JPS6018935B2 - Sample analysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sample analysis method using mass spectrometry, and in particular to a sample analysis method using a mass spectrometer that improves analysis accuracy by equalizing the secondary ionization rate of a sample to be analyzed. It is related to.

Next, the background of the technology related to the present invention will be briefly described.

The principle of secondary ion analysis is based on high energy (several keV to
The purpose of this method is to irradiate an analytical sample with ions of 1000 keV and analyze the secondary ions that are secondarily emitted from the sample using a mass spectrometer. The secondary ion analysis method has unique features not found in other devices, such as high analytical sensitivity, ability to perform depth analysis, and high-sensitivity analysis of surface layers. It is widely used for analysis. However, there are major problems with this spectroscopic method that hinder its usefulness. This is because the secondary ionization rates of elements that are important for quantitative analysis are extremely different for each element, and therefore quantitative values cannot be directly calculated from the obtained spectral intensities. The secondary ionization rate of each element is influenced by the primary ion species and the atmosphere in the analysis room.
Qualitatively, it is explained as follows. Regarding the primary ion species, when using ions made of highly electronegative elements, such as 0-ions, the ionization rate of each element is as shown in Figure 1, and the ionization rate of each element is as shown in Figure 1. It can be seen that the ion ratio of elements is high, and it is extremely low for elements that are inert to oxygen, such as noble metals such as Al and Ag.

In this case, the difference in ionization rate of the elements is more than five orders of magnitude, and the spectral intensity also appears in a state that reflects this ionization rate. In addition, the results of measuring the ionization rate of each element using ions consisting of so-called electropositive elements, such as Cs + ions, which have low electronegativity, in other words, high electronegativity, as the primary ion species. Shown in Figure 2. Comparing Figure 2 and Figure 1, the secondary ionization rates of each element maintain a complementary relationship with each other, and in the case of ion irradiation consisting of electronegative elements such as 0-ions, the ionization rate is high. It can be seen that the ionization rate of elements exhibiting this is low when irradiated with ions made of electropositive elements such as Cs+ ions. The above are primary ions, or electropositive ions.

This is the result when using ions made of negative elements, but a similar effect can be obtained using gases or electropositive elements. It can also be obtained when a gas consisting of a negative element is introduced into the sample chamber. On the other hand, in the prior art, analysis is proceeding using the following analysis means.

{1} The sample chamber is kept in a high vacuum, and monatomic (for example, 0, Ne, Ar, N, etc.) or dichotomous (Q, etc.) ions are used as primary ions.

[21 Inert ions as primary ions (e.g. ~10,
Introduce active gas (02, etc.) into the sample chamber.

・In '11, the difference in ionization rate between elements is large and it is difficult to directly determine quantitative values from the spectral intensity. Various correction methods have been attempted, but an accurate analytical method has not yet been found. .

Regarding '21, although an improvement in the ionization rate of specific elements can be expected, the difference in sensitivity does not decrease, and when performing quantitative analysis, it is necessary to correct the secondary ion intensity. As briefly mentioned above, in the conventional method, the difference in secondary ionization rate between elements varies significantly, and it is not only difficult to calculate a quantitative value from the spectral intensity, but also a correction method for the secondary ion intensity has not been established. Therefore, the path to quantitative analysis was closed.
The present invention has been made in order to solve the problems in sample analysis using a mass spectrometer as described above.

Next, the present invention will be explained in detail with respect to its basic concept and embodiments.

The principle of the present invention is to use an electropositive element as the primary ion, and to introduce into the sample chamber a gas consisting of an electronegative element that has a complementary role to the primary ion in terms of ionization rate. Or, using an electronegative element as the primary ion and introducing into the sample chamber a gas containing an electropositive element that has a complementary role to the primary ion in terms of ionization rate. By keeping the ionization rate of each element approximately equal, quantitative values can be determined directly from the spectral intensity. In the above, electropositive elements include, for example, alkali metals and alkali metal elements, and electronegative elements include, for example, halogen group elements, oxygen, sulfur, nitrogen, and phosphorus.

Further, to generate primary ions of electropositive elements, for example, K0 can be generated by irradiating the compound with an ionized gas such as oxygen. In FIG. 3, the relative secondary ionization rate of each element was determined using electropositive Cs 10 ions as primary ions and introducing electronegative 02 gas into the sample chamber.

From FIG. 3, it can be seen that the variation in the relative secondary ion failure rate has been suppressed to approximately one digit, which is a significant improvement compared to the conventional variation of about five digits. Here, we have described the results of using Cs 10 ions as primary ions and introducing 02 gas, but Na+, K+ ions and
It was also confirmed in the same manner that similar effects could be obtained in combination with 2 gas and N2 gas. Furthermore, exactly the same effect was observed when the electrical polarities of the primary ions and the gas introduced into the sample chamber were opposite to those described above, that is, when electronegative ions and electropositive gas were used. From the above results, it has become clear that the present invention provides the following effects in sample analysis using a mass spectrometer.

[11] The secondary ionization rate of each element is significantly improved, making highly sensitive analysis possible.

'21 The secondary ionization rate of each element is approximately within one digit, and the quantitative accuracy is improved.

[Brief explanation of the drawing]

Figure 1 shows 13. as primary ions. Figure 2 is a diagram showing the secondary ionization rate of each element measured in high vacuum (~10-7Ton) using spherical eV ○-ions as primary ions. Figure 3 shows the secondary ionization rate of each element measured in high vacuum (~10-7 Tom) using spherical eV CS ions. FIG. 2 is a diagram showing the secondary ionization rate of each element measured by introducing 02 gas. Younger brother/Zuta 2 Zujol Mimi Pu sister, Chi Shio Go to Zuto Shizuku!・ Asako number

Claims (1)

[Claims] 1. In a secondary ion analysis method in which a sample is irradiated with an ion beam and secondary ions generated by sample atoms or molecules secondarily generated from the sample are analyzed by a mass spectrometer, primary ion species are by using an electropositive element as the sample chamber and introducing a gas consisting of an electronegative element into the sample chamber, or
A sample analysis method characterized by using an electronegative element as a primary ion species and introducing a gas containing an electropositive element into the sample chamber. 2. The sample analysis method according to claim 1, wherein the electropositive element is at least one selected from alkali metals and alkaline earth metal elements. 3. The sample analysis method according to claim 1 or 2, wherein the electronegative element is at least one selected from halogen group elements, oxygen, sulfur, nitrogen, and phosphorus.