Bonding structure
According to an example aspect of the present invention, there is provided a bonding structure for forming at least one electrical connection between an optoelectronic component and a photonic substrate. The bonding structure comprises a pillar structure between the optoelectronic component and the photonic substrate, and a bonding layer comprising bonding material on the pillar structure. The pillar structure for at least one individual electrical connection comprises at least two portions and at least one gap between the portions for receiving extra bonding material of the bonding layer.
1 . A bonding structure for forming at least one electrical connection between an optoelectronic component and a photonic substrate, the bonding structure comprising:
a pillar structure between the optoelectronic component and the photonic substrate, and
a bonding layer comprising bonding material on the pillar structure,
wherein the pillar structure for at least one individual electrical connection comprises at least two portions and at least one gap between the portions for receiving extra bonding material of the bonding layer,
wherein the bonding layer comprises a eutectic alloy and has a thickness of 1 to 10 μm, and
wherein the bonding structure allows an optical connection between the optoelectronic component and the photonic substrate.
2 . The bonding structure of claim 1 , wherein the bonding structure comprises a contact pad on a surface of the photonic substrate.
3 . The bonding structure of claim 1 , wherein the pillar structure has a predetermined height of 1 to 10 μm.
4 . The bonding structure of claim 1 , wherein the bonding layer has a bonding area of 250 μm 2 to 1 mm 2 .
5 . The bonding structure of claim 1 , wherein the gap has a predetermined width of 5 to 100 μm.
6 . The bonding structure of claim 1 , wherein the pillar structure defines a closed path on the surface of the photonic substrate for enclosing a cavity inside the closed path and between the optoelectronic component and the photonic substrate.
7 . A VCSEL chip on a silicon photonics substrate comprising the bonding structure of claim 1 .
8 . The bonding structure according to claim 1 , further comprising a passivation layer on a surface of the photonic substrate.
9 . A method for forming at least one electrical connection between an optoelectronic component and a photonic substrate comprising:
making a pillar structure on a surface of the photonic substrate;
making a first bonding material layer on the pillar structure;
making a second bonding material layer on the optoelectronic component; and
bonding the first bonding material layer with the second bonding material layer for forming a bonding layer;
wherein the pillar structure for at least one individual electrical connection comprises at least two portions and at least one gap between the portions for receiving extra bonding material of the bonding layer,
wherein bonding of the first bonding material layer with the second bonding material layer is provided by eutectic bonding, and
wherein an optical connection between the optoelectronic component and the photonic substrate is present after the bonding step.
10 . The method of claim 9 , wherein the method comprises making a contact pad on a surface of the photonic substrate.
11 . The method of claim 9 , wherein the pillar structure has a predetermined height of 1 to 10 μm.
12 . The method of claim 9 , wherein a bonding temperature for bonding the first bonding material layer with the second bonding material layer is lower than a melting temperature of the pillar structure.
13 . The method of claim 9 , wherein the method comprises making a seed layer on the contact pad and a photoresist mask on the seed layer.
14 . The method of claim 13 , wherein the method comprises making the pillar structure and the first bonding material layer on the pillar structure by electroplating using the photoresist mask.
15 . The method of claim 13 , wherein the method comprises removing the photoresist mask and the seed layer after making the first bonding material layer on the pillar structure.
16 . A bonding structure for forming at least one electrical connection between an optoelectronic component and a photonic substrate, the bonding structure comprising:
a pillar structure between the optoelectronic component and the photonic substrate, and
a bonding layer comprising bonding material on the pillar structure,
wherein the pillar structure for at least one individual electrical connection comprises at least two portions and at least one gap between the portions for receiving extra bonding material of the bonding layer,
wherein the bonding layer comprises a eutectic alloy and has a thickness of 1 to 10 μm, and
wherein the pillar structure defines a closed path on the surface of the photonic substrate for enclosing a cavity inside the closed path and between the optoelectronic component and the photonic substrate.