Chemical vapor deposition reactor having multiple inlets

Abstract

A chemical vapor deposition reactor has a wafer carrier which cooperates with a chamber of the reactor to facilitate laminar flow of reaction gas within the chamber and a plurality of injectors configured in flow controllable zones so as to mitigate depletion.

Description

RELATED APPLICATION [0001] This patent application is a continuation-in-part (CIP) patent application of co-pending patent application Ser. No. 10 / 621,049, filed Jul. 15, 2003 and entitled CHEMICAL VAPOR DEPOSITION REACTOR, the entire contents of which are hereby incorporate explicitly by reference.FIELD OF THE INVENTION [0002] The present invention relates generally to chemical vapor deposition (CVD) reactors, such as those used for group III-V semiconductor epitaxy. The present invention relates more particularly to a CVD reactor that is configured to provide laminar flow of reactant gases while mitigating undesirable depletion of reactants, so as to achieve enhanced deposition uniformity. BACKGROUND OF THE INVENTION [0003] Metal organic chemical vapor deposition (MOCVD) of group III-V compounds is a thin film deposition process utilizing a chemical reaction between a periodic table group III organic metal and a periodic table group V hydride. Various combinations of group III org...

AI Technical Summary

Benefits of technology

[0031] According to another aspect, the present invention comprises a chemical vapor deposition reactor comprising a rotatable wafer carrier which is sealed at a periphery thereof to a chamber of the reactor such that laminar flow within the chamber is facilitated.

[0032] According to another aspect, the present invention comprises a chemical vapor deposition reactor comprising a chamber and a rotatable wafer carrier disposed within the chamber, the wafer carrier being configured so as to enhance outward flow of reaction gas within the chamber.

[0037] According to another aspect, the present invention comprises a chemical vapor deposition reactor comprising a chamber, a wafer carrier, a gas inlet located generally centrally within the chamber, and at least one gas outlet formed in the chamber entirely above an upper surface of the wafer carrier so as to enhance laminar gas flow through the chamber.

[0042] According to another aspect, the present invention comprises a method for chemical vapor deposition comprising injecting reactant gas into a reactor chamber in a manner that mitigates depletion. More particularly, the method can comprise rotating a wafer carrier within a chamber of a reactor, the wafer carrier cooperating with the chamber to facilitate laminar flow of reaction gas within the chamber; and injecting a gas reactant into the chamber via plurality of injectors configured so as to mitigate depletion.

Problems solved by technology

However, such contemporary reactors suffer from inherent deficiencies which detract from their overall desirability, particularly with respect to high pressure and / or high temperature CVD processes.

When using the aforementioned reactor designs under high pressure and temperature conditions, heavy thermal convection inherently occurs.

Such thermal convection undesirably interferes with the growth process, so as to degrade efficiency and yield.

This situation worsens when the gas phase is majority ammonia.

Thermal convection is detrimental to growing high quality thin films since hard-to-control complex chemical reactions occur due to the extended duration of the presence of reactant gases in the growth chamber.

This inherently results in a decrease in growth efficiency and poor film uniformity.

Therefore, high consumption of ammonia results, particularly at high growth pressure conditions.

This high consumption of ammonia results in the corresponding high costs.

Reaction between source chemicals in the gas phase is another important issue in the contemporary MOCVD process for growth of GaN.

Gas phase reaction is usually not desirable.

However, it is not avoidable in the group III nitride MOCVD process because the reaction is severe and fast.

When the group III alkyls (such as trimethylgallium, trimethylindium, trimethylaluminum) encounter ammonia, a reaction occurs almost immediately, resulting in the undesirable formation of adducts

This process will eventually deplete the sources, thereby making the growth process undesirably vary between runs and / or will clog the gas entrance.

An efficient reactor design for III-nitride growth does not avoid gas phase reaction, but rather controls the reaction so that it does not create such undesirable situations.

However, when a reactor is scaled up this way, several new issues arise.

Because thermal convection is as severe (or even more sever) in a larger reactor as in a smaller reactor, film uniformity, as well as wafer-to-wafer uniformity, are not any better (and may be much worse).

Further, at higher growth pressures, a very high gas flow rate is needed to suppress thermal convection.

Additionally, because of the high temperature requirements, the larger mechanical parts of such a scaled up (larger) reactor are inherently placed under higher thermal stress and consequently tend to break prematurely.

Because of hydrogenation of the metals utilized (making them become brittle) and because of etching of graphite by ammonia at high temperatures, the larger metal and graphite parts tend to break down much sooner than the corresponding parts of smaller reactors.

Larger quartz parts also become more susceptible to breakage because higher thermal stress.

Another issue associated with large size reactors is the difficulty in maintaining high temperature uniformity.

The reliability of the heater assembly is usually poor due to the aforementioned high thermal stress and ammonia degradation.

These issues of process inconsistency and extensive hardware maintenance have a significant impact on production yield and therefore product cost.

However, when growing GaN at high pressures and temperatures in a high ammonia ambient gas, then thermal convection occurs and gas flow tends to be undesirably turbulent.

It is clear that turbulence increase as the size of the chamber and / or the distance between the wafer carrier and the top of the chamber increases.

As those skilled in the art will appreciate, such recirculation is undesirable because it results in undesirable variations in reactant concentration and temperature.

Further, such recirculation generally results in reduced growth efficiency due to ineffective use of the reactant gas.

This, of course, undesirably complicates the construction of such larger reactors and increases the cost thereof.

From this comparison, it is clear that such scaling up of a reactor to accommodate more wafers greatly increases the size, particularly the volume, thereof.

This increase in the size of the reactor results in the undesirable effects of thermal convection and the additional complexities of construction discussed above.

It is well known, however, that the depletion effect is one major drawback in contemporary horizontal reactors.

This undesirably makes the thin film deposited thinner and thinner along the radial direction upon the wafer.

The drawback of this approach is an inherent decrease in growth efficiency.

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