Abstract:
Gas delivery devices for PECVD systems and methods for using such systems are described. The delivery device goes directly through the powered electrode and thereby bypasses components of the PECVD systems used to support that electrode. The delivery device contains a coupling device between the powered electrode of the PECVD reactor and the gas inlet line. The gas inlet line is electrically and thermally isolated from the powered electrode and is sealed to maintain the vacuum integrity of the PECVD reactor through the use of a coupling device. Thus, gases from the heated gas lines can be routed directly through the powered electrode and fed into the reactor via the showerhead without having a cold area between the showerhead and gas inlet line.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention generally relates to thin film deposition and etching apparatus and methods for using the same. More particularly, this invention relates to chemical vapor deposition apparatus and methods for using the same. Even more particularly, this invention relates to gas delivery systems for plasma enhanced chemical vapor deposition apparatus and methods for using such systems.  
         [0002]     There are numerous methods for depositing and etching films on substrates. One method for film deposition is by chemical vapor deposition (CVD). In CVD, the materials that are to be deposited as the films are formed as a result of a chemical reaction between gaseous reactants at elevated temperatures in the vicinity of the substrate. The product of the reaction is then deposited on the surface of the substrate. CVD can be used to deposit films of semiconducting materials (crystalline and non-crystalline), insulating materials, as well as metals.  
         [0003]     There are variants of CVD processes, including Atmospheric Pressure CVD (APCVD), Low Pressure CVD (LPCVD) and Plasma Enhanced CVD (PECVD). In PECVD, the materials to be deposited are generated in a gas-phase plasma located in fairly close proximity to the substrate. Thus, when using the same source gases as other CVD processes, PECVD can operate at a lower temperature than such other CVD where a higher temperature is needed to break the chemical bonds of the gaseous reactants and to generate the species needed to form the film.  
         [0004]     As shown in  FIG. 1 , a typical PECVD apparatus  10  includes a PECVD reactor chamber  12  and a powered electrode  16 . The powered electrode  16  is connected to a gas delivery system  60  to allow the introduction of gases  64  and  72 . A gas mixture  28  flows through the powered electrode  16  to its center and are then vented into an open space above the showerhead  15 . The showerhead  15  allows gases to pass into the interior region of the chamber  12 . The showerhead  15  also serves as a gas distribution mechanism that provides a substantially uniform gas flow to the interior of the chamber  12 .  
         [0005]     Also shown in  FIG. 1 , the showerhead  15  is part of the powered electrode  16  and carries the same voltage as the powered electrode  16 . Special precautions are often necessary, however, in the powered electrode  16  to keep the potentials electrically isolated from the rest of the PECVD apparatus  10  and the gas lines  42  and  77 . The powered electrode  16  is connected to an external RF power source  36 . In addition, the powered electrode  16  usually contains some mechanism (not shown) for heating the gas mixture  28 , such as water circulation coils. Typically, the showerhead  15  is composed of aluminum or an aluminum alloy with small holes  17  extending from a top surface  24  of the showerhead  15  to a bottom surface  26 . An electrical insulator  80  is provided to isolate the powered electrode  16  from other portions of the PECVD apparatus  10 . In addition, O-rings (or other sealing devices)  82  are provided between the powered electrode  16  and the sidewalls  32  of the chamber  12  to isolate the powered electrode  16  and assist in maintaining vacuum or near-vacuum conditions in the chamber  12 .  
         [0006]     A lower (powered or un-powered) electrode  18  in the form of a plate supports substrate  38  and extends within the chamber  12  parallel to the powered electrode  16 .  
         [0007]     The lower electrode  18  is often formed of aluminum and coated with a layer of aluminum oxide. Embedded within the lower electrode  18  is one or more heating elements (not shown) to control its temperature. The lower electrode  18  is connected to ground and is mounted on shaft  20  that extends vertically through a bottom wall  22  of the chamber  12 . The shaft  20  can move vertically, e.g., toward and away from the powered electrode  16 .  
         [0008]     Gas outlet  30  extends through a wall  22  of the chamber  12  and is connected to a pump (not shown) for evacuating the chamber  12 . There can be other gas outlets  30  that can be located in any wall  22 ,  32  of the chamber  12 . A gas inlet line  42  is connected to reservoirs of various gases, such as, for example, primary gas supply  72  and secondary gas supply  64 . The flow of the primary gas supply  72  and the secondary gas supply  64  are controlled by a valve/control mechanism  73  and  70 , respectively. The gases supplies  72  and  64  are then mixed in mixer  66  to obtain a homogenous gas mixture. The gas mixture flows through conduit  77 , through the gas inlet pipe  42  into the powered electrode  16 , and then through the showerhead  15  into the chamber  12 . A valve/flow mechanism  79  controls the flow of the gas mixture  28 .  
         [0009]     As further shown in  FIG. 1 , the gas mixture  28  enters the chamber  12  via the gas inlet line  42  that is often composed of aluminum and/or a ceramic material. The gas mixture  28  flows through gas inlet line  42  into chamber  12  around a first corner  54 , around a second corner  56 , and then to the powered electrode  16  and the showerhead  15 . Such configurations for delivering the gas mixture  28  to the chamber  12  routes the gas mixture  28  through the unheated areas of gas inlet line  42 . At these unheated areas, the gas mixture  28  can condense easily and clog the gas inlet line  42  especially at corners  54  and  56 . Typically, elevated heating of the gas inlet line  42  is not performed because the materials used to structurally hold the powered electrode  16  have low melting points. In addition, the gas inlet line  42  is imbedded in a thick block of aluminum which is difficult to heat. As such, the gas inlet line  42  is usually maintained at relatively low temperatures.  
         [0010]     Other methods have been used to compensate for these problems mentioned above. For example, one such method dilutes the gas mixture  28  using carrier gases, such as, argon, nitrogen, helium, hydrogen, or oxygen, etc. The diluted gas mixture is able to flow through conventional delivery systems without significant heating. However, this method decreases the efficiency and increases the cost of the CVD operation.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The invention relates to gas delivery systems for PECVD reactors and methods for using such systems. The delivery system goes directly through the powered electrode and thereby bypasses components of the PECVD reactor used to support that electrode. The delivery system contains a coupling device between the powered electrode of the PECVD reactor and the gas inlet line. The gas inlet line is electrically and thermally isolated from the powered electrode and is sealed to maintain the vacuum integrity of the PECVD reactor through the use of a coupling device. Thus, gases from the heated gas lines can be routed directly through the powered electrode and fed into the reactor via the showerhead without having a cold area between the showerhead and gas inlet line.  
         [0012]     The invention includes a delivery device for a thin film deposition or etching apparatus containing a heated gas inlet line for delivering a gas to a powered electrode of the apparatus, the gas inlet line maintained under a vacuum and a coupling device located between the powered electrode and the gas inlet line, the coupling device comprising insulation portion. The invention also includes a system for delivering a gas to a thin film deposition or etching apparatus with the system containing a heated gas inlet line maintained under a vacuum and a coupling device located between a powered electrode of the apparatus and the gas inlet line wherein the coupling device comprises the thermal and electrical insulation portion. The invention further includes a PECVD apparatus containing a delivery system with the system containing a heated gas inlet line maintained under a vacuum and a coupling device located between the powered electrode of the PECVD apparatus and the gas inlet line, the coupling device comprising insulation portion and flange for helping maintain the gas inlet line under a vacuum.  
         [0013]     The invention also includes a method for supplying a gas to a thin film deposition or etching apparatus by providing a delivery system containing a heated gas inlet line maintained under a vacuum, and containing a coupling device located between a powered electrode of the apparatus and the gas inlet line, wherein the coupling device comprises electrical and thermal insulation portion, and then providing a gas to the delivery system. The invention also includes a method for supplying a gas to a PECVD apparatus by providing a gas, flowing the gas through a heated gas inlet line, flowing the gas through a coupling device containing insulation device, and flowing the gas to a powered electrode of the PECVD apparatus. The invention further includes a method for depositing a film on a substrate by providing a gas, flowing the gas through a heated gas inlet line, flowing the gas through a coupling device containing insulation device, and flowing the gas to a deposition apparatus where the gas is converted to a plasma and then deposited as a film on a substrate contained within the deposition apparatus. The invention still further includes a method for etching a film from a substrate by providing a gas, flowing the gas through a heated gas inlet line, flowing the gas through a coupling device containing insulation device, and flowing the gas to an etching apparatus where the gas is converted to a plasma and then used to remove a portion of a film on a substrate contained within the etching apparatus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIGS. 1-3  are views of one aspect of the gas delivery systems and methods of using such systems according to the invention, in which:  
         [0015]      FIG. 1  is a cut-away view of a conventional, prior art PECVD apparatus;  
         [0016]      FIG. 2  is a cut-away view of one exemplary embodiment of a PECVD delivery system; and  
         [0017]      FIG. 3  is another cut-away view of another exemplary embodiment of a PECVD delivery system. 
