JP2952019B2 - Charged beam intensity profile measuring apparatus and measuring method using the same - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to a charged beam intensity profile measuring apparatus and a measuring method using the same, and more particularly to a charged beam intensity profile measuring apparatus and the like. Regarding measurement.

(Prior Art) With the progress of high integration in semiconductor devices, the necessity of miniaturization of circuit patterns has increased, and in recent years, a technology for forming finer patterns with higher precision has been required.

Charged beam lithography has attracted attention as one of the most prominent methods for forming such fine patterns. Among them, a method using a variable shaped beam (VSB) aiming to improve throughput is used. It has been adopted.

Generally, in a charged beam apparatus of the VBS system, it is necessary to measure and control a beam intensity profile as a basic performance, specifically, a beam size and a beam edge resolution with high accuracy. For example, in order to form a pattern of 0.2 μm or less required for recent advanced device development, 0.1 μm
A beam edge resolution of m or less is required, and measuring this with high accuracy is an important issue.

Conventionally, several methods have been used for measuring a beam intensity profile in a charged beam apparatus of the VBS system.

One is the knife edge method. In this method, an edge of a metal or the like is sharply thinned like a knife edge, inserted at the focal position of a charged beam, a Faraday cup is provided below the edge, and a change in beam current is measured while scanning the beam. The beam intensity profile is obtained by differentiating the beam current change. This method is excellent in principle, but when actually measuring a rectangular beam, if the parallelism between one side of the rectangle and the direction of the edge cannot be accurately measured, the error appears as an error in the beam profile. There's a problem. Specifically, the parallelism adjustment between the rectangular beam and the edge direction is performed as follows. While gradually rotating the beam, the beam profile is measured each time, and the positions in the rotation direction where the beam edge resolution is the smallest are assumed to be parallel to each other. This parallelism adjustment method is extremely complicated, and has a problem that it is difficult to determine the position in the rotation direction having the smallest beam edge resolution.

Another method is the gold particle method. According to this method, fine gold particles are placed on a substrate such as beryllium having a low efficiency of generating reflected electrons, and reflected electrons and secondary electrons generated when a beam is scanned over the particles are detected. The detection signal at this time is a beam profile. It is well known that this method can measure a two-dimensional profile of a beam, and is extremely effective not only for beam profile measurement but also for focus adjustment and shaping adjustment of a beam such as a rectangle. Gold particles used in this method have a diameter of 0.2 to 0.5 μm
However, when the beam size is equal to or smaller than this particle, there is a problem that the detection signal differs from the true beam profile. In principle, it is sufficient to use gold particles smaller than the beam size. However, in practice, there is a problem that as the particles become smaller, the SN ratio of the detection signal is remarkably reduced and measurement becomes impossible.

Still another method is a heavy metal mark method. In this method, instead of particles, a line-shaped heavy metal mark is scanned with a beam, and at the same time, reflected electrons or secondary electrons are detected. With this method, even if the line width is reduced,
Unlike the case of particles, there is no problem that the SN ratio of the detection signal decreases. However, similarly to the knife edge method, the adjustment of the parallelism between the beam and the line is complicated, and there has been a problem that high-precision measurement is difficult.

(Problems to be Solved by the Invention) As described above, in the conventional method of measuring the intensity profile of a charged beam, there is a limit to highly accurate measurement as the beam size becomes finer.

In addition, if the measurement is to be performed with high accuracy by the conventional method, the measurement procedure becomes extremely complicated, and conversely, there is a problem that it is difficult to perform high-precision measurement without complicated operations.

The present invention has been made in view of the above circumstances, and provides a charged beam intensity profile measuring apparatus and method capable of easily and accurately measuring the intensity profile of a shaped beam having a dimension of not more than deep submicron. Aim.

[Configuration of the invention]

(Means for Solving the Problems) In the present invention, a linear marker and a point marker are formed on the same plane, and the charged beam intensity profile is measured using both.

That is, in the first aspect of the present invention, a measurement plate which is installed so as to be perpendicular to the charged beam and has linear markers and dot markers disposed on the surface thereof, and which is disposed on the charged beam irradiation side of the measurement plate. Detection means for detecting a signal generated by irradiating the charged marker with the linear marker and the point marker, and controlling the rotation of the charged beam from the detection signal by the point marker to make the charged beam parallel to the linear marker. A rotation control unit configured to calculate a beam intensity profile of the charged beam from an output of the detection unit based on a detection signal of the charged beam irradiated in parallel to the linear marker.

Further, in the second aspect of the present invention, a linear marker and a point marker are arranged on the same plane, a charged beam is irradiated so as to be perpendicular to this plane, and the point marker is scanned with the charged beam and scanned. After the beam is controlled so as to be parallel to the linear marker, the beam is scanned perpendicular to the direction in which the linear marker is arranged to measure the intensity profile.

For example, a detector for detecting a signal generated when a charged beam is irradiated on the marker is disposed on the beam irradiation surface side (hereinafter referred to as “upper”) of the marker or on the opposite surface side (hereinafter referred to as “lower”) of the beam irradiation surface. Then, an intensity profile is measured using the detection signal.

Alternatively, a Faraday cup is placed, and the strength profile is measured using the knife edge method.

(Operation) According to the present invention, the parallelism between the charged beam and the linear marker is adjusted using the signal from the point marker, and after adjusting the parallelism, the linear marker is used using the signal from the linear marker. Since the intensity profile of the charged beam in a direction perpendicular to the direction can be measured with high accuracy, the intensity profile measurement can be performed with high accuracy.

Furthermore, if the point marker and the knife edge are formed on the same plane, and the parallelism is adjusted using the point marker, and then the intensity profile is measured using the knife edge method, the linear marker can be obtained. , The intensity profile measurement can be performed with higher accuracy without depending on the line width.

Also, since the linear and point markers are on the same plane,
It is possible to eliminate the influence of beam blur due to the difference in the focal point position at the time of measurement due to the difference in the installation height between the two for the charged beam.

According to the method of the present invention, the rotation angle is adjusted using a point-like marker, the charged beam is adjusted to be parallel to the linear marker, and then the intensity profile is measured by scanning the linear marker. As a result, highly accurate measurement can be easily performed in an extremely short time.

(Example) Hereinafter, a method of measuring a charged beam intensity profile according to an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 (a) is a side view showing a charged beam intensity profile measuring apparatus according to an embodiment of the present invention, and FIG. 1 (b) is an arrangement of a linear marker 1 and a dot marker 2 on a measuring plate of the apparatus. It is a top view showing an example. FIGS. 1A and 1B show a state in which the short beam 3 is irradiated near the linear marker and the dot marker. The linear marker has a line width of 0.03 μm, and the dot marker has a side of 0.3
μm square. The rectangular beam is VSB (variable sha
It is formed using a ped beam type electron beam lithography system, and the length of the short side is 0.3 μm and the length of the long side is 1.5 μm (set value).

This apparatus has a measuring plate 10 in which a linear marker 1 and a dot marker 2 each composed of a W thin film pattern are arranged at a predetermined interval on a silicon substrate surface, and a charged beam is vertically applied to the measuring plate 10. Backscattered electron detector 12 that irradiates in various directions and detects backscattered electrons from linear marker 1 or point-like marker.
And an image processing apparatus 13 that performs image processing based on this output.
A charged beam control device 14 for controlling the rotation of the charged beam based on the output of the image processing device, and a CRT display device 15 for displaying a charged beam image based on the output of the image processing device
It is composed of Although not shown here, the charged beam control device 14 slightly changes the exciting current of the reduction lens of the charged beam driving device 16 to rotate the beam.

Next, a method of measuring a charged beam intensity profile using this apparatus will be described with reference to the flowchart shown in FIG.

First, the measurement plate is set so that the scanning direction of the charged beam is orthogonal to the linear marker 1 (step 101).

Then, the charged beam 3 is scanned on the linear marker 1 and the dot marker 2, and the reflected electrons are detected by the reflected electron detector 12 (step 102). This detection signal is image-processed and displayed as an output of the CRT display device 15. (Step 103).

3 (a) and 3 (b) show a backscattered electron detector.
12 is an image of a linear or point marker projected on a CRT based on the signal detected in 12.

The dot marker image 4 is observed in a rectangular shape, while the linear marker image 5 is observed in a linear shape. Here, the linear markers are set at right angles in advance to the beam scanning direction.

When the beam itself is rotating with respect to the scanning direction of the beam, the dot marker image does not appear parallel to the linear marker image as shown in FIG. 3 (b).

As shown in FIG. 3A, when the rotation of the beam stops in the scanning direction, the beam is automatically set parallel to the linear marker.

If the beam is not parallel to the linear marker, the linear beam image becomes thicker on the CRT as shown by the arrow in FIG. 3B.

From this display result, the parallelism on the display screen of the linear marker image 5 by the linear marker 1 and the point marker image 4 by the point marker 2 is measured to determine whether or not they are parallel (step). 104).

This display screen is as shown in FIG. 3 (a), and if it is determined in the determination step 104 that they are not parallel, the charged beam control device 14 controls the beam drive device 16 based on the output of the image processing device 13. The driving is controlled to rotate the charged beam (step 105). That is, when the exciting current of the lens is minutely changed, the rotation direction of the dot marker image also changes accordingly. Manual adjustment can be performed using an image of the CRT screen.

Then, the charged beam 3 is again scanned on the linear marker 1 and the dot marker 2, and the process returns to the step 102 for detecting the reflected electrons by the reflected electron detector 12. This detection signal is image-processed and output as the output of the CRT display device 15. Then, based on the display result, the degree of parallelism of the linear marker image 5 by the linear marker 1 and the point marker image 4 by the point marker 2 on the display screen is measured to determine whether or not they are parallel. Is repeated.

Then, when it is determined in the determination step 104 that they are parallel as shown in FIG. 3 (b), a beam intensity profile is obtained from the linear marker image 5 at this time via the image processing device, and the beam width and the beam width are obtained. The beam edge resolution is measured (step 106).

In this way, the beam width and the edge resolution can be easily measured.

The beam width thus obtained was 0.3 μm, and the edge resolution was 0.05 μm.

Here, the dot marker is 0.3 μm and the linear marker is 0.0
3 μm. The linear marker is small with respect to the beam width but is linear, so that a sufficient signal can be obtained. On the other hand, the dot marker is about the same size as the beam width,
A sufficient signal can be obtained. Since the point-like marker image does not indicate the beam profile but adjusts the parallelism, there is no problem in that it is large.

In the above embodiment, the parallelism was determined by observation on the CRT display screen. However, as shown in FIGS. 4 (a) and 4 (b), the scanning output profile of the dot marker was determined by the image processing apparatus. May be created, and the parallelism may be automatically determined. In the case of automatic adjustment, FIG. 4 (a)
And the scanning output profile of the dot marker shown in FIG. 4 (b) is used. In this case, when the beam is parallel to the linear marker, that is, when the beam is in a normal direction, the signal becomes a flat signal as shown in FIG.
When the beam is not parallel to the linear marker, that is, when the beam is rotating, the beam has a peak value as shown in FIG. Will be. What is necessary is just to read this difference and rotate by the difference. The intensity profile is measured in the same manner as in the above embodiment.

In this case, since the parallelism is measured without the subjectivity of the observer, higher-precision measurement is possible.

 Next, a second embodiment of the present invention will be described.

Here, as shown in FIG. 5 (a) and FIG. 5 (b), the measurement using the linear marker is performed by the knife edge method. For adjustment, refer to the tip of the knife edge 21 and the dot marker.
Adjust by the parallelism of the charged beam on 22.

This device comprises a knife edge 21 and a dot-like marker formed of a W thin film pattern formed on a silicon substrate surface via a buffer layer B made of a material having a small backscattering coefficient.
A measuring plate 30 in which 22 are arranged at predetermined intervals, a reflected electron detector 32 that irradiates a charged beam in a direction perpendicular to the measuring plate 30 and detects reflected electrons from a point-like marker, An image processing device 33 that performs image processing based on the output, a charged beam control device 34 that controls the rotation of the charged beam based on the output of the image processing device, and a charged beam image based on the output of the image processing device A CRT display device 35 for displaying, a Faraday cup 36 provided below the knife edge 21 and having a photoelectric conversion surface configured to output a current based on the beam intensity, and an output of the Faraday cup 36 is measured. A current measuring means 37, an image processing device 38 for processing the output of the current measuring means 37, and a display means 39 for displaying the same. Although not shown here, the charged beam controller 34 slightly changes the exciting current of the reduction lens of the charged beam driving device 40 to rotate the beam.

The adjustment of the parallelism of the beam is performed in exactly the same manner as in the first embodiment.

Then, when the parallelism adjustment is completed, the charged beam is scanned from above the point-like marker 22, and the current detected by the Faraday cup 36 is output to the display means 39.

The results are shown in FIG. The vertical axis indicates the current value, and the horizontal axis indicates the moving distance. Here, the zero point is on the point marker 22. FIG. 6 (b) shows the result of calculating the differential value of this output. This value corresponds to the edge resolution.

In this way, a highly accurate measurement of the charged beam intensity profile can be easily performed.

In the above embodiment, the detection is performed using the knife edge, but a slit may be formed on the measurement plate instead of the knife edge.

The adjustment of the rotation angle by the dot marker was performed using the backscattered electron detector 32. However, the entire surface of the measurement plate was covered with a reflective film, and the dot markers and slits (linear markers) were exposed to the electron beam transmission pattern. And both may be detected by a Faraday cup.

〔The invention's effect〕

As described above, according to the present invention, a point marker and a linear marker are arranged on the same plane, and a charged beam and a linear marker are used by using a signal obtained by irradiating a point beam with a charged beam. Are adjusted in parallel with high accuracy, so that the error in measuring the beam intensity profile using the signal from the linear marker is significantly reduced, and high-precision profile measurement is performed. Becomes possible.

In addition, since the linear and point markers are on the same plane, it is possible to eliminate the influence of beam blur due to the difference in the focal point position at the time of measurement due to the difference in the installation height of the two for the charged beam, High-accuracy profile measurement can be easily performed.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) show a charged beam intensity profile measuring apparatus according to a first embodiment of the present invention, and FIG. 2 explains a charged beam intensity profile measuring method using the same apparatus. FIG. 3 (a) and FIG. 3 (b) are views showing an image on a CRT screen of the apparatus,
FIGS. 4 (a) and 4 (b) show the scanning output profile of the dot marker, and FIGS. 5 (a) and 5 (b) show the charged beam of the second embodiment of the present invention. FIGS. 6 (a) and 6 (b) are diagrams showing an intensity profile measuring device, and are diagrams showing a change in a beam current detected by a Faraday cup of the same device and a signal obtained by first-order differentiation of a detection signal. . 1 ... Linear marker, 2 ... Point marker, 3 ... Rectangular beam, 4,4 '... Point marker image on CRT, 5,5' ... Linear marker image on CRT, 10 ... ... Measurement plate, 12 ... Backscattered electron detector, 13 ... Image processing device, 14 ... Charge beam controller, 15 ... CRT display device, 16 ... Charge beam drive device, 21 ... Knife edge, 22 ... ... Point marker, 30 ... Measurement plate, 32 ... Backscattered electron detector, 33 ... Image processing device, 34 ... Charge beam control device, 35 ... CRT display device, 36 ... Faraday cup, 37 ... Current measuring means 38 Image processing device 39 Display means 40 Charge beam driving device B Buffer layer made of a material having a small backscattering coefficient.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027

Claims (5)

(57) [Claims] 1. A measuring plate which is installed so as to be perpendicular to a charged beam and has a linear marker and a dot marker disposed on a surface thereof; and a charged beam disposed on a charged beam irradiation side of the measuring plate. Detecting means for detecting a signal generated by irradiating the linear marker and the point-shaped marker, controlling rotation of the charged beam from a detection signal by the point-shaped marker, and parallelizing the charged beam to the linear marker. Rotation control means for adjusting so as to be, and arithmetic means for calculating a beam intensity profile of the charged beam from an output of the detection means based on a detection signal of the charged beam irradiated in parallel to the linear marker. Characterized charged beam intensity profile measurement device. 2. The point-like marker is made of a beam-reflective material, and the detecting means is provided on a beam irradiation surface side of the measurement plate, and a charged beam is applied to the point-like marker or the linear marker. 2. A charged beam intensity profile measuring apparatus according to claim 1, wherein said detecting means is an electron detecting means for detecting reflected electrons or secondary electrons generated by irradiating the charged beam intensity. 3. The point-like marker is made of a beam-reflective material and the linear marker is made of a beam-transmissive material, and the detecting means is provided on a beam irradiation surface side of the measurement plate. A first electron detecting means for detecting a reflected electron or a secondary electron generated by irradiating the point marker with a charged beam; and 2. A charged beam intensity profile measuring apparatus according to claim 1, further comprising second electron detecting means for detecting a charged beam transmitted through the marker. 4. The point marker and the linear marker are made of a beam transmitting material, and the detecting means is provided on a side of the measuring plate facing a beam irradiation surface, and the point marker is provided. The charged beam intensity profile measuring apparatus according to claim 1, further comprising an electron detecting means for detecting a charged beam transmitted through the linear marker. 5. A measuring plate which is installed so as to be perpendicular to a charged beam and has a linear marker and a point marker disposed on a surface thereof is provided, and a charge to be measured on the point marker of the measuring plate is provided. A rotation angle adjusting step of irradiating a beam and adjusting the charged beam so as to be parallel to the linear marker; and adjusting the charged beam adjusted to be parallel to the linear marker on the linear marker. A beam intensity profile calculating step of calculating a beam intensity profile of the charged beam from a detection signal by the linear marker.