segmentation allows the via system to suppress substrate modes more effectively while reducing the total number of vias needed, as the part-way vias can be positioned strategically without requiring full through-via complexity
Solution Approach 2:
The invention introduces a new dimensional parameter - the depth of via penetration - rather than only varying via density in the planar dimension. By controlling how far vias extend into the substrate (full depth vs. partial depth), the solution suppresses substrate modes without proportionally increasing via density, thus reducing manufacturing complexity
2Speed
If the operating frequency is increased, then circuit performance is improved, but substrate mode attenuation increases
Solution Approach 1:
The invention changes the physical parameters of the via system - specifically the depth and distribution of vias - to match higher operating frequencies. By adjusting via depth (using part-way vias instead of full through-vias) and spatial distribution, the system maintains effective substrate mode suppression at higher frequencies without the proportional increase in power requirements that would otherwise be needed
3Productivity
If component density is increased, then circuit integration is improved, but the ability to place suppression vias is reduced
Solution Approach 1:
Instead of requiring vias to extend fully through the substrate (excessive action), the invention uses part-way vias that extend only to the depth necessary for suppression. This partial action approach reduces via placement constraints, allowing higher component density on the substrate surface while maintaining the ability to place suppression vias in appropriate locations
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 approach effectively reduces signal loss by strategically placing part-way through vias to break up substrate propagation modes, allowing for higher frequency operation without increasing power requirements, even with dense component configurations.
Implementation Method 1
substrates for integrated circuits are made of various semiconductor materials, such as silicon, InP, GaAs, etc., that promote substrate signal propagation modes that allow the RF signals used by the circuit to propagate through the substrate
Data Source
Figure 1~2
AI summary
An integrated circuit comprising a substrate including a top-side surface and a backside surface and a plurality of circuit components fabricated on the top-side surface of the substrate. The circuit includes a plurality of electrically conductive vias extending into the substrate from the backside surface of the substrate. Some of the plurality of vias are through vias that extend completely through the substrate and make electrical contact with a circuit component on the top-side surface of the substrate and some of the plurality of vias are part-way through vias that extend only part-way through the substrate and are positioned directly opposite to a circuit component on the top-side surface of the substrate, where the part-way through vias extend at least half-way through the substrate. The number of part-way through vias is determined based on the number of part-way through vias that are necessary to suppress substrate modes in the substrate.