Patent Publication Number: US-2010124410-A1

Title: System for supplying water vapor in semiconductor wafer treatment

Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 61/199,580 filed on Nov. 18, 2008, entitled “SYSTEM FOR SUPPLYING WATER VAPOR IN SEMICONDUCTOR WAFER TREATMENT,” which application is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system for supplying water vapor in a process for treatment of semiconductor wafers. More specifically, the present invention relates to a system whereby water vapor is delivered to the interior of a treatment chamber in an efficient manner. 
     BACKGROUND OF THE INVENTION 
     Advances in electronic technology cause integrated circuits to be formed on substrates such as silicon wafers with ever increasing packing density of active components. The formation of circuits is carried out by sequential application, processing, and selective removal of various components from the substrate. 
     At times it is desirable to deliver steam to the semiconductor wafer treatment chamber as an aspect of the treatment process. U.S. Pat. No. 6,837,252 describes an apparatus for treating a workpiece with steam and ozone. The disclosure of this patent describes alternative configurations, whereby liquid is dispensed into the chamber, as shown in  FIG. 4  of the patent, and steam is dispensed as shown in  FIG. 5  of the patent. As described therein, steam is generated by a steam generator or boiler. See column  15 , lines  37 - 56 . 
     In US Patent Application Publication No. 2007/0161248, various methods for introducing water vapor into a treatment chamber by generating the vapor outside of the treatment chamber were described at paragraph [0047]. Specifically, the disclosure stated that “For instance, externally produced water vapor could be supplied to the chamber as a gas, or as component of a mixture of gasses. In one embodiment, vapor could be produced by bubbling a gas (e.g. N 2 ) through a column of water (preferably hot water). In another embodiment, the gas could pass over the surface of a quantity of water. In another embodiment, the gas could pass through an irrigated packed column as commonly used in chemical engineering. In another embodiment, substantially pure water vapor could be produced by boiling liquid water. The gaseous products from any of these alternatives could be further heated. Other embodiments are also possible.” 
     It would be desirable to identify alternative techniques and systems for treatment of semiconductor wafers using water vapor. 
     SUMMARY OF THE INVENTION 
     The present invention provides a simple and low cost system for providing water vapor in the environment of a treatment chamber treating a semiconductor wafer. As noted above, steam has previously been provided in this context in a number of ways, typically involving use of a steam generator or boiler. Such a system requires generation of a great deal of heat using a direct boiling system, or a complex, double boiling system to provide a consistent flow of steam. Steam generators and boilers are designed to produce steam in large quantities, and the output of such systems is predominantly if not exclusively steam (as contrasted with liquid water). Such steam generators are both initially costly and can be complex. Additionally, conventional steam generators can be large, taking up valuable space in an industry where manufacturing footprint is at a premium. 
     The present invention provides a system for supplying water vapor in a process for treatment of a semiconductor wafer, comprising a treatment chamber having an interior for receiving a semiconductor wafer and a water vapor dispenser. The water vapor dispenser comprises
         i) a hot water source,   ii) a water vapor separator,   iii) a first conduit fluidly connecting the hot water source to the water vapor separator,   iii) a fluid control valve in the first conduit controlling the flow of fluid between the hot water source and the water vapor separator, and   iv) a second conduit fluidly connecting the water vapor separator to the treatment chamber for delivery of water vapor to the interior of the treatment chamber.       

     Because the water vapor dispenser incorporates a water vapor separator in line between the hot water source and the treatment chamber, the performance requirements of the hot water source, which preferably is a water heater, can be much less stringent than required for conventional steam generators/boilers previously used in the semiconductor wafer treatment art. Thus, the output of the water heater need not be 100% water vapor, because the water vapor separator will collect non-water vapor fluids for removal or recycling. The water vapor portion of the output of the water vapor dispenser at the water vapor separator can then be directed to the treatment chamber without delivery of deleterious amounts of liquid fluid to the treatment chamber. 
