Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/42—Stripping or agents therefor
  • G03F7/422—Stripping or agents therefor using liquids only
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/02—Cleaning by the force of jets or sprays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/044—Cleaning involving contact with liquid using agitated containers in which the liquid and articles or material are placed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
• • 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
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/42—Stripping or agents therefor
  • G03F7/427—Stripping or agents therefor using plasma means only
• • 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
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02041—Cleaning
  • H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
  • H01L21/02052—Wet cleaning only
• • 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
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/3105—After-treatment
  • H01L21/311—Etching the insulating layers by chemical or physical means
  • H01L21/31105—Etching inorganic layers
  • H01L21/31111—Etching inorganic layers by chemical means
• • 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
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/3105—After-treatment
  • H01L21/311—Etching the insulating layers by chemical or physical means
  • H01L21/31127—Etching organic layers
  • H01L21/31133—Etching organic layers by chemical means
• • 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
  • H01L21/67028—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like
  • H01L21/6704—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing
  • H01L21/67051—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing using mainly spraying means, e.g. nozzles
• • 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
  • H01L21/67075—Apparatus for fluid treatment for etching for wet etching
  • H01L21/6708—Apparatus for fluid treatment for etching for wet etching using mainly spraying means, e.g. nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B2203/00—Details of cleaning machines or methods involving the use or presence of liquid or steam
  • B08B2203/005—Details of cleaning machines or methods involving the use or presence of liquid or steam the liquid being ozonated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B2203/00—Details of cleaning machines or methods involving the use or presence of liquid or steam
  • B08B2203/007—Heating the liquid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B2230/00—Other cleaning aspects applicable to all B08B range
  • B08B2230/01—Cleaning with steam

Definitions

• the first step of the RCA cleaning sequence involves removal of organic contamination using sulfuric acid and hydrogen peroxide mixtures. Ratios are typically in the range of 2:1 to 20:1, with temperatures in the range of 90 - 140 degrees Celsius. This mixture is commonly called "piranha.” A recent enhancement to the removal of organic contamination replaces the hydrogen peroxide with ozone that is bubbled or injected into the sulfuric acid line.
• the second step of the process involves removal of oxide films with water and HF (49%) in ratios of 200:1 to 10:1, usually at ambient temperatures. This processing typically leaves regions of the wafer in a hydrophobic condition.
• the next step of the process involves the removal of particles and the re-oxidation of hydrophobic silicon surfaces using a mixture of water, hydrogen peroxide, and ammonium hydroxide, usually at a temperature of about 60 - 70 degrees Celsius. Historically, ratios of these components have been on the order of 5:1:1. In recent years, that ratio has more commonly become 5:1:0.25, or even more dilute. This mixture is commonly called “SCI” (standard clean 1) or RCA1 Alternatively, it is also known as HUANG 1.
• pre- diffusion clean Such a pre-diffusion clean insures that wafers are in a highly clean state prior to thermal operations which might incorporate impurities into the device layer or cause them to diffuse in such a manner as to render the device useless.
• this four-step cleaning process is considered to be the standard cleaning process in the semiconductor industry, there are many variations of the process that use the same sub-components.
• the piranha solution may be dropped from the process, resulting in a processing sequence of: HF ->SC1 ->SC2.
• thin oxides have been cause for concern in device performance, so "hydrochloric acid last" chemistries have been developed.
• one or more of the above-noted cleaning steps are employed with the final clean including hydrochloric acid in order to remove the silicon backside from the wafer surface.
• HF immersion processes on bare silicon wafers can be configured to be particle neutral.
• HF spraying on bare silicon wafers typically shows particle additions of a few hundred or more for particles at 0.2 microns nominal diameter.
• a novel chemistry, application technique, and system is used to reduce the contamination and speed up processing in the manufacturing of semiconductor wafers, memory disks, photomasks, optical media, and other substrates (collectively referred to here as "wafers") requiring a high level of clean. Contamination can result from organics, particles, metal/ions, and silicon dioxide.
• Cleaning of wafers is accomplished by delivery of a chemical stream to the workpiece surface. Ozone is delivered either into the liquid process stream or into the process environment.
• the chemical stream which may be in the form of a liquid or vapor, is applied to the wafer in a system which enables control of the boundary layer which forms on the workpiece surface.
• the chemical stream may include ammonium hydroxide for simultaneous particle and organic removal, another chemical to raise the pH of the solution, or other chemical additives designed to accomplish one or more specific cleaning steps.
• Wafers are preferably placed in a standard Teflon wafer cassette, or in a process chamber utilizing a carrierless rotor design.
• the cassette or wafers are placed in an enclosed environment, such as a processing chamber of a centrifugal processing apparatus. During processing, the wafers and/or cassette are preferably rotated in the chamber.
• a processing solution is preferably sprayed from a temperature controlled, re-circulating chemical tank onto the wafer surface. This heats the surfaces of the wafers as well as the environment. If the spray is shut off, a thin liquid film remains on the wafer surfaces. However, preferably the liquid spray is continued for the duration of the chemical process step. If the wafer surface is hydrophobic, a surfactant may be added to the liquid chemical to create a thin film of liquid on the surfaces.
• the boundary layer of the processing solution at the wafer surface is advantageously controlled through the use of the rotation rate, the flow rate of the processing solution, and/or the injection technique (nozzle design) used to deliver the liquid (or steam) stream to the surfaces of the wafers.
• Ozone is concurrently injected into the enclosed chamber during the liquid spray, either through the same manifold as the liquid delivery or through a separate manifold. Ozone injection may continue after the spray has shut off. If the wafer surfaces begin to dry (as in the case of a non-continuous spray), a brief spray may be used to replenish the liquid. This insures that the exposed wafer surfaces remain wetted at all times and that the elevated temperature at the wafer surfaces is also maintained. The process may also be used on a single wafer, rather than on an entire batch. While ozone has a limited solubility in the hot liquid solution, it is still able to diffuse through the solution and react with the surface of the wafer (whether it is silicon, photoresist, etc.) at the liquid/solid interface.
• diffusion rather than dissolution, is the primary mechanism used to deliver ozone to the surfaces of the wafers.
• Water apparently helps to hydrolyze carbon-carbon bonds or accelerate the oxidation of silicon surfaces by hydrolyzing silicon-hydrogen or silicon-hydroxyl bonds.
• the elevated temperature promotes the reaction kinetics and the high concentration of ozone in the gas phase promotes diffusion of the ozone through the liquid film even though the increased temperature of the liquid film does not result in a solution having a high concentration of ozone dissolved in it.
• the flow of ozone can be delivered to the process chamber through a vapor generator or the like. Such a generator is filled with water, which is temperature controlled.
• the ozone gas stream is enriched with water vapor which maintains the boundary layer on each wafer surface at a minimal thickness so that the layer does not inhibit diffusion. At the same time, such delivery assists in preventing the wafers from drying completely during the process.
• a high capacity ozone generator is preferably used to produce a mixed effluent containing a high concentration of ozone in combination with a high flow rate.
• a higher concentration of ozone increases the quantity of ozone provided to the surface of the wafer.
• a higher flow rate increases the rate at which fresh reactants are replenished, and spent or exhausted reactants are carried away from the wafer.
• wafer rotational speeds are in the range of 10 - 100 rpm. Such low speeds tend to allow a thick boundary layer of liquid to build up on the surfaces of the wafers to create a diffusion barrier, which, in turn, inhibits the reaction rate. It has been found, however, that a continuous spray of liquid, such as the de-ionized water that is heated to maintain the surface temperature of the wafers, combined with high rotational speeds (> 300 rpm), generates a very thin boundary layer that minimizes the diffusion layer thickness thereby leading to an enhanced stripping rate. It has also been found that increases in the rotational rate of the wafers during processing results in a corresponding increase in the strip rate.
• the temperature of the liquid supply can be heated to generate a supply of saturated steam under pressure to the process chamber.
• a steam generator may be used to pressurize the process chamber to achieve the desired temperatures.
• saturated steam at 126 degrees Celsius may be used with a corresponding increase in the pressure of the process chamber to 240 K Pa (35 psia).
• the increased pressure within the processing chamber also provides for use of higher ozone concentrations, thereby generating a higher diffusion gradient across the boundary layer at the surface of each wafer.
• the use of steam also allows for the use of lower rotation rates to achieve the requisite thin boundary layers at the surfaces of the wafers.
• the oxidation rate of the ozone may also be enhanced by irradiating the surfaces of the wafers with ultra-violet light.
• the invention allows particles, metals, and organics to be removed in a single processing step. Further, it is now possible to regenerate a fresh, clean, controlled chemical oxide film in that same step.
• certain additives may be provided in the processing liquid to specifically target certain contaminants and/or to enhance the effectiveness of the overall process.
• ammonium hydroxide may be added to the processing liquid (e.g., deionized water) to reduce particle counts on the workpieces. In such a process, the ozone prevents pitting of the silicon surface by the ammonium hydroxide.
• Other additives that enhance the cleaning capability of the overall process include HF and HC1.
• Such additives have the following benefits/effects: 1) removal of organic contaminants; 2) removal of oxide and regeneration of a controlled chemical oxide; 3) removal of particles; 4) removal of metals.
• the wafers are prepared for subsequent cleaning steps.
• the wafers are preferably rinsed with deionized water or a suitable aqueous solution.
• the ozone within the processing chamber may also be purged with, for example, a nitrogen flush.
• metal and/or silicon dioxide may be removed from the surfaces of the wafers by applying a temperature controlled mixture containing hydrofluoric acid and/or hydrochloric acid, chloroacetic acid, or other halogenated chemistry.
• Ozone may or may not be introduced into the liquid stream or the process environment during this step.
• the wafers are subject to a final rinsing in deionized water or an aqueous solution.
• the wafers may be dried in a manner that may include the use of heated nitrogen, another inert gas flow, or organic vapors. Additionally, the wafers may be rotated during the drying process.
