JP2006090969A - Secondary ion mass spectrometry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary ion mass spectrometry capable of measuring highly accurately Al or Cu in a specimen sample. <P>SOLUTION: This secondary ion mass spectrometry has a process for adjusting an ion optical system by using an ion beam adjusting sample, and a process for measuring the secondary ion intensity of a detection object element in the specimen sample under the adjusted ion optical system. The mass spectrometry has a characteristic wherein, when the detection object element is Al or Cu, the ion beam adjusting sample is formed from a material comprising only elements substantially different from the detection object element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to secondary ion mass spectrometry.

(1) Sample Holder First, a sample holder 50 generally used in conventional secondary ion mass spectrometry (hereinafter referred to as “SIMS”) will be described with reference to FIG. 4A is a perspective view showing the structure of the sample holder 50, and FIG. 4B is a cross-sectional view taken along the line II in FIG. 4A.

  The sample holder 50 includes nine windows 52 on the upper surface of a stainless steel casing 51. The size of the window 52 is, for example, about 5 × 5 mm. A sample to be used for ion beam adjustment, a standard sample, and a sample (hereinafter referred to as “analyte sample”) are attached to this portion. The number of windows, that is, nine samples can be mounted on the sample holder 50. There are also sample holders having nine or fewer windows or nine or more windows depending on the sample size and intended use.

  As shown in FIG. 4B, a sample 53 is attached to the window 52 from the inside. The sample 53 is cut out slightly larger than the window. The sample 53 is mounted so that the measurement surface of the sample 53 can be seen from the window 52 with the measurement surface facing upward. The sample 53 is fixed using a spring 57 and a cover 55 so as not to fall down. Further, the cover 55 is fixed with screws 59 on the side surface of the casing 51. Thus, the sample 53, the spring 57, and the cover 55 are fixed without falling down.

(2) SIMS depth direction analysis Here, the measurement procedure of SIMS depth direction analysis is demonstrated using FIG.

  First, in S <b> 1, the specimen (ion beam adjustment specimen / standard specimen and specimen specimen) is cut so as to fit in the sample holder 50. Further, in the case where the sample is insulative, as a pretreatment, Au, Pt or the like is deposited on the surface of the sample so as to have conductivity.

  Next, in S <b> 2, the processed and pretreated sample is attached to the sample holder 50. The attachment method and the like are as described above. Here, normally, an ion beam adjustment sample is attached to one part of the window frame 52, a standard sample is attached to another part, and a specimen sample is attached to the remaining part (in this case, seven parts).

  Next, in S3, the sample holder 50 is carried into the SIMS apparatus. The SIMS apparatus normally includes an introduction chamber and a main chamber maintained in an ultra-high vacuum, and the sample holder 50 is carried into the main chamber via the introduction chamber.

  Next, in S4, the primary ion and secondary ion optical systems are adjusted using the ion beam adjusting sample. As adjustment of the ion optical system, adjustment of the magnetic field of the ion beam, adjustment of the optical axis of the electrostatic lens, correction of the measurement region, and the like are performed.

  Next, in S5, the depth direction measurement of the standard sample is performed. As the standard sample, generally, a sample having the same element composition as the measurement sample serving as the specimen sample and having a known concentration of the element to be measured is used. The measurement of the standard sample is to obtain the secondary ion intensity of each element contained in the standard sample, and the measurement in the depth direction is to repeat the measurement of the sample while digging the sample. The reason why the standard sample is measured in the depth direction is to remove the influence of oxidation or contamination on the surface of the standard sample by using the measurement data inside the standard sample for calculation of the relative sensitivity factor (RSF).

Next, in S6, RSF is calculated using the measurement result in S5. The RSF is used later to calculate the atomic concentration of each element contained in the specimen sample.
Next, in S7, the specimen sample is measured in the depth direction.
Next, in S8, the atomic concentration of each element contained in the sample is calculated from the measurement result obtained in S7 and the relative sensitivity factor calculated in S6.

