JPH0299847A - Analysis of insulating material by aes - Google Patents

Abstract

PURPOSE:To enable a local analysis at a desired point even on an insulating sample by making an converted electron beam for analysis irradiate the sample at a specified point. CONSTITUTION:An energy distribution of an auger electron from a sample 3 is measured by an energy analyzer to perform an identification of an element. An electron beam 1 for analysis is converged to irradiate sample at a desired specified point 10 by a deflector. An electron beam 2 for preventing chargeup which is made substantially big as compared with the electron beam 1 for analysis is made to irradiate an area 20 as containing both of the specific point 10 where the electron beam 1 is irradiated and a sample holder 4 spatially in continuity. Hence, under such a condition, it looks as if a coating of a conducting film is applied entirely over the a hatching area 20 from the sample holder 4 to the surface of the sample 3. Thus, as charge caused by the electron beams 2 and 1 are allowed to escape to an earth surface without retaining at the irradiation point, there is no chargeup caused, thereby enabling a local analysis even on an insulating sample.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is an AES (Auger Electron 5pe
ctroscopy: Auger electron spectroscopy),
Analysis of insulating samples, especially analysis of specific minute parts (local analysis)
This is an introduction to how to do this.

(Prior art and its problems) In AES, it is necessary to irradiate the sample with an electron beam, which is a charged particle, so in extinguishable samples, charge-up occurs at the electron irradiation point (=analysis point), causing damage to that part. The surface potential changes.

As a result, the energy of the Auger electrons emitted from the sample is the sum of this surface potential added to the specific energy of the Auger electrons themselves, and the measurement principle of identifying elements from the energy of the Auger electrons is established. I don't do it anymore.

Conventional countermeasures have been: 1) irradiating the electron beam obliquely so that it grazes the sample surface;

■ Cover the sample with a conductive mesh connected to earth.

Although such methods are being used, they are not sufficiently effective, and
Other problems such as those described below also occurred, and the results were by no means satisfactory.

That is, this method (2) increases the secondary electron generation efficiency to 1 or more by obliquely incident the electron beam, thereby achieving a balance in the surface potential. However, since the electrons are incident from a shallow angle, it is difficult to control the irradiation point (analysis point), which reduces analysis accuracy and makes it impossible to analyze specific microscopic areas (local analysis). There were drawbacks. Furthermore, this method could only be applied to very special samples with no irregularities on the sample surface.

The next method (2) utilizes a surface conductive layer generated by electron beam irradiation to release charges to the mesh, thereby maintaining the surface potential of the analysis point at ground potential.

However, it requires a mesh with a mesh smaller than the electron irradiation area (in other words, local analysis of a part smaller than the mesh is impossible), and signals from the mesh and adsorbates on the mesh are mixed. However, there was a problem in that they could not be distinguished from the original signal.It is also said that this method is effective for analysis of a specific location inside the mesh, that is, local analysis; In the case of analysis, instead of taking countermeasures based on a clear principle like the one using the surface conductive layer mentioned above, the distance between the electron irradiation point and the ground potential area is simply brought closer, and the insulation resistance becomes relatively small.
It only reduces charge-up. In other words, it can be said that it may be somewhat effective depending on the conditions, but it cannot be said to be a perfect method.

In addition, SIMS (Second
Dary ton Mass Spectrometer
In y), a method is used in which charges are released using a surface conductive layer generated by electron beam irradiation.

However, in the case of SIMS, ions are used as the primary line, and the generated secondary ions are subjected to mass spectrometry, and although the information obtained is advantageous for trace elements, it is difficult to quantify and local analysis. It lacks ability and there is a big difference from analysis by AES.

In particular, it is essentially different from AES in that secondary ions are not generated depending on the charge-up prevention electron beam.

(Objective of the Invention) The present invention solves these problems, is not limited by the uneven shape of the surface, does not require a special mesh, and can perform local analysis at any location on an insulating sample. The purpose of this study is to provide a novel AES analysis method that can also be used in

(Means for Solving the Problems) The present invention provides an AES analysis method for performing elemental analysis on a sample surface by irradiating the sample with an electron beam and detecting Auger electrons generated from the sample surface. At the same time, the ionization accelerated beam for charge-up prevention, which can generate a conductive layer on the surface of an insulating sample, is applied to the specific location and the sample holder, etc. The irradiation is carried out spatially and continuously so as to include both points of the grounding part, thereby preventing charge-up at the specific location.

(Embodiment) FIG. 1 shows a diagram of the main parts of a first embodiment of the present invention. 1 is an electron beam for excitation of Auger electrons, that is, for analysis; 2 is an electron beam for generating a surface conductive layer newly provided in the present invention, that is, for preventing charge-up; 3 is an insulating sample; and 4 is at ground potential. The conductive sample holder 5 is a conductive film having a thickness of 1 μni or less.

The energy distribution of the Auger electrons emitted from the sample 3 is measured by an energy analyzer (not shown), and the elements are identified.

The electron beam 1 for analysis is narrowly focused, and is irradiated onto any specific location 10 on the sample by a deflector (not shown). The electron beam 2 for charge-up prevention is considerably thicker than the electron beam 1 for analysis, and is spatially continuous with both the specific location 10, which is the irradiation point of the electron beam 1, and the sample holder 4. The area 20 including the area 20 is irradiated.

That is, the irradiation surface 20 of the electron beam 2 continues without a break between the specific location 1°, which is the irradiation point of the electron beam 1, and the sample holder 4.

As explained in section (2) of the conventional example, it is known that when an insulator is irradiated with an electron beam, ionization occurs on the surface of the insulator due to the action of the electrons, and that region has characteristics as a conductor.
(Electron Bombardment.

Induced Conduc Tivit, y: E
B I C'yA elephant). That is, a conductive layer is generated on the surface of the electron beam irradiated surface, as if the sample surface was coated with a very thin conductive film.

Therefore, under the situation shown in Figure 1, the sample holder 4
It appears as if a conductive film was coated over the entire hatching area 20 from the sample 3 to the top of the sample 3. Therefore, not only the electron beam 2 but also the charge generated by the electron beam 1 does not stay at the irradiation point and the ground plane 4
Since it escapes, charge-up does not occur.

At this time, as shown in the figure, from the bottom of the sample 3 to a part of the side surface of the sample 3 that is irradiated with the electron beam 2, the distance is 1 μm.
If a conductive film 5 with the following thickness is coated, the electron beam will also pass through this film, so this film and the sample directly under it will become conductive due to ionization, and the resistance here will be small. As a result, the escape of the charge to the ground becomes more reliable.

Now, in the above case, Auger electrons excited by the electron beam 2 are also generated. Therefore, the next
Using the method (2), only Auger electrons generated from a specific location 10 by the electron beam 1 are detected.

(2) Reduce the current amount of electron beam 2 to a negligible amount compared to electron beam 1.

(2) Lower the energy of electron beam 2 to such an extent that Auger field is negligible compared to electron beam 1.

(2) Blanking (intermittent irradiation) is applied to only the electron beam 1, and phase detection is performed using a lock-in amplifier or the like in synchronization with this to detect the amount of Auger electrons in the electron beam 1.

The following methods are adopted. A detailed explanation of these is as follows.

That is, the method (2) requires the following conditions: 13. The amount of Auger electrons generated is proportional to the amount of current of the electron beam; 21. A current density of about μA/cm2 is sufficient for the generation of a surface conductive layer; 3.
．． The detection limit for AES local analysis is 1% for another reason.
It utilizes three factors: being of a certain degree. For example, assume that the current of the electron beam 1 for analysis is 1 μA, the current amount of the electron beam 2 for preventing char shrinkage is 1/100 of that, 0.01 μA, and the diameter is lrnmφ. In this case, the current density of the charge-up prevention electron beam 2 is lμΔ,
/crr+', and the surface conductive layer should be sufficiently formed.

However, the ratio of Auger electrons generated from the electron beam for analysis and for charge-up prevention is 100:
1, and signals from other than the specific location are equal to the detection limit and can be almost ignored. In reality, the focus of the energy analyzer is on a very narrow area including the specific location 10, so this ratio becomes even larger and becomes completely negligible.

Next, method (2) utilizes the fact that the amount of Auger electrons generated is largely dependent on the energy of the electron beam. Since the generation of Auger electrons requires ionization of the fourth position, which is very high, when the energy of the electron beam becomes less than 51 (V), the yield rapidly decreases and begins to reach 0,5 k.
When it reaches the level of ■, Auger electrons of most elements cease to be generated. On the other hand, for the EBIC phenomenon occurring in the surface layer, ionization at a low level is sufficient, and a voltage of about 0.5 kV is sufficiently effective.

Therefore, the energy of the analytical electron beam 1 is set to 5kV.
If the charge-up prevention electron beam is set to 0.5 (■), signals from other than the specific location 10 can be almost ignored or obtained.

Next, method (2) utilizes the fact that phase detection using a lock-in amplifier or the like can selectively detect only signals having the same frequency, and completely eliminate other signals. Therefore, constant Auger electrons generated by the charge-up prevention beam 2 that is not blanked are not detected.

A diagram of the main parts of a second embodiment of the present invention is shown in FIG.

In this embodiment, the analysis electron beam 1 is also used as a charge-up prevention electron beam.

That is, the electron beam 1 is moved at high speed by a deflector (not shown) and reciprocated between the desired analysis location 10 and the surface of the sample holder 4.

At this time, if the electron beam is moved back and forth so that it is irradiated again in a time shorter than the relaxation time until the conductive layer disappears,
A conductive layer is always present in the reciprocating line area 11,
Therefore, in this case, the beams are irradiated substantially continuously in space, and charge-up can be prevented as in the case of the first embodiment.

In order to detect Auger electrons only from the desired analysis location 10, (1) reduce the amount of current of the electron beam at locations other than the desired analysis location 10 to such an extent that it can be ignored compared to the desired analysis location;

(2) The energy of the electron beam at locations other than the desired analysis location 10 is reduced to a negligible level compared to the OJ field or the desired analysis location.

■ Flanking is applied to the electron beam 1 only when it is at the desired analysis location 10, and phase detection is performed using a lock-in amplifier or the like in the same month. A game is made so that the detection signal is not outputted by any means other than the desired analysis location 10.

etc. methods are adopted.

Naturally, many analysis methods can be considered that are variations of 1.2 of the above embodiment.

For example, it is also possible to make the electron beam 2 narrow in the first embodiment and move it at high speed as in the second embodiment. Further, in the first embodiment, it is also possible to make the electron beam 2 elongated so that the analysis point and the sample holder are connected with the minimum amount of current.

Furthermore, in Embodiment 1 and 2, instead of the electron beam 2, it is also possible to use an ionization-enhanced beam capable of generating a surface conductive layer, such as an ion beam, an X-ray, an ultraviolet ray, or the like.

In addition, instead of sample holder 4, sample holder 4ty)
Of course, it is also possible to conduct electrically with a bottle or the like that is attached to fix the sample.

(Effects of the Invention) As described above, according to the present invention, local analysis of any point on an insulating sample is possible using AES.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the present invention, and FIG. 2 shows a second embodiment. 1... Electron beam for analysis, 2... Electron beam for charge-up prevention, 3... Insulating sample, 4... Sample holder 5... Thin conductive film. Patent applicant: Nichiden Anelva Co., Ltd. Patent attorney: Kenji Murakami

Claims (1)

[Scope of Claims] (1) In the AES analysis method, which performs elemental analysis of the sample surface by irradiating the sample with an electron beam and detecting Auger electrons generated from the sample surface, a specific analysis point on the sample is used. At the same time, the ionization-enhanced beam for charge-up prevention, which can generate a conductive layer on the surface of an insulating sample, is irradiated with the narrowly focused electron beam for analysis. An AES analysis method characterized by irradiating spatially continuously so as to include both points to prevent charge-up at the specific location. (2) The AES analysis method according to claim 1, characterized in that an electron beam is used as an ionization-promoting beam for preventing charge-up and generating a conductive layer on the surface of a sample. (3) An AES according to claim 2, characterized in that an independent electron beam is used as the charge-up prevention electron beam, separate from the analysis electron beam.
Analysis method. (4) Claim 3 is characterized in that the charge-up prevention electron beam uses a thick beam that simultaneously irradiates the irradiation point of the analytical electron beam and the ground portion of the sample holder, etc. AES
Analysis method. (5) In claim 3, as the charge-up prevention electron beam, a narrow beam that cannot simultaneously irradiate the irradiation point of the analysis electron beam and the ground portion of the sample holder, An AES analysis method characterized by repeatedly moving back and forth between two points at high speed. (6) The AES analysis method according to claim 3, characterized in that the current amount of the charge-up prevention electron beam is smaller than that of the analysis electron beam. (7) Claim 3 is characterized in that the energy of the charge-up prevention electron beam is lowered so that the OJ yield due to the charge-up prevention electron beam is smaller than that of the analysis electron beam. AES analysis method. (8) The AES analysis method according to claim 3, characterized in that blanking (intermittent irradiation) is applied to the analytical electron beam and, at the same time, phase detection is performed on the detection side in synchronization with the blanking. (9) In claim 2, the analytical electron beam is repeatedly moved back and forth between the specific location, which is the analysis point, and the sample holder at high speed. An AES analysis method characterized by using an electron beam for charge-up prevention. (10) The AES analysis method according to claim 9, characterized in that the amount of current of the electron beam at a location other than a specific location serving as an analysis point is made smaller than the value at the specific location. (11) In claim 9, the electron beam at a specific location other than the analysis point,
An AES analysis method characterized in that the energy value of the electron beam is set so as to be smaller than the OJ field at the specific location. (12) Claim 9 is characterized in that while blanking is applied to the electron beam at a specific location that is an analysis point, phase detection is performed on the detection side in synchronization with the blanking. AES analysis method. (13) In claim 9, a gate mechanism that can intermittent the signal is provided on the detection side, and the gate is opened to detect the signal only when the electron beam is staying at a specific location that is the analysis point. An AES analysis method characterized by: (14) Claim 2 is characterized in that a conductive thin film with a thickness of 1 μm or less is attached to a part of the sample irradiated with the electron beam for charge-up prevention, and the part is set at ground potential. AES analysis method.