Method of fabricating a polymer waveguide

• US 9,036,956 B2
• Filed: 02/17/2012
• Issued: 05/19/2015
• Est. Priority Date: 02/17/2012
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Haynes and Boone, LLP
• Inventors: Tseng, Chun-Hao, Chen, Hai-Ching, Bao, Tien-I, Lee, Wan-Yu
• Primary Examiner(s): PENG, CHARLIE YU
• Application Number:
  US13/399,098
• Publication Number:
  US 20130216177A1
• Time in Patent Office: 1,187 Days
• Field of Search: 385/14, 385/132
• US Class Current: 385/14
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 2006/12121 Laser
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/132 by deposition of thin films
• CPC Class Codes: G02B 6/136 by etching
• CPC Class Codes: G02B 6/138 by using polymerisation
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence

Abstract

A method of fabricating a waveguide device is disclosed. The method includes providing a substrate having an elector-interconnection region and a waveguide region and forming a patterned dielectric layer and a patterned redistribution layer (RDL) over the substrate in the electro-interconnection region. The method also includes bonding the patterned RDL to a vertical-cavity surface-emitting laser (VCSEL) through a bonding stack. A reflecting-mirror trench is formed in the substrate in the waveguide region, and a reflecting layer is formed over a reflecting-mirror region inside the waveguide region. The method further includes forming and patterning a bottom cladding layer in a wave-tunnel region inside the waveguide region and forming and patterning a core layer and a top cladding layer in the waveguide region.

Claims

1. A method of fabricating a polymer waveguide device, the method comprising:

providing a substrate having an electro-interconnection region and a waveguide region;

forming a patterned dielectric layer, a patterned redistribution layer (RDL), and a patterned passivation layer over the substrate in the electro-interconnection region;

bonding the patterned RDL to a vertical-cavity surface-emitting laser (VCSEL) through a bonding stack;

forming a reflecting-mirror trench in the substrate in the waveguide region, wherein the waveguide region has a reflecting-mirror region and a wave-tunnel region;

forming a reflecting layer over the patterned passivation layer, the patterned RDL, the reflecting-mirror region, and the wave-tunnel region;

forming a patterned bottom cladding layer over the reflecting layer in the wave-tunnel region; and

forming a patterned core layer and a patterned top cladding layer over the reflecting layer in the reflecting-mirror region and over the bottom cladding layer in the wave-tunnel region.

2. The method of claim 1, wherein the substrate includes Si with a (100) crystal orientation.

3. The method of claim 1, wherein the reflecting-mirror trench is formed with a 45°

inclined slope sidewall profile in the Si (100) substrate.

4. The method of claim 3, wherein the 45°

inclined slope sidewall reflecting-mirror trench is formed with a larger than 30 um depth by a wet etch process including etchants from the group consisting of ethylene diamine pyrocatechol (EDP), potassium hydroxide (KOH), and tetramethyl ammonium hydroxide (TMAH).

5. The method of claim 1, wherein the bottom and top cladding layers and the core layer each include a photo-sensitive polymer.

6. The method of claim 1, wherein the core layer is configured to have a thickness of half or larger than the depth of the reflecting-mirror trench and have a refractive index 0.025 or more larger than the refractive index of the bottom/top cladding layers.

7. The method of claim 1, wherein the bottom and top cladding layers and the core layer are selected to be transparent to a wavelength from 600 nm to 1600 nm.

8. The method of claim 1, wherein the bottom and top cladding layers and the core layer are selected to have a less than 2% volume and thickness variation during the bonding process.

9. The method of claim 1, wherein the bottom and top cladding layers and the core layer are deposited by a spin-on coating technique.

10. The method of claim 1, wherein the bottom and top cladding layers and the core layer are patterned by a photolithography technique, wherein the bottom cladding layer is patterned to be formed at the wave-tunnel region only, and the core layer and the top cladding layer are patterned to be formed at the reflecting-mirror region and the wave-tunnel region.

11. The method of claim 1, wherein the bonding of the patterned RDL to the VCSEL through the bonding stack includes coupling the bonding stack to the patterned RDL through the reflecting layer.

12. A method of fabricating a polymer waveguide device, the method comprising:

providing a substrate having an electro-interconnection region and a waveguide region;

forming a patterned dielectric layer, a patterned redistribution layer (RDL), and a patterned passivation layer over the substrate in the electro-interconnection region;

bonding the patterned RDL to a vertical-cavity surface-emitting laser (VCSEL) through a bonding stack;

forming a 45°

inclined sidewall reflecting-mirror trench in the substrate in the waveguide region, wherein the waveguide region having a reflecting-mirror region and a wave-tunnel region;

forming a reflecting layer over the patterned passivation layer, the patterned RDL, the reflecting-mirror region, and the wave-tunnel region;

performing spin-on coating and lithography patterning techniques to form a patterned bottom cladding layer over the reflecting layer in the wave-tunnel region; and

performing spin-on coating and lithography patterning processes to form a patterned core layer and a patterned top cladding layer in the waveguide region.

13. The method of claim 12, wherein a vacancy space is formed above the reflecting layer in the reflecting-mirror region.

14. The method of claim 13, wherein a functional element is built in the vacancy space.

15. The method of claim 12, wherein the bonding of the patterned RDL to the VCSEL through the bonding stack uses the reflecting layer as a wetting layer.

16. A polymer waveguide device comprising:

a substrate having an electro-interconnection region and a waveguide region;

a patterned dielectric layer disposed over the substrate in the electro-interconnection region;

a patterned redistribution metal layer (RDL) disposed over the dielectric layer;

a patterned passivation layer disposed over the patterned RDL;

a bond stack over the patterned RDL, through which a wave source connects to the patterned RDL;

a reflecting-mirror trench in the substrate, with a 45°

inclined sidewall in a reflecting-mirror region and a flat bottom in a wave-tunnel region;

a reflecting layer disposed over the patterned passivation layer, the patterned RDL, the reflecting-mirror region, and the wave-tunnel region;

a patterned bottom cladding layer disposed over the reflecting layer in the wave-tunnel region by spin-on coating and photolithography techniques; and

a patterned core layer and a patterned top cladding layer disposed over the reflecting-mirror region and the wave-tunnel region by spin-on coating and photolithography techniques.

17. The polymer waveguide device of claim 16, wherein the patterned core layer has a refractive index of about 0.025 larger than a refractive index of the patterned bottom and top cladding layers.

18. The polymer waveguide device of claim 16, wherein the patterned bottom and top cladding layers and the patterned core layer are transparent to a wavelength from 600 nm to 1600 nm.

19. The polymer waveguide device of claim 16, configured such that a light beam from the wave source passes through the patterned top cladding layer and the patterned core layer, reflect 90°

on a surface of the reflecting-mirror region, and passes within the patterned core layer in the wave-tunnel region.

20. The polymer waveguide device of claim 16, wherein the bond stack is coupled to the patterned RDL through the reflecting layer.