JPH09186062A - Position detection by means of charged particle beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform detection of mark positions and beam positions with good accuracy by changing a distance between a charged particle beam optical axis and a member every multi-scanning and averaging a plurality of obtained position signals with no regard to accuracy of a DA converter. SOLUTION: Reflected electrons generated from drawn materials 8 and marks 18 and detected by a reflection electron detector 19 by scanning an electronic beam. Then, this detection signal is supplied to a control device 14 through an amplifier 20 and an AD converter. The control device 14 finds an intermediate position of the detection signals basing on two peak positions obtained on the edge parts of a mark for making it a mark position. Further, at this time, the electron beam FB is scanned crossing the multi-number mark 18. Then, the SN ratio of the mark position detection can be improved by finding an average of the mark positions obtained by respective scannings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of detecting a position of a mark or the like by a charged particle beam in an apparatus using a charged particle beam such as an electron beam drawing apparatus or an ion beam apparatus.

[0002]

2. Description of the Related Art For example, in an electron beam drawing apparatus, the size and position of the electron beam used for drawing or the focus state of the electron beam is measured before the actual drawing operation, and the electron beam is drawn based on the measurement result. Is being adjusted. FIG. 1 shows an example of an apparatus used for measuring such an electron beam, and 1 is the electron beam to be measured. Although not shown, the electron beam 1 has a rectangular cross section formed by two rectangular slits and a deflector provided between the two rectangular slits.

The electron beam 1 is focused by the final stage lens 2 and further deflected by the electrostatic deflector 3.
A knife edge member 4 is arranged below the deflector 3, and the knife edge member 4 is provided with a rectangular opening, and each inner side thereof is formed thin and linear. An aperture 5 that cuts the scattered electron beam is provided below the knife edge member 4, and further below that,
A Faraday cup 6 for detecting the amount of electron beam current is arranged.

When the saw-toothed deflection signal shown in FIG. 2 (a) is applied to the deflector 2 with the above configuration, the rectangular electron beam 1
Is deflected in the X direction. By deflecting the electron beam,
The electron beam is gradually shielded by the knife edge member 4, and the amount of the electron beam incident on the Faraday cup 6 decreases. When the electron beam 1 is completely shielded by the knife edge member 4, the detection current of the Faraday cup 6 becomes zero.
Becomes

FIG. 2B shows the detected current of the Faraday cup 6. When the detected current signal is differentiated once, the signal shown in FIG. 2C is obtained. Further, when the signal of FIG. 2 (c) is differentiated again, the signal of FIG. 2 (d) is obtained.
In FIG. 2D, the horizontal axis is the scanning position of the electron beam,
The size of the electron beam is determined based on the distance between the two peaks of the signal. Further, the position of the electron beam is found based on the intermediate position between the two peak positions. Furthermore, the peak value of the peak indicates the focus state of the electron beam. Various adjustments of the electron beam are performed according to the beam size, beam position, and focus state obtained in this way, and then the regular drawing operation is executed.

[0006]

In the measurement of the position of the electron beam, the electron beam is scanned by the scanning signal supplied to the deflector 2. The scanning signal supplied to the deflector 2 is created by converting a digital scanning signal into an analog signal by a DA converter. Here, assuming that the electron beam is scanned with the signal converted by the 4-bit DA converter, 16 pieces of data at this time are represented by four bits 2 ⁰ to 2 ³ and the voltage of each bit is changed. Is the sum of

Now, 2 ⁰ (= 1) bits are -0.5 LS
At B (0.5V), 2 ¹ (= 2) bits are + 0.5LS
If the accuracy is B (2.5 V), the voltages in the entire data range are as shown in FIG. Further, FIG. 4 shows the relationship between each bit of 2 ⁰ , 2 ¹ , 2 ² and 2 ³ and the voltage. The voltage satisfies the condition of ± 0.5 LSB or less in the entire data range, which is the standard accuracy of a normal DA converter. A graph showing the deviation from the data of FIG. 3 and the set voltage is shown in FIG.

As is clear from the graph of FIG. 5, the deviation from the set voltage at each data (point) changes periodically, and the mark or knife edge is scanned by the scanning signal having such a deviation to move the mark position. Even if the position of the electron beam is detected, the position cannot be detected accurately. Usually, in order to improve the detection accuracy of the mark position and the like, scanning is performed a plurality of times at the same position and the position signals obtained by each scanning are averaged. However, the deviation as shown in FIG.
Even if it is averaged, its influence cannot be eliminated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a charged particle beam capable of accurately detecting a mark position and a beam position regardless of the accuracy of a DA converter. It is to realize a position detection method.

[0010]

A position detecting method using a charged particle beam according to the invention of claim 1 supplies a scanning signal via a DA converter to a deflector for deflecting the charged particle beam so as to generate the charged particle beam. Scan a number of times across a member having a linear edge, average the signal of the charged particle beam detected with this number of scans, and based on the averaged signal between the charged particle beam and the member In the method of detecting the relative position, the charged particle beam is scanned a number of times across the member, and the distance between the optical axis of the charged particle beam and the member is changed for each scanning. It is characterized in that a plurality of position signals obtained based on each of the multiple scannings are averaged.

A position detecting method using a charged particle beam according to a second aspect of the invention is characterized in that the position of the member is mechanically moved for each scanning of the charged particle beam.

The position detecting method using a charged particle beam based on the third aspect of the invention is characterized in that the optical axis of the charged particle beam is moved for each scanning of the charged particle beam.

In the position detecting method using the charged particle beam according to the present invention, the distance between the optical axis of the charged particle beam and the member is changed by a distance corresponding to ± 1/2 LSB of the DA converter. It is characterized by having done.

In the present invention, the charged particle beam is scanned a number of times across the member a plurality of times, and the distance between the optical axis of the charged particle beam and the member is changed for each number of scans. By doing so, a plurality of position signals obtained based on each of the multiple scans are averaged to perform accurate position detection regardless of the accuracy of the DA converter.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 6 shows an example of an electron beam drawing apparatus for carrying out the present invention. When performing electron beam drawing, a mark is provided on the material to be drawn, the position of this mark is detected, and the actual drawing position is accurately set based on the mark position. The method of the present invention is used to detect this mark position.

In FIG. 6, reference numeral 7 denotes a final-stage focusing lens (objective lens), and the electron beam EB is focused on the drawing material 8 by the final-stage focusing lens 7. An electrostatic deflector 9 is used to scan the electron beam EB. The material 8 to be drawn is placed on a moving stage 10, and the moving stage 10 is driven by a driving mechanism 11.
It can be moved dimensionally.

A reflecting mirror 12 is provided at the end of the moving stage 10, and this reflecting mirror 12 has a laser length measuring device 1.
As is well known, the laser beam from the laser beam 3 is used to measure the amount of movement and the position of the stage by utilizing laser interference. The position signal of the stage 10 measured by the laser length measuring device 13 is supplied to the control device 14. The control device 14 controls the drive mechanism 11.

A scanning signal from the scanning circuit 15 is supplied to the electrostatic deflector 9 via the DA converter 16. A mark 18 is provided on the material 8 to be drawn.
The electron beam EB is scanned across 8. For example, backscattered electrons generated by the irradiation of the drawing material 8 with the electron beam are detected by the backscattered electron detector 19. The detection signal from the detector 19 is the amplifier 20 and the AD converter 2
1 to the control device 14. The operation of such a configuration will now be described.

First, a normal drawing operation will be described.
The focused electron beam EB is irradiated to the drawing material 8, and the irradiation position of the electron beam on the material is set to the electrostatic deflector 9
By providing a deflection signal to. Drawing data is stored in advance in the control device 14, the scanning circuit 15 is controlled based on the drawing data, and a deflection signal corresponding to the drawing pattern is applied to the electrostatic deflector 9.

Drawing on the drawing material 8 is performed by supplying a deflection signal to the electrostatic deflector 9 and moving the stage 10 by the driving mechanism 11. The control device 14
The drive mechanism 11 is controlled according to the drawing data. The moving amount of the stage 10 is monitored by the laser length measuring device 13, and the position signal of the stage 10 from the laser length measuring device 13 is supplied to the control device 14. The control device 14
The movement error of the stage is fed back to the drive mechanism 11 to accurately move the stage. Alternatively, the control device 14 feeds back the movement error of the stage 10 to the electron beam deflection system, and corrects the movement error based on the deflection amount of the electron beam.

When writing on the drawing material 8, as is well known, the position of the mark 18 provided on the drawing material 8 is detected and a pattern is drawn according to the mark position. I have decided the position. The position of the mark 18 is detected by scanning the electron beam a number of times across the mark 18,
This is performed based on the edge signal of the mark 18 obtained by each scan.

That is, the backscattered electrons generated from the drawing material 8 and the marks 18 by scanning the electron beam are detected by the backscattered electron detector 19, and the detection signal is passed through the amplifier 20 and the AD converter 21. Supply to 14. The control device 14 obtains an intermediate position between the two peak positions obtained at the edge portion of the mark in the detection signal, and sets it as the mark position. At this time, the electron beam EB is scanned across the mark 18 many times, and the SN ratio of the mark position detection is improved by obtaining the average of the mark positions obtained by each scanning.

FIG. 7 is a diagram for explaining the mark position detecting method according to the present invention, in which the electron beam EB is deflected by the deflector 9.
Is scanned across the mark 18. Mark 18
a shows the state of being arranged at the first position,
The electron beam EB is scanned many times across the mark 18a at this position. At this time, the center position Pa of the mark 18a is obtained as described above by the reflected electron signal based on the two edges of the mark 18a.

Next, the stage 10 is moved by a command from the control device 14, and accordingly, the mark 18 is displaced by L from the position of the mark 18a and 18b.
Can be moved to the position. The electron beam EB is also scanned across the mark 18b to obtain the center position Pb of the mark.

Here, as described in the section of the problem, the detected mark position Pa has a detection error based on the accuracy of the DA converter 16. Therefore, the mark 18
The error component Δa is added to the position Pa of a. Further, the error component Δb is added to the position Pb of the mark 18b. That is, the first mark detection result A and the second mark detection result B are respectively expressed as follows.

A = Pa + Δa B = Pb + Δb−L = Pa + Δb The average (A + B) / 2 of the two mark detection results is as follows.

(A + B) / 2 = Pa + (Δa + Δb) / 2 Here, if L is selected so as to be Δa = −Δb, the average of the first and second mark detection results is Pa, and DA
The mark position can be accurately detected without being affected by the accuracy of the converter 16. The length of L varies depending on the accuracy of the DA converter used, but as an example, L is 0.4 μm.
By setting m, the condition of Δa = −Δb can be satisfied. The length of L can be accurately adjusted by measuring the moving distance of the stage 10 by the laser length measuring device 13 and feeding back the measurement result to the drive mechanism 11 via the control device 14.

FIG. 8 shows another embodiment of the present invention. In this embodiment, the mark 18 is not mechanically moved but the optical axis of the electron beam EB is moved by L. . In the figure, reference numerals 22 and 23 are deflection coils for adjusting the optical axis, and these two coils 22 and 23 are used for moving the optical axis.

In the initial state, the deflection coils 22 and 23 are not operated, and the mark 18 is scanned by the electron beam of the optical axis O ₁ , and the first mark position detection is performed. Next, the deflection coil 22 deflects the electron beam EB by a certain amount as shown by a dotted line, and the deflection coil 23 further deflects the electron beam so as to be parallel to the optical axis O ₁ .

As a result, the optical axis becomes the optical axis O _{2 which is} away from O ₁ by the distance L, and by performing the second mark position detection in this state, the accurate mark position can be obtained regardless of the accuracy of the DA converter. Detection can be performed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, although the above embodiment has been described using an electron beam, the present invention can be applied to an ion beam apparatus. Further, the detection of the position of the mark on the material to be drawn has been described as an example, but as in the conventional example shown in FIG. The present invention can be applied to the case of measuring the position and size of the. Further, although the reflected electrons from the material are detected, the secondary electrons may be detected.

[0032]

As described above, according to the present invention, a large number of scannings of the charged particle beam across the member are performed a plurality of times, and the scanning between the optical axis of the charged particle beam optical member and the member is performed for each scanning. The distance was changed, and a plurality of position signals obtained based on each of the multiple scans were averaged. As a result, accurate position detection can be performed regardless of the accuracy of the DA converter.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus used for conventional electron beam measurement.

FIG. 2 is a waveform diagram for explaining basic signal processing for electron beam measurement.

FIG. 3 is a diagram showing each data and a deviation from a set voltage.

FIG. 4 is a diagram showing a relationship between each bit and a voltage.

FIG. 5 is a graph showing a deviation from data and a set voltage.

FIG. 6 is a diagram showing an example of an apparatus for carrying out the present invention.

FIG. 7 is a diagram showing how a mark moves when the position of the mark is detected using the method of the present invention.

FIG. 8 is a diagram for explaining another embodiment of the present invention in which the optical axis is moved.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron beam 2 Final stage focusing lens 3 Electrostatic deflector 4 Knife edge member 5 Aperture 6 Faraday cup 7 Final stage focusing lens 8 Drawing material 9 Electrostatic deflector 10 Moving stage 11 Driving mechanism 12 Mirror 13 Laser measuring device 14 Control device 15 Scanning circuit 16 DA converter 18 Mark 19 Backscattered electron detector 20 Amplifier 21 AD converter

Claims (4)

[Claims] 1. A DA for a deflector for deflecting a charged particle beam.
A scanning signal is provided through the transducer, the charged particle beam is scanned multiple times across a member having straight edges, and the signals of the charged particle beam detected with the multiple scanning are averaged. In a method for detecting the relative position of a charged particle beam and a member based on an averaged signal, a charged particle beam is scanned across the member a number of times multiple times, and a charge is generated for each number of scans. A position detection method using a charged particle beam, in which a distance between an optical axis of a particle beam and a member is changed, and a plurality of position signals obtained based on a plurality of scannings are averaged. 2. The position detecting method using a charged particle beam according to claim 1, wherein the position of the member is mechanically moved for each scanning of the charged particle beam. 3. The position detecting method using a charged particle beam according to claim 1, wherein the optical axis of the charged particle beam is moved for each scanning of the charged particle beam. 4. The position detecting method using a charged particle beam according to claim 1, wherein the distance between the optical axis of the charged particle beam and the member is changed by a distance corresponding to ± 1/2 LSB of the DA converter.