Abstract:
Methods and apparatus are disclosed for measuring controlling characteristics of clusters in a cluster ion beam, including average cluster ion velocity {overscore (v)}, average cluster ion mass {overscore (m)}, average cluster ion energy Ē, average cluster ion charge state {overscore (q)}, average cluster ion mass per charge 
                 (     m   q     )     average     ,         
and average energy/charge
 
                 (     E   q     )     average     .         
The measurements are employed in gas cluster ion beam processing systems to monitor and control gas cluster ion beam characteristics that are critical for optimal processing of workpieces by gas cluster ion beam irradiation.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS 
   This application claims priority of U.S. Provisional Application Ser. No. 60/442,854 entitled “Method And Apparatus For Measurement And Control Of A Gas Cluster Ion Beam”, filed Jan. 27, 2003, the contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to the measurement and control of characteristics of a cluster ion beam and, more particularly, to measuring and/or controlling the average charge state, average cluster ion mass, and/or average cluster ion energy of cluster ions in a gas cluster ion beam. 
   The use of a cluster ion beam for processing surfaces is known (see for example, U.S. Pat. No. 5,814,194, Deguchi et al., incorporated herein by reference) in the art. For purposes of this discussion, gas clusters are nano-sized aggregates of materials that are gaseous under conditions of standard temperature and pressure. Such gas clusters typically are comprised of aggregates of from a few to several thousand molecules loosely bound to form the cluster. The clusters can be ionized by electron bombardment or other means, permitting them to be formed into directed beams of controllable energy. Such ions each typically carry positive charges of q·e (where e is the electronic charge and q is an integer of from one to several representing the charge state of the cluster ion). Non-ionized clusters may also exist within a cluster ion beam. The larger sized cluster ions are often the most useful because of their ability to carry substantial energy per cluster ion, while yet having only modest energy per molecule. The clusters disintegrate on impact, with each individual molecule carrying only a small fraction of the total cluster ion energy. Consequently, the impact effects of large cluster ions are substantial, but are limited to a very shallow surface region. This makes cluster ions effective for a variety of surface modification processes, without the tendency to produce deeper subsurface damage characteristic of conventional monomer ion beam processing. 
   Means for creation of and acceleration of such gas cluster ion beams (GCIBs) are described in the reference (U.S. Pat. No. 5,814,194) previously cited. Presently available cluster ion sources produce clusters ions having a wide distribution of sizes, N (where N=the number of molecules in each cluster ion—in the case of monatomic gases like argon, an atom of the monatomic gas will be referred to as a molecule and an ionized atom of such a monatomic gas will be referred to as a molecular ion—or simply a monomer ion—throughout this discussion). 
   Many useful surface processing effects can be achieved by bombarding surfaces with GCIBs. These processing effects include, but are not necessarily limited to, cleaning, smoothing, etching, and film growth. There is need for improved diagnostic measurements to predict and control the gas cluster ion beam physics that affect processing rates of surfaces and hence permit these rates to be optimized. The fundamentals of GCIB-surface interactions are individual cluster ions impacting a surface, moving and ejecting material by direct sputtering and/or through melting and evaporation, creating nano-scale craters of various depths and diameters. GCIB craters can be on the on the scale of tens to hundreds of Angstroms, and depend on cluster ion mass and velocity. The nature of the craters formed (and thus the surface processing characteristics) by a GCIB depends on the mass of the cluster ions and their impact velocity. 
   Cluster ion velocity may be measured using time-of-flight techniques (as taught in U.S. Patent Application Publications 2002-0036261A1, Dykstra, Jerald P., and 2002-0070361A1, Mack, et al., for example, which are incorporated herein by reference). Also, by a variety magnetic and electrostatic measurement techniques sensitive to the mass/charge state ratio (m/q), the momentum, energy and mass of ionized clusters can be determined, when using ionization conditions such that the ions are predominantly singly charged, thus assuring that q was known to be approximately one. Additionally, it is known that techniques exist for measuring average mass/charge state ratio, 
               (     m   q     )     average     ,         
or can be based on existing techniques (as taught in U.S. Patent Application Publication 2001-0054686A1, Torti. et al., for example, incorporated by reference).
 
   In many cases, it is found that in order to achieve industrially practical throughputs in GCIB processing, GCIB currents on the order of hundreds to thousands of microamps are required. Recent efforts to increase the intensity and ionization of GCIBs are producing additional higher charge state clusters (q&gt;1). When ionization is performed by electron bombardment, ionization is produced by random electron impacts. In order to produce a high ratio of ionized to non-ionized clusters, the electron impact probability must be high and the resulting charge state distribution follows approximately Poisson statistics, with the approximate probability, P(q), of charge state q given by: 
   
     
       
         
           
             
               
                 
                   
                     
                       P 
                       _ 
                     
                     ⁡ 
                     
                       ( 
                       q 
                       ) 
                     
                   
                   = 
                   
                     
                       
                         q 
                         q 
                       
                       
                         q 
                         ! 
                       
                     
                     ⁢ 
                     
                       ⅇ 
                       
                         - 
                         
                           q 
                           _ 
                         
                       
                     
                   
                 
                 , 
               
             
             
               
                 ( 
                 
                   Eqn 
                   . 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 ) 
               
             
           
         
       
     
   
   where {overscore (q)} is the average ionized cluster charge state after leaving the ionizer. Thus an ionized cluster beam with a highly ionized fraction will also be a multiply charged beam. For example, theoretically the average cluster charge state of a GCIB beam where 95% of the clusters are ionized would be 3, with more than 8% of the beam in charge states 6 and higher. However, such highly charged clusters can fragment, resulting in a different charge state distribution. The interaction of the cluster ions with residual gas in the vacuum system can also cause charge exchange reactions and cluster ion fragmentation and so in a practical beam, the precise charge state is not readily predicted. The existence of high charge state clusters cannot be determined using present instrumentation such as magnetic spectrometers, electrostatic spectrometers, RF quadrupole mass spectrometers, time-of-flight, retarding potential mass spectrometers, and pressure gauge measurements, all of which measure either m/q or the energy/charge state ratio, E/q. It should be noted that for ionized cluster m/q on the order of 10000 AMU or less, it is possible to resolve different charge state families in the m/q spectra but this is not practical for more massive cluster ions where m/q states cannot be practically resolved or overlap. Other methods have been used to determine these parameters for very-large very-highly-charged (q&gt;1000) molecules produced by electro-spray techniques, and also for the case of highly-charged atoms in the solar wind or electrostatically accelerated dust particles. These techniques are not applicable to GCIBs because, for the former case, the charge states are too low, and with respect to the latter technique, because the cluster ion&#39;s collision energy is nearly all deposited thermally and hence cannot be detected using practical known methods. Thus, improved methods and apparatus are needed to measure and control m, q and E of these cluster ions. 
   It is therefore an object of this invention to provide methods and apparatus for measuring the average charge state {overscore (q)} of a cluster ion beam. 
   It is a further object of this invention to provide methods and apparatus for measuring average mass {overscore (m)} and/or average energy Ē of energetic ionized clusters in a beam. 
   Another object of this invention is to provide an improved method and apparatus for measuring and controlling the properties of a gas cluster ion beam in a GCIB processing system for improved GCIB processing of a workpiece. 
   SUMMARY OF THE INVENTION 
   The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention described hereinbelow. 
   In a first embodiment, the present invention provides a method involving separate measurements of average energy per charge 
               (     E   q     )     average     ,         
average velocity {overscore (v)}, and average charge state {overscore (q)} on a sample of cluster ion beam. The average energy per charge is measured using an electrostatic spectrometer, and the velocity is measured using time-of-flight. The average charge state {overscore (q)} is measured and used in combination with the other measurements to determine averages of m and E for the ionized cluster distribution. The average charge state is calculated by measuring the flow rate of particles (clusters), Γ, using a fast particle counter and by measuring the electrical beam current, I, using a current sensor, preferably a faraday cup, for a small sample of the ion beam. The ratio of electrical current to particle flow (according to Eqn. 2 below) yields the cluster average charge state, {overscore (q)} measurement. This average charge state measurement is combined with the electrostatic spectrometer measurements of
 
             (     E   q     )     average         
to determine the average cluster ion energy, and with time-of-flight measurements of average velocity, {overscore (v)}, to determine average mass, {overscore (m)}, as described in Eqn. 2, Eqn. 3, and Eqn. 5 below.
 
   In a second embodiment, the present invention provides a method of making measurements of average mass per charge 
               (     m   q     )     average     ,         
of the beam and of average energy per charge
 
               (     E   q     )     average     ,         
and average charge state {overscore (q)} on a sample of the cluster ion beam. The average energy per charge is measured using an electrostatic spectrometer, and the average mass per charge is measured using a pressure-charge sensor. The average charge state {overscore (q)} is measured and used in combination with the other measurements to determine averages of m and E for the ionized cluster distribution. As in the first embodiment, the average charge state is measured by measuring the flow rate of particles (clusters), Γ, using a fast particle counter and by measuring the electrical beam current, I, using a current sensor, preferably a faraday cup for a small sample of the ion beam. The ratio of electrical current to particle flow (according to Eqn. 2) yields the cluster average charge state, {overscore (q)} measurement. This average charge state measurement is combined with the electrostatic spectrometer measurements of
 
             (     E   q     )     average         
to determine the average cluster ion energy, and with average mass per charge,
 
               (     m   q     )     average     ,         
measurements to determine average mass, {overscore (m)}, as described in Eqn. 2, Eqn. 3, and Eqn. 4 below.
 
   In Eqn. 2, α and β are the detection efficiencies for the current and particle detectors respectively. 
   
     
       
         
           
             
               
                 
                   q 
                   _ 
                 
                 = 
                 
                   
                     α 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     I 
                   
                   
                     β 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     e 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Γ 
                   
                 
               
             
             
               
                 ( 
                 
                   Eqn 
                   . 
                   
                       
                   
                   ⁢ 
                   2 
                 
                 ) 
               
             
           
           
             
               
                 
                   E 
                   _ 
                 
                 = 
                 
                   
                     
                       q 
                       _ 
                     
                     ⁡ 
                     
                       ( 
                       
                         E 
                         q 
                       
                       ) 
                     
                   
                   average 
                 
               
             
             
               
                 ( 
                 
                   Eqn 
                   . 
                   
                       
                   
                   ⁢ 
                   3 
                 
                 ) 
               
             
           
           
             
               
                 
                   m 
                   _ 
                 
                 = 
                 
                   
                     
                       q 
                       _ 
                     
                     ⁡ 
                     
                       ( 
                       
                         m 
                         q 
                       
                       ) 
                     
                   
                   average 
                 
               
             
             
               
                 ( 
                 
                   Eqn 
                   . 
                   
                       
                   
                   ⁢ 
                   4 
                 
                 ) 
               
             
           
           
             
               
                 
                   m 
                   _ 
                 
                 = 
                 
                   
                     2 
                     ⁢ 
                     
                       E 
                       _ 
                     
                   
                   
                     
                       v 
                       _ 
                     
                     2 
                   
                 
               
             
             
               
                 ( 
                 
                   Eqn 
                   . 
                   
                       
                   
                   ⁢ 
                   5 
                 
                 ) 
               
             
           
         
       
     
   

