MICROFABRICATED TEMPLATE FOR MULTIPLE CHARGED PARTICLE BEAM CALIBRATIONS AND SHIELDED CHARGED PARTICLE BEAM LITHOGRAPHY

Abstract: A method, an associated structure, and an apparatus for multiple charged particle beam calibration and shielded charged particle lithography. A template defining an array of membranes is positioned above a target (e.g., a semiconductor wafer of the electron beams). Each membrane defines a through slot (opening) and a set of registration marks which are located with respect to registration marks of the other membranes. Patterns are written onto the target by scanning each electron beam through its associated through slot. Intra- and inter-charged particle beam calibrations for each charged particle beam are carried out using its associated set of registration marks. The template also suppresses undesirable electrical charging of any resist present on the target during the exposure process.

Description: MICROFABRICATED TEMPLATE FOR MULTIPLE CHARGED PARTICLE BEAM CALIBRATIONS AND SHIELDED CHARGED PARTICLE BEAM LITHOGRAPHY FIELD OF THE INVENTION This invention relates to charged particle beam lithography, and in particular to charged particle beam lithography using multiple charged particle beams. BACKGROUND Manufacturing of integrated circuit devices is dependent upon the accurate transferring of the patterns onto various layers on the surface of the semiconductor wafer, which after processing is sawn to provide the integrated circuit die. These patterns define the various regions in the integrated circuit (IC) die and are generally formed by transferring patterns to the surface of the wafer by a number of different processes, e.g., photolithography, ion beam lithography, and electron-beam lithography. In the case of a single charged particle beam system, a precise beam of charged particles is directed to a specific point on the surface of a substrate coated with a layer of resist sensitive to the incident charged particle beam. The resist is then developed and the exposed areas either remain or are removed, defining a pattern on the surface of the wafer. Subsequent steps etch away the exposed portions of the wafer surface to define semiconductor features. Charged beam lithography such as the electron beam lithography is also well known for fabricating the masks (reticles) used subsequently in optical lithography for IC fabrication. In the case of a multiple charged particle beam system, multiple beams of particles are directed to various die on a wafer in the same time. Integrated circuits (ICs) are typically each one die. A typical semiconductor wafer contains many (for instance hundreds of) such die arranged in a grid. Microcolumn is a well known technology in the electron beam lithography field. A typical electron beam lithography machine has a single source of electrons, an associated accelerator (electrostatic) device for accelerating the electrons, and a set of elements which are typically coaxial electro-magnets for focusing the beam onto the substrate. However, it is known (see e.g., U.S. Patent Nos. 5,155,412 and 5,122,663 assignee IBM and "Electron-Beam Microcolumns for Lithography and Related Applications," by Chang, T. et al . , Journal of Vacuum Science Technology Bulletin 14(6), pp. 3774- 3781, Nov. /Dec. 1996, incorporated herein by reference) to provide an array of microcolumns, called a multiple-electron- beam exposure system, which uses a plurality of charged particle beams to write identical patterns on a plurality of die at the same time to thereby improve productivity. Each individual microcolumn in the multiple-electron-beam exposure system is a complete electron-beam column having a typical diameter of approximately 1 to 2 centimeters. For lithography, microcolumns build on the demonstrated ability of scanning electron beams to direct-write device features with critical dimensions down to well below lOOnm, and to perform the essential alignment and overlay of patterns in multilayer processes. Operating at low beam energies, 1-2 keV, the microcolumns also have the advantage of not requiring proximity effect corrections and are significantly more efficient in resist exposure. Nevertheless, electron-beam exposure of the resist generates a net positive or negative electrical charge on the resist surface, which is normally non-conductive. When not properly discharged, the electrical charge creates an electric field which adversely affects the incident electron beam, causing distortions and beam placement errors. With the demands put on electron-beam systems by the continually decreasing feature size of IC devices, such distortions and placement errors may be detrimental to the system. However, at low electron beam voltage, it is impractical to use a discharge layer, which is typically positioned on top of the resist layer, due to the lack of penetration of the incident electrons . Accordingly, what is needed is suppression of resist charging during the exposure process. Conventional arrayed (microcolumn) lithography is shown in FIG. 1 (prior art) . One or more columns 106, 108 expose die 102, 104, respectively, which are arranged in a grid pattern on a wafer 100. Patterns on wafer 100 can be written in either vector or raster scan modes over a relatively narrow stripe of about 50-100 μm in width. The patterns are "stitched" using a laser 112 controlled table 110 moving in synchronism with pattern writing. One requirement for parallel multiple charged particle beam lithography (such as a system based on an array of electron microcolumns) is intra- and inter-column (or beam) calibrations so that the patterns are accurately transferred onto various layers on various die on the semiconductor wafer surface. For a single writing tool, e.g., a single electron- beam microcolumn, a set of registration marks is used to align one pattern layer of metal, insulator, or semiconductor material on a substrate with another pattern layer to ensure that features of the successive layers bear the correct spatial relationship to one another. The features of the registration marks are typically used to align the substrate with the lithographic writing tool for optical or direct electron-beam writing lithography. During the lithography process, the registration marks are observed and used to properly align the lithographic pattern with the underlying layer. A multiple-charged-particle-beam lithographic system includes multiple writing tools, e.g., a microcolumn array, each microcolumn being discrete. Therefore, in addition to intra-column calibrations, inter-column calibrations must be carried out to coordinate the microcolumns in relation to one another. The calibrations must not only be accurate but also efficient for good throughput. Accordingly, what is also needed is efficient and accurate calibration of multiple charged particle beams for multiple charged particle beam lithography. SUMMARY In accordance with the present invention, a method, an associated structure, and an apparatus for in-situ and in- parallel multiple charged particle beam calibrations and shielded charged particle beam lithography are provided. A template opaque to the charged particle beams and defining an array of membranes is placed above the target substrate, e.g., a semiconductor wafer or perhaps a reticle being fabricated. Each membrane in the template defines a through slot (a portion transmissive to the electron beam such as an opening) and a set of registration marks which are located with respect to the registration marks of the other membranes. In other embodiments, the transmissive portions and registration marks are defined in the template with no membranes. Patterns are written onto the resist-coated target substrate through the slots by the charged particle beams. The registration marks are used by each individual charged particle beam to perform inter- charged particle beam calibrations, i.e. positional calibration relative to other charged particle beams in the charged particle beam array, as well as intra-charged particle beam calibrations, i.e. system calibrations for individual charged particle beams. In one embodiment, the charged particle beams are electron beams. In another embodiment, the charged particle beams are ion beams. The template with its slots allows intra- and inter- charged particle beam calibrations, and suppresses undesirable resist charging during the exposure process. The template is, e.g., of crystalline silicon for ease of fabrication. In one embodiment, the template is held in close proximity to the target wafer with a predetermined distance therebetween. In another embodiment, the membrane is doped such that it "sags" from the template toward the target substrate. In yet another embodiment, the membrane is fashioned into a cantilever that is actuated into contact with the target substrate during exposure. In another embodiment, the entire template is placed in contact with the target substrate. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a prior art arrayed microcolumn exposure system using one or more microcolumns per die. FIG. 2A shows multiple charged particle beam lithography through a template. FIG. 2B shows an embodiment of the template, where the through slot is circular. FIG. 3A shows a system for shielded charged particle beam lithography. FIG. 3B shows a capacitive gap sensor. FIG. 4 shows an embodiment of the template, having a sagging membrane. FIG. 5A shows a top plane view of a template having multiple membrane cantilevers. FIG. 5B shows a partial side view of the FIG. 5A structure . FIG. 6 shows a application of a current in the membrane. DETAILED DESCRIPTION The present invention is directed to a calibration method using a template having in one embodiment a plurality of membranes each corresponding to an incident charged particle beam and each defining a through slot and a set of registration marks, to achieve high positional accuracy and precise calibration for lithography using multiple charged particle beams . The detailed description is directed toward an electron- beam system. However, the systems and methods described herein are equally applicable to other charged particle beam systems such as an ion beam system. FIG. 2A shows an implementation of multiple electron beam lithography through such a template. It is understood that the target substrate (e.g., the wafer) 202 is held on conventional x-y wafer stage 215 which is a part of the arrayed lithography system. Stage 215 facilitates wafer movement in synchronism with pattern writing. The movement of stage 215 is conventionally controlled by, e.g., laser interferometry location measurement. FIG. 2A shows template 204 supporting an array of membranes 206a, 206b, 206c, 206d, each defining a through slot 208a, 208b, 208c, 208d, respectively, and a corresponding set of registration marks 210a, 210b, 210c, 210d that are located with respect to the other sets of registration marks in the array, respectively. Template 204 and membranes 206a, 206b, 206c, 206d may be made of, but are not limited to, crystalline silicon (Si), diamond, silicon carbide (SiC) and thin metallic foils such as beryllium (Be) and aluminum (Al) . In one embodiment, the membranes are integral parts of template 204. However, membranes 206a, 206b, 206c, 206d and template 204 need not be of the same material. Template 204 and membranes 206a, 206b, 206c and 206d are doped to be conductive. Relevant characteristics of template 204 and membranes 206a, 206b, 206c, 206d are: (1) opacity to electron beams; (2) easily fabricated to precise dimensions; and (3) conductive. Silicon has the advantages of manufacturability, strength, and electric conductivity where necessary. For direct write lithography on a silicon substrate, silicon template 204 also provides the advantage of having the same thermal expansion coefficient as the target silicon wafer 202. As an alternative, template 204 may be made of any other material having a similar thermal expansion coefficient as the target substrate 202, but this is not limiting. Template 204 is either in "contact mode", i.e., placed in contact with the substrate of target wafer 202 (target substrate) or in "proximity mode", i.e., placed in close proximity to target substrate 202 and there being a predetermined distance between template 204 and target substrate 202 during exposure. For contact mode, template 204 either remains in contact with target substrate 202 or is moved out of contact during the wafer movement on its stage 606. Lifting template 204 out of contact with target substrate 202 is achieved by using, for example, piezo actuators 604, as shown in FIG. 3A. In one embodiment, template 204 is held to a template stage 606 by clamping the edges of template 204, above the target substrate stage 215 holding target substrate 202. In an alternative embodiment, template 204 is held to a template stage 602 by electrostatic means. Piezo actuators 608 move template stage 606 up and down, thus in and out of contact with target substrate 202. Height reference posts 612 or LED based height sensing system 610 controls the vertical movement of piezo actuators 608, as will be discussed in details below. Proximity mode operation has the advantage of avoiding possible damage and contamination to template 204 and target substrate 202. In one embodiment, template 204 is held by an appropriate template stage 606 (FIG. 3A) as described above and placed close to target substrate 202 very precisely. The desired gap between template 204 and target substrate 202 during exposure is maintained, in one embodiment, by predefining a gap using precisely machined height reference posts 612, as shown in FIG. 3A. During exposure, template stage 606, along with template 204, are pushed by piezo actuators 608 downwards until height reference posts 612 are in contact with wafer stage 215, or other reference structures. After exposure, piezo actuators 608 lift template 204 and template stage 606 upwards for subsequent wafer move. In another embodiment, the gap between template 204 and target substrate 202 is measured precisely using an LED-based height sensing system 610. In this embodiment, the sensor in LED-based height sensing system 610 references either template stage 606, template 204, or both, in measuring the gap. In yet another embodiment, the gap between template 204 and target substrate 202 is measured precisely using a capacitive gap sensor 614 (FIG. 3B) located proximate to template 204 and target substrate 202 to