Patent Number: 044619545
Section: claims

1. A method of processing a workpiece with a beam of energetic ions, comprising the steps of: positioning a slender tubular member to bring an open end thereof into spaced juxtaposition with a workpiece across a small gap of a size ranging between 10 and 1000 .mu.m in an evacuated space;  supplying said tubular member with an ionizable gas for feeding it into said gap through said open end;  energizing said supplied gas to form ions thereof and supplying an electrical potential to said ions to propel them in a beam across said small gap to impinge onto a limited area of the surface of said workpiece juxtaposed with said open end; and  maintaining the pressure within said small gap in excess of the pressure in said space surrounding said small gap.  a slender tubular member having an open end and communicating with an inlet conduit;  means for positioning said slender tubular member to bring said open end into spaced juxtaposition with the workpiece across a small gap of a size ranging between 10 and 1000 .mu.m in an evacuated space;  means for supplying an ionizable gas into said slender tubular member through said inlet conduit and feeding said gas into said small gap through said open end;  means for energizing said supplied gas to form ions and applying an electrical potential to said ions to propel them in a beam across said small gap to impinge on a limited area of the surface of said workpiece juxtaposed with said open end; and  means for maintaining the pressure within said small gap in excess of the pressure of said space surrounding said small gap. 2. The method defined in claim 1 wherein said gap size is not greater than 50 .mu.m. 3. The method defined in claim 1 or claim 2 wherein the pressures in said atmosphere and within said small gap are maintained in the range between 10.sup.-6 and 10.sup.-4 Torr and in the range between 10.sup.-4 and 10.sup.-1 Torr, respectively. 4. The method defined in claim 1 wherein the pressure within said small gap is maintained so as to be greater by at least one order in Torr than the pressure in said space. 5. The method defined in claim 1 wherein said pressures are maintained by continuously replenishing said ionizable gas into said slender tube member while continuously evacuating said space. 6. The method defined in claim 1 wherein said ionizable gas is at least one substance selected from the group which consists of argon, nitrogen, hydrogen and oxygen. 7. The method defined in claim 1 wherein said ionizable gas is at least one substance selected from the group which consists of polyhalogenated hydrocarbons containing fluorine and chlorine; fluorides; and chlorides. 8. The method defined in claim 1, further comprising the step of applying a magnetic field of a magnetic flux density in excess of 500 Gauss to said ions in the region of said small gap to controlledly facilitate dispersion of said ions impinging on said workpiece in said small gap. 9. The method defined in claim 1, further comprising the step of relatively displacing said workpiece and said slender tubular member in a plane substantially orthogonal to the longitudinal axis of said slender tubular member along a prescribed path to successively process said surface in a scanning manner over a predetermined area thereof. 10. The method defined in claim 1 or claim 9, further comprising the step of displacing said slender tubular member relative to said workpiece in the direction of the longitudinal axis of said slender tubular member to maintain said gap size substantially constant. 11. The method defined in claim 10, further comprising the steps of electrically sensing said gap size to provide a control signal and, in response to said control signal, axially displacing said slender tubular member towards said workpiece so as to maintain said gap size substantially at a predetermined value. 12. The method defined in claim 1 wherein said slender tubular member is composed at least in part of an electrically conductive material to constitute one of a pair of electrodes with respect to said workpiece constituting the other electrode for establishing said electrical potential therebetween. 13. The method defined in claim 12 wherein said slender tubular member is composed at least in a region of said open end of said electrically conductive material constituting said one electrode. 14. The method defined in claim 13 wherein said ions are formed within said small gap under said electrical potential. 15. The method defined in claim 1 or claim 14 wherein said electrical potential ranges between 1 and 10 kV. 16. An apparatus for processing a workpiece with a beam of ions, comprising: 17. The apparatus defined in claim 16 wherein the last-mentioned means include a receptacle for receiving said workpiece and at least a portion of said open end of the slender tubular member and vacuum pump means for maintaining the pressure in said space within said receptacle in a range between 10.sup.-6 and 10.sup.-4 Torr. 18. The apparatus defined in claim 17 wherein said supply means includes valve means constituting a portion of said pressure-maintaining means and arranged between said inlet conduit and a source of said gas, said valve means being adjustable so as to maintain the pressure within said small gap in a range between 10.sup.-4 and 10.sup.-1 Torr. 19. The apparatus defined in claim 18, further comprising means responsive to a change in the pressure within said small gap for controlling at least one of said vacuum pump means and said valve means. 20. The apparatus defined in claim 16, further comprising means responsive to a change in said gap size for relatively displacing said slender tubular member at said workpiece so as to maintain said gap size substantially at a predetermined value. 21. The apparatus defined in claim 16 or claim 20, further comprising means for relatively displacing said workpiece and said slender tubular member in a plane substantially orthogonal to the longitudinal axis of said slender tubular member along a prescribed path to successively process said workpiece surface in a scanning manner over a predetermined area. 22. The apparatus defined in claim 16 wherein said tubular element is composed at least in part of an electrically conductive material to constitute one of a pair of electrodes with respect to said workpiece constituting the other electrode for establishing said electrical potential therebetween. 23. The apparatus defined in claim 22 wherein said slender tubular member is composed at least in a region of said open end of said electrically conductive material constituting said one electrode. 24. The apparatus defined in claim 22 or 23 wherein said one electrode is poled to be anodic and said other electrode is poled to be cathodic. 25. The apparatus defined in claim 16 or claim 23 wherein said slender tubular member has an inner diameter ranging between 0.1 and 0.5 mm. 26. The apparatus defined in claim 16 or claim 23, further comprising means for applying a magnetic field of a flux magnetic density in excess of 500 Gauss to said beam of ions in the region of said small gap to controlledly facilitate dispersion of said ions impinging on said workpiece.