Abstract:
A method including in a wafer processing environment, introducing a liquid via a carrier gas, and separate from the liquid, introducing a first gas comprising ozone and a legacy amount of oxygen and a second gas comprising an effective amount of oxygen to modify a process operation. A system including a chamber, a liquid source, a first gas source, and a second gas source, a controller configured to control the introduction into the chamber of a liquid from the liquid source, a first gas comprising ozone and a legacy amount of oxygen from the first source, a second gas comprising oxygen from the second gas source, and a memory coupled to the controller comprising a machine-readable medium having a program embodied therein for controlling the second gas to introduce an effective amount of oxygen into the chamber to modify a process operation.

Description:
BACKGROUND  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to microelectronic structure fabrication.  
           [0003]    2. Background  
           [0004]    In the fabrication of modem microelectronic structures, such as microprocessor and memory structures, oxidation processes are used to passivate or oxidize a substrate or film, such as semiconductor substrates or films. Typical methods of passivation of silicon surfaces and films, such as for example, polycrystalline silicon gate electrodes and silicon substrates, include oxygen (O 2 ) and water vapor or steam oxidation processes.  
           [0005]    Oxide (e.g., silicon dioxide (SiO 2 ) films are also often used to electrically isolate one device from another in a circuit structure and one level of conductor from another in multi-level interconnect systems such as found in many microelectronic structures. A microprocessor, for example, may have five or more levels of interconnect over a substrate such as a semiconductor substrate. Typical oxide film material includes undoped silicate glass (USG), borosilicate glass (BSG), phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG).  
           [0006]    Chemical vapor deposition (CVD) is a typical process for introducing (e.g., depositing) various types of films on substrates and is used extensively in the fabrication of microelectronic structures. In a typical CVD process, a wafer or wafers are placed in a deposition or reaction chamber and reactant gases are introduced into the chamber and are decomposed and combined or reacted at a heated surface to form a film on the wafer or wafers.  
           [0007]    One example of a CVD film formation process involves the introduction of a liquid, such as tetraethylorthosilicate (TEOS), tetraethylborosilicate (TEB), or tetraethylphosphosilicate (TEPO) into a deposition chamber. Such liquids may be introduced with a carrier gas such as helium (He), nitrogen (N 2 ), or a combination of helium and nitrogen. The liquid is injected into the carrier gas and carried to the chamber through what is representatively referred to as a liquid line. At the same time, ozone (O 3 ) is introduced to the chamber through what is representatively referred to as a gas line. Prior to entering the chamber, the contents of the gas line and the contents of the liquid line may be mixed in, for example, a mixing block. The mixture is then introduced into the chamber.  
           [0008]    One way to form ozone is by exposing oxygen to an energy source (e.g., electrical discharge or ultraviolet light) in an ozonator. Typically, for a given amount of oxygen introduced into an ozonator, the ozonator will have a discharge of ozone with a legacy amount of oxygen.  
           [0009]    One goal of any film formation process is to attempt to improve the film properties. Such film properties may include introduction (e.g., deposition) rate, uniformity, moisture absorption, shrinkage, index of refraction, gap fill and electrical properties as well as dopant concentrations and levels.  
         SUMMARY  
         [0010]    In one embodiment, a method is described. One example of the method includes, in a wafer processing environment, introducing a liquid via a carrier gas and, separate from the liquid, introducing a gas. The gas includes a first gas comprising ozone and a legacy amount of oxygen and a second gas comprising an effective amount of oxygen to modify a process operation. The second gas comprising an effective amount of oxygen supplements the ozone source and, in combination with the liquid, provides improved properties with regard to film formation or etch characteristic.  
           [0011]    In another embodiment, a system is disclosed. The system includes a chamber, a liquid source coupled to the chamber, and a first and second gas source coupled to the chamber. A system controller is configured to control the introduction into the chamber of a liquid from the liquid source, a first gas comprising ozone and the legacy amount of oxygen from the first gas source, and a second gas comprising oxygen from the second gas source. The system further includes a memory coupled to the controller comprising a machine-readable medium having a machine-readable program embodied therein for directing operation of the system. The machine-readable program comprises instructions for controlling the second gas source to introduce an effective amount of oxygen into the chamber to modify a process operation.  
