JP4939076B2 - Charged particle beam writing method - Google Patents

Description

  The present invention relates to a charged particle beam writing method, for example, a writing method for irradiating a sample with a charged particle beam while variably shaping the charged particle 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. 9 is a conceptual diagram for explaining the operation of a conventional variable shaping type electron beam drawing apparatus.
In a first aperture 410 in a variable shaping type electron beam drawing apparatus (EB (Electron beam) drawing apparatus), a rectangular, for example, rectangular opening 411 for forming the electron beam 330 is formed. Further, the second aperture 420 is formed with a variable shaping opening 421 for shaping the electron beam 330 having passed through the opening 411 of the first aperture 410 into a desired rectangular shape. The electron beam 330 irradiated from the charged particle source 430 and passed through the opening 411 of the first aperture 410 is deflected by the deflector, passes through a part of the variable shaping opening 421 of the second aperture 420, and passes through a predetermined range. The sample 340 mounted on a stage that continuously moves in one direction (for example, the X direction) is irradiated. That is, the drawing area of the sample 340 mounted on the stage in which the rectangular shape that can pass through both the opening 411 of the first aperture 410 and the variable shaping opening 421 of the second aperture 420 is continuously moved in the X direction. Drawn on. A method of creating an arbitrary shape by passing both the opening 411 of the first aperture 410 and the variable shaping opening 421 of the second aperture 420 is referred to as a variable shaping method.

Here, when the electron beam is irradiated onto the sample 340 mounted on the stage described above, the focus is adjusted by the objective lens. When a part of the magnetic field of the objective lens leaks on the stage, an eddy current is generated in the conductive component on the stage. Such an eddy current generates a magnetic field on the stage, causing an error in the drawing position. The electrodynamics related to such eddy current is described in the literature (for example, see Non-Patent Document 1).
Toshihisa Honma et al., Hokkaido University "Basics and Applications of" Numerical Electrodynamics "", Japan Society for Simulation Technology / Edition, June 2002

  As described above, when a part of the magnetic field of the objective lens leaks on the stage, the magnetic field is generated on the stage due to the eddy current generated in the conductive parts on the stage, and the error due to the deviation of the drawing position of the beam. There was a problem that would occur.

  Therefore, an object of the present invention is to provide a drawing method that overcomes such problems and reduces the deviation of the drawing position of the beam.

The charged particle beam drawing method of one embodiment of the present invention includes:
In a charged particle beam drawing method for drawing on a sample using a charged particle beam while continuously moving the stage on which the sample is placed,
Draw in one direction to measure the error dimension of the pattern, then draw in the one-way reverse direction and measure the error dimension of the pattern again, the one-way error dimension and the one-way reverse error dimension The region where the magnetic field due to the eddy current occurs is calculated by calculating the difference between
A region where a magnetic field due to the specified eddy current is generated is drawn at a moving speed of the stage which is lowered so as to be equal to or less than a speed inversely proportional to an error size generated by the magnetic field.

  As will be described later, the magnetic field generated by the eddy current is proportional to the moving speed of the stage. Therefore, the magnetic flux density (intensity) of the magnetic field can be weakened by reducing the speed of the region. By weakening the magnetic field, the influence of the irradiated charged particle beam from the magnetic field can be reduced.

  Here, it is preferable that the moving speed of the stage is lowered so as to be equal to or lower than the speed inversely proportional to the error size caused by the magnetic field.

  The amount of misalignment is proportional to the influence of the charged particle beam on the magnetic field (magnetic flux density of the magnetic field). Therefore, the amount of positional deviation is proportional to the moving speed of the stage. Accordingly, the influence of the magnetic field can be eliminated by setting the moving speed of the stage to a speed that is inversely proportional to the error dimension.

  The stage moving speed to be lowered is preferably set to be equal to or lower than the speed obtained by multiplying the stage moving speed when no magnetic field is generated by the value obtained by dividing the allowable error dimension by the error dimension generated by the magnetic field.

