JPH083988B2 - Secondary ion mass spectrometry - Google Patents

Description

The present invention relates to a secondary ion mass spectrometry (SIMS) method.

[Conventional technology]

In SIMS, the secondary ion yield changes greatly depending on the primary ion species. The difference between sample components, that is, the difference between elements is as large as 4 to 5 digits, and a calibration curve method is used for quantitative analysis. Therefore, it has a drawback that the concentration cannot be immediately determined from the data. Especially when there is no standard sample, only qualitative or comparative analysis can be performed.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, no consideration is given to the quantification of raw data, and (1) the quantitative value is not known from the raw data.

(2) The concentration may be erroneously determined.

(3) Quantification is not possible without standard samples.

There was a problem such as.

An object of the present invention is to provide a secondary ion mass spectrometric method capable of easily determining the concentration of a sample without a standard sample.

[Means for solving problems]

In order to achieve the above object, in the present invention, based on the output value of the ion scattering spectrum analysis (ISS) of a specific mass and the output value of SIMS of a specific mass, from the subsequent output value of SIMS, a quantitative value for the sample concentration. Configured to ask.

[Action]

Such a correction causes quantification of SIMS data, and therefore the present invention makes it possible to easily determine the concentration of a sample without a standard sample.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The primary ion generation source 1A generates light mass ions 2A, and the primary ion generation source 1B generates analysis ions 2B. The primary ion separation device 3 selects the ions 2A and 2B and selectively sends the primary ions 2 to the irradiation system 5. A drive source 4 is connected to the primary ion separation device 3 to match selection conditions. When the sample 6 is irradiated with the primary ions, the secondary ions 9 are emitted. The secondary ions 9 are the energy separator 10 and the energy separation slit 11
To the second detector 15 via the mass separator 13 and the separation slit 14. After the energy separating slit 11, there is a first detector 12. The first detector 12 detects each signal of the energy distribution of the secondary ion 9, and the second detector 15 detects each signal of the mass spectrum. The signals 12A and 15A are collected and stored in the control storage circuit 16. This data is output by the various arithmetic processing output device 17. A voltage source 7 and a scanning circuit 8 are connected to the sample 6, and a scanning state is selected by a control signal 8A from a control storage circuit 16. The primary ion separation drive source is also selected by the signal 4A.

Now, when operating the ISS, the primary ion separation device 3 selects the light element ion 2A as the primary ion by the signal 4A and irradiates the sample 6 with it. The sample potential is scanned from V _A to OV by the signal 8A as shown in FIG. The composition of sample 6 is the element m ₁
When it is composed of m ₂ , the first detector 12 receives the reflected ion 9 of the primary ion 2A, and the energy spectrum is obtained as shown in FIG. Voltage Vs ₁ has m ₁ peak and Vs ₂ has m ₂ peak m ₂
Appears. The ion amounts Is ₁ and Is ₂ are quantitative.

Next, in the SIMS mode, the primary ion separation device 3 selects the primary ion 1B and fixes the sample potential at V _A. Secondary ions obtained in the second detector 15 focusing on the elements m ₁ and m ₂ are as shown in FIG. 4A. The ionic strengths I _m1 and I _m2 are not directly related to the concentration. It depends on the ionization rate K of each element.

In the ISS, the sample with energy E ₀ and mass number M ₀ is irradiated to the sample with mass number M ₁ . Primary ions are reflected with energy of E ₁ . A secondary ion energy spectrum is obtained by fixing the electric field and scanning the sample potential. The following relation holds when the primary ion incident angle is 45 °.

M ₁ = M ₀ (1 + E ₁ + E ₀ ) / (1−E ₁ + E ₀ ) ... (1) That is, the sample component, that is, the element M ₁ can be obtained by obtaining the energy of the reflected ions.

 On the other hand, in SIMS, the amount of secondary ions obtained is as follows.

I _M2 = I ₁ · K · C (2) where I ₁ is the primary ion, the ionization rate of K, and C is the concentration. K changes depending on the sample component, that is, the element, resulting in a difference in sensitivity. In the equation (1), the factor similar to K is extremely close to 1, and the value of the equation (2) is corrected with the value of the equation (1).

The relationship between the SIMS analysis value Im ₁ and the ISS analysis value I _SI can be expressed by the following equation.

I _m1 = k · I _s1 (3) _Let I _m10 = k ₀ · I _s10 where I _m10 , I _s10 is the instantaneous value at t _{0 of} each ion current, and I _m1 t, I _s1 t is the value at t. (4) I _m1 t = kt · I _s1 t (5) When t ₀ and t are short times, and the analysis depth ΔZ between them is shallow and can be omitted, it is approximated by the following equation.

k ₀ ≈ kt… (6) When formulas (4) and (5) are rearranged from formulas (6), I _m1 t = (I _m10 / I _s10 ) · I _s1 t… (7) (7) The output of SIMS is converted and output as I _m1 t ′. However, k is a constant.

I _m1 t ′ = k · (I _s10 / I _m10 ) · I _m1 t (8) The SIMS data corrected by the equation (8) does not substantially depend on the ionization rate which differs for each sample component as shown in FIG. 4B. The data will be quantitative.

〔The invention's effect〕

According to the present invention, since SIMS data has quantitativeness,
The problems of the conventional technology are eliminated, and easy-to-read data can be provided. As a result, it is possible to determine the concentration of a sample without a standard sample.

[Brief description of drawings]

1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing scanning of a sample potential, FIG. 3 is a diagram showing secondary ion energy spectrum, FIG. 4A is a diagram showing SIMS profile, FIG. 4B is a diagram showing the SIMS profile after correction. 1 ... Primary ion generator, 2 ... Primary ion separator,
6 ... Sample, 10 ... energy separator, 12 ... first detector, 13 ... mass separator, 15 ... second detector.

Claims (1)

[Claims] 1. (a): Detecting the mass of the sample at the portion where the primary ions collide by irradiating the sample with the primary ions and analyzing the energy of the reflected ions generated thereby. A step of irradiating the sample used in the step (a) with primary ions and mass-separating the secondary ions generated thereby, thereby detecting the mass of the sample in the portion where the primary ions collide, (c) : Irradiate the sample with primary ions, detect secondary ions generated from the sample by mass separation, and collide with the primary ions based on the detection value of the step (a) and the detection value of the step (b). And a mass spectrometric step for obtaining a quantitative value with respect to the concentration of the sample in the selected portion, and a secondary ion mass spectrometric method.