Deflection position adjustment method of electric charge particle beam drawing and electric charge particle beam drawing method

Abstract

To adjust a deflection sensitivity of a deflector with high accuracy, and improve a drawing accuracy.SOLUTION: A deflection position adjustment method of an electric charge particle beam includes steps of: measuring a position of a stage on which a drawing target substrate is placed using a laser interferometer in an electric charge particle beam drawing apparatus; scanning a mark on the stage with the electric charge particle beam while moving the stage by a predetermined amount using a stage position measurement result of the laser interferometer to detect a position of the mark; correcting a plurality of positional deviation amounts obtained from a position of the stage measured at a predetermined pitch using the laser interferometer and a position of the detected mark based on non-linear error information of the position of the mark depending on the laser interferometer; and adjusting a bias position of the electric charge particle beam based on the plurality of corrected positional deviation amounts.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] With the high integration of LSIs, the circuit line width of semiconductor devices has been gradually miniaturized year by year. In order to form a desired circuit pattern on a semiconductor device, a method of reducing and transferring a high-precision original pattern (mask, or particularly those used in steppers and scanners are also called reticles) formed on quartz onto a wafer using a reduction projection exposure apparatus is adopted. The high-precision original pattern is drawn by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

[0003] An electron beam drawing apparatus moves a stage on which a sample is placed in a vacuum chamber, deflects an electron beam by a deflector, irradiates a predetermined position of the sample on the stage, and draws a pattern on the sample.

[0004] In order to accurately irradiate a predetermined position of the sample with an electron beam, before pattern drawing, the deflection sensitivity of the deflector is adjusted, and the beam deflection position is calibrated (corrected). For example, a mark on the stage is scanned with the beam, the beam position is detected based on the reflected electrons from the mark, and the beam position error is calculated from the deviation from the stage position. While moving the stage in the x-direction and the y-direction at a predetermined pitch respectively, the calculation of the beam position error is performed at a plurality of locations, and a matrix-like position error distribution as shown in FIG. 5A is obtained. This position error distribution is approximated by a polynomial, the error at the beam irradiation position is obtained from the approximate formula, and the deflection amount of the deflector is adjusted so as to correct the obtained error, so that, as shown in FIG. 5B, the beam can be irradiated with a desired position accuracy.

[0005] In such beam deflection sensitivity adjustment, in order to obtain the beam position error based on the stage position, it is necessary to accurately measure the stage position. A laser interferometer is used to measure the stage position, but there is a problem that non-linear errors occur due to the measurement method. For example, when the polarization separation of the laser is incomplete, non-linear errors occur at 1 / 4 (or 1 / 2) of the laser wavelength period. And since such a length measurement error becomes an error component not caused by the deflector, the accuracy of beam deflection sensitivity adjustment deteriorates, hindering the achievement of the target accuracy of beam deflection sensitivity adjustment and the evaluation of deflector degradation.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0008] A method for adjusting the deflection position of a charged particle beam according to an aspect of the present invention includes, 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 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 correcting a plurality of position deviation amounts obtained from the position of the stage measured at a predetermined pitch using the laser interferometer and the detected position of the mark based on non-linear error information of the position of the mark depending on the laser interferometer; and a step of adjusting the deflection position of the charged particle beam based on the corrected plurality of position deviation amounts.

[0009] A charged particle beam lithography method according to an aspect of the present invention is to adjust the deflection position of the charged particle beam by the above-described method for adjusting the deflection position of the charged particle beam and draw a pattern.

Advantages of the Invention

[0010] According to the present invention, the deflection sensitivity of the deflector can be adjusted accurately, and the lithography accuracy can be improved.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] FIG. 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-shaped mask lithography apparatus including a drawing unit 2 that irradiates an electron beam onto a substrate W to be drawn to draw a desired pattern, and a control unit 3 that controls the operation of the drawing unit 2.

[0014] The drawing unit 2 has a drawing chamber 2a that houses a sample W to be drawn, and an optical lens barrel 2b connected to the drawing chamber 2a. This optical lens barrel 2b is provided on the upper surface of the drawing chamber 2a, forms and deflects an electron beam, and irradiates the sample W in the drawing chamber 2a. The interiors of the drawing chamber 2a and the optical lens barrel 2b are depressurized to a vacuum state.

[0015] In the drawing chamber 2a, a stage 11 for supporting the sample W is provided. This stage 11 is movable in the X-axis direction and the Y-axis direction (hereinafter simply referred to as the X direction and the Y direction) that are orthogonal to each other in the horizontal plane. On the stage 11, a sample W such as a mask blank is placed.

[0016] Also, on the XY stage 11, a mark M for measuring the drift amount of the electron beam is provided. The mark M has, for example, a cross shape or a dot shape, and is formed of a heavy metal such as tantalum or tungsten on a silicon substrate.

[0017] Above the XY stage 11, a detector 12 for detecting the reflected electrons reflected from the mark M as a current value when the mark M is irradiated with an electron beam is provided. The detection result by the detector 12 is transmitted and input to a control computer 3b described later. The mark M may be formed on a mask. Also, the mark M may be a transmission mark, and in that case, the detector 12 may be provided below the mark M to detect the current value of the electrons that have passed through the mark M.

[0018] On the outer periphery of the drawing chamber 2a, a measuring unit 4 for measuring the position of the stage 11 is provided. The position of the stage 11 is controlled via a drive mechanism 36 by a position control unit 35 described later based on the measurement result by the measuring unit 4. The configuration of the measuring unit 4 will be described later.

[0019] Inside the optical lens barrel 2b, an emitting unit 21 such as an electron gun that emits an electron beam B, an illumination lens 22 that condenses 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 forms a beam focus on the sample W, and a sub-deflector 28 and a main deflector 29 for controlling the beam shot position with respect to the sample W are arranged.

[0020] In the drawing unit 2, the electron beam B is emitted from the emitting unit 21 and irradiated onto the first shaping aperture 23 by the 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-sectional shape of the electron beam is shaped into a rectangular shape and projected onto the second shaping aperture 26 by the projection lens 24. The projection position onto the second shaping aperture 26 can be deflected by the shaping deflector 25, and by changing the projection position, it is possible to control the shape and dimensions of the electron beam B. The electron beam B that has passed through the second shaping aperture 26 has its focus aligned with and irradiated onto the sample W on the stage 11 by the objective lens 27. At this time, the shot position of the electron beam B with respect to the sample W on the stage 11 is deflected by the sub-deflector 28 and the main deflector 29.

[0021] The control unit 3 includes a storage unit 3a that stores drawing data and a control computer 3b. The control computer 3b includes a shot data generation unit 31, a drawing 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 drawing control unit 32, the mark position detection unit 33, the error calculation unit 34, and the position control unit 35 may be constituted by hardware such as an electric circuit, may be constituted by software such as a program that executes each function, or may be constituted by a combination of both of them.

[0022] The shot data generation unit 31 processes the drawing data to generate shot data. The drawing control unit 32 controls each part of the drawing unit 2.

[0023] 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 the change in the current value of the reflected electrons detected by the detector 12.

[0024] The error calculation unit 34 calculates the error of the beam irradiation position from the difference between the stage position and the mark position detected by beam scanning.

[0025] The drawing data is data that has been converted into a format for the drawing apparatus 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 apparatus 1, and is input from an external apparatus to the storage unit 3a and stored. As the storage unit 3a, for example, a magnetic disk apparatus, a semiconductor disk apparatus (flash memory), or the like can be used.

[0026] When drawing a pattern, the drawing control unit 32 moves the stage 11 in the longitudinal direction (X direction) of the stripe region, positions the electron beam B in each sub-region by the main deflector 29, and shoots at a predetermined position in the sub-region by the sub deflector 28 to draw a figure. After that, when the drawing of one stripe region is completed, the stage 11 is stepped in the Y direction and then the drawing of the next stripe region is performed, and this is repeated to perform drawing by the electron beam B over the entire drawing region of the sample W. During drawing, since the stage 11 is continuously moving in one direction, the drawing origin of the sub-region is tracked by the main deflector 29 so that the drawing origin follows the movement of the stage 11.

[0027] 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 drawing time can be shortened.

[0028] 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., that is, to control the beam irradiation position, and also to control the position of the stage 11.

[0029] 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 the laser light, for example, a helium-neon laser can be used. For the light receiving unit 7, for example, a photodiode can be used.

[0030] In FIG. 2, the measurement unit 4 for measuring the position of the stage 11 in the y direction is shown, and the illustration of the measurement unit for measuring the position of the stage 11 in the x direction is omitted.

[0031] The laser beam (wavelength λ) emitted from the laser source 5 is split by the laser interferometer 6. One of the laser beams split by the laser interferometer 6 travels to the stage 11, is reflected by the mirror on the stage 11, and returns to the laser interferometer 6. On the other hand, the other of the split laser beams travels to and is reflected by a mirror (not shown) inside the laser interferometer 6.

[0032] The laser beam reflected by the mirror on the stage 11 and the laser beam reflected by the mirror inside the laser interferometer 6 interfere with each other in the laser interferometer 6. The interfered laser beam (interference beat signal) is received by the light receiving unit 7, and the interference fringes generated by the optical path difference are observed. The observation result is notified to the drawing control unit 32. In this embodiment, laser interference observation in a two-pass system is performed in which the laser beam makes two round trips between the laser interferometer 6 and the mirror on the stage 11.

[0033] Due to the movement of the stage 11, the frequency of the reflected light from the stage 11 changes, and the interference fringes also change. The drawing control unit 32 grasps the position of the stage 11 from the change in the interference fringes.

[0034] In order to accurately irradiate the sample W with the beam, the electron beam lithography apparatus performs adjustment of the deflection sensitivity of the deflectors (main deflector 29, sub-deflector 28) before the drawing process. For example, the deflection sensitivity adjustment scans the mark M on the stage 11 with the beam, detects the beam position based on the reflected electrons from the mark M, and calculates the beam position error from the deviation from the stage position. The stage 11 is moved in the x-direction and the y-direction at a predetermined pitch respectively, and the calculation of the beam position error is performed at a plurality of locations to obtain a matrix-like position error distribution as shown in FIG. 5A. This position error distribution is approximated by a polynomial, the error at the beam irradiation position is obtained from the approximate formula, and the obtained error is corrected to adjust the deflection sensitivity of the deflector and realize a deflection region shape as shown in FIG. 5B.

[0035] However, the stage position measurement results obtained using the laser interferometer 6 include non-linear errors. For example, as described above, when performing two-pass laser interference observation in which laser light makes two round trips between the laser interferometer 6 and the mirror on the stage 11, when the stage 11 moves by λ / 4, the phase makes one full cycle, so a non-linear error with a period of λ / 4 occurs.

[0036] In the conventional deflection sensitivity adjustment, the interval (pitch P) between the mark position measurement points was set without considering the non-linear error. Therefore, as shown in FIG. 3, the phase of the non-linear error at each measurement point was different, and the amount of non-linear error included in the mark position measurement results was different.

[0037] If different amounts of non-linear error are included at each measurement point, the error cannot be corrected by polynomial approximation, which hinders achieving the target accuracy of the deflection sensitivity adjustment and evaluating the deterioration of the deflector.

[0038] Therefore, in this embodiment, the non-linear error information around the mark position measurement points is acquired in advance, and then the deflection sensitivity adjustment is performed. Such a deflection sensitivity adjustment method will be described along the flowchart shown in FIG. 6.

[0039] The stage 11 is moved at a constant speed around the mark position measurement points (step S101). During this time, the measurement unit 4 samples the stage position at high speed and continuously measures it (step S102) to acquire the non-linear error information around the mark position measurement points (step S103). The non-linear error information is stored in the storage unit 3a.

[0040] When performing the deflection sensitivity adjustment of the main deflector 29, the stage 11 is moved so that the mark M is located at the measurement start position within the beam deflection range by the main deflector 29 (step S104). The movement amount of the stage 11 is controlled using the measurement result of the measurement unit 4 which is a laser length measurement system.

[0041] With the stage 11 stopped, the main deflector 29 deflects the beam B to scan the mark M (step S105). The detector 12 detects the reflected electrons from the mark M. The mark position detector 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 calculator 34 calculates the deviation of the mark position (error of the beam irradiation position) detected by scanning the mark M with the beam, with reference to the mark position based on the stage position measured by the measurement unit 4 (step S107).

[0042] From the non-linear error information obtained in step S103, the non-linear error amount at this mark position measurement point is estimated (step S108). The non-linear error amount 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 (deviation amount of the deflection position by the main deflector 29) (step S109).

[0043] The stage 11 is moved in the x-direction and / or y-direction at a predetermined pitch P, and the error of the beam irradiation position is obtained at each position (steps S110_No, S111). By obtaining the errors of the beam irradiation position at a plurality of predetermined locations (step S110_Yes), a lattice-like position error distribution as shown in FIG. 5A can be obtained. This position error distribution (deflection region shape) is approximated by a polynomial (step S112).

[0044] Substitute the design drawing position into the polynomial to calculate the deviation amount from the design drawing position. By irradiating the beam at the position obtained by subtracting the deviation amount calculated from the design drawing position, the pattern can be drawn at the design position. FIG. 5B shows the deflection region shape after the deviation amount correction.

[0045] By performing such deflection sensitivity adjustment, it is possible to prevent the influence of non-linear errors from appearing. According to the present embodiment, the error of the beam irradiation position can be approximated by a polynomial and corrected, enabling accurate adjustment of the deflection sensitivity of the deflector and improving the drawing accuracy. However, it is not limited to polynomial approximation, and other functions or maps may be used for approximation.

[0046] When the stage 11 has high-resolution stop position accuracy, steps S101 to S103 in FIG. 6 can be omitted, and the interval (pitch P) between the mark position measurement points can be set to an integer multiple of the period (λ / 4) of the non-linear error, and the deflection sensitivity can be adjusted. For example, when the laser wavelength λ is 632.8 nm, the period of the non-linear 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).

