System and method for delivery of precursor material

Abstract: According to the invention, an inert gas is bubbled through the product, in particular pyrophoric, to be purified in the liquid state in order to generate a mixture, the mixture is preferably routed close to the use point, the product, in particular pyrophoric, is separated from the inert gas and from some light impurities, to generate a purified final product, in particular pyrophoric, in liquid or solid form. The purified product is supplied in a quantity just necessary to the use point, particularly when it is solidified in the heat exchanger after the transport of the mixture. The present invention relates to a method for distributing products, in particular pyrophoric, from a storage point to a use point. (end of abstract)

System and method for delivery of precursor material description/claims

Brief Patent Description

Full Patent Description

Patent Application Claims

The present invention relates to a method for distributing liquid, in particular pyrophoric, products from a storage point to a use point, and an apparatus for distributing these products, comprising in particular means for condensing/melting the purified product.

The semiconductor industry is led to use novel products in order to meet the performance and miniaturization requirements of integrated circuits. These precursors are not only usable for manufacturing the semiconductors, but also in optoelectronics, for depositing layers of these products. These products include in particular metal, organometallic, silicon precursors, and precursors of nitride, carbide layers, derived or not from these products, and for the manufacture of flat screens of solar cells.

Some of these precursors, like trimethyl aluminum (TMA) or trimethyl gallium (TMGa), dimethyl zinc (DiZ), DMAH (dimethyl aluminum hydride), in particular, have the particular feature of being pyrophoric, that is, of igniting spontaneously in contact with air, and some of them also react explosively in contact with water.

In general, these products are currently employed using bubblers, that is, the products in liquid form are traversed by a gas such as, for example, an inert gas (nitrogen, argon, helium, etc.) usable in the manufacturing process, these bubblers being placed as close as possible to the semiconductor production equipment in the clean room. The product in liquid form is supplied in small prepacked bubbler receptacles which are disconnected when they become empty.

Such an operation entails numerous connections and disconnections in this clean room, of the systems which supply these precursors, incurring many risks in terms of safety, whether for the surrounding installations, or for the operators who cannot, in a clean room, wear the appropriate protective equipment for handling pyrophoric or explosive products in particular.

When the bubbler replacement frequency becomes too high, one solution has been provided in which these bubblers are fed by a central system for distributing the liquid product, a system which can be installed in a protected zone.

This solution has the advantage of eliminating the need for bubbler replacements in a clean room, but requires routing the pressurized liquid between its protected central storage point to the various bubblers near the use point.

Various complementary methods, such as purging the lines between each filling at the bubbler use points, or the use of pressurized double jackets with an inert gas around the pressurized liquid lines, have been developed in order to further safeguard the distribution of these liquids.

However, such a method has a number of drawbacks: among these, mention can be made in particular of the fact that the bubblers can only be filled sequentially and not simultaneously, and that this overall installation incurs a rather high additional cost during the installation of the system for distributing these precursors in the production unit.

In general, the invention relates to the distribution of liquid products by bubbling an inert gas in a receptacle containing said liquid. The invention is suitable for purifying a liquid, in particular pyrophoric, product, thereby stripping it of at least some of its residual impurities during its transport in the distribution line.

The present invention is further suitable for routing the product, in particular pyrophoric, safely to the use point, and for providing, as close as possible to the equipment, the quantity of liquid just necessary for the immediate or virtually immediate needs of the apparatus where the semiconductors or other optoelectronic devices, flat screens, etc. are manufactured.

This serves in particular to supply a less pure (hence less costly) liquid than the one which is supplied in the bubbler receptacles in current use, while supplying a product with at least equivalent or higher purity than that of the products currently supplied in said bubbler receptacles. This also serves, starting with “electrical” grade products, that is, already very pure, to supply an even purer product, with improved quality.

According to the invention, this product is distributed from a storage point (which may be a central system) by bubbling an inert gas into the liquid, in particular pyrophoric, to be purified, contained in this storage unit (that is, the liquid, in particular pyrophoric, product as sold on the market) in order to generate a mixture of inert gas and product, in particular pyrophoric, the mixture of product vapors, in particular pyrophoric, diluted in the inert gas no longer being pyrophoric (and the least volatile impurities remain in the liquid). The vapors contained in the mixture are then condensed (after transport) in liquid form as close as possible to the production equipment, in order to recover the purified, in particular pyrophoric, product, optionally by passing through a phase in the solid state according to the type of precursor used, after transport of this gas mixture under adequate safety conditions over the desired distance (the transport line can also be heated to prevent the condensation of liquid during this transport).

The other components of the mixture (such as, for example, light hydrocarbons, or more volatile impurities than the precursor depending on the temperature and pressure conditions of the mixture, and also the inert gas) remain in the gas state and are removed with the gas phase from the mixture, which then essentially contains the inert gas and some of these light impurities. This is especially important in applications pertaining particularly to the field of optoelectronics.

For example, since trimethyl aluminum solidifies at 15° C., the distribution of this product in this case generally passes through a liquid phase, and then a solid phase; since trimethyl gallium has a melting point of −15° C., it is not always necessary to pass through the solid phase.

Underlying the implementation of the invention is an apparatus for separating the vapors of products, in particular pyrophoric (after transport) from the other components of the mixture and particularly the inert gases. The vapors can be condensed or even solidified using an apparatus which generates cold. The use of this apparatus to cool the transported mixture obviously represents the best compromise for implementation, because the cooling step serves both to separate the product, in particular pyrophoric, from the impurities it initially contains, and from the inert gas, and to condense it (in liquid and/or solid form).

Solidification is preferred insofar as it serves to recover nearly all the product vapors after preferably passing through a phase of product recovery in liquid form. This solidification step is only carried out when the temperatures are compatible with a moderate use of energy. (For a reasonable energy cost, temperatures of −30° C. to −40° C. can easily be obtained).

In case of solidification, the solid can then be melted by heating the receptacle in which the product has been solidified or the walls thereof, in order to obtain a volume of liquid in a quantity just necessary and directly usable by the equipment. This is one important aspect of the inventive apparatus and method.

The inventive method is characterized in that an inert gas is bubbled through the product, in particular pyrophoric, to be purified in the liquid state, the mixture is preferably routed close to the use point or to a second storage point, the product, in particular pyrophoric, is then separated in liquid and/or solid form from the inert gas and from at least part of the light impurities possibly contained in the product, in particular pyrophoric, to be purified, in order to obtain a purified product, in particular pyrophoric, close to the use point. Preferably, this separation takes place using cold generating means in order to convert the gaseous product, in particular pyrophoric, to a liquid and/or solid product, in particular pyrophoric, while (generally) removing some of the impurities contained in the impure pyrophoric product.

According to various alternatives of the inventive method used alone or in combination: