MEMS device with integral packaging

• US 20050168306A1
• Filed: 03/23/2005
• Published: 08/04/2005
• Est. Priority Date: 11/29/2000
• Status: Abandoned Application

• Current Assignee: Ji-Hai Xu, Michael B. Cohn
• Original Assignee: Ji-Hai Xu, Michael B. Cohn
• Inventors: Cohn, Michael B., Xu, Ji-Hai
• Application Number:
  US11/088,411
• Publication Number:
  US 20050168306A1
• Time in Patent Office: Days
• US Class Current: 335/78
• CPC Class Codes: B81B 2201/018 Switches not provided for in B81B2201/014 - B81B2201/016
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2207/093 Conductive package seal
• CPC Class Codes: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: B81C 1/00357 involving bonding one or several substrates on a non-temporary support, e.g. another substrate
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: B81C 2203/0109 Bonding an individual cap on the substrate
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: B81C 3/001 Bonding of two components
• CPC Class Codes: H01H 2059/0018 Special provisions for avoiding charge trapping, e.g. insulation layer between actuating electrodes being permanently polarised by charge trapping so that actuating or release voltage is altered
• CPC Class Codes: H01H 2059/0072 with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A MEMS device and method of making same is disclosed. In one embodiment, a micro-switch includes a base assembly comprising a movable structure bearing a contact pad. The base assembly is wafer-scale bonded to a lid assembly comprising an activator and a signal path. The movable structure moves within a sealed cavity formed during the bonding process. The signal path includes an input line and an output line separated by a gap, which prevents signals from propagating through the micro-switch when the switch is deactivated. In operation, a signal is launched into the signal path. When the micro-switch is activated, a force is established by the actuator, which pulls a portion of the movable structure upwards towards the gap in the signal path, until the contact pad bridges the gap between the input line and output line, allowing the signal to propagate through the micro-switch. Prior to bonding, the MEMS structures are annealed on a first wafer and the conductive traces and other metals are annealed on a second wafer to allow each wafer to be processed separately using different processes, e.g., different annealing temperatures.

Claims

1. A micro-switch, comprising:

a first substrate and a second substrate bonded together to form a cavity;

on the first substrate, at least one signal path that runs from inside the cavity to outside the cavity at two locations; and

at least one movable structure on the second substrate, said movable structure comprising at least one conductive contact area, wherein at least one portion of said movable structure is inside said cavity, and the movable structure is moved in response to an attractive force provided by an actuator on the first substrate, wherein a state of electrical contact of said micro-switch is changed by moving said movable structure.

4. The micro-switch of claim 1, wherein said force is provided from an actuator selected from a list of actuators consisting of:

electrostatic, electromagnetic, thermal, electro-thermal, and shape-memory alloy.

5. The micro-switch of claim 1, wherein the electrical contact is selected from a list of electrical contacts consisting of:

metal contact, capacitive, and shunt.

17. The micro-switch of claim 1, wherein at least one of said first substrate and said second substrate includes at least one mechanical stop for bonding.

18. The micro-switch of claim 1, wherein said movable structure comprises at least one layer of a material selected from a list of materials consisting of:

silicon, polysilicon, gold, silicon nitride, silicon oxynitride, nickel, silicon oxide and aluminum.

32. The micro-switch of claim 1, wherein said cavity is a hermetic cavity sealed by at least one seal ring.

33. The micro-switch of claim 32, wherein said seal ring is at least 5 microns wide.

34. The micro-switch of claim 32, wherein said seal ring further comprises metal layers deposited on said first substrate and said second substrate before bonding.

35. The micro-switch of claim 34, wherein said metal layers include a deformable metal deposited on said first substrate and said second substrate before bonding.

37. The micro-switch of claim 1, wherein said movable structure further comprises at least one layer of silicon, and at least one state of electrical contact of the micro-switch results from physical contact between said at least one conductive contact area and at least one portion of said first substrate.

39. The micro-switch of claim 37, wherein said at least one conductive contact area is in electrical contact with said at least one signal path on said first substrate through at least one conductive structure bonded to said first substrate.

66. The micro-switch of claim 1, wherein said micro-switch further comprises at least one getter.

67. The micro-switch of claim 1, wherein at least one layer of said movable structure comprises a part of a top silicon layer on a silicon-on-insulator substrate.

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68. A micro-switch, comprising:

a first substrate and a second substrate bonded together to form a cavity using gold thermocompression bonding;

on the first substrate, at least one movable structure, said movable structure comprising at least one conductive contact area, wherein at least one portion of said movable structure is inside said cavity, said movable structure being moved in response to a magnetic force, wherein a state of electrical contract of said micro-switch is changed by moving said movable structure and wherein said movable structure is a seesaw structure; and

one or more signal paths that run from inside the cavity to outside the cavity.

69. The micro-switch of claim 68, wherein said gold thermocompression bonding further comprises heatless bonding of said first substrate and said second substrate.

70. The micro-switch of claim 68, wherein said cavity is a hermetic cavity.

71. The micro-switch of claim 68, wherein said cavity is sealed by at least one seal ring that is at least 5 microns wide.

72. The micro-switch of claim 68, wherein said gold thermocompression bonding is performed below 400 degrees Celsius.

73. The micro-switch of claim 68, wherein said gold thermocompression bonding is performed below 300 degrees Celsius during bonding.

74. The micro-switch of claim 68, wherein said gold thermocompression bonding bonds more than one micro-switch at a time.

75. A micro-switch, comprising:

a first substrate and a second substrate bonded together to form a cavity using gold thermocompression bonding;

on the first substrate, at least one movable structure, said movable structure comprising at least one conductive contact area, wherein at least one portion of said movable structure is inside said cavity, said movable structure being moved in response to a thermal actuator, wherein a state of electrical contract of said micro-switch is changed by moving said movable structure; and

one or more signal paths that run from inside the cavity to outside the cavity.

76. A micro-switch, comprising:

a first substrate and a second substrate bonded together to form a cavity using gold thermocompression bonding;

on the first substrate, at least one movable structure, said movable structure comprising at least one capacitive contact area, wherein at least one portion of said movable structure is inside said cavity, said movable structure being moved in response to an electrostatic force, wherein a state of electrical contract of said micro-switch is changed by moving said movable structure and wherein said movable structure is a membrane; and

one or more signal paths that run from inside the cavity to outside the cavity.