Plasma annealing of substrates to improve adhesion

Details Plasma annealing of substrates to improve adhesion Plasma annealing of substrates to improve adhesion

1998-01-20

2001-09-18

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S643000, C438S513000, C438S681000, C438S685000, C427S532000, C427S533000

Reexamination Certificate

active

06291343

ABSTRACT:

BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention is directed toward the field of manufacturing integrated circuits.
B. Description of the Related Art
In the manufacture of integrated circuits, diffusion barriers are employed to inhibit the diffusion of metals into regions underlying the diffusion barrier. These underlying regions include transistor gates, capacitor dielectrics, semiconductor substrates, metal lines, and many other structures that appear in integrated circuits. The prevention of metal diffusion is important, because metal diffusion can cause highly resistive pockets to form in regions into which it diffuses. The formation of such resistive pockets can render an integrated circuit defective.
For example, when an electrode is being formed for a transistor's gate, a diffusion barrier is often formed between the gate and a metal that serves as the contact portion of the electrode. The diffusion barrier inhibits the diffusion of the metal into the gate, which may be composed of polysilicon. Diffusion barriers are also employed between the dielectric of a capacitor and the contact portion of the capacitor's electrode. The dielectric may be composed of a material such as tantalum pentoxide, while the electrode's contact portion consists of a metal, such as tungsten, titanium, aluminum or copper. The diffusion barrier prevents the diffusion of the metal into the dielectric. Otherwise, such a diffusion would render the capacitor inoperable.
Refractory metal nitrides have been employed as diffusion barriers. For example, titanium nitride has been employed to inhibit the diffusion of metals, such as copper and aluminum. However, titanium nitride's adhesion to certain surfaces, such as polysilicon and tantalum oxides, is not as high as is desired. Good adhesion is important to provide for the structural integrity of the integrated circuit being manufactured. Good adhesion also provides for better conductivity between the diffusion barrier and an underlying region.
Further, when titanium nitride is deposited on tantalum pentoxide, a reaction occurs. The oxygen from the tantalum pentoxide mixes with the titanium nitride and oxidizes the titanium nitride. This intermixing of the oxygen and the titanium nitride is undesirable, because the presence of oxygen raises the resistivity of the titanium nitride film.
Rapid thermal nitridation has been employed to improve the adhesion of titanium nitride to tantalum pentoxide and reduce the oxidation of titanium nitride. Before the titanium nitride is deposited, rapid thermal nitridation is performed on the tantalum pentoxide substrate to form tantalum oxynitride on the surface of the substrate. The titanium nitride is then deposited on the tantalum oxynitride to which it has better adhesion.
Currently, the rapid thermal nitridation of the tantalum pentoxide substrate and the deposition of titanium nitride cannot be carried out as in-situ operations in the same chamber. As a result, the wafer has to be placed in a rapid thermal nitridation chamber following the deposition of tantalum pentoxide and transferred to a titanium nitride deposition chamber after the rapid thermal nitridation is performed.
It is desirable to minimize the number of different processing chambers that are employed. This limits the number of chamber transfers that must be undergone by a wafer. Chamber transfers are undesirable, because they cause a wafer to be exposed to contaminants in the environment outside of the chamber. Such contaminants can render the wafer defective. Further, the wafer may be exposed to oxygen during transfers. The oxygen can then react with materials on the wafer's surface to increase the resistivity of the wafer's surface material to unacceptable levels.
Accordingly, it is desirable to provide for the formation of a refractory metal nitride film, such as titanium nitride, on a substrate, so that the refractory metal nitride has acceptable diffusion barrier properties and adhesion to the substrate. It is also desirable for any substrate treatment that is performed prior to the deposition of the refractory metal nitride to be carried out in the same chamber as the deposition of the refractory metal nitride.
SUMMARY OF THE INVENTION
In accordance with the present invention, a refractory metal nitride film is formed on an exposed substrate in a partially formed integrated circuit on a wafer so that the film adheres to the substrate. Further, the entire formation of the film may be performed in-situ in a single processing chamber.
In forming such a film, the substrate is plasma annealed prior to the deposition of any film materials. During the plasma annealing, the substrate is bombarded with ions. After the substrate is plasma annealed, a layer of refractory metal nitride is deposited on the substrate. In one embodiment of the present invention, the refractory metal nitride is titanium nitride. As a result of plasma annealing the substrate, there is a good adhesive bond between the substrate and the refractory metal nitride.
Next, the deposited refractory metal nitride undergoes a first plasma annealing, during which the refractory metal nitride is bombarded with a first set of ions. In embodiments of the present invention, the refractory metal nitride also undergoes a second plasma annealing after the first plasma annealing is completed. During the second plasma annealing, the refractory metal nitride is bombarded with a second set of ions. In embodiments of the present invention, the plasma annealing of the substrate, deposition of refractory metal nitride, and plasma annealing of the refractory metal nitride may all be performed in-situ in the same chamber.
When plasma annealing the substrate, the substrate is exposed to a plasma containing ions. The plasma is generated by providing a gas and energizing the gas with the energy generated with a radio frequency. In one embodiment of the present invention, the gas that is provided is a nitrogen gas. In further embodiments of the present invention, the gas may include a mixture of nitrogen and other elements such as hydrogen and helium.


REFERENCES:
patent: 4173661 (1979-11-01), Bourdon
patent: 4480010 (1984-10-01), Sasanuma
patent: 4844775 (1989-07-01), Keeble
patent: 5017403 (1991-05-01), Pang et al.
patent: 5127988 (1992-07-01), Kawamura et al.
patent: 5202280 (1993-04-01), Kamiyama et al.
patent: 5232871 (1993-08-01), Huei-Min Ho
patent: 5296404 (1994-03-01), Akahori et al.
patent: 5308655 (1994-05-01), Eichman et al.
patent: 5312774 (1994-05-01), Nakamura et al.
patent: 5314603 (1994-05-01), Sugiyama et al.
patent: 5352623 (1994-10-01), Kamiyama
patent: 5451258 (1995-09-01), Hillman et al.
patent: 5576071 (1996-11-01), Sandhu
patent: 5593511 (1997-01-01), Foster et al.
patent: 0 397 131 A2 (1990-11-01), None
patent: 477990 (1992-01-01), None
patent: 0 545 602 A1 (1993-06-01), None
patent: 0 630 989 A2 (1994-12-01), None
patent: 0 678 903 A1 (1995-10-01), None
patent: 0 720 214 A2 (1996-07-01), None
patent: 0 738 002 A2 (1996-10-01), None
patent: 0 776 991 A1 (1997-06-01), None
patent: 0 840 363 A1 (1998-05-01), None
patent: WO 95/33865 (1995-12-01), None
Park et al. “A Novel A1-Reflow Process Using Surface Modification by the ECR Plasma Treatment and its Application to the 256Mbit DRAM” International Electron Devices Meeting, US, New York, IEEE, pp. 108-112, Dec. 11, 1994.

Affiliated with

Also associated with

Rating

Plasma annealing of substrates to improve adhesion does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Plasma annealing of substrates to improve adhesion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plasma annealing of substrates to improve adhesion will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2493655