Charged particle beam drawing method and charged particle beam drawing device

Abstract

The charged amount of the substrate is calculated quickly and accurately. The charged particle beam drawing method includes: a process of virtually dividing the drawing area of ​​the substrate of the drawing object into a grid shape, and calculating the pattern density representing the configuration ratio of the above-mentioned pattern in each grid area (S100); a process of calculating the dose of each grid area using the above-mentioned pattern density (S102); a process of calculating the charge amount according to the film thickness of the above-mentioned resist film formed on the above-mentioned substrate and the calculated dose using a function for charge amount calculation that uses the film thickness and dose of the above-mentioned resist film obtained in advance as variables (S104); a process of calculating the positional deviation of the drawing position according to the calculated above-mentioned charge amount (S106); and a process of correcting the irradiation position of the above-mentioned charged particle beam using the above-mentioned positional deviation (S108).

Description

Technical Field

[0001] The present invention relates to a charged particle beam drawing method and a charged particle beam drawing device. Background Art

[0002] With the high integration of LSI, the circuit line width required by semiconductor devices is becoming smaller and smaller year by year. In order to form the desired circuit pattern on the semiconductor device, the following method is adopted: using a reduced projection exposure device, the high-precision original pattern (mask, or especially used in steppers and scanners, also called intermediate mask) formed on quartz is reduced and transferred to the wafer. The high-precision original pattern is drawn by an electron beam drawing device, using the so-called electron beam lithography technology.

[0003] When an electron beam is irradiated onto a substrate such as a mask, the irradiation position and its surroundings are charged due to the electron beam irradiated in the past, and the irradiation position is shifted. In the past, as one of the methods for eliminating the beam irradiation position shift, it is known to form an anti-charge film (CDL: Charge Dissipation Layer) on the substrate to prevent the surface of the substrate from being charged. However, the anti-charge film basically has acidic properties, and therefore, has poor compatibility when a chemically amplified resist is coated on the substrate. In addition, new equipment needs to be set up to form the anti-charge film, which further increases the manufacturing cost. Therefore, it is desired to perform charging effect correction (CEC: Charging Effect Correction) without using an anti-charge film.

[0004] In the previous charging effect correction, the beam irradiation amount dependence of the charge amount was calculated based on the drawing evaluation of each substrate. Therefore, every time the resist film thickness is changed or the concentration of the oxygen generating agent contained in the resist is changed, in order to predict the charge amount of the substrate, it is necessary to draw the evaluation pattern and evaluate the drawing results, which takes time. In addition, the downtime of the device is prolonged.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-158167

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 10-027753

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 61-142740

[0008] Patent Document 4: Japanese Patent No. 5480555

[0009] Patent Document 5: Japanese Patent No. 5480496 Summary of the invention

[0010] An object of the present invention is to provide a charged particle beam drawing method and a charged particle beam drawing device capable of quickly and accurately calculating the charge amount of a substrate.

[0011] A charged particle beam drawing method according to one embodiment of the present invention deflects a charged particle beam by a deflector, and irradiates the charged particle beam onto a substrate formed with a resist film to draw a pattern, comprising: a process of virtually dividing the drawing area of ​​the substrate into a grid, and calculating a pattern density representing the configuration ratio of the pattern in each grid area; a process of using the pattern density to calculate the dose of each grid area; a process of using a function for calculating the charge amount that uses the film thickness of the resist film and the dose that are previously determined as variables, and calculating the charge amount based on the film thickness of the resist film formed on the substrate and the calculated dose; a process of calculating a positional offset of the drawing position based on the calculated charge amount; and a process of using the positional offset to correct the irradiation position of the charged particle beam.

[0012] A charged particle beam drawing device according to one embodiment of the present invention deflects a charged particle beam by a deflector, and irradiates the charged particle beam to a substrate formed with a resist film to draw a pattern, and comprises: an emitting unit that emits the charged particle beam; a pattern density calculating unit that virtually divides the drawing area of ​​the substrate into a grid shape, and calculates a pattern density representing the configuration ratio of the pattern in each grid area; a dose calculating unit that uses the pattern density to calculate the dose representing each grid area; a storage unit that stores a function for calculating a charge quantity that uses the film thickness and dose of the resist film as variables; a charge quantity calculating unit that reads the function from the storage unit, and uses the function to calculate the charge quantity based on the film thickness of the resist film formed on the substrate and the dose calculated by the dose calculating unit; a position offset calculating unit that calculates a position offset of a drawing position based on the charge quantity; a correction unit that uses the position offset to correct the irradiation position of the charged particle beam; and a drawing unit that irradiates the charged particle beam to the corrected irradiation position.

[0013] Effects of the Invention

[0014] According to the present invention, the charge amount of a substrate can be calculated quickly and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of a drawing device according to an embodiment of the present invention.

[0016] Figure 2 This is a diagram for explaining how the table moves.

[0017] Figure 3a is a schematic diagram showing ionization in a resist layer, Figure 3bThis is a diagram showing an equivalent circuit simulated by a resist film.

[0018] Figure 4a is a diagram showing a test layout used to measure the resist charging effect. Figure 4b is a schematic diagram of a box array.

[0019] Figure 5 This is a diagram showing an example of the positional shift amount distribution obtained by evaluation of the test layout.

[0020] Figure 6 This is a diagram showing an example of the positional deviation amount distribution obtained by the calculation formula.

[0021] Figure 7a , Figure 7b It is a graph showing the correlation of the position shift amount distribution.

[0022] Figure 8a to Figure 8d It is a graph comparing the evaluation results with the function calculation results.

[0023] Fig. 9 This is a flowchart for explaining the drawing method of this embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a configuration using an electron beam is described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and may be a particle beam or the like.

[0025] Figure 1 This is a schematic diagram of the structure of a drawing device according to an embodiment. Figure 1 The drawing device 100 shown includes a drawing unit W and a control unit C. The drawing device 100 is an example of an electron beam drawing device. The drawing unit W includes an electron lens barrel 1 and a drawing chamber 14. An electron gun 5, an illumination lens 7, a first aperture plate 8, a projection lens 9, a molding deflector 10, a second aperture plate 11, an objective lens 12, an objective lens deflector 13, and an electrostatic lens 15 are arranged in the electron lens barrel 1.

[0026] An XY stage 3 is arranged in the drawing chamber 14. A substrate 2 to be drawn is arranged on the XY stage 3. The substrate 2 includes a photomask for exposure used in semiconductor manufacturing, a semiconductor wafer for forming a semiconductor device, and the like. In addition, the photomask to be drawn includes a mask blank on which nothing has been drawn yet. For example, the substrate 2 includes quartz, a chrome film provided on the quartz, and a resist layer provided on the chrome film. On the XY stage 3, a reflector 4 for measuring the stage position is arranged at a position different from the position where the substrate 2 is arranged.

[0027] On the XY table 3, a calibration mark M is provided at a position different from the position where the substrate 2 is arranged. For example, the mark M is a metal cross shape, and the mark M is scanned by an electron beam, and the reflected electrons from the mark M are detected by a detector (not shown), and focus adjustment, position adjustment, deflection shape correction coefficient adjustment, etc. are performed.

[0028] The control unit C includes control computers 110 and 120 , a stage position detection unit 45 , a stage control unit 46 , a deflection control circuit 130 , a memory 142 , storage devices 21 and 140 such as magnetic disks, etc. The deflection control circuit 130 is connected to the molding deflector 10 and the objective lens deflector 13 .

[0029] The control computer 110 has the functions of a drawing control unit 30 for controlling the entire device, a pattern density distribution calculation unit 32, a dose distribution calculation unit 34, a charge distribution calculation unit 36, and a position shift distribution calculation unit 38. Each unit of the control computer 110 may be composed of hardware including a circuit, a computer, a processor, a circuit substrate, a quantum circuit, or a semiconductor device, or may be composed of software. Input data and calculation results of each unit of the control computer 110 are stored in the memory 142.

[0030] The control computer 120 has the functions of a transmission data generating unit 41 and a position shift correcting unit 42. The transmission data generating unit 41 and the position shift correcting unit 42 may be configured by software or hardware.

[0031] The deflection control circuit 130 has the functions of the forming deflector control unit 43 and the objective lens deflector control unit 44. The forming deflector control unit 43 and the objective lens deflector control unit 44 may be configured by software or hardware.

[0032] The storage device 140 stores drawing data (layout data) that defines a plurality of graphic patterns to be drawn.

