JPH08203970A - X-ray utilization semiconductor evaluation device - Google Patents

Abstract

PURPOSE: To estimate energy level, formation-extinction process of charges, etc., by defining a defect portion by using the change of electric characteristics of a semiconductor device which is generated when a local part of the semiconductor device is irradiated with an X-ray beam. CONSTITUTION: A glass capillary 3 forms a fine X-ray beam 2 from X-rays generated from an X-ray generator 1. A specimen stand 6 is inplane-movable, and can rotate about an irradiation point as the center, so as to change the X-ray irradiation angle 5 to a specimen 4. An imaging plate 7 obtains the image of X-rays 36 which have penetrated the specimen 4. A semiconductor detector 9 is composed of L;doped Si for detecting X-rays or fluorescent X-rays 8 which have been diffracted by the specimen. A measuring apparatus 10 estimates electric characteristics of a semiconductor device like an LSI. A data processsing equipment 11 makes data obtained by various kinds of detectors correspond with data of electric characteristics. A computer display 12 displays data processing results, as two-dimensional distribution. Thereby imperfection factors can be easily made clear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray utilizing semiconductor evaluation apparatus suitable for finding a defective portion of a semiconductor device.

[0002]

2. Description of the Related Art LSI (Large Scale Integrated Circui)
In t), peculiar points such as defects in the Si substrate crystal or insulating film influence the reliability and yield, so in the manufacturing process and the finishing stage, analyze them and investigate the cause of occurrence, and reduce them. Efforts are being made to prevent this. Conventionally, an X-ray topography technique is often used for observing a defect in a Si single crystal substrate, and this technique is generally used for evaluating the quality of a Si wafer. This method is characterized in that it is possible to nondestructively specify the existence location of the Si wafer without breaking or shaving the Si wafer to evaluate the crystal defects.

However, when an LSI pattern is formed on a wafer, some defect is often observed on the topography image at almost the edge of the pattern.
It is difficult to apply it to the cause analysis of the electrical characteristic defect of the element at a specific portion of SI. For this reason, the heat treatment similar to that in the LSI manufacturing process is applied to a dummy wafer on which no pattern is formed, and the defect distribution and density generated in the wafer due to the difference in heat treatment temperature and time are observed to determine the cause of the defect generated in the LSI. A method of estimating is used.

[0004]

With the above X-ray topography method, it is possible to observe the defect distribution in the dummy wafer. However, defects often occur in association with a plurality of processes such as film formation, heat treatment, misalignment of element structure and pattern, and the cause of the electrical defect generated in the LSI is clarified by inspection of a dummy wafer having no pattern. Is difficult. Moreover, in the X-ray topography technique, it is not possible to evaluate these important items for elucidating the cause of the defect occurrence, such as the crystal structure of each defect portion, the strain amount, or the identification of the impurity element that is the nucleus of the defect. Have difficulty.

Furthermore, this technique cannot specify the presence or absence and location of electrical defects in the LSI. As described above, when the above method is applied to an LSI, a defect is observed at the end of the pattern. However, just because the defect is observed does not necessarily mean that there is an electrical defect of the LSI at the defect position.

Incidentally, in the conventional X-ray topography apparatus,
Since the position resolution is poor, from a few microns to a few tens of microns,
It is difficult to analyze a minute defect of a few microns or less that occurs in the element part in the LSI. In addition, there is a drawback that it cannot be applied to the analysis of defects in an insulating film or a polycrystalline layer that constitutes an LSI such as a gate oxide film.

The problem to be solved by the present invention is to identify local defects in material or structure without destroying the test object geometrically or mechanically, and to find these defects and the electrical properties of the semiconductor device. An object of the present invention is to provide a semiconductor device evaluation apparatus that can be associated with characteristic defects. That is,
The purpose of the present invention is to analyze the crystal structure of the defect portion, strain amount, elemental species, energy level such as impurity level in semiconductor and interface level of oxide film / semiconductor interface, etc. An object of the present invention is to provide a device capable of evaluating the generation-disappearance process of charges.

[0008]

A defect is evaluated by providing a means for extracting a signal generated by X-ray irradiation from any part of a semiconductor device. Specifically, a defect is formed by utilizing the fact that a fine X-ray beam is formed and a change in electrical characteristics of a semiconductor device caused when a local portion of the semiconductor device is irradiated with the X-ray beam is different between a normal portion and a defective portion. Identify the point. Further, along with these electrical characteristics, X-rays diffracted by the Si substrate, metal layers such as electrodes and wirings, insulating films, and the like, and fluorescent X-rays and photoelectrons are detected when X-ray irradiation is performed.

[0009]

When irradiated with X-rays, holes and electrons are generated in the semiconductor device, and the potential and current change. The generation and extinction speeds of holes and electrons differ between electrically normal positions and defect positions. Therefore, the electric defect position can be specified by measuring the potential and the current while changing the irradiation position of the fine X-ray beam. By analyzing the diffracted X-rays, fluorescent X-rays, photoelectrons, etc. detected at the specified positions, the crystal structure, strain, bonding state of the element or compound at the electrical defect can be known.

The change in the electrical characteristics due to the above-mentioned X-ray irradiation will be described in more detail. When an insulating film or a semiconductor is irradiated with X-rays, it is ionized to generate electrons and holes. These charges disappear after being generated, but if there is a defect, the disappearance speed becomes faster or slower than that in a normal portion. In some cases these charges may even persist for long periods of time. These charges affect the energy band structure near the interface between the electrode of the semiconductor device and the insulating film or the semiconductor, and the charges existing in the insulating film, the interface state of the semiconductor element, the flat band voltage, the threshold voltage of the transistor, It causes changes in amplification factor, capacity, carrier mobility, junction leakage current, wiring leakage current, etc. Further, the electric charge generated in the semiconductor material has a higher annihilation speed of the generated electric charge when a crystal defect exists. Therefore, the normal portion and the defective portion can be distinguished by comparing and observing the temporal change of the semiconductor characteristics immediately after the irradiation is stopped after the X-ray irradiation.

The position resolution that can be identified is better as the diameter of the X-ray beam irradiated is smaller. Since the number of charges generated by X-ray irradiation varies depending on the presence / absence of a defect, the defective portion can be identified even by measuring the electrical characteristics of the semiconductor while irradiating.

By this X-ray irradiation, diffracted X-rays and X-rays and electron beams which show the characteristics of the material properties of the semiconductor device are emitted together with the generation of electric charges. Therefore, by evaluating the irradiation angle and the radiation angle of X-rays or their energies, it is possible to identify the location where the electrical characteristics are defective and analyze the crystal structure, element or bond (electronic) state of that location. It is to be noted that the amount of charges generated when X-rays are irradiated and the recombination process of the charges are detected in the state in which the voltage or current is not supplied to the semiconductor device from the outside, and the current flowing through the electrode or the semiconductor substrate provided in the semiconductor device is detected. The defect location can also be specified by.

Although these measurements can be performed while irradiating X-rays, X-rays are intermittently radiated to measure the electric characteristics during the rest period, and the data obtained by repeating these measurements are integrated. As a result, a minute difference in characteristics between the normal portion and the defective portion can be revealed and the measurement accuracy can be improved.

The above-mentioned various measurements are performed while moving the X-ray irradiation position on the object to be examined, and the data obtained at each moving position is two-dimensionally rearranged so as to correspond to the irradiation position. By doing so, the defective portion can be detected from a peculiar portion of the distribution.

Since the diameter of the irradiation X-ray beam used in the present invention is sufficiently smaller than that of the semiconductor device, a local defect location can be specified with high accuracy, such as a minute portion at the end of the gate electrode of a MOS transistor or a corner portion of an element pattern. Yes, and
It is possible to elucidate the material cause such as the crystal structure, the contamination or foreign matter mixed in the manufacturing process of the semiconductor device, or the abnormality of the compound state, as the cause of the defective element. Since the generation and disappearance processes of charges generated in the semiconductor and the insulating film by X-ray irradiation are evaluated, it is possible to perform evaluation and analysis while associating the influence of material defects on the electrical characteristics. Further, unlike the visible light beam and electron beam used in the conventional induced current method, the X-ray beam can easily penetrate through the thin film multilayer structure, so that the deep layer portion of the sample such as in the LSI substrate can be easily penetrated. Can evaluate defects.

Further, since the X-ray is used for the probe, the object to be inspected as in the conventional evaluation technique is not destroyed geometrically or mechanically, and therefore preliminary measurement and repeated measurement for finding analysis conditions can be performed. .

[0017]

【Example】

(Embodiment 1) An embodiment of the present invention will be described with reference to FIG.
The evaluation device is an X-ray generator 1, a glass capillary 3 for forming a fine X-ray beam 2, movable in a plane, and rotated so that an X-ray irradiation angle 5 to a sample 4 can be changed around an irradiation point. Possible sample stage 6, Imaging plate 7 for obtaining an image of X-rays 36 transmitted through the sample, Li-doped Si for detecting X-rays and fluorescent X-rays diffracted by the sample
A semiconductor X-ray detector 9, a measuring device 10 for evaluating electrical characteristics of a semiconductor device such as an LSI, a data processing device 11 for associating data obtained by various detectors with electrical characteristic data, and It is composed of a computer and a display device 12 capable of displaying a two-dimensional distribution of the results.
Here, the beam diameter of X-rays formed by the glass capillary was 0.1 μm on the sample.

In this embodiment, L having the sectional structure shown in FIG.
SI was used as an evaluation sample. This LSI is composed of a MOS transistor section 14, a memory capacitor section 15, and a multi-layer wiring section 16, in which a gate electrode 17 having a structure in which tungsten silicide and polycrystalline Si are superposed with a width of 0.5 μm is formed, and has a thickness of 13 nm. The MOS transistor having the gate oxide film 18 was evaluated.

When a stress voltage is applied to the transistor, hot carriers are injected into the gate oxide film and the threshold voltage V
Although the th, the transconductance gm, and the interface state Dit fluctuate, the deterioration (fluctuation) speed is high, that is, the device of this embodiment was applied to elucidate the cause of a transistor in a defective manufacturing lot. Hot carrier injection is to inject electrons or holes into the gate oxide film from the Si substrate 13 side, and as a result, the interface state is increased. When the gate oxide film is irradiated with X-rays, electrons and holes are generated, which has the same effect as hot carrier injection.

From the same manufacturing lot, transistors having threshold voltage and transconductance characteristics which are almost the same were selected. And for each MOS transistor,
In the plane, any one of the positions (1) to (8) and (a) to (m) shown in FIG. 3 was selected, and each X-ray beam was irradiated for 10 minutes. This irradiation positioning was performed by the X-ray transmission image of the transistor projected on the imaging plate installed on the back surface side of the Si substrate. Further, at this time, the diffraction X-ray from the (400) plane of the Si substrate is simultaneously measured using the energy dispersive X-ray diffraction method to obtain the lattice spacing, and the Si substrate is exposed at the scribe line around the LSI chip. The rate of change from the (400) lattice plane spacing obtained in step 1 was defined as the in-substrate lattice strain ε at each X-ray irradiation position in the transistor. When the X-ray irradiation angle was set to 30 degrees, the energy of the diffracted X-ray from the (400) plane was about 9.1 keV.

FIG. 4 shows the irradiation position dependence of the transconductance change rate Δgm / gm and the interface state change rate ΔDit / Dit of the MOS transistor before and after X-ray irradiation. The figure shows the X-ray irradiation position dependence 19 of a transistor in an LSI manufacturing lot showing normal characteristics and the irradiation position dependence 20 of a lot in which the deterioration rate of the transistor characteristics due to hot carriers is high.

The rate of change in transconductance and interface state due to X-ray irradiation is large at the end portions such as the gate electrode 17 and the element isolation insulating film region 21, but the rate of change is higher in the defective lot. Several times larger. It was found from these dependencies that hot carriers were injected and deteriorated mainly at the interface between the gate oxide film at these ends and the Si substrate, and these parts were particularly bad in a defective lot.

Since the characteristic deterioration is remarkable at the end,
It was predicted that some external force was applied to the gate oxide film in these portions. However, it is difficult to measure the local force in the gate oxide film. Therefore, using the device of the present invention, the force applied to the gate oxide film at the end portion was evaluated from the strain distribution in the Si substrate.

FIG. 5 shows the lattice strain distribution in the plane of the Si substrate. This distribution agrees relatively well with the irradiation position dependence of electrical properties such as mutual conductance and interface state.
Therefore, it was found that the stress concentration at the edges of the gate electrode and the inter-element isolation insulating film causes strain at the interface of the gate oxide film and its Si substrate and facilitates the increase of the interface state by hot carrier injection. Incidentally, the increase of the interface state causes the deterioration of mutual conductance and threshold voltage, as is well known.

Further, it can be seen from FIG. 5 that the defective lot has a larger strain amount at the end portion of the gate electrode or the element isolation insulating film, that is, the force applied to the gate oxide film at the end portion is larger than that in the non-defective lot. Therefore, for the non-defective lot and the defective lot, the film thickness of the tungsten silicide forming the gate electrode was obtained from the luminance of the fluorescent X-ray of tungsten that was detected at the same time as the previous X-ray irradiation. As a result, it was found that the film thickness of the defective lot was 20% thicker than that of the non-defective lot, and the force applied to the gate edge was large. Furthermore, since the defective lot has a narrower strain distribution area at the end of the element isolation insulating film,
It was found that the end shape was steep and a large force was concentrated on the local part. These are the causes of lot defects. As described above, according to the present invention, it is possible to elucidate the cause of the defect in the local portion, which could not be clarified only by the conventional electric characteristics, from both the material and the electric characteristics without breaking or cutting the element.

