JP2008042173A - Charged-particle beam drawing method, charged-particle beam drawing device, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drawing method and device that corrects a shift in a drawing position owing to variations in the atmospheric pressure. <P>SOLUTION: A drawing device 100 as one embodiment of the invention is characterized by comprising an outside atmospheric pressure measuring part 122 that measures a value of the outside atmospheric pressure, a coordinate value correction part 126 that corrects a three-dimensional coordinate value using the measured value of the outside atmospheric pressure, a deflection voltage operation part 146 that carries out the operation of a deflection voltage of an electron beam 200 using the corrected three-dimensional coordinate value, an electron gun 201 that irradiates the electron beam 200, and a main deflector 214 that deflects the electron beam 200 based on the amount of deflection. According to the present invention, it is possible to irradiate a deflection position of which the shift in position of the drawing position owing to the variations in atmospheric pressure has been corrected with the beam. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charged particle beam drawing method, a charged particle beam drawing apparatus, and a program. For example, the present invention relates to a correction method of an electron beam deflection position in a drawing apparatus that draws a predetermined pattern on a sample using an electron beam.

  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. 13 is a conceptual diagram for explaining the operation of the variable shaped electron beam drawing apparatus.
A rectangular aperture, for example, a rectangular opening 411 for forming the electron beam 330 is formed in the first aperture 410 in the variable electron beam (EB) drawing apparatus. Further, the second aperture 420 is formed with a variable shaping opening 421 for shaping the electron beam 330 that has passed through the opening 411 into a desired rectangular shape. The electron beam 330 irradiated from the charged particle source 430 and passed through the opening 411 is deflected by a deflector, passes through a part of the variable shaping opening 421, and continues in a predetermined direction (for example, the X direction). The sample 340 mounted on the moving stage is irradiated. That is, a rectangular shape that can pass through both the opening 411 and the variable shaping opening 421 is drawn in the drawing region of the sample 340 mounted on the stage that continuously moves in the X direction. A method of creating an arbitrary shape by passing both the opening 411 and the variable forming opening 421 is referred to as a variable forming method.

  Here, in the electron beam drawing apparatus, when the outside air pressure fluctuates, the drawing chamber is deformed in conjunction with the change in the outside air pressure. This deformation affects the relative distance between the electron optical column arranged on the drawing chamber and the mask surface serving as a sample arranged in the drawing chamber. Therefore, if the relative distance is deviated due to fluctuations in the external air pressure, the position of the pattern to be drawn and the focus of the electron beam will be deviated, making it impossible to perform drawing with high accuracy. In particular, while high drawing accuracy is required with the recent miniaturization of the circuit line width, the deterioration of drawing accuracy caused by relative positional shift and defocus due to atmospheric pressure fluctuation cannot be ignored.

Here, although it is not electron beam drawing, an ultraviolet exposure apparatus that exposes a mask image onto a wafer obtains the amount of field curvature due to atmospheric pressure fluctuation and moves the stage to an appropriate position in the Z direction (for example, a patent) Reference 1) is disclosed in the literature.
Japanese Unexamined Patent Publication No. 7-211612

  As described above, while high drawing accuracy has been demanded with the recent miniaturization of circuit line width, deterioration of drawing accuracy caused by relative positional shift and defocus due to atmospheric pressure fluctuation has become ignorable. Further, the drawing position on the sample surface is defined in two dimensions in the x and y directions, and the correction of the deflection position for deflecting the electron beam is also normally corrected in two dimensions in the x and y directions. However, relative positional shifts due to atmospheric pressure fluctuations occur in three dimensions in the x, y, and z directions, respectively. Therefore, correction that takes these into consideration is desired. Conventionally, a method for correcting the deflection position due to atmospheric pressure variation has not been established.

  Therefore, an object of the present invention is to provide a drawing method and apparatus that overcomes such problems and corrects a position shift and a focus shift of a drawing position due to a change in atmospheric pressure.

A charged particle beam drawing apparatus according to one embodiment of the present invention includes:
An atmospheric pressure measurement unit for measuring the value of the external atmospheric pressure;
A coordinate value correction unit that corrects a three-dimensional coordinate value using the measured value of the external pressure;
A deflection amount calculation unit that calculates the deflection amount of the charged particle beam using the corrected three-dimensional coordinate value;
An irradiation unit for irradiating a charged particle beam;
A deflecting unit for deflecting the charged particle beam based on the deflection amount;
It is provided with.

Further, the charged particle beam drawing apparatus further performs an x-coordinate correction value for correcting an x-coordinate value indicating a position in a first direction parallel to the drawing surface of the sample, and an orthogonal to the first direction parallel to the drawing surface. A coordinate correction value for calculating a y coordinate correction value for correcting the y coordinate value indicating the position in the second direction and a z coordinate correction value for correcting the z coordinate value indicating the position in the third direction orthogonal to the drawing surface. With a calculator
The three-dimensional coordinate value is defined by an x-coordinate value, a y-coordinate value, and a z-coordinate value.
The coordinate value correction unit corrects the x coordinate value using the x coordinate correction value, corrects the y coordinate value using the y coordinate correction value, and corrects the z coordinate value using the z coordinate correction value. And

Further, the charged particle beam drawing apparatus further uses a corrected z coordinate value to convert a coefficient of a predetermined expression for calculating a deflection amount of the charged particle beam with x and y as variables. Part
The deflection amount calculation unit preferably substitutes the corrected x-coordinate value and the corrected y-coordinate value as variables in a predetermined xy function equation whose coefficient has been converted.

  The deflecting unit electrostatically deflects the charged particle beam and corrects the x-coordinate value and the y-coordinate value based on the external pressure, and the x-coordinate based on the external pressure by electromagnetically deflecting the charged particle beam. It is preferable to have at least one of an alignment coil that corrects the value and the y-coordinate value.

  Alternatively, the deflection unit electrostatically deflects the charged particle beam and corrects the x coordinate value and the y coordinate value based on the external atmospheric pressure, and corrects the focal position by superimposing a constant voltage to adjust the external pressure to the external atmospheric pressure. It is preferable to provide an electrostatic deflector that corrects the z coordinate value based thereon.

  Alternatively, the charged particle beam drawing apparatus may further include an objective lens that adjusts the focal position of the charged particle beam and corrects the z coordinate value based on the external air pressure by changing excitation.

  Alternatively, the charged particle beam drawing apparatus may further include a second electrostatic deflector that corrects the z coordinate value based on the external air pressure by correcting a focal position by superimposing a constant voltage. .

  The coordinate correction unit operates independently of the drawing process and the beam adjustment process. For each subfield operation unit, the x-coordinate correction value and the y coordinate are converted into a three-dimensional coordinate value in one of the drawing process and the beam adjustment process. It is preferable to perform addition control in synchronization with the correction value and the z coordinate correction value.

In the charged particle beam drawing apparatus, the main and sub two-stage deflection amounts are calculated,
The coordinate correction unit preferably inputs the x-coordinate correction value, the y-coordinate correction value, and the z-coordinate correction value from the outside during a waiting time other than during the calculation of the main deflection amount.

Moreover, the charged particle beam drawing apparatus further includes:
A measurement sensor for measuring the z-coordinate value of the drawing surface of the sample,
A reference mark for calibrating the measurement sensor;
With
The amount of deflection of the charged particle beam is calculated based on the value obtained by adding the z coordinate correction value obtained based on the external pressure to the z coordinate value measured during drawing using the measurement sensor calibrated with the reference mark before drawing. Is preferred.

The charged particle beam drawing method of one embodiment of the present invention includes:
Measure the outside air pressure value,
Correct the three-dimensional coordinate value using the measured external pressure value,
Calculate the deflection amount of the charged particle beam using the corrected three-dimensional coordinate value,
A desired pattern is drawn on a sample by irradiating a charged particle beam deflected based on a deflection amount.

The charged particle beam drawing method further includes an x-coordinate correction value for correcting the x-coordinate value indicating the position in the first direction parallel to the drawing surface of the sample, and the first direction parallel to the drawing surface. Calculating a y-coordinate correction value for correcting the y-coordinate value indicating the position in the second direction, and a z-coordinate correction value for correcting the z-coordinate value indicating the position in the third direction orthogonal to the drawing surface;
The three-dimensional coordinate value is defined by the above-described x coordinate value, y coordinate value, and z coordinate value,
When correcting the three-dimensional coordinate value, the x coordinate value is corrected using the x coordinate correction value, the y coordinate value is corrected using the y coordinate correction value, and the z coordinate value is corrected using the z coordinate correction value. It is preferable.

Further, the charged particle beam drawing method further uses the corrected z coordinate value to convert a coefficient of a predetermined equation using x and y used as variables to calculate the deflection amount of the charged particle beam. ,
When calculating the deflection amount, the corrected x-coordinate value and the corrected y-coordinate value may be substituted as variables into a predetermined xy function expression whose coefficient has been converted.

Further, a program for causing the logical operation device according to one aspect of the present invention to execute is as follows.
The first, second, and third coordinates are stored in the storage device that stores the first, second, and third coordinate correction values that correct the first, second, and third coordinate values based on the value of the external air pressure. Coordinate correction value is read out, and the first, second, and third coordinate values are corrected using the read first, second, and third coordinate correction values, and stored in a storage device. Processing,
A conversion process for reading the third coordinate value from the storage device and converting a coefficient of a predetermined formula for calculating the deflection amount of the charged particle beam using the read third coordinate value;
A deflection amount calculation process for calculating a deflection amount of the charged particle beam using the first and second coordinate values and the coefficient of the predetermined formula, and outputting the result;
Should be provided.

  According to the present invention, it is possible to irradiate a beam to a deflection position in which a positional deviation of a drawing position due to a change in atmospheric pressure is corrected. Therefore, it is possible to perform drawing in which the positional deviation due to the atmospheric pressure variation is corrected. As a result, highly accurate drawing can be performed.

Embodiment 1 FIG.
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. As an example of the charged particle beam apparatus, a charged particle beam drawing apparatus, particularly, a variable shaping type electron beam drawing apparatus will be described.

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 an electron beam apparatus. The drawing apparatus 100 draws a pattern on the sample 101. The sample 101 includes a mask for manufacturing a semiconductor device. The drawing unit 150 includes a drawing chamber 103 and an electronic lens barrel 102 disposed on the upper portion of the drawing chamber 103. In the electron column 102, an electron gun 201, an illumination lens 202, a first aperture 203, a projection lens 204, a deflector 205, a second aperture 206, an objective lens 207, a sub deflector 212, and a main deflector 214 are provided. Have. An XY stage 105 is arranged in the drawing chamber 103, and a sample 101 to be drawn is arranged on the XY stage 105. A mirror 192 is disposed on the XY stage 105. Further, on the upper surface side of the drawing chamber 103, a z sensor having a projector 532 and a light receiver 534 for detecting the z direction of the sample 101 (a direction orthogonal to the drawing surface of the sample 101) is disposed. For example, a projector element is preferably used as the projector 532. In addition, as the light receiver 534, a position detection element (PSD: Position Sensitive Device) is preferably used.

  On the other hand, the control unit 160 includes a drawing control circuit 110, a deflection control circuit 140, a barometer 170 that measures the external atmospheric pressure in the installation environment of the electron column 102, a digital analog converter (DAC) 172, an amplifier 174, a DAC 182, an amplifier 184, It has a DAC 192, an amplifier 194, and a laser length measuring device 190. The drawing control circuit 110 includes a control computer (CPU) 120 and a storage device 130. The deflection control circuit 140 also includes a control computer (CPU) 142 and a storage device 144. A barometer 170, a deflection control circuit 140, a light receiver 534, and a laser length measuring device 190 are connected to the drawing control circuit 110 via a bus (not shown). The output of the laser length measuring device 190 is also connected to the deflection control circuit 140 via a bus (not shown). The sub deflection output signal (DAC value) from the deflection control circuit 140 is converted into an analog signal by the DAC 172, amplified by the amplifier 174, and output to the sub deflector 212. The electron beam 200 is deflected in the sub-deflection plane by the voltage of this output value. The main deflection output signal (DAC value) from the deflection control circuit 140 is converted into an analog signal by the DAC 182, amplified by the amplifier 184, and output to the main deflector 214. The electron beam 200 is deflected in the main deflection plane by the voltage of this output value. The shaping deflection output signal (DAC value) from the deflection control circuit 140 is converted into an analog signal by the DAC 192, amplified by the amplifier 194, and output to the deflector 205. The electron beam 200 is shaped and deflected by the voltage of this output value. The CPU 120 has various functions such as an external air pressure measurement unit 122 and a coordinate correction value calculation unit 124. Information input to the CPU 120 or information during and after the arithmetic processing is stored in the storage device 130 each time. The CPU 142 has various functions such as a coordinate value correction unit 126, a coefficient conversion unit 128, a deflection voltage calculation unit 146, a correction value confirmation unit 147, and an update unit 148. Information input to the CPU 142 or information during and after the arithmetic processing is stored in the storage device 144 each time. In FIG. 1, description of components other than those necessary for describing the first embodiment is omitted. It goes without saying that the drawing apparatus 100 usually includes other necessary configurations.

  In FIG. 1, it is described that the CPU 120, which is an example of a computer, executes processing of each function such as the external air pressure measurement unit 122 and the coordinate correction value calculation unit 124. However, the present invention is not limited to this. You may carry out by the hardware by a simple circuit. Or you may make it implement by the combination of the hardware and software by an electrical circuit. Alternatively, a combination of such hardware and firmware may be used. Similarly, it is described that the CPU 142, which is an example of a computer, executes processing of each function such as a coordinate value correction unit 126, a coefficient conversion unit 128, a deflection voltage calculation unit 146, a correction value confirmation unit 147, and an update unit 148. However, the present invention is not limited to this, and hardware using an electric circuit may be used. Or you may make it implement by the combination of the hardware and software by an electrical circuit. Alternatively, a combination of such hardware and firmware may be used.

  An electron beam 200 emitted from an electron gun 201 that is an example of an irradiation unit illuminates the entire first aperture 203 having a rectangular hole, for example, a rectangular hole, by an illumination lens 202. 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 aperture 203 is projected onto the second aperture 206 by the projection lens 204. The position of the first aperture image on the second aperture 206 is controlled by the deflector 205, and the beam shape and size can be changed. Then, the electron beam 200 of the second aperture image that has passed through the second aperture 206 is focused by the objective lens 207, deflected by the sub-deflector 212 and the main deflector 214 serving as a deflection unit, and is movable. The desired position of the sample 101 on the arranged XY stage 105 is irradiated. The position in the xy direction parallel to the sample surface (drawing surface) of the XY stage 105 is measured by irradiating the mirror 192 with a laser from the laser length measuring device 190 and receiving the reflected light from the mirror 192. In FIG. 1, only one mirror 192 and one laser length measuring device 190 are shown, but a plurality of combinations are arranged so that the positions in the x and y directions can be measured.

FIG. 2 is a diagram showing a main part of the steps of the electron beam writing method according to the first embodiment.
FIG. 2 shows processing in the drawing control circuit 110 and processing in the deflection control circuit 140 necessary for correcting the drawing position due to fluctuations in external atmospheric pressure. As processing in the drawing control circuit 110, a series of steps of an external air pressure measurement step (S102) and a coordinate correction value calculation step (S104) are performed. In the process in the deflection control circuit 140, a dual task method is used in which two tasks such as an atmospheric pressure correction task and a drawing task are started simultaneously. The drawing task includes a series of a coordinate value correction step (S302), a coefficient conversion step (S304), a deflection voltage calculation step (S306), a drawing processing step (S308), a settling step (S310), and a determination step (S312). Perform the process. As the atmospheric pressure correction task, a series of steps of a correction value confirmation step (S202) and an update step (S204) are performed.

FIG. 3 is a diagram for explaining how the XY stage moves.
When drawing on the sample 101, the drawing (exposure) surface is virtually arranged in a plurality of strip-like stripe regions where the electron beam 200 can be deflected while continuously moving the XY stage 105 in the x direction by a driving unit (not shown). The electron beam 200 irradiates one stripe region of the divided sample 101. Simultaneously with the movement of the XY stage 105 in the x direction, the shot position of the electron beam 200 also follows the stage movement. The drawing time can be shortened by continuously moving. When drawing of one stripe area is completed, the XY stage 105 is stepped in the y direction, and the next stripe area is drawn in the x direction (in this case, the opposite direction). The moving time of the XY stage 105 can be shortened by making the drawing operation of each stripe region meander.

  Here, when performing electron beam drawing, it is necessary to measure (calibrate) the electron optical system in advance. This measurement (calibration) is performed on all the electron optical systems shown by the drawing unit in FIG. By this measurement and adjustment, a correction coefficient necessary for adjusting the deflection sensitivity of the beam and deflecting the beam is calculated. These measurements and adjustments are a beam adjustment process, and are performed separately from the drawing process as a preparation for the drawing process for drawing a desired pattern on the sample.

  The deflection sensitivity of the deflector, for example, the main deflector 214 is measured (calibrated) by the beam adjustment process, and output to the DAC 182 that determines, for example, a voltage value set in the main deflector 214 to be corrected by the correction. The DAC value to be performed is defined using the X value and the Y value that are the DAC value data. As an example, the X value and the Y value can be obtained by the following expressions (1) and (2). Here, the equations (1) and (2) are called a beam deflection sensitivity correction function.

  In order to obtain these equations, first, it is necessary to measure an error between the designed position and the actual position measured by the laser length measuring device 190.

FIG. 4 is a diagram for explaining the mark position measuring method according to the first embodiment, and is a top conceptual view of the XY stage.
As shown in FIG. 4, a mark 152 for measuring the deflection sensitivity of the electron beam 200 is provided on the XY stage 105 on which the sample 101 is placed. The mark position coordinates are searched by moving the stage and deflecting the electron beam. The reflected electrons when the electron beam 200 irradiates the mark 152 is measured, and the coordinate when it is maximum is determined as the mark position coordinate. Since the mark position coordinates are calculated using the deflection of the electron beam 200, fluctuations depending on the atmospheric pressure value are observed. The correction coefficient for the atmospheric pressure variation can be derived from the relativity between the atmospheric pressure value and the mark position coordinate deviation.

Here, a region where the main deflector 214 deflects and a region where the sub deflector 212 deflects will be described.
FIG. 5 is a diagram showing a main deflection region and a sub deflection region in the first embodiment.
As shown in FIG. 5, when a predetermined pattern is drawn by the drawing apparatus 100, for example, the drawing area of the mask that becomes the sample 101 has a width that can be deflected by the main deflector 214, for example, a plurality of stripes in the y direction. Are divided into unit drawing areas (stripes). An area that can be deflected by the main deflector 214 in each stripe is a main deflection area. A region obtained by further subdividing the main deflection region is a sub deflection region (or called a subfield).

  The sub deflector 212 is used to control the position of the electron beam 200 for each shot at high speed and with high accuracy. For this reason, the deflection range is limited to the subfield as shown in FIG. 5, and the drawing beyond the area moves the position of the subfield by the main deflector 214. The main deflector 214 is used to control the position of the subfield, and the XY stage 105 continuously moves in the x direction during drawing. It is moved (tracked) to follow the movement of the XY stage 105.

FIG. 6 is a diagram for explaining how to measure the mark position in the first embodiment.
As shown in FIG. 6, the XY stage 105 is moved to move the mark 152 to each desired position in the main deflection region 10. Then, the electron beam 200 is deflected to each position in the main deflection region 10 to measure the position of the mark 152, and the residual is obtained. Here, a total of 25 points of 5 points × 5 points are performed in the main deflection region 10. Then, by fitting the obtained residual with a cubic function expression using xy in the above-described expressions (1) and (2) as a variable, the coefficients a _{0 to} a ₉ and b ₀ to b ₉ can be obtained.

  Then, the deflection control circuit 140 receives shot data (not shown) together with the position information from the drawing control circuit 110, and the X value that becomes one of the DAC value data in Expression (1) is converted into the DAC value data in Expression (2). The other Y value is obtained. Then, the electron beam 200 is deflected with a value obtained by DA-converting and amplifying the DAC value (deflection voltage) using the X value and the Y value as parameters. For example, when an 8-pole electrostatic deflector provided with the electrodes (1) to (8) clockwise as viewed from above is used as the main deflector 214, the DAC value may be set as follows. In order to deflect in a predetermined direction in the xy direction, the electrode (1) has Y, the electrode (2) has (X + Y) / √2, the electrode (3) has X, the electrode (4) has (XY) / √2, -Y for electrode (5), (-XY) / √2 for electrode (6), -X for electrode (7), electrode (8) Is set to a value such as (−X + Y) / √2. Then, each value obtained by DA-converting each set DAC value may be applied to each corresponding electrode. Here, depending on the position of the sample 101 in the z direction, the beam to be drawn may be distorted, or the beam focus may be shifted, or both. ) And the coefficient of equation (2) are preferably converted. The coefficient conversion can be defined by the following equation (3).

FIG. 6 is a diagram for explaining the process of calculating the coefficients in the equations (1) and (2). As shown in FIG. 6, by moving the XY stage 105, the mark 152 is moved to each desired position within the main deflection region. Then, after determining the reference mark, the electron beam 200 is deflected to each position in the main deflection area to measure the mark position, and the residual between the movement of the laser coordinates and the deflection distance is obtained. Here, a total of 25 points of 5 points × 5 points are performed in the main deflection region. Then, from the obtained residual, fitting is performed by a cubic function expression using x and y in the above-described expressions (1) and (2) as variables, and each coefficient a _{0 of the} deflection sensitivity correction function (xy function expression). calculating a ~a ₉ and _b 0 ~b _9.

FIG. 7 is a diagram for explaining how to measure the mark height in the first embodiment.
FIG. 8 is a diagram for explaining rotation and magnification errors in defocusing of the electron beam depending on the height of the sample surface in the first embodiment.
FIG. 9 is a simplified graph for explaining an error in rotation and magnification in defocusing of the electron beam depending on the height of the sample surface in the first embodiment.
Hereinafter, it will be described with reference to FIGS. 7 to 9 that the electron beam defocusing and deflection sensitivity deviation occur according to the height of the sample surface. As shown in FIG. 7, when the mark 152 with Z = 0 is used as a reference point and the electron beam 200 is irradiated to the mark 152 having a height difference, the deflection region is rotated and reduced by the electron beam 200 as shown in FIG. Or enlargement is seen. If the focus of the beam is deviated, the magnification component, the rotation component, and the shift component of the deflection region are shifted. Therefore, when correcting the focus of the beam according to the height of the sample surface, the magnification correction and the rotation correction of the deflection region, Shift correction is required. However, there is no need for shift correction if the current center of the correction lens is adjusted. Here, when an arbitrary height reference point is determined, rotation and magnification errors from the reference point can be expressed by linear functions of height (Z) as shown in FIG. These magnification, rotation, and shift corrections can be obtained with sufficient correction accuracy by the linear expression shown by the following expression (3).

Here, a ₀ and b ₀ are axis deviation corrections, a ₁ and b ₂ are magnification corrections, and a ₂ and b ₁ are rotation corrections, which are substituted into equations (1) and (2), respectively. Also, the value measured by the z sensor before drawing is substituted for z shown in Equation (3). Prior to drawing, the sample surface is divided into meshes, and the height of the grid (z) in the sample surface can be mapped by measuring the height of each mesh grid with the z sensor. As a result, the z value at an arbitrary position can be obtained. By substituting this z value into equation (3), focusing according to the height of the sample surface in the main deflection region becomes possible.

Thus, by obtaining the respective coefficients a _{0 to} a ₂ and b _{0 to} b ₂ from the relationship shown in FIG. 9, even when focus correction is performed according to the height deviation of the data surface, z is set. It is possible to correct the rotation, magnification, shift correction, and the like caused by the deflection sensitivity.

Here, the above description holds when the external air pressure is assumed to be constant. Further errors occur due to fluctuations in the outside air pressure.
FIG. 10 is a conceptual diagram for explaining an example of a distortion state of the drawing apparatus when the external air pressure increases in the first embodiment.
For example, when the external pressure P rises, the ceiling portion on the upper surface side of the drawing chamber 103 whose inside is evacuated by a vacuum pump or the like (not shown) is pushed by the external pressure P and deformed toward the inside of the drawing chamber 103. To do. For example, it dents in nm order. In that case, since the position of the electron column 102 installed on the drawing chamber 103 is shifted, the optical system in the electron column 102 and the surface of the sample 101 are respectively in three-dimensional (x, y, z) directions. The relative position will shift. For example, the value z deviates from the value z in the z direction. And since the installation position of the light projector 532 and the light receiver 534 will also shift | deviate because a ceiling part dents, an error will arise in the measured value itself of z sensor. Therefore, in the first embodiment, this deviation is corrected along the flow shown in FIG.

  In S102, as an external air pressure measurement step, the external air pressure measurement unit 122 inputs the value of the external air pressure P from the barometer 170 and measures the value of the external air pressure.

  In S104, as the coordinate correction value calculation step, the coordinate correction value calculation unit 124 uses the measured value of the external air pressure P to calculate the coordinate value (x, y, z) (first, second, and third coordinate values). ) Is corrected, and the first, second, and third coordinate correction values are calculated and stored in the storage device 130. The coordinate value indicates an x coordinate value indicating a position in a first direction (x direction) parallel to the drawing surface of the sample 101, and a position in a second direction (y direction) parallel to the drawing surface and perpendicular to the x direction. The y coordinate value shown and the z coordinate value showing the position (height) of the drawing surface in the third direction (z direction) orthogonal to the drawing surface. In this coordinate correction value calculation step, as coordinate correction values, an x coordinate correction value Δx for correcting the x coordinate value, a y coordinate correction value Δy for correcting the y coordinate value, and a z coordinate correction for correcting the z coordinate value. The value Δz is calculated.

First, the x-coordinate correction value Δx has a proportional coefficient c _{1 in} the x direction (for example, the unit is [nm / hPa]) and an offset value P ₁ of the external air pressure P (for example, the unit is [hPa]). ) Can be obtained by the following equation (4).

The y coordinate correction value Δy is expressed by the following equation (5) using the proportional coefficient c _{2 in} the y direction (for example, the unit is [nm / hPa]) and the offset value P ₁ of the external air pressure P described above. ).

The z coordinate correction value Δz is expressed by the following equation (6) using the proportional coefficient c _{3 in} the z direction (for example, the unit is [nm / hPa]) and the offset value P ₁ of the external pressure P described above. ).

  The coordinate correction values (Δx, Δy, Δz) obtained as described above are temporarily stored in the storage device 130. The series of steps (S102 to S104) is repeated at predetermined intervals to update the coordinate correction values (Δx, Δy, Δz) to the latest values. For example, it is updated at 1 minute intervals. Alternatively, a shorter cycle may be used. Or, although the real-time property is inferior, a longer cycle may be used. The coordinate correction value calculation process is a process independent of the drawing process or the beam adjustment process, and operates asynchronously with these processes.

  On the other hand, a drawing task is activated in the deflection control circuit 140. First, as will be described later, the latest coordinate correction values (Δx, Δy, Δz) are stored in the storage device 144 by an update process.

  In S302, as a coordinate value correction process, the coordinate value correction unit 126 reads the coordinate correction values (Δx, Δy, Δz) from the storage device 144, and uses the read coordinate correction values (Δx, Δy, Δz). The coordinate value (x, y, z) is corrected. Then, the coordinate value correcting unit 126 calculates and calculates the corrected coordinate values (x ′, y ′, z ′) after correction. In the coordinate value correction step, the x coordinate value is corrected using the x coordinate correction value Δx, the y coordinate value is corrected using the y coordinate correction value Δy, and the z coordinate value is corrected using the z coordinate correction value Δz. .

  First, the corrected coordinate value x ′ (an example of the first coordinate value) can be obtained by the following equation (7) in which the x coordinate correction value Δx is added to the x coordinate value.

  The corrected coordinate value y ′ (an example of the second coordinate value) can be obtained by the following equation (8) in which the y coordinate correction value Δy is added to the y coordinate value.

  The corrected coordinate value z ′ (an example of the third coordinate value) can be obtained by the following equation (9) in which the z coordinate correction value Δz is added to the z coordinate value.

In S304, as the coefficient conversion step, the coefficient conversion unit 128 reads the corrected z coordinate value z ′ (third coordinate value) from the storage device 144, and uses the read corrected z coordinate value z ′. Thus, the coefficients of the equations (1) and (2) described above are corrected. Among the coefficients of the above-described formulas (1) and (2), the first-order and lower-order coefficients a _{0 to} a ₂ and b _{0 to} b ₂ shown in the formula (3) affected by the z value are calculated. Specifically, when the coefficients a _{0 to} a ₂ and b _{0 to} b ₂ are obtained in the equation (3), the corrected z coordinate value z ′ is substituted for the z value. This makes it possible to calculate the coefficients of the primary less in consideration of the variation of the outside air pressure P _a 0 ~a ₂ and _b 0 ~b _2.

  In S306, as the deflection voltage calculation step, the deflection voltage calculation unit 146 calculates the deflection voltage of the electron beam 200 using the coordinate value after the previous correction.

  In S308, as a drawing processing step, the electron beam 200 irradiated from the electron gun 201 as an example of the irradiation unit is deflected by the main deflector 214 or the like as an example of the deflection unit, and the obtained deflection voltage is used. Irradiated with the deflected electron beam 200, a desired pattern is drawn on the sample 101. That is, the main deflector 214 electrostatically deflects the electron beam 200 to correct the x coordinate value and the y coordinate value based on the external pressure. Further, by correcting the focal position by changing the excitation to the objective lens 207 based on the corrected z-coordinate value z ′, the z-coordinate value based on the external air pressure can also be corrected.

  In S310, as a settling process, a time (settling time) is set in which data is set in the DAC of the deflector after the drawing of a predetermined drawing unit is finished and the output voltage settles. For example, after the drawing of one subfield (SF) is completed, when the deflection position of the main deflector 214 is changed to the next SF, data is set in the main deflection DAC 182 and then a waiting state is provided for the settling time. ing. In this embodiment, the settling time is about 20 μs.

  On the other hand, in the atmospheric pressure correction task in the deflection control circuit 140 instructed by the CPU 120 in the drawing control circuit 110, the following processing is executed.

  In S202, as a correction value confirmation step, the correction value confirmation unit 147 in the deflection control circuit 140 receives a command from the CPU 120 in the drawing control circuit 110, and when the drawing task is settling time, the coordinate correction value due to fluctuations in external air pressure. It is confirmed whether or not (Δx, Δy, Δz) is changed. Information on whether or not there is a change may be obtained from the CPU 120 in the drawing control circuit 110.

  In S204, as an update process, the update unit 148 in the deflection control circuit 140, when there is a change as a result of the above-described confirmation process, reads the coordinate correction value (Δx, [Delta] y, [Delta] z) is read out and updated by overwriting the previous data stored in the storage device 144 in the deflection control circuit 140. Data transfer load can be reduced by inputting data only when there is a change.

  As described above, first, a task executed by the CPU 142 in the deflection control circuit 140 receives real-time data by receiving an access at an interval of 1 minute from the execution process of the CPU 120 in the drawing control circuit 110 serving as an atmospheric pressure correction process. Updates can be made. Here, the update from the atmospheric pressure correction process may be batting with a drawing process or a beam adjustment process executed in the deflection control circuit 140. Therefore, in the present embodiment, since the dual task configuration in which two tasks are executed in the deflection control circuit 140 is adopted, the above-described batting can be avoided. That is, in one task, in order to receive a command from the drawing process and to access the atmospheric pressure correction process during the drawing in operation, the original drawing task is paused and the atmospheric pressure correction process is performed. A problem arises that a task must be launched. On the other hand, by using the dual task, the pressure correction task can be started in parallel without temporarily stopping the drawing task.

  In a drawing task, the drawing time of a stripe having a high shot density may exceed 1 minute. The atmospheric pressure correction process always accesses the deflection control circuit 140 at a predetermined interval (for example, 1 minute interval) set in advance as described above. Since the deflection control circuit 140 must monitor asynchronous access from the atmospheric pressure correction process, it takes some time for processing. Therefore, by calling the atmospheric pressure correction task during the drawing task, the update can be completed within the settling time, and for example, real-time correction can be performed at intervals of 1 minute. In the drawing process task, the settling time of the main deflection DAC amplifier having the DAC 182 and the amplifier 184 requires about 20 μs. Therefore, when the core is idle during the settling time, it is possible to enable real-time communication with the pressure correction process by switching to the pressure correction task once.

  In S312, as a determination step, the CPU 142 of the deflection control circuit 140 determines whether or not drawing is finished. If the drawing is finished, the drawing task is finished. If the drawing is not finished yet, the process returns to S301.

In the drawing task, the coordinate values x ′, y ′, z ′ are calculated in S302 using the coordinate correction values (Δx, Δy, Δz) corrected in real time. Then, the coefficient is converted in S304 using z ′. Then, using the converted coefficients and the corrected coordinate values x ′ and y ′, the DAC value data that is the source of the next deflection voltage is calculated in S306. Specifically, in the deflection voltage calculation step, the deflection sensitivity correction function (xy function formula) is applied to each coefficient a _{0 to} a ₂ and b _{0 to} b ₂ calculated in Formula (3) using z ′ as the coefficient. By substituting the corrected x ′ and the corrected y ′ as variables into the equations (1) and (2), the X value and the Y value as the DAC value data are obtained. Then, the DAC value (deflection voltage) for each electrode of the deflector 214 is calculated from the X value and the Y value. Then, it is possible to perform drawing with a value obtained by DA-converting and amplifying the DAC value corrected with respect to the fluctuation in the external air pressure in S308.

As described above, the correction of the beam position and the focus correction in consideration of the coordinate position error (Δx, Δy, Δz) due to the fluctuation of the external atmospheric pressure, the coefficients a _{0 to} a ₂ and b of the deflection sensitivity correction function for calculating the deflection voltage. seeking ₀ ~b _2, the DAC value data to input and 'y and the corrected' x corrected seeking in real time, by performing the drawing processing while correcting these, a more accurate sample A pattern can be formed at the drawing position 101.

FIG. 11 is a conceptual diagram showing the drawing operation and the pressure correction operation timing in the first embodiment.
FIG. 11 shows a drawing operation in one stripe and one subfield, and a pressure correction operation synchronized with the drawing operation. One stripe drawing operation is performed by repeating an arbitrary number of subfield drawing operations. The drawing operation for one subfield starts from reading of the main deflection coordinate value, is performed by calculating the main deflection amount, and repeating an arbitrary number of shots. The deflection control circuit 140 calculates the main deflection amount by substituting the read main deflection coordinate value (x, y) into the deflection sensitivity correction function (Equation (1), Equation (2)) in the deflection amount calculation unit 146. I do. Here, when performing atmospheric pressure correction, in this process, the coordinate value correction unit 126 adds the correction amount calculated by the correction value calculation unit 124. The coefficient converter 128 further performs coefficient conversion using the corrected z ′. The correction value calculation unit 124 operates asynchronously with the drawing operation and the beam adjustment process. For example, the correction value calculation unit 124 calculates correction amounts Δx, Δy, and Δz of the three-dimensional coordinate values of x, y, and z at 1-minute intervals, Transfer to the deflection control circuit 140. The deflection control circuit unit 140 reads the atmospheric pressure correction amount from the correction value calculation unit 124 during a waiting time other than during the calculation of the main deflection amount. Here, for example, it is performed during the main deflection settling time in the subfield drawing operation. Thereby, the atmospheric pressure correction can be synchronized with the subfield drawing operation unit. In addition, this operation principle enables real-time pressure correction. As described above, the drawing process and the beam adjustment process operate independently, and Δx, Δy, and Δz are added in synchronization with the three-dimensional coordinate values in one of the drawing process and the beam adjustment process for each subfield operation unit. Control.

  Here, an operation method including a drawing process and a beam adjustment process will be described. The beam adjustment process is executed for each processing menu and adjustment period set in advance. In the present embodiment, a case will be described in which focusing is performed at a rate of once a week, for example. When the focus shift due to fluctuations in the external air pressure is not corrected, the excitation current at the optimum focus changes depending on the external air pressure. For this reason, if focusing is performed at a low pressure, a pattern is drawn with the beam blurred in normal weather. In the beam calibration for correcting the deflection error of the beam, a deflection rotation and a magnification error are generated according to the atmospheric pressure. For this reason, if the beam is calibrated at low atmospheric pressure, there is a problem that in a drawing process in normal weather, drawing is performed with a deviation in deflection sensitivity and a batting error increases.

  Therefore, as described in the present embodiment, when a three-dimensional (x, y, z) beam position error that depends on fluctuations in external atmospheric pressure is corrected, the focal point of the beam is always constant, and the beam deflection error is reduced. Variations can also be suppressed. Therefore, it is possible to draw a pattern with high accuracy without increasing the beam defocus or deflection sensitivity error depending on the pressure fluctuation timing.

Embodiment 2. FIG.
In the first embodiment, the case where the height distribution (z map) of the sample surface is measured in advance in the drawing process has been described. In this case, as described above, drawing was performed after correction using the z ′ value newly calculated by adding the Δz fluctuation amount depending on the outside air pressure fluctuation to the z map data measured in advance. This is because the measured value of the z sensor for measuring the height (z) of the sample surface is shifted depending on the fluctuation of the external atmospheric pressure. However, this z sensor can also be commercialized with a structure in which fluctuations in external atmospheric pressure are reduced. In the second embodiment, a z sensor that is resistant to such an outside air pressure fluctuation is used. Other configurations are the same as those in the first embodiment. When using a z sensor that is resistant to such external pressure fluctuations, it is preferable to use a configuration that performs z correction in real time during drawing rather than the z map method. Specifically, for each subfield, the height (z) data is read from the z sensor, the equation (3) is calculated, and the coefficients of the equations (1) and (2) are obtained. The same applies if the position information (x ′, y ′) obtained by correcting the position error that fluctuates in accordance with the variation in the external air pressure is input to the deflection sensitivity correction functions of the expressions (1) and (2) obtained here and drawn. Effects can be obtained.

Embodiment 3 FIG.
In the first and second embodiments, the position of the beam is corrected by electrostatic deflection using the main deflector 214 which is an electrostatic deflector. That is, the electron beam 200 is electrostatically deflected by the main deflector 214 to correct the x coordinate value and the y coordinate value based on the external air pressure, and the z coordinate value based on the external air pressure is corrected by the objective lens 207 (focal position). Correction). However, the beam correction is not limited to this. In the third embodiment, a description will be given of a case where the deflection position and the focal position of the beam are corrected with other configurations.

FIG. 12 is a conceptual diagram illustrating a part of the configuration of the drawing apparatus according to the third embodiment.
12 is the same as FIG. 1 except that alignment coils 215, 216, 217 and an electrostatic lens 218 are added to the configuration of FIG. Other configurations are the same as those of the first embodiment except for the points described below. The alignment coils 215, 216, and 217 above the objective lens 207 perform beam deflection using a magnetic field generated by the excitation current. The position of the beam may be corrected using this coil. That is, instead of the main deflector 214, it is preferable to correct the x coordinate value and the y coordinate value based on the external pressure by electromagnetically deflecting the electron beam 200 with at least one of the alignment coils 215, 216, and 217. is there.

  For the correction of the z coordinate value based on the external atmospheric pressure, the main deflector 214 or the electrostatic lens 218 (second electrostatic deflector) arranged independently can be used instead of the correction with the objective lens. . For example, the z coordinate value based on the external air pressure can be corrected by correcting the focal position by superimposing a constant voltage on the main deflector 214. Similarly, the z coordinate value based on the external air pressure can be corrected by correcting the focal position by superimposing a constant voltage on the electrostatic lens 218.

  In the above description, the processing content or operation content described as “˜part” or “˜process” can be configured by a program that can be operated by a logical operation device such as a computer. Or you may make it implement by not only the program used as software but the combination of hardware and software. Alternatively, a combination with firmware may be used. When configured by a program, the program is recorded on a readable recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (Read Only Memory) (not shown). For example, it is stored in the storage device 130 or the storage device 144.

  In FIG. 1, the CPU 120 and / or the CPU 142 serving as a computer further includes a RAM (random access memory), a ROM, a magnetic disk (HD) device, an input as an example of a storage device via a bus (not shown). Connected to a keyboard (K / B), an example of a means, a monitor, a printer, an example of an output means, an external interface (I / F), an example of an input output means, FD, DVD, CD, etc. It does not matter.

  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 drawing methods, charged particle beam drawing apparatuses, and programs 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.

1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to Embodiment 1. FIG. FIG. 3 is a diagram showing a main part of the steps of the electron beam drawing method in the first embodiment. It is a figure for demonstrating the mode of XY stage movement. It is a top surface conceptual diagram of an XY stage. FIG. 3 is a diagram showing a main deflection region and a sub deflection region in the first embodiment. 7 is a diagram for explaining how to measure the position of a mark in Embodiment 1. FIG. 7 is a diagram for explaining how to measure the mark height in the first embodiment. FIG. FIG. 6 is a diagram for explaining rotation and magnification errors in defocusing of an electron beam depending on the height of a sample surface in the first embodiment. 4 is a simple graph for explaining an error in rotation and magnification in defocusing of an electron beam depending on the height of a sample surface in the first embodiment. FIG. 6 is a conceptual diagram for explaining an example of a distortion state of the drawing apparatus when the external air pressure increases in the first embodiment. FIG. 3 is a conceptual diagram illustrating a drawing operation and a pressure correction operation timing in the first embodiment. FIG. 10 is a conceptual diagram illustrating a part of the configuration of a drawing apparatus according to a third embodiment. It is a conceptual diagram for demonstrating operation | movement of the conventional variable shaping type | mold electron beam drawing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main deflection area 100 Drawing apparatus 101,340 Sample 102 Electron barrel 105 XY stage 110 Drawing control circuit 120,142 CPU
122 External pressure measurement unit 124 Coordinate correction value calculation unit 126 Coordinate value correction unit 128 Coefficient conversion unit 146 Deflection voltage calculation unit 147 Correction value confirmation unit 148 Update units 130 and 144 Storage device 140 Deflection control circuit 150 Drawing unit 152 Mark 160 Control unit 170 Barometer 172,182,192 DAC
174, 184, 194 Amplifier 190 Laser length measuring device 192 Mirror 200 Electron beam 201 Electron gun 202 Illumination lens 203, 410 First aperture 204 Projection lens 205 Deflector 206, 420 Second aperture 207 Objective lens 212 Sub deflector 214 Main deflector 330 Electron beam 411 Aperture 421 Variable shaping aperture 430 Charged particle source 532 Projector 534 Receiver

Claims (10)

An atmospheric pressure measurement unit for measuring the value of the external atmospheric pressure;
A coordinate value correction unit that corrects a three-dimensional coordinate value using the measured value of the external pressure;
A deflection amount calculation unit that calculates the deflection amount of the charged particle beam using the corrected three-dimensional coordinate value;
An irradiation unit for irradiating the charged particle beam;
A deflection unit for deflecting the charged particle beam based on the deflection amount;
A charged particle beam drawing apparatus comprising: The charged particle beam drawing apparatus further includes an x-coordinate correction value for correcting an x-coordinate value indicating a position in a first direction parallel to the drawing surface of the sample, and an orthogonal to the first direction parallel to the drawing surface. Coordinates for calculating a y-coordinate correction value for correcting the y-coordinate value indicating the position in the second direction and a z-coordinate correction value for correcting the z-coordinate value indicating the position in the third direction orthogonal to the drawing surface. With a correction value calculator,
The three-dimensional coordinate value is defined by the x coordinate value, the y coordinate value, and the z coordinate value,
The coordinate value correction unit corrects the x coordinate value using the x coordinate correction value, corrects the y coordinate value using the y coordinate correction value, and uses the z coordinate correction value to correct the z coordinate. The charged particle beam drawing apparatus according to claim 1, wherein the value is corrected. The charged particle beam drawing apparatus further uses the corrected z coordinate value to convert a coefficient of a predetermined equation for calculating the deflection amount of the charged particle beam with x and y as variables. With a conversion unit,
3. The deflection amount calculation unit substitutes the corrected x-coordinate value and the corrected y-coordinate value as the variable into the predetermined xy function equation in which a coefficient is converted. Charged particle beam lithography system.   The deflecting unit electrostatically deflects the charged particle beam to correct the x coordinate value and the y coordinate value based on the external atmospheric pressure, and electromagnetically deflects the charged particle beam to electromagnetically deflect the charged particle beam. 4. The charged particle beam drawing apparatus according to claim 3, further comprising at least one of an alignment coil that corrects the x coordinate value and the y coordinate value based on atmospheric pressure.   The deflecting unit electrostatically deflects the charged particle beam to correct the x-coordinate value and the y-coordinate value based on the external air pressure, and corrects the focal position by superimposing a constant voltage. The charged particle beam drawing apparatus according to claim 3, further comprising an electrostatic deflector that corrects the z-coordinate value based on the external atmospheric pressure.   The charged particle beam drawing apparatus further includes an objective lens that corrects the z coordinate value based on the external air pressure by adjusting the focal position of the charged particle beam and changing excitation. The charged particle beam drawing apparatus according to claim 3.   The coordinate correction unit operates independently of the drawing process and the beam adjustment process, and the x-coordinate correction value is added to the three-dimensional coordinate value in one of the drawing process and the beam adjustment process for each subfield operation unit. The charged particle beam drawing apparatus according to claim 2, wherein the y coordinate correction value and the z coordinate correction value are added and controlled in synchronization. The charged particle beam drawing apparatus further includes:
A measurement sensor for measuring the z-coordinate value of the drawing surface of the sample,
A reference mark for calibrating the measurement sensor;
With
The charged particle beam based on a value obtained by adding the z-coordinate correction value obtained based on the external pressure to the z-coordinate value measured during the drawing using the measurement sensor calibrated with the reference mark before the drawing. The charged particle beam drawing apparatus according to claim 3, wherein the deflection amount is calculated. Measure the outside air pressure value,
The three-dimensional coordinate value is corrected using the measured value of the external pressure,
Calculate the deflection amount of the charged particle beam using the corrected three-dimensional coordinate value,
A charged particle beam drawing method, wherein a desired pattern is drawn on a sample by irradiating the charged particle beam deflected based on the deflection amount. The first, second, and third coordinates are stored in the storage device that stores the first, second, and third coordinate correction values that correct the first, second, and third coordinate values based on the value of the external air pressure. Coordinate correction value is read out, and the first, second, and third coordinate values are corrected using the read first, second, and third coordinate correction values, and stored in a storage device. Processing,
A conversion process for reading the third coordinate value from the storage device and converting a coefficient of a predetermined formula for calculating the deflection amount of the charged particle beam using the read third coordinate value;
A deflection amount calculation process for calculating a deflection amount of the charged particle beam using the first and second coordinate values and the coefficient of the predetermined formula, and outputting the result;
A program for causing a logical operation unit to execute.

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