Process and apparatus for abating effluent gases

Abstract: A method and apparatus for abating a compound in a substrate processing system's effluent gases. The method of the present invention begins by introducing ozone and the effluent gases into an abatement device's combustion chamber. Energy is then applied to the effluent gas and ozone. The application of energy, such as thermal or radio frequency energy, then causes a reaction in and between the effluent gases and the ozone, thereby rendering the compound inert. The resultant gases produced are then exhausted out of the combustion chamber.

Description: The present invention relates to the abatement of gaseous effluents created during semiconductor substrate processing. Illustrated in Fig. 1 is a substrate processing system 100 of the prior art capable of carrying out one or more processes that may discharge effluent gases, such as CFCs, PFCs, nitrogen oxides and ozone (e.g., a CVD system). The process gases required for the process being performed are introduced into a processing chamber 105 via process gas lines 110(1)-(M). These process gases are then energized (e.g., thermally or by radio-frequency (RF) energy), to promote reactions that form the desired layer(s) on one or more substrates (not shown) disposed within processing chamber 105. The CFCs, PFCs, nitrogen oxides and other effluent gases generated by these reactions, along with unreacted portions of the process gases, are removed from processing chamber 105 by a vacuum pump (not shown) and are exhausted through effluent line 120 into an abatement device 130. Optionally, one or more combustion fuels may be introduced into a combustion chamber (not shown) of abatement device 130 via combustion fuel lines 140(1)-(N). In the combustion chamber, chemical reactions occur between the effluent gases and optional combustion fuels. One technique commonly used in the abatement of effluent gases is thermal abatement. Another common abatement technique is the use of RF energy to dissociate compounds within the effluent gas stream. An example of this is a plasma technique in which a plasma is formed from effluent gases introduced into the combustion chamber. Regardless of the abatement technique employed, energy is applied to the effluent gases and optional combustion fuels to promote combustion. The by-products of the abatement reactions are then exhausted along with any unreacted gases. Depending upon the configuration, more abatement operations may be performed to further reduce levels of undesirable compounds within the exhaust gases, using methods such as water scrubbing, catalysis and filtering. For example, Fig. 1 shows abatement device 130 connected to a water scrubber 150. In water scrubbing, effluent gases are brought into contact with water, forming inert or, at least, less hazardous compounds. As illustrated in Fig.1, substrate processing system 100 may also include an ozone generator 160 that generates ozone (O 3 ) for use in some substrate processing operations. For example, substrate processing system 100 might be capable of depositing a silicon oxide film (SiO X ). Such a film may be deposited at atmospheric pressure and at a temperature as low as 250°C by reacting tetraethylocthosilicate (Si(C 2 H 5 O) 4 ), also called tetraethoxysilane (TEOS), with ozone. Thus, ozone is directed to processing chamber 105 when the process being performed requires ozone. However, when the process being performed does not require ozone or when a substrate is not being processed (e.g., while a substrate is being transferred into or out of the chamber or during the cleaning of processing chamber 105), a bypass valve 170 directs the unused ozone through a bypass line 180 that feeds into an ozone abatement device 190. Ozone abatement device 190 normally renders ozone inert by converting the ozone into oxygen. Such conversion methods include thermal abatement, ultraviolet (UV) catalysis (in which the ozone is photolytically decomposed) and chemical catalysis (in which ozone is chemically decomposed by reaction with a compound such as manganese dioxide (MnO2)). As is evident from the above, it is desirable, from both a regulatory and an environmental perspective, to reduce or eliminate the effluents emitted by substrate processing equipment, such as CFCs, PFCs, nitrogen oxides and ozone. EP 0 839 929 A1 discloses a semiconductor processing system including a substrate processing chamber and in the forline of the substrate processing chamber, downstream of the substrate processing chamber, a plasma cleaning apparatus or combustion chamber is provided. The substrate processing chamber is a parallel plate chemical vapor deposition chamber having a distribution manifold for dispersing deposition gases to a substrate that rests on a substrate holder in the vacuum chamber. During a processing of a substrate in this substrate processing device, the above mentioned effluent gases may be produced. Such effluent gases, in particular PFC gases, are abated in the downstream plasma cleaning apparatus which includes a gas inlet for effluent gases, an ozone inlet to which a source of ozone may be coupled, a resultant gas outlet and an energy source for applying energy to the gases in the combustion chamber. In the combustion chamber of EP 0 839 929 A1 , the reaction between the ozone which is introduced into the combustion chamber and the effluent gases is promoted by applying the energy to the O 3 and the effluent gases in the combustion chamber, thereby producing a reaction product which may be discharged through the vacuum pump system. The patent abstracts of Japan vol. 018, no. 158 (E-1525), 16 March, 1994 (1994-03-16) & JP 05335256 A discloses a semiconductor manufacturing device having a chemical reaction process of atmospheric gas containing halogen and metal. The manufacturing device includes a heater for heating the outer wall of an exhaust tube which evacuates a vacuum chamber which causes chemical reaction in the inside and oxygen introduction tubes which introduce oxygen, ozone or water to the exhaust tube and the vacuum chamber. Before cleaning, oxygen, ozone or water is introduced into the exhaust tube, and the vacuum chamber and an outer wall of the exhaust tube and the vacuum chamber is heated to oxidize a reaction product deposited on the inner wall thereof. In view of the above, it is an object of the invention to provide a process and an apparatus for abating effluent gases exhausted from a substrate processing chamber wherein the abatement efficiency is increased and the need for separate ozone abatement equipment is obviated. In order to achieve this object, the invention provides a process according to claim 1 and a substrate processing system according to claim 7. Advantageous embodiments of the invention are characterized in the sub-claims. The process of the invention is simplified with respect to the prior art in that the over all process is more efficient. In a processing system which already includes an ozone source, that ozone source is connected to the abatement unit rather than connecting a separate ozone source to the abatement unit. The method of the present invention is particularly beneficial when employed in systems that already include an ozone generator to generate ozone for use as a process gas. Such systems may be modified to take advantage of the method of the present invention. Rather than shunt excess ozone provided by the ozone generator to a dedicated ozone abatement device, the excess ozone may be used instead to abate effluent gases from the system by directing the excess ozone to the abatement device for the effluent gases. This obviates the need to abate the ozone separately and improves the abatement of the other effluent gases generated by the system. A preferred embodiment of the invention will now be described in detail in conjunction with the accompanying drawings in which Fig. 1 is a block diagram of a substrate processing system of the prior art; and Fig. 2 is a block diagram of a substrate processing system employing an embodiment of the method of the present invention to abate undesirable compounds in an effluent gas stream. The method of the present invention enhances abatement of certain undesirable compounds in effluent gases generated during the operation of a substrate processing system by introducing ozone into the abatement process. In a preferred embodiment of the present invention, ozone is introduced upstream of or directly into an abatement device. The abatement technique of the present invention may be practiced with any substrate processing system that uses or generates compounds such as CFCs, PFCs, nitrogen oxides and the like. In systems that employ ozone in the processing of substrates, ozone not used in processing can be used to practice the method of the present invention, thereby increasing abatement efficiency and obviating the need for separate ozone abatement equipment. The method of the present invention introduces ozone into an effluent stream exhausted from a substrate processing chamber, such as the exemplary chamber described above, to provide more complete and more efficient abatement of undesirable compounds (e.g., CFCs and PFCs) in the effluent stream. Other combustion fuels such as hydrogen and oxygen (e.g., air) can also be added to further aid the abatement process. The present invention pertains for systems that include an ozone generator. In such a case, the generator may serve as the source of ozone for the abatement process. This arrangement has the additional benefit of obviating the need for separate ozone abatement equipment. Details of two different substrate processing systems that utilize the present invention are described below. In substrate processing systems that use ozone as a process gas, the conversion of existing equipment to a configuration employing the method of the present invention provides benefits, such as fewer system components and reduced downtime. Fig. 2 shows an embodiment of substrate processing system 200, which makes use of ozone in the processing of substrates in a manner similar to that of substrate processing system 100 (shown in Fig. 1). In this configuration, ozone generator 310 provides ozone to a bypass valve 500. Bypass valve 500, as noted, is capable of directing the ozone stream to processing chamber 205 and a bypass line 510. Unused ozone directed through bypass line 510 by bypass valve 500 is normally abated using an ozone abatement device. In a substrate processing system employing the method of the present invention, however, a separate ozone abatement device is not required to abate this unused ozone. In an abatement system of the present invention, unused ozone introduced into the combustion chamber reacts with ozone-reactive compounds present in the effluent stream, as noted. This reaction abates both the compound and the ozone. As has also been noted, ozone may be abated by conversion into oxygen using a thermal process of the type that goes on continuously within abatement device 230. Thus, even when no ozone-reactive compounds are present in the effluent stream, unused ozone introduced into the combustion chamber continues to be abated. Because the substrate processing system 200 already includes an ozone generator, only simple modifications are required to take advantage of the method of the present invention. For example, this might entail connecting bypass line 510 either directly to abatement device 230, or to effluent line 220, via an alternate bypass line 520. However, alternate bypass line 520 should not be used in conjunction with substrate processing operations which employ precursors requiring ozone, such as those which use silane or deposit nitrides. Otherwise, the ozone introduced into effluent line 220 via alternate bypass line 520 could react with any unreacted precursors, forming residues which could clog effluent line 220. The system control software would also need revision to properly control the substrate processing system. The abatement process performed in such a system parallels that described in Fig. 4. Bypass valve 500 need not simply be binary in nature. For example, bypass valve 500 may direct ozone to abatement device 230 at a minimum flow rate, regardless of the flow rate required in substrate processing operations in processing chamber 205. Another possibility is directing ozone to abatement device 230 only when there is excess ozone to be abated or when the gases supplied to processing chamber 205 require abatement using ozone. In the latter case, an example would be supplying ozone to abatement device 230 during the cleaning of processing chamber 205 using a PFC such as C 2 F 6 . Numerous other configurations for supplying ozone to abatement device 230 would be obvious to one skilled in the art and are intended to be within the scope of the invention described herein. By employing the method of the present invention, the number of components required in substrate processing system 200 may thus be reduced. Not only does the present invention obviate the need for ozone-specific abatement equipment, equipment used to abate other compounds in the effluent gas stream may also become unnecessary. For example, certain current abatement systems filter out PFCs. When the filter becomes "full" of PFCs, the filter is simply discarded (including the captured PFCs). Given the capabilities of a process according to the present invention, such a filtering device might be rendered unnecessary, leading to a reduction in the amount of solid waste generated. Without the need to interrupt processing operations (e.g., while a filter is changed), substrate processing system throughput would be increased via a reduction in downtime. Finally, the configuration shown in Fig. 5 not only provides more efficient abatement of the effluent gases created during substrate processing, but also reduces the complexity of the system, leading to a reduction in the number of components employed and an attendant increase in throughput. The method of the present invention is not intended to be limited by the specific parameters set forth in the above experiments. A person of ordinary skill in the art will realize that different processing conditions and reactant sources can be used without departing from the scope of the invention. A variety of substrate processing equipment may benefit from the method of the present invention. Other equivalent or alternative methods of using ozone to abate effluent gases created by substrate processing equipment according to the present invention will be apparent to those skilled in the art. These equivalents and alternatives are intended to be included within the scope of the present invention.

Claims: A process for abating a first compound including a chlorofluorocarbon, a perfluorocarbon or a nitrogen oxide, said first compound being in an effluent gas exhausted from a substrate processing chamber, said process comprising the following steps: introducing ozone into the substrate processing chamber during operation thereof; introducing the effluent gas into a combustion chamber communicatively coupled to the substrate processing chamber; introducing ozone into said combustion chamber; applying energy to said ozone and the effluent gas in said combustion chamber to promote a reaction between said ozone and said first compound, thereby producing a second compound which is different from said first compound; characterized in that the ozone is generated by an ozone generator and is provided from said ozone generator to the substrate processing chamber and to said combustion chamber. The process of claim 1, wherein said process further comprises the step of introducing hydrogen into said combustion chamber to promote said reaction. The process of claim 1, wherein said process further comprises the step of introducing an oxygen-containing substance into said combustion chamber to promote said reaction. The process of claim 1, wherein said energy applied is thermal energy or an electric discharge or radio frequency energy which creates a plasma from the effluent gas and said ozone. The process of claim 1, wherein said reaction proceeds at a temperature of between about 300° C and 900° C. The process of claim 1, wherein introducing ozone into said substrate processing chamber includes routing excess ozone from said generator into said combustion chamber to bypass the substrate processing chamber and wherein the excess ozone is abated in said combustion chamber. A substrate processing system having an effluent gas abatement system for abating a first compound in effluent gases generated during the operation of the substrate processing system, said substrate processing system comprising: a substrate processing chamber having an outlet from which effluent gases are exhausted; an abatement unit coupled to said outlet of said substrate processing chamber for abating said effluent gases; and an ozone source having an outlet, coupled to an inlet of said abatement unit, for providing ozone to said abatement unit to improve abatement of said effluent gases, characterized in that said outlet of said ozone source is configurable, thereby enabling said ozone source to provide ozone to said substrate processing system and to said abatement unit. The system of claim 7, wherein the combustion chamber has a first inlet for receiving the effluent gas, a second inlet for receiving ozone, and an outlet for exhausting a resultant gas, and wherein said first inlet and second inlet are the same. The apparatus of claim 7, wherein said abatement unit comprises an ignition device for promoting a reaction between said ozone and said first compound. The apparatus of claim 7, wherein said ignition device is a thermal energy source or an electrical discharge apparatus or a radio frequency energy source which creates a plasma from the effluent gas and said ozone.

Inventors: GALIANO MARIA, ROBLES STUARDO, STEARNS RANALD, SYPHERD GARY, GALIANO, MARIA, ROBLES, STUARDO, STEARNS, RANALD, SYPHERD, GARY
Applicants: APPLIED MATERIALS INC, APPLIED MATERIALS, INC.
Application year: 1998
Main classification: B01D53
IPC codes: B01D53, C23C16