Ferroelectric Gate-Stack Capacitor Integration for CMOS FRAM
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Solution Overview
Problem
Current methods face challenges in integrating ferroelectric random-access memory (FRAM) devices into complementary metal-oxide-semiconductor (CMOS) processes, particularly in enhancing endurance, retention, and reducing power consumption while simplifying the fabrication process.
Innovation Solution
A semiconductor device structure with a ferroelectric random access memory (FRAM) device featuring a fin field effect transistor (FinFET) or gate-all-around (GAA) design, where a capacitor is formed directly above and electrically connected to the gate stack, allowing for the integration of a ferroelectric layer in the CMOS middle-end of line (MEOL) processes, and the method involves recessing the gate stack to form a recess and depositing a ferroelectric layer within it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current FRAM fabrication methods are used, then basic memory functionality is achieved, but endurance and retention performance are insufficient
Solution Approach 1:
The patent changes the physical and chemical parameters of the dielectric material by transitioning from conventional dielectric materials to ferroelectric materials (such as hafnium zirconium oxide, lead zirconate titanate, or barium strontium titanate). This parameter change enables the memory device to achieve superior endurance and retention characteristics while maintaining compatibility with CMOS fabrication processes through careful selection of deposition temperatures and process conditions.
Solution Approach 2:
The patent employs composite material structures including ferroelectric layers combined with metal gate electrodes (such as tungsten, cobalt, or titanium nitride) and integrated with FinFET or GAA transistor architectures. This composite approach allows the FRAM device to achieve enhanced reliability through the synergistic properties of ferroelectric materials while maintaining manufacturability using advanced CMOS process nodes.
2Force
If advanced node FRAM devices are designed to pass through decoupled ferroelectric material, then field strength is improved, but integration into CMOS process becomes difficult
Solution Approach 1:
The patent utilizes three-dimensional transistor architectures (FinFET and gate-all-around structures) to enhance the electric field strength through increased surface area and improved gate control. This dimensional transition from planar to 3D structures allows stronger fields to be generated and maintained while the ferroelectric material is integrated into the existing CMOS process flow, managing integration complexity through architectural innovation rather than material complexity alone.
3Reliability
If FRAM devices are fabricated with improved endurance and retention, then reliability is enhanced, but power consumption management becomes critical
Solution Approach 1:
The patent exploits the inherent periodic switching characteristics of ferroelectric materials, which can rapidly switch between polarized states in response to applied electric fields. This periodic action enables fast write operations with low energy consumption, as the ferroelectric material only requires brief voltage pulses to switch states, rather than continuous power supply. The non-volatile nature of the stored state further reduces standby power consumption while maintaining high reliability.
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 enhances the endurance and retention of the FRAM device, lowers power consumption, and simplifies the fabrication process by using a relatively small number of lithography processes, effectively integrating FRAM devices into CMOS manufacturing.
Implementation Method 1
A semiconductor device structure with a ferroelectric random access memory (FRAM) device featuring a FinFET or gate-all-around (GAA) design
Data Source
AI summary
A semiconductor device structure is provided. The semiconductor device structure includes a transistor which includes a source/drain feature adjoining an active region, and a gate stack over the active region. The semiconductor device structure further includes a capacitor above the transistor, the capacitor including a bottom electrode layer on the gate stack and a ferroelectric layer on the bottom electrode layer. The ferroelectric layer is made of a Hf-based dielectric material. The semiconductor device structure further includes gate spacer layers surrounding the gate stack, the bottom electrode layer and the ferroelectric layer.