Method of forming an interconnect structure with a graded composition using a nitrided target

• US 6,028,003 A
• Filed: 07/03/1997
• Issued: 02/22/2000
• Est. Priority Date: 07/03/1997
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Frisa, Larry E., Chuang, Hak-Lay
• Primary Examiner(s): Fahmy, Wael M.
• Assistant Examiner(s): EATON, KURT M
• Application Number:
  US08/887,654
• Time in Patent Office: 964 Days
• Field of Search: 438/652, 438/656, 438/678, 438/648, 438/658, 438/685, 438/653, 438/654, 204/192.1, 204/192.15
• US Class Current: 438/653
• CPC Class Codes: C23C 14/0641 Nitrides C23C14/0617 takes precedence
• CPC Class Codes: H01L 21/7685 the layer covering a conductive structure H01L21/76849 takes precedence
• CPC Class Codes: H01L 2221/1078 Multiple stacked thin films not being formed in openings in dielectrics

Abstract

A method for forming an interconnect structure on a semiconductor wafer (114) begins by placing the wafer (114) in a process chamber (100). The process chamber (100) contains a titanium (Ti) target (102) having a thin titanium nitride (TiN) layer (104) formed thereon. An argon-based plasma (106) is used to sputter the layer (104) off of the target (102) and onto a top surface of the water (114) to form an Argon Uniquely Sputtered Titanium Nitride (AUSTiN) layer (116) which has a nitrogen concentration gradient therethrough. After forming the layer (116), an argon-nitrogen plasma (107) is initiated to reform the titanium nitride (TiN) layer (104) on the target and complete the interconnect structure by forming a top stoichiometric or near stoichiometric titanium nitride layer (118) over the layer (116).

Claims

1. A method for forming a semiconductor structure, the method comprising the steps of:

providing a semiconductor substrate having a region comprising a first metal;

providing a processing chamber;

providing, in the processing chamber, a target having a first layer comprising a first target metal composition and a second layer having a second target metal composition;

placing the semiconductor substrate in the processing chamber;

creating an inert gas plasma in the processing chamber;

forming a first target metal region over the semiconductor substrate;

introducing nitrogen into the processing chamber in situ with the inert gas plasma; and

forming a second target metal region over the semiconductor substrate and forming a new first layer on the target by reacting the nitrogen with the second layer.

2. The method of claim 1, wherein the step of providing a target further comprises the target being a refractory metal, wherein the first layer is a refractory metal-nitrogen composition and the second layer is substantially comprises the refractory metal.

3. The method of claim 2, wherein the step of providing a target further comprises the refractory metal comprising titanium.

4. The method of claim 2, wherein the step of providing a target further comprises the refractory metal comprising tantalum.

5. The method of claim 1, wherein the step of forming a first target metal region further comprises the first target metal region being formed by sputtering the first layer directly on the semiconductor substrate.

6. The method of claim 5, wherein the step of forming a first target metal region further comprises the first target metal region having a greater nitrogen content at a first point near the semiconductor substrate than at a second point which is further away from the semiconductor substrate than the first point.

7. The method of claim 6, wherein the step of forming a second target metal region further comprises the second target metal region'"'"'s nitrogen composition being substantially stoichiometric.

8. The method of claim 5, wherein the step of forming a first target metal region further comprises the first target metal region being a graded metal region, wherein the graded metal region is graded from a substantially stoichiometric nitrogen composition near the semiconductor substrate to being target metal rich.

9. The method of claim 1, wherein the step of forming a second target metal region further comprises the second target metal region'"'"'s nitrogen composition being substantially stoichiometric.

10. The method of claim 1, wherein:

the step of forming a first target metal region further comprises the first target metal region having a first location and a second location, wherein the first location is closer to the semiconductor substrate than the second location;

the step of forming a second target metal region further comprises the first target metal region having a third location; and

wherein

a second atomic concentration of nitrogen at the second location is less than a first atomic concentration of nitrogen at the first location and the second atomic concentration of nitrogen is less than a third atomic concentration of nitrogen at the third location.

11. The method of claim 1, wherein the step of forming a first target metal region further comprises the first target metal region being a barrier preventing nitrogen, introduced during the step of introducing nitrogen into the processing chamber, from substantially reacting with the first metal to form compounds containing nitrogen molecules.

12. The method of claim 11, wherein the step of forming a first target metal region further comprises the first metal being aluminum and the nitrogen containing molecule being AlN.

13. The method of claim 1, wherein the step of forming a first target metal region further comprises the first target metal region being a barrier preventing titanium from substantially reacting with the first metal to form compounds containing titanium atoms.

14. The method of claim 13, wherein the step of forming a first target metal region further comprises the first metal being aluminum and the compound containing titanium atoms being Al₃ Ti.

15. The method of claim 1, wherein the step of forming a first target metal region further comprises the substep of:

sputtering the first target metal region by applying to the processing chamber between 5000 watt-seconds to 15000 watt-seconds.

16. A method of forming a semiconductor interconnect structure comprising the steps of:

providing a processing chamber;

placing a refractory metal target into the processing chamber;

conditioning the refractory metal target to form a nitrided target layer;

providing a semiconductor substrate;

forming a dielectric region over the semiconductor substrate;

forming a first metal region over the dielectric region;

placing the semiconductor substrate in the processing chamber;

introducing an inert gas into the processing chamber;

forming a first nitrided metal region over the first metal region based upon the nitrided target layer;

introducing nitrogen into the processing chamber in situ with the inert gas;

forming a second nitrided metal region over the first nitrided metal region, where the second nitrided metal region is substantially stoichiometric; and

reconditioning the nitrided target layer to form a nitrided target layer at substantially as same time as forming the second nitrided metal region.

17. The method of claim 16, wherein the steps forming first and second nitrided metal regions further comprise using sputtered technology to form the first and second nitrided metal regions.

18. The method of claim 17, wherein the steps forming first and second nitrided metal regions further comprise forming the first and second nitrided metal regions as titanium nitride regions.

19. The method of claim 17, wherein the steps forming first and second nitrided metal regions further comprise forming the first and second nitrided metal regions as tantalum nitride regions.

20. The method of claim 16, wherein the steps providing the refractory metal target comprises:

providing a refractory metal target comprising titanium.

21. The method of claim 16, wherein the steps providing the refractory metal target comprises:

providing a refractory metal target comprising tantalum.