# US 2019/0169023 A1 · Method for Forming Hermetic Seals in MEMS Devices > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0169023 A1 - Document ID: US20190169023A1 - Status: Published application - Kind: A1 - Application number: 15/829,314 - Filed: 2017-12-01 - Published: 2019-06-06 - Earliest claimed: 2017-12-01 - Assignees: Eagle Technology, LLC - Applicants: Eagle Technology, LLC - Inventors: Arlynn W. SMITH; Dan CHILCOTT - Web page: https://patentgrep.com/patent/US20190169023A1 ## CPC - B81C 1/00269: {Bonding of solid lids or wafers to the substrate} - B32B 3/30: characterised by a layer formed with recesses or projections, e.g. {hollows, grooves, protuberances, ribs (apertured layer B32B3/266; layer with cavities or internal voids B32B3/26)} - B32B 7/12: using interposed adhesives or interposed materials with bonding properties - B32B 9/04: comprising such {particular} substance as the main or only constituent of a layer, {which is} next to another layer of {the same or of} a {different material (next to a glass layer B32B17/06; layered products with at least two ceramic layers composed mainly of ceramic B32B18/00)} - B32B 17/06: comprising glass as the main or only constituent of a layer, next to another layer of a specific {material} - B32B 37/12: characterised by using adhesives - B32B 37/18: involving the assembly of discrete sheets or panels only - B81B 7/0041: {maintaining a controlled atmosphere with techniques not provided for in B81B7/0038} - B81C 3/001: {Bonding of two components} - C03C 27/046: {of metals, metal oxides or metal salts only} - G02B 23/12: with means for image conversion or intensification - B32B 2313/00: Elements other than metals - B32B 2315/08: Glass - B32B 2457/00: Electrical equipment - B81B 2201/047: Optical MEMS not provided for in B81B2201/042 - B81B2201/045 - B81B 2203/0315: Cavities - B81C 2201/013: Etching - B81C 2201/019: Bonding or gluing multiple substrate layers - B81C 2203/035: Soldering - B81C 2203/037: Thermal bonding techniques not provided for in B81C2203/035 - B81C2203/036 - B81C 2203/038: Bonding techniques not provided for in B81C2203/031 - B81C2203/037 - 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) - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00) - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A method of processing a double sided wafer of a microelectromechanical device includes spinning a resist onto a first side of a first wafer. The method further includes forming pathways within the resist to expose portions of the first side of the first wafer. The method also includes etching one or more depressions in the first side of the first wafer through the pathways, where each of the depressions have a planar surface and edges. Furthermore, the method includes depositing one or more adhesion metals over the resist such that the one or more adhesion metals are deposited within the depressions, and then removing the resist from the first wafer. The method finally includes depositing indium onto the adhesion metals deposited within the depressions and bonding a second wafer to the first wafer by compressing the indium between the second wafer and the first wafer. ## Claims ### Claim 1 A method for forming a low temperature bond between wafers, the method comprising: spinning a resist onto a first side of a first wafer; forming one or more pathways within the resist to expose portions of the first side of the first wafer; etching the first side of the first wafer through the one or more pathways to form one or more depressions that align with the pathways, each of the one or more depressions having a planar surface and edges; depositing one or more adhesion metals over the resist such that the one or more adhesion metals is deposited within each of the one or more depressions; removing the resist; depositing indium onto the one or more adhesion metals deposited within the one or more depressions; compressing the indium between a second wafer and the first side of the first wafer to form a low temperature bond between the second wafer and the first wafer. ### Claim 2 (depends on 1) The method of claim 1, wherein the one or more depressions are concentric to the first wafer. ### Claim 3 (depends on 1) The method of claim 1, wherein each of the one or more depressions extend continuously around a peripheral region of the first side of the first wafer. ### Claim 4 (depends on 1) The method of claim 1, wherein the one or more adhesion metals comprise: a first adhesion metal of titanium; and a second adhesion metal of gold. ### Claim 5 (depends on 1) The method of claim 1, wherein the edges of the one or more depressions form shear points for the indium when the indium is compressed. ### Claim 6 (depends on 1) The method of claim 1, further comprising, prior to depositing the indium: bonding a third wafer to a second surface of the first wafer. ### Claim 7 (depends on 6) The method of claim 6, wherein the bond between the second wafer and the first side of the first wafer is a hermetic bond, and the bonding of the third wafer of the first wafer is a high temperature bond. ### Claim 8 (depends on 6) The method of claim 6, wherein the second and third wafers are silicon wafers. ### Claim 9 (depends on 1) The method of claim 1, wherein the first wafer is a glass wafer. ### Claim 10 (depends on 1) The method of claim 1, wherein the one or more depressions are etched into the first side of the first wafer via isotropic etching. ### Claim 11 A microelectromechanical system, comprising: a first wafer, the first wafer comprising: a first side having a peripheral region surrounding a central region, a second side opposite the first side, and one or more depressions disposed within the peripheral region of first side of the first wafer, each of the one or more depressions including edges; one or more adhesive metals disposed within the one or more depressions; indium disposed on the one or more adhesive metals; and a second wafer bonded to the first side of the first wafer via the indium, wherein the indium is compressed between the first wafer and the second wafer such that the edges of the one or more depressions form shear points for the indium. ### Claim 12 (depends on 11) The microelectromechanical system of claim 11, further comprising: a third wafer bonded to the second side of the first wafer via a high temperature bond. ### Claim 13 (depends on 12) The microelectromechanical system of claim 12, wherein the second and third wafers are silicon wafers, and the first wafer is a glass wafer. ### Claim 14 (depends on 13) The microelectromechanical system of claim 13, wherein the second wafer is hermetically bonded to the first side of the first wafer. ### Claim 15 (depends on 11) The microelectromechanical system of claim 11, wherein each of the depressions have a first depth, the adhesive metals have a first height, and the first depth is greater than the first height. ### Claim 16 (depends on 11) The microelectromechanical system of claim 11, the one or more depressions extend continuously around the peripheral region of the first wafer. ### Claim 17 A method for forming a low temperature bond between wafers, the method comprising: spinning a resist onto a peripheral region of a first side of a first wafer; forming one or more pathways into the resist; etching one or more depressions into the first side of the first wafer through the one or more pathways; depositing one or more adhesion metals into the one or more depressions; bonding a second wafer to a second side of the first wafer via a high temperature bond; depositing indium within the depressions and onto the adhesion metals deposited within the depressions such that the indium extends out from the one or more depressions; and bonding a third wafer to the first side of the first wafer by compressing the indium between a third wafer and the first side of the first wafer. ### Claim 18 (depends on 17) The method of claim 17, wherein the third wafer is bonded to the first wafer via a hermetic bond. ### Claim 19 (depends on 18) The method of claim 18, wherein the second and third wafers are silicon wafers, and the first wafer is a glass wafer. ### Claim 20 (depends on 17) The method of claim 17, wherein the one or more depressions extend continuously around the peripheral region of the first wafer.