Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state – With decomposition of a precursor
Reexamination Certificate
1999-06-16
2001-08-14
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
With decomposition of a precursor
C117S089000, C117S099000, C546S002000, C556S112000
Reexamination Certificate
active
06273951
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to precursor mixtures for the preparation of layers on substrates, particularly layers on semiconductor device structures. Specifically, such mixtures are particularly suitable for forming layers, such as metal oxide layers, especially barium-strontium-titanate (BST) layers.
BACKGROUND OF THE INVENTION
Capacitors are the basic energy storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs).
High quality thin oxide layers of metals, such as barium-strontium-titanates and strontium-bismuth-tantalates, for example, deposited on semiconductor wafers have recently gained interest for use in memory devices. These materials have very high dielectric constants and excellent resistance to fatigue. They also have suitable properties for a variety of other uses, such as electrooptic materials, pyroelectric materials, and antireflective coatings.
Suitable metal oxides are typically delivered to a substrate in the vapor phase; however, many oxides are difficult to deliver using vapor deposition technology. Many precursors are sensitive to thermal decomposition. Also, many precursors have vapor pressures that are too low for effective vapor deposition.
Thus, there is a continuing need for methods and materials for the formation of layers on substrates. This is particularly true for the formation of metal oxide layers, as well as other layers, on semiconductor structures, particularly random access memory devices, using vapor deposition processes. There is a particular need for methods that use volatile liquid precursors of low valent metals, which are suitable for use in vapor deposition processes without undue particle formation.
SUMMARY OF THE INVENTION
The present invention is directed to precursor mixtures and methods for forming metal-containing layers on substrates, such as semiconductor substrates or substrate assemblies during the manufacture of semiconductor structures, particularly memory devices. The method involves forming a layer using a precursor mixture of two or more complexes of the formula:
L
y
MY
z
, (Formula I)
wherein: M is a metal (main group, transition metal, or lanthanide); each L group is independently a neutral ligand containing one or more Lewis-base donor atoms (e.g., O, S, N, P, As, Se, or halogen); each Y group is independently an anionic ligand; y=a nonzero integer; and z=a nonzero integer corresponding to the valence state of the metal. It is further required that there are at least two different L groups present in the mixture, whether they be in the same complex (e.g., L′
x
L″
y-x
MY
z
) or different complexes (e.g., L′
y
MY
z
plus L″
y
MY
z
).
Typically and preferably, the layer is a metal-containing, and more preferably a dielectric metal-containing, material. The metal-containing film can be a single metal or a metal alloy containing a mixture of metals. The metal-containing layer can also be an oxide, sulfide, selenide, telluride, nitride, or combination thereof, for example. Preferably, the layer is a metal-containing oxide layer. The layer can be used as a dielectric layer in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device.
The methods of the present invention involve vaporizing a precursor composition (i.e., precursor mixture) comprising two or more complexes of Formula I and directing it toward a substrate, such as a semiconductor substrate or substrate assembly, (preferably, using a chemical vapor deposition technique) to form a metal-containing layer on a surface of the substrate. Preferably, the metal of the complexes of Formula I is selected from the group of the Group IA (i.e., Group 1), Group IIA (i.e., Group 2) metals, the Group IVB (i.e., Group 4) metals, the Group VA (i.e., Group 15), and the Group VB (i.e., Group 5) metals. More preferably, the complexes include a metal selected from the group of Ba, Sr, Ti, Nb, and Ta. Particularly preferred metals M include Ba and Sr.
Preferably, the neutral ligand L of Formula I is selected from the group of polyamines, polyethers, aminoalcohols, ether-alcohols, and the like. Each complex can include various combinations of L groups. More preferably, the neutral ligand is selected from the group of alkyl-substituted polyamines.
Preferably, the anionic ligand Y of Formula I is selected from the group of carboxylates, ketoiminates, amidinates, diketonates, diiminates, and the like. Each complex can include various combinations of Y groups. More preferably, the anionic ligand is selected from the group of diketonates and ketoiminates.
The complexes of Formula I are neutral complexes, which are preferably liquids at room temperature. Preferably, precursor mixtures of the present invention include two or more complexes of Formula I that are miscible liquids. More preferably, they are miscible liquids at room temperature. As used herein, “miscible liquids” are complexes in the liquid phase (whether at room temperature or an elevated temperature) that are substantially uniformly dissolved in each other such that only one phase is observed by the human eye.
Methods of the present invention are particularly well suited for forming layers (i.e., films) on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. For example, the methods can involve manufacturing a memory device by providing a substrate having a first electrode thereon, vaporizing a precursor composition and directing it toward the substrate to form a dielectric layer comprising an oxide layer on the first electrode of the substrate, and forming a second electrode on the dielectric layer.
It is to be understood that methods of the present invention are not limited to deposition on silicon substrates, such as silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies can be used in methods of the present invention. These include, for example, fibers, wires, etc. If the substrate is a semiconductor substrate or substrate assembly, the layers can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term “semiconductor substrate” refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term “semiconductor substrate assembly” refers to the semiconductor substrate having one or more layers or structures formed thereon.
A particularly preferred embodiment of the present invention is a method of forming a layer using a liquid precursor composition. The liquid precursor composition includes two or more complexes of Formula I. The method involves vaporizing the precursor composition to form vaporized precursor composition; and directing the vaporized precursor composition toward the substrate to form a layer on the substrate. Herein, vaporized precursor composition includes vaporized molecules of complexes of Formula I described herein either alone or optionally with vaporized molecules of other compounds in the precursor composition, including solvent molecules, if used.
The present invention further provides a chemical vapor deposition precursor composition comprising two or more complexes of Formula I describe
Kunemund Robert
Micro)n Technology, Inc.
Mueting Raasch & Gebhardt, P.A.
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