Charged particle beam writing method and charged particle beam writing apparatus

Abstract

To suppress time-dependent pattern drawing position deviation without lowering throughput.SOLUTION: In a charged particle beam drawing method according to this embodiment, while a drawing chamber of a charged particle beam drawing apparatus and a transfer mechanism for transferring a substrate are maintained at predetermined temperatures, respectively, the transfer mechanism transfers the substrate to the drawing chamber; the correction amount of each charged particle beam is calculated on the basis of correction data of the irradiation position of each charged particle beam according to an elapsed time from a predetermined starting point of the transfer of the substrate obtained in advance, and each of the elapsed times at the time of irradiation of each of the charged particle beams; and each charged particle beam is applied to a position corrected on the basis of the calculated correction amount of each charged particle beam to draw a pattern on the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charged particle beam writing method and a charged particle beam writing apparatus. [Background technology]

[0002] 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 (called a mask, or a reticle, especially when used in steppers and scanners) formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure system. The high-precision original pattern is drawn using an electron beam drawing system, using so-called electron beam lithography technology.

[0003] If there is a discrepancy between the initial temperature of the mask at the start of writing and the environmental temperature (the temperature inside the writing chamber), the mask will expand or contract until it adjusts to the environmental temperature, causing a shift in the pattern writing position. If the mask is transported to the writing chamber and then waits until it adjusts to the environmental temperature before starting writing, the shift in the pattern writing position can be avoided, but throughput will decrease.

[0004] Conventionally, the temperature of the drawing preparation room, such as a robot room equipped with a robot for handling the mask, or the drawing room has been adjusted by controlling the temperature of the constant temperature water, so that the initial temperature of the mask after transport to the drawing room matches the ambient temperature of the drawing room as closely as possible, thereby shortening the soaking time (the waiting time for the mask temperature to adjust to the ambient temperature).

[0005] The temperatures of the preparation chamber and the drawing chamber on the transport path can be stabilized by controlling the temperature of the constant temperature water to an accuracy that is generally negligible relative to the drawing accuracy (approximately ±0.03°C, which is 3.3E-2 ppm assuming a linear thermal expansion coefficient of 5E-7 for the quartz substrate commonly used in photomasks, or a maximum position error of approximately 0.5 nm when converted to a 6-inch photomask).

[0006] However, due to limitations in the setting resolution of the constant-temperature water temperature control, it was not possible to completely eliminate the difference in absolute values ​​between the temperature of the transfer path and the temperature of the writing chamber. Furthermore, heat transfer from the mask holder of the transfer robot causes uneven temperature distribution on the mask, which cannot be eliminated by adjusting the temperature of the constant-temperature water. Therefore, if writing is performed without soaking time, mask deformation due to these factors will reduce positional accuracy. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 10-261565 [Patent Document 2] Japanese Patent Application Publication No. 6-36997 [Patent Document 3] Japanese Patent Application Publication No. 9-251941 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a charged particle beam drawing method and a charged particle beam drawing apparatus that can suppress time-dependent pattern drawing position deviation without reducing throughput. [Means for solving the problem]

[0009] A charged particle beam drawing method according to one aspect of the present invention involves maintaining a drawing chamber of a charged particle beam drawing apparatus and a transport mechanism for transporting a substrate at predetermined temperatures, transporting a substrate to the drawing chamber using the transport mechanism, calculating a correction amount for each of the charged particle beams based on correction data for the irradiation position of each charged particle beam corresponding to the elapsed time from a predetermined starting point for transporting the substrate that has been acquired in advance, and each of the elapsed times at the time of irradiation of each of the charged particle beams, and irradiating each of the charged particle beams at a position corrected based on the calculated correction amount for each of the charged particle beams, thereby drawing a pattern on the substrate.