(Embodiment 2) An embodiment of the present invention will be described with reference to FIG. In this embodiment, the apparatus shown in the first embodiment is basically used, and an X-ray filter 22 is inserted between the glass capillary and the X-ray generator to monochromate the X-ray beam formed by the capillary. Vacuum chamber 23 around the sample
And an energy analyzer 25 for detecting the energy of the electrons 24 emitted from the sample due to the photoelectric effect when X-rays are irradiated.

The apparatus of this embodiment is shown in FIG.
It was applied to the evaluation of the interlayer insulating film 26 in the SI multi-layer wiring section 16. Here evaluated interlayer insulating film SiO _2, a chemical vapor deposition SiO ₂ containing phosphorus To boron was formed by chemical vapor deposition (CVD) formed by a sputtering method, and an SiO ₂ film called a spin-on glass. X for evaluation of interlayer insulation film
0.1μ with energy of 5 keV using line filter
A beam of m diameter was applied. This beam is applied to the interlayer insulating film 28 at the intersection of the first layer and second layer Al wirings having the cross-sectional structure shown in FIG. The change in the current-voltage characteristic between the wirings was observed.

As shown in FIG. 7, when the voltage applied between the wirings is gradually increased, a small amount of displacement current 43 flows in the low voltage region, and when the voltage is further increased, the rate of increase of the current with respect to the increase of the voltage becomes remarkable. , So-called tunnel current 44
A region appears, and if it continues to increase, the insulating film is destroyed and the current 45 rapidly increases. In this measurement, the applied voltage was fixed with the tunnel current slightly flowing, and the X-ray beam was irradiated for 10 minutes. In most cases, the X-ray irradiation reduced the leak current flowing through the insulating film. The tunnel current is determined by the electric field strength applied to the interface between the Al wiring and the insulating film. Therefore, the phenomenon that the current decreases despite the constant applied voltage indicates that the electric field strength near the interface was relaxed by the X-ray irradiation. It is considered that this is because the electrons generated in the insulating film by X-ray irradiation were captured by the positive charge portion existing at the interface, that is, the electron trap. This reduction is spin-on-glass is the largest, followed by a phosphorus To order SiO ₂ formed by SiO ₂ and sputtering containing boron. In particular, the amount of decrease was large in a film having a high water content.

(Embodiment 3) This embodiment will be described with reference to FIG. In this embodiment, the light source 31 for irradiating the sample with the ultraviolet rays 30 is provided in the first and second embodiments. In Examples 1 and 2, changes in interface states and charge traps due to radiation damage due to X-ray irradiation were investigated. Since the element is damaged by X-ray irradiation, when determining the irradiation position dependency, select elements with similar initial characteristics as many as the irradiation positions,
It was necessary to irradiate each element with only one point. However, even the elements taken out from the same lot have variations in characteristics, and there is an inconvenience that many elements have to be prepared when examining the irradiation position dependency of a large number of points.

In the present embodiment, this defect is eliminated, and the irradiation position dependence can be obtained from one element. That is, after irradiating one point with X-rays, various characteristics described in Examples 1 and 2 were measured, and when the characteristics were completed, ultraviolet rays were irradiated. By this irradiation, the electric characteristics of the transistor could be returned to the state before the X-ray irradiation. After that, the X-ray irradiation position was moved to a desired position and the same measurement was performed again. By repeating these steps, the irradiation position dependency is required from one element, so there is little variation in data, and it is no longer necessary to prepare a large number of samples. By repeating the above while moving the irradiation position two-dimensionally within the sample plane, the two-dimensional distribution of the characteristics could be obtained. In this case, since there is no factor due to the variation between the samples as in the previous embodiment, the defect portion could be easily extracted from the distribution. Further, this example was used for evaluation of an ultrathin oxide film described below.

When the gate oxide film becomes thinner than 5 nm, a tunnel current flows. Therefore, the capacitance-voltage (CV; Capacita) which has been conventionally used for evaluating the film quality of the oxide film.
It becomes difficult to apply the nce-Voltage method. Therefore, the device of this embodiment is applied. The X-ray beam system used is the same as in Example 2.

