Gas injection system with precursor for planar deprocessing of semiconductor devices using a focused ion beam

Patent metadata

Field	Value
Publication number	US-9761467-B2
Application number	US-201514747491-A
Country	US
Kind code	B2
Filing date	Jun 23, 2015
Priority date	May 28, 2013
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A method and system for improved planar deprocessing of semiconductor devices using a focused ion beam system. The method comprises defining a target area to be removed, the target area including at least a portion of a mixed copper and dielectric layer of a semiconductor device; directing a precursor gas toward the target area; and directing a focused ion beam toward the target area in the presence of the precursor gas, thereby removing at least a portion of a first mixed copper and dielectric layer and producing a uniformly smooth floor in the milled target area. The precursor gas causes the focused ion beam to mill the copper at substantially the same rate as the dielectric. In a preferred embodiment, the precursor gas comprises methyl nitroacetate. In alternative embodiments, the precursor gas is methyl acetate, ethyl acetate, ethyl nitroacetate, propyl acetate, propyl nitroacetate, nitro ethyl acetate, methyl methoxyacetate, or methoxy acetylchloride.

First claim

We claim as follows:

1. A focused ion beam system for removing multiple layers of material, the system comprising:
an ion source;
an ion beam column configured to mill at least a portion of a target area on a sample by focusing ions from the ion source into a focused ion beam and directing the focused ion beam onto the target area; and
a gas injection system comprising a precursor gas selected from the group consisting of methyl acetate, methyl nitroacetate, ethyl acetate, ethyl nitroacetate, propyl acetate, propyl nitroacetate, nitro ethyl acetate, methyl methoxyacetate, and methoxy acetylchloride.

2. The focused ion beam system of claim 1 , in which the ion source is a plasma ion source.

3. The focused ion beam system of claim 1 , in which the ions are selected from the group consisting of Xe + , Ga + , Ar + , Kr + , O + , O 2 + , N + , NO + , NO 2 + , Au + , Bi + , Si + , Ge + .

4. The focused ion beam system of claim 1 , in which the sample comprises a semiconductor device having a mixed layer of copper and dielectric.

5. The focused ion beam system of claim 4 , in which the gas injection system is configured to direct the precursor gas toward the at least a portion of the target area such that the precursor gas causes the focused ion beam to mill the copper and the dielectric at substantially the same rate.

6. The focused ion beam system of claim 5 , in which the ion beam column is programmed to direct the focused ion beam to mill away the at least a portion of the target area such that a milling floor in the semiconductor device having a substantially planar, uniform surface is produced.

7. The focused ion beam system of claim 6 , in which the dielectric comprises a low-k dielectric.

8. The focused ion beam system of claim 7 , in which the dielectric is selected from a group comprising: carbon-doped silicon dioxide, porous silicon dioxide, and porous carbon- doped silicon dioxide.

9. The focused ion beam system of claim 1 , further comprising a lower vacuum chamber configured to contain the sample as the focused ion beam mills the at least a portion of the target area.

10. The focused ion beam system of claim 9 , further comprising a vacuum system configured to maintain pressures in the lower vacuum chamber in a range of from approximately 1×10 −7 Torr to approximately 5×10 −4 Torr as the focused ion beam mills the at least a portion of the target area.

11. The focused ion beam system of claim 10 , in which the ion source is capable of producing ions that can be focused into a sub one-tenth micron wide focused ion beam.

12. A gas injection system, comprising:
a precursor gas selected from the group consisting of methyl acetate, methyl nitroacetate, ethyl acetate, ethyl nitroacetate, propyl acetate, propyl nitroacetate, nitro ethyl acetate, methyl methoxyacetate, and methoxy acetylchloride,
wherein the gas injection system is configured to direct the precursor gas toward a target area on a sample disposed within a lower chamber of a focused ion beam system.

13. The gas injection system of claim 12 , in which the sample is a sample positioned on a stage located within the lower chamber.

14. The gas injection system of claim 13 , in which the stage is a movable X-Y stage.

15. The gas injection system of claim 12 , in which the lower chamber is a vacuum chamber.

16. The gas injection system of claim 12 , in which the gas injection system is configured to direct the precursor gas toward a target area on a sample inside a focused ion beam system as the sample is milled by a focused ion beam.

17. The gas injection system of claim 16 , in which the sample comprises a semiconductor device having a mixed layer of copper and dielectric.

18. The gas injection system of claim 17 , in which the focused ion beam system is a focused ion beam system comprising an ion source, a high voltage power supply, a focused ion beam column, a lower chamber containing the semiconductor device, and a vacuum system.

19. The gas injection system of claim 18 , in which the gas injection system is configured to direct the precursor gas toward a target area on the semiconductor device as the focused ion beam column directs a focused ion beam onto the target area such that the precursor gas causes the focused ion beam to mill the copper and the dielectric at substantially the same rate.

20. The gas injection system of claim 19 , in which:
the ion source is capable of producing ions that can be focused into a focused ion beam having a sub one-tenth micron width at the target;
the vacuum system is a vacuum system configured to maintain pressures in the lower chamber in a range of from approximately 1×10 −7 Torr to approximately 5×10 −4 Torr; and
the high voltage power supply configured to produce focused ion beams having energies in a range of from approximately 1 keV to approximately 60 keV.

Assignees

• Fei Co

Inventors

• Rue Chad
• Chandler Clive D

Classifications

• H10P50/283

  by chemical means · CPC title

• H10P50/282

  of inorganic materials · CPC title

• H10P50/267

  using plasmas · CPC title

• H10P50/262

  by physical means only · CPC title

• H10P50/242

  of Group IV materials · CPC title