JPH0590145A - Alignment equipment of multi charged beam aligner - Google Patents

Abstract

PURPOSE:To highly precisely detect alignment mark position and enable accurate alignment in a multi charged beam aligner. CONSTITUTION:A specimen 8 is irradiated with a charged beam 101, via a main deflector 4, a beam limiting aperture 5, a deflector 6 for correction use, and a screen lens 7. A permanent magnet 33 for forming a nearly uniform magnetostatic field is arranged above the beam limiting aperture 5, and a secondary electron detector 32 is installed between the main deflector 4 and the permanent magnet 33. The secondary electrons emitted from the specimen 8 by irradiation of the charged beam 101 is deflected by the magnetic field of the permanent magnet 33, and enter the secondary electron detector 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment apparatus for a charged electron beam exposure apparatus which draws a fine pattern on a sample of a wafer or a mask substrate in a manufacturing process of integrated circuit elements and the like, and more particularly, can draw a large number of chips at the same time. The present invention relates to improvement of an alignment device for a multi-charge electron beam exposure apparatus.

[0002]

2. Description of the Related Art In a charged electron beam exposure apparatus, it is important to accurately position a wafer to be drawn (alignment). Therefore, in general, alignment marks are formed on a substrate such as a wafer, and the alignment mark positions are detected to perform positioning. As this alignment mark position detection device, an alignment mark of a substance different from that of the substrate is formed on a substrate to be exposed, and a change in the type of secondary ions generated when a valence electron beam is irradiated is detected to perform alignment. A device that detects a mark position has been conventionally known (Japanese Patent Laid-Open No. 2-79412).

Further, attention has been paid to the fact that when the secondary ions are generated, a current flows through the substrate, and this current value changes at the alignment mark position, and a method of detecting the alignment mark position based on the current change position has also been proposed. (Japanese Patent Application No. 1-333492 filed by the present applicant).

Further, in an alignment apparatus for a multi-charge electron beam exposure apparatus, alignment marks have already been formed at different positions for each of a plurality of chips on a substrate so that alignment can be performed for each chip. Proposed (Japanese Patent Application No. 1-343 by the present applicant)
218).

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since the detector disclosed in Japanese Patent No. 12 only has a detector for detecting secondary ions arranged above the substrate to be exposed, the amount of secondary ions detected is small and the alignment mark position detection accuracy is sufficiently secured. There is a problem that you cannot do it.

Further, when the detection method of Japanese Patent Application No. 1-333492 is applied to a multi-charge electron beam exposure apparatus, it is necessary to detect a minute current in the state where a high voltage is applied. Sufficient detection accuracy cannot be secured.

In the alignment apparatus of Japanese Patent Application No. 1-343218, it is difficult to form the alignment marks at different positions for each chip, and the marks are detected by the above current detection method. There is a problem.

The present invention has been made in view of the above points, and in a multi-charge electron beam exposure apparatus, it is possible to detect the position of an alignment mark formed for each chip with high accuracy and perform more accurate alignment. It is an object of the present invention to provide an aligned device.

[0009]

In order to achieve the above object, the present invention provides a multi-charge electron beam exposure for irradiating an object to be exposed with a charge electron beam through a deflector and a screen lens to draw a plurality of chips simultaneously. In the alignment device of the apparatus, which is provided between the deflector and the screen lens, and is generated when the object electron beam is irradiated with the charged electron beam.
Based on the magnetic field generating means for generating a magnetic field for deflecting the secondary electrons, the secondary electron detecting means for detecting the secondary electrons deflected by the magnetic field generating means, and the output of the secondary electron detecting means, An alignment mark position detecting means for detecting the position of the alignment mark formed on the object to be exposed is provided.

The secondary electron detecting means preferably has an energy filter to which a predetermined voltage is applied.

[0011]

The secondary electrons emitted from the object to be exposed are deflected in a certain direction by the magnetic field generated by the magnetic field generating means and enter the secondary electron detecting means. The alignment mark position is detected based on the output of the secondary electron detection means.

Energy filters eliminate stray electrons that are not secondary electrons.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram of a main part of a multi-charge electron beam exposure apparatus according to an embodiment of the present invention. In the figure, 1 is an ion beam (charged electron beam source) that outputs an ion beam (charged electron beam) 101. Below the ion beam source 1, a blanker 2, an object aperture 3, a main deflector 4, and a beam limiting aperture. 5, the correction deflector 6 and the screen lens 7 are arranged in this order. The ion beam 101 is passed through a blanker 2, an object aperture 3, a main deflector 4, a beam limiting aperture 5, a correction deflector 6, and a screen lens 7, and the sample (exposed object,
For example, a silicon wafer) 8 is irradiated and a pattern is drawn on the sample 8. The sample 8 is placed on the conductive plate 9 insulated from the XY stage 11 by the insulating plate 10 and fixed by the stopper 12. The conductive plate 9 is connected to the negative electrode of a power supply (for example, one that generates a voltage of about 40 KV) 20, and the positive electrode of the power supply 20 is connected to the ground.

The ion beam source is composed of an ion source for generating ions (charged electrons), a focusing lens, etc., and in the present embodiment, generates a positively charged ion beam. Blanka 2
Is a kind of deflector, and if necessary, the ion beam 10
1 is deflected so that the ion beam 101 is blocked by the object aperture 3, and the ion beam 101 is turned on (irradiation of the sample 8) and turned off (blocked). The object aperture 3 is for shaping the shape of the ion beam 101.
An image corresponding to the shape of the beam shaping hole 3a is projected on the sample 8. The main deflector 4 includes a first electrode 4a and a second electrode 4
b) and is used for adjusting the imaging range of the beam shaping hole 3a on the sample 8.

The beam limiting aperture 5 is provided with a plurality of forming holes respectively corresponding to the lens holes of the screen lens, and limits the electron beam passing through the lens holes of the screen lens. The beam limiting aperture 5 is made of a conductive material and a non-magnetic material (for example, stainless steel, tungsten, silicon, molybdenum).

As shown in FIG. 2, the correction deflector 6 is provided by the number of the lens holes 7a of the screen lens 7 in order to deflect each of the plurality of charged electron beams that have passed through the beam limiting aperture 5. 2 is partially omitted). The correction deflector 6 will be described later. The screen lens 7 is formed by vapor-depositing a metal (for example, gold) which is not easily oxidized on silicon or aluminum, and is provided with a large number of lens holes (for example, circular holes having a diameter of 1 mm). With this screen lens 7, an image of the beam shaping hole 3a of the object aperture 3 (for example, 1 μm ×) is formed on the sample 8 corresponding to each lens hole 7a.
A rectangular image of 1 μm) is projected and a plurality of the same patterns are simultaneously drawn on the sample 8. Here, the distance between the screen lens 7 and the sample 8 is set to about 20 mm,
A negative voltage (for example, −40 KV) is applied to the sample 8 with respect to the screen lens 7.

The XY stage 11 is a table that can be moved in the directions of the X axis and the Y axis which are orthogonal to each other by the stage drive motor 18, and moves the sample 8 to a predetermined irradiation position. A length measuring mirror 13 is provided on the XY stage 11, and the position of the XY stage 11 is measured with high accuracy by the length measuring mirror 13 and the laser length measuring device 16.

Above the beam limiting aperture 5, a permanent magnet 33 as a magnetic field generating means is arranged, and this permanent magnet 33 forms a substantially uniform static magnetic field above the beam limiting aperture 5. Further, the permanent magnet 33 and the main deflector 4
A secondary electron detector 32 and an energy filter 31 are provided between and. The secondary electron detector 33 detects secondary electrons generated from the sample 8 during ion beam irradiation, and is provided corresponding to each of the plurality of chips on the sample 8 (see FIG. 7). The energy filter 31 is made of, for example, a metal mesh, and a voltage slightly lower than the voltage applied to the sample 8 is applied. As a result, stray electrons other than secondary electrons are detected by the secondary electron detector 32.
Can be prevented.

It goes without saying that the magnetic field generating means may use an electromagnet.

1 to 13 and 3 of the above-mentioned components
1-33 are accommodated in a vacuum chamber 14, and the vacuum chamber 14 is exhausted to a predetermined pressure (for example, 10
- ⁶ ~10- ⁵ [torr]) until exhausted. Incidentally, definitive hereby Shochu ^10-6, the ^10-5 or the like 1/10 ^6, 1/10 ⁵
And so on.

The ion beam source 1, the blanker 2, the main deflector 4, the correction deflector 6 and the exhaust device 15 are respectively provided with an ion beam source controller 22, a blanker controller 23, a main deflection controller 24 and a correction deflection controller 25. And an exhaust controller 26 are connected, and these controllers 22 to 26 include the ion beam source 1, the blanker 2, the main deflector 4, the correction deflector 6, and the exhaust device 1.
5 are driven and controlled.

The laser length measuring device 16 and the stage driving motor 18 are connected to a stage driving device 17,
The stage drive device 17 detects and drives the position of the XY stage 11.

The secondary electron detector 32 comprises an electron multiplier and a current detector, and when secondary electrons are incident on the secondary electron detector 32, the electron multiplier increases the number of electrons several thousand times. The current detector converts the output electrons of the electron multiplier into a current and supplies it as a secondary electron detection signal to the mark position calculation circuit 21.

The controllers 22 to 26, the stage driving device 17, and the mark position calculation circuit 21 are connected to a control computer 28 via a CPU interface control circuit 27, and the control computer 28 controls the entire exposure apparatus. The operation is controlled. An input / output device 29 is connected to the control computer 28, and irradiation position data, deflection amount data of the correction deflector 6 and the like are input.

As shown in FIG. 3, the correction deflector 6 includes deflection electrodes 6a and 6b, two deflection electrodes 6a and 6b provided in each of the lens holes 7a of the screen lens 7 in the X and Y directions.
6c and 6d, between terminals X _{1 and} X ₂ and Y ₁
By applying a voltage between the -Y _2, moves to state deflects the valence beam 101, indicated by the solid line from the state shown in the focus position P is corrected (e.g. the same figure one point chain point on the sample 8 Be done). The movement amount of the focal position for this correction is about ± 1 μm at maximum. The voltage between the electrodes is 50
The range is up to 200 V, and is set according to the diameter of the lens hole 7a of the screen lens 7 and the center distance of the lens hole 7a.

The alignment method in the charged electron beam exposure apparatus configured as described above will be described in detail below.

FIG. 4 is a diagram showing the position of the alignment mark on the sample 8. An alignment mark 8b is formed on each of the plurality of chips 8a on the sample 8. The relative positions of the alignment marks 8b with respect to the chip 8a are all the same.

The alignment mark 8b is formed of a substance (eg, a metal substance such as gold) different from the base material portion (portion other than the alignment mark) of the sample 8 and emits secondary electrons when the ion beam 101 is irradiated. The amount is significantly different from the base material. Therefore, the main deflector 4 scans the ion beam 101 based on the deflection information from the control computer 28, and the alignment mark position is detected based on the detection signal of the secondary electron detector 32 and the deflection information.

Next, the action of a substantially uniform static magnetic field formed by the permanent magnet 33 will be described with reference to FIGS.

As shown in FIG. 5, the width of the magnetic field 33a is b.
[M] and magnetic flux density is B [T], initial velocity Vo [ev]
When the electrons of the above pass through the magnetic field 33a, they are deflected as shown. The deflection distance Y [m] is calculated by the following equation (1).
The trajectory of the electrons in the magnetic field 33a shown in the figure is a straight line (a broken line) for convenience, but is actually a curve. This point is the same in FIGS. 6 and 7.

[0032]

[Equation 1] Here, q is the charge of the electron and m is the mass of the electron.

Next, in this embodiment, since the ion beam 101 also passes through the magnetic field 33a, the effect of the magnetic field 33a on the ions in the ion beam will be described with reference to FIG.

In the figure, Ye is the deflection distance of secondary electrons traveling from the lower part of the figure, Yi is the deflection distance of ions (positive charges) traveling from the upper part of the figure, and is represented by the following equation (2):
It is represented by (3).

[0035]

[Equation 2] Here, q'and m'are the charge and mass of the ion, respectively, and Ve and Vi are the initial velocities of the electron and ion, respectively.

From the structure of the apparatus, Le = 200 [mm], Li
= 20 [mm], the ion is monovalent, and the mass is a proton
When represented by the mass of q = q ′, m ′ = 1.67 × 10
-²⁷It is [kg]. Also, m = 9.11 × 10 −³¹[kg]
And, from the principle of multi-ion beam imaging, Ve≈9V
i. Substituting these values into equations (2) and (3), Y
When i / Ye is calculated, Yi / Ye = 7.01 × 10 −³  Becomes

Therefore, if Ye = 150 mm, Yi =
It becomes 1.05 mm, and the influence of this degree can be sufficiently corrected by the main deflector 4. That is, since the influence of the magnetic field 33a on the ion beam 101 is small, it can be removed by the correction by the main deflector 4.

Further, the magnetic flux density B required at this time is calculated from the above equation (2).

[0039]

[Equation 3] Therefore, Ye = 150 [mm], b = 20 [mm], L
e = 200 [mm], m = 9.11 × 10- 31, Ve = 4
5 [KeV], by substituting ^{q = 1.60 × 10- 19 [C} ], B = 0.027 a [T].

The secondary electrons emitted from each chip 8a on the sample 8 are deflected by the magnetic field 33a as shown in FIG. 7 and travel toward the secondary electron detector 32 in parallel with each other. Therefore, as shown in FIG.
By providing the secondary electron detector 32, each chip 8
The alignment mark of a can be detected at the same time.

The secondary electrons emitted from the sample 8 are
Since the sample has energy proportional to the voltage applied to the sample 8, an energy filter 31 is provided immediately before the secondary electron detector 32 and a voltage slightly lower than the voltage applied to the sample is applied, so Can be prevented from entering the secondary electron detector 32.

As described above, according to this embodiment, the magnetic field 33
By the action of a, the secondary electrons emitted from the sample 8 are deflected in a certain direction, so that the secondary electrons can be efficiently detected. As a result, the intensity of the detection signal increases, the alignment mark position is detected with high accuracy, and more accurate alignment becomes possible.

Further, since the secondary electron detector 32 is provided corresponding to each chip of the sample 8, the alignment mark position of each chip can be detected at the same time.

Furthermore, the energy filter 31 can eliminate the influence of stray electrons other than the secondary electrons emitted from the sample 8.

The secondary electron detector 32 may be composed of a fluorescent plate and a photodiode, and secondary electrons may be applied to the fluorescent plate, and the intensity of light emitted at that time may be detected by a photodiode. In this case, even if the energy filter 39 is not provided, the influence of low energy electrons can be easily removed because the emission intensity is low.

[0046]

As described in detail above, according to the present invention, the secondary electrons emitted from the object to be exposed are deflected in a certain direction by the magnetic field generated by the magnetic field generating means and enter the secondary electron detecting means. Therefore, secondary electrons can be efficiently detected. As a result, the intensity of the detection signal increases, the alignment mark position is detected with high accuracy, and more accurate alignment becomes possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of a multi-charge electron beam exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a part of FIG. 1 in an enlarged manner.

FIG. 3 is a diagram showing focus correction by a correction deflector.

FIG. 4 is a diagram showing alignment mark positions on a sample.

FIG. 5 is a diagram for explaining the deflection of electrons by a magnetic field.

FIG. 6 is a diagram for explaining deflection of secondary electrons and ions due to a magnetic field.

FIG. 7 is a diagram for explaining the progress of secondary electrons emitted from a plurality of chips on a sample.

[Explanation of symbols]

 1 Ion beam source (charged electron beam source) 4 Main deflector 5 Beam limiting aperture 6 Correction deflector 7 Screen lens 8 Sample (exposed object) 31 Energy filter 32 Secondary electron detector 33 Permanent magnet

Claims (1)

[Claims] 1. An alignment apparatus for a multi-charge electron beam exposure apparatus, which irradiates an object to be exposed with a valence electron beam through a deflector and a screen lens to draw a plurality of chips at the same time. A magnetic field generating means which is provided between the magnetic field generating means and a magnetic field for deflecting secondary electrons generated when the object to be exposed is irradiated with a charged electron beam, and the secondary electrons deflected by the magnetic field generating means are detected. A secondary electron detecting means and an alignment mark position detecting means for detecting a position of an alignment mark formed on the object to be exposed based on an output of the secondary electron detecting means are provided. Alignment device for electron beam exposure equipment.