[0033] The electron beam 6 emitted from the electron gun 5 (emitting unit) illuminates the entire first aperture plate 8 having a rectangular hole through the illumination lens 7. Here, the electron beam 6 is first shaped into a rectangle. The electron beam 6 of the first aperture image after passing through the first aperture plate 8 is projected onto the second aperture plate 11 by the projection lens 9. The position of the first aperture image on the second aperture plate 11 is deflected by the forming deflector 10 controlled by the forming deflector control unit 43, which can change the beam shape and size (variable forming).

[0034] The electron beam 6 of the second aperture image after passing through the second aperture plate 11 is focused by the objective lens 12, deflected by a deflector (objective lens deflector 13) of, for example, an electrostatic type controlled by the objective lens deflector control unit 44, and irradiated to a desired position of the substrate 2 on the XY table 3 configured to be movable. The XY table 3 is driven and controlled by the table control unit 46. The position of the XY table 3 is detected by the table position detection unit 45. The table position detection unit 45 includes, for example, a laser length measuring device that irradiates a laser to the reflector 4 and measures the position based on the interference between the incident light and the reflected light. The electrostatic lens 15 dynamically corrects the focal position of the electron beam 6 (dynamic focusing) corresponding to the concavoconvexity of the surface of the substrate 2.

[0035] Figure 2 This is a diagram for explaining the movement of the worktable. When drawing on the substrate 2, the XY worktable 3 is continuously moved, for example, in the X direction. The drawing area is virtually divided into a plurality of long strip regions (SR) according to the deflectable width of the electron beam 6. The drawing process is performed in units of the strip regions. The movement of the X direction of the XY worktable 3 is, for example, continuous movement, and the emission position of the electron beam 6 is also caused to follow the movement of the worktable. By continuously moving, the drawing time can be shortened.

[0036] After drawing one stripe area, the XY table 3 is fed in the Y direction and the drawing operation of the next stripe area is performed in the X direction (reverse direction). By making the drawing operation of each stripe area proceed in a serpentine manner, the movement time of the XY table 3 can be shortened.

[0037] In the drawing device 100, when processing the layout data (drawing data), the drawing area is virtually divided into a plurality of long strip-shaped frame areas, and data processing is performed on each frame area. When multiple exposure is not performed, the frame area and the strip area are usually the same area. When multiple exposure is performed, the frame area and the strip area are offset according to the multiplicity. In this way, the drawing area of ​​the substrate 2 is virtually divided into a plurality of frame areas (strip areas) that become drawing unit areas, and the drawing unit W draws each frame area (strip area).

[0038] It is known that when an electron beam is irradiated to the resist layer of the substrate 2, the beam irradiation position is shifted due to the resist charging effect. In this embodiment, the resist film thickness d and the irradiated electron beam dose D are determined in advance to calculate the charge amount on the substrate surface (total charge amount per unit area = charge density). exp The function σ(d, D exp ) and stored in the storage device 21. When performing the drawing process, based on the function σ(d, D exp) is used to calculate the charge, calculate the position offset of the electron beam on the substrate 2, and correct the beam irradiation position.

[0039] For the function σ(d, D exp ) is explained below.

[0040] When the pattern density of the substrate is set to p, the backscatter coefficient is set to η, and the reference dose (the dose when the pattern density is 100%) is set to D 100 In the case of proximity effect correction, the dose D exp It is represented by the following formula (1).

[0041] (1)D exp =D 100 *{(1 / 2+η) / (1 / 2+η*ρ)}

[0042] The number of electrons incident on the resist per unit area is n p Using the elementary charge e, it is expressed by the following equation (2).

[0043] (2)n p =D exp *p / e

[0044] Here, when the energy of the incident electron beam is high (e.g., 50 keV), Figure 3a As shown, the incident electrons themselves almost completely penetrate the resist layer and the light-shielding film layer (such as Cr) and accumulate in the glass layer. In electron beam lithography, usually, the light-shielding film layer is maintained at a ground potential (0V), so the electric field formed by the incident electrons is shielded by the light-shielding film layer and does not contribute to the charging effect of the resist. On the other hand, when the incident electrons pass through the resist layer, they interact with the substances that constitute the resist and ionize in the resist layer. In the case of ionization near the surface of the resist, a part of the electrons generated by the ionization fly toward the side of the drawing chamber and become secondary electrons, generating holes in the place where the electrons originally existed. At this time, the probability of generating a secondary electron / hole pair relative to one incident electron (secondary electron emission probability) is set to α.

