Crystalline AlN Layer Growth Using MX2 Bond Conversion
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Solution Overview
Problem
Existing methods for manufacturing thick crystalline layers of aluminum nitride (AlN) greater than 200 nm often result in low crystalline quality and are prone to delamination, which is unsatisfactory for applications such as power electronic devices and acoustic filters.
Innovation Solution
A method involving the use of a substrate with a surface film made of a dichalcogenide of a transition metal, where metallic elements are diffused into the surface film through the grain boundaries of a polycrystalline AlN film, triggering an oxidation-reduction reaction to transform van der Waals bonds into covalent bonds, thereby stabilizing the crystalline layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a thick crystalline layer of aluminum nitride AlN (greater than 200 nm) is formed directly on a dielectric layer, then the thickness requirement for acoustic filters is met, but the crystalline quality is low and delamination occurs
Solution Approach 1:
The patent introduces a surface film made of transition metal dichalcogenide (MX2) as an intermediary layer between the dielectric layer and the crystalline AlN layer. This intermediate layer acts as a nucleation layer that improves crystalline quality and prevents delamination, while allowing the formation of thick AlN layers greater than 200 nm. The MX2 film mediates the interface between the dielectric substrate and the crystalline layer, resolving the contradiction between thickness and reliability.
2Reliability
If a surface film of transition metal dichalcogenide MX2 is used as a nucleation layer, then the crystalline quality of AlN layer is improved, but the van der Waals bonds in MX2 are weak and may lead to delamination
Solution Approach 1:
The patent changes the bonding parameter of the MX2 surface film by diffusing metallic elements through the grain boundaries of the polycrystalline AlN layer. This diffusion process transforms the weak van der Waals bonds in the MX2 film into stronger covalent bonds, thereby maintaining high crystalline quality while preventing delamination. The metallic elements act as a means to change the bonding strength parameter of the surface film.
3Strength
If metallic elements are diffused into the MX2 surface film through grain boundaries, then covalent bonds are formed and delamination is prevented, but additional process steps are required
Solution Approach 1:
The patent performs the diffusion of metallic elements into the MX2 surface film during the growth process of the polycrystalline AlN layer, rather than as a separate post-processing step. By incorporating the bond-strengthening action into the existing layer formation process, the patent achieves strong covalent bonding in the MX2 film without significantly increasing the overall process complexity. The preliminary diffusion action occurs concurrently with the AlN layer growth.
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 method effectively reduces the risk of delamination and enhances the crystalline quality of thick AlN layers, enabling the manufacture of high-quality components such as acoustic filters.
Implementation Method 1
diffusing metallic elements into the surface film, through the grain boundaries of the polycrystalline aluminum nitride AlN film
Implementation Method 2
the metallic elements being chosen to react chemically with MX 2 by an oxidation-reduction reaction so as to transform the van der Waals bonds into covalent bonds
Implementation Method 3
the surface film comprising a set of monolayers linked together by van der Waals bonds
Implementation Method 4
transform the van der Waals bonds into covalent bonds
Data Source
Figure 1~2
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Figure 5~6
AI summary
This method comprises the steps: a) using a substrate (1) comprising a surface film (2) made of a dichalcogenide of a transition metal, denoted MX2, where “M” denotes a transition metal and “X” denotes a chalcogen; the surface film (2) comprising a set of monolayers linked together by van der Waals bonds; b) forming a film (3) of polycrystalline aluminum nitride AlN, having grain boundaries, on the surface film (2); c) diffusing metallic elements (E) into the surface film (2), through the grain boundaries of the film (3) of polycrystalline aluminum nitride AlN, the metallic elements (E) being chosen to react chemically with MX2 by an oxidation-reduction reaction so as to transform the van der Waals bonds into covalent bonds; d) forming a crystalline layer on the polycrystalline aluminum nitride AlN film (3) after step c).