JPH0378955A - Method and device for inspection of solid surface - Google Patents

Abstract

PURPOSE:To provide possibility of sensing impurity contained in a specimen in a ultra-micro amount by irradiating the object area of the specimen with two types of laser beam together with a primary ion beam. CONSTITUTION:In the attitude to allow the optical axes to intersect, different types of laser beam source 13a, laser beam source 13b, laser beam source 13c are arranged on the surface of a specimen 6 in its position to be inspected where irradiation is made with primary ion beam 4 and primary electron beam 4a, and this position of specimen 6 to be inspected is irradiated with laser beam 14a, laser beam 14b, and laser beam 14c emitted from these sources. This provided ultra-high sensitivity and precision sensing of the type of secondary ions 11 generated from the object inspection part of specimen 6 by irradiation with the primary ion beam 4, primary electron beam 4a, and laser beams 14a, 14b, and 14c.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to solid surface inspection technology, and in particular to the detection of ultratrace impurity elements in the manufacturing process of semiconductor integrated circuit devices by secondary ion mass spectrometry and the detection of impurity elements. This paper relates to solid surface inspection technology for process evaluation by detecting the state of compounds.

[Conventional technology]

In the manufacturing process of semiconductor integrated circuit devices, as devices become more highly integrated and miniaturized, the presence of ultra-trace amounts of impurity elements of less than ppm and ppt, and the presence of impurity elements of several ppm.
The presence of compounds of only a few tens of micrometers has come to have a great effect on device performance and yield, and is not limited to minute areas, but
High-sensitivity detection of ultra-trace impurity elements in the 2nd region and detection of compound states of these elements are essential.

In response to such demands, in recent years, the following secondary ion mass spectrometers and techniques for detecting trace elements using radar light have come into use.

Their outline is as follows. In other words, in a secondary ion mass spectrometer, a primary ion beam is irradiated onto the inspection area of a sample, and at that time, secondary particles such as ionized particles, secondary electrons, and Auger electrons are detected among the secondary particles sputtered on the sample surface. By mass spectrometry and energy analysis of particles to measure the elemental analysis and compound state of the sample surface itself, we can determine the presence and distribution of ultratrace impurity elements on the surface and cross-sectional direction of specific parts of the sample. The aim is to use actual samples to clarify the causes of electrical malfunctions in semiconductor integrated circuit devices and to determine the optimal values for the manufacturing conditions for these devices.

For example, in semiconductor integrated circuit devices, it is necessary to analyze defective products by detecting impurities in submicron-sized regions. When it comes to such minute parts, detection sensitivity is generally inversely proportional to the area of the analysis site, making it difficult to detect even impurities on the order of ppm even with a normal secondary ion mass spectrometer. Therefore, even if a defective product is compared with a non-defective product, there may be no significant difference. As a countermeasure, we create a simulated sample with as wide an area as possible and analyze and evaluate it.

However, it is increasingly becoming impossible to determine the cause of failures without analyzing the minute parts of the actual sample (device).

Regarding the conventional secondary ion mass spectrometer, an outline is described in documents such as "Surface Analysis" edited by Dan Someno and Iwao Yasumori, published by Kodansha Co., Ltd., August 1, 1976, 8th edition.

On the other hand, among the ultra-trace impurities, a new detection method for Fe in the case where Fe is contained in a Si single crystal has been proposed at the Argonne National Laboratory in the United States.
Photoionization method developed by researchers at the National Laboratory (Electronics Week) ; Dec
ember 17.

1984, P22.24 or scanning electron microscope (S
canning Electron Miocrosc
opy), 1986.

1, see page 21.22). In this method, when a sample is irradiated with Ar+ ions, sputtered neutral particles (
Neutrals), first of all, Gui Laser (
This is a method in which desired impurities are ionized by irradiating and exciting a laser (dye La5er) and then irradiating with an excimer laser (excimer La5er). Here, we selected conditions in which neither excitation nor ionization occurs even when the main component element Si is irradiated with the Gouy laser or excimer laser, and only the impurity element Fe can be selectively ionized, so these ions are not mass-separated. A method is used to detect all ions in the form of all ions.

If such a method is adopted, a commercially available secondary ion mass spectrometer (SIMS;
It has been reported that the sensitivity is four orders of magnitude higher than that of ran mass spectrometry. This method is
Resonance ionization spectrometry (RIS; Re5onan
ce Ionizat+on 5pectroscope
y), which can selectively ionize only a specific element to be analyzed, Fe, so ion detection is performed in the form of all ion detection described above, but only Fe is excited and ionized, and the main component element or Fe In order to create conditions that do not excite or ionize other elements, it is necessary to use a Gouy laser or excimer laser with a narrow wavelength and a sharp radar beam with a narrow half-value width. Nb-Y-Al garnet type, 302.065 nm.

It is stated that the excimer lede is of the Xe-C1 type and needs to be precisely tuned to 308 nm. That is, for elements other than Fe as well, it is necessary to precisely adjust the excitation wavelength and ionization wavelength unique to that element.

[Problem to be solved by the invention]

However, the conventional secondary ion mass spectrometer (SIMS;
Mass Spectrometer), the primary ion species (Ch, C-0
-,G.

etc.), the incident angle, the current density, and the secondary ion species (positive ions, negative ions, compound ions, etc.), there is a limit to the ionization efficiency with current equipment. In addition, when the amount of impurities to be detected is small, it is impossible to detect the target element. Of course, many attempts have been made to increase the ionization efficiency, including bombarding neutral particles with electrons and irradiating them with light, which have not been used so far. However, the amount of ions increased by only a few tens of percent, and an improvement of several orders of magnitude could not be achieved, necessitating the development of a new high-sensitivity ionization method.

