Recessed access devices and methods of forming a recessed access devices

Patent metadata

Field	Value
Publication number	US-11929411-B2
Application number	US-202117411643-A
Country	US
Kind code	B2
Filing date	Aug 25, 2021
Priority date	Aug 25, 2021
Publication date	Mar 12, 2024
Grant date	Mar 12, 2024

Abstract

A method of forming a recessed access device comprises forming a trench in semiconductor material. Sidewalls and a bottom of the trench are lined with low-k gate-insulator material. The low-k gate-insulator material is characterized by its dielectric constant k being no greater than 4.0. Sacrificial material is formed in a bottom portion of the trench over the low-k gate-insulator material and over the trench bottom. A high-k gate-insulator material is formed in an upper portion of the trench above the sacrificial material and laterally-inward of the low-k gate-insulator material that is in the upper portion of the trench. The high-k gate-insulator material is characterized by its dielectric constant k being greater than 4.0. The sacrificial material is replaced with a conductive gate that has its top above a bottom of the high-k gate-insulator material. A pair of source/drain regions is formed in upper portions of the semiconductor material on opposing lateral sides of the trench. A channel region is in the semiconductor material below the pair of source/drain regions and extends along the trench sidewalls and around the trench bottom. Other embodiments, including structure independent of method, are disclosed.

First claim

The invention claimed is:

1. A recessed access device comprising:
a conductive gate in a trench in semiconductor material;
a gate insulator extending along sidewalls and around a bottom of the conductive gate between the conductive gate and the semiconductor material;
a pair of source/drain regions in upper portions of the semiconductor material on opposing lateral sides of the trench;
a channel region in the semiconductor material below the pair of source/drain regions extending along sidewalls and around a bottom of the trench;
the gate insulator comprising a low-k material and a high-k material, the low-k material being characterized by its dielectric constant k being no greater than 4.0, the high-k material being characterized by its dielectric constant k being greater than 4.0, the low-k material extending completely along all of the sidewalls of and directly under the bottom of the conductive gate, the high-k material being laterally-inward of the low-k material and at least one of (a) and (b), where:
(a): extending less-than-completely along all of the sidewalls of the conductive gate; and
(b): not being directly under the bottom of the conductive gate;

comprising the (a);
the high-k material covers 10% to 95% of the sidewalls of the conductive gate; and
the high-k material covers less than 50% of the sidewalls of the conductive gate.

2. The recessed access device of claim 1 wherein the high-k material covers 10% to 25% of the sidewalls of the conductive gate.

3. A recessed access device comprising:
a conductive gate in a trench in semiconductor material;
a gate insulator extending along sidewalls and around a bottom of the conductive gate between the conductive gate and the semiconductor material;
a pair of source/drain regions in upper portions of the semiconductor material on opposing lateral sides of the trench;
a channel region in the semiconductor material below the pair of source/drain regions extending along sidewalls and around a bottom of the trench;
the gate insulator comprising a low-k material and a high-k material, the low-k material being characterized by its dielectric constant k being no greater than 4.0, the high-k material being characterized by its dielectric constant k being greater than 4.0, the low-k material extending completely along all of the sidewalls of and directly under the bottom of the conductive gate, the high-k material being laterally-inward of the low-k material and at least one of (a) and (b), where:
(a): extending less-than-completely along all of the sidewalls of the conductive gate; and
(b): not being directly under the bottom of the conductive gate;

comprising the (a); and
comprising the (b).

4. The recessed access device of claim 3 wherein the high-k material extends completely along all of the sidewalls of the conductive gate.

5. A recessed access device comprising:
a conductive gate in a trench in semiconductor material;
a gate insulator extending along sidewalls and around a bottom of the conductive gate between the conductive gate and the semiconductor material;
a pair of source/drain regions in upper portions of the semiconductor material on opposing lateral sides of the trench;
a channel region in the semiconductor material below the pair of source/drain regions extending along sidewalls and around a bottom of the trench;
the gate insulator comprising a low-k material and a high-k material, the low-k material being characterized by its dielectric constant k being no greater than 4.0, the high-k material being characterized by its dielectric constant k being greater than 4.0, the low-k material extending completely along all of the sidewalls of and directly under the bottom of the conductive gate, the high-k material being laterally-inward of the low-k material and at least one of (a) and (b), where:
(a): extending less-than-completely along all of the sidewalls of the conductive gate; and
(b): not being directly under the bottom of the conductive gate;

comprising the (a); and
comprising the (a) and the (b).

6. A recessed access device comprising:
a conductive gate in a trench in semiconductor material;
a gate insulator extending along sidewalls and around a bottom of the conductive gate between the conductive gate and the semiconductor material;
a pair of source/drain regions in upper portions of the semiconductor material on opposing lateral sides of the trench;
a channel region in the semiconductor material below the pair of source/drain regions extending along sidewalls and around a bottom of the trench;
the gate insulator comprising a low-k material and a high-k material, the low-k material being characterized by its dielectric constant k being no greater than 4.0, the high-k material being characterized by its dielectric constant k being greater than 4.0, the low-k material extending completely along all of the sidewalls of and directly under the bottom of the conductive gate, the high-k material being laterally-inward of the low-k material and at least one of (a) and (b), where:
(a): extending less-than-completely along all of the sidewalls of the conductive gate; and
(b): not being directly under the bottom of the conductive gate;

comprising the (a); and
the high-k material is aside a top of the conductive gate at an elevation of the top of the conductive gate.

7. The recessed access device of claim 6 wherein the high-k material has a top that is at the elevation of the top of the conductive gate.

8. The recessed access device of claim 7 wherein the top of the conductive gate and the top of the high-k material are planar and collectively co-planar.

9. The recessed access device of claim 6 wherein the high-k material has a top that is above the elevation of the top of the conductive gate.

10. The recessed access device of claim 9 wherein the low-k material has a top that is above the elevation of the top of the conductive gate.

11. A recessed access device comprising:
a conductive gate in a trench in semiconductor material;
a gate insulator extending along sidewalls and around a bottom of the conductive gate between the conductive gate and the semiconductor material;
a pair of source/drain regions in upper portions of the semiconductor material on opposing lateral sides of the trench;
a channel region in the semiconductor material below the pair of source/drain regions extending along sidewalls and around a bottom of the trench;
the gate insulator comprising a low-k material and a high-k material, the low-k material being characterized by its dielectric constant k being no greater than 4.0, the high-k material being characterized by its dielectric constant k being greater than 4.0, the low-k material extending completely along all of the sidewalls of and directly under the bottom of the conductive gate, the high-k material being laterally-inward of the low-k material and at least one of (a) and (b), where:
(a): extending less-than-completely along all of the sidewalls of the conductive gate; and
(b): not being directly under the bottom of the conductive gate;

comprising the (a); and
the high-k material is thinner than the low-k material.

12. The recessed access device of claim 11 wherein the high-k material has maximum lateral thickness that is 1% to 60% of that of the low-k material.

13. The recessed access device of claim 12 wherein the high-k material has maximum lateral thickness that is no more than 50% of that of the low-k material.

14. The recessed access device of claim 13 wherein the high-k material has maximum lateral thickness that is no more than 10% of that of the low-k material.

Assignees

• Micron Technology Inc

Inventors

• Cheung Sau Ha
• Sugiura Soichi
• Guha Jaydip
• Kanago Anthony
• Beeler Richard

Classifications

• H10D64/683

  being parallel to the channel plane · CPC title

• H10D64/516

  the thicknesses being non-uniform · CPC title

• H10D64/01 Primary

  Manufacture or treatment · CPC title

• H10D64/685

  being perpendicular to the channel plane · CPC title

• H10D64/513 Primary

  within recesses in the substrate, e.g. trench gates, groove gates or buried gates · CPC title