           [0012]    In a further embodiment, a machine-readable storage medium is also disclosed. The machine-readable storage medium, in one example, contains executable program instructions which, when executed, cause a digital processing system to form a method comprising introducing a liquid via a carrier gas, and separate from the liquid, introducing a first gas and a second gas. The first gas comprises ozone and a legacy amount of oxygen and the second gas comprises an effective amount of oxygen to modify a process operation, such as an etching operation or a film formation operation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 illustrates a schematic view of one embodiment of a wafer processing environment.  
         [0014]    [0014]FIG. 2 shows a schematic illustration of one embodiment of a gas panel for use in conjunction with the wafer processing environment of FIG. 1.  
         [0015]    [0015]FIG. 3 shows a schematic illustration of a second embodiment of a gas panel for use in conjunction with the wafer processing environment of FIG. 1.  
         [0016]    [0016]FIG. 4 shows a schematic illustration of one embodiment of a gas panel for introducing a gas source into the wafer processing environment of FIG. 1.  
         [0017]    [0017]FIG. 5 shows a schematic top view of one embodiment of a mixing block for use in conjunction with the wafer processing environment of FIG. 1.  
         [0018]    [0018]FIG. 6 shows one representation of a process flow for forming a film on a substrate. 
     
    
     DETAILED DESCRIPTION  
       [0019]    Disclosed is a method, a system for implementing a method, and a machine-readable storage medium embodying a method of introducing a liquid and a gas into a wafer processing environment. The introduction described, in one embodiment, is in the context of introducing a liquid source with an ozone gas source to form, for example, oxide (e.g., silicon dioxide) films. Suitable films include undoped silicate glass (USG), borosilicate glass (BSG), phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG). In addition to the introduction of ozone in the environment, perhaps with a legacy amount of oxygen, the method and system describe the introduction of supplemental oxygen to improve a process operation, and/or the film characteristics. Such process operation may include a film formation operation or an etch operation.  
         [0020]    [0020]FIG. 1 shows a schematic side view of one embodiment of a wafer processing system. Included in the illustration is a cross-sectional side view of a single-wafer chamber. The single-wafer chamber in the system of FIG. 1 is suitable, for example, in a film-formation process, such as a chemical vapor deposition (CVD) process, including atmospheric CVD (ACVD), sub-atmospheric CVD (SACVD), and low pressure CVD (LPCVD) processes. Suitable single-wafer chambers include, but are not limited to GIGAFILL™ and DXZ™ chambers commercially available from Applied Materials, Inc. of Santa Clara, Calif. A twin chamber such as a PRODUCER™ commercially available from Applied Materials is also a suitable chamber for a processing system adapted to process multiple wafers at a time.  
         [0021]    [0021]FIG. 1 shows chamber body  100  that defines reaction chamber  145  where the reaction between a process gas or gases and the wafer takes place, e.g., a CVD reaction. In this sense, a process gas or gases include a liquid injected into a carrier gas. Chamber body  100  is constructed, in one embodiment, of aluminum and has passages  102  for water to be pumped therethrough to cool chamber body  100  (e.g., a “cold-wall” reaction chamber). Resident in chamber  145  is resistive heater  150  including, in this view, susceptor  155  supported by shaft  158 . In one embodiment, susceptor  155  has a surface area sufficient to support a semiconductor wafer. A cylindrical susceptor having a diameter of approximately 9.33 inches supported by a shaft having a length of approximately 10 inches is suitable to support an eight inch diameter wafer.  
         [0022]    Process gas enters otherwise sealed chamber  145  through distribution port  175  in a top surface of chamber lid  170  of chamber body  100 . The process gas is distributed throughout chamber  145  by perforated blocker and face plate  180  located, in this view, above resistive heater  150  and coupled to chamber lid  170  inside chamber  145 .  
         [0023]    A wafer is placed in chamber  145  on susceptor  155  through entry port  105  in a side portion of chamber body  100 . To accommodate a wafer for processing, heater  150  is lowered so that the surface of susceptor  155  is below entry port  105 . Typically by a robotic transfer mechanism, a wafer is loaded by way of, for example, a transfer blade into chamber  145  onto the superior surface of susceptor  155 . Once loaded, entry port  105  is sealed and heater  150  is advanced in a superior (e.g., upward) direction toward face plate  180  by lifter assembly  160  that is, for example, a step motor. The advancement stops when the wafer is a short distance (e.g., 400-700 mils) from blocker and face plate  180 . At this point, a process gas or process gases controlled by a gas panel (as described below) flow into chamber  145  through gas distribution port  175 , through perforated blocker and face plate  180 , and typically react or are deposited on a wafer to form a film. In a pressure controlled system, the pressure in chamber  145  is established and maintained by a pressure regulator or regulators coupled to chamber  145 . In one embodiment, for example, the pressure is established and maintained by baratome pressure regulator(s) coupled to chamber body  100  as known in the art.  
         [0024]    After processing, residual process gas or gases are pumped from chamber  145  through pumping channel  185  to a collection vessel. Chamber  145  may then be purged, for example, with an inert gas, such as nitrogen. After processing and purging, heater  150  is advanced in an inferior direction (e.g., lowered) by lifter assembly  160 . As heater  150  is moved, lift pins  195 , having an end extending through openings or throughbores in a surface of susceptor  155  and a second end extending in a cantilevered fashion from an inferior (e.g., lower) surface of susceptor  155 , contact lift plate  190  positioned at the base of chamber  145 . In one embodiment, at this point, lift plate  190  does not advance from a wafer-load position to a wafer-separate position as does heater  150 . Instead, lift plate  190  remains at a reference level on shaft  158 . As heater  150  continues to move in an inferior direction through the action of lifter assembly  160 , lift pins  195  remain stationary and ultimately extend above the superior or top surface of susceptor  155  to separate a processed wafer from the surface of susceptor  155 .  
         [0025]    Once a processed wafer is separated from the surface of susceptor  155 , a transfer blade of a robotic mechanism is inserted through entry port  105  to a “pick out” position inside chamber  145 . The “pick out” position is below the processed wafer. Next, lifter assembly  160  inferiorly moves (e.g., lowers) lift plate  190  to, for example, a second reference level on shaft  158 . By moving lift plate  190  in an inferior direction, lift pins  195  are also moved in an inferior direction, until the underside of the processed wafer contacts the transfer blade. The processed wafer is then removed through entry port  105  by, for example, a robotic transfer mechanism that removes the wafer and transfers the wafer to the next processing step. A second wafer may then be loaded into chamber  145 . The steps described above are reversed to bring the wafer into a process position. A detailed description of one suitable lifter assembly  160  is described in U.S. Pat. No. 5,772,773, assigned to Applied Materials, Inc., of Santa Clara, Calif.  
         [0026]    In high temperature operation, the reaction temperature inside chamber  145  can be as high as 750° C. or more. Accordingly, the exposed components in chamber  145  must be compatible with such high temperature processing. Such materials should also be compatible with the process gases and other chemicals, such as cleaning chemicals, that may be introduced into chamber  145 . In one embodiment, exposed surfaces of heater  150  are comprised of aluminum nitride (AIN). For example, susceptor  155  and shaft  158  may be comprised of similar aluminum nitride material. Alternatively, the surface of susceptor  155  may be comprised of high thermally conductive aluminum nitride material (on the order of 95% purity with a thermal conductivity from 140 W/mK to 200 W/mK) while shaft  158  is comprised of a lower thermally conductive aluminum nitride (on the order of 60 W/mK to 100 W/mK). Susceptor  155  of heater  150  is typically bonded to shaft  158  through diffusion bonding or brazing as such coupling will similarly withstand the environment of chamber  145 .  
         [0027]    Lift pins  195  are also present in chamber  145  during processing. Accordingly, lift pins  195  must be compatible with the operating conditions within chamber  145 . A suitable material for lift pins  195  includes, but is not limited to, sapphire or aluminum nitride. A further component that is exposed to the environment of chamber  145  is lift plate  190 . Accordingly, in one embodiment, lift plate  190 , including a portion of the shaft of lift plate  190 , is comprised of an aluminum nitride (e.g., thermally conductive aluminum nitride on the order of 140 W/mK to 200 W/mK) composition.  