     
    
       [0018]      FIGS. 1-3  presented in conjunction with this description depicts only particular-rather than complete-portions of the gas delivery systems and methods of using such systems in one aspect of the invention. Together with the following description, the Figures demonstrate and explain the principles of the invention.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The following description presents specific details in order to provide a thorough understanding of the invention. The one skilled in the art, however, would understand that the invention can be practiced without employing these specific details. Indeed, the present invention can be practiced by modifying the illustrated system and method and can be used in conjunction with apparatus and techniques conventionally used in the industry. For example, the invention is described with reference to parallel-plate PECVD reactors, but could be used for other types of PECVD, and even other CVD apparatus. In fact, the invention could be used in combination with other thin film deposition (and etching) apparatus.  
         [0020]     As shown in  FIG. 2 , one exemplary embodiment of the invention generally pertains to a system  100  for delivering gases into a PECVD reactor chamber  112 . The system  100  supplies inlet gases directly into the powered electrode  116  and allows heating of the entire gas inlet line  142  including in areas near the powered electrode  116 . The system  100  is able to perform these functions while also maintaining the vacuum integrity of the chamber  112 .  
         [0021]     It should be appreciated that any gas delivery system, including the embodiment shown in  FIG. 1 , can be used in the invention, including the system  100  depicted in  FIG. 2 . As shown in  FIG. 2 , the  100  includes a PECVD reactor chamber  112  and a powered electrode  116 . The powered electrode  116  can similarly be connected to a gas delivery system  60  ( FIG. 1 ) to allow the introduction of gases  64  ( FIG. 1 ) and  72  ( FIG. 1 ). In  FIG. 2 , the gas mixture  128  flows directly through the powered electrode  116  and directly into an open space above the showerhead  115 . The showerhead  115  allows gases to pass into the interior region of the chamber  112 . The showerhead  115  also serves as a gas distribution mechanism that provides a substantially uniform gas flow to the interior of the chamber  112 .  
         [0022]     As further shown in  FIG. 2 , the showerhead  115  is part of the powered electrode  116  that is connected to an external RF power source  136 . In addition, the powered electrode  116  can also contains some mechanism (not shown) for heating the gas mixture  128 , such as water circulation coils and other heating devices. In one embodiment, the showerhead  15  is composed of aluminum or an aluminum alloy. Further, the showerhead  115  contains small holes  117  extending from a top surface  124  of the showerhead  115  to a bottom surface  126 . An electrical insulator  180  is provided to isolate the powered electrode  116  from other portions of the PECVD apparatus  100 . In addition, o-rings (or other sealing devices)  182  are provided between the powered electrode  116  and the sidewalls  132  of the chamber  112  to isolate the powered electrode  116  and assist in maintaining vacuum or near-vacuum conditions in the chamber  112 .  
         [0023]     A lower electrode  118  supports substrate  138  and extends within the chamber  112  parallel to the powered electrode  116 . In another embodiment, the lower electrode  118  can comprise a powered or non-powered electrode. In even another embodiment, the lower electrode can comprise a plate structure. However, it should be appreciated that the lower electrode  118  can comprise other configurations. In another embodiment, the lower electrode  18  is comprised of aluminum and coated with a layer of aluminum oxide. In yet another embodiment, the lower electrode  118  can be embedded with one or more heating elements (not shown) to control the temperature of the lower electrode  118 . Further, when unpowered, the lower electrode  118  is connected to ground and is mounted on shaft  120  that extends vertically through a bottom wall  122  of the chamber  112 . It should be appreciated that, in one embodiment, the shaft  120  can move vertically, e.g., toward and/or away from the powered electrode  116 .  
         [0024]     Gas outlet  130  extends through a wall  122  of the chamber  112  and is connected to a pump (not shown) for evacuating the chamber  112 . In another embodiment, other gas outlets  130  and these gas outlets can be located in any wall  122 ,  132  of the chamber  112 .  
         [0025]     In one aspect as shown in  FIG. 2 , the gas mixture  128  is inserted directly into the powered electrode  116  and showerhead  115  via gas inlet line  142 . By configuring the gas inlet line  142  into the powered electrode  116  using coupling  200 , the accumulation of the gas mixture  128  on the walls of the gas inlet line  142  is reduced or eliminated. It should be appreciated that, in one embodiment, gas inlet line  142  can be heated using external or imbedded heating mechanisms (not shown).  