• the disclosed process is applicable to various manufacturing steps that require cleaning or selective removal of contaminants from the surface of a workpiece.
• one or more of the steps may be used to remove photoresist from the surface of a semiconductor wafer.
• a layer of photoresist and a corresponding layer of an anti-reflective coating (ARC) may be removed in a single processing step using a single processing solution.
• An aqueous solution having a high pH such as a solution of ammonium hydroxide and/or tetra-methyl ammonium hydroxide and deionized water, may be used to form a controlled boundary layer that cooperate with ozone to remove both the photoresist and the anti-reflective coating.
• Novel aspects include:
• the boundary layer may be controlled through the control of wafer rotation rate, vapor delivery, controlled liquid spray, the use of steam, the use of surfactants or a combination of more than one of these techniques.
• the process utilizes a mixed effluent having a higher concentration of ozone in combination with a higher flow rate for increasing the rate at which fresh reactants are supplied to the surface of the wafer.
• the invention resides as well in sub-combinations of the methods and apparatus
• Fig. 1 is a schematic block diagram of one embodiment of an apparatus for treating a semiconductor workpiece in which ozone is injected into a line containing a pressurized treatment liquid.
• Fig. 2 is a schematic block diagram of one embodiment of an apparatus for treating a semiconductor workpiece in which the semiconductor workpiece is indirectly heated by heating a treatment liquid that is sprayed on the surface of the workpiece.
• Fig. 3 is a flow diagram illustrating one embodiment of a process flow for treating a semiconductor workpiece with a treatment fluid and ozone.
• Fig. 4 is a schematic block diagram of an alternative embodiment of the system set forth in Fig. 2 wherein the ozone and treatment fluid are provided to the semiconductor workpiece along different flow paths.
• Fig. 5 is a schematic block diagram of an embodiment of an apparatus for treating a semiconductor workpiece in which pressurized steam and ozone are provided in a pressurized chamber containing a semiconductor workpiece.
• Fig. 6 is a schematic block diagram of an embodiment of an apparatus for treating a semiconductor workpiece in which an ultra-violet lamp is used to enhance the kinetic reactions at the surface of the workpiece.
• Fig. 7 is a schematic block diagram of an embodiment of an apparatus for treating a semiconductor workpiece in which liquid gas contactors are used to enhance the kinetic reactions at the surface of the workpiece.
• the preferred embodiment of the apparatus comprises a liquid supply line that is used to provide fluid commumcation between a reservoir containing the treatment liquid and a treatment chamber housing the semiconductor workpiece.
• a heater heats the workpiece, either directly or indirectly.
• the workpiece is heated by heating the treatment liquid that is supplied to the workpiece.
• One or more nozzles accept the treatment liquid from the liquid supply line and spray it onto the surface of the workpiece while an ozone generator provides ozone into an environment containing the workpiece.
• the treatment system shown generally at 10, includes a treatment chamber 15 that contains one or more workpieces 20, such as semiconductor wafer workpieces.
• a treatment chamber 15 that contains one or more workpieces 20, such as semiconductor wafer workpieces.
• workpieces 20 such as semiconductor wafer workpieces.
• the illustrated system is directed to a batch workpiece apparatus, it is readily adaptable for use in single workpiece processing as well.
• the semiconductor workpieces 20 are preferably supported within the chamber 15 by one or more supports 25 extending from, for example, a rotor assembly 30.
• Rotor assembly 30 may seal with the housing of the treatment chamber 15 to form a sealed, closed processing environment. Further, rotor assembly 30 is provided so that the semiconductor workpieces 20 may be spun about axis 35 during or after treatment with the ozone and treatment liquid.
• the chamber 15 has a volume which is minimized, and is as small as permitted by design considerations for any given capacity (i.e., the number and size of the substrates to be treated).
• the chamber 15 is preferably cylindrical for processing multiple wafers in a batch, or a flatter disk-shaped chamber may be used for single wafer processing. Typically, the chamber volume will range from about 5 liters, (for a single wafer) to about 50 liters (for a 50 wafer system).
• One or more nozzles 40 are disposed within the treatment chamber 15 to direct a spray mixture of ozone and treatment liquid onto the surfaces of the semiconductor workpieces 20 that are to be treated.
• the nozzles 40 direct a spray of treatment fluid to the underside of the semiconductor workpieces 20.
• the fluid spray may be directed alternatively, or in addition, to the upper surface of the semiconductor workpieces 20.
• the fluid may also be applied in other ways besides spraying, such as flouring, bulk deposition, immersion, etc.
• Treatment liquid and ozone are preferably supplied to the nozzles 40 by system components uniquely arranged to provide a single fluid line comprising ozone mixed with the treating liquid.
• a reservoir 45 defines a chamber 50 in which the liquid that is to be mixed with the ozone is stored.
• the chamber 50 is in fluid communication with, or connected to, the input of a pump mechanism 55.
• the pump mechanism 55 provides the liquid under pressure along a fluid flow path, shown generally at 60, for ultimate supply to the input of the nozzles 40.
