Charged particle beam drawing method and charged particle beam drawing apparatus

Abstract

Provided is a charged particle beam drawing method and a charged particle beam drawing apparatus capable of suppressing time-dependent pattern drawing position deviation without reducing throughput. In the charged particle beam drawing method of the present embodiment, a drawing chamber of a charged particle beam drawing apparatus and a transport mechanism that transports a substrate are each maintained at a prescribed temperature, and the substrate is transported to the drawing chamber by the transport mechanism; a correction amount of each charged particle beam is calculated based on correction data of an irradiation position of each charged particle beam corresponding to an elapsed time, and each of the elapsed times at which each charged particle beam is irradiated, the elapsed times being times from a prescribed start point related to transport of the substrate that are obtained in advance; and each charged particle beam is irradiated at a position that has been corrected based on the correction amount of each charged particle beam calculated, and a pattern is drawn on the substrate.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2021-163581 (filed on October 4, 2021) and Japanese Patent Application No. 2022-084654 (filed on May 24, 2022). This application incorporates the entire contents of the basic applications by reference. Technical Field

[0002] This invention relates to a method and apparatus for depicting charged particle beams. Background Technology

[0003] With the increasing integration of LSIs, the linewidths required for semiconductor devices have been miniaturized year by year. To form the desired circuit patterns on semiconductor devices, a method is used to transfer a high-precision original pattern (mask, or also called a reticule, especially used in stepper or scanner) formed on quartz onto the wafer using a reduction projection exposure device. The high-precision original pattern is then drawn using an electron beam etching device, employing a technique known as electron beam etching.

[0004] If the initial temperature of the mask at the start of the drawing process deviates from the ambient temperature (the indoor temperature of the drawing chamber), the mask will expand or contract until it adapts to the ambient temperature, resulting in a deviation in the pattern drawing position. If the mask is transported to the drawing chamber and allowed to adapt to the ambient temperature before drawing begins, this deviation in the pattern drawing position can be avoided, but the throughput will decrease.

[0005] Previously, the following measures were taken: the temperature of the drawing preparation room or drawing room, such as the robot room where the robot is installed to manipulate the mask, was adjusted by means of temperature control of constant temperature water, so that the initial temperature of the mask after being transported to the drawing room is as close as possible to the ambient temperature of the drawing room, thereby shortening the heat-adjusting time (the standby time used to adapt the mask temperature to the ambient temperature).

[0006] By controlling the temperature of the constant-temperature water, the temperatures of the preparation chamber and the drawing chamber in the transport path can be stabilized with an accuracy that is usually negligible relative to the drawing precision (around ±0.03℃; if we assume that the linear thermal expansion coefficient of the quartz substrate commonly used in photomasks is 5E-7, then it is 3.3E-2ppm, which translates to a maximum position error of around 0.5nm for a 6-inch photomask).

[0007] However, since the temperature control of the constant-temperature water has a limited resolution, the absolute difference between the temperature of the transport path and the temperature of the drawing chamber cannot be completely eliminated. Furthermore, although uneven temperature distribution occurs in the mask due to heat conduction from the mask holding section of the transport robot, this temperature distribution cannot be eliminated by adjusting the temperature of the constant-temperature water. Therefore, when drawing is performed without a homogenization time, the positional accuracy decreases due to mask deformation caused by these factors. Summary of the Invention

[0008] The purpose of this invention is to provide a charged particle beam drawing method and apparatus that can suppress time-dependent pattern drawing position deviations without reducing the processing capacity.

[0009] One aspect of the present invention is a charged particle beam drawing method, in which the drawing chamber of the charged particle beam drawing apparatus and the transport mechanism for transporting the substrate are maintained at a predetermined temperature, and the substrate is transported to the drawing chamber by the transport mechanism; based on correction data of the irradiation position of each charged particle beam corresponding to the elapsed time, and the elapsed time of each charged particle beam during irradiation, a correction amount for each charged particle beam is calculated, wherein the elapsed time is a predetermined time obtained in advance from a predetermined starting point related to the transport of the substrate; and each charged particle beam is irradiated at the position corrected based on the calculated correction amount of each charged particle beam, thereby drawing a pattern on the substrate. Attached Figure Description

[0010] Figure 1 This is a top view of an electron beam mapping apparatus relating to an embodiment of the present invention.

