Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2000-02-24
2001-04-17
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S787000, C438S680000
Reexamination Certificate
active
06218315
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention is directed to a method for forming a reliable high temperature oxide (HTO) which is useful as a dielectric material in various semiconductor devices such as capacitors, transistors and other like devices which require at least one dielectric material therein. The present invention also relates to various semiconductor devices such as capacitors and transistors which include at least the high temperature oxide of the present invention as a dielectric material.
2. Background of the Invention
Dielectric materials in high density circuits appear as capacitors in dynamic random access memory (DRAM) applications, gate dielectrics in transistors and as decoupling capacitors. The dielectric material in these structures is typically silicon dioxide (SiO
2
) which is formed by ozone deposition of tetraethylorthosilicate (TEOS).
Several problems however exist with dielectrics that are formed by ozone TEOS deposition. For instance, dielectrics that are formed from ozone TEOS are typically thick (200 Åor more) and it is difficult to control the uniformity and repeatability of the thickness using such a deposition process. Thus, alternative methods of forming dielectrics that are thin, yet have a good uniformity control are continuously being sought.
One solution to the above problem is to use high temperature oxides (HTOs) which are deposited using low pressure chemical vapor deposition (LPCVD) at temperatures of 500° C. or higher. Under such conditions, and if deposited directly on silicon, interfacial layers form which may degrade device performance. In addition, grain boundary leakage paths and lowered barrier heights may result which could lead to high device leakage. Thus, HTOs formed from prior art LPCVD processes are not reliable enough for use in the current generation of semiconductor devices, nor will they be reliable in future generations either.
In addition, processing with LPCVD batch furnace systems historically produces poor HTO deposition results. Only when substrates are loaded into a holding structure—designed to extend the wafer edge boundary condition— and then placed in the LPCVD furnace are uniformities improved. Use of such a jig, however, does not present a manufacturable process because loading the wafers in such a manner is extremely time consuming and risks wafer damage and contamination.
Moreover, prior art processes of fabricating HTOs produce oxides that are not sufficiently dense and/or the oxides contain impurities such as hydrogen therein. These properties also lead to a HTO dielectric that is not reliable. Additionally, prior art processes typically produce oxides that are not stoichiometric, i.e., the quantitative relationship between Si and oxide is significantly less than two oxygens to one silicon.
In view of the drawbacks with prior art dielectric materials, it would be beneficial if a new method was developed which produces a HTO dielectric that is reliable, yet thin enough to be employed in today's generation of devices. Such a method should also be capable of producing HTOs that are substantially stoichiometric.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a method of forming a high temperature oxide (HTO) in which the method provides improved thickness uniformity control.
Another object of the present invention is to provide a method of forming a thin HTO dielectric whose thickness is below 50 Å, preferably below 20 Å.
A yet further object of the present invention is to provide a method of forming a HTO dielectric that has improved reliability, lower etch rates, yet is formed using a lower thermal budget than conventional oxides.
These and other objects and advantages are achieved in the present invention by forming a HTO dielectric by a rapid thermal chemical vapor deposition (RTCVD) process in which a low pressure and a high ratio of reactants, e.g., oxygen-containing gas and silane-containing gas, is employed.
Specifically, the method of the present invention comprises forming a high temperature oxide on the surface of a substrate, wherein said high temperature oxide is formed by a rapid thermal chemical vapor deposition process at temperatures of from about 500° C. or above, said rapid thermal chemical vapor deposition process being carried out at a pressure of less than 80 Torr and in the presence of at least one oxygen-containing reactant and at least one silane-containing reactant, said reactants having a ratio of oxygen-containing to silane-containing of about 25:1 or greater.
The term “substrate” is employed herein to denote any material layer in which a dielectric material is required to isolate the same from an overlaying material layer. Thus, the term “substrate” is used herein to denote semiconductor substrates such as Si, Ge, SiGe, GaAs, InP InAs and other III/V semiconductor compounds, layered semiconductor substrates, i.e., Si/SiGe, silicon-on-insulators (SIOs), interconnect structures containing wiring layers, conductive materials such as electrodes and other like material layers which require isolation. A preferred substrate employed in the present invention is an electrode that is composed of a conductive material such as Cu, W, Pt, Pd, Ta, Au, Ag, Cr and other like metals, alloys or silicates of said metals, doped single-crystal silicon, doped polysilicon and other like conductive materials.
Another aspect of the present invention relates to semiconductor structures such as capacitors and transistors that include at least a layer of the high temperature oxide of the present invention used as a dielectric material. In the case of a capacitor, the HTO dielectric of the present invention is formed on the surface of a bottom electrode, e.g., polysilicon. A top electrode, e.g., polysilicon, can be formed over the HTO dielectric.
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Ballamine Arne Watson
Chan Kevin K.
Coolbaugh Douglas Duane
Johnson Donna Kaye
International Business Machines - Corporation
Rocchegiani Renzo N.
Sabo, Esq. William D.
Scully Scott Murphy & Presser
Smith Matthew
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