JP2012023279A - Charged particle beam lithography apparatus and charged particle beam lithography method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus which is for calculating an irradiation amount for correcting a proximity effect and a loading effect and is capable of judging whether a combination of a plurality of tolerances which are input is proper.SOLUTION: A lithography apparatus 100, which is a charged particle beam lithography apparatus including a pattern size correction function by irradiation amount control, includes an irradiation amount calculation unit 10 to which tolerances for a plurality of proximity effect densities as a coefficient indicating a relation between a pattern size and an irradiation amount of a charged particle beam are input, and which calculates the irradiation amount in relation to each proximity effect density for a predetermined pattern size correction amount from the tolerance of each proximity effect density, based on a first equation using the tolerance as a parameter. The apparatus further includes: a fitting operation part 12 fitting the irradiation amount for each tolerance, which is calculated based on the first equation using the tolerance, based on a second equation not using the tolerance as a parameter; and a judgment part 14 judging whether or not the tolerances for the plurality of input proximity effect densities are proper values, using the fitting results.

Description

  The present invention relates to a charged particle beam drawing apparatus and a charged particle beam drawing method, and for example, relates to a method for determining the appropriateness of tolerance used as an input parameter in electron beam drawing.

  Lithography technology, which is responsible for the progress of miniaturization of semiconductor devices, is an extremely important process for generating a pattern among semiconductor manufacturing processes. In recent years, with the high integration of LSI, circuit line widths required for semiconductor devices have been reduced year by year. In order to form a desired circuit pattern on these semiconductor devices, a highly accurate original pattern (also referred to as a reticle or a mask) is required. Here, the electron beam (electron beam) drawing technique has an essentially excellent resolution, and is used for producing a high-precision original pattern.

FIG. 7 is a conceptual diagram for explaining the operation of a conventional variable shaping type electron beam drawing apparatus.
The variable shaped electron beam (EB) drawing apparatus operates as follows. In the first aperture 410, a rectangular opening for forming the electron beam 330, for example, a rectangular opening 411 is formed. Further, the second aperture 420 is formed with a variable shaping opening 421 for shaping the electron beam 330 having passed through the opening 411 of the first aperture 410 into a desired rectangular shape. The electron beam 330 irradiated from the charged particle source 430 and passed through the opening 411 of the first aperture 410 is deflected by the deflector, passes through a part of the variable shaping opening 421 of the second aperture 420, and passes through a predetermined range. The sample 340 mounted on a stage that continuously moves in one direction (for example, the X direction) is irradiated. That is, the drawing area of the sample 340 mounted on the stage in which the rectangular shape that can pass through both the opening 411 of the first aperture 410 and the variable shaping opening 421 of the second aperture 420 is continuously moved in the X direction. Drawn on. A method of creating an arbitrary shape by passing both the opening 411 of the first aperture 410 and the variable shaping opening 421 of the second aperture 420 is referred to as a variable shaping method (VSB method).

  In the above-described electron beam drawing, line width uniformity within a sample surface, for example, a mask surface with higher accuracy is required. Here, in such electron beam drawing, when a circuit pattern is drawn by irradiating a resist-coated mask with an electron beam, the electron beam passes through the resist layer and reaches the layer below it, and then reappears on the resist layer again. A phenomenon called a proximity effect due to incident backscattering occurs. Thereby, at the time of drawing, the dimension fluctuation | variation which will be drawn in the dimension shifted | deviated from the desired dimension will arise. On the other hand, even when development or etching after drawing is performed, a dimensional variation called a loading effect due to the density of the circuit pattern occurs.

The irradiation amount of the electron beam corrected for the proximity effect and the loading effect is, for example, a reference dose D _base , a proximity effect correction coefficient η for correcting the proximity effect, a pattern area density ρ, or a proximity depending on the proximity effect density U. It is calculated by an equation using the effect correction dose Dp (η, U), the pattern dimension error ΔCD, and the tolerance DL as parameters. Therefore, the irradiation amount of the beam with which the proximity effect and the loading effect are corrected is obtained by inputting, as parameters, a plurality of tolerance sets in which the proximity effect density U is changed to the drawing apparatus.

  However, conventionally, it has not been determined whether or not a plurality of input tolerance sets are appropriate values. For this reason, there are cases where the proximity effect and the loading effect cannot be corrected with high accuracy when drawing with the calculated dose.

Here, there is a proximity effect correction coefficient η with which the proximity effect correction matches well for each reference dose D _base . Therefore, without inputting the tolerance as a parameter, changing the set of the reference irradiation amount D _base and the proximity effect correction coefficient η and maintaining the proximity effect correction, the irradiation dose corrected in accordance with the dimensional variation due to the loading effect is also obtained. A calculation method is disclosed (for example, see Patent Document 1).

JP 2007-150423 A

  As described above, conventionally, it has not been determined whether or not a plurality of tolerance sets input from the user side are appropriate values. For this reason, there is a problem that the proximity effect and the loading effect may not be corrected with high accuracy when drawing is performed with the dose obtained using a set of input tolerances. Further, conventionally, a sufficient method for determining whether or not a plurality of input tolerance sets are appropriate values has not been established.

  Therefore, the present invention can determine whether or not a combination of a plurality of input tolerances is appropriate for overcoming the above-described problems and calculating a dose for correcting the proximity effect and the loading effect. An object is to provide an apparatus and method.

A charged particle beam drawing apparatus according to one embodiment of the present invention includes:
A charged particle beam drawing apparatus having a pattern dimension correction function by irradiation amount control,
A tolerance for each of a plurality of proximity effect densities, which is a coefficient indicating the relationship between the pattern dimension and the irradiation amount of the charged particle beam, is input, and the first expression using the tolerance as a parameter is a predetermined pattern dimension correction amount. A dose calculation unit for calculating the dose for each proximity effect density from the margin of each proximity effect density;
A fitting calculation unit that fits the irradiation amount for each tolerance calculated by the first equation using the tolerance using the second equation that does not use the tolerance as a parameter;
Using the fitting result, a determination unit that determines whether the tolerance for each of the plurality of input proximity effect densities is an appropriate value,
It is provided with.

  With this configuration, by fitting each dose calculated by the first formula using the second formula, the difference between each dose calculated by the first formula and each dose after fitting is compared. Can do.

  In addition, it is preferable to further include a tolerance function calculation unit that calculates a tolerance function depending on the proximity effect density using the fitting result.

  In addition, it is preferable that the fitting calculation unit calculates the parameter of the second expression using the tolerance for each of the plurality of proximity effect densities that is input during the fitting.

  Further, it is preferable that the reference irradiation amount and the proximity effect correction coefficient are used as the parameters of the second equation.

The charged particle beam drawing method of one embodiment of the present invention includes:
A charged particle beam writing method performed using a charged particle beam writing apparatus having a pattern dimension correction function by irradiation amount control,
A tolerance for each of a plurality of proximity effect densities, which is a coefficient indicating the relationship between the pattern dimension and the irradiation amount of the charged particle beam, is input, and the first expression using the tolerance as a parameter is a predetermined pattern dimension correction amount. Calculating a dose for each proximity effect density from the margin of each proximity effect density;
Fitting the irradiation amount for each tolerance calculated by the first equation using the tolerance by the second equation not using the tolerance as a parameter;
Using the fitting result, determining whether the tolerance for each of the plurality of input proximity effect densities is an appropriate value, and outputting the result;
It is provided with.

  According to one aspect of the present invention, it is possible to determine whether or not a combination of a plurality of input tolerances for calculating a dose for correcting the proximity effect and the loading effect is appropriate. Therefore, the irradiation dose can be calculated using a combination of appropriate margins. As a result, highly accurate drawing can be performed.

1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to Embodiment 1. FIG. 3 is a graph showing an example of a relationship between a pattern dimension and an irradiation amount in the first embodiment. FIG. 4 is a flowchart showing main steps of the drawing method according to Embodiment 1. 6 is a graph showing an example of a relationship between an irradiation amount and a proximity effect density in the first embodiment. 4 is a graph showing an example of a ratio of an irradiation amount in Expression (2) and an irradiation amount in Expression (1) in Embodiment 1. 6 is a graph showing an example of an interpolated tolerance function DL (U) in the first embodiment. It is a conceptual diagram for demonstrating operation | movement of the conventional variable shaping type | mold electron beam drawing apparatus.

  Hereinafter, in the embodiment, a configuration using an electron beam will be described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam, and a beam using charged particles such as an ion beam may be used. Further, a variable shaping type drawing apparatus will be described as an example of the charged particle beam apparatus.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to the first embodiment. In FIG. 1, the drawing apparatus 100 includes a drawing unit 150 and a control unit 160. The drawing apparatus 100 is an example of a charged particle beam drawing apparatus. In particular, it is an example of a variable shaping type (VSB type) drawing apparatus. The drawing unit 150 includes an electron column 102 and a drawing chamber 103. In the electron column 102, there are an electron gun 201, an illumination lens 202, a blanking deflector 212, a blanking aperture 214, a first shaping aperture 203, a projection lens 204, a deflector 205, a second shaping aperture 206, an objective. A lens 207, a main deflector 208, and a sub deflector 209 are disposed. An XY stage 105 that can move at least in the XY direction is disposed in the drawing chamber 103. On the XY stage 105, a sample 101 to be drawn is arranged. The sample 101 includes an exposure mask and a silicon wafer for manufacturing a semiconductor device. Masks include mask blanks. Further, a resist film that is exposed to an electron beam is formed on the mask to be drawn.

  The control unit 160 includes a control computer 110, a memory 111, a control circuit 120, and storage devices 140, 142, 144, 146, 148 such as a magnetic disk device. The control computer 110, the memory 111, the control circuit 120, and the storage devices 140, 142, 144, 146, and 148 such as a magnetic disk device are connected to each other via a bus (not shown).

  The drawing apparatus 100 has a pattern dimension correction function by dose control. Such a function is executed in the control computer 110. Further, in the control computer 110, an irradiation amount calculation unit 10, a fitting calculation unit 12, a determination unit 14, a tolerance DL (U) calculation unit 16, an irradiation amount calculation unit 18, a proximity effect density calculation unit 20, and drawing data A processing unit 22 is arranged. The functions such as the dose calculation unit 10, the fitting calculation unit 12, the determination unit 14, the tolerance DL (U) calculation unit 16, the dose calculation unit 18, the proximity effect density calculation unit 20, and the drawing data processing unit 22 are programmed. Such software may be used. Alternatively, it may be configured by hardware such as an electronic circuit. Alternatively, a combination thereof may be used. The input data necessary for the control computer 110 or the calculated result is stored in the memory 111 each time. Here, FIG. 1 shows a configuration necessary for explaining the first embodiment. The drawing apparatus 100 may normally have other necessary configurations. For example, the main and sub two-stage main deflector 208 and sub-deflector 209 are used here, but one stage or three or more stages of deflectors may be used.

  The storage device 140 stores drawing data necessary for drawing such as a pattern layout, a graphic code, and coordinates from the outside. A plurality of tolerances DL (U) are input to the storage device 142 as parameters. First, for each proximity effect density U, correlation data between the pattern dimension CD and the dose D is acquired by experiments. Here, the proximity effect density U (x, y) is obtained by convolving and integrating the distribution function g (x, y) with the pattern area density ρ (x, y) in the proximity effect mesh within the range of the influence range of the proximity effect. Defined by value. The proximity effect mesh preferably has a size of, for example, about 1/10 of the influence range of the proximity effect, and for example, a size of about 1 μm is preferable. For example, a Gaussian function may be used as the distribution function g (x, y). Both x indicating the position in the x direction and y indicating the position in the y direction indicate a vector.

  FIG. 2 is a graph showing an example of the relationship between the pattern dimension and the dose in the first embodiment. In FIG. 2, the vertical axis indicates the dimension CD of the pattern drawn by the electron beam. The horizontal axis indicates the logarithm (log) of the irradiation amount of the electron beam. Here, for example, the proximity effect density U (x, y) = 0 (0%), 0.5 (50%), and 1 (100%) are obtained by experiments. Since the proximity effect density U (x, y) = 0 actually means that there is no pattern, it is approximated by drawing one line pattern for measurement in a state where there is nothing around. Can do. On the contrary, the proximity effect density U (x, y) = 1 is a pattern in the entire mesh including the periphery and the dimension cannot be measured. Therefore, the measurement line pattern is filled with the pattern filled with the periphery. For example, it can be obtained by approximation by drawing one. Also, for example, assuming a density of 50%, when a 1: 1 line and space pattern is drawn, the mesh size is small, so only one line pattern is used for one mesh, and only a space pattern is used for the adjacent mesh. Things can happen. In such a case, the pattern area density ρ (x, y) directly becomes the density in the mesh regardless of the surroundings. On the other hand, by using the proximity effect density U (x, y), each mesh can be calculated as a density of 50%. Here, the proximity effect density U (x, y) to be set is not limited to 0%, 50%, and 100%. For example, it is also preferable to use any one of 10% or less, 50%, and 90% or more. Moreover, you may measure by not only three types but another number. For example, four or more types may be measured.

  The tolerance DL (U) indicates the relationship between the pattern dimension CD and the dose D (U). The tolerance DL (U) depends on the proximity effect density U (x, y) and is defined by, for example, the slope (proportional coefficient) of the graph for each proximity effect density U (x, y) in FIG. In the example of FIG. 2, the logarithm of the dose D is shown on the horizontal axis, so that a graph close to a straight line can be obtained, which is a proportional coefficient, but is not limited thereto. The margin DL (U) only needs to be defined as a parameter (coefficient) indicating the relationship between the pattern dimension CD and the dose D (U).

  A plurality of tolerances DL (U) are input to the storage device 142 from the user side (outside the device) and stored. Here, the tolerance DL (Ui) in each case of the proximity effect density U (x, y) = 0 (0%), 0.5 (50%), 1 (100%) is input. Here, the tolerance DL (Ui) with respect to the proximity effect density U (x, y) of 3 points is input, but as long as it is 3 points or more, it may be 4 points or more.

  In addition, a pattern dimension correction amount ΔCD for correcting a pattern dimension error caused by the loading effect is input from the outside, and the input pattern dimension correction amount ΔCD is stored in the storage device 144. Such a pattern dimension correction amount ΔCD can be assumed from experience to some extent depending on the type of resist material applied on the sample 101 to be drawn, the type of developing device after drawing, and the like.

The electron beam dose D (U) corrected for the proximity effect and loading effect is, for example, the proximity reference dose D _base , the proximity effect correction coefficient η for correcting the proximity effect, the pattern area density ρ, or the proximity effect density. The proximity effect correction dose Dp (η, U) depending on U, the pattern dimension correction amount ΔCD, and the tolerance DL can be defined by the following equation (1). Here, the proximity reference dose D _base and the proximity effect correction coefficient η in the equation (1) are set as a set of values for correcting pattern dimension errors caused by the proximity effect, and the tolerance DL is set for each proximity effect density. The relationship between an irradiation amount and a pattern dimension is shown. As the pattern dimension correction amount ΔCD, a correction amount for correcting a pattern dimension error caused by the loading effect is set.

  In the drawing apparatus 100, the proximity effect and the loading effect are corrected by calculating the optimal dose D (U) using the equation (1). For this reason, if the tolerance DL input from the user side is not appropriate, the calculated dose D (U) may not be an appropriate value. For example, when the proximity effect density U (x, y) = 1 (100%) and the tolerance DL (U1) is set to a value larger than an appropriate value, the proximity effect density U (x, y) = 1 ( 100%) is thicker (larger) than the other proximity effect density U (x, y) patterns. Therefore, the correction for the proximity effect and the loading effect is shifted. Therefore, it is desired to detect whether the tolerance DL input from the user side is appropriate. Therefore, in the first embodiment, it is determined whether or not the set of tolerance DL input from the user side is appropriate before drawing. If it is inappropriate, the appropriate value is re-input.

Here, the irradiation dose D (U) of the electron beam corrected for the proximity effect and the loading effect is, for example, a reference dose D ′ _base , a proximity effect correction coefficient η ′ for correcting the proximity effect, and a pattern area density ρ. Or it can also define with the following formula | equation (2) used as a product with proximity effect correction | amendment dose Dp ((eta '), U) depending on the proximity effect density U. FIG.

For example, when the proximity effect density U (x, y) is 50% as the reference proximity effect density, the correlation data between the proximity effect correction coefficient η and the reference dose D _{base at} which the pattern dimension CD is constant at the reference proximity effect density is obtained. calculate. This correlation data is obtained as a relationship between D _base , η, the size of the reference proximity effect density, and the size of other proximity effect densities (for example, 0% and 100%). From this correlation data, it is possible to obtain the reference doses D _base and η that minimize the dimensional difference between the proximity effect densities. Similar correlation data is obtained for irradiation conditions with different reference proximity effect density pattern dimensions. As a result, D _base and η with which proximity correction is well suited are obtained for each different pattern dimension. Such correlation data may be stored in the storage device 144, for example. In Equation (2), a set of the reference dose D ′ _base and the proximity effect correction coefficient η ′ corresponding to the pattern size after correcting the proximity effect and the loading effect may be set with reference to the correlation data. .

  Further, the proximity effect correction dose Dp (η ′, U) in the formula (2) can be defined by the following formula (3) using the proximity effect correction coefficient η ′ and the proximity effect density U as parameters.

As described above, the irradiation amount D (U) of the electron beam corrected for the proximity effect and the loading effect can be defined by the equation (1) using the above-described tolerance DL (U) as a parameter. The degree DL (U) can also be defined by Expression (2) that does not use it as a parameter. Here, it goes without saying that the set of the reference dose D _base and the proximity effect correction coefficient η in the formula (1) is different from the set of the reference dose D ′ _base and the proximity effect correction coefficient η ′ in the formula (2). Therefore, in the first embodiment, it is determined whether or not the set of tolerance DL (U) input to the drawing apparatus 100 is appropriate using the above two different expressions (1) and (2).

  FIG. 3 is a flowchart showing main steps of the drawing method according to the first embodiment. 3, the drawing method according to the first embodiment includes a tolerance input step (S102), a pattern dimension error setting step (S104), a dose calculation step (S106), a fitting step (S108), and a determination step. (S110), interpolation tolerance calculation step (S112), proximity effect density calculation step (S114), dose calculation step (S116), drawing step (S118), and parameter output step (S120). Perform the process. Further, the tolerance determination method includes the tolerance input step (S102), the pattern dimension error setting step (S104), the dose calculation step (S106), the fitting step (S108), and the determination step (S110). Configure.

  In the drawing apparatus 100, the drawing data processing unit 22 reads drawing data input from the outside and stored in the storage device 140 from the storage device 140, and performs a plurality of stages of data conversion processing. Then, shot data unique to the drawing apparatus is generated by such multi-stage data conversion processing. The shot data is output to the storage device 148 and stored. Then, drawing processing is performed according to the shot data.

  As the tolerance input step (S102), the dose calculation unit 10 inputs a set of a plurality of tolerances DL (Ui) from the storage device 142. Here, as described above, the tolerance DL (Ui) in each case of the proximity effect density U (x, y) = 0 (0%), 0.5 (50%), and 1 (100%) is input. . Thus, the tolerance for each of the plurality of proximity effect densities is input.

  In the pattern dimension error setting step (S104), the dose calculation unit 10 inputs and sets the pattern dimension correction amount ΔCD from the storage device 142.

  As the dose calculation step (S106), the dose calculation unit 10 calculates the dose D (U) for each proximity effect density U using Equation (1). In other words, the radiation dose D (U) for each proximity effect density with a predetermined pattern dimension correction amount ΔCD is expressed by the equation (1) (first equation) using the tolerance DL (U) as a parameter. Calculated from the tolerance of each proximity effect density. Thereby, the irradiation dose D (U) in each case of the proximity effect density U (x, y) = 0 (0%), 0.5 (50%), 1 (100%) is calculated.

In the fitting step (S108), the fitting calculation unit 12 uses the equation (2) (second equation) that does not use the tolerance DL (U) as a parameter, and the irradiation dose D for each obtained tolerance DL (Ui). Fitting (U). The fitting calculation unit 12 also calculates a set of the reference dose D ′ _base and the proximity effect correction coefficient η ′, which are parameters of the equation (2), by using the tolerances for each of the input proximity effect densities. it can.

FIG. 4 is a graph showing an example of the relationship between the dose and the proximity effect density in the first embodiment. In FIG. 4, the vertical axis represents the dose and the horizontal axis represents the proximity effect density. As described above, the irradiation amount D (U) in each case of the proximity effect density U (x, y) = 0 (0%), 0.5 (50%), and 1 (100%) is expressed by Equation (2). By fitting, an approximate curve indicated by a dotted line is obtained. FIG. 4 also shows an example of a dose curve when only proximity effect correction is performed and loading effect correction is not performed. That is, it is shown that the loading effect is corrected by the terms of the pattern dimension correction amount ΔCD and the tolerance DL (U) in the equation (1). The formula of the dose curve when only the proximity effect correction is performed and the loading effect correction is not performed has the same configuration as the formula (2) in which the set of the reference dose D _base and the proximity effect correction coefficient η is different.

  As a determination step (S110), the determination unit 14 determines whether or not a set of a plurality of input tolerances DL (Ui) is an appropriate value using the fitting result.

  FIG. 5 is a graph showing an example of the ratio of the dose in equation (2) to the dose in equation (1) in the first embodiment. By fitting with the equation (2), the irradiation dose on the fitting curve in each case of proximity effect density U (x, y) = 0 (0%), 0.5 (50%), 1 (100%) Since it is obtained, this irradiation amount is set as the irradiation amount in the formula (2). Then, it is determined whether or not the dose ratio obtained by dividing the dose in equation (2) by equation (1) is within a preset threshold. In the example of FIG. 5, when the set of input tolerance DL (Ui) is, for example, (0.71, 1.06, 1.42), the expressions (2) and (1) The case where all the proximity effect densities U to which the dose ratio is input is 0 is shown. For example, when the absolute value of the dose ratio is within 1, the threshold value is determined to be appropriate (normal) because all the input proximity effect densities U are within the threshold value. On the other hand, when the set of input tolerance DL (Ui) is, for example, (0.71, 1.06, 2.0), the dose ratio of the expressions (2) and (1) Of the proximity effect densities U for which absolute values are input, since U exceeds 0.5 when U = 0.5 and = 1, the set of (0.71, 1.06, 2.0) is not appropriate. Is determined. That is, it is determined as inappropriate (abnormal). If it is determined to be inappropriate (abnormal), the drawing process is stopped. Then, a new tolerance DL (Ui) set is re-input from the outside. On the other hand, if it is determined to be appropriate (normal), the drawing process proceeds. Such a determination result is output to a monitor (not shown) or the like. Alternatively, it is stored in the storage device 146 or the like.

  As the interpolation tolerance calculation step (S112), the tolerance DL (U) calculation unit 16 calculates a tolerance function DL (U) depending on the proximity effect density using the fitting result. The tolerance DL (U) calculation unit 16 is an example of a tolerance function calculation unit. Since the input tolerance DL (Ui) is only the value at three proximity effect densities U, the tolerance at other proximity effect densities U is not known. Therefore, the tolerance DL (U) calculation unit 16 calculates a tolerance function DL (U) at a continuous proximity effect density U by substituting into the following equation (4).

  Expression (4) is obtained from Expression (1) and Expression (2). If the input tolerance DL (Ui) is an appropriate value, the doses are almost the same in the equations (1) and (2). Therefore, Expression (4) is established. As described above, the tolerance function DL (U) at the continuous proximity effect density U can be obtained by interpolation using the three input tolerances DL (Ui). Therefore, the tolerance DL (U) at various proximity effect densities U can be obtained hereinafter.

  FIG. 6 is a graph showing an example of the interpolated tolerance function DL (U) in the first embodiment. In FIG. 6, the vertical axis indicates the tolerance DL (U), and the horizontal axis indicates the proximity effect density U. In the example of FIG. 6, since the case where the input DL (U1) = 2.0 is shown, the interpolation curve is off, but if the combination is an appropriate DL (Ui), the input value and the interpolation curve Will almost match.

  As the proximity effect density calculation step (S114), the proximity effect density calculation unit 20 reads the drawing data from the storage device 140, and calculates the pattern area density ρ at each position for each proximity effect mesh obtained by virtually dividing the drawing region. Further, the proximity effect density U (x, y) at each position is calculated.

  As the dose calculation step (S116), the dose calculation unit 18 uses a tolerance DL (U) function that depends on the proximity effect density U interpolated using the tolerance DL (Ui) determined to be appropriate. For each proximity effect mesh, the dose D (U) is calculated using equation (1). The irradiation amount D (U) is an irradiation amount in which the proximity effect and the loading effect are corrected. Since the irradiation amount D (U) can be defined by the product of the irradiation time T and the current density J, the irradiation time T of the electron beam 200 at each position in the drawing region can be calculated. The irradiation time T can be obtained by dividing the irradiation amount D by the current density J. The calculated irradiation time is output to the control circuit 120.

  As the drawing step (S118), the drawing unit 150 draws a desired pattern on the sample 101 using the irradiation amount of the electron beam 200 obtained for each proximity effect mesh. Specifically, it operates as follows.

  When the electron beam 200 emitted from the electron gun 201 (emission unit) passes through the blanking deflector 212, it is controlled by the blanking deflector 212 so as to pass through the blanking aperture 214 in the beam ON state. In the beam OFF state, the entire beam is deflected so as to be shielded by the blanking aperture 214. The electron beam 200 that has passed through the blanking aperture 214 until the beam is turned off after the beam is turned off becomes one shot of the electron beam. The blanking deflector 212 controls the direction of the passing electron beam 200 to alternately generate a beam ON state and a beam OFF state. For example, the voltage may be applied to the blanking deflector 212 when the beam is OFF, without applying a voltage when the beam is ON. The irradiation amount per shot of the electron beam 200 irradiated on the sample 101 is adjusted with the irradiation time T of each shot.

  As described above, the electron beam 200 of each shot generated by passing through the blanking deflector 212 and the blanking aperture 214 illuminates the entire first shaping aperture 203 having a rectangular hole, for example, a rectangular hole, by the illumination lens 202. To do. Here, the electron beam 200 is first formed into a rectangle, for example, a rectangle. Then, the electron beam 200 of the first aperture image that has passed through the first shaping aperture 203 is projected onto the second shaping aperture 206 by the projection lens 204. The deflector 205 controls the deflection of the first aperture image on the second shaping aperture 206 and can change the beam shape and dimensions (variable shaping is performed). Such variable shaping is performed for each shot, and is usually shaped into different beam shapes and dimensions for each shot. The electron beam 200 of the second aperture image that has passed through the second shaping aperture 206 is focused by the objective lens 207, deflected by the main deflector 208 and the sub deflector 209, and continuously moved. The desired position of the sample arranged at 105 is irradiated. As described above, a plurality of shots of the electron beam 200 are sequentially deflected onto the sample 101 serving as the substrate by each deflector.

  As described above, according to the first embodiment, it is possible to determine whether or not a combination of a plurality of input tolerances for calculating the dose for correcting the proximity effect and the loading effect is appropriate. Therefore, the irradiation dose can be calculated using a combination of appropriate margins. As a result, highly accurate drawing can be performed. On the other hand, if the input tolerance set is inappropriate, the drawing can be interrupted. Furthermore, it is possible to obtain a continuous value (proximity function depending on proximity effect density) appropriately interpolated based on a threshold model of a combination process of appropriate tolerances inputted for discrete proximity effect densities.

Further, as the parameter output step (S120), the fitting calculation unit 12 calculates the reference dose D ′ _base and the proximity effect correction coefficient η ′, which are parameters of the formula (2) obtained by the fitting calculation in the formula (2). The set and the set pattern dimension correction amount ΔCD are output to the storage device 146, and the set of the reference irradiation amount D ′ _base and the proximity effect correction coefficient η ′ and the set pattern dimension correction amount ΔCD are stored in the storage device 146. Stored in

By obtaining a set of the reference dose D ′ _base and the proximity effect correction coefficient η ′, which are parameters of the formula (2), the dose is calculated by the formula (2) instead of the formula (1) in the dose calculation step (S116). The amount can also be calculated.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  In addition, although descriptions are omitted for parts and the like that are not directly required for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used. For example, although the description of the control unit configuration for controlling the drawing apparatus 100 is omitted, it goes without saying that the required control unit configuration is appropriately selected and used.

  In addition, all charged particle beam writing apparatuses and methods that include elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Irradiation amount calculation part 12 Fitting calculation part 14 Judgment part 16 Tolerance calculation part 18 Irradiation amount calculation part 20 Proximity effect density calculation part 22 Drawing data processing part 100 Drawing apparatus 101 Sample 102 Electronic lens tube 103 Drawing room 105 XY stage 110 Control Computer 111 Memory 120 Control circuit 140, 142, 144, 146, 148 Storage device 150 Drawing unit 160 Control unit 200 Electron beam 201 Electron gun 202 Illumination lens 203 First shaping aperture 204 Projection lens 205 Deflector 206 Second shaping aperture 207 Objective lens 208 Deflector 212 Blanking deflector 214 Blanking aperture 330 Electron beam 340 Sample 410 First aperture 411 Opening 420 Second aperture 421 Variable shaping opening 430 Charged particle source

Claims (5)

A charged particle beam drawing apparatus having a pattern dimension correction function by irradiation amount control,
A tolerance for each of a plurality of proximity effect densities, which is a coefficient indicating the relationship between the pattern dimension and the irradiation amount of the charged particle beam, is input, and the first expression using the tolerance as a parameter is a predetermined pattern dimension correction amount. A dose calculation unit for calculating the dose for each proximity effect density from the margin of each proximity effect density;
A fitting calculation unit that fits the irradiation amount for each tolerance calculated by the first equation using a tolerance by a second equation that does not use the tolerance as a parameter;
Using a fitting result, a determination unit that determines whether or not the tolerance for each of the input proximity effect densities is an appropriate value;
A charged particle beam drawing apparatus comprising:   The charged particle beam drawing apparatus according to claim 1, further comprising a tolerance function calculation unit that calculates a tolerance function depending on the proximity effect density using the fitting result.   3. The charged particle according to claim 1, wherein the fitting calculation unit calculates the parameter of the second equation using a tolerance for each of the plurality of proximity effect densities input at the time of fitting. 4. Beam drawing device.   The charged particle beam drawing apparatus according to claim 3, wherein a reference irradiation amount and a proximity effect correction coefficient are used as the parameters of the second equation. A charged particle beam writing method performed using a charged particle beam writing apparatus having a pattern dimension correction function by irradiation amount control,
A tolerance for each of a plurality of proximity effect densities, which is a coefficient indicating the relationship between the pattern dimension and the irradiation amount of the charged particle beam, is input, and the first expression using the tolerance as a parameter is a predetermined pattern dimension correction amount. Calculating a dose for each proximity effect density from the margin of each proximity effect density;
Fitting the irradiation dose for each tolerance calculated by the first equation using a tolerance with a second equation that does not use the tolerance as a parameter;
Using the fitting result, determining whether the tolerance for each of the input proximity effect densities is an appropriate value, and outputting the result;
A charged particle beam drawing method comprising:

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