[0045] When ionization occurs inside the resist, multiple electron-hole pairs are generated. Figure 3a As shown in the figure, the electric fields generated by them cancel each other out, so these charges do not contribute to the charging of the resist. However, since the carrier concentration inside the resist increases, the electron beam induced conduction phenomenon described later occurs. Since the electron-hole pairs recombine and disappear immediately after they are generated, electrical conduction occurs only during beam irradiation and disappears when beam irradiation ends.

[0046] Assume that the number of secondary electrons generated by the resist surface is n SEThe same number of holes (hall), in n p When electrons are incident on the resist, the number of holes generated on the resist surface is n. h It is represented by the following formula (3).

[0047] (3)n h =n SE =n p *α

[0048] Next, consider the holes accumulated on the resist surface. When electrical conduction occurs inside the resist due to the EBIC (Electron Beam Induced Conductivity) effect, the resist layer can be considered as Figure 3b The equivalent circuit (RC circuit) shown in FIG. 1 is a circuit diagram of an electron beam. The charge accumulated in the capacitor of the equivalent circuit becomes the charge accumulated on the surface of the resist. The charge Q(t) can be expressed by the general charging formula (4) of the RC circuit. In formula (4), t represents the irradiation time of the electron beam, C represents the electrostatic capacitance per unit area of ​​the resist, and R represents the conductivity that appears only when the beam is irradiated due to the EBIC effect. I is the charge supplied per unit time, which is considered to be the holes supplied by the detachment of secondary electrons from the resist.

[0049] (4)Q(t)=RCI{1-exp(-t / RC)}

[0050] If the charge I is considered per unit area, it can be replaced as in the following equation (5) using the current density J of the incident electron beam.

[0051] (5) I = αJ

[0052] As described above, since the equivalent circuit is completed due to the EBIC effect only during beam irradiation, t in equation (4) is replaced by the irradiation time in the equation shown in the following equation (6).

[0053] (6) t = en p / J

[0054] Therefore, n p The total charge amount of holes when electrons are incident on the resist is expressed by the following formula (7).

[0055] (7)Q(n p )=αJRC{1-exp(-en p / JRC)}

[0056] The number of holes accumulated on the resist surface is n rh By Q(n p ) divided by the elementary charge e. Thus, n rhIt is represented by the following equation (8). If the dielectric constant of the resist is ε, the thickness of the resist is d, and the resistivity of the resist during beam irradiation is ρ, then C=ε / d, R=ρd, and thus it can be replaced by RC=ρε.

[0057] (8)n rh =αJRC{1-exp(-en p / JRC)} / e

[0058] =αJρε{1-exp(-en p / Jρε)} / e

[0059] Among the secondary electrons generated by the electron beam irradiation, the secondary electrons with energy below the surface potential Vs of the resist are pulled back to the resist and contribute to the charging. Therefore, it is necessary to consider the number n of secondary electrons accumulated on the resist surface. rSE . In the case of increasing the irradiated electrons by dn p The secondary electrons generated are set as dn SE In the case of rSE It is represented by the following equation (9). P(E) in equation (9) is the generation probability (spectrum) of secondary electrons of energy E, and is represented by the following equation (10).

[0060] (9)

[0061] ∴

[0062] (10)∫0 ∞ P(E)dE=1

[0063] The surface potential Vs of the resist can be expressed by the following formula (11) using the charge amount on the resist surface and the electrostatic capacitance of the resist.

[0064] (11)Vs=e(n rh -n rSE ) / C

[0065] By substituting equation (11) into equation (9) and replacing it with C=ε / d, the following equation (12) is obtained as a differential equation.

[0066] (12)

[0067] It is known that the standardized secondary electron emission spectrum P(E) can be expressed by the following formula (13) (BL Henke, et.al., Journal of Applied Physics 48, 1852 (1977); "0.1-10-keV x-ray-induced electron emissions from solids-Models and secondary electron measurements".) In formula (13), W is the work function of the resist.

[0068] (13) P(E) = 2W 2 E / (E+W) 4

[0069] In drawing for correction of charging effect, it is known that by taking into account the attenuated charge amount, a higher precision drawing can be performed (for example, Japanese Patent Gazette No. 5480555). Therefore, it is preferable to find the charge amount after sufficient time has passed since drawing. At this time, consider the case where the holes accumulated in the holes of the resist and near the chromium film located in the lower layer of the resist move toward the chromium film and decay. Therefore, it is assumed that regardless of the pattern density, the holes located at a certain distance from the chromium film move toward the chromium film, and the number of accumulated holes decreases. The number of holes accumulated after decay n rh(static) It can be expressed by the following formula (14). In the formula (14), β is the residual rate of holes after decay.

[0070] (14)n rh(static) =βn rh

[0071] In addition, since the secondary electrons are accumulated on the resist surface and away from the chromium film, it is considered that they do not decay.

[0072] Function σ(d, D exp ) is represented by the following formula (15). It uses the above formulas (2), (8), (12), (13), and (14) as a parameter group representing the physical properties of the resist to determine the secondary electron emission probability α, the dielectric constant ε of the resist, the resistivity ρ of the resist during beam irradiation, the work function W of the resist, and the residual rate of holes after attenuation β, thereby obtaining the film thickness d of the resist and the dose D exp As a function of a variable. For at least one substrate with a film thickness, the function σ(d, D exp ) is fitted with the experimental results of the relationship between the exposure amount per unit and the charge amount obtained in advance by drawing and evaluating, thereby determining the secondary electron emission probability α, dielectric constant ε, resistivity ρ, work function W, and residual rate β.

[0073] (15)

[0074] Substrates (mask blanks) on which the following four types of resists A to D with different film thicknesses or dose sensitivities were prepared were prepared. The relationship between the dose and the charge amount was evaluated by plotting and compared with the result based on the function σ(d, D exp ) are compared with the calculation results.

[0075] Resist A: Film thickness 300nm, dose sensitivity ~7μC / cm 2

[0076] Resist B: Film thickness 165nm, dose sensitivity ~23μC / cm 2

[0077] Resist C: Film thickness 80nm, dose sensitivity ~60μC / cm 2

[0078] Resist D: Film thickness 80nm, dose sensitivity ~100μC / cm 2

[0079] Function σ(d, D exp ) parameters use the following values.

[0080] α=0.036

[0081] ρ=13.6[Ωm]

[0082] β=0.65

[0083] ε=3.1*ε0 (dielectric constant 3.1, ε0: dielectric constant of vacuum)

[0084] W=3.0[eV]

[0085] The resist charge amount (charge amount per unit area) during electron beam irradiation can be measured by drawing evaluation as follows, for example, in the same method as disclosed in Examples of Japanese Patent No. 5480555. Figure 4a FIG. 1 is a diagram showing a test layout used to measure the resist charging effect. Figure 4a In order to make it easier to understand the contents of each part, the scale is changed.

[0086] for Figure 4a The test layout TL shown in FIG. 1 is a test layout TL in which a dose D is applied to the center of the test layout TL. expAn irradiation pad with a pattern density p having a side length L3 of 10 mm is drawn. Just after the irradiation pad is drawn, the first box array is drawn on a grid (81×81 grid) having a pitch L1 of 200 μm and a side length L2 of 20 mm. Then, after sufficient time has passed since the irradiation pad was drawn (for example, 10 minutes), the second box array is drawn on the same grid as the first box array, thereby obtaining a test layout TL.

[0087] like Figure 4b As shown in the enlarged view in FIG. 1 , the first cell array is a square pattern with a length L4 of 4 μm on one side, for example. The second cell array is a frame-shaped pattern with a length L5 of 14 μm on one side and a larger size than the first cell array with a hollowed-out center.

[0088] In this way, by measuring the positions of the first and second box arrays drawn, the position deviation distributions P1 and P2 caused by the charging effect of the irradiation pad from the design position are obtained. P1 is drawn immediately after the irradiation pad is charged, so it can be used to evaluate the charge amount just after irradiation, and P2 is drawn after a sufficient time has passed after the irradiation pad is charged, so it can be used to evaluate the charge amount after attenuation.

[0089] Figure 5 This is an example of the positional shift amount distribution obtained by evaluating such a test layout.

[0090] The charge amount can be obtained from the positional deviation distribution as follows using the response function r(x, y) assumed for calculating the positional deviation from the charge amount distribution. First, as shown in the following equation (16), by setting the area on the irradiation pad to 1 nC / cm 2 , the convolution integral of the function C0(x, y) which is zero in the area outside the irradiation pad and the response function r(x, y) is calculated by assuming that the irradiation pad is uniformly irradiated at 1nC / cm 2 Position deviation distribution P0 when powered.

[0091] (16)

[0092] Figure 6 is the distribution of the position offset P0 obtained from the above formula.

[0093] The charge amount of the irradiation amount pad can be obtained from the slopes when P0 is correlated with P1 and P2 which are measurement results.

[0094] Figure 7a , Figure 7b It means that the dose is 23μC / cm 2The correlation curves of P1 and P2 with P0 when the irradiation pad is irradiated with a pattern density of 25%. As a result of linear approximation of the correlation, the slopes are 1.57 and 0.75 respectively. This indicates that the positional shift of P1 and P2 is related to the irradiation pad being irradiated with a density of 1 nC / cm 2 The positional shifts of the model when charged are set to be the same when the 1.57 and 0.75 times are equal, so it can be seen that the irradiation pad is 1.57nC / cm 2 and 0.75nC / cm 2 charged.

[0095] exist Figure 8a to Figure 8d The results obtained by plotting the evaluation and the function σ(d, D exp ) calculation results. The horizontal axis of the curve graph of each figure represents the dose, and the vertical axis represents the charge amount. The marks on the curve graph of each figure represent the results obtained by drawing and evaluating, and the solid line represents the function σ(d, D exp ) is the calculated value of Figure 8a to Figure 8d In the figure, the horizontal axis is D for the charge amount represented by the mark. exp *p is used to describe the pattern density p and dose D in each substrate exp The values ​​obtained by various changes and evaluation through the above plotting were obtained.

[0096] The quadrilateral marks indicate immediately after drawing, and the triangular marks indicate after attenuation. From this result, it can be confirmed that if the physical properties of the resist do not change, even if the film thickness and sensitivity of the resist change, the function σ(d, D) determined by the same parameter group can be used. exp ) Calculate the charge with high precision.

[0097] The resist is composed of a base polymer and a small amount of a dissolution inhibitor and an oxygen-generating material, and most of the volume of the resist is occupied by the base polymer. Therefore, it is considered that the physical properties of the resist related to the charge during beam irradiation recorded in the model of this embodiment are determined only by the properties of the polymer. Therefore, for the four substrates with different sensitivities, the charge amount can be calculated using a function determined by the same parameters. That is, in this embodiment, as long as there is no significant change in the polymer composition such as a change in the physical properties of the resist such as the secondary electron emission probability α, the dielectric constant ε, and the work function W, for various substrates whose sensitivity is changed by changing the film thickness of the resist or the concentration of additives such as the oxygen generator, the function σ(d, D) using the same parameters can be used. exp ) quickly and accurately calculate the charge.

[0098] exist Figure 1 The storage device 21 of the rendering device 100 shown in the figure stores the function σ(d, D exp), a parameter group representing the physical properties of the resist formed on the substrate 2.

[0099] Fig. 9 This is a flowchart for explaining the drawing method of this embodiment. The method includes a pattern density distribution calculation process (step S100), a dose distribution calculation process (step S102), a charge distribution calculation process (step S104), a position offset distribution calculation process (step S106), a deflection position correction process (step S108), and a drawing process (step S110).

[0100] In the pattern density distribution calculation process (step S100), the pattern density distribution calculation unit 32 reads the drawing data from the storage device 140, virtually divides the drawing area (or frame area) into grids with a predetermined size (grid size), and calculates the pattern density representing the arrangement ratio of the graphic pattern defined in the drawing data for each grid area. Then, the distribution of the pattern density of each grid area is generated.

[0101] In the dose distribution calculation step (step S102), the dose distribution calculation unit 34 calculates the dose D for each grid area using the pattern density distribution. exp Distribution of Dose D exp It can be calculated by the above formula (1).

[0102] In the charge distribution calculation step (step S104), the charge distribution calculation unit 36 ​​reads the function σ(d, D exp ) and parameter group, in setting the function σ(d, D exp ), the film thickness d of the resist formed on the substrate 2 and the dose D calculated in step S102 are substituted. exp , calculate the distribution of charge in each grid area.

[0103] In the position shift amount distribution calculation process (step S106), the position shift amount distribution calculation unit 38 (position shift amount calculation unit) calculates the position shift amount based on the charge amount distribution. Specifically, the position shift amount distribution calculation unit 38 calculates the position shift amount of the drawing position caused by the charge amount at each position of the charge amount distribution by convolving the charge amount distribution calculated in step S104 with the response function r (x, y).

[0104] Assume that the charge distribution is converted into a response function r(x, y) of the position offset distribution. Here, (x', y') represents the charged position represented by each position of the charge distribution, and (x, y) represents the beam irradiation position of the corresponding frame area currently undergoing data processing. Here, the position offset of the beam can be expressed as a function of the distance from the beam irradiation position (x, y) to the charged position (x', y'), so the response function can be described as r(x-x', y-y'). The response function r(x-x', y-y') can be obtained in advance by conducting experiments in advance in a manner consistent with the experimental results, or by numerical calculation. In the following, (x, y) represents the beam irradiation position of the corresponding frame area currently undergoing data processing.

[0105] Then, the positional deviation distribution calculation unit 38 generates a positional deviation distribution based on the positional deviation of each position (x, y) of the frame region to be drawn. The generated positional deviation distribution is stored in the storage device 21 and output to the control computer 120.

[0106] On the other hand, in the control computer 120, the emission data generating unit 41 reads the depiction data from the storage device 140, performs multi-stage data conversion processing, and generates the emission data of the format inherent to the drawing device 100. The size of the graphic pattern defined in the depiction data is usually larger than the emission size that the drawing device 100 can form by one emission. Therefore, in the drawing device 100, each graphic pattern is divided (emission division) into a plurality of emission graphics to become the size that the drawing device 100 can form by one emission. Then, for each emission graphic, the data such as the graphic code, coordinates and size representing the type of graphics are defined as the emission data.

[0107] In the deflection position correction process (step S108) (position offset correction process), the position offset correction unit 42 uses the position offset calculated in step S106 to correct the irradiation position. Here, the emission data of each position is corrected. Specifically, each position (x, y) of the emission data is added to the correction value of the position offset shown in the correction position offset distribution. The correction value, for example, preferably uses a value that makes the positive and negative signs of the position offset shown in the position offset distribution opposite. Thus, in the case of irradiating the electron beam 6, the coordinates of the irradiation destination are corrected, and therefore, the deflection position deflected by the objective lens deflector 13 is corrected. The emission data is defined in the data file in a manner arranged in the order of emission.

[0108] In the drawing process (step S110), in the deflection control circuit 130, according to the emission order, the forming deflector control unit 43 calculates the deflection amount of the forming deflector 10 for making the electron beam 6 variable-shaped according to the type and size of the pattern defined in the emission data for each emission pattern. In addition, the objective lens deflector control unit 44 calculates the deflection amount of the objective lens deflector 13 for deflecting to the position on the substrate 2 that irradiates the emission pattern. In other words, the objective lens deflector control unit 44 (deflection amount calculation unit) calculates the deflection amount for deflecting the electron beam to the corrected irradiation position. Then, the objective lens deflector 13 arranged in the electron lens barrel 1 deflects the electron beam according to the calculated deflection amount, thereby irradiating the electron beam to the corrected irradiation position. Thus, the drawing unit W draws the pattern at the charged corrected position of the substrate 2.

[0109] In this embodiment, if the physical properties of the resist such as the secondary electron emission probability α, the dielectric constant ε, and the work function W remain unchanged, the same function σ(d, D exp ) quickly and accurately calculates the charge amount. This can shorten the downtime of the device associated with the substrate change.

[0110] For example, when a substrate with a different resist film thickness is intentionally used, the changed resist film thickness can be substituted into the function σ(d, D exp )

[0111] In the case where the resist film thickness unexpectedly changes between multiple substrates, the resist film thickness can also be measured regularly, and the resist film thickness of the substrate currently used can be predicted based on the change in the resist film thickness of the substrate used in the past, and the predicted value can be substituted into the function σ(d, D exp ).

[0112] When the resist film thickness distribution occurs in one substrate, the film thickness distribution can be measured in advance, and the film thickness at the position where the charge amount is calculated can be substituted into the function σ(d, D exp ). A measuring device for measuring the film thickness of the resist may be provided in the drawing apparatus.

[0113] The displacement of the irradiation position due to the charging phenomenon is not limited to the electron beam imaging device. The present invention can be applied to a charged particle beam device that uses the result obtained by irradiating a target position with a charged particle beam, such as an electron beam, or the like.

[0114] In the above embodiment, a positive potential is preferably applied to the lower surface of the objective lens 12 (objective optical system) to reduce the influence of fog charging caused by electrons scattered in the drawing chamber falling onto the substrate, and direct charging caused by the irradiated electron beam becomes dominant to prevent secondary electrons from returning to the substrate surface.

[0115] While the present invention has been described in detail using specific embodiments, it will be apparent to one skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention.

[0116] This application is based on Japanese Patent Application No. 2020-78344 filed on April 27, 2020, the entire contents of which are incorporated herein by reference.

[0117] Explanation of symbols

[0118] 1: electron lens barrel; 2: substrate; 3: XY table; 4: reflector; 5: electron gun; 6: electron beam; 7: illumination lens; 8: 1st aperture plate; 9: projection lens; 10: deflector; 11: 2nd aperture plate; 12: objective lens; 13: deflector; 14: drawing chamber; 15: electrostatic lens; 21, 140: storage device; 30: drawing control unit; 32: pattern density distribution calculation unit; 34: dose distribution calculation unit; 36: charge distribution calculation unit; 38: position offset distribution calculation unit; 41: emission data generation unit; 42: position offset correction unit; 43: molding deflector control unit; 44: objective lens deflector control unit; 45: table position detection unit; 46: table control unit; 100: drawing device.

Claims

1. A charged particle beam drawing method, wherein a charged particle beam is deflected by a deflector, and a substrate having a resist film formed thereon is irradiated with the charged particle beam to draw a pattern, comprising: A step of virtually dividing the drawing area of ​​the substrate into a grid shape and calculating a pattern density representing a configuration ratio of the pattern in each grid area; a step of calculating the dose for each grid area using the above pattern density; A step of calculating the charge amount based on the thickness of the resist film formed on the substrate and the calculated dose using a function for calculating the charge amount that uses the previously determined film thickness and dose of the resist film as variables; A step of calculating a positional deviation amount of a drawing position based on the calculated charge amount; and a step of correcting the irradiation position of the charged particle beam using the positional deviation, The function for calculating the charge amount is determined by parameters representing the physical properties of the resist film, the physical properties including at least one of the secondary electron emission probability, dielectric constant, resistivity during beam irradiation, work function, and hole residual rate of the resist. The function for calculating the charge amount can calculate the charge amount even when the dose sensitivity of the resist film is different.

2. The charged particle beam drawing method according to claim 1, characterized in that: The charge amount is calculated based on the film thickness distribution of the resist film formed on the substrate and the function for calculating the charge amount.

3. The charged particle beam drawing method according to claim 1, characterized in that: Regularly measure the resist film thickness. Based on the change in the resist film thickness of substrates on which patterns have been drawn in the past, the resist film thickness of the substrate to be drawn is predicted. The charge amount is calculated based on the predicted value of the resist film thickness and the above-mentioned function for charge amount calculation.

4. A charged particle beam drawing device, which deflects a charged particle beam by a deflector and irradiates the charged particle beam to a substrate on which a resist film is formed to draw a pattern, comprising: An emitting unit, emitting the charged particle beam; A pattern density calculation unit that virtually divides the drawing area of ​​the substrate into a grid shape and calculates a pattern density representing a configuration ratio of the pattern in each grid area; a dose calculation unit that calculates a dose representing a dose for each grid area using the pattern density; a storage unit storing a function for calculating the charge amount using the film thickness and the dose of the resist film as variables; a charge amount calculation unit that reads the function from the storage unit and uses the function to calculate the charge amount based on the film thickness of the resist film formed on the substrate and the dose calculated by the dose calculation unit; a position shift amount calculation unit that calculates a position shift amount of a drawing position based on the charge amount; a correction unit that corrects an irradiation position of the charged particle beam using the position shift amount; and a drawing unit that irradiates the charged particle beam to the corrected irradiation position; The function for calculating the charge amount is determined by parameters representing the physical properties of the resist film, the physical properties including at least one of the secondary electron emission probability, dielectric constant, resistivity during beam irradiation, work function, and hole residual rate of the resist. The function for calculating the charge amount can calculate the charge amount even when the dose sensitivity of the resist film is different.

5. The charged particle beam drawing device according to claim 4, characterized in that: The charge amount calculation unit calculates the charge amount based on a film thickness distribution of the resist film formed on the substrate and the charge amount calculation function.

6. The charged particle beam drawing device according to claim 4, characterized in that: The charge amount calculation unit predicts the resist film thickness of the substrate to be drawn based on changes in the resist film thickness of substrates on which patterns have been drawn in the past, and calculates the charge amount based on the predicted value of the resist film thickness and the charge amount calculation function.

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