Doped-AlN Film Pinning Layers for Conical Defect Reduction
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Solution Overview
Problem
Conventional methods for manufacturing aluminum nitride films fail to effectively minimize conical defects, leading to misoriented grains that degrade piezoelectric performance and increase dielectric loss, particularly in RF filters and 5G technologies.
Innovation Solution
The use of alternating pinning layers and doped-AlN layers with dopants such as Sc, Y, Hf, Mg, Zr, and Cr to pin the doped-AlN layers to a c-axis orientation, reducing the occurrence of conical defects and enhancing crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional process-tuning techniques (gas ratios, temperature, RF bias) are used during deposition, then the manufacturing process is simple and easy to control, but the concentration of conical defects increases significantly
Solution Approach 1:
The film is divided into alternating pinning layers and doped-AlN layers, where each pinning layer acts as an independent orientation anchor. This segmentation allows each layer to maintain c-axis orientation independently, preventing the accumulation of conical defects throughout the entire film thickness.
Solution Approach 2:
Pinning layers serve as intermediary structures between the substrate and the doped-AlN layers. These intermediary pinning layers provide continuous orientation guidance, ensuring that each doped-AlN layer maintains proper c-axis alignment regardless of the overall film thickness.
2Reliability
If film thickness is increased to achieve desired performance, then the piezoelectric performance improves, but the bottom electrode lattice becomes less effective at pinning doped-AlN layers, leading to increased conical defects
Solution Approach 1:
Pinning layers are periodically inserted throughout the film structure in advance to establish and maintain orientation. These preliminary orientation anchors ensure that each subsequent doped-AlN layer is properly oriented from the outset, preventing the degradation of crystalline orientation that occurs in thick films without intermediate pinning structures.
3Stress or pressure
If stress relaxation occurs in thick films, then the mechanical stress is relieved, but the doped-AlN layers and grains develop crystalline orientation other than c-axis, increasing conical defects
Solution Approach 1:
Pinning layers are strategically placed throughout the film structure to provide continuous orientation guidance before stress-induced misorientation can occur. These pinning layers act as preventive measures, cushioning against the development of conical defects by maintaining lattice alignment even when stress relaxation occurs in thick films.
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 significantly reduces the concentration of conical defects, improving the crystalline orientation and piezoelectric performance of films and devices by maintaining a high number of grains with a c-axis orientation, thereby enhancing the reliability of RF filters and 5G communications.
Implementation Method 1
the pinning layers pin the doped-AlN layers to a c-axis orientation
Implementation Method 2
the ability of a bottom electrode lattice to pin doped-AlN layers to the same orientation becomes limited
Data Source
AI summary
Doped-aluminum nitride (doped-AlN) films and methods of manufacturing doped-AlN films are disclosed. Some methods comprise forming alternating pinning layers and doped-AlN layers including a dopant selected from the group consisting of Sc, Y, Hf, Mg, Zr and Cr, wherein the pinning layers pin the doped-AlN layers to a c-axis orientation. Some methods include forming a conducting layer including a material selected from the group consisting of Mo, Pt, Ta, Ru, LaNiO3 and SrRuO3. Some methods include forming a thermal oxide layer having silicon oxide on a silicon substrate. Piezoelectric devices comprising the doped-AlN film are also disclosed.