JP2794885B2 - Analyzer using charged particle beam - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voltage regulator for a lens power supply in an apparatus for detecting a charged particle beam emitted from a sample and performing sample analysis.

(Prior Art) In X-ray photoelectron analysis or Auger electron analysis, energy analysis of X-ray photoelectrons or Auger electrons emitted from a sample is performed, and the surface of the sample is analyzed based on the energy spectrum.

In such an apparatus, an electron lens is arranged between the sample and the energy analyzer in order to make electrons emitted from one point on the sample surface incident on the energy analyzer. The focal length of such an electron lens depends on the energy of the electron in the charged particles of interest, so if the voltage applied to the electron lens is kept constant, the lens transmittance of the electron will be affected by the energy of the incident electron. The sensitivity differs depending on the energy of the electrons to be analyzed.
For this reason, it is desirable that the voltage applied to the electron lens is always set to be optimal for the energy of the electrons to be analyzed. For this reason, the following method has conventionally been used.

The optimum lens voltage is determined for each energy of the electron to be measured by theoretical calculation or trial experiment, and the lens voltage can be adjusted for variations in lens performance for each actual product. Is measured, and the optimum voltage is set by referring to the previously obtained optimum voltage.

(Problems to be Solved by the Invention) In the conventional method for setting the optimum voltage of the electronic lens, a tentative measure of the optimum voltage of the lens is given according to the energy of the charged particles to be measured by calculation or experiment. However, due to variations in the equipment, it is necessary to detect the optimum voltage for each actual sample by actual measurement.When there are many lens electrodes, the optimum voltage is searched for each voltage, which is very troublesome. Puru.

An object of the present invention is to eliminate the above-mentioned trouble for setting a lens voltage for each sample.

(Means for solving the problem) A particle beam source whose energy is known and which changes continuously or stepwise is arranged at the sample position so as to be exchangeable with the sample, and the detection intensity of the particle beam emitted from the same beam source is maximized. And a controller for storing the lens applied voltage at the point where the detection intensity is maximized.

As the above-mentioned particle beam source of known energy, there can be used a particle beam gun whose acceleration voltage is variable or several kinds of standard samples which emit a particle beam of known energy by irradiation with an excitation beam from an excitation beam source attached to the apparatus.

(Operation) If a variable energy source with known energy is placed at the position of the sample, particles from the source can be detected in exactly the same manner as detection of particles emitted from the sample. If the lens voltage is adjusted so that the detection signal of the particles is maximized, the relationship between the energy of the particles to be detected and the lens voltage can be known. Therefore, the optimum value of the lens voltage is searched for each sample to be measured. Since there is no need to obtain the lens voltage for the particles having the energy to be detected as described above, the lens voltage may be set accordingly.

(Embodiment) FIG. 1 shows an embodiment of the invention of claim 1 of the present application.
The apparatus of this embodiment is an X-ray photoelectron analyzer, 1 is an X-ray source for irradiating a sample, 2 is an energy analyzer, and 3 is an electron lens arranged between the energy analyzer 2 and the sample. It is intended to optimally set the applied voltage of the electron lens. 4 is an electronic detector. Reference numeral 5 denotes a rotating disk on which a plurality of samples S are set along a circumference on a sample table. By rotating the disk, a plurality of samples can be sequentially brought to an analysis position. I have. One of a plurality of holes h for setting a sample on the sample stage 5 is open toward the circumference of the sample stage, and the figure shows a state where h is at the analysis position. Reference numeral 6 denotes an electron gun which can move left and right in the figure, and can enter the opening h of the sample stage 5. When the electron gun 6 enters the opening h, the anode opening of the electron gun is positioned exactly at the sample analysis position. FIG. 2 shows a vertical cross section of the electron gun 6, wherein a is an anode, w is Wehnelt, and f is a filament, and the voltage between the anode filaments can be arbitrarily changed.
Thereby, when the anode opening is placed at the sample analysis position, the energy of electrons emitted from the anode opening can be arbitrarily changed.

Returning to FIG. 1, E is the power supply for the energy analyzer, L is the power supply for the electron lens, A is the anode power supply for the electron gun and the voltage between the filaments.
Controlled by U. F is a filament power supply, which is driven by the output pulse of the rectangular pulse oscillator P to pulse light the filament f. The filament is pulsed for the following reason. In order to search for the optimum lens voltage, it is desirable that the energy width of electrons emitted from the electron gun 6 be as small as possible. When the filament is energized, the voltage drop in the filament is added to the voltage between the filament and the anode, and the energy width of the electrons emitted from the electron gun increases by the voltage drop in the filament. By detecting only the thermoelectrons, it is possible to eliminate the spread of the energy width corresponding to the voltage drop due to the current in the filament. The output of the electronic detector 4 is converted into a count rate signal by the rate meter 8 via the preamplifier 7 and is taken into the CPU. The gate G which is opened when the output of the pulse oscillator P is at the O level.
The output of the electronic detector 4 is sent to the rate meter 8 only when the filament is not energized as described above. At the time of actual sample measurement, since the pulse oscillator P is not operated, the gate G remains open,
There is no problem in measurement.