In addition, conventional resonance ionization analysis method (RIS) using laser beam irradiation is used.
ion 5pectroscopy), when ionizing Fe in a Si single crystal, a 3G laser is used.
There is no problem if you select and precisely tune the wavelength of 02.065 nm to the wavelength of 303 nm for excimer radar, but if the precisely adjusted wavelength deviates slightly, then Fe ions and other In addition, there is a possibility that the main component, Si, will also be ionized, which poses a problem with the detection technique based on the all-ion detection method shown in the literature. Furthermore, even when Ar= ions are irradiated as primary ions, there is a probability that Si, the main component, will be ionized due to this irradiation, and it is extremely difficult to distinguish between Si' ions and Fe' ions using all-ion detection technology. Furthermore, F in the S1 single crystal
For impurities other than e, it is difficult to select a laser beam with a wavelength sufficiently tuned to this impurity, and multiple elements other than the specific impurity will be ionized at the same time. If there is no way to differentiate, there is a problem that even if the ionization efficiency becomes significantly high, it will not be able to contribute to the improvement of detection sensitivity.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a solid surface inspection method capable of detecting impurities contained in a super-polarized sample.

Another object of the present invention is to provide a solid surface inspection device capable of detecting impurities contained in a sample in a super-polar position.

Still another object of the present invention is to provide a solid surface inspection device that can accurately perform various inspections.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the solid surface inspection method of the present invention detects at least one of secondary ions and secondary electrons generated by irradiation of a target region of a sample with a primary ion beam, and detects the distribution state of substances in the target region of the sample. This is a known solid surface inspection method in which a target area of a sample is irradiated with two or more types of laser light along with a primary ion beam.

The solid surface inspection device of the present invention also includes a sample stage that supports a sample, a primary ion beam irradiation system that irradiates a target area of the sample with a primary ion beam, and a secondary ion beam irradiation system that observes secondary ions generated from the sample. This is a solid surface inspection device consisting of an ion mass spectrometry system, and is equipped with a laser light source that irradiates a target area of a sample with two or more types of laser light along with a primary ion beam.

[Effect]

According to the solid surface inspection method of the present invention described above, for example, it is possible to control the difference between the irradiation time of the primary ion beam and the irradiation time of each of two or more types of laser beams, and to control the amount of secondary ions and secondary electrons (both By combining the control of the difference between one detection time and each irradiation time, for the reasons described later,
The ionization of neutral particles that are sputtered together with secondary ions from the sample is promoted, and it becomes possible to ionize up to about 90% of the neutral particles irradiated with laser light, and approximately 90% of these ions are transferred to the mass spectrometer. About 80% of the neutral particles can be analyzed by mass spectrometry.

As a result, not only the constituent elements of the main components of the sample but also trace impurities and 0. It is possible to elucidate even ultra-trace impurities on the order of OO1 ppb.

As a result, for example, it is possible to elucidate the causes of process-related failures of semiconductor integrated circuit devices involving ultra-trace impurities and trace impurities, and to obtain basic data for setting process conditions.

Further, according to the solid surface inspection apparatus of the present invention described above, for example, as a laser light source, it emits light as strong as the resonance line or the resonance line of a specific wavelength that excites the target neutral particles of ultra-trace impurities. Alternatively, by using a laser light source that can be controlled so that the oscillation times of Raded light of two or more wavelengths have a correlation, it is possible to reduce the amount of time that is sputtered from the sample together with secondary ions for the reasons described below. The ionization of neutral particles is promoted, and the neutral particles irradiated with laser light can be ionized to about 90%, and nearly 90% of these ions can be guided to the mass spectrometer. Approximately 80% can be analyzed by mass spectrometry.

This makes it possible to elucidate not only the constituent elements of the main components of the sample but also trace impurities and ultra-trace impurities on the order of 0.001 p p b.

Further, it includes an electron beam irradiation system that irradiates a target region of the sample with an electron beam, and an image observation means that detects charged particles generated from the target region and configures an image,
By providing a monitor that monitors the detection intensity of a specific element, it is possible to stop measurement when a certain detection intensity of a specific element is reached, or continue measurement work from that point until a desired time or desired depth. or transfer the inspection work to another measurement site or another sample.
Various tests can be accurately performed on samples such as semiconductor integrated circuit devices exhibiting a multilayer structure.

As a result, for example, it is possible to elucidate the causes of process-related defects in semiconductor integrated circuit devices involving ultra-trace impurities and trace impurities, and to quickly and accurately obtain basic data for setting process conditions.

In other words, the energy required to ionize neutral particles is also called ionization voltage, and is shown in Figures 12 (a) and (b).
As shown in , it varies greatly depending on the element, but it is several ev ~
It is about 20 ev. The same figure shows the ionization voltages of various elements detailed on pages 419 to 421 of the complete editorial committee of Experimental Chemistry Handbook: Experimental Chemistry Handbook (new edition), Kyoritsu Publishing Co., Ltd. (October 1978, 22nd edition). This is a diagram showing the values of , in order of atomic number. From the figure, it can be seen that the magnitude of the ionization voltage changes like a periodic law. In other words, the ionization voltage of Group 1 alkali metals and Group 2 alkaline earth metal elements is small, gradually increases in Groups 3 and 4, and tends to reach its maximum value in Group 8 noble gases. .

The relationship shown in equation (1) exists between the wavelength λ (nm) of light and its energy E (ev).

That is, the energy of light with a wavelength of 123.9 nm is approximately IQev. Therefore, many of the elements shown in FIG. 12 will be ionized.

On the other hand, even for elements with an ionization voltage of 1Qev or more, about 1Qe
If v has an excited state, if it is exposed to light again in that state, elements up to about 20 ev can be ionized. However, an element that does not have an excited state around 1 Qev will not be ionized even if it is irradiated with light twice. This example will be described in the first section for detecting Fe in a Si single crystal.
This will be explained with reference to FIG. When detecting Fe contained in a Si single crystal, first irradiation with 3key-Ar" ions causes the S1 sample surface to sputter and release neutral particles of Si and Fe. These neutral particles are in the ground state or The state is close to that.This particle has 302.065n
When irradiated with a Gui laser of m, exactly 4.10 e v
Receives energy equivalent to , Fe becomes excited! ! lF
e'', but Sl remains in the ground state or a state close to it.

Next, when irradiated with 308 nm light from an excimer laser, the ionization of Fe becomes a higher energy state than 7.83 ev (4.10 ev + 4.02 ev).
ev=s, 12 ev), Fe'' becomes Fe'' ion. In any case, Si is in the ground state or a state close to it, and cannot be ionized even at an ionization voltage of 81 g, osev.

Therefore, if the element to be analyzed is irradiated with light of a wavelength corresponding to the excitation unit energy, then another light is irradiated, and the sum of both excitation energies exceeds the ionization voltage, the element can be ionized. As described above, when detecting iron in a Si single crystal, a Gouy laser with a wavelength of 302.65 nm is first used, and then an excimer laser with a wavelength of 308 nm is used. Here, the iron resonance line includes 371.99 nm in addition to the above 302.065 nm.
36nm, 430.7904nm, 438.3547T
1m, 440.4752nm, etc. exist, so even if you use a corresponding Gouy laser, if the sum of the excimer laser wavelengths exceeds the ionization voltage of iron, 7g3ev, even by a little, the iron element will be ionized. , can be detected after mass spectrometry.

On the other hand, in addition to iron, the presence of metals and heavy metals such as Cu, Mo, and W, even in minute amounts, can cause defects in device characteristics in semiconductor integrated circuit devices, causing a serious problem.

To detect them, the wavelength of the Gouy laser can be selected to be approximately close to the excitation level (resonance level) of each metal, and the wavelength can be finely adjusted. For example, 51 for Cu
0.55nm, 327.40nm, 324.75nm,
296.12 nm, 553.30 nm for Mo, 379
．． 80 nm, 317. O3nm.

313.26nm, 281.62nmSW: 430°21nm, 429.46nm, 400.88nm, 29
4.70 nm, 286.61 nm, etc. and,
The ionization voltage of each element is CuNia, 68evSFaNia, and 83ev as the excimer Rede wavelength.

Monia, 06ev, W: 8. It is sufficient to select one having an energy greater than the value obtained by subtracting the energy of the light of the Gouy laser from lev.

The wavelength of currently available LED light is approximately 10Qnm~
1. Various sizes and shapes are being manufactured one after another, ranging from those with outputs that are in the OOOnm range and powerful to those that are easy to use. In particular, with the recent worldwide research on laser fusion and the need for and development of ultra-fine processing technology using lasers, we have developed a compact, high-density, extremely excellent GUI laser and excimer that can operate from short to long wavelengths.・Since lasers have been developed and are commercially available, or prototypes have been made and are in operation, it is possible to select one suitable for excitation and ionization of neutral particles.

Ionization of particles by light bombardment is due to electromagnetic waves, unlike the physical collision of objects, as in the case of ion bombardment, electron bombardment, radiation bombardment, etc.

Therefore, even if charged particles exist in the vicinity of particles to be ionized or a strong electric field is applied, there is almost no adverse effect from them. Furthermore, since light has the speed of light, it is possible to bombard sputtered neutral particles with multiple photons. The time it takes for the irradiated particles to become excited and then transition to an ionized state, or to transition to an ionized state at -degrees, varies depending on the type of element and compound, so it cannot be stated unconditionally. The moving speed of the primary ion beam and the secondary ion beam (about 10-" seconds) is very short.

In addition, when the sample surface is bombarded with ions, the sputtered neutral particles are not affected even if a secondary ion extraction electric field (an electric field in combination with an immersion lens, etc.) is applied. It stays near the sample surface for some time. Only after they are ionized by laser or laser light irradiation are they guided by this extraction electric field and subjected to mass spectrometry, allowing for accurate ionization.

Furthermore, if the primary ion beam is an element other than the target, o2, o-, c, c ions, etc. (the ions currently used in SIMS) can be used to irradiate solids by irradiating these ions. The elements on the sample surface are Ar
``It is possible to ionize more (higher ionization efficiency) than with ion irradiation, and it is also possible to increase or decrease the generation efficiency of neutral particles. When selecting ions, etc., it is possible to determine the optimal combination for the types of elements to be analyzed.

[Embodiment 1] FIG. 1 is a plan view showing an example of the configuration of a solid surface inspection apparatus that is an embodiment of the present invention.

Samples such as semiconductor wafers and semiconductor pellets on which various patterns are formed are placed on the sample stage 5, which can be freely moved in parallel or rotationally in a vertical plane using a well-known x-y table mechanism or rotary table mechanism. 6 is placed.

On the side of the sample stage 5, a primary ion mass spectrometer/primary electron energy analyzer 3 whose axis is inclined at a predetermined angle with respect to the sample 6 placed on the sample stage 5 in the horizontal plane is installed.
A charged particle source 1a and a charged particle source 1b are provided at positions sandwiching therebetween.

Then, ion group 2a or electron group 2 generated from each
b is passed through a primary ion mass spectrometer/primary electron energy analyzer 3, thereby forming a primary ion beam 4 and a primary electron beam 4a composed of selected ions of a desired element.

These charged particle sources 1a, lb include, for example, a gas discharge type ion gun such as a duoplasmatron, a hot cathode type electron gun,
It consists of a combination of cold cathode electron guns, Tsurugi cathode electron guns, field emission ion guns, field emission electron guns, etc.

On the other hand, the paths of the primary ion beam 4 and primary electron beam 4a from the charged particle sources 1a and lb to the sample 6 placed on the sample stage 5 via the primary ion mass spectrometer/primary electron energy analyzer 3 include primary An ion mass spectrometer/primary electron energy analyzer 3, an electrostatic or electromagnetic focusing lens 8, an orifice 7 for primary particles, a charged particle scanning deflector (not shown), an axis adjustment deflector, etc. are arranged in this order. and
For example, several 100 to several 100 microns for the surface of 60 samples.
The primary ion beam 4 and primary electron beam 4a, which are focused to a size of m, are configured to stand still or scan.

The above-mentioned axis adjustment deflector etc. include a 6-electrode lens so that various aberrations that occur when focusing the primary ion beam 4 and the primary electron beam 4a as described above are removed or reduced.
It is composed of an 8-electrode lens, a 4-electrode lens, etc.