measure the capacitance between template 204 and target substrate 202. The measured capcitance is then translated into a gap width. In one embodiment, each membrane 206a, 206b, 206c, 206d has dimensions of 1mm by 1mm or less and a thickness of 1 micron or less. Membranes 206a, 206b, 206c, 206d are fabricated by conventional micromachining processes well known in the art, such as a combination of lithography and etching, to define the thinned out membranes 206, 206b, 206c, 206d and slots 208a, 208b, 208c, 208d. In one embodiment, template 204 contains as many membranes 206 as there are microcolumns 213 in the microcolumn array so that each microcolumn 213a, 213b, 213c, 213d is calibrated individually using its own associated set of registration marks 210. The template 204 is aligned to the electron beams, e.g., first by a coarse alignment using mechanical and optical microscopes and then by a fine alignment using electron beams by monitoring current and detecting registration marks 210. A typical thickness of template 204 (exclusive of the membrane portions) is approximately 200μm to approximately 300μm. In one embodiment, the size of template 204 is determined by the size necessary to accommodate the microcolumn array. In another embodiment, the size of template 204 is the same size as target substrate 202. Each through slot 208 is formed in the associated membrane 206, for example, by a combination of lithography and dry etching. Through slot 208 is, e.g., a rectangle shape having a length slightly longer than the incident electron beam 212 scan length (e.g. < 100 μm) and a width slightly larger than the incident electron beam 212 scan width (e.g. < 10 μm) . Each microcolumn 213a, etc. writes a pattern (typically a stripe) onto the target substrate 202 using the microcolumn' s incident electron beam 212 passing the through slot 208 in membrane 206. (One reason to have the membrane is to enable fabrication of the slots by conventional micromachining processes; in some embodiments, there are slots in the template and no membranes.) Template 204 shields exposed areas on the target wafer 202 from incident electron beams 212a, 212b, 212c, 212d after exposure, thereby suppressing potential resist charging problems associated with electron beam lithography. This is because template 204, except for through slots 208a, etc., is opaque to the incident electron beams 212a, 212b, 212c, 212d. Template 204 shields exposed areas from incident electron beams 212a, 212b, 212c, 212d after exposure by moving target wafer 202 to the next exposure location following each exposure. In other words, except for the area under through slots 208a, 208b, 208c, 208d, the resist surface is normally covered by template 204 during exposure. As a result, through slots 208a, 208b, 208c, 208d in template 204, and incident electron beams 212a, 212b, 212c, 212d are shielded from any electric fields near the target wafer 202 generated at previously exposed regions . To obtain spatial coherence (exact location) in the placement of registration marks 210a, 210b, 210c, 210b on membranes 206a, 206b, 206c, 206d, respectively, registration marks 210a, 210b, 210c, 210d are patterned using, e.g., a commercially available very precise electron-beam lithography system or a conventional long-range spatially-coherent lithography system using conventional interferometric alignment. Registration marks 210a, etc. are then transferred, for example, by using an additive technique such as, but not limited to, lift-off or plating, or a subtractive technique such as, but not limited to, partial etching of membranes 206a, etc. Intra- and inter-column calibrations for positional accuracy for each microcolumn 213a, etc., i.e. relative to the other microcolumns in the array and to target wafer 202, are carried out in-situ (i.e. at the point of exposure) and in parallel. Calibrating microcolumns 213a, 213b, 213c, 213d in- situ and in parallel is possible because each microcolumn 213a, etc. has its own set of registration marks 210a, etc., respectively, rather than sharing a set of registration marks. The spatially coherent registration marks 210 in addition to facilitate each microcolumn 213 in the microcolumn array to calibrate itself for positional accuracy relative to each other as well as to target wafer 202, registration marks 210a, etc. are also used for system calibrations for individual microcolumns 213a, etc. such as to correct for drift, magnification or distortion. In one embodiment, the sum of the membrane thickness and the spacing between template 204 and target wafer 202 (if in proximity mode) is within the focal depth of incident electron beam 212 of microcolumn 213, which is typically 0.5 to a few microns. In another embodiment, each electron beam is focused individually and the calibration is performed with, e.g., each