A charged particle beam writing method according to another aspect of the present invention includes:
In a charged particle beam drawing method for drawing on a sample using a charged particle beam while continuously moving the stage on which the sample is placed at a constant speed,
The stage moving speed when the edge of the drawing area of the sample is drawn at a constant speed is made slower than the moving speed when the center of the drawing area is drawn at a constant speed.

  As will be described later, the inventor has found that the region where the magnetic field due to the eddy current is generated is concentrated at the end of the drawing region. Therefore, the influence of the magnetic field due to the eddy current is eliminated by making the stage moving speed when drawing the edge of the drawing area at a constant speed slower than the moving speed when drawing the center part of the drawing area at a constant speed. can do.

A charged particle beam writing method according to another aspect of the present invention includes:
In a charged particle beam writing method for drawing on a sample using a charged particle beam while continuously moving the stage on which the sample is mounted at a variable speed according to the pattern density,
The stage moving speed when drawing the end of the drawing area of the sample is made slower than the moving speed of the stage in an area having the same pattern density in the center of the drawing area.

  When the stage is continuously moved at a variable speed, the moving speed of the stage is set depending on the pattern density. Therefore, when drawing the edge of the drawing area where a magnetic field due to eddy current is drawn, the stage moving speed when drawing the edge is higher than the stage moving speed in the area of the equivalent pattern density in the center of the drawing area. By slowing down, the influence of the magnetic field due to the eddy current can be eliminated.

  According to the present invention, since the influence of the magnetic field due to the eddy current can be eliminated, it is possible to reduce the deviation of the drawing position of the beam.

  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 may be a beam using other charged particles such as an ion beam.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to the first embodiment.
In FIG. 1, a drawing apparatus 100, which is an example of a charged particle beam drawing apparatus, includes an electron column 102, a drawing chamber 103, an XY stage 105, an electron gun 201, and an illumination lens 202 that constitute a drawing unit 150 that is an example of an irradiation unit. , First aperture 203, projection lens 204, deflector 205, second aperture 206, objective lens 207, deflector 208, support pin 222, pedestal 312, reflection mirror 314, reference mirror 216, column 332, drive unit 106 The control unit 160 includes a drawing control circuit 110, a deflection control circuit 112 as an example of a deflection control unit, a stage driving circuit 114, a CPU 120, a memory 122, a laser interferometer 132, and a laser interferometer 134. A drawing control circuit 110, a deflection control circuit 112, a stage drive circuit 114, a memory 122, a laser interferometer 132, and a laser interferometer 134 are connected to a CPU 120 serving as a computer via a bus (not shown). The drawing control circuit 110, the deflection control circuit 112, and the stage drive circuit 114 are controlled by control signals output from the CPU 120. Further, input data or output data calculated by the CPU 120 is stored in the memory 122. The CPU 120 has a function such as a differential operation unit 124.

  In the electron barrel 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, and a deflector 208 are arranged. . In the drawing chamber 103, an XY stage 105, a pedestal 312, a reflection mirror 314, a reference mirror 216, a support pin 222, and a support column 332 are disposed. 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, the CPU 120 serving as a computer is described so as to execute processing of a function such as the differential operation unit 124. However, the present invention is not limited to this, and may be implemented by hardware using an electric circuit. Absent. Or you may make it implement by the combination of the hardware and software by an electric circuit. Alternatively, a combination of such hardware and firmware may be used.

  An electron beam 200 as an example of a charged particle beam emitted from the electron gun 201 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 deflection-controlled by the deflector 205 controlled by the drawing control circuit 110, and the beam shape and size can be changed. 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 deflector 208 controlled by the deflection control circuit 112, and controlled by the stage driving circuit 114. The desired position of the sample 101 on the XY stage 105 that continuously moves by the driving unit 106 is irradiated.

