Abstract:
A method and system for measuring contamination, such as metal contamination, on a substrate. A dry cleaning system is utilized for non-destructive, occasional removal of contamination, such as metal containing contamination, on a substrate, whereby a monitoring system coupled to the exhaust of the dry cleaning system is employed to determine the relative level of contamination on the substrate prior to dry cleaning.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a method and system for performing a dry cleaning process on a substrate, and more particularly to a method and system for utilizing a dry cleaning process to determine an amount of contamination on the substrate. 
     2. Description of Related Art 
     From silicon ingot fabrication through semiconductor device manufacturing, including etching processes, epitaxial or non-epitaxial deposition processes, polishing processes, oxidation processes, implant processes, etc., the semiconductor substrate is exposed to metal contaminants, and these contaminants accumulate throughout the multitude of steps. The evolution of metal contamination on such substrates leads to poor device performance, catastrophic device failure and a subsequent reduction in the yield of usable devices from processed substrates. 
     As a result, much effort is dedicated to the identification of the sources of metal contamination and the determination of means to reduce the amount of metal contamination exposed to the substrate. Additionally, much effort is devoted to the development of cleaning processes to frequently remove such contamination from contaminated substrates. 
     SUMMARY OF THE INVENTION 
     Accordingly, one embodiment is to provide a method and system for performing a dry cleaning process on a substrate. 
     Another embodiment is to provide a method and system for performing a dry cleaning process in order to determine an amount of contamination on the substrate. 
     These and/or other embodiments may be provided by a method of monitoring contamination on a substrate. The method includes: disposing the substrate having the contamination in a cleaning system configured to remove the contamination; chemically treating the contamination within the cleaning system in order to chemically alter the contamination; thermally treating the chemically altered contamination in order to evaporate the chemically altered contamination; monitoring the exhaust of gaseous effluent from the thermal treatment of the substrate to determine an amount of contamination on the substrate prior to the disposing the substrate in the cleaning system. 
     Another method includes: introducing a production substrate to a manufacturing process flow in order to initiate fabrication of an electronic device on the production substrate; during the manufacturing process flow, performing a dry, non-plasma cleaning process on the substrate in order to remove contamination accumulated on the production substrate; and monitoring the exhaust of effluent from the dry, non-plasma cleaning process in order to determine an amount of contamination on the production substrate prior to performing the cleaning process. 
     Yet another embodiment includes a system for treating a substrate. The system includes: a dry, non-plasma cleaning system having a chemical treatment component configured to chemically alter contamination on the substrate and a thermal treatment component configured to evaporate the chemically altered contamination on the substrate; and an exhaust monitoring system coupled to an exhaust of the dry, non-plasma cleaning system and configured to analyze effluent in the exhaust of the dry, non-plasma cleaning system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  depicts a method of determining the level of metal contamination in a manufacturing process flow according to an embodiment; 
         FIGS. 2A through 2C  depict an exemplary sequence for dry cleaning a film on a substrate; 
         FIG. 3  illustrates a method of processing a substrate according to an embodiment; 
         FIGS. 4A through 4C  present schematic representations of a treatment system according to another embodiment; 
         FIG. 5  presents a chemical treatment system according to another embodiment; and 
         FIG. 6  presents a thermal treatment system according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following description, in order to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the dry cleaning system and descriptions of various components and processes used therein. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1 , illustrates a method  100  of monitoring contamination on a substrate in a manufacturing process flow  110  according to an embodiment. The method  100  comprises inserting a cleaning system  120  within the manufacturing process flow  110 , and monitoring the exhaust passing from the cleaning system  120  to an exhaust system  130  using an exhaust monitoring system  140 . 
     The cleaning system can comprise a dry, non-plasma cleaning system configured to chemically treat the contamination on the substrate, followed by desorption of the chemically treated contamination. For example,  FIGS. 2A through 2C  illustrate a method of cleaning a pattern in a thin film. Additionally,  FIG. 3  presents a flow chart  300  of performing the method according to one embodiment. 
