Abstract:
The present invention relates to an apparatus for dynamically blending two or more fluids to form a blended gaseous mixture. The apparatus integrates a pressure regulation section and a dynamic adjusted blending panel into a single enclosure that allows for custom blending at the fabrication tool site which permits such blending in a more efficient and less complex manner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation in part of Ser. No. 09/799,644 filed on Mar. 6, 2001 which in turn is a divisional application of Ser. No. 09/174,196, filed Oct. 16, 1998, now U.S. Pat. No. 6,217,659, all of which are assigned to Air Products and Chemical, Inc. and all of whose entire disclosures are incorporated by reference herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to an apparatus for dynamically blending two or more fluids to form a blended gaseous mixture and more particularly, for combining a semiconductor liquid or gas with a carrier gas for delivery to a fabrication tool in a more efficient and less complex manner by integrating a pressure regulation panel with a dynamically adjusted blending panel all within the same enclosure.  
           [0003]    Current practice for chemical vapor deposition and etching applications is to either provide pre-manufactured gaseous mixtures or to blend within the semiconductor manufacturing tool to enable chemically balanced reactions. Pre-manufactured mixtures, which typically include a minor high-value component mixed with a major low-value carrier or co-reactant are limited to the operating storage volume and pressure in the delivery container. Blending at the tool may require evaporation of liquefied compressed gases from the supply source and delivery in gas phase directly to the process mass flow controller (MFC). Heat jacketing of the cylinders, and tracing of the gas cabinet and transfer lines may be required to inhibit re-condensation in the delivery line and pressure fluctuations which adversely impact the manufacturing process. This depends on the dew-point temperature of the process fluids, the process chamber operating pressure and dynamic pressure drop in the transfer line, Heating and heat tracing add operating expense, and create operational and maintenance concerns for semiconductor production facilities. Recent increases in the product flow and chamber pressure requirements have made it difficult to maintain the current practice.  
           [0004]    In particular, semiconductor materials can be delivered as liquids or gases to the customer site, but it is typical to consume materials in the gaseous phase inside the fabrication tool. Liquids may therefore have to be evaporated before final process application. One way to accomplish this is via a bubbling technique, where an inert or co-reactant gas (the carrier) flows through a liquid inventory to evaporate the liquid. The bubbling technique typically strives to saturate the carrier gas to a specified temperature and pressure, thereby insuring a consistent mixed stream composition. However, one problem of using this technique is that the bubbled stream is saturated at a given temperature, and a decrease in temperature in the delivery line may lead to re-liquefaction of the evaporated liquid. Re-liquefaction impacts the stream composition and disturbs the manufacturing process.  
           [0005]    As is well-known in the art, another way to evaporate liquid is to drop the pressure of the liquid. This is typically done by placing a pressure regulator in the delivery line between the source container and the fabrication tool. This technique is fine for liquids that have a significant (approximately greater than 80 psig) vapor pressure, but becomes a concern for lower vapor pressure liquids. In those systems, the delivery pressure may approach the liquid vapor pressure since a limited amount of pressure drop may be taken across the pressure regulator. Since the vapor pressure and delivery pressure are close, the evaporated liquid has the potential to re-liquefy in the delivery line and, as mentioned earlier, re-liquefaction causes processing problems in the fabrication tool.  
           [0006]    For these lower vapor pressure materials or the saturated stream from the bubbling technique, customers are typically required to heat and insulate the delivery line. A heat trace is a flexible heating wire that can be attached to the outside of the delivery line. In combination with insulation, the heat trace maintains the delivery piping temperature above the re-liquefaction temperature. However, one problem with using the heat trace is that the heat trace is unreliable and expensive to maintain and operate.  
           [0007]    One way to circumvent the re-liquefaction issue is to pre-mix the evaporated liquid and the carrier gas to a fixed composition, where the pre-mixed stream cannot be re-liquefied even at the lowest delivery line operating temperature. This can be done in batches, delivered to the site in fixed volume containers. There are benefits to mixing at the customer site. These benefits include improved supply logistics, flexibility of stream composition, potential safety implications, and mixture stability.  
