JP4745739B2 - Electrostatic lens apparatus, exposure apparatus, and device manufacturing method - Google Patents

Description

The present invention relates to an electrostatic lens apparatus and a charged particle beam exposure apparatus including the electrostatic lens apparatus.

In an electrostatic lens used in a conventional electron beam exposure apparatus, for example, an Einzel lens is generally used. Of the three electrode substrates constituting the Einzel lens, the two electrode substrates at the upper and lower ends are usually given a ground potential, and a negative or positive potential is applied to the intermediate electrode substrate. Each electrode substrate has a circular opening, and the Einzel lens produces a convergence effect on the electron beam passing through the opening.
Electron / Ion Beam Optics Katsuaki Ura Kyoritsu Publishing P. 48

  However, the electrostatic lens is easy to manufacture as compared with the magnetic lens, but the sensitivity of optical aberration to the manufacturing error of the lens aperture is high. In particular, astigmatism with respect to the roundness of the aperture is sensitive. When a minute opening of 1 mm or less is produced using a semiconductor process or the like, the roundness may be deteriorated due to the influence of dust or the like during the production. As a result, the electron beam converged by the electrostatic lens has astigmatism and other high-order aberrations.

  In particular, when there are a plurality of electron beams and each beam has different astigmatism, it cannot be corrected using a normal astigmatism corrector. In order to individually correct the astigmatism of each beam, a complicated mechanism is required such as disposing an astigmatism corrector that can be controlled independently on the optical path through which each beam passes.

The present invention aims at providing a in terms of small advantageous electrostatic lens arrangement of astigmatism.

A first aspect of the present invention is an electrostatic lens device including a plurality of stages of electrostatic lenses, each of the plurality of stages of electrostatic lenses having a plurality of electrode substrates, wherein the plurality of electrode substrates includes a plurality of electrode substrates. Each of the plurality of electrode substrates has substantially the same shape, and each of the plurality of stages of electrostatic lenses extends over the plurality of electrode substrates. The direction defined by the mark is aligned, and the direction defined by the mark is rotated 90 degrees between two adjacent electrostatic lenses among the plurality of stages of electrostatic lenses. Features.
A second aspect of the present invention relates to an exposure apparatus, wherein the exposure apparatus includes the electrostatic lens device, and exposes an exposure target with a plurality of charged particle beams via the electrostatic lens device. Features.
A third aspect of the present invention relates to a device manufacturing method, wherein the device manufacturing method includes a step of exposing an exposure target using the exposure apparatus, a step of developing the exposure target exposed in the step, It is characterized by including .

According to the present invention, it is possible to provide an advantageous electrostatic lens arrangement in view of smallness of astigmatism.

  The best mode for carrying out the present invention will be described in detail with reference to the drawings, taking an example of an electron beam exposure apparatus of a multi-beam system (using a plurality of charged particle beams).

FIG. 1 is a schematic view of a main part of a multi-beam electron beam exposure apparatus according to Embodiment 1 of the present invention.
Reference numerals 101 to 109 form a multi-source module that forms a plurality of electron source images and emits an electron beam from the electron source images. In the case of FIG. 1, 25 of 5 × 5 multi-source modules are two-dimensionally arranged. Reference numeral 101 denotes an electron source (crossover image) formed by the electron gun. The electron beam emitted from the electron source 101 becomes a substantially parallel electron beam by the condenser lens 102. Reference numeral 103 denotes an aperture array in which openings are two-dimensionally arranged. Reference numeral 104 denotes a lens array formed by two-dimensionally arranging electrostatic lenses (Einzel lenses) having the same optical power. Reference numerals 105, 106, 107, and 108 denote multi-deflector arrays formed by two-dimensionally arranging electrostatic deflectors that can be individually driven. Reference numeral 109 denotes a blanker array formed by two-dimensionally arranging electrostatic blankers that can be individually driven.

  Each function will be described with reference to FIG. The substantially parallel electron beam from the condenser lens 102 (see FIG. 1) is divided into a plurality of electron beams by the aperture array 103. The divided electron beam forms an intermediate image 201 of the electron source 101 on the corresponding blanker of the blanker array 109 via the electrostatic lens of the corresponding lens array 104. At this time, the multi deflector arrays 105, 106, 107, and 108 individually adjust the position of the intermediate image 201 of the electron source formed on the blanker array 109 (position in the plane orthogonal to the optical axis). Further, since the electron beam deflected by the blanker array 109 is blocked by the blanking aperture 110 in FIG. 1, the wafer 120 is not irradiated. On the other hand, the electron beam that is not deflected by the blanker array 109 is not blocked by the blanking aperture 110 in FIG.

