JP7484491B2 - Charged particle beam drawing method and charged particle beam drawing apparatus - Google Patents

Description

The present invention relates to a charged particle beam drawing method and a charged particle beam drawing device.

As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer every year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern (a mask, or a reticle, particularly one used in steppers and scanners) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure apparatus. The high-precision original pattern is drawn by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

In electron beam lithography systems, a phenomenon called beam drift can occur, in which the irradiation position of the electron beam shifts over time during lithography, due to various factors. For example, beam drift occurs when contamination adheres to the irradiation system of the lithography system, such as the deflection electrodes, and the contamination becomes charged by scattered electrons from the substrate to be lithographed. Drift correction is performed to cancel this beam drift.

In conventional drift correction, a measurement mark formed on a mark substrate placed on a stage during the drawing process is scanned with an electron beam, the irradiation position of the electron beam is measured at a specified timing, and the difference from the previous measurement value is used as the drift correction amount.

JP 2001-102278 A Japanese Patent Application Laid-Open No. 9-102452 Japanese Patent Application Laid-Open No. 5-166708

However, the measurement results of the beam irradiation position contain drift components caused by reflected electrons and secondary electrons from the measurement mark. Since contamination changes as the writing process progresses, the drift components when measuring the beam irradiation position also change. However, in the past, this change in drift component was not taken into account, resulting in drift correction errors.

The present invention aims to provide a charged particle beam drawing method and a charged particle beam drawing apparatus that can perform drift correction with high accuracy and improve pattern drawing accuracy.

A charged particle beam drawing method according to one aspect of the present invention is a charged particle beam drawing method for drawing a pattern by irradiating a substrate to be drawn placed on a stage with the charged particle beam, and includes the steps of irradiating a mark provided on the stage with charged particle beams having different amounts of charge per shot cycle, respectively, and calculating the drift amount from the detected irradiation positions, calculating a drift correction amount based on the correlation between the amount of charge per shot cycle and the drift amount, and correcting the irradiation position of the charged particle beam based on the drift correction amount, and drawing a pattern on the substrate.

The charged particle beam drawing apparatus according to one aspect of the present invention includes a drawing unit that draws a pattern by irradiating a charged particle beam onto a substrate to be drawn that is placed on a stage, an irradiation position detection unit that detects the irradiation positions of the charged particle beams by irradiating marks provided on the stage with the charged particle beams having different amounts of charge per shot cycle onto the marks, a drift correction unit that calculates a drift correction amount based on the correlation between the drift amount of the charged particle beam calculated from each of the detected irradiation positions and the amount of charge per shot cycle, and a drawing control unit that corrects the irradiation position of the charged particle beam based on the drift correction amount and controls the drawing unit to draw a pattern on the substrate.

According to the present invention, drift correction can be performed with high precision, improving the pattern drawing accuracy.

1 is a schematic diagram of an electron beam writing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating variable shaping of an electron beam. FIG. 4 is a schematic diagram showing a change in drift amount. 11 is a graph showing the amount of drift when the beam current is set to zero. 1 is a flowchart illustrating a drawing method according to an embodiment. 11 is a graph showing the amount of drift when the beam current is set to zero. FIG. 13 is a diagram showing the dependency of the drift amount on the deflection position.

Embodiments of the present invention will be described below with reference to the drawings. In the embodiments, a configuration using an electron beam will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and may be an ion beam, etc.

Figure 1 is a schematic diagram of an electron beam drawing apparatus according to an embodiment of the present invention. The drawing apparatus 1 shown in Figure 1 is a variable-shape drawing apparatus that includes a drawing unit 30 that irradiates an electron beam onto a substrate 56 to be drawn to draw a desired pattern, and a control unit 10 that controls the operation of the drawing unit 30.

The drawing section 30 has an electron lens barrel 32 and a drawing chamber 34. Inside the electron lens barrel 32, 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, an illumination lens 47, a projection lens 48, and an objective lens 49 are arranged.

A movably arranged stage 50 is disposed within the drawing chamber 34. The stage 50 moves in mutually orthogonal X and Y directions within a horizontal plane. A substrate 56 is placed on the stage 50. The substrate 56 is, for example, an exposure mask used in manufacturing a semiconductor device, a mask blank, a semiconductor substrate (silicon wafer) on which the semiconductor device is manufactured, etc.

A mirror 51 is provided on the stage 50 to measure the position of the stage 50 in a horizontal plane. Also provided on the stage 50 is a mark substrate 20 on which a mark is formed that is used when measuring the amount of drift of the electron beam B. For example, the mark substrate 20 is a silicon substrate on which a mark made of a heavy metal such as tantalum or tungsten is formed.

Above the stage 50, a detector 52 is provided that detects, as a current value, the reflected electrons (or secondary electrons) reflected by the mark when the mark on the mark substrate 20 is irradiated with the electron beam B. The detected current value is sent to the control computer 11, which will be described later.

The control unit 10 has a control computer 11, a stage position measurement unit 16, a storage device 18, etc. The control computer 11 has a shot data generation unit 12, a drawing control unit 13, an irradiation position detection unit 14, and a drift correction unit 15. Input/output data of each unit of the control computer 11 and data during calculation are appropriately stored in a memory (not shown).

Each part of the control computer 11 may be configured as hardware or software. If configured as software, a program that realizes at least some of the functions may be stored on a recording medium such as a CD-ROM, and may be read and executed by a computer having electrical circuits.

The stage position measurement unit 16 includes a laser length measurement device that measures the position of the stage 50 by irradiating and reflecting laser light on a mirror 51 fixed on the stage 50. The stage position measurement unit 16 notifies the control computer 11 of the measured stage position.

The memory device 18 (memory unit) stores drawing data that is the layout data in which the designed geometric patterns are arranged, converted into a format that can be input to the drawing device 1.

The shot data generator 12 reads the drawing data from the storage device 18 and performs multiple stages of data conversion processing to generate device-specific shot data. The shot data defines, for example, the figure type, figure size, irradiation position, irradiation time, etc. The drawing controller 13 controls the drawing unit 30 based on the shot data to perform drawing processing.

The irradiation position detection unit 14 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 16.

The drift correction unit 15 calculates the amount of drift and determines the amount of drift correction that cancels the amount of drift. The method of calculating the amount of drift will be described later. The drift correction unit 15 generates correction information for the amount of deflection (beam irradiation position) of the electron beam B based on the amount of drift correction, and provides it to the drawing control unit 13. The drawing control unit 13 uses this correction information to control the drawing unit 30 and correct the beam irradiation position.

Figure 1 shows the configuration necessary for explaining the embodiment. The drawing device 1 may also include other configurations.

When the electron beam B emitted from the electron gun 40 provided in the electron lens barrel 32 passes through the blanking deflector 44, it is deflected by the blanking deflector 44 so that in the beam-on state, it passes through the blanking aperture substrate 41, and in the beam-off state, the entire beam is blocked by the blanking aperture substrate 41. When the beam goes from the beam-off state to the beam-on state, the electron beam B that passes through the blanking aperture substrate 41 before it goes to beam-off 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 irradiated by the illumination lens 47 onto the first shaping aperture substrate 42 having a rectangular opening 42a (see FIG. 2). 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 passes through the first shaping aperture substrate 42 is projected onto the second shaping aperture substrate 43 by the projection lens 48. The position of the first aperture image on the second shaping aperture substrate 43 is controlled by the shaping deflector 45. This makes it possible to change the shape and dimensions of the electron beam passing through the opening 43a of the second shaping aperture substrate 43 (perform variable shaping).

The electron beam that passes through the second shaping aperture substrate 43 is focused by the objective lens 49, deflected by the objective deflector 46, and irradiated at the desired position on the substrate 56 to be drawn, which is placed on the XY stage 50. At this time, the beam current amount of the electron beam irradiated to the substrate 56 (or the mark substrate 20) can be changed by changing the size of the electron beam passing through the opening 43a of the second shaping aperture substrate 43. In addition, the beam current amount can be changed by changing the beam current density by varying the emission current of the electron gun 40 or the setting of the illumination lens 47. Note that it is not limited to the beam current amount, as long as the amount of charge per shot cycle is changed. For example, the irradiation time can be changed.

In the drawing device 1, beam drift occurs due to charging of contamination attached to electrodes such as the objective deflector 46, so drift correction is necessary. In drift correction, the mark on the mark substrate 20 is scanned with the electron beam B to detect the beam irradiation position, and the amount of deviation from the reference position is calculated as the drift amount.

The calculated drift amount includes the drift component Dw during drawing and the drift component Dp during beam irradiation position detection caused by reflected electrons and secondary electrons from the mark. If the drift component Dp during beam irradiation position detection is included in the correction, excessive correction will occur, so it is necessary to perform the correction based on this drift component Dw during drawing.

As shown in FIG. 3, the contamination changes as the drawing process progresses, and the drawing drift component Dw changes. Specifically, the contamination increases as the drawing process progresses, and the drawing drift component Dw increases.

On the other hand, the drift component Dp (shaded area in the figure) at the time of detecting the beam irradiation position depends not only on contamination but also on the amount of beam current of the electron beam B that scans the mark. Therefore, as the drawing process progresses, contamination increases and the drift component Dp at the time of detecting the beam irradiation position also increases. Furthermore, as the amount of beam current of the electron beam B that scans the mark increases, the drift component Dp at the time of detecting the beam irradiation position also increases.

The writing drift component Dw is estimated as a value excluding the effect of the beam current of the electron beam B that scans the mark, i.e., the drift amount when the beam current amount is set to zero. However, if the beam current of the electron beam B that actually scans the mark is set to zero, nothing is detected by the detector 52, and naturally the beam irradiation position cannot be detected, so the drift amount cannot be obtained.

In this embodiment, as shown in FIG. 4, the beam current of the electron beam B that scans the mark is varied to detect the beam irradiation position, and drift amounts Dp1 to Dp3 are measured for multiple beam current amounts C1 to C3. Then, the writing drift component Dw is calculated based on the correlation between the beam current amounts C1 to C3 and the drift amounts Dp1 to Dp3. For example, an approximation formula F of the drift amounts Dp1 to Dp3 for the beam currents C1 to C3 is calculated, and the drift amount (writing drift component Dw) when the beam current amount is set to zero by extrapolation is calculated as the drift correction amount using this approximation formula F. Note that it is not necessary to use the estimated drift amount when the beam current amount is set to zero as the drift correction amount, and the drift amount when the influence of the beam current amount is removed to some extent, that is, the drift amount when the beam current amount is brought close to zero so that overcorrection is suppressed to some extent, can be used as the drift correction amount. Drift correction is performed based on the calculated drift correction amount.

A drawing method including such drift correction processing will be explained using the flowchart shown in Figure 5.

The stage 50 is moved to align the mark with the center position of the objective lens 49, the mark is scanned with electron beam B with a predetermined beam current, and the detector 52 detects reflected electrons (secondary electrons) (step S1). The irradiation position detection unit 14 measures the beam profile from the detection result of the detector 52 and detects the beam irradiation position on the mark surface. The beam irradiation position is detected in both the X and Y directions. The drift correction unit 15 calculates the amount of deviation between the detected beam irradiation position and a reference position as the drift amount on the mark surface (step S2). The drift amount is calculated for each of the X and Y directions.

If N drift amounts (N is an integer equal to or greater than 2) have not been calculated (step S3_No), the beam current is changed (step S4) and the drift amount is further calculated (steps S1 and S2). Mark scanning, drift amount calculation, and beam current change are repeated until N drift amounts (first drift amounts) with different beam currents are obtained.

When N drift amounts have been calculated (step S3_Yes), the drift correction unit 15 obtains an approximation formula and calculates the drift amount when the beam current is set to zero as the drift correction amount (step S5).

The drawing control unit 13 performs drawing processing while correcting the beam irradiation position based on the drawing data read from the storage device 18 and the calculated drift correction amount (step S6).

Until the next drift amount measurement time (step S7: Yes, step S8: No), the drawing process is performed using the drift correction amount calculated in step S5.

As shown in FIG. 6, in the drift correction process at the beginning of drawing, an approximation formula F1 is obtained from multiple drift amounts with different beam currents, and the drift amount Dw1 when the beam current is set to zero is calculated. The beam irradiation position is corrected based on the drift amount Dw1.

In the drift correction process in the middle of drawing, an approximation formula F2 is found from multiple drift amounts with different beam currents, and the drift amount Dw2 when the beam current is set to zero is calculated. The beam irradiation position is corrected based on the drift amount Dw2.

In the drift correction process at the end of the drawing, an approximation formula F3 is found from multiple drift amounts with different beam currents, and the drift amount Dw3 when the beam current is set to zero is calculated. The beam irradiation position is corrected based on the drift amount Dw3.

In this way, in this embodiment, the drift amount is calculated without including the drift component Dp when detecting the beam irradiation position, so drift correction can be performed with high precision, and the pattern drawing precision can be improved.

If the drift amount varies depending on the beam deflection position, the drift correction amount may be calculated for each beam deflection position. For example, as shown in FIG. 7, steps S1 to S5 of the flowchart in FIG. 5 are performed at multiple locations within the deflection region R by the objective deflector 46 to calculate multiple drift correction amounts corresponding to the multiple locations. For example, the mark is moved to multiple locations in the center and periphery of the deflection region R, and the drift correction amount is calculated at each location. When drawing a pattern, the beam irradiation position is corrected using the drift correction amount at the position closest to the beam deflection position out of the multiple drift correction amounts, or using the drift correction amount calculated by interpolating multiple drift correction amounts near the beam irradiation position.

In the above embodiment, the approximation formula F for the multiple drift amounts with different beam currents is not limited to a linear formula, but may be a quadratic or higher order formula.

In the above embodiment, a single-beam drawing device that irradiates a single beam onto a substrate to be drawn has been described, but a similar technique can also be applied to a multi-beam drawing device that uses multiple beams to irradiate many beams at once. In a multi-beam drawing device, for example, an electron beam emitted from an electron gun passes through an aperture member having multiple openings to form multiple beams, and each beam is controlled to be turned on and off by a blanking plate. A beam that is turned off by the blanking plate is blocked by a limiting aperture member. A beam that is turned on by the blanking plate passes through the limiting aperture member, is reduced by the optical system, and is irradiated to the desired position on the substrate to be drawn.

In a multi-beam lithography device, the amount of charge per shot cycle can be changed by changing the number of beams irradiated, the beam current density, the irradiation time, and the dimensions of each beam. In the drift correction process, for example, the amount of drift when the beam current is set to zero is calculated from an approximation equation between the amount of charge per shot cycle and the amount of drift.

In the graphs of Figures 4 and 6, the horizontal axis represents the beam current, but it may also represent the beam dimensions, beam current density (emission current, illumination lens setting value), or irradiation time. In the case of a multi-beam drawing device, the horizontal axis may also represent the number of beams being irradiated.

The present invention is not limited to the above-described embodiment as it is, and in the implementation stage, the components can be modified and embodied 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.

REFERENCE SIGNS LIST 1 Writing apparatus 10 Control unit 11 Control computer 12 Shot data generation unit 13 Writing control unit 14 Irradiation position detection unit 15 Drift correction unit 18 Memory device 20 Mark substrate 30 Writing unit 32 Electron lens barrel 34 Writing 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 lithography method for irradiating a charged particle beam onto a substrate to be lithographed, the substrate being placed on a stage, to lithograph a pattern, the method comprising the steps of:
a step of irradiating a mark provided on the stage with a charged particle beam having a different charge amount per shot cycle, and calculating the drift amount from the detected irradiation position;
calculating a drift correction amount based on a correlation between the charge amount per shot cycle and the drift amount;
correcting an irradiation position of the charged particle beam based on the drift correction amount, and writing a pattern on the substrate;
Equipped with
a charged particle beam writing method comprising: determining an approximation of the amount of drift with respect to the beam current from the correlation; and using the approximation, calculating the amount of drift when the amount of beam current is set to zero by extrapolation as the drift correction amount . 2. The charged particle beam writing method according to claim 1, further comprising the steps of: calculating the drift correction amount at a plurality of points within a deflection region of the charged particle beam; and calculating the drift correction amount for correcting the irradiation position of the charged particle beam based on a relationship between the beam position and the deflection position thus obtained. 3. The charged particle beam writing method according to claim 1, wherein the amount of charge per shot cycle is changed by changing at least one of the dimensions, beam current density, and irradiation time of the charged particle beam passing through an opening formed in an aperture substrate. the charged particle beam is a multi-beam including a plurality of beams,
3. The charged particle beam writing method according to claim 1, wherein the charge amount per shot cycle is changed by changing at least one of the number of beams irradiated, the beam current density, the dimensions of the charged particle beam, and the irradiation time. a pattern writing unit that irradiates a charged particle beam onto a substrate to be written that is placed on a stage to write a pattern;
A mark provided on the stage;
an irradiation position detection unit that detects an irradiation position of each of the charged particle beams by irradiating the mark with the charged particle beams having different charge amounts per shot cycle;
a drift correction unit that calculates a drift correction amount based on a correlation between an amount of drift of the charged particle beam calculated from each of the detected irradiation positions and an amount of charge per shot cycle;
a writing control unit that corrects an irradiation position of the charged particle beam based on the drift correction amount and controls the writing unit to write a pattern on the substrate;
Equipped with
the drift correction unit obtains an approximation equation for the amount of drift with respect to the beam current from the correlation, and uses the approximation equation to calculate the amount of drift when the amount of beam current is set to zero by extrapolation, as the drift correction amount .

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