Abstract:
A preventive maintenance tool which may be installed on a metal chemical vapor deposition (CVD) chamber to prevent escape of contaminating and toxic gases from the chamber interior during preventative maintenance (PM) cleaning of the chamber. The tool comprises a cylindrical tool body which fits to the lid O-ring of the chamber to form a gas-tight seal therewith; a vacuum line connector nipple extending from the body for connection to a vacuum line; and a lid panel rotatably mounted in the body and fitted with a pair of hinged closing panels for reversibly sealing the chamber and facilitating chamber cleaning.

Description:
FIELD OF THE INVENTION 
     The present invention relates to CVD (chemical vapor deposition) chambers for depositing conductive and insulative material layers on semiconductor wafer substrates. More particularly, the present invention relates to a tool for preventing diffusion of toxic, corrosive and/or flammable process or cleaning gases from a CVD chamber during periodic chamber cleaning and maintenance. 
     BACKGROUND OF THE INVENTION 
     Semiconductor processing is carried out in specialized apparatus including multiple chambers wherein semiconductor wafers are processed by the deposition of multiple conductive and insulative layers on the wafers and treatment of the layers to form integrated circuits on the wafers. A common process involved in manufacturing integrated circuits on semiconductor wafer substrates includes depositing a dielectric layer over a metal region on a substrate; etching multiple openings in the dielectric layer such that each opening exposes a contact area on the region; and then filling each opening with an electrically-conductive material using a chemical vapor deposition (CVD) process to form a plug that establishes electrical contact with the contact region. Tungsten is one of the metals most commonly used to form the electrically-conducting plug. However, formation of a tungsten plug using tungsten chemical vapor deposition processes requires the use of several toxic, corrosive, and pyrophoric process chemicals and gases. Table 1 lists some of the common hazardous gases used in a typical tungsten chemical vapor deposition processes, along with the chemical symbol/formula, health and fire hazards and hazardous concentrations of each. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Tungsten CVD Process Gas and Chemical Hazards 
               
             
          
           
               
                 Chemical 
                 Symbol/ 
                 Health 
                   
                 Fire 
               
               
                 Name 
                 Formula 
                 Hazard 
                 TLV-TWAa 
                 Hazard 
               
               
                   
               
               
                 Argon 
                 Ar 
                 Simple 
                 n/a 
                 Non- 
               
               
                   
                   
                 asphyxiant 
                   
                 flammable 
               
               
                 Hydrogen 
                 H 2   
                 Simple 
                 n/a 
                 Flammable 
               
               
                   
                   
                 asphyxiant 
                   
               
               
                 Nitrogen 
                 N 2   
                 Simple 
                 n/a 
                 Non- 
               
               
                   
                   
                 asphyxiant 
                   
                 flammable 
               
               
                 Silane 
                 SiH 4   
                 Poison gas 
                 5 ppm 
                 Pyrophoric 
               
               
                   
                   
                   
                   
                 gas 
               
               
                 Tungsten 
                 WF 6   
                 Poison gas 
                 3 ppm 
                 Non- 
               
               
                 Hexa- 
                   
                   
                 (as HF) 
                 flammable 
               
               
                 fluoride 
               
               
                   
               
             
          
         
       
     
     Argon and nitrogen, while common, innocuous and nonflammable gases, must be handled with caution because these gases can cause asphyxiation by displacing oxygen necessary for breathing. Hydrogen, another relatively innocuous gas, is a flammable asphyxiant. SiH 4  is toxic and reacts with atmospheric air to form corrosive silicic acid. WF 6  is also toxic and reacts with atmospheric moisture to form hydrofluoric acid. To avoid leakage of these gases from the chamber during wafer substrate processing, a vacuum is continually maintained in the chamber by operation of a vacuum line connected to the chamber. The gases are thus drawn from the chamber interior through the vacuum line, where they are disposed of using conventional equipment and techniques. 
     In active semiconductor fabrication process chambers, particularly those in which etching or chemical vapor deposition processes are carried out, residues frequently form on the walls and other surfaces of the chambers during processing. Accordingly, regular periodic chamber cleanings between wafer processing cycles is necessary for maintaining CVD system performance in the production of high-quality integrated circuit devices. Such periodic chamber cleanings may be conducted without breaking the chamber vacuum seal. Preventative maintenance (PM) chamber cleanings, on the other hand, are performed between multiple periodic chamber cleanings and do require that the chamber vacuum seal be broken because the chamber lid must be opened in order to facilitate physically wiping down the chamber interior. 
     Table 2 lists two potentially hazardous gases, HC-116-hexafluoroethane and oxygen, which are commonly used in the periodic cleaning of CVD chambers, along with the chemical symbol/formula, health and fire hazards and hazardous concentrations of each. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 CVD Clean Cycle Gases 
               
             
          
           
               
                 Chemical 
                 Symbol/ 
                 Health 
                   
                   
               
               
                 Name 
                 Formula 
                 Hazard 
                 TLV-TWAa 
                 Fire Hazard 
               
               
                   
               
               
                 HC-116 
                 C 2 F 6   
                 Narcotic (at 
                 1000 ppm 
                 Flammable 
               
               
                 Hexa- 
                   
                 high 
                   
                 liquid 
               
               
                 fluoro- 
                   
                 con- 
                   
                 decomposes 
               
               
                 ethane 
                   
                 centration) 
                   
                 in water 
               
               
                 Oxygen 
                 O 2   
                 Irritant (at 
                 n/a 
                 Strong 
               
               
                   
                   
                 high con- 
                   
                 Oxidizer 
               
               
                   
                   
                 centration) 
               
               
                   
               
             
          
         
       
     
     Although the vacuum seal maintained in the chamber system during the periodic chamber cleanings facilitates removal of most of the process gases and cleaning gases from the chamber, small quantities of these gases typically remain in the chamber interior when the chamber lid is opened to commence PM chamber cleaning. Because these process gases and cleaning gases are potentially harmful to process engineers and other cleaning or maintenance personnel in the immediate vicinity of the processing chambers, great care must be taken by such personnel to avoid exposure to these residual gases during PM chamber cleanings. Moreover, hydrogen peroxide, commonly used in the wet cleaning of the chamber interior during PM chamber cleanings, breaks down into water and hydrogen, and the water reacts with chamber deposits to form the corrosive and toxic hydrogen fluoride (HF). 
     According to industrial sanitation and safety standards, if potential toxic substances exist in a workplace, the first priority of health and safety personnel should be to eliminate or control the root causes or sources of such substances. The next priority is to eliminate or reduce toxin transference from the source to the personnel. The last priority is the direct protection of personnel by the use of masks, respirators or other equipment. Because no such method of direct protection is suitable for all situations and is incapable of total protection, however, the most effective prevention methods involve eliminating or controlling the root causes or sources of the toxic substances. Accordingly, a device is needed for preventing escape of toxic and corrosive gases from a CVD chamber during periodic maintenance chamber cleanings. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a preventative maintenance tool for preventing exposure of personnel to harmful gases emanating from a process chamber. 
     Another object of the present invention is to provide a preventative maintenance tool for containing corrosive and toxic gases in a chemical vapor deposition (CVD) chamber during maintenance of the chamber. 
     Still another object of the present invention is to provide a preventative maintenance tool which provides access to the interior of a CVD chamber while preventing escape of potentially corrosive, toxic and harmful gases and chemicals from the chamber interior. 
     Yet another object of the present invention is to provide a preventative maintenance tool which may be removably installed on a variety of CVD chambers. 
     A still further object of the present invention is to provide a preventative maintenance tool which is simple in construction and installation. 
     Yet another object of the present invention is to provide a preventative maintenance tool which is versatile and simple in operation and enables complete access to the interior of a CVD chamber for thorough cleaning thereof. 
     Still another object of the present invention is to provide a preventative maintenance tool which substantially eliminates the need for chamber cleaning and maintenance personnel to wear protective equipment during preventative maintenance cleaning of a CVD chamber. 
     In accordance with these and other objects and advantages, the present invention is a preventative maintenance tool which may be installed on a metal chemical vapor deposition (CVD) chamber to prevent escape of contaminating and toxic gases from the chamber interior during preventative maintenance (PM) cleaning of the chamber. The tool comprises a cylindrical tool body which fits to the lid O-ring of the chamber to form a gas-tight seal therewith; a vacuum line connector nipple extending from the body for connection to a vacuum line; and a lid panel rotatably mounted in the body and fitted with a pair of hinged closing panels for reversibly sealing the chamber and facilitating chamber cleaning. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, wherein: 
     FIG. 1 is a schematic view illustrating a typical conventional chemical vapor deposition (CVD) system; 
     FIG. 1A is a sectional view, taken along section line  1 A in FIG. 1, illustrating a lid conventionally removably mounted on the CVD system; 
     FIG. 2 is a perspective view of an illustrative embodiment of the PM (preventative maintenance) aided tool of the present invention; 
     FIG. 3 is a front view of the PM aided tool illustrated in FIG. 2; 
     FIG. 4 is a sectional view, taken along section line  4  in FIG. 3; 
     FIG. 5 is a sectional view, taken along section lines  5 — 5  in FIG. 2; 
     FIG. 6 is a cross-sectional view of the lid panel and closing panel components of the PM aided tool, with the lid panels shown disposed in the closed, sealing configuration; 
     FIG. 7 is a schematic view of the CVD system, with the PM aided tool removably mounted on the system in typical application of the tool; 
     FIG. 8 is a sectional view, taken along section line  8  in FIG. 7, more particularly illustrating a typical flanged configuration of the bottom edge of the PM aided tool of the present invention, sealably engaging the CVD system; and 
     FIG. 9 is a sectional view, illustrating an alternative configuration of the bottom edge of the PM aided tool of the present invention, sealably engaging the CVD system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention has particularly beneficial utility in preventing escape of toxic, corrosive and/or flammable gases from a chemical vapor deposition chamber during periodic maintenance cleaning of the chamber. However, the invention is not so limited in application, and while references may be made to such chemical vapor deposition chambers, the invention is not so limited in application and may be applicable to a variety of mechanical and process applications. 
     A typical conventional CVD (chemical vapor deposition) system is illustrated schematically by reference numeral  10  in FIG.  1 . The CVD system  10  generally includes an enclosure assembly  6 , having a vertically-movable wafer support pedestal  12  disposed beneath a showerhead  30 , through which process gases enter a vacuum chamber  15 . A pumping plate  17  may extend around the wafer support pedestal  12  for discharging process gases and other plasma residue from the chamber  15  and into a pumping channel  14  partially circumscribing the chamber  15 , as indicated by the arrows  21 . 
     The enclosure assembly  6  is typically an integral housing constructed of a process-compatible material such as anodized aluminum. The enclosure assembly  6  includes a continuous sidewall  11  and a top  7  that includes a top opening (not illustrated) sealed by a removable lid  18 . As illustrated in FIG. 1A, the lid  18  may include an annular lid seal flange  19  which mates with a companion top seal flange  8  provided on the top  7  of the enclosure assembly  6 . A gasket or o-ring  9  is typically provided on the top seal flange  8  to provide a gas-tight seal between the lid seal flange  19  and the top seal flange  8  when the lid  18  is mounted on the top  7  as illustrated. The lid  18  is typically provided with an inlet tube  16  for allowing deposition gases to enter the showerhead  30 , where the gases are uniformly dispersed throughout the chamber  15  onto a wafer (not illustrated) supported on the wafer support pedestal  12 . The deposition process performed in the apparatus  10  may be a thermal process, a plasma-enhanced process or other chemical vapor deposition process. 
     In a typical metal deposition process such as that used in the formation of a tungsten plug (not shown) in an opening formed in a dielectric layer on a wafer (not shown), deposition gases are introduced into the chamber  15  through the inlet tube  16  and the showerhead  30 , respectively, where the gases are deposited into the opening (not illustrated) in the dielectric layer on the wafer. Upon completion of the CVD process, the gases are evacuated from the chamber  15  by operation of a pump (not illustrated) which induces vacuum pressure in the pumping channel  14  to draw the gases out of the chamber  15  and through the pumping channel  14 , where the gases are discharged from the apparatus  10  through a discharge conduit  31  and throttle valve  32 . 
     During the chemical deposition process, solid residues frequently form on the sidewalls  11 , wafer support pedestal  12  and other interior surfaces of the chamber  15 . Accordingly, regular periodic cleanings of the chamber  15  between CVD process cycles is necessary for maintaining performance of the CVD system  10  at optimum levels in the production of high-quality integrated circuit devices. Such periodic chamber cleanings are facilitated by introducing cleaning gases and chemicals into the chamber  15  through the inlet tube  16  and showerhead  30 , respectively, while maintaining a vacuum in the chamber  15  by evacuating the gases through the discharge conduit  31  and throttle valve  32 . While such periodic chamber cleaning cycles are effective in removing much of the residues from the interior surfaces of the CVD system  10 , the residues tend to accumulate on the surfaces over time, and these must be removed using periodic preventative maintenance (PM) cleanings. In a PM cleaning, the lid  18  and showerhead  30  components of the CVD system  10  are removed and the vacuum pressure inside the chamber  15  is dispelled to facilitate manually wiping down the interior surfaces of the chamber  15  in order to remove the accumulated residues from the surfaces. Upon commencing the PM cleaning process, however, some toxic, corrosive and/or flammable residual deposition gases may remain in the chamber  15 , and additional potentially harmful gases such as HF may be formed upon contact of hydrogen peroxide, a common cleaning agent, or water with the residues. These potentially harmful gases tend to escape from the open chamber  15  and into the ambient environment of the CVD system  10 , where the gases may injure persons involved in the chamber-cleaning operation or other persons in the vicinity of the CVD system  10 . 
     Referring next to FIGS. 2-6,  8  and  9  of the drawings, an illustrative embodiment of the preventative maintenance (PM) aided tool of the present invention is generally indicated by reference numeral  40  and is typically capable of use with any type of chemical vapor deposition system sold by Applied Materials, Inc., of Santa Clara, Calif. The PM aided tool  40  includes a tool body  42 , typically constructed of clear, translucent acrylic or other lightweight, translucent plastic. It is understood that the tool body  42  may be constructed of any other suitable material. The body  42  includes a generally cylindrical sidewall  44  which has a bottom opening  45  and defines a body interior  43 , and an annular wall bevel  46  may angle inwardly from the upper edge of the sidewall  44 . An annular bevel flange  47 , the purpose of which will be hereinafter described, defines the extending end portion of the wall bevel  46  and is disposed generally perpendicularly with respect to the sidewall  44 . A top opening  50  of the body interior  43 , closed by a typically rotatable, circular lid panel  51  as hereinafter described, is defined by the bevel flange  47  opposite the bottom opening  45 . A leading gap design vacuum line connector  48  extends from the sidewall  44  in fluid communication with the body interior  43 , and may be fitted with a suitable quick connect/disconnect coupler (not illustrated) or other coupling mechanism for removable attachment to a vacuum line  67  (FIG.  7 ). As illustrated in FIGS. 3,  5  and  8 , the bottom edge of the sidewall  44  may be characterized by an annular seal flange  65  which defines an annular o-ring notch  63 , the purpose of which will be hereinafter described. Alternatively, the bottom edge of the sidewall  44  may be flat, as illustrated in FIG.  9 . The diameter of the cylindrical sidewall  44  is sized to close the top opening (not illustrated) on the enclosure assembly  6  of the CVD system  10  upon removal of the lid  18  from the enclosure assembly  6 . 
     As illustrated in FIG. 4, an annular lid panel support flange  52  extends from the wall bevel  46  or alternatively, the sidewall  44 , in spaced-apart relationship to the bevel flange  47 . The circular lid panel  51  is rotatably mounted between the bevel flange  47  and the lid panel support flange  52  and closes the top opening  50  of the body  42 . A gasket, o-ring or other suitable sealing mechanism (not illustrated) may be interposed between the lid panel  51  and the bevel flange  47  or between the lid panel  51  and the lid panel support flange  52  to substantially seal the body interior  43  from the exterior of the PM aided tool  40 . 
     It is understood that the lid panel  51  may be rotatably mounted in the top opening  50  by any mechanism known by those skilled in the art other than by means of the continuous, annular lid panel support flange  52 . For example, the lid panel support flange  52  may be replaced by multiple, individual lid panel support tabs (not illustrated) that are spaced around the periphery of the wall bevel  46  or sidewall  44  and engage the bottom surface of the lid panel  51  to hold the lid panel  51  in place in the top opening  50 . 
     As particularly illustrated in FIGS. 2 and 5, a pair of typically semicircular panel openings  53  is provided in the lid panel  51 , and each panel opening  53  is selectively opened and closed by a correspondingly-shaped closing panel  55 . While the panel openings  53  and closing panels  55  are herein shown and described as having a generally semicircular shape, it is understood that the panel openings  53  and closing panels  55  may have any suitable alternative shape. Accordingly, the straight edge of each typically semicircular closing panel  55  is hingedly attached to the lid panel  51  by means of a pair of panel hinges  57 . A panel knob  59  may be provided on the upper surface of each closing panel  55  for selectively opening and closing the corresponding panel opening  53 . As illustrated in FIG. 6, the curved edge of each closing panel  55  may be fitted with a closing panel seal flange  56  which mates with a companion lid panel seal flange  54  that is shaped in the lid panel  51  along the curved edge of the panel opening  53 . An o-ring, gasket or other suitable sealing mechanism  61  may be provided on the lid panel seal flange  54 , the closing panel seal flange  56  or both of these elements to provide a gas-tight seal between the lid panel  51  and the closing panel  55  when the closing panel  55  is in the closed position of FIG.  6 . It is understood that the pair of closing panels  55  may be replaced by a single, large closing panel  55  of any desired size and shape for selectively closing a single, correspondingly sized and shaped panel opening  53  in the lid panel  51 . 
     Referring next to FIGS. 7-9 of the drawings, in typical application of the PM aided tool  40  of the present invention, the lid  18  and showerhead  30  components of the CVD system  10  are initially removed from the top  7  of the enclosure assembly  6  using methods which are well-known in the art. Upon such removal of the lid  18  and showerhead  30 , the lid o-ring  9  on the top seal flange  8  of the top  7  is exposed. The sidewall  44  of the PM aided tool  40  is next lowered into the lid opening (not illustrated), and the o-ring notch  63  in the bottom edge of the sidewall  44  receives the lid o-ring  9  and top seal flange  8  of the top  7 , as illustrated in FIG.  8 . Alternatively, in the embodiment of the PM aided tool  40  in which the bottom edge of the sidewall  44  has a flat configuration, the flat bottom edge of the sidewall  44  engages the lid o-ring  9 , as illustrated in FIG.  9 . In each case, the sidewall  44  forms a gas-tight seal against the top  7  of the enclosure assembly  6 , at the lid o-ring  9 , and the body interior  43  of the tool body  42  is disposed in fluid communication with the chamber  15 . A vacuum line  67  in the clean room environment of the CVD system  10  is removably connected to the vacuum line connector  48 . 
     After the PM aided tool  40  is mounted on the CVD system  10  in the manner heretofore described, the vacuum pump (not illustrated) connected to the vacuum line  67  is energized to induce vacuum pressure in the chamber  15 . This action causes suction-induced closing of the closing panels  55  on the PM aided tool  40 , against the gasket or o-ring  61  in the manner illustrated with respect to FIG. 6, to initially seal the body interior  43  from the ambient environment of the CVD system  10 . Next, one of the closing panels  55  is opened to provide access to the chamber  15  for cleaning purposes. Accordingly, as illustrated in FIG. 7, a chemical dispensing tube  69  or other cleaning instrument can be inserted in the open panel opening  53  to facilitate dispensing water and cleansing chemicals  73  into the chamber  15 . Due to the vacuum pressure induced the body interior  43  and chamber  15  through the vacuum line  67 , residual process gases and other potentially toxic, flammable, and/or corrosive gases  71  generated in the chamber  15  during the cleansing process are drawn from the chamber  15  and body interior  43  and to a suitable disposal container or system (not shown) through the vacuum line connector  48  and vacuum line  67 , respectively. It will be appreciated by those skilled in the art that the gases  71  are incapable of flowing from the chamber  15  and body interior  43  through the open panel opening or openings  53  since the air or gas pressure in the chamber  15  and body interior  43  is negative with respect to the ambient air pressure around the CVD system  10 . By rotating the lid panel  51  in the manner indicated by the curved arrow in FIG. 2, the panel openings  53  may be positioned at the desired locations around the top of the tool body  42  for multi-positioning capability of the chemical dispensing tube  69  or other cleaning implement and thus, optimum cleaning of the chamber  15 . Furthermore, it will be appreciated by those skilled in the art that the typically translucent appearance of the PM aided tool  40  enables cleaning personnel to locate the chemical dispensing tube  40  or other cleaning implement precisely where needed in the chamber interior  15  for optimum cleaning thereof. 
     After the PM maintenance operation is completed, the vacuum pressure in the chamber  15  is dispelled by turning off the vacuum pump (not illustrated) attached to the vacuum line  67 , the tool body  42  is removed from the enclosure assembly  6  and the showerhead  30  and lid  18  are replaced on the enclosure assembly  6  in conventional fashion to resume normal operation thereof. 
     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.