Patent Publication Number: US-2002009861-A1

Title: Method and apparatus for the formation of dielectric layers

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to the field of dielectric formation and more specifically to a method and apparatus for annealing a dielectric film.  
       [0003] 2. Discussion of Related Art  
       [0004] Integrated circuits are made up of literally millions of active and passive devices such as transistors, capacitors and resistors. In order to provide more computational power and/or more storage capability in an integrated circuit, device features are reduced or scaled down in order to provide higher packing density of devices. An important feature to enable scaling of devices is the ability to form high quality, high dielectric constant films for capacitor and gate dielectrics.  
       [0005] High dielectric constant films are generally ceramic films (i.e., metal-oxides) such as tantalum pentaoxide and titanium oxide. When these films are deposited they tend to have vacancies at the anionic (oxygen) sites in the lattice. Presently these vacancies are filled by annealing the film in a gas mixture which can provide an active species to occupy the lattice vacancies. For example, furnace anneals and rapid thermal oxidation (RNO) are presently used to anneal dielectric films. In such processes a substrate is placed in a furnace or a chamber of a rapid thermal apparatus and heated to a high temperature, greater than 800° C., while an anneal gas such as O 2  or N 2  is fed directly into the furnace or chamber, respectively, where the substrate is located. These processes must be performed at very high temperatures, greater than 800° C., in order to generate the active species from the anneal gas.  
       [0006] A problem with utilizing such high anneal temperatures is that dielectric films such as tantalum pentaoxide crystallize when exposed to high temperatures which can lead to high leakage currents. Additionally high anneal temperatures can cause other ions to diffuse into the film, especially at the interfaces of the devices, and cause poor electrical performance. Still further, many modern high density processes require a reduced thermal budget in order to prevent or minimize dopant diffusion or redistribution in a device. Still further some processes utilize materials with low melting points which preclude subsequent use of high temperature processing.  
       [0007] Thus, what is desired is a method and apparatus for forming a high quality, high dielectric constant dielectric film at a low temperature.  
       SUMMARY OF THE INVENTION  
       [0008] A method and apparatus for annealing a dielectric layer is described. According to the present invention active atomic species are generated in a first chamber. A dielectric layer formed on a substrate is then exposed to the active atomic species in a second chamber which is remote from the first chamber.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 is a flow chart which illustrates a process of forming a dielectric layer in accordance with the present invention.  
     [0010]FIG. 2 a  is an illustration of a cross-section view of a substrate including a interlayer dielectric and a bottom electrode.  
     [0011]FIG. 2 b  is an illustration of a cross-sectional view showing the passivation of the substrate of FIG. 2 a.    
     [0012]FIG. 2 c  is an illustration of a cross-sectional view showing the formation of a dielectric film on the substrate of FIG. 2 b.    
     [0013]FIG. 2 d  is an illustration of a cross-sectional view showing the formation of an annealed dielectric film on the substrate of FIG. 2 b.    
     [0014]FIG. 2 e  is an illustration of a cross-sectional view showing the formation of a top electrode on the substrate of FIG. 2 d.    
     [0015]FIG. 3 a  is an illustration of an apparatus which may be utilized to anneal a dielectric layer in accordance with the present invention.  
     [0016]FIG. 3 b  is an illustration of a chamber which may be used in the apparatus of FIG. 3 a.    
     [0017]FIG. 4 is a graph which illustrates how leakage current varies for different electrode voltages for a capacitor formed with a unannealed tantalum pentaoxide dielectric layer and for a capacitor formed with a tantalum pentaoxide dielectric layer annealed with remotely generated active atomic species.  
     [0018]FIG. 5 a  is an illustration of a cross-section view of a substrate having been passivated with active atomic species.  
     [0019]FIG. 5 b  is an illustration of the cross-sectional view as showing the formation of the dielectric film on the substrate of FIG. 5 a.    
     [0020]FIG. 5 c  is an illustration of cross-sectional view showing the formation of an annealed dielectric on the substrate of FIG. 5 a.    
     [0021]FIG. 5 d  is an illustration of the cross-sectional view showing the formation of a gate electrode and source/drain regions on the substrate of FIG. 5 c.    
