IGZO DRAM Memory Cells for Low-Leakage Refresh Reduction
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Solution Overview
Problem
Conventional volatile memory cells, such as DRAM cells, experience sub-threshold leakage current, leading to frequent refreshing and increased power consumption, which affects battery life in portable devices and complicates memory cell density and thermal budget considerations during fabrication.
Innovation Solution
The use of indium gallium zinc oxide (IGZO) as the channel material in memory cells reduces sub-threshold leakage current, allowing for higher packing densities and less frequent refreshing, while enabling low-temperature fabrication suitable for stacked array structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional volatile memory cells are used, then the memory cell structure is simple and well-established, but sub-threshold leakage current causes frequent refreshing and increased power consumption
Solution Approach 1:
The patent changes the material parameter of the channel region from conventional silicon to indium gallium zinc oxide (IGZO), which fundamentally alters the electrical characteristics to achieve ultra-low off-state leakage current while maintaining compatibility with existing memory cell architectures
Solution Approach 2:
The patent employs a composite material approach by using IGZO (indium gallium zinc oxide) as the channel material, combining multiple elements to achieve superior electrical properties that reduce leakage current while maintaining structural compatibility with conventional memory cells
2Loss of energy
If channel material is changed to reduce leakage current, then off-state leakage current is reduced, but fabrication temperature requirements increase
Solution Approach 1:
The patent optimizes the fabrication temperature parameter by developing processes that deposit IGZO at temperatures below 300°C, fundamentally changing the thermal budget requirements while achieving the desired low leakage current characteristics
3Quantity of substance
If memory cell density is increased, then packing density improves, but thermal budget constraints during fabrication become more challenging
Solution Approach 1:
The patent changes the temperature parameter to enable low-temperature fabrication processes that are compatible with high-density memory cell arrays, allowing multiple cells to be fabricated on a single substrate without excessive thermal budgets that would constrain density
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
IGZO-based memory cells exhibit significantly reduced off-state leakage current, enabling longer refresh intervals and improved battery life in portable devices, along with increased packing density and compatibility with low-temperature fabrication processes.
Implementation Method 1
Conventional volatile memory cells, such as dynamic random access memory (DRAM) cells, may include a capacitor and a transistor... even in the 'off' state, a conventional volatile memory cell will often still undergo some flow of current from the capacitor. This off-state leakage current is known in the industry as a sub-threshold leakage current.
Data Source
AI summary
A memory cell is disclosed. The memory cell includes a transistor and a capacitor. The transistor includes a source region, a drain region, and a channel region including an indium gallium zinc oxide (IGZO, which is also known in the art as GIZO) material. The capacitor is in operative communication with the transistor, and the capacitor includes a top capacitor electrode and a bottom capacitor electrode. Also disclosed is a semiconductor device including a dynamic random access memory (DRAM) array of DRAM cells. Also disclosed is a system including a memory array of DRAM cells and methods for forming the disclosed memory cells and arrays of cells.