Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2001-08-07
2002-06-11
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S240000, C438S243000, C438S250000, C438S386000, C438S387000, C438S393000, C438S396000, C438S003000, C438S648000, C438S650000, C438S656000, C427S099300, C427S125000, C257S295000, C257S300000, C257S301000, C257S306000
Reexamination Certificate
active
06403414
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the preparation of semiconductor device structures. Particularly, the present invention pertains to methods of forming substantially carbon-free, and, optionally, oxygen-free, conductive layers using an organometallic catalyst.
BACKGROUND OF THE INVENTION
Chemical vapor deposition (hereinafter “CVD”) is defined as the formation of a non-volatile solid layer or film on a substrate by the reaction of vapor phase reactants that contain desired components. The vapors are introduced into a reactor vessel or chamber, and decompose and/or react at a heated surface on a wafer to form the desired layer. CVD is but one process of forming relatively thin layers on semiconductor wafers, such as layers of elemental metals or compounds. It is a favored layer formation process primarily because of its ability to provide highly conformal layers even within deep contacts and other openings.
For example, a compound, typically a heat decomposable volatile compound (also known as a precursor), is delivered to a substrate surface in the vapor phase. The precursor is contacted with a surface which has been heated to a temperature above the decomposition temperature of the precursor. A coating or layer forms on the surface. The layer generally contains a metal, metalloid, alloy, or mixtures thereof, depending upon the type of precursor and deposition conditions employed.
Precursors typically utilized in CVD are generally organometallic compounds, wherein a hydrocarbon portion of the precursor functions as the carrier for the metal or metalloid portion of the precursor during vaporization of the liquid precursor. For microelectronic applications, it is often desirable to deposit layers having high conductivity, which generally means that the layers should contain minimal carbon and oxygen contaminants. However, one problem of a CVD deposited layer formed from an organometallic precursor is incorporation of residual carbon from the hydrocarbon portion of the precursor and oxygen that may be present in the atmosphere during deposition. For example, oxygen incorporation into the layer before or after deposition generally results in higher resistivity. Further, it is also believed that organic incorporation (such as pure carbon or hydrocarbon) into the resultant layer reduces density and conductivity. A low density layer can subsequently lead to oxygen incorporation into the layer when it is exposed to ambient air.
Conductive layers formed by CVD processing can be used in the fabrication of various integrated circuits. For example, capacitors are the basic energy storage components in storage cells of memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and even in ferroelectric memory (FE) devices. As memory devices become more dense, it is necessary to decrease the size of circuit components. One way to retain storage capacity of memory devices and decrease its size is to increase the dielectric constant of the dielectric layer of the capacitor component. Such components typically consist of two conductive electrodes insulated from each other by a dielectric material. In order to retain storage capacity and to decrease the size of memory devices, materials having a relatively high dielectric constant can be used as the dielectric layer of a storage cell. Materials having relatively high dielectric constants are generally formed on a device surface as thin layers. Generally, high quality thin layers of metals and conductive metal oxides, nitrides, and silicides, are used as electrode materials for storage cell capacitors. To be effective electrodes, low resistivity is desired. Therefore, layers having low carbon and/or oxygen content are desired. Further, various applications also require such low resistivity conductive layers, e.g., contacts, interconnects, etc. In addition, the presence of carbon in an electrode layer may “poison” the dielectric layer thus, reducing the effectiveness of the capacitor.
SUMMARY OF THE INVENTION
Thus, what is yet needed are methods for forming substantially carbon- and oxygen-free conductive layers useful for semiconductor structures, that can be used in microelectronic devices, such as memory devices. For example, a substantially carbon- and oxygen-free layer is desirable when a conductive material, e.g., ruthenium, is used as a conductive layer. In general, such a conductive layer preferably contains unoxidized or relatively minor amounts of oxidized metal or metalloid which, in large amounts, can adversely affect its characteristics. Further, conductive layers containing relatively large amounts of carbon and/or oxygen do not provide adequate conductivity characteristics.
Advantageously, the present invention provides a method for forming a substantially carbon-free and, optionally, oxygen-free layer including a metal- or metalloid containing material. Preferably, a method according to the present invention includes forming a layer in the presence of an organometallic catalyst. The present invention also provides a substantially carbon-free and, optionally, a substantially oxygen-free conductive layer that can be used as a barrier layer, and/or an adhesion layer, on an electrode, or any other conductive layer in an integrated circuit structure, such as in a capacitor of a memory device.
A method according to the present invention is 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 a method according to the present invention is not to be limited to layer formation on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. A method according to the present invention can also be used in silicon-on-insulator technology. 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 layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term “semiconductor substrate” refers herein to a 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 or sapphire. The term “semiconductor substrate assembly” refers herein to a semiconductor substrate or a substrate having one or more layers or structures formed thereon.
Accordingly, one aspect of the present invention provides a method for use in fabrication of integrated circuits. Preferably, the method includes the steps of forming a substrate assembly having a surface and forming a substantially carbon- and oxygen-free layer from a precursor comprising a conductive material in an oxidizing atmosphere and in the presence of an organometallic catalyst. A metal portion of the organometallic catalyst is preferably different than the conductive material of the precursor.
As used herein, “substantially carbon-free” refers to an amount of carbon present in a layer that is preferably about 1.0% by atomic percent or less, more preferably about 0.1% by atomic percent or less, and most preferably about 0.05% by atomic percent or less. If used, “substantially oxygen-free” refers to an amount of oxygen present in a layer that is preferably about 1.0% by atomic or less, more preferably about 0.5% by atomic or less, and most preferably about 0.1% by atomic or less.
Preferably, the metal portion of the organometallic catalyst is selected from the group consisting essentially of platinum, paladium, rhodium, and iridium and the material is selected from the group consisting essentially of a metal, a metalloid, and mixtures thereof. The metal and the metalloid can each be in the form of a sulfide, a selenide, a telluride, a nitride, a silicide, an oxide, and mixtures thereof. The material is preferably selected from the group consisting essentially of titanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel, iri
Chaudhari Chandra
Micro)n Technology, Inc.
Mueting Raasch & Gebhardt, P.A.
Pham Thanhha
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