           [0008]    The following U.S. patents pertain to gas or liquid blending or mixture systems: U.S. Pat. Nos. 3,751,644 (Mayer); 3,771,260 (Arenson); 3,856,033 (Strain, et al.); 3,948,281 (Strain, et al.); 4,277,254 (Hanson); 4,345,612 (Koni, et al.); 5,419,924 (Nagashima, et al.); 5,476,115 (Lalumandier, et al.); 5,495,875 (Benning, et al.); 5,575,854 (Jinnouchi, et al.); 5,690,743 (Murakami, et al.); 5,989,345 (Hatano); and 6,217,659 (Botelho et al.). With particular regard to U.S. Pat. No. 5,989,345 (Hatano), it should be noted the Hatano patent is limited to liquid or liquefied compressed gas minor-components; requires static mixing volumes as opposed to dynamic blending; fails to recognize the potential to eliminate heat tracing of delivery lines; and does not cover the improvement in delivery pressure.  
           [0009]    Thus, there remains a need for an apparatus that can blend a fluid, either a liquid or a gas, with a carrier gas for delivery to a fabrication tool in a more efficient and less complex manner by integrating pressure regulation panels with a dynamically adjusted blending panel all within the same enclosure.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    An apparatus for dynamically blending a semiconductor fluid with a carrier gas for use by a fabrication tool at the fabrication tool site. The apparatus comprises a single enclosure and comprises: a first and second source of semiconductor fluid (e.g., a gas or a liquid) that supply the semiconductor fluid in alternation to a fluid blender and wherein the first and second sources operate so that one of the first and second sources is providing the semiconductor fluid to the fluid blender while the other one of the first and second sources is in standby; the fluid blender comprises a first and second flow train for passing the semiconductor fluid from the first or second source that is providing the semiconductor fluid, and wherein each of the first and second flow trains comprises: a semiconductor fluid flow path having a first output; a carrier gas flow path, coupled to a source of carrier gas, and having a second output; and a mixer for mixing the first and second outputs into a third output which forms an output flow to the fabrication tool; and wherein the first and second flow trains operate in alternation such that one of the first and second flow trains is providing the output flow while the other one of the first and second flow trains is in standby.  
           [0011]    A method for dynamically blending a semiconductor fluid with a carrier gas for use by a fabrication tool at the fabrication tool site. The method comprises the steps of: providing a single enclosure that houses two semiconductor fluid sources; operating the two semiconductor fluid sources such that one of the sources supplies the semiconductor fluid (e.g., a gas or a liquid) to a downstream fluid blender located in the single enclosure while the other one of the sources is on standby; configuring the fluid blender to provide two semiconductor fluid flow paths, and wherein each of the paths is mixed with a carrier gas from a carrier gas supply and forms two mixture outputs; and operating the two semiconductor fluid flow paths such that one of the two mixture outputs supplies the semiconductor fluid blended with the carrier gas to the fabrication tool and wherein the other one of the two mixture outputs is on standby. 
       
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       [0012]    The invention will be described by way of example with reference to the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a block diagram of the apparatus of the present invention;  
         [0014]    [0014]FIG. 2A is a process flow diagram of the minor component source supply and dual process panels in the present invention; and  
         [0015]    [0015]FIG. 2B is a process flow diagram of the component blender and dual flow trains of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The concept of the present invention is an advantage over current technology, as it enables greater flexibility in process recipes and reduces the onsite facilitation requirements. In particular, the present invention is an improvement of the apparatus disclosed in U.S. Pat. No. 6,217,659 B1 (Botelho, et al.), whose entire disclosure is incorporated by reference herein. U.S. Pat. No. 6,217,659 (Botelho, et al.) discloses an apparatus for dynamically blending a vaporized liquid with a carrier gas to deliver an unsaturated vapor mixture. As will be discussed in detail later, the present invention improves on this apparatus via an integral gas cabinet with dynamic blending panel, thereby enabling delivery of adjustable mixtures to chemical vapor deposition and etching processes.  
         [0017]    As can be seen most clearly in FIG. 1, the present invention replaces all of the hardware to the left of the check valve  138  in the purge path and all of the hardware to the left of the flow elements (FE)  122 / 48  in the carrier gas path and the semiconductor liquid path, respectively. In addition, the present invention  320  comprises a semiconductor (SC) liquid or gas supply  322  therein and may also comprise a carrier gas supply  324  therein, or the carrier gas supply  324  may be external to the present invention  320 ; similarly, the present invention may also comprise a purge gas supply  326  therein, or the purge gas supply  326  may be external to the present invention  320 . It should be noted that another improvement over the system of U.S. Pat. No. 6,217,659 (Botelho, et al.) is that the SC supply can be either a gas or a liquid, not just a liquid as shown in U.S. Pat. No. 6,217,659 (Botelho, et al.).  
         [0018]    The present invention  320  integrates pressure regulation panels with a dynamic blending panel into a single enclosure, or gas cabinet,  321 . In particular, FIG. 2A comprises a process flow diagram for a pressure regulation section  328  of the present invention  320  and FIG. 2B comprises a process flow diagram for a dynamic adjusted blending panel section  330  of the present invention  320 .  
