Patent Publication Number: US-2005142291-A1

Title: Chemical vapor deposition methods

Description:
TECHNICAL FIELD  
      This invention relates to chemical vapor deposition methods.  
     BACKGROUND OF THE INVENTION  
      Semiconductor processing in the fabrication of integrated circuitry typically includes the deposition of layers on semiconductor substrates. Exemplary processes include physical vapor deposition (PVD), and chemical vapor deposition (CVD) which herein includes atomic layer deposition (ALD). With typical ALD, successive mono-atomic layers are adsorbed to a substrate and/or reacted with the outer layer on the substrate, typically by successive feeding of different precursors to the substrate surface.  
      Chemical vapor depositions can be conducted within chambers or reactors which retain a single substrate upon a wafer holder or susceptor. Typically, depositions are conducted at subatmospheric pressure. The chambers are maintained at subatmospheric pressure by one or more vacuum exhaust lines extending therefrom and through which undeposited effluent material flows. In certain chemical vapor deposition processes, for example in ALD, a deposition precursor might be pulsed to the chamber. When the flow of such precursor is not occurring to the chamber, the precursor might be diverted to flow directly to the exhaust line and thereby by-pass the deposition chamber. Further in certain of these and other processes, another deposition precursor might be continuously flowed to the chamber while an intermittent precursor is pulsed between the chamber and the exhaust line. These and other processings can result in considerable deposition of product within the exhaust line(s). If allowed to build up, this can lead to less vacuum pressure, and eventually result in nearly complete occluding of the exhaust line. Exemplary prior art methods for contending with the cleaning of the exhaust line includes the complete removal and cleaning of the exhaust line from the deposition equipment, thereby undesirably providing considerable downtime for the equipment. Alternately, a cleaning fluid jacket is provided along the internal exhaust line surfaces, with the cleaning fluid flowing during the deposition of product onto precursors within the chamber to avoid any deposition in the first place.  
      The invention was motivated in addressing or overcoming the above-described drawbacks, although it is in no way so limited. The invention is only limited by the accompanying claims as literally worded without interpretative or other limiting reference to the specification or drawings, and in accordance with the doctrine of equivalents.  
     SUMMARY  
      The invention includes chemical vapor deposition methods. In one implementation, a chemical vapor deposition chamber has a vacuum exhaust line extending therefrom. Material is deposited over a first plurality of substrates within the deposition chamber under conditions effective to deposit effluent product over internal walls of the vacuum exhaust line. At least a portion of the vacuum exhaust line is isolated from the deposition chamber. While isolating, a cleaning fluid is flowed to the vacuum exhaust line effective to at least reduce thickness of the effluent product over the internal walls within the vacuum exhaust line from what it was prior to initiating said flowing. After said flowing, the portion of the vacuum exhaust line and the deposition chamber are provided in fluid communication with one another and material is deposited over a second plurality of substrates within the deposition chamber under conditions effective to deposit effluent product over internal walls of the vacuum exhaust line.  
      Further implementations are contemplated.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred embodiments of the invention are described below with reference to the following accompanying drawings.  
       FIG. 1  is a diagrammatic sectional view of an exemplary chemical vapor deposition apparatus.  
       FIG. 2  is a diagrammatic sectional view of an exemplary chemical vapor deposition apparatus.  
       FIG. 3  is a diagrammatic sectional view of an exemplary chemical vapor deposition apparatus.  
       FIG. 4  is a diagrammatic sectional view of an exemplary chemical vapor deposition apparatus.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).  
      Referring to  FIG. 1 , exemplary chemical vapor deposition equipment utilizable in a chemical vapor deposition method in accordance with preferred aspects of the invention is diagrammatically depicted and indicated generally with reference numeral  10 . Such comprises a chemical vapor deposition chamber  12  having a vacuum exhaust line  14  extending therefrom. Vacuum exhaust line  14  extends between and interconnects with chamber  12  and at least one deposition vacuum pump  16 . In the context of this document, a “deposition vacuum pump” is any vacuum pump which operates at least during the deposition of material onto substrates within a deposition chamber, and which is in fluid communication therewith during such deposition. Exemplary apparatus  10  is depicted as including a first isolation valve  18  and a second isolation valve  20 . First isolation valve  18  is configured to isolate at least first majorities of exhaust line  14  and deposition chamber  12  from one another. First isolation valve  18  is preferably within 12 inches of an outlet from deposition chamber  12 , and more preferably within 6 inches of the outlet from deposition chamber  12 . Second isolation valve  20  is shown as being downstream of first isolation valve  18 , and is configured to isolate at least a second majority of exhaust line  14  and deposition vacuum pump  16  from one another. Second isolation valve  20  is preferably received within 12 inches of an inlet to the deposition vacuum pump, and more preferably within 6 inches of such inlet.  
      Exhaust line  14  includes a cleaning fluid inlet  22  thereto which is proximate to and downstream of isolation valve  18 , and upstream of second isolation valve  20 . Inlet  22  is also preferably within 12 inches of an outlet of isolation valve  18 , and more preferably within 6 inches of such outlet. Inlet  22  might be configured for feeding one or both of gas and liquid to vacuum exhaust line  14 .  
      A valve  24  is shown as being associated with a cleaning fluid inlet line  26  feeding to cleaning fluid inlet  22 . A cleaning fluid outlet  30  is depicted within exhaust line  14  proximate second isolation valve  20 . Such connects with a cleaning line  32  having an outlet control valve  34  associated therewith. A pressure regulator/controller  36  is shown associated with vacuum exhaust line  14 , and would be associated with pump  16  for controlling vacuum pressure within exhaust line  14  and, accordingly, deposition chamber  12  during operation.  
      The above-described equipment is diagrammatically shown and exemplary only. No method claim appended hereto is in any way limited by this or any other structural aspect of chemical vapor deposition equipment unless literally appearing in such claim(s), and without limiting or other interpretative reference to the specification or drawings.  
      In accordance with an aspect of the invention, material is deposited over a first plurality of substrates within a deposition chamber, for example deposition chamber  12 , under conditions effective to deposit effluent product over the internal walls of a vacuum exhaust line, for example exhaust line  14 . Typically, the depositing on the substrates would occur within the deposition chamber one wafer/substrate at a time, although multiple substrate depositions within a chamber at the same time are also of course contemplated. The deposited effluent product might comprise multiple different materials or, by way of example only, a single homogenous material.  
      After such, depositing,. at least a portion of the vacuum exhaust line is isolated from the deposition chamber. Such isolating preferably results from the operation of one or more valves, for example with first isolation valve  18  in the  FIG. 1  depicted embodiment. Preferably and as shown in  FIG. 1 , such isolating results in at least a majority of vacuum exhaust line  14  and at least a majority of chamber  12  being isolated from one another. In one embodiment, at least a second majority (might be the same as the first) of a vacuum exhaust line is isolated from the deposition vacuum pump utilizing a second isolation valve, for example isolation valve  20 .  
      Regardless, while isolating, a cleaning fluid is flowed to the vacuum exhaust line effective to at least reduce the thickness of the effluent product over the internal walls within the vacuum exhaust line from what it was prior to initiating such flowing. In one preferred embodiment, the isolating starts before flowing any cleaning fluid to the vacuum exhaust line. In another preferred embodiment, the isolating starts after the flowing of the cleaning fluid has begun. The cleaning fluid might comprise gas or liquid, consist essentially of gas or essentially of liquid, or comprise a mixture of gas and liquid, for example at least 10% gas and at least 10% liquid by volume. In the depicted example, the cleaning fluid might be directed to flow through isolation valve  20 , or partially or totally diverted through cleaning fluid outlet  30  into line  32 . For example, and by way of example only, where the cleaning fluid is predominately gas, such might desirably be directed through isolation valve  20  and pump  16  where the cleaning fluid is compatible with such valve and pump. Further by way of example only, where the cleaning fluid is predominately liquid, isolation valve  20  might be closed to isolate deposition vacuum pump  16  from the flowing cleaning fluid, which could be diverted through outlet  30  into line  32 , for example where the pumping equipment is not configured or otherwise adapted for the liquid or material of the cleaning fluid.  
      Cleaning with such fluid might be conducted to be effective to remove all of the effluent product from the walls of exhaust line  14 , or only effective to reduce the thickness of such product from what it was prior to the cleaning fluid flowing. In one preferred embodiment, the cleaning fluid flowing is effective to reduce the thickness of the effluent product by at least 50%. In one preferred embodiment, the cleaning fluid flowing is effective to expose at least some of the internal walls of the portion of the vacuum line which is being cleaned, and in a more preferred embodiment to expose at least 90% of such internal walls, and even more preferably to expose at least 99% of such internal walls.  
      After flowing the cleaning fluid, the portion of the vacuum exhaust line and the deposition chamber are provided back in fluid communication with one another, and material is deposited over a second plurality of substrates within the deposition chamber and under conditions effective to deposit effluent over the internal walls of the vacuum exhaust line. The material deposited on the second plurality of substrates may be the same or different as some or all of the material deposited.- over the first plurality of substrates. Further of course, the first plurality of substrates could be the same or different from the second plurality of substrates, or include overlapping substrates in both the first and second pluralities. Further, the effluent product deposited over the internal walls of the vacuum exhaust line could be the same or different as that deposited initially, and might also deposit directly on such walls or over material within the vacuum exhaust gas line which was not completely or otherwise removed during the cleaning fluid flowing. In one preferred embodiment, the flow of all the cleaning fluid is ceased prior to providing the portion of the vacuum exhaust line and the deposition chamber back in fluid communication with one another. In one preferred embodiment, the flowing of all the cleaning fluid is ceased after providing the portion of the vacuum exhaust line and the deposition chamber back in fluid communication with one another.  
      An alternate embodiment chemical vapor deposition method is described with respect alternate chemical vapor deposition equipment  10   a,  as shown in  FIG. 2 . Like numerals from the first-described embodiment are utilized where appropriate, with differences being indicated with the suffix “a” or with different numerals. Vacuum exhaust line  14   a  is depicted as including a suitable heating jacket  50 . Such can be utilized in an exemplary method in accordance with an aspect of the invention to heat the cleaning fluid while it is within vacuum exhaust  14   a  during the cleaning fluid flowing.  
      In accordance with aspects of the invention, a further chemical vapor deposition method is described with respect to chemical vapor deposition equipment  10   b  in  FIG. 3 . Like numerals from the first-described embodiment are utilized where appropriate, with differences being indicated with the suffix “b” or with different numerals. In  FIG. 3 , a vacuum exhaust line  14   b  is provided with a suitable exemplary RF coil  60 , or other appropriate generator. Such could be utilized in a method in accordance with an aspect of the invention which includes generating a plasma with/from a cleaning gas flowing within exhaust line  14   b  during such cleaning fluid flowing.  
      Another exemplary chemical vapor deposition method is described in connection with chemical vapor deposition equipment  10   c  as depicted in  FIG. 4 . Like numerals from the first-described embodiment are utilized where appropriate, with differences being indicated with the suffix “c” or with different numerals.  FIG. 4  depicts a remote plasma generating apparatus  70  associated with cleaning fluid inlet line  26   c.  Such could be utilized for generating a plasma with cleaning gas external of exhaust line  14  during the flowing of the cleaning fluid thereto.  
      By way of example only, exemplary deposited effluent within vacuum exhaust  14  might include any of Al 2 O 3 , NH 4 Cl, TiCl 4 , TiCl 3  and TiCl 2 . Exemplary materials for cleaning the Al 2 O 3  include liquid or gaseous H 2 O, HCl, NH 4 OH and CIF 3 . Exemplary cleaning fluids for NH 4 Cl include liquid or gaseous H 2 O 2 , H 2 O and CIF 3 . Exemplary cleaning fluids for removing any of TiCl 4 , TiCl 3  and TiCl 2  include liquid or gaseous CIF 3 , Cl 2 , H 2 O 2  and H 2 O.  
      In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.