         [0026]     Using the coupling  200 , the gas mixture  128  is directly supplied into the powered electrode  116 . In one embodiment, the coupling  200  is connected so that the gas inlet line  142  is electrically and thermally isolated from the powered electrode  116  and so that the gas inlet line  142  is capable of being maintained under vacuum pressure or near vacuum pressure.  
         [0027]     As shown in  FIG. 3 , the coupling  200  is comprised in a delivery device  280  of a PECVD apparatus  100  ( FIG. 2 ). In one embodiment, the coupling  200  is installed on the upper side  202  of powered electrode  116  in a PECVD apparatus  100  ( FIG. 2 ) to facilitate the gas mixture  128  being supplied directly provided to powered electrode  116 . The coupling device  200  connects and/or couples the gas inlet line  142  with the powered electrode  116  positioned proximate to shower head  115 , while as the same time electrically and thermally isolating the gas inlet line  142  from the powered electrode  116  and sealing the gas inlet line  142  under vacuum conditions. In one embodiment, the coupling device  200  operates in this manner by using an electrical and thermal insulation portion  205  and incorporating a flange  207  for maintaining a vacuum-tight or near-vacuum-tight seal.  
         [0028]     The insulation portion  205  electrically isolates the gas inlet line  142  from the upper surface  202  of the powered electrode  116 . The insulation portion  205  also thermally isolates the gas inlet line  142  from the upper surface  202  of the powered electrode  116 . It should be appreciated that the insulation portion  205  can comprise any suitable shape and/or be composed of made a material that achieves the objectives discussed herein. Consistent with these insulation functions, the insulation portion  205  can be composed of electrical and thermal insulating materials, such as plastics or ceramic materials. In one embodiment, the insulation portion  205  is made of a ceramic material, such as MACOR™.  
         [0029]     In one embodiment, the insulation portion  205  is shaped similar to flange  207 . For example, the flange  207  can comprise a vacuum flange, and the insulation portion  205  can comprise an isolation ring as shown in  FIG. 3 . In this embodiment, the insulation portion  205  is configured to connect flush with flange  207  as well as the upper surface  202  of the powered electrode  116 .  
         [0030]     The flange  207  serves to connect the insulation portion  205  with gas inlet line  142  while maintaining the existing vacuum conditions. It should be appreciated, in one embodiment, that gas inlet line  142  can be connected to or integrally formed as a part of flange  207 . It should be further appreciated that the flange  207  can be any suitable shape and can be composed of any material to achieve the objectives discussed herein. As discussed above, in one embodiment, the flange  207  comprises a vacuum flange.  
         [0031]     As shown in  FIG. 3 , the coupling device  200  is connected to both the gas inlet line  142  and the upper surface  202  of the powered electrode  116  in any suitable manner. As well, the two components of the coupling device  200  (insulation portion  205  and flange  207 ) are interconnected in any suitable manner. One embodiment of such a connection is shown in  FIG. 3  where a plurality of fastening bolts (not shown) secure the insulation portion  205  to the upper surface  202  though a corresponding plurality of holes  210 . In one embodiment, the holes  210  are countersunk for bolts (not shown) that are used to attach the coupling device  200  to the top surface  202  of the powered electrode  116 , thereby avoiding contact of the fastening bolt heads with the flange  207 . In another embodiment, the bolts (not shown) and corresponding holes  210  are offset by about 120 degrees to fasten the coupling device  200  to the upper surface  202  of the powered electrode  116 . It should be appreciated that with more (or less) holes  210  and corresponding bolts, the offset angle may be different than about 120 degrees.  
         [0032]     As further shown in  FIG. 3 , the flange  207  is fastened to insulation portion  205  via fastening bolts (not shown) though a corresponding plurality of holes  212 . The bolts can be configured to avoid electrically contacting the powered electrode  116 . In one embodiment, the holes  212  have channels that allow for clearance between the bolts and the powered electrode  116 . In another embodiment, the flange  207  and the insulation portion  205  comprise three bolts and three corresponding holes  212  that are each offset from one another by about 120 degrees. Further, the bolts and corresponding holes  212  are, in turn, offset by about 60 degrees from the previously set of three fastening bolts and holes  210  described above in relation to the insulation portion  205  and the upper side  202  of the powered electrode  116 . It should be appreciated that the offset angle may be different with more (or less) holes  212  and corresponding bolts.  