The CPU is a control means for setting the lens voltage, and FIG. 3 is a flowchart of the lens voltage optimum value search operation (calibration operation). First, the energy range to be calibrated and the calibration step, that is, the point in the energy range at which the calibration is to be performed, are set (a), and then the reference electrode voltage of the electron lens 3 is optimally designed for the energy to be calibrated. Set the voltage to (b) and set the energy analyzer voltage to (b)
(C), and set the energy of the electron gun, that is, the voltage between the filament anodes, to that energy (d).
The output of the rate meter 8 is taken into the CPU (e), and the data of the count rate is stored in the memory (f). In this case, it goes without saying that the filament f is pulsed.
Then, it is checked (g) whether the scanning of the predetermined range of the lens voltage has been completed, and if not, the voltage of the first electrode of the lens 3 is changed by one step (h), and the operation returns to (v). That is, the electron lens is composed of n electrodes, and a design voltage is applied to each electrode in advance, and the voltage of each electrode is sequentially changed to record the count rate. Therefore, when the step (g) becomes YES, the same operation as that of (c) ... (g) and (h) is performed while changing the voltage of the second electrode. The voltage at which the rate is maximized is found (R), and stored as the optimal voltage of the electron lens at that energy (N), and it is checked whether or not the lens voltage search has been completed for all points of the initially set energy (L) If not, the operation returns to step (b) and performs the same as above for another energy. Since the optimum voltage of the electron lens is obtained and stored at the designated point in the energy range set in this way, the calibration operation ends. In the case of sample measurement, the CPU calculates the lens voltage for arbitrary energy from the electron lens voltage stored in step (nu) by interpolation formula, and sets the voltage of the electron lens 2 in conjunction with the voltage setting in the energy analyzer. I do.

FIG. 4 shows an embodiment of the second aspect of the present invention.
This figure shows only the main parts, and other parts which are the same as those in FIG. 1 are omitted. This embodiment does not require an electron gun as in the previous embodiment. Samples S1 to Sn of overlapping species having known peaks in the X-ray photoelectron energy spectrum are set as a plurality of samples on the sample stage 5, and the electron lens is set so that the output of the electron detector is maximized for each of these samples. The voltage is determined, and the calibration operation is the same as in FIG.
In the step, set the energy value of the peak of known energy in the energy spectrum of the sample S1 ~ S1, (R)
In step (1), it is checked whether or not the search has been completed for all the samples S1 to Sn.

(Effect of the Invention) According to the present invention, the energy of the charged particles to be detected can be intentionally changed, so that the optimum voltage of the lens can be determined over a wide range, and the optimum lens voltage can be determined for each sample to be measured. There is no need to check the values, and the analysis efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the invention of claim 1 of the present application, FIG. 2 is a vertical side view of the electron gun of the embodiment, FIG. 3 is a block diagram of a calibration operation of the embodiment, FIG. The figure is a perspective view of a main part of an embodiment of the invention of claim 2 of the present application. DESCRIPTION OF SYMBOLS 1 ... X-ray source, 2 ... Energy analyzer, 3 ... Electronic lens, 4 ... Electron detector, 5 ... Sample stage, 6 ... Electron gun, 7 ... Preamplifier, 8 ... Rate meter, E: Energy analyzer power supply, L: Lens power supply, A: Anode and filament voltage power supply, F: Filament power supply, P: Pulse oscillator, S1 to Sn: Sample with known energy at energy peak.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 23/00-23/227 H01J 49/44 H01J 37/244

Claims (2)

(57) [Claims] An apparatus provided with a lens for charged particles for detecting charged particles emitted from a sample, wherein a charged particle beam gun capable of changing an accelerating voltage is provided so as to be able to freely enter and exit a sample position, and said particle is provided. A charged particle beam characterized by comprising a control means for detecting an applied voltage of the charged particle lens such that the charged particle detection output is maximized in a state where the ray gun is advanced to the sample position, and setting the voltage. By analyzer. 2. An apparatus provided with a lens for charged particles for detecting charged particles emitted from the sample, sequentially analyzing a plurality of types of samples whose peak energy of the energy spectrum of the emitted charged particles is known. Means for bringing the lens to a position, and control means for detecting an applied voltage of the lens for each of the samples so that the detection output of the charged particle beam emitted from each of the samples is maximized and setting the voltage. An analyzer using a charged particle beam.