Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
  • H10P14/63—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the formation processes
  • H10P14/6326—Deposition processes
  • H10P14/6328—Deposition from the gas or vapour phase
  • H10P14/6334—Deposition from the gas or vapour phase using decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition
  • H10P14/6336—Deposition from the gas or vapour phase using decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition in the presence of a plasma [PECVD]
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/4401—Means for minimising impurities, e.g. dust, moisture or residual gas, in the reaction chamber
  • C23C16/4402—Reduction of impurities in the source gas
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/448—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for generating reactive gas streams, e.g. by evaporation or sublimation of precursor materials
  • C23C16/452—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for generating reactive gas streams, e.g. by evaporation or sublimation of precursor materials by activating reactive gas streams before their introduction into the reaction chamber, e.g. by ionisation or addition of reactive species
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/34—Deposited materials, e.g. layers
  • H10P14/3402—Deposited materials, e.g. layers characterised by the chemical composition
  • H10P14/3424—Deposited materials, e.g. layers characterised by the chemical composition being Group IIB-VIA materials
  • H10P14/3426—Oxides
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
  • H10P14/42—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials using a gas or vapour
  • H10P14/43—Chemical deposition, e.g. chemical vapour deposition [CVD]
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
  • H10P14/69—Inorganic materials
  • H10P14/692—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses
  • H10P14/6921—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses containing silicon
  • H10P14/69215—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses containing silicon the material being a silicon oxide, e.g. SiO2

Definitions

• This invention relates generally to the formation of films on semiconductor and integrated circuit substrates, and more particularly to a method of forming dielectric layers having reduced metal contamination by chemical vapor deposition (CVD)
• Dielectric lavers are generally used to electrically isolate conductive layers and enable useful interconnects between such layers
• Dielectric layers are often formed by chemical vapor deposition (CVD)
• CVD chemical vapor deposition
• the CVD process deposits a mate ⁇ al on a surface bv transport and reaction of certain gaseous precursors on the surface CVD reactors come in many forms Low pressure
• LPCVD low pressure CVD systems
• APCVD atmospheric pressure CVD systems
• PECVD plasma enhanced CVD systems
• CVD deposits the components of the precursor chemicals, it is important for the precursors to be of high purity and substantially free of contaminants because such contaminants may react and become deposited in the resultant film Contaminants in the film damage the function of the devices on the wafer and reduce the device yields
• TEOS TEOS
• ozone oxygen and small amounts of nitrogen (typically l %-5% by weight)
• the plasma accelerates the reaction with the oxygen and nitrogen to form ozone (O,), generally in a mixture of up to 5 5 weight % 0 3 in oxygen (0 : )
• the nitrogen acts as a catalyst to the reaction, aiding in the generation of ozone at high concentrations with a concentration stability in the range of approximately +/- ] 4%
• nitric acid Nitrogen and moisture in the ozone system generate nitric acid when sub
• the nitric acid affects the CVD svstem in a va ⁇ etv of ways
• One occurrence is that nitric acid collects in small orifices with low flow rates, such as mass flow controller (MFC) sensor tubes used in the CVD svstem, This causes clogging of the MFC sensor tubes, and ultimately leads to failure of gas flow control
• MFC mass flow controller
• nitric acid has been found to attack the metal conduits and components of the CVD svstem
• nitric acid attacks surface hydroxide layers of the stainless steel conduits which causes the release of metal contaminants such as volatile chromium oxides into the gas stream
• the contaminant is delivered, along with the ozone, to the semiconductor substrate where it deposits as a contaminant in the film
• a further object of this mvention is to provide a method of delivering ozone from an ozonator through a system containing metal conduits wherein the ozone is substantially free of corrosive contaminants
• An alternative embodiment of the invention provides for a method of depositing oxide layers having reduced metal atom concentration on the surface of a substrate in a chemical vapor deposition (CVD) system
• the CVD svstem includes an ozone svstem and a CVD reactor Oxygen gas and a dilution gas, excluding nitrogen.
