JPH03278516A - Mark position detector in charged particle beam apparatus - Google Patents

Abstract

PURPOSE:To obtain an apparatus which can detect a mark position accurately through a correlation processing, even if there is a slope in the base line of a mark detection signal waveform, by providing respectively specific scanning means, detecting means, differentiation means, memory, integrating means, and correlation processing unit. CONSTITUTION:An apparatus is composed of a means 4 for scanning a charged particle beam across a mark provided on a material 3, a detecting means 5 for detecting a signal obtained with scanning, a differentiation means 10 for differentiating a signal from the detecting means 5, a memory 12 for storing a differentiated signal, an integrating means 13 for setting data of each picture element stored in the memory 12 as M(i) and obtaining m(i) by equations I and II, and a correlation processing unit 14 for obtaining the mark position on the basis of data obtained by the integrating means 13. Thus, the slope of a signal supplied to the correlation processing unit is eliminated by digital integration processing of data stored in the memory so that the mark position can be detected accurately through a correlation processing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mark position detection device suitable for use in detecting marks on a material in a charged particle beam device such as an electron beam lithography device.

(Prior art) When drawing a desired pattern on a material to be drawn, an electron beam drawing device detects the position of a mark provided on the material in advance, and irradiates the material with an electron beam according to the mark position. I am trying to correct the position. In normal mark position detection, an electron beam is linearly scanned across the mark, and reflected electrons and the like obtained during this scanning are detected to determine the mark position. That is, the mark position is determined from the change in signal intensity at the edge portion of the mark.

When detecting a mark position in a drawing device, a situation sometimes arises in which the S/N of the detection signal becomes poor.

For example, this may occur when the beam current of the electron beam irradiating the material is small, or when a thick resist is applied. In such a case, it becomes difficult to accurately detect the mark position.

In view of the above points, recently, a method of detecting mark positions by correlation processing has begun to be used. With the correlation method, mark positions can be stably detected even when the signal strength is low, which has been difficult to process in the past, and this method has the advantage of being less susceptible to random components. Furthermore, this method can reduce the number of scans, shorten the conventional signal averaging processing time, and improve the throughput of the drawing device.

(Problem to be Solved by the Invention) FIG. 3(a) shows the mark detection signal waveform. By performing correlation processing on this signal, the correlation processed waveform shown in FIG. 3(b) is obtained. Peak position of processed waveform al P
o is the mark position. This figure 3 (a) and figure 3 (
In the example b), the baseline of the waveform data is linear, but if the baseline of the mark detection signal waveform has a slope as shown in FIG. As shown in (d), the peak position al of the correlation processing waveform
P1 deviates from the original peak position.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to accurately detect the mark position by correlation processing even when the baseline of the mark detection signal waveform has a slope. The object of the present invention is to realize a mark position detection device in a charged particle beam device.

(Means for Solving the Problems) A mark position detection device in a charged particle beam device based on the present invention includes a means for scanning a charged particle beam across a mark provided on a material, and a means for scanning a charged particle beam across a mark provided on a material. A detection means for detecting, a differentiating means for differentiating the signal from the detection means, a memory for storing the differentiated signal, the data of each pixel stored in the memory is M(f), and V+ = (1/n) ・Assuming Σ M (i), it is assumed that the system consists of an integrating means for calculating m (i) −Σ (M(j) V+)−1, and a correlation processing unit for determining the position of the mark based on the data obtained by the integrating means. It is a feature.

(Function) By storing the mark detection signal data in the memory and digitally integrating the data stored in the memory, the slope of the signal supplied to the correlation processing unit is eliminated.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIG. FIG. 1 shows an electron beam drawing apparatus using a mark position detection apparatus based on the present invention, and 1 is an electron gun. An accelerated electron beam EB generated from the electron gun 1 is focused onto a material 3 to be imaged by an objective lens 2 . The electron beam EB is scanned across a mark (not shown) provided on the material 3 by the deflector 4, and backscattered electrons generated as the material is irradiated with the electron beam are detected by the detector 5. be done.