(3) SIMS composition analysis Next, the measurement procedure of SIMS composition analysis is demonstrated using FIG.
First, the steps up to the adjustment of the primary ion and secondary ion optical system are performed by the same procedure of S1 to S4 (S11 to S14).
Next, in S15, the specimen sample is measured.
In SIMS composition analysis, it is not necessary to calculate the concentration of each element contained in the specimen sample, so that it is not necessary to calculate RSF.

(4) Ion Beam Adjustment Sample Next, an ion beam adjustment sample that is normally used in the conventional method will be described with reference to FIG. FIG. 7A is a perspective view showing the structure of the ion beam adjusting sample 61, and FIG. 7B is an enlarged view of a part of the lattice-like thin film 63 of FIG. 7A. (c) is II sectional drawing of FIG.7 (b).

  Usually, the sample 61 for ion beam adjustment has Cu plated or deposited on the surface of the Al plate 61a in a thin film, and the Cu thin film has a predetermined size of windows arranged in a grid and the underlying Al is open. It is in the state of coming out on the surface. This state is shown in more detail in FIG. The Al plate 61a is covered with a Cu thin film. Further, Cu is removed by using a lithography method or the like, and the square windows 62 are opened in a lattice shape. Al is exposed from the window 62. The size of the square window 62 and the thickness of the window frame 63a are set to arbitrary sizes in order to correct the raster size, the length of the measurement portion, etc. during SIMS beam adjustment. The size is 20 μm, and the thickness of the window frame portion 63a is 5 μm. Al is often used because of its excellent secondary ion yield and easy sample preparation.

  However, if the specimen sample contains a small amount of Al or Cu and the concentration is further measured, if Al or Cu is used for ion beam adjustment, Al or Cu scattered as secondary ions will adhere to the slit or aperture in the main measurement chamber. As a result, there are cases where the accuracy of concentration measurement is lowered during measurement of a specimen sample. For example, when measuring the concentration of a very small amount of Al atoms mixed in a GaAs crystal, Al scattered by ion beam adjustment may cause a decrease in concentration measurement accuracy.

  Further, the number of samples attached to the sample holder is limited. For example, in the case of the sample holder shown in FIG. 1, only up to seven specimen samples can be attached out of the nine mounting positions. (1 ion beam adjustment sample + 1 standard sample + 7 specimen samples = 9 in total)

  Further, it is desirable to adjust the primary ion and secondary ion optical systems and measure the standard sample at the center of the sample holder as much as possible in order to improve the measurement system. However, in the conventional method, only one of the ion beam adjusting sample (metal mesh) and the standard sample can be placed.

  The present invention has been made in view of such circumstances, and (1) provides a secondary ion mass spectrometry method capable of measuring Al or Cu in a specimen sample with high accuracy, and (2) a sample. The present invention provides a secondary ion mass spectrometry method that can increase the number of specimen samples that can be placed on a holder.

  The secondary ion mass spectrometry method according to the first aspect of the present invention includes a step of adjusting an ion optical system using an ion beam adjustment sample, and a step of detecting elements to be detected in a specimen sample under the adjusted ion optical system. A secondary ion mass spectrometry method comprising a step of measuring the secondary ion intensity, wherein when the detection target element is Al or Cu, the ion beam adjustment sample is made of only an element substantially different from the detection target element It is formed by these.

  The ion beam adjusting sample is preferably composed of a substrate and a lattice-like thin film formed thereon. In this case, the length correction such as the correction of the observation area is facilitated. The lattice-like thin film is obtained, for example, by forming a thin film on the entire surface of the substrate and etching the obtained thin film in a lattice shape by a lithographic method. According to this method, a lattice-like thin film can be easily formed. Preferably, the substrate is an insulator, and the lattice-shaped thin film is formed of a conductive material. This is because if the lattice-shaped thin film is formed of a conductive material when the substrate is an insulator, charge accumulation on the substrate surface can be prevented.

  The secondary ion mass spectrometry method according to the second invention includes a step of adjusting an ion optical system using a sample for ion beam adjustment, and a relative sensitivity factor using a standard sample under the adjusted ion optical system. A step of calculating, a step of measuring the secondary ion intensity of the detection target element in the specimen sample under the adjusted ion optical system, a calculated relative sensitivity factor and the measured secondary ion intensity of the detection target element A secondary ion mass spectrometry method comprising a step of calculating an atomic concentration of an element to be detected in a specimen sample from a sample, wherein the standard sample comprises a substrate and a thin film containing the element to be detected formed thereon, Is characterized in that a part of the surface is etched in a lattice shape, the lattice region is used for ion beam adjustment as an ion beam adjustment sample, and the remaining region is used for calculation of the relative sensitivity factor. Do

  The thin film containing the detection target element is preferably a thin film doped with the detection target element. In this case, the atomic concentration of the detection target element contained in the thin film can be easily known, and the relationship between the atomic concentration of the detection target element in the thin film and the measured secondary ion intensity can be easily known. is there. The doping of the detection target element is preferably performed by ion implantation of the detection target element. This is because the doping amount can be easily controlled in this case.

  The step of adjusting the ion optical system using the sample for secondary ion mass spectrometry ion beam adjustment according to the third invention, and the secondary ion of the detection target element in the specimen sample under the adjusted ion optical system A secondary ion mass spectrometry method including a step of measuring an intensity, wherein the specimen sample includes a substrate and a thin film formed on the substrate, and the thin film has a partial region of the surface etched into a lattice shape, The lattice area is used for ion beam adjustment as an ion beam adjustment sample, and the remaining area is used for measuring the secondary ion intensity of an element to be detected in the specimen sample.

  According to the first invention, when the detection target element is Al or Cu, the ion beam adjustment sample is formed of a material composed only of an element different from the detection target element in the specimen sample. At this time, the SIMS device is not contaminated by the detection target element, and high-precision measurement is possible.

  According to the second invention, since a part of one substrate is used as a sample for ion beam adjustment and the other part is used as a standard sample, the number of specimen samples that can be placed on the sample holder can be increased. Further, in this case, since both the ion beam adjustment and the calculation of the relative sensitivity factor can be performed using the sample attached to the center of the sample holder, the measurement accuracy can be improved.

  According to the third invention, since the specimen sample substrate is used as the ion beam adjusting specimen, the number of specimen specimens that can be placed on the sample holder can be increased.

(First invention)
Example 1 includes a step of adjusting an ion optical system using an ion beam adjustment sample, and a step of measuring secondary ion intensity of an element to be detected in a specimen sample under the adjusted ion optical system. It relates to secondary ion mass spectrometry, the detection target element is Al, and the ion beam adjustment sample is a material that is substantially composed only of an element different from the detection target element (Al), that is, a material that does not contain Al. Formed with.
Here, the ion beam adjusting sample of Example 1 will be described in more detail with reference to FIG. FIG. 1A is a perspective view showing the structure of the ion beam adjusting sample 1, and FIG. 1B is an enlarged view of a part of the lattice-shaped thin film 3 in FIG. (c) is II sectional drawing of FIG.1 (b).
As shown in FIG. 1, the sample 1 for ion beam adjustment of Example 1 has GaInP crystal grown on the surface of a GaAs plate 1a in a thin film shape, and the GaInP thin film has a predetermined size of windows arranged in a lattice pattern. It is open and the underlying GaAs is exposed on the surface. This state is shown in more detail in FIG. The GaAs plate 1a is covered with a GaInP thin film, and GaInP is further removed by using a lithography method or the like, and the square windows 2 are opened in a lattice shape. GaAs is exposed from the window 2. The size of the square window 2 and the thickness of the window frame 3a are set to arbitrary sizes in order to correct the raster size and the length of the measurement part at the time of SIMS beam adjustment. The size is 20 μm, and the thickness of the window frame portion 3a is 5 μm.

  This ion beam adjustment sample is used for SIMS depth direction analysis or SIMS composition analysis, and the method is basically as described above with reference to FIG.

  According to Example 1, since the ion beam adjustment sample does not substantially contain Al as an element to be measured, the SIMS apparatus is not contaminated at the time of ion beam adjustment, and Al in the specimen sample can be measured with high accuracy. It can be carried out. The same applies to the case where the element to be measured is Cu.

(First invention, forming a lattice-like thin film with a conductive material)
In Example 2, the substrate is sapphire, and the lattice-shaped thin film is formed of GaN doped with magnesium which is a conductive material. Other points are the same as in the first embodiment. According to the second embodiment, since the lattice-shaped thin film is formed of a conductive material, it is possible to prevent charges from being accumulated on the substrate.

(Second invention)
Example 3 includes a step of adjusting an ion optical system using an ion beam adjustment sample, a step of calculating a relative sensitivity factor using a standard sample under the adjusted ion optical system, and an adjusted ion The step of measuring the secondary ion intensity of the detection target element in the specimen sample under the optical system, and the calculated relative sensitivity factor and the measured secondary ion intensity of the detection target element of the detection target element in the specimen sample The present invention relates to secondary ion mass spectrometry including a step of calculating an atomic concentration, and a standard sample includes a substrate and a thin film including a detection target element formed thereon, and the thin film is a partial region of the surface. Is etched into a lattice shape, the lattice-shaped region is used as an ion beam adjustment sample for ion beam adjustment, and the remaining region is used for calculation of a relative sensitivity factor. That is, in Example 3, one substrate is used as both a standard sample and an ion beam adjusting sample.

  Specifically, as shown in FIG. 2, the standard sample 11 has a GaInP thin film 13 grown on the surface of a GaAs plate 11a, and the GaInP thin film 13 has a predetermined size in a partial region 13a of the surface. The windows are open in a grid, and the underlying GaAs is exposed on the surface. The lattice-shaped region 13a is used for ion beam adjustment as an ion beam adjustment sample. The remaining region 13b is used for calculating the relative sensitivity factor. The detailed structure of the lattice-shaped region 13a is the same as that shown in FIGS. The method for forming the lattice shape, the ion beam adjusting method using the lattice shape, and the like are as described in the first embodiment.

  For example, when the Be sample is measured with BeIn doped GaInP, the GaInP thin film 13 contains Be as an impurity with a known concentration. This impurity Be can be doped during crystal growth of the GaInP thin film, and may be introduced into the GaInP thin film by ion implantation after the GaInP thin film is formed.

  In the third embodiment, ion beam adjustment and calculation of the relative sensitivity factor (RSF) by the standard sample can be performed from one sample, and another sample sample can be mounted on the sample holder. Further, both ion beam adjustment and standard sample measurement can be performed at the center of the sample holder, and the measurement system can be improved.

(Third invention)
Example 4 includes a step of adjusting an ion optical system using a sample for ion beam adjustment, and a step of measuring the secondary ion intensity of a detection target element in a specimen sample under the adjusted ion optical system. It relates to secondary ion mass spectrometry, and a specimen sample is composed of a substrate and a thin film formed thereon, and the thin film has a part of the surface etched into a lattice shape, and the lattice-shaped region is The ion beam adjustment sample is used for ion beam adjustment, and the remaining region is used for measuring the secondary ion intensity of the detection target element in the specimen sample. That is, in Example 4, one substrate is used as both the specimen sample and the ion beam adjusting sample.

  Specifically, as shown in FIG. 3, the specimen sample 21 has a GaInP thin film 23 grown on the surface of a GaAs plate 21a, and the GaInP thin film 23 has a predetermined size in a partial region 23a of the surface. The windows are open in a grid, and the underlying GaAs is exposed on the surface. The lattice-shaped region 23a is used for ion beam adjustment as an ion beam adjustment sample. The remaining region 23b is used for measuring the secondary ion intensity of the detection target element in the specimen sample. The detailed structure of the lattice-like region 23a is the same as that shown in FIGS. The method for forming the lattice shape, the ion beam adjusting method using the lattice shape, and the like are as described in the first embodiment.

In Example 4, ion beam adjustment and composition analysis of the specimen sample can be performed from one specimen, and another specimen specimen can be mounted on the sample holder.

The structure of the sample for ion beam adjustment used by SIMS which concerns on Example 1 and 2 is shown. (A) is a perspective view, (b) is an enlarged view of a part of a lattice-shaped thin film, and (c) is a cross-sectional view taken along the line II of (b). 6 is a perspective view showing a structure of a standard sample used in SIMS according to Example 3. FIG. 6 is a perspective view showing a structure of a specimen sample used in SIMS according to Example 4. FIG. The structure of the sample holder used by conventional SIMS is shown. (A) is a perspective view, (b) is II sectional drawing of (a). It is process drawing which shows the measurement procedure of the conventional SIMS depth direction analysis. It is process drawing which shows the measurement procedure of the conventional SIMS composition analysis. The structure of a sample for ion beam adjustment used in conventional SIMS is shown. (A) is a perspective view, (b) is an enlarged view of a part of a lattice-shaped thin film, and (c) is a cross-sectional view taken along the line II of (b).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,61: Sample for ion beam adjustment 1a, 61a: Substrate 2, 62: Window 3, 63: Lattice thin film 3a, 63a: Lattice 11: Standard sample 11a: Substrate 13: Thin film 13a: Ion beam adjustment region 13b: Relative sensitivity factor calculation area 21: Specimen sample 21a: Substrate 23: Thin film 23a: Ion beam adjustment area 23b: Measurement area of secondary ion intensity of element to be detected 50: Sample holder 51: Housing 52: Window 53: Sample 55: Cover 57: Spring 59: Screw

Claims (8)

Secondary ion mass spectrometry comprising a step of adjusting an ion optical system using a sample for ion beam adjustment, and a step of measuring the secondary ion intensity of a detection target element in a specimen sample under the adjusted ion optical system Secondary ion mass spectrometry characterized in that, when the detection target element is Al or Cu, the ion beam adjustment sample is formed of a material that is substantially composed only of an element different from the detection target element. Law. The secondary ion mass spectrometry method according to claim 1, wherein the ion beam adjusting sample includes a substrate and a lattice-shaped thin film formed thereon. The secondary ion mass spectrometry method according to claim 2, wherein the lattice-shaped thin film is obtained by forming a thin film on the entire surface of the substrate and etching the obtained thin film in a lattice shape by a lithographic method. The secondary ion mass spectrometry method according to claim 2, wherein the substrate is an insulator, and the lattice-shaped thin film is formed of a conductive material. Adjusting the ion optical system using the ion beam adjustment sample, calculating the relative sensitivity factor using the standard sample under the adjusted ion optical system, and under the adjusted ion optical system The step of measuring the secondary ion intensity of the detection target element in the specimen sample, and the atomic concentration of the detection target element in the specimen sample are calculated from the calculated relative sensitivity factor and the measured secondary ion intensity of the detection target element. A secondary ion mass spectrometry method comprising the steps of:
The standard sample is composed of a substrate and a thin film containing the detection target element formed on the substrate, and the thin film is partially etched on the surface in a lattice shape, and the lattice region is used as an ion beam adjustment sample. Secondary ion mass spectrometry, which is used for ion beam adjustment and the remaining region is used for calculation of relative sensitivity factor. The secondary ion mass spectrometry method according to claim 5, wherein the thin film containing the detection target element is a thin film doped with the detection target element. The secondary ion mass spectrometry method according to claim 6, wherein the doping of the detection target element is performed by ion implantation of the detection target element. Secondary ion mass spectrometry comprising a step of adjusting an ion optical system using a sample for ion beam adjustment, and a step of measuring the secondary ion intensity of a detection target element in a specimen sample under the adjusted ion optical system Law,
The specimen sample is composed of a substrate and a thin film formed on the substrate, and the thin film has a part of the surface etched into a lattice shape, and the lattice region is used as an ion beam adjustment sample for ion beam adjustment. And the remaining region is used for measuring the secondary ion intensity of the element to be detected in the specimen sample.

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