JPH05102019A - Detection apparatus of position of alignment mark - Google Patents

Abstract

PURPOSE:To reduce the detection error of the position of an alignment mark and to shorten the time of an alignment treatment. CONSTITUTION:An alignment mark 10 which is extended radially from the center at equipment intervals is formed on a substrate 9 as an object to be exposed. The alignment mark 10 is scanned circularly by means of a charged electron beam 8. At this time, the central position of the alignment mark 10 is computed on the basis of the output of a secondary-electron detector 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment mark position detecting apparatus for a charged electron beam exposure apparatus for drawing a fine pattern on a sample of a wafer or a mask substrate in the manufacturing process of integrated circuit elements and the like.

[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, in order to shorten the alignment processing time, the charge electron beam is applied to the alignment mark on the substrate while vibrating at a predetermined frequency and amplitude, and secondary electrons generated at this time respond to the predetermined frequency component. An alignment mark position detecting method is also known in the related art, which detects the deviation between the center position of the alignment mark and the vibration center of the valence electron beam by frequency analysis of the response appearing on this detection element. We are (Japanese public Sho 56
No. 20694).

[0004]

According to the above-mentioned conventional detection method, the alignment marks formed in the X direction and the Y direction as shown in FIG. 6 are separately scanned by the charged electron beam to obtain the coordinates. Therefore, there was room for improvement in terms of shortening the alignment processing time.

In particular, in the detection method disclosed in Japanese Patent Laid-Open No. 2-79412, since the surface state of the alignment mark changes between the position on the substrate and the process, the detection signal level and the noise level greatly change and the detection result is changed. There was a problem that it was easy to make an error.

The present invention has been made in view of the above points, and an object of the present invention is to provide an alignment mark position detecting apparatus capable of reducing the alignment mark position detection error and shortening the alignment processing time. ..

[0007]

To achieve the above object, the present invention provides a valence electron beam source, a lens for focusing the valence electron beam emitted from the beam source on a substrate, and a deflection of the valence electron beam. In the alignment mark position detecting device for irradiating the alignment mark on the substrate with the beam deflected by the deflecting device and detecting the position of the alignment mark, the alignment mark has an equal angle from the center. Scanning control means, which are formed to extend radially at intervals and which control the deflection means so that the charged electron beam irradiated onto the alignment mark draws a circular locus, and secondary light emitted from the alignment mark. Alignment signal detecting means for detecting electrons, and the alignment marker based on the output of the alignment signal detecting means. It is obtained as provided with the center position calculation means for calculating the center position of.

[0008]

The alignment mark is circularly scanned by the charged electron beam, and the center position of the alignment mark is calculated based on the output of the alignment signal detection means at that time.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing the arrangement of an alignment mark position detecting device of a charged electron beam exposure apparatus according to an embodiment of the present invention. In the figure, the main control computer 1 is connected to the first and second signal generators 2 and 3 and the time interval discriminator 14, and controls the operation of these signal generators 2 and 3 and discriminator 14. The outputs of the signal generators 2 and 3 are connected to one inputs of the first and second signal adders 5 and 6, respectively, and the first signal generator 2 is connected to Asi.
nωt (A is a constant value, ω is an angular frequency, and t is time)
The sine wave signal represented by is supplied to the first signal adder 5,
The second signal generator 3 supplies the sine wave signal represented by Acos ωt to the second signal adder 6. Signal adders 5, 6
The other input of is connected to the deflection voltage setting device 4,
The predetermined DC voltage X1 in the X direction is supplied to the first signal adder 5, and the predetermined DC voltage Y1 in the Y direction is supplied to the second signal adder 6.

The output S2 (X1 + A of the first signal adder 5
sinωt) is X of the polarizer 7 of the charged electron beam exposure apparatus.
The axial polarization voltage is supplied to the X-axis deflection plate 7a, and the output S3 (Y1 + Acosωt) of the second signal adder is supplied to the Y-axis deflection plate 7b as the Y-axis polarization voltage of the deflector 7.
The deflector 7 changes the irradiation position of the charged electron beam 8 on the substrate 9. Reference numeral 10 is an alignment mark, and in this embodiment, it is formed so as to divide 360 degrees into eight equal parts, that is, extend radially from the center at intervals of 45 degrees.

A secondary electron detector 11 generated when the charged electron beam is irradiated is arranged above the substrate 9, and the detection signal is transmitted to the waveform shaper 13 and the lock-in amplifier 15 via the amplifier 12. It is supplied (S4). Wave shaper 1
The output of No. 3 is connected to the time interval discriminator 14, and the time interval discriminator 14 determines the direction of the center position of the alignment mark based on the time interval of the detection signal pulse, and supplies the determination result to the deflection voltage setting device 4. To do.

An oscillator 16 is connected to the lock-in amplifier 15, and the oscillator 16 has a frequency (8ω) that is eight times the output signal frequency of the first and second signal generators, and And a reference signal synchronized with the output signal of the second signal generator is supplied to the lock-in amplifier 15. The output of the lock-in amplifier 15 is connected to the deflection voltage setting device 4 and the threshold discriminator 17, and the output of the threshold discriminator 17 is connected to the main control computer 1.

Next, the operation of the alignment mark position detecting device configured as described above will be described.

First, when the trigger signal S1 is output from the main control computer 1, the first and second signal generators 2 and 3 output sinusoidal wave signals represented by Asin ωt and Acos ωt which are synchronized with each other. The predetermined DC voltages X1 and Y1 are output from the deflection voltage setting device 4. Therefore, the output signal S of the signal adders 5 and 6
2 and S3 are (X1 + Asinωt) and (Y1 +
Acosωt) (see FIGS. 3A and 3B). These signals S2 and S3 are the X-axis deflection plates 7a and Y, respectively.
The valence electron beam 8 applied to the axis deflection plate 7b is shown in FIG.
As shown in, the diameter D is centered on the point Ob on the substrate 9.
(D is proportional to the amplitude A of the sine wave signal), and draws a circular locus with an angular velocity ω. At this time, a pulse-shaped mark detection signal is obtained from the output of the secondary electron detector 17 according to the unevenness of the alignment mark 10 (see FIG. 3C).

If the center Oa of the alignment mark 10 (hereinafter referred to as “mark center”) and the center Ob of the circular locus of the beam (hereinafter referred to as “beam center”) Ob match, the mark detection signal pulse is generated. The generation intervals t of all are equal, but when the mark center Oa and the beam center Ob do not match as shown in FIG. 2A, the generation intervals of the mark detection signal pulses become non-uniform, In the illustrated example, t4 is the minimum and t8 is the maximum (see FIG. 2B).
From this, the mark center Oa is in the direction (the lower left of Ob 2 2) of the beam center Ob as shown in FIG.
2.5 degree direction) is detected. Further, for example, when t3 and t4 are substantially equal to each other and are minimum,
It is detected that the mark center Oa is in the direction substantially as shown in FIG.

In this way, it is possible to detect in which direction the mark center Oa is with respect to the beam center Ob based on the relative magnitude relationship between the mark detection signal pulse generation intervals t1 to t8. This direction detection is performed by the time interval discriminator 14, and the detection result (direction information)
Is supplied to the deflection voltage setting device 4.

On the other hand, the lock-in amplifier 15 amplifies and outputs only the component of the frequency 8ω contained in the mark detection signal, and the 8ω component in the mark detection signal corresponds to the mark center Oa as shown in FIG. It becomes maximum when the beam center Ob coincides, and the distance d between Oa and Ob (Fig. 4 (a)
(See) becomes larger as it becomes larger. Therefore, the center-to-center distance d can be detected from the output VL of the lock-in amplifier 15.

This detection signal is supplied to the deflection voltage setting unit 4 as distance information, and the deflection voltage setting unit 4 sets the setting voltages X1 and Y1 based on the direction information and the distance information, the mark center Oa and the beam center Ob. Change so that and match.

Since the direction information has an accuracy corresponding to a value obtained by dividing 360 degrees into eight equal parts (= 45 degrees), the deflection voltages X1 and Y1 are actually changed and the distance and direction are detected. The beam center Ob can be aligned with the mark center Oa by repeating and several times. In this embodiment, the change amounts of the deflection voltages X1 and Y1 are set to a value proportional to the reciprocal of the lock-in amplifier output VL.

As a result, the output VL of the lock-in amplifier 15 changes in the increasing direction, so that the threshold discriminator 17
Outputs a trigger stop signal S6 to the main control computer 1 when the VL value exceeds a predetermined value.

When the trigger stop signal S6 is input, the main control computer 1 stops the output of the trigger signal S1. This also stops the operation of the signal generators 2 and 3,
The process of detecting the alignment mark position is completed. The values of the deflection voltages X1 and Y1 of the deflection voltage setting device 4 at this time are taken into the main control computer 1 and processed as origin position information.

According to this embodiment, since the alignment mark is circularly scanned by the charged electron beam, the X-direction position and the Y-direction position can be detected at the same time, and the alignment processing time can be shortened. ..

Further, since a continuous detection signal is obtained by the circular scanning, only the desired frequency component can be amplified and the detection error due to the noise component can be greatly reduced.

[0025]

As described in detail above, according to the present invention, the alignment mark is circularly scanned by the charged electron beam, and the center position of the alignment mark is calculated based on the output of the alignment signal detection means at that time. Therefore, the X-direction position and the Y-axis direction position can be detected at the same time, and the alignment processing time can be shortened.

Further, since a continuous detection signal is obtained by the circular scanning, only the desired frequency component can be amplified and the detection error due to the noise component can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an alignment mark position detection device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a method of detecting an alignment mark.

FIG. 3 is a diagram showing a signal waveform of each part.

FIG. 4 is a diagram showing a relationship between a center (Oa) of an alignment mark and a center (Ob) of a circular trajectory of a valence electron beam.

FIG. 5 is a diagram showing a relationship between a distance (d) between a center of an alignment mark and a center of a circular trajectory of a charged electron beam and a lock-in amplifier output (VL).

FIG. 6 is a diagram showing a conventional alignment mark and its scanning method.

[Explanation of symbols]

 1 Main Control Computer 2, 3 Signal Generator 5, 6 Signal Adder 7 Deflector 9 Substrate 10 Alignment Mark 11 Secondary Electron Detector 12 Amplifier

Claims (1)

[Claims] 1. A valence electron beam source, a lens for focusing a valence electron beam emitted from the beam source on a substrate, and a deflection means for deflecting the valence electron beam. The deflection means deflects the valence electron beam. In the alignment mark position detection device for irradiating the alignment mark on the substrate with the generated beam and detecting the position of the alignment mark, the alignment mark is formed to extend radially from the center at equal angular intervals, and the alignment mark is formed. Scanning control means for controlling the deflection means so that the charged electron beam irradiated on the surface draws a circular trajectory, alignment signal detection means for detecting secondary electrons emitted from the alignment mark, and the alignment signal detection. Center position calculating means for calculating the center position of the alignment mark based on the output of the means. An alignment mark position detection device characterized by the above.