• the preferred treatment fluid is deionized water. Other treatment fluids, such as other aqueous or non-aqueous solutions, may also be used.
• Fluid flow path 60 may include a filter 65 to filter out microscopic contaminants from the treatment fluid.
• the treatment fluid still under pressure, is provided at the output of the filter 65 (if used) along fluid flow line 70.
• Ozone is injected along fluid flow line 70.
• the ozone is generated by ozone generator 75 and is supplied along fluid flow line 80 under pressure to fluid flow line 70.
• the treatment liquid now injected with ozone, is supplied to the input of a mixer 90 that mixes the ozone and the treatment liquid.
• the mixer 90 may be static or active.
• the treatment liquid and ozone are provided to be input of nozzles 40 which, in turn, spray the liquid on the surface of the semiconductor workpieces 20 that are to be treated and, further, introduce the ozone into the environment of the treatment chamber 15.
• an output of the ozone generator 75 may be supplied to a dispersion unit 95 disposed in the liquid chamber 50 of the reservoir 45.
• the dispersion unit 95 provides a dispersed flow of ozone through the treatment liquid to thereby add ozone to the fluid stream prior to injection of a further amount of ozone along the fluid path 60.
• spent liquid in chamber 15 is provided along fluid line 105 to, for example, a valve mechanism 110.
• the valve mechanism 110 may be operated to provide the spent liquid to either a drain output 115 or back to the liquid chamber 50 of the reservoir 45. Repeated cycling of the treatment liquid through the system and back to the reservoir 45 assists in elevating the ozone concentration in the liquid through repeated ozone injection and/or ozone dispersion.
• the ozone generator 75 is preferably a high capacity ozone generator.
• a high capacity ozone generator is the ASTeX 8403 Ozone Generator, manufactured by Applied Science and Technology, Inc., Woburn, Massachusetts, U.S.A.
• the ASTeX 8403 has an ozone production rating of 160 grams per hour. At this rate a flow of approximately 12 liters/minute and having a concentration of 19% ozone, by weight, can be supported.
• Another example of a suitable high capacity ozone generator is the Sumitomo GR-RL Ozone Generator, manufactured by Sumitomo Precision Products Co., Ltd., Hyogo, Japan which has an ozone production rating of 180g/hr.
• the ozone generator 75 preferably has a capacity of at least 90 or 100 grams per hour, or 110 or 120 grams per hour, with the capacity more preferably of at least 135 grams per hour. In terms of flow rate and concentration, the capacity should be at least 10 liters per minute at 12%, 13%, 14%, 15%) (or higher) concentration by weight. Lower flow rate applications, such as with single wafer processing, may have higher concentrations of 16-19% or higher. Use of a high capacity ozone generator is especially useful in connection with the methods and apparatus of the present application, because the present methods and apparatus provide for the delivery of ozone independent of the processing fluid.
• Fig. 1 (as well as the other Figures) illustrates various components and connections. While showing preferred designs, the drawings include elements which may or may not be essential to the invention. The elements essential to the invention are set forth in the claims. The drawings show both essential and non-essential elements.
• FIG. 2 A further embodiment of a system for delivering a fluid mixture for treating the surface of a semiconductor workpiece is illustrated in Fig. 2.
• the system 120 of Fig. 2 appears to be substantially similar to the system 10 of Fig. 1, there are significant differences.
• the system 120 of Fig. 2 is based in part on the concept that the heating of the surfaces of the semiconductor workpieces 20 with a heated liquid that is supplied along with a flow of ozone that creates an ozonated atmosphere is highly effective in photoresist stripping, ash removal, and/or cleaning processes.
• the system 120 therefore preferably includes one or more heaters 125 that are used to heat the treatment liquid so that it is supplied to the surfaces of the semiconductor workpieces at an elevated temperature that accelerates the surface reactions.
• supports 25 may include heating elements that may be used to heat the workpieces 20.
• the chamber 15 may include a heater for elevating the temperature of the chamber environment and workpieces.
• the preferred treatment liquid is deionized water, since it appears to be required to initiate the cleaning/removal reactions at the workpiece surface, apparently through hydrolysis of the carbon-carbon bonds of organic molecules.
• significant amounts of water can form a continuous film on the semiconductor workpiece surface. This film acts as a diffusion barrier to the ozone, thereby inhibiting reaction rates.
• the boundary layer thickness is controlled by controlling the rpm of the semiconductor workpiece, vapor delivery, and controlled spraying of the treatment liquid, or a combination of one or more of these techniques. By reducing the boundary layer thickness, the ozone is allowed to diffuse to the surface of the workpieces and react with the organic materials that are to be removed.
• Fig. 3 illustrates one embodiment of a process that may be implemented in the system of Fig.
• the workpieces 20 that are to be stripped are placed in, for example, a Teflon wafer cassette.
• This cassette is placed in a closed environment, such as in chamber 15.
• Chamber 15 and its corresponding components may be constructed based on a well known spray solvent system or spray acid such as those available from Semitool, Inc., of Kalispell, Montana, U.S.A..
