Compound Semiconductor IC with Segmented Au and Cu Metal Layers
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Solution Overview
Problem
The high cost and limited thickness of Au in compound semiconductor MMICs lead to increased resistance and signal loss in transmission lines, restricting circuit performance and increasing manufacturing costs, while Au's replacement with Cu offers better conductivity and lower cost but poses contamination risks.
Innovation Solution
A compound semiconductor integrated circuit with multiple metal layers, including a Cu layer, where a Au first metal layer is connected to a compound semiconductor device and protected by a SiN layer, with Cu layers forming passive components and a backside Cu layer for ground connection through a substrate via hole, using PBO dielectric layers for isolation and contamination prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Au is used for passive components and interconnects to prevent cross contamination, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent divides the metal interconnect system into two distinct segments: Au layers for direct contact with compound semiconductor devices (to prevent cross contamination) and Cu layers for passive components and transmission lines (to reduce cost and resistance). This segmentation allows each material to perform its optimal function without compromising the other.
Solution Approach 2:
Different metal materials are assigned to different locations based on specific functional requirements. Au is used locally where device contact is needed, while Cu is used locally for passive components and interconnects where cost and conductivity are critical. This local quality approach optimizes both reliability and manufacturing cost.
2Reliability
If the thickness of Au layer is increased to improve circuit performance, then electrical conductivity is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive Au with much cheaper Cu for the thick metal layers forming passive components and transmission lines. Cu's superior conductivity allows for thinner layers to achieve the same performance, dramatically reducing material cost while maintaining circuit performance.
Solution Approach 2:
The patent changes the material parameter from Au to Cu for specific interconnect layers, leveraging Cu's superior electrical and thermal conductivity. This parameter change allows for optimized layer thickness and geometry that reduces both material cost and resistance.
3Reliability
If Cu is used to replace Au for better conductivity and lower cost, then electrical conductivity is improved and manufacturing cost is reduced, but cross contamination risk increases
Solution Approach 1:
The patent segments the metal interconnect structure into Au-contact regions and Cu-interconnect regions, physically separating the two materials to prevent cross contamination while maintaining the benefits of Cu's superior conductivity for passive components and transmission lines.
Solution Approach 2:
The patent uses dielectric layers and protective structures as intermediaries to separate Cu layers from compound semiconductor devices, preventing direct contact and potential cross contamination while allowing electrical connection through controlled vias and contacts.
4Productivity
If the width of transmission line is narrowed to increase integration, then device integration is improved, but resistance increases leading to signal loss
Solution Approach 1:
The patent changes the material parameter from Au to Cu for transmission lines, leveraging Cu's superior conductivity to compensate for the increased resistance caused by narrower line widths. This allows for higher integration density while maintaining signal quality.
Solution Approach 2:
The patent employs composite interconnect structures combining Cu layers with dielectric materials and protective coatings, creating a composite transmission line system that achieves both narrow width for high integration and low resistance for signal integrity through optimized multi-layer construction.
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 use of Cu layers reduces resistance and manufacturing costs, enhances circuit performance, prevents Au contamination, and improves power gain by allowing ground connection near the devices, while PBO dielectric layers provide humidity resistance and mechanical stability.
Implementation Method 1
the electrical and the thermal conductivity of Cu is also much better
Implementation Method 2
using PBO dielectric layers for isolation and contamination prevention
Implementation Method 3
a Au first metal layer is connected to a compound semiconductor device and protected by a SiN layer
Implementation Method 4
a backside Cu layer for ground connection through a substrate via hole
Data Source
AI summary
A compound semiconductor integrated circuit is provided, comprising a substrate, at least one compound semiconductor electronic device, a first metal layer, a protection layer, a plurality of second metal layers, and at least one dielectric layer. The first metal layer contains Au but does not contain Cu, and is at least partly electrically connected to the compound semiconductor electronic device. The protection layer covers the compound semiconductor electronic device and at least part of the first metal layer. Each of the plurality of second metal layers contains at least a Cu layer, and at least one of the plurality of second metal layers is partly electrically connected to the first metal layer described above. The at least one dielectric layer separates each pair of adjacent second metal layers. The second metal layers are used to form passive electronic components.