Forming of quantum dots

• US 20020039833A1
• Filed: 08/03/2001
• Published: 04/04/2002
• Est. Priority Date: 08/04/2000
• Status: Active Grant

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Bensahel, Daniel, Campidelli, Yves, Kermarrec, Olivier
• Granted Patent: US 6,596,555 B2
• Time in Patent Office: Days
• US Class Current: 438/503
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/0245 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02505 consisting of more than two layers
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 29/127 Quantum box structures
• CPC Class Codes: H01L 33/0054 for devices with an active region comprising only group IV elements
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: Y10S 438/962 Quantum dots and lines
• CPC Class Codes: Y10S 977/721 On a silicon substrate
• CPC Class Codes: Y10S 977/891 Vapor phase deposition

Abstract

A method of forming, on a single-crystal semiconductor substrate of a first material, quantum dots of a second material, including growing by vapor phase epitaxy the second material on the first material in optimal conditions adapted to ensuring a growth at a maximum controllable rate. In an initial step, a puff of a gas containing the second material is sent on the substrate, in conditions corresponding to a deposition rate much faster than the maximum controllable rate.

Claims

1. A method of forming, on a single-crystal semiconductor substrate of a first material, quantum dots of a second material, the method comprising:

growing by vapor phase epitaxy the second material on the first material in optimal conditions adapted to ensuring a growth at a maximum controllable rate, and including an initial step consisting of sending on the substrate a puff of a gas containing the second material, in conditions corresponding to a deposition rate much faster than said maximum controllable rate.

2. The method of claim 1, wherein the first material forming the substrate is silicon and the second material forming the dots is germanium.

3. The method of claim 2, implemented in an epitaxy reactor at a temperature from 630 to 670°

C., at a pressure from 0.02 to 0.04 * 10⁵ Pa, said optimal conditions corresponding to a flow rate on the order of 15 to 25 cm³/mn of germane with a 10% dilution in hydrogen, and the puff of germane comprises a 10% dilution in hydrogen sent at a mean flow rate of about 200 cm³/mn for a duration ranging from 1 to 5 s.

4. The method of claim 3, wherein the sending a puff is followed by an injection of germane in said optimal conditions for 25 to 40 s.

5. The method of claim 1, wherein the first material forming the substrate is silicon or germanium and the second material forming the dots is a rare earth.

6. The method of claim 1, wherein the first material forming the substrate is silicon oxide and the second material forming the dots is silicon nitride.

7. A method of forming, on a single-crystal semiconductor substrate of a first material, quantum dots of a second material, the method comprising:

in an epitaxy reactor, determining a first range of flow rates of the second material to obtain a controllable deposition rate of the second material on the substrate of the first material at or below a maximum controllable deposition rate;

injecting the second material into the epitaxy reactor for a short duration at a mean flow rate much greater than the first range of flow rates; and

subsequently injecting the second material into the epitaxy reactor for a longer duration at a mean flow rate in the first range of flow rates.

8. The method of claim 7, wherein the first material forming the substrate is one of silicon and germanium and the second material forming the quantum dots is a rare earth.

9. The method of claim 7, wherein the first material forming the substrate is silicon oxide and the second material forming the quantum dots is silicon nitride.

10. The method of claim 7, wherein the first material forming the substrate is silicon and the second material forming the quantum dots is germanium.

11. The method of claim 10, wherein:

the epitaxy reactor is operated at a temperature from 630 to 670°

C. and a pressure from 0.02 to 0.04 * 10⁵ Pa;

the second m material is provided as germane diluted at 10% in hydrogen;

the first range of flow rates is 15 to 25 cm³/mn of germane;

the mean flow rate of the second material during the short duration is about 200 cm³/mn; and

the short duration is a duration ranging from 1 to 5 s.

12. The method of claim 11, wherein the longer duration of injecting the second material into the epitaxy reactor at a mean flow rate in the first range of flow rates is in the range of 25 to 40 s.

14. The method of claim 13, wherein injecting the gas at an optimal flow rate comprises injecting the gas at an optimal flow rate that provides a maximum controllable deposition rate for the epitaxy reactor.

15. The method of claim 14, wherein injecting a puff of a gas comprises injecting the gas at a mean flow rate that is much greater than the optimal flow rate.

16. The method of claim 15, wherein the gas containing germanium comprises germane diluted at 10% in hydrogen.

17. The method of claim 16, wherein injecting a puff of a gas comprises injecting the gas at a mean flow rate of approximately 200 cm³/mn for a duration of approximately 2 s.

18. The method of claim 17, wherein continuing injecting the gas into the epitaxy reactor at an optimal flow rate comprises continuing injecting the gas into the epitaxy reactor at a flow rate ranging between 15 and 25 cm³/mn for a duration from 25 to 30 s.

19. The method of claim 18, wherein the temperature of the epitaxy reactor is maintained at a constant value between 600 and 700°

C.

20. The method of claim 19, wherein the pressure of the epitaxy reactor is maintained at a value between 0.025 and 0.040 * 10⁵ Pa.

13. A method for forming quantum dots in a substrate, the method comprising:

cleaning and preparing a surface of a single-crystal silicon substrate;

installing the substrate into an epitaxy reactor;

injecting a puff of a gas containing germanium into the epitaxy reactor;

continuing injecting the gas containing germanium into the epitaxy reactor at an optimal flow rate; and

growing a silicon encapsulation layer.