Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-08-31
2003-11-04
Tran, Minh Loan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S303000, C257S310000, C257S309000, C257S305000, C257S532000
Reexamination Certificate
active
06642567
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the preparation of zirconium- and platinum-containing materials, particularly films on substrates such as semiconductor device structures.
BACKGROUND OF THE INVENTION
Films of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. This is at least because many of the Group VIII metal films are generally unreactive, 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, films 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 the plate (i.e., electrode) itself in capacitors. In addition, Group VIII metals are useful in catalysts.
Platinum is one of the candidates for use as an electrode for high dielectric capacitors. 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. Also, oxidation of the underlying silicon will result in decreased series capacitance, thus degrading the cell capacitor.
In order to function well in a bottom electrode, the electrode film or film stack must be able to withstand the high temperature anneals required to recrystallize the dielectric layer. As stated above, platinum is one of the candidates for use as an electrode material for high dielectric capacitors. Platinum, alone, however, in the form of films deposited by chemical vapor deposition techniques can be unstable when annealed at temperatures 650° C. and above. For example, as shown in
FIG. 1
, a platinum layer can form islands during the anneal process, which suggests high mobility of platinum at temperatures far below its melting temperature. One solution is to combine (e.g., alloy) the platinum with rhodium to enhance the barrier properties and stability of the layer; however, rhodium precursors can be very expensive.
Thus, there is a continuing need for methods and materials for the deposition of stable platinum-containing films, particularly those that can be subjected to relatively high annealing temperatures.
SUMMARY OF THE INVENTION
The present invention is directed to methods for forming materials containing both zirconium and platinum. Preferably the materials are films deposited on substrates, such as those formed in the manufacture of a semiconductor device, such as a ferroelectric device. The substrates are preferably semiconductor substrates or substrate assemblies. Preferably, the films are formed by various vapor deposition techniques, preferably, chemical vapor deposition techniques.
Significantly and preferably, the zirconium, which is typically in the form of an oxide (zirconia) stabilizes the platinum film, such that upon annealing at temperatures of at least about 650° C. there are substantially no signs of island formation. Thus, zirconium serves to mechanically stabilize platinum films against migration during annealing. Surprisingly, this occurs without substantially degrading the conductivity of the film.
Typically and preferably, the films are electrically conductive. The resultant film can be used as an electrode in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device. The platinum-zirconium films (i.e., layers) overcome some of the problems associated with the use of platinum alone as an electrode material, without adversely affecting the properties of the platinum layer, such as its electrical conductivity.
Other materials that can be formed using the present invention include catalyst materials. Such materials typically include a roughened surface (e.g., a surface that includes a plurality of columnar pedestals, preferably that are at least about 400 Angstroms tall).
In the context of the present invention, the term “metal-containing film” includes, complexes of zirconium and platinum with other elements (e.g., O, N, and S), particularly oxygen, and/or other metals or metalloids. Zirconia (ZrO
2
) is a particularly desirable component of a metal-containing film because of its ability to stabilize platinum films against migration during annealing without substantially degrading the conductivity of the film, as described herein.
One preferred method of the present invention involves forming a film 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 that includes one or more zirconium complexes; providing a precursor composition that includes one or more platinum complexes; and forming a platinum-zirconium-containing film from the precursor compositions on a surface of the substrate (preferably, the semiconductor substrate or substrate assembly). Preferably, the precursor composition that includes one or more zirconium complexes is the same as the precursor composition that includes one or more platinum complexes.
In certain embodiments, the process is carried out in a nonhydrogen atmosphere (i.e., an atmosphere that does not include H
2
), and preferably in an oxidizing atmosphere. Using such methods, the precursor complexes of zirconium and platinum are converted in some manner (e.g., decomposed thermally while ligands are oxidized) and deposited on a surface to form a metal-containing film. Thus, the film is not simply a film of the complex of the precursors. Herein, “platinum-zirconium film” and “platinum-zirconium-containing film” are used interchangeably. Preferably, such films are in the form of a platinum-zirconia-containing film, also referred to herein as a platinum-zirconia (Pt—ZrO
2
) film.
Preferably, the precursor complexes 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 vapor deposition techniques including chemical vapor deposition and atomic layer deposition techniques. Thus, the precursor compositions of the present invention can be in solid or liquid form. As used herein, “liquid” refers 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, a “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.
The methods described herein preferably involve the use of vapor deposition techniques such as chemical vapor deposition and atomic layer deposition, although this is not a requirement for all embodim
Micro)n Technology, Inc.
Mueting Raasch & Gebhardt, P.A.
Tran Minh Loan
Tran Tan
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