In addition, a magnetic field-type electron beam corrector (not shown) for correcting various aberrations of the primary electron beam 4a, which is more susceptible to the influence of magnetic fields than the primary ion beam 4, is arranged upstream of the axis adjustment deflector (not shown). There is.

Furthermore, in this case, the primary ion beam 4 on the surface of the sample 60
Various laser light sources 13a, laser light sources 13b, and laser light sources 13C are arranged in such a manner that their optical axes intersect with the inspection area to be irradiated with the primary electron beam 4a, and laser light 14a and laser light 14b are emitted from each of them. The structure is such that the laser beam 14G is irradiated onto the inspection site of the sample 6.

In addition to the method of directly irradiating the surface of the sample 60 as in this embodiment, an arbitrary optical path may be set by passing the light through a prism, a lens, or the like, or by using a mirror or the like.

In addition, since the atmosphere in the sample chamber (not shown) in which the sample stage 5 is housed is maintained at an ultra-high vacuum, the laser beam 14 is emitted from the outside.
A, 14b, and 14c can be irradiated by passing through a window (not shown) that separates the vacuum region from the atmosphere.

Laser oscillation in the atmosphere is commonly carried out in many experiments, and those conducting the experiment must wear safety goggles that comply with occupational safety standards, but special problems arise especially when incorporating laser oscillation into equipment. Not yet.

Near the sample 6, primary ion beam 4 and primary electron beam 4a are irradiated, and laser beams 14a, 14b,
A field immersion lens 9 and a field immersion lens 10 are provided to form an electric field for extracting the secondary ions 11 generated by the irradiation of the sample 14c with high efficiency. It also serves as a fixture for fixing to the sample stage 5.

Furthermore, the path of the secondary ions 11 extracted by the immersion lens system includes an electrostatic lens 15 that captures the secondary ions 11, an α slit 16, a toroidal electric field/spherical electric field generator 17, a β slit 18, and an electromagnetic field. The secondary ions 2 pass through the generator 19 and the toroidal electric field/spherical electric field generator 23.
4 directly with a Faraday cup 25 or converted into secondary electrons and amplified, and a two-dimensional secondary electron multiplier 27 that visualizes the state of the secondary ions 24. A secondary ion mass spectrometry system M consisting of a fluorescent substance 28 and the like is provided.

As a result, the primary ion beam 4 and the primary electron beam 4a (mainly insulator samples are irradiated to the same part of the sample at the same time or almost simultaneously in order to stably analyze the sample without being charged, so the electron beam is generated sources (including those not shown), and laser light 14
a, 14b.

The type of secondary ions 11 generated from the target inspection site of the sample 6 by the irradiation with the rays 14c can be detected with ultra-high sensitivity and precision.

In addition, the output of the signal amplifier 29 or signal amplifier 30 that reflects the detection intensity of the target secondary ions 24 is output as a brightness modulation signal of a cathode ray tube (not shown) synchronized with the scanning of the primary ion beam 4 or the primary electron beam 4a with respect to the sample 6. By inputting , the intensity distribution regarding a specific element on the surface of the sample 6 can be drawn as an image.

In addition, for signal detection of secondary ions, by connecting a two-dimensional position detector and a computer to process and record the signal, it is possible to obtain a two-dimensional elemental intensity distribution image and depth direction after measurement. Concentration distribution images can also be drawn and these images can be observed.

Although not particularly shown, a concentric cylindrical energy analyzer or the like is arranged near the sample 6, and secondary electrons 12H emitted from the surface of the sample 6 by irradiation with the primary ion beam 4 or the primary electron beam 4a are used. By analyzing the energy of AES (Auger Electro
n5pectroscopy), ESC A(
Electron IEnergy 5pectro
Scopy for Chemical＾nalysi
information such as s) and the radar lights 14a, 14b.

P E S (Photoelectron 5pec
troscopy), it is now possible to estimate the content, compounds, and chemical bonding states of elements that are present at 0.1% or more.

Further, each of the above-mentioned parts is housed in a vacuum container that is evacuated to a desired degree of vacuum.

Hereinafter, the operation of the solid surface inspection apparatus of this embodiment will be explained in detail with reference to the drawings.

First, the primary ion beam 4 and the primary electron beam 4a formed by monochromating the ion group 2a or the electron group 2b emitted from the charged particle source 1a or 1b by the primary ion mass analyzer/primary electron energy analyzer 3 are shown in the figure. The sample 6 is irradiated with the beam focused to a desired size while adjusting the beam using a lens system that does not cover the beam, a deflection system, an axis adjustment lens system, etc.

At this time, secondary electrons 1
2a, uncharged neutral particles 12, and secondary ions 11 are emitted, and the secondary ions 11 are mass-separated by a secondary ion mass spectrometry system M to identify the elements constituting the sample surface. I can do it.

In particular, in this case, it is possible to detect from the main component element, and since the ionization efficiency differs depending on the type of element, the minimum amount that can be detected, that is, the detection sensitivity differs, but ppt (10-")
impurities on the order of .

Here, elemental analysis and the combination of constituent elements of the compound can be revealed. On the other hand, although not shown in FIG. 12, by performing energy analysis (Auger electron energy analysis) of the secondary electrons 12a, it is possible to know the bonding state of the elements at the same time as the elemental analysis. Here, elements can be identified from 0.1% to 100%. By combining secondary ion mass spectrometry, secondary electron energy analysis, and information, the bonding state of compounds and elements on the surface of the actual sample 6 becomes clear. In particular, if highly sensitive analytical techniques are used here, it is possible to detect significant differences in impurities mixed in between non-defective products and defective products. However, if there is no significant difference between the two, it is necessary to conduct an even more sensitive analysis.

Therefore, in the case of this embodiment, as described above, the sample 6 is irradiated with the laser beams 14a, 14b, 14C, etc. almost simultaneously or a little later than the irradiation with the primary ion beam 4. Then, in addition to the secondary ions 11 emitted by the irradiation with the primary ion beam 4 or the -' electron beam 4a, the neutral particles 12 are emitted by the Radhe beams 14a, 14b, 14.
The secondary ions 11 that undergo photoexcitation such as c are photoionized and are extracted almost simultaneously from the sample surface by an electric field using an immersion lens, and then analyzed and detected by a secondary ion mass spectrometer. Become.

As a result, the neutral particles 12 are ionized and become secondary ions 11 by the irradiation with the laser beams 14a, 14b, and 14c. The wavelength of the Gouy laser was finely adjusted to 302.065 nm, and the excimer
When the laser wavelength is 308 nm, it can be increased approximately 10,000 times, and the analysis area of 1 μmφ or several 110
Even in a 0n thin film, Fe in the Si single crystal can be detected up to the order of 10@-.

At this time, if the analysis area is expanded to 100 μmφ, 10-
” can now be detected.

Then, the primary ion beam 4 is scanned in a two-dimensional direction,
By using signals from the signal amplifiers 29 and 30 as brightness modulation signals of the cathode ray tube in synchronization with this, it is possible to measure the two-dimensional elemental distribution on the sample surface. In particular, if there is a difference in the distribution of impurities between good and defective products,
Defective locations can be identified.

In addition, irradiating the sample surface with the primary ion beam 4 utilizes the ion sputtering phenomenon from time to time on the surface, so that temporal changes in the intensity of secondary ions are caused by changes in the intensity of elements in the depth direction. Information corresponding to changes and changes in the composition of compounds can be obtained.

An example in which Fe was analyzed as a trace impurity contained in an Sl single crystal using the solid surface inspection apparatus having the configuration shown in FIG. 1 will be described below. When a Si single crystal sample 6 containing a trace amount of Fe is irradiated with 02 ions as the primary ion beam 4, the surface of the sample 6 is sputtered, as shown in FIG. 2, for example. Here, the positive ions among the sputtered secondary particles are immediately drawn out by an electric field (not shown), while the neutral particles 12 generate a Goo laser when they slowly move near the sample 6. The laser light source 13a is activated to emit laser light 14a to the neutral particles 12.
As shown in Figure 13, Si particles and Fe
Among the particles, only Fe particles are excited by light with a wavelength of 302.06571 m (Fe*). In the state of 20Fe0,
It remains there, unaffected by the electric field. This Fe”
When the laser light source 13b that generates an excimer laser is operated to irradiate the laser beam 14b, the light with a wavelength of 3Q3 nm becomes Fe'' ions as explained in FIG. 13. These Fe'' ions are extracted by the electric field. and move toward the secondary ion mass spectrometry system. However, Si particles are
Even if these two laser beams are irradiated, it will not be ionized, so
When analyzing Fe" ions, there is an increase due to laser beam irradiation, but there is no increase in Si0 ions, so F
There were no problems during ion detection.

Figure 3 shows how the Fe content in the S1 single crystal was measured from the surface to the depth direction using the phenomenon illustrated in Figure 2 using the solid surface inspection device configured as shown in Figure 1. It is a diagram showing the situation. It can be seen from the figure that Fe up to the order of ppt (10-12") can be detected. Also, in the figure, the two-dot chain line (I) indicates the minimum detectable concentration when measured by conventional SIMS alone. The three-dot chain line [II] indicates the minimum detection concentration when all secondary ions are detected by conventional laser beam irradiation. It can be seen that the sensitivity has been achieved.In this measurement example, in the primary ion analysis region, the sensitivity is 4.
00 μmφ was used, but when the analysis area is set to 1 μmφ, the detection sensitivity becomes lower in inverse proportion to the analysis area. However, even in this case, the method of the present invention is able to achieve a sensitivity that is one order of magnitude higher than any of the conventional methods.

FIG. 13, FIG. 2, and FIG. 3 show that Fe in a Si single crystal can be detected with high sensitivity. This device can detect elements other than iron with the same high sensitivity as iron by using a laser beam with energy corresponding to the excitation level unique to that element. In other words, it becomes possible to detect ultra-trace amounts of impurities. Furthermore, even if elements with similar excited levels are mixed together, each element can be separated in the secondary ion mass spectrometer, so this is not as much of a problem as compared to conventional all-ion detection. .

In addition, by changing the wavelength of the Gouy laser and paying attention to changes in the intensity of secondary ions, it is possible to experimentally measure the excitation level of the element of interest, making it possible to quickly identify elements in unknown samples. become.

Detection sensitivity has been improved by more than one order of magnitude, and in some cases nearly four orders of magnitude, compared to conventional high-sensitivity analyzers, making it possible to elucidate the cause of failures in elements where trace impurity contamination causes poor operating characteristics. Measures have been taken to prevent these defects, and recurrence can now be prevented.

In addition, in FIG. 1, the Rede light sources 13a and 13b.

As 13c, a gas discharge type, solid-state laser oscillation type, or miniaturized synchrotron synchrotron radiation light source is used, and the selection of these depends on the analyte, and similar effects can be obtained by using a single type or a combination of several types. It is being

Further, in the configuration shown in FIG. 1, the primary ion irradiation system and the secondary ion mass spectrometer may be arranged horizontally or vertically. For example, the advantage of arranging each part horizontally is that if the vacuum exhaust system is placed below the device, mechanical structures can be supported from the floor, and bellows etc. Since it can be supported through rubber, the device is shorter than when assembled vertically, and has the characteristics of being able to increase pumping speed and speed up sample exchange. Furthermore, when placed vertically, the device becomes tall, but if you take into account the use of off-the-shelf laser light sources and can assemble them mechanically and stably, the floor space can be reduced. Furthermore, when placed horizontally,
Since the surface of the sample is vertical, foreign matter adhering to the surface is easily removed by gravity, allowing highly accurate analysis. At the same time, various particles and foreign substances are generated inside the charged particle sources 1a and lb, but even if they adhere to the orifice area of the particle generation part due to gravity, they will quickly fall off, so the orifice will not be blocked, so the particle source cannot be closed. It was able to operate stably for several years.