     In an embodiment of the present invention, the water heater does not itself generate water vapor, but rather only heats the water to the superheated state with little or no water vapor. In this embodiment, the fluid control valve is a throttling valve configured to reduce the pressure of superheated water passing through the valve, causing a portion of the water to flash to steam. Although the throttling valve reduces the pressure of the superheated water substantially, enough pressure remains in the separator to force the water vapor into the delivery jets of the processing chamber. 
     The present system supplies water vapor in a process for treatment of a semiconductor wafer in a cost efficient and non-complex manner. The components of the present system are relatively inexpensive and easy to maintain and repair. Additionally, the components of the present system are relatively small, so that the present system does not take up valuable space, thereby assisting in providing tools using a minimal manufacturing footprint. Because the present system comprises a water vapor separator in line between the hot water source and the treatment chamber, the resulting water vapor as delivered may contain fewer particles than water vapor generated using conventional equipment assemblies. Additionally, the resulting water vapor may be more pure than water vapor generated using conventional equipment assemblies. Because little or no liquid water is introduced into the treatment chamber during the delivery of the water vapor in preferred embodiments, contamination by splash of liquid on the wafer is avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate several aspects of the invention and together with a description of the embodiments serve to explain the principles of the invention. A brief description of the drawings is as follows: 
         FIG. 1  is a schematic diagram of one preferred embodiment of the present system. 
     
    
    
     DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS 
     The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather a purpose of the embodiments chosen and described is so that the appreciation and understanding by others skilled in the art of the principles and practices of the present invention can be facilitated. 
     For purposes of the present invention, water vapor is defined as water in the gaseous form, and distinguished from small droplets of water commonly called “mist.” Because mist is water that is condensed in the form of small droplets, there is essentially no net warming effect when mist settles on a surface that would correspond to a heat of vaporization. For purposes of the present invention, steam is vaporized water at or above the boiling point of water, which depends on the pressure, e.g. 100° C. if the pressure is 1 atmosphere. When steam is provided at a temperature greater than the boiling point of water, is it called superheated steam. Water vapor optionally may be provided from compositions comprising components in addition to water, such as dissolved gasses such as ozone, or inert gasses such as nitrogen. It is contemplated that water vapor may be supplied to the treatment chamber in any manner, either essentially pure, or in compositions, either above, or below or at 100° C., and having pressures or partial pressures of water vapor either above, below or at 1 atm. The water vapor optionally may further comprise additional ingredients, such as an oxidizing agent as discussed above. Other ingredients, such as surfactants, cosolvents or the like, are additionally contemplated. 
     Preferably the water vapor is introduced so that it is exposed to the substrate at a water vapor temperature of from about 70° C. to about 160° C. More preferably, the water vapor is introduced so that it is exposed to the substrate at a water vapor temperature of from about 100° C. to about 150° C. In a particularly advantageous embodiment, the water vapor is introduced so that it is exposed to the substrate at a water vapor temperature of from about 105° C. to about 120° C. 
     In another aspect of this embodiment, the water vapor is introduced into the treatment chamber as a mixture of water vapor and a gas, such as N 2 . 
     Turning now to  FIG. 1 , a water vapor supplying system  10  is provided comprising a hot water source  12  fluidly connected to a water vapor separator  16  by a first conduit  14 . The first conduit  14  is provided with a fluid control valve  18 , thereby defining a first portion  14   a  of first conduit  14  and a second portion  14   b  of first conduit  14 . A second conduit  20  fluidly connects the water vapor separator  16  to a treatment chamber  22 , for delivery of water vapor to the interior of the treatment chamber (not shown). 
     The hot water source  12  may be selected from any suitable device capable of heating water to a temperature suitable for formation of water vapor. In an embodiment of the invention, the hot water source is a water heater capable of heating water to a temperature of from boiling to superheating temperature. Advantageously, the hot water source is not a steam generator or boiler as understood in the semiconductor wafer art, which requires complete conversion of any water in the system to steam in order to provide liquid-free dispensing of steam in the wafer treatment environment. Rather, the present invention utilizes a hot water source that dispenses fluid material that is at least partially in the form of a liquid. Hot water sources include conventional water heaters such as those manufactured by Trebor International, or Process Technology Inc. Often, semiconductor processing equipment or facilities already contain a hot water heater for other purposes, e.g. hot rinsing. In an embodiment of the present invention, the water heater can be adjusted and/or modified to produce higher temperature, superheated water, thereby eliminating the need for an additional heater (i.e. boiler) to produce steam. In an embodiment of the present invention, the semiconductor wafer treatment tool contains a single water heater that is used both for production of water vapor as described herein and also to provide hot water for other process steps, such as wafer or chamber washing steps and the like. 
     In an embodiment of the present invention, the hot water source  12  is capable of heating water to a temperature of from about 100 to about 150° C. In an embodiment of the present invention, the hot water source  12  is capable of heating such that steam is dispensed therefrom. 
     In an embodiment of the present invention, the hot water source  12  does not itself generate water vapor, but rather only heats the water to the superheated state with little or no water vapor. The output of hot water source to first portion  14   a  of first conduit  14  in an embodiment may be completely in the form of hot liquid water. In this embodiment, fluid control valve  18  is a throttling valve configured to reduce the pressure of heated water passing through the valve. In an embodiment of the present invention, the hot water source  12  is configured to dispense superheated fluid having less than about 30% by volume water vapor to first portion  14   a  of first conduit  14 . In an embodiment of the present invention, the hot water source  12  is configured to dispense superheated fluid having less than about 5% by volume water vapor to first portion  14   a  of first conduit  14 . 
     As the hot liquid water passes through fluid control valve  18 , at least a portion of the water flashes to water vapor and is delivered by second portion  14   b  of first conduit  14  to water vapor separator  16 . 
     In an embodiment of the present invention, the fluid that is being delivered to treatment chamber  22  in second portion  14   b  of first conduit  14  has from about 40% to about 95% by volume water vapor. In another embodiment of the present invention, the fluid that is being delivered to treatment chamber  22  in second portion  14   b  of first conduit  14  has from about 50% to about 90% by volume water vapor. 
     Standard, readily available hot water sources can be used in the context of the present invention because the water vapor dispenser comprises a water vapor separator  16 . The water vapor separator  16  is essentially a collection vessel accepting flow of liquid water and water vapor from first conduit  14   a  and  14   b . Water vapor separator  16  collects liquid hot water  24  at the bottom of the vessel, and water vapor  26  is located at the top of the vessel. The liquid hot water may be removed from the water vapor separator  16  by drain line  28  as necessary. Drain line  28  optionally comprises restriction  30  to control drainage of liquid hot water from water vapor separator  16 . Preferably, restriction  30  is sized to provide drainage from water vapor separator  16  at approximately the same rate as introduction of hot liquid water into water vapor separator  16 . If hot liquid water drains from water vapor separator  16  too quickly, water vapor may exit water vapor separator  16  through drain line  28  and not be available for use in treatment chamber  22 . If hot liquid water drains from water vapor separator  16  too slowly, the level of liquid hot water  24  in water vapor separator  16  may rise, with liquid water passing through second conduit  20  to treatment chamber  22 . Optionally, drain line  28  may be provided with a fluid control valve to provide additional control of the rate of removal of the liquid hot water  24  from the water vapor separator  16 . Optionally, water vapor separator  16  may be provided with a sensor to measure the level of liquid hot water  24  therein, with a feedback to adjust an optional fluid control valve to maintain a desired level of liquid hot water  24 . The thus drained liquid hot water can be routed to a heat exchanger to provide heat as needed for other process functions. The drained liquid hot water can additionally or alternatively be routed back to the hot water source  12  or otherwise recycled. 
     Water vapor  26  collected at the top of water vapor separator  16  is delivered to the interior of treatment chamber  22  via the second conduit  20 , which fluidly connects the water vapor separator  16  to the treatment chamber  22 . Optionally, second conduit  20  may be provided with a fluid control valve (not shown) to provide additional control of the delivery of water vapor. Optionally, the water vapor separator comprises a mist eliminator. Optionally, additional components may be introduced in line in second conduit  20 , such as filters, purifiers, scrubbers and similar equipment to treat or process the water vapor prior to delivery to the interior of treatment chamber  22 . Optionally, additional wafer treatment components may be introduced in line in second conduit  20 , such as component used for wafer cleaning including NH 4 OH, sulfuric acid, HF, ammonium fluoride, H 3 PO 4 , HCl, hydrogen peroxide, ozone and combinations thereof, prior to delivery to the interior of treatment chamber  22 . Optionally, a stream of an inert gas or a treatment gas may be introduced to second conduit  20  to be added to the water vapor prior to delivery to the interior of treatment chamber  22 . 
     Treatment chamber  22  may be adapted from any system capable of having at least one semiconductor wafer disposed therein. The treatment chamber can be one designed to accommodate one semiconductor wafer at a time or a plurality of semiconductor wafers. In an embodiment, the treatment chamber is a spray processor. Spray processors have generally been known, and provide an ability to remove liquids with centrifugal force by spinning or rotating the wafer(s) on a turntable or carousel, either about their own axis or about a common axis. Exemplary spray processor machines suitable for adaptation in accordance with the present invention are described in U.S. Pat. Nos. 6,406,551 and 6,488,272, which are fully incorporated herein by reference in their entireties. Spray processor type machines are available from FSI International, Inc. of Chaska, Minn., e.g., under one or more of the trade designations MERCURY® or ZETA®. An example of a single-wafer spray processor system suitable for adaptation in accordance with the present invention is available from SEZ AG, Villach, Austria and sold under the trade designation SEZ  323 . Another example of a tool system suitable for adaptation in accordance with the present invention is described in U.S. patent application Ser. No. 11/376,996, entitled BARRIER STRUCTURE AND NOZZLE DEVICE FOR USE IN TOOLS USED TO PROCESS MICROELECTRONIC WORKPIECES WITH ONE OR MORE TREATMENT FLUIDS, filed on Mar. 15, 2006; or as described in US Patent Application Publication No. 2005/0205115. 
     Water vapor is delivered to the interior of treatment chamber  22  by any appropriate internal chamber delivery system, such as a nozzle or array of nozzles to deliver water vapor to the desired location within the chamber. In an embodiment of the invention, the internal chamber delivery system is configured to completely envelop the semiconductor wafer(s) to be treated in moisture vapor, as described in U.S. application Ser. No. 12/152,641, filed May 15, 2008, entitled PROCESS FOR TREATMENT OF SUBSTRATES WITH WATER VAPOR OR STEAM; or in the manner as described in U.S. Provisional Patent Application Ser. No. 61/199,581 entitled PROCESS FOR TREATMENT OF SEMICONDUCTOR WAFER USING WATER VAPOR CONTAINING ENVIRONMENT, filed on even date with the present application, the disclosure of which is incorporated by reference herein for all purposes. A preferred internal chamber delivery system is the spray bar configuration described in U.S. Patent Application Ser. No. 60/819,133, entitled BARRIER STRUCTURE AND NOZZLE DEVICE FOR USE IN TOOLS USED TO PROCESS MICROELECTRONIC WORKPIECES WITH ONE OR MORE TREATMENT FLUIDS, filed on Jul. 7, 2006. 
     Optionally, additional wafer treatment components may be introduced to the interior of treatment chamber  22  in conjunction with the water vapor, as a side-by-side co-spray or in impinging streams with other liquids, air or the water vapor produced by the present invention. Examples of such wafer treatment components include NH 4 OH, sulfuric acid, HF, ammonium fluoride, H 3 PO 4 , HCl, hydrogen peroxide, ozone and combinations thereof. 
     The present system may be used in any desired treatment processes to be performed on a semiconductor wafer. Examples of such treatment processed include removing material from a surface of the wafer, conditioning the surface of the wafer and the like. 
     All percentages and ratios used herein are weight percentages and ratios unless otherwise indicated. All patents, patent applications (including provisional applications), and publications cited herein are incorporated by reference as if individually incorporated for all purposes. Numerous characteristics and advantages of the invention meant to be described by this document have been set forth in the foregoing description. It is to be understood, however, that while particular forms or embodiments of the invention have been illustrated, various modifications, including modifications to shape, and arrangement of parts, and the like, can be made without departing from the spirit and scope of the invention.