   
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying figures and detailed description, wherein: 
       FIG. 1  is a schematic showing the basic elements of a prior art GCIB processing apparatus that uses an electrostatically scanned beam; 
       FIG. 2  is a schematic showing the basic elements of a GCIB processing apparatus that uses a stationary beam with mechanical scanning of the workpiece; 
       FIG. 3A  is a schematic showing a first embodiment of the apparatus for making the beam measurements of the invention, wherein is depicted a case for an analyzer voltage of zero; 
       FIG. 3A  is a schematic showing a first embodiment of the apparatus for making the beam measurements of the invention, wherein is depicted a case for a non-zero analyzer voltage; 
       FIG. 4  is a schematic showing a first embodiment of the apparatus for making the beam measurements of the invention configured for measuring the current I of a sample of the beam; 
       FIG. 5  is a schematic showing a first embodiment of the apparatus for making the beam measurements of the invention, illustrating beam gating for time-of-flight measurements on a sample of the beam; 
       FIG. 6  is a schematic showing a first embodiment of the apparatus of the invention for making the beam measurements, with improvements removed from the beam path to permit measurement of the current of the entire beam; 
       FIG. 7  is a schematic of a second embodiment of the apparatus of the invention for making the beam measurements; 
       FIG. 8  is a schematic showing a first embodiment of the apparatus of the invention for making the beam measurements, with improvements removed from the beam and a workpiece inserted into the beam for processing; 
       FIG. 9  is a schematic showing a GCIB processing apparatus according to the first embodiment of the invention; 
       FIG. 10  is a schematic showing a GCIB processing apparatus according to the first embodiment of the invention, with the beam measurement apparatus removed from the beam to allow workpiece processing; and 
       FIG. 11  is a schematic showing the improved GCIB processing apparatus according to the second embodiment of the invention, with the beam measurement apparatus removed from the beam to allow workpiece processing. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a schematic of the basic elements of a typical configuration for a GCIB processor  100 , which may be described as follows: a vacuum vessel  102  is divided into three communicating chambers, a source chamber  104 , an ionization/acceleration chamber  106 , and a processing chamber  108 . The three chambers are evacuated to suitable operating pressures by vacuum pumping systems  146   a ,  146   b , and  146   c , respectively. A condensable source gas  112  (for example argon or N 2 ) stored in a gas storage cylinder  111  is admitted under pressure through gas metering valve  113  and gas feed tube  114  into stagnation chamber  116  and is ejected into the substantially lower pressure vacuum through a properly shaped nozzle  110 . A supersonic gas jet  118  results. Cooling, which results from the expansion in the jet, causes a portion of the gas jet  118  to condense into clusters, each consisting of from several to several thousand weakly bound atoms or molecules. A gas skimmer aperture  120  partially separates the gas molecules that have not condensed into a cluster jet from the cluster jet so as to minimize pressure in the downstream regions where such higher pressures would be detrimental (e.g., ionizer  122 , high voltage electrodes  126 , and processing chamber  108 ). Suitable condensable source gases  112  include, but are not necessarily limited to argon, nitrogen, carbon dioxide, oxygen, and other gases. 
   After the supersonic gas jet  118  containing gas clusters has been formed, the clusters are ionized in an ionizer  122 . The ionizer  122  is typically an electron impact ionizer that produces thermoelectrons from one or more incandescent filaments  124  and accelerates and directs the electrons causing them to collide with the gas clusters in the gas jet  118 , where the jet passes through the ionizer  122 . The electron impact ejects electrons from the clusters, causing a portion the clusters to become positively ionized. A set of suitably biased high voltage electrodes  126  extracts the cluster ions from the ionizer, forming a beam, then accelerates them to a desired energy (typically from 1 keV to several tens of keV) and focuses them to form a GCIB  128  having a GCIB axis  129 . Filament power supply  136  provides filament voltage V f  to heat the ionizer filament  124 . Anode power supply  134  provides anode voltage V A  to accelerate thermoelectrons emitted from filament  124  to cause them to irradiate the cluster containing gas jet  118  to produce ions. Extraction power supply  138  provides extraction voltage V E  to bias a high voltage electrode to extract ions from the ionizing region of ionizer  122  and to form a GCIB  128 . Accelerator power supply  140  provides acceleration voltage V Acc  to bias a high voltage electrode with respect to the ionizer  122  so as to result in a total GCIB acceleration energy equal to V Acc  electron volts (eV). One or more lens power supplies ( 142  and  144  shown for example) may be provided to bias high voltage electrodes with focusing voltages (V L1  and V L2  for example) to focus the GCIB  128 . 
   A workpiece  152 , which may be a semiconductor wafer or other workpiece to be processed by GCIB processing, is held on a workpiece holder  150 , disposed in the path of the GCIB  128 . Since most applications contemplate the processing of large workpieces with spatially uniform results, a scanning system is desirable to uniformly scan the GCIB  128  across large areas to produce spatially homogeneous results. Two pairs of orthogonally oriented electrostatic scan plates  130  and  132  can be utilized to produce a raster or other scanning pattern across the desired processing area. When beam scanning is performed, the GCIB  128  is converted into a scanned GCIB  148 , which scans the entire surface of workpiece  152 . 
     FIG. 2  shows a schematic of the basic elements of a prior art mechanically scanning GCIB processing apparatus  200  having a stationary beam with a mechanically scanned workpiece  152 , and having a conventional faraday cup for beam measurement and a conventional thermionic neutralizer. GCIB generation is similar to as is shown in  FIG. 1 , but in the mechanically scanning GCIB processing apparatus  200  of  FIG. 2 , the GCIB  128  is stationary (not scanned) and the workpiece  152  is mechanically scanned through the GCIB  128  to distribute the effects of the GCIB  128  over a surface of the workpiece  152 . An X-scan actuator  202  provides linear motion of the workpiece holder  150  in the direction of X-scan motion  208  (into and out of the plane of the paper). A Y-scan actuator  204  provides linear motion of the workpiece holder  150  in the direction of Y-scan motion  210 , which is typically orthogonal to the X-scan motion  208 . The combination of X-scanning and Y-scanning motions moves the workpiece  152 , held by the workpiece holder  150  in a raster-like scanning motion through GCIB  128  to cause a uniform irradiation of a surface of the workpiece  152  by the GCIB  128  for uniform processing of the workpiece  152 . The workpiece holder  150  disposes the workpiece  152  at an angle with respect to the GCIB axis  129  of the GCIB  128  so that the GCIB  128  has an angle of beam incidence  206  with respect to the workpiece  152  surface. The angle of beam incidence  206  may be 90 degrees or some other angle, but is typically 90 degrees or very near 90 degrees. During Y-scanning, the workpiece  152  held by workpiece holder  150  moves from the position shown to the alternate position “A”, indicated by the designators  152 A and  150 A respectively. Notice that in moving between the two positions, the workpiece  152  is scanned through the GCIB  128  and in both extreme positions, is moved completely out of the path of the GCIB  128  (over-scanned). Though not shown explicitly in  FIG. 2 , similar scanning and over-scan is performed in the (typically) orthogonal X-scan motion  208  direction (in and out of the plane of the paper). A total beam current sensor  218  is disposed beyond the workpiece holder  150  in the path of the GCIB  128  so as to intercept a sample of the total GCIB beam current I T  of GCIB  128  when the workpiece holder  150  is scanned out of the path of the GCIB  128 . The beam current sensor  218  is typically a faraday cup or the like, closed except for a beam-entry opening, and is affixed to the wall of the vacuum vessel  102  with an electrically insulating mount  212 . A controller  220 , which may be a microcomputer based controller connects to the X-scan actuator  202  and the Y-scan actuator  204  through electrical cable  216  and controls the X-scan actuator  202  and the Y-scan actuator  204  so as to place the workpiece  152  into or out of the GCIB  128  and to scan the workpiece  152  uniformly relative to the GCIB  128  to achieve uniform processing of the workpiece  152  by the GCIB  128 . Controller  220  receives the sampled beam current collected by the beam current sensor  218  by way of lead  214  and thereby monitors the GCIB and controls the GCIB dose received by the workpiece  152  by removing the workpiece  152  from the GCIB  128  when a predetermined desired dose has been delivered. 
     FIGS. 3A and 3B  show schematics of a first embodiment of a GCIB measurement apparatus  300  for making the beam measurements of a GCIB  128  in accordance with the present invention.  FIG. 3A  depicts a case for an analyzer voltage of zero and  FIG. 3B  depicts a case for a non-zero analyzer voltage. The GCIB measurement apparatus  300  is intended to be situated (with the exception, optionally, of some or all supporting electronic circuits, power supplies, and controls) within the vacuum vessel  102  ( FIG. 2 ) of a GCIB processing apparatus  200  ( FIG. 2 ) having an unscanned GCIB  128 , like that shown in  FIG. 2 , for example. The GCIB measurement apparatus  300  comprises a GCIB attenuation subsystem, a GCIB collimation subsystem, a GCIB switching subsystem, a GCIB energy spectrum measuring subsystem, a GCIB particle flow measurement subsystem, a GCIB current measurement subsystem, a GCIB time-of-flight measurement system, repositioning actuators for repositioning various elements with respect to the gas cluster ion beam being measured, and various electronic, power, and control systems. 
   Referring to  FIG. 3A , the GCIB attenuation subsystem comprises a beam attenuator  302 , and related actuators and controls. Beam attenuator  302  is (for example) a metal plate having a small circular attenuator aperture  303  through which an attenuated sample (attenuated GCIB  306 ) of the GCIB  128  can be made to pass. It is recognized that the attenuator aperture  303  may (for example) be a small circular aperture or a rectangular slit aperture or even an array of circular apertures and can be an adjustable aperture such as an iris or adjustable slit. In a preferred, non-limiting embodiment, the attenuator aperture  303  is a circular knife edge hole with 1 millimeter diameter. Beam attenuator  302  is mounted rigidly to analyzer mounting and alignment plate  324  and is thereby electrically grounded and thermally heat sunk. Analyzer mounting and alignment plate  324  is connected by mechanical linkage  326  to mechanical actuator  328  to provide bi-directional actuation (in the direction of arrows  380 ) for inserting the beam attenuator  302  into the GCIB  128  with attenuator aperture  303  aligned with the GCIB axis  129  or for removing the GCIB attenuator subsystem entirely from the GCIB  128 . 
   Continuing to refer to  FIG. 3A , the GCIB collimation subsystem comprises a beam attenuator  302 , an attenuator aperture  303 , and a beam collimator  304  having a collimator aperture  305 , and related actuators and controls. Beam attenuator  302  and beam collimator  304  are mounted rigidly to analyzer mounting and alignment plate  324  and are thereby electrically grounded, thermally heat sunk, and maintained in alignment thereby. Attenuator aperture  303  and collimator aperture  305  are fixed in alignment by analyzer mounting and alignment plate  324  so as to be aligned substantially parallel with GCIB axis  129 . It is recognized that the collimator aperture  305  may (for example) be a small circular aperture or a rectangular slit aperture or even an array of circular apertures and can be an adjustable aperture such as an iris or adjustable slit. Preferably the collimator aperture is the same shape (circular or slit) as is the attenuator aperture  303  and is of approximately equal size or smaller than the attenuator aperture  303 . Thus the collimator aperture serves to collimate the attenuated GCIB  306  and to further attenuate the attenuated GCIB  306 . In a preferred embodiment, the collimator aperture  305  is a circular knife edge hole with a diameter in the range of from 20 to 160 micrometers. Analyzer mounting and alignment plate  324  is connected by mechanical linkage  326  to mechanical actuator  328  to provide bi-directional actuation (in the direction of arrows  380 ) for inserting GCIB collimation subsystem into the GCIB  128  with attenuator aperture  303  and collimator aperture  305  both aligned with the GCIB axis  129  or for removing the GCIB collimation subsystem entirely from the GCIB  128 . When the GCIB collimation subsystem is inserted, as shown in  FIG. 3A , beam attenuator  302  and beam collimator  304  transmit (respectively) an attenuated GCIB  306  and an attenuated and collimated GCIB  307 . Attenuated and collimated GCIB  307  is thus a sample of GCIB  128 . 
   Continuing to refer to  FIG. 3A , the GCIB switching subsystem comprises a beam attenuator  302 , an attenuator aperture  303 , a beam collimator  304  having a collimator aperture  305 , an electrostatic deflector plate  394 , and related actuators, power supplies and controls. Beam attenuator  302  and beam collimator  304  are mounted rigidly to analyzer mounting and alignment plate  324  and are thereby electrically grounded, thermally heat sunk, and maintained in alignment. Attenuator aperture  303  and collimator aperture  305  are fixed in alignment by analyzer mounting and alignment plate  324  so as to be aligned substantially parallel with GCIB axis  129 . Analyzer mounting and alignment plate  324  is connected by mechanical linkage  326  to mechanical actuator  328  to provide bi-directional actuation  380  for inserting GCIB collimation subsystem into the GCIB  128  with attenuator aperture  303  and collimator aperture  305  both aligned with the GCIB axis  129  for transmitting an attenuated and collimated sample (attenuated and collimated GCIB  307 ) of GCIB  128  or for removing the GCIB collimation subsystem entirely from the GCIB  128 . An electrostatic deflector plate  394  is positioned proximal to and substantially parallel to attenuated GCIB  306  where GCIB  306  passes between beam attenuator  302  and beam collimator  304  and is rigidly fixed to analyzer mounting and alignment plate  324  by electrical insulating means not shown. Electrical lead  396  connects electrostatic deflector plate  394  to a beam gating controller  398  for conducting beam gating potentials from beam gating controller  398  to electrostatic deflector plate  394 . Beam gating controller  398  provides electrical signals to controllably deflect or not deflect attenuated GCIB  306  in the region between beam attenuator  302  and beam collimator  304 . It is realized that beam gating controller  398  can be remotely controlled by a higher level control system (not shown in this figure) for controllably providing deflection signals to electrostatic deflector plate  394 . By deflecting or not deflecting attenuated GCIB  306 , attenuated and collimated GCIB  307  may be gated off or on. Accordingly when the GCIB switching subsystem is inserted into GCIB  128 , it can form a beam switch for time-of-flight beam measurements as will be described in additional detail hereinafter. 
   Continuing to refer to  FIG. 3A , the GCIB energy spectrum measuring subsystem (energy spectrometer) comprises a beam attenuator  302 , an attenuator aperture  303 , a beam collimator  304 , a collimator aperture  305 , a grounded electrode  312 , an energy analyzer electrode  308 , an analyzing slit  318 , a current sensor  322 , and related actuators, power supplies and controls. The grounded electrode  312  has three apertures—a first grounded electrode aperture  313  for admitting attenuated and collimated GCIB  307 , a second grounded electrode aperture  314  to permit transmission of the attenuated and collimated GCIB  307 ′, and a third grounded electrode aperture  315  for transmitting an analyzed beamlet  316  (shown in  FIG. 3B ). A beam energy analyzer comprises grounded electrode  312  and energy analyzer electrode  308 . The grounded electrode  312  and the energy analyzer electrode  308  are disposed at an angle (preferably approximately 45 degrees) to the path of the attenuated GCIB  306  (thus to the GCIB axis  129 ). The grounded electrode  312  is rigidly fixed to the analyzer mounting and alignment plate  324  so is to be electrically grounded thereby. The energy analyzer electrode  308  is rigidly fixed to analyzer mounting and alignment plate  324  by electrical insulating means not shown. Electrical lead  336  connects energy analyzer electrode  308  to an analyzer power supply  386  for supplying an analyzer voltage V An  to energy analyzer electrode  308 . Analyzer power supply  386  is adjustable and preferably remotely controllable by a higher-level controller not shown in this figure. Analyzing voltage V An  is controllable throughout the range from zero to a voltage approximately equal to the maximum acceleration voltage V Acc  used for accelerating the GCIB  128 . For example if the maximum expected value of V Acc  is 25 kV, then V An  can be chosen to be controllable over the range of from zero to 25 kV. Energy analyzer electrode  308  has an energy analyzer electrode aperture  310  through the electrode to allow transmission of attenuated and collimated GCIB  307 . When transmitted through energy analyzer electrode aperture  310 , the continuation of attenuated and collimated GCIB  307  is designated as attenuated and collimated GCIB  307 ′. Energy analyzer electrode aperture  310  is maintained in fixed alignment with attenuator aperture  303  and collimator aperture  305  by analyzer mounting and alignment plate  324 . When V An  is zero, the attenuated and collimated GCIB  307 ′ travels straight through attenuator aperture  303  and collimator aperture  305  and first grounded electrode aperture  313  and through energy analyzer electrode aperture  310  and through second grounded electrode aperture  314 . 
   Referring to  FIG. 3B , but continuing discussion of the GCIB energy spectrum measuring subsystem (energy spectrometer), when V An  is greater than zero, an electrostatic field gradient exists between energy analyzer electrode  308  and grounded electrode  312  such that the attenuated and collimated GCIB  307  is deflected and dispersed, with cluster ions being dispersed as a function of their E/q (energy per charge). An analyzing slit  318  forms an acceptance aperture for a current sensor  322 , which is preferably a faraday cup having an electron suppressor electrode  320 . An electrical lead  330  connects suppressor electrode  320  to suppressor power supply  384  for supplying a suppressor voltage, V S1  to suppressor electrode  320  for suppressing secondary electrons in current sensor  322 . V S1  is preferably in the range of from 500 to 1500 volts. According to known principles, different values of V An  result in cluster ions of a specific range of energies, dependent on V An , being deflected so as to pass through third grounded electrode aperture  315  and to form an analyzed beamlet  316  passing through analyzing slit  318  for measurement by the current sensor  322 . Cluster ions having E/q differing from the range of E/q of the cluster ions in analyzed beamlet  316  are deflected greater or lesser amounts than analyzed beamlet  316  and form dispersed beamlets  317 . Dispersed beamlets  317  do not pass through analyzing slit  318  and are not measured by current sensor  322 . Current sensor  322  has an electrical lead  332  for connecting it to a current measurement system  334 . According to known principles of electrostatic energy spectroscopy, by coordinating adjustment of V An  through its voltage range, with current measurements in current sensor  322  the energy spectrum (data in the form of beam current as a function of cluster ion energy or alternatively in the form of cluster ion energy as a function of beam current) of the attenuated and collimated GCIB  307  sample of GCIB  128  are measured and an average value of E/q (corresponding to 
             (     E   q     )     average         
in Eqn. 3) is calculated. Furthermore, the total cluster ion current, I, in the attenuated and collimated GCIB  307  can be obtained by integrating the measurement of beam current as a function of cluster ion energy with respect to cluster ion energy. Such a measurement of cluster ion current, I, can be used in combination with a flow rate, Γ, measurement for calculating average charge state of the attenuated and collimated GCIB  307 .
 
   Referring again to  FIG. 3A , the GCIB particle flow measurement subsystem comprises a beam attenuator  302 , an attenuator aperture  303 , a beam collimator  304 , a collimator aperture  305 , an energy analyzer electrode aperture  310 , a grounded electrode  342  with a fourth grounded electrode aperture  343 , a dynode  338 , an optional electron lens assembly  344 , a scintillation measurement system, and related actuators, power supplies and controls. The GCIB particle flow measurement subsystem measures the flow rate Γ of clusters in a sample of the GCIB  100 . Beam attenuator  302  and beam collimator  304  are mounted rigidly to analyzer mounting and alignment plate  324  and are thereby electrically grounded, thermally heat sunk, and maintained in alignment. Analyzer voltage V An  is set to zero so that attenuated and collimated GCIB  307  is transmitted through the energy analyzer electrode aperture  310  as attenuated and collimated GCIB  307 ′. Grounded electrode  342  with a fourth grounded electrode aperture, dynode  338 , optional electron lens assembly  344 , which if used, is preferably an einzel lens, scintillator  348 , and a photomultiplier tube (PMT)  350  are all rigidly mounted to a particle detector mounting and alignment plate  352 . When electron lens assembly is used, an electrical lead  358  connects electron lens assembly to lens power supply  388  for providing focusing voltage V L3  for focusing secondary electron trajectories  346  onto scintillator  348 . 
   Particle detector mounting and alignment plate  352  supports and maintains alignment of elements mounted to it and permits their positioning, as a group. Particle detector mounting and alignment plate  352  is connected by mechanical linkage  362  to mechanical actuator  360  to provide bi-directional actuation (in the direction of arrows  382 ) for inserting the dynode  340  into the attenuated and collimated GCIB  307 ′ for cluster ion flow rate measurement. The grounded electrode  342  is rigidly mounted to the particle detector and mounting plate  352  and is electrically grounded thereby. The dynode is rigidly mounted to the particle detector and mounting plate  352  by electrical insulating means not shown. Both the grounded electrode  342  and the dynode are disposed at an angle (preferably approximately 45 degrees) to the path of the attenuated and collimated GCIB  307 ′ (thus to the GCIB axis  129 ). Dynode  338  is an electrical conductor, preferably aluminum, and has a dynode surface  340 , preferably a thin native aluminum oxide film. An electrical lead 364 connects the dynode  338  to a dynode power supply  390  for supplying a dynode voltage V Dy  to the dynode  338 . Dynode power supply  390  is preferably remotely controllable by a higher level controller for setting V Dy  to zero volts when particle detection is not being performed and to set it to a fixed value, preferably in the range of 20–45 kV and typically 30 kV when particle detection is performed. In operation, attenuated and collimated GCIB  307 ′ passes through fourth grounded electrode aperture  343  in the grounded electrode  342 . An electric potential gradient between the dynode  338  and grounded electrode  342  accelerates the attenuated and collimated GCIB  307 ′ into the dynode  338 . As each accelerated cluster ion strikes the dynode surface  340 , it induces release of one or more secondary electrons. 
   The secondary electrons are accelerated by the electric field gradient between the dynode  338  and the grounded electrode  342  along trajectories  346  in a direction substantially normal to the dynode surface  340  and are focused by electron lens assembly  344  onto a scintillator  348 . The electron lens assembly  344  is optional, but is useful for assuring detection of electrons at the scintillator with a relatively small scintillator. Each cluster ion arriving at the dynode surface releases a burst of one or more secondary electrons, which is converted by the scintillator  348  to a photon pulse. Scintillator  348  is a conventional particle detecting scintillator known in the art (preferably a plastic scintillator). Scintillator  348  and is shielded from external light sources by a thin aluminized Mylar film and is optically coupled to a high speed PMT  350 . An electrical cable  354  connects PMT  350  to a conventional PMT controller/pulse counter/sampling system  356 . The PMT controller/pulse counter/sampling system  356  provides and controls power supply potentials to the PMT and processes the PMT output pulses to provide pulse rate measurements and also processes the PMT output to collect periodic samples of the PMT output signal for measuring the fall-off of the signal during time-of-flight measurement, as further described hereinafter. The PMT  350  produces a pulse output corresponding to each photon pulse detected, thus corresponding to each cluster ion that strikes the dynode surface  340 . PMTs capable of counting photon pulse rates of at least 100 MHz are commercially available. The PMT controller/pulse counter/sampling system  356  is remotely controllable and can output its pulse rate and sampling measurements for remote reading. The beam attenuator aperture  303  is pre-selected to have a diameter so as to provide an overall attenuation of the GCIB  128  as to assure that the cluster ion flow rate in the attenuated and collimated GCIB  107 ′ is at an accurately countable rate by the PMT  350 . For presently typical examples of GCIB  100  this attenuation factor is on the order of 10 −6  to 10 −7 , which can be achieved by using an attenuator aperture on the order of 20 micrometers diameter. The measured cluster ion flow rate in the attenuated and collimated GCIB  307 ′ is designated Γ, and corresponds to the Γ in Eqn. 2. 
   Continuing to refer to  FIG. 3A , a first example of a GCIB current measurement subsystem for implementing the invention comprises a grounded aperture  372 , a secondary electron suppressor  374 , and a beam current sensor  376 . The aperture  372 , secondary electron suppressor, and beam current sensor  376  are rigidly mounted (not shown here) so as to be aligned with the GCIB axis  129  of GCIB  128  (and thus also aligned with attenuated and collimated GCIB  307 ′). In the absence of intervening elements, GCIB  128  or a sample of GCIB  128  (attenuated and collimated GCIB  307 ′, for example) is collected by current sensor  376  for measurement. Current sensor  376  is preferably a faraday cup. An electrical lead  366  connects secondary electron suppressor  374  to a suppressor power supply  392  for supplying a suppressor voltage V S2  to the secondary electron suppressor  374  for suppressing secondary electrons in the current sensor  376 . V S2  is preferably in the range of from 500 to 1500 volts. An electrical lead  368  connects current sensor  376  to electrical current measuring system  370  for electrical current measurement. 
   Referring again to  FIG. 3B , a second and preferred example of a GCIB current measurement subsystem for implementing the invention utilizes the current sensor  322  (preferably a faraday cup) of the energy spectrum measuring subsystem for measuring the beam current, I, of the attenuated and collimated GCIB  307 . When V An  is greater than zero, an electrostatic field gradient exists between energy analyzer electrode  308  and grounded electrode  312  such that the attenuated and collimated GCIB  307  is deflected and dispersed, with cluster ions being dispersed as a function of their E/q (energy per charge). An analyzing slit  318  forms an acceptance aperture for the current sensor  322 , which is preferably a faraday cup having an electron suppressor electrode  320 . An electrical lead  330  connects suppressor electrode  320  to suppressor power supply  384  for supplying a suppressor voltage, V S1  to suppressor electrode  320  for suppressing secondary electrons in current sensor  322 . V S1  is preferably in the range of from 500 to 1500 volts. By coordinating adjustment of V An  through its voltage range, with current measurements in current sensor  322  the energy spectrum (in the form of beam current as a function of cluster ion energy) of the attenuated and collimated GCIB  307  sample of GCIB  128  is measured and the cluster ion current, I, in the attenuated and collimated GCIB  307  can be obtained by integrating the measurement of beam current as a function of cluster ion energy with respect to cluster ion energy. Γ is the corresponding measured cluster ion flow rate in the attenuated and collimated GCIB  307 . Collection efficiencies α and β are determined by conventional calibration techniques and thus {overscore (q)} is calculated according to Eqn. 2. Average energy/charge, 
             (     E   q     )     average         
is also measured as described hereinbefore and accordingly Ē is calculated according to Eqn. 3. Since attenuated and collimated GCIB  307 ′ is a sample of GCIB  128 , the calculated values of {overscore (q)} and Ē correspond to those for GCIB  128 .
 
     FIG. 4  shows a schematic  400  of the first embodiment of a GCIB measurement apparatus configured for making a sample beam current measurement using the first example GCIB current measurement subsystem. Mechanical actuator  360  removes the particle detector mounting and alignment plate  352  from the path of the attenuated and collimated GCIB  307 ′, which is a sample of GCIB  128 . When the analyzer mounting and alignment plate  324  is positioned so that the GCIB attenuation and collimation subsystems are inserted into the GCIB  128  and the particle detector mounting and alignment plate  352  is removed from the path of attenuated and collimated GCIB  307 ′ (as shown in  FIG. 4 ), then the attenuated and collimated GCIB  307 ′, which is a sample of GCIB  128  is collected by the current sensor  376  for measurement as the sample beam current value I of Eqn. 2 is the current in the attenuated and collimated GCIB  307 ′, while Γ is the corresponding measured cluster ion flow rate in the attenuated and collimated GCIB  307 ′. Collection efficiencies α and β are determined by conventional calibration techniques and thus {overscore (q)} is calculated according to Eqn. 2. Average energy/charge, 
             (     E   q     )     average         
is also measured as described hereinbefore and accordingly Ē is calculated according to Eqn. 3. Since attenuated and collimated GCIB  307 ′ is a sample of GCIB  128 , the calculated values of {overscore (q)} and Ē correspond to those for GCIB  128 .
 
     FIG. 5  shows a schematic  410  of the first embodiment of the GCIB measurement apparatus of the invention, configured for gating a sample of the GCIB  128  for making time-of-flight measurements on the beam sample. The analyzer mounting and alignment plate  324  and the particle detector mounting and alignment plate  352  are both positioned so that the GCIB attenuation and collimation subsystems are inserted into the GCIB  128  and the particle detector mounting and alignment plate  352  is in the path of attenuated and collimated GCIB  307 ′ (as was shown in  FIG. 3A ). The time-of-flight measurement is done by beginning with the beam conditions shown in  FIG. 3A , with the attenuated and collimated GCIB  307 ′striking dynode  338  and being sensed by PMT  350 . Referring again to  FIG. 5 , beam gating controller  398  provides electrical signals to controllably deflect the attenuated GCIB  306  in the region between beam attenuator  302  and beam collimator  304 . This results in attenuated GCIB  306  ( FIG. 3A ) being deflected as attenuated and deflected GCIB  412  ( FIG. 5 ). The deflection results in abrupt gating off of the previously (as was shown in  FIG. 3A ) attenuated and collimated GCIB  307 – 307 ′, which results in a delayed (according to the times-of-flight of the component clusters having various energies in the attenuated and collimated GCIB  307 – 307 ′) fall-off of signal in the PMT  350 . The electrical cable  354  connects PMT  350  to PMT controller/pulse counter/sampling system  356  for measuring the delayed fall-off signal in the PMT  350 , which occurs after the gating off of the attenuated and collimated GCIB  307 — 307 . 
   A time-of-flight analysis and control system  414  is controllably connected to both the beam gating controller  389  and the PMT controller/pulse counter/sampling system  356  by electrical cables  416  and  418  respectively. The time-of-flight analysis and control system  414  also receives measurement information about the delayed fall-off signal in the PMT  350  via the electrical cable  418 . The process for measuring cluster ion time-of-flight begins with the GCIB measurement apparatus  300  configured as shown in the previous  FIG. 3A , with attenuated and collimated GCIB  307 ′ being collected by the beam current sensor  376 . The time-of-flight analysis and control system  414  sends control signals to the PMT controller/pulse counter/sampling system  356  to cause it to collect and send periodic samples of the signal sensed at PMT  350 . At a time T 0 , the time-of-flight analysis and control system  414  sends control signals to beam gating controller  398  commanding the attenuated and collimated GCIB  307 ′ to be gated off, as shown in  FIG. 5 . The resulting fall-off of signal at beam PMT  350  is periodically sampled and sent to the time-of-flight analysis and control system  414  by the PMT controller/pulse counter/sampling system  356 . The rate and timing of the fall-off of signal at the PMT  350  is analyzed in relation to the time T 0  of beam gating by the beam gating controller  398  according to principles as taught in US patent application publications 2002-0036261A1, Dykstra; and 2002-0070361A1, Mack et al., for example. US patent application publications 2002-0036261A1, Dykstra; and 2002-0070361A1, Mack et al. are incorporated herein by reference. Accordingly, the time-of-flight distribution for the attenuated and collimated GCIB  307 – 307 ′ is measured. By conventional averaging techniques, the average time-of-flight is calculated from the time-of-flight distribution and the average velocity, {overscore (v)}, is the inverse of the average time-of-flight. This calculated value of average velocity {overscore (v)} is the value {overscore (v)} for Eqn. 5. By combining this value of {overscore (v)} with the value of Ē calculated according to Eqn. 3, next is calculated the value of average mass {overscore (m)} according to Eqn. 5. Therefore, according to the methods and apparatus of the first embodiment of the invention, average mass {overscore (m)}, average velocity {overscore (v)}, average energy Ē, average charge state {overscore (q)}, and average energy/charge 
             (     E   q     )     average         
are determined for the sample of the beam and therefore for the GCIB  128 . It is recognized that the time-of-flight analysis and control system  414  could optionally be implemented as part of a higher level or more general control system, a microcomputer system, or other general-purpose computer system, which might be part of an overall control system for a GCIB processing system.
 
     FIG. 6  shows a schematic  420  of the first embodiment of the GCIB measurement apparatus of the invention, but with the measurement improvements removed from the beam path to permit measurement of the current of the entire GCIB  128 . The analyzer mounting and alignment plate  324  is positioned so that the subsystems it supports are removed entirely from the GCIB  128  and the particle detector mounting and alignment plate  352  is also positioned so that the subsystems it supports are removed entirely from the GCIB  128 . GCIB  128  travels uninterrupted to the current sensor  376  where it is collected for measurement. This permits measurement of total beam current I T  of the GCIB  128  for workpiece processing dosimetry purposes. 
     FIG. 7  shows a schematic of a second embodiment of a GCIB measurement apparatus  430  for making the beam measurements of the invention upon a GCIB  128 . In the second embodiment, the method does not include a time-of-flight measurement, but rather makes measurements of average mass per charge 
             (     m   q     )     average         
of the beam, and of average energy per charge,
 
               (     E   q     )     average     ,         
and average charge state {overscore (q)} on a sample of the cluster ion beam. The average energy per charge and the average charge state are measured identically and with the same apparatus as used for the first embodiment and as has been described hereinbefore. The average mass per charge is measured using a pressure-charge sensor, according to known techniques. The measurement apparatus is like the apparatus of the first embodiment described hereinbefore, except that since no time-of-flight measurement is required, the previously described electrostatic deflector plate  394 , electrical lead  396 , and beam gating controller  398  of the GCIB switching subsystem are not required. Also the separate secondary electron suppressor  374 , the beam current sensor  376 , electrical lead  368  and current measuring system  370  previously described are not required. Beam current measurement and average mass per charge are performed using apparatus and methods as are now described. A (m/q) sensor  432  comprises a perforated faraday cup  434  with a secondary electron suppressor  436  and a pressure sensor  442 . The grounded aperture  372  and (m/q) sensor  432  are rigidly mounted (not shown here) so as to be aligned with the GCIB axis  129  of GCIB  128 . In the absence of intervening elements, the perforated faraday cup  434  collects GCIB  128  for current measurement. Gas cluster ions in the GCIB  128  are fully dissociated upon impact with the perforated faraday cup  434  and they raise the pressure in the (m/q) sensor  432  as they escape. Pressure sensor  442  measures the pressure increase due to dissociated gas cluster ions and measures the temperature of the sensor. An electrical lead  366  connects secondary electron suppressor  436  to a suppressor power supply  392  for supplying a suppressor voltage V S2  to the secondary electron suppressor  374  for suppressing secondary electrons in the perforated faraday cup  434 . V S2  is preferably in the range of from 500 to 1500 volts. An electrical lead  448  connects perforated faraday cup to a conventional current measurement system  446  for electrical current measurement. An electrical cable  438  connects pressure sensor  442  to a (m/q) measurement system  440  for transmitting pressure and temperature signals and sensor power. An electrical lead  444  transmits electrical current measurement signals from current measurement system  446  to the (m/q) measurement system  440 . The current measurement system  446  and the (m/q) measurement system  440  are both remotely controllable and able to provide data signals to a higher-level controller, not shown here. The (m/q) sensor  432 , the current measurement system  446 , and the (m/q) measurement system  440  operate according to principles taught in US patent application publication 2001-0054686A1 Torti et al., for example. US patent application publication 2001-0054686A1 Torti et al. is incorporated herein by reference. Equation 10 of 2001-0054686A1 Torti et al. describes the measurement for {overscore (N)}, the average number of molecules per cluster. By multiplying {overscore (N)}, thus obtained, by  40  (the atomic mass of Argon) and by the value of the atomic mass unit in kg, is obtained the value of average mass per charge,
 
               (     m   q     )     average     ,         
for the clusters in the GCIB  128 . This value for average mass per charge is the
 
             (     m   q     )     average         
required in Eqn. 4. The current measurement of the GCIB  128  from the current measurement system  446  is I T , the total beam current for the GCIB  128  and is used for GCIB processing dosimetry. By combining this value for average mass per charge with measurements of Γ, I, and average energy per charge,
 
               (     E   q     )     average     ,         
obtained according to the methods and apparatus of the first embodiment of the invention described above, and by applying Eqn. 2, Eqn. 3, and Eqn. 4, average mass {overscore (m)}, average charge state {overscore (q)}, and average energy Ē are determined for the GCIB  128  according to the second embodiment of the invention.
 
     FIG. 8  shows a schematic  450  of the first embodiment of the GCIB measurement apparatus of the invention, but with the measurement improvements removed from the beam path to permit processing of a workpiece by GCIB irradiation using the entire GCIB  128 . The analyzer mounting and alignment plate  324  is positioned so that the subsystems it supports are removed entirely from the GCIB  128  and the particle detector mounting and alignment plate  352  is also positioned so that the subsystems it supports are removed entirely from the GCIB  128  and from the scanning path of a mechanically scanning workpiece holder  150  with a workpiece  152 . GCIB  128  travels uninterrupted to the workpiece  152  where it irradiates the workpiece for GCIB processing of the workpiece  152 . The workpiece holder  150  and workpiece  152  are scanned through the GCIB  128  with X-scan and Y-scan motions  208  and  210 , using apparatus and methods equivalent to those previously described in more detail in the discussion of the mechanically scanning GCIB processing apparatus  200  (see discussion of  FIG. 2 , hereinbefore). 
     FIG. 9  is a schematic showing an improved GCIB measurement and processing apparatus  500  according to a preferred first embodiment of the invention. GCIB measurement and processing apparatus  500  is similar to the prior art mechanically scanning GCIB processing apparatus  200 , but having GCIB measurement, monitoring, and control improvements for implementing the first embodiment of the invention. Gas metering valve  113  of the prior art processing system is replaced by electronically controllable gas metering valve  512 . The beam current sensor  218  of the prior art system and its electrical lead  214  are replaced by aperture  372 , secondary electron suppressor  374 , beam current sensor  376 , and electrical lead  368  of the hereinbefore described GCIB measurement apparatus  300 . Controller  220  of the prior art system is replaced by digital processing and control system  510  having improved capabilities and functions, including but not limited to all the hereinbefore described functionality of controller  220  and time-of-flight analysis and control system  414 . Digital processing and control system  510  also includes the capability to control analyzer power supply  386  and to receive signals from current measurement system  334  and to coordinate adjustment of V an  with measurement of current signals from current sensor  322  to perform beam energy spectrum measurement, with data in the form of beam current as a function of cluster ion energy or alternatively in the form of cluster ion energy as a function of beam current, of the attenuated and collimated GCIB  307  sample of GCIB  128  and to integrate the measurement of beam current as a function of cluster ion energy with respect to cluster ion energy to determine the cluster ion current, I, in the attenuated and collimated GCIB  307 . 
   Digital processing and control system  510  may be, for example, a small general-purpose computer for general control of a GCIB processing system. Digital processing and control system  510  has a control bus  504  for communicating with and controlling other devices and/or subsystems. Anode power supply  134 , filament power supply  136 , and accelerator power supply  140  are each equipped with remote control capabilities and are controllably connected to the digital processing and control system  510  for control thereby via control bus  504 . Electronically controllable gas metering valve  512  is also controllably connected to the digital processing and control system  510  for control thereby via control bus  504 . Electrical lead  508  connects current measurement system  334  with digital processing and control system  510  for transmitting current measurement signals from current sensor  322 . The improved GCIB measurement and processing apparatus  500  additionally incorporates all of the elements of the hereinbefore-described GCIB measurement apparatus  300 . Digital processing and control system  510  communicates with and controls (via control bus  504 ) at least the following devices: suppressor power supply  384 , for switching V S1  on or off; the beam gating controller  398  for sending beam gating commands; mechanical actuators  328  and  360  for commanding positioning of (respectively) analyzer mounting and alignment plate  324  and particle detector mounting and alignment plate  352  with respect to GCIB axis  129 ; anode power supply  134 , for controlling V A ; filament power supply  136 , for controlling V F ; accelerator power supply  140 , for controlling V Acc ; electronically controllable gas metering valve  512 , for controlling source gas  112  flow through nozzle  110  and/or source gas pressure in stagnation chamber  116 ; analyzer power supply  386 , for controlling V An ; optionally, if included, lens power supply  388  for controlling V L3 ; dynode power supply  390 , for controlling V Dy ; suppressor power supply  392 , for switching V S2  on or off; and PMT controller/pulse counter/sampling system  356  for controlling supply voltages for PMT  350  and for enabling or disabling pulse detection and signal sampling by PMT  350  and for controlling transmission of pulse count (Γ measurement) information from PMT controller/pulse counter/sampling system  356  to  510  via electrical lead  506 . The digital processing and control system  510  controllably connects to the X-scan actuator  202  and the Y-scan actuator  204  through electrical cable  216  and controls the X-scan actuator  202  and the Y-scan actuator  204  so as to place the workpiece  152  into or out of the path of GCIB axis  129  and can remove the workpiece holder  150  to a position, as shown in  FIG. 9 , where it does not collide with nor interfere with the function of components mounted on particle detector mounting and alignment plate  352 . When the analyzer mounting and alignment plate  324 , the particle detector mounting and alignment plate  354 , and the workpiece holder  152  are positioned as shown in  FIG. 9 , then 
             (     E   q     )     average         
and Γ are measured by the digital processing and control system  510  according to the methods hereinbefore-described. When the digital processing and control system  510  commands retraction of the particle detector mounting and alignment plate  352  from the GCIB axis  129 , the configuration shown in  FIG. 4  is obtained and beam current value I is measured according to the method hereinbefore-described. Using the configuration shown in  FIGS. 4 and 5 , the digital processing and control system  510  commands beam gating controller  398  to gate the beam off and measures the average velocity {overscore (v)} by time of methods hereinbefore-described. Digital processing and control system  510  calculates {overscore (q)} according to Eqn. 2, and calculates Ē according to Eqn. 3, and calculates {overscore (m)} according to Eqn. 5.
 
