Method using glass substrate anodic bonding
A bonding technology is disclosed that can form an anodic, conductive bond between two optically transparent substrates. The anodic bond may be accompanied by a metal alloy, solder, eutectic and polymer bond. The first anodic bond may provide one attribute such as hermeticity, whereas the second bond may provide another attribute, such as electrical conductivity.
1. A method of forming a substrate pair assembly, comprising:
providing a first optically transparent substrate and a second optically transparent substrate;
depositing a first layer of metal material on the first optically transparent substrate;
forming a first layer of metal oxide material wherein the metal oxide is the oxidation product of the metal material and the first optically transparent substrate, and is formed during the depositing of the metal material;
patterning the first layer of the metal material to create a metal feature;
forming a second layer of metal oxide material, wherein the second layer of metal oxide is the oxidation product of the metal material and the second optically transparent substrate; and is disposed between the second optically transparent substrate and the metal feature, wherein the layer of metal material and the first and second layers of metal oxide form a first anodic bond between the first optically transparent substrate and the second optically transparent substrate and
forming a first layer of a second bonding material on at least one of the first and the second optically transparent substrate, and patterning the first layer to form a first feature of the second bonding material; and
bonding the first optically transparent substrate to the second optically transparent substrate with a second bond of the second bonding material.
2. The method of claim 1 , wherein forming the second layer of metal oxide comprises applying at least one of temperature, pressure and voltage to the first optically transparent substrate and the second optically transparent substrate for at least about 3 minutes, to form an anodic bond between the first and the second optically transparent substrates.
3. The method of claim 1 , wherein the first anodic bond provides an attribute selected from the group of hermeticity, electrically conductivity, low rf loss, high adhesive strength, leak resistance, thermal conductivity, and the second bond provides a second, different attribute chosen from the same group.
4. The method of claim 1 , wherein the second bond is laterally separated from the first anodic bond by a distance of about 100 microns or more.
5. The method of claim 1 , wherein the second bond comprises one of a polymer, a thermocompression, a solder, a metal alloy and a eutectic bond.
6. The method of claim 1 , wherein the second bond comprises a thermocompression bond using at least one of gold (Au), silver (Ag), platinum (Pt), and indium (In).
7. The method of claim 1 , further comprising:
forming a second layer of the second bonding material on the other of the first and the second optically transparent substrates; and
patterning the second layer to form a second feature of the second bonding material.
8. The method of claim 7 , wherein a width of the first feature of the second bonding material is between about 1 to about 5 microns wide, and a width of the second feature of the second bonding material is about 100 microns wide.
9. The method of claim 7 , wherein the metal feature is about 500 nm thick, and a thickness of the first feature of the second bonding material is at least about 50 nm thicker than the thickness of the metal feature.
10. The method of claim 7 , further comprising forming at least one of the first feature and the second feature of the second bonding material so as to have a yield strength of less that about 500 MPa, and applying a pressure of about 1.5 atm between the first and the second optically transparent substrates, in order to form the first anodic bond and the second bond.
11. The method of claim 7 , wherein the thickness of at least one of the first feature and the second feature relative to a thickness of the metal feature determines whether the first anodic bond is formed before or after the second bond.
12. The method of claim 1 , further comprising applying a first combination of temperature, pressure and voltage to achieve the first anodic bond, and a second combination of temperature, pressure and voltage sufficient to achieve the second bond with the second bonding material.
13. The method of claim 12 , wherein the first combination of conditions and the second combination of conditions determines whether the first anodic bond is formed before or after the second bond.
14. The method of claim 1 , wherein at least one of the first feature and the second feature of the second bonding material comprises a multilayer stack.
15. The method of claim 14 , wherein the multilayer stack includes layers of silicon, gold, molydenum, silver, indium, tin, antimony, lead, and copper, each layer having a thickness of about 1-10 microns, and the multilayer stack having a yield strength of of less than about 500 MPa.
16. The method claim 1 , further comprising:
forming a first layer of a third bonding material on at least one of the first and the second optically transparent substrates;
patterning the first layer of the third bonding material to form a first feature of the third bonding material; and
bonding the first optically transparent substrate to the second optically transparent substrate with the third bonding material.
17. The method of claim 1 , further comprising:
forming a device on at least one of the first and the second optically transparent substrate; and
forming the metal layer in a perimeter around the device, wherein the anodic bond and the metal layer form a device cavity which encloses the device between the first and the second optically transparent substrate.
18. The method of claim 17 , wherein the device comprises at least one of an emitter, detector, reflector or attenuator of electromagnetic radiation.
19. The method of claim 1 , wherein the first optically transparent substrate and the second optically transparent substrate each have a resistivity of less than about 8 ohm-cm, and wherein the metal material comprises at least one of titanium (Ti), chrome (Cr), silicon (Si), cobalt (Co), aluminum (Al) and zirconium (Zr).