JPH0356877A - electron beam device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding an electron beam device, the purpose of the present invention is to provide an electron beam device that can obtain accurate terminal position measurement results even if there is contamination on the measurement location of the sample. An electron beam device for measuring a secondary electron signal obtained from a measurement location on a sample, the electron beam device including means for applying a pulse voltage, and means for irradiating a measurement location on the sample with an electron beam synchronized with the sample pulse, Regarding the measurement location of the sample when performing a line scan, the pulse voltage is alternately in the L level phase and the pulse voltage in the H level phase.
The secondary electron signal is sampled and the difference between the two secondary electron signals is determined.

[Industrial application field]

The present invention relates to an electron beam device.

An electron beam device irradiates a measurement location of a sample with an electron beam synchronized with a sample pulse of the sample, and measures a secondary electron signal obtained from the measurement location of the sample. When using this electron beam device, if contamination adheres to the measurement location of the sample, such as the measurement terminal of an LSI, the amount of secondary electron signals emitted from the measurement terminal will be small, making it difficult to obtain accurate measurement results. I can't. Therefore, there is a need for an electron beam apparatus that can obtain accurate measurement results even when contamination is present at the measurement location of the sample.

[Conventional technology]

When manufacturing an LSI, it is necessary to conduct tests to increase the reliability of the product. For this test, an electron beam device is used, and in this electron beam device,
A board is placed as a partition wall separating a vacuum part and an atmospheric part, and the LSI to be tested is installed on the atmospheric part side of the board.
Measurement terminals electrically connected to the individual input/output bins of I are installed on the vacuum side of the board. Then, by irradiating the measurement terminal with an electron beam, the voltage appearing on the surface of the measurement terminal is measured, thereby measuring the signal at the input/output pin of the LSI connected to the measurement terminal.

In such an electron beam device, in order to accurately detect the terminal position in advance before measuring the characteristics of the LSI,
A line scanning image of the terminal is obtained by line scanning with an electron beam, which is then binarized, the terminal position is detected, and the deflection coordinates of the electron beam are determined. That is, as shown in FIG. 4, a line profile is obtained corresponding to the measurement terminal image, and a binarization result is obtained from this line profile.

[Problem to be solved by the invention]

When an electron beam device is used to perform long-term measurements, the irradiated electron beam causes dirt (hydrocarbons) called contamination to adhere to the measurement terminals. As shown in FIG. 5, when contamination adheres to the measurement terminal, the amount of secondary electron signal emitted is small in the area 10 where the contamination has adhered, so SEM (scanning electron microscope) images etc. are observed. Then it looks dark. Therefore, even if a line profile is obtained by line scanning, a correct measurement terminal image will not be obtained, and therefore, even if binarization is performed, a correct binarization result will not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electron beam device that can obtain accurate terminal position measurement results even if there is contamination at a measurement location on a sample.

[Means to solve the problem]

The present invention provides a means (20) for applying a pulse voltage to a sample (20).
26) and an electron beam (1
4) to the measurement point (22) of the sample (20);
In an electron beam device that measures secondary electron signals obtained from The configuration is such that a secondary electron signal is sampled at a time, and a difference between the two secondary electron signals is determined.

[Effect]

In the present invention, the sample (
Regarding the measurement point (22) in 20), a secondary electron signal is obtained in the phase when the pulse voltage is at the L level, and a secondary electron signal is obtained at the phase when the pulse voltage is at the H level. We are looking for the difference between two secondary electron signals.

Hereinafter, a time chart of an electron beam apparatus according to the principle of the present invention will be explained based on FIG.

When a dirty measurement terminal is irradiated with an electron beam, an electric charge accumulates on the dirt. At this time, if a pulse voltage is applied to the measurement terminal, the charge on the dirt changes in accordance with the change in the pulse voltage. Therefore, the secondary electron signal is measured when the pulse voltage is at the L level, and the secondary electron signal is measured when the pulse voltage is at the H level.
By measuring the secondary electron signals alternately at the level and finding the difference between the two secondary electron signals, the influence of dirt (contamination) is reduced because charges caused by dirt are not accumulated in one direction, and the pulse voltage The contrast in the area where the voltage is applied appears strong.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 2 shows a circuit of an electron beam device according to an embodiment of the invention.

In FIG. 2, reference numeral 12 denotes an EB (electron beam) lens barrel that irradiates an electron beam 14, and in the EB lens barrel 12, a substrate 16 is arranged as a partition wall that separates a vacuum region from an atmospheric region. A socket 18 is provided on the atmospheric side of the board l6.
The LSI 20 to be tested is arranged through the board 16, and measurement terminals 22-22 are arranged on the vacuum side of the board 16, and the measurement terminals 22-22 are connected to the input/output bins 24-24 of the LSf 20. electrically connected to.

Note that a pulse voltage (sample pulse clock) 28 is supplied to the LS 120 from the LSI drive circuit 26 via input/output pins 24 to 24.

Inside the EB lens barrel 12, an electron gun 30, an electron lens 32, a deflector 34, and a scan coil 36 are arranged, and the deflector 34 and the scan coil 36 are connected to an EB pulse pulse driver 38 and a scan coil driver 40, respectively. activated by

Reference numeral 42 indicates a line scan image measurement circuit, and in the line scan image measurement circuit 42, an EB pulse irradiation phase control circuit 44 controls the pulse voltage of the LSI drive circuit 26 at the phase specified by the scan control circuit 46. EB pulse trigger 48 synchronized with (sample pulse clock) 28
is supplied to the EB pulse pulse driver 38.

Further, the deflection coordinate control circuit 50 supplies the EB deflection coordinate data 52 designated by the scan control circuit 46 to the scan coil driver 40 .

When the measurement terminals 22 to 22 connected to the LSI 20 are irradiated with the electron beam 14, secondary electrons are obtained from the measurement terminals 22 to 22, and these secondary electrons are detected by the detection circuit 54. Secondary electronic signal data 56 from detection circuit 54 is stored in either buffer 60 or 62 via switch 58. Note that the switch 58 is controlled by a switching control signal 63 from the scan control circuit 46, and stores the secondary electronic signal data 56 in one of the buffers 60 and 62 corresponding to the phase of the pulse voltage 28. For example, secondary electron signal data 56 corresponding to the L level of the pulse voltage 28 is stored in the buffer 60, and secondary electron signal data 56 corresponding to the H level of the pulse voltage 28 is stored in the buffer 62.

Then, only once for one deflection coordinate, the buffer 6
The difference between the data of 0 and the data of the buffer 62 is determined,
This is supplied to the line scan data memory 66 at the address corresponding to the deflection coordinate designated by the buffer address control signal 64 from the scan control circuit 46.

? FIG. 3 shows a flowchart of an electron beam apparatus according to an embodiment of the present invention.

In FIG. 3, the start is at step 100, and at step 102, phase=01, deflection coordinates=(x1y)...scan center coordinates, step 104 requires application of a sample pulse (pulse voltage), and step 106: X=X
-X % 7-7 7, ”'W Set scan start coordinates.

Measurement 1 is made in steps 108, 110, i.e.
Measure the secondary electron signal with phase = φ(, dV) (S
e(v,v)).

Furthermore, a measurement 2 is made in steps 112, 114, ie measuring the secondary electron signal (y=v) with phase=φ (S e (V■)).

In step 116, the deflection coordinates (x, y) are set to syd. If the scan is not completed in step 120, the process returns to step 108, and if the scan is completed, the process proceeds to step 122, and the flow ends.

〔Effect of the invention〕

As explained above, according to the present invention, even if there is contamination at the measurement location of the sample,
Accurate measurement results can be obtained. Therefore, a line scan image with less influence of contamination can be obtained, and later processing such as binarization can be easily performed.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a circuit diagram of an electron beam device according to an embodiment of the present invention, Fig. 3 is a flowchart of the embodiment, and Fig. 4 shows measurement results of a clean sample. FIG. 5 is a time chart showing the measurement results of a sample with dirt. 12... EB (electron beam) lens barrel 14... Electron beam 20... LSI (sample) 22-22... Measurement terminal 26... LSI drive circuit 28... Pulse voltage 30... Electron gun 32...electron lens 34...deflector 36...scan driver 38...pulse driver 40 for EB pulse...scan coil driver 42...line scan image measurement circuit 44...EB Pulse irradiation phase control circuit 46...Scanning control circuit 50...Deflection coordinate control circuit 54...Secondary electron detection circuit 58...Switchers 60, 62...Buffer 66...Line scan data memory 100-122
...Step 4 Figure 5

Claims (1)

[Scope of Claims] Means (26) for applying a pulse voltage to the sample (20), and means (26) for irradiating the measuring point (22) of the sample (20) with an electron beam (14) synchronized with the sample pulse. 12)
In an electron beam device that measures a secondary electron signal obtained from a measurement point (22) of a sample (20), the measurement point (22) of the sample (20) is used when performing a line scan.
Regarding 22), an electron beam device characterized in that the secondary electron signal is sampled alternately in the phase where the pulse voltage is at L level and the phase where the pulse voltage is at H level, and the difference between the two secondary electron signals is determined.