[0011] Figure 2 It is a schematic diagram depicting the structure of the organization.

[0012] Figure 3 This is a diagram illustrating an example of an evaluation pattern.

[0013] Figure 4 (a) is a graph showing the change over time of the scaling term resulting from the first-order shape fitting of the evaluation pattern's position measurement results. Figure 4 (b) Figure 4 (c) is a diagram showing an example of the position measurement results.

[0014] Figure 5 This is a flowchart illustrating the method of describing this embodiment. Detailed Implementation

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0016] Figure 1This is a top view of an electron beam mapping apparatus relating to an embodiment of the present invention. Figure 2 This is a cross-sectional view of the writing chamber (W chamber) 400 and the electron beam tube 500, which are part of the electron beam drawing apparatus. Figure 1 , Figure 2 As shown, the electron beam mapping apparatus includes a substrate transport system 100, an input / output (I / O) chamber 200, a robot chamber (R chamber) 300, a W chamber 400, an electron beam lens 500, a control device 600, a storage unit 700, and gate valves G1 to G3. Figure 1 The diagram of the electron beam tube 500 is omitted in the text.

[0017] The drawing data, which is input from the outside and stored as layout data, is stored in the storage unit 700. In addition, correction data is stored in the storage unit 700, which is used to correct deviations in the beam position caused by changes in the shape of the mask substrate M. The correction data will be described later.

[0018] The substrate transport system 100, as a transport mechanism, has a transport arm 110 for transporting the mask substrate M. It receives the mask substrate M from the outside and transports it to the rear chamber while removing static electricity from the mask substrate M. In addition, the substrate transport system 100 outputs the mask substrate M to the outside while removing static electricity from the drawn mask substrate M.

[0019] The I / O chamber 200 is a so-called loading and locking chamber used to input and output a mask substrate M while maintaining a vacuum (low pressure) state within the R chamber 300. The I / O chamber 200 includes a vacuum pump 210 and a gas supply system 220, and a gate valve G1 is provided between it and the substrate transport system 100. The vacuum pump 210, such as a dry pump or a turbomolecular pump, evacuates the I / O chamber 200. The gas supply system 220 supplies a venting gas (e.g., nitrogen or CDA) into the I / O chamber 200 when the I / O chamber 200 reaches atmospheric pressure.

[0020] When evacuating the I / O chamber 200, a vacuum pump 210 connected to the I / O chamber 200 is used. Furthermore, when restoring the I / O chamber 200 to atmospheric pressure, ventilation gas is supplied from the gas supply system 220, bringing the I / O chamber 200 to atmospheric pressure. Additionally, when evacuating the I / O chamber 200 and when restoring it to atmospheric pressure, gate valves G1 and G2 are set to Close.

[0021] R chamber 300 includes a vacuum pump 310, a calibration chamber 320, a mask housing chamber 330, and a delivery arm 340. R chamber 300 is connected to I / O chamber 200 via gate valve G2.

[0022] Vacuum pump 310 is, for example, a cryogenic pump or a turbomolecular pump. Vacuum pump 310 is connected to R chamber 300 to evacuate and maintain a high vacuum in R chamber 300. Calibration chamber 320 is a chamber used to position (calibrate) the mask substrate M.

[0023] The mask housing chamber 330 is a cavity that houses the mask H. The mask H is conductive and has a frame-shaped structure with an opening in the center, on which multiple grounding mechanisms are provided. The frame is slightly larger than the mask substrate M. The mask H is used to discharge the charge accumulated in the mask substrate M by irradiation with an electron beam.

[0024] The transport arm 340 transports the mask substrate M between the I / O chamber 200, the calibration chamber 320, the mask housing chamber 330, and the W chamber 400. The temperature of the transport arm 340 in the R chamber 300 and the temperature in the W chamber 400 are maintained at a predetermined temperature by using a temperature control mechanism (not shown) such as constant temperature water.

