JPH0654638B2 - Alignment device for charged particle beam device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an alignment device for a charged particle beam device such as an electron beam device equipped with a field emission electron gun and the like.

[Prior Art] In an electron beam apparatus equipped with a field emission electron gun, the electron gun section is provided with an electrostatic lens, and the electron gun section and the lower barrel including the electron gun alignment coil are It is partitioned by an anode with a minute aperture to keep the gun in a high vacuum.

[Problems to be Solved by the Invention] In order to observe an excellent image by passing an electron beam generated from an emitter tip of a field emission electron gun through the center of a focusing lens and a center of an objective lens, Although alignment is performed, in the above-mentioned device, the axis alignment cannot be easily performed because the aperture of the anode is extremely small.

The present invention solves such a conventional problem, and provides an axis aligning device in a charged particle beam device which can easily perform axis alignment when an aperture provided in an electrode such as an anode is minute. It is an object.

[Means for Solving Problems] An axis aligning device in a charged particle beam device according to the present invention includes a first lens for focusing charged particles from a charged particle beam source that has passed through a minute aperture, and the first lens. Disposed between the second lens for focusing the charged particles focused by the lens, first and second deflection signal generating means for generating a deflection signal, and the minute aperture and the first lens. The distance between the charged particle beam source and the first deflecting means, and the distance between the first and second deflecting means is b, and the distance between the first and second deflecting means is b. When the distance between the second deflecting means and the first lens is c, and the deflection angles by the first and second deflecting means are θ ₁ and θ ₂ , signals from the first deflecting signal generating means To convert two signals into two signals based on the relationship of θ ₁ / θ ₂ = (a + b) / a. 1 distribution means,
The signal from the second deflection signal generating means is represented by θ ₁ / θ ₂ =
Second distribution means for converting into two signals based on the relationship c / (b + c), one of the two signals from the first distribution means and two signals from the second distribution means And means for supplying the addition signal to the first deflection means, and the other signal from the first distribution means and the other signal from the second distribution means. And a means for supplying the addition signal to the second deflecting means.

EXAMPLES Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is for showing an embodiment in which the present invention is applied to a scanning electron microscope equipped with a field emission electron gun, and FIG. 1 (a) is for explaining an axial alignment operation at a first stage. It is a figure and Drawing 1 (b) is a figure for explaining axis alignment operation of the 2nd step.

In FIG. 1, 1 is an emitter tip of a field emission electron gun, and 2 is an extraction electrode. Reference numeral 3 is an anode, and the anode 3 is provided with a minute aperture 3a.
Reference numerals 4 and 5 are first and second deflection coils for axis alignment.
Reference numeral 6 is a focusing lens, 7 is an objective lens, and 8 is a sample. 9
Is a scanning coil, and although not shown, the scanning coil 9 is supplied with sawtooth horizontal and vertical scanning signals from a scanning signal generating circuit. Reference numeral 10 is a secondary electron detector. Although not shown, the detection signal from the secondary electron detector 10 is sent to a CRT which is synchronously scanned based on the scanning signal. 1
Reference numerals 3 and 14 denote first and second adder circuits, and the output signals of these adder circuits are sent to the deflection coils 4 and 5 via amplifiers 11 and 12, respectively. The output signal of the first distribution circuit 15 and the output signal of the second distribution circuit 16 are supplied to the first addition circuit 13. The output signals of the first distribution circuit 15 and the second distribution circuit 16 are also supplied to the second addition circuit 14. Reference numeral 17 is a first deflection signal generation circuit for supplying a deflection signal to the first distribution circuit 15, and 18 is a second deflection signal generation circuit for supplying a deflection signal to the second distribution circuit 16. is there. Here, the first distribution circuit 15 distributes the signal from the first deflection signal generation circuit 17 to the first and second addition circuits 13 and 14 so as to maintain the following conditions. That is, as shown in FIG. 1 (a), the circuit 1 is arranged so that the extension line R of the electron beam deflected by the deflection coil 4 and then swung back in the deflection coil 5 always intersects with the chip 1.
The signal from 7 is distributed to the circuits 13 and 14. This condition can also be expressed as follows. That is, in FIG. 1A, the distance between the chip 1 and the first deflection coil 4 is a, the distance between the first and second deflection coils 4 and 5 is b, and the electron beam EB.
As shown in FIG. 1, the electron beam EB from the first deflection coil 4
Is θ ₁ , the deflection angle of the electron beam EB by the second deflection coil is θ ₂ , the angle formed by the extension line R of the electron beam EB1 and the electron beam EB is θ, the extension line R of the electron beam EB1 and the electron beam EB. When the distance between the EB and the deflection coil on the surface of the deflection coil 4 is δ, it corresponds to the fact that approximately θ = δ / a θ ₂ = δ / b is always established for θ ₂ and θ which are actually minute.

By the way, since θ ₁ = θ ₂ + θ, the following relational expression can be obtained by using the above conditional expression.

θ ₁ / θ ₂ = (θ ₂ + θ) / θ ₂ = (δ / b + δ / a) / (δ / b) Therefore, the first distribution circuit 15 is always approximately θ ₁ / θ ₂ = (a + b) / a. (1) It has the function of maintaining the following relationship.

Further, the second distribution circuit 16 distributes the signal from the second deflection signal generation circuit 18 to the first and second addition circuits 13 and 14 so as to maintain the following conditions. That is, an electron beam adjusted to pass through the center O of the focusing lens 6 as shown by the electron beam EB3 in FIG. This center O
The distribution circuit 16 distributes the signal so as to maintain the condition of passing the signal. This condition can also be expressed as follows.

In FIGS. 1 (a) and 1 (b), the position of the chip 1 is drawn far away from the axis Z of the lenses 6 and 7 in order to make it easy to understand the axis deviation, but the actual axis deviation is very small. Now, the above conditions will be described based on the ray diagram of FIG. 2 in which this axis deviation angle is ignored.

In FIG. 2 in which the same components as in FIG. 1 (b) are assigned the same reference numerals, the distance between the deflection coil 5 and the focusing lens 6 is c, and the deflection coil 4 is used as in the first case. The deflection angle is θ ₁ , the deflection angle by the deflection coil 5 is θ ₂ , and the angle formed by the extension line Q of the electron beam EB and the electron beam EB 3 is θ ′,
If the distance between the electron beam EB3 and the extension line Q of the electron beam EB on the plane of the deflection coil 5 is δ ', then the second distribution circuit 1 described above is used.
6 is the first deflection signal from the second adder circuit 18 so that approximately θ ′ = δ ′ / c θ ₁ = δ ′ / b is always established for θ ₁ and θ ′, which are very small. , To the second adder circuits 13 and 14.

By the way, since θ ₂ = θ ₁ + θ ′, the following relational expression can be obtained by using the above conditional expression.

θ ₁ / θ ₂ = θ ₁ / (θ ₁ + θ ′) = (δ ′ / b) / (δ ′ / b + δ ′ / c) Therefore, the function of the second distribution circuit 16 is approximately θ ₁ / θ ₂ = c / (b + c) (2) Corresponds to always maintaining the relationship.

Using the apparatus having such a configuration, axis alignment is performed as follows.

First, a scanning signal is supplied to the scanning deflection coil 9 so that the sample 8 is two-dimensionally scanned, and a signal from the detector 10 obtained from the sample 8 along with this scanning is synchronously scanned with the CRT ( (Not shown) so that the sample image can be displayed. Therefore, with the output signal from the second deflection signal generation circuit 18 set to 0, the deflection signal is generated from the first deflection signal generation circuit 17 and the magnitude of the deflection signal is adjusted. This deflection signal is distributed in the first distribution circuit 15 and then supplied to the deflection coils 4 and 5 via the first and second adder circuits 13 and 14, so that the electron beam EB is transmitted through the electron beam EB shown in FIG. ), The extension angle R always crosses the chip 1, that is, the expression (1) is substantially satisfied, and the deflection angles θ of the first and second deflection coils 4 and 5 are equal to each other.
₁ and θ ₂ are changed. In this way, in the adjustment, when the electron beam EB passes through the focusing lens 6 like the electron beam EB2, the image displayed on the CRT becomes bright. Therefore, when the output signal from the first deflection signal generating circuit 17 is adjusted while observing the CRT image while periodically oscillating (wobbling) the exciting current of the focusing lens 6, the image displayed on the CRT is A state where the player cannot move despite the wobbler appears. In this state, the electron beam EB is deflected by the deflection coils 4 and 5 and then the first beam
It passes through the center O of the focusing lens 6 as shown by the electron beam EB3 in FIG.

Therefore, in this state, the output signal of the first deflection signal generation circuit 17 is fixed, and then the second deflection signal generation circuit 18 is used to perform the second-stage axis alignment.

That is, the wobbling of the first focusing lens 6 is stopped, and the output signal from the second deflection signal generating circuit 18 is adjusted while observing the CRT with the objective lens 7 in the wobbling state. As a result, due to the action of the second distribution circuit 16, the electron beam EB moves to the first position as shown in FIG.
While maintaining the state of passing through the center O of the focusing lens 6 of, that is, substantially satisfying the relationship of the formula (2),
The deflection angles θ ₁ and θ ₂ by the second deflection coils 4 and 5 are changed. When observing the CRT while performing such adjustment, a state in which the image does not move appears although the objective lens 7 is wobbled. In this state, the electron beam EB passes not only the center O of the focusing lens 6 but also the center O of the objective lens 7 as shown in the electron beam EB5 of FIG. Can be done.

The above-described embodiment is merely one embodiment of the present invention and can be modified and implemented.

For example, the above-described embodiment is an example in which the present invention is applied to an electron beam apparatus equipped with a field emission electron gun, but the present invention can be similarly applied to an ion beam apparatus equipped with a field emission type ion gun. .

EFFECTS OF THE INVENTION In the present invention, the charged particle beam that has passed through the minute aperture can be passed through the center of the first lens.
Since the incident position of the charged particle beam on the second lens can be arbitrarily changed while maintaining the state in which the charged particle beam passes through the center of the first lens, the axes can be easily aligned.

[Brief description of drawings]

FIG. 1 (a) is a diagram for explaining the first-stage axial alignment operation in the apparatus of one embodiment of the present invention, and FIG. 1 (b) is the second-stage axial alignment operation in the apparatus of one embodiment of the present invention. FIG. 2 is a diagram for explaining the operation, and FIG. 2 is a diagram for explaining the operation of the second distribution circuit 16 in FIG. 1: Emitter chip 2: Extraction electrode, 3: Anode 3a: Aperture, 4,5: Deflection coil 6: Focusing lens, 7: Objective lens 8: Sample, 9: Scanning coil 10: Secondary electron detector 11, 12: Amplifiers 13, 14: Adder circuit 15, 16: Distribution circuit 17, 18: Deflection signal generation circuit Z: Optical axis, EB, EB1, EB2, EB3, EB4, E
B5: electron beam R, Q: extension line of electron beam O, O ': lens center θ ₁ , θ ₂ : electron beam deflection angle

Claims (1)

[Claims] 1. A first lens for focusing a charged particle beam from a charged particle beam source that has passed through a minute aperture, and a second lens for focusing the charged particle beam focused by the first lens.
Lens, first and second deflection signal generation means for generating a deflection signal, and first and second deflection means for axis alignment arranged between the minute aperture and the first lens. , A is a distance between the charged particle beam source and the first deflecting means, b is a distance between the first and second deflecting means, and a distance between the second deflecting means and the first lens. c, when the deflection angles by the first and second deflecting means are θ ₁ and θ ₂ , the signal from the first deflecting signal generating means is θ ₁ / θ ₂ = (a +
b) / a, the first distribution means for converting into two signals based on the relationship and the signal from the second deflection signal generation means have a relationship of θ ₁ / θ ₂ = c / (b + c). Second dividing means for converting into two signals based on the above, one of the two signals from the first dividing means and one of the two signals from the second dividing means are added, and the addition is performed. A means for supplying a signal to the first deflection means, the other signal from the first distribution means and the other signal from the second distribution means are added, and the added signal is added to the second signal. Aligning device in a charged particle beam device, comprising: