JP2653056B2 - Surface analysis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field The present invention relates to a surface analysis apparatus capable of accurately knowing the position of a proton beam immediately before irradiating a sample and correlating the position with the position of the sample.

The surface analyzer accelerates the proton beam, strikes the sample in an ultra-high vacuum, decelerates the proton beam scattered by atoms on the sample surface, and obtains the distribution of scattering loss ΔE. It is a device that detects the atomic distribution, interatomic reaction, etc.

Acceleration U, protons of mass m collide with atoms of mass M, Θ
, The velocity V of the proton after scattering
Is Γ = M / m (2) Since Γ indicates how many times the atomic mass M corresponds to the proton mass m, it is substantially equal to the common number.

If the proton kinetic energy before scattering is E ₀ and the kinetic energy after scattering is E ₁ , these ratios K (は) are It means that. When the energy loss and ΔE (Θ), which is because minus the E ₁ from _{E 0 ΔE (Θ) = {} 1-K (Θ)} E 0 (4).

The scattering angle Θ is a value fixed by the apparatus. Θ =
It may be 0 (low scattering angle).

However, it is also possible to set に す る = 180 °. In this case, the energy loss ΔE (Θ) becomes the largest.

If Θ = 180 °, omit the display of variable の た め for simplicity. Becomes

 Equation (6) means the following.

The smaller the mass of the atom that scatters the protons, the greater the proton scattering energy loss ΔE. The larger the mass of the atom, the smaller the proton scattering energy loss ΔE. If the energy loss distribution f (ΔE) is determined, this gives the distribution of atoms on the sample surface.

Since the atomic composition and composition of the sample surface are examined by obtaining the energy loss distribution of protons, Proton Ene
rgy Loss Spectroscopy (PELS).

(B) Conventional technology The PELS device is composed of an ion source, magnet, accelerating tube, ultra-high vacuum chamber, decelerating tube, analyzer and the like. Since all of these spaces are kept at a high vacuum, a vacuum exhaust device is provided.

Further, these vacuum chambers have different degrees of vacuum, and are separated by a plate having a small gap. The plate must maintain the vacuum and allow the proton beam to pass. This plate is called slit.

The proton beam is a thin beam, but it is not visible light and therefore invisible to the naked eye.

In the ultra-high vacuum chamber, a sample is mounted on a holder.
The holder can move in three directions xyz and rotate around three axes.

The three-dimensional position and rotation angle of the holder can be freely set from outside.

The proton beam is applied to the sample attached to the holder. But,
Since the proton beam is not visible, it is not actually known whether the beam hits the sample or the holder.

The constituent elements are different between the sample and the holder. Therefore, if the loss spectrum f (ΔE) is measured, it is clear whether the sample is hit by a proton, is a sample, or is a holder. However, this has to be done once when the PELS measurement is performed. This is a time-consuming determination method.

Even if it is known that the sample is hit, it is not clear which part of the sample is hit. For example, when PELS measurement is performed on a sample whose atomic composition is not uniform,
Where on the sample surface is the proton beam striking? It is not very meaningful if you do not know that.

For example, in the case of CO ₂ laser light invisible to the eye, it is matched light of Yotsute He-Ne laser to the half mirror, to visualize the CO ₂ laser beam, the fact that is carried out.

In the case of a proton beam, such a method cannot be used. Because protons are objects, they cannot be reflected by a half mirror.

(C) Purpose It is an object of the present invention to provide a surface analysis apparatus which can determine the exact position of a proton beam immediately before being irradiated on a sample and can know which point of the sample the proton beam hits. It is.

(D) Configuration A two-dimensional position detector is provided immediately before the sample.

When a proton beam is incident on a two-dimensional position detector, its position can be determined from its output. By associating the movement of the two-dimensional position detector in the XY direction with the movement of the sample stage in the XY direction, the proton beam position in the sample plane can be known.

A position detector is an arrangement of a number of microchannels. A one-dimensional array of micro-channels is called a one-dimensional position detector. One that is two-dimensional is called a two-dimensional position detector.

The microchannel is a cell having a small area, but an electrode is provided in the depth direction to apply a voltage. When a proton hits the electrode, many secondary electrons are generated. This is accelerated and hits another electrode. More secondary electrons are emitted.
Thus, the incidence of one proton causes the emission of 10 ⁹ to 10 ¹⁰ secondary electrons. Then, 10 ² -1
It is about ³ pC. This is a detectable charge. Thus, the number of protons incident can be counted. Because it is two-dimensional, you can also see where the protons entered.

Since the set position of the two-dimensional position detector is known and the beam position in the plane of the two-dimensional position detector is known, the proton beam position is known.

 Hereinafter, description will be made with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an example of a surface analysis device according to the present invention.

It comprises an ion source 1, a magnet 2, an acceleration / deceleration tube 3, an ultrahigh vacuum chamber 8, a position detector 5, and the like. All of these are in a high vacuum.

The ion source 1 is a device that generates proton ions. Hydrogen gas is introduced from a hydrogen cylinder. This is a hot cathode,
It is ionized by the action of a grid electrode, an extraction electrode, and the like, and is extracted outside at an extraction voltage Vex.

The ion source 1 is evacuated by the evacuation device 31.
Proton ions exiting the slit 21, travels with the energy E _e.

E _e = qVex (7). q is the proton charge.

The proton ions enter the magnet 2, where they fly in an arc trajectory. Further, the light enters the acceleration / deceleration pipe 3 through the collimator 6 and the slit 22. These spaces are maintained in a vacuum by vacuum pumping devices 33 and 34.

When the vehicle passes through the acceleration / deceleration tube 3 from left to right, it is accelerated. The accelerating voltage is Vacc.

The energy E ₀ after acceleration is E ₀ = qVex + qVacc (8). After passing through a Q lens (not shown) and the like, it enters the ultrahigh vacuum chamber 8.

The ultra-high vacuum chamber 8 is operated by the evacuation device 35 to
It is drawn to an ultra-high vacuum of ^-11 to 10 ^-10 Torr.

 The sample 4 is supported by the holder 10.

The holder 10 can be translated in three directions XYZ and rotated about three axes by a manipulator 7.

In the present invention, a position detector 11 is further provided in front of the sample.
Is provided. The position detector 11 detects the A position immediately before the sample,
It is possible to take the B position avoiding the proton beam. The drive mechanism is not shown for simplicity.

 At the position A, the incident position Λ of the proton beam is checked.

When a proton beam is applied to the sample 4 to perform PELS measurement, the position detector 11 is retracted to the position B.

As shown in FIG. 2, the position detector 11 has many microchannels two-dimensionally. By assigning the number x in the horizontal direction and the number y in the vertical direction, the microchannels can be numbered.

When the proton beam is incident, its incident position Λ (x, y)
Is found from the output of the position detector.

In practice, the proton beam is divergent and does not impinge on just one microchannel. Enter some microchannels. Then, the number of protons incident C
(X, y) can be obtained as a function of x and y. Third
A beam profile having a peak as shown in the figure is obtained. The position of this peak is the center の of the proton beam.

 Thus, the center of the proton beam is known.

In order to correctly position the sample, the amount of movement of the manipulator 7 can be determined relative to the two-dimensional detector 11 at the position A.

When irradiating the sample 4 with a proton beam, the position detector 11 is retracted to the position B.

The proton beam scattered by the sample loses energy ΔE due to scattering. Of these, only those having a scattering angle of Θ = 180 ° pass through the acceleration / deceleration tube 3 in the opposite direction. The deceleration voltage is
It is equal to Vacc, proton energy E _a of the after deceleration is _{E a = qVex-ΔE (9} ).

This enters the analyzer consisting of the magnet 2 and the position detector 5. This position detector 5 is one-dimensional.

The analyzer calculates the proton energy distribution f (E _a ) or f
(ΔE) is measured.

The beam is bent by the force of a magnetic or electric field. The higher the energy, the harder it is to bend. In other words, fly farther. The range L is measured by the position detector 5. From L projected range, it is possible to know the proton kinetic energy E _a. In other words, the position x of the micro-channel, and the energy E _a one-to-one correspondence.

By accumulating the number of protons entering each microchannel, the energy distribution f (E _a ) of the scattered protons can be obtained.

The analyzer may use a magnetic field as in this example, or may use an electric field. In this example, the range L is Given by

The present invention can be applied to the case where the scattering angle で な い is not 180 °. In this case, the path of the scattered beam is different from the path of the incident beam. The deceleration pipe and the acceleration pipe are different devices.

(E) Function The position detector 11 is set to the position A.

 A proton beam is applied to the position detector 11.

The proton beam enters one of the position detectors 11. Therefore, current flows through those microchannels. The amount of current flowing in which microchannel is transmitted by the lead 14 and the external position calculation circuit 12. The lead 14 passes through a feedthrough 15 so as not to damage the vacuum.

The position calculation circuit 12 calculates from which ratio of the amount of current flowing through the plurality of signal lines of the lead 14 to which microchannel the proton has entered. The microchannel can be specified by x and y coordinates.

The position of the proton beam is measured at an appropriate time, and the amount of proton beam incident for each micro-channel of the two-dimensional position detector is displayed on the display 13 by shading or color. Then, the incident position of the proton beam can be intuitively understood. Also find the center position Λ.

Since the position A of the position detector 11 is determined in advance, when the center position 決 ま る is determined, the position of the proton beam is absolutely determined in the ultra-high vacuum chamber.

The displacement of the manipulator 7 in the XY direction is set based on the position of an appropriate portion of the position detector 11 placed at the position A.

Since the proton beam position has been determined, the manipulator 7 is operated to move the sample 4 so that the proton beam hits an appropriate position.

If the proton ion beam is misaligned,
As shown in the figure, the proton beam may hit the boundary between the sample 4 and the holder 10. Further, there is also a case where only the holder 10 is hit.

In the conventional method, since the exact position of the proton beam is not known, such a deviation of the proton beam is not immediately known. It may happen that the surface analysis of the holder is performed.

 The device of the present invention can prevent such a situation.

In some cases, the sample is not uniform and is composed of a plurality of films A, B, C,. In this case, the scattered proton energy spectra from the individual films must be examined. The present invention is best suited for such a case. Since the exact position of the proton beam is known, the proton beam can be applied to any position on any film.

Further, there is a case where it is desired to check the in-plane uniformity even for a sample having a uniform surface. As shown in FIG. In such a case, since the beam positions are known, a plurality of sample points on the sample surface can be correctly identified.

(F) Effect Since the position of the proton beam is accurately known, the proton beam can be correctly applied to the sample.

When the sample is made of a plurality of different films, it is possible to measure the surface state of any film at any position.

For a sample with a uniform surface and multiple sample points
If you want to perform PELS measurements, you can accurately determine the beam incident point.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a surface analysis device of the present invention. FIG. 2 is a front view of a two-dimensional position detector. FIG. 3 is a perspective view showing a proton beam profile obtained by a two-dimensional position detector. FIG. 4 is a diagram showing a state where a proton beam is correctly hitting a sample. FIG. 5 is a diagram showing a state in which a proton beam hits a boundary between a sample and a holder surface. FIG. 6 is a diagram of a sample having a plurality of films on the surface. FIG. 7 is a view for explaining a measurement method in which a proton beam is applied to a plurality of sample points on a sample surface. DESCRIPTION OF SYMBOLS 1 ... Ion source 2 ... Magnet 3 ... Acceleration / deceleration tube 4 ... Sample 5 ... Position detector 6 ... Collimator 7 ... Manipulator 8 ... Ultra high vacuum chamber 10 ... Holder 11 ... Position detector 12 Position calculation circuit 13 Display 14 Lead 15 Feedthrough 21-23 Slit 31-36 Vacuum pump

Claims (1)

(57) [Claims] An ion source maintained in a vacuum for generating a proton beam, a magnet for bending a trajectory of the proton beam emitted from the ion source in a vacuum, and an accelerating tube for accelerating the proton beam in a vacuum. An ultra-high vacuum chamber for holding a sample in an ultra-high vacuum, a holder for supporting the sample in the ultra-high vacuum chamber, a manipulator for operating the holder, and an ultra-high vacuum chamber. A two-dimensional position detector which can move to a position A for intercepting the incident proton beam and a position B for evacuation, a position calculation circuit for calculating the position of the incident proton beam by the output of the position detector, and a position calculation circuit A display that displays the amount of proton beam incident for each microchannel at each detection position of the position detector based on the output from the detector, a deceleration tube that decelerates the protons scattered by the sample in a vacuum, and a deceleration tube Consists of a analyzer for measuring the energy E _a child, the manipulator is configured as a reference the A position of the position detector, surface analysis, characterized in that the amount of movement is constructed as can be seen relatively apparatus.