JPS631910A - Dimension measuring apparatus - Google Patents

Abstract

PURPOSE:To accurately measure the dimension of the edge lower part of a pattern having a trapezoidal cross-section, by detecting the secondary electron from a specimen scanned by charged particle beam and applying predetermined operational processing to the detection signal being obtained. CONSTITUTION:A specimen stand 10 moves by the command of a control computer 5 so that the pattern 24 to be measured on a wafer reaches directly under beam. The pattern 24 is scanned by electron beam by a deflection control circuit 12 to generate a secondary electron which is, in turn, detected by signal detectors 11a, 11b. The detection signals thereof are sent to a signal processing circuit 22 to calculate the dimension between the lower parts (f), (g) of a line pattern (a) and a space pattern (b) comprising the substance A having a trapezoidal cross-section on a substrate substance B. In this case, the interval between the differentiated max. point and min. point of the detection signals is calculated to obtain the lower part dimension of the trapezoidal pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dimension measuring device using a charged particle beam, and relates to a dimension measuring device that accurately determines the dimension of the lower edge of a pattern having a trapezoidal cross section on a wafer. Regarding equipment.

[Conventional technology]

As described in JP-A-59-112217, conventional devices have a method of automatically determining the dimensions between pattern edge parts, but it is difficult to determine which part of the edge part with a certain width the calculated dimension corresponds to. There was no experimental stratification as to whether the Further, in semiconductor processes, there are many patterns having a trapezoidal cross-section, and a method for accurately determining the dimensions of the lower part of the pattern edge has been needed.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into account where the calculated dimensions correspond to the edge portions of the pattern cross section, and there is a problem in that the accuracy is insufficient for dimension evaluation of submicron patterns.

An object of the present invention is to provide a dimension measuring device capable of accurately determining the dimension of the lower edge of a pattern having a trapezoidal cross section.

[Means for solving problems]

The above object is achieved by providing an arithmetic processing means for finding points corresponding to the maximum and minimum differentials of the secondary electron signal waveform corresponding to the lower edge of the pattern having a trapezoidal cross section.

[Effect]

The maximum and minimum points of the secondary electron signal waveform differentiation correspond to the lower part of the pattern edge of the trapezoidal cross section. Therefore, if this point is automatically determined, the dimension of the lower part of the pattern edge can be determined accurately regardless of individual differences.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 is a schematic configuration diagram of the electron beam length measuring device of this embodiment. It is composed of a main body part 3, an electric circuit part 4, and a control computer 5. The main body 3 includes an electron gun that generates an electron beam, a lens system 8 that focuses the electron beam onto a sample wafer 9, and a lens system 8 that focuses the electron beam on the sample wafer 9. a deflector 7 for scanning, a sample stage 10 movable in the X and y directions on which the sample Ueno-- is placed, and X- and The electric circuit unit 4 includes a deflection control circuit 12 that supplies a deflection signal to the deflector 7, a lens system control circuit 13 that controls a lens system, and a signal detector 11a.

a signal processing circuit 14 that processes and stores the signal from b;
A sample stand control circuit 15 that moves the sample stand 10 in the x and y directions, and an S that displays a scanning electron microscope (SEM) image.
It consists of an EM image display device 16 and a signal waveform display device 17 that displays the signal waveform transferred from the signal processing circuit 14.

The SEM image display device 16 also displays the scanning position and position of the electron beam.
A marker indicating the range is displayed superimposed on the SEM image, and two cursors are superimposed on the signal waveform display device 17. The control computer 5 controls the electric circuit section 4 through the interface 18, performs signal processing operations, and outputs the results to the CRT.
to be displayed.

Next, details of the signal processing circuit 14 will be explained with reference to FIG. In Figure 2, there are two signal detectors 1, X''' and X+.
The signals from 1a and 1b are converted to X−+X by the adder circuit 19.
+, and the three signals of the sum of X-1
24 times) in the averaging circuit 20, and A
/D conversion circuit 21 performs analog-to-digital (A/D) conversion to 12 x 12 bits.
It is stored in memory 2'2. The sum signal stored in the memory 22 is differentiated by a differentiating circuit 23 and stored as a differential signal in the memory 22, and is also displayed on the waveform display device 17.

Next, the operation of the above-mentioned component device will be explained.

First, according to a command from the control computer 5, the sample stage 10 is moved so that the pattern to be measured on the wafer is directly under the beam. At this time, as shown in FIG.
6 displays an SEM image of the pattern to be measured 24, and a marker 25 indicating the electron beam scanning position and range is aligned across this. The deflection control circuit 12 digitally scans the range of the marker 25 with the electron beam 2048 times, and the secondary electrons generated from the sample are detected by the signal detector 11a.
.

b, the signal waveform is stored in the memory 22, the sum signal waveform is displayed on the waveform display device 16, and the X-, X+ and differential signal waveforms are transferred from the memory 22 to the control computer.

Line pattern (a) and space pattern Φ) consisting of material A with a trapezoidal cross section on base material B as shown in FIG.
It is required in the semiconductor process to determine the dimension between the lower portions 128 of the pattern (pattern lower dimension). When such a pattern is scanned with an electron beam, a sum signal waveform 1 as shown in FIG. 5(a) is displayed on the waveform display device 17. The two cursors 2 superimposed on this are adjusted to determine the signal waveform processing area, and the address Xt of this cursor position is determined.

Load Xi into the control computer. Next, Fig. 5(b), (
The area X t of the X″ and X9 signal waveforms shown in C),
Corresponds to the maximum value within X r. Address x1'
+ Find X2'. Compare the magnitudes of X1' and x, /, and if xl' is smaller, it is a line pattern, and if the opposite is the case, it is a space pattern. In the case of a line pattern, as shown in FIG. 5(d),
2', that is, Xt≦X≦xl/l x2/
Find the address XI+"2 corresponding to the maximum value and minimum value of the differential signal in the region X of ≦x x xr. In the case of a space pattern,
Addresses X1#X2 corresponding to the maximum and minimum values of the differential signal in the area X where X+'< X <xz'
seek.

From these l) Pattern bottom dimension t=l Xl -X3
1 is found.

Further, the secondary electron signal waveform obtained when scanning a line pattern with a trapezoidal cross section as shown in FIG. 4(a) with an electron beam is determined by the incident angle of the secondary electron emission ratio into the material and the dependence of the material. If the dependence on the angle of incidence on the substance is the main one, the waveform will have a peak appearing at the edge of the pattern as shown in FIG. - If the substance dependence is stronger, the sum signal waveform 1 will have a contrast difference at the edges, as shown in FIG. In such a case, xt
, x, the address XI corresponding to the maximum value of the differential signal in the region
Find z x2 and find pattern bottom dimension 1=l Xl
−x21 is obtained.

Next, as an actual sample with a trapezoidal cross section, Re5tst/5j
When using 3N4, the dimensions and pattern obtained by the above method are divided perpendicular to the longitudinal direction to calculate the SE of the pattern cross section.
The results of comparing the lower pattern dimensions obtained from the M images are shown.

The line width design value of each line pattern is 0°6. 0.
8. 1.0. 1.2. 1.5. The thickness was 2.0 μm, and the inclination angle of the edge was 5° above 80°. In FIG. 7, the horizontal axis is the dimension of the lower part of the pattern obtained from the cross-sectional SEM image, and the vertical axis is the difference between this dimension and the dimension obtained by the above processing, where 0 is the measurement point. In this way, the difference between the two is ~±0
, 05 μm or less.

As described above, according to this embodiment, the advantage is that the dimension of the lower edge of a pattern having a trapezoidal cross section can be accurately and automatically determined according to the line or space.

〔Effect of the invention〕

According to the present invention, since the dimensions are calculated by processing the differential signal waveform, the dimensions of the lower edge of a pattern having a trapezoidal cross section can be automatically determined with an accuracy of within ±0.05 μm.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a dimension measuring device showing an embodiment of the present invention, FIG. 2 is a detailed diagram of the signal processing circuit in FIG. 1, FIG. Fig. 4 is a cross-sectional view of a pattern with a trapezoidal cross-sectional shape, Fig. 5 is an explanatory diagram of the signal processing procedure of an embodiment of the present invention, and Fig. 6 is a diagram showing the case where the main factor of the secondary electron signal waveform is material difference. Signal waveform diagram, 7th
The figure is a graph showing the difference between the pattern bottom dimensions and the dimensions obtained from the process of the present invention. 1... Sum signal forming, 2... Cursor, 3... Main body, 4... Electric circuit diagram, 5... Control computer, 6...
・Electron gun, 7... Deflector, 8... Lens system, 9...
・Sample Ueno・-110...Sample stand, lla...X
- Signal detector, llb...in "Signal detector, 12..."
- Deflection control circuit, 13... Lens system control circuit, 14.
...Signal processing circuit, 15...Sample stage control circuit, 16.
... SEM image display device, 17... Waveform display device, 18
...Interface, 19...Addition circuit, 20.
...Averaging circuit, 21...A/D conversion circuit (12X
12bit), 22...Memory (12X12bit)
, 23... Differential circuit, 24... Pattern to be measured, 2
5... Marker, 26... Differential signal waveform. Agent Patent Attorney Katsuo Ogawa 7/Tsumeゝ(lO) Figure 2, Figure 3, Figure 4, Figure 6, Figure 70, l\・Turn Shimo Genchoho (Aki)

Claims (1)

[Claims] 1. A focusing device that focuses the charged particle beam onto a microprose on the measurement sample, a deflection device that scans the charged particle beam on the sample surface, and two devices that detect signals such as secondary electrons emitted from the sample. In a dimension measuring device comprising the above-mentioned signal detection means and means for arithmetic processing of the signal from the detection means, the arithmetic processing means finds the maximum and minimum points of the differential of the detection signal, and calculates the difference between these points. A dimension measuring device characterized in that it is configured to measure the dimensions of the lower edge of a sample having a trapezoidal cross section at intervals.