[0010] A charged particle beam drawing apparatus according to one aspect of the present invention includes a transport mechanism for transporting a substrate, a drawing chamber in which the transported substrate is placed, a thermostatic means for maintaining the drawing chamber and the transport mechanism at predetermined temperatures, an elapsed time calculation unit for calculating an elapsed time from a predetermined starting point for transporting the substrate to the drawing chamber, a memory unit for storing correction data for the irradiation position of the charged particle beam according to the elapsed time acquired in advance, a correction unit for calculating a correction amount for each of the charged particle beams based on the correction data and the elapsed time of each of the charged particle beams at the time of irradiation of each of the charged particle beams, and a drawing unit for irradiating each of the charged particle beams at a position corrected based on the calculated correction amount for each of the charged particle beams, and drawing a pattern on the substrate. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress time-dependent pattern writing position deviation without reducing throughput. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a plan view of an electron beam drawing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a drawing mechanism. [Figure 3] FIG. 10 is a diagram illustrating an example of an evaluation pattern. [Figure 4] 10A is a graph showing the change over time in the expansion / contraction term due to linear shape fitting of the position measurement result of the evaluation pattern, and FIGS. 10B and 10C are diagrams showing examples of the position measurement result. [Figure 5] 10 is a flowchart illustrating a drawing method according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] Fig. 1 is a plan view of an electron beam lithography apparatus according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view of a writing chamber (W chamber) 400 and an electron beam tube 500, which are parts of the electron beam lithography apparatus. As shown in Figs. 1 and 2, the electron beam lithography apparatus includes a substrate transfer system 100, an input / output (I / O) chamber 200, a robot chamber (R chamber) 300, a W chamber 400, the electron beam tube 500, a control device 600, a storage unit 700, and gate valves G1 to G3. The electron beam tube 500 is not shown in Fig. 1.

[0015] Drawing data that serves as layout data is input from the outside and stored in the storage unit 700. The storage unit 700 also stores correction data for correcting deviations in beam position caused by changes in the shape of the mask substrate M. The correction data will be described later.

[0016] The substrate transfer system 100 has a transfer arm 110 as a transfer mechanism for transferring the mask substrate M, and receives the mask substrate M from the outside and transfers it to a subsequent chamber while neutralizing the charge on the mask substrate M. The substrate transfer system 100 also transfers the mask substrate M to the outside after drawing while neutralizing the charge on the mask substrate M.

[0017] The I / O chamber 200 is a so-called load lock chamber for loading and unloading the mask substrate M while maintaining a vacuum (low pressure) inside the R chamber 300. The I / O chamber 200 is equipped with a vacuum pump 210 and a gas supply system 220, and a gate valve G1 is provided between the I / O chamber 200 and the substrate transfer system 100. The vacuum pump 210 is, for example, a dry pump or a turbo molecular pump, and evacuates the inside of the I / O chamber 200. The gas supply system 220 supplies a vent gas (for example, nitrogen gas or CDA) into the I / O chamber 200 when the pressure inside the I / O chamber 200 is atmospheric.

[0018] When evacuating the inside of the I / O chamber 200, a vacuum pump 210 connected to the I / O chamber 200 is used to evacuate the inside of the I / O chamber 200. When returning the inside of the I / O chamber 200 to atmospheric pressure, a vent gas is supplied from a gas supply system 220, and the inside of the I / O chamber 200 becomes atmospheric pressure. When evacuating the inside of the I / O chamber 200 and when returning it to atmospheric pressure, the gate valves G1 and G2 are closed.

[0019] The R chamber 300 includes a vacuum pump 310, an alignment chamber 320, a mask cover housing chamber 330, and a transfer arm 340. The R chamber 300 is connected to the I / O chamber 200 via a gate valve G2.

[0020] The vacuum pump 310 is, for example, a cryopump, a turbomolecular pump, etc. The vacuum pump 310 is connected to the R chamber 300, and maintains a high vacuum by evacuating the inside of the R chamber 300. The alignment chamber 320 is a chamber for positioning (aligning) the mask substrate M.

[0021] The mask cover storage chamber 330 is a chamber that stores the mask cover H. The mask cover H is conductive and has a frame-shaped frame with an opening in the center, on which multiple earthing mechanisms are provided. The size of the frame is slightly larger than that of the mask substrate M. The mask cover H is used to discharge the electric charge that accumulates on the mask substrate M due to irradiation with the electron beam.