[Embodiment 2] FIG. 4 shows the irradiation time of the primary ion beam 4 and two types of laser beams 14a, which are applied to the solid surface inspection apparatus having the configuration shown in FIG.
A timing generator 37 that adjusts the timing with the irradiation time of , 14b, and the time difference with the detection time of secondary electrons, secondary ions, etc. using a timer, a gate circuit, etc.
is added.

That is, in the figure, the path of the primary ion beam 4 or the primary electron beam 4a and the laser beams 14a, 14b are
A primary particle beam interrupter 31 and a laser beam interrupter 32a are provided in the optical path of
, a laser beam interrupter 32b, and a secondary ion beam interrupter 33 are interposed, and each receives an ion 0N10FF signal 34 from a timing generator 37 and an optical 0N beam interrupter 33.
10FF signal 35a, optical ON/OFF signal 35b
Then, mutually synchronized opening and closing operations are performed by the next ion 0N10FF signal 36.

Further, in the case of the second embodiment, a secondary electron detector 38 for detecting the secondary electrons 12a is provided, and the path of the secondary electrons 12a incident on the secondary electron detector 38 is similarly A secondary electronic circuit breaker 39 is provided which operates synchronously with the secondary electronic ON/OFF signal 40.

For example, the timing of the irradiation time of the primary ion beam 4 and the irradiation time of the two types of laser beams 14a and 14b may be adjusted as shown in the timing chart shown in FIG. , secondary ion 21
By adjusting the time difference between the detection time and the like using a timer, gate circuit, etc., the signal S caused by ultra-trace impurities contained in the sample 6 and the background noise caused by residual gas components in the sample chamber atmosphere can be adjusted. The present inventors have confirmed that the ratio S/(B+N) of other noises (B+N) is improved by about -0.

[Embodiment 3] FIG. 6 is a perspective view schematically showing an example of the configuration of a solid surface inspection apparatus which is still another embodiment of the present invention.

In the case of the third embodiment, a primary particle deflector 41 provided in the path of the primary ion beam 4 and the primary electron beam 4a
A control computer 46 controls the scanning by the primary particle scanning signal 42 and the detection signals of the secondary ions 11 and secondary electrons 12a.
secondary ions 11 and secondary electrons 1
By manually inputting the intensity of the detection signal 2a as a brightness modulation signal 45 to the cathode ray tube 44 which is synchronized with the primary scanning signal 42 via the scanning signal 43, a secondary electron image (SEM image),
An observation image 6a such as a secondary ion image (SIM image) or a three-dimensional ion image is constructed and observed.

This has the effect that, for example, a distribution image of an arbitrary target element can be easily constructed, and test results can be clearly understood visually.

Although not particularly shown, a non-volatile storage medium such as a floppy disk may be connected to the control computer 46 as appropriate, so that the obtained images can be saved and reused at any time.

[Embodiment 4] FIG. 7 is an explanatory diagram schematically showing an example of the configuration of a solid surface inspection apparatus which is still another embodiment of the present invention.

That is, in Example 1, the secondary ion mass spectrometry system M
Although a double convergence type mass spectrometer centered on a fan-shaped magnetic field is shown as an example, in the case of the fourth embodiment, a quadrupole type mass spectrometer 47 is used instead.

In the fourth embodiment, the same effects as in the first embodiment can be obtained.

[Embodiment 5] FIG. 8 is an explanatory diagram schematically showing an example of the configuration of a solid surface inspection apparatus which is still another embodiment of the present invention.

In the case of the fifth embodiment, the time-of-flight mass spectrometry method is used to discriminate the secondary ions 11 by utilizing the fact that the time required for the flight of the secondary ions 11 over a unit distance depends on the mass of the ions. This is what I did.

That is, a primary particle high speed circuit breaker 48 is interposed in the path of the primary ion beam 4, and the opening/closing operation of the primary particle high speed circuit breaker 48 is controlled by a primary particle high speed circuit breaker 49 from a timing generator 50. ing.

Further, a timing pulse 51 indicating the control timing of the timing generator 50 is inputted to a high-speed signal recording device 52 together with a secondary ion intensity signal 53.

Then, a predetermined correction is applied to the time difference between the time when the primary particle high-speed circuit breaker 48 is opened for a predetermined time and the time when the secondary ion intensity signal is detected, and a predetermined distance known in advance is The time required for the energy-selected secondary ions 20 to fly after passing through the spherical electric field generator 17 is known, and the elements constituting the secondary ions 20 are analyzed.

In the fifth embodiment, the same effects as in the first embodiment can be obtained.

[Embodiment 6] FIG. 9 is an explanatory diagram showing an example of the configuration of a solid surface inspection apparatus which is still another embodiment of the present invention.

In the case of the sixth embodiment, the laser light sources 13a and 13b are
It is composed of a material that can emit light at a resonance line or as strong as a resonance line at a desired specific wavelength, and both of them are
The oscillation wavelength or oscillation time is controlled in a correlated manner by being synchronously controlled by the laser light source drive system 54 that works with the timing generator 37 in the second embodiment described above using the drive signal 55 and the drive signal 56. At the same time, it is controlled in synchronization with the timing of irradiating the sample 6 with the laser beams 14a and 14b and the timing of detecting the secondary electrons 12a and secondary ions 11.

In this way, the optimum conditions are selected for the correlation between the oscillation wavelengths or oscillation times of the laser light sources t3a and 13b in accordance with the excitation level of the element to be analyzed. For example, for gas/laser light sources, the laser light source drive system 5
4 can be freely adjusted.

This makes it possible to selectively excite and ionize only the target analysis element from among the generated neutral particles 12, thereby further improving detection sensitivity.

[Embodiment 7] FIG. 10 is an explanatory diagram showing an example of the configuration of a solid surface inspection apparatus which is still another embodiment of the present invention.

In the case of this embodiment, by monitoring the progress of the inspection based on the detection results of the secondary ions 11, for example, a large number of inspection sites inside the - samples 6 and a plurality of sample 6
This makes it possible to carry out a variety of inspection tasks, such as continuous inspection.

That is, the sample stand 5 is moved by a sample stand drive mechanism 60 whose movement amount is precisely controlled by well-known closed loop control using a sample stand drive signal 58 from a sample stand drive signal generator 57 and a sample stand position detection signal 59. Displacement is controlled three-dimensionally in the x, y, and z directions.

