Patent Number: 
Section: description

An electron beam exposure apparatus according to a preferred embodiment of the present invention will be described below with reference to the accompanying drawings. The electron beam exposure apparatus is merely an application of the present invention, and the present invention can be applied to an exposure apparatus using a charged-particle beam such as an ion beam other than an electron beam. (Description of Building Component of Electron Beam Exposure Apparatus) FIG. 1A is a sectional view schematically showing the main part of the electron beam exposure apparatus according to the preferred embodiment of the present invention. FIG. 1B is a plan view showing the electron beam exposure apparatus in FIG. 1A when viewed from above. FIG. 1A illustrates the sections of magnetic lens arrays 21, 22, 23, and 24. The exposure apparatus comprises a plurality of multi-source modules 1 serving as an electron beam source which emits an electron beam. Each multi-source module 1 forms a plurality of electron source images, and emits a plurality of electron beams corresponding to the respective electron source images. The multi-source modules 1 are arrayed in a 3xc3x973 matrix in this embodiment. The multi-source modules 1 will be described in detail below. The magnetic lens arrays 21, 22, 23, and 24 are interposed between the plurality of multi-source modules 1 and a stage 5. Each magnetic lens array is constituted by vertically arranging, at an interval, two magnetic disks MD having openings of the same shape which are arrayed in a 3xc3x973 matrix in correspondence with the array of the multi-source modules 1. The magnetic disks MD of the magnetic lens arrays 21, 22, 23, and 24 are excited by common coils CC1, CC2, CC3, and CC4. Each opening functions as the magnetic pole of each magnetic lens ML, and generates the same lens magnetic field in design. A plurality of electron source images formed by each multi-source module 1 are projected on a wafer 4 held on the stage 5 via corresponding four magnetic lenses (ML1, ML2, ML3, and ML4) of the magnetic lens arrays 21, 22, 23, and 24. An electron-optic system which causes a field such as a magnetic field to act on an electron beam until the electron beam emitted by one multi-source module 1 irradiates the wafer is defined as a column. The exposure apparatus of this embodiment has nine columns (col.1 to col.9). The intermediate image of the electron source in the multi-source module 1 is formed by the magnetic lens of the magnetic lens array 21 and a corresponding magnetic lens of the magnetic lens array 22. Another intermediate image of the electron source is formed on the wafer 4 by the magnetic lens of the magnetic lens array 23 and a corresponding magnetic lens of the magnetic lens array 24. That is, the image of the electron source in the multi-source module 1 is projected on the wafer 4. By individually controlling the excitation conditions of the magnetic lens arrays 21, 22, 23, and 24 by the coils CC1, CC2, CC3, and CC4, the optical characteristics (focal position, image rotation, and magnification) of the columns can be adjusted almost uniformly (i.e., by the same amount). Each column has a main deflector 3. The main deflector 3 deflects a plurality of electron beams from a corresponding multi-source module 1, and displaces a plurality of electron source images in the X and Y directions on the wafer 4. The stage 5 can move the wafer 4 set on it in the X and Y directions perpendicular to an optical axis AX (Z-axis) and the rotation direction around the Z-axis. A stage reference plate 6 is fixed to the stage 5. A reflected-electron detector 7 detects reflected electrons generated when a mark on the stage reference plate 6 is irradiated with an electron beam. FIG. 2 is a sectional view showing one column in FIG. 1A in detail. The detailed arrangements of the multi-source module 1 and column will be explained with reference to FIG. 2. The multi-source module 1 has an electron gun (not shown) which forms an electron source (crossover image) 101. The flow of electrons radiated by the electron source 101 is changed into an almost collimated electron beam by a condenser lens 102. The condenser lens 102 of this embodiment is an electrostatic lens made up of three aperture electrodes. One almost collimated electron beam formed through the condenser lens 102 enters an aperture array 103 formed by two-dimensionally arraying a plurality of apertures. The electron beam passes through the plurality of apertures. A plurality of electron beams having passed through the aperture array 103 pass through a lens array 104 formed by two-dimensionally arraying electrostatic lenses having the same optical power. The electron beams pass through deflector arrays 105 and 106 each formed by two-dimensionally arraying individually drivable electrostatic octupole deflectors. The electron beams further pass through a blanker array 107 formed by two-dimensionally arraying individually drivable electrostatic blankers. FIG. 3 is an enlarged view showing part of the multi-source module 1. The function of each portion of the multi-source module 1 will be explained with reference to FIG. 3. An almost collimated electron beam formed by the condenser lens 102 is split into a plurality of electron beams by the aperture array 103 having a plurality of apertures. The split electron beams form the intermediate images of the electron source on corresponding blankers (more accurately, between blanker electrodes) of the blanker array 107 via the electrostatic lenses of a corresponding lens array 104. The deflectors of the deflector arrays 105 and 106 have a function of individually adjusting the position (position within a plane perpendicular to the optical axis AX) of the intermediate image of the electron source formed at the position of a corresponding blanker on the blanker array 107. An electron beam deflected by each blanker of the blanker array 107 is cut off by a blanking aperture AP in FIG. 2, and does not enter the wafer 4. An electron beam not deflected by the blanker array 107 is not cut off by the blanking aperture AP, and enters the wafer 4. In other words, a desired pattern can be drawn on the wafer 4 by individually controlling whether to allow a plurality of electron beams to enter the wafer 4 by a plurality of blankers of the blanker array 107 while a plurality of electron beams are deflected by the main deflector 3. Referring back to FIG. 2, a plurality of intermediate images of the electron source formed by each multi-source module 1 are projected on the wafer 4 via corresponding four magnetic lenses (four magnetic lenses of the same column) of the magnetic lens arrays 21, 22, 23, and 24. Of the optical characteristics of each column in projecting a plurality of intermediate images on the wafer 4, the image rotation and magnification can be individually corrected by the deflector arrays 105 and 106 each having a plurality of independent deflectors for separately adjusting the position of each intermediate image on the blanker array 107 (i.e., the incident position of an electron beam on the magnetic lens array). That is, the deflector arrays 105 and 106 function as an electron-optic element for individually correcting the rotation and magnification of an image projected on the wafer 4 every column. The focal position of each column can be individually adjusted by dynamic focus lenses (electrostatic or magnetic lenses) 108 and 109 arranged for each column. That is, the dynamic focus lenses 108 and 109 function as an electron-optic element for individually correcting the focal position every column. FIG. 4 is a block diagram showing the system configuration of the electron beam exposure apparatus. Each blanker array control circuit 41 individually controls a plurality of blankers which constitute the blanker array 107. Each deflector array control circuit 42 individually controls a plurality of deflectors which constitute the deflector arrays 105 and 106. Each D_FOCUS control circuit 43 individually controls the dynamic focus lenses 108 and 109. Each main deflector control circuit 44 controls the main deflector 3. Each reflected-electron detection circuit 45 processes a signal from the reflected-electron detector 7. The blanker array control circuits 41, deflector array control circuits 42, D_FOCUS control circuits 43, main deflector control circuits 44, and reflected-electron detection circuits 45 are equipped by the same number as the columns (nine columns col.1 to col.9). A magnetic lens array control circuit 46 controls the common coils CC1, CC2, CC3, and CC4 of the magnetic lens arrays 21, 22, 23, and 24. A stage driving control circuit 47 drives and controls the stage 5 in cooperation with a laser interferometer (not shown) which detects the position of the stage 5. A main control system 48 controls the above control circuits and manages the overall electron beam exposure apparatus. (Description of Optical Characteristic Adjustment Method) In the electron beam exposure apparatus of this embodiment, the electron-optic characteristics of a plurality of magnetic lenses which constitute the magnetic lens array are slightly different from each other owing to nonuniformity in the permeability and aperture shape of the magnetic disk. For example, different image rotations and magnifications of columns result in actual incident positions of electron beams on the wafer, as shown in FIG. 5 (incident positions are exaggerated in FIG. 5). In other words, the electron-optic characteristics (focal position, image rotation, magnification, and the like) change between columns. As a method which solves this problem, an electron-optic characteristic adjustment method in the electron beam exposure apparatus according to the preferred embodiment of the present invention will be described. The main control system 48 executes electron-optic characteristic adjustment processing as shown in FIG. 6. The main control system 48 executes electron-optic characteristic adjustment processing in consideration of a change in the electron-optic characteristic of the column over time and a change in the target value of the electron-optic characteristic, e.g., every time the pattern to be drawn on the wafer is changed (i.e., every time the job is changed). The respective steps will be explained below. In step S101, in order to detect the focal position of an electron beam on the wafer that represents each column (in this case, an electron beam at the center out of a plurality of electron beams of each column), the main control system 48 instructs the blanker array control circuit 41 to control the blanker array 107 which allows only an electron beam selected as a focal position detection target to enter the wafer 4. At this time, the stage 5 is moved in advance by the stage driving control circuit 47 to locate the reference mark of the reference plate 6 near the irradiation position of the selected electron beam. The main control system 48 instructs the D_FOCUS control circuit 43 to oscillate the focal position of the electron beam by the dynamic focus lens 108 and/or 109. The main control system 48 instructs the main deflector control circuit 44 to scan the reference mark with the selected electron beam. The main control system 48 obtains, from the reflected-electron detection circuit 45, information about electrons reflected by the reference mark. As a result, the main control system 48 detects the current focal position of the electron beam. In step S101, this processing is executed for all electron beams which represent respective columns. In step S102, as shown in FIG. 7A, the main control system 48 detects a maximum position (MAXP) and minimum position (MINP) from actual focal positions detected for electron beams which represent respective columns, and determines an intermediate position (CP). In step S103, the main control system 48 instructs the magnetic lens array control circuit 46 to adjust the common coils of the magnetic lens arrays 21, 22, 23, and 24 and move their focal positions by almost the same amount for all the columns so as to set the intermediate position (CP) to a target position (TP). The result is shown in FIG. 7B. More specifically, the maximum value (xcex4max) of the difference between the target position and the actual focal position of each column is minimized. In the next step, the adjustment amount by the dynamic focus lenses 108 and 109 serving as focal position correction units arranged for each column can be minimized. This means that the plurality of focal position correction units 108 and 109 arranged for each column can be downsized and their interference can be minimized. In step S104, the main control system 48 causes the dynamic focus lenses 108 and 109 to adjust the focal position so as to make the focal position coincide with the target position for each column on the basis of the difference between the target position and the actual focal position of each column as shown in FIG. 7B. In step S105, the main control system 48 instructs the blanker array control circuit 41 to allow only the selected electron beam to enter the wafer in order to detect the incident position of each electron beam on the wafer. At this time, the stage 5 is moved in advance by the stage driving control circuit 47 to locate the reference mark of the reference plate 6 at the ideal irradiation position (design irradiation position) of the selected electron beam. The main control system 48 instructs the main deflector control circuit 44 to scan the reference mark with the selected electron beam. The main control system 48 obtains, from the reflected-electron detection circuit 45, information about electrons reflected by the reference mark. Hence, the main control system 48 can detect the current irradiation position of the electron beam. In step S105, this processing is executed for all electron beams. Based on the actual electron beam irradiation position for each column, the main control system 48 obtains the image rotation/magnification of the column. In step S106, as shown in FIG. 8A, the main control system 48 detects a maximum value (MAXV) and minimum value (MINV) from image rotations/magnifications obtained for respective columns, and determines an intermediate value (CV). In step S107, the main control system 48 instructs the magnetic lens array control circuit 46 to adjust the common coils of the magnetic lens arrays 21, 22, 23, and 24 and move their image rotations/magnifications (without changing the focal positions) by almost the same amount for all the columns so as to set the intermediate value (CV) to a target value (TV). The result is shown in FIG. 8B. More specifically, the maximum value (xcex4max) of the difference between the target value and the actual image rotation/magnification of each column is minimized. In the next step, the adjustment amount by the deflector arrays 105 and 106 serving as an image rotation/magnification correction unit arranged for each column can be minimized. This means that a plurality of deflectors which constitute each of the deflector arrays 105 and 106 serving as the image rotation/magnification correction unit arranged for each column can be downsized and the interference between the deflectors can be reduced. In step S108, the main control system 48 causes the deflector arrays 105 and 106 serving as the image rotation/magnification correction unit to adjust the image rotation/magnification so as to make the image rotation/magnification coincide with the target value for each column on the basis of the difference between the target value and the actual image rotation/magnification of each column as shown in FIG. 8B. At this time, the image rotation/magnification is corrected by individually controlling a plurality of deflectors which constitute each of the deflector arrays 105 and 106. (Device Manufacturing Method) An embodiment of a device manufacturing method using the above-described electron beam exposure apparatus will be described. FIG. 9 is a flow chart showing the manufacturing flow of a microdevice (semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, or the like). In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (exposure control data formation), exposure control data for the exposure apparatus is formed on the basis of a designed circuit pattern. In step 3 (wafer formation), a wafer is formed using a material such as silicon. In step 4 (wafer process) called a pre-process, an actual circuit is formed on the wafer by lithography using the wafer and the exposure apparatus to which the prepared exposure control data is input. Step 5 (assembly) called a post-process is the step of forming a semiconductor chip by using the wafer formed in step 4, and includes an assembly process (dicing and bonding) and packaging process (chip encapsulation). In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and durability test. After these steps, the semiconductor device is completed and shipped (step 7). FIG. 10 shows the detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), a circuit pattern is drawn on the wafer by the above-mentioned exposure apparatus exposes. Prior to exposure processing, the exposure apparatus adjusts the focal position by the above method every column, and adjusts the image rotation and magnification every column. In step 17 (developing), the exposed wafer is developed. In step 18 (etching), the resist is etched except the developed resist image. In step 19 (resist removal), an unnecessary resist after etching is removed. These steps are repeated to form multiple circuit patterns on the wafer. This manufacturing method enables manufacturing a highly integrated semiconductor device at low cost, which has conventionally been difficult to manufacture. The present invention can accurately correct the electron-optic characteristics of a plurality of magnetic lenses which constitute a magnetic lens array. As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.