[0047] As a result, as shown in FIG. 4, the phases of the non-linear errors at each measurement point coincide, and the same non-linear error amount is included in the mark position measurement result.

[0048] Such a deflection sensitivity adjustment method will be described according to the flowchart shown in FIG. 7.

[0049] For example, when adjusting the deflection sensitivity of the main deflector 29, first, the stage 11 is moved so that the mark M is located at a predetermined position within the beam deflection range by the main deflector 29, and the stage 11 is stopped (step S201). The movement amount of the stage 11 is controlled using the measurement result of the measurement unit 4 which is a laser length measurement system.

[0050] With the stage 11 stopped, the beam B is deflected by the main deflector 29 to scan the mark M (step S202). The detector 12 detects the reflected electrons from the mark M. The mark position detector 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 detected by scanning the mark M (error of the beam irradiation position) with reference to the mark position based on the stage position measured by the measurement unit 4 (step S204).

[0051] While moving the stage 11 in the x and y directions at a predetermined pitch (which is an integer multiple of the period of the non-linear error (λ / 4)), the error in the beam irradiation position (the amount of deviation of the deflection position by the main deflector 29) is calculated at each position (steps S205_No, S201 to S204). By obtaining the errors in the beam irradiation position at a plurality of predetermined locations (step S205_Yes), a lattice-shaped position error distribution as shown in FIG. 5A can be obtained. This position error distribution (deflection region shape) is approximated by a polynomial (step S206). The designed drawing position is substituted into the polynomial to calculate the amount of deviation from the designed drawing position. By irradiating the beam at the position obtained by subtracting the amount of deviation calculated from the designed drawing position, a pattern can be drawn at the designed position. FIG. 5B shows the deflection region shape after the deviation amount correction.

[0052] In this way, by setting the interval (pitch P) between the mark position measurement points to be an integer multiple of the period of the non-linear error (λ / 4) and suppressing the variation in the non-linear error amount included in the mark position measurement results at each measurement point, the deflection sensitivity adjustment of the deflector can be accurately performed, and the drawing accuracy can be improved.

[0053] In the above embodiment, since the 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, the period of the non-linear error is λ / 4. When performing the one-pass laser interference observation 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 non-linear error is λ / 2. Therefore, the interval (pitch P) between the mark position measurement points may be an integer multiple of λ / 2.

[0054] By the above-described deflection position adjustment method, the deflection sensitivity adjustment of the deflector can be accurately performed, and the drawing accuracy can be improved. Note that the deflection position adjustment is to perform the deflection sensitivity adjustment for adjusting the deflection sensitivity coefficient from the position deviation information so that the deflection position can be corrected by the coefficient.

[0055] In the above-described embodiment, a drawing apparatus that irradiates an electron beam has been described, but it may be one that irradiates other charged particle beams such as an ion beam. Further, the drawing apparatus may be a multi-beam drawing apparatus.

[0056] Note that the present invention is not limited to the above-described embodiment as it is, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Further, components from different embodiments may be appropriately combined.

Explanation of Reference Numerals

[0057] 1 Drawing apparatus 2 Drawing unit 2a Drawing chamber 2b Optical lens barrel 3 Control unit 3a Storage unit 3b Control computer 4 Measurement unit 5 Laser source 6 Laser interferometer 7 Light receiving unit 11 Stage

Claims

1. measuring the position of a stage on which a substrate to be drawn is placed using a laser interferometer in a charged particle beam drawing apparatus; a step of scanning a mark on the stage with a 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; a step of correcting a plurality of positional deviation amounts obtained from the position of the stage measured at a predetermined pitch using the laser interferometer and the detected position of the mark based on nonlinear error information of the position of the mark that depends on the laser interferometer; adjusting a deflection position of the charged particle beam based on the corrected positional deviation amounts; A method for adjusting a deflection position of a charged particle beam, comprising:

2. 2. The method for adjusting a deflection position of a charged particle beam according to claim 1, wherein the nonlinear error information is acquired by previously measuring the position of the stage continuously while moving the stage at a constant velocity.

3. 2. The method for adjusting a deflection position of a charged particle beam according to claim 1, wherein the nonlinear error information includes a period of a nonlinear error obtained by moving the stage by a predetermined amount and measuring a mark position on the stage while the stage is stopped, and the positional deviation amount is corrected by synchronizing the predetermined pitch with the period of the nonlinear error.

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

5. 2. A charged particle beam writing method, comprising: adjusting a deflection position of the charged particle beam by the method for adjusting a deflection position of the charged particle beam according to claim 1, to write a pattern.

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