JPH0520856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a surface analysis device using PELS (proton energy loss spectrum analysis).

[Background technology]

FIG. 4 is a schematic plan view showing a conventional surface analysis device using PELS, and a similar device is disclosed in, for example, Japanese Patent Laid-Open No. 151958/1983. That is, an ion beam, such as a proton beam, extracted from the ion source 2 is accelerated by an acceleration tube 6, and the accelerated ion beam is focused by a focusing system 8 as required. Thereafter, beam deflection (mass analysis) is performed using a mass analysis magnet 10. After deflection, the sample (not shown) in the scattering chamber 14 is irradiated with the ion beam. In order to irradiate a part of the sample with the ion beam, a 1 mm diameter slit (not shown) is placed on the beam line before entering the scattering chamber 14. is installed. Note that when He or the like is used as the ion beam, there is a possibility that divalent ions are scattered in addition to singly charged ions, which complicates the measurement, so in reality, protons, which only have singly charged ions, are used. In the figure, 12 is a vacuum pump.

The ion beam irradiated onto the sample is scattered by several layers on the sample surface. This scattered beam generally has various energies, and in order to suppress the energy width, a slit (not shown) of about 2 mm diameter is installed on the beam line after scattering. The scattered beam passing through this slit is then transferred to the deceleration tube 18.
After decelerating it, the measuring device 20 measures its energy spectrum. The potential after deceleration in this case is determined as follows.

That is, with reference also to FIG. 5, if the extraction voltage of the ion beam in the ion source 2 is Ve, the acceleration voltage Va in the acceleration tube 6, and the scattering chamber 14 is assumed to be grounded, its potential is 0. , the total accelerating voltage Vt of the ion beam is Vt=Va+Ve. If the potential Vd, which is lowered by the offset voltage Vo from this voltage, is the potential of the high potential table 19 on which the measuring device 20 is installed (that is, if the deceleration potential at the deceleration tube 18 is (Va - Vo)), then the deceleration is The energy of the scattered beam entering the measuring instrument 20 is q
×Vo [eV] (if energy loss upon collision with the sample is ignored). Here q is an ion,
For example, it is the unit charge of a proton.

In this case, the acceleration energy of the ion beam irradiated to the sample is preferably high, for example, about 100 KeV, in order to reduce the probability of neutralization of the ion beam on the sample surface. In order to be able to measure the energy spectrum with precision, it is preferable to reduce the speed to a lower value, for example, to about 1 KeV or less.

By measuring the energy spectrum of the scattered beam decelerated as described above, physical properties such as the crystal structure of the surface of a solid sample can be investigated.
For example, referring to FIG. 6, if the energy loss of the ion beam 3 caused by the collision between the ion beam 3 and the sample 15 is ΔE, and the energy of the scattered beam 4 incident on the measuring instrument 20 is E, the following relational expression is obtained. To establish.

ΔE=qVo−E ……(1) Because the energy E of the scattered beam 4 incident on the measuring device 20 is expressed as follows, E=qVt−ΔE−q(Vt−Vo) ……(2) This is because by transforming this, equation (1) can be obtained.

In addition, here, as the measuring device 20, for example, an energy analyzer 21 and a detector 22 such as a channeltron are used.
is used, and if the voltage applied to the energy analyzer 21 is V _ESA , the above energy E can also be expressed as follows. Here k is a constant.

E=kqV _ESA (3) Therefore, as can be seen from equations (1) and (3), the energy loss spectrum can be obtained by changing the offset voltage Vo or the voltage V _ESA . For example, the atoms in the first layer on the sample surface and the atoms in the second layer
Comparing the beams scattered by atoms in the second layer, etc., the scattered beam from the second layer has a longer distance in the lattice, so the energy loss ΔE becomes larger.
For example, a spectrum as shown in FIG. 7 is obtained.

