# US 2020/0391997 A1 · Mems cavity with non-contaminating seal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0391997 A1 - Document ID: US20200391997A1 - Status: Published application - Kind: A1 - Application number: 16/880,209 - Filed: 2020-05-21 - Published: 2020-12-17 - Earliest claimed: 2017-02-14 - Assignees: SiTime Corporation - Applicants: SiTime Corporation - Inventors: Michael Julian Daneman; Charles I. Grosjean; Paul M. Hagelin - Web page: https://patentgrep.com/patent/US20200391997A1 ## CPC - B81C 1/00293: {maintaining a controlled atmosphere with processes not provided for in B81C1/00285} - B81B 7/0041: {maintaining a controlled atmosphere with techniques not provided for in B81B7/0038} - B81B 2201/0271: Resonators; ultrasonic resonators - B81B 2201/032: Bimorph and unimorph actuators, e.g. piezo and thermo - B81C 2203/0145: Hermetically sealing an opening in the lid - B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01) - B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00) ## Abstract A semiconductor device includes a first silicon layer disposed between second and third silicon layers and separated therefrom by respective first and second oxide layers. A cavity within the first silicon layer is bounded by interior surfaces of the second and third silicon layers, and a passageway extends through the second silicon layer to enable material removal from within the semiconductor device to form the cavity. A metal feature is disposed within the passageway to hermetically seal the cavity. ## Claims ### Claim 1 (canceled) ### Claim 2 A method of fabricating a semiconductor device, the method comprising: forming a microelectromechanical systems (MEMS) structure including a body, an electrode to perform at least one of exciting or sensing motion of the body, and an oxide adjacent the body; forming a lid layer over MEMS structure; wherein the method further includes forming at least one oxide-release vent through the lid layer, and etching the oxide through the at least one oxide-release vent so as to thereby free at least part of the body to move; forming a conductive path through the lid layer to the electrode; and sealing the at least one oxide-release vent; wherein the forming of the conductive path and the sealing of the at least one oxide-release vent each comprise a common fabrication step in which a material is used to plug the at least one oxide-release vent and in which the material is also used to form at least part of the conductive path to the electrode. ### Claim 3 (depends on 2) The method of claim 2, wherein the MEMS structure comprises a piezoelectric material layer and wherein the common fabrication step comprises a low-temperature deposition process which deposits the material so as to plug the at least one oxide-release vent and to form the at least part of the conductive path using an ambient temperature of no more than four hundred degrees Centigrade. ### Claim 4 (depends on 3) The method of claim 3, wherein the low-temperature deposition process comprises sputtering a metal material, and wherein the metal material comprises at least one of aluminum, copper, tungsten, or an alloy thereof. ### Claim 5 (depends on 2) The method of claim 2, wherein the material comprises a non-metal. ### Claim 6 (depends on 5) The method of claim 5, wherein the non-metal comprises a silicon-based substance. ### Claim 7 (depends on 2) The method of claim 2, wherein forming the M EMS structure comprises forming each vent of the at least one oxide-release vent so as to feature at least one bend, so as to not present a line-of-sight access between a cavity formed by release of oxide and an external surface of the lid layer. ### Claim 8 (depends on 2) The method of claim 2, wherein forming the MEMS structure comprises forming a MEMS resonator. ### Claim 9 (depends on 8) The method of claim 8, wherein the body comprises a beam having a first end and a second end, and wherein etching the at least one oxide comprises etching oxide adjacent the first end but not the second end, the first end thereby being free to vibrate, and the second end tethering the body to the semiconductor device. ### Claim 10 (depends on 2) The method of claim 2, further comprising fabricating a contact, the contact in conductive relationship with the material in the at least one oxide-release vent, the contact to electrically couple the material in the at least one oxide-release vent to ground. ### Claim 11 (depends on 2) The method of claim 2, wherein forming the lid layer comprises epitaxially growing silicon crystal to form the lid layer. ### Claim 12 (depends on 2) The method of claim 2, wherein: forming the MEMS structure comprises patterning a silicon layer of a silicon on-insulator wafer, and doping a region the patterned silicon layer with an n-type dopant to have a dopant concentration of at least 1E19 atoms per cubic centimeter, the electrode to be formed by the doped region, depositing the oxide above the doped region, and forming the body above the oxide layer, the body