[0025] The W chamber 400 (drawing chamber) is equipped with a vacuum pump 410, an XY stage 420 and drive mechanisms 430A and 430B, and is connected to the R chamber 300 via a gate valve G3.

[0026] Vacuum pump 410 is, for example, a cryogenic pump or a turbomolecular pump. Vacuum pump 410 is connected to chamber W 400, evacuating and maintaining a high vacuum within chamber W 400. XY stage 420 is used to hold the mask substrate M. Drive mechanism 430A drives XY stage 420 in the X direction. Drive mechanism 430B drives XY stage 420 in the Y direction. Processing within each chamber and the opening and closing of gate valves are controlled by control device 600.

[0027] like Figure 2 As shown, the electron beam tube 500 includes an electron beam irradiation mechanism composed of an electron gun 510, a blanking aperture 520, a first aperture component 522, a second aperture component 524, a blanking deflector 530, a shaping deflector 532, an object deflector 534, and lenses 540 (illumination lens (CL), projection lens (PL), and objective lens (OL)), which irradiates an electron beam onto a mask substrate M mounted on an XY stage 420. A mask cover H is provided on the mask substrate M to which the irradiated electron beam is applied, but... Figure 2 The diagram of mask H is omitted.

[0028] The following description, as an example, illustrates a variable-shape electron beam mapping apparatus. An electron beam 502, an example of a charged particle beam emitted from an electron gun 510, illuminates the entire first aperture member 522 through an illumination lens CL. The first aperture member 522 has a rectangular, for example, square, opening. Here, the electron beam 502 is first shaped into a rectangular, for example, square shape. Next, the electron beam, passing through the first aperture member 522 and forming a first aperture image, is projected onto a second aperture member 524 through a projection lens PL. The position of the first aperture image on the second aperture member 524 is controlled by a shaping deflector 532, allowing for variations in beam shape and size. Next, the electron beam, passing through the second aperture member 524 and forming a second aperture image, is focused by an objective lens OL and deflected by an object deflector 534, illuminating the desired position on a mask substrate M on a movably configured XY stage 420. The application of deflection voltage to the forming deflector 532 and the object deflector 534, as well as the movement of the XY stage 420, are controlled by the control device 600.

[0029] The electron beam 502 emitted from the electron gun 510 is controlled by the blanking deflector 530 to pass through the blanking aperture 520 in the beam-on state and to be deflected by the blanking aperture 520 in the beam-off state. From the beam-off state to the beam-on state and then back to the beam-off state, the electron beam passing through the blanking aperture 520 constitutes one electron beam emission. The irradiation amount of the electron beam irradiating the mask substrate M for each emission is adjusted by the irradiation time of each emission.

[0030] The initial temperature of the mask substrate M, which is transported into the W chamber 400, is inconsistent with the ambient temperature (the temperature inside the W chamber 400). The mask substrate M expands / contracts until it adapts to the ambient temperature. Since beam irradiation position deviation occurs due to the expansion / contraction of the mask substrate M, it is possible to consider starting the drawing process after waiting for the mask substrate M to adapt to the ambient temperature, but this method reduces the throughput.

[0031] Therefore, in this embodiment, after the mask substrate M is transported to the W chamber 400, the drawing process is started quickly without reducing the processing volume, the beam irradiation position is corrected, and the beam irradiation position deviation caused by the expansion / contraction of the mask substrate M is suppressed.

[0032] In the correction of the beam irradiation position, correction data stored in the storage unit 700 is used. After the evaluation mask substrate is transported to the W chamber 400, the drawing process is quickly started to draw the evaluation pattern, and correction data is generated based on the drawing results.

[0033] For example, such as Figure 3As shown, the first evaluation pattern P1 is sequentially drawn at predetermined intervals on the entire surface of the evaluation mask substrate M1. Mask ID and calibration marks are not drawn. The drawing of the first evaluation pattern P1 across the entire substrate surface is preferably completed within 5 minutes.

[0034] After the first evaluation pattern P1 is drawn on the entire surface of the mask substrate M1, the second evaluation pattern P2 is then drawn sequentially on the entire surface of the substrate. The drawing of the second evaluation pattern P2 begins rapidly after the drawing of the first evaluation pattern P1 is completed. Multiple second evaluation patterns P2 are drawn near the first evaluation pattern P1, and the drawing order is set to be the same. Similar to the first evaluation pattern P1, the drawing of the second evaluation pattern P2 on the entire surface of the substrate is preferably completed within 5 minutes.

[0035] Subsequently, the third evaluation pattern P3 to the ninth evaluation pattern P9 are drawn onto the entire surface of the substrate. In parallel with the drawing process of the first evaluation pattern P1 to the ninth evaluation pattern P9, the elapsed time from the moment the mask substrate M1 is transported to the W chamber 400 is measured. Furthermore, the elapsed time is not limited to the time from the moment of transport to the W chamber 400; it can also be the time from the moment of transport to the I / O chamber 200, etc., as long as it is the time from a predetermined starting point (event) related to the transport.

[0036] The shapes of evaluation patterns P1 to P9 are not particularly limited; for example, a cross pattern is preferred for measuring the location.

[0037] After the evaluation patterns are drawn, the mask substrate M1 is output for development and etching to form the patterns. Next, the drawing positions of the first evaluation pattern P1 to the ninth evaluation pattern P9 are measured using a position measuring device (illustration omitted). Figure 4 (a) represents the change over time of the scaling term resulting from the first-order shape fitting of the measured values. Figure 4 (b) represents the measurement results immediately after transmission. Figure 4 (c) indicates the measurement results after a specified time.

[0038] Using the measurement results, correction diagrams are created. These correction diagrams are obtained by plotting the deviations of each position within the substrate depicting the evaluation pattern from the ideal position. Correction diagrams are created for each of the first evaluation pattern P1 to the ninth evaluation pattern P9.

[0039] The data combining the correction pattern and the elapsed time is saved as correction data in the storage unit 700. The elapsed time is the time from when the mask substrate M1 is transported to the W chamber 400 when the evaluation pattern is drawn.

[0040] For example, if the time when the mask substrate M1 is transported to the W chamber 400 is taken as the reference time (t=0), and the drawing start time of the first evaluation pattern P1 is t0, the drawing end time of the first evaluation pattern P1 is t1, the drawing end time of the second evaluation pattern P2 is t2, the drawing end time of the third evaluation pattern P3 is t3, ..., the drawing end time of the ninth evaluation pattern P9 is t9, the correction data stored in the storage unit 700 establishes a correspondence between the times t0 to t1 and the first correction map based on the drawing position measurement result of the first evaluation pattern P1.

[0041] Similarly, times t1 to t2 are mapped to the second corrected image based on the position measurement results of the second evaluation pattern P2. Times t2 to t3 are mapped to the third corrected image based on the position measurement results of the third evaluation pattern P3. Times t3 to t4 are mapped to the fourth corrected image based on the position measurement results of the fourth evaluation pattern P4. Times t4 to t5 are mapped to the fifth corrected image based on the position measurement results of the fifth evaluation pattern P5. Times t5 to t6 are mapped to the sixth corrected image based on the position measurement results of the sixth evaluation pattern P6. Times t6 to t7 are mapped to the seventh corrected image based on the position measurement results of the seventh evaluation pattern P7. Times t7 to t8 are mapped to the eighth corrected image based on the position measurement results of the eighth evaluation pattern P8. Times t8 to t9 are mapped to the ninth corrected image based on the position measurement results of the ninth evaluation pattern P9.

[0042] The correction maps 1 through 9 can be stored in the storage unit 700 as correction data, or, if the positional deviation in the middle is sufficiently reduced, the correction maps up to that point can be stored in the storage unit 700 as correction data. Alternatively, instead of using the actual drawing results as is, the correction value map can be ΔP*exp(-t1 / λ), which is obtained by fitting the drawing results from times t1 to t9 with an exponential function of a time constant λ such as exp(-t / λ). Since the actual measurement results contain measurement noise, the correction accuracy can be improved by using the value fitted using an exponential function compared to using the measurement results as is.

[0043] like Figure 2As shown, the control device 600 includes a transmission 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 can be composed of hardware such as a circuit, or can be composed of software. In the case of being composed of software, a program that implements at least part of the functions of the control device 600 can also be stored in a recording medium, and a computer including a CPU reads and executes it. The recording medium is not limited to a detachable recording medium such as a magnetic disk or an optical disc, and can also be a fixed recording medium such as a hard disk device or a memory. Use Figure 5 The flowchart shown is used to illustrate the processing of each part of the control device 600.

[0044] The transmission data generation unit 610 reads the drawing data from the storage unit 700, performs a multi-stage data transformation process, and generates transmission data (step S2). The transmission data contains information such as the emission shape, emission size, emission position (irradiation position), and emission time.

[0045] The elapsed time calculation unit 620 records the moment 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 emission (step S3).

[0046] The correction unit 630 corrects the emission position in the emission data for each emission by referring to a correction map corresponding to the elapsed time calculated by the elapsed time calculation unit 620 (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 emission position. Well-known methods can be used for the correction of the emission position using the correction map. The emission position can be corrected either by beam control or by correcting the emission position on the emission data.

[0047] The drawing control unit 640 controls the deflection amounts of the blanking deflector 530, the shaping deflector 532, and the object deflector 534, and performs a drawing process so that the beam is irradiated at the corrected emission position (step S5).

[0048] If enough time for the mask substrate M to adapt to the ambient temperature has passed before the drawing of all patterns is completed and the elapsed time from the mask substrate loading exceeds the threshold (step S6_ No, S7_ Yes), it is also possible to transfer to a normal drawing process without position correction based on correction data (step S8).

[0049] Thus, according to this embodiment, a set of correction maps corresponding to the time-varying shape of the mask, based on the moment the mask substrate is moved into the drawing chamber, is prepared in advance. During the actual pattern drawing, the position is corrected by referring to the correction maps corresponding to the elapsed time since the mask substrate was moved in. Therefore, the effects of expansion / contraction accompanying temperature changes of the mask substrate are suppressed, and patterns can be drawn with high precision. Furthermore, since it is not necessary to wait for the mask substrate to adapt to the ambient temperature, the throughput does not decrease.

[0050] Although the mask substrate generates an uneven temperature distribution due to heat conduction from the transport arm 340, according to this embodiment, it is not necessary to measure the temperature distribution or to simulate the mask shape using the measured temperature distribution.

[0051] In the above embodiment, an example using a correction map specifying the positional deviation of each grid as correction data was described. However, it is also possible to calculate a polynomial that approximates the positional deviation within the mask surface for each evaluation pattern, and store the coefficients of the polynomial as correction data in the storage unit 700. In this case, the correction unit 630 calculates the correction amount using the coefficients corresponding to the elapsed time retrieved from the storage unit 700 and the emission position. For example, the coefficients a1(t) to a9(t) and b1(t) to b9(t) of the following polynomials are stored in the storage unit 700.

[0052] 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

[0053] 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

[0054] In the above embodiment, an example of preparing a set of correction patterns corresponding to the elapsed time from when the mask substrate is moved into the drawing chamber was described. However, it is also possible to prepare a set of correction patterns that corresponds not only to the elapsed time but also to the number of calibrations of the mask substrate (total number of contacts with the transport arm 340) or the total calibration time (total contact time with the transport arm 340). This is because the number of calibrations can affect the temperature distribution of the mask substrate. The mask substrate is moved into the drawing chamber with the number of calibrations changed, and an evaluation pattern is drawn. A set of correction patterns is then created based on the drawing results. Furthermore, the correction amount is calculated based on the number of calibrations.

[0055] Furthermore, when homogenizing the I / O chamber 200 and the R chamber 300, correction data such as correction charts corresponding to the homogenization location and homogenization time can also be prepared.

[0056] In the above embodiments, an electron beam structure was described as an example of a charged particle beam, but the charged particle beam is not limited to an electron beam, and may also be a beam that uses charged particles, such as an ion beam.

[0057] In the above embodiments, a structure using a single beam was described, but a structure using multiple beams may also be used.

[0058] Furthermore, the present invention is not limited to the embodiments described above, and the constituent elements can be modified and embodied in practice without departing from its spirit. Moreover, various inventions can be formed by appropriately combining the multiple constituent elements disclosed in the above embodiments. For example, several constituent elements may be deleted from all the constituent elements shown in the embodiments. Furthermore, constituent elements across different embodiments may be appropriately combined.

[0059] Label Explanation

[0060] 100 Substrate transport system; 200 Input / output chamber; 300 Robot chamber; 400 Writing chamber; 500 Electron beam lens; 600 Control device.

Claims

1. A method for depicting charged particle beams, wherein, While maintaining the drawing chamber of the charged particle beam drawing device and the substrate transport mechanism at a specified temperature, the substrate is transported to the drawing chamber using the aforementioned transport mechanism. Correction data for each irradiation position of a plurality of charged particle beams prefabricated according to the elapsed time from a predetermined starting point related to the transport of each of the aforementioned substrates is obtained, and the correction amount for each of the aforementioned charged particle beams is calculated by referring to the correction data corresponding to each elapsed time during the irradiation of each of the aforementioned charged particle beams. The charged particle beams are irradiated at positions corrected based on calculated correction amounts for each of the aforementioned charged particle beams, and a pattern is drawn on the substrate. The aforementioned revised data is also based on the total number of contacts or total contact time between the substrate and the conveying mechanism.

2. The charged particle beam mapping method as described in claim 1, wherein, If the elapsed time exceeds the threshold, the pattern is drawn on the substrate without calculating the correction amount based on the elapsed time.

3. The charged particle beam mapping method as described in claim 1, wherein, The evaluation substrate is transported into the above-mentioned drawing chamber; After sequentially drawing multiple first evaluation patterns at a predetermined interval on the entire surface of the aforementioned evaluation substrate, multiple second to nth evaluation patterns are then sequentially drawn at different positions on the entire surface of the aforementioned evaluation substrate at a predetermined interval, where n is 2 or more. Measure the positions of each of the first evaluation patterns and each of the nth evaluation patterns that are drawn sequentially. The above-mentioned correction data is obtained using the results of the above-mentioned measurements and the elapsed time from the specified starting point related to the transport of the above-mentioned substrate to the time when the first evaluation pattern to each of the above-mentioned nth evaluation patterns is drawn.

4. The charged particle beam mapping method as described in claim 3, wherein, The aforementioned correction data includes a plotted correction diagram of the positional deviation of the depicted position, created using the results of the aforementioned measurements for each of the aforementioned first to nth evaluation patterns.

5. The charged particle beam mapping method as described in claim 4, wherein, The above-mentioned correction graph is made using the following value, which is obtained by fitting the above-mentioned measurement results for each of the above-mentioned evaluation patterns from the first to the nth evaluation patterns with an exponential function.

6. The charged particle beam mapping method as described in claim 3, wherein, The aforementioned correction data includes the coefficients of a polynomial approximating the positional deviation of the depicted position, calculated using the results of the aforementioned measurements for each of the aforementioned first to nth evaluation patterns.

7. A charged particle beam mapping device, wherein, have: Conveying mechanism, conveying substrate; The drawing chamber holds the aforementioned substrate that has been transported. The temperature control mechanism maintains the above-mentioned drawing chamber and the above-mentioned conveying mechanism at a specified temperature; The time calculation unit calculates the elapsed time from the predetermined starting point in relation to the transport of the aforementioned substrate to the aforementioned drawing chamber; The storage unit stores correction data for each irradiation position of each of the multiple charged particle beams pre-made according to the aforementioned elapsed time. The correction unit acquires multiple correction data sets, refers to the correction data corresponding to the elapsed time during irradiation by each of the aforementioned charged particle beams, and calculates the correction amount for each of the aforementioned charged particle beams; and The drawing unit irradiates each of the charged particle beams at positions corrected based on calculated correction amounts for each of the aforementioned charged particle beams, and draws a pattern on the substrate. The aforementioned revised data is also based on the total number of contacts or total contact time between the substrate and the conveying mechanism.

8. The charged particle beam mapping apparatus as claimed in claim 7, wherein, If the elapsed time exceeds the threshold, the pattern is drawn on the substrate without calculating the correction amount based on the elapsed time.

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