JPS59218906A - Measuring method by electronic beam - Google Patents

Abstract

PURPOSE:To shorten the scanning time of an electronic beam and also to shorten measuring time by scanning the electronic beam selectively only at a position close to the end part of a pattern to be measured. CONSTITUTION:In the measurement of an wafer W which is a material 4 to be measured, the wafer W has many chips T1-Tn and the same kind of patterns are formed on respective chips. After completing the measurement of the width of a required pattern P on the chip T1, a stage 12 is moved, the chip T2 is arranged on the optical axis of an electronic beam and then width of the same pattern on the chip T2 is measured. Since the position to be measured of the pattern P and the position of the end part of the pattern P have been already shown by a computer 10 at the measurement of the chip T1, line-like scanning of the electronic beam is not continuously executed and only the position close to the end part of the band-like pattern P is selectively scanned like a line at the measurement of the width of the band-like pattern P on the chip T2 on which the same pattern as the chip T1 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sub-length measurement method using an electron beam, and particularly to a length measurement method that can shorten measurement time.

In recent years, the degree of integration of devices such as LSI has become extremely high, and the viscosity of the patterns formed on each chip on silicon chips during the manufacturing process has become extremely high, on the order of submicrons. ing. Whether the patterns within these chips are formed with desired accuracy can be inspected by irradiating the pattern portions with an electron beam. In this length measurement method using an electron beam, the electron beam is scanned linearly in a predetermined area including the length measurement liebe pattern in each depth, and based on the scan, the ltA gain, for example, The next electron is detected, and the width of a specific pattern is measured from the detected signal. Usually, a silicon wafer as a material to be measured is divided into a number of chips, and each chip has the same pattern formed on it. Move the monthly strip, place each chip in turn on the electron beam optical axis, and scan the electron beam linearly in the area where a specific pattern is formed for each chip. I try to do this. The scanning of the electron beam is repeated several times in the same part for each chip in order to improve the signal-to-noise ratio of the detection signal. With this scanning, a considerable amount of time is lent to the sub-directors in all the chips included in one wafer.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a sub-length method using an electron beam that can shorten measurement time.

The sub-lengthening method based on the present invention scans a desired area on a material to be sub-lengthened with an electron beam, which has a large number of reference sections, each of which has the same type of pattern formed thereon, and determines the target area based on the scanning. detecting the lζ information signal obtained from the material;
In a sub-length method in which the length of a specific portion of a pattern formed on the material is measured based on the detection signal, in a specific reference section, a predetermined range including the pattern to be sub-length is continuously measured by an electron beam. When measuring the length of other reference sections, the electron beam is selectively scanned only in the vicinity of both ends of the sub-length pattern based on the length measurement results. The features are right on point.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an example of an electron beam sub-head apparatus for carrying out the method of the present invention, and numeral 1 in the figure is an electron gun. The electron beam generated from the electron gun 1 is passed through a focusing lens 2. The objective lens 3 narrowly focuses the light onto the sub-length material 4 . The electron beam is further deflected according to a scanning signal supplied to the deflection coil 5, so that a desired area on the material is scanned by the electron beam. For example, secondary electrons generated when the material is irradiated with an electron beam are detected by a secondary electron detector 6, and the detection signal is supplied to a cathode ray tube 8 as a glow modulation signal via an amplifier 7. At the same time, it is also supplied to the computer 10 via the A-D converter 9. The computer 10 controls a scanning signal generation circuit 11 that generates a scanning signal to be supplied to the deflection coil 5 of 011 and the deflection coil of the cathode ray tube 8, and also controls a drive mechanism 13 for the material stage 12 on which the material is placed. control. The scanning signal generated from the scanning signal generation circuit 11 is supplied to the deflection coil via a magnification adjustment circuit 14 controlled by the computer 10.

A case will be described in which sub-lengthening is performed on a wafer W shown in FIG. 2 as the material 4 to be sub-lengthened using the above-described configuration. The wafer W has a large number of chips T1 to Tn, and the same type of pattern is formed on each chip. First, the material stage 12 is moved so that the desired region of the tube T+ is placed on the electron beam optical axis, and a normal scanning electron microscope image is generated by the scanning signal generation circuit 11 according to instructions from the computer 10. A scanning signal is generated for viewing. FIG. 3(a) shows an image displayed on the cathode ray tube 8 in this scanning electron microscope image observation mode, and P in the figure is a strip pattern whose width is measured. A cursor C is also displayed on the screen of the cathode ray tube 8, and by moving the cursor C on the screen, the position to be measured can be designated. After the measurement position is specified by the cursor C, according to a command from the computer 8,
The scanning signal from the scanning signal generating circuit 11 is changed to a line scanning mode. FIG. 4(a) shows a digital scanning signal that changes stepwise during this line scanning.
With such a scanning signal, a predetermined range corresponding to the position of the cursor on the chip T+ is linearly scanned, and the signal shown in FIG. 5(a) is obtained from the secondary electron detector 6.

Note that the linear digital scanning is performed multiple times (
By integrating the many obtained signals,
An attempt is made to improve the S/N ratio of the signal, which is not shown in FIG. 5(a). The obtained signal is supplied to the microcoater 10 and integrated, and the number of digital scanning steps S+ and Sz until a signal of a predetermined level I is obtained is determined.
The width of the pattern is determined by the number of scanning steps Z (S2-8+). In this way, chip T1
After the sub-length of the width of the desired pattern P is completed, the stage 12 is moved, the chip T2 is placed on the electron beam optical axis, and the width of the same pattern P in the lower chip 2 is measured. be done. Here, since the position at which the length of the pattern P should be measured and the position of the end of the pattern P have already been determined by the computer 10 at the time of sub-lengthening the chip T1,
When measuring the width of the strip pattern P in the lower chip 2 where the same pattern as the depth T1 is formed, the linear scanning of the electron beam is not performed continuously, but is performed according to instructions from the computer 10. (Only the vicinity of the end of the strip pattern P is selectively scanned in a line. FIG. 3(b)
shows the strip pattern P and the scanning lines L1, 12, and FIG. 4(b) shows the digital scanning signal at this time, the fifth line
Figure (b) shows the secondary electron detection signal at °C. The signal shown in FIG. 5(b) is supplied to the computer 10, and the computer determines the number of steps 33.34 until a signal with a signal strength of 1 is obtained for each scan. Furthermore, the computer 10 calculates the number of virtual digital scanning steps Ss from the scanning start point to the starting points of scanning line L+ and scanning line L2 when continuous digital scanning is performed in the same way as in chip T1. , Ss, and from these step numbers the computer calculates the next performance (S6 +84) - (Ss
+3a), and the width of the strip pattern P is determined based on this calculation. In this way, when the sub-length of the predetermined pattern P that reaches the depth T2 is completed, the stage 12 is moved, and the length of the sub-length of the pattern P that reaches the chips T3 to Tn is measured. This is done in a similar manner.

As described in detail above, the sub-chief method based on the present invention is as follows.

When measuring the length of a material to be measured that has a large number of reference chips with the same type of pattern, C continuously scans a predetermined range with an electron beam in the first reference section. , J5 is placed in the sub-length of the other reference section, and the electron beam is selectively applied to J5 only near the end of the pattern to be measured, based on the length measurement result applied to the first reference section. Since the electron beam is scanned in the same manner, the scanning time of the electron beam can be extremely controlled, and the measurement time can be shortened.

Note that the present invention is not limited to the embodiments described above, and can be modified in many ways. For example, only the first reference section (chip T+) was continuously scanned with the electron beam, but the second or third reference section was continuously scanned with the electron beam, and based on the results of multiple length measurements, , the starting point of the selective scanning may be determined, and furthermore, the starting point of the selective scanning may be always determined or modified based on the previous measurement results. good. Further, in the embodiment, the width at one point within each reference section is determined, but the present invention can also be applied to the case where the lengths at a plurality of points within each reference section are measured.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of an electron beam sub-length device for carrying out the present invention, Fig. 2 is a diagram showing a material to be sub-lengthened, and Fig. 3 is a diagram showing a belt-like pattern whose length is to be measured and an electron beam. 4 is a diagram showing a digital scanning signal, and FIG. 5 is a diagram showing secondary electron detection (No. 5) obtained based on scanning of an electron beam. 1...Electron Gun 2...Converging lens 3...Objective lens 4...Length measurement material (Wu Ding Ha) 5...Deflection coil 6...Secondary electron detector 7...Amplifier 8... Cathode ray tube 9...A-D
Converter 10...Computer 11...Scanning signal generation circuit 12...Screening stage 13...Stage drive 11 structure Patent applicant: Mr. Ito, representative of Honda Electronics Co., Ltd. Figure 3 (a) 4 Figure (a) Figure 5 (a) Figure 3 (, b) Figure 4 (b) Figure 5 (b)

Claims (1)

[Claims] A desired area on the length-measuring material having a large number of reference sections, each of which has the same type of pattern, is scanned by an electron beam, and information obtained from the monthly profit based on the scanning. In a sub-length method in which a signal is detected and the length of a specific portion of a pattern formed on the material is measured based on the detected signal, the sub-length pattern is measured by an electron beam in a specific reference section. A signal is obtained by continuously scanning a desired range including the area, and when measuring the length of the reference section, based on the length measurement result in the specific reference section,
A sub-length method using an electron beam in which the electron beam is selectively scanned only near both ends of a sub-length pattern.