Coating processes – Coating by vapor – gas – or smoke – Metal coating
Reexamination Certificate
2000-04-10
2003-03-25
Chen, Bret (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Metal coating
C427S240000, C427S455000
Reexamination Certificate
active
06537613
ABSTRACT:
BACKGROUND OF THE INVENTION
Multicomponent metal containing materials, such as mixed-metal/metalloid oxides and nitrides often have unique physical properties that each individual metal/metalloid oxide
itride component does not possess. For example, some mixed metal oxides can be used for high dielectric constant materials, R. Cava et al., Nature, vol. 377, p.215, (1995), ferroelectrics, L. M. Sheppard, Ceramic Bulletin, vol.71, p.85, (1992), high temperature superconductors, D. L. Schulz et al. Adv. Mater., vol.6, p.719, (1994), catalysts, M. Gugliemi et al., J. Electrochem. Soc., vol.139, p.1655, (1992), and corrosion resistent coating, N. Hara et al., J. Electrochem. Soc., vol.146, p.510, (1999). Also some mixed metal nitrides show good diffusion barrier properties, X. Sun et al., J. Appl. Phys. Vol.81, p.664, (1997), superconducting, R. B. Van Dover, Chem. Mater., vol. 5, p.32, (1993), and magnetic properties, K. Schunitzke et al., Appl. Phys. Lett., vol. 57, p. 2853, (1990).
As the size of integrated circuits (IC) devices becomes aggressively smaller, thin films deposited by chemical vapor deposition (CVD) demonstrates an advantage over physical vapor deposition (PVD) methods in terms of conformal coverage on various non-planer surfaces. In general, liquid precursors are preferred for CVD applications due to the ease and reproducibility in precursor delivery.
Common precursor delivery methods used in CVD processing include vapor draw, bubbling with carrier gas, mist droplet (aerosol) delivery, and direct liquid injection (DLI). DLI is particularly a preferred method for the consistent delivery of multi-components because it delivers the same ratio of constituents to the reactor as are in the source container. DLI has the added advantage of storing the precursor at room temperature and heating only the amount required to be delivered, and therefore, improving precursor shelf life.
Metal silicates for electronic materials have been studied by those skilled in the art. For instance, Wilk, et. al., Hafnium and Zirconium silicates for advanced gate dielectrics, Journal of Applied Physics, Vol. 87, No. 1, 2000, pp. 484-492 describe the use of metal silicates as gate dielectric films with varying metal contents. Depositions were by sputtering and e-beam evaporation. Separate films were deposited at specific temperatures chosen over the range of 25° C. to 600° C. Kolawa, et. al., Amorphous Ta—Si—N thin-film alloys as diffusion barrier in Al/Si metallizations, J. Vac. Sci. Technol. A 8 (3), May/June 1990, pp. 3006-3010, indicates that Ta—Si—N films of a wide range of compositions were prepared by rf reactive sputtering. The films were used as diffusion barriers. Nitrogen incorporation was varied by varying the amount of nitrogen in the reaction atmosphere. Sun, et. al., Reactively sputtered Ti—Si—N films. II. Diffusion barriers for Al and Cu metallizations on Si, J. Appl. Phys. 81 (2) Jan. 15, 1997, pp. 664-671, describes sputtered films of Ti—Si—N for interfacing with Al and Cu. Nitrogen content was varied during the depositions. Wilk, et. al., Electrical properties of hafnium silicate gate dielectrics deposited directly on silicon, Applied Physics Letters, Vol. 74, No. 19, 10 May 1999, pp. 2854-2856, describes HfSi
x
O
y
gate dielectric films. Films were deposited at 500° C.
