JPH04110709A - Method and device for measuring length by electron beam - Google Patents

Abstract

PURPOSE:To enable the high accurate length measurement by irradiating a length measuring part on a sample with light, and heating there, and obtaining the pattern. CONSTITUTION:Electron beams 102 radiated from an electron gun part 101 and passed through an electron optical system 103 are condensed narrow to irradiate a wafer 111. At this stage, the beam 102 is scanned on a part to be measured of the wafer 111, and the secondary electron generated from a irradiated part is caught by a secondary electron detecting unit 108, and is processed by a control unit 109, and dimension thereof is obtained. Furthermore, the light 113 radiated from a light source 112 irradiates a pattern part on the wafer 111 to be measured, and heat there. Strength of this light 113 can be controlled by the control unit 109, and temperature of the pattern part is controlled by controlling the strength of the light 113. The signal having excellent S/N can be thereby obtained by heating the pattern part, and high accurate length measuring is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam length measurement method and apparatus for measuring the dimensions of a pattern accurately and with good reproducibility using an electron beam.

[Conventional technology]

In recent years, as semiconductor integrated circuits have become more highly integrated, higher reliability has been sought for semiconductor inspection equipment. With regard to higher integration of semiconductor circuits, high-density memory circuit devices called VLSIs are being developed due to advances in microfabrication technology. In order to shorten the construction period, inspection during the manufacturing process, especially pattern dimension measurement, is becoming more important as miniaturization progresses.

On the other hand, in order to obtain higher quality integrated circuit pattern dimensions, highly accurate dimension measurement is required.

FIG. 6 is a schematic diagram showing a conventional electron beam length measuring device.

As shown in the figure, the conventional device includes a snow protection stand 107, a vacuum mirror unit 100E installed on the snow protection stand 107 and evacuated by vacuum pumps 105 and 106, and a vacuum mirror unit 100E installed inside the vacuum mirror unit 100. It is composed of an electron optical system 103, a control section 109 that controls the stage system 104, and a CRTIIO that displays the length measurement section pattern. Stage series 10
4 is movable in the rotational direction and in the XY force direction within a plane perpendicular to the Z direction, and above it is a wafer 11 that requires length measurement.
1 is retained. The electron beam +02 emitted from the electron gun section 101 and passed through the electron optical system 103 is narrowly focused and irradiated onto the wafer Ill.

At this time, the electron beam 102 is scanned by the length measurement section on the wafer Ill, and the secondary electrons generated from the irradiation section are collected by the secondary electron detector 108, and the obtained signal is sent to the control section 109. Processed and dimensions determined.

FIG. 7 is a sectional view showing the positional relationship between the length measuring section of the wafer and the electron beam, and FIG. 8 is a secondary electron signal waveform diagram. When scanning the pattern 1lla on the wafer 111 with the electron beam 102, the S/N ratio of the signal waveform obtained by only one scan is poor and reliability is poor, so the same spot is usually scanned multiple times from 2 to 100 times. . The pattern size S is calculated from the obtained signal waveform 305 using various algorithms.

[Problems to be Solved by the Invention] The conventional electron beam length measurement device described above detects secondary electrons and calculates pattern dimensions based on the waveform, but if the S/N of the signal waveform is poor, the length measurement The accuracy is poor, and in order to improve the S/N ratio, it is necessary to repeatedly scan the same location with an electron beam. However, if the length measuring section is repeatedly irradiated with an electron beam, the effect of charge-up becomes large, which not only deteriorates the length measurement accuracy but also damages the pattern, deforming the pattern, or changing the characteristics of the device. will deteriorate. Further, there is a problem in that contamination adheres to the beam irradiation section.

The purpose of the present invention is to provide an electron beam length measurement method and apparatus that reduces the number of electron beam scans on a sample, eliminates the effects of charge-up, eliminates damage to patterns and devices, and prevents contamination. It's about doing.

[Means for Solving the Problems] In order to achieve the above object, in the electron beam length measurement method according to the present invention, an electron beam is focused and scanned on a sample, and the dimensions of a pattern formed on the sample are measured. This is an electron beam length measurement method for measuring length, in which the length measurement section on the sample is irradiated with light and heated to determine the dimension of the pattern.

Further, the electron beam length measuring device according to the present invention includes an electron optical system, a secondary electron detector, and a light source, and focuses and scans an electron beam on a sample to form a This is an electron beam length measurement device that measures the dimensions of a pattern, and the electron optical system focuses and focuses an electron beam onto a sample in a vacuum atmosphere.
The secondary electron detector collects and detects secondary electrons generated from the sample using an electron beam, and the light source irradiates light onto the length measurement section on the sample to heat it. It is something.

[Function] The length measuring section on the sample (wafer) is heated by light irradiation. This improves the efficiency of secondary electron generation and improves the S/N of the secondary electron signal waveform.

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

(Example 1) FIG. 1 is a schematic cross-sectional view showing Example 1 of the present invention.

In the figure, the device according to the present invention is installed on a snow protection stand 107 and a vacuum pump +05 and 106.
A vacuum mirror body 100 that is evacuated by the vacuum mirror body 100, an electron optical system 103 installed in the vacuum mirror body 100, a control unit 109 that controls the stage system 104, and a CRT +10 that displays the length measurement pattern. have The stage system 104 is movable in the rotation direction and the XY force direction within a plane perpendicular to the Z direction, and holds thereon a wafer 111 that requires length measurement. The electron beam 102 emitted from the electron gun section 101 and passed through the electron optical system 103 is directed to the wafer 11.
1 and is narrowly focused and irradiated. At this time, electron beam 1
02 is scanned by the length measuring section on the wafer 111, and the secondary electrons generated from the irradiation section are detected by the secondary electron detector +0
8, and the obtained signal is processed by a control unit 109 to determine the dimensions.

Furthermore, the present invention is equipped with a light source 112. light source 11
The light 113 emitted from the wafer 2 irradiates the pattern portion to be measured on the wafer III and heats it. The intensity of the light 113 can be controlled from the control section 109, and by controlling the intensity, the temperature of the pattern section is controlled.

FIG. 2 is a diagram qualitatively showing the relationship between the accelerating voltage of the irradiation electron beam and the secondary electron generation efficiency δ from the irradiation part, for explaining the present invention in detail.

The secondary electron generation efficiency δ is the ratio between the number of secondary electrons generated and the number of irradiated electrons, and when δ>1, the number of secondary electrons generated is greater than the number of irradiated electrons. The larger δ is, the higher the secondary electron generation efficiency is, and a signal with a better S/N ratio can be obtained. curve 201
is at room temperature (23°C), and curve 202 is when the pattern portion is heated to about 110°C. By heating, the secondary electron emission efficiency δ is improved. However, if the heating temperature is too high, thermoelectrons and light will be generated from the pattern part, reducing the contrast of secondary electrons, and resist patterns will be deformed, so the heating temperature should not be set too high. , room temperature to 150°C.

FIG. 3 shows a cross section of the pattern when the pattern portion is heated to 110° C. in this manner, and FIG. 4 shows a secondary electron signal waveform. By heating the pattern portion, it is possible to obtain a signal with a good S/N ratio and to reduce the number of times the electron beam is scanned. In addition, by heating the pattern part, 1
It has the advantage that almost no contamination adheres even if scanning is repeated 00 times or more.

(Example 2) FIG. 5 is a schematic sectional view showing Example 2 of the present invention.

In this embodiment, by adding another light source +14 to the light source 112, the pattern portion can be heated more uniformly in a shorter time. The light source 114 may have a variable irradiation position, and a method may be used in which the light source 112 heats the length measuring section and the light 71) itl 14 heats the next length measuring section. Furthermore, by appropriately adjusting the irradiation range, it is possible to irradiate from a very narrow area to a wider area (11 Lmφ or less to the entire wafer surface).

It is also possible to install more light sources to further increase efficiency. As a light source, infrared lamps, ultraviolet lamps, He-Ne lasers, YAG lasers, C03 lasers, etc. that generate light with wavelengths in the range of about 200 to 1l100n can be used to heat the wafer, but in particular It is not limited.

[Effects of the Invention] As explained above, the electron beam length measurement method of the present invention irradiates the length measurement section on the sample with light having a wavelength in the range of 200 to 1]00 nm, and Because it is heated to a set temperature, it is possible to improve the generation efficiency of secondary electrons and improve the S/N of the secondary electron signal waveform when converging and scanning the electron beam on the sample. This has the effect of reducing the number of electron beam scans in the process, eliminating the effects of charge-up, preventing damage to patterns and devices, and preventing contamination, allowing highly accurate length measurements. .

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing Example 1 of the present invention, Fig. 2 is a secondary electron generation efficiency diagram, Fig. 3 is a sectional view showing the pattern section, Fig. 4 is a waveform diagram, and Fig. 5 is a diagram of the present invention. FIG. 6 is a schematic sectional view showing a second embodiment of the invention, FIG. 6 is a schematic sectional view showing a conventional example, FIG. 7 is a sectional view showing a pattern portion in the conventional example, and FIG. 8 is a waveform diagram. 100...Vacuum mirror body part lot...Electron gun part+
02303... Electron beam 103... Electron optical system 104... Stage system 105.106...
Vacuum pump 107... Earthquake isolation stand 108...
・Secondary electron detector 109...control unit 110
...CRTIII, 301...Wafer 11
2.114...Light source 113...Light 20
1,202...Secondary electron generation efficiency 302...Pattern 304...Secondary electron signal (Fig. 4) Beam position (Fig. 4) (Fig. 8)

Claims (2)

[Claims] (1) An electron beam length measurement method in which an electron beam is focused and scanned on a sample to measure the length of a pattern formed on the sample, the length measurement section on the sample being irradiated with light and heated. , an electron beam length measurement method characterized by determining the dimensions of the pattern. (2) An electron beam length measurement device that has an electron optical system, a secondary electron detector, and a light source, focuses and scans an electron beam on a sample, and measures the dimensions of a pattern formed on the sample. The electron optical system focuses and focuses an electron beam onto a sample in a vacuum atmosphere.
The secondary electron detector collects and detects secondary electrons generated from the sample using an electron beam, and the light source irradiates light onto the length measurement section on the sample to heat it. An electron beam length measuring device characterized in that: