Cooling system for a semiconductor device and method of fabricating same

• US 7,170,164 B2
• Filed: 12/23/2005
• Issued: 01/30/2007
• Est. Priority Date: 09/12/2003
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Hsu, Louis L., Shepard, Joseph F. Jr., Chen, Howard Hao
• Primary Examiner(s): Kebede; Brook
• Application Number:
  US11/317,298
• Publication Number:
  US 20060099815A1
• Time in Patent Office: 403 Days
• Field of Search: 257/625, 257/675, 257/706, 257/796, 257/E23.051, 257/E23.088, 257/717, 257/720, 257/666, 257/678, 257/701, 257/712, 257/714, 257/721, 257/787, 257/E23.097, 257/E23.099, 257/E23.101, 257/E23.103
• US Class Current: 257/712
• CPC Class Codes: H01L 21/4871 Bases, plates or heatsinks
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05008 Bonding area integrally formed with a redistribution layer on the semiconductor or solid-state body, e.g.
• CPC Class Codes: H01L 2224/05099 Material
• CPC Class Codes: H01L 2224/05548 Bonding area integrally formed with a redistribution layer on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 23/473 by flowing liquids H01L23/4332, H01L23/4338 take precedence
• CPC Class Codes: H01L 25/0655 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/10158 at the passive surface
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA

Abstract

A cooling system for a semiconductor substrate incudes a plurality of trenches formed from a backside of the semiconductor substrate, and thermally conductive material deposited in the plurality of trenches. A method of forming cooling elements in a semiconductor substrate, includes coating a backside of the semiconductor substrate with a first mask layer, forming a plurality of trench patterns in the first mask layer, etching the semiconductor substrate to form a plurality of trenches along the plurality of trench patterns, and depositing thermally conductive material in the plurality of trenches. Trenches constructed from the backside of a wafer improve efficiency of heat transfer from a front-side to the backside of an integrated-circuit chip. The fabrication of trenches from the backside of the wafer allows for increases in the depth and number of trenches, and provides a means to attach passive and active cooling devices directly to the backside of a wafer.

Claims

1. A cooling system for a semiconductor substrate, comprising:

a plurality of trenches formed from a backside of the semiconductor substrate;

thermally conductive material deposited in the plurality of trenches;

a first diffusion layer formed in the semiconductor substrate; and

a second diffusion layer formed in the first diffusion layer, wherein the second diffusion layer is doped with a dopant having a polarity opposite a polarity of the semiconductor substrate.

2. The cooling system as recited in claim 1, wherein the depth of the plurality of trenches ends at the second diffusion layer.

3. The cooling system as recited in claim 1, wherein the plurality of trenches are formed by etching the semiconductor substrate, from the backside of the semiconductor substrate, down to the second diffusion layer.

4. The cooling system as recited in claim 1, wherein the plurality of trenches are formed by etching the semiconductor substrate, from the backside of the semiconductor substrate, with Cl₂-based plasma.

5. The cooling system as recited in claim 1, wherein the plurality of trenches are formed in the vertical direction.

6. The cooling system as recited in claim 1, wherein the plurality of trenches are one of cylindrical, oval, square, triangular, S-shaped, T-shaped and U-shaped.

7. The cooling system as recited in claim 1, wherein deposition of the thermally conductive material is performed by one of chemical vapor deposition, atomic layer deposition, physical vapor deposition and electroplating.

8. The cooling system as recited in claim 1, wherein the thermally conductive material is made from one of aluminum nitride, aluminum, Cu—

W, silicon carbide, gold, copper, diamond and silver.

9. The cooling system as recited in claim 1, wherein the semiconductor substrate is one or a complimentary metal oxide semiconductor wafer and a silicon-on-insulator wafer.

10. The cooling system as recited in claim 1, wherein the plurality of trenches are formed in an integrated-circuit chip of the semiconductor substrate.

11. The cooling system as recited in claim 1, wherein the plurality of trenches are formed away from at least one of a passivation layer, an interconnect layer, a device layer and a doped well structure of the semiconductor substrate.

12. The cooling system as recited in claim 1, wherein the plurality of trenches are formed one of before and after processing of remaining portions of the semiconductor substrate.

13. The cooling system as recited in claim 1, further comprising an external heat sink on the backside of the semiconductor substrate.

14. The cooling system as recited in claim 1, further comprising an active cooling apparatus on the backside of the semiconductor substrate.

15. The cooling system as recited in claim 14, wherein the active cooling apparatus is connected to a continuous trench formed in the backside of the semiconductor substrate and to at least one opening in the continuous trench for allowing coolant to enter the continuous trench from the active cooling apparatus.

16. The cooling system as recited in claim 14, wherein the active cooling apparatus is one of a thermal electric cooling component, a micro-fan device and a micropump.

17. The cooling system as recited in claim 14, wherein the active cooling apparatus is one of directly fabricated on the backside of the semiconductor substrate and separately built and mounted on the backside of the semiconductor substrate.