• gas stream including ozone is produced
• the gas stream is delivered through metal conduits to the CVD reactor
• the gas stream is substantially free from corrosive elements and as the gas stream flows throughout the system the gas does not substantially react with the metal conduits, thereby generally eliminating metal atom contamination in the gas stream
• the gas stream and a reactive gas are separately conveyed through an iniector whereby they exit the injector and enter the CVD reactor, wherein said gases interact and deposit a layer of material substantially free of metal contamination on the surface of a wafer positioned proximate to said injector
• FIG 1 is a schematic view, partially in cross-section, of a chemical vapor deposition (CVD) system apparatus which may be employed to practice the method of the invention
• FIG 2 is a schematic of an ozonator apparatus suitable for delivering a gas stream in accordance with one embodiment of the invention
• FIG 3 is a table illustrating metal contamination levels achieved according to one embodiment ofthe method of the invention set forth in Example 1
• FIG 4 is a table showing resultant metal contamination levels according to an alternative embodiment of the invention set forth in Example 3
• FIGs 5A and 5B are a photographs made by Scanning Electron Microscope (SEM) of a cross-section of dielectric layer showing the gap fill and step coverage achieved according to the method of the invention
• FIG 6 is a graph showing a SIMS plot of Cr content in a film deposited in accordance with the invention
• FIGs 1 and 2 are schematical representations of apparatus that can be employed to deiiver a gas stream containing low metal contamination according to the method of the present invention
• FIG 1 depicts a chemical vapor deposition (CVD) svstem 10 which can be used with the invenm e method
• the system 10 generally includes an ozone generator 1 5 which generates a gas stream containing ozone and other gaseous chemicals
• the gas stream is delivered via metal conduits 16 and mass flow controller 17 to a CVD reactor 20
• CVD reactor 20 is shown as a conveyorized atmospheric pressure CVD (APCVD) type reactor, which is more fully described in U S Patent No 4,834,020, and which is incorporated by reference herein
• APCVD conveyorized atmospheric pressure CVD
• LPCVD reactor 20 shown in FIG 1 typically includes a muffle 3 1 , a plurality of miectors 30 defining multiple stages (for simplicity only one iniector 30, and thus one stage is shown) and a convevor belt 34 Typically the reactor 20 comprises four stages, each of which are substantially identical
• a plurality of curtains 32 are placed around both sides of the injector 30 to isolate an area, and therebetween forming a deposition chamber area 33
• the curtains 32 include a plurality of inert gas plenums 36 which causes inert gases to flow downwardly and along the belt 34, thereby aiding to isolate the deposition chamber area 33
• a substrate 35 is placed on the conveyor belt 34 and is delivered into the muffle 3 1 and through the deposition chamber area 33
• gaseous chemicals are conveyed by the injector 30 to the area proximate the surface o the
• the gaseous chemicals are delivered to the reactor 20 via gas delivery system 39, wherein said gaseous chemicals are individually conveyed to the injector 30 through gas delivery lines 16, 26 and 27
• the gases conveyed though gas delivery lines 1 6, 26 and 27 are ozone/oxygen mixture, TEOS, and a nitrogen/ oxygen mixture (separator N-,), respectively
• the TEOS and ozone gases react to form a layer of silicon dioxide (S ⁇ 0 2 ) on the surface of the substrate 35
• S ⁇ 0 2 silicon dioxide
• byproducts and unreacted chemicals are generally removed through exhaust lines 37 as shown by the general direction of the arrows
• the present invention promotes the deposition of such desired films by the method of delivering an ozone gas stream substantially free of metal contamination
• the method is described in detail with reference to the ozone system depicted therein
• the inventor discovered that a significant source of metal contamination in the deposited film is due to corrosive contaminant vapors present in the ozone gas stream produced by the ozone generator
• These corrosive contaminant vapors attack metal conduits in the svstem causing the release of metal atoms, most notablv Cr atoms
• the Cr atoms pass through the svstem along with the ozone gas stream, and are delivered into the CVD system whereby the Cr ends up as a metal contaminant in the deposited film
• the method ofthe present invention provides for the use of different dilution gases to produce an ozone gas stream which is characterized in that the ozone gas stream is substantially free of corrosive contaminant vapors that attack metal, while maintaining acceptable ozone concentration and stability
• the present invention provides for the use of helium, argon or carbon dioxide as the dilution gas which is introduced through gas line 14
• Oxygen is introduced through gas line 12
• the gases are mixed and introduced into ozonator 40 via line 1 8 Power is applied to discharge plate 41 which creates a plasma discharge within discharge area 47
• the plasma in association with the dilution gas aids the reaction of the oxygen into ozone
• the ozone gas stream exits the ozonator 40 through gas line 46, and generally comprises a mixture in the range of substantially 2 to 5 5 wt % O, in O Referring now to FIG 1 , the ozone gas stream is conveyed throughout the gas delivery system
• the ozone gas stream interacts with reactive gases also exiting the injector 30 and forms a iayer of material on the surface of the substrate 35
• the ozone gas stream does not substantially react with the metal conduits and components, thereby enabling the delivery of an ozone gas stream substantially free of metal contamination
• the ozone gas stream is substantially free of nitrates which are found to clog MFC sensor tubes and ultimately lead to failure of the MFC in prior art systems
• the ozone gas stream will contain a metal atom contamination level of equal to or less 0 07 ng metal atoms per gas-liter, and preferably less than or equal to 0 02 ng metal atoms per gas-liter after the ozone gas stream has
• the inventive method may be practiced with other types of ozone generators Moreover, the method of the present invention may be employed using any one of the recited dilution gases, i.e. Ar , He or CO : , with various types of ozone generators.
• dilution gases i.e. Ar , He or CO :
• CO is employed as the dilution gas with an ASTeX type ozonator known in the art
• the ASTeX ozonator is of the all-metal, sealed-cell plasma discharge type with water cooling
• Example 1 In this example, an oil-cooled discharge ozone generator was used Two separate tests were conducted, each test using a different gas (Ar and He) as the dilution gas. Typical test process conditions are set forth in Table 1 .
• ozone To produce ozone, power is applied to plate 41 via power source 48, thereby creating a plasma discharge in discharge area 47 In the discharge area 47, oxygen reacts to form ozone, and a gas stream of approximately 2 to 5 5 , wt % in , is produced and delivered through gas outlet line 46
• the concentration of ozone in the gas stream is shown in Table 1 for each test, and is within desired specifications
• the ratio of dilution gas to oxygen introduced in the ozone generator was found to affect the concentration and stability ofthe ozone produced in the ozone gas stream
• Experiments were conducted to determine the most desirable ratio, and preferably the volume % ratio of Ar ranges substantially from 3 5% to 9 4%, when Ar is used as the dilution gas, and the preferred volume % ratio of He is substantially from 8 8% to 1 8% when He is used as the dilution gas
• a single wafer sampling device 38 was installed in the ozone gas line 16 between the MFC 21 and the injector 30 as shown in FIG 1
• the device 38 serves to test contaminant levels in the ozone gas stream by exposing a wafer to the ozone gas stream for a specified amount of time, at a particular flow rate and ozone concentration Typical test conditions are an ozone gas stream flow rate of 6 slm for 1 5 minutes at 4 0 - 4 5 wt% O, in 0 ;
• To perform the test a wafer is placed in the device 38, and the ozone gas stream is generated in ozonator 40 and is conveyed through lines 16 and then sprayed into the top of the device 38 and onto the topside of the wafer surface The effluent is directed out of the bottom of the device 38 and into the injector 30, where the gases were exhausted
• An ozone gas stream was produced as generally described in Example 1
• dielectric layers were deposited on substrates using the ozone gas stream as a precursor
• the substrates were placed in the deposition chamber area 33, under the injector 30 in the CVD reactor 20 as shown in FIG 1
• the dielectric lavers were deposited utilizing the ozone gas stream generated with Ar as the dilution gas pursuant to the operating conditions associated with the Ar test in Table 2A CVD deposition was achieved according to the parameters set forth below in Table 2B
• the ozone gas stream is conveyed through each of the four injectors at the gas flow rates depicted in Table 2 Dilution N ; is provided to each injector, and is tied into the ozone gas stream line generally at point A on FIG 1 Since nitrogen is introduced down stream from the plasma discharge ozonator, none of the aforementioned prior art problems of formation of nitric acid and associated metal contamination occur
• the Separator N is conveyed into one port of each of the four injector stages as shown by reference 27 in FIG 1
• the Liquid Source Dilution N flow rate represents the introduction of dopants to the chamber, such as boron or phosphorous, using nitrogen as the carrier gas Such dopants may be used to deposit a boro-phospho-silicate glass (BPSG) oxide film TEOS is introduced via delivery line 24 with nitrogen as the carrier gas, as shown in
• an ASTeX ozone generator known in the art was used to generate the ozone gas stream in accordance with a third embodiment of the present invention
• Three dilution gases, Ar. He and CO, were tested independently in three experiments pursuant to the exemplary ozone generating process conditions set forth in Table 3 A
• an ozone gas stream is produced as described above
• the preferred method of practicing the invention utilizes the ASTeX generation with CO as the dilution gas and preferably the weight % ratio of CO ranges substantially from 2% to 3 6%
• the concentration level of contaminants present in the various ozone gas streams was tested by a number of means
• a bench test was conducted on the ozone gas stream produced using C02 as the dilution gas The bench test was similar to that performed in Example 1 above, whereby the single wafer sampling device 38 was installed in the ozone gas line 16 between the MFC 21 and the injector 30 as shown in FIG 1 Generally, wafers placed in device 38 were sprayed with the o
• dielectric layers were deposited on substrates according to the method of he present invention Such layers were formed with the desirable result of low metal contamination in the film
• dielectnc lavers were deposited using an APCVD reactor generally as depicted in FIG 1 , and pursuant to the process conditions set forth in Table 3B below
• Dielectric films of 4800 angstroms to 7000 angstroms thickness were deposited on 6" silicon substrates by placing the silicon substrates 35 on the convevor belt 34 and passing the substrate through each of four stages Within each stage, the substrate 35 passes under the injector 30 in deposition area 33 Reactive gases O, and TEOS, among other gases, exit injector 30 and interact proximate the surface of the substrate 35 whereby the gases form a layer of material on said surface
• SIMS Secondary Ion Mass Spectrometry
• each deposition chamber area 33 stage is represented by a letter A through H
• Letters A-D represent the first pass with four deposition chamber area 33 stages
• Letters E-H represent the second pass with four deposition chamber area 33 stages
• the film was deposited using He as the dilution gas to generate the ozone gas stream 16 from the ozone generator 15, and the CVD apparatus 20 was operated generally according to the process conditions set forth in Table 3B
• the graph shows the Cr abundance (Cr atoms/cm J ) as a function ofthe film thickness (microns) deposited on the silicon wafer Chromium is deposited onto the wafer in varying amounts depending on the location of the wafer as it travels through the apparatus 20
• the dielectric film exhibits a Cr content of less than I x l O 14 metal atoms/cm 1 deposited in the film placed under each of the injectors 30 in each deposition chamber area 33
• the chromium values greater than 10' are in the areas outside of the deposition chamber areas 33, in the so called inter-injector zones, where vapor phase Cr accumulation occurs
• the Cr content in this area is within a standard deviation value of I O 1 "1 which meets desired target content levels sought by the semiconductor industry
• FIGs 5a and 5b show SEM photographs of a portion of the cross-section of wafers with a dielectric layer formed according to two embodiments of the present invention
• the wafer contains aluminum lines 51 and 52 formed on the surface of substrate 35
• the nes 51 and 52 were spaced apart at one micron
• the aspect ratio of the gap between lines 51 and 52 was 0 4 microns high to 1 0 microns wide
• a silicon oxide dielectric layer 53 was deposited atop the lines 5 1 and 52 and the substrate 35 using ozone and TEOS as precursor gases
• the ozone gas stream was produced by the water cooled 4-stack ozone generator using Ar as the dilution gas pursuant to the operating conditions shown in Table 2A CVD deposition was performed pursuant to the operating parameters in Table 2B
• the dielectric layer has uniformly filled the one micron gap without any voids, hillocks or other defects
• FIG 5b is a SEM photograph ofa cross-section portion of a wafer and a dielectric layer deposited according to the preferred embodiment of the invention
• the wafer contains aluminum lines 55 and 56 formed on the surface of substrate 35 and spaced apart at 1 5 microns
• the aspect ratio of the gap between lines 55 and 56 was 0 4 micron high to 1 0 microns wide Silicon oxide dielectric layer 57 was deposited using ozone and TEOS as precursor gases
• the ozone gas stream was produced by using CO : as the dilution gas pursuant to the operating conditions shown in Table A CVD deposition was performed pursuant to the operating parameters in Table 3B
• the dielectric layer has uniformly filled the one micron gap without voids, hillocks and other defects

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Vapour Deposition (AREA)
• Formation Of Insulating Films (AREA)

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• 1996
  • 1996-12-11 AU AU12881/97A patent/AU1288197A/en not_active Abandoned
  • 1996-12-11 CN CN96198872A patent/CN1114937C/zh not_active Expired - Fee Related
  • 1996-12-11 EP EP96943723A patent/EP0867037A1/de not_active Withdrawn
  • 1996-12-11 JP JP09522910A patent/JP2000502212A/ja not_active Ceased
  • 1996-12-11 WO PCT/US1996/019819 patent/WO1997022992A1/en not_active Ceased
  • 1996-12-11 KR KR10-1998-0704363A patent/KR100373434B1/ko not_active Expired - Fee Related

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