  Returning to FIG. 1, the plurality of intermediate images 201 of the electron source formed by the multi-source module are projected onto the wafer 120 via the reduction projection system of the magnetic lenses 115, 116, 117, and 118. At this time, when a plurality of intermediate images are projected onto the wafer 120, the focal position can be adjusted by the dynamic focus lenses (electrostatic or magnetic field lenses) 111 and 112. Reference numerals 113 and 114 denote a main deflector and a sub deflector for deflecting each electron beam to a position to be exposed. 119 is a backscattered electron detector for measuring the position of each intermediate image of the electron source formed on the wafer 120. Reference numeral 121 denotes a stage for moving the wafer 120. Reference numeral 122 denotes a mark for detecting the position and beam shape of the electron beam.

  Next, a mechanism in which the lens array 104 converges the electron beam will be described. FIG. 3 shows that among the three electrode substrates constituting the Einzellene Einzel lens, the electrode substrate 301 and the electrode substrate 303 have a ground potential applied thereto, and the electrode substrate 302 has a negative potential applied thereto. Yes. FIG. 3 is a view for explaining the electron beam convergence action of the Einzel lens, and is a view seen from the side when the Einzel lens is cut along a plane parallel to the optical axis.

  The electric lines of force in this state are indicated by solid arrows. Further, an area where Z is equal to or less than Z1 is "area 1", an area where Z is from Z1 to Z2 is "area 2", an area where Z is from Z2 to Z3 is "area 3", and Z is an area from Z3 to Z4 Is “region 4”, a region where Z is from Z4 to Z5 is “region 5”, and a region where Z is equal to or greater than Z5 is “region 6”. It is assumed that there is no potential in region 1 and region 6.

  The potential Er in the r direction in the region where r> 0 is negative in region 2, positive in region 3, positive in region 4, and negative in region 5. Therefore, the trajectory 304 of the electron beam passing through a certain image height r0 is as shown by the dotted arrow. That is, the electron beam is diverged in the region 2, the electron beam is converged in the region 3, the electron beam is converged in the region 4, and the electron beam is diverged in the region 5. This is equivalent to an optical concave lens / convex lens / convex lens / concave lens being arranged in the Z-axis direction.

  The reason why the electron beam is converged is the following two points. The first reason is that since the force received by the electron beam increases as the image height increases, the convergence effect in the regions 3 and 4 exceeds the divergence effect in the regions 2 and 5. The second reason is that since a negative potential is applied to the electrode substrate 302, the traveling time of the electron beam is longer in the region 3 than in the region 2 and in the region 4 compared with the region 5. Because. Since the change in momentum is equal to the impulse, the effect that the region having a long traveling time gives to the electron beam becomes large. For these reasons, the electron beam is converged. Even when a positive potential is applied to the electrode substrate 302, the electron beam is similarly converged.

  Next, the fact that the optical aberration is canceled by the concave lens and the convex lens will be described. In general, in lens design in optics, optical aberration is corrected by combining a concave lens and a convex lens. This is a method in which the optical aberration amount generated in the concave lens portion and the optical aberration amount generated in the convex lens portion are matched as much as possible, and the added optical aberration amount approaches zero.

  Similarly, in the case of an electron beam, the optical aberration can be canceled by matching the aperture shape of the electrode substrate to make the potential distribution isotropic with respect to the optical axis.

  If the aperture shape of each electrode substrate in the Einzel lens does not match, the potential distribution in the lens is not isotropic, and the amount of optical aberration generated in the concave lens portion differs from the amount of optical aberration generated in the convex lens portion. Aberration cannot be canceled. As a result, the converged electron beam has astigmatism and other high-order aberrations.

  In particular, when each of the plurality of electron beams has different astigmatism, it cannot be corrected using a normal astigmatism corrector. In order to individually correct the astigmatism of each beam, a complicated mechanism is required such as disposing an astigmatism corrector that can be controlled independently on the optical path through which each beam passes.

  In order to cancel the optical aberration, it is necessary to match the aperture shape of each electrode substrate in the electrostatic lens. Hereinafter, a method for matching the aperture shapes of the electrode substrates in the electrostatic lens will be described. FIG. 4 is a schematic view of a main part of the lens array 104 having a mark that can define the direction. The lens array 104 includes 5 × 5 lens openings, and includes three electrode substrates 401, 402, and 403. Each electrode substrate 401, 402, 403 is provided with marks 404, 405, 406 that can define the direction. FIG. 5 shows a manufacturing flow of the lens array 104.

  In (Step 51), as shown in FIG. 5, a mark whose direction can be defined in a portion that does not interfere with the lens opening of the electrode substrate is produced. After producing the mark, the process proceeds to step 52.

  In step 52, all electrode substrates are processed under the same conditions using means such as machining, electrical discharge machining, and semiconductor process. Alternatively, all electrode substrates are integrally processed under the same conditions. After processing the electrode substrate, the process proceeds to step 53.

  In step 53, the electrodes 404, 405, and 406 on the electrode substrates 401, 402, and 403 are assembled in the same direction. After assembly, the process proceeds to step 54.

  In (Step 54), it is determined whether there are a plurality of electrostatic lenses. When there are a plurality of electrostatic lenses, the process proceeds to step 55. When there is only one electrostatic lens, the process is terminated.

  In (Step 55), among the plurality of stages of electrostatic lenses, each stage of the electrostatic lens is alternately shifted 90 degrees and assembled. For example, when there is a three-stage electrostatic lens, the first stage is rotated by 0 degrees, the second stage is rotated by 90 degrees, and the third stage is rotated by 0 degrees.

  By the above method, the mark directions of the electrode substrates can be aligned and assembled, and the opening shapes of the electrode substrates in the electrostatic lens can be matched.

  That is, in a charged particle beam exposure apparatus having an electrostatic lens composed of a plurality of electrode substrates, a mark capable of defining a direction and an opening formed by aligning the directions of the mark in a plane perpendicular to the optical axis are provided. In addition, it is possible to manufacture a charged particle beam exposure apparatus having an electrostatic lens in which a plurality of electrode substrates are assembled and formed based on the direction of the mark in a plane perpendicular to the optical axis.

  Further, a plurality of electrostatic lenses can be arranged in the optical axis direction by rotating the mark direction of the electrode substrate by 90 degrees in a plane perpendicular to the optical axis.

FIG. 6 shows calculation results of astigmatism when the electrode substrate shape of the electrostatic lens is not matched.
No. 1 is a case where the electrode substrate shape of the electrostatic lens is not matched, and No. 2 is a case where the electrode substrate shape of the electrostatic lens is matched. There are three stages of electrostatic lenses, each of which has three electrode substrates, and each electrode substrate has an elliptical opening. The size of the opening is 80 micrometers, and the roundness is 50 nanometers. No. 1 shows the amount of astigmatism on the image plane when the elliptical direction of the opening in the middle electrode substrate of each electrostatic lens is rotated by 30 degrees, 60 degrees, and 90 degrees, respectively. No. 2 shows the astigmatism amount AS. (Nm) on the image plane when the elliptical directions of the openings in all the electrode substrates of each electrostatic lens are aligned. In comparison with No. 1 in which the electrode substrate shape of the electrostatic lens is not matched, in No. 2 in which the electrode substrate shape of the electrostatic lens is matched, the astigmatism amount AS. (Nm) is about 1/12. I understand that

Furthermore, calculation results of astigmatism when the mark directions of a plurality of stages of electrostatic lenses are aligned and when they are alternately shifted by 90 degrees are shown.
No. 2 is a case where the mark directions of a plurality of stages of electrostatic lenses are aligned, and No. 3 is a case where the mark directions of the plurality of stages of electrostatic lenses are alternately shifted by 90 degrees. There are three stages of electrostatic lenses, each of which has three electrode substrates, and each electrode substrate has an elliptical opening. The size of the opening is 80 micrometers, and the roundness is 50 nanometers. No. 2 shows the astigmatism amount AS. (Nm) on the image plane when the elliptical directions of the openings in all the electrode substrates of each electrostatic lens are aligned.

  No. 3 shows the astigmatism amount AS. (Nm) on the image plane when the middle lens among the three-stage electrostatic lenses is rotated by 90 degrees. In comparison with No. 2 in which the mark directions of the multi-stage electrostatic lenses are aligned, in No. 3 in which the mark directions of the multi-stage electrostatic lenses are alternately shifted by 90 degrees, the astigmatism amount AS. (Nm) It can be seen that is about 1/5.

  In other words, in comparison with No. 1 in which the electrode substrate shape of the electrostatic lens is not matched, in No. 3 in which the electrostatic lens having the matched electrode substrate shape is alternately shifted by 90 degrees, the astigmatism amount AS. ) Is about 1/60.

  The above method can also be applied to an electrostatic lens of a scanning electron microscope, an electron beam length measuring device, an ion microscope, a focused ion beam device, or a secondary ion mass spectrometer.

Next, a device production method using the electron beam exposure apparatus described in the first embodiment will be described as a second embodiment of the present invention.
FIG. 7 shows a flow of manufacturing a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 71 (circuit design), a semiconductor device circuit is designed. In step 72 (EB data conversion), exposure control data for the exposure apparatus is created based on the designed circuit pattern. On the other hand, in step 73 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 74 (wafer process) is called a pre-process, and 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. The next step 75 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 74, and is a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), or the like. including. In step 76 (inspection), the semiconductor device manufactured in step 75 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, a semiconductor device is completed and shipped (step 77).

  FIG. 8 shows a detailed flow of the wafer process. In step 81 (oxidation), the wafer surface is oxidized. In step 82 (CVD), an insulating film is formed on the wafer surface. In step 83 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 84 (ion implantation), ions are implanted into the wafer. In step 85 (resist process), a photosensitive agent is applied to the wafer. In step 86 (exposure), the circuit pattern is printed onto the wafer by exposure using the exposure apparatus described above. In step 87 (development), the exposed wafer is developed. In step 88 (etching), portions other than the developed resist image are removed. In step 89 (resist stripping), unnecessary resist after etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

  By using the manufacturing method of this embodiment, a highly integrated semiconductor device can be manufactured with high pattern dimension accuracy.

It is a figure explaining the principal part outline of the electron beam exposure apparatus of a multi-beam system based on Example 1 of this invention. It is a figure for demonstrating the function of the multi source module in FIG. It is a figure for demonstrating the electron beam convergence effect | action of the Einzel lens based on Example 1 of this invention. It is a figure for demonstrating the principal part outline of the lens array which has the mark which can prescribe | regulate a direction based on Example 1 of this invention. It is a figure for demonstrating the manufacturing flow of a lens array based on Example 1 of this invention. It is a figure for comparing and explaining the astigmatism of the electrostatic lens according to Example 1 of the present invention. It is a figure for demonstrating the manufacturing flow of a microdevice based on Example 2 of this invention. It is a figure for demonstrating the wafer process in FIG.

Explanation of symbols

  101: electron source (crossover image), 102: condenser lens, 103: aperture array, 104: lens array, 105: multi-deflector array, 106: multi-deflector array, 107: multi-deflector array, 108: multi-deflection 109: Blanker array, 110: Blanking aperture, 111: Dynamic focus lens, 112: Dynamic focus lens, 113: Main deflector, 114: Sub deflector, 115: Magnetic lens, 116: Magnetic lens, 117: Magnetic lens, 118: Magnetic lens, 119: Backscattered electron detector, 120: Wafer, 121: Stage, 122: Mark, 201: Intermediate image of electron source, 301: Electron substrate of Einzel lens, 302: Einzel lens Electrode substrate, 303: Einze Lens electrode substrate 304: Electron beam trajectory 401: Einzel lens electrode substrate 402: Einzel lens electrode substrate 403: Einzel lens electrode substrate 404: Direction-definable mark 405: Direction 406: A mark that can define the direction.

Claims (3)

An electrostatic lens device including a plurality of stages of electrostatic lenses, each of the plurality of stages of electrostatic lenses having a plurality of electrode substrates,
Wherein the plurality of electrode substrate has a plurality of openings, and the mark for defining a rectangular direction, were provided respectively,
The plurality of electrode substrates substantially coincide in shape, and in each of the plurality of stages of electrostatic lenses, the direction defined by the mark is aligned across the plurality of electrode substrates ,
Between two adjacent electrostatic lenses among the plurality of stages of electrostatic lenses, directions defined by the marks are rotated by 90 degrees with each other.
An electrostatic lens device. It has an electrostatic lens arrangement according to claim 1, through the electrostatic lens arrangement you exposing the exposure target with a plurality of charged particle beams, the exposure apparatus characterized by. A step of exposing an exposure target using the exposure apparatus according to claim 2 , and a step of developing the exposure target exposed in the step;
Device manufacturing method comprising a.

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