Optical system adjustment method of multi-beam charged particle beam device and computer readable storage medium

Abstract

Provided is an optical system adjustment method for a multi-charged particle beam device and a computer-readable storage medium, which can effectively reduce multi-charged particle beam illumination system aberration. In an optical system adjustment method for a multi-charged particle beam device in which a multi-charged particle beam is sequentially irradiated to a substrate placed on a stage via an illumination optical system including a plurality of elements and an objective lens, a positional shift amount of a plurality of individual beams included in the multi-charged particle beam is measured as a height in two or more optical axis directions in which an imaging position of the multi-charged particle beam or a measurement surface is different, a normalized position difference based on the two or more heights and the positional shift amount is calculated as an equivalent amount of illumination system aberration of the illumination optical system, and a setting value of at least any one of the plurality of elements is adjusted using a value of the normalized position difference for each of the plurality of individual beams.

Description

[0001] This application is based on Japanese Patent Application No. 2022-021384 (filed on February 15, 2022) and claims preference to that basic application. This application incorporates the entire contents of that basic application by reference. Technical Field

[0002] This invention relates to an optical system adjustment method for a multi-charged particle beam device and a computer-readable storage medium. Background Technology

[0003] With the increasing integration of LSIs, the linewidths required for semiconductor devices are becoming smaller year by year. To form the desired circuit patterns on semiconductor devices, the following method is used: a reduction projection exposure device is used to transfer a high-precision original pattern formed on quartz onto the wafer. The high-precision original pattern is then drawn using an electron beam lithography device, employing a technique known as electron beam lithography.

[0004] For example, there are drawing apparatuses that use multiple beams. Compared to drawing with a single electron beam, using multiple beams allows for the illumination of more beams at once, thus significantly increasing throughput. In multi-beam drawing apparatuses, for example, an electron beam emitted from an electron gun is passed through a substrate with a shaped aperture array having multiple openings to form multiple beams. Each beam is blanked, and the unblocked beams are reduced by an optical system and deflected by deflectors to irradiate the desired location on the sample.

[0005] In multi-beam drawing apparatuses, to improve the positional accuracy and resolution of the drawn pattern, it is necessary to reduce the distortion and aberrations of the multi-beams on the drawing surface (sample surface). Since illumination system aberrations significantly affect the strain and aberrations of the multi-beams on the drawing surface, reduction of illumination system aberrations is required. Furthermore, illumination system aberrations are deviations from the ideal design trajectory generated in the illumination system, contributing to the aberrations that form the intersections (actual light source images) midway along the beam trajectory. Therefore, illumination system aberrations and intersection aberrations are essentially the same, but this specification uses the term illumination system aberrations.

[0006] However, in the past, due to the inability to measure the aberrations of the lighting system with high precision, it was impossible to confirm whether the aberrations had been sufficiently reduced, resulting in insufficient adjustment of the lighting system. Summary of the Invention

[0007] An optical system adjustment method for a multi-charged particle beam device that can effectively reduce aberrations in a multi-charged particle beam illumination system, and a computer-readable storage medium are provided.

[0008] An optical system adjustment method for a multi-charged particle beam device according to one aspect of the present invention is as follows: the multi-charged particle beam device sequentially illuminates a substrate placed on a worktable with multiple charged particle beams via an illumination optical system comprising multiple elements and an objective lens. The method involves measuring the positional offset of multiple individual beams included in the multi-charged particle beam, using the heights of two or more optical axis directions that cause the measurement surface or the imaging position of the multi-charged particle beam to differ, calculating a standardized positional difference as an equivalent of the illumination system aberration of the illumination optical system based on the two or more heights and positional offsets, and adjusting the set value of at least one of the multiple elements using the value of the standardized positional difference for each of the multiple individual beams. Attached Figure Description

[0009] Figure 1 This is a schematic diagram depicting an embodiment of the apparatus of the present invention.

[0010] Figure 2 This is a top view of a substrate with a shaped aperture array.

[0011] Figure 3 This is a flowchart illustrating the adjustment method of the optical system in this embodiment.

[0012] Figure 4 This is a flowchart illustrating the adjustment method of the optical system in this embodiment.

[0013] Figure 5A , Figure 5B This diagram illustrates an example of a method for measuring changes in height when determining the positional offset of a single beam.

[0014] Explanation of symbols:

[0015] 10: Substrate; 20: Marker; 102: Electron optical lens barrel; 103: Drawing chamber; 105: XY stage; 110: Control computer; 120: Control circuit; 200: Electron beam; 201: Electron gun; 202: Illumination lens; 203: Forming aperture array substrate; 204: Blanking aperture array mechanism; 206: Limiting aperture substrate; 208: Deflector; 210: Objective lens; 230: Alignment deflector; 232: Astigmatism corrector; 234: Hexapole; 236: Octapole; 238: Grating lens. Detailed Implementation

[0016] Hereinafter, in the embodiments, as an example of the optical system of a multi-beam drawing apparatus using an electron beam, the configuration of the optical system will be described. However, the charged particle beam is not limited to an electron beam, and may also be a beam using charged particles such as an ion beam. Furthermore, it may not be applied to a drawing apparatus, but to an optical system such as SEM.

[0017] Figure 1 This is a schematic diagram of the multi-beam drawing apparatus according to an embodiment of the present invention. Figure 1 As shown, the multi-beam mapping apparatus includes a mapping unit W and a control unit C. The mapping unit W includes an electron optical tube 102 and a mapping chamber 103. An electron gun 201, an illumination optical system 11, a forming aperture array substrate 203, a blanking aperture array mechanism 204, a limiting aperture substrate 206, a deflector 208, and an objective lens 210 are disposed within the electron optical tube 102.

[0018] The illumination optical system IL operates, irradiating the shaped aperture array substrate 203 with a beam and forming a cross CO at a predetermined downstream position. The cross CO is the point where the center tracks of the individual beams from each aperture of the shaped aperture array substrate 203 converge into one. In multiple optical systems, such as in this embodiment, it becomes an image of a cross formed near the electron gun 201 (there may also be actual light sources or virtual images).

[0019] exist Figure 1 In the example shown, the illumination optical system IL is positioned above the shaped aperture array substrate 203 (upstream of the beam travel direction), and a lens upstream performs the functions of beam illumination and cross CO formation. Unlike this configuration, there are also examples where, in an optical system that irradiates an electron beam perpendicularly to the shaped aperture array substrate 203, a lens positioned downstream of the shaped aperture array substrate 203 again converges the beam to form cross CO at a predetermined position downstream. In this case, the lens positioned downstream of the shaped aperture array substrate 203 (the lens for cross CO formation) functionally becomes part of the illumination optical system IL.

[0020] An illumination optics system (IL) comprises several components. Figure 1 In the example shown, the illumination optical system IL has an illumination lens 202, an alignment deflector 230, an astigmatism corrector 232, a hexapole 234, an octapole 236, and a grating lens 238.

[0021] The alignment deflector 230 has the function of deflecting the beam, adjusting the position and angle of the beam on the illumination lens 202 and the shaped aperture array substrate 203, mainly correcting the coma and cross CO position of the illumination lens system in the plane.

[0022] Astigmatism corrector 232 corrects astigmatism in illumination lens systems.

[0023] The hexapole aberration components of the hexapole 234 correction illumination lens system.

[0024] Octapole 236 correction illumination lens system octapole aberration components.

[0025] The grating lens 238 corrects the spherical aberration of the illumination lens system.

[0026] Aligners and multipole (astigmatism corrector, hexapole, octapole, etc.) are also disposed below the illumination optical system IL and the shaped aperture array substrate 203 (downstream of the beam travel direction), but are not shown in the figure.

[0027] An XY stage 105 and a detector 220, capable of moving in the XY direction (perpendicular to the optical axis of the electron-optical system), are disposed within the drawing chamber 103. The XY stage 105 can also move in the Z direction (the direction of the optical axis of the electron-optical system). A substrate 10, the object to be drawn, is disposed on the XY stage 105. The substrate 10 includes an exposure mask used in manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) used in manufacturing a semiconductor device, etc. Furthermore, the substrate 10 includes a mask blank coated with resist that has not yet been drawn.

[0028] A marker 20 is also provided on the XY stage 105. The marker 20 is also movable in the Z direction. The marker 20 is, for example, a cross-shaped or dot-shaped metal marker. The detector 220 detects reflected electrons (or secondary electrons) when the marker 20 is beam-scanned.

[0029] In addition, a reflector 30 for determining the position of the worktable is installed on the XY worktable 105.

[0030] The control unit C includes a control computer 110, a control circuit 120, a detection circuit 122, and a table position detector 124. The table position detector 124 is illuminated by a laser and receives reflected light from the reflector 30, and detects the position of the XY table 105 according to the principle of laser interferometry.

[0031] exist Figure 1 The diagram shows the necessary components based on the described embodiments, omitting illustrations of other components. For example, in Figure 1 In this case, objective lens 210 is set to first-order, but it can also be set to second-order or multiple-order. Even illumination lens 202 can be multi-order.

[0032] Figure 2 This is a conceptual diagram showing the structure of the shaped aperture array substrate 203. Figure 2 In the shaped aperture array substrate 203, openings (first openings) 203a are formed in a matrix shape with a predetermined arrangement spacing of p columns (y-direction) × q columns (x-direction) (p, q ≥ 2). Each opening 203a is formed as a rectangle with the same size and shape. The openings 203a can also be circular. A portion of the electron beam 200 passes through the above-mentioned multiple openings 203a, thereby forming a multi-beam MB.

[0033] A blanking aperture array mechanism 204 is disposed below the shaped aperture array substrate 203, and through-holes (second openings) are formed to match the arrangement positions of each opening 203a of the shaped aperture array substrate 203. A blanking device consisting of a pair of electrodes is disposed in each through-hole. One electrode of the blanking device is fixed at ground potential, while the other electrode is switched to a potential different from ground potential. The electron beam passing through each through-hole is independently deflected by the voltage applied to the blanking device. In this way, multiple blanking devices blank and deflect each corresponding beam in the multiple beams MB passing through the multiple openings 203a of the shaped aperture array substrate 203.

[0034] An electron beam 200 emitted from the electron gun 201 (emitting unit) is refracted by the illumination lens 202 and illuminates the entire shaped aperture array substrate 203. The electron beam 200 illuminates the area containing multiple (all) openings 203a. A portion of the electron beam 200 passes through the multiple openings 203a of the shaped aperture array substrate 203, thereby forming multiple electron beams (multi-beam MB). The multi-beam MB pass through corresponding blanking devices in the blanking aperture array mechanism 204. The blanking devices respectively control the blanking of the passing beams, so that the beams are in the on state at a set drawing time (irradiation time).

[0035] The multi-beam MB receives refraction generated by the illumination lens 202, and by means of this refraction, the multi-beam MB, passing through the blanking aperture array mechanism 204, travels toward the opening (third opening) formed at the center of the limiting aperture substrate 206. Then, the multi-beam MB forms a cross CO at the height position of the opening of the limiting aperture substrate 206.

[0036] Here, the beam deflected by the blanking devices of the blanking aperture array mechanism 204 is positioned offset from the opening of the limiting aperture substrate 206 and is blocked by the limiting aperture substrate 206. On the other hand, the beam not deflected by the blanking devices of the blanking aperture array mechanism 204 passes through the opening of the limiting aperture substrate 206. In this way, the limiting aperture substrate 206 blocks the deflected beam, making the beam cut-off state achieved by each blanking device.

[0037] Each beam emitted in a single emission is formed by the beam passing through the aperture-limiting substrate 206, which is formed from the moment the beam is turned on to the moment it is turned off. Each beam of the multiple beams MB passing through the aperture-limiting substrate 206 is used by the objective lens 210 to form an aperture image of the opening 203a of the shaped aperture array substrate 203 at the desired magnification, and the image is focused on the substrate 10. Then, each beam (the entire multiple beams) passing through the aperture-limiting substrate 206 is converged and deflected in the same direction by the deflector 208, and each beam is irradiated at its respective irradiation position on the substrate 10.

[0038] For example, as the XY stage 105 moves continuously, the beam irradiation position is controlled by the deflector 208 to follow the movement of the XY stage 105. Ideally, the multiple beams MB irradiated in a single pass are arranged with a spacing obtained by multiplying the arrangement spacing of the multiple openings 203a of the shaped aperture array substrate 203 by the desired reduction rate. The drawing apparatus performs a drawing operation using a raster scanning method that sequentially irradiates the emitted beams. When drawing the desired pattern, unwanted beams are controlled to be cut off by blanking control.

[0039] To improve the positional accuracy and resolution of the pattern drawn on the substrate 10, it is necessary to reduce the illumination system aberrations generated by the illumination optics IL. According to... Figure 3 , Figure 4 The flowchart shown illustrates an optical system adjustment method for reducing illumination system aberrations.

[0040] First, at two or more different heights near the depicted surface, the positional offset of each of the multiple individual beams constituting the multi-beam system is measured (step S1). For example, the individual beams of the object being measured are turned on one by one in sequence, and the deflector 208 deflects the beams to scan the mark 20. The detector 220 detects the electrons reflected by the mark 20. The detection circuit 122 notifies the control computer 110 of the amount of electrons detected by the detector 220. The control computer 110 acquires a scanning waveform (including a scanning image) based on the detected amount of electrons and calculates the position of each individual beam with the position of the XY stage 105 as a reference. The difference between the calculated beam position and the ideal position is the positional offset. The positional offset is sometimes also called distortion. Alternatively, the average positional offset of the multiple beams obtained by scanning multiple beams that converge close to each other (e.g., 16×16 beams) can be set as the positional offset of the beam assumed to be at the center of the multiple beams.

[0041] Sequentially switch the individual beams that are set to "on" and calculate the positional offset of each beam. The reason for measuring the positional offset of multiple beams is that since illumination system aberrations affect the overall multi-beam configuration, information from multiple beams is needed to calculate illumination system aberrations. Illumination system aberrations cannot be evaluated based on the positional offset of a single beam or the average positional offset of the entire beam configuration. Based on the number of individual beams whose positional offsets were calculated, for example, 512×512 beams constituting the multi-beam configuration, select 5×5 beams at equal intervals as the measurement targets.

[0042] Furthermore, the minimum required number of individual beams is determined based on the aberration representative value calculation method described later. For example, when using the third-order components of the polynomial approximation of the standardized position difference as the aberration representative value calculation, it is sufficient to measure the position offset of individual beams as many as the number of coefficients of the third-order polynomial (i.e., 10).

[0043] In addition, the so-called "different height" or "change in height" can be as follows: Figure 5A The "measurement surface height change, imaging height fixation" shown, which moves the XY stage 105 in the Z direction (optical axis direction), changes the height of the surface (measurement surface) of the mark 20 used for position measurement in the optical axis direction, and keeps the imaging height of the multi-beam fixed, can also be as follows: Figure 5B The concept of "fixed measurement surface height, changed imaging height" refers to a situation where the height of the measurement surface remains unchanged while the height of the imaging position of the multi-beam is altered. Here, the change in imaging height is achieved by changing the excitation of the objective lens 210.

[0044] In this embodiment, an example of measuring at two heights, z1 and z2, will be described. The difference between height z1 and height z2 is preferably around a few μm to tens of μm. Furthermore, at heights z1 and z2, the beam does not need to be focused on the surface (measuring surface) of mark 20. For example, focusing can occur at one height and focus shift at the other height, or focus shift can occur at both heights.

[0045] Let the ideal position (reference position) of the individual beam of the j-th measuring object at height z1 be set as (x j y j Let the corresponding complex coordinates be β. j =x j +iy j Set the position offset to δw(β) j ,z1). δw(β) j (z1) is a complex number, with its real part corresponding to the position offset in the x-direction and its imaginary part corresponding to the position offset in the y-direction. This position offset, being a deviation from the ideal position, is equivalent to distortion. When the number of individual beams of the measured object is set to N, 1 ≤ j ≤ N. Furthermore, similar to typical electron optical system analysis, the ideal position (x...j ... j y j The origin of the optical system is set as the optical axis of the electron optical system (that is, the point where the optical axis of the electron optical system intersects with the measurement surface is set as the origin).

[0046] Similarly, the positional offset of the individual beam of the measured object at height z2 is expressed as δw(β). j , z2).

[0047] Next, the position offsets δw(β) at the two heights obtained in step S1 are used. j ,z1) and δw(β) j The following formula (z2) is used to calculate the equivalent quantity of illumination system aberrations corresponding to optical system aberrations, i.e., the standardized position difference δw. H (β j (Step S2). Hereinafter, δw H (β j This is called the standardized position difference. As described later, the standardized position difference is an equivalent of an aberration in the lighting system. Standardized position difference δw H (β j The calculation formula for ) varies depending on the height setting method in step S1.

[0048] In step S1, when the height setting method is "the measurement surface height is fixed and the imaging height is changed", the standardized position difference δw is calculated using the following formula (1). H (β j ).

[0049]

[0050] The beam passing position within the objective lens changes proportionally to the aberrations of the illumination system. Here, when the objective lens excitation changes, the beam position on the imaging plane changes proportionally to the distance from the lens center at the beam passing position. Furthermore, the imaging height also changes proportionally to the change in objective lens excitation. The first term of equation (1) above calculates the ratio of the change in beam position to the change in imaging height, which is proportional to the aberrations of the illumination system.

[0051] However, the first term of equation (1) includes not only the component generated by illumination system aberrations, but also the component generated under the ideal state without illumination system aberrations. When the height setting method in step S1 is "fixed measurement surface height and changed imaging height", the component generated under the ideal state without illumination system aberrations is obtained by multiplying the constant representing the rate of change of beam magnification and rotation relative to imaging height when the objective lens excitation is changed by the beam position coordinates.

[0052] Therefore, by subtracting the component generated under the ideal condition of no lighting system aberrations, i.e., the second term, from the first term of equation (1), the standardized position difference δw, which is equivalent to the lighting system aberrations, is obtained. H (β j k in equation (1) H It is a complex number, and it is a constant. This constant is... Figure 1The depiction apparatus shown, under ideal manufacturing and adjustment conditions, represents the rate of change of beam magnification and rotation when the objective lens excitation is varied while the measurement plane height is fixed. Constant k H The real part corresponds to the multiplication factor, and the imaginary part corresponds to the rotation factor. This constant k H This can be calculated using beam trajectory simulation. Furthermore, the heights z1 and z2 are set as positive directions and constants k. H The selection of coordinates in the calculation is determined by matching.

[0053] The chromatic aberration coefficient can also be calculated by simulation, using the on-axis chromatic aberration coefficient k. X Magnification chromatic aberration coefficient k T , such as k H =k T / k X That's how to calculate the constant k H Furthermore, when the objective lens is an electrostatic lens, the same constant can be calculated for the applied voltage change rather than the excitation change. The imaging height of the multi-beam can also be changed by changing the applied voltage of the electrostatic focus correction lens (illustration omitted) without changing the applied voltage of the objective lens. In addition, the previous explanation illustrated an example of changing the imaging height by changing the excitation of one objective lens, but it is also possible to change the excitation of multiple objectives. In this case, the excitation amounts of the multiple objectives are changed at a certain ratio, with the constant k... H The calculation is performed by performing track simulation under the condition that the excitation quantity is changed at a certain ratio as described above.

[0054] When the height setting method in step S1 is "the measurement surface height changes and the imaging height is fixed", the following formula (2) is used to calculate the standardized position difference δw. H (β j The first term of Equation (2) calculates the ratio of the change in beam position relative to the height of the measuring surface. The first term of Equation (1) is for the height of the imaging surface, and the first term of Equation (2) is for the height of the measuring surface, but at the same time calculates the ratio of the change in beam position relative to the height.

[0055]

[0056] The beam position within the objective lens changes proportionally to the aberrations of the illumination system, resulting in a change in the landing angle (angle of incidence) towards the measurement surface. Here, when the height of the measurement surface changes, the beam position on the measurement surface changes proportionally to the landing angle. The first term of equation (2) above calculates the ratio of the change in beam position to the height of the measurement surface, i.e., the landing angle, which is proportional to the aberrations of the illumination system.

[0057] However, the first term of equation (2) includes not only the component caused by illumination system aberrations, but also the component generated under ideal conditions without illumination system aberrations.

[0058] In step S1, the height setting method is "the height of the measuring surface changes while the imaging height remains fixed." The component generated under ideal conditions without illumination system aberrations is obtained by multiplying a constant representing the ratio of the beam position to the landing angle (the ideal landing angle in design) by the beam position coordinates. Therefore, by subtracting the component generated under ideal conditions without illumination system aberrations, i.e., the second term, from the first term of equation (2), the standardized position difference δw, which is equivalent to the illumination system aberration, is obtained. H (β j ).

[0059] L in equation (2) A It is a plural number, in Figure 1 The depiction device shown, assuming ideal manufacturing and adjustment, is a constant representing the ratio of the incident position of the depiction surface of a single beam to the landing angle. Constant L A The real part corresponds to the landing angle in the radial direction, and the imaginary part corresponds to the landing angle in the rotation direction. This constant L... A Using the off-axis trajectory w calculated from the beam trajectory simulation b Such as L A =w b '(z i ) / w b (z i This is how it is calculated. Here, z i These are the image plane coordinates (image plane position). Additionally, the heights z1 and z2 are positive and related to the constant L. A The selection of coordinates in the calculation is determined by matching.

[0060] Next, based on the illumination system aberration equivalent (i.e., the standardized position difference δw) H (β j )) Calculate the representative aberration value (step S3). The representative aberration value is, for example, the standardized position difference δw. H (β j The square root of the sum of the squares of the absolute values ​​of the elements (values ​​for each beam).

[0061] The position difference δw is normalized by a polynomial approximation with the beam position as a parameter. H (β j The sum of its lower-order components (e.g., the sum of the absolute values ​​of the components from 0th to 3rd order at the beam region ends) can be used as the aberration representative value. Furthermore, the normalized position difference δw can be... H (β jPerform Fourier transform and appropriately select the absolute values ​​of lower-order components, etc.

[0062] Next, the settings of the components of the illumination optical system IL are adjusted sequentially. The components of the illumination optical system IL include the illumination lens 202, the alignment deflector 230, the astigmatism corrector 232, the hexapole 234, the octapole 236, and the grating lens 238. One of these components is selected from those that were not previously selected (step S4). Additionally, components with two settings, X and Y, such as the alignment deflector, can be treated as other components; for example, the alignment deflector X is initially selected, followed by the alignment deflector Y.

[0063] The set value of the selected component is changed by a specified amount (micro-motion) (step S5). The set value is the excitation current, applied voltage, etc.

[0064] After the set value is changed, the position offset of individual beams at two or more heights is measured (step S6), the standardized position difference is calculated (step S7), and the aberration representative value is calculated (step S8). Since the processing of steps S6 to S8 is the same as that of steps S1 to S3 described above, the explanation is omitted.

[0065] If the aberration representative value decreases due to the change in the setting value of the constituent element (as in step S9), return to step S5 and change the setting value of the constituent element by a predetermined amount in the same direction as the previous change. Repeat steps S5 to S8 until the aberration representative value no longer decreases.

[0066] The relationship and trend between the change in the set value, the standardized position difference, and the change in the aberration representative value are determined in advance for each component through actual measurement, simulation, etc., and can be used for the change of the set value in step S5 (that is, it can be used for the determination of the above-mentioned specified quantity).

[0067] Based on the change in the setting value of the constituent element, if the aberration representative value increases or remains unchanged (No in step S9), the setting value of the constituent element is restored to the previous state (step S10). The number of times the setting value has changed in step S5 is determined (step S11). If the number of changes is one, the direction of the setting value change is reversed (step S12), returning to step S5, and the setting value of the constituent element changes by a predetermined amount.

[0068] For example, when the applied voltage is increased by a specified amount in the first setting change, and the aberration representative value increases, the setting is restored to the initial value; and when the applied voltage is decreased by a specified amount in the second setting change.

[0069] If the setpoint is changed more than twice, the setpoint adjustment for that component ends. If there are components for which the setpoint is not adjusted (No in step S13), return to step S4. Process steps S5 to S12 sequentially for all components of the lighting optical system IL, and adjust the setpoints accordingly.

[0070] The order in which the settings of the components of the illumination optical system IL are adjusted is not particularly limited, but as an example, the settings are adjusted in the following order: alignment deflector 230, illumination lens 202, astigmatism corrector 232, hexapole 234, octapole 236, and grating lens 238. When the settings of the alignment deflector 230 are changed, since the beam trajectory and aberrations usually change significantly, the initial adjustment of the settings of the alignment deflector 230 is often effective.

[0071] After adjusting the settings of all constituent elements (as in step S13), return to step S4. Repeat this cycle (the cycle from step S4 to step S13) a predetermined number of times (usually around 2 to 5 times).

[0072] After performing the cycle from step S4 to step S13 a predetermined number of times (as in step S14), the excitation of the aligner, multipole, etc., which are located below the blanking aperture array mechanism 204 (downstream of the beam travel direction), is adjusted using a known method, and the distortion of the beam array image on the drawing plane is adjusted (step S15). Furthermore, the beam movement on the drawing plane (the average movement of the entire beam or the movement of the beam near the center of the entire beam) when the excitation of the objective lens 210 is slightly changed is measured, and the excitation of the aligner, multipole, etc., is adjusted to minimize the amount of beam movement.

[0073] In this way, a pattern is drawn on the substrate 10 using a drawing device with adjusted optical system. First, the control computer 110 reads the drawing data from the storage device (not shown), performs multi-level data transformation processing on the drawing data, and generates emission data inherent to the device. The illumination amount and illumination position coordinates of each emission are defined in the emission data.

[0074] The control computer 110 outputs the illumination amount of each emission to the control circuit 120 based on the emission data. The control circuit 120 divides the input illumination amount by the current density to calculate the illumination time t. Then, when performing the corresponding emission, the control circuit 120 controls the deflection voltage applied to the corresponding blanking device so that the beam is activated only for the illumination time t.

[0075] The control computer 110 outputs deflection position data to the control circuit 120, causing each beam to deflect to the position (coordinates) indicated by the transmission data. The control circuit 120 calculates the deflection amount and applies a deflection voltage to the deflector 208. As a result, the multiple beams transmitted in this transmission are deflected together.

[0076] As described above, according to this embodiment, the aberration efficiency of the illumination system can be reduced reliably, and patterns with high positional accuracy and resolution can be drawn on the substrate.

[0077] The standardized position difference δw can be obtained using a simple mathematical expression such as equation (3) below. H (β j This formula is a simplified mathematical expression that omits the second term of the above formulas (1) and (2), and can be applied without relying on the height setting method in steps S1 and S6. When comparing with the above formulas (1) and (2), k is omitted. H Or L A However, since optical designs often involve reducing these coefficients, omitting these terms usually has little impact. Furthermore, the sign of the first term in equation (2) differs from that in equation (3). This can be mitigated by removing the sign effect when calculating the representative aberration value through absolute values.

[0078]

[0079] Furthermore, when the heights z1 and z2 are constant, the standardized position difference δw can also be obtained using a simplified mathematical expression such as equation (4) below. H (β j ).

[0080] δw H (β j )=δw(β j ,z2)-δw(β j ,z1)…(4)

[0081] In the above embodiments, as shown in the first term of equations (1) and (2), the difference in positional offsets between two heights is calculated, but the difference in the positions of each beam at the two heights can also be used. Furthermore, the positional offsets at two heights can be used, but the positional offsets at three or more heights can also be used. When using three or more heights, the first term of equations (1) and (2) is not a simple division calculation; the rate of change of positional offset relative to height is used. The rate of change can be calculated, for example, using the least squares method.

[0082] Each step of the aforementioned optical system adjustment method is executed by the control computer 110 controlling the control circuit 120, the detection circuit 122, and the stage position detector 124, and causing the various parts of the drawing unit W to operate. The control computer 110 can be constructed of hardware such as circuits, or it can be constructed of software. In the case of software construction, the program for implementing at least some of the functions of the control computer 110 can be stored in a non-volatile storage medium, or it can be read into a computer containing circuits for execution.

[0083] The description up to this point has shown an example of measuring the position offset of the beam by using a signal obtained from scanning markers, but this can also be done by measuring the distortion of a drawn pattern. For example, the beam imaging position can be changed by altering the objective lens excitation to create a pattern, and the distortion of this pattern can be measured.

[0084] Furthermore, while sequentially changing the setting values ​​of the constituent elements, two excitations can be used to draw patterns, measure the distortion of their patterns, calculate the standardized position difference, calculate the aberration representative value, and select the constituent element setting value that minimizes the change in aberration representative value.

[0085] Furthermore, the present invention is not limited to the above-described embodiments, but can be embodied by modifying the constituent elements during the implementation stage without departing from its spirit. Moreover, various inventions can be formed by appropriately combining the multiple constituent elements disclosed in the above embodiments. For example, some constituent elements can be deleted from all the constituent elements shown in the embodiments. Furthermore, constituent elements distributed in different embodiments can be appropriately combined.

Claims

1. A method for adjusting the optical system of a multi-charged particle beam device, wherein the multi-charged particle beam device sequentially illuminates a substrate placed on a worktable via an illumination optical system comprising multiple elements and an objective lens, wherein in the optical system adjustment method, The positional offset of multiple individual beams contained in the multi-charged particle beam is measured at heights along two or more optical axes at different imaging positions on the measurement surface or the multi-charged particle beam. Based on the above two or more heights and the above position offsets, the standardized position difference is calculated as the equivalent of the illumination system aberrations of the above illumination optical system. Using the standardized position difference values ​​for each of the plurality of individual beams, adjust the setting value of at least one of the plurality of elements.

2. The optical system adjustment method for the multi-charged particle beam device according to claim 1, wherein, The aberration representative value is calculated using the standardized position difference value, and the setting value of at least one of the above-mentioned factors is adjusted to reduce the aberration representative value.

3. The optical system adjustment method for the multi-charged particle beam device according to claim 1, wherein, The height along the aforementioned optical axis is the height along the optical axis of the imaging position of the aforementioned multi-charged particle beam. By changing the height of the imaging position of the multiple charged particle beams, the positional offset of each individual beam is measured. The standardized position difference is calculated by subtracting the value obtained by multiplying the beam position coordinates by a constant from the rate of change of the position offset relative to the height of the imaging position. The constant represents the rate of change of the beam magnification and rotation relative to the height of the imaging position due to the change in the height of the imaging position.

4. The optical system adjustment method for the multi-charged particle beam device according to claim 3, wherein, The height of the imaging position is changed by altering the excitation of the objective lens.

5. The optical system adjustment method for the multi-charged particle beam device according to claim 1, wherein, The aforementioned height along the optical axis refers to the height of the surface of the mark used for beam position measurement on the aforementioned worktable, along the optical axis. The height of the marker used for beam position determination is changed by moving it up and down, and the positional offset of the multiple individual beams is measured. The standardized position difference is calculated by subtracting the rate of change of the position offset relative to the height of the marked surface from the value obtained by multiplying the beam position coordinates by a constant representing the ratio of the incident position of the beam's depicted surface to the landing angle.

6. The optical system adjustment method for a multi-charged particle beam device according to claim 1, wherein, The aforementioned elements include at least one of an illumination lens, an alignment deflector, an astigmatism corrector, a hexapole, an octapole, and a grating lens.

7. The optical system adjustment method for a multi-charged particle beam device according to claim 2, wherein, As a representative value of the aforementioned aberrations, the square root of the sum of the squares of the absolute values ​​of the aforementioned standardized positional differences for each of the aforementioned plurality of individual beams is calculated.

8. The optical system adjustment method for a multi-charged particle beam device according to claim 2, wherein, The standardized position difference for each of the plurality of individual beams is approximated by a polynomial with the beam position of the individual beam as a parameter, and the aberration representative value is calculated based on the polynomial.

9. The optical system adjustment method for a multi-charged particle beam device according to claim 8, wherein, The sum of the lower-order components of the above polynomial is calculated as the representative value of the aberration.

10. A computer-readable storage medium storing a program that adjusts the optical system of a multi-charged particle beam device to sequentially illuminate a substrate mounted on a worktable via an illumination optical system comprising multiple elements and an objective lens. The program causes the computer to perform the following steps: The positional offset of multiple individual beams contained in the multi-charged particle beam is measured at the height of two or more optical axis directions at different imaging positions of the measurement surface or the multi-charged particle beam. Based on the above two or more heights and the above positional offsets, a standardized positional difference is calculated as the equivalent of the illumination system aberrations of the above-mentioned illumination optical system; and Using the standardized position difference values ​​described above, adjust the setting value of at least one of the above-mentioned elements.

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