MIM Decoupling Capacitors Under Contact Pads
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Solution Overview
Problem
The integration of metal-insulator-metal (MIM) decoupling capacitors on-chip is limited by the available area and routing lines, leading to increased chip size due to the significant space requirements and complex placement needs.
Innovation Solution
Placing one or more MIM decoupling capacitors directly under external contact pads, with the option to include dummy MIM capacitors, allows for a more efficient use of chip area and reduces overall chip size by utilizing the space under the contact pads for capacitor arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MIM decoupling capacitors are placed on-chip to increase capacitance, then the decoupling capability is improved, but the chip area increases significantly
Solution Approach 1:
The patent utilizes the vertical dimension by placing MIM capacitors directly under the contact pad, effectively using the area under the pad that would otherwise be unused. This three-dimensional placement strategy allows the capacitor to occupy space in the vertical direction rather than only in the planar area, thereby improving decoupling capability without significantly increasing the overall chip area.
Solution Approach 2:
The MIM capacitor is nested under the contact pad structure, with the capacitor occupying the space beneath the pad. This nesting approach allows the capacitor to be integrated into the existing contact pad area, utilizing the vertical space under the pad to house the capacitor structure without requiring additional lateral space.
2Quantity of substance
If MIM capacitors are used to increase capacitance density, then the capacitance per unit area is improved, but the routing complexity and placement difficulty increase
Solution Approach 1:
The contact pad area serves multiple functions: it provides the external electrical connection interface and simultaneously houses the MIM decoupling capacitor beneath it. This multi-functionality eliminates the need for separate routing to connect the capacitor, as the pad itself provides the electrical connection, thereby reducing routing complexity while maintaining high capacitance density.
Solution Approach 2:
The contact pad structure serves its own electrical connection function while also providing the housing and electrical connection for the underlying capacitor. The capacitor utilizes the pad's electrical infrastructure, eliminating the need for additional complex routing to connect the capacitor to the power lines, thus simplifying the overall routing architecture.
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 configuration enables a higher capacitance density, such as 5 fF/cell or 85 fF/μm² in a 40 nm design, while maintaining standard semiconductor processing compatibility, thus addressing the area constraints and improving chip design efficiency.
Implementation Method 1
MIM capacitors comprise metallic layers with a dielectric layer interposed therebetween
Implementation Method 2
MIM capacitors comprise metallic layers with a dielectric layer interposed therebetween formed in a trench of a dielectric layer
Data Source
AI summary
An integrated circuit structure includes one or more external contact pads with decoupling capacitors, such as metal-insulator-metal (MIM) capacitors, formed directly thereunder. In an embodiment, the decoupling capacitors are formed below the first metallization layer, and in another embodiment, the decoupling capacitors are formed in the uppermost inter-metal dielectric layer. A bottom plate of the decoupling capacitors is electrically coupled to one of Vdd and Vss, and the top plate of the decoupling capacitors is electrically coupled to the other. The decoupling capacitors may include an array of decoupling capacitors formed under the external contact pads and may include one or more dummy decoupling capacitors. The one or more dummy decoupling capacitors are MIM capacitors in which at least one of the top plate and the bottom plate is not electrically coupled to an external contact pad.