JPS61220259A - Electron beam apparatus - Google Patents

Abstract

PURPOSE:To improve the accuracy by correcting deflection of secondary electrons due to the deflection of electron beam in an electron beam apparatus having an energy analyzer for detecting the potential of specimen comprising a take-out electrode, a deceleration electrode, a deflector, etc. arranged for an objective lens. CONSTITUTION:The secondary electrons emitted from a specimen 4 are passed through a take-out electrode 8 and a deceleration electrode 9 arranged for an objective lens 3 then detected through a detector 7. Here, deflection signals (x), (y) are fed through drivers 11, 12 to a deflector 5 while to the amplifiers 13, 14 to be amplified. Then predetermined constant voltage is added through adder/amplifiers 15, 16 to provide (x) and (y) signals to repspective grid 7a of a pair of detectors 7 arranged while crossing perpendicularly with the advancing axis of electron beam then the outputs are amplified through an amplifier 17 and fed to a CRT. Consequently, the deflection of secondary electrons caused through deflection of electron beam can be correct resulting in highly accurate potential measurement.

Description

[Detailed Description of the Invention] [Summary] In an electron beam device that irradiates a sample with an electron beam and detects secondary electrons emitted by the sample, the secondary electrons input to a detector facing the sample with an objective lens in between are detected. By providing means for correcting the deflection caused by the deflector used to swing the electron beam, it is possible to detect a spatially uniform secondary electron signal.

[Industrial application field]

The present invention relates to an improvement in an electron beam device that irradiates a sample with an electron beam and detects secondary electrons emitted by the sample.

A secondary electron signal obtained when a sample is irradiated with an electron beam includes potential information on the sample surface. Therefore, electron beam blobbing, which utilizes this phenomenon, is based on scanning electron microscope technology and has already been put into practical use as an electron beam device that measures the potential of minute patterns that cannot be touched by metal probes and its temporal changes. ing.

[Conventional technology]

FIG. 6 is a schematic diagram showing the main parts of an electron beam device according to the prior art.

In FIG. 6, an electron beam 1 emitted from an electron gun (not shown) is connected to a condenser lens (not shown) and a lens barrel 2.
The light is focused on the surface of the sample 4 by the objective lens 3, and is deflected by a deflector 5 controlled by a deflection power source (not shown) to scan the surface.

The secondary electrons 6 emitted from the sample 4 by irradiation with the electron beam l are: an extraction electrode 8 that provides an electric field for emitting the secondary electrons 6, and the extracted secondary electrons 6 are sorted according to their energy levels. After being transmitted through the deceleration electrode 9 and detected by the detector 7, it is amplified by an amplifier (not shown) and displayed on a cathode ray tube (not shown) as a value that is approximately inversely proportional to the voltage value of the wiring pattern of the sample 4, for example. will be done.

The detector 7 consists of a grid 7a, a scintillator 7b, a light pipe 7c, a photomultiplier 7d, etc., and an extraction electrode 8 is provided on the front (lower surface) of the objective lens 3.
A deceleration electrode 9 is provided on the rear surface (upper surface) of the objective lens 3, and a detector 7 is provided behind (above) the deceleration electrode 9.

[Problem that the invention seeks to solve]

However, the electron beam device, which is the prior art,
Since the energy of the secondary electrons 6 emitted from the sample 4 is smaller than the energy of the electron beam 1, the secondary electrons 6 are deflected under the influence of the horizontal magnetic field of the deflector 5, and the position of incidence on the deceleration electrode 9 changes. I will do it.

As a result, the spatial distribution of the secondary electrons 6 (secondary electron signal) transmitted through the deceleration electrode 9 is as shown in FIG. beam 1
If the amount of deviation is d from the straight line center of
0 does not match. This is due to the deflection of electron beam 1.
This is because the secondary electrons are also deflected and the signal strength of the secondary electrons changes, which reduces the accuracy of potential measurement of the sample 4, and an improvement has been desired.

[Means for solving problems]

The above problem consists of an objective lens (3) that focuses the electron beam (1) onto a sample (4), an extraction electrode (6) and a deceleration electrode (9) arranged on the objective lens (3), and a deflector ( 5), etc., and a secondary electron detector (
7), and means for correcting the deflection of the secondary electrons (6) accompanying the deflection of the electron beam (1) by the deflector (5); 1) changing the secondary electron trapping electric field in synchronization with the deflection of the deflector (
5) is an electrostatic deflector (22) and an electromagnetic deflector (2I), and the means keeps the total amount of deflection by the two types of deflectors (2L22) constant and deflects each of the deflectors (21, 22). an intermediate electrode (31) facing the extraction electrode (8) with the deflector (5) in between is provided within the objective lens (3); The problem is solved by an electron beam device characterized by: applying a secondary electron velocity adjustment voltage to ).

