JPH02218904A - Two-dimensional micropattern measuring apparatus - Google Patents

Abstract

PURPOSE:To perform highly accurate measurement by detecting the edge voltage of a material to be measured based on the voltage values of first and second electric signals when the maximum and minimum differentiated strengths are obtained, and measuring the two-dimensional micropattern based on the edge voltage pattern. CONSTITUTION:Laser light 100 from a laser light source 1 is deflected with an acoustooptic element 110 which is driven by the first electric signal from a two-dimensional scanning driver 3. The light is further deflected in the perpendicular direction with the direction of the first deflected light with a special prism 120 which is driven by the second electric signal from the driver 3. The light is projected on a material to be measured 4. The intensity of the reflected light from the material to be measured 4 is detected with a reflected light detecting part 5. The differentiated intensity pattern which is obtained by differentiating the reflected light intensity pattern is formed in a reflected-light-intensity-pattern forming part 6. The maximum and minimum differentiated intensities of the differentiated intensity pattern are detected in a differentiated-intensity-pattern forming part 7. The edge voltage of the material to be measured 4 is detected in an edge detecting part 8 based on the voltage values of the first and second electric signal when the maximum and minimum differentiated intensities are obtained. The two-dimensional micropattern of the material to be measured 4 is measured based on the edge voltage pattern in a micropattern judging part 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a one-two-dimensional micropattern measuring device using laser light.

[Conventional technology]

With recent advances in precision processing technology, microfabrication has progressed in the fields of semiconductor integrated circuits, magnetic heads, etc., and micropatterns with two-dimensional shapes on the order of submicrometers to several micrometers can now be fabricated in minute areas. There is an increasing need for precise measurement of their shapes and dimensions.

As a conventional means for measuring the shape and dimensions of a micropattern, an image processing method using a TV right camera is often used. In this method, an object to be measured is illuminated with a white light source, and the reflected light is received by an image sensor, which is a light receiving element of a TV camera, and converted into a video signal. This video signal is A/D converted into a digital signal, binarized using a preset slice level, the number of pixels included in the binarized level is counted, and the size and shape are calculated from the number of pixels. This is to make a judgment.

As another conventional measuring means, a laser microscope has recently been realized for measuring two-dimensional micropatterns. In this method, the laser light emitted from a laser light source is focused into a spot using a combination of a galvanomirror and an acousto-optic element, and the laser light is focused in a two-dimensional manner, and the intensity of the reflected light is detected. This method performs binarization processing to measure the dimensions and shape of the micropattern.

[Problem to be solved by the invention]

In the former measurement method, the spatial resolution of the image sensor is low, so the pattern detection resolution in the sub-micron region is reduced, and the slice level for binarization fluctuates due to fluctuations in illumination light intensity because it uses white color. However, stable pattern measurement is difficult. In the latter measurement method, a galvano mirror is used for one side of the deflection of the laser beam, making minute deflection control difficult and resulting in a decrease in spatial resolution. In addition, since the same binarization process as the former measurement method is performed, if there is dust or dirt on the pattern area, the intensity of the reflected light will be modulated, and the slice level will change, resulting in erroneous 2nd measurements. Accurate pattern measurement is difficult because value conversion processing is performed.

The purpose of the present invention is to solve the above-mentioned problems, and to use a two-dimensional scanning optical system with high spatial resolution to accurately detect the edge of a micropattern without being affected by fluctuations in reflected light intensity. The object of this invention is to realize a device for measuring the dimensions and shapes of two-dimensional micropatterns.

[Means to solve the problem]

In order to achieve the above object, the present invention has the following configuration.

A first scan driver driven by a first electric signal from a two-dimensional scan driver transmits a laser beam emitted from a laser light source.
A second optical deflection element driven by a second electric signal from the two-dimensional scan driver performs a first optical deflection in a direction perpendicular to the direction of the first optical deflection. to perform a second optical deflection, and the first
The first and second polarized laser beams are focused and irradiated onto an object to be measured on which a two-dimensional micropattern is formed, and the intensity of reflected light from the object is detected. A reflected light intensity pattern synchronized with the period of light deflection in step 2 and a differential intensity pattern obtained by differentiating the reflected light intensity pattern are created, a differential maximum intensity and a differential minimum intensity of the differential intensity pattern are detected, and the differential maximum intensity is detected. detecting an edge voltage of the object to be measured from the voltage values of the first and second electric signals when the differential minimum intensity is reached, and measuring a two-dimensional micropattern of the object to be measured from the pattern of the edge voltage; It is something.

[Effect]

Using two types of optical deflection elements controlled by electrical signals, two-dimensional scanning is performed with high spatial resolution in mutually orthogonal directions. To measure the size and shape of a micropattern, it is necessary to detect the edge of the pattern with high precision.In general, the edge of the pattern is detected by focusing on the falling and rising parts of the intensity change of the U-shaped reflected light intensity pattern. The position where the intensity change rate is maximum is determined as the edge position from the differential intensity pattern obtained by differentiating the reflected light intensity pattern.

The micropattern is measured by analyzing the edge voltage pattern corresponding to this edge position.

〔Example〕

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

FIG. 1 shows a system block diagram for explaining the present invention in detail.

1 is a laser light source, and 100 is a laser beam emitted from the laser light source 1. As the laser light source 1, for example, a He-Ne laser, a semiconductor laser, or the like is used.

2 is a two-dimensional scanning optical system that performs two-dimensional scanning, and includes a first light deflection element 110 and a second light polarization pixel element 120.
and other lenses.

In this embodiment, the first optical deflection element 110 is an acousto-optic element (hereinafter abbreviated as A-0), and the second optical deflection element is composed of a special prism 120 with a special shape. 3 is a two-dimensional scan driver that generates a first electrical signal 130 and a second electrical signal 140. 1st
electrical signal 160 is applied to A-0 driver 165 to control the first optical deflection operation by A-0110.

The second electric signal 140 is applied to a piezo driver 145 to drive a piezo translator (hereinafter abbreviated as PZT) 150 to control the second light deflection operation by the special prism 120.

Here, the first optical deflection by A.0110 and the second optical deflection by the special prism 120 are performed in directions directly opposite to each other. 4 is an object to be measured on which a two-dimensional micropattern is formed. Laser beam 10 scanned two-dimensionally
5, the objective lens 108 condenses the light into a minute spot diameter and irradiates the object 4 to be measured, and the reflected light detection section 5 detects the reflected light. Reference numeral 6 denotes a reflected light intensity pattern creation unit that creates a reflected light intensity pattern in synchronization with the polarization cycles of the first light deflection and the second light deflection. Part B is the differential intensity pattern creation department,
A differential intensity pattern is created by differentiating the reflected light intensity pattern. Reference numeral 8 denotes an edge detection unit that detects the maximum differential intensity and minimum differential intensity of the differential intensity pattern, and detects the above-mentioned first electric signal 130 and second electric signal 140 when these intensities are reached.
The voltage value of is detected as the edge voltage value. The edge voltage value determined at this time corresponds to the edge portion of the micropattern. Reference numeral 9 denotes a micropattern determination unit that determines the shape, dimensions, etc. of the actual pattern from the edge voltage pattern detected by the edge detection unit 8. A voltage-dimension conversion coefficient is determined in advance from the correspondence of the dimensional change to the change, and the edge voltage pattern is converted into a pattern corresponding to the actual dimension from the voltage-dimension conversion coefficient to perform micropattern measurement.

In FIG. 2, a two-dimensional scanning operation by the two-dimensional scanning optical system 2 shown in FIG. 1 will be explained.

Figure 2 (a) is an optical path diagram of light deflection by A-0110, Figure 2 (b) is an optical path diagram of light deflection by special prism 120, and Figures 2 (C) and 2 (d) are special prisms. 120
FIG. 3 is an optical path diagram illustrating a single optical deflection operation.

102.104.106 in Figure 2 (a) and (b)
．． 108 has focal lengths f, f2, f8, and f, respectively.

The lens 108 is the objective lens.

2(a) shows the optical deflection in the X direction in a plane parallel to the paper plane in FIG. 1, and FIG. 2(b) shows the optical deflection in two directions in the plane perpendicular to the paper plane in FIG. 1. A-0110 contributes to deflection only in the X direction, and special prism 120 contributes to deflection only in two directions. Regarding the optical deflection in the X direction in FIG. Since it has no refracting effect in the direction, it travels straight, is not refracted in the X direction by the special prism 120, and travels straight, is refracted by the lens 106, and further travels parallel to the objective lens 108 and at a position distanced by Dx from the optical axis. I am made to do so.

For the light deflection in two directions in Figure 2(b),
0 has no deflection effect in two directions, so the lens 102.1
04, it goes straight without being refracted, so the lens 10
The optical axes in the two directions when passing through lens 1040 are constant before and after passing through lens 1040.

The special prism 120 is changed in position by h in two directions to change the height of the optical axis, thereby deflecting light. After passing through the special prism 120, it proceeds parallel to the optical axis as in the case of FIG. 2(a), and the lens 106.10
After passing through point 8, the light beam travels along the optical path at a distance of D2 from the optical axis. The deflection operation will be described with reference to FIGS. 2(C) and 2(d) showing specific configuration examples of the special prism 120. 200 is an equilateral triangular prism with an apex angle of 60°, 210 is an equilateral triangular prism with an apex angle of 30°
They are 60'90° right angle prisms and are used by stacking them as shown in the figure. Reference numeral 220 denotes incident light that is perpendicularly incident on the vertical surface of the equilateral triangular prism 200, and exits perpendicularly from the vertical surface of the right-angle prism 210 after passing through a V-shaped reflection path within the prism medium. Outgoing light 230 is in the same direction as incoming light 220. FIG. 2(C) shows a case where the bottom surface of the special prism 120 is installed at the reference position, and this example shows the incident light 220 and the output light 2.
30 is the same optical axis height. FIG. 2(d) shows a case where the bottom surface position of the rectangular prism 210 is moved by h in two directions, and this movement is performed by the piezo translator 150. The optical axis height position of the incident light 240 is the incident light 220
is the same as Since the bottom surface position of the right angle prism 210 is shifted by h, the incident position with respect to the equilateral triangular prism 200 changes. Inside the prism medium, there is a V-shaped reflection path as in (C), but since the reflection position at the bottom of the right-angle prism 210 is shifted (the amount of shift is 2).
h /y/'), the optical axis height position of the emitted light 250 changes with respect to the incident light 240, but the amount of change is twice the change in the bottom surface position. By moving the special prism 120 in this manner, efficient deflection is possible.

Deflection amount Dx of the two-dimensional scanning optical system with the above configuration,
D2 is expressed by the following formula.

Dx=(fo/f,)・f,・θ D, = (fo/f,)-2h FIG. 3 shows an example of a two-dimensional micropattern.

This is an example of a pattern called a pole no-ite formed in a track portion of a Wintier-type magnetic head. 60 is a track portion, the dimension W of which is ~15 μm. 61 is a gap portion, the dimension W2 of which is ~0.7 μm
It is. 62 is a pole hide part, which is formed on an extension of the gap part 61, and is a pole!・Measurement of the light dimension L is required. To measure the pole hide dimensions, it is necessary to measure the track edge 304, the edge of the gap extension 300, and the edges 60 and 302 of the pole hide section 62 to determine the kink position 606 of the ball knot pattern. .

Scanning in two directions is performed by a second optical deflection element (special prism) 120 driven by a second electric signal 140,
Scanning in the direction is performed by the first optical deflection element (A.0) 110 driven by the first electric signal 130. When performing a two-dimensional raster scan as in this example, the first electrical signal 160 may be a ramp wave voltage, and the second electrical signal 140 may be a step wave voltage.

FIG. 4 shows examples of reflected light intensity patterns and differential intensity patterns detected when a ball hide part is two-dimensionally scanned. 4(A), ←→, and (E) are reflected light intensity pattern waveforms, and the horizontal axis of each graph is the amount of light deflection, and the vertical axis is the reflected light intensity. FIG. 4(a) shows when the gap extension part 600 is scanned by A-0110, and FIG.
This is a waveform when the ball hide part 32 is scanned by 0110.

Figure 4 (E) shows the special prism 12 made of PZT150.
This is a waveform obtained when the track edge portion 604 is scanned in two directions by moving 0. Since the pole hide portion 62 is made of glass, its reflectance is lower than that of the ferrite base material, so that it generally has a U-shaped reflected light intensity pattern. FIGS. 4(b), 4(b), and 4(f) are differential intensity pattern waveforms, the horizontal axis of the graph is the amount of light deflection, and the vertical axis is the differential intensity. Figure 4 (b) is the differential intensity pattern of Figure 4 (a), Figure 4 (ni) is the differential intensity pattern of Figure 4 (c), and Figure 4 (f) is the differential intensity pattern of Figure 4 (e). It is a differential intensity pattern.

In the case of the differential intensity pattern shown in Figure 4 (b), the minimum and maximum values of the differential intensity do not correspond to the actual edges, so the intermediate voltage between the voltage values of the first electrical signal when the minimum and maximum values occur. , is detected as a voltage value corresponding to the center of the pattern. This occurs when the pattern width is about half or less of the beam spot diameter of the irradiated laser light.

4), the pattern width is larger than the beam spot diameter of the laser beam, so the voltage value v2 of the first electrical signal when the minimum differential intensity is 404, the maximum differential intensity 40
6, the voltage value (2) of the first electrical signal can be detected directly corresponding to the edge of the pattern. In this way, the center position of the edge of the gap extension part 600 and the edges 60 and 302 of the pole hide part 62 can be determined. In the case of FIG. 4(f), the maximum differential intensity 408 is obtained, and the voltage V4 of the second electric signal at that time can be detected as the position of the track edge 304.

FIG. 5 shows an example of a pattern of edge positions based on voltage values obtained from the reflected light intensity pattern and differential intensity pattern explained in FIG. 4. The horizontal axis of the graph is the voltage value due to the second electric signal, and the vertical axis is the voltage value due to the first electric signal. X
The marks are measured values, the line 51 is the center line of the gap extension part 600, the edge line 52 is a line connecting one edge 601 of the pole hide part 32, and the edge line 53 is a line connecting the other edge 602. At this time, the least squares method may be used to connect the edges.

Line 54 is a midpoint line between two edge lines 52 and 53.

An intersection point 55 between the lines 51 and 54 corresponds to the pole-hyde kink point 303 shown in FIG. If the voltage value of the second electrical signal corresponding to the position at this time is V, then the voltage difference V
Since =V and -V correspond to the pole-hide dimensions, the pole-hide dimensions can be determined from the relationship between the amount of deflection of the special prism 120 by the second electric signal.

FIG. 6 shows a flowchart for carrying out the measurements shown in FIG. 5.

The reflected light intensity pattern creation section 6 shown in FIG. 1 can be implemented by a semiconductor memory circuit, and the differential intensity pattern creation section 7 can be implemented by hardware using a combination of a shift register and a flip-flop circuit, or by a microcomputer. This can also be done in software by calculating -.

If you want to do it in terms of hardware, you can easily configure the circuit by using differences.

The edge detection section 8 and micropattern determination section 9 are performed by software calculations of a slim microcomputer.

In step 600, a PZT scan set is performed, and the step voltage width and step start voltage of the second electric signal 140 that changes with the step voltage are set, and the PZT scan set is performed.
150 is set. Step 602
4 creates a reflected light intensity pattern when the track edge portion 604 is scanned in two directions by driving the PZT 150.
Obtain the waveform shown in e). In step 604, a differential intensity pattern is created, and the waveform shown in FIG. 4 is obtained by differentiating the reflected light intensity pattern. Step 606
is for determining the track edge, and is for determining the voltage value of the second electrical signal when the differential intensity of the differential intensity pattern reaches the maximum differential intensity, and determines the voltage value v4 shown in FIG. 4(f). Step 608 is to perform gap extension scan set, which is the same as step 600 (step voltage width when driving PZT 150 with second electrical signal 140, step start voltage, and first electrical signal for scanning A-0110). Set 160.

Step 610 is a reflected light intensity pattern creation section, step 612 is a differential intensity pattern creation section, and step 614 is pattern center determination. The differential intensity pattern obtained in step 612 has a waveform as shown in FIG. 4 (b),
From the voltage value of the first electric signal when the differential intensity is minimum and maximum, the voltage value (1) at the midpoint is determined, and the center position of the pattern is determined. Step 616 is the gap extension 3
This is to determine whether or not the 00 pattern ends. If the pattern continues, loop 618 returns to step 6.
Return to step 10 and repeat the above operation.

If the pattern has ended, the process moves to step 620 and the voltage at the center of the pattern is stored. The end of the pattern of the gap extension portion 300 can be determined from the change in the voltage value at the center of the pattern determined in step 614. Step 622 is the pole hide part scan set, Step 6
Similarly to 00.608, the first electric signal 160 is set to drive A-0110 when scanning is performed across the two edge portions 60 and 302 of the pole-hide portion 320 shown in FIG. Steps 624 and 626 are for creating a reflected light intensity pattern and a differential intensity pattern when scanning the pole-hide portion, and the differential intensity pattern has a waveform as shown in FIG. 4). Step 628 is for determining the pole-hide part edge, which is determined based on the voltage value of the first electric signal 160 when the differential intensity pattern has the minimum and maximum differential intensity. This ball hide portion edge determining operation is repeated a certain number of times using a loop 630. Step 632 performs memory of edge voltages. Step 634 performs abnormal data determination. The presence or absence of abnormal data is determined from the pattern (pattern in Fig. 5) of the voltage values of the first electric signal 130 and the second electric signal 140 obtained in steps 614 and 628, and if there is an abnormality, it is determined. The data is skipped without being adopted as a measurement value.

Step 636 performs linear approximation, for example, by linearly approximating the measured values using the least squares method to obtain the three straight lines 51 and edge lines 52 and 53 shown in FIG. Step 668 is to perform a pole-hide intersection calculation, in which the line 54 which is the midpoint of the pole-hide part 32 and the line 51 which is the midpoint of the gap extension part as explained in FIG.
Determine the intersection position 55 with . Step 640 is to calculate the pole-hide dimension, and the voltage value v4 of the second electric signal that becomes the track edge and the voltage value V of the second electric signal that becomes the pole-hide kink point obtained in step 668 are calculated.
, the actual dimensions are calculated using a dimension conversion coefficient from the voltage difference between.

〔Effect of the invention〕

As is clear from the above explanation (according to the present invention, it is possible to measure two-dimensional micropatterns with high precision by performing stable edge detection using a stable two-dimensional scanning optical system with high spatial resolution. .

[Brief explanation of the drawing]

FIG. 1 is a system block diagram explaining the present invention in detail;
29. Optical path diagram illustrating the configuration of the optical system and the scanning optical path when performing a 2-dimensional ski scan; FIG. 3 is a perspective view showing the shape of a pole-hide part of a magnetic head, which is an example of forming a two-dimensional micro pattern; (a) ～(f) 4th neck ball... A waveform diagram showing an example of the reflected light intensity pattern and differential intensity pattern waveform detected when the light part was scanned two-dimensionally. FIG. 6 is a graph showing a pattern of edges that are sometimes detected. FIG. 6 is a flowchart explaining the operation when calculating the dimensions of the pole hide part. 1... Laser light source, 2... Two-dimensional scanning optical system, 6...
Two-dimensional scan driver 4...Object to be measured, 6...Reflected light intensity pattern creation unit, 7...
... Differential intensity pattern creation section, 8 ... Edge detection section, 9 ... Micro pattern judgment section, 110 ...
...Acousto-optic element, 120...Special prism. (A) Figure 4 (B) (PZT') (PXT) Figure 4

Claims (1)

[Claims] A first scan driver driven by a first electric signal from a two-dimensional scan driver transmits a laser beam emitted from a laser light source.
A second optical deflection element driven by a second electric signal from the two-dimensional scan driver performs a first optical deflection in a direction perpendicular to the direction of the first optical deflection. to perform a second optical deflection, and the first
A laser beam that is two-dimensionally scanned by the optical deflection element and the second optical deflection element is focused and irradiated onto an object to be measured on which a two-dimensional pattern is formed, and the reflected light from the object to be measured is detected. A reflected light intensity pattern of the reflected light and a differential intensity pattern obtained by differentiating the reflected light intensity pattern are created in synchronization with the deflection cycles of the first light deflection and the second light deflection, and A differential maximum intensity and a differential minimum intensity of the differential intensity pattern are detected, and the first electric signal and the second electric signal are detected when the differential maximum intensity and the differential minimum intensity are reached.
An edge voltage of the object to be measured is detected from the voltage value of the electric signal, and a two-dimensional micropattern of the object to be measured is measured from a pattern of the edge voltage.
Dimensional micropattern measurement device.