Oxide Semiconductor Memory Cell Structure for Low Leakage Scaling
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Solution Overview
Problem
The integration and miniaturization of transistors with oxide semiconductors face challenges in achieving favorable electrical characteristics, low off-state current, high on-state current, low power consumption, and high productivity while maintaining data retention and high-speed data writing capabilities.
Innovation Solution
A semiconductor device design incorporating a specific structure with multiple conductors and insulators, including a metal oxide with In and elements like Al, Ga, Y, or Sn, to enhance electrical performance and integration density, and a manufacturing process that involves heat treatment and metal element addition to reduce impurities and improve channel formation regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transistors are miniaturized and highly integrated, then device density and performance increase, but electrical characteristics and reliability deteriorate
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional silicon-based semiconductors to oxide semiconductor materials (such as In-Ga-Zn-O), which fundamentally alter the electrical characteristics to achieve low off-state current and high reliability even at miniaturized dimensions. The process conditions, material compositions, and structural parameters are optimized to maintain electrical performance during miniaturization.
Solution Approach 2:
The patent employs composite material structures including stacked layers of oxide semiconductors, insulators, and conductors. Specific composite structures like the In-Ga-Zn-O-based oxide semiconductor combined with aluminum oxide insulating layers create devices that maintain electrical characteristics while enabling high integration density through compact design.
2Loss of energy
If off-state current is reduced, then power consumption decreases, but on-state current and switching performance may worsen
Solution Approach 1:
The patent utilizes parameter changes in oxide semiconductor materials to achieve a unique electrical characteristic profile where off-state current density is extremely low (≤1 aA/μm at room temperature) while on-state current is maintained through optimized material composition (In-Ga-Zn-O ratios) and device structure (channel width, length, and thickness parameters).
Solution Approach 2:
The patent applies local quality by creating different functional regions within the oxide semiconductor layer, including channel formation regions with specific compositions and insulator regions with different material properties. This allows simultaneous optimization of off-state leakage control in insulator regions and on-state current drive in channel regions.
3Reliability
If heat treatment is applied to reduce impurities, then electrical characteristics improve, but manufacturing complexity and time increase
Solution Approach 1:
The patent applies preliminary action by incorporating impurity reduction measures during the material deposition and initial processing stages, rather than relying solely on subsequent heat treatment. This includes using high-purity starting materials, controlling deposition conditions to minimize contamination, and performing in-situ treatments that combine impurity removal with device formation, thereby reducing manufacturing complexity.
Data Source
AI summary
A semiconductor device that can be highly integrated is provided.The semiconductor device includes first and second transistors and first and second capacitors. Each of the first and second transistors includes a gate insulator and a gate electrode over an oxide. Each of the first and second capacitors includes a conductor, a dielectric over the conductor, and the oxide. The first and second transistors are provided between the first capacitor and the second capacitor. One of a source and a drain of the first transistor is also used as one of a source and a drain of the second transistor. The other of the source and the drain of the first transistor is also used as one electrode of the first capacitor. The other of the source and the drain of the second transistor is also used as one electrode of the second capacitor. The channel lengths of the first and second transistors are larger than the lengths in a direction parallel to short sides of fourth and fifth conductors.