US 12,269,734 B2
Microelectromechanical microphone with membrane trench reinforcements and method of fabrication
Pirmin Rombach, Kongens Lyngby (DK); Kurt Rasmussen, Herlev (DK); Dennis Mortensen, Bagsvard (DK); Cheng-Yen Liu, Søborg (DK); Morten Ginnerup, Kongens Lyngby (DK); Jan Ravnkilde, Hedehusene (DK); and Jotaro Akiyama, Tokyo (JP)
Assigned to TDK Corporation, Tokyo (JP)
Filed by TDK Corporation, Tokyo (JP)
Filed on Dec. 20, 2022, as Appl. No. 18/068,908.
Application 18/068,908 is a continuation in part of application No. 17/308,340, filed on May 5, 2021, granted, now 11,746,001.
Claims priority of provisional application 63/066,652, filed on Aug. 17, 2020.
Claims priority of provisional application 63/020,216, filed on May 5, 2020.
Prior Publication US 2023/0118429 A1, Apr. 20, 2023
Int. Cl. B81C 1/00 (2006.01); B81B 3/00 (2006.01)
CPC B81C 1/00158 (2013.01) [B81B 3/0021 (2013.01); B81B 2201/0257 (2013.01); B81B 2203/0315 (2013.01); B81B 2203/033 (2013.01); B81B 2203/0353 (2013.01); B81B 2203/04 (2013.01); B81B 2207/11 (2013.01); B81C 2201/0132 (2013.01); B81C 2201/014 (2013.01); B81C 2201/0174 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A method of fabricating a Microelectromechanical System (MEMS) microphone, comprising:
depositing, on a frontside of a wafer, a first oxide layer over a silicon nitride thin film and over and adjacent the wafer, wherein the silicon nitride thin film is disposed over the wafer;
depositing a membrane protection layer over the first oxide layer between a first side of a first cavity formed in the wafer and a second side of a second cavity formed in the wafer;
depositing a second oxide layer over and adjacent the membrane protection layer;
depositing a first membrane nitride layer over the second oxide layer;
depositing a membrane polysilicon layer over the first membrane nitride layer;
depositing a second membrane nitride layer over the membrane polysilicon layer;
depositing a third oxide layer over the second membrane nitride layer
depositing a fourth oxide layer over the third oxide layer and opening a lateral etch stop;
depositing a backplate nitride underlayer over and adjacent the fourth oxide layer and the lateral etch stop;
depositing a first backplate polysilicon layer over and adjacent the backplate nitride underlayer;
depositing a fifth oxide layer at respective portions of the first backplate polysilicon layer and filling the lateral etch stop;
depositing a second backplate polysilicon layer over the fifth oxide layer and the first backplate polysilicon layer;
depositing metal over the second backplate polysilicon layer and over the first backplate polysilicon layer;
defining a cavity on a backside of the wafer, resulting in a defined structure;
performing a first release of the defined structure;
removing the membrane protection layer;
performing a second release of the defined structure; and
depositing a self-assembled monolayer coating.