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION  
     [0022] The present invention describes a novel method and apparatus for annealing a dielectric film. In the following description numerous specific details such as specific equipment configurations, and process parameters are set forth in order to provide a thorough understanding of the present invention. One skilled in the art will appreciate the ability to use alternative configurations and process details to the disclosed specifics without departing from the scope of the present invention. In other instances, well known semiconductor processing equipment and methodology have not been described in detail in order to not unnecessarily obscure the present invention.  
     [0023] The present invention describes a novel method and apparatus for passivating and/or annealing films. According to the present invention highly reactive atomic species are used to nitridate, passivate, deposit and anneal films. The highly reactive atomic species are formed in a plasma created by exposing an anneal gas such as O 2  and N 2 O, and N 2  to microwaves. The plasma creates electrically neutral highly energized atoms from the molecular anneal gas. The plasma used to generate the active atomic species is created in a cavity or chamber which is separate (remote) from the chamber in which the substrate to be annealed or passivated is located. Because the atomic species are in a highly energized state when they enter the anneal chamber, they readily react with films and substrates, and so do not require high substrate temperatures to initiate reaction. Because the present invention utilizes remotely generated highly reactive atomic species low substrate temperatures, less than or equal to 400° C., can be used nitridating, passivating, depositing, and annealing films and substrate. The low temperature processes of the present invention can substantially reduce the thermal budget necessary to manufacturer integrated circuits. Additionally because the active atomic species are remotely generated, the substrate to be annealed or passivated is not exposed to the harmful plasma used for generating the active atomic species.  
     [0024] In one embodiment of the present invention remotely generated active atomic species are used to passivate a silicon substrate prior to the formation of a gate dielectric layer or are used to passivate a capacitor electrode prior to the formation of a capacitor dielectric layer thereon. It is to be appreciated that as gate and capacitor dielectric film thicknesses shrink, to enable the fabrication of high density integrated circuits, the atomic level interfaces between the substrate and dielectric are becoming increasingly more important for device reliability and performance. By passivating a substrate with remotely generated active atomic species one can improve the atomic level interfaces between the substrate and the dielectric film and thereby improve device reliability and performance.  
     [0025] In another embodiment of the present invention, remotely generated active atomic species are used to anneal an active dielectric film, such as a gate dielectric or a capacitor dielectric. According to this embodiment of the present invention a dielectric film is deposited over substrate. The dielectric film is then exposed to remotely generated active atomic species, such as reactive oxygen atoms or reactive nitrogen atoms. The highly energized atomic species readily react with the dielectric film to fill vacancies in the lattice which left unfilled can lead to high leakage currents and poor device performance. The remotely generated active atomic species can be used to anneal a wide range of dielectrics such as but not limited to silicon oxides, such as silicon dioxide and silicon oxynitride, transition-metal dielectrics such as tantalum pentaoxide (Ta 2 O 5 ), titanium oxide (TiO 2 ) and titanium doped tanatalum pentaoxide, as well as ferroelectric and piezoelectric dielectrics such as BST, and PZT. Additionally, active atomic species, such as reactive nitrogen atoms can be used to anneal dielectric barrier layers, such as silicon nitride, to improve their barrier qualities.  
     [0026] In an embodiment of the present invention the remotely generated active atomic species are provided into the deposition chamber while the dielectric film is being deposited. In this way the dielectric film is annealed as it is deposited thereby eliminating the need for a separate anneal step.  
     [0027] As such remotely generated active atomic species can be used in all phases of dielectric film formation including substrate passivation prior to dielectric layer deposition, annealing during dielectric deposition and annealing after dielectric deposition. In this way high quality, high performance capacitor and gate dielectrics as well as barrier layers can be fabricated.  
     [0028] In one specific embodiment of the present invention, remotely generated reactive oxygen atoms are used to anneal a transition-metal dielectric used as a capacitor dielectric in a dynamic random access memory (DRAM). In this embodiment of the present invention a transition-metal dielectric film is formed by chemical vapor deposition (CVD) over a bottom electrode of a DRAM cell. The transition-metal film is then annealed at a temperature less than 400° C. with reactive oxygen atoms formed in a chamber separate from the anneal chamber. The remotely generated reactive oxygen atoms readily react with the deposited transition-metal film and satisfy open sites in the film. Additionally, the reactive oxygen atoms remove carbon contaminates by chemically reacting with carbon and forming carbon dioxide (CO 2 ) vapor which is then exhausted from the chamber. By annealing the dielectric film with remotely generated reactive oxygen atoms, the leakage current of the film can be substantially reduced. A top capacitor electrode can then be formed on the high quality high dielectric constant film thereby improving the performance and reliability of the fabricated cell.  
     [0029] A method of forming and annealing a dielectric layer in accordance with the present invention will be described in reference to FIG. 1 and FIGS. 2 a - 2   e . FIG. 1 illustrates a flow chart which depictsasingle process which utilizes the different nitridation, passivation, deposition, and anneal processes of the present invention. FIGS. 2 a - 2   e  illustrate an embodiment of the present invention where the processes of the present invention are used to form a capacitor of a DRAM cell. It is to be appreciated that these specific details are only illustrative of an embodiment of the present invention and are not to be taken as limiting to the present invention. Additionally, it is to be appreciated that the nitridation, passivation, deposition and anneal processes of the present invention need not all be used in a single process and can be used independently or in different combination with one another to form a wide variety of different integrated circuits.  
     [0030] An example of an apparatus  300  which can be used to provide active atomics species for the anneal and/or passivation steps of the present invention is illustrated in FIGS. 3 a  and  3   b . An example of a commercially available apparatus which can be used to provide active atomic species is the Applied Materials Centura Advanced Strip Passivation Plus (ASP) chamber. Apparatus  300  includes a remote plasma generator  301  which generates and provides active atomic species to a process chamber  350  in which the substrate to be passivated or annealed is located. Remote plasma generator  301  includes a magnatron  302  which generates microwaves with a microwave source. Magnatron  302  can preferably generate up to 10,000 watts of 2.5 Ghz microwave energy. It is to be noted that the amount of power required is dependent (proportional) to the size of anneal chamber  350 . For an anneal chamber used to process 300 mm wafers, 10,000 watts of power should be sufficient. Although a microwave source is used to generate a plasma in apparatus  300 , other energy sources such as radio frequency (RF) may be used.  
     [0031] Magnatron  302  is coupled to an isolator and dummy load  304  which is provided for impedance matching. The dummy load absorbs the reflected power so no reflective power goes to the magnatron head. Isolator and dummy load  304  is coupled by a wave guide  306 , which transmits microwave energy to an autotuner  308 . Autotuner  308  consist of an impedance matching head and a separate detector module that uses three stepper motor driven impedance matching stubs to reduce the reflective power of the microwave energy directed to the power source. Autotuner  308  focuses the microwave energy into the center of a microwave applicator cavity (or chamber)  310  so that energy is absorbed by annealed gas fed into the applicator cavity  310 . Although an autotuner is preferred a manual tuner may be employed.  
     [0032] Applicator  310  uses microwave energy received from magnatron  302  to create a plasma from the anneal gas as it flows down through a quartz plasma tube located inside applicator  310 . A source  312 , such as a tank, of a anneal gas such as but not limited to O 2 ,N 2 O, and N 2  used for generating the active atomic species is coupled to microwave applicator  310 . Additionally, a source of an inert gas such as argon (Ar) or helium (He) can also be coupled to applicator  310 . A prefire mercury lamp can be used to radiate ultraviolet light into the plasma tube to partially ionize the process gases and thereby make it easier for the microwave energy to ignite the plasma.  
     [0033] The microwave energy from magnetron  302  converts the anneal gas into a plasma which consist of essentially three components; ionized or charged atoms (radicals), activated (reactive) atomic species, and nondissociated anneal gas. For example when O 2  is the anneal gas, microwave energy disassociates the O 2  gas into oxygen radicals, reactive oxygen atoms, and some anneal gas remains as O 2  molecules. When N 2  is the anneal gas, microwaves disassociate the N 2  gas into nitrogen radicals, reactive nitrogen atoms, and some anneal gas remains as N 2  molecules. Reactive atomic species such as reactive oxygen atoms or reactive nitrogen atoms are not charged or ionized but are highly energized atoms. Because the reactive atomic species are highly energized they are in a highly reactive state so they readily react with dielectric films to fill vacancies therein or to passivate films or substrates. Because the atomic species are highly energized when they enter anneal chamber  350 , high temperatures are not necessary in chamber  350  to activate the anneal gas.  
     [0034] Applicator  310  is bolted to the lid of chamber  350 . The concentrated plasma mixture flows downstream through conduit  314  to chamber  350 . As a plasma flows through the conduit  314  the ionized atoms become electrically neutral before reaching chamber  350  and become highly reactive atomic species. Thus, only electrically neutral, highly reactive atoms flow into chamber  350 . Although the process gas at this point is highly reactive, the mixture is no longer electrically damaging to the substrate or electrical devices such as transistors formed therein. Because the active atomic species are generated at location (chamber  310 ) which is separate or remote from the chamber  350  in which the substrate to be annealed is located, the active atomic species are said to be “remotely generated”.  
     [0035] Chamber of  350  of apparatus  300 , as shown in FIG. 3 b , includes a wafer support  352  for supporting a wafer or substrate  351  face up in chamber  350 . Wafer support  352  can include an aluminum chuck  354 . Chamber  350  includes a quartz window  356  through which infrared radiation from a plurality (14) of quartz tungsten halogen lamp  358  is transmitted. During processing, the lamps mounted directly below the process chamber radiantly heat the chuck which in turn heats the wafer by conduction. A closed loop temperature control system senses the temperature of the substrate or wafer using a thermocouple mounted in the chuck. The temperature control system regulates the temperature of the wafer by varying the intensity of lamps  358 . Although lamps are preferably used as the heat source for heating the wafer, other heat sources, such as resistive heaters, can be used. A vacuum source  360 , such as the pump, is coupled to an exhaust outlet  362  and controls the chamber pressure and removes gas by products. A shower head or gas distribution plate  364  is mounted directly above the wafer. Shower head  364  consist of three quartz plates having a plurality of holes formed therein to evenly distribute the active atomic species over the wafer as they flow through gas inlet  366 .  
     [0036] In one embodiment of the present invention, chamber  350  is also configured to receive deposition gases used to deposit a film by chemical vapor deposition (CVD). In this way, a dielectric film can be annealed in the same chamber as used to deposit the film, or the dielectric film can be annealed as it is deposited. Additionally, chamber  350  can be a thermal reactor such as the Applied Material&#39;s Poly Centura single wafer chemical vapor deposition reactor or the Applied Material&#39;s RTP Centura with the honeycomb source, each configured to receive active atomic species from remote plasma generator  301 . In one embodiment of the present invention apparatus  300  is part of a cluster tool which includes among other chambers, a chemical vapor deposition (CVD) chamber, a load lock, and a transfer chamber with a robot arm. Configuring the various chambers around a transfer chamber in the form of a cluster tool enables wafers or substrates to be transferred between the various chambers of the cluster tool without being exposed to an oxygen ambient.  
     [0037] The nitridation, passivation, deposition and anneal steps of the present invention occur on a substrate. For the purpose of the present invention a substrate is the material on which dielectric films are deposited and annealed in accordance with the present invention. The substrate can be a substrate used in the manufacturing of semiconductor products such as silicon substrates and gallium arsenide substrates and can be other substrates used for other purposes such as glass substrates used for the production of flat panel displays.  
     [0038] In one embodiment of the present invention, the substrate is a substrate used in the fabrication of a dynamic random access memory (DRAM) cells such as substrate  200  shown in FIG. 2 a . Substrate  200  includes well known silicon epitaxial substrate  201  having a doped region  202  and a patterned interlayer dielectric  204 . A bottom capacitor electrode  206  is formed in contact with the diffusion region  202  and over ILD  204 . Bottom capacitor electrode  206  can be formed by any well known technique such as by blanket depositing a polysilicon layer by chemical vapor deposition (CVD) utilizing a reactive gas comprising silane (SiH 4 ) and H 2  and then patterning the blanket deposited material into an electrode with well known photolithography and etching techniques. If bottom electrode  206  is a polysilicon electrode it will typically be doped to a density between 2-5×10 20  atoms/cm 3 . Bottom electrode  206  can also be other types of capacitor electrodes such as but not limited to hemispherical grained polysilicon (HSG) or “rough poly” electrodes and metal electrodes such as titanium nitride (TiN) and tugsten (W) electrodes. In still other cases, the monocyrstalline silicon substrate  201  can act as the bottom electrode.  