This sample stage drive signal generator 57 generates an electromagnetic field drive signal 63
By controlling the electromagnetic field generator 19 via the electromagnetic field strength signal 64, the control operation is performed in conjunction with the timing generator 37, which selects the ion species to be detected.

For example, changes in the secondary ions 11 of a specific element during the test are monitored, and when the measured value of the element reaches a predetermined value, the analysis of the secondary ions 11 is stopped. By performing control operations such as moving the sample stage 5, an operation for automatically sequentially inspecting a plurality of samples 6 placed on the sample stage 5 is realized.

As an example, an operation is performed when depth analysis of a sample 6 consisting of four layers (layers A, B, C, and D) is attempted with high sensitivity, and analysis of multiple points on the surface of the sample 6 is automatically proceeded sequentially. becomes as follows.

After the sample 6 is appropriately moved in the x, y, and z directions by the sample stage drive mechanism 60 to position the first inspection site, inspection by irradiation with the primary ion beam 4 is started.

Then, by controlling the electromagnetic field generator 19 as appropriate, A.

The elements Si, P, 0, etc. contained in each film of B, C, and D are measured. And a secondary ion 1 such as 00
Focusing on and monitoring the detected value of No. 1, recognizing that the detected value exceeds a predetermined threshold, detecting the boundary between layer 0 and layer D, for example, and completing the test at the relevant test site. By recognizing this, the irradiation of the primary ion beam 4 is stopped, and the sample stage drive mechanism 60 is appropriately driven, thereby performing a positioning operation for the next preset inspection site with respect to the primary ion beam 4.

For example, in the measurement example shown in Figure 11, when depth analysis is performed from the surface and the intensity of 0+ ions reaches 2X102, measurement of this sample is stopped after about 40 seconds and the next inspection site or sample is analyzed. Move to.

In this way, for example, a sample 6 such as a semiconductor integrated circuit element, etc.
When inspecting a multilayer film structure, it is possible to stop measurement when a certain specific element is detected, measure from that point to a desired time or thickness, or move to another measurement point or another sample 6. This makes it possible to perform a variety of tests, such as arranging multiple samples 6 and predetermining the order of analysis. There is an effect.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

In the above explanation, the invention made by the present inventor will mainly be applied to solid surface inspection technology using secondary ion mass spectrometry technology used for evaluating the manufacturing process of semiconductor integrated circuit devices, which is the field of application that formed the background of the invention. Although we have explained the case where
It can be widely applied to techniques that require the detection of ultratrace impurity elements ranging from 10% to IQ-12 order.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, according to the solid surface inspection device of the present invention, at least one of secondary ions and secondary electrons generated by irradiation of a target region of a sample with a primary ion beam is detected, and the distribution of substances in the target region of the sample is detected. This is a solid surface inspection method for determining the state of a solid surface, in which the target area of the sample is irradiated with two or more types of laser beams together with the primary ion beam. By combining the control of the difference between each irradiation time of light and the control of the difference between the detection time of at least one of secondary ions and secondary electrons and each irradiation time, it is possible to detect The ionization of neutral particles is promoted, and the neutral particles irradiated with laser light can be ionized to about 90%, and nearly 90% of these ions can be guided to the mass spectrometer. Approximately 80% can be analyzed by mass spectrometry.

This makes it possible to elucidate not only the constituent elements of the main components of the sample but also trace impurities and ultra-trace impurities on the order of O, OO1p p b.

As a result, for example, it is possible to elucidate the causes of process-related failures of semiconductor integrated circuit devices involving ultra-trace impurities and trace impurities, and to obtain basic data for setting process conditions.

Further, according to the solid surface inspection apparatus of the present invention, there is provided a sample stage that supports a sample, a primary ion beam irradiation system that irradiates a target area of the sample with a primary ion beam, and a secondary ion beam that is generated from the sample. The solid surface inspection apparatus includes a secondary ion mass spectrometry system for observation, and includes a laser light source that irradiates the target area of the sample with two or more types of laser light together with the primary ion beam, so that, for example,
As a laser light source, it emits a resonance line of a specific wavelength that excites the target neutral particles of ultra-trace impurities, or a light as strong as the resonance line, or the oscillation time of each laser beam of two or more wavelengths is set. By using a laser light source that can be controlled to have a correlation, the ionization of neutral particles that are sputtered from the sample together with secondary ions is promoted, and the neutral particles that are irradiated with Rade light are ionized to about 90%. This makes it possible to reduce these ions to about 90
Since approximately 80% of the neutral particles can be guided to the mass spectrometer, approximately 80% of the neutral particles can be subjected to mass spectrometry.

This makes it possible to elucidate not only the constituent elements of the main components of the sample but also trace impurities and ultra-trace impurities on the order of 0.001 p p b.

Further, it includes an electron beam irradiation system that irradiates a target region of the sample with an electron beam, and an image observation means that detects charged particles generated from the target region and configures an image,
By providing a monitor that monitors the detection intensity of a specific element, it is possible to stop measurement when a certain detection intensity of a specific element is reached, or continue measurement work from that point until a desired time or desired depth. or transfer the inspection work to another measurement site or another sample.
Various tests can be accurately performed on samples such as semiconductor integrated circuit devices exhibiting a multilayer structure.

