Method for adjusting deflection position of charged particle beam drawing, and charged particle beam drawing method

Abstract

The purpose of the present invention is to improve drawing accuracy by accurately adjusting the deflection sensitivity of a deflector.　This method for adjusting the deflection position of a charged particle beam, in a charged particle beam drawing device, includes: a step (S102) for measuring, at a predetermined pitch using a laser interferometer, the position of a stage on which a substrate to draw on is placed; a step (S105) for scanning, with the charged particle beam, a mark on the stage while moving the stage by a predetermined amount, using a stage position measurement result obtained by the laser interferometer; a step (S106) for detecting the position of the mark; a step (S108) for acquiring non-linear error information of the position of the mark that depends on the laser interferometer; a step for acquiring a plurality of positional deviation amounts on the basis of the measured position of the stage and the detected position of the mark using the non-linear error information; and a step (S109) for adjusting the deflection position of the charged particle beam on the basis of the acquired plurality of positional deviation amounts.

Description

Charged particle beam writing deflection position adjusting method and charged particle beam writing method

[0001] The present invention relates to a method for adjusting the deflection position of a charged particle beam and a method for writing with a charged particle beam.

[0002] As LSIs become more highly integrated, the circuit line width of semiconductor devices has become finer year by year. To form desired circuit patterns on semiconductor devices, a method is adopted in which a high-precision original pattern (called a mask, or a reticle, particularly when 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 using an electron beam drawing apparatus, a technique known as electron beam lithography.

[0003] The electron beam lithography system moves a stage on which a sample is placed within a vacuum chamber, deflects an electron beam using a deflector, and irradiates the electron beam onto a predetermined position on the sample on the stage, thereby drawing a pattern on the sample.

[0004] In order to accurately irradiate the electron beam at a predetermined position on the sample, the deflection sensitivity of the deflector is adjusted and the beam deflection position is calibrated (corrected) before pattern writing. For example, the beam scans a mark on a stage, the beam position is detected based on electrons reflected from the mark, and the beam position error is calculated from the deviation from the stage position. While moving the stage at a predetermined pitch in the x and y directions, the beam position error is calculated at multiple locations, resulting in a matrix-like position error distribution as shown in FIG. 5A. This position error distribution is polynomial-approximated, and the error in the beam irradiation position is found from the approximation equation. The deflection amount of the deflector is adjusted to correct the found error, thereby enabling the beam to be irradiated with the desired positional accuracy as shown in FIG. 5B.

[0005] In this type of deflection sensitivity adjustment, the beam position error is calculated based on the stage position, so the stage position must be accurately measured. A laser interferometer is used to measure the stage position, but this measurement method can cause nonlinear errors. For example, if the laser polarization separation is imperfect, nonlinear errors occur at a period of 1 / 4 (or 1 / 2) of the laser wavelength. Since these measurement errors are error components that are not caused by the deflector, they degrade the accuracy of the deflection sensitivity adjustment, preventing the target accuracy of the deflection sensitivity adjustment and the evaluation of deflector deterioration.

[0006] JP 2012-173218 A JP 10-160408 A JP 2012-015227 A

[0007] An object of the present invention is to provide a method for adjusting the deflection position of a charged particle beam and a charged particle beam writing method that can accurately adjust the deflection sensitivity of a deflector and improve writing accuracy.

[0008] A method for adjusting the deflection position of a charged particle beam according to one aspect of the present invention comprises the steps of: measuring the position of a stage on which a substrate to be drawn is placed at a predetermined pitch using a laser interferometer in a charged particle beam drawing apparatus; scanning a mark on the stage with the charged particle beam while moving the stage by a predetermined amount using a result of the stage position measurement by the laser interferometer, and detecting the position of the mark; acquiring nonlinear error information of the position of the mark that depends on the laser interferometer; acquiring a plurality of positional deviation amounts based on the measured position of the stage and the detected position of the mark using the nonlinear error information; and adjusting the deflection position of the charged particle beam based on the acquired plurality of positional deviation amounts.

[0009] According to the present invention, the deflection sensitivity of the deflector can be adjusted with high precision, thereby improving the drawing precision.

[0010] 5A and 5B are diagrams illustrating an example of the distribution of beam irradiation positions; FIG. 5B is a flowchart illustrating a deflection sensitivity adjustment method; FIG. 5C is a flowchart illustrating a deflection sensitivity adjustment method; FIG. 5D is a diagram illustrating an example of the phase of a nonlinear error at each measurement point; FIG. 5E is a diagram illustrating an example of the phase of a nonlinear error at each measurement point; FIG. 5F is a diagram illustrating an example of the distribution of beam irradiation positions; FIG. 5G is a flowchart illustrating a deflection sensitivity adjustment method;

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 1 is a schematic diagram of an electron beam lithography apparatus according to an embodiment of the present invention. The lithography apparatus 1 shown in Fig. 1 is a variable-shape lithography apparatus including a lithography unit 2 that irradiates an electron beam onto a substrate W to be lithographed, thereby lithographing a desired pattern, and a control unit 3 that controls the operation of the lithography unit 2.

[0013] The imaging unit 2 has a imaging chamber 2a that houses a workpiece W to be imaged, and an optical lens barrel 2b that is connected to the imaging chamber 2a. The optical lens barrel 2b is provided on the upper surface of the imaging chamber 2a and shapes and deflects the electron beam to irradiate the workpiece W in the imaging chamber 2a. The interiors of the imaging chamber 2a and the optical lens barrel 2b are depressurized and in a vacuum state.

[0014] A stage 11 is provided in the writing chamber 2a to support a sample W. The stage 11 is movable in X-axis and Y-axis directions (hereinafter simply referred to as the X-axis and Y-axis directions) that are perpendicular to each other within a horizontal plane. A sample W, such as a mask blank, is placed on the stage 11.

[0015] Furthermore, a mark M for measuring the drift amount of the electron beam is provided on the XY stage 11. The mark M has, for example, a cross shape or a dot shape, and is formed on a silicon substrate from a heavy metal such as tantalum or tungsten.

[0016] A detector 12 is provided above the XY stage 11 to detect, as a current value, electrons reflected from the mark M when the mark M is irradiated with an electron beam. The detection results by the detector 12 are transmitted to and input into a control computer 3b, which will be described later. The mark M may be formed on a mask. Alternatively, the mark M may be a transmission mark, in which case the detector 12 may be provided below the mark M to detect the current value of electrons that have transmitted through the mark M.

[0017] A measurement unit 4 that measures the position of the stage 11 is provided on the outer periphery of the writing chamber 2a. The position of the stage 11 is controlled by a position control unit 35 (described later) via a drive mechanism 36 based on the measurement results by the measurement unit 4. The configuration of the measurement unit 4 will be described later.

[0018] Arranged within the optical barrel 2b are an emission section 21 such as an electron gun that emits an electron beam B, an illumination lens 22 that focuses the electron beam B, a first shaping aperture 23 for beam shaping, a projection lens 24, a shaping deflector 25, a second shaping aperture 26 for beam shaping, an objective lens 27 that focuses the beam on the sample W, and a sub-deflector 28 and a main deflector 29 for controlling the beam shot position relative to the sample W.

[0019] In the writing unit 2, an electron beam B is emitted from an emission unit 21 and irradiated onto a first shaping aperture 23 by an illumination lens 22. The first shaping aperture 23 has, for example, a rectangular opening. When the electron beam B passes through the first shaping aperture 23, the cross section of the electron beam is shaped into a rectangular shape and projected onto a second shaping aperture 26 by a projection lens 24. The projection position onto the second shaping aperture 26 can be deflected by a shaping deflector 25, and the shape and size of the electron beam B can be controlled by changing the projection position. The electron beam B that has passed through the second shaping aperture 26 is focused by an objective lens 27 onto a sample W on the stage 11 and irradiated thereon. At this time, the shot position of the electron beam B relative to the sample W on the stage 11 is deflected by a sub-deflector 28 and a main deflector 29.

[0020] The control unit 3 has a storage unit 3a that stores writing data, and a control computer 3b. The control computer 3b has a shot data generation unit 31, a writing control unit 32, a mark position detection unit 33, an error calculation unit 34, and a position control unit 35. The shot data generation unit 31, the writing control unit 32, the mark position detection unit 33, the error calculation unit 34, and the position control unit 35 may be configured by hardware such as an electric circuit, or may be configured by software such as a program that executes each function, or may be configured by a combination of both.

[0021] The shot data generating unit 31 processes the drawing data to generate shot data. The drawing control unit 32 controls each unit of the drawing unit 2.

[0022] The mark position detection unit 33 detects the mark position (beam irradiation position) using the detection result of the detector 12. For example, when the mark M is scanned with an electron beam, the mark position is detected based on a change in the current value of the reflected electrons detected by the detector 12.

[0023] The error calculation unit 34 calculates the error in the beam irradiation position from the difference between the stage position and the mark position detected by beam scanning.

[0024] The drawing data is data converted into a format for the drawing device 1 so that design data (layout data) created by a designer of a semiconductor integrated circuit or the like can be input to the drawing device 1, and is input from an external device to the storage unit 3a and stored therein. As the storage unit 3a, for example, a magnetic disk device or a semiconductor disk device (flash memory) can be used.

[0025] When drawing a pattern, the drawing control unit 32 moves the stage 11 in the longitudinal direction (X direction) of the stripe region, while positioning the electron beam B in each sub-region using the main deflector 29, and then shoots the electron beam B at a predetermined position in the sub-region using the sub-deflector 28 to draw a figure. After that, when drawing of one stripe region is completed, the stage 11 is moved stepwise in the Y direction and then drawing of the next stripe region is performed, and this is repeated to perform drawing with the electron beam B over the entire drawing region of the sample W. Note that during drawing, since the stage 11 moves continuously in one direction, the main deflector 29 tracks the drawing origin of the sub-region so that the drawing origin follows the movement of the stage 11.

[0026] In this way, the electron beam B is deflected by the sub-deflector 28 and the main deflector 29, and its irradiation position is determined while following the continuously moving stage 11. By continuously moving the stage 11 in the X direction and making the shot position of the electron beam B follow the movement of the stage 11, the writing time can be shortened.

[0027] The drawing control unit 32 uses the position information of the stage 11 measured by the measurement unit 4 to control the sub-deflector 28, the main deflector 29, etc., i.e., control the beam irradiation position, and also control the position of the stage 11.

[0028] Next, the configuration of the measurement unit 4 will be described. As shown in Fig. 2, the measurement unit 4 (stage position measurement system) includes a laser source 5, a laser interferometer 6, and a light receiving unit 7. For example, a helium-neon laser can be used as the laser light. For example, a photodiode can be used as the light receiving unit 7.

[0029] FIG. 2 illustrates the measurement unit 4 that measures the position of the stage 11 in the y direction, but does not illustrate the measurement unit that measures the position of the stage 11 in the x direction.

[0030] A laser beam (wavelength λ) emitted from a laser source 5 is split by a laser interferometer 6. One of the split laser beams travels to a stage 11, is reflected by a mirror on the stage 11, and returns to the laser interferometer 6. Meanwhile, the other split laser beam travels to a mirror (not shown) within the laser interferometer 6 and is reflected therefrom.

[0031] The laser light reflected by the mirror on the stage 11 and the laser light reflected by the mirror in the laser interferometer 6 interfere with each other in the laser interferometer 6. The interfered laser light (interference beat signal) is received by the light receiving unit 7, and interference fringes generated by the optical path difference are observed. The observation results are notified to the drawing control unit 32. In this embodiment, two-pass laser interference observation is performed in which the laser light makes two round trips between the laser interferometer 6 and the mirror on the stage 11.

[0032] The movement of the stage 11 changes the frequency of the light reflected from the stage 11, and the interference fringes also change. The drawing control unit 32 determines the position of the stage 11 from the change in the interference fringes.

[0033] In order to accurately irradiate the sample W with the beam, the electron beam lithography system adjusts the deflection sensitivity of the deflectors (main deflector 29, sub-deflector 28) before the lithography process. For example, the deflection sensitivity adjustment is performed by scanning the mark M on the stage 11 with the beam, detecting the beam position based on electrons reflected from the mark M, and calculating the beam position error from the deviation from the stage position. The stage 11 is moved at a predetermined pitch in each of the x and y directions, and the beam position error is calculated at multiple locations, resulting in a matrix-like position error distribution as shown in FIG. 5A. This position error distribution is polynomial-approximated, and the error in the beam irradiation position is found from the approximation formula. The deflection sensitivity of the deflector is adjusted by correcting the found error, thereby achieving the deflection region shape as shown in FIG. 5B.

[0034] However, nonlinear errors are included in the results of stage position measurement using the laser interferometer 6. For example, as described above, when performing two-path laser interference observation in which the laser light makes two round trips between the laser interferometer 6 and the mirror on the stage 11, the phase makes one revolution when the stage 11 moves by λ / 4, resulting in a nonlinear error with a period of λ / 4.

[0035] In conventional deflection sensitivity adjustment, the interval (pitch P) between mark position measurement points was set without taking nonlinear error into consideration, and as a result, as shown in FIG. 3, the phase of the nonlinear error at each measurement point was different, and the amount of nonlinear error included in the mark position measurement results was different.

[0036] If nonlinear error amounts that vary from one measurement point to another are included, it becomes impossible to correct the errors by polynomial approximation, which hinders the achievement of the target accuracy in deflection sensitivity adjustment and the evaluation of deflector deterioration.

[0037] Therefore, in this embodiment, the deflection sensitivity is adjusted after nonlinear error information in the vicinity of the mark position measurement point is acquired in advance. Such a deflection sensitivity adjustment method will be described with reference to the flowchart shown in FIG.

[0038] The stage 11 is moved at a constant speed around the mark position measurement point (step S101), and during this time, the measurement unit 4 samples the stage position at high speed and continuously measures it (step S102), and obtains nonlinear error information around the mark position measurement point (step S103). The nonlinear error information is stored in the memory unit 3a.

[0039] When adjusting the deflection sensitivity of the main deflector 29, the stage 11 is moved so that the mark M is positioned at the measurement start point within the beam deflection range of the main deflector 29 (step S104). The amount of movement of the stage 11 is controlled using the measurement results of the measurement unit 4, which is a laser length measurement system.

[0040] With the stage 11 stopped, the main deflector 29 deflects the beam B to scan the mark M (step S105). The detector 12 detects reflected electrons from the mark M. The mark position detection unit 33 detects the mark position based on the reflected electron detection result by the detector 12 and the deflection amount of the main deflector 29 (step S106). The error calculation unit 34 calculates the deviation of the mark position (error in the beam irradiation position) detected by scanning the mark M with the beam, using the mark position based on the stage position measured by the measurement unit 4 as a reference (step S107).

[0041] The amount of nonlinear error at this mark position measurement point is estimated from the nonlinear error information acquired in step S103 (step S108).The amount of nonlinear error estimated in step S108 is subtracted from the error of the beam irradiation position calculated in step S107 to correct the error of the beam irradiation position (the amount of deviation of the deflection position by the main deflector 29) (step S109).

[0042] The stage 11 is moved in the x and / or y directions at a predetermined pitch P, and the beam irradiation position error is obtained at each position (step S110_No, S111). By obtaining the beam irradiation position error at a predetermined number of locations (step S110_Yes), a lattice-like position error distribution as shown in Fig. 5A can be obtained. This position error distribution (deflection area shape) is approximated by a polynomial (step S112).

[0043] The designed writing position is substituted into the polynomial to calculate the deviation from the designed writing position. The beam is irradiated at a position obtained by subtracting the calculated deviation from the designed writing position, thereby writing the pattern at the designed position. Figure 5B shows the shape of the deflection region after the deviation amount correction.

[0044] By adjusting the deflection sensitivity in this way, it is possible to prevent the effects of nonlinear errors from appearing. According to this embodiment, it is possible to correct errors in the beam irradiation position by polynomial approximation, thereby enabling accurate adjustment of the deflector's deflection sensitivity and improving drawing accuracy. However, the approximation is not limited to polynomial approximation, and other functions or maps may also be used.

[0045] 6, the deflection sensitivity may be adjusted by setting the interval (pitch P) between the mark position measurement points to be an integer multiple of the period (λ / 4) of the nonlinear error. For example, when the laser wavelength λ is 632.8 nm, the period of the nonlinear error is 158.2 nm, and the interval (pitch P) between the mark position measurement points is set to 90.174 μm (= 158.2 nm × 570).

[0046] As a result, as shown in FIG. 4, the phases of the nonlinear errors at the respective measurement points match, and the mark position measurement results contain the same amount of nonlinear error.

[0047] Such a deflection sensitivity adjustment method will be described with reference to the flowchart shown in FIG.

[0048] For example, when adjusting the deflection sensitivity of the main deflector 29, first, the stage 11 is moved so that the mark M is positioned at a predetermined position within the beam deflection range of the main deflector 29, and then the stage 11 is stopped (step S201). The amount of movement of the stage 11 is controlled using the measurement results of the measurement unit 4, which is a laser length measurement system.

