Methods and apparatus for cleaning an object using an electron beam, and device-fabrication apparatus comprising same

Abstract

Apparatus and methods are disclosed for cleaning an object, such as a reticle or electron-optical component used in performing electron-beam microlithography, using an electron beam. The cleaning can be performed in the presence or absence of a treatment gas. When performed without a treatment gas, an electron beam is directed to impinge on the object at an energy sufficient to volatilize contaminant deposits on the object. When performed with a treatment gas, the electron beam need not be directed at the object, but electrons from the beam have an energy sufficient to ionize molecules of the treatment gas. The ionized molecules volatilize the contaminant deposits for removal using a vacuum pump. For example, the beam can be directed to a scattering body that produces scattered electrons having sufficient energy to volatilize the contaminant deposits.

What is claimed is:  
     
         1 . A contamination-removal device, comprising: 
 a treatment chamber defining an interior space in which an object, having a deposit of a contaminant substance and requiring cleaning to remove the deposit, can be situated;    a chamber-evacuation pump in communication with the treatment chamber, the chamber-evacuation device being configured to evacuate the interior space of the treatment chamber;    a gas-inlet in communication with the treatment chamber, the gas-inlet being configured to introduce a treatment gas into the interior space of the treatment chamber; and    an electron-beam irradiator situated and configured to irradiate an electron beam in the interior space of the treatment chamber such that the electron beam ionizes molecules of the treatment gas, and the ionized molecules of the treatment gas react with molecules of the contaminant substance on the object to volatilize the contaminant substance from the object.    
     
     
         2 . The contamination-removal device of  claim 1 , wherein the treatment gas comprises at least one gas selected from a group consisting of water vapor, oxygen, ozone, and oxygen radicals.  
     
     
         3 . The contamination-removal device of  claim 1 , further comprising a lens column and a wafer chamber, wherein the wafer chamber comprises the treatment chamber.  
     
     
         4 . The contamination-removal device of  claim 1 , wherein the lens column contains the electron-beam irradiator.  
     
     
         5 . The contamination-removal device of  claim 4 , further comprising an electron-optical system for illuminating the reticle with an electron beam.  
     
     
         6 . The contamination-removal device of  claim 5 , wherein: 
 the electron-optical system comprises the electron-beam irradiator; and    the electron-optical system is situated within the lens column.    
     
     
         7 . The contamination-removal device of  claim 3 , further comprising a scattering body situated within either the lens column or the wafer chamber so as to be bombarded with incident electrons from the electron-beam irradiator and form scattered electrons.  
     
     
         8 . A microelectronic-device fabrication apparatus, comprising the contamination-removal device of  claim 1 .  
     
     
         9 . An electron-beam microlithography apparatus, comprising: 
 a lens column containing an electron-optical system configured to illuminate a reticle with an electron beam;    a wafer chamber defining an interior space configured to enclose a substrate to be exposed with a pattern defined on the reticle and transferred to the substrate by the electron beam propagating from the reticle to the substrate;    at least one vacuum pump in communication with the lens column and wafer chamber, the vacuum pump being configured to evacuate the interior spaces of the lens column and wafer chamber;    a gas-inlet in communication with the wafer chamber, the gas-inlet being configured to introduce a treatment gas into the interior space of the wafer chamber; and    the wafer chamber being configured to contain a scattering body situated so as to be irradiated by the electron beam from the electron-optical system, the electron beam irradiating the scattering body causing the scattering body to produce scattered electrons that propagate to any of various locations in the wafer chamber and lens column to impinge on contaminant deposits at the various locations and to ionize molecules of the treatment gas introduced into the interior space, the ionized molecules reacting with and volatilizing the contaminant deposits.    
     
     
         10 . The apparatus of  claim 9 , further comprising an electron-beam source situated in the lens column.  
     
     
         11 . The apparatus of  claim 9 , wherein the treatment gas is at least one gas selected from a group consisting of water vapor, oxygen, ozone, and oxygen radicals.  
     
