Classifications

• • 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
  • H01J37/32431—Constructional details of the reactor
  • H01J37/32798—Further details of plasma apparatus not provided for in groups H01J37/3244 - H01J37/32788; special provisions for cleaning or maintenance of the apparatus
  • H01J37/32853—Hygiene
  • H01J37/32862—In situ cleaning of vessels and/or internal parts
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
  • B08B7/0035—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like
• • 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
  • C23C16/4405—Cleaning of reactor or parts inside the reactor by using reactive gases
• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F4/00—Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/30—Capture or disposal of greenhouse gases of perfluorocarbons [PFC], hydrofluorocarbons [HFC] or sulfur hexafluoride [SF6]

Definitions

• the present invention relates to methods for removing surface deposits by using an activated gas created by remotely activating a gas mixture comprising of oxygen and fluorocarbon. More specifically,the present invention relates to methods for removing surface deposits from the interior of a chemical vapor deposition chamber using an activated gas created by remotely activating a gas mixture comprising of oxygen and perfluorocarbon.
• Remote plasma sources for the production of atomic fluorine are widely used for chamber cleaning in the semiconductor processing industry, particularly in the cleaning of chambers used for Chemical Vapor Deposition (CVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD).
• remote plasma sources avoids some of the erosion of the interior chamber materials that occurs with in situ chamber cleans in which the cleaning is performed by creating a plasma discharge within the PECVD chamber.
• capacitively and inductively coupled RF as we ll as microwave remote sources have been developed for these sorts of applications, the industry is rapidly moving toward transformer coupled inductively coupled sources in which the plasma has a torroidal configuration and acts as the secondary of the transformer.
• the use of lower frequency RF power allows the use of magnetic cores which enhance the inductive coupling with respect to capacitive coupling; thereby allowing the more efficient transfer of energy to the plasma without excessive ion bombardment which limits the lifetime of the remote plasma source chamber interior.
• the present invention relates to a method for removing surface deposits, said method comprising: (a) activating in a remote chamber a gas mixture comprising oxygen and fluorocarbon, wherein the molar ratio of oxygen and fluorocarbon is at least 1 :4, using sufficient power for a sufficient time such that said gas mixture reaches a neutral temperature of at least about 3,000 K to form an activated gas mixture; and thereafter (b) contacting said activated gas mixture with the surface deposits and thereby removing at least some of said surface deposits.
• FIG. 1 Schematic diagram of an apparatus useful for carrying out the present process.
• Figure 2. Plot of etch rate of silicon dioxide at 100°C as a function of 0 2 percentage in perfluorocarbon and 0 2 mixture.
• Figure 3. Plots of Fourier Transformed Infrared Spectroscopy (FTIR) measurements of the concentration of emission gases from the pump of (a) NF 3 + Ar, (b) C 3 F 8 + 0 2 + Ar, (c) C 4 F 8 + 0 2 + Ar, and (d) CF 4 + 0 2 + Ar discharges.
• Figure 4. Schematic diagram of an apparatus useful for carrying out the present process.
• Figure 2. Plot of etch rate of silicon dioxide at 100°C as a function of 0 2 percentage in perfluorocarbon and 0 2 mixture.
• Figure 3. Plots of Fourier Transformed Infrared Spectroscopy (FTIR) measurements of the concentration of emission gases from the pump of (a) NF 3 + Ar, (b) C 3 F 8 +
• Surface deposits removed in this invention comprise those materials commonly deposited by chemical vapor deposition or plasma- enhanced chemical vapor deposition or similar processes. Such materials include silicon, doped silicon, silicon nitride, tungsten, silicon dioxide, silicon oxynitride, silicon carbide and various silicon oxygen compounds referred to as low K materials, such as FSG (fluorosilicate glass) and SiCOH or PECVD OSG including Black Diamond (Applied Materials), Coral (Novellus Systems) and Aurora (ASM International).
• FSG fluorosilicate glass
• SiCOH or PECVD OSG including Black Diamond (Applied Materials), Coral (Novellus Systems) and Aurora (ASM International).
• One embodiment of this invention is removing surface deposits from the interior of a process chamber that is used in fabricating electronic devices.
• Such process chamber could be a Chemical Vapor Deposition (CVD) chamber or a Plasma Enhanced Chemical Vapor Deposition (PECVD) chamber.
• the process of the present invention involves an activating step using sufficient power to form an activated gas mixture having neutral temperature of at least about 3,000 K. Activation may be accomplished by any means allowing for the achievement of dissociation of a large fraction of the feed gas, such as: RF energy, DC energy, laser illumination and microwave energy.
• the neutral temperature of the resulting plasma depends on the power and the residence time of the gas mixture in the remote chamber. Under certain power input and conditions, neutral temperature will be higher with longer residence time. Here, preferred neutral temperature is over about 3,000 K.
• the activated gas is formed in a remote chamber that is outside of the process chamber, but in close proximity to the process chamber.
• the remote chamber is connected to the process chamber by any means allowing for transfer of the activated gas from the remote chamber to the process chamber.
• the remote chamber and means for connecting the remote chamber with the process chamber are constructed of materials known in this field to be capable of containing activated gas mixtures. For instance, aluminum and stainless steel are commonly used for the chamber components. Sometimes Al 2 0 3 is coated on the interior surface to reduce the surface recombination.
• the gas mixture that is activated to form the activated gas comprises oxygen and fluorocarbon.
• a fluorocarbon of the invention is herein referred to as a compound comprising of C and F.
• Preferred fluorocarbon in this invention is perfluorocarbon compound.
• a perfluorocarbon compound in this invention is herein referred to as a compound consisting of C, F and optionally oxygen.
• Such perfluorocarbon compounds include, but are not limited to tetrafluoromethane, hexafluoroethane, octafluoropropane, hexafluorocyclopropane decafluorobutane, octafluorocyclobutane, carbonyl fluoride and octafluorotetrahydrofuran.
• Preferred of the perfluorocarbons is octafluorocyclobutane.
• the gas mixture that is activated to form the activated gas may further comprise a carrier gas such as nitrogen, argon and helium.
• the total pressure in the remote chamber during the activating step may be between about 0.5 Torr and about 20 Torr.
• the gas mixture comprises oxygen and fluorocarbon in a molar ratio of at least about 1 :4.
• oxygen in excess of 10 molar percent of the stoichiometric requirement i.e., the amount of oxygen necessary to convert all carbon in the fluorocarbon to CO 2
• results in surprisingly good deposition chamber cleaning rates eliminates fluorocarbon emissions except COF 2 and prevents fluorocarbon polymer depositions on the deposition surfaces.
• the gas mixture is activated using sufficient power for a sufficient time such that said gas mixture reaches a neutral temperature of at least about 3,000 K to form an activated gas mixture.
• a power range of from about 3,000-15,000 watts in a 0.25 liter remote chamber corresponds to a power density of from about 12,000-60,000 watts/liter. These values scale both up and down for remote chambers of different sizes.
• the residence time of the gas mixture in the remote chamber under such power input must be sufficient such that the gas mixture achieves a neutral temperature of at least about 3,000K.
• neutral temperatures of at least about 6000K may be achieved, for example, with octafluorocyclobutane.
• a preferred embodiment of the present invention is a method for removing surface deposits from the interior of a process chamber that is used in fabricating electronic devices, said method comprising: (a) activating in a remote chamber a gas mixture comprising oxygen and perfluorocyclobutane in a mole ratio of at least from about 2:1 to about 20:1 using power of at least from about 3,000 watts for a sufficient time such that said gas mixture reaches a neutral temperature of at least about 3,000 K to form an activated gas mixture; and thereafter (b) contacting said activated gas mixture with the interior of said deposition chamber and thereby removing at least some of said surface deposits. It was also found that at the similar conditions of this invention, the drawbacks of the perfluorocarbon compound, i.e.
• Fig. 1 shows a schematic diagram of the remote plasma source and apparatus used to measure the etching rates, plasma neutral temperatures, and exhaust emissions.
• the remote plasma source is a commercial toroidal-type MKS ASTRON®ex reactive gas generator unit made by MKS Instruments, Andover, MA, USA.
• the feed gases e.g. oxygen, fluorocarbon, Argon
• the oxygen is manufactured by Airgas with 99.999% purity.
• the fluorocarbon is Zyron® 8020 manufactured by DuPont with minimum 99.9 vol % of octafluorocyclobutane.
• Argon is manufactured by Airgas with grade of 5.0.
• the activated gas then passed through an aluminum water-cooled heat exchanger to reduce the thermal loading of the aluminum process chamber.
• the surface deposits covered wafer was placed on a temperature controlled mounting in the process chamber.
• the neutral temperature is measured by Optical Emission Spectroscopy (OES), in which rovibrational transition bands of diatomic species like C 2 and N 2 are theoretically fitted to yield neutral temperature. See also B. Bai and H. Sawin, Journal of Vacuum Science & Technology A 22 (5), 2014 (2004), herein incorporated as a reference.
• the etching rate of the surface deposits by the activated gas is measured by interferometry equipment in the process chamber.
• N 2 gas is added at the entrance of the pump both to dilute the products to a proper concentration for FTIR measurement and to reduce the hang-up of products in the pump.
• FTIR was used to measure the concentration of species in the pump exhaust.
• EXAMPLE 1 The feeding gas composed of 0 2 , perfluorocarbon and Ar, wherein the perfluorocarbon is Zyron® 8020 (C 4 F 8 ), C 3 F 8 , C 2 F 6 , or CF .
• the flow rates of perfluo rocarbons in this Example were adjusted so that the molar flow rate of elemental fluorine into the remote chamber was the same for all mixtures.
• the flow rates for C F 8 , C 3 F 8 , C 2 F 6 , and CF 4 were 250, 250, 333 and 500 seem respectively, which are all equivalent to 2000 seem of elemental fluorine.
• the percentage flow rate of 0 2 to the total of 0 2 and perfluorocarbon was changed to detect the etching rate dependence on the 0 2 percentage. See Figure 2.
• the total feeding gas flow rate was fixed at 4000 seem by adjusting argon flow. Nitrogen was added between the process chamber and the pump at a flow rate of 20,000 seem. Chamber pressure is 2 torr.
• the feeding gas was activated by 400 KHz RF power to a neutral temperature of more than 5000 K. The activated gas then entered the process chamber and etched the Si0 2 surface deposits on the mounting with the temperature controlled at 100° C. The results are showed in Figure 2.
• the etching rate of NF 3 + Ar plasma is shown in Figure 2 since it is the standard gas used for remote chamber cleaning.
• FTIR was used to measure the concentration of emission species in the pump exhaust.
• Figure 3a, 3b, 3c, and 3d show the concentration of emission species in the pump exhaust as measured by FTIR.
• Figure 3a show that NF 3 was nearly completely decomposed by the ASTRON®ex plasma. Similarly, C 3 F 8 , CF 4 , and C 4 F 8 were nearly completely destroyed at their respective optimum oxygen mixtures with no measurable perfluorocarbons observed in the purnp exhaust. However, large amounts of COF 2 were present in the pump discharge. Result from C 2 F 6 was similar and not shown here. Obviously under current inventive conditions, there is no perfluorocarbon emission except COF 2 for perfluorocarbon containing mixture discharges. This is quite different from results of in situ chamber cleaning with perfluorocarbon gases where the perfluorocarbon emissions are significant.
• FIG. 4a and 4b demonstrate the effects of perfluorocarbon flow rate and 0 2 percentage (0 2 /(C x F y +0 2 )) on the concentration of emission gases.
• the bars in each group indicate emission concentrations of C 4 F 8 , C 2 F 6 , C 3 F 8 , CF 4 and COF 2 .
• the C 4 F 8 flow rates was 93.75 seem, 125 seem, 187.5 seem or 250 seem, as shown at axis X of the Figure.
• the corresponding 0 2 flow rates are 656, 875, 1313 and 1750 seem, respectively.
• the total feeding gas flow rate was fixed at 4000 seem by adjusting Argon flow. Chamber pressure was 2 torr.
• the feeding gas was activated by 400 KHz RF power to a neutral temperature of more than 5000 K.
• the activated gas then entered the process chamber and etched the Si0 2 surface deposits on the mou nting with the temperature controlled at 100° C.
• FTIR was used to measure the concentration of emission species in the pump exhaust.
• the C 4 F 8 flow rates was 250 seem.
• the 0 2 flow rate was 250, 375 , 750, 1000, 1417, 2250 and 2875 seem, indicated as 0 2 percentage at axis X of the Figure.
• the total feeding gas flow rate was fixed at 40O0 seem by adjusting Argon flow. Chamber pressure was 2 torr.
• the feeding gas was activated by 400 KHz RF power to a neutral temperature of more than 5000 K.
• the activated gas then entered the process chamber and etched the Si0 2 surface deposits on the mounting with the temperature controlled at 100° C.
• FTIR was used to measure the concentration of emission species in the pump exhaust.
• Figure 4a the perfluorocarbon emission was measured when C 4 F 8 flow rate was varied while 0 2 pe rcentage was kept at the optimum condition. No measurable perfluorocarbon emission was detected.
• Figure 4b demonstrates that when 0 2 percentages were close to or higher than the optimum value, no measurable perfluorocarbon emission was detected under the current inventive conditions. However, when 0 2 percentages were much lower than the optimum value, perfluorocarbon emissions began to appear.
• Figure 5a and 5fc> are the X-ray Photoelectron Spectroscopy (XPS) of the sapphire surfaces.
• Figure 6a, 6b, and 6c are Atomic Force Microscope (AFM) measurements of sapphire surfaces.
• the feeding gas composed of 2233 seem of 0 2 , 667 se m of C 2 F ⁇ and 1100 seem of Ar. Chamber pressure is 2 torr.
• the feeding gas was activated by 400 KHz RF power to a neutral temperature of more than 5000 K.
• Figure 6a was the measurement of the sapphire surface efore exposure and Figure 6b was the measurement of the sapphire surface after a 10 minute exposure. Figures 6a and 6b show no measurable changes, indicating no significant perfluorocarbon polymer deposition on the sapphire surface.
• Figure 5b was the measurement of the sapphire surface after a 10 minute exposure to the oxygen-free activated gas. With no O2 in the feeding gas, only signals of carbon and fluorine were observed in Figure 5b, indicating a deposition of a perfluorocarbon polymer film that covered the sapphire sufficiently that the substrate could not be seen. This result was confirmed by AFM measurement of Figure 6c where the smooth surface suggested the deposition of a perfluorocarbon polymer film on the surface.

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