Method of forming complex oxide nanodots for a charge trap

• US 7,851,307 B2
• Filed: 08/17/2007
• Issued: 12/14/2010
• Est. Priority Date: 08/17/2007
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Sandhu, Gurtej, Smythe, John, Srinivasan, Bhaskar, Ramaswamy, Nirmal
• Primary Examiner(s): Le; Dung A.
• Application Number:
  US11/840,485
• Publication Number:
  US 20090045447A1
• Time in Patent Office: 1,215 Days
• Field of Search: 438257-258, 438/287, 438/485, 438583-776
• US Class Current: 438/258
• CPC Class Codes: H01L 21/02197 the material having a perovskite structure, e.g. BaTiO3
• CPC Class Codes: H01L 21/0228 deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/3142 of nano-laminates, e.g. alternating layers of Al203-Hf02
• CPC Class Codes: H01L 21/31691 with perovskite structure
• CPC Class Codes: H01L 29/40114 the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
• CPC Class Codes: H01L 29/42332 with the floating gate formed by two or more non connected parts, e.g. multi-particles flating gate
• CPC Class Codes: H01L 29/7881 Programmable transistors with only two possible levels of programmation H01L29/7888 takes precedence

Abstract

Methods and devices are disclosed, such as those involving forming a charge trap for, e.g., a memory device, which can include flash memory cells. A substrate is exposed to temporally-separated pulses of a titanium source material, a strontium source material, and an oxygen source material capable of forming an oxide with the titanium source material and the strontium source material to form the charge trapping layer on the substrate.

Claims

1. A method comprising:

forming spaced-apart nanodots over a substrate by exposing the substrate in a reaction space to pulses of a titanium source material, a strontium source material, an oxygen source material capable of forming an oxide with the titanium source material, and an oxygen source material capable of forming an oxide with the strontium source material to form a charge trap of a memory cell on the substrate,

wherein the pulses are separated from one another in time.

4. The method according to claim 1, wherein the substrate is exposed to the titanium source material first before exposure to the pulses of the strontium source material.

5. The method according to claim 1, wherein the substrate is exposed to the strontium source material first before exposure to the pulses of the titanium source material.

15. The method according to claim 1, wherein the oxygen source material capable of forming an oxide with the titanium source material and the oxygen source material capable of forming an oxide with the strontium source material comprises ozone.

16. The method according to claim 1, wherein the oxygen source material capable of forming an oxide with the titanium source material is selected from the group consisting of water, oxygen, hydrogen peroxide, oxides of nitrogen, halide-oxygen compounds, peracids, alcohols, alkoxides, and oxygen-containing radicals.

17. The method according to claim 16, wherein the oxygen source material capable of forming an oxide with the strontium source material is selected from the group consisting of water, oxygen, hydrogen peroxide, oxides of nitrogen, halide-oxygen compounds, peracids, alcohols, alkoxides, and oxygen-containing radicals.

2. A method comprising:

exposing a substrate in a reaction space to temporally-separated pulses of a titanium source material, a strontium source material, an oxygen source material capable of forming an oxide with the titanium source material, and an oxygen source material capable of forming an oxide with the strontium source material to form a charge trap of a memory cell on the substrate,

wherein each pulse of the titanium source material is followed by a pulse of the oxygen source material capable of forming an oxide with the titanium source material and wherein each pulse of the strontium source material is followed by a pulse of the oxygen source material capable of forming an oxide with the strontium source material.

3. A method comprising:

exposing a substrate in a reaction space to temporally-separated pulses of a titanium source material, a strontium source material, an oxygen source material capable of forming an oxide with the titanium source material, and an oxygen source material capable of forming an oxide with the strontium source material to form a charge trap of a memory cell on the substrate, and

purging the reaction space with an inactive gas between the pulses of the titanium source material, the oxygen source material capable of forming an oxide with the titanium source material, the strontium source material, and the oxygen source material capable of forming an oxide with the strontium source material.

6. A method comprising:

exposing a substrate in a reaction space to temporally-separated pulses of a titanium source material, a strontium source material, an oxygen source material capable of forming an oxide with the titanium source material, and an oxygen source material capable of forming an oxide with the strontium source material to form a charge trap of a memory cell on the substrate,

wherein the pulses are arranged in one or more titanium cycles and one or more strontium cycles, wherein each titanium cycle comprises a pulse of the titanium source material followed by a pulse of the oxygen source material, and each strontium cycle comprises a pulse of the strontium source material followed by a pulse of the oxygen source material.

7. The method according to claim 6, wherein a ratio of titanium cycles to strontium cycles is about 3:

1.

8. The method according to claim 7, wherein exposing the substrate comprises performing between about 1 to about 10 sets of cycles, wherein each set comprises performing 9 consecutive titanium cycles and 3 consecutive strontium cycles.

9. The method according to claim 8, wherein the 9 consecutive titanium cycles are performed before the 3 consecutive strontium cycles.

10. The method according to claim 8, wherein the 3 consecutive strontium cycles are performed before the 9 consecutive titanium cycles.

11. The method according to claim 8, wherein the pulses form strontium titanate (STO).

12. The method according to claim 11, further comprising terminating the pulses after 9 consecutive titanium cycles to form a TiO₂ cap.

13. The method according to claim 11, further comprising terminating the pulses before a continuous STO layer is formed.

14. The method according to claim 11, further comprising terminating the pulses after a continuous STO layer is formed.

18. A method comprising:

alternately exposing a substrate to pulses of a first metal source material and a first oxygen source material, and

alternately exposing the substrate to pulses of a second metal source material and a second oxygen source material to form spaced-apart nanodots over the substrate, the nanodots forming a charge trap for a memory device,

wherein metals from the first and second metal source materials form a perovskite structure with oxygen from the first and second oxygen source materials.

19. The method according to claim 18, wherein the pulses produce strontium titanate (STO).

20. The method according to claim 18, wherein the perovskite structure is formed of a material selected from the group consisting of STO, BaTiO₃, Pb(Mg_1/3Nb_2/3)O₃, SrBi₂Ta₂O₉ and Ta₂O₅(Nb).

21. The method according to claim 18, wherein the pulses of the first and second metal source materials are each followed by a pulse of the first or the second oxygen source materials.

22. The method according to claim 18, further comprising terminating the pulses before a continuous layer is formed.

23. The method according to claim 18, wherein the charge trap is formed over a tunneling dielectric over the substrate.

24. The method according to claim 23, further comprising forming a barrier dielectric over the charge trap.

25. The method according to claim 24, further comprising forming a control gate over the barrier dielectric.

26. The method according to claim 18, the first and second oxygen source materials are a same material.