     FIG. 10  is a schematic  550  showing the improved GCIB measurement and processing apparatus according to the preferred first embodiment of the invention, with the beam measurement apparatus removed from the beam to allow workpiece processing. As shown, both the analyzer mounting and alignment plate  324  and the particle detector mounting and alignment plate have been retracted from the path of the GCIB  128  by command of the digital processing and control system  510 . A workpiece  152 , which may be a semiconductor wafer, is held by workpiece holder  150 . Workpiece holder is manipulated by the X-scan actuator  202  and the Y-scan actuator  204  under control of the digital processing and control system  510  so as to place the workpiece  152  into or out of the path of GCIB  128  and to scan the workpiece  152  uniformly relative to the GCIB  128  to achieve uniform processing of the workpiece  152  by the GCIB  128 . Controller  510  receives the sampled beam current collected by the beam current sensor  376  by way of lead  368  and current measuring system  370  and thereby monitors the GCIB  128  and controls the GCIB dose received by the workpiece  152  by removing the workpiece  152  from the GCIB  128  when a predetermined desired dose has been delivered. Prior to initiation of processing of a workpiece by GCIB, desired target values or limiting values for any or all of Ē, I T , {overscore (m)} and {overscore (q)} are chosen and stored within the digital processing and control system  510 . For the GCIB parameters for which target or limiting values are stored, the digital processing and control system  510  measures those GCIB parameters on the GCIB  128  as described hereinbefore. Any GCIB parameters that are measured as not in compliance with the stored limits or targets are adjusted under control of the digital processing and control system  510 . Ē is adjusted, for example, by adjusting V Acc . I T  is adjusted, for example, by adjusting electronically controllable gas metering valve  512  and/or by adjusting V A  and/or by adjusting V F . {overscore (m)} is adjusted, for example, by adjusting electronically controllable gas metering valve  512 . {overscore (q)} is adjusted, for example, by adjusting V A  and/or V F . When GCIB parameters, for which desired target values or limiting values have been stored, have all been obtained by automatic adjustment, the digital processing and control system  510  proceeds with the processing of the workpiece  152 . The digital processing and control system  510  monitors and, if necessary adjusts, GCIB parameters for which desired target values or limiting values have been stored prior to the processing of each workpiece. If the digital processing and control system  510  is unable, by system adjustments, to achieve the stored beam target or limit values, it halts processing and signals (through display means, not shown) a human operator, thus avoiding mis-processing of the workpiece or workpieces. 
     FIG. 11  is a schematic showing an improved GCIB measurement and processing apparatus  600  according to a preferred second embodiment of the invention. GCIB measurement and processing apparatus  600  is similar to the prior art mechanically scanning GCIB processing apparatus  200 , but having GCIB measurement, monitoring, and control improvements for implementing the second embodiment of the invention. Gas metering valve  113  of the prior art processing system is replaced by electronically controllable gas metering valve  512 . The beam current sensor  218  of the prior art system and its electrical lead  214  are replaced by aperture  372 , (m/q) sensor  432  and electrical lead  448 . Controller  220  of the prior art system is replaced by digital processing and control system  510  having improved capabilities and functions, including but not limited to all the hereinbefore described functionality of controller  220 . Digital processing and control system  510  may be, for example, a small general-purpose computer for general control of a GCIB processing system. Digital processing and control system  510  has a control bus  504  for communicating with and controlling other devices and/or subsystems. Anode power supply  134 , filament power supply  136 , and accelerator power supply  140  are each equipped with remote control capabilities and are controllably connected to the digital processing and control system  510  for control thereby via control bus  504 . Electronically controllable gas metering valve  512  is also controllably connected to the digital processing and control system  510  for control thereby via control bus  504 . The improved GCIB measurement and processing apparatus  500  additionally incorporates all of the elements of the hereinbefore-described GCIB measurement apparatus  300 , except that the previously described electrostatic deflector plate  394 , electrical lead  396 , and beam gating controller  398  of the GCIB switching subsystem are not used. Also the separate secondary electron suppressor  374 , the beam current sensor  376 , electrical lead  368  and current measuring system  370  previously described are not used. The (m/q) sensor  432  comprises a perforated faraday cup  434  with a secondary electron suppressor  436  and a pressure sensor  442 . An electrical lead  448  connects perforated faraday cup to a conventional current measurement system  446  for electrical current measurement. An electrical cable  438  connects pressure sensor  442  to a (m/q) measurement system  440  for transmitting pressure and temperature signals and sensor power. An electrical lead  444  transmits electrical current measurement signals from current measurement system  446  to the (m/q) measurement system  440 . The current measurement system  446  and the (m/q) measurement system  440  are both remotely controllable and able to provide data signals to digital processing and control system  510 . 
   The digital processing and control system  510  communicates with and controls (via control bus  504 ) at least the following devices: suppressor power supply  384 , for switching V S1  on or off; mechanical actuators  328  and  360  for commanding positioning of (respectively) analyzer mounting and alignment plate  324  and particle detector mounting and alignment plate  352  with respect to GCIB axis  129 ; anode power supply  134 , for controlling V A ; filament power supply  136 , for controlling V F ; accelerator power supply  140 , for controlling V Acc ; electronically controllable gas metering valve  512 , for controlling source gas  112  flow through nozzle  110  and/or source gas pressure in stagnation chamber  116 ; analyzer power supply  386 , for controlling V An ; optionally, if included, lens power supply  388 , for controlling V L3 ; dynode power supply  390 , for controlling V Dy ; suppressor power supply  392 , for switching V S2  on or off; (m/q) measurement system  440 , for controlling pressure sensor power and for commanding (m/q) measurement and transmission; and PMT controller/pulse counter/sampling system  356  for controlling supply voltages for PMT  350  and for enabling or disabling pulse detection by PMT  350  and for controlling transmission of pulse count (Γ measurement) information from PMT controller/pulse counter/sampling system  356  to  510  via electrical lead  506 . Current measurement system  446  supplies total beam current I T  measurement signals to (m/q) measurement system  440  via electrical lead  444  and also to digital processing and control system  510  via electrical lead  604 . (m/q) measurement system  440  provides (m/q) measurement signals to digital processing and control system  510  via electrical lead  602 . The digital processing and control system  510  controllably connects to the X-scan actuator  202  and the Y-scan actuator  204  through electrical cable  216  and controls the X-scan actuator  202  and the Y-scan actuator  204  so as to place the workpiece  152  into or out of the path of GCIB axis  129  and can remove the workpiece holder  150  to a position as shown to facilitate GCIB  128  total beam current I T  measurement or to facilitate other GCIB parameter measurements. The digital processing and control system  510  commands the analyzer mounting and alignment plate  324 , the particle detector mounting and alignment plate  354 , and the workpiece holder  152  into positions analogous to those shown in  FIG. 9 , and then 
             (     E   q     )     average         
and Γ are measured by the digital processing and control system  510  according to the methods hereinbefore-described. The digital processing and control system  510  commands the analyzer mounting and alignment plate  324 , the particle detector mounting and alignment plate  354 , and the workpiece holder  152  into positions as shown in  FIG. 11  and I T  and (m/q) are measured according to the methods hereinbefore-described. The digital processing and control system  510  calculates {overscore (q)} according to Eqn. 2, and calculates Ē according to Eqn. 3, and calculates {overscore (m)} according to Eqn. 4. As shown in  FIG. 11 , both the analyzer mounting and alignment plate  324  and the particle detector mounting and alignment plate have been retracted from the path of the GCIB  128  by command of the digital processing and control system  510  for workpiece processing by GCIB irradiation. A workpiece  152 , which may be a semiconductor wafer, is held by workpiece holder  150 . Workpiece holder is manipulated by the X-scan actuator  202  and the Y-scan actuator  204  under control of the digital processing and control system  510  so as to place the workpiece  152  into or out of the path of GCIB  128  and to scan the workpiece  152  uniformly relative to the GCIB  128  to achieve uniform processing of the workpiece  152  by the GCIB  128 . Controller  510  receives the sampled beam current collected by the perforated faraday cup  434  by way of lead  448  and current measuring system  446  and electrical lead  604  and thereby monitors the GCIB  128  total beam current I T  and controls the GCIB dose received by the workpiece  152  by removing the workpiece  152  from the GCIB  128  when a predetermined desired dose has been delivered.
 
   Prior to initiation of processing of a workpiece by GCIB, desired target values or limiting values for any or all of Ē, I T , {overscore (m)} and {overscore (q)} are chosen and stored within the digital processing and control system  510 . For the GCIB parameters for which target or limiting values have been stored, the digital processing and control system  510  measures those GCIB parameters on the GCIB  128  as described hereinbefore. Any GCIB parameters that are measured as not in compliance with the stored limits or targets are adjusted under control of the digital processing and control system  510 . Ē is adjusted, for example, by adjusting V Acc . I T  is adjusted, for example, by adjusting electronically controllable gas metering valve  512  and/or by adjusting V A  and/or by adjusting V F . {overscore (m)} is adjusted, for example, by adjusting electronically controllable gas metering valve  512 . {overscore (q)} is adjusted, for example, by adjusting V A  and/or V F . When GCIB parameters, for which desired target values or limiting values have been stored, have all been obtained by automatic adjustment, the digital processing and control system  510  proceeds with the processing of the workpiece  152 . The digital processing and control system  510  monitors and, if necessary, adjusts GCIB parameters for which desired target values or limiting values have been stored prior to the processing of each workpiece. If the digital processing and control system  510  is unable, by system adjustments, to achieve the stored beam target or limit values, it halts processing and signals (through display means, not shown) a human operator, thus avoiding mis-processing of the workpiece or workpieces. 
   Although the invention has been described with respect to measurement of gas cluster ion beams, it is recognized by the inventor that the invention is also applicable to measurement of parameters of cluster ion beams that do not comprise source materials that are gaseous under conditions of standard temperature and pressure and thus is useful in the more general case of measurement of cluster ion beams, including gas cluster ion beams and non-gas cluster ion beams such as, for example, metal cluster ion beams. It is further recognized by the inventor that the invention is useful for measuring parameters of molecular ion beams comprising very heavy molecules. Although the invention has been described with respect to various embodiments, it should be realized this invention is also capable of a wide variety of further and other embodiments within the spirit of the invention.