JP2012015227A - Method and apparatus for positioning electron beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for positioning an electron beam device, and provide a method for positioning an electron beam with less periodical fluctuation and an electron beam apparatus having the function.SOLUTION: An electron beam device comprises: an electron source 1 for generating an electron beam; an optical system for accelerating, decelerating, converging, and deflecting the electron beam; a control system for scanning the electron beam or for controlling blanking; a stage 6 for holding a material 7 which is irradiated with the electron beam; a stage length measurement system 16a for measuring the position of the stage 6; an electron detection section 18 for detecting the electron beam emitted from the material 7; and a signal processing system 19 for processing a detection signal obtained from the electron detection section 18. A periodic signal whose amplitude and phase can be adjusted is added to a compensation signal from the stage length measurement system 16a.

Description

  The present invention relates to an electron beam apparatus positioning method and apparatus for improving electron beam irradiation position accuracy in an electron beam apparatus such as a scanning electron microscope or an electron beam drawing apparatus.

  A mask substrate is placed on the stage, a reflecting mirror is attached to the end of the stage, and the stage is moved while measuring the position with a laser length measuring system using the reflecting mirror to move the mask substrate to the electron beam. In the exposure method, the plurality of members having marks formed on the end portions of the mask substrate are separately attached, and the marks on each member are detected by an electron beam (hereinafter also referred to as an electron beam). A technique is known in which exposure is performed by detecting the displacement and rotation amount of the mask substrate and thermal expansion and contraction of the substrate itself, and correcting the deflection amount of the electron beam and / or the movement amount of the stage based on the detection ( For example, see Patent Document 1).

  FIG. 5 is a diagram showing a configuration example of a conventional apparatus. The electron beam EB emitted from the electron source 1 passes through the focusing lens 21, the intermediate lens 2, and the blanking electrode 3, and is finely focused on the material 7 placed on the stage 6 via the objective lens 5. Irradiated as EB. Scanning on the material 7 is performed by the deflection electrode 8. When the material 7 is scanned with the electron beam EB, various electrons are emitted from the material surface.

  The emitted electrons are detected by the electron detector 18 and sent to the signal processing system 19. A predetermined calculation is performed on the detection signal taken in by the calculation unit 19 a in the signal processing system 19, and the result is sent to the computer 20. The computer 20 displays the transmitted signal on the display unit 20a. The storage unit 17 stores an image of the material 7 processed by the computer 20 and its position information. The image stored in the storage unit 17 and its position information are sent to the CPU 13.

  The CPU 13 determines the electron source control system 10, the electron source barrel control system 11, the electron optical system control system 12, the blanking control system 14, the beam scanning control system 15 and the stage drive control system 16 from the received image and its position information. A control signal corresponding to each is given. The electron source control system 10 controls the amount of electrons generated from the electron source 1, the electron source barrel control system 11 controls the focusing lens 21, and the electron optical system control system 12 controls the excitation current of the intermediate lens 2.

  The blanking control system 14 controls the voltage applied to the blanking electrode 3 and controls on / off of the electron beam EB. The beam scanning control system 15 controls the deflection electrode 8 and controls the scanning of the beam on the material 7. The stage drive control system 16 controls the amount of movement of the stage 6. In this case, the stage length measurement system 16a accurately measures the amount of movement of the stage 6 using the laser length measurement system. The length measurement result of the stage length measurement system 16a is given to the CPU 13, and the CPU 13 drives and controls various control systems 10-12 and 14-16 described above.

  In the apparatus configured as described above, the electron beam EB emitted from the electron source 1 is focused by the focusing lens 21, passes through the intermediate lens 2, and then passes only the optimum electron beam EB at the diaphragm 22. A finely focused beam is irradiated onto the material 7 by the objective lens 5. At this time, a signal such as secondary electrons emitted from the material 7 is detected by the electron detector 18 and sent to the signal processing system 19. The detected signal of secondary electrons or the like is given to the computer 20 after being subjected to predetermined arithmetic processing by the arithmetic unit 19 a in the signal processing system 19. The computer 20 displays the detected image on the display unit 20a.

  In such a series of operations, the position of the stage 6 is gradually shifted due to drift or the like. The stage length measurement system 16 a in the stage drive control system 16 determines the amount of movement of the stage 6. This movement amount is given to the CPU 13, and the CPU 13 can apply a signal for correcting the movement amount of the stage 6 to the deflection electrode 8 to perform beam scanning with the influence of drift removed.

FIG. 6 is a diagram illustrating a configuration example of a main part of a conventional apparatus. The same components as those in FIG. 5 are denoted by the same reference numerals. The laser emitted from the laser light source 26 is incident on the mirror 28 attached to the stage 6 and reflected. The reflected laser light is incident on an interferometer (interferometer) 27, and interference light corresponding to the position variation of the stage 6 is generated and incident on the receiver 29. An interference signal based on the position change of the stage 6 is input from the interferometer 27 to the receiver 29. The interference signal from the receiver 29 at this time is processed by the subsequent signal processor 30 and converted into a position correction signal from the original position. The position correction signal of this stage 6 is applied to the deflection amplifier 31 and moved. A deflection signal whose amount is corrected is given, and the deflector 8 is driven. The electron beam EB is moved from the designated position A to the stop position A ′, and scanning with the position corrected is performed. Here, the stepping motor 25 is used to move the stage 6.

  In the case of operating the apparatus as described above, in the conventional apparatus, when the SEM image is observed, a phenomenon that the SEM image is shaken at a high magnification may occur. This vibration causes mechanical vibrations of the vacuum pump, resonance of the electron beam column, stray electromagnetic fields such as radio waves generated from the motors of the vacuum pump and cooling fan, and noise of commercial power supply frequency on the power supply circuit of the electron gun and lens. This is due to such disturbances. In the electron beam apparatus, as the resolution becomes higher, the fluctuation of the SEM image due to such disturbance becomes more problematic.

  Conventionally, with respect to stray magnetic fields, passive measures such as covering the periphery of the electron beam column or the entire device with a magnetic shield plate, preparing a dedicated room for the device equipped with a magnetic shield plate, An active control method is adopted in which a magnetic field for detection is generated by feeding back a detection signal to a Helmholtz coil that covers the entire apparatus by detecting a magnetic field. For mechanical vibration, a vibration isolation table with a natural frequency of a few hertz, a passive countermeasure that suppresses vibration transmission from the floor to the electron beam device, and a sample that detects shaking of the sample with a laser interferometer. An active control method for feeding back to the beam is used (see, for example, Patent Document 2).

Japanese Examined Patent Publication No. 63-55777 (page 2, right column, lines 14 to 34) Japanese Patent No. 3767872 (paragraphs 0002 to 0003, FIG. 9)

  However, the conventional technique has a problem that periodic fluctuations caused by electric noise at the commercial frequency cannot be removed when the fluctuation signal is superimposed on the correction signal from the laser length measurement system or the deflection signal of the deflector. there were.

  The present invention has been made in view of such problems, and an object thereof is to provide an electron beam positioning method capable of reducing periodic fluctuations and an electron beam apparatus having the function.

  In order to solve the above problem, the present invention has the following configuration.

  (1) The invention according to claim 1 is an electron source for generating an electron beam, an optical system for accelerating, decelerating, converging and deflecting the electron beam, and scanning or blanking control of the electron beam. A control system, a stage for holding the material irradiated with the electron beam, a stage length measuring system for measuring the position of the stage, and an electron beam detector for detecting an electron beam emitted from the material And a signal processing system for processing a detection signal obtained from the electron detection unit, a periodic signal whose amplitude and phase can be adjusted is added to the correction signal from the stage length measurement system. The periodic signal is determined so that the amount of positional fluctuation obtained from the detection signal obtained by scanning the reference mark on the stage a plurality of times by changing the amplitude and phase in stages is minimized. To

  (2) The invention described in claim 2 is an electron source for generating an electron beam, an optical system for accelerating, decelerating, converging and deflecting the electron beam, and scanning or blanking control of the electron beam. A control system, a stage for holding the material irradiated with the electron beam, a stage length measuring system for measuring the position of the stage, an electron detection unit for detecting electrons emitted from the material, In an electron beam apparatus comprising a signal processing system for processing a detection signal obtained from the electron detector, an adding means for adding a periodic signal whose amplitude and phase can be adjusted to a correction signal from the stage length measurement system And a periodic signal for determining the periodic signal so that the amount of positional fluctuation obtained from the detection signal obtained by scanning the reference mark on the stage a plurality of times by changing the amplitude and the phase in stages is minimized. And having a constant section.

  (3) The invention according to claim 3 is characterized in that the stage length measurement system measures the movement of the stage in the X and Y directions by a laser interferometer.

  (4) In the invention according to claim 4, the periodic signal can be selected from a plurality of reference signals prepared in advance, and one of the periodic signals has an opposite phase at the same frequency as the commercial frequency in the apparatus installation environment. It is the periodic signal produced | generated by this.

  (5) The invention according to claim 5 is characterized in that the reference mark is arranged directly on the stage, or arranged on the material placed on the stage, and is a convex type formed of Au or Ta. It is a cross mark or a concave cross mark formed by etching Si.

  (6) The invention according to claim 6 is characterized in that the amplitude and phase change amount, the reference mark scanning number, and the number of trials of this procedure can all be set and changed from the outside.

  (7) The invention according to claim 7 has a storage unit for storing the position variation amount and the amplitude and phase of the periodic signal as means for determining the periodic signal having the smallest position variation amount, and a predetermined number of trials. Amplitude and phase corresponding to the smallest position fluctuation amount stored in the storage unit after completion are employed.

  The present invention has the following effects.

  (1) According to the first aspect of the present invention, a periodic signal whose amplitude and phase can be adjusted is added to the correction signal from the stage length measurement system, and the amplitude and phase are changed stepwise to change the amplitude on the stage. By determining the periodic signal so that the positional fluctuation amount obtained from the detection signal obtained by scanning the reference mark a plurality of times is minimized, the influence of periodic fluctuations can be reduced.

  (2) According to the invention described in claim 2, addition means for adding a periodic signal capable of adjusting the amplitude and phase to the correction signal from the stage length measurement system, and changing the amplitude and phase in a stepwise manner. By having periodic signal determining means for determining the periodic signal so as to minimize the amount of positional fluctuation obtained from the detection signal obtained by scanning the reference mark on the stage a plurality of times, the influence of periodic fluctuations Can be reduced.

  (3) According to the invention described in claim 3, the movement of the stage can be measured by the laser interferometer.

  (4) According to invention of Claim 4, the fluctuation | variation based on a commercial frequency is removable by making the said periodic signal into the opposite phase with the same frequency as a commercial frequency.

  (5) According to the invention described in claim 5, a detection signal can be obtained using a predetermined reference mark.

  (6) According to the invention described in claim 6, it is possible to set and change the number of scans of the reference mark and the number of trials of this procedure, and an optimum position variation amount can be selected.

  (7) According to the invention described in claim 7, the storage unit stores the position variation amount and the amplitude and phase of the periodic signal, and the position variation amount stored in the storage unit is the largest after the predetermined number of trials. Corresponding amplitudes and phases can be employed in ascending order.

It is a figure which shows the structural example of this invention. It is a figure which shows the structural example of the principal part of this invention. It is a figure which shows the structural example of a mark. It is a flowchart which shows an example of operation | movement of this invention. It is a figure which shows the structural example of a conventional apparatus. It is a figure which shows the structural example of the principal part of a conventional apparatus.

Example 1
Examples of the present invention will be described in detail below. FIG. 1 is a diagram showing a configuration example of the present invention. The same components as those in FIG. 5 are denoted by the same reference numerals. In the figure, the electron source 1 to the computer 20 are the same as those in FIG. In the figure, reference numeral 20a denotes a display unit that is connected to the computer 20 and displays an image of the material 7 or the like. As the display unit 20a, a CRT, a liquid crystal display, or the like is used. Reference numeral 20b denotes a storage unit that is connected to the computer 20 and stores the amount of mark position fluctuation detected by the electronic detection unit 18, the number of scans, and the number of trials. The data stored in the storage unit 20b is read as necessary. The computer 20 outputs image data and correction data to the CPU 13. Reference numeral 40 denotes an operation unit for inputting various data and commands to the computer 20. For example, a keyboard or a mouse is used as the operation unit 40. The operation of the apparatus configured as described above will be described as follows.

  The present invention relates to an electron source 1 that generates an electron beam and an optical that accelerates, decelerates, and converges an electron beam EB emitted from the electron source 1 in an electron beam apparatus such as a scanning electron microscope or an electron beam drawing apparatus. Systems 21, 2 and 5, a control system 3 and 8 for scanning or blanking control of the electron beam EB, a stage 6 for holding the material 7 irradiated with the electron beam EB, and the stage 6 A stage length measurement system 16a for measuring the position of the electron, an electron detector 18 for detecting electrons emitted from the material 7, and a signal processing system 19 for processing a detection signal obtained from the electron detector 18. Consists of.

  In the electron beam apparatus having such a configuration, a reference signal on the stage 6 is added by adding a periodic signal whose amplitude and phase can be adjusted to the correction signal from the stage length measurement system 16a, and changing the amplitude and phase stepwise. The periodic signal is determined so that the amount of positional fluctuation obtained from the detection signal obtained by scanning the plurality of times is minimized.

  The stage length measurement system 16a obtains the difference from the previous measurement as the stage displacement amount from the position of the stage 6 obtained by measuring the position of the mirror 28 attached to the end of the stage 6, and uses it as the material 7 A correction signal for feedback to the upper electron beam irradiation position is transmitted. In this correction signal, a periodic signal whose amplitude and phase can be adjusted is outputted from the periodic signal generator 33, and the correction signal is added to this periodic signal and applied to the deflection electrode 8.

  In the above state, the reference mark provided on the stage 6 is scanned a plurality of times to detect the position of the reference mark, and the position fluctuation amount is calculated. Next, the position fluctuation amount is calculated in the same manner by changing the amplitude and phase by a certain amount. This is repeated, and the periodic signal is determined so that the amount of position fluctuation is minimized. The storage unit 20b stores a plurality of amplitude and phase values, reads out the amplitude and phase values, and applies a periodic signal having a predetermined amplitude and phase to the deflector 8.

  FIG. 2 is a diagram showing a configuration example of a main part of the present invention. 1 and 6 are denoted by the same reference numerals. Laser light emitted from a laser light source 26 that generates laser light for length measurement is applied to a mirror 28 mounted on the stage 6 via an interferometer 27. If there is a phase difference between the light reflected from the mirror 28 and the incident light, the interferometer 27 generates interference light.

  The interference light is input to the receiver 29, and after performing predetermined processing, enters the signal processor 30. The signal processor 30 outputs a correction signal corresponding to the position variation of the stage 6. A periodic signal having a constant amplitude and phase is output from the periodic signal generator 33. A memory 20b stores data related to the amplitude and phase of the periodic signal. The periodic signal generator 33 accesses the storage unit 20b to generate the stored amplitude and phase signals.

  On the other hand, a stepping motor 25 is attached to the stage 6, and the stepping motor 25 can move in the XY two-dimensional direction by rotating. A reference mark as shown in FIG. 3 is attached to the stage 6 or the material 7. (A) is a convex cross mark, and (b) is a concave cross mark.

  When the material 7 is irradiated with the electron beam EB, the material 7 generates reflected electrons such as secondary electrons and reflected electrons from the portion marked with the cross mark. The generated electrons are detected by the subsequent electron detector 18 and then enter the signal processing system 19. The signal processing system 19 performs predetermined signal processing on the received signal to calculate a mark position fluctuation amount, and supplies the signal to the periodic signal generator 33.

  As a result, the position correction signal from the signal processor 30 is added to the output from the periodic signal generator 33 by the adder 32 to drive the deflection amplifier 31. As a result, the deflector 8 corrects predetermined position data to the electron beam EB. The electron beam EB is irradiated with a beam whose position is corrected from the designated position A to the stop position A ′. According to this embodiment, a periodic signal whose amplitude and phase can be adjusted is added to the correction signal from the stage length measurement system, and the amplitude and phase are changed stepwise, so that the reference mark on the stage 6 or the material 7 is obtained. By determining the periodic signal so that the position fluctuation amount obtained from the detection signal obtained by scanning a plurality of times is minimized, the influence of periodic fluctuations can be reduced.

  FIG. 4 is a flowchart showing an example of the operation of the present invention. Hereinafter, an example of the operation of the present invention will be described with reference to this flowchart. The system shown in FIGS. 1 and 2 is used. The subject of the operation is the computer 20. First, the operator sets initial values of the amplitude and phase of the periodic signal from the operation unit 40 (S1). The set amplitude and phase are input to the computer 20. In addition, the number of scans described later is also input. These data are stored in the storage unit 20b. Next, a position variation signal (correction signal) that enters the signal processor 30 from the stage length measurement system (laser light source 26, interferometer 27, mirror 28, stage 6, receiver 29) is predetermined by the signal processor 30. Then, the adder 32 adds the signal to the periodic signal from the periodic signal generator 33 (S2). The deflector 8 is driven via the deflection amplifier 31 with the added signal.

  In this way, the reference mark on the stage 6 or the material 7 is scanned with the electron beam EB (S3). The electrons emitted from the mark are detected by the electron detector 18 and then enter the signal processing system 19 to calculate the mark position (S4). The calculated position data is stored in the storage unit 20b every time scanning is performed. Next, it is checked whether or not scanning has been performed for the designated number of scans (S5). If the specified number of scans is not reached, the process returns to step S3 and the reference mark is scanned.

  When the number of scans is equal to or greater than the specified number, the mark position fluctuation amount in each case is calculated (S6). Then, the amplitude and phase values and the mark position fluctuation amount are stored in the storage unit 20b (S7). When the storage (save) in the storage unit 20b is completed, it is checked whether the operation so far is equal to or more than the designated number of trials (S8). If the number of trials is less than the specified number of trials, the amplitude and phase values of the periodic signal are read from the storage unit 20b, the amplitude and phase values are changed (S9), and the process returns to step S2, and the stage length measurement system A process of adding a periodic signal to the correction signal from is performed (S2). When the specified number of trials is reached, the amplitude and phase values are determined from the data stored in the storage unit 20b (S10).

  As described above, according to the present invention, the periodic signal whose amplitude and phase can be adjusted is added to the correction signal from the stage length measurement system, and the reference mark on the stage is changed by changing the amplitude and phase stepwise. By determining the periodic signal so that the position fluctuation amount obtained from the detection signal obtained by scanning a plurality of times is minimized, the influence of periodic fluctuations can be reduced.

(Example 2)
In the second embodiment of the present invention, the stage length measurement system of the first embodiment is configured such that the movement of the stage in the X and Y directions is measured by a laser interferometer. By using a laser interferometer for the movement of the stage in the X direction and the Y direction, the amount of movement of the stage can be measured very accurately.

(Example 3)
In the third embodiment, the periodic signal described above can be selected from a plurality of reference signals prepared in advance, and one of them is a period generated so as to have an opposite phase at the same frequency as the commercial frequency in the apparatus installation environment. It is a signal. If comprised in this way, the fluctuation | variation based on a commercial frequency can be removed by applying the correction signal which has the phase which is opposite in the fluctuation | variation based on the commercial frequency which has generate | occur | produced from the apparatus, and an equal amplitude.

Example 4
The substrate mark used in the above-described embodiment is directly placed on the stage 6 or placed on the material 7 placed on the stage 6 and is a convex cross mark formed of Au or Ta. Alternatively, a concave cross mark formed by etching Si can be used. By using such a reference mark, it is possible to make the position variation amount extremely small from the detection signal.

(Example 5)
As a means for determining the periodic signal with the smallest position variation amount, a storage unit for storing the position variation amount and the amplitude and phase of the periodic signal is provided. If comprised in this way, the amplitude and phase corresponding to the smallest value among the amount of position fluctuation memorized by the storage part after the end of the predetermined number of trials can be adopted, and the most accurate positioning can be performed. it can.

  As described above in detail, according to the present invention, by adding a periodic signal so as to cancel out periodic fluctuations caused by electrical noise at commercial frequencies, the fluctuations from the laser length measurement system can be reduced. It is possible to reduce the influence when superimposed on the correction signal or the deflection signal of the deflector. Further, for example, by using a periodic signal having a phase opposite to that of the periodic noise in the commercial frequency band superimposed on the ground line, the influence of the noise can be effectively removed.

  The present invention can effectively eliminate not only the fluctuation based on the commercial frequency but also the fluctuation based on other causes.

DESCRIPTION OF SYMBOLS 1 Electron source 2 Intermediate lens 3 Blanking electrode 5 Objective lens 6 Stage 7 Material 8 Deflection electrode 10 Electron source control system 11 Electron source barrel control system 12 Electron optical system control system 13 CPU
14 Blanking control system 15 Beam scanning control system 16 Stage drive control system 16a Stage length measurement system 18 Electron detection unit 19 Signal processing system 19a Calculation unit 20 Computer 20a Display unit 20b Storage unit 21 Focusing lens 40 Operation unit

Claims (7)

An electron source for generating an electron beam, an optical system for accelerating, decelerating, converging and deflecting the electron beam, a control system for scanning or blanking the electron beam, and the electron beam are irradiated. A stage for holding the material, a stage length measurement system for measuring the position of the stage, an electron detector for detecting electrons emitted from the material, and a detection signal obtained from the electron detector In an electron beam apparatus comprising a signal processing system for processing,
Detection obtained by adding a periodic signal whose amplitude and phase can be adjusted to the correction signal from the stage length measurement system and scanning the reference mark on the stage a plurality of times by changing the amplitude and phase in stages. A positioning method for an electron beam apparatus, wherein the periodic signal is determined so that a positional fluctuation amount obtained from the signal is minimized. An electron source for generating an electron beam, an optical system for accelerating, decelerating, converging and deflecting the electron beam, a control system for scanning or blanking the electron beam, and the electron beam are irradiated. A stage for holding the material, a stage length measurement system for measuring the position of the stage, an electron detector for detecting electrons emitted from the material, and a detection signal obtained from the electron detector In an electron beam apparatus comprising a signal processing system for processing,
Adding means for adding a periodic signal capable of adjusting the amplitude and phase to the correction signal from the stage length measurement system;
Periodic signal determining means for determining the periodic signal so that the amount of positional fluctuation obtained from the detection signal obtained by scanning the reference mark on the stage a plurality of times by changing the amplitude and phase in stages is minimized. When,
An electron beam apparatus comprising:   3. The positioning apparatus for an electron beam apparatus according to claim 2, wherein the stage length measurement system measures the movement of the stage in the X and Y directions with a laser interferometer.   The periodic signal can be selected from a plurality of reference signals prepared in advance, and one of them is a periodic signal generated so as to have an opposite phase at the same frequency as the commercial frequency in the apparatus installation environment. The electron beam apparatus according to claim 2 or 3, characterized in that   The reference mark is directly placed on the stage or placed on the material placed on the stage and is formed by etching a convex cross mark made of Au or Ta or Si. 5. The electron beam apparatus according to claim 2, wherein the electron beam apparatus is a concave cross mark.   6. The electron beam according to claim 2, wherein the amplitude and phase change amount, the reference mark scanning number, and the number of trials of this procedure can all be set and changed from the outside. apparatus.   As a means for determining the periodic signal that minimizes the positional variation amount, the storage unit stores a positional variation amount and the amplitude and phase of the periodic signal. The electron beam apparatus according to any one of claims 2 to 6, wherein the amplitude and phase corresponding to the smallest amount are employed.

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