KR960000808B1 - Secondary ion mass analyzer - Google Patents

Abstract

The secondary ion mass spectrometry including a first ion generator, a first ion filter, a first ion beam controller, a second ion generator, a spectrometer, and a detector is characterized in that a first ion emission direction regulating unit is arranged in the first ion beam regulating unit and installed in front of a lens right before a sample.

Description

Secondary ion mass spectrometer

1 is a cross-sectional view showing a primary ion control unit of the secondary ion mass spectrometer according to the prior art,

2 is a cross-sectional view showing a primary ion control unit of the secondary ion mass spectrometer according to the present invention;

3 is a schematic cross-sectional view of a secondary ion mass spectrometer according to the present invention,

4 is a conceptual diagram showing the basic operating principle of the primary ion beam in accordance with the formation of a dual electromagnetic magnetic field,

5 is a characteristic diagram showing the relationship between the depth of the impurity ion implantation sample and the ion concentration distribution.

Industrial use

The present invention relates to Secondary Ion Mass Spectrometry (SIMS), in particular attaching a double electromagnet that can change the size and direction of the magnetic field in the primary ion (Column) device Therefore, the present invention relates to a secondary ion mass spectrometer capable of adjusting an incident angle of an incident primary ion beam to a sample.

Conventional Techniques and Problems

Secondary ion mass spectrometers have a unique position in trace element depth profiling, especially with the highest detection snsitivity and depth resolution. .

General techniques for such secondary ion mass spectrometry have already been known in the "Method of Surface Analysis", 1989, Cambridge University press, p231.

The detection limit of the secondary ion mass spectrometer (SIMS) can be precisely analyzed at the ppm-ppb level over the entire range of the periodic table, but it is difficult to apply to the analysis of the main matrix of the sample. This is because the SIMS detection range is adapted to the trace amount analysis, so it is difficult to see the change state when the number of elements is large, and the ionization intensity is affected by the change in the composition ratio of the material, thereby affecting the element detection intensity.

In the case of trace impurities, the SIMS has a large change in the ionization rate of the element due to the change of the matrix element. Therefore, in the case of two or more multilayered membrane samples, the impurity concentration measurement value is different for each layer unlike the actual distribution. do. This phenomenon makes it difficult to quantify the impurity concentration, there was a problem that a standard sample must be present for quantification.

However, it is impossible to fabricate all the standard samples under the same conditions for each thin film to be analyzed. As such, a sputtered neutral mass spectrometer was used to compensate for the disadvantages of the secondary ion mass spectrometer (SIMS). SNMS) has been developed, and there is a method using an electron gun or a laser, and recently, it can be applied to trace impurity element analysis without adding any equipment to SIMS, and to improve the quantification effect. CsX ⁺ was developed to import.

In MAS composition ratio analysis, SIMS analysis includes dynamic method to see impurity distribution by depth, imaging method to map impurity distribution, and surface impurity types. There is a static method. However, these analytical methods have the disadvantage of not knowing the distribution ratio of each element due to excellent detection sensitivity.

On the other hand, CsX ⁺ SNMS can be applied to the analysis of the principal component composition, which is impossible for SIMS, and the detection limit of 10 ppm and the dynamic range through impurity analysis can be obtained up to 10 ⁴ .

However, the secondary ion mass spectrometer (SIMS) such as CsX ⁺ SNMS has a fixed angle with respect to the incident beam of the sample, and thus the incident angle of the incident ion beam becomes constant, so that the sample is inclined at a predetermined angle so that the sample is flat when the surface is etched. It will not be sharpened but will be sawed in a jagged shape. Accordingly, there was a problem that accurate analysis was difficult due to the change of secondary ion yield due to the formation of a tooth-shaped non-uniform surface in the concentration depth profile analysis of the impurity ion implantation sample.

This conventional secondary ion mass spectrometer will be described in detail with reference to the drawings.

1 is a cross-sectional view showing a primary ion beam control unit A according to a conventional secondary ion mass spectrometer.

As shown in FIG. 1, the conventional primary ion beam controller includes primary ions 1 accelerated from the primary ion generator, beam path limiters 2 and 4, and beam blocking slits. (Slit) (6), Faradaycup (12) for measuring the ion current, and Stigma tor (7), Double deflector (8), three electromagnetic lenses (Lens) (3, 5, 9), which is connected to the sample 11 and the secondary ion extracting section 10 as shown in FIG.

The operation principle of the conventional secondary ion generating device is described below with reference to FIGS. 1 and 3.

Primary ions produced by the cesium ion generator 21 or the oxygen ion generator 22 are accelerated to a constant energy and enter the primary ion control unit A through the primary ion filter 23. At this time, only the ion beam 1 passing through the center of the beam path restrictor 2 is connected to the first electromagnetic lens 3.

Then, once more, the beam focused past the beam path restrictor 4 and the electromagnetic lens 5 is corrected by the stirrer 7 and scanned in the double deflector 8. At this time, the Faraday cup 12 can be used to measure the ion beam current.

The scanned beam is connected to the electromagnetic lens 9 once again before entering the sample 11 and passes through the secondary ion extracting section 10 to reach the sample.

At this time, the angle of the incident beam (1) and the surface of the sample 11 is constant because the angle of the incident beam is fixed, and the sample 11 and the secondary ion extraction to accelerate the secondary ions generated in the sample A voltage of 4.5 kV is applied between the units 10.

However, the secondary ion mass spectrometer needs to maintain a constant distance between the sample surface and the secondary ion extractor 10 due to the high voltage for secondary ion acceleration, and thus cannot change the angle of the sample with respect to the incident ion. The incident angle of the incident ion beam 1 becomes constant.

In this case, since the sample is inclined at a certain angle, the sample is not flattened in the case of etching the sample surface, but it is sharpened in the form of a sawtooth. Changes in ion yield have made flaws difficult to accurately analyze.

As described above, in the mass spectrometer according to the present invention, when the secondary ion path is fixed and the beam path angle with respect to the sample is also changed at right angles, the incident angle of the primary ion incident on the sample can be changed only by the incident beam itself. By attaching a double electromagnet that can change the size and direction of the magnetic field to the primary ion control unit, it becomes possible to maintain the original angle when the magnetic field is not applied to the electromagnet. By changing the angle of incidence, it can be applied to an analytical device that can not tilt the sample, and it is possible to flatten the sawtooth non-uniform surface generated during etching of the sample surface.

In addition, in the depth analysis of a conventional impurity ion implantation sample, the number of secondary ions is increased when the angle of the incident primary ions and the valleys formed in the sawtooth-shaped bones generated by the cutting of the sample approaches the right angle. As a result, an ion beam concentration difference occurred, and a change in concentration distribution appeared. On the other hand, in the present invention, the secondary ion mass spectrometer can improve the concentration distribution analysis accuracy by not changing the secondary ion generation amount by not forming a tooth-shaped bone by injecting the incident primary ion beam at the optimum etching angle for each sample. Can be provided.

In order to solve the above problems, the present invention adds an electromagnet capable of changing the size and direction of the magnetic field to the incident primary ion control unit, and thus the secondary ion mass capable of changing the incident angle of the incident primary ion to the sample. We want to provide an analyzer.

Composition of the Invention

The present invention for achieving the above object is the primary ion generating unit, the primary ion filter, the primary ion beam control unit beam path limiter, electromagnetic lens, beam blocking slit, stigmatizer, double deflector, Faraday Cup and 2 A secondary ion mass spectrometer including a secondary ion generator (sample chamber), a spectrometer, and a detector, wherein two electromagnetic stones are provided between an electromagnetic lens and a double deflector positioned above the secondary ion generator. do.

Action

According to the present invention, the angle of incidence of the incident primary ions can be adjusted. Thus, when scanning the incident beam near 90 ° C. during the SIMS analysis of the impurity ion implantation sample, the jagged non-uniform surface generated during the etching of the sample surface is reduced. In addition to accurate concentration analysis of secondary ion generation, the first ion beam is incident at the optimal etching angle for each sample, which is closer to the horizontal angle of the sample surface, thereby improving the accuracy of analysis by adjusting the sample etching rate. .

Example

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view showing a primary ion beam control unit of the secondary ion mass spectrometer according to the present invention, and FIG. 3 is a schematic cross-sectional view of a secondary ion mass spectrometer including the primary ion beam control unit according to the present invention.

As shown in FIG. 3, the secondary ion mass spectrometer according to the present invention has approximately a primary ion generator, a primary ion filter, a primary ion beam control unit A, a secondary ion generator (sample chamber), and a spectrometer. (B), it can be divided into a detection system. Here, the spectrometer (B), which is the core for mass spectrometry, consists of an electrostatic energy spectrometer (27) capable of electrical instantaneous switching, a magnetic spectrometer (30) having a bidirectional outlet, and the detection system includes the magnetic spectrometer. It is roughly composed of two mass select slits and two electrostatic spectrometers connected to each outlet of.

The primary ion beam control unit A, which includes the gist of the present invention, is connected to the sample 11 and the secondary ion extracting unit 10 of the secondary ion mass spectrometer, which will be described with reference to FIG. do.

The second cross-sectional view includes accelerated primary ions 1 and beam path limiters (Limitor (2,4), beam blocking slit (6), Faraday cup 12 for measuring ion current). In the basic configuration consisting of a Stigmator (7), a Double Deflector (8), and three Electron Lenses (3, 5, 9), the electromagnetic lens (9) and the Double Deflector (8). ), Two electromagnets 13 and 14 are included between them.

Referring to the basic operation principle of the secondary ion generating device according to the present invention as follows.

Primary ions produced by the cesium ion generator 21 or the oxygen ion generator 22 are accelerated to a constant energy and enter the primary ion control unit A through the primary ion filter 23. At this time, only the ion beam 1 passing through the center of the beam path restrictor 2 is connected to the first electromagnetic lens 3.

The beam that is then focused once more through the beam path restrictor 4 and the electromagnetic lens 5 is straightened by the stigmatizer 7 and scanned in the double deflector 8. At this time, the Faraday cup 12 can be used to measure the ion beam current.

The beam scanned by the double deflector 8 is again adjusted in the incident beam direction by two electromagnets 13 and 14.

First, the principle that the incident beam direction is controlled by the two electromagnets 13 and 14 will be described.

First, consider the case where the charged particles enter the magnetic field. When the charge enters the magnetic field, Fleming's left law The force is applied in the direction perpendicular to both the direction of movement and the magnetic field.

The direction of the ion beam can be adjusted by adjusting the direction of the magnetic field of the electromagnets 13 and 14 shown in FIG. 1 in the direction of entering or exiting perpendicular to the paper, and by changing the size of the magnetic field, the size of the incident angle of the ion beam can be changed. Can be.

The principle of changing the direction of the ion beam and the magnitude of the incident angle will be described with reference to the drawings shown in FIGS. 4A and 4B.

In case of FIG. 4 (a), the direction in which the magnetic field enters perpendicular to the paper ( (B) shows a case in which the magnetic field is perpendicular to the paper (⊙). In case of FIG. 4 (a), the charged particles (ions) are oriented. , The force is perpendicular to each of the magnetic field and the direction Direction, the force is perpendicular to each of the directions It is bent in a direction because it is subjected to a force in the direction, and also in the case of Figure 4 (b), that is, the charged particles (ions) even in the direction of the magnetic field perpendicular to the paper Direction, the force is also perpendicular to the magnetic field and the ion Will receive force in the direction. However, in the case of FIGS. 4A and 4B, the directions of the forces acting in opposite directions are different from each other.

Therefore, if the magnetic field is applied to the primary ion direction adjusting electromagnet 13 on the upper side and the primary ion direction adjusting electromagnet 14 on the lower side in opposite directions, for example, the upper electromagnet 13 enters perpendicular to the paper. The charged particles In the case of movement in the direction, the force is applied in a direction perpendicular to each other, so that it is circular in the magnetic field and bent along the a direction.

The magnetic field in the opposite direction to the upper electromagnet 13, i.e., perpendicular to the paper, is applied to the lower electromagnet 14 so that the charged particles are the same. When moving in the direction, the direction of the force is reversed and the direction is bent to a 'as it returns to its original position.

At this time, even if the magnetic field directions of the upper and lower electromagnetic types in the electromagnet are set to the opposite direction, the magnetic field is bent to b 'by b in the same principle (see FIG. 2).

At this time, the electromagnetic SIMS as described above, because the sample must be maintained perpendicular to the secondary ion beam traveling direction because of the secondary ion acceleration voltage, it is not possible to adjust the incident ion angle by tilting the sample. The ion incident angle can only be changed by the incident beam itself.

However, the SIMS according to the present invention can maintain the original angle when the magnetic field is not applied, and can change the incident angle of the ion beam when the magnetic field is applied.

Meanwhile, after the primary ion beam 1 whose incident beam direction is controlled by the two electromagnets is incident, a sputtering phenomenon occurs on the sample surface 11 to generate secondary ions. In order to accelerate the secondary ions, an acceleration voltage of 4.5 kV is applied between the sample 11 and the secondary ion extracting unit 10.

The secondary ions accelerated to the voltage pass through the dynamic transfer 24, the dense optical system 25, and the incident slit 26 to enter the electrolytic decomposer 27 to be decomposed by energy.

Subsequently, it passes through the energy slit 28 and the spectrometer lens 29, and is mass-resolved in an electromagnetizer (magnetic mass spectrometer) 30, and then passes through the slit 31 and the projection lens 32.

The secondary ions passing through the projection lens exit the channel plate 36 and the florescence screen 37 by the electrostatic analyzer 33 to show the secondary ion image, or the electron multiplier 34 or Faraday cup ( Go to 35) and the number of ions (ion current amount) is recorded in the detector.

5 (a) and 5 (b) are characteristic charts showing relative ion concentration distributions according to the depth of impurity ion implantation samples, and FIG. 5 (a) is a jagged bone formed in the sample surface analysis region. 5 (b) shows the conventional ion concentration distribution (solid line) and the ion concentration distribution (dashed line) according to the present invention.

As can be seen from the figure, when the impurity ion implantation sample is deeply analyzed by the method of the prior art, for example, when the angle of the sample is fixed at 60 ° C., sawtooth-shaped bone is formed in the analysis region as shown in FIG. The concentration is changed based on the point A as shown in FIG. 5 (b). This phenomenon occurs because the number of secondary ions generated increases as the angle between the incident primary ions and the site where the bone is formed is closer to the right angle in the sawtooth-shaped bone generated by the cutting of the sample. That is, when the primary ion beam is incident on the floor of the analysis region at 60 ° C. in the sample, the angle between the interface of the thin film (sample) and the incident beam is close to the right angle when considering the tangent component of the thin film. When a curve having the same shape as the region of 1) is formed and the bone is incident at the same angle, the angle formed between the incident beam and the thin film interface is substantially horizontal to the thin film interface, that is, the sample, so that the number of secondary ions is increased. Since the number is increased, a curve having the same shape as that of the AB section 2 is formed. Since the sawtooth is arranged repeatedly, the nonuniform surface of FIG. 5 (b) is repeatedly displayed, and thus the analysis precision cannot be improved.

On the other hand, the analysis using the apparatus to which the present invention is applied does not result in the formation of bones. Therefore, when incident at 90 ° C., the angle at which the thin film (sample) interface and the incident beam are formed is almost horizontal to the interface of the thin film, that is, the sample. Since the number of s increases, the concentration of secondary ions does not occur as in (1) and (2), and the ion concentration is observed in the form of section (2) even in section (1) (dotted form). There is no detection concentration is relatively high compared to the prior art, it is easy to analyze the concentration distribution of the components according to each depth.

Claims (7)

In a secondary ion mass spectrometer including a primary ion generator, a primary ion filter, a primary ion beam controller, a secondary ion generator, a spectrometer, and a detector, a first and a second electronic type in the primary ion beam controller Secondary ion mass spectrometer, characterized in that the primary ion incident direction adjusting means composed of. The secondary ion mass spectrometer of claim 1, wherein the primary ion incident direction adjusting means composed of the first and second electrons is attached in front of the focusing lens in front of the sample. First and second beam path restrictors, which are formed from an ion generator and restrict the paths of the accelerated primary ions, are formed at the bottom of the first and second beam path limiters, respectively, and pass through the center of the beam path limiter in the ion beam. First and second electromagnetic lenses focusing only the beam, a stirrer for correcting the distortion of the focused beam past the beam-blocking slit lens, a double deflector for scanning the beam passing through the stigmat, a Faradaycom for measuring the ion beam current, And first and second electromagnets for adjusting the incident beam direction of the beam scanned by the double deflector, and third electromagnet lenses formed after the first and second electromagnets to focus the incident beam on a sample. Primary ion ratio controller of secondary ion mass spectrometer. 4. The apparatus of claim 3, wherein the first and second electromagnets are configured to be incident of primary ions at their original angle of incidence without applying a magnetic field. The secondary ion mass spectrometer of claim 3, wherein the first and second electromagnets can make the incident angle to the sample surface larger or smaller than when the magnetic field is not applied by changing the direction of the magnetic field. Primary ion beam control device. The apparatus of claim 3, wherein the first and second electromagnets can adjust an incident angle size change by changing a magnitude of a magnetic field. The method of claim 3, wherein the first and second electromagnets adjust magnetic field sizes of the electromagnets according to intervals by applying magnetic fields in a half-fold direction to focus the incident beams having different directions at a predetermined position of the connection lens. Primary ion beam control device of a secondary ion mass spectrometer, characterized in that.