Method of forming electrode for saw device
View Patent ↗A method of forming an electrode for a surface acoustic wave (SAW) device comprises the steps of forming an alloy film ( 32 ) made of aluminum (Al) and magnesium (Mg) on a substrate ( 31 ) and selectively etching the alloy film ( 32 ) by using a gaseous mixture composed of BCl 3 , Cl 2 , and N2 to form the electrode such that the electrode has at least one sidewall polymer film ( 33 ). The method controls the production of hillocks and voids to provide high withstand voltage.
1. A method of forming an SAW electrode for a surface acoustic wave (SAW) device, comprising the steps of:
providing a substrate;
selecting, as a material of said SAW electrode, an alloy made of aluminum (Al) and magnesium (Mg) to form an alloy film on said substrate; and
selectively etching said alloy film to form said SAW electrode such that said SAW electrode has at least one sidewall film.
2. The method according to claim 1 , wherein said etching is performed with a gaseous mixture composed of Bl3, Cl2, and N2.
3. The method according to claim 1 , wherein said alloy film contains 1-10 weight percent of Mg.
4. The method according to claim 1 , which further comprises the step of forming a film of chromium (Cr) on said substrate before the step of forming said alloy film so that said alloy film is formed on said Cr film.
5. The method according to claim 4 , wherein said Cr film is selectively etched by using said alloy film as a mask.
6. The method according to claim 4 , wherein said Cr and alloy films are alternately formed a plurality of times.
7. The method according to claim 1 , wherein said etching is performed by applying a high-frequency voltage.
8. The method according to claim 1 , wherein a content of Mg in said alloy film is changed so that said electrode has a different shape.
9. The method according to claim 2 , wherein said N 2 gas contained in said gaseous mixture has a throughput of 5-10 sccm.