         [0028]    In addition to the process chamber, FIG. 1 schematically illustrates a gas panel coupled to the process chamber through a mixing block. Referring to FIG. 1, in one embodiment, gas panel  290  regulates the delivery of a gas source and a liquid source to mixing block  280  and then to chamber  145 . In a CVD operation to form an oxide film, for example, a liquid source and a gas source may be introduced into chamber  145 . In FIG. 1, the liquid source enters mixing block  280  through liquid line  300  while the gas source enters mixing block  280  through gas line  310 . Liquid line  300  is shown, in this embodiment, to include heating jacket  305  wrapped around it. Heating jacket  305  may include a filament to heat the liquid source prior to the introduction of the liquid source into mixing block  280 . A representative temperature of a liquid source for a CVD oxide deposition process is on the order of 90° to 100° C.  
         [0029]    [0029]FIG. 1 also shows controller  350  coupled to gas panel  290  and mixing block  280 . In one aspect, controller  350  controls the flow of constituents (e.g., liquid(s) and/or gas(es)) to mixing block  280  and chamber  145 . Controller  350  is supplied with software instruction logic that is, for example, a computer program stored in a computer readable medium such as memory  355  in controller  350 . Memory  355  is, for example, a portion of a hard disk drive. Controller  350  may also be coupled to a user interface that allows an operator to enter the reaction parameters, such as the desired flow rate of process gas or gases and the reaction temperature. In a CVD process, controller  350  may further be coupled to a pressure indicator that measures the pressure in chamber  145  as well as a vacuum source to adjust the pressure in chamber  145 .  
         [0030]    Referring to FIG. 2, the liquid portion of the gas panel is described. In this embodiment, liquid sources  230 A,  230 B, and  230 C are coupled to gas panel  290 . Liquid sources  230 A,  230 B, and  230 C may be supply tanks of the desired liquid for a process operation. In terms of a process operation to form an oxide film, the liquid sources are, for example, tetraethylorthosilicate (TEOS), tetraethylboron (TEB), and tetraethylphosphorous (TEP). Within gas panel  290  are liquid flow meters  240 A,  240 B, and  240 C coupled to liquid source  230 A, liquid source  230 B, and liquid source  230 C, respectively. Controller  350  is coupled to liquid flow meter  240 A, liquid flow meter  240 B, and liquid flow meter  240 C to control the introduction of liquid into liquid line  300 . In the introduction of one or more liquids from liquid source  230 A, liquid source  230 B, and liquid source  230 C, into liquid line  300 , such liquid is aided by a carrier gas of, for example, helium (He), nitrogen (N 2 ), or He/N 2 . Carrier gas from carrier gas source  270  is injected at injection valve  285 A, injection valve  285 B, and/or injection valve  285 C. Controller  350  controls the amount/volume of carrier gas introduced from carrier gas source  270  through mass flow meter  275 . Thus, the liquid sources (liquid source  230 A, liquid source  230 B, and/or liquid source  230 C) are injected with carrier gas into liquid line  300  to mixing block  280  (shown in FIG. 1). As illustrated in FIG. 2, the injection of carrier gas into the liquid from liquid sources  230 A,  230 B, and/or  230 C is accomplished in a parallel injection scheme.  
         [0031]    As one example of a liquid flow to form an oxide film on a  200  millimeter wafer in a GIGAFILL™ chamber, a liquid flow rate on the order of one to four standard liters per minute (SLM) of, for example, TEOS may be combined with a carrier gas having a flow rate of 8 SLM.  
         [0032]    [0032]FIG. 3 shows an alternative serial injection of carrier gas from carrier gas source  270  into the liquids from liquid sources  230 A,  230 B, and  230 C. In FIG. 3, like references in FIG. 2 are given similar numeral references. Thus, gas panel  290  includes liquid flow meter  240 A, liquid flow meter  240 B, and liquid flow meter  240 C, respective ones for liquid source  230 A, liquid source  230 B, and liquid source  230 C. Again, each of the liquid flow meters is coupled to controller  350  to control the introduction of liquid from liquid source  230 A, liquid source  230 B, and/or liquid source  230 C.  
         [0033]    In FIG. 3, carrier gas from carrier gas source  270  is injected through injection valves  285 A,  285 B, and/or  285 C, in a serial fashion. The carrier gas is first injected into injection valve  285 A and, if liquid from liquid source  230 A is present, such liquid is carried with carrier gas to injection valve  285 B. If liquid from liquid source  230 B is introduced at injection valve  285 B, the combined carrier gas, liquid from liquid source  230 A if present, and liquid from liquid source  230 B is carried to injection valve  285 C where it may or may not pick up liquid introduced from liquid source  230 C. The combination of the carrier gas and liquid from one or more liquid sources is then introduced into liquid line  300 .  
         [0034]    In addition to the liquid in liquid line  300 , gas panel  290  also controls the introduction of a separate gas into mixing block  280  through gas line  310 . FIG. 4 schematically illustrates one embodiment demonstrating the introduction of a gas or gases into gas line  310 . In this embodiment, the gas introduced into gas line  310  includes ozone, a legacy amount of oxygen, and a supplemental amount of oxygen. Referring to FIG. 4, there is shown oxygen source  330 A and oxygen source  330 B. It is appreciated that the oxygen sources  330 A and  330 B may be a single oxygen source.  
         [0035]    A certain amount of ozone may be desired in the formation of an oxide film in the process as described herein. In this embodiment, oxygen source  330 A introduces oxygen into ozonator  340  to form ozone. Oxygen gas from oxygen source  330 A is metered into ozonator  340  through mass flow controller  335 . Mass flow controller  335  is coupled to controller  350  to control the introduction of oxygen gas into ozonator  340 . Ozonator  340  includes energy source  345  (e.g., electrical discharge or ultraviolet light) to energize the oxygen gas and form ozone. The discharge of the ozonator may include ozone and a legacy amount of oxygen. An additional mass flow controller, such as mass flow controller  360 A may be included at the discharge of ozonator  340  to control the introduction of the ozone/legacy oxygen into gas line  310 . Mass flow controller  360  may be controlled, in this example, by controller  350 .  
         [0036]    In addition to the ozone and legacy oxygen introduced into gas line  310 , FIG. 4 also shows the introduction of a supplemental amount of oxygen into gas line  310 . In this example, oxygen gas from oxygen source  330 B (which may be the same as oxygen source  330 A) is introduced into gas line  310  through mass flow controller  360 B within gas panel  290 .  
         [0037]    In FIG. 4, a separate supplementation of oxygen is described (i.e., through a separate mass flow meter) and combining with ozone and a legacy amount of oxygen in gas line  310 . It is appreciated that the supplemental oxygen may also be introduced as a single source from oxygen source  330 A into ozonator  340  and, through mass flow controller  360 A and into gas line  310 . In one instance, an ozonator acts by breaking down oxygen with an energy source. Thus, the introduction of a larger volume of oxygen into ozonator  340  may be controlled such that a similar amount of ozone is produced and the discharge also includes a legacy amount of oxygen as well as the supplemental amount of oxygen.  
         [0038]    In one example where five liters of oxygen is introduced into ozonator  340  in connection with the formation of an oxide film, suitable supplementation with additional oxygen from oxygen source  330 B may be on the order of one to 10 liters of oxygen and, preferably 2 to 8 liters of oxygen to modify a film formation process.  
         [0039]    [0039]FIG. 5 shows a schematic top view of an embodiment of mixing block  280 . In this embodiment, a liquid/carrier gas through liquid line  300  enters a generally cylindrical chamber mixing block  280  at one side and in one direction. An ozone/legacy oxygen and supplemental oxygen through gas line  310  enter the chamber of mixing block  280  in a direction different than the direction for the liquid/carrier gas through liquid line  300 . Once in the chamber of mixing block  280 , the components from liquid line  300  and gas line  310  mix prior to entering chamber  145  (see FIG. 1). Thus, the mixture of liquid/carrier gas and ozone/legacy oxygen/supplemental oxygen is introduced as a process gas through distribution port  175  and blocker and perforated face plate  180  (FIG. 1). In one regard, it is believed that the supplementation of process gas with oxygen contributes to the mixing of the individual constituents within mixing block  280 .  