[0049] With the stage 11 stopped, the main deflector 29 deflects the beam B to scan the mark M (step S202). The detector 12 detects reflected electrons from the mark M. The mark position detection unit 33 detects the mark position based on the reflected electron detection result by the detector 12 and the deflection amount of the main deflector 29 (step S203). The error calculation unit 34 calculates the deviation of the mark position (error in the beam irradiation position) detected by scanning the mark M with the beam, using the mark position based on the stage position measured by the measurement unit 4 as a reference (step S204).

[0050] While moving the stage 11 in the x and y directions at a predetermined pitch (= an integer multiple of the period (λ / 4) of the nonlinear error), the beam irradiation position error (the deviation of the deflection position by the main deflector 29) is calculated at each position (step S205_No, S201 to S204). By obtaining the beam irradiation position error at a predetermined number of locations (step S205_Yes), a grid-like position error distribution as shown in FIG. 5A can be obtained. This position error distribution (deflection area shape) is approximated by a polynomial (step S206). The designed writing position is substituted into the polynomial to calculate the deviation from the designed writing position. By irradiating the beam at a position obtained by subtracting the calculated deviation from the designed writing position, a pattern can be written at the designed position. FIG. 5B shows the deflection area shape after the deviation amount correction.

[0051] In this way, by setting the spacing (pitch P) between mark position measurement points to be an integer multiple of the period (λ / 4) of the nonlinear error and suppressing the variation in the amount of nonlinear error contained in the mark position measurement results at each measurement point, the deflection sensitivity of the deflector can be adjusted accurately, thereby improving drawing accuracy.

[0052] In the above embodiment, the period of the nonlinear error is λ / 4 because two-pass laser interference observation is performed in which the laser light makes two round trips between the laser interferometer 6 and the mirror on the stage 11. When one-pass laser interference observation is performed in which the laser light makes one round trip between the laser interferometer 6 and the mirror on the stage 11, the period of the nonlinear error is λ / 2, so the interval (pitch P) between the mark position measurement points should be an integer multiple of λ / 2.

[0053] The above-described deflection position adjustment method enables the deflection sensitivity of the deflector to be adjusted with high precision, thereby improving the drawing accuracy. Note that the deflection position adjustment is a method of adjusting the deflection sensitivity coefficient based on positional deviation information, and enabling the deflection position to be corrected using the coefficient.

[0054] In the above embodiment, a drawing apparatus that irradiates an electron beam has been described, but the drawing apparatus may also irradiate other charged particle beams such as an ion beam. Also, the drawing apparatus may be a multi-beam drawing apparatus.

[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. 2024-004690, filed on January 16, 2024, and is incorporated by reference in its entirety.

[0056] REFERENCE SIGNS LIST 1 Drawing device 2 Drawing section 2a Drawing chamber 2b Optical lens barrel 3 Control section 3a Storage section 3b Control computer 4 Meter section 5 Laser source 6 Laser interferometer 7 Light receiving section 11 Stage

Claims

1. In a charged particle beam lithography apparatus, a step of measuring the position of a stage on which a substrate to be lithographed is placed at a predetermined pitch using a laser interferometer; a step of scanning a mark on the stage with a charged particle beam while moving the stage by a predetermined amount using the stage position measurement result by the laser interferometer and detecting the position of the mark; a step of obtaining non-linear error information of the position of the mark depending on the laser interferometer; a step of obtaining a plurality of amounts of misalignment based on the measured position of the stage and the detected position of the mark using the non-linear error information; and a step of adjusting the deflection position of the charged particle beam based on the obtained plurality of amounts of misalignment. A method for adjusting the deflection position of a charged particle beam comprising the steps above.

2. The non-linear error information includes a non-linear error amount of the mark position obtained by continuously measuring the position of the stage while moving the stage at a constant speed in advance, and the amount of misalignment is obtained by correcting the obtained mark position with the non-linear error amount. The method for adjusting the deflection position of a charged particle beam according to claim 1.

3. The non-linear error information includes a period of non-linear error obtained by moving the stage by a predetermined amount and measuring the mark position on the stage in a stopped state of the stage, and the amount of misalignment is obtained by synchronizing the predetermined pitch with the period of the non-linear error. The method for adjusting the deflection position of a charged particle beam according to claim 1.

4. The method for adjusting the deflection position of a charged particle beam according to claim 1, wherein the deflection position is adjusted by polynomial approximation.

5. A charged particle beam lithography method of adjusting the deflection position of the charged particle beam by the method for adjusting the deflection position of a charged particle beam according to claim 1 and lithographing a pattern.

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