incident electron beam 212a focused on its respective registration mark 210a on membrane 206a. The results are then compensated to account for the difference of the result obtained from focusing the electron beam 212a in the focal plane of registration marks 210a and the result obtained from focusing the electron beam 212a in the focal plane of the target wafer 202 by computational means. By focusing on registration marks 210a, the height constraint limited by the focal depth of incident electron beam 212a is eliminated. FIG. 2B shows an embodiment of template 204, where through slot 208 is circular. Through slot 208 may be of other shapes as well because any arbitrary shapes may be defined by etching through crystalline structure using reactive ion etching (RIE) or dry etching. In one embodiment, RIE or dry etching is made anisotropic (i.e., independent of the crystal direction) to etch features with straight sidewalls. FIG. 4 shows an embodiment of the template, having a "sagging" membrane. Membrane 306 is compressively stressed, e.g., by doping, such that membrane 306 extends (sags) from template 304 toward target wafer 302. (A thin crystalline membrane is known to take on this shape when subject to doping at appropriate levels so that the crystalline membrane is conductive.) Sagging membrane 306 allows template 304 to maintain a gap from target wafer 302 such that template 304 avoids contact with target wafer 302. Depending on the doping level and membrane thickness, membrane 306 may or may not come into direct contact with target wafer 302. In one embodiment, the entire template surface is doped to a depth equivalent to the membrane thickness by, e.g., ion-implantation, thermal diffusion or eiptaxial growth. The microcolumns (not shown) are calibrated using their respective registration marks 310 as discussed above. An incident electron beam (not shown) from the microcolumn then writes a pattern through through slot 308. FIG. 5A shows a top plane view of a template having multiple membrane cantilevers. FIG. 5B shows a partial side view of the FIG. 4A structure. Template 404 is in proximity mode and membranes 406a, 406b, 406c, 406d are fashioned into cantilevers 414a, 414b, 414c, 414d, respectively. Membranes 406a, 406b, 406c and 406d are shaped by conventional lithography and etching process into cantilevers 414a, 414b, 414c and 414d, respectively. A piezo electric material, such as, but not limited to, tin oxide, is patterned on the back surface of cantilevers 414a, 414b, 414c, 414d for bending the cantilevers 414a etc. By fashioning membrane 406 into cantilever 414, the cantilever 414 portion of template 404 may be positioned in close proximity to target wafer 402, thus facilitating wafer movement without the remainder of template 404 coming into contact with target wafer 402. During exposure, membrane cantilever 414 with its through slot 408 is actuated into contact with target wafer 402 while maintaining the gap between template 404 and target wafer 402 by, e.g., application of a voltage. In one embodiment, the voltage is generated by electrostatic means which generate an electric field between template 404 and target wafer 402. In another embodiment, the voltage is generated by piezo electric means where a piezo electric material is deposited on cantilever 414 as described above. Cantilever 414 is then actuated by application of a voltage via, e.g., interconnects formed using conventional interconnect technology. In one embodiment, template 404 is supported above wafer 402 by a template stage (not shown) . The template may be covered by resist material over time, thereby giving rise to resist charging problem. This resist charging problem may be reduced or eliminated by heating the template with, for example, an electric current. By passing a current through the silicon membrane, the membrane is heated and the resist buildup is burned off. FIG. 6 shows electrodes 500 and 501 having voltage potentials +V and -V, respectively, connected directly to template 504 on either side of membrane 506. A current I thus flows through membrane 506 from electrode 500 toward electrode 501. In one embodiment, the membrane is kept warm to prevent buildup of organic materials. In an alternative embodiment, the template is removed and cleaned regularly or on an as-needed basis. In yet another embodiment, the template is removed and replaced regularly or on an as-needed basis. Although the invention has been described with reference to particular embodiments, the description is only an example of the invention's application and should not be taken as a limitation. For example, the above description also applies to low-energy ion microcolumns and in fabrication of masks (reticles) . Various other adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as defined by the following claims.

Claims: CLAIMS We claim: 1. A method for charged particle lithography, comprising the acts of: providing a template defining at least one transmissive portion corresponding to a charged particle beam; positioning the template between a target and a source of the charged particle beam; and directing each charged particle beam through the corresponding transmissive portion onto the target. 2. The method of Claim 1, wherein the charged particle beam is an electron beam. .3. The method of Claim 2, wherein the electron beams each has an energy level in the range of approximately 1 KeV to approximately 2 KeV. 4. The method of Claim 1, wherein the charged particle beam is an ion beam. 5. The method of Claim 4, wherein the ion beam is a low- energy ion beam. 6. The method of Claim 1, wherein the target is a substrate coated with a resist layer, whereby the template suppresses resist charging on the resist layer. 7. The method of Claim 1, wherein each transmissive portion is an opening defined in a membrane in the template, the membrane being thinner than a remainder of the template. 8. The method of Claim 7, further comprising the act of compressively stressing the membrane so that the membrane extends from the template toward the target. 9. The method of Claim 7, further comprising the act of cantilevering the membrane. 10. The method of Claim 9, further comprising the act of applying a voltage to actuate the cantilever into contact with the target wafer. 11. The method of Claim 7, wherein a sum of the membrane thickness and a spacing between the template and the target is within a focal depth of the incident beam. 12. The method of Claim 1, further comprising the act of scanning each beam through the corresponding transmissive portion. 13. The method of Claim 1, further comprising the act of providing a set of registration marks on the template associated with each transmissive portion. 14. The method of Claim 1, further comprising providing a plurality of charged particle beams and a plurality of transmissive portions, each transmissive portion corresponding to one of the charged particle beams. 15. The method of Claim 14, further comprising the act of calibrating each charged particle beam in-situ and in parallel. 16. The method of Claim 15, wherein calibrating each charged particle beam comprises the act of performing inter- charged particle beam calibrations. 17. The method of Claim 16, wherein the inter-charged particle beam calibrations comprise the act of calibrating each charged particle beam for positional accuracy relative to the other charged particle beams and the target using a set of registration marks on the template associated with each transmissive portion. 18. The method of Claim 14, wherein calibrating each charged particle beam comprises the act of performing intra- charged particle beam calibrations. 19. The method of Claim 18, wherein the intra-charged particle beam calibrations comprise the act of calibrating each charged particle beam for drift corrections. 20. The method of Claim 18, wherein the intra-charged particle beam calibrations comprise the act of calibrating each charged particle beam for distortion corrections. 21. The method of Claim 18, wherein the intra-charged particle beam calibrations comprise the act of calibrating each charged particle beam for magnification corrections. 22. The method of Claim 14, wherein calibrating each charged particle beam comprises the act of focusing the charged particle beam on a set of registration marks on the template associated with each transmissive portion. 23. The method of Claim 22, further comprising the act of compensating for a difference between a result from focusing the charged particle beam in a first focal plane of the registration marks and a result from focusing the charged particle beam in a second focal plane of the target. 24. The method of Claim 1, wherein positioning the template comprises the act of placing the template at a predetermined distance from a surface of the target. 25. The method of Claim 1, further comprising the act of sensing a gap between the template and a surface the target. 26. The method of Claim 1, wherein positioning the template comprises the act of placing the template in contact with a surface of the target. 27. The method of Claim 26, further comprising the act of moving the template out of contact with the target during movement of the target in a plane normal to an axis of the charged particle beam. 28. The method of Claim 27, further comprising the act of using an actuator to lift the template out of contact with the target . 29. The method of Claim 1, further comprising the act of heating at least a portion of the template with an electric current, thereby to reduce resist buildup thereon. 30. A structure for lithography, for interposition between a charged particle beam source and a target thereof, the structure comprising: a template opaque to the beam and defining a portion transmissive to the charged particle beam, the transmissive portion being arranged in correspondence to the incident charged particle beam so that the charged particle beam passes through the transmissive portion. 31. The structure of Claim 30, further comprising an electrical current connection to the template, thereby to heat the template. 32. The structure of Claim 30, wherein the transmissive portion is an opening defined in a membrane in the template. 33. The structure of Claim 32, wherein the membrane has a dimension of 1 mm by 1 mm. 34. The structure of Claim 32, wherein the membrane has a thickness equal to or less than one micron. 35. The structure of Claim 32, wherein the membrane extends from the template toward the target. 36. The structure of Claim 32, wherein the membrane comprises a cantilever. 37. The structure of Claim 32, wherein a sum of the membrane thickness and a spacing between the template and the target is within a focal depth of the incident charged particle beam. 38. The structure of Claim 30, wherein the transmissive portion is selected from the group consisting a rectangular transmissive portion and a circular transmissive portion. 39. The structure of Claim 38, wherein the length of the transmissive portion is slightly longer than an incident charged particle beam scan length. 40. The structure of Claim 39, wherein the incident charged particle beam scan length is less than or equal to 100 μm. 41. The structure of Claim 38, wherein the width of the transmissive portion is slightly larger than an incident charged particle beam scan width. 42. The structure of Claim 41, wherein the incident charged particle beam scan width is less than or equal to 10 μm. 43. The structure of Claim 30, further comprising a set of registration marks on the template associated with the transmissive portion. 44. The structure of Claim 30, wherein the template comprises crystalline silicon. 45. The structure of Claim 30, wherein the template comprises a material having a similar thermal expansion coefficient as the target. 46. The structure of Claim 30, wherein the source is a source with a plurality of parallel charged particle beams and the template defines a plurality of corresponding transmissive portions. 47. The structure of Claim 30, wherein the charged particle beam is an electron beam. 48. The structure of Claim 30, wherein the charged particle beam is an ion beam. 49. The structure of Claim 48, wherein the ion beam is a low-energy ion beam. 50. An electron beam system, comprising: a source of multiple electron beams; a template interpositioned between the source and a target, the template being opaque to the electron beams and defining a plurality of portions transmissive to the electron beams, the transmissive portions each being arranged so an associated electron beam passes through it; and a stage for holding the target. 51. The system of Claim 50, wherein the source is a microcolumn array. 52. The system of Claim 51, wherein the microcolumns are low-voltage microcolumns. 53. The system of Claim 52, wherein the electron beams each has an energy level less than approximately 2 KeV. 54. The system of Claim 50, wherein each transmissive portion is an opening defined in a membrane in the template. 55. The system of Claim 54, wherein each membrane extends from the template toward the target. 56. The system of Claim 54, wherein each membrane comprises a cantilever. 57. The system of Claim 56, further comprising a voltage source coupled to the template, the voltage source providing a voltage to actuate the cantilever into contact with the target. 58. The system of Claim 54, wherein a sum of the membrane thickness and a spacing between the template and the target is within a focal depth of the incident electron beam. 59. The system of Claim 50, wherein the template further comprises a set of registration marks associated with each transmissive portion. 60. The system of Claim 50, wherein each electron beam is calibrated in-situ and in parallel. 61. The system of Claim 60, wherein each electron beam is calibrated for positional accuracy relative to the other electron beams and the target. 62. The system of Claim 60, wherein each electron beam is calibrated for drift corrections. 63. The system of Claim 60, wherein each electron beam is calibrated for distortion corrections. 64. The system of Claim 60, wherein each electron beam is calibrated for magnification corrections. 65. The system of Claim 60, wherein each electron beam focuses on a set of registration marks on the template associated with each transmissive portion. 66. The system of Claim 50, wherein the template is placed at a predetermined distance from the target. 67. The system of Claim 50, further comprising a sensor located proximate to the target for sensing a distance between the template and a surface of the target. 68. The system of Claim 50, further comprising a height reference post for setting a predetermined distance between the template and a surface of the target. 69. The system of Claim 50, wherein the template is in contact with a surface of the target. 70. The system of Claim 69, further comprising an actuator in contact with the template thereby to move the template out of contact with the target. 71. The system of Claim 50, further comprising an electric current source coupled to heat the template.

Inventors: CHANG T H P, KIM HO-SEOB, LEE KIM Y, MANKOS MARIAN, MURAY LAWRENCE, CHANG, T., H., P., KIM, HO-SEOB, LEE, KIM, Y., MANKOS, MARIAN, MURAY, LAWRENCE
Applicants: ETEC SYSTEMS INC, ETEC SYSTEMS, INC.
Application year: 2000
Main classification: H01J37
IPC codes: G03F1, G03F7, G03F9, H01J37, H01L21