[Effect]

According to the above means, the secondary electron detector detects the peak of the spatial distribution characteristic of the extracted secondary electrons, and as a result, highly accurate and efficient potential information can be detected.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the main parts of an electron beam device according to the first embodiment of the present invention, and FIG. 2 is a schematic diagram showing the main parts of the electron beam device according to the first embodiment of the present invention. FIG. 3 is a schematic diagram showing the main parts of an electron beam device according to a third embodiment of the present invention, and FIG. FIG. 5 is a schematic diagram for explaining the deflection of electrons, and is a schematic diagram showing the main parts of an electron beam device according to a fourth embodiment of the present invention. However, the same symbols are used for parts common to the previous figure.

In FIG. 1, 11 and 12 are deflector drivers, 13 and 14 are amplifiers, and 15, 16, and 17 are summing amplifiers.
A pair of detectors 7 are provided so as to be orthogonal to each other in the same plane orthogonal to the electron beam rectilinear axis. Deflection signal X is input to driver 11 and amplifier 13, and deflection signal y is input to driver 1
2 and the amplifier 14, and the deflection signals x and y input to the drivers 11 and 12 drive the deflector 5.

On the other hand, the signals x and y input to the amplifiers 13 and 14 are respectively multiplied by a fixed value (a times) to become ax and ay, which are input to the summing amplifier I5 or 16 connected to the grid of each of the pair of detectors 7. . Therefore, a predetermined voltage is applied to the summing amplifiers 15 and 16, and the predetermined voltage and the voltage of the signal aX are added and amplified by the amplifier 15 and applied to the grid of one detector 7, while the other The predetermined voltage and the voltage of the signal ay are added and amplified by an amplifier 16 and applied to the grid of the detector 7, and the detection signals of each detector 7 are added and amplified by the amplifier 17 and input to a cathode ray tube (not shown).

In such a device, since the secondary electron trapping electric field created above the deceleration electrode 9 changes in synchronization with the deflection of the electron beam 1, it cancels out the fluctuations in the secondary electron detection efficiency shown in FIG.
Highly accurate potential information can be detected.

In FIG. 2, 18 is an electrode facing the detector 7 with the electron beam 1 in between, and 19 is a summing amplifier that receives a predetermined voltage and the voltage of the signal ax and applies the summing amplified signal to the electrode 18. device drivers 11 and 12° amplifiers 13 and 1
4. Summing amplifiers 16 and 17 are arranged similarly to the device of FIG.

In this device, the objective lens 3, deflector 5, and detector 7 operate on signals x and y in the same way as in the device shown in FIG. A predetermined voltage is added and amplified and applied to the electrode 18. As a result, the secondary electron trapping electric field created above the deceleration electrode 9 can be changed in synchronization with the deflection of the electron beam l, canceling out the fluctuations in the secondary electron detection efficiency shown in FIG. Information becomes detectable.

In FIG. 3, 21 is an electromagnetic deflector, 22 is an electrostatic deflector, 23 is an arithmetic circuit, and 24.25 is a multiplier (MDA).
C), 26 is an electromagnetic deflector driver, 27 is an electrostatic deflector driver, and the deflection signal X is transmitted to a pair of MDACs 24, 25.
Enter.

Now, the amount of deflection by the electrostatic deflector 22 is Xl, the amount of deflection by the electromagnetic deflector 21 is X2, the required excitation current to be applied to the electromagnetic deflector 21 is Id, and the required voltage to be applied to the electrostatic deflector 22. When v4 and k,,kt are constants, the total deflection 1x of the electron beam 1 is: X=X++Xt =, ・V, +, ・■.

becomes.

Therefore, for the amount of electrostatic deflection, the ratio of ・■4 to the total amount of deflection
Then, α = ・■d/X, and to ensure the total deflection amount X, V, = α・X / k I Ia = (1-α)・X / k good.

Therefore, the arithmetic circuit 23 inputting the ratio constant α sends data of + to α/ and 2 to (1−α)/ to the MDAC 24 for electrostatic deflector and the MDAC 25 for electromagnetic deflector, respectively.

Then, the MDAC 25 to which the deflection signal X has been input sends a signal obtained by multiplying the deflection signal X by α711 to the electrostatic deflector driver 27.
The MDAC 24, to which the deflection signal X is input, sends a signal obtained by doubling the deflection signal 22.21.

In FIG. 4(a), the electron beam 1 is connected to the electrostatic deflector 22.
and is deflected in two stages by an electromagnetic deflector 21.

In FIG. 4(b), the secondary electrons 6 shown by solid lines are deflected when the deflector drivers 24 and 25 are driven as described above, and are divided into two stages by the electromagnetic deflector 21 and the electrostatic deflector 22. It is deflected and passes approximately through the center of the deceleration electrode 9.

However, if the proportionality constant α=0, as shown by the dashed line,
Since it is not deflected by the electrostatic deflector 22, it deviates from the solid line path and intersects the central axis of the deceleration electrode 9 below the deceleration electrode 9. On the other hand, when the proportionality constant α is set to 1, the electromagnetic deflector Since it is not deflected in the second direction, it deviates from the solid line path and passes through the deceleration electrode 9 without intersecting the central axis of the deceleration electrode 9.

Therefore, such a device uses two types of deflectors and utilizes the difference in their deflection characteristics to control the deflection direction of the secondary electrons 6, thereby obtaining stable and efficient potential information.

In FIG. 5, 31 is an intermediate electrode provided between the deflector 5 and the deceleration electrode 9.
Extraction voltage (Ve) of about V, -1 Ov to deceleration electrode 9
While a variable voltage of +IOV is applied, a voltage of approximately several hundred volts to IKV is applied to the intermediate electrode 31.

Therefore, the secondary electrons 6 emitted from the sample 4 are transferred to the extraction electrode 8.
The beam is accelerated in the vertical direction and enters the magnetic field generated by the objective lens 3 and deflector 5. Therefore, without the intermediate electrode 31, the secondary electrons 6 passing through the extraction electrode 8 are rapidly decelerated and are largely deflected by the deflection magnetic field of the deflector 5. However, by adjusting the deceleration with the intermediate electrode 31, the objective lens The amount of deflection changes within 3, making it possible to pass approximately the center of the deceleration electrode 9.

As a result, stable and efficient potential information can be obtained from the detector.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to correct the deflection of secondary electrons due to the deflection of the electron beam, and to perform high-precision potential measurement over a wide range of fields, which is useful for example in improving the performance and reliability of LSI. The effect that this contributed to was extremely large.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the main parts of an electron beam device according to the first embodiment of the present invention, FIG. 2 is a schematic diagram showing the main parts of the electron beam device according to the first embodiment of the present invention, FIG. 3 is a schematic diagram showing the main parts of an electron beam device according to a third embodiment of the present invention; FIG. 4 is a schematic diagram for explaining the electron beam and secondary electrons in the third embodiment; FIG. 5 is a schematic diagram showing the main parts of an electron beam device according to a fourth embodiment of the present invention. FIG. 6 is a schematic diagram showing the main parts of an electron beam device according to the prior art. FIG. 2 is a diagram showing an example of the spatial distribution of secondary electrons in the device. In the figure, 1 is an electron beam, 3 is an objective lens, 4 is a sample, 5.22 is a deflector, 6 is a secondary electron, 7 is a secondary electron detector, 8 is an extraction electrode, 9 is a deceleration electrode, 11 -14 is an amplifier, 15 to 17 are summing amplifiers, 22 is an electrostatic deflector, and 31 is an intermediate electrode. Explanatory diagram of i-first e shame development 3 禮 Chaos defeat 9 倚 4 Figure ILIGF4 q,! 64q Tora iL i # No. 1 Kaya 5
Fig. 2 missing electron f) Empty 1%'le;

Claims (4)

[Claims] (1) An objective lens (3) that focuses the electron beam (1) onto the sample (4), an extraction electrode (8), a deceleration electrode (9), and a deflector (5) arranged on the objective lens (3). A secondary electron detector (
7), and an electron beam device comprising means for correcting the deflection of secondary electrons (6) accompanying the deflection of the electron beam (1) by the deflector (5). (2) The electron beam device according to claim 1, wherein the means changes the secondary electron trapping electric field in synchronization with the deflection of the electron beam (1). (3) The deflector (5) is an electrostatic deflector (22) and an electromagnetic deflector (21), and the means maintains the total amount of deflection by the two types of deflectors (21, 22) constant and deflects the deflector. 2. The electron beam apparatus according to claim 1, wherein the ratio of the deflection amount of each of the beams (21, 22) is changed. (4) An intermediate electrode (31) that faces the extraction electrode (8) across the deflector (5) within the objective lens (3).
An electron beam device according to claim 1, characterized in that said means applies a secondary electron velocity adjusting voltage to said intermediate electrode (31).