Deformation Bonded and Hermetically Sealed Vacuum MEMS Cells with Stopping Layer

A method of manufacturing a micro-vacuum cell comprising at least one vacuum enclosure, the method comprising:

• providing a lid of a first material, the first material having a first coefficient of thermal expansion;
• providing a base of a second material, the second material having a second coefficient of thermal expansion, where the vacuum enclosure is to be formed above a portion of the base;
• forming around said portion of the base a first part of a cold weld compression seal, and forming on a surface of the lid a corresponding second part of said cold weld compression seal;
• baking the lid and the base under vacuum for a predetermined time;
• without breaking the vacuum, letting the lid and the base cool down, then sligning the first and second parts of the cold weld compression seal and pressing the lid and the base together until a predetermined pressure is reached;
• wherein said first and second parts of the cold weld compression seal respectively comprise one of a peripheral knife-edge wall and a seal layer;
• the peripheral knife-edge wall being made of a first harder metal having a foot and a tip, the foot being attached to a first surface of one of the lid and the base, said knife-edge wall being coated with a first softer metal, such that the tip of the knife-edge wall penetrates the seal layer, made of a second softer metal and arranged on a second surface of the other of the lid and the base, and forms a compression bond with the seal layer when the lid and the base are pressed together until the predetermined pressure is reached;
• and wherein:
• the knife-edge wall has a first height in a first direction normal to the first surface;
• the seal layer has a second height in said first direction;
• and
• at least one stop structure having a third height in said first direction has a foot attached to the first surface and a tip that forms a compression bond with the seal layer when the lid and the base are pressed together until the predetermined pressure is reached, wherein the third height is smaller than the first height and the second height is larger than a difference of the first and third height.

A micro-vacuum cell comprising at least one vacuum enclosure, the vacuum enclosure comprising:

• a lid of a first material;
• a base of a second material, wherein the vacuum enclosure is formed above a portion of the base;
• and
• a thermocompression seal attaching the lid to the base along a periphery of said portion of the base;
• wherein the thermocompression seal comprises a peripheral knife-edge wall of a first harder metal having a foot and a tip, the foot being attached to a first surface of one of the lid and the base, said knife-edge wall being coated with a first softer metal, and the tip of the knife-edge wall penetrating a seal layer of a second softer metal, arranged on a second surface of the other of the lid and the base, forming a compression bond between the peripheral knife-edge wall and the seal layer;
• and wherein:
• the knife-edge wall has a first height in a first direction normal to the first surface;
• the seal layer has a second height in said first direction;
• and at least one stop structure having a third height in said first direction has a foot attached to the first surface and a tip that forms a compression bond with the seal layer, wherein the third height is smaller than the first height and the second height is larger than a difference of the first and third height.

A method of manufacturing a micro-vacuum cell comprising at least one vacuum enclosure, the method comprising:

• providing a lid of a first material;
• providing a base of a second material, wherein the vacuum enclosure is to be formed above a portion of the base;
• forming around said portion of the base a first part of a thermocompression seal, and forming on a surface of the lid a corresponding second part of said thermocompression seal;
• baking the lid and the base under vacuum for a predetermined time;
• without breaking the vacuum, letting the lid and the base cool down to a thermocompression temperature, then aligning the first and second parts of the thermocompression seal and pressing the lid and the base together until a predetermined pressure is reached;
• wherein said first and second parts of the thermocompression seal respectively comprise one of a peripheral knife-edge wall and a seal layer;
• the peripheral knife-edge wall being made of a first harder metal having a foot and a tip, the foot being attached to a first surface of one of the lid and the base, said knife-edge wall being coated with a first softer metal, such that the tip of the knife-edge wall penetrates the seal layer, made of a second softer metal and arranged on a second surface of the other of the lid and the base, and forms a compression bond with the seal layer when the lid and the base are pressed together until the predetermined pressure is reached;
• and wherein:
• the knife-edge wall has a first height in a first direction normal to the first surface;
• the seal layer has a second height in said first direction;
• and
• at least one stop structure having a third height in said first direction has a foot attached to the first surface and a tip that forms a compression bond with the seal layer when the lid and the base are pressed together until the predetermined pressure is reached, wherein the third height is smaller than the first height and the second height is larger than a difference of the first and third height.