JP2019212680A - Multi-charged particle beam lithography apparatus and adjustment method therefor - Google Patents

Abstract

To enlarge a reduction magnification and suppress imaging distortion of an aperture image.SOLUTION: A multi-charged particle beam lithography apparatus according to the embodiment comprises: a molding aperture array substrate including a plurality of first apertures through which a charged particle beam passes to form and mold a multi-beam; a blanking aperture array mechanism including a plurality of second apertures at each of which a blanker for performing blanking deflection on the beam is provided; a limit aperture substrate on which a third aperture through which the multi-beam is to pass is provided, the limit aperture substrate screening the beam deflected to be in a beam OFF state by the blanker; an illumination lens that refracts the charged particle beam to illuminate the molding aperture array substrate with the charged particle beam; an objective lens disposed on the upstream side of the limit aperture substrate in a beam travel direction; and a distortion adjustment lens that is provided between the blanking aperture array mechanism and the objective lens to correct imaging distortion of an aperture image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multi-charged particle beam drawing apparatus and an adjustment method thereof.

  As LSIs are highly integrated, circuit line widths required for semiconductor devices have been reduced year by year. In order to form a desired circuit pattern on a semiconductor device, a technique is employed in which a high-precision original pattern formed on quartz is reduced and transferred onto a wafer using a reduction projection type exposure apparatus. A high-precision original pattern is drawn by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

  For example, there is a drawing apparatus using a multi-beam. Compared with the case of drawing with one electron beam, the use of multi-beams enables irradiation with many beams at a time, so that the throughput can be significantly improved. In a multi-beam type drawing apparatus, for example, an electron beam emitted from an electron gun is passed through an aperture array having a plurality of apertures to form a multi-beam, and each of the unshielded beams is blanked. The image is reduced by an optical system, deflected by a deflector, and irradiated to a desired position on the sample.

  In multi-beam writing, a large number of beams are required to improve throughput. However, there is a limit to reducing the inter-beam pitch for a mechanism that forms a multi-beam or performs blanking control. As the number of beams increases, the image size of the entire multi-beam increases, so an electron optical system with a high reduction magnification is required. Each shielded beam is shielded by a blanking aperture provided at the crossover position. In order to optimize the crossover aberration of the illumination system, it is necessary to increase the distance to the crossover. Therefore, it is necessary to increase the electron beam column of the drawing apparatus and lengthen the optical system.

  However, increasing the length of the optical system increases beam blur due to the Coulomb effect. Further, the height dimension of the electron beam column is limited depending on the size of the clean room or the like in which the drawing apparatus is installed. Therefore, conventionally, the reduction magnification has been increased by arranging a plurality of objective lenses. However, when the reduction magnification is increased, there is a problem that the imaging distortion of the aperture image formed on the sample surface and formed with the multi-beam is increased.

JP 2017-199758 A JP 2002-343295 A JP 2002-353122 A JP 2002-184336 A JP 2001-332473 A JP 11-67642 A

  The present invention has been made in view of the above-described conventional problems, and it is an object of the present invention to provide a multi-charged particle beam drawing apparatus that optimizes crossover aberration and suppresses image distortion of an aperture image and an adjustment method thereof. And

  According to an aspect of the present invention, there is provided a multi-charged particle beam drawing apparatus, wherein an emission unit that emits a charged particle beam and a plurality of first openings are formed, and the charged particle beam is emitted in a region including the plurality of first openings Irradiated, the charged particle beam passes through the plurality of first openings to form a multi-beam and forms a multi-beam, and the multi-beam that has passed through the plurality of first openings Among them, a plurality of second openings through which the corresponding beams pass are formed, and a blanking aperture array mechanism in which a blanker for deflecting the blanking of the beam is provided in each second opening, and the multi-beams pass therethrough. A limiting aperture base that shields the beam deflected to be in a beam OFF state by the blanker. And an illumination lens that refracts the charged particle beam and illuminates the charged particle beam on the shaped aperture array substrate, and a plurality of lenses disposed upstream of the limiting aperture substrate in the beam traveling direction. An objective lens that forms the multi-beam aperture image on the surface of the drawing target substrate; and a distortion adjustment that is provided between the blanking aperture array mechanism and the objective lens, and corrects the imaging distortion of the aperture image. And a lens.

  In the charged particle beam drawing apparatus according to an aspect of the present invention, the excitation of the illumination lens is controlled, and the crossover position of the multi-beam is adjusted to correct the imaging distortion of the aperture image.

  In the charged particle beam drawing apparatus according to one aspect of the present invention, the distortion adjustment lens is disposed in a magnetic field of the illumination lens.

  In the charged particle beam drawing apparatus according to one aspect of the present invention, a plurality of the distortion adjustment lenses are provided.

  An adjustment method for a multi-charged particle beam drawing apparatus according to an aspect of the present invention is an adjustment method for a multi-charged particle beam drawing apparatus according to the present invention, wherein the image distortion amount of the aperture image is adjusted using the distortion adjustment lens. And adjusting the image distortion amount of the aperture image by controlling the position at which the multi-beam forms a crossover using the illumination lens, and the image distortion amount becomes a predetermined value or less. This is repeated alternately.

  According to the present invention, it is possible to increase the reduction magnification and suppress the image distortion of the aperture image.

It is a schematic block diagram of the drawing apparatus which concerns on embodiment of this invention. It is a top view of a shaping | molding aperture array board | substrate. It is a flowchart explaining the adjustment method of the drawing apparatus which concerns on the same embodiment. It is a figure which shows the example of switching of ON beam. (A) (b) is a figure which shows the example of the distorted aperture image. It is a graph which shows the relationship between the excitation of a distortion adjustment lens, and the image formation distortion amount of an aperture image. It is a figure which shows the example of the aperture image which made distortion amount below predetermined value. It is a figure which shows the example of a lens magnetic field. It is a graph which shows the example of the relationship between a crossover position and distortion amount. It is a figure which shows the example of a lens magnetic field.

  Hereinafter, in the embodiment, a configuration using an electron beam will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and a beam using charged particles such as an ion beam may be used.

  FIG. 1 is a schematic configuration diagram of a multi-beam drawing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the multi-beam drawing apparatus includes a drawing unit W and a control unit C. The drawing unit W includes an electron column 102 and a drawing chamber 103. In the electron column 102, an electron gun 201, an illumination lens 202, a molded aperture array substrate 203, a blanking aperture array mechanism 204, a distortion adjustment lens 205, a limiting aperture substrate 206, a deflector 208, and an objective lens 210 are arranged. ing.

  The objective lens 210 is composed of a plurality of stages of electromagnetic lenses, and in the example shown in FIG. The electromagnetic lenses 212 and 214 are provided above the limiting aperture substrate 206 (upstream in the beam traveling direction), and the electromagnetic lens 216 is provided below (downstream in the beam traveling direction) the limiting aperture substrate 206. .

  In the drawing chamber 103, an XY stage 105 and a detector 220 are arranged. On the XY stage 105, the substrate 10 to be drawn is arranged. The substrate 10 includes an exposure mask for manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which the semiconductor device is manufactured, and the like. Further, the substrate 10 includes mask blanks to which a resist is applied and nothing is drawn yet. A mark 20 is further provided on the XY stage 105. The mark 20 is, for example, a cross-shaped metal mark. The detector 220 detects reflected electrons (or secondary electrons) when the mark 20 is scanned with a beam.

  The control unit C includes a control computer 110, a deflection control circuit 130, a lens control circuit 132, and a storage device 140. The storage device 140 (storage unit) is, for example, a magnetic disk device, and stores drawing data input from the outside. The lens control circuit 132 controls excitation of the illumination lens 202, the distortion adjustment lens 205, and the objective lens 210. A blanking aperture array mechanism 204 is connected to the deflection control circuit 130. The deflector 208 is connected to the deflection control circuit 130 via a DAC amplifier unit (not shown).

  In FIG. 1, a configuration necessary for describing the embodiment is shown, and illustration of other configurations is omitted.

  FIG. 2 is a conceptual diagram showing the configuration of the molded aperture array substrate 203. In FIG. 2, a shaped aperture array substrate 203 has a matrix of openings (first openings) 203a of vertical (y direction) p rows × horizontal (x direction) q rows (p, q ≧ 2) at a predetermined arrangement pitch. It is formed in a shape. Each opening 203a is formed of a rectangle having the same size and shape. The opening 203a may be circular. A part of the electron beam 200 passes through each of the plurality of openings 203a, thereby forming a multi-beam MB.

  The blanking aperture array mechanism 204 is provided below the shaping aperture array substrate 203, and through holes (second openings) are formed in accordance with the positions of the openings 203a of the shaping aperture array substrate 203. In each passage hole, a blanker made up of a pair of two electrodes is arranged. One electrode of the blanker is fixed at the ground potential, and the other electrode is switched between the ground potential and another potential. The electron beam passing through each through hole is deflected independently by a voltage applied to the blanker. In this way, the plurality of blankers perform blanking deflection of the corresponding beams among the multi-beams MB that have passed through the plurality of openings 203a of the shaping aperture array substrate 203.

  The electron beam 200 emitted from the electron gun 201 (emission part) is refracted by the illumination lens 202 and illuminates the entire shaped aperture array substrate 203. A plurality of rectangular openings 203a are formed in the shaped aperture array substrate 203, and the electron beam 200 illuminates a region including all of the plurality of openings 203a. A part of the electron beam 200 passes through the plurality of openings 203 a of the shaped aperture array substrate 203, thereby forming a plurality of electron beams (multi-beam MB). The multi-beam MB passes through the corresponding blanker of the blanking aperture array mechanism 204. Each blanker performs blanking control for the beam passing therethrough so that the set drawing time (irradiation time) beam is turned on.

  The multi-beam MB that has passed through the blanking aperture array mechanism 204 proceeds toward an opening (third opening) formed at the center of the limiting aperture substrate 206 due to refraction by the illumination lens 202. The multi-beam MB forms a crossover at the height position of the opening of the limiting aperture substrate 206.

  Here, the beam deflected by the blanker of the blanking aperture array mechanism 204 is displaced from the opening of the limiting aperture substrate 206 and is blocked by the limiting aperture substrate 206. On the other hand, the beam that has not been deflected by the blanker of the blanking aperture array mechanism 204 passes through the opening of the limiting aperture substrate 206. In this manner, the limiting aperture substrate 206 shields the beam deflected so as to be in a beam OFF state by each blanker.

  Each beam of one shot is formed by the beam that has passed through the limiting aperture substrate 206 formed from when the beam is turned on to when the beam is turned off. Each beam of the multi-beam MB that has passed through the limiting aperture substrate 206 is desired to be reduced by the objective lens 210 (electromagnetic lenses 212, 214, and 216) excited by the lens control circuit 132 at the opening 203a of the shaped aperture array substrate 203. And the focus is adjusted on the substrate 10. Then, each beam (entire multi-beam) that has passed through the limiting aperture substrate 206 is deflected together in the same direction by the deflector 208 and is irradiated to each irradiation position on the substrate 10 of each beam.

  For example, when the XY stage 105 is continuously moving, the beam irradiation position is controlled by the deflector 208 so as to follow the movement of the XY stage 105. The multi-beams MB irradiated at a time are ideally arranged at a pitch obtained by multiplying the arrangement pitch of the plurality of openings 203a of the shaped aperture array substrate 203 by the desired reduction ratio. The drawing apparatus performs a drawing operation by a raster scan method in which a shot beam is continuously irradiated in order, and when drawing a desired pattern, an unnecessary beam is controlled to be turned off by blanking control.

  In order to reduce the multi-beam MB at a high reduction magnification, an objective lens 210 including a plurality of stages of electromagnetic lenses is provided. When the reduction magnification is increased, the imaging distortion of the multi-beam aperture image (shaped aperture image) on the surface of the substrate 10 increases. In this embodiment, in order to suppress this imaging distortion, the excitation of the illumination lens 202 is controlled to adjust the crossover position. In addition, a distortion adjustment lens 205 is provided between the objective lens 210 (electromagnetic lenses 212 and 214) provided above the limiting aperture substrate 206 and the blanking aperture array mechanism 204, and the lens magnetic field by the distortion adjustment lens 205 is adjusted. Reducing imaging distortion. By alternately repeating the adjustment of the crossover position and the adjustment of the lens magnetic field by the distortion adjustment lens, the imaging distortion is suppressed to a predetermined allowable value or less.

  FIG. 8 shows examples of lens magnetic fields MF1, MF2, and MF3 by the illumination lens 202, the distortion adjustment lens 205, and the objective lens 210. The illumination lens 202 has a magnetic pole 202a and an electromagnetic coil 202b. In the figure, the broken line L1 indicates the imaging trajectory of the aperture image of the central beam of the multi-beam, and the alternate long and short dash line L2 indicates the optical axis. A magnetic flux is generated by passing an electric current through the electromagnetic coil 202b, and magnetic flux leaks from a gap between the magnetic poles 202a (yoke) to form an electromagnetic lens.

  A method for adjusting the drawing apparatus will be described with reference to the flowchart shown in FIG.

  By changing the excitation of the illumination lens 202, the position of the crossover in the beam traveling direction is changed. The distortion amount of the aperture image of the multi-beam MB is measured for each crossover position, and the crossover position where the distortion amount is minimized is obtained (step S1).

  When the distortion amount of the aperture image is measured, the mark 20 is scanned with a beam. For example, as shown in FIG. 4, the ON beams are sequentially switched, the mark 20 is scanned with each beam, and the reflected electrons (secondary electrons) are detected by the detector 220. The detection circuit 134 amplifies the detection value of the detector 220, converts it into digital data, and transmits it to the control computer 110. The control computer 110 measures the position of each beam from the detection result of the detector 220 and obtains an aperture image. An aperture image with distortion has a shape as shown in FIGS. 5A and 5B, for example. For example, the control computer 110 calculates the distortion amount Δr from Δr = r1 + r2 + r3 + r4.

  FIG. 9 is a graph showing an example of the relationship between the crossover position and the distortion amount Δr. By changing the crossover position, the distortion amount Δr changes.

  When the distortion amount Δr (minimized distortion amount) obtained by adjusting the position of the crossover is larger than a predetermined allowable value (step S2_No), the excitation of the distortion adjustment lens 205 is adjusted to minimize the distortion amount Δr. Excitation is calculated (step S3). The predetermined allowable value is a value that can be corrected by multiple drawing, for example, 5 nm or less, and more preferably 1 nm or less.

  The excitation of the distortion adjustment lens 205 is changed, and the distortion amount Δr for each excitation is measured. Thereby, for example, the relationship between the excitation of the distortion adjusting lens 205 and the distortion amount Δr as shown in FIG. 6 is obtained, and excitation that minimizes the distortion amount Δr (for example, Δr is made zero) is calculated.

  The calculated excitation is set in the distortion adjustment lens 205 (step S4), and steps S1 and S2 are executed again. The adjustment of the crossover position and the adjustment of the excitation of the distortion adjustment lens 205 are repeated until the distortion amount Δr becomes equal to or less than a predetermined allowable value (steps S1 to S4). When the distortion amount Δr is equal to or less than a predetermined allowable value (step S2_Yes), the excitation of the objective lens 210 (electromagnetic lenses 212, 214, 216) is adjusted so that the reduction magnification is within a desired range, and The rotation of the aperture image is adjusted (step S5).

  After adjusting the excitation of the objective lens 210, the distortion amount Δr of the aperture image is measured (step S6). If the distortion amount Δr exceeds a predetermined allowable value due to adjustment of excitation of the objective lens 210 (step S7_No), adjustment of excitation of the distortion adjustment lens 205 and adjustment of the crossover position are performed again (steps S1 to S4). ).

  The above process is repeated until the distortion amount Δr of the aperture image becomes equal to or less than a predetermined allowable value. As a result, an aperture image with a very small distortion and a high reduction magnification can be obtained as shown in FIG.

  A pattern is drawn on the substrate 10 using a drawing apparatus in which excitation of the illumination lens 202, the distortion adjustment lens 205, and the objective lens 210 is set. First, the control computer 110 reads the drawing data from the storage device 140 and performs a plurality of stages of data conversion processing on the drawing data to generate device-specific shot data. In the shot data, the irradiation amount and irradiation position coordinates of each shot are defined.

  The control computer 110 outputs the irradiation amount of each shot to the deflection control circuit 130 based on the shot data. The deflection control circuit 130 calculates the irradiation time t by dividing the input irradiation amount by the current density. The deflection control circuit 130 controls the deflection voltage applied to the corresponding blanker so that the beam is turned on for the irradiation time t when performing the corresponding shot.

  The control computer 110 outputs the deflection position data to the deflection control circuit 130 so that each beam is deflected to the position (coordinates) indicated by the shot data. The deflection control circuit 130 calculates a deflection amount and applies a deflection voltage to the deflector 208. Thereby, the multi-beams shot at that time are deflected together.

  As described above, according to this embodiment, the distortion amount of the aperture image can be extremely reduced by repeating the adjustment of the crossover position and the excitation adjustment of the distortion adjustment lens 205.

  As shown in FIG. 10, the bore diameter D of the opening on the downstream side in the beam traveling direction of the magnetic pole 202a of the illumination lens 202 is increased so that the magnetic field by the illumination lens 202 extends (maintains) downstream of the blanking aperture array mechanism 204. It is preferable to make it. For example, the magnetic field MF1 of the illumination lens 202 is extended to the position of the distortion adjustment lens 205. As described above, by disposing the distortion adjustment lens 205 in the magnetic field MF1 of the illumination lens 202, the magnetic field generated by the distortion adjustment lens 205 can be reduced.

  For example, when the peak of the magnetic field strength of the illumination lens 202 is H and the magnetic field strength by the distortion adjustment lens 205 at the position of the shaping aperture array substrate 203 (or the blanking aperture array mechanism 204) is h, h / H ≧ 0. It is preferably about 05. Further, the magnetic field strength of the strain adjustment lens 205 is set so that the beam passing through the blanking aperture array mechanism 204 does not collide with the side wall of the passage hole of the blanking aperture array mechanism 204 due to the influence of the magnetic field by the strain adjustment lens 205. .

  In order to reduce the change in the reduction magnification of the aperture image, the distortion adjustment lens 205 is preferably as close as possible to the molded aperture array substrate 203, and is preferably disposed near (directly below) the blanking aperture array mechanism 204.

  The distortion adjustment lens 205 may be composed of a plurality of stages of lenses.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

10 substrate 20 mark 102 electron column 103 drawing chamber 105 XY stage 110 control computer 130 deflection control circuit 140 storage device 200 electron beam 201 electron gun 202 illumination lens 203 molding aperture array substrate 204 blanking aperture array mechanism 205 distortion adjustment lens 206 limitation Aperture substrate 208 Deflector 210 Objective lens

Claims (5)

An emission part for emitting a charged particle beam;
A plurality of first openings are formed, a region including the plurality of first openings is irradiated with the charged particle beam, and the charged particle beam passes through the plurality of first openings to generate a multi-beam. Forming aperture array substrate for forming and forming a multi-beam; and
Among the multi-beams that have passed through the plurality of first openings, a plurality of second openings through which the corresponding beams pass are formed, and blankers that perform blanking deflection of the beams are provided in the respective second openings. Blanking aperture array mechanism,
A limiting aperture substrate that is provided with a third opening through which the multi-beam passes and shields the beam deflected to be in a beam OFF state by the blanker;
An illumination lens that refracts the charged particle beam and illuminates the charged particle beam onto the shaped aperture array substrate;
An objective lens that has a plurality of stages of lenses arranged upstream of the limiting aperture substrate in the beam traveling direction, and forms the multi-beam aperture image on the surface of the drawing target substrate;
A distortion adjusting lens that is provided between the blanking aperture array mechanism and the objective lens, and corrects the imaging distortion of the aperture image;
A multi-charged particle beam drawing apparatus.   2. The multi-charged particle beam drawing apparatus according to claim 1, wherein the excitation distortion of the illumination lens is controlled to adjust the cross-over position of the multi-beam to correct image distortion of the aperture image. 3.   The multi-charged particle beam drawing apparatus according to claim 1, wherein the distortion adjusting lens is disposed in a magnetic field of the illumination lens.   The multi-charged particle beam drawing apparatus according to claim 1, wherein a plurality of the distortion adjustment lenses are provided. It is the adjustment method of the multi charged particle beam drawing apparatus of any one of Claims 1 thru | or 4, Comprising:
Adjusting the image distortion amount of the aperture image using the distortion adjustment lens, and controlling the position where the multi-beam forms a crossover using the illumination lens to reduce the image distortion amount of the aperture image. A method of adjusting the multi-charged particle beam drawing apparatus, wherein the adjusting step is alternately repeated until the imaging distortion amount becomes a predetermined value or less.

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