Two-Side IC Metallization With Stiffening for Backside I/O Access
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Solution Overview
Problem
The increasing number of transistors in integrated circuits (ICs) necessitates more input/output (I/O) contacts, but existing technologies face challenges in providing sufficient I/O contacts due to the limited size and pitch of metal interconnects and the space occupied by through-silicon vias (TSVs).
Innovation Solution
The integration of two-side metallization with external stiffening layers in ICs, where first metallization layers are on the front side and second metallization layers are on the back side of the circuit layer, along with a stiffening layer that provides structural rigidity and supports the formation of vias to external contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the semiconductor substrate is thinned to improve access to the back side of devices and enable second metallization layers, then interconnection capabilities and external contact access are improved, but structural rigidity is significantly reduced causing mechanical and electrical failures during processing
Solution Approach 1:
A stiffening layer is formed on the back side of the semiconductor substrate before thinning operations. This preliminary structural reinforcement enables the substrate to withstand subsequent thinning processes and handling, allowing access to the back side of devices while preventing mechanical failures during manufacturing.
Solution Approach 2:
The semiconductor substrate is combined with a stiffening layer made of different material properties to create a composite structure. The stiffening layer provides the necessary mechanical strength and rigidity, while the thinned substrate regions allow electrical access to the back side of devices, achieving both structural integrity and operational access.
2Quantity of substance
If through-silicon vias (TSVs) are used to provide additional I/O contacts from the circuit layer through the substrate to the back side, then the number of I/O contacts is increased, but large cross-sectional areas are occupied creating keep-out zones where no transistors can be formed
Solution Approach 1:
Instead of creating vertical TSVs through the substrate that occupy large cross-sectional areas, the patent utilizes the back side surface plane to form metallization layers and contacts. This dimensional approach allows I/O contacts to be arranged on the back side surface without penetrating through the substrate, thereby eliminating keep-out zones and maximizing the usable area for transistor formation on the front side.
Data Source
AI summary
An integrated circuit (IC) includes a plurality of first metallization layers on a front side of a circuit layer and a plurality of second metallization layers on a back side of the circuit layer. A semiconductor substrate on the back side of the circuit layer of the IC is thinned to improve access to devices from the back side. The plurality of second metallization layers are employed to provide increased interconnection among the devices without increasing area and may provide increased access to external contacts. Thinning the semiconductor substrate reduces structural rigidity needed for processing, so the IC also includes a stiffening layer on one of the plurality of first metallization layers and the plurality of second metallization layers to increase rigidity and first vias extending through the stiffening layer to couple to first contacts.