Microelectronic mechanical system and methods
First Claim
1. A method of making a release structure from a multi-layer structure comprising first and second etch-stop layers, a first sacrificial layer between the first and the second etch-stop layers, a cap layer and a second sacrificial layer between the second etch-stop layer and the cap layer with at least one access trench, wherein the second etch-stop layer includes a release feature, the method comprising:
- a. creating an access opening in the cap layer, the cap layer serving as a passivation layer;
b. etching portions of the first and the second sacrificial layers through the at least one access opening to form the release structure;
c. sealing the at least one access opening with a sealing material to form a predetermined environment comprising one of a plurality of noble gas environments and to package a device including the release structure.
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Abstract
The current invention provides for encapsulated release structures, intermediates thereof and methods for their fabrication. The multi-layer structure has a capping layer, that preferably comprises silicon oxide and/or silicon nitride, and which is formed over an etch resistant substrate. A patterned device layer, preferably comprising silicon nitride, is embedded in a sacrificial material, preferably comprising polysilicon, and is disposed between the etch resistant substrate and the capping layer. Access trenches or holes are formed in to capping layer and the sacrificial material are selectively etched through the access trenches, such that portions of the device layer are release from sacrificial material. The etchant preferably comprises a noble gas fluoride NGF2x (wherein Ng=Xe, Kr or Ar: and where x=1, 2 or 3). After etching that sacrificial material, the access trenches are sealed to encapsulate released portions the device layer between the etch resistant substrate and the capping layer. The current invention is particularly useful for fabricating MEMS devices, multiple cavity devices and devices with multiple release features.
911 Citations
20 Claims
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1. A method of making a release structure from a multi-layer structure comprising first and second etch-stop layers, a first sacrificial layer between the first and the second etch-stop layers, a cap layer and a second sacrificial layer between the second etch-stop layer and the cap layer with at least one access trench, wherein the second etch-stop layer includes a release feature, the method comprising:
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a. creating an access opening in the cap layer, the cap layer serving as a passivation layer;
b. etching portions of the first and the second sacrificial layers through the at least one access opening to form the release structure;
c. sealing the at least one access opening with a sealing material to form a predetermined environment comprising one of a plurality of noble gas environments and to package a device including the release structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of making a MEMS device comprising:
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a. forming a first sacrificial layer on a substrate;
b. forming a MEM feature comprising an etch resistant material over the first sacrificial layer, the MEM feature having at least one gap therein;
c. forming a second sacrificial layer on the MEM feature;
d. forming a capping layer over the second sacrificial layer, the capping layer serving as a passivation layer;
e. providing at least one access opening through the capping layer exposing a portion of the first sacrificial layer therebelow;
f. etching the first and the second sacrificial layers through the at least one access trench to release a portion of the MEM feature from the first and the second sacrificial layers; and
g. sealing the at least one access opening with a sealing material to form a predetermined environment comprising one of a plurality of noble gas environments and to package the MEMS device. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification