Semiconductor Multilayer Stack with Seed Layer for High-k Dielectric Stability
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Solution Overview
Problem
The challenge is to develop a semiconductor device with a high-k dielectric layer that has a dielectric constant of 50 or higher, which is difficult to achieve with existing materials due to the inverse proportionality of dielectric constant and energy band gap, and the instability of beryllium oxide (BeO) in ambient conditions.
Innovation Solution
A multilayer stack is used, comprising a seed layer with a rocksalt crystal structure and a high-k dielectric layer, where the high-k dielectric layer is formed using BeO with a stable rocksalt crystal structure under ambient conditions, and additional high-k dielectric layers with a strain applying layer to maintain the rocksalt structure and increase thickness without destabilizing the high dielectric constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-k material is used to increase dielectric constant, then capacitance is improved, but energy band gap decreases and leakage current increases
Solution Approach 1:
The patent employs a composite multilayer structure consisting of a seed layer and a high-k dielectric layer, both with rocksalt crystal structure. This composite approach allows achieving high capacitance through the high-k dielectric layer while the seed layer provides structural stability and controls crystal orientation, thereby managing leakage current characteristics.
2Reliability
If beryllium oxide (BeO) is used to achieve high dielectric constant, then dielectric constant is improved, but structural stability deteriorates under ambient conditions
Solution Approach 1:
The seed layer acts as an intermediary between the substrate and the high-k dielectric layer. It provides a stable rocksalt crystal structure foundation that enables the high-k dielectric layer to maintain its rocksalt structure under ambient conditions, thereby stabilizing the overall composition while preserving high dielectric constant properties.
Solution Approach 2:
The patent changes the crystal structure parameter from the unstable bulk wurtzite structure to the stable rocksalt structure through controlled deposition processes. This parameter change in crystal structure enables BeO-based materials to maintain structural stability under ambient conditions while retaining high dielectric constant.
3Reliability
If high-k dielectric layer thickness is increased to improve capacitance, then capacitance is improved, but rocksalt crystal structure stability deteriorates
Solution Approach 1:
The patent segments the high-k dielectric layer into multiple thin layers separated by strain-applying layers. This segmentation allows each thin high-k layer to maintain stable rocksalt crystal structure while the cumulative thickness provides sufficient capacitance. The strain-applying layers prevent structural degradation that would occur in a single thick layer.
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 allows for the practical application of BeO with a high dielectric constant in semiconductor devices, enabling further scaling and performance improvement while maintaining the high-k dielectric properties, preventing the formation of low dielectric constant bulk wurtzite structures.
Implementation Method 1
each of the seed layer and the high-k dielectric layer may have a rocksalt crystal structure
Implementation Method 2
the strain applying layer may be interposed between adjacent high-k dielectric layers
Data Source
AI summary
A semiconductor device may include: a first electrode; a second electrode; and a multilayer stack that is interposed between the first electrode and the second electrode and includes a seed layer and a high-k dielectric layer, wherein each of the seed layer and the high-k dielectric layer may have a rocksalt crystal structure, and wherein the high-k dielectric layer may exhibit a dielectric constant (k) of fifty (50) or higher.