     
         12 . An electron-beam microlithography apparatus, comprising: 
 an electron-beam source;    a process chamber defining an interior space;    an electron-optical system situated in the process chamber relative to the electron-beam source and configured to direct an electron beam from the source to a substrate situated downstream of the source;    a wafer stage situated in the process chamber, the wafer stage being configured to hold the substrate as the substrate is being irradiated by the electron beam;    a treatment-gas source connected to and configured to introduce a treatment gas into the process chamber; and    an electron-scattering body situated in the process chamber, the electron-scattering body being positionable so as to be irradiated by the electron beam and produce, from such irradiation, scattered electrons that propagate to any of various locations in the process chamber to impinge on contaminant deposits at the various locations and to ionize molecules of the treatment gas introduced into the interior space, the ionized molecules reacting with and volatilizing the contaminant deposits.    
     
     
         13 . An electron-beam microlithography apparatus, comprising: 
 a process chamber defining an interior space;    an electron-optical system situated in the process chamber and comprising an electron-beam source, the electron-optical system being configured to irradiate a surface of a substrate selectively with an electron beam from the source;    a treatment-gas source connected to and configured to introduce a treatment gas into the process chamber; and    an electron-beam irradiation device situated in the process chamber separately from the electron-optical system, the electron-beam irradiation device being configured to produce a respective electron beam that impinges on the treatment gas in the process chamber so as to ionize molecules of the treatment gas, the ionized molecules being available to react with and volatilize a contaminant deposit in the process chamber.    
     
     
         14 . The apparatus of  claim 13 , wherein the treatment gas is at least one gas selected from a group consisting of water vapor, oxygen, ozone, and oxygen radicals.  
     
     
         15 . A method for removing a deposit of a contaminant in a process chamber of an apparatus that employs an electron beam to achieve a desired result, the method comprising the steps: 
 providing a treatment gas comprising molecules that become ionized when irradiated by electrons;    introducing molecules of the treatment gas into the process chamber;    when the process chamber contains molecules of the treatment gas, irradiating the molecules of the treatment gas in the process chamber with the electron beam to ionize the molecules of the treatment gas;    allowing the ionized molecules of the treatment gas to react with and volatilize the deposit; and    removing the volatilized deposit from the process chamber.    
     
     
         16 . The method of  claim 15 , wherein the step of removing the volatilized deposit from the process chamber comprises evacuating the process chamber.  
     
     
         17 . The method of  claim 15 , wherein the treatment gas is at least one gas selected from a group consisting of water vapor, oxygen, ozone, and oxygen radicals.  
     
     
         18 . A method for removing a deposit of a contaminant in a process chamber of an apparatus that employs an electron beam to achieve a desired result, the method comprising the steps: 
 providing a treatment gas comprising molecules that become ionized when irradiated by electrons;    introducing molecules of the treatment gas into the process chamber;    placing an electron-scattering body in the process chamber such that the electron beam can impinge on the electron-scattering body and thus cause the electron-scattering body to produce scattered electrons;    when the process chamber contains molecules of the treatment gas, irradiating the electron-scattering body with the electron beam to produce scattered electrons that ionize the molecules of the treatment gas; and    allowing the ionized molecules of the treatment gas to react with and volatilize the deposit.    
     
     
         19 . The method of  claim 18 , wherein the treatment gas is at least one gas selected from a group consisting of water vapor, oxygen, ozone, and oxygen radicals.  
     
     
         20 . A method for removing a deposit of a contaminant in a process chamber, comprising the steps: 
 providing a treatment gas comprising molecules that become ionized when irradiated by electrons;    introducing molecules of the treatment gas into the process chamber;    providing in the process chamber an electron-beam irradiation device configured to produce an electron beam;    placing an electron-scattering body in the process chamber such that the electron beam can impinge on the electron-scattering body and thus cause the electron-scattering body to produce scattered electrons;    when the process chamber contains molecules of the treatment gas, irradiating the electron-scattering body with the electron beam to produce scattered electrons that ionize the molecules of the treatment gas; and    allowing the ionized molecules of the treatment gas to react with and volatilize the deposit.    
     
     
         21 . The method of  claim 20 , wherein the treatment gas is at least one gas selected from a group consisting of water vapor, oxygen, ozone, and oxygen radicals.  
     
     
         22 . A method for cleaning a reticle in a process chamber of an electron-beam microlithography apparatus used to transfer an image of a pattern, defined by the reticle, onto a resist-coated surface of a substrate, the method comprising the steps: 
 (a) placing the reticle in an interior space defined by the process chamber;    (b) applying a subatmospheric pressure to the interior space; and    (c) directing an electron beam to impinge on the reticle in the process chamber, while deflecting electrons of the beam passing through the reticle away from the resist-coated surface so as not to expose the resist.    
     
     
         23 . The method of  claim 22 , wherein, in step (c), the electron beam impinging on the reticle has an energy sufficient to volatilize a deposit of a contaminant on the reticle as the reticle is being irradiated with the electron beam.  
     
     
         24 . The method of  claim 23 , wherein the energy of the electron beam used to clean the reticle is greater than an energy of the electron beam used to expose the resist-coated surface of the substrate with the reticle pattern.  
     
     
         25 . The method of  claim 22 , wherein, in step (c), the electron beam impinging on the reticle has an energy sufficient to confer a negative charge to a deposit of a contaminant on the reticle and to cause the deposit to detach from the surface of the reticle.  
     
     
         26 . The method of  claim 25 , further comprising the steps of: 
 providing a dust collector in the process chamber;    providing the dust collector with a positive charge sufficient to attract the detached deposit; and    collecting the detached deposit using the dust collector.    
     
     
         27 . A method for performing microlithography of a pattern, defined on a reticle, onto a resist-coated surface of a substrate, the method comprising: 
 (a) placing the reticle and substrate in the process chamber, the reticle being situated so as to be irradiated with an upstream electron beam and to produce a downstream electron beam carrying an image of an irradiated region of the reticle, and the substrate being situated such that the resist-coated surface can be exposed with the image carried by the downstream electron beam;    (b) evacuating the process chamber to produce a subatmospheric pressure in the process chamber;    (c) in a reticle-cleaning mode of operation, directing the upstream electron beam to impinge on the reticle while directing the downstream electron beam away from the resist-coated surface so as to avoid exposing the resist; and    (d) in a substrate-exposure mode of operation, directing the upstream electron beam to irradiate a region on the reticle while directing the downstream electron beam to a corresponding location on the resist-coated surface of the substrate so as to transfer the pattern from the reticle to the substrate.    
     
     
         28 . The method of  claim 27 , wherein: 
 in step (c), the electron beam has a first energy sufficient to volatilize a deposit of a contaminant on the reticle;    in step (d), the electron beam has a second energy sufficient to expose the resist; and    the first energy is greater than the second energy.    
     
     
         29 . The method of  claim 27 , further comprising the steps of: 
 providing a dust collector in the process chamber; and    during step (c), providing the dust collector with a positive charge.    
     
     
         30 . The method of  claim 29 , wherein, in step (c): 
 the electron beam impinging on the reticle has an energy sufficient to confer a negative charge to a deposit of a contaminant on the reticle and to detach the deposit from the reticle; and    the detached deposit is attracted to and collected by the dust collector.    
     
     
         31 . An electron-beam microlithography apparatus operable to project an image of a pattern, defined by a reticle, onto a resist-coated surface of a substrate, the apparatus comprising: 
 a process chamber defining an interior space;    a vacuum pump, in communication with the interior space, configured to produce a subatmospheric pressure in the interior space;    an electron-beam source situated within the interior space and configured to produce an electron beam propagating downstream of the source;    a deflector situated within the interior space and configured, when electrically energized, to deflect the electron beam propagating from the source; and    a main controller connected to the electron-beam source and to the deflector, the main controller being configured to operate in first and second operational modes, wherein in the first operational mode the electron beam from the source irradiates the reticle, and electrons of the beam passing through the reticle are deflected by the deflector away from the resist-coated surface so as not to expose the resist, and in the second operational mode the electron beam from the source irradiates a region of the reticle, and electrons of the beam passing through the reticle are deflected by the deflector to a corresponding region on the resist-coated surface so as to imprint the resist-coated surface with the pattern.    
     
     
         32 . The apparatus of  claim 31 , wherein, in the first operational mode, the main controller causes the source to produce the electron beam having a higher intensity than in the second operational mode, the higher intensity in the first operational mode being sufficient to volatilize a deposit of a contaminant on the reticle.  
     
     
         33 . The apparatus of  claim 31 , further comprising a dust collector situated in the process chamber and connected to the main controller, wherein in the first operational mode the electron beam has an energy sufficient to confer a negative charge to a deposit of a contaminant on the reticle and to detach the deposit from the reticle, and the main controller applies a positive charge to the dust collector, the positive charge being sufficient to attract the detached negatively charged deposit of the contaminant.  
     
     
         34 . A method for cleaning a reticle for use in performing charged-particle-beam (CPB) microlithography, comprising the steps: 
 (a) placing the reticle in a process chamber in which CPB microlithography of the reticle is performed;    (b) directing an ion beam or electron beam to irradiate a contaminant deposit on the reticle; and    (c) while performing step (b), introducing molecules of a reactive gas to an area where the ion beam is irradiating the deposit, wherein the irradiating beam ionizes the molecules of reactive gas that then react with and volatilize the contaminant deposit.    
     
     
         35 . The method of  claim 34 , wherein the reactive gas comprises a first gas selected from a group consisting of gaseous fluoride compounds, gaseous chloride compounds, and gaseous bromide compounds.  
     
     
         36 . The method of  claim 35 , wherein the reactive gas comprises a second gas selected from a group consisting of an inert gas, nitrogen gas, and oxygen gas.  
     
     
         37 . A charged-particle-beam (CPB) microlithography apparatus, comprising: 
 an illumination-optical system situated and configured to illuminate a reticle, defining a pattern to be transferred to a substrate, with a charged-particle illumination beam;    a reticle stage situated and configured to movably hold the reticle as the reticle is being illuminated by the illumination beam, so as to produced a patterned imaging beam propagating downstream of the reticle;    a projection-optical system situated and configured to direct and image the imaging beam on a sensitive substrate;    a substrate stage situated and configured to movably hold the sensitive substrate as the sensitive substrate is being exposed with the imaging beam;    an ion-beam source and ion-beam optical system situated and configured to irradiate a focused ion beam onto a predetermined location on the reticle; and    a process chamber enclosing the illumination-optical system, the reticle stage, the projection-optical system, the substrate stage, the ion-beam source, and the ion-beam optical system.    
     
     
         38 . A charged-particle-beam (CPB) microlithography apparatus, comprising: 
 an illumination-optical system situated and configured to illuminate a reticle, defining a pattern to be transferred to a substrate, with a charged-particle illumination beam;    a reticle stage situated and configured to movably hold the reticle as the reticle is being illuminated by the illumination beam, so as to produced a patterned imaging beam propagating downstream of the reticle;    a projection-optical system situated and configured to direct and image the imaging beam on a sensitive substrate;    a substrate stage situated and configured to movably hold the sensitive substrate as the sensitive substrate is being exposed with the imaging beam;    a probe-light source probe-light optical system situated and configured to irradiate a beam of probe light onto a surface of the reticle, the probe light being used to inspect the reticle for a contaminant deposit on the surface of the reticle;    a light detector for detecting a characteristic of the probe light as the probe light encounters a contaminant deposit on the reticle; and    a process chamber enclosing the illumination-optical system, the reticle stage, the projection-optical system, the substrate stage, the probe-light source, and the probe-light optical system.    
     
     
         39 . The apparatus of  claim 38 , wherein the probe-light optical system is configured to direct the beam of probe light selectively on an upstream-facing surface of the reticle and on a side-wall of an aperture in the reticle.  
     
     
         40 . The apparatus of  claim 39 , wherein the probe light is selected from the group consisting of UV light, deep UV light, and an electron beam.  
     
     
         41 . A charged-particle-beam (CPB) microlithography apparatus, comprising: 
 an illumination-optical system situated and configured to illuminate a reticle, defining a pattern to be transferred to a substrate, with a charged-particle illumination beam;    a reticle stage situated and configured to movably hold the reticle as the reticle is being illuminated by the illumination beam, so as to produced a patterned imaging beam propagating downstream of the reticle;    a projection-optical system situated and configured to direct and image the imaging beam on a sensitive substrate;    a substrate stage situated and configured to movably hold the sensitive substrate as the sensitive substrate is being exposed with the imaging beam;    a probe-light source probe-light optical system situated and configured to irradiate a beam of probe light onto a surface of the reticle, the probe light being used to inspect the reticle for a contaminant deposit on the surface of the reticle;    a light detector for detecting a characteristic of the probe light as the probe light encounters a contaminant deposit on the reticle;    an ion-beam source and ion-beam optical system situated and configured to irradiate a focused ion beam onto a predetermined location on the reticle; and    a process chamber enclosing the illumination-optical system, the reticle stage, the projection-optical system, the substrate stage, the probe-light source, the probe-light optical system, the ion-beam source, and the ion-beam optical system.