Classifications

• • 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
• • 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
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/32917—Plasma diagnostics
  • H01J37/32935—Monitoring and controlling tubes by information coming from the object and/or discharge
• • 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
  • H01L21/67063—Apparatus for fluid treatment for etching
  • H01L21/67069—Apparatus for fluid treatment for etching for drying etching

Definitions

• This invention relates to the control of processes used in the production of semiconductors, particularly but not exclusively for endpointing semiconductor etch processes, or for endpointing deposition machine clean up processes.
• An object of the present invention is to provide a method and apparatus which can be used in an improved form of process control.
• the invention makes use of the fact that many chemical reactions - in particular those involving free radicals and ions produced within a plasma - proceed in a number of stages through a series of intermediates before a stable state or compound is produced. These intermediate stages can have lifetimes from a few nanoseconds to a few milliseconds. Transition from one stage to another can involve the emission of light.
• a detector tuned to that wavelength can be placed at a convenient location outside and remote from the immediate site of reaction and its output used to monitor concentration of a species as a surrogate for material etch rate, and thus the progress of the clean-up of a vacuum processing system or alternatively the progress of a fabrication process that utilizes dry-etch.
• the present invention provides a method of controlling a chemical process which takes place within a low-pressure enclosure, the process being such as to produce a species that emits photons of a known wavelength or wavelength distribution by a particular chemical recombination or relaxation process, the species having a lifetime characteristic which, at the pressure of said enclosure, enables it to be detected at a significant distance from the site of the primary reaction, the method comprising detecting said photons at said distance while rejecting other photons, and using the rate at which said photons are detected to control the process .
• significant distance is used herein to mean a distance which is significant in relation to the size of the area within which the primary reaction occurs, and will typically be greater than 5cm, and preferably is of the order of 0.5m or more .
• the method may be used particularly to control the processing of silicon with fluorine radicals, the chemical relaxation process being the combination of the silicon difluoride radical with the fluorine radical to yield electronically excited silicon trifluoride radical which subsequently returns to the ground state with the emission of a photon most probably between 380 and 650nm.
• the silicon process will most typically be dry etching of silicon/silicon dioxide, or the clean- up of silicon deposited on the walls of the enclosure during other processing. It is to be understood that "Silicon” includes Silicon Dioxide or other Silicon based deposits.
• the clean-up process may be one involving plasma enhanced chemical vapor etch, the plasma typically being produced within the enclosure. The radicals may suitably be created upstream of the enclosure .
• the photon detection may advantageously be carried out in an exhaust line from the enclosure, or in a vacuum pump to which the exhaust line is connected.
• the present invention provides apparatus for use in conjunction with a low-pressure enclosure serving as a reaction chamber in which takes place a chemical process which is such as to produce s species that emits photons of a known wavelength or wavelength distribution by a particular chemical recombination or relaxation process, the species having a lifetime characteristic which, at the pressure of said enclosure, enables it to be detected at a significant distance from the site of the primary reaction, the apparatus comprising a photon detector arranged at a significant distance from the primary reaction site, and means for monitoring the rate of photon detection.
• apparatus for chemical processing comprising a low-pressure chamber and an exhaust line extending from the chamber to a vacuum pump; the chamber defining a location in which, in use, a chemical process takes place which is such as to produce a species that emits photons of a known wavelength or wavelength distribution by a particular chemical recombination or relaxation process, the species having a lifetime characteristic which, at the pressure of said enclosure, enables it to be detected at a significant distance from the site of the primary reaction; the apparatus further comprising a photon detector arranged at a significant distance from said location, and means for monitoring the rate of photon detection.
• the photon detector is preferably situated in an exhaust line of the enclosure, or in a vacuum pump to which the exhaust line is connected.
• the photon detector is provided with a light baffle to eliminate off-axis light and/or a light trap opposed to the entrance to the detector.
• Figure 1 is a schematic cross-sectional view of a chemical process system used in one form of the invention
• Figure 2 shows part of the apparatus of Figure 1 in greater detail
• Figure 3 is a graph showing one example of an output signal
• Figure 4 is a view similar to Figure 1 of a second embodiment.
• reaction a) the material is removed from the solid surface into the gas phase by combination with one or more individuals of the radical species .
• reaction b) further stepwise combination yields an electronically energetic intermediate which decays to the ground state with the release of a photon. Further stepwise addition gives the final stable product which is pumped from the system.
• the production of light at step c) will be directly proportional to the concentration of the electronically exited intermediate and can be used as an indicator that the reaction removing (etching) material M is proceeding.
• reaction b) is rate limiting the overall reaction cascade, and where the intermediate is sufficiently stable that b) is the predominant reaction, then the production of light at step c) , which is necessarily a very fast process, will be a quantitative surrogate for the rate of removal of the material . Even where reaction b) is not rate limiting the presence or absence of the production of light can be used as an endpoint indication for the removal of material M.
• the emission of light associated with the etch process will be located remotely from the surface of the material and may extend some metres into the surrounding space.
• the mean free path of the intermediates will be high compared with the geometries of typical process equipment.
• the concentration of the reactants are necessarily low thereby enhancing the halflife of the intermediate MR n# light emission due to step c) will occur as much as 1 metre away from the vacuum processing system's surfaces which are the subject of the cleaning process itself, or alternatively from the material being fabricated during a dry etch process. This distance is simply derived from the halflife of the species MR n and its diffusion rate.
• monitoring of the emitted light is carried out remotely from the reaction region it can be done with no interference or disruption to the reaction itself.
• one example of a useful reaction which is typical of the type of reaction described above, is the etching of silicon by the fluorine radical generated by plasma decomposition of compounds including, but not restricted to the perfluoronated hydrocarbons, sulphur hexafluoride and nitrogen trifluoride.
• the silicon difluoride radical produced by reaction a) has a lifetime of several milliseconds, and can diffuse a considerable distance before conversion to the trifluoride radical takes place with the immediate relaxation of the excited state and comcomitant production of a photon.
• the light emitted is a quasi-continuum ranging from 380 to 650nm. Given the geometry of a typical process chamber, a substantial amount of this light will be emitted in the exhaust line.
• FIG. 1 shows a typical vacuum processing vessel 3 the diameter of which is of the order of 1 metre.
• the processing vessel 3 is maintained at a low pressure by a vacuum pump 11 via an exhaust line 2.
• a typical vacuum processing technique which is the basic function of the vessel would be the deposition of polysilicon by introduction into the vessel a compound such as, but not restricted to, an organo- silicon compound, and then dissociating that compound at the heated substrate surface 5.
• a side effect of this procedure is to deposit silicon on the walls of the process vessel 3.
• Silicon includes Silicon Dioxide or other silicon based deposits.
• Such silicon is a disadvantage to the basic function of the vessel as it contributes to particulates and consequential failure of devices.
• a typical clean-up technique would be the introduction of nitrogen trifluoride into an up-stream plasma region 4 where it is dissociated to yield the free fluorine radical.
• the fluorine radical reacts with the silicon which has been deposited on the walls of the vessel, and follows the reaction sequence already outlined above for silicon.
• the pressure in the reaction vessel during the clean up process will be of the order of 1 to lOOmtorr .
• a detector 1 is shown connected to the exhaust line 2 of the process vessel 3.
• Figure 2 shows a detail of one suitable form of detector which in this case consists of a light-baffle 7 in front of a wavelength discriminating filter 8 and a photomultiplier tube 9.
• the light-baffle 7 in this example consists of a number of opaque parallel plates in front of the filter 8, each perforated with a multiplicity of apertures, the pattern and spacial arrangement of which has the function of rejecting light which may be reflected from the reaction region along the exhaust line 2.
• the light- trap 6 comprises an open-ended cylinder whose walls are provided with projecting baffles, all the internal surfaces being matt black for maximum light absorption.
• the light-baffle 7 would consist of a series of opaque plates with apertures in the plates arranged one after the other so that only on-axis light can reach the photon detector.
• the apertures in the plates are arranged such that their distribution pattern in the direction in the plane of the individual plates is aperiodic so as to avoid the situation where off-axis light could pass through one aperture in the first plate at a particular angle so that a multiple rule would allow it to pass through not the associated line-of-sight aperture in the next plate but one off-axis and, by virtue of the same multiple rule then pass through other line-of-sight apertures in subsequent plates.
• the size of the apertures are arranged to increase from one plate to another so that the smallest sized apertures are in the plate adjacent to the photon detector and the largest sized apertures are in the plate furthest away with the increase in size arranged in such a way that an observer located at the photon detector would only be able to see the edges of the apertures in the plate adjacent to him and not be able to view any of the edges in the apertures in plates not adjacent to him.
• Figure 3 shows a typical output from the photomultiplier in graphical form which may be used to determine the rate of removal of silicon contaminant .
• digital signal process techniques such as, but not restricted to, curve shape recognition and perturbation analysis can be used to yield an endpoint decision which can then used to automate the clean-up cycle.
• a second embodiment is used for controlling the etching of silicon.
• Figure 4 shows a typical vacuum processing vessel 3 the diameter which is of the order of 1 metre.
• a typical processing technique would be the etching of silicon by introduction into the vessel a fluorine source such as, but not restricted to, sulphur hexafluoride as a gas.
• the pressure in the reaction vessel will be in the range 1 to lOOmtorr and an electric field is applied to two electrodes 13 in such a manner that a plasma is formed between them.
• the silicon substrate 14 to be etched is placed on the ground connected electrode and the fluorine radical produced by the dissociation of the sulphur hexafluoride reagent reacts with the silicon according to the reaction sequence already outlined above .
• a detector 1 is connected to the exhaust line 2 of the process chamber 3.
• the detector 1 may suitably be the same as is shown in Figure 2, and the output from the detector will be of the same form as is shown in Figure 3.
• the detector could be placed within the processing vessel itself at a suitable distance form the reaction site, or could be incorporated in the vacuum pump; however, positioning the detector in communication with the exhaust line is likely to be the most convenient arrangement.
• the invention may be used with processes other than silicon/fluorine wherever a suitable light-emitting intermediate stage is present.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• General Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• Plasma & Fusion (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Drying Of Semiconductors (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

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• 2002
  • 2002-03-15 GB GBGB0206158.8A patent/GB0206158D0/en not_active Ceased
• 2003
  • 2003-03-14 KR KR10-2004-7014351A patent/KR20040094794A/ko not_active Application Discontinuation
  • 2003-03-14 AU AU2003226491A patent/AU2003226491A1/en not_active Abandoned
  • 2003-03-14 JP JP2003577311A patent/JP2005521242A/ja active Pending
  • 2003-03-14 EP EP03744445A patent/EP1485937A2/de not_active Withdrawn
  • 2003-03-14 US US10/508,628 patent/US20050103438A1/en not_active Abandoned
  • 2003-03-14 WO PCT/GB2003/001104 patent/WO2003079411A2/en not_active Application Discontinuation

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