JPH01227087A - Target for detecting beam - Google Patents

Abstract

PURPOSE:To form a mark corresponding to a fine particle easily and accurately, by providing a tiny hole or a recess smaller than the size of a beam to be detected on a substrate with a uniform beam reflection factor. CONSTITUTION:A monitor 33 is so arranged that a beam is scanned in a direction X while the motor is moved by steps in a direction Y. This so-called raster scanning is used and a reflected electron signal thereby is converted into an image to perform a two-dimensional display of a beam image 41. Here, in a beam scanning of a half surface containing one hole, for example, a hole 12, the level of the reflected electron signal is constant when the position of the beam separates from the position of the hole 12 and when the position thereof 12 coincides with the position of the beam, the level of the reflected electrical signal becomes less. Thus, by detecting the reflected electron signal corresponding to a beam scanning position, the size of the beam can be measured. Moreover, beam edge resolutions can be measured from the inclination of a rising and a falling of the reflected electron signal.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a beam detection target used for detecting a charged beam, and in particular, to a beam detection target used for detecting a charged beam, and particularly to a variable shaped beam shape, attitude, edge resolution, etc. This invention relates to a beam detection target suitable for measuring.

(Prior Art) In recent years, variable shaped beam type electron beam drawing equipment has been used to form fine patterns on samples such as semiconductor wafers and masks. . In this device, it is necessary to optimally set the size and shape of the variable shaped beam as well as its attitude and edge resolution, and therefore it is necessary to evaluate the variable shaped beam.

Conventionally, in order to evaluate a variable shaped beam, a beam detection target has been used in which fine particles with a large reflected electron coefficient are adhered to a substrate with a small reflected electron coefficient (Japanese Patent Publication No. 42587/1987). In this method, a particle is scanned with an electron beam to detect reflected electrons. When the beam is not located on a particle, the reflected electron is small, and when the beam is located on a particle, the reflected electron is large. Therefore, by detecting the reflected electrons in correspondence with the beam scanning position, it is possible to know the scanning position where the beam is located on the particle, and thereby the beam size can be measured. Furthermore, it is also possible to measure the beam edge resolution from the rise of the reflected electron signal.

However, this type of method has the following problems. That is, in order to attach the fine particles to the substrate surface, one fine particle is scooped out from a plurality of fine particles dispersed in a solution, and a solution containing one fine particle is dropped onto the substrate. For this reason, it is difficult to place fine particles in a desired size at a desired position on the substrate. Therefore, in order to scan the beam over the particles, the only way to do so is to thoroughly search the entire surface of the substrate to identify the desired particles, and it takes a lot of time to detect the beam. Furthermore, depending on the relationship between the particle size and the beam size, the S/N ratio of the detection signal deteriorates, and in some cases it may not be possible to measure a small beam edge resolution.

(Problems to be Solved by the Invention) As described above, in conventional beam detection targets using fine particles, it is not possible to accurately place the fine particles at desired positions, and it is difficult to place the fine particles all over the substrate in order to scan the beam over the fine particles. It was necessary to conduct a detailed search to confirm the location of the particles. Furthermore, depending on the relationship between the beam size and the size of the fine particles, the SN of the backscattered electron signal may be poor (so that the edge resolution of the fine beam cannot be measured).

The present invention has been made in consideration of the above circumstances, and its purpose is to form a mark corresponding to a fine particle at a desired position on a substrate, and to create a beam suitable for evaluating variable shaped beams. The objective is to provide a target for detection.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to provide holes or depressions instead of fine particles.

That is, in the present invention, in a beam detection target used for emitting a charged beam, a hole or a recess smaller than the size of the beam to be detected is provided on a substrate having a uniform beam reflectance. be.

Further, in the present invention, a plurality of holes or recesses smaller than the size of the beam to be detected are arranged in a straight line on a substrate having a uniform beam reflectance.

(Function) According to the present invention, when a hole or a recess formed in a substrate is scanned with a beam, the signal waveform obtained based on the backscattered electron signal has a large direct current component and the position of the beam and the microhole. When they match, a slight dent is superimposed. Therefore, if you cut the DC component and amplify only the AC component,
A waveform that is an inversion of the signal waveform obtained when scanning fine particles with a large reflected electron coefficient on a substrate with a small reflected electron coefficient is obtained. When this waveform is displayed on a CRT or the like, all information on the variable shaping beam can be obtained.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a beam detection mechanism using a beam detection target according to an embodiment of the present invention.

In the figure, reference numeral 10 denotes a substrate whose surface is mirror-polished, and mark holes of various sizes are formed on the surface. Substrate 10
Gold is deposited on the surface to a thickness of 1 μm in order to increase the reflection coefficient for electron beams. Holes 11, 12, 13, 14 as single marks each have a diameter of 20
nm.

They were 40nw, 100ns, and 200nm, and the depth was 5 μm for both. Furthermore, these are 10μm each other.
It is located at a further distance.

The composite mark 15 has 100 holes of 10n square arranged in the X direction, the composite mark 16 has similar holes arranged in the Y direction, and the composite marks 17 and 18 have similar holes arranged at an angle of 45 degrees. . Then, the hole 1 provided in the substrate 10°
1. ~, 14 and marks 15°~, 18 constitute a beam detection target.

Reference numeral 21 denotes a variable shaped beam, which in this example scans the substrate surface including the mark 16. The electron beam 22 reflected from the target is detected by a backscattered electron detector 31, amplified by an amplifier 32, and supplied to a monitor 33 such as a CRT.

Then, an image corresponding to the beam intensity distribution is displayed on the monitor 33. The amplifier 32 has a function of automatically changing the offset and amplifying only the AC component. Further, the signal amplified by the amplifier 32 is subjected to processing such as SN improvement in a signal analysis circuit 34, and is supplied to a monitor 36 such as a CRT via a signal inversion circuit 35.
37. Then, a waveform corresponding to the beam intensity distribution is displayed on the monitor 36. Further, the CPU 37 processes the above signals to measure the beam size and edge resolution.

The monitor 33 displays a beam image 41 two-dimensionally by converting the reflected electron signal into an image by scanning the beam in the X direction and moving the beam stepwise in the X direction. In this case, the beam piece in the X direction is displayed correctly, but the beam piece 42 in the X direction is blurred. This is because the detection mark 16 has a finite length in the X direction. Further, the monitor 36 displays a reflected electron signal waveform 43 in one scan of the beam.

Here, when a beam scans a plane including one of the holes, for example hole 12, as shown in FIG. 2, when the beam position is far from the hole 12, the level of the backscattered electron signal is constant, and When the position of the beam matches the position of the beam, the level of the reflected electron signal becomes small. Therefore, by detecting the backscattered electron signal corresponding to the beam scanning position, the beam size can be measured. Furthermore, the beam edge resolution can also be measured from the slope of the rise and fall of the reflected electron signal.

Further, when the size of the detection hole is small, as shown in FIG. 3(a), the S/N ratio of the signal is poor, but the rise and fall of the signal are steep. As the size of the detection hole increases, as shown in FIGS. 3(b) and 3(c), the signal-to-noise ratio increases, but the rise and fall of the signal becomes gentler. Therefore, by selecting an appropriate hole size depending on the size of the beam, accurate beam detection can be performed. In addition, in FIG. 3, the detection signal waveform of the reflected electron signal is shown inverted.

Thus, according to this embodiment, each piece of information about the beam can be detected in the same way as when fine particles are attached. In this case, unlike fine particles, holes can be formed at desired positions on the substrate with high precision. Therefore, the position of the hole is known in advance, and there is no need to spend time searching for the hole used for beam detection. Furthermore, if the relative position of the optical system and the hole is not known, it is possible to search for a large hole with a strong signal and easily find a small hole for highly accurate evaluation from there. Furthermore, since holes of any size can be selected, S
Optimal beam detection can be performed by giving priority to N or resolution.

In addition, by arranging multiple holes in a line as in the example, only the beam pieces in the X direction, Y direction, or in a direction 45@ tilted to these directions can be evaluated with high SN and fine beam edge resolution. be able to.

Note that the present invention is not limited to the embodiments described above. For example, the size, depth, etc. of the hole can be changed as appropriate depending on specifications. Furthermore, the means for forming holes is not limited to ion beams or etching (it is also possible to form holes that are sufficiently smaller than the size of the beam to be detected, preferably smaller than the edge resolution of the beam to be detected). In addition, it is not limited to electron beams.
It can also be used to detect ion beams. others,
Various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, holes are provided instead of particles, so marks corresponding to particles can be easily and accurately formed at desired positions on a substrate. This makes it possible to realize a beam detection target suitable for evaluating variable shaped beams.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a beam detection mechanism using a beam detection target according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a backscattered electron signal when a detection hole is scanned with a beam, and FIG. The figure is a schematic diagram showing changes in the reflected electron signal waveform due to differences in hole size. 10...Substrate, 11. 〜, 14...hole, 15. ~. 18...Mark, 21...Variable shaping beam, 22.
...Backscattered electron beam, 31...Backscattered electron detector, 32...
- Amplifier, 33. 36... Monitor, 34... Signal analysis circuit, 35... Signal inversion circuit, 37... CPU. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (3)

[Claims] (1) A beam detection target used for detecting a charged beam, which is characterized by having a hole or recess smaller than the size of the beam to be detected on a substrate with uniform beam reflectance. Target for detection. (2) In a beam detection target used for detecting a charged beam, a plurality of holes or depressions smaller than the size of the beam to be detected are arranged in a straight line on a substrate with uniform beam reflectance. A beam detection target characterized by being provided with a (3) The beam detection target according to claim 1 or 2, wherein the size of the hole or recess is smaller than the edge resolution of the beam to be detected.