JP4725947B2 - Electron beam equipment - Google Patents

Description

  The present invention relates to an electron beam apparatus such as an electron beam drawing apparatus or a scanning electron microscope.

  FIG. 1 shows a conventional electron beam apparatus such as an electron beam drawing apparatus or a scanning electron microscope. In FIG. 1, an electron beam apparatus main body composed of a sample chamber 1 and a lens barrel 2 has a vacuum atmosphere inside. An electron source 3 is provided in the upper part of the lens barrel 2, and an electron beam 4 generated from the electron source 3 and accelerated is supplied to a sample chamber by a condenser lens (not shown) and an objective lens 5 arranged at the lower part of the lens barrel. 1 is finely focused on the sample 6 introduced into the inside.

  When the electron beam apparatus of FIG. 1 is a scanning electron microscope, the irradiation position 7 of the electron beam 4 on the sample 6 is moved by deflection by the deflection coil 8, and an arbitrary region on the sample 6 is scanned by the electron beam 4. It will be. As the electron beam 4 scans the sample, secondary electrons and reflected electrons generated from the sample 6 are detected by a detector (not shown). The detection signal is supplied to a display such as a cathode ray tube synchronized with the scanning of the electron beam 4. As a result, a scanning image of a desired region of the sample is displayed on the display screen.

  When the electron beam apparatus of FIG. 1 is an electron beam drawing apparatus, an arbitrary pattern can be drawn on the sample by controlling the irradiation position 7 of the electron beam 4 by the deflection coil 8. The sample 6 is mounted on the sample stage 9 and is configured to be movable in at least two directions of X and Y by a moving mechanism (not shown).

Since the electron beam 4 is attenuated immediately in the atmosphere inside the lens barrel 2 and the sample chamber 1 described above, the entire electron beam trajectory is kept in a vacuum state. It is in a state of being pushed from outside to inside by atmospheric pressure. As for the relationship between the atmospheric pressure and the electron beam apparatus, an example in which an adverse effect due to atmospheric pressure fluctuation is removed is known (see, for example, Patent Document 1).
JP 2002-342953 A

  As described above, the lens barrel 2 and the sample chamber 1 are always pushed from the outside to the inside by the atmospheric pressure. For example, when the ambient atmospheric pressure increases, the two points in FIG. As shown by the chain line deformation line C, the sample chamber 1 is deformed more inwardly. Note that the amount of deformation indicated by the two-dot chain line deformation line C in FIG. 2 is exaggerated for easy understanding of the invention, and no actual deformation can be confirmed when viewed macroscopically. Trace amount.

  As the upper surface of the sample chamber 1 is deformed as indicated by the deformation line C described above, the lens barrel 2 is inclined at an angle. Moreover, the position of the sample 6 moves when the side surface of the sample chamber 1 to which the sample stage 9 is attached is deformed. As a result of the inclination of the lens barrel 2 and the movement of the position of the sample 6, the irradiation position of the electron beam 7 on the sample 6 changes. Such a phenomenon occurs similarly when the atmospheric pressure decreases.

  In addition, the same phenomenon occurs when low-frequency sound whose wavelength is considered to be sufficiently long with respect to the size of the scanning electron microscope device is present at a sufficiently large level in the device installation environment. The fluctuation of the irradiation position of the electron beam due to the inclination of the lens barrel 2 and the position fluctuation of the sample 6 is observed as image noise in the scanning electron microscope. In addition, in the electron beam drawing apparatus, such a variation in the irradiation position of the electron beam on the sample leads to deterioration of pattern drawing accuracy.

  The present invention has been made in view of the above problems, and realizes an electron beam apparatus such as a scanning electron microscope and an electron beam drawing apparatus that eliminates the influence of fluctuations in atmospheric pressure and low-frequency sound.

An electron beam apparatus according to a first aspect of the present invention is an electron beam apparatus that irradiates a sample with an electron beam generated from an electron gun via an electron optical system, and is close to the outside of the electron optical system of the evacuated electron beam apparatus. A pressure detector that generates a signal proportional to the pressure including atmospheric pressure and low-frequency sound, and a pressure fluctuation signal detected by the pressure detector in a vacuum in the electron beam device. A low-pass filter that removes a signal having a frequency higher than a frequency set based on the representative length of the container, and sends a detection signal from the pressure detector to the low-pass filter. Based on this, the deflection signal supplied to the deflector of the electron beam included in the electron optical system is changed to correct the irradiation position fluctuation of the electron beam accompanying the fluctuation of the outer pressure. It is characterized in that the sea urchin configuration.

The electron beam apparatus according to the invention of claim 2 has an X-direction deflector and a Y-direction deflector for deflecting the electron beam and moving the electron beam to a desired irradiation position on the sample. An X-direction deflector for generating an X-direction correction signal and a Y-direction correction signal having a predetermined ratio based on a signal corresponding to the external pressure detected by the detector, and deflecting the electron beam with the respective correction signals In addition to the Y-direction deflector, the correction X-direction deflector and the Y-direction deflector are provided so as to be supplied.

The electron beam apparatus according to the invention of claim 3 has an X-direction deflector and a Y-direction deflector for deflecting the electron beam and moving the electron beam to a desired irradiation position on the sample. An X-direction deflector for generating an X-direction correction signal and a Y-direction correction signal having a predetermined ratio based on a signal corresponding to the external pressure detected by the detector, and deflecting the electron beam with the respective correction signals In addition to the Y-direction deflector, the correction X-direction deflector and the Y-direction deflector are provided so as to be supplied.

The electron beam apparatus according to the invention of claim 4 previously measures the fluctuation amount δ of the irradiation position of the electron beam due to the fluctuation of the outside pressure of the electron beam apparatus, and obtains the X direction component δx and the Y direction component δy of the fluctuation quantity δ. The signal corresponding to the outside pressure is amplified by a first amplifier that amplifies the signal, the amplified signal is used as a correction signal in the X direction, and the signal amplified by the first amplifier is converted into a second gain of δy / δx. It is characterized in that it is supplied to an amplifier and the output signal of the second amplifier is used as a correction signal in the Y direction .

The electron beam apparatus according to the invention of claim 5 measures in advance the amount of fluctuation δ of the irradiation position of the electron beam due to the fluctuation of the outside pressure of the electron beam apparatus, and obtains the X direction component δx and the Y direction component δy of the fluctuation amount δ. The signal corresponding to the outside pressure is supplied to the first and second amplifiers, the signal amplified by the first amplifier having the gain K1 is used as a correction signal in the X direction, and the gain K2 [= K1 · (δx / δy) The output signal of the second amplifier is used as a correction signal in the Y direction .

An electron beam apparatus according to a first aspect of the present invention is an electron beam apparatus that irradiates a sample with an electron beam generated from an electron gun via an electron optical system, and is disposed in an atmosphere outside the evacuated electron beam apparatus. is, a pressure detector for generating a signal proportional to the pressure containing atmospheric pressure or low-frequency sound, and a low pass filter for removing high frequency signals from the predetermined frequency of the detected pressure fluctuation signal by the pressure detector Providing a detection signal from the pressure detector to the low-pass filter, and changing a deflection signal supplied to an electron beam deflector included in the electron optical system based on the signal from the low-pass filter; The present invention is characterized in that it is configured to correct the irradiation position fluctuation of the electron beam accompanying the pressure fluctuation. As a result, even if the atmospheric pressure changes or low frequency sound is generated, it is possible to always correct the fluctuation of the irradiation position of the electron beam based thereon, and if the present invention is applied to an electron beam drawing apparatus, pattern drawing Ru can be improved in accuracy. Further, if the present invention is applied to a scanning electron microscope, there is an effect of reducing scanning noise. Further, inappropriate correction of the irradiation position of the electron beam due to high frequency pressure fluctuations can be prevented.

The electron beam apparatus according to the second and third aspects of the invention is characterized by a specific configuration for supplying an electron beam irradiation position correction signal to an electron beam deflector, and has the same effect as that of the first aspect of the invention. .
The electron beam apparatus according to the invention of claim 4 previously measures the fluctuation amount δ of the irradiation position of the electron beam due to the fluctuation of the outside pressure of the electron beam apparatus, and obtains the X direction component δx and the Y direction component δy of the fluctuation quantity δ. The signal corresponding to the outside pressure is amplified by a first amplifier that amplifies the signal, the amplified signal is used as a correction signal in the X direction, and the signal amplified by the first amplifier is converted into a second gain of δy / δx. It is characterized in that it is supplied to an amplifier and the output signal of the second amplifier is used as a correction signal in the Y direction . As a result, it is possible to correct the irradiation position fluctuation of the electron beam corresponding to the deformation unique to each electron beam apparatus.

The electron beam apparatus according to the invention of claim 5 measures in advance the amount of fluctuation δ of the irradiation position of the electron beam due to the pressure fluctuation outside the electron beam apparatus, and obtains the X-direction component δx and the Y-direction component δy of the fluctuation amount δ. The signal corresponding to the outside pressure is supplied to the first and second amplifiers, the signal amplified by the first amplifier having the gain K1 is used as a correction signal in the X direction, and the gain K2 [= K1 · (δx / δy) The output signal of the second amplifier is used as a correction signal in the Y direction, and has the same effect as that of the invention of claim 4.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 shows a block diagram of an electron beam deflection correction system in the electron beam apparatus according to the present invention. The electron beam deflection correction system shown in FIG. 3 is connected to, for example, the deflection coil 8 of the conventional apparatus shown in FIG. In FIG. 3, the deflection coil 8 is composed of an X-direction deflection coil 8x and a Y-direction deflection coil 8y.

  When the electron beam deflection correction system of FIG. 3 is used in a scanning electron microscope, the irradiation position of the electron beam on the sample is moved by deflection by the deflection coils 8x and 8y, and an arbitrary region on the sample is two-dimensionally moved by the electron beam. Will be scanned. As the electron beam is scanned on the sample, secondary electrons and reflected electrons generated from the sample are detected by a detector. The detection signal is supplied to a display such as a cathode ray tube synchronized with the scanning signal of the electron beam supplied to the deflection coil 8. As a result, a scanning image of a desired region of the sample is displayed on the display screen.

  When the electron beam deflection correction system of FIG. 3 is used in an electron beam drawing apparatus, an arbitrary pattern is drawn on the sample by controlling the irradiation position 7 of the electron beam 4 by the deflection coils 8x and 8y based on the pattern data. can do.

  The electron beam deflection correction system of FIG. 3 corrects the deflection voltage applied from the X scanning voltage generation circuit 10x to the X deflection coil 8x and the deflection voltage applied from the Y scanning voltage generation circuit 10y to the Y deflection coil 8y. Provided for. The deflection correction system amplifies the pressure fluctuation measuring device 11, the low-pass filter 12 to which a voltage signal proportional to the pressure fluctuation measured by the pressure fluctuation measuring device 11 is supplied, and the signal that has passed through the low-pass filter 12. Amplifiers 13x and 13y, an adder 14x for adding the output signal voltage of the amplifier 13x and the deflection voltage from the X scanning voltage generation circuit 10x, the output signal voltage of the amplifier 13y and the deflection voltage from the Y scanning voltage generation circuit 10y, And an adder 14y for adding.

  The pressure fluctuation measuring device 11 includes a barometer, a low-frequency sound level system, and the like. The pressure fluctuation measuring device 11 is provided with an electron beam device that is a target for correcting the irradiation position of the electron beam. It is arranged in the room and at a position as close as possible to the lens barrel of the electron beam apparatus. The operation of such a configuration will be described next.

  When the electron beam deflection correction system shown in FIG. 3 is used in a scanning electron microscope, if a desired magnification is designated with a magnification control knob (not shown), the X scanning voltage generation circuit 10x and the Y scanning voltage generation circuit 10y will increase the magnification. A corresponding voltage is generated and supplied to the X deflection coil 8x and the Y deflection coil 8y, respectively, and the irradiation position of the electron beam on the sample is moved by the deflection by the deflection coils 8x and 8y, and an arbitrary region on the sample is an electron. Two-dimensional scanning is performed by the beam.

  As the electron beam is scanned on the sample, secondary electrons and reflected electrons generated from the sample are detected by a detector. The detection signal is supplied to a display such as a cathode ray tube synchronized with the scanning signal of the electron beam supplied to the deflection coil 8. As a result, a scanning image of a desired region of the sample is displayed on the display screen at a specified magnification.

  When the electron beam deflection correction system of FIG. 3 is used in an electron beam drawing apparatus, the voltage generated from the X scanning voltage generation circuit 10x and the Y scanning voltage generation circuit 10y is applied to the irradiation position 7 of the electron beam 4 based on the pattern data. By controlling, an arbitrary pattern can be drawn on the sample by changing the deflection amount of the electron beam by the deflection coils 8x and 8y.

  Now, in a scanning electron microscope and an electron beam drawing apparatus, there are a weak part and a strong part in structure. Therefore, when the atmospheric pressure around the electron beam apparatus fluctuates, the influence is exerted on a weak part of the structure of the electron beam apparatus, and the part is deformed. Therefore, in accordance with the deformation of a specific part of the electron beam apparatus, for example, the deformation of the upper surface of the sample chamber 1, the lens barrel 2 is inclined or the side surface of the sample chamber 1 to which the sample stage 9 is attached is deformed. The position of the sample 6 moves. As a result, the irradiation position of the electron beam on the sample varies with the change in atmospheric pressure, and thus the image displayed on the display also moves.

  By the way, the variation amount of the atmospheric pressure and the deformation amount of the specific structure portion of the electron beam apparatus have a linear relationship in each electron beam apparatus, and the image movement amount (electron beam irradiation) with respect to the variation amount of the atmospheric pressure. The position fluctuation amount can be expressed as a vector δ as shown in FIG. The image movement amount δ is divided into an X component δx and a Y component δy. The ratio of the X component δx and the Y component δy (corresponding to the moving direction of the image) is unique to each electron beam apparatus. .

  Therefore, if there is a change in atmospheric pressure, the electron beam deflection position on the specimen can be corrected by the atmospheric pressure fluctuation if the deflection of the electron beam is changed so as to cancel the image fluctuation according to the amount of atmospheric pressure fluctuation. It can be performed. At this time, since the moving direction of the image due to the atmospheric pressure fluctuation is always constant in each electron beam apparatus, the electron beam deflection correction amount in the Y direction is set to the electron beam deflection correction amount in the X direction. The ratio δy / δx between the X component δx and the Y component δy of the movement amount δ may be set.

  In view of such a point, in the deflection correction system of FIG. 3, a signal corresponding to the atmospheric pressure 7 and the low frequency sound is generated by the barometer 11, and the signal is passed through the low-pass filter 12 and the first gain having the gain K <b> 1. The amplifier 13x amplifies the electron beam to a value capable of correcting the deflection of the electron beam. The signal (X direction correction signal) amplified by the first amplifier 13x is added to the X scanning voltage by the adder 14y and supplied to the X deflection coil 8x.

  The signal amplified by the first amplifier 13x is also supplied to the second amplifier 13y. The gain of the amplifier 13y is a ratio δy / δx between the X component δx and the Y component δy of the image movement amount δ. The output of the second amplifier 13y is added to the Y scanning voltage from the Y scanning voltage generation circuit 10y by the adder 14y and supplied to the Y direction deflection coil 8y. In this way, the amount of deflection of the electron beam is corrected according to changes in atmospheric pressure, and the irradiation position of the electron beam on the sample changes due to fluctuations in atmospheric pressure, preventing the observed image from moving. Is done.

  Note that the ratio δy / δx between the X component δx and the Y component δy of the image movement amount δ described above is a value unique to each device, and is experimentally obtained in advance when the electron beam device is manufactured, and the amplifier 13y. It is necessary to make adjustments. For this purpose, when an electron beam apparatus is introduced into the installation chamber in which the pressure can be controlled in advance and the pressure in the installation chamber is varied, the variation amount δ of the electron beam irradiation position on the sample is measured as a vector. Then, the XY components of the fluctuation amount δ of the electron beam irradiation position are respectively obtained, and the gain of the amplifier 13y, that is, the ratio δy / δx between the X component δx and the Y component δy of the image movement amount δ is obtained.

  As described above, the amount of fluctuation of atmospheric pressure or low frequency sound measured by the barometer 10 is proportional to the amount of movement of the electron beam on the sample. The relationship between the atmospheric pressure and low frequency sound fluctuation and the movement amount of the electron beam irradiation position can be regarded as linear within a range where the atmospheric pressure and low frequency sound fluctuation are small. Therefore, by adjusting the amplification factor of the amplifier 13x so that the irradiation position of the electron beam on the sample does not fluctuate when the pressure in the installation chamber is fluctuated, according to the magnitude of the pressure fluctuation, The fluctuation of the irradiation position can always be corrected.

  By the way, in the deflection correction system of FIG. 3, a voltage signal corresponding to the atmospheric pressure detected by the barometer 11 is supplied to the low-pass filter 12, and a signal having a frequency equal to or higher than a predetermined frequency is cut. Yes. By adopting such a configuration, when the frequency of the low frequency sound is close to direct current, the wavelength is sufficiently longer than the representative length of the sample chamber 11, so that it can be regarded as a simple pressure fluctuation. However, when the frequency becomes higher than a certain level, for example, the phase shift increases on the opposing surface of the sample chamber 1 and cannot be regarded as a simple pressure fluctuation.

  For this reason, if the voltage corresponding to the pressure fluctuation of the high frequency component is included in the voltage used for correcting the fluctuation of the irradiation position of the electron beam, inappropriate correction is performed, which is not convenient. For example, when the representative length of the sample chamber 1 is 2 m, the frequency of the low frequency sound whose length is ½ wavelength is about 85 Hz at room temperature and 1 atmosphere. At this time, the phase of the sound is reversed on the opposite surface of the sample chamber 1, and the influence of the low frequency sound having this frequency component is that the sample chamber 1 is rocked rigidly rather than the force of crushing the sample chamber 1. Will work as a force.

  In this case, if the upper limit of the frequency of the low frequency sound used for correcting the irradiation position of the electron beam is set so that the representative length of the sample chamber 1 has a phase difference of about 15 ° as the phase, the upper limit frequency is That is about 7 Hz. A voltage signal having a frequency higher than this is cut by the low-pass filter 12. As an actual application, it is desirable that the set frequency of the low-pass filter 12 is variable and can be adjusted according to the size of the apparatus and the frequency distribution of the sound pressure level in the installation room.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, as shown in FIG. 5, when the output voltage of the low-pass filter 12 is supplied to both the amplifiers 13x and 13y, the amplification factor K2 of the amplifier 13y is K1, and the amplification factor of the amplifier 13x is K1, The obtained values may be used, and the output voltages of the amplifiers 13x and 13y may be supplied to the adders 14x and 14y.

K2 = (δy / δx) · K1
Further, the X deflection coil 8x for scanning the electron beam and the Y deflection coil 8y are configured to add and supply the electron beam irradiation position correction voltage, but the X deflection coil 8x for scanning the electron beam, In addition to the Y deflection coil 8y, a deflection coil for correcting the electron beam irradiation position may be newly provided, and the output voltages of the amplifiers 13x and 13y may be supplied to the correction deflection coil. Further, although an electromagnetic deflection coil is used to deflect the electron beam, an electrostatic deflector may be used.

  Further, in the above-described embodiment, the example of correcting the variation of the irradiation position of the electron beam on the sample due to the variation of the atmospheric pressure has been described in detail, but the same applies to the change of the electromagnetic field around the electron beam apparatus. The present invention can be applied. In that case, a detector for detecting the electromagnetic field is provided, a correction signal is generated according to the detected intensity and direction of the electromagnetic field, and this correction signal is supplied to the deflector of the electron beam, so that electrons due to fluctuations in the external electromagnetic field are generated. Incorrect deflection of the beam is cancelled.

  The present invention can be mainly used in the field of scanning electron microscopes such as scanning electron microscopes for inspecting semiconductor devices, and further in the field of mask production.

It is a figure which shows electron beam apparatuses, such as a scanning electron microscope and an electron beam drawing apparatus. It is a figure which shows the electron beam apparatus which deform | transforms with atmospheric pressure. It is a block diagram which shows 1st Embodiment of the deflection correction system of the electron beam in the electron beam apparatus based on this invention. It is a figure for demonstrating the movement amount (delta) of an electron beam, and its XY component. It is a block diagram which shows 2nd Embodiment of the deflection correction system of the electron beam in the electron beam apparatus based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample chamber 2 Lens tube 3 Electron source 4 Electron beam 5 Objective lens 6 Sample 7 Beam irradiation position 8 Deflection coil 9 Sample stage 10 Scanning voltage generation circuit 11 Barometer / low frequency sound level meter 12 Low pass filter 13 Amplifier 14 Adder

Claims (5)

In an electron beam apparatus that irradiates a sample with an electron beam generated from an electron gun via an electron optical system, the electron beam apparatus is disposed in the atmosphere close to the outside of the electron optical system of the evacuated electron beam apparatus, and has an atmospheric pressure or low frequency. A pressure detector that generates a signal proportional to pressure including wave noise, and a deformation caused by pressure fluctuation in the opposing surface of the evacuated container in the electron beam device among the pressure fluctuation signals detected by the pressure detector And a low-pass filter that removes frequencies higher than this with a frequency at which the phase shift of 15 ° becomes an upper limit, a detection signal from the pressure detector is sent to the low-pass filter, and the signal from the low-pass filter Based on this, the deflection signal supplied to the deflector of the electron beam included in the electron optical system is changed, and the irradiation position fluctuation of the electron beam accompanying the fluctuation of the outer pressure is changed. Configured electron beam apparatus as positive to. The electron beam apparatus has an X-direction deflector and a Y-direction deflector for deflecting the electron beam and moving it to a desired irradiation position on the sample, and a signal corresponding to the outer pressure detected by the pressure detector. The X direction correction signal and the Y direction correction signal having a predetermined ratio based on the above are generated, and the respective correction signals are converted into deflection signals supplied to the X direction deflector and the Y direction deflector for deflecting the electron beam. The electron beam apparatus according to claim 1, wherein the electron beam apparatus is configured to add. The electron beam apparatus has an X-direction deflector and a Y-direction deflector for deflecting the electron beam and moving it to a desired irradiation position on the sample, and a signal corresponding to the outer pressure detected by the pressure detector. The X direction correction signal and the Y direction correction signal having a predetermined ratio based on the above are generated, and the correction signals are provided in addition to the X direction deflector and the Y direction deflector for deflecting the electron beam. 2. The electron beam apparatus according to claim 1, wherein the electron beam apparatus is configured to be supplied to the X direction deflector for correction and the Y direction deflector for correction. First, the amount of fluctuation δ of the irradiation position of the electron beam due to the fluctuation of the outside pressure of the electron beam apparatus is measured in advance, the X-direction component δx and the Y-direction component δy of the fluctuation amount δ are obtained, and the signal corresponding to the outside pressure is amplified. The signal amplified by the first amplifier is used as a correction signal in the X direction, the signal amplified by the first amplifier is supplied to the second amplifier having a gain of δy / δx, and the output signal of the second amplifier The electron beam apparatus according to claim 2, wherein Y is a correction signal in the Y direction. The amount of fluctuation δ of the irradiation position of the electron beam due to the fluctuation of the outside pressure of the electron beam apparatus is measured in advance to obtain the X-direction component δx and the Y-direction component δy of the fluctuation amount δ, and the signals corresponding to the outside pressure are the first and first signals. 2, the signal amplified by the first amplifier having the gain K1 is used as a correction signal in the X direction, and is supplied to the second amplifier having the gain K2 [= K1 · (δx / δy)]. 3. An electron beam apparatus according to claim 2, wherein the output signal of the amplifier is a correction signal in the Y direction.

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