     As shown in  FIGS. 2A ,  2 B,  2 C, and  3 , an electronic structure  210  is depicted comprising a thin film  230 , or series of thin films, formed on an upper surface of a substrate  220  that may or may not include additional layers, wherein a feature  240 , or series of features, has been formed therein. The substrate  220  may be a semiconductor, a metallic conductor, or any other substrate to which the thin film is to be formed upon. The thin film, or series of thin films, can include a conductive material, non-conductive material, or a semi-conductor material, or combination thereof. For example, the thin film can include a silicon-containing material such as silicon dioxide, silicon nitride, silicon oxynitride, polycrystalline silicon, single crystal silicon, doped silicon, etc. Additionally, for example, the thin film  230  may comprise a high-k material, or a low dielectric constant (low-k) material. 
     As illustrated in  FIGS. 2A through 2C , the manufacturing of electronic structure  210  can lead to the accumulation of contamination  250 , which may be detrimental to the end device. Accordingly, the contamination is removed using a cleaning process as described above and the exhaust of the cleaning process is monitored to assess the level of contamination. 
     According to an embodiment, the electronic structure  210  and the contamination  250  accumulated thereon are disposed in a cleaning system as in  310  and it is exposed to a dry, non-plasma cleaning process as in  320 . The dry non-plasma cleaning process includes a self-limiting feature for removal of the contamination  250  with high selectivity to the underlying layers. Furthermore the substrate comprises a “production substrate” upon which electronic devices are fabricated. The substrate may be a “non-production substrate”, such as a blanket substrate or test substrate; however, the method does not require the insertion of non-production substrates into the manufacturing process flow. 
     The dry, non-plasma cleaning process includes a chemical process during which contamination surfaces of the electronic structure  210 , as shown in  FIG. 2B , are chemically treated by a process gas comprising HF, or ammonia (NH 3 ), or both HF and NH 3 , thus forming a chemically altered contamination layer  260 . Following the chemical treatment process, a thermal process is performed in order to desorb the chemically altered contamination layer  260 , as shown in  FIG. 2C . During the thermal process, the temperature of the substrate is raised sufficiently high to permit the volatilization of the chemically altered contamination layer  260 . Using the dry, non-plasma cleaning process, the contamination in feature  240  can be substantially removed. 
     During the chemical treatment process, each constituent of the process gas may be introduced together (i.e., mixed), or separately from one another (i.e., HF introduced independently from NH 3 ). Additionally, the process gas can further include an inert gas, such as a noble gas (i.e., argon). The inert gas may be introduced with either the HF or the NH 3 , or it may be introduced independently from each of the aforementioned gaseous constituents. 
     Additionally, during the chemical treatment process, the process pressure may be selected to affect the extent to which contamination layers on the substrate are chemically altered. The process pressure can range from approximately 1 mtorr to approximately 100 torr. Furthermore, during he chemical treatment process, the substrate temperature may be selected to affect the extent to which contamination layers on the substrate are chemically altered. The substrate temperature can range from approximately 10 degrees C. to approximately 200 degrees C. 
     During the thermal treatment process, the substrate temperature can be elevated above approximately 50 degrees C., or above approximately 100 degrees C. Additionally, an inert gas may be introduced during the thermal treatment of the substrate. The inert gas may include a noble gas or nitrogen. 
     The chemical treatment process and the thermal treatment process can be performed within the same processing chamber. Alternatively, as will be described in greater detail with regard to  FIGS. 4A-6 , the chemical treatment process and the thermal treatment process can be performed within separate chambers. 
     As shown in  FIG. 3 , in  330 , the exhaust from the thermal process is monitored and in  340 , the level of contamination is assessed. During the monitoring of the exhaust, the effluent gases may be analyzed to measure the amount of contamination, such as metal contamination. The exhaust monitoring system can, for example, comprise an Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) system coupled to the exhaust line between the cleaning system and the exhaust system. The ICP-MS system can identify the type of impurity and the respective amount of impurity present in the exhaust. For example, the ICP-MS system may include a system commercially available from Varian, Inc. (3120 Hansen Way, Palo Alto, Calif., 94304-1030). 
     Alternatively, a portion of the gaseous effluent may be condensed upon a sampling member inserted into the exhaust. Thereafter, the collected solid material may be dissolved in a solvent, such as water, and analyzed off-line. 
     According to one embodiment,  FIG. 4A  presents a processing system  400  for performing a dry, non-plasma cleaning process on a substrate. The processing system  400  comprises a first treatment system  410 , and a second treatment system  420  coupled to the first treatment system  410 . For example, the first treatment system  410  can comprise a chemical treatment system (or chemical treatment component), and the second treatment system  420  can comprise a thermal treatment system (or thermal treatment component). 
     Also, as illustrated in  FIG. 4A , a transfer system  430  can be coupled to the first treatment system  410  in order to transfer substrates into and out of the first treatment system  410  and the second treatment system  420 , and exchange substrates with a multi-element manufacturing system  440 . The first and second treatment systems  410 ,  420 , and the transfer system  430  can, for example, comprise a processing element within the multi-element manufacturing system  440 . For example, the multi-element manufacturing system  440  can permit the transfer of substrates to and from processing elements including such devices as etch systems, deposition system, coating systems, patterning systems, metrology systems, etc. In order to isolate the processes occurring in the first and second systems, an isolation assembly  450  can be utilized to couple each system. For instance, the isolation assembly  450  can comprise at least one of a thermal insulation assembly to provide thermal isolation, and a gate valve assembly to provide vacuum isolation. Of course, treatment systems  410  and  420 , and transfer system  430  can be placed in any sequence. 
     Alternately, in another embodiment,  FIG. 4B  presents a processing system  500  for performing a dry, non-plasma cleaning process on a substrate. The processing system  500  comprises a first treatment system  510 , and a second treatment system  520 . For example, the first treatment system  510  can comprise a chemical treatment system, and the second treatment system  520  can comprise a thermal treatment system. 
     Also, as illustrated in  FIG. 4B , a transfer system  530  can be coupled to the first treatment system  510  in order to transfer substrates into and out of the first treatment system  510 , and can be coupled to the second treatment system  520  in order to transfer substrates into and out of the second treatment system  520 . Additionally, transfer system  530  can exchange substrates with one or more substrate cassettes (not shown). Although only two process systems are illustrated in  FIG. 4B , other process systems can access transfer system  530  including such devices as etch systems, deposition systems, coating systems, patterning systems, metrology systems, etc. In order to isolate the processes occurring in the first and second systems, an isolation assembly  550  can be utilized to couple each system. For instance, the isolation assembly  550  can comprise at least one of a thermal insulation assembly to provide thermal isolation, and a gate valve assembly to provide vacuum isolation. Additionally, for example, the transfer system  530  can serve as part of the isolation assembly  550 . 
     Alternately, in another embodiment,  FIG. 4C  presents a processing system  600  for performing a dry, non-plasma cleaning process on a substrate. The processing system  600  comprises a first treatment system  610 , and a second treatment system  620 , wherein the first treatment system  610  is stacked atop the second treatment system  620  in a vertical direction as shown. For example, the first treatment system  610  can comprise a chemical treatment system, and the second treatment system  620  can comprise a thermal treatment system. 
     Also, as illustrated in  FIG. 4C , a transfer system  630  can be coupled to the first treatment system  610  in order to transfer substrates into and out of the first treatment system  610 , and can be coupled to the second treatment system  620  in order to transfer substrates into and out of the second treatment system  620 . Additionally, transfer system  630  can exchange substrates with one or more substrate cassettes (not shown). Although only two process systems are illustrated in  FIG. 4C , other process systems can access transfer system  630  including such devices as etch systems, deposition systems, coating systems, patterning systems, metrology systems, etc. In order to isolate the processes occurring in the first and second systems, an isolation assembly  650  can be utilized to couple each system. For instance, the isolation assembly  650  can comprise at least one of a thermal insulation assembly to provide thermal isolation, and a gate valve assembly to provide vacuum isolation. Additionally, for example, the transfer system  630  can serve as part of the isolation assembly  650 . 
     As illustrated above, the chemical treatment system and the thermal treatment system may comprise separate process chambers coupled to one another. Alternatively, the chemical treatment system and the thermal treatment system may be a component of a single process chamber. 
     Referring now to  FIG. 5 , a chemical treatment system  710  comprises a temperature controlled substrate holder  740  configured to be substantially thermally isolated from the chemical treatment chamber  711  and configured to support a substrate  742 , a vacuum pumping system  750  coupled to the chemical treatment chamber  711  to evacuate the chemical treatment chamber  711 , and a gas distribution system  760  for introducing a process gas into a process space  762  within the chemical treatment chamber  711 . Substrate  742  can be transferred into and out of chemical treatment chamber  711  through transfer opening  794 . 
     Additionally, the chemical treatment system  710  comprises a chamber temperature control element  766  coupled to a chamber temperature control system  768 . The chamber temperature control element  766  can include a heating unit, or a cooling unit, or both. Furthermore, the chemical treatment system  710  comprises a gas distribution temperature control element  767  coupled to a gas distribution temperature control system  769 . The gas distribution temperature control element  767  can include a heating unit, or a cooling unit, or both. 
     Substrate holder  740  can cooperate with substrate holder assembly  744  to provide several operational functions for thermally controlling and processing substrate  742 . For example, the substrate holder  740  and substrate holder assembly  744  may or may not comprise a substrate clamping system (i.e., electrical or mechanical clamping system), a heating system, a cooling system, a substrate backside gas supply system for improved thermal conductance between the substrate  742  and the substrate holder  740 , etc. 
     Referring still to  FIG. 5 , a controller  735  may be coupled to the substrate holder assembly  744 , the gas distribution system  760 , the vacuum pumping system  750 , the chamber temperature control system  768 , and the gas distribution temperature control system  769 . The controller  735  can include a microprocessor, memory, and a digital I/O port capable of generating control voltages sufficient to communicate and activate inputs to chemical treatment system  710  as well as monitor outputs from chemical treatment system  710 . 
     Further details regarding the chemical treatment system  710  are described in U.S. Pat. No. 6,951,821 A1, entitled “Processing system and method for chemically treating a substrate”; the entire contents of which are incorporated herein by reference in their entirety. 
     As illustrated in  FIG. 6 , a thermal treatment system  820  comprises a temperature controlled substrate holder  870  mounted within the thermal treatment chamber  821  and configured to be substantially thermally insulated from the thermal treatment chamber  821  and configured to support a substrate  842 ′, a vacuum pumping system  880  to evacuate the thermal treatment chamber  821 , and a substrate lifter assembly  890  coupled to the thermal treatment chamber  821 . Lifter assembly  890  can vertically translate the substrate  842 ″ between a holding plane (solid lines) and the substrate holder  870  (dashed lines), or a transfer plane located therebetween. The thermal treatment chamber  821  can further comprise an upper assembly  884  that may be configured to introduce a process gas, such as a purge gas, during thermal treatment of substrate  842 ′. Substrate  842 ′ (or  842 ″) can be transferred into and out of thermal treatment chamber  821  through transfer opening  898 . 
     Additionally, the thermal treatment system  820  comprises a chamber temperature control element  883  coupled to a chamber temperature control system  881 . The chamber temperature control element  883  can include a heating unit, or a cooling unit, or both. Furthermore, the thermal treatment system  820  comprises an upper assembly temperature control element  885  coupled to an upper assembly temperature control system  886 . The upper assembly temperature control element  885  can include a heating unit, or a cooling unit, or both. 
     As illustrated in  FIG. 6 , the thermal treatment system  820  comprises substrate holder  870  having a substrate holder temperature control element  876  and a substrate holder temperature control system  878 . The substrate holder temperature control element  876  can include a heating element, such as a resistive heating element. Furthermore, for example, the substrate holder  870  may or may not comprise a substrate clamping system (i.e., electrical or mechanical clamping system), an additional heating system, a cooling system, a substrate backside gas supply system for improved thermal conductance between the substrate  842 ′ and the substrate holder  870 , etc. 
     Furthermore the thermal treatment system  820  comprises an exhaust monitoring system  822  coupled to the duct upstream of the vacuum pumping system  880 . The exhaust monitoring system  882  is configured to measure an amount of impurities present in the effluent of thermal treatment chamber  821 . 
     Referring still to  FIG. 6 , a controller  875  may be coupled to the upper assembly  884 , the vacuum pumping system  880 , the chamber temperature control system  881 , the upper assembly temperate control system  886 , the substrate holder temperature control system  878 , the substrate lifter assembly  890 , and the exhaust monitoring system  882 . The controller  875  can include a microprocessor, memory, and a digital I/O port capable of generating control voltages sufficient to communicate and activate inputs to thermal treatment system  820  as well as monitor outputs from thermal treatment system  820 . 
     Further details regarding the thermal treatment system  820  are described in pending U.S. patent application Ser. No. 10/704,969, entitled “Processing system and method for thermally treating a substrate”; the entire contents are incorporated herein by reference in their entirety. 
     Internal surfaces of the chemical treatment system  710  may have a coating. Additionally, internal surfaces of the thermal treatment system  820  may have a coating. The coating may include Teflon®. 
     Although only certain exemplary embodiments of inventions have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention.