BONDED WAFER STRUCTURE HAVING CAVITIES WITH LOW PRESSURE AND METHOD FOR FORMING

摘要

A multi-wafer structure is formed by forming a cavity in a cap wafer and forming a first seal material around the cavity. A collapsible standoff structure is formed around the cavity. A movable mass is formed in a device wafer. A second seal material is formed around the movable mass. The first seal material and the second seal material are of materials that are able to form a eutectic bond at a eutectic temperature. The cap wafer and the device wafer are arranged so that the first and second seals are aligned but separated by the collapsible standoff structure. Gas is evacuated from the cavity at a temperature above the eutectic temperature using a low pressure. The temperature is lowered, the cap and device wafer are pressed together, and the temperature is raised above the eutectic temperature to form a eutectic bond with the first and second seal materials.

主权项

1. A method of forming a multi-wafer structure using cap wafer and a device wafer each having a plurality of die, comprising:
forming a cavity in a die of the cap wafer; forming a first seal material around the cavity; forming a collapsible standoff structure around the cavity; forming a movable mass in a die of the device wafer; forming a second seal material around the movable mass that is alignable to the first seal material, wherein the first seal material and the second seal material are of materials that are able to form a eutectic bond at a eutectic temperature that is below the melting temperature of each of the first and second seal materials; arranging the cap wafer and the device wafer so that the first and second seals are aligned but separated by the collapsible standoff structure; performing an evacuation of gas from the cavity at a temperature above the eutectic temperature using a low pressure; after sufficient time to provide the evacuation of gas and while maintaining the low pressure, reducing the temperature so that the first and second seal materials are below the eutectic temperature; pressing the cap wafer and device wafer together with sufficient force to cause the first and second seal materials to be in contact; and raising the temperature of the first and second seal materials above the eutectic temperature to form the eutectic bond between the first and second seal materials.