Other mixed metal systems of general interest are; VanDover, et. al., Discovery of a useful thin-film dielectric using a composition-spread approach, Nature, Vol. 392, 12 March 1998, pp. 162-164, discloses capacitance devices with high dielectric films of Zr—Sn—Ti—O. Depositions were performed below 300° C.; VanDover, et. al., Deposition of Uniform Zr—Sn—Ti—O Films by On-Axis Reactive Sputtering, IEEE Electron Device Letters, Vol. 19, No. 9, September 1998, pp. 329-331, describes sputtering at 200° C.±10° C.; Cava, et. al., enhancement of the dielectric constant of Ta
2
O
5
through Substitution with TiO
2
, Nature, Vol. 377, Sept. 21, 1995, pp. 215-217, prepared ceramic samples of Ta
2
O
5
—TiO
2
by physically mixing and firing at temperatures of 1350-1400° C.; Cava, et. al., Dielectric properties of Ta
2
O
5
—ZrO
2
polycrystalline ceramics, J. Appl. Phys. 83, (3), Feb. 1, 1998, pp. 1613-1616, synthesized ceramics by physical mixture and firing; U.S. Pat. Nos. 5,923,056 and 5,923,524 address mixed metal oxides for electronic materials.
In the field of electronic materials for device fabrication, such as interlayer dielectrics, gate oxides, capacitors and barrier layers, it is desirable to have materials which have a varying compositional gradient of mixed metals or metal/metalloid composition in either oxide, oxynitride or nitride form. The prior art has failed to provide a quick, simple and reproducible method for controllably producing a deposited layer of mixed metal/metalloid oxides, oxynitride or nitrides having a compositional gradient over the depth of the deposited layer.
The present invention overcomes this deficiency as will be set forth in greater detail below.
BRIEF SUMMARY OF THE INVENTION
A process for deposition of a multiple metal and metalloid compound layer with a compositional gradient of the metal and metalloid in the layer on a substrate of an electronic material, comprising: a) providing two or more metal-ligand and metalloid-ligand complex precursors, which preferably constitute a liquid at ambient conditions, wherein the ligands are preferably the same and are preferably selected from the group consisting of alkyls, alkoxides, halides, hydrides, amides, imides, azides, nitrates, cyclopentadienyls, carbonyls, pyrazoles, and their fluorine, oxygen and nitrogen substituted analogs; b) delivering the mixture to a deposition zone where the substrate is located; c) contacting the substrate under deposition conditions with the precursors, where the contacting the substrate under deposition conditions is preferably selected from the group consisting of chemical vapor deposition, spray pyrolysis, jet vapor deposition, sol-gel processing, spin coating, chemical solution deposition, and atomic layer deposition; d) varying the temperature of the deposition conditions from a first temperature to a second distinct temperature which is at least 40° C. from said first temperature during the contact, and e) depositing a multiple metal and metalloid compound layer on the substrate from the precursors resulting in the compositional gradient of the metal and metalloid in the layer as a result of step d). An oxygen source can be added to result in a metal-metalloid oxide, or a nitrogen source can be added to result in a metal-metalloid nitride, and a mixture of oxygen source and nitrogen source can be added to result in a metal-metalloid oxynitride. The metalloid would preferably be silicon.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a graph of atomic percent concentration and dielectric constant charted against temperature of a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention a new metal and metalloid deposition resulting in a compositional gradient is disclosed that can be used for precursor dispersing delivery methods, including DLI in CVD applications. Preferably, the precursors are a solventless mixture.
The volatile components are chosen such that:
1) They are chemically compatible, therefore, no non-volatile polymeric or multinuclear species are formed.
2) No precipitates are generated due to ligand exchange on the metals or inter ligand reactions.
3) The mixtures maintain low viscosity and thermal stability.
4) Undesired redox chemistry will not take place (eg. M
+1
+M′
+3
→M
+2
+M′
+2
).
In the preferred form, liquid mixtures can be prepared either by directly mixing liquid metal/metalloid complexes or dissolving solid metal or metalloid complex(es) in liquid metal or metalloid complex(es). In these systems, no solvent is needed to dissolve or dilute the precursor mixtures to achieve a total liquid phase of the resulting mixtures. The preferred non-solvent containing precu
Hochberg Arthur Kenneth
Norman John Anthony Thomas
Senzaki Yoshihide
Air Products and Chemicals Inc.
Chase Geoffrey L.
Chen Bret
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