Bonded Processor-SRAM Stack With Vertical Interconnects for RC Delay
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Solution Overview
Problem
The increasing size of microprocessor chips and the significant resistive-capacitive (RC) delay from the cache to the processor core degrade performance, with interconnect RC delay and SRAM yield being dominant factors.
Innovation Solution
A semiconductor device with a processor and SRAM cache integrated on a bonded chip, utilizing short-distance vertical metal interconnects instead of long-distance routing, and direct bonding technology to reduce RC delay and chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If cache is integrated closer to processor core, then data transfer speed is improved, but chip area and manufacturing complexity increase
Solution Approach 1:
The patent transitions from planar integration to three-dimensional stacked architecture, placing SRAM cache vertically above the processor core through wafer bonding. This vertical stacking reduces horizontal chip area while achieving short-distance interconnects for fast data transfer, directly resolving the contradiction between speed improvement and complexity increase.
Solution Approach 2:
The patent implements nested integration by stacking the SRAM cache structure directly on top of the processor core structure, with bonding interfaces connecting the two layers. This nested arrangement allows the cache to be physically embedded in the vertical space above the processor, reducing overall chip footprint while maintaining close proximity for high-speed data access.
2Productivity
If wafer-level bonding is used for integration, then manufacturing efficiency is improved, but alignment precision and bonding yield become more difficult to control
Solution Approach 1:
The patent performs preliminary alignment mark formation and pattern transfer on wafers before bonding, ensuring precise registration of bonding interfaces. By pre-establishing alignment features and verifying wafer compatibility prior to the bonding process, the method enables high-precision wafer-level integration while maintaining manufacturing efficiency.
Solution Approach 2:
The patent introduces alignment marks and intermediary bonding layers as mediators to facilitate precise wafer alignment and bonding. These intermediary elements serve as reference features that guide the bonding process, enabling accurate registration of bonding interfaces even at wafer-level scales where direct alignment is challenging.
3Loss of time
If vertical interconnects are used instead of long-distance routing, then RC delay is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces long-distance horizontal routing with short-distance vertical interconnects through stacked architecture. The vertical bonding interfaces and through-silicon vias create direct pathways between processor and cache, dramatically reducing interconnect length and RC delay, while the standardized vertical structure simplifies manufacturing compared to complex long-distance routing.
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 integration achieves faster data transfer, wider data bandwidth, and faster memory interface speed with reduced chip size and manufacturing cycle time, while increasing memory cell density and yield.
Implementation Method 1
The first wafer and the second wafer are bonded in a face-to-face manner, such that the at least one of the first semiconductor structures is bonded to the at least one of the second semiconductor structures
Data Source
AI summary
In an example, a semiconductor device includes a first semiconductor structure including a device layer, a first interconnect layer, and a first bonding layer. The device layer includes a processor and a logic circuit, and the first bonding layer includes a first bonding contact. The semiconductor device also includes a second semiconductor structure including an array of static random-access memory (SRAM) cells, a second interconnect layer, and a second bonding layer including a second bonding contact. The first bonding contact is in contact with the second bonding contact. The processor is electrically connected to the array of SRAM cells through the first interconnect layer, the first bonding contact, the second bonding contact, and the second interconnect layer. The logic circuit is electrically connected to the array of SRAM cells through the first interconnect layer, the first bonding contact, the second bonding contact, and the second interconnect layer.