Method for diagnosing abnormality in blanking aperture array substrate and multi-beam drawing method

Abstract

To efficiently and highly accurately inspect a blanker for abnormalities.SOLUTION: A method for diagnosing an abnormality in a blanking aperture array substrate according to the present embodiment includes the steps of grouping a plurality of individual blankers into a plurality of groups and measuring the blanking performance of the individual blankers for each group, and dividing a group having an abnormality in blanking performance into a plurality of small groups and measuring the blanking performance of the individual blankers for each small group. In the step of measuring the blanking performance, the individual blankers of the group to be measured are set to beam-on, the beam-on time set for the collective blanker is made shorter than the beam-on time of the individual blankers, and while the beam-on setting of the individual blankers is being made, the timing of the beam-on by the collective blanker is made variable, the beam currents of the plurality of beams corresponding to the group to be measured are detected for each beam-on timing, and the blanking performance of the individual blankers is measured using the detection results of the beam currents.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an abnormality diagnosis method and a multi-beam drawing method for a blanking aperture array substrate. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer year by year. In order to form a desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (mask, or particularly one used in a stepper or scanner is called a reticle) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is drawn on a substrate such as a mask blank, which is made of a Cr film and a resist film formed on a substrate such as quartz, by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

[0003] For example, there is a drawing device that uses multiple beams. Compared to drawing with a single electron beam, using multiple beams allows many beams to be emitted at one time (one shot), improving throughput. In a multi-beam drawing device, a blanking aperture array substrate performs blanking control (control to block the beam so that it does not reach the substrate) for each beam of the multiple beams.

[0004] The blanking aperture array substrate has multiple apertures corresponding to each of the multi-beams, and a blanker consisting of a pair of electrodes is placed in each aperture. By controlling the voltage applied to each blanker, the electron beam passing through each aperture is deflected independently, thereby performing blanking control.

[0005] If a blanker is defective and the desired voltage cannot be applied, the beam cannot be switched on / off, or the beam cannot be directed to the desired position, resulting in degraded writing accuracy. Therefore, it is necessary to identify which blanker is defective.

[0006] However, it takes a huge amount of time to individually measure the blanking performance of all the blankers, the number of which is the same as the number of beams in a multi-beam system. On the other hand, if the blanking performance of all the blankers is measured collectively, abnormalities in a few blankers cannot be detected. Even if there are only a few abnormal blankers, the writing accuracy may deteriorate depending on the writing method. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-073461 A [Patent Document 2] JP 2005-116743 A [Patent Document 3] JP 2020-119682 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an abnormality diagnosis method for a blanking aperture array substrate capable of efficiently and highly accurately inspecting a blanker for abnormalities, and a multi-beam writing method using the abnormality diagnosis results. [Means for solving the problem]

[0009] A method for diagnosing an abnormality in a blanking aperture array substrate according to one aspect of the present invention is a method for diagnosing an abnormality in a blanking aperture array substrate in which a plurality of individual blankers are used to individually control beam on / off for each corresponding beam among multiple beams, the method comprising the steps of: grouping the plurality of individual blankers into a plurality of groups and measuring blanking performance of the individual blankers for each group; and dividing the group having an abnormality in blanking performance into a plurality of small groups and measuring the blanking performance of the individual blankers for each small group. In the step of measuring blanking performance, the individual blankers of the group to be measured are set to beam-on, and a beam-on time for setting a collective blanker capable of collectively blanking the multiple beams is set to be shorter than the beam-on time of the individual blankers. During the beam-on setting of the individual blankers, beam currents of a plurality of beams corresponding to the group to be measured are detected for each beam-on timing while varying the beam-on timing of the collective blanker, and the blanking performance of the individual blankers included in the group to be measured is measured using the detection result of the beam current.

[0010] A multi-beam writing method according to one aspect of the present invention sets a beam corresponding to an individual blanker identified as having an abnormality in blanking performance by the blanking aperture array substrate abnormality diagnosis method of the present invention as a defective beam, and writes a pattern on a writing target substrate using a beam of the multi-beams other than the defective beam. Effect of the Invention

[0011] According to the present invention, blanker abnormality inspection can be performed efficiently and with high accuracy. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating the configuration of a drawing device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a shaping aperture array member. [Diagram 3]FIG. 2 is a schematic diagram of a blanking aperture array substrate. [Figure 4] FIG. 4A is a diagram showing pixels obtained by dividing a drawing area, and FIG. 4B is a diagram showing a beam array of multiple beams. [Diagram 5] 11 is a graph showing an example of on / off timing of a collective blanker and an individual blanker. [Figure 6] 11 is a graph showing an example of on / off timing of a collective blanker and an individual blanker. [Figure 7] 11A and 11B are diagrams for explaining a method for measuring the blanking performance of an individual blanker. [Figure 8] 10 is a flowchart illustrating a method for diagnosing an abnormality in a blanking aperture array substrate according to the embodiment. [Figure 9] 9A and 9B are graphs showing examples of comparisons of blanking performance measurement results. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a configuration using an electron beam as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and an ion beam or the like may be used.

[0014] Fig. 1 is a schematic diagram of a drawing apparatus according to an embodiment of the present invention. As shown in Fig. 1, the drawing apparatus 100 includes a drawing unit 150 and a control unit 160. The drawing apparatus 100 is an example of a multi-charged particle beam drawing apparatus. The drawing unit 150 includes an electron lens column 102 and a drawing chamber 103. In the electron lens column 102, an electron source 201, an illumination lens 202, a shaping aperture array member 203, a blanking aperture array substrate 204, a reduction lens 205, a collective blanking deflector (collective blanker) 212, a limiting aperture member 206, an objective lens 207, and a deflector 208 are arranged.

[0015] An XY stage 105 is disposed in the drawing chamber 103. A substrate 101 to be drawn is disposed on the XY stage 105. The substrate 101 includes an exposure mask used in manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which a semiconductor device is manufactured, and the like. The substrate 101 also includes a mask blank on which resist is applied and on which nothing is yet drawn. A mirror 210 for measuring the position of the XY stage 105 is disposed on the XY stage 105.

[0016] A detector 107 for detecting a beam current is provided on the XY stage 105. The detector 107 is, for example, a Faraday cup. The beam current detection result by the detector 107 is output to the control computer 110 via an amplifier 134.

[0017] The control unit 160 includes a control computer 110, a deflection control circuit 130, an amplifier 134, a stage position detector 139, and a storage device 140. Drawing data is input from the outside and stored in the storage device 140 (storage unit).

[0018] 1 shows the configuration necessary for explaining the embodiment. The drawing device 100 may also include other configurations that are normally required.

[0019] An electron beam 200 emitted from an electron source gun 201 (emitting section) is caused to illuminate the entire shaping aperture array member 203 almost perpendicularly by an illumination lens 202 .

[0020] Fig. 2 is a schematic diagram of the shaping aperture array member 203. As shown in Fig. 2, the shaping aperture array member 203 has m vertical (y direction) columns x n horizontal (x direction) columns (m, n ≥ 2) apertures 203a formed in a matrix at a predetermined arrangement pitch. All apertures 203a are rectangular or circular and of the same size and shape. Multibeams 20 are formed by portions of electron beam 200 passing through each of the multiple apertures 203a.

[0021] 3, in the blanking aperture array substrate 204, through holes (openings) H are formed in accordance with the positions of the openings 203a of the shaping aperture array substrate 203, and an individual blanker consisting of a pair of electrodes 24, 26 is disposed in each through hole H. One of the two electrodes 24, 26 for each beam (e.g., electrode 26) is fixed to the ground voltage, and blanking control for each beam is performed by changing the voltage applied to the other (e.g., electrode 24).

[0022] In this manner, the multiple individual blankers perform blanking deflection of the corresponding beams among the multiple beams that have passed through the multiple openings 203 a of the shaping aperture array member 203 .

[0023] The multi-beams 20 that have passed through the blanking aperture array substrate 204 are reduced in size by the reduction lens 205 and proceed toward the central hole formed in the limiting aperture member 206. Here, the electron beams deflected by the individual blankers of the blanking aperture array substrate 204 are displaced from the central hole of the limiting aperture member 206 and are blocked by the limiting aperture member 206. On the other hand, the electron beams that have not been deflected by the individual blankers of the blanking aperture array substrate 204 pass through the central hole of the limiting aperture member 206 unless they are deflected by the collective blanker 212.

[0024] The global blanker 212 can blank multiple beams collectively. The global blanker 212 can operate faster than the individual blankers on the blanking aperture array substrate 204 because it only performs ON / OFF control.

[0025] Blanking control is performed and the beam is turned ON / OFF by a combination of the ON / OFF of the individual blanker and the ON / OFF of the collective blanker 212. In this manner, the limiting aperture member 206 blocks each beam deflected by the individual blanker or the collective blanker 212 to be in the beam OFF state.

[0026] The multi-beams 20 that have passed through the limiting aperture member 206 are focused by the objective lens 207 to become a pattern image with the desired reduction ratio, and are deflected collectively in the same direction by the deflector 208 to be irradiated onto the substrate 101. When the XY stage 105 is moving continuously, the deflector 208 controls the irradiation position of the beam so as to follow the movement of the XY stage 105. The multi-beams 20 irradiated at one time are ideally arranged at a pitch obtained by multiplying the arrangement pitch of the multiple openings 203a of the shaping aperture array member 203 by the desired reduction ratio.

[0027] For example, in the drawing process of the substrate 101, as shown in Fig. 4A, the drawing area of ​​the substrate 101 is divided into a plurality of mesh-shaped pixels G1, G2, G3, ..., and a required amount of beam is irradiated to each pixel to draw a desired pattern. The pixel size is, for example, the size of one individual beam.

[0028] In multi-beam writing, a single pixel on the substrate 101 is irradiated multiple times using multiple beams to provide a desired irradiation amount. For example, pixel G1 shown in FIG. 4A is irradiated with beams B1, B3, B9, and B11 of the multi-beam 20 shown in FIG. 4B. Pixel G2 is irradiated with beams B2, B4, B10, and B12. Pixel G3 is irradiated with beams B5, B7, B13, and B15. Pixel G4 is irradiated with beams B6, B8, B14, and B16.

[0029] As described above, the drawing apparatus 100 performs blanking control of each beam using both beam ON / OFF control for individual blanking control and beam ON / OFF control for collective blanking control that collectively controls blanking of the entire multi-beam.

[0030] 5, when a shot command is output from the control computer 110 at time T0, the deflection control circuit 130 outputs a voltage to an individual blanker of the blanking aperture array substrate 204. This voltage output process is performed after a variable delay time t1 has elapsed. The voltage output by this process is applied to the electrode of the individual blanker after a delay time t4 due to the cable length has elapsed, and the individual blanker is set to beam ON.

[0031] Moreover, the deflection control circuit 130 outputs a voltage to the collective blanker 212 in response to the shot command, and controls the collective blanker 212 to be turned ON. After the time t2 required for digital-to-analog conversion of the shot command and the variable delay time t3 have elapsed, the collective blanker 212 is set to the beam ON state.

[0032] While the collective blanker 212 is turning the beam ON, the beam with the individual blankers set to be ON passes through the limiting aperture member 206, and the substrate is irradiated with the beam for a time t5.

[0033] As described above, the collective blanker 212 can be operated at high speed. Therefore, as shown in FIG. 6, the ON time of the collective blanker 212 can be made shorter than the ON time of the individual blankers.

[0034] By changing the delay time t3, the timing when the collective blanker 212 turns ON can be shifted as shown in FIG. 7. The ON time of the collective blanker 212 is made extremely short compared with the ON time of the individual blanker, and the beam current is detected by the detector 107 while shifting the ON timing of the collective blanker 212. By arranging the beam current detection results at each timing, a waveform that approximates the output characteristic of the individual blanker (change in the voltage applied to the individual blanker) can be obtained. The blanking performance of the individual blanker can be measured based on the time (delay time) from when the obtained approximate output waveform reaches a constant value when the beam is turned ON to when the beam is turned OFF, or the contribution rate of the excess or deficiency of the dose of irradiation to the writing accuracy (the slope of the approximate output waveform from when the beam is turned ON to when the beam is turned OFF). It should be noted that the measurement time may be set to a very short predetermined time on the detector 107 side, regardless of the collective blanker 212, for measurement.

[0035] The shorter the ON time of the batch blanker 212, the smaller the detection value of the detector 107. Therefore, the shot may be performed multiple times to obtain the average current value per unit time.

[0036] Since the blanking aperture array substrate 204 is provided with a large number of individual blankers, it would take a huge amount of time to measure the blanking performance of each individual blanker as described above. Therefore, in this embodiment, several individual blankers are grouped, and the blanking performance is measured on a group basis. Then, a group with an abnormality is divided into smaller groups, and the blanking performance is measured again.

[0037] A method for diagnosing an abnormality in a blanking aperture array substrate will be described with reference to the flowchart shown in FIG.

[0038] A writing method and the number of passes for multiple writing when writing a pattern on a substrate are determined (step S101). This determines a combination of beams that irradiate the same pixel in the writing area of ​​the substrate (step S102). For example, in the example shown in Figures 4A and 4B, beams B1, B3, B9, and B11 are combined. Also, beams B2, B4, B10, and B12 are combined. Similarly, beams B5, B7, B13, and B15 are combined. Similarly, beams B6, B8, B14, and B16 are combined.

[0039] Based on the required inspection time, some combinations of beams determined in step S102 are grouped together (step S103). For example, in the example shown in Fig. 4A and Fig. 4B, beams B1, B3, B9, B11 and individual blankers corresponding to beams B2, B4, B10, B12 are grouped together. Also, beams B5, B7, B13, B15 and individual blankers corresponding to beams B6, B8, B14, B16 are grouped together.

[0040] The blanking performance of the individual blankers is measured for each group grouped in step S103 (step S104). The blanking performance is measured using, for example, the method shown in Fig. 7. That is, while controlling the on / off of a plurality of individual blankers corresponding to the beams in the group to be measured, the beam current is detected by the detector 107 while extremely shortening the on-time of the collective blanker 212 and shifting the on-timing. The detected beam current is used to obtain an approximate waveform of the applied voltage indicating the blanking performance of the grouped individual blankers. Beams other than the group to be measured are turned off.

[0041] When the blanking performance is measured for all groups (Yes in step S105), the measurement results (approximate waveforms) of the groups are compared to detect groups having abnormal blanking performance (step S106).

[0042] For example, as shown in Fig. 9A, if the measurement results of all groups match, the blanking performance of all groups is determined to be normal (step S107_No).On the other hand, as shown in Fig. 9B, if the behavior of the measurement results of a group differs from that of other groups, the blanking performance is determined to be abnormal (step S107_Yes).

[0043] A group determined to have an abnormality is divided into multiple small groups, the blanking performance of the individual blankers is measured for each small group, and the measurement results are compared. In this manner, detection of an abnormal group, subdivision of the detected group, and measurement are repeated until each beam is measured (steps S108 to S111). In this manner, an individual blanker with an abnormality in blanking performance is detected, and the corresponding individual beam is set as a defective beam (step S112).

[0044] For example, if it is determined that there is an abnormality in the blanking performance for the group consisting of beams B1, B3, B9, B11 and beams B2, B4, B10, B12, this group is divided into a small group consisting of beams B1, B3, B9, B11 and a small group consisting of beams B2, B4, B10, B12.

[0045] The blanking performance of the two small groups is measured, and if it is determined that the small group consisting of beams B2, B4, B10, and B12 has an abnormality, this small group is divided into individual beam units. Then, the blanking performance is measured for each individual beam to detect individual blankers with abnormalities.

[0046] The detected defective beam is set not to be used during pattern writing. If there is a defective beam that is not to be used for writing, a known defect correction technique is separately applied.

[0047] As described above, in this embodiment, a plurality of individual blankers are grouped and the blanking performance is measured on a group basis. This reduces the diagnosis time and makes it possible to efficiently inspect the individual blankers for abnormalities, compared to the case where the blanking performance of all the individual blankers is measured one by one.

[0048] In addition, a group having an abnormality in blanking performance can be divided into smaller groups, and measurements are repeated for each small group to identify individual blankers having an abnormality. This allows the individual blankers to be inspected for abnormalities with high accuracy.

[0049] In the above embodiment, when comparing the results of measuring the blanking performance on a group-by-group basis, it is preferable to normalize the results with the detection value at the optimal delay time.

[0050] Instead of comparing the measurement results on a group-by-group basis, the leakage dose (or insufficient dose) due to blanking anomalies may be calculated from the measurement results before normalization, and the presence or absence of an anomaly may be determined based on the effect that the excess or deficiency of the dose has on the dimensions.

[0051] For example, if the value obtained by dividing the leakage dose (or insufficient dose) by the reference dose and multiplying it by the likelihood (Dose Latitude: a value indicating the change in line width relative to a change in dose) is equal to or greater than a predetermined value, it is determined that there is an abnormality in the blanking performance of this group.

[0052] In the above embodiment, an example has been described in which beams that irradiate the same pixel are combined and several of these combinations are grouped together, but the grouping method is not limited to this. For example, the blanking aperture array substrate 204 may be divided into multiple regions, and the individual blankers in each region may be grouped. A group (region) with an abnormality in blanking performance is further divided into smaller groups (regions) and measured.

[0053] In the above embodiment, the configuration has been described in which the detector 107 provided on the XY stage 105 detects the beam current of the beam that has not been blanked (is turned ON), but the limiting aperture member 206 may also be used as a detector. In this case, the beam current of the blanked beam is detected.

[0054] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0055] 20 Multibeam 107 Detector 203 Molded Aperture Array Member 204 Blanking aperture array board 212 Blanca

Claims

1. A method for diagnosing an abnormality in a blanking aperture array substrate, the method comprising the steps of: using a plurality of individual blankers to individually control on / off of corresponding beams among a plurality of beams; grouping the individual blankers into a plurality of groups and measuring blanking performance of the individual blankers on a group-by-group basis; dividing the group having an abnormality in blanking performance into a plurality of small groups and measuring the blanking performance of the individual blankers in units of the small groups; Equipped with In the step of measuring the blanking performance, Set the individual blankers of the group to be measured to beam on. a beam-on time set for a global blanker capable of blanking multiple beams collectively is made shorter than the beam-on time of the individual blankers, and while the individual blankers are in the beam-on setting, a beam current of a plurality of beams corresponding to a group to be measured is detected for each beam-on timing while varying a beam-on timing of the global blanker, and a blanking performance of the individual blankers included in the group to be measured is measured using the detection results of the beam current.

2. 2. The method for diagnosing an abnormality in a blanking aperture array substrate according to claim 1, wherein each beam of the multiple beams draws pixels obtained by dividing a drawing area of ​​a substrate to be drawn into a mesh shape, and blanking performance is measured by grouping individual blankers corresponding to a plurality of beams that draw the same pixel in a multiple manner.

3. 3. The method for diagnosing an abnormality in a blanking aperture array substrate according to claim 1, further comprising the steps of: dividing a group having an abnormality in blanking performance; and repeating the measurement of the blanking performance in units of the divided groups to identify individual blankers having an abnormality in blanking performance.

4. a beam corresponding to an individual blanker identified as having an abnormality in blanking performance by the method for diagnosing an abnormality in a blanking aperture array substrate according to claim 3 is set as a defective beam; a multi-beam writing method for writing a pattern on a writing target substrate by using a beam other than the defective beam among the multiple beams.

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