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

Abstract

The present invention efficiently carries out an abnormality inspection of blankers with high accuracy. A method for diagnosing an abnormality of a blanking aperture array substrate according to the present embodiment comprises: a step for grouping a plurality of individual blankers into a plurality of groups and measuring the blanking performance of the individual blankers in a group unit; and a step for dividing a group with abnormal blanking performance into a plurality of small groups and measuring the blanking performance of the individual blankers in units of small groups.

Description

Abnormality diagnosis method and multi-beam writing method for blanking aperture array substrate

[0001] The present invention relates to a method for diagnosing abnormalities in a blanking aperture array substrate and a multi-beam writing method.

[0002] With the increasing integration density of LSIs, the circuit line width required for semiconductor devices has been becoming finer year by year. To form a desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (called a mask, or a reticle, particularly when used in a stepper or scanner) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is written onto a substrate, such as a mask blank, which is made of a quartz substrate or the like and has a chromium film and a resist film formed thereon, using an electron beam writing apparatus, and so-called electron beam lithography technology is used.

[0003] For example, there is a lithography device that uses multiple beams. Compared to lithography using a single electron beam, using multiple beams allows for more beams to be irradiated at one time (in one shot), improving throughput. In a multi-beam lithography device, blanking control (control to block the beams so that they do not reach the substrate) is performed on each of the multiple beams using a blanking aperture array substrate.

[0004] The blanking aperture array substrate has multiple apertures corresponding to each beam of the multi-beam array, and each aperture is equipped with a blanker consisting of a pair of electrodes. By controlling the voltage applied to each blanker, the electron beams passing through each aperture are 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 a deterioration in writing accuracy. Therefore, it is necessary to identify which blanker is defective.

[0006] However, measuring the blanking performance of each blanker individually, which corresponds to the number of beams in a multi-beam system, requires a huge amount of time. Meanwhile, measuring the blanking performance of all blankers collectively makes it impossible to detect abnormalities in a few blankers. Even if there are only a few abnormal blankers, the writing accuracy may be degraded depending on the writing method.

[0007] JP 2017-073461 A JP 2005-116743 A JP 2020-119682 A

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

[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 on / off of corresponding beams out of multiple beams, and comprises the steps of: grouping the plurality of individual blankers into a plurality of groups and measuring the blanking performance of the individual blankers on a group-by-group basis; 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 on a small group-by-group basis.

[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.

[0011] According to the present invention, blanker abnormality inspection can be carried out efficiently and with high precision.

[0012] FIG. 4 is a schematic diagram of a drawing apparatus according to an embodiment of the present invention. FIG. 4 is a schematic diagram of a shaping aperture array member. FIG. 4 is a schematic diagram of a blanking aperture array substrate. FIG. 4A is a diagram showing pixels obtained by dividing a drawing area, and FIG. 4B is a diagram showing a multi-beam beam array. FIG. 4B is a graph showing an example of the on / off timing of a collective blanker and an individual blanker. FIG. 4C is a graph showing an example of the on / off timing of a collective blanker and an individual blanker. FIG. 4D is a diagram explaining a method for measuring the blanking performance of an individual blanker. FIG. 4E is a flowchart explaining an abnormality diagnosis method for a blanking aperture array substrate according to the embodiment. FIG. 9A and FIG. 9B are graphs showing an example of a comparison of measurement results of blanking performance.

[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 also be used.

[0014] FIG. 1 is a schematic diagram of a lithography apparatus according to an embodiment of the present invention. As shown in FIG. 1, the lithography apparatus 100 includes a lithography unit 150 and a control unit 160. The lithography apparatus 100 is an example of a multi-charged particle beam lithography apparatus. The lithography unit 150 includes an electron lens column 102 and a lithography chamber 103. Inside 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 within the patterning chamber 103. A substrate 101 to be patterned 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 coated with resist and on which nothing is yet to be patterned. 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, but the drawing device 100 may also include other configurations that are normally required.

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

[0020] 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 and n horizontal (x direction) columns (m, n≧2) of apertures 203a formed in a matrix at a predetermined arrangement pitch. Each aperture 203a has the same rectangular or circular shape and dimensions. Multibeams 20 are formed by portions of the electron beam 200 passing through each of these multiple apertures 203a.

[0021] 3, the blanking aperture array substrate 204 has passage holes (openings) H formed in alignment 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 passage hole H. One of the two electrodes 24, 26 for each beam (e.g., electrode 26) is fixed to 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 way, the plurality of individual blankers perform blanking deflection of the corresponding beams among the multiple beams that have passed through the plurality of 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 travel 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. Since the global blanker 212 only performs ON / OFF control, it can operate faster than the individual blankers on the blanking aperture array substrate 204.

[0025] Blanking control is performed, and the beam is controlled to be turned on and off, by a combination of turning on and off the individual blankers and turning on and off the collective blanker 212. In this way, 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 multibeams 20 that have passed through the limiting aperture member 206 are focused by the objective lens 207 to form 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 beams so as to follow the movement of the XY stage 105. Ideally, the multibeams 20 that are irradiated at one time are arranged at a pitch obtained by multiplying the arrangement pitch of the multiple openings 203a in the shaping aperture array member 203 by the desired reduction ratio.

[0027] For example, in the drawing process on the substrate 101, as shown in Fig. 4A, the drawing area on the substrate 101 is divided into a plurality of mesh-shaped pixels G1, G2, G3, ..., and a beam with a required dose is irradiated onto 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 achieve a desired irradiation dose. For example, pixel G1 shown in FIG. 4A is irradiated in order with beams B1, B3, B9, and B11 of the multi-beam 20 shown in FIG. 4B. Also, 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 device 100 performs blanking control for 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 the individual blanker of the blanking aperture array board 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] Furthermore, the deflection control circuit 130 outputs a voltage to the collective blanker 212 in response to the shot command, thereby controlling 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 beam ON.

[0032] While the collective blanker 212 is in the beam-on state, the beam for which the individual blankers are set to be beam-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 global blanker 212 can be operated at high speed, so that the beam ON time of the global blanker 212 can be made shorter than the beam ON time of the individual blankers, as shown in FIG.

[0034] By changing the delay time t3, the timing at which the global blanker 212 turns on can be shifted, as shown in FIG. 7 . The beam-on time of the global blanker 212 is made significantly shorter than the beam-on time of the individual blankers, and the beam current is detected by the detector 107 while shifting the global blanker 212's turn-on timing. By arranging the beam current detection results at each timing, a waveform approximating the output characteristics of the individual blanker (changes 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 approximate output waveform changes from a constant value when the beam is turned on to a constant value when the beam is turned off, and the contribution of the excess or insufficient dose 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). Note that, regardless of the global blanker 212, the measurement time may be set to a very short predetermined time on the detector 107 side for measurement.

[0035] The shorter the beam ON time of the collective blanker 212, the smaller the detected value at the detector 107. Therefore, shots may be performed multiple times to find the average current value per unit time.

[0036] Because the blanking aperture array substrate 204 is provided with a large number of individual blankers, it would take an enormous amount of time to measure the blanking performance of each individual blanker as described above. For this reason, in this embodiment, several individual blankers are grouped together, and the blanking performance is measured on a group-by-group basis. Any groups that have an abnormality are then divided into smaller groups, and the blanking performance is measured again.

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

[0038] The writing method and the number of passes for multiple writing when writing a pattern on a substrate are determined (step S101). This determines the combination of beams that will 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 Figures 4A and 4B, the individual blankers corresponding to beams B1, B3, B9, and B11 and beams B2, B4, B10, and B12 are grouped together. Also, the individual blankers corresponding to beams B5, B7, B13, and B15 and beams B6, B8, B14, and 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 on time of the collective blanker 212 is made extremely short and the on timing is staggered, and the beam current is detected by the detector 107. 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 those in the group to be measured are turned off.

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

[0042] For example, as shown in Fig. 9A, if the measurement results of all groups match, it is determined that the blanking performance of all groups is 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 the other groups, it is determined that the blanking performance is abnormal (step S107_Yes).

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

[0044] For example, if it is determined that there is an abnormality in the blanking performance of a group consisting of beams B1, B3, B9, and B11 and beams B2, B4, B10, and B12, this group is divided into a small group consisting of beams B1, B3, B9, and B11 and a small group consisting of beams B2, B4, B10, and 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 is abnormal, the small group is divided into individual beams. Then, the blanking performance is measured for each individual beam to detect individual blankers with abnormalities.

[0046] The detected defective beams are set not to be used during pattern writing, and if there are defective beams that are 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. Therefore, the diagnosis time can be reduced and the individual blankers can be inspected for abnormalities more efficiently than in the case where the blanking performance of all the individual blankers is measured one by one.

[0048] Furthermore, a group with abnormal blanking performance can be divided into smaller groups, and measurements can be repeated for each small group to identify individual blankers with abnormalities. This allows for highly accurate abnormality inspection of individual blankers.

[0049] In the above embodiment, when comparing the measurement results of blanking performance measured on a group-by-group basis, it is preferable to normalize the results with the detection value at the optimum 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 insufficiency 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 greater than or equal to 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 abnormal blanking performance is further divided into smaller groups (regions) and measured.

[0053] In the above embodiment, a configuration has been described in which the beam-ON time of the global blanker 212 is set to be shorter than the beam-ON time of the individual blankers, and the beam current is detected by the detector 107. However, the blanking performance of the individual blankers may be measured by detecting the beam current using a high-speed, high-resolution current detector without using the global blanker 212.

[0054] 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 (turned ON), but the limiting aperture member 206 may also be used as the detector. In this case, the beam current of the blanked beam is detected.

[0055] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2023-199281, filed on November 24, 2023, and is incorporated by reference in its entirety.

[0056] 20 Multi-beam 107 Detector 203 Shaping aperture array member 204 Blanking aperture array substrate 212 Collective blanker

Claims

1. A method for diagnosing anomalies in a blanking aperture array substrate which uses a plurality of individual blankers to individually control on / off of each corresponding beam among multiple beams, comprising the steps of: grouping the plurality of individual blankers into a plurality of groups and measuring the blanking performance of the individual blankers on a group-by-group basis; 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 on a small-group basis.

2. A method for diagnosing an anomaly in a blanking aperture array substrate as described in claim 1, wherein the step of measuring the blanking performance comprises setting individual blankers of the group to be measured to beam-on, setting a beam-on time for a collective blanker capable of blanking the multiple beams collectively to be shorter than the beam-on time of the individual blankers, detecting the beam currents of the multiple beams corresponding to the group to be measured for each beam-on timing while varying the beam-on timing of the collective blanker during the beam-on setting of the individual blankers, and measuring the blanking performance of the individual blankers included in the group to be measured using the detection results of the beam currents.

3. A method for diagnosing anomalies in a blanking aperture array substrate as described in claim 1, in which 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 multiple layers.

4. A method for diagnosing anomalies in a blanking aperture array substrate as claimed in claim 1, comprising the steps of dividing groups having abnormalities in blanking performance, and repeatedly measuring the blanking performance in units of the divided groups, thereby identifying individual blankers having abnormalities in blanking performance.

5. A multi-beam drawing method comprising: setting a beam corresponding to an individual blanker identified as having an abnormality in blanking performance by the blanking aperture array substrate abnormality diagnosis method described in claim 4 as a defective beam; and drawing a pattern on a drawing target substrate using a beam of the multi-beam other than the defective beam.

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