Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state – With decomposition of a precursor
Reexamination Certificate
2001-02-07
2003-04-15
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
With decomposition of a precursor
C117S101000, C117S200000, C118S715000, C118S729000, C118S730000
Reexamination Certificate
active
06547876
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to making semiconductor components and more particularly relates to devices for growing epitaxial layers on substrates, such as wafers.
BACKGROUND OF THE INVENTION
Various industries employ processes to form thin layers on solid substrates. The substrates having deposited thin layers are routinely used in microprocessors, electro-optical devices, communication devices and others. The processes for deposition of thin layers on solid substrates are especially important for the semiconductor industry. In the manufacturing of semiconductors, the coated solid substrates, such as substantially planar wafers made of silicon and silicon carbide, are used to produce semiconductor devices. After the thin firm is deposited, the coated wafers are subjected to well-known further processes to form semiconductor devices such as lasers, transistors, light-emitting diodes, and a variety of other devices. For example, the thin layers deposited on the wafer form the active elements of the light-emitting diodes.
The materials deposited on solid substrates include silicon carbide, gallium arsenide, complex metal oxides and many others. The thin films of inorganic materials are typically deposited by processes collectively known as chemical vapor deposition (CVD). It is known that the CVD processes, if properly controlled, produce thin films having organized crystal lattices. Especially important are the deposited thin films having the same crystal lattice structures as the underlying solid substrates. The layers by which such thin films grow are called the epitaxial layers.
In a typical chemical vapor deposition process, the substrate, usually a wafer, is exposed to gases inside a reaction chamber of a CVD reactor. Reactant chemicals carried by the gases are introduced over the wafer in controlled quantities and at controlled rates, while the wafer is heated and usually rotated. The reactant chemicals, commonly referred to as precursors, may be introduced into the CVD reactor by placing the reactant chemicals in a device known as a bubbler and then passing a carrier gas through the bubbler. The carrier gas picks up the molecules of the precursors to provide a reactant gas that is then fed into the reaction chamber of the CVD reactor. The precursors typically include inorganic components, which later form the epitaxial layers on the surface of the wafer (e.g., Si, Y, Nb, etc.), and organic components. Usually, the organic components are used to allow the volatilization of the precursors in the bubbler. While the inorganic components are stable to high temperatures inside the reaction chamber, the organic components readily decompose upon heating to a sufficiently high temperature.
When the reactant gas reaches the vicinity of a heated wafer, the organic components decompose, depositing the inorganic components on the surface of the wafer in the form of the epitaxial layers. If the wafer does not have a sufficiently high temperature, the extent and the rate of the decomposition reaction, and therefore the deposition, may be lower than necessary to ensure efficient deposition and growth of the epitaxial layers. Further, depending on the nature of the inorganic components and the reactant gas, different temperature requirements exist for different types of CVD processes. For example, it is known to one skilled in the art that the deposition of silicon carbide (SiC) may require wafer temperatures of up to 1600° C. or higher, while the deposition of other typical semiconductor films, such as transition metal oxides, may efficiently proceed at 600° C. to 800° C. Therefore, the requirements for heating methods and equipment may be rather demanding and may vary as a function of the specific CVD application.
Among the requirements for any heating methodology used in the CVD processes are heating uniformity, high heating rate, ease of temperature control and high temperature tolerance for component parts. Additional considerations, such as prices of the required component parts, ease of maintenance, energy efficiency and minimization of the heating assembly's thermal inertia, may be equally important. For example, if the heated components of a CVD reactor have high thermal inertia, certain reactor operations may be delayed until the heated components reach the desired temperatures. Therefore, lower thermal inertia of the heated components of the reactor increases the productivity since the throughput depends upon the length of the reactor cycle.
At present, two major heating methodologies are used in the CVD reactors: radio frequency (RF) heating and radiant heating. A typical CVD reactor with RF heating is disclosed in U.S. Pat. No. 5,186,756, and includes radio frequency coils (RF coils), typically located outside the reaction chamber. The radio frequency emitted by the RF coils is used to heat a wafer inside the reaction chamber while the wafer is held on a susceptor, which is a wafer-supporting element mounted in the reaction chamber. The typical susceptor suitable for the RF-heated CVD reactor is made from a highly temperature resistant and usually very expensive material, such as molybdenum.
RF heating permits a very high rate of heating, which is advantageous. Also, the RF coils in general have a long reactor lifetime, which is also desirable. However, at the same time, RF heating has a number of significant drawbacks and, for this reason, is less common in the modem CVD reactors than radiant heating. Among the drawbacks are high prices of the component parts, difficulties in maintenance, high thermal inertia of the heating assembly, the necessity for a specially trained work force associated with the utilization of high frequency output devices, the high level of potential health hazard and the large size of the heating assembly.
In general, the CVD reactors with radiant heating have several important advantages over the RF-heated reactors. Importantly, such CVD reactors have a smaller and less expensive heating assembly and lower maintenance/training requirements for the manufacturing personnel. Usually, the CVD reactors with radiant heating utilize one or more radiant heating elements located inside the reaction chamber in proximity to a wafer-supporting assembly. The radiant heating elements typically include heating filaments made of graphite or other similar material and are less expensive than complex RF heating coils. Very importantly, use of localized radiant heating instead of less discriminating radio frequency heating permits selective heating of various parts of the wafer-supporting assembly by separate radiant heating elements. Such selective localized heating, which is commonly referred to as the multi-zone heating, provides excellent control over heating uniformity that is highly desirable in the CVD processes. Also, the graphite construction of the heating filaments provides low thermal inertia for the heating filaments and good filament-to-filament reproducibility. All of these factors have resulted in the preferential use of radiant heating in the semiconductor industry.
However, while RF heating is on the decline in most CVD applications, it is still common in the CVD reactors used for the deposition of silicon carbide (SiC). As discussed above, the deposition of SiC requires rather high wafer temperatures, often in excess of 1600° C. The high heating rates and the thermal stability of the components of RF heating and/or wafer-supporting assemblies have allowed the CVD reactors with RF heating to maintain their presence in the commercial marketplace despite the widespread prevalence of radiant heating in other CVD applications. In addition, the presently available CVD reactors with radiant heating have a number of significant limitations with respect to their use for the deposition of SiC on wafers. These limitations will be discussed further with reference to the existing prior art CVD reactors with radiant heating.
CVD reactors with radiant heating have various designs, including horizontal reactors in which wafers are mo
Ferguson Ian
Gurary Alexander
Spencer Michael
Emcore Corporation
Kunemund Robert
Lerner David Littenberg Krumholz & Mentlik LLP
LandOfFree
Apparatus for growing epitaxial layers on wafers by chemical... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for growing epitaxial layers on wafers by chemical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for growing epitaxial layers on wafers by chemical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3058013