As a result, for example, it is possible to elucidate the causes of failures in the process of semiconductor integrated circuit devices that involve ultra-trace impurities and trace impurities, and to quickly and accurately obtain basic data for setting process conditions.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the configuration of a solid surface inspection device that is an embodiment of the present invention, and FIG. 2 is an explanatory diagram schematically showing an example of the process of ionizing neutral particles by laser beam irradiation. Fig. 3 is a diagram showing an example of the measurement results by the solid surface inspection device of Example 1, and Fig. 4 is a diagram schematically showing an example of the configuration of the solid surface inspection device of Example 2 of the present invention. FIG. 5 is a timing chart showing an example of the control operation; FIG. 6 is a perspective view schematically showing an example of the configuration of the solid surface inspection apparatus according to the third embodiment of the present invention; FIG. FIG. 8 is a plan view schematically showing an example of the configuration of a solid surface inspection apparatus according to a fourth embodiment of the present invention, and FIG. 8 is a schematic plan view showing an example of the configuration of a solid surface inspection apparatus according to a fifth embodiment of the present invention. Plan view shown in Figure 9
10 is a plan view schematically showing an example of the configuration of a solid surface inspection apparatus according to Embodiment 6 of the present invention, and FIG. 10 is a schematic plan view showing an example of the configuration of a solid surface inspection apparatus according to Embodiment 7 of the present invention. FIG. 11 is a diagram showing an example of the measurement results of the solid surface inspection device of Example 7, and FIGS. 12(a) and (5) are the operation of the solid surface inspection device of the present invention. A diagram illustrating an example of the principle, FIG. 13 is a schematic diagram illustrating an example of the operating principle of the solid surface inspection apparatus of the present invention. la, lb...Charged particle source, 2a...Ion group, 2
b...Electron group, 3...Primary ion mass analyzer/primary electron energy analyzer, 4...Primary ion beam, 4
a... Primary electron beam, 5... Sample stage, 6... Sample, 6a... Observation image, 7... Orifice for primary particles, 8... Focusing lens, 9.10... immersion lens,
11...Secondary ion, 12...Neutral particle, 12a.
...Secondary electrons, 13a, 13b, 13c...Laser light source, 14a, 14b, 14C...Laser light, 15...
・Electrostatic lens, 16... α slit, 17... Toroidal electric field/spherical electric field generator, 18... β slit,
19... Electromagnetic field generator, 20... Secondary ion, 23
...Toroidal electric field/spherical electric field generator, 24...Secondary ion, 25...Faraday cup, 26...Secondary electron multiplier, 29.30...Signal amplifier, 31...
- Primary particle beam interrupter, 32a... Laser beam interrupter, 32b... Laser beam interrupter, 33... Secondary ion beam interrupter, 34... Ion 0N10'FF signal,
35a...light 0N10FF signal, 35b...light 0N
10FF signal, 36...Secondary ion ON10FF signal, 37...Timing generator, 38...Secondary electron detector, 39...Secondary electron breaker, 40...Secondary electron 0N10FF Signal, 41... Primary particle deflector, 42
...Primary particle scanning signal, 43...Scanning signal, 44.
... Cathode ray tube, 45 ... Brightness modulation signal, 46 ... Control computer, 47 ... Quadruple seed mass spectrometer, 48 ...
Primary particle high speed circuit breaker, 49... Primary particle high speed cutoff signal, 50... Timing generator, 51... Timing pulse, 52... High speed signal recording device, 53... Secondary ion intensity signal, 54...Laser light source drive system,
55... Drive signal, 56... Drive signal, 57...
Sample stage drive signal generator, 58... Sample stage drive signal, 5
9... Sample stage position detection signal, 60... Sample stage drive mechanism, 63... Electromagnetic field drive signal, 64... Electromagnetic field strength signal, M... Secondary ion mass spectrometry system. 100 200 Depth from surface (people) 00! Se,＼Pol1lF田! Sef＼The Akeda i

Claims (1)

[Claims] 1. Solid surface inspection that detects at least one of secondary ions and secondary electrons generated by irradiating a target area of a sample with a primary ion beam to determine the state of distribution of substances in the target area of the sample. A method for inspecting a solid surface, the method comprising irradiating a target region of the sample with the primary ion beam and two or more types of laser beams. 2. Controlling the difference between the irradiation time of the primary ion beam and the irradiation time of each of the two or more types of laser beams, and the difference between the detection time of at least one of the secondary ions and secondary electrons and each of the irradiation times. 2. The solid surface inspection method according to claim 1, wherein ionization of ultra-trace impurities intended to be contained in neutral particles sputtered from the sample together with the secondary ions is promoted by combining the control with the above control. 3. a sample stage that supports a sample; a primary ion beam irradiation system that irradiates a target area of the sample with a primary ion beam;
A solid surface inspection device comprising a secondary ion mass spectrometry system for observing secondary ions generated from the sample, the laser light source irradiating a target area of the sample with two or more types of laser light together with the primary ion beam. A solid surface inspection device characterized by comprising: 4. Depending on the type of the target ultratrace impurity, one or more of a gas discharge type, a solid-state laser oscillation type, or a small synchrotron radiation light source is used as the laser light source in combination. 4. The solid surface inspection device according to claim 3. 5. The laser light source emits a resonance line of a specific wavelength that excites the target neutral particles of the ultra-trace impurity, or a light as strong as the resonance line, or each laser light source has two or more wavelengths. 5. The solid surface inspection apparatus according to claim 3, wherein the laser light source is controllable so that the oscillation times of the oscillation times are correlated with each other. 6. Equipped with an electron beam irradiation system that irradiates the target region of the sample with an electron beam, and an image observation means that detects charged particles generated from the target region and forms an image, and detects ions of specific trace impurity elements. 5. The solid surface inspection apparatus according to claim 3, wherein the observation image of the sample is constructed based on the detected intensity of at least one of secondary electrons and secondary electrons. 7. The secondary ion mass spectrometry system is characterized by using one of a double convergence type mass spectrometry system, a quadrupole type mass spectrometry system, or a time-of-flight type mass spectrometry system centered on a fan-shaped magnetic field forming means. The solid surface inspection device according to claim 3, 4, 5 or 6. 8. Equipped with a monitoring means for monitoring the detection intensity of a specific element, and capable of stopping measurement when a certain detection intensity of the specific element is reached, measuring from that point to a desired time or desired depth, and other methods. 8. The facepiece surface inspection device according to claim 3, wherein the inspection work can be transferred to a measurement site or another sample. 9. Setting the plane of the sample stage in the vertical direction,
Claims 3 and 4, wherein a plane including the axes of the primary ion beam irradiation system and the secondary ion mass spectrometry system is horizontal.
, 5, 6, 7 or 8.