Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-04-27
2001-12-11
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S260000, C427S252000
Reexamination Certificate
active
06329286
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the preparation of generally conformal iridium layers on substrates, particularly on semiconductor device structures.
BACKGROUND OF THE INVENTION
Films (i.e., layers) of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. For example, high quality RuO
2
thin films deposited on silicon wafers have recently gained interest for use in ferroelectric memories. Many of the Group VIII metal films are generally unreactive toward silicon and metal oxides, resistant to diffusion of oxygen and silicon, and are good conductors. Oxides of certain of these metals also possess these properties, although perhaps to a different extent.
Thus, layers of Group VIII metals and metal oxides, particularly the second and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt), have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for electrical contacts. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices, such as ferroelectric memories. Furthermore, they may even be suitable as the plate (i.e., electrode) itself in capacitors. Iridium oxide is of particular interest as a barrier layer because it is very conductive (30-60 &mgr;&OHgr;-cm) and is inherently a good oxidation barrier.
Capacitors are the basic charge 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). It is important for device integrity that oxygen and/or silicon not diffuse into or out of the dielectric material. This is particularly true for ferroelectric RAMs because the stoichiometry and purity of the ferroelectric material greatly affect charge storage and fatigue properties.
Thus, there is a continuing need for methods and materials for the formation of metal layers, such as iridium metal or metal oxide layers, which can function as barrier layers, for example, in integrated circuits, particularly in random access memory devices. There is a particular need for metal or metal oxide layers in contact openings which are extremely small and require conformally filled layers.
SUMMARY OF THE INVENTION
The present invention is directed to methods for manufacturing a semiconductor device, particularly a ferroelectric device. The methods involve forming generally conformal iridium layers on substrates, such as semiconductor substrates or substrate assemblies during the manufacture of semiconductor structures. The resultant generally conformal iridium layer can be used as a barrier layer or electrode in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device.
The term “iridium layer” preferably refers to relatively pure metal films of iridium optionally including oxides of iridium. The term “conformal” refers to a layer having generally uniform step coverage. Preferably, the term “conformal” refers to a step coverage of greater than about 70%, and more preferably, greater than about 80%, in greater than about 2:1 aspect ratio cavities. Herein, “step coverage” is the thickness of the layer in the bottom of a hole divided by the thickness of the layer on the top surface (outside the hole) times 100 (to convert to a percentage).
One preferred method of the present invention involves forming a layer on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure. The method includes: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a precursor composition including one or more complexes of the formula:
CpIr(CO)
2
(Formula I)
wherein Cp is a substituted or unsubstituted cyclopentadienyl ligand; vaporizing the precursor composition (which optionally includes one or more solvents) to form vaporized precursor composition; and directing the vaporized precursor composition in the presence of one or more carrier gases and one or more oxidizing gases toward the substrate to form a generally conformal iridium layer (preferably, an iridium metal layer optionally including oxides of iridium) on a surface of the substrate. Using such methods, the complexes of Formula I are converted in some manner (e.g., decomposed thermally) and deposited on a surface to form a generally conformal layer. Thus, the layer is not simply a layer of the complex of Formula I.
Preferably, in the methods of the invention the ratio of the total number of moles of carrier gases to the total number of moles of oxidizing gases is within a range of about 0.6:1.0 to about 1.4:1.0, more preferably, within a range of about 0.7:1.0 to about 1.3:1.0, and most preferably, the total number of moles of carrier gases to the total number of moles of oxidizing gases is substantially similar. In this context “substantially similar” means that the total number of moles of carrier gases to oxidizing gases are within about 10% of each other.
In certain preferred embodiments, the partial pressure of CpIr(CO)
2
in the carrier gas is about 0.001 torr to about 10 torr. In other preferred embodiments, Cp of Formula I is monomethyl cyclopentadienyl.
Complexes of Formula I are neutral complexes and may be liquids or solids at room temperature. Typically, however, they are liquids. If they are solids, they are preferably sufficiently soluble in an organic solvent or have melting points below their decomposition temperatures such that they can be used in flash vaporization, bubbling, microdroplet formation techniques, etc. However, they may also be sufficiently volatile that they can be vaporized or sublimed from the solid state using known chemical vapor deposition techniques. Thus, the precursor compositions of the present invention can be in solid or liquid form. As used herein, “liquid” refer to a solution or a neat liquid (a liquid at room temperature or a solid at room temperature that melts at an elevated temperature). As used herein, “solution” does not require complete solubility of the solid; rather, the solution may have some undissolved material, preferably, however, there is a sufficient amount of the material that can be carried by the organic solvent into the vapor phase for chemical vapor deposition processing. If solvent dilution is used in deposition, the total molar concentration of solvent vapor generated may also be considered as a carrier gas.
Herein, vaporized precursor composition includes vaporized molecules of precursor complexes of Formula I either alone or optionally with vaporized molecules of other compounds in the precursor composition, including solvent molecules, if used.
Methods of the present invention are particularly well suited for forming layers 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. It is to be understood that methods of the present invention are not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, the 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
Anya Igwe U.
Micro)n Technology, Inc.
Mueting Raasch & Gebhardt, P.A.
Smith Matthew
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