having a piezoelectric material layer; and the forming of the conductive path through the lid layer to the electrode comprises forming a trench extending through the lid layer, in a manner that extends to the doped region. ### Claim 13 A method of fabricating a semiconductor device, the method comprising: patterning a silicon layer of a silicon on-oxide wafer to form a region; doping the region with an n-type dopant, such that the region has a dopant concentration of at least 1E19 atoms per cubic centimeter; forming a first layer of oxide above the doped region; forming a body above the oxide, the body having at least one layer of a piezoelectric substance; forming a second layer of oxide above the body; forming a lid layer over the second layer of oxide; forming at least one oxide-release vent through the lid layer; etching part of the first layer of oxide and part of the second layer of oxide in a vicinity adjacent at least part of the body, through the at least one oxide-release vent, so as to thereby release the at least part of the body such that it is free to move; forming a trench extending through the lid layer to the doped region; and filling at least part of the trench with a material and sealing the at least one oxide-release vent with the material in a common fabrication step; wherein the method further comprises forming a microelectromechanical systems (MEMS) structure, the MEMS structure including the body and an electrode to perform at least one of exciting or sensing motion of the body, wherein the electrode comprises the doped region; wherein the material in the trench is to form at least part of a conductive path extending from an external surface of the lid layer to the electrode. ### Claim 14 (depends on 13) The method of claim 13, wherein the common fabrication step comprises a low-temperature deposition process which deposits the material so as to plug the at least one oxide-release vent and to form the at least part of the conductive path using an ambient temperature of no more than four hundred degrees Centigrade. ### Claim 15 (depends on 14) The method of claim 14, wherein the low-temperature deposition process comprises performing at least one of sputtering a metal material, evaporating a metal material, or using chemical vapor deposition to deposit a metal material, and wherein the metal material comprises at least one of aluminum, copper, tungsten, or an alloy thereof. ### Claim 16 (depends on 13) The method of claim 13, wherein the material comprises a non-metal. ### Claim 17 (depends on 16) The method of claim 16, wherein the non-metal comprises a conductive, silicon-based substance. ### Claim 18 (depends on 13) The method of claim 13, wherein forming the MEMS structure comprises forming each vent of the at least one oxide-release vent so as to feature at least one bend, so as to not present a line-of-sight access between a cavity formed by release of oxide from the first and second layers and an external surface of the lid layer. ### Claim 19 (depends on 13) The method of claim 13, wherein the MEMS structure is a MEMS resonator. ### Claim 20 (depends on 19) The method of claim 19, wherein the body comprises a beam having a first end and a second end, and wherein etching the first and second layers comprises etching oxide adjacent the first end but not the second end, the first end thereby being free to vibrate, and the second end tethering the body to the semiconductor device. ### Claim 21 (depends on 13) The method of claim 13, further comprising fabricating a contact to be in conductive relationship with the material in the at least one oxide-release vent, the contact to electrically couple the material in the at least one oxide-release vent to ground. ### Claim 22 (depends on 13) The method of claim 13, wherein forming the lid layer comprises epitaxially growing single-crystal silicon to form the lid layer. ### Claim 23 A method of fabricating a semiconductor device, the method comprising: forming a microelectromechanical systems (MEMS) structure including a body, an electrode to perform at least one of exciting or sensing motion of the body, and an oxide adjacent the body; forming a lid layer over MEMS structure; wherein the MEMS structure is a MEMS resonator and the body has a first end free to vibrate and a second end to tether the body to the semiconductor device; wherein the method further includes forming at least one oxide-release vent through the lid layer, and etching the oxide from an area adjacent the first end, through the at least one oxide-release vent, so as to thereby free the first end of the body to move; forming a conductive path through the lid layer to the electrode; and sealing the at least one oxide-release vent; wherein the forming of the conductive path and the sealing of the at least one oxide-release vent each comprise a common fabrication step in which a material is used to plug the at least one oxide-release vent and in which the material is also used to form at least part of the conductive path to the electrode.