JP2022153968A - Charged particle beam writing method and charged particle beam writing apparatus - Google Patents

Abstract

To improve the drawing accuracy of a pattern by performing drift correction with high accuracy.SOLUTION: A charged particle beam writing method includes the steps of dividing a drawing area into a plurality of sections, obtaining a drawing irradiation amount for each of the plurality of sections, setting a position measurement irradiation amount during beam position measurement so as to generate the same amount of charged particles as the reflected charged particle amount generated during drawing with the drawing irradiation amount on the basis of the relationship between the drawing irradiation amount and the reflected charged particle amount obtained in advance for each of the plurality of sections, irradiating a mark provided on a stage for each of the plurality of sections with a charged particle beam, detecting reflected charged particles, continuously measuring a beam irradiation position corresponding to each of the plurality of sections with a set position measurement irradiation amount, calculating the drift amount for each of the sections, and drawing a pattern on the substrate using the drawing data while correcting the irradiation position of the charged particle beam for each of the plurality of sections on the basis of the drift amount.SELECTED DRAWING: Figure 1

Description

The present invention relates to a charged particle beam writing method and a charged particle beam writing apparatus.

2. Description of the Related Art As LSIs become highly integrated, circuit line widths required for semiconductor devices are becoming finer year by year. In order to form a desired circuit pattern on a semiconductor device, a reduction projection type exposure apparatus is used to form a highly accurate original image pattern (a mask, or a reticle for those used particularly in steppers and scanners) formed on quartz. ) is reduced and transferred onto the wafer. A high-precision original image pattern is drawn by an electron beam drawing apparatus using a so-called electron beam lithography technique.

In an electron beam writing apparatus, a phenomenon called beam drift, in which the irradiation position of the electron beam shifts with time during writing, can occur due to various factors. For example, beam drift occurs when contamination adheres to an irradiation system such as a deflecting electrode of a drawing apparatus, and the contamination is charged by scattered electrons from the drawing target substrate. Drift correction is performed to cancel this beam drift.

In the conventional drift correction, the writing process is temporarily stopped, the measurement mark placed on the stage is scanned with the electron beam, the irradiation position of the electron beam is measured, and the difference from the previous measurement value is used as the drift correction amount. , resumed the drawing process. After restarting the writing process, the beam irradiation position was corrected using this drift correction amount.

JP-A-8-274002 JP-A-3-053440 JP-A-63-177516

However, in the conventional drift measurement, the measurement result of the beam irradiation position is a combination of the beam drift generated by writing and the beam drift generated by the influence of reflected electrons (including secondary electrons) due to measurement. An error occurred, which hindered improvement in accuracy of drift correction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charged particle beam writing method and a charged particle beam writing apparatus capable of performing drift correction with high accuracy and improving pattern writing accuracy.

A charged particle beam writing method according to an aspect of the present invention is a charged particle beam writing method for writing a pattern by irradiating a charged particle beam onto a substrate to be written, which is placed on a stage. dividing the drawing region into a plurality of sections based on the drawing data of the region; determining a drawing irradiation dose for each of the plurality of sections from the drawing data; Based on the relationship between the writing dose and the reflected charged particle amount, the position measurement dose during beam position measurement is adjusted so that the writing dose generates the same amount of charged particles as the amount of reflected charged particles generated during writing. irradiating marks provided on the stage for each of the plurality of sections with a charged particle beam to detect the reflected charged particles, and corresponding to each of the plurality of sections with the set position measurement dose. a step of continuously measuring the beam irradiation position to calculate the drift amount for each section; and correcting the irradiation position of the charged particle beam for each of the plurality of sections based on the drift amount, and drawing a pattern on the substrate using the data.

A charged particle beam writing apparatus according to an aspect of the present invention reads writing data of a writing area of a substrate placed on a stage, divides the writing area into a plurality of sections based on the writing data, and divides the writing area into a plurality of sections based on the writing data. , the drawing irradiation dose is obtained for each of the plurality of sections, and based on the relationship between the drawing irradiation dose and the reflected charged particle amount obtained in advance for each of the plurality of sections, the amount of reflected charged particles generated during writing is the same. a measurement condition setting unit for setting a position measurement irradiation dose during beam irradiation position measurement so that a charged particle amount is generated; The reflected charged particles are detected, the beam irradiation position corresponding to each of the plurality of sections is continuously measured with the set position measurement dose, and the amount of drift of the charged particle beam is determined based on the beam position fluctuation data. and a writing unit for writing a pattern on the substrate using the writing data while correcting the irradiation position of the charged particle beam based on the drift amount.

According to the present invention, it is possible to perform drift correction with high accuracy and improve pattern drawing accuracy.

1 is a schematic diagram of an electron beam writing apparatus according to an embodiment of the present invention; FIG. It is a figure explaining the variable shaping of an electron beam. 4 is a flowchart for explaining a method of estimating a change in beam irradiation position; It is a figure which shows the example of beam position measurement conditions. FIG. 4 is a diagram showing an example of mark scanning; It is a figure which shows the example of the measurement result of a beam irradiation position. 4 is a flowchart for explaining a drawing method; It is a figure which shows the interpolation example of a beam irradiation position.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments 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 the electron beam, and may be an ion beam or the like.

FIG. 1 is a schematic diagram of an electron beam drawing apparatus according to an embodiment of the present invention. A drawing apparatus 1 shown in FIG. is a drawing device.

The drawing unit 30 has an electronic barrel 32 and a drawing chamber 34 . Inside the electron lens barrel 32 are an electron gun 40, a blanking aperture substrate 41, a first shaping aperture substrate 42, a second shaping aperture substrate 43, a blanking deflector 44, a shaping deflector 45, an objective deflector 46, and an illumination lens. 47, a projection lens 48 and an objective lens 49 are arranged.

A movably arranged stage 50 is arranged in the writing chamber 34 . The stage 50 moves in the X and Y directions perpendicular to each other in the horizontal plane. A substrate 56 is placed on the stage 50 . The substrate 56 is, for example, an exposure mask for manufacturing a semiconductor device, mask blanks, a semiconductor substrate (silicon wafer) for manufacturing a semiconductor device, or the like.

A mirror 51 is provided on the stage 50 for measuring the position of the stage 50 in the horizontal plane. A mark M used when measuring the amount of drift of the electron beam B is provided on the stage 50 . For example, the mark M is a mark formed on a silicon substrate and made of heavy metal such as tantalum or tungsten. Although the shape of the mark is not particularly limited, for example, a cross mark J as shown in FIG. 5 is formed.

A detector 52 is provided above the stage 50 for detecting reflected electrons reflected by the mark when the mark M is irradiated with the electron beam B as a current value. Here, reflected electrons are an example of reflected charged particles and include secondary electrons. The detected current value is transmitted to the control computer 11, which will be described later.

The control unit 10 has a control computer 11, a stage position measuring unit 18, storage devices 20, 22, 24, and the like. The control computer 11 has a shot data generation unit 12 , a drawing control unit 13 , a measurement condition setting unit 14 , an irradiation position detection unit 15 and a drift correction unit 16 . The input/output data of each part of the control computer 11 and the data being operated are appropriately stored in a memory (not shown).

Each unit of the control computer 11 may be configured with hardware or software. When configured by software, a program that implements at least part of the functions may be stored in a recording medium such as a CD-ROM, and read and executed by a computer having an electric circuit.

The stage position measuring unit 18 includes a laser length measuring device that measures the position of the stage 50 by reflecting a laser beam on a mirror 51 fixed on the stage 50 . The stage position measurement unit 18 notifies the control computer 11 of the measured stage position.

The storage device 20 stores drawing data obtained by converting layout data in which designed figure patterns are arranged into a format that can be input to the drawing device 1 . The drawing data defines a graphic pattern to be drawn in the drawing area of the substrate 56 .

The shot data generation unit 12 reads the drawing data from the storage device 20 and performs multiple stages of data conversion processing to generate device-specific shot data. The shot data defines, for example, figure type, figure size, irradiation position, irradiation time, and the like. The drawing control unit 13 performs drawing processing by controlling the drawing unit 30 based on the shot data.

The irradiation position detection unit 15 detects the beam irradiation position using the beam profile based on the current value detected by the detector 52 and the stage position (mark position) measured by the stage position measurement unit 18 .

The drift correction unit 16 calculates a drift amount from the difference between the beam irradiation position detected by the irradiation position detection unit 15 and the reference irradiation position, and obtains a drift correction amount that cancels the drift amount. A method of calculating the drift amount will be described later. The drift correction unit 16 generates correction information for the deflection amount (beam irradiation position) of the electron beam B based on the drift correction amount, and supplies the correction information to the drawing control unit 13 . The drawing control unit 13 uses this correction information to control the drawing unit 30 to correct the beam irradiation position.

FIG. 1 shows the configuration necessary for explaining the embodiment. The drawing apparatus 1 may have other configurations.

The electron beam B emitted from the electron gun 40 provided in the electron lens barrel 32 is deflected by the blanking deflector 44 as it passes through the blanking deflector 44 in the beam-on state. In the passing and beam-off state, the entire beam is deflected so that it is blocked by the blanking aperture substrate 41 . The electron beam B that has passed through the blanking aperture substrate 41 from the beam-off state to the beam-on state and then to the beam-off state constitutes one electron beam shot.

The electron beam B of each shot generated by passing through the blanking deflector 44 and the blanking aperture substrate 41 is directed by the illumination lens 47 to the first shaping aperture substrate 42 having a rectangular opening 42a (see FIG. 2). be irradiated. By passing through the opening 42a of the first shaping aperture substrate 42, the electron beam B is shaped into a rectangle.

The electron beam of the first aperture image that has passed through the first shaping aperture substrate 42 is projected onto the second shaping aperture substrate 43 by the projection lens 48 . A shaping deflector 45 controls the position of the first aperture image on the second shaping aperture substrate 43 . Thereby, the shape and size of the electron beam passing through the opening 43a of the second shaping aperture substrate 43 can be changed (variable shaping).

The electron beam that has passed through the second shaping aperture substrate 43 is focused by the objective lens 49, deflected by the objective deflector 46, and irradiated onto the desired position of the substrate 56 to be drawn placed on the XY stage 50. be done. At this time, by changing the dimension of the electron beam passing through the opening 43a of the second shaping aperture substrate 43, the amount of beam current of the electron beam irradiated to the substrate 56 (or the mark M) can be changed. Also, by varying the emission current of the electron gun 40 and the setting of the illumination lens 47, the beam current density may be changed to change the beam current amount.

In the drawing apparatus 1, beam drift occurs due to electrification of contamination adhering to the electrodes of the objective deflector 46 and the like, and therefore drift correction must be performed. In the drift correction, the mark M is scanned with the electron beam B to detect the beam irradiation position, and the deviation amount from the reference position is calculated as the drift amount.

Since the calculated drift amount includes a drift component during writing and a drift component during beam irradiation position detection due to reflected electrons (including secondary electrons) from the mark, measurement errors occur. Therefore, in the present embodiment, before the writing process (actual drawing), the beam position is continuously measured under conditions simulating the amount of backscattered electrons generated during the actual drawing. variation). Then, during actual writing, the beam irradiation position is measured at predetermined time intervals, and the amount of drift between the measurement of the beam irradiation position and the next measurement is determined by referring to the previously estimated beam irradiation position fluctuation. Ask for

A method for estimating the variation of the beam irradiation position during actual writing will be described with reference to the flowchart shown in FIG.

Drawing data is read out from the storage device 20, and the drawing area of the substrate 56 to be written is virtually divided into a plurality of strip-shaped stripe areas extending in the x direction with a width that can be deflected by the objective deflector 46 (step S1). A figure pattern defined in the drawing data is assigned to each stripe area. The division into stripes and the assignment of figure patterns may be performed by the shot data generating section 12 or may be performed by the measurement condition setting section 14 .

The measurement condition setting unit 14 divides each stripe into a plurality of sections (step S2). The measurement condition setting unit 14 divides one stripe into a plurality of sections based on the positions and area densities of the figure patterns assigned to the stripe. For example, one stripe is divided into a large number of minute regions in the longitudinal direction, the areal density of each minute region is obtained, and adjacent minute regions with similar areal densities are grouped together to form one section. For example, as shown in FIG. 4, one stripe is divided into 10 partitions #1-#10.

The measurement condition setting unit 14 sets beam position measurement conditions that simulate the drawing process (actual drawing) of each section (step S3). As shown in FIG. 4, the beam position measurement conditions include a position measurement time, which is the time required to measure the beam position, and a position measurement dose, which is the beam dose during beam position measurement.

The partitions may be divided so that the time required to draw each partition matches the localization time of each partition. Here, "match" does not have to be a perfect match, and an error is allowed based on the required measurement accuracy.

The position measurement dose is set so that the amount of reflected electrons during beam position measurement (during mark scanning) is the same as the amount of reflected electrons during actual writing. For example, if the reflectance of incident electrons on the substrate 56 to be written is 50% of the reflectance of incident electrons on the mark M, the position measurement dose is set to 50% of the writing dose. It should be noted that "same" does not necessarily mean that the amounts of reflected electrons are exactly the same, and an error is allowed based on the required measurement accuracy.

The writing dose can be obtained from the shot data of the section in the shot data generated by the shot data generation unit 12 . Reflectance data indicating the reflectance of the substrate 56 and marks is stored in the storage device 22 . The measurement condition setting unit 14 reads out the reflectance data from the storage device 22, and calculates the position measurement dose that makes the reflected electron amount the same from the write dose and the reflectance. In the example of FIG. 4, the reflectance of the substrate 56 and the reflectance of the mark are assumed to be equal, and the irradiation amount during writing=the position measurement irradiation amount.

In addition, the beam position measurement conditions include parameters such as the shot time, the number of shots, and the "number of lines" indicating the number of beam position measurement points on the mark corresponding to each section, and the "number of additions" indicating the number of times the beam position is measured. include. The beam position is measured by the number of additions, and the average value of the measurement results is taken as the beam position. For example, when two beam position measurement points are set for each of the linear portions L1 to L4 extending vertically and horizontally from the center of the cross mark J shown in FIG. 5, the number of lines is eight. Here, when the number of additions is 64, the beam position is measured eight times at each of eight beam position measurement points, and the average value of the 64 measurement results is taken as the beam position. These parameters allow the localization dose and localization time to be coordinated with the writing. In addition, as described above, it is possible to adjust the position measurement dose according to the variation of the beam size and the position measurement time according to the variation of the settling time during beam irradiation at the time of position measurement.

The mark is scanned with the electron beam B under the measurement conditions for each section set in step S3, and the irradiation position detector 15 measures and detects the beam irradiation position (step S4). For example, in the example of FIG. 4, the beam position measurement corresponding to section #1 is performed by performing mark scanning at locations based on the number of lines and the number of times based on the number of additions over a first period of time at a first irradiation dose to determine the beam position. Measure. For the beam position measurement corresponding to section #2, the beam irradiation position is measured by performing mark scanning at locations based on the number of lines and the number of times based on the number of additions over a second time with a second dose. Such beam irradiation position measurement is continuously performed in order (the same order as the actual drawing) for all stripes and all sections.

For example, the measurement results of the beam irradiation positions corresponding to the sections #1 to #10 in FIG. 4 are as shown in FIG.

In this way, the mark is scanned with the irradiation amount that makes the amount of backscattered electrons the same as in actual writing, taking the same time as in actual writing, and the beam irradiation position corresponding to each section is obtained. The determined beam irradiation positions are arranged in the order of stripes and in the order of partitions to generate beam position fluctuation data estimating the fluctuation of the beam irradiation positions during actual writing. The beam position variation data is stored in storage device 24 .

Next, a method of writing a pattern while performing drift correction using beam position fluctuation data will be described with reference to the flowchart shown in FIG.

Based on the shot data, the drawing control unit 13 controls the drawing unit 30 to perform pattern drawing processing (step S11). When the predetermined drift measurement timing comes (step S12_Yes, step S13_Yes), the writing process is interrupted, the electron beam B scans the mark, and the beam irradiation position is detected (step S14). Specifically, the stage 50 is moved to align the mark with the center position of the objective lens 49, the mark is scanned with an electron beam B having a predetermined beam current, and the detector 52 detects reflected electrons (including secondary electrons). To detect. The irradiation position detector 15 measures the beam profile from the detection result of the detector 52 and detects the beam irradiation position on the mark surface.

The drift correction unit 16 calculates the amount of deviation between the detected beam irradiation position and the reference position as the amount of drift on the mark surface. The writing control unit 13 restarts the writing process, corrects the beam irradiation position based on the calculated drift amount, and writes the pattern.

The process of interrupting writing and measuring the beam irradiation position is performed at regular time intervals. For example, every time a predetermined number of stripe regions are written, writing is interrupted and the beam irradiation position is measured. Since the beam irradiation position cannot be measured while pattern writing is being performed, the beam irradiation position during that time is interpolated with the beam position fluctuation data.

The drift correction unit 16 reads the beam position fluctuation data from the storage device 24, and estimates the subsequent fluctuation of the beam irradiation position based on the beam irradiation position detected in step S14. The drift correction unit 16 obtains the amount of drift from the estimated value of the beam irradiation position and the amount of deviation from the reference position. The drawing control unit 13 performs drawing processing while correcting the beam irradiation position based on the obtained drift amount (step S15).

For example, as shown in FIG. 8, after writing the stripe region with the stripe number 132, before writing the stripe region with the stripe number 133, the writing process is interrupted to measure the beam irradiation position. After restarting the writing process, the beam position fluctuation data is referenced to estimate the fluctuation of the beam irradiation position while the stripe region with the stripe number 133 is being written. Then, the amount of drift is obtained from the estimated beam irradiation position, and the pattern is written by correcting the beam irradiation position.

The beam irradiation position of each section defined in the beam position fluctuation data is measured under conditions simulating the writing time and the amount of backscattered electrons when actually writing a pattern in this section. Therefore, the fluctuation of the beam irradiation position during pattern writing can be estimated with high accuracy, and the pattern can be written with high accuracy.

It should be noted that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the scope of the present invention at the implementation stage. Further, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. Furthermore, components across different embodiments may be combined as appropriate.

1 drawing device 10 control unit 11 control computer 12 shot data generation unit 13 drawing control unit 14 measurement condition setting unit 15 irradiation position detection unit 16 drift correction units 20, 22, 24 storage device 30 drawing unit 32 electron lens barrel 34 drawing chamber 40 electron gun 41 blanking aperture substrate 42 first shaping aperture substrate 43 second shaping aperture substrate 44 blanking deflector 45 shaping deflector 46 objective deflector 47 illumination lens 48 projection lens 49 objective lens 50 stage 52 detector

Claims (5)

A charged particle beam writing method for writing a pattern by irradiating a charged particle beam onto a substrate to be written placed on a stage, comprising:
dividing the drawing area into a plurality of sections based on the drawing data of the drawing area of the substrate;
obtaining a writing dose for each of the plurality of sections from the writing data;
For each of the plurality of sections, based on the relationship between the drawing irradiation dose and the reflected charged particle amount obtained in advance, the drawing irradiation dose generates the same amount of charged particles as the reflected charged particle amount generated during drawing. , setting a position measurement dose during beam position measurement;
A charged particle beam is irradiated to a mark provided on the stage for each of the plurality of sections, reflected charged particles are detected, and a beam irradiation position corresponding to each of the plurality of sections is determined with a set position measurement dose. A step of continuously measuring and calculating the drift amount for each of the sections;
writing a pattern on the substrate using the writing data while correcting the irradiation position of the charged particle beam for each of the plurality of sections based on the drift amount;
A charged particle beam writing method comprising: 2. The charged particle according to claim 1, wherein the plurality of sections are divided such that the drawing time for each of the plurality of sections matches the position measurement time during beam position measurement. Beam drawing method. By varying at least one of the shot time, the number of shots, the number of beam position measurement points on the mark corresponding to each section, the number of beam position measurements, the beam size, and the settling time, the position measurement time is reduced to the plurality of 3. A charged particle beam writing method according to claim 1, wherein the writing time for each section or the position measurement dose is matched to the amount of reflected charged particles. interrupting pattern drawing on the substrate at a predetermined timing, irradiating the mark with the charged particle beam, detecting reflected charged particles to detect a beam irradiation position;
4. The drift amount is calculated based on the detected beam irradiation position and a beam irradiation position measurement result corresponding to a section during pattern writing after the pattern writing is restarted. The charged particle beam writing method according to any one of 1. reading drawing data of a drawing region of a substrate placed on a stage, dividing the drawing region into a plurality of sections based on the drawing data, obtaining a drawing dose for each of the plurality of sections from the drawing data; For each of the plurality of sections, beam irradiation position measurement based on the relationship between the writing dose and the reflected charged particle amount obtained in advance so that the same amount of reflected charged particles as that generated during writing is generated. a measurement condition setting unit that sets the position measurement irradiation dose at the time of
A charged particle beam is irradiated to a mark provided on the stage for each of the plurality of sections, reflected charged particles are detected, and a beam irradiation position corresponding to each of the plurality of sections is determined with a set position measurement dose. a drift correction unit that continuously performs measurements and calculates a drift amount of the charged particle beam based on the beam position fluctuation data;
a writing unit that writes a pattern on the substrate using the writing data while correcting the irradiation position of the charged particle beam based on the drift amount;
A charged particle beam writing apparatus comprising:

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