Abstract:
One embodiment disclosed relates to an integrated electron beam inspection and contaminant removal tool. An electron beam column is configured to image an area on a substrate being inspected. A contaminant removal subsystem is integrated with the electron beam column and configured to remove contamination from a surface of the substrate. Means is advantageously included by which the substrate is kept from being exposed to air between the contaminant removal subsystem and the electron beam column.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims the benefit of U.S. Provisional Patent Application No. 60/621,989, entitled “Integrated Electron Beam and Contaminant Removal System,” filed Oct. 25, 2004 by inventors David L. Adler and Mehran Nasser-Ghodsi, the disclosure of which is hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to apparatus and methods for particle beam systems. 
   2. Description of the Background Art 
   Organic and other contaminants can adversely affect the measurement accuracy, inspection and review data, and other information received from a scanning electron microscope (SEM) or similar apparatus. This is true even when the organic contaminants are present only at low levels. In addition, contaminants can adversely reduce the lifetime of key electron beam (e-beam) tool components and increase the frequency at which such tools need servicing. 
   A conventional method  100  for semiconductor manufacturing, including a level of contaminant removal, is shown in the flow chart of  FIG. 1 . A semiconductor wafer is provided ( 102 ) in a “clean room” environment, and the wafer is cleaned ( 104 ) at a contaminant removal station to remove contaminants thereon. Thereafter, the wafer goes through various process steps. These process steps may include, for example, various deposition, lithography, etching, and other steps. After one or more of these process steps ( 106 ) (i.e. at some point during the process), it may be desired to inspect the wafer to check for defects or to gather other information. The wafer is then transported ( 108 ) to an e-beam inspection station. This transportation ( 108 ) is generally performed within the clean room environment to avoid undue contamination. The e-beam inspection station may comprise, for example, a tool based on an SEM. At the e-beam inspection station, the wafer may be scanned or otherwise inspected ( 110 ). Thereafter, the manufacturing process may continue with further process steps ( 112 ) and so on. Each time e-beam inspection is performed, the wafer is typically exposed but in the clean room environment. 
   SUMMARY 
   One embodiment of the invention relates to an integrated electron beam inspection and contaminant removal tool. An electron beam column is configured to image an area on a substrate being inspected. A contaminant removal subsystem is integrated with the electron beam column and configured to remove contamination from a surface of the substrate. Means is advantageously included by which the substrate is kept from being exposed to air between the contaminant removal subsystem and the electron beam column. 
   Another embodiment relates to a method of manufacturing a semiconductor wafer. The wafer is processed with at least one manufacturing process step, and the wafer is loaded into an integrated e-beam inspection and contaminant removal apparatus. Contaminants are removed from a surface of the wafer, and the wafer is inspected using an electron beam. The wafer is advantageously kept from being exposed to air between the contaminant removal and the electron beam inspection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a flow chart depicting a conventional method for semiconductor manufacturing including e-beam inspection. 
       FIG. 2A  is a schematic diagram of an electron beam inspection system in accordance with an embodiment of the invention. 
       FIG. 2B  is a schematic diagram of an electron beam inspection system in accordance with another embodiment of the invention. 
       FIG. 2C  is a schematic diagram of an electron beam inspection system in accordance with another embodiment of the invention. 
       FIG. 3  is a schematic diagram showing components of an e-beam inspection system with an integrated contaminant removal station in accordance with an embodiment of the invention. 
       FIG. 4A  is a schematic diagram depicting the contaminant removal station in accordance with an embodiment of the invention. 
       FIG. 4B  is a schematic diagram depicting the contaminant removal station in accordance with another embodiment of the invention. 
       FIG. 4C  is a schematic diagram depicting the contaminant removal station in accordance with another embodiment of the invention. 
   

   The above-described diagrams are not necessarily to scale and are intended be illustrative and not limiting to a particular implementation. 
   DETAILED DESCRIPTION 
   The above-discussed conventional method  100  generally relies on the fact that the substrate is maintained in a relatively clean state as a result of the manufacturing process being performed in a clean room environment. However, residual contamination may still be present and adversely affect measurement accuracy, inspection or review image data, and other information received from an SEM tool or similar tool. The present invention provides methods and apparatus wherein residual contamination is cleaned so as to reduce these adverse effects during inspection or review of the wafer. 
     FIG. 2A  is a schematic diagram of an electron beam inspection system  200  in accordance with an embodiment of the invention. The e-beam system  200  generates and directs an incident or primary electron beam  208  towards an area of interest on a wafer (or other substrate)  210  for use in generating an image of the area. 
   As shown in  FIG. 2A , the incident beam  208  may be generated by an electron gun or other source  206 . A column  202  including various components in a vacuum is used to direct the primary electron beam  208  towards the surface of the wafer  210 . The column  202  typically includes various electron lenses, apertures, and other components. 
   In accordance with an embodiment of the invention, the wafer  210  may be held on a heated chuck or stage  222 . The heated stage  222  may be advantageously controlled so as to heat the wafer  210  for the removal of contaminant therefrom while the wafer  210  is in-situ in the e-beam inspection machine. 
   Like the column  202 , because the incident beam comprises electrons, a vacuum system  204  is used to pump the chamber containing the wafer  210  and heated stage  222  (as well as the column  202 ). A wafer transport system (not shown) may be used to move wafers to be inspected in-line as part of a manufacturing process. 
   The e-beam system  200  also includes a detector  214  to detect secondary electrons  212  (and/or backscattered electrons) emitted from the sample. The e-beam system  200  may also include an image generator (not shown) for forming an image from the detected emitted particles. 
     FIG. 2B  is a schematic diagram of an electron beam inspection system  240  in accordance with another embodiment of the invention. The e-beam system  240  of  FIG. 2B  is similar to the e-beam system  200  of  FIG. 2A  with the following differences. First, instead of a heated stage  222 , the e-beam system  240  of  FIG. 2B  may include a non-heated chuck or stage  242 . Controllable heating is instead provided for by one or more radiant heaters  244 . The radiant heater(s)  244  may be advantageously controlled so as to heat the wafer  210  for the removal of contaminant therefrom while the wafer  210  is in-situ in the e-beam inspection machine. In this embodiment, the chuck or stage  242  may act as a heat sink to cool the wafer back down after the in-situ contaminant removal. 
     FIG. 2C  is a schematic diagram of an electron beam inspection system  260  in accordance with another embodiment of the invention. The e-beam system  260  of  FIG. 2C  is similar to the e-beam system  240  of  FIG. 2B . However, instead of the radiant heater(s)  244 , the e-beam system  260  of  FIG. 2C  includes one or more microwave emitters or radiators  262 . The microwave emitters or radiators  262  may be configured to advantageously excite molecules in the surface contaminants and lead to their removal from the wafer surface. 
     FIG. 3  is a schematic diagram showing components of an e-beam inspection system  300  with an integrated contaminant removal station in accordance with an embodiment of the invention. A wafer loader  302  receives a semiconductor wafer being processed (or other substrate for inspection) into the system  300 . 
   The loader  302  transfers the wafer to the transport module  304 . The transport module  304  includes mechanisms, such a robot arms or similar mechanisms, for moving the wafer mechanically into and out of the contaminant removal station  308  and into and out of the e-beam column  312 . A first gate valve  306  may be configured to atmospherically separate the transport module  304  from the contaminant removal station  308 , and a second gate valve  310  may be configured to atmospherically separate the transport module  304  from the e-beam column  312 . 
   When moving the wafer between the transport module  304  and the contaminant removal station  308 , the first gate valve  306  is opened while the second gate valve  310  remains closed and sealed. This enables the vacuum of the e-beam column  312  to remain undisturbed during such transportation. On the other hand, when moving the wafer between the transport module  304  and the e-beam column  312 , the first gate valve  306  may be closed while the second gate valve  310  is opened. This minimizes the disturbance to the vacuum of the e-beam column  312  during such transportation. 
   Here, the cleaning of the substrate surface is performed while outside the SEM vacuum. This is advantageous in that contamination of the SEM column is avoided. 
     FIG. 4A  is a schematic diagram depicting the contaminant removal station  308   a  in accordance with an embodiment of the invention. In this embodiment, the contaminant removal station  308   a  includes a radiant heat source  402 . 
   After the wafer  404  is moved via the first gate valve  306  into the station  308   a  and onto the pedestal  406 , the radiant heat source  402  is controlled to heat up the wafer  404  so as to remove contamination from the surface thereof. During the heating for contamination removal, the station  308   a  may be preferably in a vacuum or under flow of inert gas to facilitate removal of contaminants. The pedestal  406  is configured to also function as a heat sink to cool the wafer back down after the contaminant removal. 
     FIG. 4B  is a schematic diagram depicting the contaminant removal station  308   b  in accordance with another embodiment of the invention. The contaminant removal station  308   b  of  FIG. 4B  is similar to the station  308   a  of  FIG. 4A  with the following differences. The heating in the station  308   b  of  FIG. 4B  is performed by way of a heatable pedestal  410 . The heatable pedestal  410  is controlled so as to heat said wafer so as to facilitate removal of contaminants from the surface thereof. 
     FIG. 4B  is a schematic diagram depicting the contaminant removal station  308   b  in accordance with another embodiment of the invention. The contaminant removal station  308   b  of  FIG. 4B  is similar to the station  308   a  of  FIG. 4A  with the following differences. The heating in the station  308   b  of  FIG. 4B  is performed by way of a heatable pedestal  410 . The heatable pedestal  410  is controlled so as to heat said wafer so as to facilitate removal of contaminants from the surface thereof. 
     FIG. 4C  is a schematic diagram depicting the contaminant removal station  308   c  in accordance with another embodiment of the invention. The contaminant removal station  308   c  of  FIG. 4C  is similar to the station  308   a  of  FIG. 4A  with the following differences. The station  308   c  of  FIG. 4C  utilizes a microwave emitter or radiator  412  (instead of a radiant heater  402 ). The microwave emitter or radiator  412  is controlled so as to flood said wafer surface with microwave radiation so as to facilitate removal of contaminants therefrom. 
   As discussed above, embodiments of the present invention rely on a contaminant removal station which is closely associated with the e-beam tool or that is provided within the e-beam tool. The contaminant removal may occur just prior to placing the substrate under the SEM column, or may actually be performed while the substrate is under the SEM column. 
   In alternate embodiments, combinations of the above-described embodiments may be employed. For example, both radiative heating and microwave radiation may be employed together so as to further facilitate removal of surface contaminants. 
   While a preferred embodiment of the present invention is utilized for pre-cleaning a substrate in the context of an SEM-based inspector or review tool, other embodiments may use other non-SEM tools. For example, another embodiment may integrate contaminant removal with a projection (nonscanning) electron microscope, or another particle beam based system. 
   Advantageously, embodiments of the invention should provide superior accuracy in inspection or metrology results, since a cleaner surface will be imaged or measured. Embodiments of the invention may also make it easier to maintain the SEM or other particle-beam apparatus, since cleaner wafer surfaces will produce less contamination in the apparatus. For this reason, maintenance costs of these apparatus may also be advantageously reduced. 
   In the above description, numerous specific details are given to provide a thorough understanding of embodiments of the invention. However, the above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed. One skilled in the relevant art will recognize that the invention can be practiced without one or more of the specific details, or with other methods, components, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the invention. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
   These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.