Semiconductor Capacitor Asymmetric Electrode TDDB Mitigation
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Solution Overview
Problem
Ferroelectric smoothing capacitors in semiconductor devices face a limitation in product lifetime due to time-dependent dielectric breakdown (TDDB), which is exacerbated by their larger area compared to cell capacitors, leading to shorter MTTF (Mean Time To Failure).
Innovation Solution
A semiconductor device design featuring a smoothing capacitor with a capacitor region area of at least 1000 μm² and a length-to-area ratio (L/S) of 0.4 μm⁻¹, utilizing a lamination structure of a lower electrode, ferroelectric dielectric film, and upper electrode, where the upper electrode has a narrow and elongated shape to improve film quality and extend MTTF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitor area is increased to achieve larger capacitance for smoothing capacitor function, then the capacitance is improved, but the time dependent dielectric breakdown (TDDB) becomes shorter leading to reduced reliability
Solution Approach 1:
The upper electrode is designed with an asymmetric narrow and elongated shape, creating a high circumference-to-area ratio. This asymmetric geometry allows the capacitor to achieve large area (≥1000 μm²) for sufficient capacitance while maintaining a high L/S ratio (≥0.4 μm⁻¹) that improves film quality and extends TDDB, thereby resolving the contradiction between capacitance and reliability
Solution Approach 2:
The invention changes the geometric parameters of the upper electrode by specifying a minimum area S ≥ 1000 μm² and a minimum circumference-to-area ratio L/S ≥ 0.4 μm⁻¹. These parameter changes enable the capacitor to simultaneously achieve large capacitance and improved reliability by optimizing the relationship between electrode area and circumference length
2Quantity of substance
If the capacitor area is increased to achieve larger capacitance, then the capacitance is improved, but the product lifetime is limited by TDDB of smoothing capacitor
Solution Approach 1:
The asymmetric narrow and elongated upper electrode design with high L/S ratio improves film quality across the capacitor region, which directly extends the product lifetime by reducing TDDB effects, while still maintaining the large area needed for sufficient capacitance in the smoothing capacitor
3Ease of manufacture
If a conventional capacitor structure is used, then the manufacturing process is simple, but the film quality deteriorates and MTTF is shortened
Solution Approach 1:
The invention modifies the geometric parameters of the upper electrode (area S ≥ 1000 μm² and circumference-to-area ratio L/S ≥ 0.4 μm⁻¹) which can be integrated into existing manufacturing processes. This parameter change improves film quality and extends MTTF without requiring fundamental changes to the manufacturing methodology, thus maintaining ease of manufacture while improving reliability
Data Source
AI summary
A capacitor is formed over a semiconductor substrate. The capacitor includes a lower electrode, a capacitor dielectric film and an upper electrode in this order recited, and has an area S equal to or larger than 1000 μm2 and L/S equal to or larger than 0.4 μm−1, where S is an area of a capacitor region in which the lower and upper electrodes face each other across the dielectric film, and L is a total length of a circumference line of the capacitor region.