[0022] The transfer arm 340 transfers the mask substrate M between the I / O chamber 200, the alignment chamber 320, the mask cover housing chamber 330, and the W chamber 400. The temperature of the transfer arm 340 in the R chamber 300 and the temperature in the W chamber 400 are each maintained at a predetermined temperature by a constant temperature means (not shown) using constant temperature water or the like.

[0023] The W chamber 400 (writing chamber) includes a vacuum pump 410, an XY stage 420, and driving mechanisms 430A and 430B, and is connected to the R chamber 300 via a gate valve G3.

[0024] The vacuum pump 410 is, for example, a cryopump or a turbomolecular pump. The vacuum pump 410 is connected to the W chamber 400 and evacuates the inside of the W chamber 400 to maintain a high vacuum. The XY stage 420 is a stage on which the mask substrate M is placed. A driving mechanism 430A drives the XY stage 420 in the X direction. A driving mechanism 430B drives the XY stage 420 in the Y direction. The processing in each chamber and the opening and closing of the gate valves are controlled by a control device 600.

[0025] 2, the electron beam column 500 includes an electron beam irradiation means including an electron gun 510, a blanking aperture 520, a first aperture member 522, a second aperture member 524, a blanking deflector 530, a shaping deflector 532, an objective deflector 534, and lenses 540 (illumination lens (CL), projection lens (PL), objective lens (OL)), and irradiates an electron beam onto a mask substrate M placed on an XY stage 420. A mask cover H is set on the mask substrate M to be irradiated with the electron beam, but the mask cover H is not shown in FIG.

[0026] The following description will be given taking a variable-shape electron beam lithography apparatus as an example. An electron beam 502, which is an example of a charged particle beam emitted from an electron gun 510, is illuminated by an illumination lens CL onto a first aperture member 522 having a rectangular, e.g., square, aperture. Here, the electron beam 502 is first shaped into a rectangle, e.g., a square. The electron beam as a first aperture image that has passed through the first aperture member 522 is projected onto a second aperture member 524 by a projection lens PL. The position of the first aperture image on the second aperture member 524 is controlled by a shaping deflector 532, which can change the beam shape and dimensions. The electron beam as a second aperture image that has passed through the second aperture member 524 is focused by an objective lens OL and deflected by an objective deflector 534 to be irradiated onto a desired position on a mask substrate M mounted on a movably arranged XY stage 420. The application of deflection voltages to the shaping deflector 532 and the objective deflector 534, the movement of the XY stage 420, and the like are controlled by a control device 600.

[0027] An electron beam 502 emitted from an electron gun 510 is controlled by a blanking deflector 530 so that it passes through a blanking aperture 520 in the beam-on state, and is deflected so that the entire beam is blocked by the blanking aperture 520 in the beam-off state. The electron beam that passes through the blanking aperture 520 from the beam-off state to the beam-on state until the beam is subsequently turned off constitutes one electron beam shot. The irradiation amount per shot of the electron beam irradiated onto the mask substrate M is adjusted by the irradiation time of each shot.

[0028] The initial temperature of the mask substrate M transferred into the W chamber 400 does not match the environmental temperature (temperature inside the W chamber 400), and the mask substrate M expands / contracts until it adapts to the environmental temperature. Since the expansion / contraction of the mask substrate M causes deviation of the beam irradiation position, it is conceivable to wait until the mask substrate M adapts to the environmental temperature before starting the drawing process, but this method reduces throughput.

[0029] Therefore, in this embodiment, after the mask substrate M is transported to the W chamber 400, the drawing process is started promptly to correct the beam irradiation position without reducing throughput, thereby suppressing deviation of the beam irradiation position due to expansion / contraction of the mask substrate M.

[0030] The beam irradiation position is corrected using correction data stored in the storage unit 700. After the evaluation mask substrate is transported to the W chamber 400, the writing process is started immediately to write the evaluation pattern, and the correction data is created from the writing results.

[0031] For example, as shown in Fig. 3, first evaluation patterns P1 are drawn sequentially at predetermined intervals over the entire surface of an evaluation mask substrate M1. Mask IDs and alignment marks are not drawn. It is preferable to finish drawing the first evaluation patterns P1 over the entire substrate surface within five minutes.

[0032] After the first evaluation pattern P1 is drawn over the entire surface of the mask substrate M1, the second evaluation patterns P2 are then drawn in sequence over the entire surface of the substrate. The drawing of the second evaluation patterns P2 begins promptly after the drawing of the first evaluation pattern P1 is completed. The multiple second evaluation patterns P2 are each drawn near the first evaluation pattern P1, in the same drawing order. As with the first evaluation pattern P1, it is preferable to finish drawing the second evaluation patterns P2 over the entire surface of the substrate within five minutes.

[0033] Thereafter, the third evaluation pattern P3 to the ninth evaluation pattern P9 are written on the entire surface of the substrate in the same manner. In parallel with the writing process of the first evaluation pattern P1 to the ninth evaluation pattern P9, the elapsed time from the transport of the mask substrate M1 to the W chamber 400 is measured. Note that the elapsed time is not limited to the time from the transport to the W chamber 400, but may be the time from a predetermined starting point (event) related to the transport, such as the transport to the I / O chamber 200.

[0034] The shapes of the first to ninth evaluation patterns P1 to P9 are not particularly limited, but for example, a cross pattern is suitable for measuring the drawing position.

[0035] After the evaluation patterns are written, the mask substrate M1 is carried out and subjected to development and etching processes to form the patterns. Then, a position measuring device (not shown) is used to measure the writing positions of the first to ninth evaluation patterns P1 to P9. Figure 4(a) shows the time-dependent change in the expansion / contraction term obtained by linear shape fitting of the measured values, Figure 4(b) shows the measurement results immediately after the transfer, and Figure 4(c) shows the measurement results after a predetermined time has elapsed.

[0036] Using the measurement results, a correction map is created that maps the amount of deviation from the ideal position at each position within the substrate on which the evaluation patterns are written. A correction map is created for each of the first to ninth evaluation patterns P1 to P9.

[0037] The correction map and the elapsed time since the mask substrate M1 was transported into the W chamber 400 when the evaluation pattern was written are combined and stored in the storage unit 700 as correction data.

[0038] For example, if the time when the mask substrate M1 is transported into the W chamber 400 is taken as the reference time (t=0), and the writing start time of the first evaluation pattern P1 is t0, the writing end time of the first evaluation pattern P1 is t1, the writing end time of the second evaluation pattern P2 is t2, the writing end time of the third evaluation pattern P3 is t3, ..., and the writing end time of the ninth evaluation pattern P9 is t9, in the correction data stored in the storage unit 700, times t0 to t1 correspond to a first correction map based on the writing position measurement results of the first evaluation pattern P1.

[0039] Similarly, times t1 to t2 are associated with a second correction map based on the drawing position measurement results of the second evaluation pattern P2. Times t2 to t3 are associated with a third correction map based on the drawing position measurement results of the third evaluation pattern P3. Times t3 to t4 are associated with a fourth correction map based on the drawing position measurement results of the fourth evaluation pattern P4. Times t4 to t5 are associated with a fifth correction map based on the drawing position measurement results of the fifth evaluation pattern P5. Times t5 to t6 are associated with a sixth correction map based on the drawing position measurement results of the sixth evaluation pattern P6. Times t6 to t7 are associated with a seventh correction map based on the drawing position measurement results of the seventh evaluation pattern P7. Times t7 to t8 are associated with an eighth correction map based on the drawing position measurement results of the eighth evaluation pattern P8. Times t8 to t9 are associated with a ninth correction map based on the drawing position measurement results of the ninth evaluation pattern P9.

[0040] The first to ninth correction maps may be stored as correction data in the storage unit 700, or if the amount of positional deviation becomes sufficiently small along the way, the correction maps up to that point may be stored as correction data in the storage unit 700. Note that instead of using the actual drawing results as they are, the drawing results from times t1 to t9 may be fitted with an exponential function with a time constant λ, such as exp(-t / λ), to obtain ΔP*exp(-t1 / λ), which may be used as the correction value map. Because actual measurement results contain measurement noise, etc., the correction accuracy can be improved by using values ​​fitted with an exponential function rather than using the measurement results as they are.

[0041] As shown in FIG. 2, the control device 600 includes a shot data generation unit 610, an elapsed time calculation unit 620, a correction unit 630, and a drawing control unit 640. Each part of the control device 600 may be composed of hardware such as an electric circuit, or may be composed of software. When it is composed of software, a program for realizing at least a part of the functions of the control device 600 may be stored in a recording medium and read and executed by a computer including a CPU. The recording medium is not limited to a removable one such as a magnetic disk or an optical disk, and may be a fixed recording medium such as a hard disk device or a memory. The processing of each part of the control device 600 will be described using the flowchart shown in FIG. 5.

[0042] The shot data generation unit 610 reads drawing data from the storage unit 700 and performs a multi-stage data conversion process to generate shot data (step S2). The shot data includes information such as shot shape, shot size, shot position (irradiation position), and shot time.

[0043] The elapsed time calculation unit 620 records the time when the mask substrate M is carried into the W chamber 400 as the reference time (step S1), and calculates the elapsed time of the beam irradiation time from the reference time for each shot (step S3).

[0044] The correction unit 630 refers to a correction map corresponding to the elapsed time calculated by the elapsed time calculation unit 620 for each shot, and corrects the shot position in the shot data (step S4). For example, when the calculated elapsed time Tk satisfies t2 < Tk < t3, the correction unit 630 refers to the third correction map in the storage unit 700 to correct the shot position. A known method can be used for correcting the shot position using the correction map. The shot position may be corrected by beam control or the shot position on the shot data may be corrected.

[0045] The drawing control unit 640 controls the deflection amounts of the blanking deflector 530, the shaping deflector 532, and the objective deflector 534 so that the beam is irradiated at the corrected shot position, and performs a drawing process (step S5).

[0046] If sufficient time has passed for the mask substrate M to adapt to the ambient temperature before all patterns have been drawn, and the time elapsed since the mask substrate was loaded exceeds a threshold (step S6_No, S7_Yes), the process may proceed to normal drawing processing without position correction based on correction data (step S8).

[0047] As described above, according to this embodiment, a group of correction maps of the beam irradiation position corresponding to the time change of the mask shape based on the time when the mask substrate is loaded into the writing chamber is created, and when writing the actual pattern, the position correction is performed by referring to the correction map corresponding to the time elapsed since the mask substrate was loaded. This suppresses the influence of expansion / contraction due to temperature change of the mask substrate, and enables the pattern to be written with high accuracy. Furthermore, since it is not necessary to wait for the mask substrate to adjust to the environmental temperature, throughput is not reduced.

[0048] Although a non-uniform temperature distribution occurs on the mask substrate due to heat transfer from the transfer arm 340, according to this embodiment, there is no need to actually measure the temperature distribution or to simulate the mask shape using the temperature distribution.

[0049] In the above embodiment, an example has been described in which a correction map that defines the positional deviation for each grid is used as correction data, but a polynomial that approximates the amount of positional deviation within the mask surface may be calculated for each evaluation pattern, and the coefficients of the polynomial may be stored as correction data in the storage unit 700. In this case, the correction unit 630 calculates the correction amount using the coefficient corresponding to the elapsed time and the shot position retrieved from the storage unit 700. For example, the coefficients a1(t) to a9(t) and b1(t) to b9(t) of the following polynomial are stored in the storage unit 700.

[0050] Δx(x,y)=a1*x+a2*y+a3*x 2 +a4*xy+a5*y 2 +a6*x 3 +a7*x 2 y+a8*xy 2 +a9*y 3 Δy(x,y)=b1*x+b2*y+b3*x 2 +b4*xy+b5*y 2 +b6*x 3 +b7*x 2 y+b8*xy 2 +b9*y 3

[0051] In the above embodiment, an example was described in which a group of correction maps was prepared according to the time elapsed since the mask substrate was carried into the writing chamber. However, a group of correction maps may be prepared according to not only the elapsed time but also the number of alignments of the mask substrate (total number of contacts with the transfer arm 340) or the total alignment time (total contact time with the transfer arm 340). This is because the number of alignments can affect the temperature distribution on the mask substrate. The mask substrate is carried into the writing chamber with different alignment counts, and an evaluation pattern is written, and a group of correction maps is created from the writing results. Then, the correction amount is calculated taking the number of alignments into consideration.

[0052] Furthermore, when soaking is performed in the I / O chamber 200 or the R chamber 300, correction data such as a group of correction maps according to the soaking location and soaking time may be prepared.

[0053] In the above embodiment, a configuration using an electron beam has been described as an example of a charged particle beam, but the charged particle beam is not limited to an electron beam, and may be a beam using charged particles such as an ion beam.

[0054] In the above embodiment, a configuration using a single beam has been described, but a configuration using multiple beams may also be used.

[0055] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0056] 100 Substrate transport system 200 Loading / unloading chamber 300 Robot Chamber 400 Lighting Chamber 500 Electron Beam Tube 600 control device

Claims

1. a writing chamber of a charged particle beam writing apparatus and a transfer mechanism for transferring the substrate are maintained at predetermined temperatures, and the substrate is transferred to the writing chamber by the transfer mechanism; calculating a correction amount for each of the charged particle beams corresponding to each of the elapsed times at the time of irradiation with each of the charged particle beams from correction data for each irradiation position of the plurality of charged particle beams obtained by previously drawing an evaluation pattern for each elapsed time from a predetermined starting point related to the transportation of the substrate; a charged particle beam lithography method for irradiating each of the charged particle beams at a position corrected based on the calculated correction amount for each of the charged particle beams, thereby drawing a pattern on the substrate;

2. 2. The charged particle beam writing method according to claim 1, wherein the correction data is further based on a total number of contacts or a total contact time between the substrate and the transport mechanism.

3. 3. The charged particle beam drawing method according to claim 1, wherein, when the elapsed time exceeds a threshold value, the pattern is drawn on the substrate without calculating the correction amount based on the elapsed time.

4. transporting an evaluation substrate into the drawing chamber; a plurality of first evaluation patterns are sequentially drawn at predetermined intervals on the entire surface of the evaluation substrate, and then a plurality of second evaluation patterns to an n-th evaluation pattern (n is 2 or more) are sequentially drawn at predetermined intervals on the entire surface of the evaluation substrate at different positions, measuring the positions of the first evaluation pattern to the nth evaluation pattern which are sequentially written; 3. The charged particle beam drawing method according to claim 1, wherein the correction data is acquired using a result of the measurement and an elapsed time from a predetermined starting point related to transport of the substrate to the time when each of the first evaluation pattern to the nth evaluation pattern is written.

5. a transport mechanism for transporting the substrate; a drawing chamber in which the transported substrate is placed; a thermostatic unit that maintains the drawing chamber and the transport mechanism at predetermined temperatures; an elapsed time calculation unit that calculates an elapsed time from a predetermined starting point in the transport of the substrate to the writing chamber; a storage unit that stores correction data for each irradiation position of a plurality of charged particle beams obtained by drawing an evaluation pattern in advance for each elapsed time; a correction unit that calculates, from the correction data, a correction amount for each of the charged particle beams corresponding to an elapsed time of each of the charged particle beams at the time of irradiation of each of the charged particle beams; a drawing unit that draws a pattern on the substrate by irradiating each of the charged particle beams at a position corrected based on the calculated correction amount of each of the charged particle beams; A charged particle beam writing apparatus comprising:

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