     [0039] The first step, in one embodiment of the present invention, as set forth in block  102  of flow chart  100 , is to nitridate substrate  200  to form a thin, between 10-25 Å, silicon nitride barrier layer  205  on bottom electrode  206  as shown in FIG. 2 a . Nitridating bottom electrode  206  is desirable when bottom electrode  206  is a silicon electrode. Silicon nitride film  205  forms an oxidation prevention barrier layer for bottom electrode  206 . In this way, oxygen can not penetrate grain boundaries of polysilicon electrode  206  and form oxides therein which can lead to a decrease in the effective dielectric constant of a capacitor dielectric and to an increase in electrode resistance. Additionally, in well known capacitor structures where the monocrystalline silicon substrate  201  acts as the bottom electrode, nitridating substrate  201  is desirable.  
     [0040] A thin silicon nitride layer can be formed by nitridating substrate  200  by exposing substrate  200  to remotely generated reactive nitrogen atoms in anneal chamber  350  while substrate  200  is heated to a temperature between 700-900° C. and chamber  350  maintain at a pressure between 0.5 torr-2 torr. Reactive nitrogen atoms can be formed by flowing between 0.5 to 2 SLM of N 2 or ammonia (NH 3 ) into cavity  310  and applying a power between 1400-5000watts to magnatron  302  to create plasma from the N 2  or NH 3  gas in cavity  310 . The nitradation process forms silicon nitride only on those locations where silicon is available to react with the reactive nitrogen atoms, such as polysilicon electrode  206  and not on those areas where no silicon is available for reaction such as ILD  206 . A suitable silicon nitride layer  205  can be formed by nitridating substrate  200  with remotely generated reactive nitrogen atoms for between 30-120 seconds. Alternatively, a thin silicon nitride layer  205  can be formed by other well known techniques such as by thermal nitridation in a LPCVD batch type furnace.  
     [0041] Next, as set forth in step  104  of flow chart  100 , in an embodiment of the present invention, substrate  200  is passivated with remotely generated reactive nitrogen atoms, as shown in FIG. 2 b , to cure defects in silicon nitride barrier layer  205 . Silicon nitride barrier layer  205  can be passivated by placing substrate  200  on chuck  354  in chamber  350  and heating substrate  200  to a temperature between 300-500 while an N 2  anneal gas is fed into cavity  310  at a rate of between 0.5-2 SLM and a power of between 1400-5000 watts is provided to magnatron  302 . Microwaves from magnatron  302  create a plasma in cavity  310  from the N 2  process gas. Highly reactive electrically neutral nitrogen atoms  207  then flow through conduit  314  into chamber  350  where they passivate  209  substrate  200 . Exposing substrate  200  to active nitrogen atoms  207  can be used to stuff the capacitor electrode  206  with nitrogen atoms and thereby prevent subsequent oxidation of the capacitor electrode. Silicon nitride layer  205  can be sufficiently passivated by exposing substrate  200  to remotely generated reactive nitrogen atoms for between 30-120 seconds. Alternatively, silicon nitride barrier layer  205  can be passivated by subsituting forming gas (3-10% H 2  and 97-90% N 2 ) for the N 2  anneal gas. The addition of hydrogen (H 2 ) helps to cure defects and to remove contaminates.  
     [0042] Next, as set forth in block  106 , a dielectric film is formed over substrate  200 . In one embodiment of the present invention a high dielectric constant dielectric film  208  is blanket deposited over ILD  204  and bottom electrode  206  of substrate  200  as shown in FIG. 2 c . In an embodiment of the present invention the dielectric film is a transition metal dielectric film such as, but not limited to, tantalum pentaoxide (Ta 2 O 5 ) and titanium oxide (TiO 2 ). In another embodiment dielectric layer  208  is a tantalum pentaoxide film doped with titanium. Additionally dielectric layer  208  can be a composite dielectric film comprising a stack of different dielectric films such as a Ta 2 O 5 /TiO 2 /Ta 2 O 5 stacked dielectric film. Additionally, dielectric layer  208  can be a piezoelectric dielectric such as Barium Strontium Titanate (BST) and Lead Zerconium Titanate (PZT) or a ferroelectric.  
     [0043] In other embodiments of the present invention dielectric layer  208  can be a silicon-oxide dielectric such as silicon dioxide and silicon oxynitride and composite dielectric stacks of silicon-oxide and silicon nitride film such as well known ONO and NO and nitrided oxides. The fabrication of such oxides are well known and can be used in the fabrication of gate dielectric layers and capacitor dielectrics. For example a low temperature silicon dioxide film can be formed by chemical vapor deposition utilizing a silicon source, such as TEOS, and an oxygen source, such as O 2 .  
     [0044] In order to form a dielectric layer  208  onto substrate  200 , the substrate can be placed into a thermal process chamber such as the chamber of an Applied Materials CVD single wafer reactor. Alternatively, substrate  201  can be placed or left in anneal chamber  350  configured to receive deposition gases. The substrate is then heated to a desired deposition temperature while the pressure within the chamber is pumped down (reduced) to a desired deposition pressure. Deposition gases are then fed into the chamber and a dielectric layer formed therefrom.  
     [0045] To blanket deposit a tantalum pentaoxide (Ta 2 O 5 ) dielectric film by thermal chemical vapor deposition a deposition gas mix comprising, a source of tantalum, such as but not limited to, TAETO [Ta (OC 2 H 5 ) 5 ] and TAT-DMAE [Ta (OC 2 H 5 ) 4  (OCHCH 2 N(CH 3 ) 2 ], and source of oxygen such as O 2  or N 2 O can be fed into a deposition chamber while the substrate is heated to a deposition temperature of between 300-500° C. and the chamber maintained at a deposition pressure of between 0.5-10 Torr. The flow of deposition gas over the heated substrate results in thermal decomposition of the metal organic Ta-containing precursor an subsequent deposition of a tantalum pentaoxide film. In one embodiment TAETO or TAT-DMAE is fed into the chamber at a rate of between 10-50 milligrams per minute while O 2  or N 2 O is fed into the chamber at a rate of 0.3-1.0 SLM. TAETO and TAT-DMAE can be provided by direct liquid injection or vaporized with a bubbler prior to entering the deposition chamber. A carrier gas, such as N 2 ,H 2  and He, at a rate of between 0.5-2.0 SLM can be used to transport the vaporized TAETO or TAT-DMAE liquid into the deposition chamber. Deposition is continued until a dielectric film  508  of a desired thickness is formed. A tantalum pentaoxide (Ta 2 O 5 ) dielectric film having a thickness between 50-200 Å provides a suitable capacitor dielectric.  
     [0046] It has been found that the use of nitrous oxide (N 2 O) as the oxidizer (source of oxygen), as opposed to oxygen gas O 2  improves the electrical properties of the deposited tantalum pentaoxide (Ta 2 O 5 ) dielectric film during deposition. The use of N 2 O, as opposed to O 2 ,has been found to reduce the leakage current and enhance the capacitance of fabricated capacitors. The inclusion of N 2 O as an oxidizer aids in the removal of carbon from the film during growth which helps to improve the quality of the film.  
     [0047] In an embodiment of the present invention dielectric layer  208  is a tantalum pentaoxide (Ta 2 O 5 ) film doped with titanium (Ti). A tantalum pentaoxide film doped with titanium can be formed by thermal chemical vapor deposition by providing a source of titanium, such as but not limited to TIPT (C 12 H 26 O 4 Ti), into the process chamber while forming a tantalum pentaoxide film as described above. TIPT diluted by approximately 50% with a suitable solvent such as isopropyl alcohol (IPA) can be fed into the process chamber by direct liquid injection or through the use of a bubbler and carrier gas such as N 2 . A TIPT diluted flow rate of between 5-20 mg/minute can be used to produce a tantalum pentaoxide film having a titanium doping density of between 5-20 atomic percent and a dielectric constant between 20-40. The precise Ti doping density can be controlled by varying the tantalum source flow rate relative to the titanium source flow rate. It is to be appreciated that a tantalum pentaoxide film doped with titanium atoms exhibits a higher dielectric constant than an undoped tantalum pentaoxide film.  
     [0048] In another embodiment of the present invention dielectric layer  208  is a composite dielectric layer comprising a stack of different dielectric materials such as a Ta 2 O 5 /TiO 2 /Ta 2 O 5  stack. A Ta 2 O 5 /TiO 2 /Ta 2 O 5 composite film can be formed by first depositing a tantalum pentaoxide film as described above. After depositing a tantalum pentaoxide film having a thickness between 20-50 Å the flow of the tantalum source is stopped and replaced with a flow of a source of titanium, such as TIPT, at a diluted flow rate of between 5-20 mg/min. After depositing a titanium oxide film having a thickness of between 20-50 Å, the titanium source is replaced with the tantalum source and the deposition continued to form a second tantalum pentaoxide film having a thickness of between 20-50 Å. By sandwiching a higher dielectric constant titanium oxide (TiO 2 ) film between two tantalum pentaoxide (Ta 2 O 5 ) films, the dielectric constant of a composite stack is increased over that of a homogeneous layer of tantalum pentaoxide (Ta 2 O 5 ).  
     [0049] Next, as set forth in block  108  of flow chart  100 , dielectric film  208  is annealed with remotely generated active atomic species  211  as shown in FIG. 2 d , to form an annealed dielectric layer  210 . Dielectric film  208  can be annealed by placing substrate  200  into anneal chamber  350  coupled to remote plasma generator  301 . Substrate  200  is then heated to an anneal temperature and exposed to active atomic species  211  generated by disassociating an anneal gas in applicator chamber  310 . By generating the active atomic species in a chamber remote from the anneal chamber (the chamber in which the substrate is situated) a low temperature anneal can be accomplished without exposing the substrate to the harmful plasma used to form the active atomic species. With the process and apparatus of the present invention anneal temperatures of less than 400° C. can be used. The use of remotely generated active atomic species to anneal dielectric film  208  enables anneal temperatures of less than or equal to the deposition temperature of the dielectric film to be used.  
     [0050] In one embodiment of the present invention dielectric film  208  is a transition metal dielectric and is annealed with reactive oxygen atoms formed by remotely disassociating O 2  gas. Dielectric layer  208  can be annealed in chamber  350  with a reactive oxygen atoms created by providing an anneal gas comprising two SLM of O 2  and one SLM of N2 into chamber  310 , and applying a power between 500-1500 watts to magnatron  302  to generate microwaves which causes a plasma to ignite from the anneal gas. Alternatively, reactive oxygen atoms can be formed by flowing an anneal gas comprising two SLM of O 2  and three SLM of argon (Ar) into cavity  310 . While reactive oxygen atoms are fed into anneal chamber  350 , substrate  200  is heated to a temperature of approximately 300° C. and chamber  350  maintained at an anneal pressure of approximately 2 Torr. Dielectric layer  208  can be sufficiently annealed by exposing substrate  200  to reactive oxygen atoms for between 30-120 seconds.  
     [0051] An inert gas, such as N 2  or argon (Ar), is preferably included in the anneal gas stream in order to help prevent recombination of the active atomic species. It is to be noted that as the active atomic species (e.g. reactive oxygen atoms) travel from the applicator cavity  310  to the anneal chamber  350 , they collide with one another and recombine to form O 2  molecules. By including an inert gas, in the anneal gas mix, the inert gas does not disassociate and so provides atoms which the active atomic species can collide into without recombining. Additionally, in order to help prevent recombination of the active atomic species, it is advisable to keep the distance between cavity  310  and anneal chamber  350  as short as possible.  
     [0052] Annealing a transition-metal dielectric film  208  with reactive atoms oxygen fills oxygen vacancies (satisfies sites) in the dielectric film  208  which greatly reduces the leakage of the film. Additionally, annealing transition metal dielectric  208  helps to remove carbon (C) in the film which can contribute to leakage. Carbon can be incorporated into transition metal dielectrics because the tantalum and titanium sources, TAT-DMAE, TAETO, and TIPT are carbon containing compounds. The reactive oxygen atoms remove carbon from the film by reacting with carbon and forming carbon dioxide (CO 2 ) vapor which can then be exhausted out from the chamber.  
     [0053]FIG. 4 illustrates how exposing a tantalum pentaoxide dielectric film to remotely generated reactive oxygen atoms improves the quality and electrical performance of the as deposited film. Graph  402  shows how the leakage current of a capacitor having a 100 Å unannealed tantalum pentaoxide dielectric film varies for different top electrode voltages. Graph  404  shows how the leakage current of a capacitor having a 100 Å tantalum pentaoxide dielectric film annealed with remotely generated reactive oxygen atoms varies for different top electrode voltages. As can be seen from graph  402 , a capacitor utilizing an unannealed tantalum pentaoxide dielectric experiences high leakage current of about 1×10 −1  (amps/cm 2 ) when ±1.5 volts is applied to the top electrode and a high leakage current of 1×10 −6  (amps/cm 2 ) when zero volts is applied to the top electrode. In comparison, when the tantalum pentaoxide dielectric is exposed to remotely generated reactive oxygen atoms, the leakage current has a relatively low leakage current of 1×10 −5  (amps/cm 2 ) when ±1.5 volts is applied to the top electrode and a leakage current of less than 1×10 −9  (amps/cm 2 ) when zero volts is applied to the top electrode. As is readily apparent from FIG. 4, exposing the tantalum pentaoxide dielectric film to remotely generated active oxygen atoms dramatically improves (reduces) the leakage current of the film.  
     [0054] In an embodiment of the present invention, as set forth in block  107  of flow chart  100  the deposition step  106  and the anneal step  108  occur simultaneously so that the dielectric film is annealed as it is deposited. A dielectric film can be deposited and annealed simultaneously using a single deposition/anneal chamber coupled to receive a remote plasma from a remote plasma generator source and coupled to receive a deposition gas mix. For example in one embodiment of the present invention a deposition gas mix comprising a metal source such as a TAT-DMAE or TIPT, or a silicon source, such as TEOS, and a source of oxygen such as O 2  or N 2 O can be fed into a common anneal/deposition chamber while the substrate is heated to a desired deposition temperature and the chamber maintained at a desired deposition pressure. Simultaneously, an anneal gas, such as O 2 , can be supplied into applicator cavity chamber  310  of the remote plasma generator  300  at a rate of between 0.5-2 SLM. Reactive oxygen atoms can then flow from chamber  310  into the anneal/deposition chamber. The reactive oxygen atoms then react with the metal or silicon provided from the deposition gas mix to form a metal-oxide or silicon-oxide compound respectively. In one embodiment of the present invention the only source of oxygen atoms into the deposition/anneal chamber is reactive oxygen atoms from applicator  310 .  
     [0055] The next step of the present invention, as set forth in block  110  of flow chart  100  is to complete the processing of the device. For example, as shown in FIG. 2 e , a top capacitor electrode  212  can be formed over annealed dielectric layer  210 . Any well known technology can be used to form top electrode  212  including blanket depositing a polysilicon film or metal film, such as TiN, over annealed dielectric film  210  and then using well known photolithography and etching techniques to pattern the electrode film and dielectric layer.  
     [0056] In another embodiment of the present invention, remotely generated active atomic species can be used to fabricate a metal oxide semiconductor (MOS) transistor. The first step, as shown in FIG. 5 a , which is optional, is to nitridate a monocrystalline silicon substrate  502  with remotely generated reactive nitrogen atoms  503  as describe above. Nitridating substrate  502  with remotely generated reactive nitrogen atom forms a thin silicon nitride film  501  on substrate  502  which improves the interface between the silicon substrate  502  and the subsequently deposited gate dielectric layer. Next, as shown in FIG. 5 b  a gate dielectric layer  504  is formed over nitridated substrate  502 . Gate dielectric layer  504  can be a thermally grown silicon dioxide film, a CVD deposited silicon dioxide film, or a transition metal film such as tantalum pentaoxide or titanium oxide or combinations thereof. Gate dielectric  504  will typically have a thickness between 20 to 100 Å. Next, as shown in FIG. 5 c , the dielectric film  504  is annealed with remotely generated active atomic species  505 , such as reactive oxygen atoms, to form an annealed dielectric film  506  as described above. Annealing of the gate dielectric film fills vacancies in the lattice and generally improves the quality of the film. The annealing step can occur as a separate step after the deposition of the gate dielectric or can occur simultaneous with the deposition of the gate dielectric. After forming annealed gate dielectric  506 , a gate electrode material, such as polysilicon or a metal or a combination thereof, can be blanket deposited over annealed gate dielectric  506  and then patterned into a gate electrode  508 , as shown in FIG. 5 d , with well known photolithography and etching techniques. A pair of source/drain regions  510  can then be formed on opposite sides of the gate electrode  508  with well known ion implantation or solid source diffusion techniques, in order to complete fabrication of the MOS device.  
     [0057] A novel method and apparatus for forming and/or annealing a dielectric film with a remotely generated active atomic species has been described. Utilizing a, remotely generated active atomic species to anneal and/or deposit a film enables a high quality, high dielectric constant film to be formed at low temperatures. Although the present invention has been described with respect to specific equipment, and with respect to a specific processes it is to be appreciated that the described details are to be taken as illustrative rather than limiting, wherein the scope of the present invention is to be measured by the appended claims which follow.  
     [0058] Thus, a method and apparatus for annealing a dielectric film at low temperatures has been described.