Coating apparatus – Gas or vapor deposition
Reexamination Certificate
1999-11-18
2001-10-30
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
C118S7230AN, C118S7230ER
Reexamination Certificate
active
06309465
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention relates to a CVD reactor in accordance with the introductory clause the Patent Claim 1, as well as to its application.
2. Prior Art
CVD reactors are generally common and are manufactured and distributed by companies such as Aixtron AG, Aachen, Germany. For an explanation of all terms which are not described here in more details explicit reference is made to these known CVD reactors.
The known CVD reactors comprise a reactor casing with a cover, in which a heated susceptor (wafer carrier) is provided on which at least one wafer can be positioned. A central fluid inlet is provided as a rule for the supply of CVD gases or liquids. The fluid outlet is then arranged mostly on the periphery of the reactor casing.
Either central gas inlet nozzles, which permit the radial outflow of the gases from the centre of the reactor via the wafers, or so-called shower heads are used in or on the reactor cover, which are disposed directly above the wafer and spray the gas in the form of a shower through a great number of small holes in a vertical downward direction onto the wafers. Such reactors are distributed, for instance, by the company of Thomas Swan, GB.
The German Patent DE 43 30 266 discloses a similar structure, wherein a single-wafer reaction chamber includes a wafer heating stage for holding a wafer down and for heating the wafer. Moreover, a gas supply head including gas inlet nozzles is located opposite to the wafer heating stage so that a zone of constant spacing is created for the supply of reaction gas. Gases are then allowed to flow out via the gas supply head. An exhaust gas outlet is equally provided.
There are now materials for which it is expedient if the gases are introduced into the reactor in a slightly heated state. This can be achieved with the provision that the gases are pre-heated or that the inlet is heated.
For fluid inlets configured as shower heads it is common to equip the shower head with complex water passages for thermostat-controlled heating. This configuration entails not only the disadvantage that it is complicated and hence expensive but also the inexpediency that the use of water passages in CVD reactors always involves a certain risk. For instance in the event of a leakage the cooling water may leak into the interior of the reactor and undergo an explosion-type reaction with the CVD gas or gases there. Another disadvantage is the unevenness in terms of temperature in the shower head, which is linked up with the heating of the water.
In accordance with the German Patent DE 43 30 266 the gas is passed through a gas supply head and its gas inlet nozzles in the zone of constant spacing via a wafer. Here, too, a cooling-water path and a heat-maintaining element takes an influence on the temperature in the inlet zone. There, the temperature of the inner wall of a space element adjacent to the gas inlet zones is held at a constant temperature level. In this case the aforementioned disadvantages involved in water passages apply as well.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is based on the problem of improving a CVD reactor comprising a fluid inlet configured as shower head or gas inlet nozzles in such a way that the fluid inlet and hence the fluids to be introduced, i.e. gases and/or liquids, can be moderately heated in a simple manner and particularly with water passages etc. being dispensed with.
One inventive solution to this problem is defined in Patent Claim 1. Improvements of the invention are the subject matters of Claims 2 et seq. In Claims 31 and 32 methods using a reactor defined in accordance with the invention are claimed.
According to the present invention, a CVD reactor presenting the features defined in the introductory clause of Patent Claim 1 is improved in such a way
that the fluid inlet unit comprises a hollow body spaced from the reactor cover, with the underside of the hollow body, in which the openings are provided, being heated substantially by thermal radiation from the susceptor (wafer carrier),
that a flushing gas inlet device is provided which introduces a flushing gas into the space between the upper side of the hollow body and the reactor cover in such a way that the upper side radiates heat substantially by thermal convection in the gas to the environment, and
that the conditions of heat supply and dissipation to or from the hollow body are so adjusted that the underside adapts itself to a selectable temperature level without the supply of a moderately heating medium from the outside; and that a positive gradient is present between the upper side and the underside of the hollow body.
For the purpose of the present description the term “CVD media” is to be understood to denote CVD and particularly MOCVD gases, liquids, solutions or mixture of the aforementioned substances—which will also be generally referred to in the following by the general term “fluid”.
In accordance with the present invention a known CVD reactor is hence improved by the provision that the fluid inlet unit comprises a unit which has roughly the shape of a hollow disk with a plurality of outlet openings for the CVD media, etc.—i.e. of a shower head known per se—and is disposed between the susceptor (wafer carrier) and the reactor cover in such a way that the underside of the fluid inlet unit is heated by radiation from the susceptor (wafer carrier) and is hence adjusted to be a temperature between the temperature of the susceptor (wafer carrier) and the reactor cover so that the CVD media etc. will be moderately heated when they pass through the fluid inlet unit. As an (adjustable) heat sink is provided on the upper side of the fluid inlet unit a defined temperature gradient is created in the axial direction via the fluid inlet unit.
The invention starts out from the fundamental idea to simplify the complex structure of known reactors in which the adjustment of the reactor cover and of the gas inlet in the form of a shower head through which a liquid passes and of separate heating systems required to this end is performed under thermostat control, by the provision that the shower head is configured as a component separate from the reactor cover. As the susceptor (wafer carrier) is heated any how by an infrared heating, a resistance heating or a high-frequency heating to a temperature level between roughly RT° C. and 1200° C. in a typical case (RT denotes room temperature) and hence radiates a substantial heat quantity to its environment by radiation, the fluid inlet unit is heated. On account of the inventive provisions the temperature to which the fluid inlet unit is heated is set in a controlled manner.
It is preferred to arrange a thin shower head made of a metal having good heat conduction properties in the reactor below the reactor cover and possibly underneath a ceiling under the thermostat control.
This structure presents a number of advantages:
The shower head is heated directly by the radiation from below from the susceptor (wafer carrier). In particular, the spacing between the susceptor (wafer carrier) and the hollow body may be adjustable for setting the temperature of the underside of the hollow body. To this end a holding unit may be provided for the hollow body with a thread.
The heat supply or dissipation to or from the hollow body is determined by the temperature of the susceptor (wafer carrier), by the spacing from the susceptor (wafer carrier) which can now be freely adjusted, and by the conductivity of the gas in the reactor (selection of the carrier gas, e.g. nitrogen or hydrogen or a mixture of these gases and total pressure). The availability of an additional heating system, which has so far been necessary for heating and moderate heating of the shower head, is hence no longer required.
The heat dissipation from the upper side of the shower heat in an upward direction is determined by the particular flushing gas which is used above the shower head and the quartz ceiling, and by the particular flushing gas used between the quartz ceiling and the cover of the met
Deschler Marc
Jurgensen Holger
Käppeler Johannes
Schumacher Markus
Strauch Gerd
Aixtron AG.
Alejandro Luz L.
Mills Gregory
St. Onge Steward Johnston & Reens LLC
LandOfFree
CVD reactor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with CVD reactor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CVD reactor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2591007