         [0019]    It should be understood that, although not shown, a controller (e.g., a microcontroller or programmable logic controller (PLC), such General Electric&#39;s Series 90-30 PLC, etc.) is coupled to the various valves and transducers for controlling the appropriate valves, as discussed below, for operating the various process flows in order to deliver the blended semiconductor fluid with the carrier gas to the fabrication tool at the customer site, as well as for purging the various process flow paths, as described below.  
         [0020]    The SC fluid (e.g., liquid or gas) described in this application may comprise, but is not limited to, tungsten hexafluoride, trimethylsilane, etc., and is also referred to as the “minor process component.” 
         [0021]    As can be seen in FIG. 2A, the pressure regulation section  328  comprises a dual process wherein two SC fluid supplies  322 A/ 322 B are coupled to respective feed forward lines  332 A/ 332 B. These SC fluid supplies  322 A/ 322 B and their respective feed forward lines  332 A/ 332 B form redundant feed forward paths; thus, while one feed forward line  332 A or  332 B is providing the semiconductor fluid from its respective supply  322 A or  322 B, the other feed forward line is on standby. Each of these feed forward lines  332 A/ 332 B is coupled to a respective port of a 3-port automatic valve  334 ; in particular, port  334 A is coupled to feed forward line  332 A, port  334 B is coupled to feed forward line  332 B and port  334 C forms the pressure regulation section output  335  which is passed onto the dynamic adjusted blending panel section  330 . For example, during operation, when feed forward line  332 B is active all three ports  334 A- 334 C of valve  334  are open, the controller closes valve  333 A in feed forward line  332 A; therefore, only the semiconductor fluid from the source  322 B passes through the valve  334 . As this supply  322 B is depleted, and if the supply  322 B is supplying a SC gas, then a pressure transducer PT 1 B detects the low pressure of the supply  322 B and informs the controller which then closes the port  334 B while opening the valve  333 A, thereby allowing the standby feed forward line  332 A to now supply the SC gas from the supply  322 A. With the feed forward line  332 B now on standby, a new canister can be introduced for supply  322 B. Once the supply  322 A becomes depleted, a corresponding pressure transducer PT 1 A detects the low pressure of the supply  322 A and informs the controller which then closes valve  333 A while opening the port  334 B, thereby restoring the feed forward line  332 B as the active SC gas supply line, and thus the cycle is repeated.  
         [0022]    It should be understood that where the SC supplies  322 A and  322 B supply SC liquid rather than a gas, the pressure transducers PT 1 A/PT 1 B are replaced with mass detectors, e.g., scales, for detecting the weight of the canisters of the supplies  322 A/ 322 B. These scales inform the controller when the SC liquid in the respective canisters are being depleted and the controller then operates the valves as discussed previously with respect to the use of SC gas.  
         [0023]    Each feed forward line  332 A/ 332 B comprises a respective vent path  336 A/ 336 B that supplies a vent  338  and Venturi source  340  to each feed forward line  332 A/ 332 B through a respective 3-port automatic valve  342 A/ 342 B. It should be noted that a blender vent path  339  is provided from a vent  338  Nenturi source  340  to the dynamic blending panel  330 . Furthermore, to purge each of the feed forward lines  332 A/ 332 B, a respective purge path  344 A/ 344 B is coupled through a respective 3-port automatic valve  346 A/ 346 B to the purge gas supply  326 . It should also be noted that a blender purge path  347  is provided from the purge gas supply  326  to the dynamic blending panel  330  for purging the SC fluid lines and the carrier gas lines in the dynamic adjusted blending panel  330 . The purge gas may comprise gases such as nitrogen, argon, etc.  
         [0024]    As can be seen in FIG. 2B, the dynamic adjusted blending panel  330  comprises a dual flow train wherein the pressure regulation section output  335  is divided into two distinct SC fluid paths  348 A and  348 B. In addition, a corresponding pair of carrier gas paths  350 A and  350 B, supplied from the carrier gas supply  324 , are provided for mixing with their respective carrier gas paths  350 A/ 350 B via respective mixers  352  and  354 ; the carrier gas is also referred to as the “major process component” and may comprise gases such as oxygen, nitrogen, hydrogen, etc. The output of each mixer  352  and  352 , namely  356  and  358 , respectively, is coupled to a respective port of a 3-port automatic valve  360 ; in particular, port  360 A is coupled to mixer output  356 , port  360 B is coupled to mixer output  358  and port  360 C is coupled to the tool supply/system purge output  362 . This dual flow train configuration of SC fluid path/carrier gas path also provides redundancy with one of the SC fluid paths  348 A/ 348 B and its corresponding carrier gas path  350 A/ 350 B being active while the other is a standby. Alternatively, these two flow trains can be simultaneously active for delivering a higher flow capacity to the fabrication tool but the preferred method is the redundant configuration, with one being active and the other on standby. There are two basic triggers for switching between these two flow trains:  
         [0025]    (1) in the event that one of the monitored process parameters (e.g., flow, pressure, composition, etc.) falls outside of specification, for example, indicative of a component failure in the SC fluid path  348 A/ 348 B and/or its corresponding carrier gas path  350 A/ 350 B; or,  
         [0026]    (2) maintenance routine needs to be performed on one of the dual flow trains. In either of these events, the controller can switch to the standby flow train.  
         [0027]    For example, during operation, when the SC fluid path  348 A and its corresponding carrier gas path  350 A are active, all three ports  360 A- 360 C are open and the controller closes a port  364 B of another 3-port automatic valve  364  while leaving the other ports  364 A and  364 C open. Furthermore, the controller also opens a port  365 A of an L-port automatic valve  365  which has another port  365 B that is always open. Simultaneously, the controller also closes a port  366 B of another 3-port automatic valve  366  while leaving the other ports  366 A and  366 C open; in addition, the controller also opens a port  367 A of another L-port automatic valve  367  which has another port  367 B that is always open. Controlling these valves in this manner, permits the SC fluid path  348 A and its corresponding gas path  350 A to supply the SC fluid/carrier gas mixture to the fabrication tool through the output  362 , while the SC fluid path  348 B and its corresponding gas path  350 B is on standby. Should it be necessary to switch to the standby flow train, namely, SC fluid path  348 B and its corresponding carrier gas path  350 B, the controller reverses this process by closing port  360 A of valve  360 , closing port  365 A of valve  365  while opening port  364 B of valve  364 , closing port  367 A of valve  367  and opening port  366 B of valve  366 .  
         [0028]    It should be noted that both the SC fluid paths  348 A/ 348 B, as well as the two carrier gas paths  350 A/ 350 B are coupled through respective 3-port automatic valves  370 - 376  to the blender purge path  347  to permit all of these paths to be purged at the appropriate time. The purge flow from all of these paths exhausts through the tool supply output  362  also, hence the reference to the output  362  as the “tool supply and system purge.” 
         [0029]    By combining the pressure regulation section  328  and the dynamic adjusted blending panel  330  into one enclosure  321  as an integral apparatus, the present invention  320 , which is located at the customer site, provides the following benefits:  
         [0030]    1) Utilizes source reactants at 100% composition, so that more product can be delivered per unit volume of delivery container. The carrier or coreactant gases are typically the major component in the mixture (&gt;50% composition), and widely available at the customer site.  
         [0031]    2) Allows flexibility of stream composition. Pre-mixed streams have a fixed composition. Streams mixed onsite can be directly modified to meet the specific process requirements. In particular, the present invention  320  allows for the direct mixing of two components to process-recipe specific composition, variable by the customer from the PLC (not shown) instead of waiting for a new mix or having to mix within the tool.  
         [0032]    3) Avoids heat trace by blending a stream so that its composition remains below the re-liquefaction temperature in the delivery line. In particular, the present invention  320  permits the elimination of delivery heat tracing for low vapor pressure liquefied compressed gases when dew-point-suppression exists.  
         [0033]    4) Potential to significantly increase the connection life cycle of the delivery supplies  322 A/ 322 B in the gas cabinet  321 , since the delivered content of the minor process component (i.e., the SC liquid or gas) can be maximized when compared to pre-manufactured mixes.  
         [0034]    5) Following on point 3 above, if condensation concerns can be eliminated, the delivery/blending system can be remotely located from the general tool area, improving space availability around the tool.  
         [0035]    6) Following on point 5 above, the mixed stream may be available at a much higher delivery pressure since the minor component delivery pressure would not have to be reduced below the dew-point pressure at the lowest delivery line temperature. Also, higher available pressure assists the performance of downstream pressure (VMB) and flow (MFC) regulation components.  
         [0036]    7) Potential elimination of delivery heat tracing for low vapor pressure liquefied compressed gases when dew-point-suppression exists.  
         [0037]    The present invention has been illustrated with reference to one or more specific embodiments, however, the full scope of the present invention should be ascertained from the claims which follow.