Semiconductor trench capacitor cell having a buried strap

• US 5,770,876 A
• Filed: 11/13/1996
• Issued: 06/23/1998
• Est. Priority Date: 04/13/1995
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wright, Judith A., Lord, David K., Lam, Chung Hon
• Primary Examiner(s): Thomas, Tom
• Assistant Examiner(s): Hardy, David B.
• Application Number:
  US08/748,961
• Time in Patent Office: 587 Days
• Field of Search: 257/296, 257/301, 257/304
• US Class Current: 257/301
• CPC Class Codes: H01L 29/66181 Conductor-insulator-semiconductor capacitors, e.g. trench capacitors
• CPC Class Codes: H01L 29/945 Trench capacitors
• CPC Class Codes: H10B 12/038 the capacitor being in a trench in the substrate

Abstract

A semiconductor trench capacitor structure having a first level aligned insulation structure and buried strap that extends from within the trench into the semiconductor substrate. The semiconductor trench capacitor structure may be fabricated by forming a shallow trench extending into both the trench capacitor and the semiconductor substrate, depositing and densifying an insulating material within the shallow trench and using a resist layer to define and etch a strap trench aligned with the wall of the shallow trench, depositing a layer of conductive material within the strap trench and followed by depositing an insulating material therein.

Claims

1. A semiconductor structure comprising:

a semiconductor substrate;

a trench capacitor, said trench capacitor having an insulating layer and a conductive material situated therein;

a buried strap recessed below a surface of said semiconductor substrate, said buried strap comprising a contiguous layer of conductive material extending into a section of said semiconductor substrate adjacent said trench capacitor and into a section of said trench capacitor;

an upper insulation layer positioned above said buried strap; and

a lower insulation layer positioned beneath and adjacent said buried strap, wherein said upper insulation layer and said lower insulation layer together form a planar surface and wherein a single edge of said buried strap is in electrical contact with said semiconductor substrate and with the conductive material of said trench capacitor.

2. The semiconductor structure of claim 1 wherein the bottom of said lower insulation layer is substantially planar.

3. The semiconductor structure of claim 1 wherein said buried strap comprises undoped polysilicon.

4. The semiconductor structure of claim 1 wherein said insulating material of said upper and lower insulation layers comprises a dense silicon oxide.

5. The semiconductor structure of claim 1 further comprising a dielectric layer over the surface of said semiconductor substrate.

6. The semiconductor structure of claim 5 wherein said dielectric layer comprises a layer of silicon nitride over a layer of silicon oxide.