JP2011228501A - Charged particle beam drawing method and charged particle beam drawing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam drawing method and a charged particle beam drawing system for drawing by operating a charged particle gun at an optimum condition.SOLUTION: An electron beam drawing system includes a high-voltage power supply 43 for applying a high voltage to a cathode, a measurement part 41 for measuring a change with time of a bias voltage while making filament power constant, and an arithmetic part 42 for obtaining change amount of the bias voltage measured in the measurement part 41. When the change amount becomes a predetermined value or less, the system measures a change of the bias voltage for the filament power when making a filament current constant in the measurement part 41, obtains a bias saturation point that the bias voltage saturates for the filament power in the arithmetic part 42, and controls the high-voltage power supply 43 based on this bias saturation point.

Description

  The present invention relates to a charged particle beam drawing method and a charged particle beam drawing apparatus.

  In recent years, the circuit line width required for a semiconductor element has become increasingly narrower as the large scale integrated circuit (LSI) is highly integrated and has a large capacity. The semiconductor element uses an original pattern pattern (a mask or a reticle, which will be collectively referred to as a mask hereinafter) on which a circuit pattern is formed, and the circuit is exposed and transferred onto a wafer by a reduction projection exposure apparatus called a stepper. Manufactured by forming. In manufacturing a mask for transferring such a fine circuit pattern onto a wafer, a charged particle beam drawing apparatus such as an electron beam drawing apparatus is used.

  The electron beam lithography system has an essentially excellent resolution because the electron beam used is a charged particle beam, and can secure a large depth of focus, so that it is possible to suppress dimensional fluctuations even on high steps. Have advantages. Patent Document 1 discloses a method for manufacturing a semiconductor integrated circuit device using an electron beam drawing apparatus.

  In a conventional electron beam drawing apparatus, an electron gun that irradiates an electron beam, a first shaping aperture, a second shaping aperture, and a shaping deflector, and several electron lenses for focusing the electron beam Have The electron beam emitted from the electron gun is imaged on the first shaping aperture and then on the second shaping aperture. Then, the size and shape of the electron beam are variably shaped by being deflected by the shaping deflector and optically superposing the first shaping aperture image and the second shaping aperture. The shaped electron beam is shot on a mask to be drawn, and a pattern is drawn by connecting shot figures with high accuracy.

  As the electron gun, a thermionic emission type electron gun using a cathode filament is used. In this electron gun, electrons are emitted by heating the cathode with filament power. The emitted electrons are accelerated by an acceleration voltage and controlled by a bias voltage to become a predetermined emission current and irradiate the mask (for example, refer to Patent Document 2).

  The operating conditions of the electron gun as described above are usually determined from the relationship between the filament power and the bias voltage when the emission current is set to a predetermined value. Specifically, the emission current is set to a predetermined value, and the relationship between the filament power and the bias voltage (bias saturation characteristic) is measured. Next, the filament power at the boundary between the temperature limiting region and the space charge limiting region (to be described later), that is, the point at which the bias voltage is saturated with respect to the change in the filament power (bias saturation point) is obtained. A predetermined margin is given to the obtained filament power to obtain an optimum operating point.

  FIG. 10 is an example of bias saturation characteristics. In this example, the emission current is set to 100 μA, and the change of the bias voltage when the filament current is changed is measured. In FIG. 10, region A is a temperature limited region. In this region, the electric field at the tip of the cathode is sufficiently high, and all the electrons emitted from the cathode go out of the cathode. Also, the amount of electrons emitted under these conditions is determined by the temperature of the cathode. On the other hand, the region B is a space charge limited region. In this region, the electric field at the cathode tip is low, and electrons emitted from the cathode stay in the space in front of the cathode to form space charges. Since the space charge suppresses the change in the amount of electrons emitted, the amount of electrons is stabilized even if the temperature of the cathode changes somewhat.

JP-A-11-312634 Japanese Patent Laid-Open No. 5-166481

  Filament power and cathode temperature are correlated. When the cathode temperature is high, the cathode evaporation is accelerated and the cathode life is shortened. Therefore, it is necessary to set the filament power so that the cathode temperature is as low as possible. The optimum operating point of the filament power obtained from the bias saturation characteristic described above is determined in consideration of this point. That is, the optimum operating point is set so that the electron gun is operated within the space charge limited region and at a lower cathode temperature. However, the bias saturation characteristics change with time due to differences in heat capacity and measurement conditions due to the structure of the electron gun. Here, the measurement conditions include a time from heating the filament to measurement, a time from turning on the high voltage power source to measurement, and the like.

  A change in the bias saturation characteristic means a change in the optimum operating point. In the conventional method, since the bias saturation characteristic is obtained without considering the time factor, there is a problem that the electron gun is operated with a filament power which is not originally optimum.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a charged particle beam drawing method for drawing by operating a charged particle gun under optimum conditions. It is another object of the present invention to provide a charged particle beam drawing apparatus that operates a charged particle gun under optimum conditions.

  Other objects and advantages of the present invention will become apparent from the following description.

A first aspect of the present invention is a charged particle beam writing method in which charged particles emitted by heating a cathode with filament power are controlled by a bias voltage and irradiated onto a sample with a predetermined emission current.
The change in the bias voltage with time is examined with the filament power kept constant. When the amount of change is less than the predetermined value, the change in the bias voltage with respect to the filament power when the emission current is made constant is obtained. It is characterized by obtaining a bias saturation point that saturates.

According to a second aspect of the present invention, there is provided a charged particle beam writing method in which charged particles emitted by heating a cathode with filament power are controlled by a bias voltage and irradiated onto a sample with a predetermined emission current.
The bias saturation characteristic indicating the change of the bias voltage with respect to the filament power when the emission current is constant is repeatedly obtained at regular time intervals. When the rate of change of the bias saturation characteristic becomes a predetermined value or less, the bias voltage is less than the filament power. It is characterized by obtaining a bias saturation point that saturates.

In the second aspect of the present invention, the change of the bias voltage with respect to the filament power when the emission current is constant is measured, and the discrete set of the obtained filament power and the bias voltage is approximated by the equation (1). fitting formula, the coefficient _{a n-1} in the (n-1) th _{measurement, b n-1, c n} -1, d and _n-1, the coefficient of n th measurement _{a n,} b n, _{c n} it is preferable to determine the rate of change with d _n Tocharian formula (2).

According to a third aspect of the present invention, there is provided a charged particle gun that emits a charged particle beam having a predetermined emission current by controlling, by a bias voltage, charged particles that are emitted by heating the cathode with filament power.
A high voltage power supply for applying a voltage to the cathode;
A measurement unit for measuring a change in bias voltage over time with a constant filament power;
A calculation unit for obtaining a change amount of the bias voltage measured by the measurement unit,
When the amount of change is less than or equal to the specified value, the bias saturation point at which the bias voltage is saturated with respect to the filament power is measured by the calculation unit by measuring the change in the bias voltage relative to the filament power when the emission current is constant in the measurement unit. And a high-voltage power supply unit is controlled based on the bias saturation point.

According to a fourth aspect of the present invention, there is provided a charged particle gun that emits a charged particle beam having a predetermined emission current by controlling a charged particle emitted by heating a cathode with a filament power by a bias voltage;
A high voltage power supply for applying a voltage to the cathode;
A measurement unit that repeatedly measures a bias saturation characteristic indicating a change in a bias voltage with respect to a filament power when the emission current is constant;
A calculation unit for obtaining a rate of change of the bias saturation characteristic measured by the measurement unit,
Charged particles characterized in that, when the rate of change becomes a predetermined value or less, a bias saturation point at which the bias voltage saturates with respect to the filament power is obtained in the arithmetic unit, and the high-voltage power supply unit is controlled based on the bias saturation point The present invention relates to a beam drawing apparatus.

  According to the present invention, there is provided a charged particle beam writing method for drawing by operating a charged particle gun under optimum conditions. In addition, according to the present invention, a charged particle beam drawing apparatus that operates a charged particle gun under optimum conditions is provided.

It is a block diagram of the thermoelectron emission type electron gun in this Embodiment. It is an example which shows a time-dependent change of a bias saturation characteristic. It is a figure which shows the change of the bias saturation point calculated | required from FIG. FIG. 4 shows an example of how to obtain the bias saturation point. It is a figure explaining one form of the operating condition determination method of an electron gun. It is a figure which shows the bias saturation characteristic of the 1st measurement in time t1. It is a figure which shows the bias saturation characteristic of each measurement of (n-1) th time, nth time, and (n + 1) th time. It is a block diagram of the electron beam drawing apparatus in this Embodiment. It is explanatory drawing of the drawing method by an electron beam. It is a figure which shows an example of a bias saturation characteristic.

  FIG. 1 is a configuration diagram of a thermionic emission electron gun in the present embodiment. As shown in this figure, the electron gun 101 has a cathode 102 that is an electron source, a Wehnelt 105 that focuses electrons emitted from the cathode 102, and an anode 107 that is disposed below the Wehnelt 105. The tip of the cathode 104 has a convex shape. This is to improve the luminance by concentrating the electric field in a minute region.

  In FIG. 1, a cathode 102 is connected via a filament 103 to a filament supply power source 104 for heating the cathode 102, thereby forming a filament circuit. A Wehnelt 105 is arranged so as to surround the cathode 102 and the filament 103. The Wehnelt 105 has an opening below the cathode 102 and converges and controls electrons emitted from the cathode 102. A bias power source 106 for applying a bias voltage is connected between the Wehnelt 105 and the cathode 102, thereby forming a bias circuit.

  An anode 107 is disposed below the Wehnelt 105. The anode 107, the filament circuit, and the bias circuit are connected to an acceleration power source 108 that applies an acceleration voltage and supplies an emission current between the cathode 102 and the anode 107.

  In electron beam drawing using such an electron gun, operating conditions of the electron gun are determined prior to drawing.

  FIG. 2 is an example showing a change with time in the bias saturation characteristic. FIG. 3 shows changes in the bias saturation point obtained from FIG. FIG. 4 shows an example of how to obtain the bias saturation point. According to this example, the bias saturation point can be obtained as W1 from the intersection of the straight line connecting the measurement points in the temperature limited region and the straight line connecting the measurement points in the space charge limited region.

  In FIG. 3, the horizontal axis represents the elapsed time from the start of heating of the filament, and the vertical axis represents the bias saturation point. As can be seen from this figure, a sudden change in the bias saturation point is observed for a while after the filament is heated, and the degree of change decreases with time and becomes constant over time. Therefore, the present inventor has considered that the electron gun can be operated under the optimum conditions if the operating conditions are determined when no substantial change with time is observed at the bias saturation point.

  One mode of the operating condition determination method in the present invention is to examine the change of the bias voltage with time while keeping the filament power constant, and obtain the bias saturation characteristic when the amount of change becomes a predetermined value or less. Here, the value of the filament power to be constant is a value within the temperature limit region. This will be described in detail with reference to FIG.

  When the change with time in the bias voltage is measured with the filament power set to the predetermined value W, the bias voltage changes greatly for a while from the start of the measurement as shown in FIG. 5, but the amount of change gradually decreases and eventually becomes substantially constant. . In FIG. 5, the bias voltage at the measurement start time t1 is V1, but after reaching V2 at the time t2, this value remains substantially constant. Therefore, the amount of change (ΔV / Δt) in the bias voltage per unit time is obtained, and when this value becomes a predetermined value or less, the bias saturation characteristic as shown in FIG. 2 is examined to determine the bias saturation point. According to this method, the fluctuation amount of the bias saturation point is grasped from the change in the bias voltage with time, and the operating condition is determined when no substantial change with time is seen at the bias saturation point. It is possible to obtain the optimum conditions for operating.

  Another aspect of the operating condition determination method in the present invention is to repeatedly obtain the bias saturation characteristic at regular time intervals, and to obtain the bias saturation point when the change rate of the bias saturation characteristic becomes a predetermined value or less.

  FIG. 6 shows the bias saturation characteristics of the first measurement at time t1, and ◯ in the figure is a measurement point. In this example, a discrete set of filament power and bias voltage is spline interpolated and fitted with an appropriate approximate expression to obtain a continuous value. Here, fitting is understood as a mathematical optimization method for determining the best fitting parameters or coefficients of a continuous function for discrete values. The term generally encompasses all mathematical methods for curve fitting calculations. The purpose of such curve fitting calculations is to derive the function that best fits the data.

As the fitting function in the example of FIG. 6, the following equation (1) is preferable.

The curve shown in FIG. 6 is a fitting curve obtained by complementing the measurement points with a spline function and fitting with the equation (1). Such a curve is repeatedly obtained at regular time intervals to calculate the rate of change in bias saturation characteristics. Specifically, the change of the bias voltage with respect to the filament power when the emission current is constant is measured, and the obtained discrete set of the filament power and the bias voltage is fitted with the approximate expression of Expression (1). Then, the (n-1) coefficient _{a n-1} at th _{measurement, b n-1, c n} -1, d n-1, coefficient _a n in n-th _measurement, b _n, c n, _{d n} From these, the rate of change is obtained using equation (2).

  FIG. 7 shows bias saturation characteristics corresponding to the (n−1) th, nth and (n + 1) th measurements. As in FIG. 6, these are fitting curves obtained by complementing the measurement points with a spline function and fitting with equation (1). For each, the coefficients a, b, c, and d of Equation (1) are obtained, and the change rate of the bias saturation characteristic is obtained using Equation (2). Note that the change rate in this case is the change rate of the measurement n-th bias characteristic with respect to the measurement (n−1) -th bias characteristic and the change rate of the measurement (n + 1) -th bias characteristic with respect to the measurement n-th bias characteristic. Say.

  Table 1 shows the coefficients and rate of change in the example of FIG. For example, if the bias saturation point is obtained when the rate of change is 0.5% or less, the rate of change is 0.5% or less in the (n + 1) th measurement. Will be asked.

  According to the above method, the operating condition is determined when a substantial change with time is not observed at the bias saturation point, so that the electron gun can be operated under an optimal condition. In addition, the bias saturation characteristics are repeatedly determined at regular time intervals, and the bias saturation point is determined when the rate of change of the bias saturation characteristics falls below a predetermined value. Compared with the method, it is possible to more accurately determine the point at which no substantial change with time is observed at the bias saturation point.

  FIG. 8 is a configuration diagram of the electron beam drawing apparatus according to the present embodiment.

  As shown in FIG. 8, a stage 3 on which a mask 2 as a sample is placed is provided in a sample chamber 1 of the electron beam drawing apparatus. The mask 2 is formed by forming a chromium (Cr) film as a light shielding film on a mask substrate such as quartz, and further forming a resist film thereon. A molybdenum silicon (MoSi) film or the like may be used instead of the chromium film. The resist film can be a film formed using a chemically amplified resist.

  In this embodiment mode, writing is performed on the resist film with an electron beam. The stage 3 is driven by the stage drive circuit 4 in the X direction (left and right direction on the paper surface) and the Y direction (vertical direction on the paper surface). The moving position of the stage 3 is measured by a position circuit 5 using a laser length meter or the like.

  An electron beam optical system 10 is installed above the sample chamber 1. The optical system 10 includes an electron gun 6, various lenses 7, 8, 9, 11, 12, a blanking deflector 13, a shaping deflector 14, a beam scanning main deflector 15, and a beam scanning sub deflector. 16 and two beam shaping apertures 17, 18 and the like.

  The electron gun 6 emits an electron beam having a predetermined emission current by controlling the electrons emitted by heating the cathode with filament power using a bias voltage. The electron gun 6 is connected to a high voltage power supply unit 43 that applies a voltage to the cathode. The cathode of the electron gun 6 has an emitter and a Wehnelt electrode, and these are controlled by a high voltage power supply unit 43. Although not shown, the high-voltage power supply unit 43 includes a filament supply power supply, a relay, a filament circuit, a bias power supply, a bias circuit, and an acceleration power supply.

  Connected to the high-voltage power supply unit 43 are a measurement unit 41 that measures a change in the bias voltage with time while keeping the filament power constant, and a calculation unit 42 that calculates the amount of change in the bias voltage measured by the measurement unit 41. In the present embodiment, the operating conditions of the electron gun 6 are determined by these. That is, when the amount of change becomes equal to or less than a predetermined value, the measurement unit 41 measures the change in the bias voltage with respect to the filament power when the emission current is constant. Then, the calculation unit 42 obtains a bias saturation point at which the bias voltage is saturated with respect to the filament power, and controls the high-voltage power supply unit 43 based on the bias saturation point.

  According to another aspect of the present embodiment, the measurement unit 41 repeatedly measures the bias saturation characteristic indicating the change of the bias voltage with respect to the filament power when the emission current is constant at regular time intervals. it can. Further, the calculation unit 42 can obtain the rate of change of the bias saturation characteristic measured by the measurement unit 41. In this case, the electron beam drawing apparatus obtains a bias saturation point at which the bias voltage saturates with respect to the filament power at the calculation unit 42 when the above change rate becomes equal to or less than a predetermined value. The power supply unit 43 is configured to be controlled.

  FIG. 9 is an explanatory diagram of a drawing method using an electron beam. As shown in this figure, the pattern 51 drawn on the mask 2 is divided into strip-shaped frame regions 52. Drawing with the electron beam 54 is performed for each frame region 52 while the stage 3 continuously moves in one direction (for example, the X direction). The frame area 52 is further divided into sub-deflection areas 53, and the electron beam 54 draws only necessary portions in the sub-deflection areas 53. The frame area 52 is a strip-shaped drawing area determined by the deflection width of the main deflector 15, and the sub-deflection area 53 is a unit drawing area determined by the deflection width of the sub-deflector 16.

  Positioning of the reference position of the sub deflection area is performed by the main deflector 15, and drawing in the sub deflection area 53 is controlled by the sub deflector 16. That is, the main deflector 15 positions the electron beam 54 in a predetermined sub-deflection region 53, and the sub-deflector 16 determines the drawing position in the sub-deflection region 53. Further, the shape and size of the electron beam 54 are determined by the shaping deflector 14 and the beam shaping apertures 17 and 18. Then, the sub-deflection area 53 is drawn while continuously moving the stage 3 in one direction. When drawing of one sub-deflection area 53 is completed, the next sub-deflection area 53 is drawn. When drawing of all the sub-deflection areas 53 in the frame area 52 is completed, the stage 3 is stepped in a direction orthogonal to the direction in which the stage 3 is continuously moved (for example, the Y direction). Thereafter, the same processing is repeated, and the frame area 52 is sequentially drawn.

  The sub-deflection region is a region where the electron beam 54 is scanned by the sub-deflector 16 at a speed higher than that of the main deflection region, and is generally a minimum drawing unit. When the inside of the sub deflection region is drawn, a shot having a size and shape prepared according to the pattern figure is formed by the shaping deflector 14. Specifically, the electron beam 54 emitted from the electron gun 6 is shaped into a rectangular shape by the first aperture 17, and then projected onto the second aperture 18 by the shaping deflector 14. Change the dimensions. Thereafter, as described above, the electron beam 54 is deflected by the sub-deflector 16 and the main deflector 15 and is applied to the mask 2 placed on the stage 3.

  CAD data created by a designer (user) is converted into design intermediate data in a hierarchical format such as OASIS. The design intermediate data stores design pattern data created for each layer and formed on each mask. Here, generally, the electron beam drawing apparatus is not configured to directly read OASIS data. That is, unique format data is used for each manufacturer of the electron beam drawing apparatus. For this reason, the OASIS data is converted into format data unique to each electron beam drawing apparatus for each layer and then input to the apparatus.

  In FIG. 8, reference numeral 20 denotes an input unit, which is a part where format data is input to the electron beam drawing apparatus through a magnetic disk as a storage medium. Since the figure included in the design pattern is a basic figure of a rectangle or a triangle, for example, the coordinates (x, y) at the reference position of the figure, the length of the side, a rectangle, a triangle, etc. Information such as a graphic code serving as an identifier for discriminating between graphic types, and graphic data defining the shape, size, position, etc. of each pattern graphic is stored.

  Furthermore, a set of figures existing in a range of about several tens of μm is generally called a cluster or a cell, and data is hierarchized using this. In the cluster or cell, arrangement coordinates and repeated description when various figures are arranged alone or repeatedly at a certain interval are also defined. The cluster or cell data is further arranged in a strip-shaped region called a frame or stripe having a width of several hundreds μm and a length of about 100 mm corresponding to the total length of the photomask in the X direction or Y direction. .

  The graphic pattern division processing is performed in units of the maximum shot size defined by the size of the electron beam, and the coordinate position, size, and irradiation time of each divided shot are also set. Then, drawing data is created so that a shot is formed according to the shape and size of the graphic pattern to be drawn. The drawing data is divided into strip-shaped frames (main deflection areas) and further divided into sub-deflection areas. That is, the drawing data of the entire chip has a data hierarchical structure including a plurality of strip-shaped frame data according to the size of the main deflection area and a plurality of sub deflection area units smaller than the main deflection area in the frame. .

  In the electron beam drawing apparatus, it is necessary to perform correction processing for changing the beam irradiation amount so that the pattern size after drawing becomes the same as the size of the design data. This processing is performed by the drawing data correction unit 31 shown in FIG. 8 for factors that cause pattern variation such as proximity effect, fogging effect, and loading effect. The drawing data correction unit 31 includes a dimension correction map creation unit 31a, a correction dose calculation unit 31b that calculates a correction dose corresponding to the dimension correction map, and an electron beam dose at a predetermined position of the mask from the correction dose. A dose calculation unit 31c to be obtained. Here, the correction dose can be at least one of a proximity effect correction dose, a fog correction dose, and a loading effect correction dose.

  As described above, drawing data converted into format data unique to the electron beam drawing apparatus is input to the input unit 20 in FIG. The drawing data read from the input unit 20 by the control computer 19 is temporarily stored in the pattern memory 21 for each frame region 52. The pattern data for each frame region 52 stored in the pattern memory 21, that is, the frame information composed of the drawing position, drawing graphic data, and the like is sent to the drawing data correction unit 31.

  The frame information corrected by the drawing data correction unit 31 is sent to the pattern data decoder 22 and the drawing data decoder 23 which are data analysis units.

  Information from the pattern data decoder 22 is sent to a blanking circuit 24 and a beam shaper driver 25. Specifically, blanking data based on the data is created by the pattern data decoder 22 and sent to the blanking circuit 24. Desired beam size data is also created and sent to the beam shaper driver 25. Then, a predetermined deflection signal is applied from the beam shaper driver 25 to the shaping deflector 14 of the optical system 10 to control the size of the electron beam 54.

  The deflection control unit 30 of FIG. 8 is connected to a settling time determination unit 29, the settling time determination unit 29 is connected to a sub deflection region deflection amount calculation unit 28, and the sub deflection region deflection amount calculation unit 28 is a pattern data decoder. 22 is connected. The deflection control unit 30 is connected to a blanking circuit 24, a beam shaper driver 25, a main deflector driver 26, and a sub deflector driver 27.

  The output of the drawing data decoder 23 is sent to the main deflector driver 26 and the sub deflector driver 27. Then, a predetermined deflection signal is applied from the main deflector driver 26 to the main deflector 15, and the electron beam 54 is deflected and scanned to a predetermined main deflection position. Further, a predetermined sub deflection signal is applied from the sub deflector driver 27 to the sub deflector 16, and drawing in the sub deflection area 53 is performed.

  Next, a drawing method by the electron beam drawing apparatus will be described.

  First, the operating condition of the electron gun 6 is determined. This is performed, for example, every time the cathode is replaced. Specifically, the measurement unit 41 examines the change in the bias voltage with time while keeping the filament power constant. Next, the calculation unit 42 obtains the amount of change in the bias voltage measured by the measurement unit 41. When the amount of change becomes a predetermined value or less, a bias saturation characteristic is obtained to determine a bias saturation point, and the electron gun 6 is operated by controlling the high-voltage power supply unit 43 according to the filament power obtained from this value.

  In the present embodiment, the operating condition of the electron gun 6 may be determined as follows. That is, the measurement unit 41 repeatedly obtains the bias saturation characteristic at regular time intervals. Then, the change rate of the bias saturation characteristic is obtained by the calculation unit 42 from the measurement result of the measurement unit 41. When the rate of change becomes a predetermined value or less, a bias saturation characteristic is obtained to determine a bias saturation point, and the electron gun 6 is operated by controlling the high-voltage power supply unit 43 according to the filament power obtained from this value.

  Next, the mask 2 is placed on the stage 3 in the sample chamber 1. Next, the position of the stage 3 is detected by the position circuit 5, and the stage 3 is moved to a position where drawing can be performed by the stage drive circuit 4 based on a signal from the control computer 19.

  Next, an electron beam 54 is emitted from the electron gun 6. The emitted electron beam 54 is collected by the illumination lens 7. Then, the blanking deflector 13 performs an operation for irradiating the mask 2 with the electron beam 54.

  The electron beam 54 incident on the first aperture 17 passes through the opening of the first aperture 17 and is then deflected by the shaping deflector 14 controlled by the beam shaper driver 25. And it passes through the opening part provided in the 2nd aperture 18, and becomes a beam shape which has a desired shape and a dimension. This beam shape is a drawing unit of the electron beam 54 applied to the mask 2.

  The electron beam 54 is shaped into a beam shape and then reduced by the reduction lens 11. The irradiation position of the electron beam 54 on the mask 2 is controlled by the main deflector 15 controlled by the main deflector driver 26 and the sub deflector 16 controlled by the sub deflector driver 27. The main deflector 15 positions the electron beam 54 in the sub deflection region 53 on the mask 2. The sub deflector 16 positions the drawing position in the sub deflection region 53.

  Drawing with the electron beam 54 on the mask 2 is performed by scanning the electron beam 54 while moving the stage 3 in one direction. Specifically, the pattern is drawn in each sub deflection region 53 while moving the stage 3 in one direction. After all the sub-deflection areas 53 in one frame area 52 have been drawn, the stage 3 is moved to a new frame area 52 and drawn similarly.

  After drawing all the frame regions 52 of the mask 2 as described above, the drawing is replaced with a new mask and drawing by the same method as described above is repeated.

  Next, drawing control by the control computer 19 will be described.

  The control computer 19 reads the drawing data of the mask recorded on the magnetic disk by the input unit 20. The read drawing data is temporarily stored in the pattern memory 21 for each frame area 52.

  The drawing data for each frame area 52 stored in the pattern memory 21, that is, the frame information composed of the drawing position and drawing graphic data, etc. is corrected by the drawing data correction unit 31 according to the film thickness of the resist film. The sub-deflection area deflection amount calculation unit 28, the blanking circuit 24, the beam shaper driver 25, the main deflector driver 26, and the sub-deflector driver 27 are passed through the pattern data decoder 22 and the drawing data decoder 23 which are data analysis units. Sent to.

  The pattern data decoder 22 generates blanking data based on the drawing data and sends it to the blanking circuit 24. Further, desired beam shape data is created based on the drawing data, and is sent to the sub deflection region deflection amount calculation unit 28 and the beam shaper driver 25.

  The sub deflection region deflection amount calculation unit 28 calculates the deflection amount (movement distance) of the electron beam for each shot in the sub deflection region 53 from the beam shape data created by the pattern data decoder 22. The calculated information is sent to the settling time determination unit 29, and the settling time corresponding to the movement distance by the sub deflection is determined.

  The settling time determined by the settling time determination unit 29 is sent to the deflection control unit 30, and then the deflection control unit 30 measures the blanking circuit 24, the beam shaper driver 25, the main pattern while timing the pattern drawing. It is appropriately sent to either the deflector driver 26 or the sub deflector driver 27.

  In the beam shaper driver 25, a predetermined deflection signal is applied to the shaping deflector 14 of the optical system 10, and the shape and size of the electron beam 54 are controlled.

  The drawing data decoder 23 generates positioning data for the sub deflection region 53 based on the drawing data, and this data is sent to the main deflector driver 26. Next, a predetermined deflection signal is applied from the main deflector driver 26 to the main deflector 15, and the electron beam 54 is deflected and scanned to a predetermined position in the sub deflection region 53.

  The drawing data decoder 23 generates a control signal for scanning the sub deflector 16 based on the drawing data. After the control signal is sent to the sub deflector driver 27, a predetermined sub deflection signal is applied from the sub deflector driver 27 to the sub deflector 16. Drawing in the sub deflection region 53 is performed by repeatedly irradiating the electron beam 54 after the settling time has elapsed.

  As described above, according to the present embodiment, it is possible to perform drawing by operating the electron gun under optimum conditions. In other words, according to one aspect of the present embodiment, the fluctuation amount of the bias saturation point is grasped from the change with time of the bias voltage, and the operating condition is determined when no substantial change with time is seen at the bias saturation point. Therefore, according to this method, the optimum condition for operating the electron gun can be obtained relatively easily. Further, according to another aspect of the present embodiment, in addition to the above effect, the bias saturation characteristic is repeatedly obtained at a constant time interval, and the bias saturation point is obtained when the rate of change of the bias saturation characteristic becomes a predetermined value or less. Therefore, it is possible to more accurately determine where no substantial change with time is seen at the bias saturation point, compared to the above-described method of grasping the variation amount of the bias saturation point from the change with time of the bias voltage.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, although the electron beam is used in the above embodiment, the present invention is not limited to this. The charged particle beam drawing method and the charged particle having a charged particle gun that emits another charged particle beam such as an ion beam. The present invention can also be applied to a beam drawing apparatus.

DESCRIPTION OF SYMBOLS 1 Sample chamber 2 Mask 3 Stage 4 Stage drive circuit 5 Position circuit 6 Electron gun 7, 8, 9, 11, 12 Lens 10 Optical system 13 Blanking deflector 14 Molding deflector 15 Main deflector 16 Sub deflector 17 1st 1 aperture 18 second aperture 19 control computer 20 input unit 21 pattern memory 22 pattern data decoder 23 drawing data decoder 24 blanking circuit 25 beam shaper driver 26 main deflector driver 27 sub deflector driver 28 sub deflection region deflection amount Calculation unit 29 Settling time determination unit 30 Deflection control unit 31 Drawing data correction unit 31a Dimension correction map creation unit 31b Correction irradiation amount calculation unit 31c Irradiation amount calculation unit 41 Measurement unit 42 Calculation unit 43 High voltage power supply unit 51 Pattern to be drawn 52 Frame Area 53 Sub-deflection area 54 Electricity Child beam 101 Electron gun 102 Cathode 103 Filament 104 Filament supply power supply 105 Wehnelt 106 Bias power supply 107 Anode 108 Acceleration power supply

Claims (5)

In a charged particle beam writing method in which charged particles emitted by heating a cathode with filament power are controlled by a bias voltage and irradiated onto a sample with a predetermined emission current,
The change in the bias voltage with time is examined while keeping the filament power constant, and when the amount of change becomes a predetermined value or less, the change in the bias voltage with respect to the filament power when the emission current is made constant is obtained. A charged particle beam drawing method characterized by obtaining a bias saturation point at which a voltage is saturated with respect to the filament power. In a charged particle beam writing method in which charged particles emitted by heating a cathode with filament power are controlled by a bias voltage and irradiated onto a sample with a predetermined emission current,
A bias saturation characteristic indicating a change in the bias voltage with respect to the filament power when the emission current is constant is repeatedly obtained at regular time intervals, and when the rate of change in the bias saturation characteristic becomes a predetermined value or less, the bias voltage Finds a bias saturation point at which the filament power is saturated with respect to the filament power. Measure the change of the bias voltage relative to the filament power when the emission current is constant, and fit the obtained discrete set of the filament power and the bias voltage with the approximate expression of Equation (1), (N-1) From the coefficients a _n−1 , b _n−1 , c _n−1 , dn ₋₁ in the second measurement and the coefficients an _n , b _n , c _n , dn in the _nth measurement The charged particle beam drawing method according to claim 2, wherein the rate of change is obtained using Equation (2).

A charged particle gun that emits a charged particle beam of a predetermined emission current by controlling the charged particles emitted by heating the cathode with filament power by a bias voltage;
A high voltage power supply for applying a voltage to the cathode;
A measurement unit for measuring a change in the bias voltage with time while keeping the filament power constant;
A calculation unit that obtains a change amount of the bias voltage measured by the measurement unit;
When the amount of change becomes equal to or less than a predetermined value, the measurement unit measures the change in the bias voltage with respect to the filament power when the emission current is constant, and the operation unit calculates the bias voltage as the filament power. A charged particle beam drawing apparatus characterized in that a bias saturation point that saturates is obtained and the high-voltage power supply unit is controlled based on the bias saturation point. A charged particle gun that emits a charged particle beam of a predetermined emission current by controlling the charged particles emitted by heating the cathode with filament power by a bias voltage;
A high voltage power supply for applying a voltage to the cathode;
A measurement unit that repeatedly measures a bias saturation characteristic indicating a change in the bias voltage with respect to the filament power when the emission current is constant;
A calculation unit for obtaining a change rate of the bias saturation characteristic measured by the measurement unit,
When the rate of change becomes a predetermined value or less, the calculation unit obtains a bias saturation point at which the bias voltage saturates with respect to the filament power, and controls the high-voltage power source unit based on the bias saturation point. Characterized charged particle beam drawing apparatus.

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