Method for integrating complementary metal-oxide-semiconductor (CMOS) devices with microelectromechanical systems (MEMS) devices using a flat surface above a sacrificial layer

A method for manufacturing an integrated circuit (IC), the method comprising:

• forming a back-end-of-line (BEOL) interconnect structure and a sacrificial layer overlying a semiconductor substrate, wherein the BEOL interconnect structure comprises a dielectric layer, and further comprises multiple wires and multiple vias alternatingly stacked in the dielectric layer, and wherein the sacrificial layer is in the dielectric layer;
• performing a planarization into the dielectric layer and/or the sacrificial layer to form a planarized surface;
• forming a microelectromechanical systems (MEMS) structure overlying the sacrificial and dielectric layers, directly on the planarized surface, wherein the forming of the MEMS structure comprises:
• depositing a first MEMS layer over and directly contacting the planarized surface;
• forming an inter-device via extending through the first MEMS layer and the planarized surface to a top wire of the BEOL interconnect structure;
• and
• forming a first-level electrode on the first MEMS layer, wherein the first-level electrode directly contacts the inter-device via and is electrically coupled to the top wire of the BEOL interconnect structure through the inter-device via;
• and
• removing the sacrificial layer after the forming of the MEMS structure to form a cavity in place of the sacrificial layer.

A method for manufacturing an integrated circuit (IC), the method comprising:

• forming an interconnect structure covering a substrate, wherein the interconnect structure comprises a dielectric layer, and further comprises multiple wires and multiple vias alternatingly stacked in the dielectric layer;
• forming a sacrificial layer sunken into the dielectric layer and having a top surface that is flush with a top surface of the dielectric layer;
• forming a microelectromechanical systems (MEMS) structure on the top surfaces of the sacrificial and dielectric layers, wherein the forming of the MEMS structure comprises:
• depositing a first piezoelectric layer on the top surfaces respectively of the sacrificial layer and the dielectric layer;
• forming an inter-device via extending through the first piezoelectric layer to a top wire of the interconnect structure;
• and depositing a second piezoelectric layer covering the inter-device via and the first piezoelectric layer;
• and
• removing the sacrificial layer after the forming of the MEMS structure to form a cavity in place of the sacrificial layer.