Stacked IC Passive Device Integration for Simpler BEOL
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Solution Overview
Problem
Existing integrated circuit devices face challenges in increasing integration density, particularly in the middle-of-line (MOL) and back-end-of-line (BEOL) portions of device fabrication, with existing bonding processes being inefficient and limiting the thickness of passive devices.
Innovation Solution
The integration of a transistor and passive devices in a stacked configuration, where the passive devices are formed on a separate substrate with sufficient thickness, allowing for simplified BEOL processes and enhanced integration density, with conductive elements connecting the stacked elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a bonding process is used to attach two separate substrates including elements, then integration density is increased, but the fabrication process complexity increases and passive device thickness is limited
Solution Approach 1:
The device is divided into two separate substrates: a first substrate containing the transistor and a second substrate containing the passive device. This segmentation allows each substrate to be fabricated independently with optimized processes, avoiding the complexity of integrating all elements on a single substrate while achieving high integration density through subsequent bonding.
Solution Approach 2:
The patent transitions from planar integration to three-dimensional stacking by bonding two substrates together vertically. This dimensional change enables increased integration density without proportionally increasing the footprint area, as elements are arranged in multiple layers along the vertical axis.
2Quantity of substance
If a bonding process is used to attach two separate substrates, then integration density is increased, but the passive device thickness is constrained
Solution Approach 1:
By separating the passive device onto its own dedicated substrate, the design decouples the passive device thickness from the overall device height constraints. The second substrate can be fabricated with sufficient thickness to accommodate the passive device requirements without compromising the transistor structure on the first substrate.
Solution Approach 2:
The vertical stacking architecture allows the passive device to extend through the thickness of the second substrate independently, as the bonding interface provides structural support. This enables greater passive device thickness compared to planar configurations where height would be constrained by the total device envelope.
3Ease of manufacture
If separate substrates are used for transistor and passive device, then BEOL fabrication is simplified, but additional bonding steps are required
Solution Approach 1:
Each substrate can be fabricated using standard, well-established BEOL processes independently, allowing manufacturers to leverage existing process knowledge and tooling. The segmentation enables parallel fabrication of both substrates, potentially reducing overall manufacturing cycle time despite the additional bonding step.
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 enables increased integration density and simplifies the BEOL fabrication, facilitating the formation of various passive devices without thickness limitations, thereby improving the overall performance and efficiency of integrated circuit devices.
Implementation Method 1
a bonding process in which two separate substrates including elements (e.g., a transistor, a diode or a resistor) are attached to each other
Data Source
AI summary
Integrated circuit devices may include a transistor, a passive device, a substrate extending between the transistor and the passive device and a power rail. The passive device may be spaced apart from the substrate. Each of the passive device and the power rail may have a first surface facing the substrate, and the first surface of the passive device is closer than the first surface of the power rail to the substrate.