Method for fabricating a memory cell

• US 7,122,423 B2
• Filed: 02/10/2005
• Issued: 10/17/2006
• Est. Priority Date: 02/16/2004
• Status: Expired due to Fees

• Current Assignee: Polaris Innovations Limited (Wi-LAN Inc.)
• Original Assignee: Infineon Technologies AG
• Inventors: Gutsche, Martin, Seidl, Harald
• Primary Examiner(s): TSAI, H JEY
• Application Number:
  US11/055,431
• Publication Number:
  US 20050191806A1
• Time in Patent Office: 614 Days
• Field of Search: 438243-249, 438386-392
• US Class Current: 438/243
• CPC Class Codes: H10B 12/0387 Making the trench

Abstract

The invention provides a method for fabricating a memory cell for storing electric charge, which has a substrate (101), which forms a first electrode, a trench-like recess (102) etched into the substrate (101), conductive material, which is provided as a projection in a central region of the trench-like recess (102) and spaced apart from the side walls (107) of the trench-like recess (102) and is in electrical contact with the substrate at the base (104) of the trench-like recess (102), a dielectric layer (108), which has been deposited on the side walls (107) of the trench-like recess (102), the base (104) of the trench-like recess (102) and the surfaces of the conductive material (105), and an electrode layer (110), which has been deposited on the dielectric layer (108) and forms a second electrode.

Claims

1. Method for fabricating a memory cell, comprising the steps of:

a) etching a trench-like recess, which has side walls and a base, into a substrate;

b) depositing a first protective layer at the inner surfaces of the trench-like recess;

c) etching anisotropically the first protective layer, in such a manner that the first protective layer is removed at the base of the trench-like recess but is retained at the side walls of the trench-like recess;

d) filling the trench-like recess with an electrically conductive material in such a manner that an electrical contact is provided between the electrically conductive material and the substrate;

e) etching isotropically back the conductive material to a predetermined filling height;

f) removing the first protective layer in such a manner that the conductive material is retained as a projection in the trench-like recess, spaced apart from the side walls of the trench-like recess;

g) depositing a dielectric layer on the side walls of the trench-like recess, the base of the trench-like recess and the surfaces of the conductive material; and

h) depositing an electrode layer on the dielectric layer, in which method, prior to step g) of depositing a dielectric layer, a second protective layer is deposited nonconformally in an upper region of the trench-like recess, an embedded electrode is produced by means of gas phase doping in the trench-like recess, and the second protective layer is removed again by wet-chemical means.

2. Method according to claim 1, wherein the dielectric layer is deposited on the side walls of the trench-like recess, the base of the trench-like recess and the surfaces of the conductive material by means of atomic layer deposition.

3. Method according to claim 1 wherein the dielectric layer is annealed after it has been deposited.

4. Method according to claim 1, wherein the trench-like recess is widened in a lower region by means of a side wall etch.

5. Method according to claim 1, wherein the first protective layer is provided as a sacrificial layer of a carbon material.

6. Method according to claim 1, wherein the second protective layer is formed from an aluminum oxide material.

7. Method according to claim 1, wherein the removal of the first protective layer is carried out selectively with respect to silicon nitride and silicon oxide, in such a manner that the conductive material is retained as a projection in the trench-like recess, spaced apart from the side walls of the trench-like recess.

8. Method according to claim 1 wherein the removal of the first protective layer is carried out by dry-chemical means, by means of an isotropic etch and/or by means of an anisotropic etch.

9. Method according to claim 1, wherein during the deposition of the electrode layer on the dielectric layer the space which remains in the trench-like recess is completely filled.