• the semiconductor workpieces 20 may be disposed in chamber 15 in a carrierless manner, with an automated processing system, such as described in U.S. Patent No. 5,784,797.
• heated deionized water is sprayed onto the surfaces of the semiconductor workpieces 20.
• the heated deionized water heats the surfaces of the semiconductor workpieces 20 as well as the enclosed environment of the chamber 15.
• a thin liquid film remains on the workpiece surfaces.
• a surfactant may be added to the deionized water to assist in creating a thin liquid boundary layer on the workpiece surfaces.
• the surfactant may be used in connection with hydrophilic surfaces as well.
• Corrosion inhibitors may also be used with the aqueous ozone, thin boundary layer process.
• the surface boundary layer of deionized water is controlled at step 210 using one or more techniques.
• the semiconductor workpieces 20 may be rotated about axis 35 by rotor 30 to thereby generate centripetal accelerations that thin the boundary layer.
• the flow rate of the deionized water may also be used to control the thickness of the surface boundary layer. Lowering of the flow rate results in decreased boundary layer thickness.
• the manner in which the deionized water is injected into the chamber 15 may be used to control the boundary layer thickness.
• Nozzles 40 may be designed to provide the deionized water as micro-droplets thereby resulting in a thin boundary layer.
• ozone is injected into the fluid flow path 60 during the water spray, or otherwise provided to the internal chamber environment of chamber 15. If the apparatus of Fig. 2 is utilized, the injection of the ozone continues after the spray has shut off. If the workpiece surface begins to dry, a brief spray is preferably activated to replenish the liquid film on the workpiece surface. This ensures that the exposed workpiece surfaces remain wetted at all times and, further, ensures that the workpiece temperature is and remains elevated at the desired reaction temperature.
• the surface layer thickness may range from a few molecular layers (e.g., about 1 micron), up to 100 microns, (typically 50-100 microns), or greater.
• ozone has a limited solubility in the heated deionized water, the ozone is able to diffuse through the water and react with photoresist at the liquid/resist interface. It is believed that the presence of the deionized water itself further assists in the reactions by hydrolyzing the carbon-carbon bonds of organic deposits, such as photoresist, on the surface of the wafer.
• the higher temperature promotes the reaction kinetics while the high concentration of ozone in the gas phase promotes diffusion of ozone through the boundary layer film even though the high temperature of the boundary layer film does not actually have a high concentration of dissolved ozone.
• Elevated or higher temperatures means temperatures above ambient or room temperature, that is temperatures above 20 or 25° and up to about 200°C. Preferred temperature ranges are 25-150°, more preferably 55-120° or 75-115°C, and still more preferably 85-105°C. In the methods described, temperatures of 90-100°C, and preferably centering around 95°C may be used.
• the workpieces are subject to a rinse at 220 and are dried at step 225.
• the workpieces may be sprayed with a flow of deionized water during the rinse at step 220. They may then be subject to any one or more known drying techniques thereafter at step 225.
• elevated temperatures are used to accelerate the reaction rates at the wafer surface.
• One manner in which the surface temperature of the wafer may be maximized is to maintain a constant delivery of heated processing liquid, such as water or steam, during the process.
• heated processing liquid contacts and heats the wafer during processing.
• a constant delivery may result in significant waste of the water or other processing liquid.
• a "pulsed flow" of liquid or steam may be used.
• an alternative manner of maintaining the wafer surface temperature may be needed.
• One such alternative is the use of a "hot wall” reactor that maintains the wafer surface and processing environment temperatures at the desired level.
• the process chamber may be heated by, for example, one or more embedded heated recirculating coils, a heating blanket, irradiation from a thermal source (e.g., and infrared lamp), etc.
• a thermal source e.g., and infrared lamp
• the processing chamber was pre-heated by spraying deionized water that was heated to 95 degrees Celsius into the processing chamber for 10 minutes. During the cleaning process, a pulsed flow of deionized water heated to 95 degrees Celsius was used. The pulsed flow included an "on time" of approximately five seconds followed by an "off time” of 10 seconds.
• the wafer was rotated at 800 rpm and the pulsed flow of deionized water was sprayed into the processing chamber through nine nozzles at a rate of 3 liters per minute. Ozone was injected into the processing chamber through a separate manifold at a rate of 8 liters per minute at a concentration of 12 percent. The resultant strip rate was 7234 Angstroms/min.
• the resultant strip rates can be further increased to in excess of 8800 Angstroms/minute.
• One of the most significant benefits is that the conventional 4- chem clean process may be reduced to a two-chemical step process while retaining the ability to remove organics, remove particulates, reduce metals and remove silicon dioxide. Process times, chemical consumption, water consumption and waste generation are all also significantly reduced.
• a further benefit of the foregoing process is its applicability to both FEOL and BEOL wafers and strip processes.
• a still further benefit is the higher ozone flow rates and concentrations can be used to produce higher strip rates under various processing conditions including lower wafer rotational speeds and reduced temperatures.
• Use of lower temperatures between 25 and 75°C and preferably from 25-65°C (rather than at e.g., 95°C as described above) may be useful where higher temperatures are undesirable.
• One example where this is beneficial is the use of the process with BEOL wafers, wherein metal corrosion may occur if the metal films are exposed to high temperature de-ionized water.
• the gain in strip rates not realized, as a result of not using higher temperatures can be offset by increases in strip rate due to the increased ozone flow rates and concentrations.
• the use of higher ozone concentration can offset the loss of kinetic energy from using lower temperatures.
• process steps 205 - 215 may be executed in a substantially concurrent manner. Additionally, it will be recognized that process steps 205 - 215 may be sequentially repeated using different processing liquids. In such instances, each of the processing liquids that are used may be specifically tailored to remove a respective set of contaminants. Preferably, however, it is desirable to use as few different processing liquids as possible. By reducing the number of different processing liquids utilized, the overall cleaning process is simplified and reducing the number of different processing liquids utilized minimizes chemical consumption.
• a single processing liquid may be used to remove organic contaminants, metals, and particles in a single cycle of process steps 205-215.
• the processing liquid is comprised of a solution of deionized water and one or more compounds, such as HF or HC1, so as to form an acidic processing liquid solution.
• hydrofluoric acid solution in the process steps set forth at 205-215 provides numerous advantages, including the following: 1. Removal of organic contaminants - The oxidation capability of the process has been demonstrated repeatedly on photoresist. Strip rates often exceed 8800 A/minute. Considering the fact that in cleaning applications, organic contamination is generally on the molecular level, the disclosed process has ample oxidation capacity. 2. Removal of oxide and regeneration of a controlled chemical oxide - Depending on the temperature of the solution and the concentration of HF in solution, a specific etch rate may be defined. However, the ozone will diffuse through the controlled boundary layer and regenerate the oxide to prevent the wafer from becoming hydrophobic.
• a 500:1 H 2 0:HF mixture at 65 degrees C will etch Si0 2 at a rate of about 6A/minute.
• the same solution at 25 degrees C will etch Si0 at about 2A/minute.
• a typical "native" oxide is generally self limiting at a thickness of 8 - 12 A, which is generally the targeted thickness for the oxide removal.
• An oxide-free (hydrophobic) surface may be generated, if desired, by using a final HF step in an immersion cell or by use of an HF vapor step after the metals removal.
• the uniformity of the thickness of the liquid boundary layer on the wafer or workpiece becomes important in providing uniform etching across the wafer.
• Thin spots in the boundary layer will etch more slowly, and hence are preferably avoided.
• the rpm speed is preferably reduced into the range of 5-100 ⁇ m, preferably 10-80 ⁇ m or 20-70 ⁇ m, and more preferably 25-50 ⁇ m (for workpieces typically having a diameter or edge dimension of e.g., 100-400 or 200 or 300 mm).
• the lower ⁇ m provides a thicker boundary layer, providing more uniform processing. If other boundary layer controls are used, such as flow rate or spray control, similar adjustments are preferably made for use of HF, or when using HC1 and HF.
• the HC1 or HF may be provided in a solution injected into the process liquid, or provided into the chamber as a dry gas.
• the boundary layer is preferably maintained thick enough to achieve good etch uniformity, by selecting flow rates of liquid onto the workpiece surface, and removal rates of liquid from the workpiece surface.
• the boundary layer of the liquid on the workpiece surface is preferably maintained thick enough so that the etch uniformity is on the order of less than 5%, and preferably less than 3% or 2% ( 3-sigma divided by the mean).
• the ozone concentration is preferably about 3 - 35% or 10-20% by weight (in oxygen).
• the ozone concentration is largely dependent on the etch rate of the aqueous HF solution used.
• HF concentration used is typically .001 to 10% or .01 to 1.0% (by weight). In general, the lower concentrations are preferred, with a concentration of about 0.1 % providing very good cleaning performance (with an etch rate of 8A of thermal oxide per minute at 95C).
• the HF solution may include hydrochloric acid to enhance metal removal capability. If used, the HC1 typically has a range of concentrations similar to the ranges described above for HF.
• a temperature range from 0°C up to 100°C may be used. Higher temperatures may be used if the process is conducted under pressure. Particle removal capability of this process is enhanced at elevated temperatures. At ambient temperature, the particle removal efficiency of dried silicon dioxide slurry particles with starting counts of around 60,000 particles larger than 0.15 microns, was about 95%). At 65°C, this efficiency increased to 99%). At 95°C, the efficiency increased to 99.7%). Although this may appear to be a slight improvement, the difference in final particle count went from 3000 to 300 to about 100 particles, which can be very significant in the manufacture of semiconductor devices.
• the HF and ozone process may be included as part of a cleaning sequence, for example: 3:00 ( minutes ) of HF/O3 > 3:00 SCI > 3:00 HF/O3.
• the cleaning efficiency increased to over 99.9%.
• the SCI alone had a cleaning efficiency of only 50% or less. Similar results have been achieved when cleaning silicon nitride particles as well.
• Typical chemical application times are in the range of 1:00 to 5:00 minutes. Compared to a 4-chem clean process time of around 20:00 minutes, the disclosed process with an HF and/or HC1 containing processing liquid becomes very attractive.
• Typical H 2 0:HF:HCI concentration ratios are on the order of 500: 1 :1 to 50: 1 : 1, with and without HF and/or HC1. Higher concentrations are possible, but the economic benefits are diminished. It is important to note that gaseous HF or HCI could be injected into water to create the desired cleaning chemistry as well. Due to differences in processor configurations and desired cleaning requirements, definition of specific cleaning process parameters will vary based on these differences and requirements.
• the process benefits include the following:
• aqueous ozone processes show a strip rate on photoresist (a hydrocarbon film) of around 200 - 700 angstroms per minute.
• photoresist a hydrocarbon film
• the rate is accelerated to 2500 to 8800. angstroms per minute in a spray controlled boundary layer, or higher when the boundary layer is generated and controlled using steam at 15 psi and 126 degrees C.
• the disclosed processes are suitable for use in a wide range of microelectronic fabrication applications.
• One issue which is of concern in the manufacture of semiconductor devices is reflective notching.
• the wafer In order to expose a pattern on a semiconductor wafer, the wafer is coated with a photo-active compound called photoresist.
• the resistance film is exposed to a light pattern, thereby "exposing" the regions to which the light is conveyed.
• topographic features may exist under the photoresist, it is possible for the light to pass through the photoresist and reflect off of a topographic feature. This results in resist exposure in an undesirable region. This phenomenon is known as "reflective notching.” As device density increases, reflective notching becomes more of a problem.
• the process of Figure 3 may be used with a processing liquid comprised of water and ammonium hydroxide to remove both the photoresist and the anti- reflective coating in a single processing step (e.g., the steps illustrated at 210-215). Although this has been demonstrated at concentrations between 0.02% and 0.04% ammomum hydroxide by weight in water, other concentrations are also considered to be viable.
• the process for concurrently removing photoresist and the corresponding anti- reflective layer is not necessarily restricted to processing liquids that include ammonium hydroxide. Rather, the principal goal of the additive is to elevate the pH of the solution that is sprayed onto the wafer surface. Preferably, the pH should be raised so that it is between about 8.5 and 11. Although bases such as sodium hydroxide and/or potassium hydroxide may be used for such removal, they are deemed to be less desirable due to concerns over mobile ion contamination. However, chemistries such as TMAH (tetra- methyl ammonium hydroxide) are suitable and do not elicit the same a mobile ion contamination concerns. Ionized water that is rich in hydroxyl radicals may also be used.
• bases such as sodium hydroxide and/or potassium hydroxide may be used for such removal, they are deemed to be less desirable due to concerns over mobile ion contamination.
• chemistries such as TMAH (tetra- methyl ammonium hydroxide) are suitable and
• the dilute ammonium hydroxide solution may be applied in the process in any number of manners.
• syringe pumps or other precision chemical applicators, can be used to enable single-use of the solution stream.
• the application apparatus may also be capable of monitoring and controlling the pH the using the appropriate sensors and actuators, for example, by use of microprocessor control.
• nozzles 230 are disposed within the treatment chamber 15 to conduct ozone from ozone generator 75 directly into the reaction environment.
• the heated treatment fluid is provided to the chamber 15 through nozzles 40 that receive the treatment fluid, such as heated deionized water, through a supply line that is separate from the ozone supply line.
• injection of ozone in fluid path 60 is optional.
• FIG. 5 Another embodiment of an ozone treatment system is shown generally at 250 in Fig. 5.
• a steam boiler 260 that supplies saturated steam under pressure to the process chamber 15 has replaced the pump mechanism.
• the reaction chamber 15 is preferably sealed to thereby form a pressurized atmosphere for the reactions.
• saturated steam at 126 degrees Celsius could be generated by steam boiler 260 and supplied to reaction chamber 15 to generate a pressure of 35 psia therein during the workpiece processing.
• Ozone may be directly injected into the chamber 15 as shown, and/or may be injected into the path 60 for concurrent supply with the steam.
• the steam generator in Fig. 5 may be replaced with a heater(s) as shown in Figs. 1-4. While Figs. 4 and 5 show the fluid and ozone delivered via separate nozzles 40, they may also be delivered from the same nozzles, using appropriate valves.
• an ultra-violet or infrared lamp 300 is used to irradiate the surface of the semiconductor workpiece 20 during processing. Such irradiation further enhances the reaction kinetics.
• this irradiation technique is applicable to batch semiconductor workpiece processing, it is more easily and economically implemented in the illustrated single wafer processing environment where the workpiece is more easily completely exposed to the UV radiation. Megasonic or ultrasonic nozzles 40 may also be used.
• a further system 310 for implementing one or more of the foregoing processes is set forth.
• system 3 10 is the use of one or more liquid-gas contactors 315 that are used to promote the dissolution of ozone into the aqueous stream.
