Polysilicon pillar heat sinks for semiconductor on insulator circuits

• US 6,080,608 A
• Filed: 08/06/1998
• Issued: 06/27/2000
• Est. Priority Date: 10/29/1993
• Status: Expired due to Fees

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: VLSI Technology, Inc. (Koninklijke Philips N.V.)
• Inventors: Nowak, Edward D.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): LEBENTRITT, MICHAEL
• Application Number:
  US09/130,423
• Time in Patent Office: 691 Days
• Field of Search: 438/151, 438/152, 438/426, 438/432
• US Class Current: 438/151
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A heat sink is formed on a bonded semiconductor on insulator (SOI) wafer. A trench is formed which extends from a top of the bonded SOI wafer through an isolation region of the bonded SOI wafer to a base of the bonded SOI wafer. The base of the bonded SOI wafer is located below the isolation region of the bonded SOI wafer. A conductive pillar is formed in the trench. The conductive pillar extends from the top of the bonded SOI wafer through the isolation region of the bonded SOI wafer and is physically in contact with but electrically insulated from the base of the bonded SOI wafer. In the preferred embodiment, the conductive pillar is formed of doped polysilicon. The doped polysilicon is of a conductivity type which is different than the conductivity type of the base. Out-diffusion from the doped polysilicon forms a region within the base which electrically insulates the conductive pillar from the base.

Claims

1. A method for constructing a heat sink on a bonded semiconductor on insulator (SOI) wafer, the method comprising the steps of:

(a) forming a trench which extends from a top of the bonded SOI wafer through an isolation region of the bonded SOI wafer to a base of the bonded SOI wafer, the base of the bonded SOI wafer being located below the isolation region of the bonded SOI wafer; and

,

(b) forming a conductive pillar in the trench, the conductive pillar extending from the top of the bonded SOI wafer through the isolation region of the bonded SOI wafer and is physically in contact with the base of the bonded SOI wafer, including;

forming the conductive pillar from doped polysilicon, doping for the polysilicon out-diffusing from the polysilicon into the base, thereby forming a region within the base which electrically insulates the conductive pillar from the base.

2. A method as in claim 1 wherein in step (b) the doped polysilicon is of a conductivity type which is different than the conductivity type of the base.