         [0040]    [0040]FIG. 6 demonstrates a method of forming a film on a substrate such as a wafer. In one embodiment, the film formation is in the context of a CVD process to form an oxide film on a substrate. It is appreciated that instruction logic embedded in a machine-readable medium stored in a memory of a process controller (e.g., controller  350 ) may direct the operation of the described method.  
         [0041]    Referring to process  400  of FIG. 6, a liquid from a liquid source (block  410 ) and preferably injected into a carrier gas is introduced into a mixing chamber (e.g., a mixing block). Concurrent with the introduction of a liquid, a gas from a gas source (block  420 ) is introduced into the mixing chamber. In one embodiment, the gas includes ozone with a legacy amount of oxygen. In addition to the ozone and legacy amount of oxygen, the process is supplemented with an additional amount (volume) of oxygen (block  430 ). It is appreciated that the ozone/legacy oxygen and supplemental oxygen may be introduced from a single source (e.g., a single oxygen source) or from separate sources (or separate lines from the same source).  
         [0042]    Referring to block  440 , in the mixing chamber the liquid and gas (ozone/legacy oxygen/supplemental oxygen) are mixed. The mixture represents a process gas (block  450 ). The process gas is introduced into a process chamber (block  460 ). According to the process parameters of the chamber, the process gas reacts with and/or combines and/or is deposited as a film on a substrate in the chamber. In terms of a wafer, the film may be introduced (deposited) on a bare substrate or a substrate such as a wafer having one or more device or interconnect levels.  
         [0043]    In terms of introducing (depositing) an oxide film, the film characteristics of an undoped silicate glass (USG) were analyzed with and without supplemental oxygen. To form a first USG film on a substrate (e.g., wafer) a liquid (e.g., TEOS) was injected into a carrier gas of helium in a liquid line (e.g., liquid line  300 ) into mixing block  280 . A separate gas source including ozone and legacy oxygen is also introduced through a gas line (e.g., gas line  310 ) into mixing block  280 . The gas source comprised a 5 liter ozone/oxygen mixture of 12.5 percent by weight ozone. The process gas mixture from the mixing block was introduced into a chamber as part of an SACVD process of forming an oxide film.  
         [0044]    As a comparison, a second USG film was formed according to an SACVD process on a second substrate (e.g., wafer) according to similar process conditions of temperature and pressure. The process gas utilized to form the second USG film, was supplemented with up to eight liters of oxygen (at gas line  310 ) so as to increase the volume within the mixing block.  
         [0045]    A comparison of the film formation properties of the first USG film and the second USG film showed an increase in the deposition rate of the second film (approximately 50 angstroms per minute (Å/min.) at conventional deposition rates of 800 to 1000 Å/min.). The characteristics of the two films showed the second USG also had improved film uniformity (350 Å range to 100 Å range) and improved gap fill by visual inspection. Film uniformity is represented as a “range uniformity” that examines the maximum and minimum film thickness over a range. A percent uniformity is an average of the range uniformity. For a film thickness on the order of 6000 Å, range uniformity of 350 Å showed a three percent uniformity improvement and a range uniformity of 100 Å showed a 0.8 percent uniformity for oxygen supplemented deposition.  
         [0046]    The above-described example related to an SACVD process for forming a USG film. It is appreciated that oxygen supplementation of a process gas may be used in other CVD environments, including ACVD and CPCVD to improve the performance and/or characteristics of films according to such conditions. Under controlled conditions, oxygen supplementation may also be incorporated into high density plasma (HDP) processes to improve the performance and/or characteristics of films formed in this manner.  
         [0047]    The above-described SACVD process of forming an oxide film utilizes a carrier gas of helium to deliver an undoped liquid oxide precursor to the mixing block. It is appreciated that oxygen supplementation as described herein is not confined to oxide formation environments utilizing a particular oxide precursor or carrier gas. Similar improved performance and/or characteristics may be achieved with other oxide precursors (TEB, TEP, etc.) and other carrier gases (e.g., nitrogen, helium and nitrogen, etc.)  
         [0048]    Various embodiments of a method of oxygen supplementation, a system for oxygen supplementation, and a machine-readable storage medium embodying a method of oxygen supplementation involving microelectronic structure fabrication have been described. In the foregoing specification, the embodiments are described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.