• Such contactors are of particular benefit when the temperature of the processing liquid is, for example, at or near ambient. Such low temperatures may be required to control corrosion that may be promoted on films such as aluminum/silicon/copper.
• the contactor 315 is preferably of a parallel counter-flow design in which liquid is introduced into one end and the ozone gas is introduced into the opposite end.
• Such contactors are available from e.g., W. L. Gore Co ⁇ oration, Newark, Delaware, USA.
• contactors operate under pressure, typically from about 1 to 4 atmospheres (gauge).
• the undissolved gas exiting the contactor 315 may be optionally directed to the process chamber 320 to minimize gas losses.
• the ozone supply 330 for the contactor 315 may or may not be the same as the supply for direct delivery to the process chamber 320.
• the ozone gas may be separately sprayed, or otherwise introduced as a gas into the process chamber, where it can diffuse through the liquid boundary layer on the workpiece.
• the fluid is preferably heated and sprayed or otherwise applied to the workpiece, without ozone injected into the fluid before the fluid is applied to the workpiece.
• the ozone may be injected into the fluid, and then the ozone containing fluid applied to the workpiece.
• the heating preferably is performed before the ozone is injected into the fluid, to reduce the amount of ozone breakdown in the fluid during the fluid heating.
• the fluid will contain some dissolved ozone, and may also contain ozone bubbles.
• both embodiments that is to introduce ozone gas directly into the process chamber, and to also introduce ozone into the fluid before the fluid is delivered into the process chamber.
• various methods may be used for introducing ozone into the chamber.
• the presently disclosed apparatus and methods may be used to treat workpieces beyond the semiconductor workpieces described above.
• other workpieces such as flat panel displays, hard disk media, CD glass, etc, may also have their surfaces treated using the foregoing apparatus and methods.
• prefened treatment liquid for the disclosed application is deionized water
• other treatment liquids may also be used.
• acidic and basic solutions may be used, depending on the particular surface to be treated and the material that is to be removed.
• Treatment liquids comprising sulfuric acid, hydrochloric acid, and ammonium hydroxide may be useful in various applications.
• one aspect of the process is the use of steam (water vapor at temperatures exceeding 100C) to enhance the strip rate of photoresist in the presence of an ozone environment.
• steam water vapor at temperatures exceeding 100C
• Preliminary testing shows that a process using hot water at 95C produces a photoresist strip rate of around 3000 - 4000 angstroms per minute.
• Performing a similar process using steam at 120 - 130C results in a strip rate of around 7000 - 8000 angstroms per minute.
• the resultant strip rate is not sustainable.
• the high strip rate is achieved only when the steam condenses on the wafer surface.
• the wafer temperature rapidly approaches thermal equilibrium with the steam, and as equilibrium is achieved, there is no longer a thermal gradient to promote the formation of the condensate film. This results in the loss of the liquid boundary layer on the wafer surface.
• the boundary layer appears to be essential to promote the oxidation of the organic materials on the wafer surface.
• the absence of the liquid film results in a significant drop in the strip rate on photoresist.
• a method for maintaining the temperature of a surface such as a semiconductor wafer surface is provided to ensure that condensation from a steam environment continues indefinitely, thereby enabling the use of steam in applications such as photoresist strip in the presence of ozone.
• the formation of the liquid boundary layer is assured, as well as the release of significant amounts of energy as the steam condenses.
• the wafer surface must be maintained at a temperature lower than that of the steam delivered to the process chamber. This may be achieved by attaching the wafer to a temperature-controlled surface or plate 350 which will act as a heat sink. This surface may then be temperature controlled either through the use of cooling coils, a solid-state heat exchanger, or other means.
• a temperature-controlled stream of liquid is delivered to the back surface of a wafer, while steam and ozone are delivered to an enclosed process region and the steam is allowed to condense on the wafer surface.
• the wafer may be rotated to promote uniform distribution of the boundary layer, as well as helping to define the thickness of the boundary layer through centrifugal force. However, rotation is not an absolute requirement.
• the cooling stream must be at a temperature lower than the steam. If the cooling stream is water, a temperature of 75 or 85 - 95C is preferably used, with steam temperatures in excess of lOOC.
• pulsed spray of cooling liquid is applied periodically to reduce the wafer temperature.
• Steam delivery may either be continuous or pulsed as well.
• the wafer may be in any orientation and additives such as hydrofluoric acid, ammomum hydroxide or some other chemical may be added to the system to promote the cleaning of the surface or the removal of specific classes of materials other than or in addition to organic materials.
• additives such as hydrofluoric acid, ammomum hydroxide or some other chemical may be added to the system to promote the cleaning of the surface or the removal of specific classes of materials other than or in addition to organic materials.
• This process enables the use of temperatures greater than 100C to promote reaction kinetics in the water/ozone system for the pu ⁇ ose of removing organic or other materials from a surface. It helps ensure the continuous formation of a condensate film by preventing the surface from achieving thermal equilibrium with the steam. It also takes advantage of the liberated heat of vaporization in order to promote reaction rates and potentially allow the removal of more difficult materials which may require more energy than can be readily delivered in a hot water process.

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