         [0033]     It should further be appreciated that the coupling device  200  can contain additional component that assist in operation as described above. For example, in one embodiment, the coupling device  200  can comprise additional components to assist in the connection of the gas inlet line  142  to the powered electrode  116 . In another embodiment, the flange  207  and the insulation portion  205  can comprise additional components to assist in their interconnection. In yet another embodiment, the coupling device  200  can contain internal sealing portions disposed between the various components, for example, O-rings  220  (and, if necessary, corresponding grooves for the O-rings  220 ) can be used form a tight seal.  
         [0034]     The coupling device  200  can be used in any PECVD apparatus known in the art and may be extended to those systems developed in the future. In the embodiments described herein, the coupling device  200  is used in combination with a parallel-plate PECVD reactor, but the coupling device  200  could be used in other CVD reactors (e.g., LPCVD reactors). In yet another embodiment, the coupling device  200  can be used in a sputtering apparatus. In addition, the coupling device  200  can be used in any thin film deposition or etching apparatus where the gas needs to be directly inserted into the apparatus and the gas inlet line needs to be electrically and thermally isolated from the remainder of the apparatus.  
         [0035]     In operation, the coupling device  200  is disposed in the PECVD apparatus  100  between the gas inlet line  142  and the powered electrode  116 . In one embodiment, when the PECVD apparatus  100  is operated, the coupling device  200  allows the entire gas line (including the gas inlet line  142 ) to remain heated. In embodiments where aluminum is used, the inlet gas line  142  can be operated at a temperature ranging from about 25 to about 110 degrees Celsius. In another embodiment, the inlet gas line  142  can be operated at a temperature ranging from about 25 to about 90 degrees Celsius. It should be appreciated that other operating temperatures could be used where other materials are used, e.g., the operating temperature could range up to about 400 degree Celsius.  
         [0036]     In another embodiment of operation, a film is deposited on a substrate  138  by providing a gas mixture  128 . The gas mixture  128  flows through a heated gas inlet line  128 , and the coupling device  200 . In this embodiment, the gas mixture  128  is provided into chamber  112  where the gas mixture  128  is converted to a plasma and then deposited as a film on the substrate  138  contained within the chamber  112 . In even another embodiment, a film can be etched from the substrate  138  by providing the gas mixture  128  via the heated gas inlet line  142  through the coupling device  200 . When the gas mixture  128  is provided in the chamber  112 , the gas mixture  112  is converted to a plasma and then used to remove a portion of a film on a substrate  138  contained within the etching apparatus  100 .  
         [0037]     By using the coupling device  200 , a PECVD apparatus  100  can have improved performance with relation to conventional systems. For example, one measurement of such performance is less clogging in the channel of the inlet gas line  142 . Using the coupling device  200 , up to about 95% (and even to about 100%) less gas mixture residue is left on the walls of the gas inlet line  142 .  
         [0038]     The following non-limiting example illustrates the invention.  
       EXAMPLE  
       [0039]     A parallel-plate PECVD apparatus  100  including coupling device  200  similar to  FIGS. 2 and 3  was constructed. The PECVD apparatus  100  was used to feed TaF 5  to the PECVD reactor chamber under the following conditions: 300 mT, PE mode, 300 sccm Argon, 5 sccm TaF 5 , 200 sccm Hydrogen, 200 sccm Oxygen, and 150 Watts. The gas lines leading up to the reactor were kept at 160 degrees Celsius, and the reactor electrodes were operated at 100 degrees C. The PECVD operation failed after 30 minutes due to extreme clogging of TaF 5  at the juncture between the gas line and the chamber.  
         [0040]     A PECVD apparatus similar to  FIGS. 2 and 3  was then constructed for the PECVD reactor. The PECVD reactor was then operated under the following conditions: 300 mT, PE mode, 300 sccm Argon, 5 sccm TaF 5 , 200 sccm Hydrogen, 200 sccm Oxygen, and 150 Watts. The gas line leading up to the reactor was kept at 160 degrees Celsius, the powered electrode was heated to 145 degrees Celsius, and the lower electrode was heated to 275 degrees C. The PECVD reactor was operated for 30 minutes with negligible clogging of the gas line.  
         [0041]     Having described these aspects of the invention, it is understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof.