KR100253867B1 - An impurity concentrator and a method for concentrating impurity, an impurity analyzer and a method for analyzing impurity - Google Patents

Abstract

The present invention provides a method for concentrating impurities contained in a semiconductor crystal sample 11 by repeatedly irradiating a predetermined position of the semiconductor crystal sample 11 with a laser beam having a predetermined intensity by the laser oscillator 13. do. The present invention also provides a method for analyzing impurities contained in an impurity concentration region of the semiconductor crystal sample 11 with high sensitivity by predetermined physical analysis means. According to the demand, the method of the present invention forms an insulating film such as an oxide film and then concentrates the impurities by the laser light by irradiating the laser light onto the surface of the semiconductor crystal sample. At the same time, the present invention provides a concentration apparatus and an analysis apparatus using these concentration methods and analysis methods.

Description

Impurity concentrators and methods for concentrating impurities, impurity analyzers and methods for analyzing impurities

1 is a view showing a structural example of an impurity concentrating device according to a first embodiment of the present invention;

2 is a view showing a structural example of an impurity analyzer according to a first embodiment of the present invention;

3 is a view showing a structural example of an impurity concentration device according to a second embodiment of the present invention;

4 is a view showing a structural example of another impurity concentrator according to a second embodiment of the present invention;

5 is a view showing a structural example of an impurity analyzer according to a second embodiment of the present invention;

6 is a view showing a structural example of an impurity concentration device according to a third embodiment of the present invention.

[Objective of the invention]

[Technical Field to which the Invention belongs and Conventional Technology in the Field]

The present invention provides an impurity concentration method for concentrating a small amount of impurities in a semiconductor crystal such as a silicon (Si) crystal, an impurity concentration apparatus using the concentration method, an impurity analysis method for analyzing concentrated impurities, and an analysis method. It relates to an impurity analyzer used.

In general, silicon crystals are widely used as materials for semiconductor devices, and the presence of extremely small amounts of impurities such as Fe, Cu, Cr, and the like greatly affects the electrical properties of semiconductor devices formed on silicon crystals. Therefore, in order to improve the performance of the VLSI apparatus or the like, it is necessary to make these impurity concentrations contained in the silicon crystal as low as possible, and to do so, it is necessary to accurately measure the impurity concentration contained in the silicon crystal.

Until now, a wet chemical analysis method of dissolving a sample analyzed with an acid solution or an acid vapor, separating and concentrating impurities contained therein, and then measuring impurity concentrations by flameless atomic absorption spectrometry or inductively coupled plasma mass spectrometry; Secondary Ion Mass Spectrometry (SIMS), Total Reflection X-ray Fluorescence Spectrometry (TRXRF), Auger Electron Spectrometry (AES) and Particle Excited X-ray Spectroscopy (AES) Physical analysis such as PIXE (Particle Induced X-ray Emissin Spectrometry) has been commonly used as a method for measuring impurities in semiconductor crystals. However, wet chemical analysis requires a large amount of analyte to be analyzed, and since the dissolution of the analyte and the separation and concentration of impurities are considerably complicated, this method requires skill in chemical treatment technology and requires a long analysis time. Moreover, since this method uses acid solution or acid vapor, it is necessary to install a special acid-specific draft, gas exhaust system, and acid treatment facility from the viewpoint of environment and safety.

On the other hand, the physical analysis method does not need to be chemically treated as described above, and is essentially different from the above-described wet chemical analysis method, and since it is possible to directly measure the impurity concentration from the solid analysis sample, it is superior in the wet chemical analysis method. Can be said. In addition, the physics analysis method can analyze with a trace amount of sample, and is also superior in the deep direction resolution than the wet chemical analysis method. However, the above-described physical analysis methods other than the SIMS method have an analysis sensitivity of about 10 ppm to 10,000 ppm, and are not suitable for the detection of ultra trace impurities. Also in the SIMS method, impurity analysis of ppb or less is impossible.

As described above, the conventional wet chemical analysis method has a problem that a large amount of analytical sample is required, and that an expert in chemical treatment technology is required. In addition, the conventional wet chemical analysis has a problem that the draft, gas exhaust and acid treatment equipment dedicated to the acid must be installed.

On the other hand, the conventional physical analysis method has a problem that the analysis sensitivity for detecting an extremely small amount of impurities is insufficient.

[Technical Challenges to Invent]

The present invention has been made in view of the above, and provides an impurity concentration method for concentrating impurities contained in a solid sample such as a semiconductor crystal sample without chemically dissolving the sample, and an impurity concentration apparatus using the concentration method. The purpose is to do that.

It is another object of the present invention to provide an impurity analysis method for quickly, simply and accurately analyzing impurities contained in a solid sample such as a semiconductor crystal.

Composition and Action of the Invention

A first aspect of the present invention for achieving the above object is a sealed container provided with a supply port and an exhaust port of the carrier gas, a window (optical window) provided on the top of the sealed container, the sealed container so that the holder does not move during irradiation of the laser light. A sample holding holder for safely holding and holding a semiconductor crystal sample installed opposite to the window in the inside, a gas controller for controlling the supply amount of the supplied carrier gas, and a laser beam at a predetermined position on the sample through the window. An impurity concentrating device and impurity concentrating method comprising an irradiator such as a laser oscillator for repeatedly irradiating, and an observation means (observing device) for observing a change in the surface state of a sample through a window.

In the first aspect, the irradiating means comprises a plurality of laser oscillators having different wavelengths, and irradiates the sample with laser light having different wavelengths. 3 shows a concentrator using a plurality of laser oscillators, and the concentrator is equipped with three or more laser oscillators instead of two laser oscillators 13a and 13b as shown in FIG.

Furthermore, in the first aspect, the concentrator is equipped with a magnetic field generator for applying a magnetic field to the sample. 6 shows an example of such a device. The magnetic field generating means 25 of FIG. 6 is installed on the upper part of the sealed container 1, but if magnetic force is generated to move the ferromagnetic material (impurity) contained in the sample to the surface of the sample, the same as the lower part of the sealed container. It will be installed in another location.

Carrier gases such as hydrogen (H ₂ ), argon (Ar), helium (He), oxygen (O ₂ ), nitrogen (N ₂ ) and the like can be used here, but hydrogen is most preferred as described below. .

The impurity concentration method according to the first aspect of the present invention is a method for concentrating impurities in a semiconductor crystal by the impurity concentration apparatus described above. The method supplies a carrier gas into a sealed vessel at a predetermined flow rate, and exhausts it from the sealed vessel while repeatedly irradiating a predetermined position on the surface of the semiconductor crystal sample with laser light whose energy intensity is weaker than the intensity at which evaporation of the semiconductor crystal starts. It is a way.

According to the concentration method of the first aspect of the present invention, by repeatedly irradiating a laser light on the surface of a semiconductor crystal sample, it can be concentrated locally without contacting impurities contained in the sample. The reason for this is that defects, which are cooled by irradiating the surface of the sample with a laser beam and then cooled to become a gettering site, are generated near the crystal surface. This is because impurities such as Fe, Cu, Cr, etc., which are easily diffused into the crystal due to the heat generated by the laser light irradiation, have precipitated in the vicinity of the defect. The sample is securely held by the sample holding holder. It is for preventing the sample from moving by heat shock caused by the laser light during laser light irradiation. This is because the movement of the sample causes fluctuations in the laser light irradiation conditions and causes an imbalance in the degree of concentration that essentially coincides with the predetermined range.

In particular, the enrichment method using the plurality of laser oscillators 13a and 13b is the first laser light emitted by the short wavelength (first wavelength) laser oscillator 13a and whose energy intensity is weaker than the intensity at which evaporation of the semiconductor crystal starts. A first step of repeatedly irradiating a predetermined position on the surface of the semiconductor crystal sample; After the first step, the laser oscillator 13b having the second wavelength longer than the first laser light repeats the predetermined position on the surface of the semiconductor crystal sample with the second laser light whose energy intensity is weaker than the intensity at which evaporation of the semiconductor crystal starts. And a second step of irradiation. As a result, impurities contained in the deep region of the crystal are obtained by the first step of repeatedly irradiating the surface of the sample with the first laser light of short wavelength and by the second step of irradiating the surface of the sample with the second laser light of long wavelength. Can be concentrated locally without physical contact. The reason is that the surface of the crystal is melted by the first step of irradiating the surface of the sample with the first laser light having a short wavelength, and then cooled to generate defects that become gettering sites during the crystal, and then the second laser having a long wavelength. This is because impurities such as Fe, Cu, Cr, Ni, Mn, V, Ti, etc. contained in the deep region of the crystal are diffused upward and precipitated in the vicinity of the defect by the second step of applying heat to the crystal by irradiation of light.

Since the surface is cooled by introducing a flow rate of carrier gas into the surface of the semiconductor crystal, evaporation of the sample can be suppressed. Therefore, the energy intensity of the laser light used is relatively increased to improve the concentration efficiency of the metal impurity. Furthermore, since the sealed container, the crystal sample holding holder and the like are cooled by the carrier gas, impurity contamination can also be suppressed therefrom.

In particular, when a sample is irradiated with a long wavelength laser light while supplying a carrier gas such as pure hydrogen or a hydrogen gas mixture and an insertion gas such as argon or helium, metal impurities such as Fe, Cu, Cr, etc. are thermal energy in a deep region of a crystal. It becomes easy to diffuse by and moves around a defect, and is concentrated. In particular, the movement of impurities is enhanced in the hydrogen environment. Therefore, by repeatedly irradiating the surface of the semiconductor crystal with the laser light as described above, it is possible to densely concentrate the metal impurity in the crystal near the surface without contacting it.

In addition, as shown in FIG. 6, the first feature of the present invention is to repeatedly apply a sample surface with a laser beam while applying a magnetic field to the sample surface by a magnetic field generating means 25 provided outside or inside the sealed container 1. By irradiating, impurities contained in the crystal can be concentrated locally without contacting. This further improves the concentration efficiency by moving the ferromagnetic material (impurity) such as Fe and Ni in the crystal toward the surface of the crystal by the magnetic force applied to the semiconductor crystal sample by the magnetic field generating means 25.

A method for concentrating an impurity in a semiconductor crystal of the first aspect of the present invention is a method for rapidly, simply and densely concentrating an impurity without chemically dissolving the semiconductor crystal, but in this case, the laser beam is exposed before the laser beam irradiation. It is preferable to apply the surface of the semiconductor crystal sample in advance with an insulating film such as a silicon oxide film (SiO ₂ film), a silicon oxynitride film (SiON film), or a silicon nitride film (Si ₃ N ₄ film) to be transmitted. By applying the surface of the semiconductor crystal sample in advance with an insulating film such as a silicon oxide film, a silicon oxynitride film, or a silicon nitride film having low light absorption and high transmittance to laser light, the semiconductor crystal sample can be heated efficiently with laser light. . Therefore, it is possible to improve the concentration efficiency of metal impurities in semiconductor crystals and the like. At the same time, these insulating films formed on the surface of the semiconductor crystal can not only suppress secondary contamination of the semiconductor crystal sample from the environment or equipment, but also suppress evaporation loss of impurities in the semiconductor crystal. The silicon oxide film, silicon oxynitride film, and silicon nitride film are made by photoexcitation process with UV laser light to oxygen (O ₂ ), ammonia (NH ₃ ), nitrogen oxide (NO, N ₂ O), etc. Can be carried out in a container. The oxynitride film can be obtained by annealing the oxide film of the NO / insert gas mixture or the N ₂ O insert gas mixture by UV irradiation.

The second aspect of the present invention is to provide a sealed container provided with a carrier gas supply port and an exhaust port, and a semiconductor crystal sample provided to face the window in a sealed container so as not to move during a laser beam irradiation. Sample holding holder for securely holding and holding, gas control means for controlling the supply amount of the supplied carrier gas, laser oscillator for repeatedly irradiating laser light to a predetermined position on the sample through the window, and surface of the sample through the window An impurity concentrating device comprising an observation means for observing a change of state; Provided are an impurity analysis device and an impurity analysis method provided with analysis means for analyzing impurities concentrated by laser light.

The second aspect of the present invention is a physical analysis means such as secondary ion mass spectrometry (SIMS), total reflection fluorescence X-ray analysis (TRXRF), auger electron spectroscopy (AES), and particle excitation X-ray spectroscopy (PIXE), etc. Analyze the sample with concentrated impurities by the concentrator. Here, before starting the analysis, it is preferable to irradiate and mark a laser beam having an energy value at which crystal evaporation starts, around the outer side of the impurity concentration region on the sample surface. Then, the laser light for marking is emitted by a laser oscillator installed in the impurity concentrator. Since laser light having a high energy intensity at which semiconductor crystal evaporation can start is irradiated and marked around the outside of a predetermined position on the surface of the semiconductor crystal sample, it is easier to find an impurity concentration region, that is, an analysis region on the surface of the semiconductor crystal sample. This greatly improves sensitivity and accuracy.

In the second aspect of the present invention, since the irradiation of the laser light is performed inside the hermetically sealed container, contamination from the atmosphere can be suppressed, and an extremely small amount of impurities can be detected with high sensitivity.

EXAMPLE

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In this invention, the same code | symbol is attached | subjected to the same part and detailed description is abbreviate | omitted.

[First Embodiment]

1 is a diagram showing a structural example of an impurity concentrating device according to a first embodiment of the present invention. In FIG. 1, the impurity concentrator is configured to pass a carrier gas to cool the surface of a sample 11 such as a cylindrical hermetic container 1, a window (optical window) provided on top of the hermetic container, a semiconductor crystal, or the like. The supply port 5a and the exhaust port 5b provided on the side wall of the sealed container 1 are installed on the bottom surface 7 opposite the window 3 in the sealed container 1 so as not to move during the irradiation of the laser beam. The sample holding holder (9) for holding and holding (11) safely, the laser oscillator (13) provided as irradiation means for radiating laser light irradiated onto the sample (11), and the sample (11) with laser light. Gas control means 19 for controlling the supply amount of the carrier gas supplied in the condenser lens 15, the reflection mirror 17, and the sealed container 1 installed on the optical path of the laser light emitted from the laser oscillator 13 for irradiation. And, to observe the change of the surface state of the sample 11 through the window (3) It consists of a TV camera 21 and a TV monitor 23 for. Here, it is necessary for the sample to be accurately held at the correct position during the irradiation of the laser light a plurality of times. This is because when the sample 11 is moved by the heat shock caused by the laser light, the laser irradiation conditions in the predetermined range and the irradiation angle in the predetermined range that are essentially required to coincide vary.

Anything that effectively passes the laser light without directly or indirectly disturbing the analysis of the target component (impurity) can be used as the material for the optical window 3. Specifically, quartz, sapphire, pyrex glass, or the like is preferable. In addition, the window 3 is set in the sealed container 1 by a metal gasket or an O-ring so that it can be replaced. As the material of the airtight container 1, any material can be used as long as it does not directly or indirectly interfere with the analysis of the target impurity. For example, a fluorine resin such as PTFE, quartz, sapphire, Pyrex glass, metal, metal alloy, etc. may be used. Can be.

As the material of the sample holding holder 9, any material can be used as long as it does not directly or indirectly interfere with the analysis of target impurities. Fluorine resins, such as PTFE, a metal, a metal alloy, etc. are preferable from a viewpoint of workability. In addition, it is preferable that the sample holding holder 9 be replaceable with respect to the sealed container 1 or the sample 11. Oxygen, nitrogen, argon, helium, hydrogen and the like can be used as the carrier gas. As the laser oscillator 13, the laser energy value can be selectively changed, and any one can be used as long as it has sufficient laser energy to evaporate the semiconductor crystal sample. For example, Nd-YAG laser, ruby laser, excimer laser, etc. Can be used. As the TV camera 21 and the TV monitor 23, any type can be used as long as it can be used to observe the change of the crystal sample surface state under the irradiation of laser light.

Although not shown in FIG. 1, the impurity analyzer includes a physical analyzer and an impurity concentrator arranged adjacent to the impurity concentrator. Physical analysis means include secondary ion mass spectrometer (SIMS), total reflection fluorescence X-ray analyzer (TRXRF), auger electron spectroscopic analyzer (AES), and particle excitation X-ray spectrometer (PIXE). The analyzing means analyzes the impurities of the sample 11 in which the impurities are concentrated by the impurity concentrator.

As shown in FIG. 2, the impurity analyzing apparatus is made by connecting the sealed container 41 of the impurity concentrating apparatus together with the analysis chamber 42 of the analyzing means such as SIMS, TRXRF, AES, PIXE, etc. through the gate valve 62. will be. In the analysis chamber 42 of the impurity analyzer of the first embodiment of the present invention shown in FIG. 2, a radiation source 51 and an analytical detector 52 such as ion light, X-ray, and electron light are provided, and the sealed container 41 is provided. ) And the analysis chamber 42 may be vacuumed by a turbo molecular pump, a cryopump, an ion pump, and the like through the gate valves 63 and 64. In FIG. 2, the window 3 is provided on the upper portion of the cylindrical sealed container 41, and the supply port 5a and the exhaust port 5b for passing the carrier gas to cool the surface of the sample 11 such as semiconductor crystals. ) Is installed on the side wall of the hermetic container 41. Then, the sample holding holder 9 for safely holding and holding the sample 11 so as not to move during laser light irradiation is disposed on a position opposite to the inner window 3 of the sealed container 41. Similarly to FIG. 1, the impurity analyzer of the first embodiment of the present invention includes a laser oscillator 13 for emitting a laser beam irradiated onto a sample 11, and a laser oscillator for irradiating the sample 11 with laser light. 13 and gas control means 19 for controlling the supply amount of the carrier gas supplied into the condenser lens 15, the reflection mirror 17, and the sealed container 41 provided on the optical path of the laser light emitted from the light 13; (3) A TV camera 21 and a TV monitor 23 are provided for observing the change of the surface state of the sample 11.

Then, the sample preparation chamber 43 is installed in front of the sealed container 41 and connected to the sealed container 41 through the gate valve 61, the impurity-concentrated sample 11 is a vacuum transfer system 44 (transfer rod) It can be transferred from the sealed container 41 to the analysis chamber 42 in vacuum. The transfer rod may be driven by electromagnetic force or another mechanical drive system. According to the configuration as shown in FIG. 2, an extremely small amount of impurities can be measured without contamination of impurities in the air or adsorbate (impurity) on the surface of the impurity-concentrated sample. Although not shown, a sample vertical movement mechanism for transferring the sample in vacuum is provided in the analysis chamber 42, the sealed container 41, and the preparation chamber 43. For example, the sample holding holder 9 in the hermetic container 41 may receive the sample from the horizontal transfer rod 44 and may transfer the sample to the rod 44 by being moved vertically by the sample vertical movement mechanism. Of course, the sample holding holder that is vertically movable in the same manner is provided in the analysis chamber 42 and the preparation chamber 43.

According to the impurity concentrator and impurity analyzer of the first embodiment of the present invention shown in FIG. 1 and FIG. 2, impurities contained in the sample can be concentrated locally, and the surface of the sample such as semiconductor crystals can be By repeatedly examining, the analysis can be performed without contact. The reason for this is that Fe, which melts and then cools the surface of the sample by laser light irradiation and becomes a gettering site, occurs near the crystal surface, and further, Fe, which easily diffuses into the crystal by thermal energy generated by laser light irradiation, This is because impurities such as Cu and Cr precipitate in the vicinity of the defect.

The greater the energy value of the laser light, the higher the concentration efficiency. However, since the analysis cannot be performed when the sample evaporates, the energy value of the laser light is preferably 80 to 97% of the minimum energy value at which the crystal is evaporated. By supplying the carrier gas into the sealed container 41 through the supply port 5a and the exhaust port 5b, the surface of the sample can be cooled to suppress evaporation of the crystal sample. The flow rate of the carrier gas is controlled at a predetermined flow rate by gas flow rate control means (gas control means) such as a mass flow rate control device, a needle valve, or the like. By cooling the sample surface, the energy value of the laser used is set relatively high so that the concentration efficiency of impurities can be improved. In addition, the sealed container 41, the sample holding holder 9 and the like are also simultaneously cooled by the carrier gas, and contamination can be suppressed by impurities generated from them. In addition, according to the impurity concentrating device of the first embodiment of the present invention, since the laser light is irradiated into the sealed container 41, contamination of the air can be suppressed.

In the first embodiment of the present invention, a simple and high sensitivity analysis can be performed by analyzing the sample 11 in which impurities are concentrated by the impurity concentrator shown in FIG. Impurities are analyzed by physical analysis means such as SIMS, TRXRF, AES, PIXE, and the analysis means are arranged close to the impurity concentrator. In this case, laser light having an energy value at which evaporation of the sample starts is irradiated and marked around the outer side of the impurity concentration region on the sample surface, so that the impurity concentration region can be easily identified at the start of the next analysis. Laser light for marking is emitted by a laser oscillator installed in the impurity concentrator.

Example 1.1 Analysis of p-type Substrate

Metal impurities contained in the boron-doped silicon single crystal substrate (specific resistance: 6.9? Cm, thickness: 320 mu m) were concentrated by the impurity concentrator mentioned above and analyzed by secondary ion mass spectrometry (SIMS). When measuring the impurity concentration range by SIMS, the impurity concentration range is marked in advance by a laser installed in the impurity concentration apparatus for easy identification of the impurity concentration range.

Impurity concentration conditions, marking conditions, and SIMS measurement conditions of the silicon single crystal substrate are described below.

(1) Impurity Concentration Conditions

Laser oscillator: YAG laser (wavelength: 1064nm),

Pulse energy: 170mJ, pulse width: 200μs,

Pulse repetition rate: 10 pulses / sec

Pulse irradiation time: 600 seconds

Light diameter: 100㎛

Space volume of airtight container: about 80cm3

Carrier gas (Ar): 2 liters / minute.

(2) Marking conditions

Laser oscillator: YAG laser (wavelength: 1064nm),

Pulse energy: 210mJ, pulse width: 200μs,

Pulse repetition rate: 2 pulses / sec

Pulse irradiation time: 1 second

Light diameter: 100㎛, Marking range: 1mm × 1mm

(3) Measurement condition

Measuring device: IMS4F manufactured by Cameca, Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5㎂, Secondary ion acceleration voltage: 4.5kV,

Others: High mass resolution measurement.

The ionic strength (cps) of Cu, Fe, and Cr from the upper surface of the silicon substrate to the inside of 10 nm in depth under the above-mentioned conditions is shown in Table 1 as a comparative example.

TABLE 1

Example 1.2 Analysis of an n-type Substrate

Next, the metallic impurities contained in the indoped silicon single crystal substrate (specific resistance: 1.9? Cm, thickness: 430 µm) were concentrated by the impurity concentrator mentioned above and analyzed by secondary ion mass spectrometry (SIMS). .

Impurity concentration conditions, SIMS measurement conditions, and analysis results of the silicon single crystal substrate are described below.

(1) Impurity Concentration Conditions

Laser oscillator: YAG laser (wavelength: 1064nm),

Pulse energy: 180mJ, pulse width: 200μs,

Pulse repetition rate: 10 pulses / sec

Pulse irradiation time: 600 seconds

Light diameter: 100㎛

Space volume of airtight container: about 80cm3

Carrier gas (Ar): 2 liters / minute.

(2) Measurement condition

Measuring device: IMS4F manufactured by Cameca, Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5㎂, Secondary ion acceleration voltage: 4.5kV,

Others: High mass resolution measurement.

The ionic strength (cps) of Cu, Fe, and Cr was measured from the surface of the silicon substrate to a depth of 10 nm under the above-mentioned conditions.

TABLE 2

Second Embodiment

3 is a diagram showing a structural example of an impurity concentrating device according to a second embodiment of the present invention. In FIG. 3, the impurity concentrator is a sealed container for supplying a carrier gas so as to cool the surface of the cylindrical sealed container 1, the optical window 3 installed on the sealed container 1, and the surface of the sample 11. Samples provided on the bottom surface 7 in the airtight container 1 opposite to the window 3 in the sealed container 1 so that the supply port 5a, the exhaust port 5b, and the holder, which are provided on the side wall of the container 1, do not move during the irradiation of the laser light ( 11) the sample holding holder 9 for safely holding and holding the sample 11, the laser oscillators 13a and 13b provided as irradiation means for radiating the laser beam irradiated onto the sample 11, and the sample 11 as the laser beam. Gas control for controlling the supply amount of the carrier gas supplied in the condenser lens 15, the reflection mirror 17, and the sealed container 1 installed on the optical path of the laser light emitted from the laser oscillators 13a and 13b to irradiate Observing the change of the surface state of the sample 11 through the means 19 and the window 3 It consists of a TV camera 21 and a TV monitor 23 for. Here, the sample needs to be accurately held at the correct position by the sample holding holder 9 during the irradiation of the laser light a plurality of times. The reason why the sample holding holder is used is that when the sample moves, the laser irradiation condition of a predetermined range changes and an accurate analysis value cannot be obtained or an analysis error becomes large.

Any material can be used as the material of the window 3 as long as it effectively passes the laser light without directly or indirectly disturbing the analysis of the target component. Specifically, quartz, sapphire, pyrex glass, or the like is preferable. Further, the window 3 is set in the sealed container 1 by a metal gasket or an O-ring so that the window 3 can be replaced. As the material of the airtight container 1, any material can be used as long as it does not directly or indirectly interfere with the analysis of the target impurity. For example, heat-resistant glass such as fluorine resin such as PTFE, quartz, sapphire, pyrex glass, metal, Alloys can be used. As the material of the sample holding holder 9, any material can be used as long as it does not directly or indirectly interfere with the analysis of target impurities. A fluorine resin, a metal, an alloy, etc. are preferable from a viewpoint of workability. In addition, it is preferable that the sample holding holder 9 be replaceable with respect to the sealed container 1 or the sample 11. Oxygen, nitrogen, argon, helium, hydrogen and the like can be used as the carrier gas.

As the laser oscillators 13a and 13b, the energy value (output) can be arbitrarily changed, and any one can be used as long as it has sufficient laser energy to evaporate the semiconductor crystal sample. For example, Nd-YAG laser, SHG-YAG laser, A short wavelength laser oscillator (13a: first laser oscillator) and a long wavelength laser oscillator (13b: second laser oscillator) are selected from among a ruby laser, a die laser, an argon laser, a carbon dioxide laser, an excimer laser, and the like. Specifically, a combination of a 532 nm SHG-YAG laser as the short wavelength laser oscillator 13a and Nd-YAG of 1064 nm as the long wavelength laser oscillator 13b will be used as an example. As the TV camera 21 and the TV monitor 23, any type can be used as long as it can be used to observe the change of the crystal sample surface state caused by the irradiation of the laser light.

Although not shown in FIG. 3, the impurity analyzer comprises impurity concentrators and physical analysis means such as SIMS, TRXRF, AES, PIXE, etc., for analyzing impurities in the sample 11 in which the impurities are concentrated by the impurity concentrator. The analyzing means is arranged adjacent to the impurity concentrator. And, as shown in FIG. 2, the impurity analyzing apparatus will be made by connecting the analysis chamber of the physical analysis means and the sealed container of the impurity concentrating apparatus through the gate valve.

In the second embodiment of the present invention, the process for concentrating impurities is carried out by supplying a carrier gas to the inside from the sealed container 1 shown in FIG. 3 and exhausting the carrier gas to the outside. A first step of irradiating the first laser light of short wavelength (first wavelength) having an energy intensity weaker than the energy intensity at which evaporation of the semiconductor crystal starts by the short wavelength laser oscillator 13a; Next, the second laser light of a long wavelength (second wavelength longer than the first wavelength) having a predetermined position on the surface of the semiconductor crystal sample having an energy intensity weaker than the energy intensity at which evaporation of the semiconductor crystal starts by the long wavelength laser oscillator 13b. It consists of a second process irradiated with. The wavelength of the short wavelength laser oscillator 13a is 100 to 1100 nm, preferably 150 to 600 nm. The wavelength of the long wavelength laser oscillator 13b is 500 to 15000 nm, preferably 500 to 11000 nm. When the first laser light of short wavelength is first irradiated to the surface of the semiconductor crystal in the first step by the impurity concentration apparatus shown in FIG. 3, the crystal defect becomes a gettering site when the surface of the crystal melts and then cools. Occurs near the surface. Subsequently, when the second laser light having a long wavelength is irradiated to the crystal surface while the carrier gas is flowed in the second step, metal impurities such as Fe, Cu, Cr, Ni, Mn, V, Ti, etc. present in the deep region of the crystal are irradiated. The heat generated by the laser irradiation tends to diffuse, and the impurity is concentrated in the defect generating region. Therefore, by repeatedly irradiating the surface of the semiconductor crystal with the first and second laser light as described above, it is possible to concentrate densely and locally without contacting the metal impurity in the vicinity of the surface. In order to improve the defect formation efficiency and the concentration efficiency, it is preferable to perform laser light irradiation for a considerable time in the first and second processes. When irradiating a laser beam several times, you may perform a 1st and 2nd process alternately, but the last irradiation must necessarily be a 2nd process. The stronger the energy intensity of the laser light, the higher the effect. However, since the sample evaporates if the energy intensity is too high, the energy intensity of the laser light is actually required to be 80 to 97% of the energy intensity at which evaporation of the crystal sample can start.

In the second embodiment of the present invention, it is preferable to form a silicon oxide film, a silicon oxynitride film or a silicon nitride film on the surface of the sample 11 such as a semiconductor crystal in advance. The silicon oxide film, silicon oxynitride film or silicon nitride film can not only suppress secondary contamination on the semiconductor crystal sample from the environment, but also suppress the loss caused by evaporation of impurities from the semiconductor crystal. From the viewpoint of impurity suppression and secondary pollution suppression, the film thickness is preferably as thin as possible. However, if the thickness is too thin, it takes a long time to analyze the semiconductor crystal, so the thickness is preferably in the range of 10 to 200 nm, which is not larger than 300 nm. These films will be formed by any method such as CVD, sputtering, spin-on-glass, thermal oxidation, thermal oxynitride, thermal nitriding, photoexcited oxidation, photoexcited oxynitride, photoexcited nitriding, or the like. For example, in the case of the photoexcited oxidation method, a SHG-YAG laser having a wavelength of 266 nm can be suitably used. The silicon oxynitride film will be formed by heat treatment of the oxide film in an N ₂ O gas or NO gas atmosphere. Like the silicon oxide film, the silicon oxynitride film, or the silicon nitride film, only the semiconductor crystal sample can be effectively heat treated by the laser light by pre-coating the surface of the semiconductor crystal sample with an insulating film having high transmittance of laser light and low light absorption. Therefore, the concentration efficiency of the metallic impurities in the semiconductor crystal can be improved.

When a silicon oxide film, a silicon oxynitride film or a silicon nitride film is formed by the photoexcited oxidation method, the photoexcited oxynitride method or the photoexcited nitriding method, these films are formed in the airtight container 1 in the form of O ₂ , N ₂ O, NO, NH ₃ It can form by irradiating a laser beam, supplying gases, such as these. In order to form a permeable insulating film such as a silicon oxide film and the like and to concentrate impurities in the same sealed container, it is preferable to use a reaction tube 49 (closed container) provided with a sapphire window in a transparent quartz tube or a transparent quartz tube as shown in FIG. . In FIG. 4, the reaction tube 49 is wound with a water-colled induction coil 91 so as to perform high frequency (RF) induction heating. In the case of performing RF induction heating, a SiC-coated carbon susceptor is used as the sample holding holder 9. In addition, an infrared (IR) lamp heating method using a halogen lamp or the like may also be performed instead of RF induction heating, and a substrate heating device such as a water-cooled induction coil 91 or an IR lamp is unnecessary in the case of an optical excitation process. In FIG. 4, the flow rate of the reaction gas or the carrier gas is controlled by gas control means 71, 72, 73, 74, 75, 76, such as a mass flow rate control device. In order to form an excellent oxide film, an oxynitride film and a nitride film, it is desirable to clean the surface of the semiconductor. Therefore, a mixed gas of HCI gas and H ₂ gas is introduced on the surface of the semiconductor substrate immediately before the oxidation, oxynitride and nitride. Thus, it is preferable to clean and remove the native oxide film or the like on the substrate surface. In order to form a nitride film, the substrate is heated to 700 to 1300 ° C by flowing NH ₃ gas or argon-diluted NH ₃ gas, or irradiated with UV rays at a low temperature of 400 ° C or lower. As shown in Fig. 4, in the case of using a reaction tube, it is not usually necessary to use a movable window for laser light, but employing the movable window further saves labor in cleaning. This is because the cleaning frequency of the entire reaction tube is generally smaller than the window cleaning frequency. As shown in FIG. 4, by using a reaction tube such as quartz, it is possible to easily handle highly reactive gases such as NH ₃ , HCI, etc., thereby facilitating film formation and impurity concentration in the same container. Otherwise, as shown in FIG. 5, the sealed container 41 and the film formation chamber 45 of the impurity concentration apparatus are connected to each other through the gate valve 61. As shown in FIG. In FIG. 5, the semiconductor crystal sample 11 is heated by a halogen lamp (IR lamp) in the film formation chamber 45, and the nitride film can be formed by supplying NH ₃ gas. The light of the halogen lamp 82 is efficiently focused on the surface of the semiconductor crystal sample by the reflection mirror 81 such as a spheroidal mirror. IR lamps other than halogen lamps are used. The oxide film may be formed by flowing oxygen gas, and the oxynitride film may be formed in an O ₂ , N ₂ O, NO, or NH ₃ atmosphere. The oxynitride film can also be formed by annealing the oxide film in N ₂ O gas or NO / insert gas at 850 to 1000 ° C. An oxynitride film having a thickness of about 10 nm may be formed by heat treatment at 850 ° C. for 30 minutes in N ₂ O. After the film is formed, the gate valve 61 is opened to transfer the semiconductor crystal sample to the sealed container 41, and then impurity concentration is performed.

Furthermore, as shown in FIG. 5, the impurity analyzer is provided with a sealed container 41 of the impurity concentrator and an analysis chamber 42 of analytical means such as SIMS, TRXRF, AES, and PIXE via the gate valve 62. It is comprised by connecting. In FIG. 5, a radiation source 51 and an analytical detector 52 such as ion light, X-ray, and electron light are installed in the analysis chamber 42, and the sealed container 41 and the analysis chamber 42 are gate valves 63, 64 may be vacuumed by a turbo molecular pump, a cryopump, an ion pump, or the like. In FIG. 5, the semiconductor crystal sample 11 is transferred in vacuum from the deposition chamber 45 to the sealed container 41 by the transfer rod 44 in the sealed container 41 to the analysis chamber 42 in vacuum. The window 3 is provided on the upper portion of the cylindrical sealed container 41 of the second embodiment of the present invention shown in FIG. 5, and the supply port 5a and the exhaust port 5b for passing the carrier gas to cool the surface of the sample. ) Is installed on the side wall of the sealed container 41, and the sample holding holder 9 for holding the sample 11 safely so as not to move during the laser light irradiation is attached to the inner window 3 of the sealed container 41. To face. Laser oscillators 13a and 13b for emitting a laser beam irradiated onto the sample 11 on the sealed container 41 and laser beams emitted from the laser oscillators 13a and 13b for irradiating the sample 11 with laser light. Condensing lenses 15a and 15b and reflecting mirrors 17a and 17b provided on the optical path of the laser beam are arranged. Then, the TV camera 21 and the TV monitor 23 for observing the change of the surface state of the sample 11 through the window 3 are arranged to divide the optical path into the optical system.

According to the structure as shown in FIG. 5, very small amount of impurities can be measured without adhering a small amount of impurities in the air on the surface of the impurity-concentrated sample. Although not shown, a sample vertical moving mechanism for transferring the sample in vacuum is installed in the film formation chamber 45, the analysis chamber 42, and the sealed container 41. For example, the sample holding holder 9 in the hermetically sealed container 41 may transfer the sample from the transfer rod 44 while being vertically moved by the sample vertical movement mechanism. Similarly, of course, a vertically movable sample holding holder is installed in the analysis chamber 42.

According to the impurity concentrator and the impurity analyzer shown in FIGS. 3 to 5, the surface of the semiconductor crystal is cooled by flowing a carrier gas into the sealed container 1 through the supply port 5a and the exhaust port 5b. This has the effect of suppressing evaporation of the crystal sample. Therefore, the energy intensity of the laser light used can be relatively increased, and the concentration efficiency of the metal impurities in the crystal can be improved. Moreover, since the sealed containers 1, 41, 49, the crystal sample holding member 9, and the like are also cooled, impurity contamination can be suppressed therefrom. In particular, when irradiating a crystal sample with a long-wavelength laser light by injecting a carrier gas of H ₂ or H ₂ / inserted gas mixture, metal impurities such as Re, Cu, Cr, etc., which exist in a deep range in the crystal, are transferred to heat and H ₂ . As a result, it becomes easy to diffuse, and impurities move to the defect region and are concentrated.

The reason is as follows. This is because H ₂ is inherently more easily adsorbed on a silicon substrate than Ar, N ₂ and the like, and further has a larger diffusion coefficient inside the wafer. The diffusion coefficient of the metal impurity in the silicon wafer is further increased by changing the carrier gas to H ₂ when the laser light is irradiated. And since H ₂ is a reducing gas, the density of defects (mostly caused by oxygen) in the silicon wafer is reduced, as a result of the above-mentioned reaction, and the diffusion rate of transition metal components such as Cu, Fe, etc. is increased. . Therefore, by repeatedly irradiating a laser beam while supplying a H ₂ or H ₂ / insert gas mixture to the semiconductor crystal surface, it is thought that the transition metal impurities in the wafer are locally concentrated at a high concentration near the wafer surface where the defect density increases. do.

According to the second embodiment of the present invention, by irradiating a laser beam into the sealed container 1, since it is concentrated at a high concentration locally in the vicinity of the crystal surface without contacting metal impurities in the crystal, impurity contamination is suppressed from the environment. can do. Further, by positioning and marking the area around the outside of a predetermined position on the surface of the semiconductor crystal sample with a laser beam of energy intensity sufficient to initiate evaporation of the semiconductor crystal, the concentration of the impurity concentration region, that is, the analysis region on the surface of the semiconductor crystal sample is determined. This becomes easier. Therefore, the analysis sensitivity and accuracy can be further improved. The laser light used for marking is emitted from a laser oscillator provided in the impurity concentrator or impurity analyzer shown in Figs. The wavelength of the laser beam used for marking is 100 nm-15000 nm, Preferably it is 500 nm-11000 nm. Although only _two laser lights are shown in FIGS. 3 to 5, a third laser oscillator, such as a CO ₂ laser or the like, will be added for use in the marking. By measuring a semiconductor crystal sample in which impurities are locally concentrated by the impurity concentrators shown in FIGS. 3 and 4 by SIMS, TRXRF, PIXE, and AES, a simple and highly sensitive analysis can be performed. The marking process may be performed before or after laser light irradiation (first process or second process) of the concentration process. However, it is more effective to carry out the marking before the concentration process.

Example 2.1 Analysis of p-type Substrate

Metal impurities contained in the boron-doped silicon single crystal substrate (resistance: 2.0? Cm, thickness: 330 µm) are concentrated by the impurity concentrator mentioned above, and analyzed by secondary ion mass spectrometry (SIMS).

Impurity concentration conditions, SIMS measurement conditions, and analysis results of the silicon single crystal substrate are described below.

(1) Concentration Conditions of Impurities

Laser oscillator (13a): SHG-YAG laser (wavelength: 532nm),

Laser oscillator (13b): YAG laser (wavelength: 1064 nm),

Pulse energy: 170mJ, pulse width: 200μs,

Pulse repetition rate: 10 pulses / sec

Pulse irradiation time: 300 seconds

Light diameter: 100㎛

Space volume of airtight container: about 80cm3

Carrier gas (Ar): 2 liters / minute.

(2) Measurement condition

Measuring device: IMS4F manufactured by Cameca, Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5㎂, Secondary ion acceleration voltage: 4.5kV,

Others: High mass resolution measurement.

The measurement results of the ionic strengths (cps) of Cu, Fe and Cr from the upper surface of the silicon substrate to a depth of 10 nm under the above-mentioned measurement conditions are shown in Table 3 as a comparative example.

TABLE 3

Example 2.2 Analysis of n-type Substrate

Next, the metal impurity contained in the indoped silicon single crystal substrate (specific resistance: 3.7? Cm, thickness: 420 µm) is concentrated by the impurity concentrator mentioned above and analyzed by secondary ion mass spectrometer (SIMS). .

Impurity concentration conditions, SIMS measurement conditions, and analysis results of the silicon single crystal substrate are described below.

(1) Concentration Conditions of Impurities

Laser oscillator (13a): SHG-YAG laser (wavelength: 532nm),

Laser oscillator (13b): YAG laser (wavelength: 1064 nm),

Pulse energy: 170mJ, pulse width: 200μs,

Pulse repetition rate: 10 pulses / sec

Pulse irradiation time: 300 seconds

Light diameter: 100㎛

Space volume of airtight container: about 80cm3

Carrier gas (Ar): 2 liters / minute.

(2) Measurement condition

Measuring device: IMS4F manufactured by Cameca, Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5㎂, Secondary ion acceleration voltage: 4.5kV,

Others: High mass resolution measurement.

The ionic strength (cps) of Cu, Fe, and Cr was measured from the surface of the silicon substrate to a depth of 10 nm under the above-mentioned measurement conditions.

TABLE 4

Example 2.3 Analysis of p-type Substrate

A boron-doped silicon single crystal wafer having a specific resistance of 2.6 OMEGA cm and a thickness of 350 µm (square of 10 mm on one side) was prepared, and the surface of the wafer was coated with a SiON film (20 nm) made by CVD, and shown in FIG. The impurity concentrator was irradiated with a short wavelength laser light under the following conditions and then with a long wavelength laser light. Next, the ionic strength of the impurities was measured under the following conditions by SIMS.

(1) Impurity Concentration Conditions

1st process: SHG-YAG laser (wavelength: 355nm) and carrier gas Ar,

Second process: YAG laser (wavelength: 1064 nm) and carrier gas H ₂ ,

Irradiation condition: Pulse energy 170mJ, Pulse width 200μs,

Pulse repetition rate: 10 pulses / sec,

Pulse irradiation time: 300 seconds

Light diameter: 100㎛ (common to the first and second process),

Space volume of airtight container: about 80cm3

Carrier gas: 2 liters / minute.

Prior to the irradiation of the laser light of the first and second steps, four pulses of 200 mJ of pulse energy (wavelength 1064 nm) are irradiated and marked at each pulse on four points of a square whose side is 2 mm in the surface of the silicon wafer.

(2) Measurement condition

Analytical device: Model NO. Manufactured by Cameca Inc., IMS4F,

Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5 mA, Secondary ion acceleration voltage: 4.5 kV,

Others: high mass resolution measurement.

The ionic strengths (cps) of Cu, Fe and Cr from the surface of the silicon wafer to a depth of 10 nm under the above-mentioned measurement conditions are shown in Table 5 as a comparative example and a reference example.

TABLE 5

Example 2.4 Analysis of an n-type Substrate

A guided silicon single crystal wafer having a specific resistance of 3.4? Cm and a thickness of 390 [mu] m is set on the sample holding holder 9 of the apparatus shown in FIG. A SiON film having a thickness of 11 nm was formed on the surface of the sample in order to oxynitride the silicon wafer surface by irradiating a laser beam while supplying a mixed gas of oxygen and ammonia.

The concentration step was applied to this silicon wafer in the same manner as in Example 2.3, and the ionic strength of impurities in the obtained silicon wafer was measured in the same manner as in Example 2.3. The ionic strengths of Cu, Fe and Cr from the surface of the silicon wafer to a depth of 10 nm are shown in Table 6 as a comparative example and a reference example.

TABLE 6

Example 2.5 Analysis of p-type Substrate

A boron-doped silicon single crystal wafer having a specific resistance of 2.3 Ωcm and a thickness of 330 µm (square of 10 mm on one side) was prepared, and the surface of the wafer was coated with an SiO ₂ film (20 nm) made by CVD, and the impurities shown in FIG. The concentrator was irradiated with a short wavelength laser light under the following conditions and then with a long wavelength laser light. Next, the ionic strength of the impurities was measured under the following conditions by SIMS.

(1) Impurity Concentration Conditions

1st process: SHG-YAG laser (wavelength: 355nm),

2nd process: YAG laser (wavelength: 1064nm),

Irradiation condition: Pulse energy 170mJ, Pulse width 200μs,

Pulse repetition rate: 10 pulses / sec,

Pulse irradiation time: 300 seconds

Light diameter: 100㎛ (common to the first and second process),

Space volume of airtight container: about 80cm3

Carrier Gas: Ar

Carrier gas feed rate: 2 liters / minute.

Prior to the irradiation of the laser light in the first and second steps, four square points each having a side of 2 mm in the surface of the silicon wafer are marked by irradiating laser pulses having a pulse energy of 200 mJ (wavelength of 1064 nm) for each pulse.

(2) Measurement condition

Analytical device: Model NO. Manufactured by Cameca Inc., IMS4F,

Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5 mA, Secondary ion acceleration voltage: 4.5 kV,

Others: high mass resolution measurement.

The ionic strengths (cps) of Cu, Fe, and Cr from the surface of the silicon wafer to a depth of 10 nm under the above-mentioned measurement conditions are shown in Table 7 as a comparative example and a reference example.

TABLE 7

Example 2.6 Analysis of an n-type Substrate

A guided silicon single crystal wafer having a specific resistance of 3.7 Ωcm and a thickness of 420 µm is set on the sample holding holder 9 of the apparatus shown in FIG. 3, and the SiO ₂ film having a thickness of 10 nm is supplied with oxygen gas for oxidation. It formed on the surface of a wafer by irradiating the surface of a silicon wafer with a laser beam.

The concentration step was applied to this silicon wafer in the same manner as in Example 2.5, and the metal ion strength of the impurities from the surface of the obtained silicon wafer to 10 nm inside was measured in the same manner as in Example 2.5. The measurement results are shown in Table 8 as a comparative example and a reference example.

TABLE 8

Third Embodiment

6 is a diagram showing an example of the structure of an impurity concentrating device according to a third embodiment of the present invention. In FIG. 6, the impurity concentrator is a sealed container for passing a carrier gas to cool the surface of the cylindrical sealed container 1, the optical window 3 provided above the sealed container 1, and the surface of the sample 11. Samples provided on the bottom surface 7 in the airtight container 1 opposite the window 3 in the airtight container 1 so that the supply port 5a, the exhaust port 5b and the holder do not move during irradiation of the laser light. A sample holding holder 9 for holding and holding 11 securely, a laser oscillator 13 for emitting a laser beam irradiated onto the sample 11, and a laser oscillator 13 for irradiating the sample 11 with laser light. Gas control means (19) and window (3) for controlling the supply amount of the carrier gas supplied into the condenser lens (15), the reflection mirror (17), and the sealed container (1) installed on the optical path of the laser beam emitted from A TV camera 21 and a TV monitor 23 for observing changes in the surface state of the sample 11 through It consists of magnetic field generating means 25 for applying a magnetic force to the sample 11. The magnetic field generating means 25 is arranged such that a magnetic force is generated to move the ferromagnetic material toward the surface of the sample, and is not limited to the structure shown in FIG. For example, the magnetic field generating means configured to surround the side wall or the bottom of the sealed container may generate a magnetic field acting in a predetermined direction.

Here, H ₂ , Ar, He, O ₂ , N ₂ and the like can be used as a carrier gas, but a small amount of H ₂ will be added to the insert gas, such as Ar, He as needed. Fluorine resins, quartz, sapphire, Pyrex glass, metals, alloys, etc. do not directly or indirectly interfere with the analysis of the target impurities, so they are used as materials for the airtight container (1). It is preferable that it is a sexual substance. The optical window 3 is preferably made of a transmission material such as quartz, sapphire, pyrex glass or the like that can efficiently transmit the laser light without directly or indirectly disturbing the analysis of the target impurity. Then, the window 3 is preferably set in the sealed container 1 by a metal gasket or an O-ring. As the material of the sample holding holder 9, any material can be used as long as it does not directly or indirectly interfere with the analysis of target impurities. Fluorine resins, metals, alloys and the like are preferable from the viewpoint of mechanical capability. In addition, it is preferable that the sample holding holder 9 can be replaced with respect to the sealed container 1 or the sample 11.

The laser oscillator 13 is preferably an Nd-YAG laser, a ruby laser or the like from the viewpoint that it is necessary to have an energy value capable of evaporating a sample while allowing the energy value to be arbitrarily changed. The TV camera 21 and the TV monitor 23 may be of any type as long as they can be used to control the change of the surface state of the sample caused by the irradiation of the laser light.

The magnetic field generating means 25 installed to attract ferromagnetic materials such as Fe and Ni contained in the surface of the sample to the surface may be any one of a permanent magnet and an electromagnet. In terms of pollution prevention, the magnetic field generating means 25 is preferably disposed outside the sealed container 1, as shown in FIG. However, when coated with a material excellent in heat resistance, oxidation resistance and chemical resistance, such as Teflon, it is arrange | positioned inside the airtight container 1. When placed inside the container 1, it can be placed in the magnetic field generating means 25 very close to the sample 11 can increase the strength of the magnetic field.

Although not shown in FIG. 6, physical analysis means such as SIMS, TRXRF, AES, and PIXE for analyzing impurities in the sample 11 enriched by the impurity concentrator are disposed adjacent to the impurity concentrator so that the impurity analyzer Configure

According to the configuration shown in FIG. 6, by repeatedly irradiating a sample surface such as a semiconductor crystal with a laser beam, the impurities contained in the sample can be concentrated locally without contact. The reason is that after irradiating a laser beam to the surface of the sample and melting the surface, cooling occurs to generate crystal defects in the vicinity of the crystal surface, which become gettering sites. This is because thermal energy generated by laser light irradiation enhances diffusion of impurities such as Fe, Cu, Cr, etc. in the crystal, and impurities precipitate in the vicinity of the defect. In particular, by repeatedly irradiating the surface of the sample with a laser beam while applying a magnetic field to the surface of the sample 11 by the magnetic field generating means, the impurities contained in the crystal 11 can be locally concentrated without contact. Therefore, ferromagnetic materials such as Fe and Ni are moved to the upper surface of the semiconductor crystal sample due to the magnetic force. By applying the magnetic field directed to the upper surface of the semiconductor crystal sample 11 by the magnetic field generating means 25, the concentration efficiency is greatly improved. As the energy value of the laser light increases, the concentration efficiency also improves. However, since the analysis cannot be performed when the sample evaporates, the energy value of the laser light is preferably 80 to 97% of the energy value at which the crystal starts to evaporate.

In the third embodiment of the present invention, a simple and high sensitivity analysis can be performed by analyzing the sample 11 enriched by the impurity concentrator shown in FIG. Impurities are analyzed by physical analysis means such as SIMS, TRXRF, AES, PIXE and the like. The analyzing means is arranged adjacent to the impurity concentrator. In this case, the impurity concentration region is marked by irradiating and marking the outer periphery of the impurity concentration region on the surface of the sample with a laser beam having an energy value capable of initiating evaporation of crystals, thereby further identifying and restoring the subsequent analysis region. It becomes easy. Laser light for marking is emitted from a laser oscillator installed in the impurity concentrator.

Example 3.1 Analysis of p-type Substrate

The metallic impurities contained in the boron-doped silicon single crystal substrate (specific resistance: 2.0 Ωcm, thickness: 330 µm) were concentrated by the impurity concentrator mentioned above and analyzed by secondary ion mass spectrometry (SIMS).

The impurity concentration conditions of the silicon single crystal substrate and the measurement conditions of the SIMS are described below.

(1) Concentration Conditions of Impurities

Laser oscillator: YAG laser (wavelength: 1064nm),

Pulse energy: 170mJ, pulse width: 200μs,

Pulse repetition rate: 10 pulses / sec

Pulse irradiation time: 600 seconds

Light diameter: 100㎛

Space volume of airtight container: about 80cm3

Carrier gas (Ar): 2 liters / minute.

Magnetic field generating means: Teflon-coated permanent magnet (8k gauss, 20mm length × 20mm width × 3mm thickness × 3mm diameter hole in the center).

(2) Measurement condition

Measuring device: IMS4F manufactured by Cameca, Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5㎂, Secondary ion acceleration voltage: 4.5kV,

Others: High mass resolution measurement.

The measurement results of the ionic strengths (cps) of Cu, Fe, and Cr from the upper surface of the silicon substrate to a depth of 10 nm under the above-mentioned measurement conditions are shown in Table 9 as a comparative example.

TABLE 9

Example 3.2 Analysis of an n-type Substrate

Next, the metallic impurities contained in the indoped silicon single crystal substrate (specific resistance: 3.7? Cm, thickness: 420 µm) were concentrated by the impurity concentrator mentioned above and analyzed by secondary ion mass spectrometry (SIMS). .

Impurity concentration conditions and SIMS measurement conditions of the silicon single crystal substrate are described below.

(1) Concentration Conditions of Impurities

Laser oscillator: YAG laser (wavelength: 1064nm),

Pulse energy: 180mJ, pulse width: 200μs,

Pulse repetition rate: 10 pulses / sec

Pulse irradiation time: 600 seconds

Light diameter: 100㎛

Space volume of airtight container: about 80cm3

Carrier gas (Ar): 2 liters / minute.

Magnetic field generating means: Teflon-coated permanent magnet (8k gauss, 20mm length × 20mm width × 3mm thickness × 3mm diameter hole in the center).

(2) Measurement condition

Measuring device: IMS4F manufactured by Cameca, Primary ion light: O ₂ ⁺ ,

Acceleration voltage: 12kV, Scanning range: 500㎛ × 500㎛

Current: 0.5㎂, Secondary ion acceleration voltage: 4.5kV,

Others: High mass resolution measurement.

The ionic strengths (cps) of Cu, Fe, and Cr were measured from the surface of the silicon substrate to a depth of 10 nm under the above-mentioned conditions.

TABLE 10

Claims (23)

(a) a sealed container provided with a supply gas exhaust port and an exhaust port; (b) a window installed on top of the hermetic container, (c) a sample holding holder for securely holding and holding a single crystal sample installed opposite the window in the sealed container; (d) gas control means for controlling the amount of carrier gas supplied; (e) irradiation means for repeatedly irradiating a predetermined position of the sample with a laser beam through the window; (f) observation means for observing a change in the surface state of the sample through the window; (g) an impurity analysis device for analyzing impurities in a single crystal, characterized by comprising an analysis device for analyzing impurities in the sample irradiated with the laser light. (a) placing a semiconductor crystal sample in a sealed container; (b) repeatedly supplying a carrier gas into the hermetic container at a predetermined flow rate and repeating a predetermined position on the surface of the semiconductor crystal sample with first laser light having an energy intensity and a first wavelength that are weaker than the energy intensity at which evaporation of the semiconductor crystal starts. The first step of investigation and (c) on the surface of the semiconductor crystal sample with second laser light having an energy intensity weaker than the energy intensity at which evaporation of the semiconductor crystal starts and supplying a carrier gas into the closed vessel at a predetermined flow rate and having a second wavelength longer than the first wavelength. And a second step of repeatedly irradiating the predetermined position. 3. The method according to claim 2, wherein the carrier gas of the second step is hydrogen gas or a mixture of hydrogen and intercalation gas. 3. The semiconductor according to claim 2, further comprising a step of applying the surface of the semiconductor crystal sample in advance with an insulating film that transmits through the first and second laser light prior to the first and second steps. Method for concentrating impurities in crystalline sample. 5. The method according to claim 4, wherein the coating step is performed by oxidizing, oxynitriding or nitriding the surface of the semiconductor crystal sample. The method of claim 5, wherein the coating step comprises concentrating impurities in the semiconductor crystal sample by oxidizing the surface of the semiconductor crystal sample by irradiating with a laser beam while supplying a mixed gas or oxygen containing oxygen into the hermetic container. Way. The method of claim 2, wherein the first and second laser light have an energy intensity of 80 to 97% at which evaporation of the semiconductor crystal starts. 3. The method according to claim 2, wherein the first and second steps are alternately repeated and finished with the second step. (a) Irradiating a predetermined position of the surface of the semiconductor crystal sample irradiated by the first and second laser light with the first laser light having a first wavelength in a carrier gas atmosphere supplied at a constant flow rate in a sealed container in which the semiconductor crystal is disposed. Thereafter, concentrating impurities in the semiconductor crystal by irradiating a predetermined position on the surface of the semiconductor crystal sample with a second laser light having a second wavelength longer than the first wavelength; (b) measuring a semiconductor crystal sample by secondary ion mass spectrometry, total reflection fluorescence X-ray analysis, PIXE method, or AES method at the predetermined position where the impurities are locally concentrated through the impurity concentration step; A method for analyzing impurities in a semiconductor crystal sample, characterized in that made. 10. The method of claim 9, wherein the impurity concentration step irradiates the second laser light at a mixture of hydrogen and intercalation gas or at a flow rate of hydrogen. A semiconductor according to claim 9, further comprising a film forming step for forming an insulating film that transmits the first and second laser light on the surface of the semiconductor crystal sample prior to the impurity concentration step. Method for analyzing impurities in crystal samples. 10. The surface of the semiconductor crystal sample according to claim 9, wherein before and after the impurity concentration step, the outer surface of the semiconductor crystal sample is irradiated with a laser beam having an energy intensity greater than or equal to the energy intensity required for evaporation of the semiconductor crystal. A method for analyzing impurities in a semiconductor crystal sample, characterized by further comprising a step of. 10. The method of claim 9, wherein the first and second laser light have an energy intensity of 80 to 97% necessary for evaporation of the semiconductor crystal. (a) a sealed container provided with a supply gas exhaust port and an exhaust port; (b) a window installed on top of the hermetic container, (c) a sample holding holder for securely holding and holding a single crystal sample installed opposite the window in the sealed container; (d) gas control means for controlling the amount of carrier gas supplied; (e) repeatedly irradiating a predetermined position of the sample through the window with a laser light having an energy intensity weaker than the value at which evaporation of the single crystal sample starts so that impurities precipitate in the vicinity of the surface irradiated by the laser light. Research means for, (f) an impurity concentrating device for concentrating impurities of a single crystal, characterized by comprising observation means for observing a change in the surface state of said sample through said window. 15. The impurity concentrator of claim 14, wherein the energy intensity is between 80% and 90% of the maximum energy intensity at which evaporation of the single crystal sample starts. The method of claim 14, further comprising a marker for irradiating the surface of the single crystal sample on the outer periphery of the impurity precipitation region, The marker is an impurity concentrating device for concentrating impurities of a single crystal, characterized in that for using the laser light having an energy intensity to start the evaporation of the single crystal sample. 16. The impurity concentrating device for concentrating impurities of a single crystal according to claim 15, wherein another laser light is emitted by a laser oscillator included in said irradiating means. 15. The impurity concentrator of claim 14, wherein the carrier gas is supplied to a surface of the single crystal sample to suppress evaporation of the single crystal sample. 15. The impurity concentrating device according to claim 14, wherein said sample holding holder prevents movement of said single crystal sample by application of heat shock to said single crystal sample from said laser light. 15. The impurity concentrating device for concentrating impurities according to claim 14, wherein the sample holding holder has a groove into which the single crystal sample is inserted. 15. The impurity concentrating device for concentrating impurities according to claim 14, wherein the sample holding holder has a flange for safely holding the single crystal sample. (a) a sealed container provided with a supply gas exhaust port and an exhaust port; (b) a window installed on top of the hermetic container, (c) a sample holding holder for securely holding and holding a single crystal sample installed opposite the window in the sealed container; (d) gas control means for controlling the amount of carrier gas supplied; (e) irradiating means for irradiating the sample repeatedly with a laser beam through the window, and for irradiating the sample with a laser beam having a wavelength different from that of another, the laser oscillator having a wavelength different from that of another; , (f) Impurity concentrator for concentrating single crystal impurities, characterized in that it comprises an observation means for observing the change of the surface state of said sample through said window. (a) a sealed container provided with a supply gas exhaust port and an exhaust port; (b) a window installed on top of the hermetic container, (c) a sample holding holder for securely holding and holding a single crystal sample installed opposite the window in the sealed container; (d) gas control means for controlling the amount of carrier gas supplied; (e) irradiation means for repeatedly irradiating a predetermined position of the sample with a laser beam through the window; (f) observation means for observing a change in the surface state of the sample through the window; (g) Impurity concentrator for concentrating single crystal impurities, characterized in that it comprises a magnetic field generating means for applying a magnetic field to the sample.