Abstract:
A canister guard for preventing liquid contamination of an oulet to a canister containing liquid. The canister guard may include baffles extending from a sidewall. Additionally, the canister guard may be configured to be replacable or for retrofitting to conventional liquid chemical containing canisters.

Description:
BACKGROUND  
         [0001]    Embodiments described relate to a guard for preventing liquid contamination to an inlet of a canister containing a liquid. In particular, embodiments include a guard and a guarded coupling coupled to the inlet during purging of a liquid chemical from lines coupled to the canister.  
         BACKGROUND OF THE RELATED ART  
         [0002]    The importance of high purity chemical maintenance has increased over the years. For example, chemical impurities can have a significant affect when present in chemicals used in the fabrication of semiconductor devices. That is, as semiconductor device features, such as metal lines, become smaller and smaller, the impact any particular contaminant may have increases.  
           [0003]    Maintaining the condition of high purity chemicals requires added care in packaging, transport and delivery to, for example, a semiconductor tool. By way of example, a high purity semiconductor liquid chemical may be transported in a canister. The canister may be coupled to a semiconductor tool such as a chemical vapor deposition apparatus. The canister is coupled to the tool by way of an outlet from the canister. In particular, a delivery line may be coupled to the outlet. By way of depressurization through the delivery line, the high purity semiconductor chemical is delivered from the canister, through the outlet and eventually to the semiconductor tool. An inlet orifice may also be provided to the canister to allow cooperative pressurization during this process. For example, an inert gas such as helium may be forced into the canister through the inlet orifice to help evacuate the high purity liquid chemical therefrom. In this manner, the high purity liquid semiconductor chemical is made available for use by the tool for semiconductor processing applications.  
           [0004]    When a particular semiconductor processing application is completed, depressurization through the delivery line and pressurization through the inlet orifice is terminated. Additionally, the canister of liquid chemical may be replaced. In order to ensure purity from one semiconductor application, such as that described above, to another, it is often necessary to first purge the delivery line before replacing the canister. In this manner, a clean delivery line may be coupled to a subsequent canister without risk of contamination by the initial high purity chemical. That is, this is an attempt to allow a clean delivery of a subsequent high purity semiconductor chemical by the same tool and through the same delivery line. Purging of the delivery line in this manner also ensures safety for the user attempting to replace the initial canister.  
           [0005]    Any number of line purging techniques may be employed through pressurization and depressurization of the canister through the delivery and other lines. In many cases, this may include pressurization applied through the delivery line and into the canister as a manner of purging the delivery line. In this manner, any residual high purity liquid chemical in the delivery line is purged back into the canister.  
           [0006]    As the purged high purity chemical is forced back into the canister, the inlet orifice remains open to allow the rapid pressurization through the delivery line. However, at this time, splashing and spattering often occurs. Unfortunately, this may lead to contamination of the inlet orifice and its associated line with the high purity liquid chemical. As a result, a subsequent canister cannot be coupled to the system without risk of contamination by the high purity liquid chemical. Additionally, replacement of the canister as described above now poses a potential health risk to the user by exposure to the high purity liquid chemical contaminant at the inlet.  
         SUMMARY  
         [0007]    In one embodiment a canister guard is provided for coupling to a canister at an outlet thereof. The canister guard may prevent liquid from exiting through the outlet when pressure is applied through a canister inlet of the canister. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of a chemical delivery system employing a container having an embodiment of a guarded line.  
         [0009]    [0009]FIG. 2 is a side cross sectional view of the container taken from section lines  2 - 2  of FIG. 1 and having an embodiment of a canister guard.  
         [0010]    [0010]FIG. 3 is an exploded cross sectional view of the canister guard taken from section lines  3 - 3  of FIG. 2.  
         [0011]    [0011]FIG. 4 is a side view of an alternate embodiment of a container having a canister guard.  
         [0012]    [0012]FIG. 5 is a flow-chart summarizing methods of employing a canister guard. 
     
    
     DETAILED DESCRIPTION  
       [0013]    While embodiments are described with reference to certain liquid delivery systems, embodiments may be applicable to any liquid delivery system requiring a purge of a liquid delivery line. Additionally, embodiments may be particularly useful when the liquid is susceptible to contamination or poses a potential health risk.  
         [0014]    Referring to FIG. 1, a chemical delivery system  101  is shown. The chemical delivery system  101  includes a remote cabinet  125  which is physically and electronically coupled to a reactor  175  as shown. In other embodiments, the remote cabinet  125  may be coupled to other semiconductor fabrication equipment. However, in the embodiment shown, the reactor  175  is for chemical vapor deposition (CVD) where a liquid chemical such as tetraethylorthosilicate (TEOS) is delivered to a surface of a semiconductor substrate to form a TEOS film thereat. The TEOS may be delivered in this manner as part of a conventional semiconductor fabrication technique. Additionally, other semiconductor materials such as titanium tetrachloride, tetramethylcyclotetrasiloxane, tetrikis dimethylamino titanium, tetraethylorthosilicate, trimethylborate, triethylborate, trimethylphosphite, trimethylphosphate, triethylphosphate, trimethyl silane, and others may be employed.  
         [0015]    In the embodiment shown in FIG. 1, a bulk canister  105  is coupled to a process canister  120  (or ampule) through a manifold assembly  106 . The manifold assembly  106  couples to the bulk canister  105  through a delivery line  115  and a guarded coupling  100 . The manifold assembly  106  similarly couples to the process canister through a refill line  107 . Through a series of pressurization and depressurization techniques, the manifold assembly  106  allows delivery of liquid chemical from the bulk canister  105  and for purging of the delivery line  115  as described further herein.  
         [0016]    With the chemical delivery system  101  of FIG. 1, a liquid chemical, such as that indicated above, may be driven from the bulk canister  105  to the process canister  120  for eventual delivery to the reactor  175  through a transfer line  150 . The bulk canister  105  may be a removable container for storing between about 5 and about 10 gallons of liquid chemical, whereas the process canister  120  may be a smaller container remaining in place within the remote cabinet  125 . In another embodiment, however, the bulk canister  105  is coupled directly to the reactor  175  and no process canister  120  is present.  
         [0017]    Delivery of liquid chemical may be directed by a user at a user interface  127  of the remote cabinet  125 . The user interface  127  may be a touch screen coupled to a central processor of the chemical delivery system  101  for directing a delivery procedure. In the embodiment shown, the central processor is contained within cabinet hardware  128  of the remote cabinet  125  and coupled to reactor hardware  176  of the reactor  175  by manifold wiring  155 . In this manner, communication is provided between the central processor and the reactor hardware  176  which further directs a CVD procedure of the reactor  175  as described further below.  
         [0018]    During a CVD procedure the bulk canister  105  may be depressurized by a conventional technique. The delivery line  115  is opened to allow a liquid chemical, such as high purity TEOS, to be removed from the bulk canister  105  and into the process canister  120  as directed through the manifold assembly  106 . The manifold assembly  106  may simultaneously direct an inert gas, such as helium, into the bulk canister  105  to help force the high purity TEOS out of the bulk canister  105 .  
         [0019]    The process canister  120  includes a process level sensor  111  coupled to the central processor for indicating when the process canister  120  is filled. Once filled, the process canister  120  may deliver a liquid chemical therefrom to a storage chamber  177  of the reactor  175  through the transfer line  150  as described above.  
         [0020]    Depending upon the parameters of the delivery procedure, the reactor hardware  176  directs the high purity liquid material from the storage chamber  177  to a reaction chamber  179  where a CVD technique is used to form a film of semiconductor material on a substrate.  
         [0021]    As procedures such as that described above are run, the bulk canister  105  may periodically deliver liquid chemical to the process canister  120 . The bulk canister  105  is configured for removal from the remote cabinet  125  and replacement. Thus, the bulk canister  105  includes a bulk level sensor  110  to indicate when replacement of the bulk canister  105  is required.  
         [0022]    Before the bulk canister  105  is changed, a line purge procedure may be employed to ensure that any liquid chemical is removed from the delivery line  115 . In one embodiment, purging is coordinated through the manifold assembly  106  wherein the bulk canister  105  is pressurized through the delivery line  115  following removal of high purity chemical therethrough. That is, once the bulk canister  105  is substantially emptied through the delivery line  115 , air pressure is applied through the delivery line  115  in the opposite direction toward the bulk canister  105 . The pressure applied may be in the range of between about 45 psi and about 60 psi. This purges the delivery line  115  forcing any remaining high purity liquid chemical back into the bulk canister  105 .  
         [0023]    Referring to FIGS. 1 and 2, the guarded coupling  100  is open as the purging described above takes place. This allows the escape of air, which may include an inert gas as described above, as pressure is applied to the bulk canister  105  during the pressure applied through the delivery line  115 .  
         [0024]    In the embodiment shown, purging as described above substantially removes all of the high purity chemical from the delivery line  115 . Thus, the bulk canister  120  may be replaced without contamination or safety concerns through the delivery line  115 . In order to ensure that similar concerns are not present with respect to the guarded coupling  100 , a guard  200  is provided as described further herein.  
         [0025]    [0025]FIG. 5 is a flow-chart summarizing an embodiment of employing the guard  200  in a canister such as the bulk canister  120  during a liquid delivery and line purging process. FIG. 5 is referenced throughout the remainder of the specification as an aid in describing embodiments of the guard  200  and chemical delivery system  101  generally.  
         [0026]    Referring now to FIGS. 2 and 5 a guard  200  is shown coupled to the guarded coupling  100  at the bulk canister  105  as indicated at  520 . The guard  200  is about a 4 inch to about 6 inch long shield which may be removably inserted into the bulk canister  105  as indicated at  520 . The bulk canister  120  may then be coupled to the chemical delivery system  101  as indicated at  530  for removal of a liquid chemical therefrom as indicatd at  540 . Continuing with reference to FIG. 5, a purge, for example, of the delivery line  115 , may be applied as indicated at  550 . As the bulk canister  105  is pressurized through the delivery line  115  during purging, splattering and splashing of the high purity chemical may occur. As described below, the guard  200  is configured to prevent liquid chemical from escaping the bulk canister  105  through the guarded coupling  100 .  
         [0027]    Referring to FIGS. 2 and 3, guard  200  is equipped with lower inlets  350  with baffle inlets  310  thereabove to allow air through to the guarded coupling  100  exterior of the bulk canister  105 . As shown in FIG. 3, air may exit the bulk canister  105  during purging as shown by arrows  375 . As described further herein, the air must traverse baffles  300  as it escapes the bulk canister  105 . Thus, as the air escapes the bulk canister  105 , the baffles  300  shield any high purity chemical from also escaping the bulk canister  105 .  
         [0028]    The guard  200  terminates at a sealed bottom  325  limiting the likelihood of high purity chemical entering the guard  200 . Air may only enter the guard  200  through the lower inlets  350  and the baffle inlets  310  at the side of the guard  200 . Once air enters the guard  200  it encounters and passes around the baffles  300  as described above. The baffles  300  may extend at least half the distance (d) across the guard  200  from sidewalls thereof. Thus, the baffles  300  may overlap one another to ensure that the path of air exiting through the guard  200  is not linear. In this manner, any high purity chemical traveling with the air as shown at arrows  375  must encounter the baffles  300 . This configuration serves to block the high purity chemical from exiting the guard  200  with the exiting air. In one embodiment, the uppermost baffles  300  lack baffle inlets  310  in order to ensure that exiting air and any high purity chemical are forced to traverse lower positioned baffles  300 . This further prevents any direct escape route of exiting air and high purity liquid chemical.  
         [0029]    The guard  200  and baffles  300  may be formed of stainless steel, a synthetic fluorinated hydrocarbon, or other suitable material. The materials chosen may be selected based on the high purity chemical contained within the bulk canister  105 , ease of manufacture, and other factors. Additionally, in one embodiment, the entire guard may be replaceable for cleaning and reuse with the same or another bulk canister  105  as described below.  
         [0030]    Continuing with reference to FIGS. 2 and 3, a replaceable guard  200  may be used to retrofit currently existing bulk canisters  105 . For example, where the guarded coupling  100  as shown in FIG. 2, couples to about a 1 inch orifice at the top of an industry standard bulk canister  105 , the guard  200  may have a diameter (d) which does not exceed 1 inch. In such an embodiment, the guard  200  may be between about ½ and about ¾ inches allowing it to fit through the orifice at the top of the bulk canister  105 . The guard  200  may further include a lip  360  greater than about 1 inch in diameter at the top thereof to allow the guard  200  to rest within the bulk canister  105  without falling through the orifice. In this embodiment, the lip  360  may rest at a rim of the orifice similar to a gasket for a conventional fitting for coupling to the guarded line  100 . Similarly, in an alternate embodiment, where the orifice is about ½inch in diameter, the guard may have a diameter (d) of between about ⅛ and about ¼ inches with a lip  360  exceeding about ½ inches in diameter.  
         [0031]    With reference to FIGS. 1-3 and  5 , once a purge of the delivery line  115 , as indicated above, is complete, the bulk canister  120  may be disconnected of or disassociated from the chemical delivery system  101  as indicated at  560 . The guard  200  may then be removed as indicated at  570 . The user then has the option of refilling and reusing the bulk canister  120  with a new guard (see  540 ), coupling the used guard  200  to a new canister (see  580 ), or neither, before coupling the canister to the chemical delivery system  101  to begin delivery and purge anew.  
         [0032]    Referring to FIG. 4 an alternate configuration of a bulk canister  405  is shown employing a guard  401 . In the embodiment shown, the delivery line  415  enters the bulk canister  405  from a position opposite the guard  401  and guarded coupling  400 . Preferably, the delivery line  415  enters from the bottom of the bulk canister  405  to facilitate emptying of the bulk canister  405 . Additionally, the delivery line  415  terminates at an angled portion  450  within the bulk canister  405 . The angled portion  450  is directed away from the guard  401  to discourage splashing of residual liquid chemical toward the guard  401  during purging as described above.  
         [0033]    The embodiments described substantially prevent liquid chemical from exiting a canister through an outlet even though the canister is being pressurized through an inlet. In this manner a liquid chemical line of a liquid delivery system may be purged into the canister without subsequent contamination or health risk concerns once the canister is removed from the system. Although exemplary embodiments describe particular liquid delivery systems and guard configurations additional embodiments are possible. Additionally many changes, modifications, and substitutions may be made without departing from the spirit and scope of these embodiments.