A scanning signal for scanning the electron beam across the mark is supplied to the deflector 4 from a deflector control unit 7 controlled by a computer 6 via a DA converter 8 . Further, the signal detected by the detector 5 is amplified by an amplifier 9 and then supplied to a differentiating circuit 10.

The differential signal from the differential circuit 10 is converted into a digital signal by the AD converter 11, and then stored in the signal waveform memory 12.
is supplied to and stored. 13 is an integration processing unit that performs integration processing of data stored in the memory 12 under the control of the computer 6; the integration processing results are stored in the memory 12;
is stored in The data stored in the memory 12 is supplied to a correlation processing unit 14 and subjected to correlation processing.

The operation of the above-described configuration is as follows. A scanning signal is supplied from the deflector control unit 7 to the deflector 4 via a DA converter 8, which linearly scans across the mark whose position on the material 3 is to be measured. The mark on the material is scanned by the electron beam EB, and backscattered electrons obtained along with this scanning are detected by the detector 5. Figure 2 (a
) shows this detection signal waveform, and the baseline of the waveform has a slope. The detection signal having such a waveform is supplied to a differentiating circuit 10 via an amplifier 9 and differentiated. FIG. 2(b) shows a differential waveform produced by the differentiating circuit 9, and the slope component of the waveform in FIG. 2(a) appears as a DC component V of the differential waveform. Scanning of the electron beam across the mark on the material 3 is performed many times, and the resulting detected signals are integrated on the memory 12 to measure the improvement of the signal-to-noise ratio.

The differential waveform data shown in FIG. 3 stored in the memory 12 is supplied to the integration processing unit 13.

In this integration processing unit 13, first, the average value V of the differential waveform signal is determined. This average value V1 is calculated by setting the address in the memory 12 to i and the data of each pixel to M.
(i), it is obtained by calculating V+-(1/n)·ΣM(i).

Next, the differential signal data stored in the memory 12 is integrated. This integration processing is performed by digitally integrating the differential waveform data, processing each address, and overriding the integration result to the same address.

This integration result m (i) can be expressed as follows. Note that at this time, the average value V1 of the differential waveform signal is subtracted from the integrated data.

m (i) -Σ (M(OV+) 1-) When the integration process as shown in 1- is completed, the signal waveform stored in the memory 12 becomes a waveform with the slope component removed, as shown in FIG. 2(c). The data stored in the memory 12 is supplied to the correlation processing unit 14, where correlation processing is performed and the position of the mark is detected. This detected mark position is accurate because the signal waveform for correlation processing does not include a slope component.

Although the present invention has been described in detail above, the present invention is not limited to this embodiment. For example, although the memory in which the differential waveform is stored is overwritten with the integrated data, another memory may be prepared and the integrated data may be stored in that memory. Furthermore, the present invention can be applied not only to electron beam devices but also to ion beam writing devices and the like.

(Effects of the Invention) As described above in detail, according to the present invention, the mark detection signal data is stored in the memory, and the data stored in the memory is digitally integrated, thereby being supplied to the correlation processing unit. Since the slope of the signal MP is eliminated, the position of the mark can be accurately detected by correlation processing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a mark position detection device for an electron beam drawing apparatus according to the present invention, and FIGS. 2(a) to (C)
are signal waveform diagrams used to explain the present invention in detail, and FIGS. 3(a) to 3(d) are diagrams used to explain the problems of the prior art. 1...Electron gun 2...Objective lens 3...
Material to be drawn 4... Deflector 5... Detector
6...Computer 7...Deflector control unit 8...DA converter 9...Amplifier 10...Differentiating circuit 11...AD converter 12...Memory
13... Integration processing unit 14... Correlation processing unit

Claims (1)

[Claims] Means for scanning a charged particle beam across a mark provided on a material, a detection means for detecting a signal obtained with the scanning, a differentiating means for differentiating a signal from the detecting means, a differentiator. Let M(i) be the data of each pixel stored in the memory, and let ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Then, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A mark position detection device in a charged particle beam device, comprising a correlation processing unit that determines the position of a mark based on data obtained by an integrating means.