Air Gap Between Stacked Chips Reduces Capacitive Coupling
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Solution Overview
Problem
As feature sizes of integrated circuits shrink, interconnect structures face increased power consumption and delay due to capacitive coupling between compact signal lines, which worsens in multi-chip systems with reduced stacking distances, limiting performance and data rate.
Innovation Solution
Implementing an air gap between conductive lines in semiconductor structures to reduce capacitive coupling, achieved by creating a semiconductor package with a microbump of 0.3 μm to 5 μm height between stacked chips, using a low dielectric constant material to maintain signal integrity and increase data rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple chips are stacked with reduced spacing to improve integration density, then integration density and bandwidth are improved, but capacitive coupling between conductive lines increases causing higher power consumption and delay
Solution Approach 1:
An air gap is introduced as an intermediary layer between the first and second chips. This air gap acts as a mediator that reduces capacitive coupling between conductive lines on different chips while maintaining electrical connectivity through microbumps. The air gap material (air or low-k dielectric) has lower permittivity than conventional dielectric materials, thereby reducing the capacitive coupling effect and associated power consumption and delay.
Solution Approach 2:
The dielectric parameter (permittivity) is changed by replacing conventional dielectric material with air or low-k dielectric material in the gap between chips. This parameter change reduces the capacitive coupling between conductive lines, thereby reducing power consumption and signal delay while maintaining the reduced spacing for high integration density.
2Productivity
If multiple chips are stacked with reduced spacing to improve integration density, then integration density and bandwidth are improved, but signal integrity deteriorates due to increased capacitive coupling
Solution Approach 1:
The air gap serves as an intermediary that isolates the electromagnetic fields between conductive lines on different chips. By placing air or low-k dielectric material between the chips, the capacitive coupling is reduced, which prevents signal interference and maintains signal integrity even at reduced stacking distances.
3Ease of manufacture
If conventional dielectric material is used between stacked chips, then manufacturing is simplified, but capacitive coupling increases causing power loss and signal degradation
Solution Approach 1:
The dielectric parameter (permittivity) is changed from conventional high-k dielectric material to air or low-k dielectric material. This parameter change directly reduces capacitive coupling and switching power loss. The manufacturing process is adapted to create this air gap structure through techniques such as selective removal of dielectric material or direct bonding with controlled spacing.
4Speed
If chip stacking distance is reduced to improve integration density, then bandwidth and speed are improved, but capacitive coupling between adjacent chips increases
Solution Approach 1:
The air gap is introduced as a mediator layer between chips at reduced stacking distance. This intermediary layer with low permittivity reduces the capacitive coupling effect that would otherwise increase with reduced spacing, thereby enabling high-speed data transmission without excessive capacitive interference.
Solution Approach 2:
The local dielectric quality is optimized by using air or low-k dielectric material specifically in the gap region between chips, while maintaining conventional dielectric materials within the chips themselves. This localized quality change reduces capacitive coupling at the critical interface between chips without affecting the internal chip structure.
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 air gap effectively reduces switching power loss and improves signal integrity by minimizing electrical coupling between conductive lines, allowing for a compact and efficient multi-chip semiconductor package with enhanced performance.
Implementation Method 1
capacitive coupling between compact signal lines
Implementation Method 2
low dielectric constant material to maintain signal integrity
Implementation Method 3
multiple conventional wafers are arranged together in a stack with some means of interconnecting the conventional circuits
Data Source
AI summary
The present disclosure provides a semiconductor structure including a first chip having a first dielectric surface, a second chip having a second dielectric surface facing the first dielectric surface and maintaining a distance thereto, and an air gap between the second dielectric surface and the first dielectric surface. The first chip includes a plurality of first conductive lines in proximity to the first dielectric surface and parallel to each other, two adjacent first conductive lines each having a sidewall partially exposed from the first dielectric surface. The present disclosure further provides a method for manufacturing the semiconductor structure described herein.