JPH05325868A - Electron beam device - Google Patents

Abstract

PURPOSE:To achieve reduction of probe diameter and enlargement of the probe scanning range simultaneously so as to enable measurement corresponding to miniaturization of LSI by providing independent tubes to correspond to two kinds of modes. CONSTITUTION:A tube 11 for the scanning electron microscope mode (SEM) has a deflecting system 15 and an objective lens 16 and the amount D of deflection of the tube 11 is larger than that (d) of deflection of a voltage measuring tube 21 so that a wide scanning range is provided. Secondary electrons that a sample W generates are converted by the tube 21 into pulses at a blanker 22 and measured as voltages. The use of the two sets of tubes corresponding to that mode simultaneously enables reduction of probe diameter and enlargement of the probe scanning range which are inconsistent with each other, thus providing an electron beam device which can deal with miniaturization of LSI.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam apparatus for measuring the voltage of a sample, such as an electron beam tester for testing LSIs and analyzing defects.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional electron beam apparatus for measuring the voltage of a sample by detecting secondary electrons generated from the sample irradiated with an electron beam.

FIG. 2 is a sectional view of an electron beam apparatus according to a conventional example. In the figure, 1 is an electron beam column, 2 is an electron gun, 3 is a condenser lens, 4 is a reflector, 5 is an objective lens, 6 is a secondary electron extraction electrode, 7 is a buffer electrode, 8 is an analysis electrode, and 9 is two. Secondary electron collector, 10 is a detector [PMT (photomultiplier tube, etc.), PE is a primary electron, SE is a secondary electron, and W is a sample.

Electrons emitted from the electron gun 2 are converged through a multistage lens system composed of a condenser lens 3 and an objective lens 5, and at the same time, a convergent electron beam is scanned by a deflector (not shown) and pulsed by a blanker (not shown). Perform and illuminate the sample.

Secondary electrons are emitted from the irradiation point, and the secondary electrons are collected by the collector 9 via the secondary electron extraction electrode 6, the buffer electrode 7, and the analysis electrode 8, reach the detector 10, and reach the voltage signal. Is processed and processed.

At this time, the analysis voltage V _R applied to the analysis electrode
By sweeping, only secondary electrons with energy above a certain value can reach the detector. As a result,
An analytical curve in the form of integrating the energy distribution of the secondary electrons with respect to the analytical voltage V _R is obtained as shown in FIG.

FIG. 3 illustrates the principle of voltage measurement. The figure is an analysis curve showing the relationship of the secondary electron count S with respect to the analysis voltage V _R. The parameters are sample voltages V ₁ and V ₂ , and the analysis voltages corresponding to the slice level are represented by V _R1 and V _R2 , respectively.

If the sample voltage increases by V (V), for example,
The energy distribution of the secondary electrons at the analysis electrode shifts by V (eV) to the lower energy side, and as a result, the analysis curve shifts to the right by the change in the sample voltage. The sample voltage can be measured conversely by measuring this shift amount.

[0009]

In the prior art, as the LSI wiring to be measured is miniaturized, the electron beam to be a probe must be converged to the width of the wiring or less. However, increasing the reduction ratio of the lens to reduce the electron beam diameter and scanning the electron beam over a wide range to position the irradiation point are mutually exclusive, and it is difficult to achieve both at the same time.

It is an object of the present invention to provide an electron beam apparatus which is a trade-off between the probe diameter reduction and the probe scanning range expansion, and which enables measurement corresponding to the miniaturization of LSI.

[0011]

[Means for Solving the Problems] The above-mentioned problems can be solved by an electron beam apparatus which measures the voltage of a sample by irradiating a sample with a primary electron beam and measuring the energy of secondary electrons generated by an energy analyzer. The electron beam column for image acquisition so that the same sample surface can be irradiated with the electron beam.
11 and an electron beam column 21 for voltage measurement are separately provided, a deflector 15 and an objective lens 16 are provided in the image acquisition column, and an electron beam is pulsed in the voltage measurement column. Blanker 23 to be turned into a deflector and a deflector 25 having a smaller deflection amount than the deflector
Objective lens with built-in secondary electron energy analyzer 26
And a lens system having a magnification of 1 or less.

[0012]

The present invention has been made by paying attention to the following two types of modes when irradiating an electron beam in the prior art.

Image acquisition mode [SEM (scanning electron microscope) mode]: A rectangular area is scanned with a continuous beam to acquire information such as a wiring pattern inside the area. Voltage measurement mode: A pulsed electron beam is applied only to the voltage measurement point, and the beam is not scanned.

In the present invention, independent electron beam lens barrels having the following characteristics are provided for these two types of modes. The main purpose of the lens barrel corresponding to the mode is to obtain a wide scanning range, and the probe diameter may be equal to or larger than the wiring width. Therefore, the magnification of the lens system is> 1 (magnification).

Further, since the electron beam uses a continuous beam, blanking means for the electron beam is unnecessary. Energy analysis means is not necessary for secondary electrons, and only detection means is required.

The lens barrel corresponding to the mode (1) does not require a large deflection angle because its main purpose is to reduce the probe diameter and the beam scanning is necessary only when positioning the irradiation point. Therefore, the magnification of the lens system is ≤1 (reduction or equal magnification).

In addition, a beam pulsing means and a secondary electron energy analysis / detection means are required for voltage measurement.

[0018]

1 is a sectional view of an embodiment of the present invention. In the figure, the left is the SEM barrel and the right is the voltage measurement barrel.

In the figure, 11 is an SEM lens barrel, 15 is a deflector, 16 is an objective lens, 21 is a voltage measuring lens barrel, 22 is a blanker, 24 is an aperture, 25 is a deflector, and 26 is an objective lens (Fig. 2 built-in energy analyzer). D and d are SEM
Deflection distance of beam for measurement and voltage measurement, D> d.

In the lens barrel for SEM, the entire lens system is a magnifying lens. Therefore, the beam displacement at the deflector position is magnified at the image plane (sample plane) position, and a wide scanning range can be obtained.

On the other hand, in the voltage measuring lens barrel, the electron beam pulsed by the blanker is deflected by the deflector,
The sample surface is convergently irradiated by the objective lens. The lens system is a reduction lens, so the scanning range is limited,
It is easy to reduce the beam diameter.

Secondary electrons generated from the sample are guided to the detector after performing energy analysis in the voltage measuring lens barrel, and are detected without passing through the energy analyzer in the SEM lens barrel.

Further, if the optical axis distance between the two lens barrels is less than 1/2 of the scanning range of the SEM lens barrel, the stage on which the sample is placed does not need to be moved, and only two modes can be selected by switching. Can be switched.

[0024]

According to the present invention, by using the two lens barrels for image acquisition and voltage measurement, it is possible to simultaneously realize the reduction in probe diameter and the increase in probe scanning range, which were difficult to achieve at the same time. We were able to make measurements that correspond to the miniaturization of LSIs.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of an electron beam device according to a conventional example.

FIG. 3 is a diagram for explaining the principle of voltage measurement.

[Explanation of symbols]

 11 SEM lens barrel 15 Deflector 16 Objective lens 21 Voltage measuring lens barrel 22 Blanker 24 Aperture 25 Deflector 26 Objective lens (with built-in energy analyzer)

Claims (1)

[Claims] 1. An electron beam device for irradiating a sample with a primary electron beam and measuring the energy of secondary electrons generated by an energy analyzer to measure the voltage of the sample. Electron beam column for image acquisition (11) and electron beam column for voltage measurement so that irradiation can be performed
(21) is provided separately, the image acquisition lens barrel has a deflector (15) and an objective lens (16), and the voltage measurement lens barrel has a blanker () for pulsing an electron beam. 23) and the deflector (1
5) An electron beam apparatus comprising a deflector (25) having a smaller deflection amount and an objective lens (26) having a secondary electron energy analyzer therein and a magnification of 1 or less.