Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0205—Investigating particle size or size distribution by optical means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/06—Investigating concentration of particle suspensions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
  • H01L21/67005—Apparatus not specifically provided for elsewhere
  • H01L21/67011—Apparatus for manufacture or treatment
  • H01L21/67017—Apparatus for fluid treatment
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
  • H01L21/67005—Apparatus not specifically provided for elsewhere
  • H01L21/67242—Apparatus for monitoring, sorting or marking
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
  • H01L21/67005—Apparatus not specifically provided for elsewhere
  • H01L21/67242—Apparatus for monitoring, sorting or marking
  • H01L21/67253—Process monitoring, e.g. flow or thickness monitoring
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
  • H01L22/10—Measuring as part of the manufacturing process
  • H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
  • H01L22/20—Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
  • H01L22/24—Optical enhancement of defects or not directly visible states, e.g. selective electrolytic deposition, bubbles in liquids, light emission, colour change
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
  • H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements

Definitions

• Embodiments of the present disclosure generally relate to the field of electronic device manufacturing, and more particularly, to systems and methods used to deliver a processing gas having a desired diborane concentration therein to a processing volume of a processing chamber.
• Boron containing (boron doped) material layers such as boron doped silicon or germanium semiconductor layers, boron doped dielectric layers, boron doped silicon hardmask layers, or boron doped tungsten nucleation layers, are widely used in the field of electronic device manufacturing. Often, boron doped material layers are formed using a chemical vapor deposition (CVD) process where a boron containing gas is reacted with, or dissociated in the presence of, one or more material precursor gases to deposit a boron doped material layer on a surface of a substrate.
• CVD chemical vapor deposition
• Diborane (B2H6) is commonly chosen as a boron precursor for doping because diborane is relatively easy to store and transport and desirably dissociates at relatively lower temperatures when compared to other boron dopant source gases.
• Diborane is typically stored in a pressurized gas cylinder with a diluent gas such as one, or a combination, of hydrogen (H2), Argon (Ar), nitrogen (N2), or helium (He) to form a doping gas mixture, i.e. , the boron doping gas.
• the boron doping gas is typically delivered from the pressurized gas cylinder to a processing volume of a CVD processing chamber using a gas delivery conduit fluidly coupled therebetween.
• the diborane in the pressurized gas cylinder will undesirably decompose to yield free hydrogen and higher order boranes, thereby resulting in a reduced concentration of diborane therein.
• This undesirable change in diborane concentration will, over time, cause undesirable substrate to substrate variation of boron concentration in the CVD deposited material layers formed thereon.
• Embodiments of the present disclosure generally relate to the field of electronic device manufacturing, and more particularly, to processing systems, diborane sensors, and methods used to deliver a doping gas mixture, having a desired diborane concentration, to a processing volume of a processing chamber.
• a borane concentration sensor includes a body and a plurality of windows.
• individual ones of the plurality of windows are disposed at opposite ends of the body and the body and the plurality of windows collectively define a cell volume.
• the borane concentration sensor further includes a radiation source disposed outside of the cell volume proximate to a first window of the plurality of windows, and a first radiation detector disposed outside the cell volume proximate to a second window of the plurality of windows.
• a method of processing a substrate includes determining a diborane concentration in a gas sample taken from a gas conduit fluidly coupling a first gas source and a processing chamber.
• determining the diborane concentration comprises using an optical sensor.
• the method further includes mixing a boron doping gas, having a desired diborane concentration, by changing a flowrate of a first gas from the first gas source, a second gas from a second gas source, or both and delivering the boron doping gas to a processing volume of the processing chamber.
• a processing system featuring a computer readable medium having instructions stored thereon for a method of processing a substrate.
• the method includes determining a diborane concentration in a gas sample taken from a gas conduit fluidly coupling a first gas source and a processing chamber.
• determining the diborane concentration comprises using an optical sensor.
• the method further includes mixing a boron doping gas, having a desired diborane concentration, by changing a flowrate of a first gas from the first gas source, a second gas from a second gas source, or both and delivering the boron doping gas to a processing volume of the processing chamber.
• Figure 1 is a schematic cross-sectional view of a substrate processing system configured to practice the methods set forth herein, according to one embodiment.
• Figure 2A is a schematic cross-sectional view of an optical sensor, according to one embodiment, which may be used with the substrate processing system described in Figure 1.
• Figure 2B is a schematic cross-sectional view of an optical sensor, according to another embodiment, which may be used with the substrate processing system described in Figure 1.
• Figure 3 is a graph illustrating the UV absorption spectrum of diborane.
• Figure 4A is a graph illustrating the IR absorption spectrum of diborane.
• Figure 4B is a graph illustrating the IR absorption spectrum of tetraborane.
• Figure 5 is a graph schematically illustrating the attenuation of radiation passing through gas samples having various concentrations of diborane and tetraborane, according to one embodiment.
• Figure 6A is a schematic cross-sectional view of an optical sensor, according to another embodiment, which may be used with the substrate processing system described in Figure 1.
• Figure 6B is a schematic cross-sectional view of an optical sensor, according to another embodiment, which may be used with the substrate processing system described in Figure 1.
• Figure 7 is a graph schematically illustrating the attenuation of radiation passing through gas samples having various concentrations of diborane and tetraborane, according to another embodiment.
• Figure 8 is a flow diagram setting forth a method of processing a substrate, according to one embodiment.
• Embodiments of the present disclosure generally relate to the field of electronic device manufacturing.
• embodiments herein relate to processing systems, borane concentration sensors, and methods used to deliver a boron doping gas, having a desired diborane concentration, to a processing volume of a processing chamber.
• diborane is delivered to a processing volume of a processing chamber from a diborane gas source.
• the diborane gas source is often a pressurized cylinder comprising diborane and a diluent gas such as hydrogen (H2), Argon (Ar), nitrogen (N2), or helium (He).
• H2 hydrogen
• Ar Argon
• N2 nitrogen
• He helium
• embodiments herein compensate for variations in diborane concentration from the diborane gas source by further mixing the gas provided by the pressurized cylinder with an additional diluent gas to provide a boron doping gas having a desired, and known, diborane concentration.
• the concentration of diborane in the boron doping gas is desirably controlled using in-situ measurements taken by one or more of the borane concentration sensors provided herein.
• the one or more borane concentration sensors are light-absorption based sensors, i.e. , optical spectrometers.
• the light- absorption based sensors are configured to selectively measure the absorption of UV or IR radiation (emitted by a radiation source of the sensor) by borane molecules, such as diborane, tetraborane, or both in a gas sample. The concentration of one or both of the diborane and tetraborane molecules is then determined from the measured absorption(s).
• FIG. 1 is a schematic cross-sectional view of a substrate processing system 100 configured to practice the methods set forth herein, according to one embodiment.
• the processing system 100 features a processing chamber 101 and a precursor delivery system 102.
• Other processing chambers which may be used in combination with the precursor delivery system 102 to practice the methods set forth herein include processing chambers in a Producer ® ETERNA CVD ® system, an Ultima HDP CVD ® system, or a Producer ® XP PrecisionTM CVD system, all available from Applied Materials, Inc., of Santa Clara, California as well as suitable processing chambers from other manufacturers.
• the processing chamber 101 includes a chamber lid assembly 103, one or more sidewalls 104, and a chamber base 105.
• the chamber lid assembly 103 includes a chamber lid 106, a showerhead 107 disposed in the chamber lid 106, and an electrically insulating ring 108, interposed between the chamber lid 106 and the one or more sidewalls 104.
• the showerhead 107, the one or more sidewalls 104, and the chamber base 105 collectively define a processing volume 109.
• a gas inlet 110 disposed through the chamber lid 106, is fluidly coupled to the precursor delivery system 102.
• the showerhead 107 having a plurality of openings 111 disposed therethrough, is used to uniformly distribute processing gases provided by the precursor delivery system 102 into the processing volume 109.
• the showerhead 107 is electrically coupled to a first power supply 112, such as an RF power supply, which supplies power to ignite and maintain a plasma 113 of the processing gas through capacitive coupling therewith.
• the processing chamber 101 comprises an inductive plasma generator and the plasma is formed through inductively coupling an RF power to the processing gas.
• the processing chamber is not a plasma processing chamber.
• the processing volume 109 is fluidly coupled to a vacuum source, such as to one or more dedicated vacuum pumps, through a vacuum outlet 114, which maintains the processing volume 109 at sub-atmospheric conditions and evacuates the processing gas and other gases therefrom.
• a substrate support 115 disposed in the processing volume 109, is disposed on a movable support shaft 116 sealingly extending through the chamber base 105, such as being surrounded by bellows (not shown) in the region below the chamber base 105.
• the processing chamber 101 is configured to facilitate transferring of a substrate 117 to and from the substrate support 115 through an opening 118 in one of the one or more sidewalls 104, which is sealed with a door or a valve (not shown) during substrate processing.
• a substrate 117, disposed on the substrate support 115 is maintained at a desired processing temperature using one or both of a heater, such as a resistive heating element 119, and one or more cooling channels 120 disposed in the substrate support 115.
• a heater such as a resistive heating element 119
• the one or more cooling channels 120 are fluidly coupled to a coolant source (not shown), such as a modified water source having relatively high electrical resistance or a refrigerant source.
• the precursor delivery system 102 features a diborane gas source, e.g., the first gas source 121 , a diluent gas source, e.g., the second gas source 122, and first and second delivery conduits 123a-b fluidly coupling the respective first gas source 121 and second gas source 122 to a mixing point 124.
• the mixing point 124 is fluidly coupled to the processing chamber 101 through a third delivery conduit 123c.
• the precursor delivery system 102 further includes one or more borane concentration sensors 125, one or more flow controller’s 126a-c, and one or more pressure sensors 127, each coupled to a delivery conduit 123a-c at location upstream of the mixing point, downstream of the mixing point, or both.
• a first gas comprising an unknown concentration of diborane is flowed from the first gas source 121 into the first delivery conduit 123a and a second gas comprising a diluent is flowed from the second gas source 122 into the second delivery conduit 123b.
• the second gas e.g., H2 is not reactive with diborane.
• the first and second gases mix at the mixing point 124 to form a boron doping gas.
• the boron doping gas flows from the mixing point 124 into the processing volume 109 through a third delivery conduit 123c fluidly coupled therebetween.
• the one or more borane concentration sensors 125 are used to determine the concentration of diborane in the first gas from a location upstream of the mixing point 124, determine the concentration of diborane in the boron doping gas (the mixture of the first gas and the second gas) at a location downstream from the mixing point, or both. In some embodiments, one or more of the borane concentration sensors 125 are used to determine the concentration of tetraborane in the first gas or the boron doping gas.
• One or both of the diborane and tetraborane concentration(s) are communicated to a system controller 130 of the processing system 100 which adjusts the flowrate of one or both of the first gas or second gas using a respective first flow controller 126a or second flow controller 126b.
• the system controller 130 includes a programmable central processing unit (CPU 131 ) that is operable with a memory 132 (e.g., non-volatile memory) and support circuits 133.
• the support circuits 133 are conventionally coupled to the CPU 131 and comprise cache, clock circuits, input/output subsystems, power supplies, and the like, and combinations thereof coupled to the various components of the processing system 100 to facilitate control thereof.
• the CPU 131 is one of any form of general purpose computer processor used in an industrial setting, such as a programmable logic controller (PLC), for controlling various components and sub-processors of the processing system 100.
• PLC programmable logic controller
• the memory 132 coupled to the CPU 131 , is non-transitory and is typically one or more of readily available memories such as random access memory (RAM), read only memory (ROM), floppy disk drive, hard disk, or any other form of digital storage, local or remote.
• RAM random access memory
• ROM read only memory
• floppy disk drive hard disk
• hard disk any other form of digital storage, local or remote.
• the memory 132 is in the form of a computer-readable storage media containing instructions (e.g., non-volatile memory), that when executed by the CPU 131 , facilitates the operation of the processing system 100.
• the instructions in the memory 132 are in the form of a program product such as a program that implements the methods of the present disclosure.
• the program code may conform to any one of a number of different programming languages.
• the disclosure may be implemented as a program product stored on computer-readable storage media for use with a computer system.
• the program (s) of the program product define functions of the embodiments (including the methods described herein).
• Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks within a diskette drive or hard- disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored.
• non-writable storage media e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory
• writable storage media e.g., floppy disks within a diskette drive or hard- disk drive or any type of solid-state random-access semiconductor memory
• the methods described herein, or portions thereof, are performed by one or more application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other types of hardware implementations.
• ASICs application specific integrated circuits
• FPGAs field-programmable gate arrays
• the processes described herein are performed by a combination of software routines, ASIC(s), FPGAs, or other types of hardware implementations.
• one or more of the borane concentration sensors 125 is an optical sensor configured to selectivity measure the attenuation of one or more specific wavelengths of introduced radiation, i.e., one or more target wavelengths, passing through a gas sample disposed therein.
• the target wavelength(s) correspond to an absorption peak of the absorption spectrum of a to-be-measured molecular species, i.e., a target molecular species such as diborane or tetraborane.
• the selective attenuation measurement(s) are used to determine the concentration of the target molecular species in the gas sample.
• Figures 2A-2B are schematic cross-sectional views of respective optical sensors 200a and 200b which may be used as one or more of the borane concentration sensors 125 described in Figure 1 , according to one embodiment.
• Figure 3 is a graph 300 showing the UV absorption spectrum 301 of diborane, shown here as the absorption cross-section (cm 2 /molecule) across a range of wavelengths (nm) in the UV spectrum.
• Figure 4A is a graph 400a showing the IR absorption spectrum 401 of diborane, shown here as the absorbance (Au.) across a range of wavelengths (pm) in the IR spectrum.
• Figure 4B is a graph 400b showing the IR absorption spectrum 403 of tetraborane across a range of wavelengths (pm) in the IR spectrum.
• the UV absorption spectrum 301 and the IR absorption spectrum 401 of diborane each comprise a respective plurality of UV absorption peaks 302 and IR absorption peaks 402.
• the IR absorption spectrum 403 of tetraborane comprises a plurality of IR absorption peaks 404.
• one or a combination of the optical sensors 200a and 200b are used to determine the concentration of diborane, tetraborane, or both in a gas sample by selectively measuring the attenuation of a target wavelength, or target wavelengths, of radiation passing therethrough.
• the target wavelengths correspond to an absorption peak 302 or 402 of diborane on the UV absorption spectrum 301 or the IR absorption spectrum 401 respectively, or to an absorption peak 404 on the tetraborane IR absorption spectrum 403.
• the optical sensor 200a features a body 202 and a plurality of windows (showing two windows 204a and 204b).
• individual ones of the plurality of windows 204a and 204b are disposed at opposite ends of the body 202 to collectively therewith define a cell volume 206.
• the cell volume 206 is in fluid communication with a gas inlet 208 and a gas outlet 210.
• the optical sensor 200 further includes a radiation source 212, one or more radiation detectors 214a-b, and one or more optical filters 216a-b.
• the optical sensor 200, or the individual components thereof is disposed on and electrically coupled to a printed circuit board (PCB) 217.
• PCB printed circuit board
• the radiation source 212 and the one or more radiation detectors 214a-b are disposed outside of the cell volume 206 at, or proximate to, opposite ends of the body 202.
• the radiation source 212 is disposed outside the cell volume 206 proximate to a first window 204a at a first end of the body 202.
• the one or more radiation detectors 214a-b are disposed proximate to one or more optical filters 216a-b interposed between the second window 204b and the one or more radiation detectors 214a-b at, or proximate to, a second end of the body 202.
• Each of the plurality of windows 204a-b is formed of a material suitable for transmission therethrough of a broad band of UV or IR radiation emitted by the radiation source 212.
• suitable window materials include MgF2, KBr, sapphire, or combinations thereof.
• the broad band of UV or IR radiation emitted by the radiation source includes the target UV or IR wavelengths to be measured by the one or more radiation detectors 214a-b.
• the radiation source 212 comprises one or more UV lamps, or one or more UV laser sources, configured to emit UV radiation comprising a wavelength of 132 nm or less, such as 115 nm or less.
• the radiation source 212 comprises one or more IR lamps, or one or moreIR laser sources, configured to emit IR radiation comprising a wavelength of 3.831 pm or more, such as 3.968 pm or more, 6.250 pm or more, 8.532 pm or more, or 10.256 pm or more.
• the radiation source 212 comprises a UV lamp, or a UV laser source, configured to emit UV radiation comprising a wavelength of 132 nm or less, such as 115 nm or less, and an IR lamp, or an IR laser source, configured to emit IR radiation of comprising a wavelength of 3.831 pm or more, such as 3.968 pm or more, 6.250 pm or more, 8.532 pm or more, or 10.256 pm or more.
• a gas sample comprising diborane molecules 218, diluent gas molecules 220, and tetraborane molecules 222 flows into the cell volume 206 through the inlet 208 and flows out of the cell volume 206 through the outlet 210.
• the optical sensor 200 is coupled to a delivery conduit, such as one of the plurality of delivery conduits 123a-c described in Figure 1.
• both the inlet 208 and the outlet are fluidly coupled to the delivery conduit 123a-c.
• the outlet 210 is fluidly coupled to an exhaust conduit (not shown) which evacuates the gas sample from the cell volume 206.
• the optical sensor 200 further includes a pressure sensor 224 fluidly coupled to the cell volume 206.
• the optical sensor 200a is configured to determine the concentration of diborane molecules 218 in the gas sample.
• radiation from the radiation source 213 is simultaneously transmitted along a first optical pathway and a second optical pathway.
• the first optical pathway is used to selectively measure the attenuation of a target wavelength of radiation.
• the target wavelength of radiation corresponds to a UV absorption peak 302 (shown in Figure 3) or an IR absorption peak 402 (shown in Figure 4A) of the diborane molecules 218.
• a target wavelength corresponding to a UV absorption peak 302 is typically within about +/- 2 nm of 115 nm or 132 nm.
• a target wavelength corresponding to an IR absorption peak 402 is typically within about +/- 10 nm of 3.831 pm, 3.968 pm, 6.25 pm, 8.532 pm, or 10.253 pm.
• the optical sensor 200a is configured to determine the concentration of tetraborane molecules 222 in the gas sample.
• the first optical pathway is configured to selectively measure a target wavelength of radiation corresponding to an IR absorption peak 404 (shown in Figure 4B) of the tetraborane molecules 222.
• Suitable target wavelengths for determining tetraborane are within +/- 10 nm of an IR absorption peak 404 of the tetraborane IR absorption spectrum 403, such as within about +/- 10 nm of about 4.68 pm or of about 8.85 pm.
• the second optical pathway is used to selectively measure the intensity of radiation at a reference wavelength to provide a reference intensity measurement.
• the reference wavelength does not correspond to an absorption peak of a molecular species anticipated to be found in the gas sample.
• the reference intensity measurement is used to compensate for environmental, electrical, and mechanical variations which affect the first and second radiation detectors 214a-b equally, such as variations in the intensity of radiation provided by the radiation source 212 and variations of ambient pressure and temperature.
• the first optical pathway extends from the radiation source 212 to the first radiation detector 214a and sequentially includes the radiation source 212, the first window 204a, the cell volume 206, the second window 204b, and a first radiation detector 214a.
• the first optical pathway further includes a first optical filter 216a disposed between the second window 204b and the first radiation detector 214a.
• the first optical filter 216a selectively transmits radiation in a target wavelength corresponding to an IR absorption peak 402 ( Figure 4) of the diborane molecules 218.
• the first optical filter 216a is an optical bandpass filter having a center transmission wavelength Ac and a bandwidth Aw. Suitable filter center transmission wavelengths Ac correspond to desired target wavelengths, i.e. IR absorption peaks 402 of diborane molecules 218.
• the optical sensor 200a is configured to determine the concentration of diborane molecules the first optical filter 216a has a center transmission wavelength Ac corresponding to a target wavelength of one of 3.831 pm, 3.968 pm, 6.25 pm, 8.532 pm, or 10.253 pm.
• the center transmission wavelength Ac is within about +/- 250 nm of the corresponding target wavelength, such as within about +/- 100 nm, or for example within about +/- 50 nm.
• the first optical filter 216a has a center transmission wavelength Aci within about +/- 250 nm, about +/- 100 nm, or within about +/- 50 nm of an IR absorption peak 404 e.g., about 4.680 pm or about 8.850 pm.
• the first optical filter 216a has a bandwidth Aw of about 1 pm or less, such as about 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, for example about 500 nm or less.
• the first optical pathway does not include the first optical filter 216a.
• the second optical pathway extends from the radiation source 212 to the second radiation detector 214b and sequentially includes the radiation source 212, the first window 204a, the cell volume 206, the second window 204b, a second optical filter 216b, and the second radiation detector 214b.
• the second optical filter 216b selectivity transmits radiation which does not correspond to an absorption peak of diborane or a desired diluent gas.
• the second optical filter 216b excludes radiation wavelengths corresponding to an absorption peak of diborane or a desired diluent gas.
• Figure 2B is a schematic cross sectional view of an optical sensor 200b configured to determine the concentration of both diborane and tetraborane in a gas sample disposed therein.
• the optical sensor 200b is similar to the optical sensor 200a described in Figure 2a (when configured to determine diborane concentration) and further includes a third optical pathway used to determine tetraborane concentration.
• the third optical pathway extends from the radiation source 212, here an IR radiation source, to a third radiation detector 214c.
• the third optical pathway sequentially includes the radiation source 212, the first window 204a, the cell volume 206, the second window 204b, a third optical filter 216c, and the third radiation detector 214c.
• the third optical filter 216c has a center transmission wavelength Ac within about +/- 250 nm, about +/- 100 nm, or within about +/- 50 nm of an IR absorption peak 404 of tetraborane, e.g., about 4.680 pm or about 8.850 pm.
• the third optical filter 216c has a bandwidth Aw of about 1 pm or less, such as about 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, for example about 500 nm or less.
• Figure 5 is a graph 500 schematically illustrating one or more measurements taken using an optical sensor, here one of the optical sensors 200a or 200b described in Figure 2A and 2B respectively.
• Graph 500 schematically shows absorption measurements of three different gas samples 501 a-c having varying concentrations of diborane.
• radiation from the radiation source 212 is transmitted along each of the two or three optical pathways described in Figures 2A and 2B respectively.
• the optical pathways include at least the radiation source 212, the first window 204a, the cell volume 206 having one of the gas samples 501 a-c disposed therein, and the second window 204b.
• the first optical pathway further includes the first optical filter 216a and the first radiation detector 214a.
• the first optical filter 216a has a center transmission wavelength Aci and a bandwidth Awi corresponding to an IR absorption peak of diborane or tetraborane as described above and shown in Figure 4A and 4B respectively.
• the second optical pathway further includes the second optical filter 216b and the second radiation detector 214b.
• the second optical filter 216b has a center transmission wavelength Ac2 and a bandwidth Aw2 that does not correspond to an absorption peak of a molecular species anticipated to be found in the gas sample.
• the third optical pathway further includes the third optical filter 216c and the third radiation detector 214c.
• the third optical filter 216c has a center transmission wavelength Ac3 and a bandwidth Aw3 which corresponds to an IR absorption peak of tetraborane.
• the center transmission wavelength Ac2 of the second optical filter 216b may be more or less than the center transmission wavelength Aci of the first optical filter 216a or the center transmission wavelength Ac3 of the third optical filter 216c.
• the center transmission wavelength Ac3 of the third optical filter 216c may be more or less than the center transmission wavelength Aci of the first optical filter 216a.
• the intensity measurement taken by the second radiation detector 214b i.e. , the reference intensity 503, is used to compensate for environmental, electrical, and mechanical variations which affect the radiation detectors 214a-c equally.
• the reference intensity 503 is the same for each of the three gas samples 501 a-c indicating no substantial environmental, electrical, and mechanical variations between measurements for each sample 501 a-c.
• the difference, i.e. the attenuations 502a-c, between the reference intensity 503 and the intensity for each of the samples 501 a-c measured using the first radiation detector 214a is used to determine the diborane concentrations therein.
• radiation passed through the first gas sample 501 a has the highest attenuation 502a between radiation transmitted along the first and second optical pathways and thus the highest diborane concentration of the plurality of samples 501 a-c.
• Radiation passed through the third gas sample 501 c has the lowest attenuation 502c and thus the lowest diborane concentration.
• Radiation passed through the first gas sample 501 a has the lowest attenuation 503a between radiation transmitted along the second and third optical pathways and thus the lowest tetraborane concentration of the plurality of samples 501 a-c. Because diborane in a pressurized gas cylinder decomposes over time to yield free hydrogen and tetraborane, the attenuations 503a-c measured using the third radiation detector 214c will increase as the attenuations 502a-c decrease. Thus, the radiation passed through the third gas sample 501c has the highest attenuation 503c and thus the highest tetraborane concentration of the plurality of samples 501 a-c.
• Figures 6A and 6B are schematic cross-sectional views of respective optical sensors 600a and 600b which may be used as one or more of the borane concentration sensors 125 described in Figure 1 , according to another embodiment.
• the optical sensor 600a features a body 602 a plurality of windows 604a-b disposed at opposite ends of the body 602, and a divider 605 which collectively define a first cell volume 606a and a second cell volume 606b.
• the first cell volume 606a is in fluid communication with an inlet 608, used to deliver gas samples thereinto, and an outlet 610, used to exhaust the gas samples therefrom.
• the second cell volume 606b is fluidly isolated from the first cell volume 606a by the divider 605 disposed therebetween.
• the optical sensor 600a further includes a radiation source 612, one or more radiation detectors 614a-b, and one or more optical filters 616a-b.
• the optical sensor 600a or the individual components thereof, are disposed on and electrically coupled to a printed circuit board (PCB) 617.
• PCB printed circuit board
• the radiation source 612 and the one or more radiation detectors 614a-b are disposed outside of the first and second cell volumes 606a-b at or proximate to opposite ends of the body 602.
• the radiation source 612 is disposed outside the first and second cell volumes 606a-b proximate to the first window 604a at a first end of the body 602.
• the one or more radiation detectors 614a-b are disposed proximate to one or more optical filters 616a-b, interposed between the second window 604b and the one or more radiation detectors 614a-b, at or proximate to a second end of the body 602.
• Each of the plurality of windows 604a-b is formed of a material suitable for transmission therethrough of a broad band of UV or IR radiation emitted by the radiation source 612.
• suitable window materials include MgF2, KBr, sapphire, or combinations thereof.
• the broad band of UV or IR radiation emitted by the radiation source includes the target UV or IR wavelengths to be measured by the one or more radiation detectors 614a-b.
• the radiation source 612 comprises one or more UV lamps, or UV laser sources, configured to emit UV radiation comprising a wavelength of 132 nm or less, such as 115 nm or less.
• the radiation source 612 comprises one or more IR lamps, or IR laser sources, configured to emit IR radiation comprising a wavelength of 3.831 pm or more, such as 3.968 pm or more, 6.250 pm or more, 8.532 pm or more, or 10.256 pm or more.
• a gas sample comprising diborane molecules 218, diluent gas molecules 220, and tetraborane molecules 222 flows into the first cell volume 606a through the inlet 608 and flows out of the first cell volume 606a through the outlet 610.
• the optical sensor 600 is coupled to a delivery conduit, such as one of the plurality of delivery conduits 123a-c described in Figure 1.
• the inlet 608 is fluidly coupled to the delivery conduit 123a-c and the outlet 610 is fluidly coupled to an exhaust conduit (not shown) which evacuates the gas sample from the first cell volume 606a.
• the first optical pathway is used to selectively measure the attenuation of a target wavelength of radiation corresponding to an UV absorption peak 302 (shown in Figure 3) or an IR absorption peak 402 or 404 (shown in Figures 4A and 4B respectively) of the diborane molecules 218 or tetraborane molecules 222.
• the second optical pathway is used to selectively measure the intensity of radiation at a reference wavelength to provide a reference intensity measurement.
• the reference wavelength may be the same or different from an absorption peak of a molecular species anticipated to be found in the gas sample.
• the first optical pathway extends from the radiation source 612 to the first radiation detector 614a.
• the first optical pathway sequentially includes the radiation source 612, the first window 604a, the first cell volume 606a, the second window 604b, a first optical filter 616a, and a first radiation detector 614a.
• the first optical filter 616a selectively transmits radiation in a target wavelength corresponding to an IR absorption peak 402 ( Figure 4A) of the diborane molecules 218 or an IR absorption peak 404 ( Figure 4B) of the tetraborane molecules 222.
• the first optical filter 616a is an optical bandpass filter having a center transmission wavelength Ac and a bandwidth Aw.
• the first optical filter 216a has a center transmission wavelength Aci corresponding to a target wavelength of diborane or tetraborane as described above and as shown in Figures 4A-4B respectively.
• the first optical filter 616a has a bandwidth Aw of about 1 pm or less, such as about 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, for example about 500 nm or less.
• the second optical pathway extends from the radiation source 612 to the second radiation detector 614b.
• the second optical pathway sequentially includes the radiation source 612, the first window 604a, the second cell volume 606b, the second window 604b, a second optical filter 616b, and the second radiation detector 614b.
• the second optical filter 616b may allow transmission of radiation therethrough which does or does not correspond to an absorption peak of diborane or a desired diluent gas.
• the second cell volume 606b is maintained in a vacuum condition or comprises an inert gas 618.
• one or both of the first or second optical pathways do not include a respective first or second optical filter 616a-b.
• the optical sensor 600a further includes a pressure sensor 622 fluidly coupled to the first cell volume 606a which is used to monitor the pressure of the gas sample disposed therein.
• the optical sensor further includes one or more mirrors 624 used to direct radiation from the radiation source 612 through the first and second cell volumes 606a-b.
• Figure 6B is a schematic cross sectional view of an optical sensor 600b configured to determine the concentration of both diborane and tetraborane in a gas sample disposed therein.
• the optical sensor 600b is similar to the optical sensor 600a described in Figure 6a (when configured to determine diborane concentration) and further includes a third optical pathway used to determine tetraborane concentration.
• the third optical pathway extends from the radiation source 612, here an IR radiation source, to a third radiation detector 614c.
• the third optical pathway sequentially includes the radiation source 612, the first window 604a, the cell volume 606a, the second window 604b, a third optical filter 616c, and the third radiation detector 614c.
• the third optical filter 616c selectively transmits radiation in a target wavelength corresponding to an IR absorption peak 404 ( Figure 4B) of the tetraborane molecules 222 such as described above with respect to the third optical filter 216c in Figure 2B.
• the optical sensors described herein are calibrated prior to installation on a processing system.
• the optical sensors are calibrated using a low toxicity (relative to diborane) proxy gas having a UV or IR absorption peak similar to an absorption peak of diborane.
• suitable proxy gases include Nhh, methanethiol, ethanethiol, or combinations thereof.
• Figure 7 is a graph 700 illustrating measurements taken using an optical sensor, here the optical sensor 600b described in Figure 6B, of three gas samples 701 a-c each having different diborane and tetraborane concentrations.
• Flere radiation from the radiation source 612 is transmitted along the optical pathways described in Figure 6B.
• the first optical pathway includes the radiation source 612, the first window 604a, the first cell volume 606a, having one of the gas samples 701 a-c disposed therein, the second window 604b, the first optical filter 616a and the first radiation detector 614a.
• the first optical filter 616a has a center transmission wavelength Aci and a bandwidth Awi corresponding to an IR absorption peak of diborane described above and shown in Figure 4A.
• the second optical pathway includes the radiation source 612, the first window 604a, the second cell volume 606b, having an inert gas 618 disposed therein, the second window 604b, the second optical filter 616b, and the second radiation detector 614b.
• the second optical filter 616b has a center transmission wavelength Ac2 and a bandwidth Aw2 that may or may not correspond to an absorption peak of a molecular species anticipated to be found in the gas sample.
• the third optical pathway includes the radiation source 612, the first window 604a, the first cell volume 606a, having one of the gas samples 701 a-c disposed therein, the second window 604b, the third optical filter 616c and the third radiation detector 614c.
• the third optical filter 616c has a center transmission wavelength Ac3 and a bandwidth Aw3 corresponding to an IR absorption peak of tetraborane described above and shown in Figure 4B.
• the center transmission wavelength Ac2 of the second optical filter 616b may be more, less, or the same as the center transmission wavelength Aci of the first optical filter 616a.
• the center transmission wavelength Ac3 of the third optical filter 616c may be more or less than the center transmission wavelength Aci of the first optical filter 616a and more or less than the center transmission wavelength Ac2 0f the second optical filter 616b.
• the intensity measurement taken by the second radiation detector 614b i.e. , the reference intensity 703 is used to compensate for environmental, electrical, and mechanical variations which affect the first and second radiation detectors 614a-b equally.
• the difference, i.e. the attenuations 702a-c, between the reference intensity 703 and the intensity for each of the samples 701 a-c transmitted along the first optical pathway are used to determine the diborane concentration in the respective sample.
• the attenuations 703a-c, between the reference intensity 703 and the intensity for each of the samples 701 a-c transmitted along the third optical pathway are used to determine the tetraborane concentration in the respective sample.
• radiation passed through the first gas sample 701 a has the highest attenuation 702a and thus the highest diborane concentration and the lowest attenuation 703a and thus the lowest tetraborane concentration of the three samples 701 a-c.
• Radiation passed through the third gas sample 701 c has the lowest attenuation 702c and the highest attenuation 703c and thus the lowest diborane concentration and the highest tetraborane concentration of the three samples 701 a-c.
• FIG. 8 is a flow diagram setting forth a method of processing a substrate, according to one embodiment.
• the method 800 includes determining a diborane concentration in a gas sample taken from a gas conduit fluidly coupling a first gas source and a processing chamber.
• determining the diborane concentration comprises using an optical sensor, such as one of the optical sensors 200a, b or 600a, b respectively described in Figures 2A-2B or 6A-6B.
• the method 800 includes mixing a boron doping gas having a desired diborane concentration by changing a flowrate of a first gas from the first gas source, a second gas from a second gas source, or both.
• the method includes delivering the boron doping gas to a processing volume of the processing chamber.
• the method 800 further includes determining a tetraborane concentration a gas sample taken from a gas conduit fluidly coupling a first gas source and a processing chamber.
• determining the tetraborane concentration comprises using the same optical sensor used to determine the diborane concentration or using a different optical sensor, such as using one or a combination of the optical sensors 200 a, b and 600 a,b described herein.

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