In FIG. 4, 1 is a high potential table of potential Va on which the ion source 2 etc. are placed, 5 is an extraction power source for supplying extraction voltage Ve, 7 is an acceleration power source for supplying acceleration voltage Va, and 24 is an offset voltage. An offset power supply 26 for supplying Vo connects the output power supply 5 etc. and the offset power supply 24 to obtain the voltage Vt, and also supplies power to the acceleration power supply 7 and the offset power supply 24 from the same power supply to eliminate mutual voltage fluctuations (ripples). This is a high voltage cable for canceling.

However, in the conventional device as shown in Fig. 4,
The confusion angle θ (see Figure 6) can only be set to about 10 degrees, which results in a broad spectrum and poor analysis accuracy.When measuring the origin of energy loss in the measuring device 20 or the energy resolution of the device, There is a problem in that it is necessary to reconnect the beam transport lines after the scattering chamber 14 so that the scattering angle θ becomes 0 degrees, but this work is not easy. A surface analysis device as shown in the figure has been separately proposed by the same applicant.

Mainly explaining the differences from the device shown in FIG. 4, this device has a generally T-shaped deflection magnet (electromagnet) 30 provided on the front side of the scattering chamber 14.
The trajectories of the ion beam 3 irradiating the sample 15 and the scattered beam 4 from the sample 15 are separated to the left and right, thereby enabling measurement at a scattering angle θ of 180 degrees.

In that case, the scattered beam 4 passing through the deflection magnet 30 is affected by the energy loss ΔE in the sample 15 due to the difference in the degree of energy loss ΔE in the sample 15, for example, 4a in FIG.
(its energy loss ΔE=0) and 4b (its energy loss ΔE≠0) are dispersed by the deflecting magnet 30, so that the scattered beam at the deflecting magnet 30 is on the path of the scattered beam 4. A deflection magnet (electromagnet) 32 having a structure almost symmetrical to the path side of the deceleration tube 1 is provided to combine the separated scattered beams 4a and 4b into one orbit again.
8. By this,
Differences in the efficiency of incidence on the measuring device 20 due to differences in energy loss ΔE are eliminated, making it possible to accurately measure a wide energy range.

FIG. 9 is a diagram showing the change in the optimized solid angle with respect to the change in the scattering angle, and the vertical axis is on a logarithmic scale. As can be seen from this figure, when the scattering angle θ is set to 180 degrees, the optimized solid angle ΔΩ [str], that is, the beam detection efficiency, is several hundred times ( (if sample 15 is gold) to several thousand times (if sample 15 is silicon). Moreover, when the scattering angle θ is 180 degrees, the scattered beam 4 is not affected by disturbances on the surface of the sample 15. In other words, the scattered beam 4 is affected only by the atoms on the sample surface, resulting in a sharp spectrum. can be obtained, thereby improving the analysis accuracy.

On the other hand, when measuring the origin of energy loss mentioned above or the energy resolution of the device, the deflection magnet 3
0, in particular, in this example, by simply turning off the excitation of the deflection magnet 30, the ion beam 3 incident on the deflection magnet 30 is directly affected by the energy loss ΔE as shown by A in FIG.
It can be emitted on the same trajectory as the scattered beam 4a with =0, and there is no need to change the arrangement of the device as in the conventional case, and measurements such as energy resolution can be carried out extremely easily.

[Purpose of the invention]

However, even in the apparatus shown in FIG. 8, there is still room for improvement in the following points, and it is an object of the present invention to provide a surface analysis apparatus that is further improved in these points.

The classification of potentials in this device is as shown in Figure 5, and the potentials Vt, Va, and Vd are Vt≠Va≠
Vd, and therefore there are three high potential parts corresponding to these potentials. Therefore, a large space is required due to the structure of the device and the insulation distance.

The above-mentioned high voltage cable 26 is required, and since the ion source 2 side and the measuring device 20 side are far apart from each other, the high voltage cable 26 has to be wired long, and the power supply may be affected by noise entering the cable. There is a concern that the above-mentioned ripple cancellation may be incomplete and the energy resolution of the device may be reduced.

[Means to achieve the purpose]

The surface analysis device of the present invention includes a first deflection magnet that deflects both the ion beam and the scattered beam from the sample onto the path of the ion beam before irradiating the sample,
and a second deflecting magnet is provided on the path of the scattered beam passing through the first deflecting magnet, the deflecting magnet deflecting the scattered beam in the same direction as the first deflecting magnet and causing the scattered beam to enter the measuring instrument; The present invention is characterized in that an acceleration/deceleration tube is provided between the deflection magnet and the sample to accelerate the ion beam irradiated onto the sample and to decelerate the scattered beam from the sample.

[Effect]

The actions of the first deflection magnet and the second deflection magnet are similar to those of the previous example. On the other hand, a common acceleration/deceleration tube provided between the first deflection magnet and the sample accelerates the ion beam irradiating the sample and decelerates the scattered beam from the sample. In this way, the functions of the accelerating tube and decelerating tube of the prior example can be performed by one accelerating/decelerating tube, so that the potential can be simplified accordingly.

〔Example〕

FIG. 1 is a schematic plan view showing a surface analysis device according to an embodiment of the present invention. Parts that are the same as or correspond to those of the device shown in FIG. 8 are given the same reference numerals, and the differences therefrom will be mainly explained below.

In this embodiment, the ion beam 3 to be irradiated onto the sample 15 is accelerated between the first deflection magnet 30 and the sample 15 in the scattering chamber 14 instead of the acceleration tube 6 and deceleration tube 18 as described above. At the same time, an acceleration/deceleration tube 36 is provided to decelerate the scattered beam 4 from the sample 15. 37 is an acceleration/deceleration power supply for supplying acceleration/deceleration voltage Vad thereto.

Ion beam 3 extracted from ion source 2
is deflected by, for example, 90 degrees in the deflection magnet 30,
The scattering chamber 1 is accelerated in the acceleration/deceleration tube 36.
The sample 15, which is set within 4 so that the scattering angle θ is, for example, 180 degrees is irradiated. and sample 15
The scattered beam 4 enters the acceleration/deceleration tube 36 in the opposite direction to the ion beam 3 and is decelerated there, is deflected by, for example, 90 degrees to the opposite side from the ion beam 3 at the deflection magnet 30, and is again deflected at the deflection magnet 32. For example, the beam is deflected by 90 degrees and enters the measuring device 20.

In that case, the potential division in this device is
As shown in the figure, the sample 15 is at a potential of 0, the deflection magnets 30, 32 and the measuring device 20 are at a location where the acceleration/deceleration voltage Vad has increased, and the acceleration/deceleration tube 36 is located between the two potentials. , and further the potential Vad and the potential
There is an ion source 2 between Vt (=Vad+Ve).

Therefore, the energy E of the scattered beam 4 incident on the measuring device 20 is expressed as follows based on the same idea as the above equation (2), and E>0 is the operating condition of this device.

E=qVt−ΔE−qVad=qVe−ΔE ……(4) This equation (4) corresponds to the above equation (1), so in this device, the energy loss spectrum depends on the extraction voltage Ve. Alternatively, it can be determined by changing the voltage V _ESA that ignites the energy analyzer 21 described above.

The features of this device compared to the prior example shown in FIG. 8 are listed below.

Since the potential is simplified and there are two high potential parts, the potential Vt part and the potential Vad part, the electrical circuit becomes simple and the high voltage cable 26 in the previous example is not required. As a result, troubles such as power supply noise can be reduced and performance deterioration such as energy resolution of the device can be prevented.

Since there are two high potential parts, less space is required for insulation, etc., and the device can therefore be made more compact. Moreover, since it becomes possible to install the equipment surrounding the ion source 2, the measuring device 20, and the deflection magnets 30 and 32 on one high-potential cable 38, the apparatus can be made more compact in this respect as well.

The offset power supply 24 in the previous example is not required, and only one acceleration/deceleration tube 36 is required instead of the acceleration tube 6 and deceleration tube 18, so the number of parts is reduced and the cost of the device can be reduced.

Incidentally, to explain in detail the relationship between the deflection magnets 30 and 32, which is the _same in the apparatus shown in FIG _. Loss ΔE
When the radius of curvature of the scattered beam 4a with = 0 is r ₁ , the deflection angle at the deflection magnet 32 is φ ₂ , the angle of incidence is α ₂ , and the radius of curvature of the scattered beam 4a is r ₂ , φ ₁ =φ ₂ , α ₁ =α ₂ =(φ ₁ /2)−90 [degrees] and r ₁ =r ₂ (5). More specifically, in this example, φ ₁ =φ ₂ =90°, α ₁ =α ₂ =−45° (α ₁ and α ₂ are generally expressed as negative values in the illustrated case. )
It is said that

When the above formula (5) is satisfied, the scattered beams 4a and 4b separated from one orbit in the deflecting magnet 30 become parallel to each other when they exit from the deflecting magnet 30, and It is deflected in exactly the opposite manner to that at 30 and leaves the deflection magnet 32 in a single orbit again. As a result, the scattered beam 4, regardless of the difference in its energy loss ΔE,
Because it enters the measuring device 20 with one central orbit, there is no difference in the efficiency of incidence into the measuring device 20 due to differences in energy loss ΔE, and it is possible to accurately measure a wide range of energy losses ΔE from large to small. Become.

Furthermore, if the measuring device 20 is configured as shown in FIG. 3, for example, it is possible to measure energy over a wide range at once. That is, in this example, the measuring device 20 is equipped with a parallel plate analyzer 41, a microchannel plate 42, a position detector 43, etc., and the scattered beam 4 is transmitted to the microchannel plate 42 depending on the difference in energy, that is, energy loss ΔE. The incident position is detected by a position detector 43 and a position calculator 44, and the count at each position is displayed on a multi-channel analyzer 45. Therefore, according to such a measuring device 20,
By simply tilting the sample 15 (the angle varies depending on the sample and which layer of atoms scatters the beam), the amount of scattered beams from each layer on the surface can be measured all at once, as described above. For example, a spectrum as shown in FIG. 7 can be efficiently obtained without changing the extraction voltage Ve or the voltage _VESA applied to the energy analyzer 21. Therefore, there is an advantage that the influence of state changes during spectrum analysis can be eliminated.

〔Effect of the invention〕

As described above, this invention is a further improvement over the previous device shown in FIG. 8, and can reduce power supply troubles and prevent deterioration in device performance, as well as make the device more compact and cost-effective. An additional effect is obtained in that it is possible to realize the

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing a surface analysis device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the potential distribution of the device of FIG. 1. Figure 3 shows
It is a schematic diagram showing an example of a measuring device. FIG. 4 is a schematic plan view showing a conventional surface analysis device. Fifth
The figure is a diagram showing the potential divisions of the device of FIG. 4. FIG. 6 is a diagram for explaining the principle of the apparatus shown in FIG. 4. FIG. 7 is a diagram for explaining a spectrum obtained by the apparatus shown in FIG. 4.
FIG. 8 is a schematic plan view showing a surface analysis device prior to this invention. FIG. 9 is a diagram showing a change in the optimized solid angle with respect to a change in the scattering angle. 2...Ion source, 3...Ion beam, 4,4
a, 4b...Scattered beam, 15...Sample, 20...
... Measuring instrument, 30 ... First deflection magnet, 32 ... Second deflection magnet, 36 ... Acceleration/deceleration tube.

Claims (1)

[Claims] 1 Analyze the physical properties of the sample surface by accelerating the ion beam and irradiating it onto the sample, and measuring the energy of the resulting scattered beam from several layers on the sample surface with a measuring instrument after decelerating the beam. In an apparatus configured to A second deflection magnet is provided on the path of the scattering beam, which deflects the scattered beam in the same direction as the first deflection magnet and causes it to enter the measuring instrument, and is further provided between the first deflection magnet and the sample to irradiate the sample. A surface analysis device comprising an acceleration/deceleration tube that accelerates an ion beam and decelerates a scattered beam from a sample.