FIG. 2 is a diagram for explaining the stage movement in the first embodiment.
In the case of drawing on the sample 101, the drawing (exposure) surface of the sample 101 virtually divided into 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, for example. The electron beam 200 irradiates one stripe region. The movement of the XY stage 105 in the X direction is a continuous movement, and at the same time, the shot position of the electron beam 200 also follows the stage movement. 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 to perform the drawing operation for the next stripe area 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.

FIG. 3 is a diagram showing an example of the stage speed distribution in the first embodiment.
FIG. 3 shows an electron beam writing method in which the XY stage 105 draws on the sample 101 using the electron beam 200 while continuously moving at a constant speed. The magnetic field due to the eddy current is proportional to the moving speed of the stage. Therefore, as shown in FIG. 3, the magnetic flux density (intensity) of the magnetic field can be weakened by reducing the moving speed of the XY stage 105 when drawing the eddy current generation region on the drawing region of the sample 101. By weakening the magnetic field, the influence of the irradiated electron beam from the magnetic field can be reduced.

FIG. 4 is a conceptual diagram for explaining the generation mechanism of the eddy current in the first embodiment.
In the drawing apparatus 100, when a part of the magnetic field 10 of the electron lens such as the objective lens 207 leaks onto the XY stage 105, an eddy current 20 is generated in the conductive parts on the XY stage 105. Here, when the eddy current density is J, the electrical conductivity determined by the material is σ, the electric field determined by the boundary condition such as the shape is E, the stage speed is v, and the magnetic field (magnetic flux density) from the objective lens is B, The current density J can be expressed by the following formula (Formula 1).
Formula 1: J = σ (E + v × B)

Here, when the eddy current density J is partially differentiated at the position (x, y, z), it can be expressed as the following equation (Equation 2).
Equation _{2: divJ = ∂J x / ∂x} + ∂J y / ∂y + ∂J z / ∂z = 0

Since Expression 2 diverges except for 0, the value “0” is taken. Therefore, when Formula 1 is differentiated, it can be expressed as the following Formula (Formula 3).
Formula 3: divJ = σdivE + σdiv (v × B) = 0

  Therefore, div (v × B) = − divE, and E is proportional to v (E 比例 v). Since (v × B) is also {(v × B) ∝v} proportional to v, (E + v × B) is also {(E + v × B) ∝v} proportional to v. Therefore, the eddy current density J is proportional to the stage speed v (J∝v).

FIG. 5 is a conceptual diagram showing the state of the magnetic field on the stage due to the eddy current in the first embodiment.
As shown in FIG. 5, when an eddy current 20 is generated on the XY stage 105, a magnetic field 30 due to the eddy current 20 is generated on the XY stage 105. When the magnetic flux density of the magnetic field 30 is B ′, the magnetic flux density B of the magnetic field 10 in Equation 1 is replaced with the magnetic flux density B ′ of the magnetic field 30, and the eddy current density J is the magnetic flux density B ′ of the magnetic field 30. Therefore, the magnetic flux density B ′ of the magnetic field 30 is also proportional to the stage speed v (B ′） v). Since the irradiated electron beam 200 is bent by the magnetic flux density of the magnetic field 30 by B ′, the beam position shift amount (error dimension x) caused thereby is proportional to the stage velocity v (x∝v). .

  Therefore, when the magnetic field 30 due to the eddy current 20 is generated on the sample 101, the moving speed of the XY stage 105 when drawing the region where the magnetic field 30 due to the eddy current 20 is drawn is reduced, so that the beam position deviation amount (error) The dimension x) can be reduced accordingly. Therefore, it is preferable that the moving speed of the XY stage 105 is lowered so as to be equal to or lower than the speed inversely proportional to the error dimension x caused by the magnetic field 30. Thereby, the influence received from the magnetic field 30 can be eliminated.

  Here, if the allowable error dimension is x ′ and the moving speed of the lowered XY stage 105 is v ′, the relationship of x ′ / x = v ′ / v is established. Therefore, the lowered movement of the XY stage 105 is achieved. The speed is v ′ = v · x ′ / x. Therefore, if the XY stage 105 is moved at a slower speed that is equal to or lower than v ′, the influence from the magnetic field 30 can be eliminated. That is, the moving speed v ′ of the stage to be reduced is equal to or lower than the speed obtained by multiplying the moving speed v of the stage when the magnetic field 30 is not generated by the value obtained by dividing the allowable error dimension x ′ by the error dimension x generated by the magnetic field 30. It is preferable to set so.

FIG. 6 is a diagram showing a misalignment region due to eddy current in the first embodiment.
As a cause of the positional deviation of the pattern drawn in the electron beam drawing, the positional deviation due to such eddy current and the positional deviation depending on the position can be considered. Therefore, for example, when drawing while continuously moving the XY stage 105 in the X direction, the drawing is first performed in the X direction (positive direction) to measure the amount of pattern misalignment, and then the X direction reverse direction (negative) Direction) and measure the amount of pattern displacement. Then, if the difference between the obtained positional deviation amounts is taken, a positional deviation amount distribution independent of the position can be obtained. Since the position shift due to the eddy current does not depend on the position, the position shift area due to the eddy current exists in the area obtained by the difference. FIG. 6 shows a distribution of misalignment amounts that does not depend on such positions. According to FIG. 6, it can be seen that the misregistration region 40 is concentrated at the end (both ends) of the drawing area of the sample 101, not at the center of the drawing area of the sample 101.

FIG. 7 is a diagram illustrating an example of a speed limiting region in the first embodiment.
In FIG. 7, the position shift area 40 is an eddy current generation area 42, and the area surrounding the eddy current generation area 42 is a speed limit area 50. The influence of the eddy current from the magnetic field 30 can be eliminated by reducing the moving speed of the XY stage 105 when drawing the speed limiting region 50.

  Therefore, in the drawing method for drawing while continuously moving the XY stage 105 at a constant speed, the speed limit region 50 of the drawing area of the sample 101, that is, the stage moving speed v ′ when drawing the end portion at a constant speed is shown in FIG. As shown in FIG. 4, the influence of the eddy current from the magnetic field 30 is eliminated by making the central portion of the drawing region slower than the moving speed v when drawing at a constant speed. As a result, misalignment due to the eddy current 20 can be reduced.

In the drawing apparatus 100, the CPU 120 differentiates the displacement amount of the position of the reflection mirror 314, which is the position of the stage input from the laser interferometer 132 and the laser interferometer 134, at the time t in the differential calculation unit 124, thereby the XY stage 105. Is measured. Then, based on a product of a predetermined coefficient k ₁ and the velocity v, the deflector 208 is to control the position to be deflected.

FIG. 8 is a diagram showing another example of the stage speed distribution in the first embodiment.
FIG. 8 shows an electron beam drawing method in which the XY stage 105 draws on the sample 101 using the electron beam 200 while continuously moving at a variable speed. The moving speed of the XY stage 105 is changed according to the pattern density of the pattern to be drawn. In the example of FIG. 8, the case where it divided into four types of groups of pattern density AD is shown. The distribution indicated by the solid line is the speed when no eddy current is generated. As described above, the eddy current generation region 42 is concentrated not on the center portion of the drawing region of the sample 101 but on the end portions (both ends) of the drawing region of the sample 101. Therefore, the eddy current magnetic field 30 is set by making the moving speed v ′ of the stage when drawing the end of the drawing area of the sample 101 slower than the moving speed of the stage in the area having the same pattern density in the center of the drawing area. Eliminate the effects of As a result, misalignment due to the eddy current 20 can be reduced. In the example of FIG. 8, when the pattern density at the end of the sample 101 belongs to the A group, the speed is lower than the speed of the region belonging to the same A group at the center of the sample 101 (dotted line). By doing so, it is possible to reduce misalignment due to the eddy current 20. For example, when the pattern density is set in the drawing apparatus 100, by setting a value that is larger (dense) than the actual value in advance, the effect can be exhibited without improving the speed calculation program.

  Here, limiting the structure and material of the upper stage has a limit for realizing the necessary functions. Therefore, as described above, the magnetic flux density (intensity) of the magnetic field is obtained by partially lowering the moving speed of the XY stage 105 when drawing the drawing area of the sample 101 in the eddy current generation area on the drawing area of the sample 101. Can be weakened. By weakening the magnetic field, the influence of the irradiated electron beam from the magnetic field can be reduced or eliminated. Therefore, it is possible to cope with the stage function being maintained.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In the embodiment described above, the pattern density is used as a parameter for determining the stage speed comparison area. However, the present invention is not limited to this, and the stage speed comparison area may be determined using other parameters for determining the stage speed. Good. In addition, as a method of actually reducing the stage speed, it has been explained that the pattern density is set to be high in advance, but this is not limited to this, and other parameter values that determine the stage speed can be changed in advance. Also good.

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

  In addition, all charged particle beam writing methods and apparatuses 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. 6 is a diagram for explaining a state of stage movement in the first embodiment. 6 is a diagram showing an example of a stage speed distribution in the first embodiment. FIG. FIG. 3 is a conceptual diagram for explaining an eddy current generation mechanism in the first embodiment. FIG. 3 is a conceptual diagram illustrating a state of a magnetic field on a stage due to eddy current in the first embodiment. FIG. 3 is a diagram showing a misalignment region due to eddy current in the first embodiment. 6 is a diagram illustrating an example of a speed limit region in Embodiment 1. FIG. It is a figure which shows the other example of the stage speed distribution in Embodiment 1. FIG. 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 10,30 Magnetic field 20 Eddy current 40 Position shift area 42 Eddy current generation area 50 Speed limit area 100 Drawing apparatus 101,340 Sample 102 Electron barrel 103 Drawing chamber 105 XY stage 106 Drive part 107 Moving part 110 Drawing control circuit 112 Deflection control Circuit 114 Stage drive circuit 120 CPU
122 Memory 124 Differential operation unit 132, 134 Laser interferometer 150 Drawing unit 160 Control unit 200 Electron beam 201 Electron gun 202 Illumination lens 203, 410 First aperture 204 Projection lens 205, 208 Deflector 206, 420 Second aperture 207 Objective lenses 214 and 314 Reflection mirror 216 Reference mirror 222 Support pin 312 Base 330 Electron beam 332 Support column 411 Opening 421 Variable shaped opening 430 Charged particle source

Claims (4)

In a charged particle beam drawing method for drawing on a sample using a charged particle beam while continuously moving the stage on which the sample is placed,
Draw in one direction to measure the error dimension of the pattern, then draw in the one-way reverse direction and measure the error dimension of the pattern again, the one-way error dimension and the one-way reverse error dimension The region where the magnetic field due to the eddy current occurs is calculated by calculating the difference between
A charged particle beam writing method characterized by drawing a region where the magnetic field by the specific eddy current is generated in the moving speed of the stage is lowered so that the following rate that is inversely proportional to the error dimension caused by pre Symbol field.   The moving speed of the stage to be lowered is set to be equal to or lower than a speed obtained by multiplying a moving speed of the stage when the magnetic field is not generated by a value obtained by dividing an allowable error dimension by an error dimension generated by the magnetic field. The charged particle beam drawing method according to claim 1. Drawing on the sample using a charged particle beam while moving the stage on which the sample is placed at a constant speed ,
Claim 1, wherein the slower than the moving speed of the case of drawing at a constant speed a central portion of the moving speed of the stage the drawing area when drawing an end of the drawing area of the sample at a constant speed a charged particle beam writing method. Drawing on the sample using a charged particle beam while continuously moving the stage on which the sample is placed at a variable speed according to the pattern density ,
The moving speed of the stage for plotting the end of the drawing area of the sample, according to claim 1, wherein the slower than the moving speed of the stage in the region of the same pattern density at the central portion of the drawing area a charged particle beam writing method.

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