Lids for wafer-scale optoelectronic packages
View Patent ↗A lid for a wafer-scale package includes a body having a bond area around a cavity defined by the body, an oxide layer atop the bond area and the cavity, and a reflective layer atop the oxide layer. The cavity has an angled sidewall where a portion of the reflective layer over the angled sidewall forms a mirror for reflecting a light. The lid further includes a solder layer atop another portion of the reflective layer over the bond area, and a barrier layer atop the mirror. The barrier layer is solder non-wettable so it prevents the solder layer from wicking into the cavity and interfering with the mirror. The barrier layer is also transparent to the light and has a thickness that either does not affect the light reflection or improves the light reflection.
1. A lid for a wafer scale package, comprising:
a body comprising a bond area around a cavity defined by the body, the cavity having an angled sidewall;
an oxide layer atop the bond area and the cavity;
a reflective layer atop the oxide layer, wherein a portion of the reflective layer over the angled sidewall forms a mirror for reflecting a light;
a solder layer atop another portion of the reflective layer over the bond area; and
a barrier layer atop the mirror, wherein:
the barrier layer is solder non-wettable so it prevents the solder layer from wicking into the cavity and interfering with the mirror;
the barrier layer is transparent to the light and has a thickness less than a quarter wavelength of the light reflected by the mirror so it does not affect the light reflection.
2. The lid of claim 1 , wherein the angled sidewall is oriented at 45 degrees along a first crystallographic plane and the body comprises a second crystallographic plane oriented at an offset from a top surface of the body.
3. The lid of claim 1 , wherein the reflective layer comprises a titanium-platinum-gold metal stack.
4. The lid of claim 3 , wherein the barrier layer comprises a titanium dioxide layer.
5. The lid of claim 1 , wherein the solder layer comprises a gold-tin solder.
6. The lid of claim 1 , wherein the barrier layer is selected from the group consisting of nitride, boride, fluoride, fluorocarbon, and polyimide.
7. The lid of claim 4 , wherein the gold has a thickness of substantially 1,500 angstroms and the titanium dioxide has a thickness of substantially 500 angstroms.
8. A lid for a wafer-scale package, comprising:
a body comprising a bond area around a cavity defined by the body, the cavity having an angled sidewall;
an oxide layer atop the bond area and the cavity;
a reflective layer atop the oxide layer, wherein a portion of the reflective layer over the angled sidewall forms a mirror for reflecting a collimated light;
a solder layer atop another portion of the reflective layer over the bond area; and
a barrier layer atop the mirror, wherein:
the barrier layer is solder non-wettable so it prevents the solder layer from wicking into the cavity and interfering with the mirror;
the barrier layer is transparent to the collimated light and has a thickness that improves the reflection of the collimated light.
9. The lid of claim 8 , wherein the angled sidewall is oriented at 45 degrees along a first crystallographic plane and the body comprises a second crystallographic plane oriented at an offset from a top surface of the body.
10. The lid of claim 8 , wherein the reflective layer comprises a titanium-platinum-gold metal stack.
11. The lid of claim 10 , wherein the barrier layer comprises a titanium dioxide layer.
12. The lid of claim 8 , wherein the solder layer comprises a gold-tin solder.
13. The lid of claim 8 , wherein the barrier layer is selected from the group consisting of nitride, boride, fluoride, fluorocarbon, and polyimide.
14. The lid of claim 11 , wherein the gold bas a thickness of substantially 1,500 angstroms and the titanium dioxide has a thickness of substantially 500 angstroms.