A 3 nm Si oxide film was formed on the surface of the Si substrate in an oxygen atmosphere containing water and an oxygen atmosphere not containing water.
The dependence of the kinetic energy of O1s photoelectrons emitted when these oxide films were irradiated with X-rays on the X-ray irradiation time was examined. The type of traps existing in the oxide film can be determined from this X-ray irradiation time dependency, that is, the charging characteristics of the charges generated by X-ray irradiation. This method has already been used. 7, 863-864, 1992.
Reported in years.

As a result of evaluation using this method, many oxide traps are trapped in the oxide film formed in an oxygen atmosphere containing water, and many hole traps occupy in an atmosphere containing no water. all right.

Alternate between this measurement and UV irradiation to 0.1 μm
When the two-dimensional distribution in the oxide film surface was obtained by repeating the measurement with a pitch, it was found that some oxide films had portions where charging was difficult. In this measurement, Si2p photoelectrons from Si not oxidized with O1s and Si from oxidized Si
The ratio of 2p photoelectrons was measured simultaneously. As a result, it was found that this ratio was large in the non-charged portion, and the oxidation of Si was insufficient.

Therefore, the X-ray irradiation angle was set to a low angle of 0.15 degrees, and fluorescent X-ray analysis was performed in the vicinity of this angle. as a result,
In regions where Si oxidation is insufficient, Fe and Z are more than in other regions.
It was found that the fluorescent X-ray luminance of r was high, and these traces (possibly in the Si substrate) contained these trace amounts of impurities. In this fluorescent X-ray analysis, W-Lα characteristic X-rays from the target of the X-ray generator were used as irradiation X-rays.

As another application of this embodiment, the present invention is applied to evaluation of a gate oxide film of a flash memory that can be written and read. The gate electrode (including the floating gate electrode) having a width of 0.5 μm was irradiated with an X-ray beam having an energy of 2 to 10 keV. The oxide film under the floating gate electrode had a thickness of 7 nm. Similar to (1) to (8) of FIG. 3, the potential change of the gate electrode after the X-ray irradiation so as to cross the gate electrode was examined. The speed of returning to the potential before X-ray irradiation closer to the edge of the electrode is about 40% faster than when it is applied to the central portion in the width direction of the gate electrode, and the decrease in write charge in the flash memory occurs mainly at the edge. I found out that

According to the present embodiment, it becomes possible to evaluate the electrical and material evaluation of a local portion with an ultrathin film, which is difficult with the conventional electrical evaluation method, without scraping or breaking the sample. It was

In addition, in the above measurement, X was mainly used for evaluation of the oxide film.
X-ray Photoelectron Spectroscopy was used, but X-ray absorption edge fine structure analysis (Extended X-ray A
Other analysis methods such as the absorption fine structure method can also be applied.

(Embodiment 4) This embodiment will be described with reference to FIG. In this embodiment, the apparatus of each of the above embodiments is provided with a heating chamber 32 for heat-treating a sample in a hydrogen atmosphere. Radiation damage due to X-rays can be almost eliminated by the ultraviolet irradiation shown in Example 3, but the element characteristics may not be recovered depending on the sample. When it did not recover even by irradiation with ultraviolet rays, the lid 33 on the upper surface of the heating chamber was closed, hydrogen was introduced from the gas inlet 34, and the gas was exhausted from the gas outlet 35 while heating at a temperature of 300 to 500 degrees. After this, hydrogen was removed (vacuum evacuation was performed in the apparatus of FIG. 9 after this), the lid was opened, and the same measurement as in each of the above-described examples was performed. By this heat treatment, the characteristics of the transistor and the like could be returned to the initial values.

Next, the insulating film 29 between the wirings of the second layer was evaluated in the same manner as in Example 2. Here, 1.5k
An X-ray beam with eV energy was used. The insulating film between the wirings was evaluated by a SiO ₂ film whose surface was flattened by a chemical mechanical polishing method after being formed by a sputtering method and a SiO ₂ film which was flattened by a plasma organic CVD method. In this case, the measurement was performed in a state where these insulating films were exposed without coating other layers on this. The method of evaluating the current-voltage characteristics between the wirings before and after the X-ray irradiation is the same as that in the second embodiment.

In the case of a chemical mechanically polished SiO ₂ film, X
It was found that the leak current may increase or decrease depending on the position of the line irradiation, even though a constant voltage is applied before and after the irradiation, that is, the electron trap and the hole trap are mixed. On the other hand, in the case of the SiO ₂ film formed by the plasma organic CVD method, it was found that the current was reduced by the X-ray irradiation and the electron trap was present.

In these measurements, the intensity ratio of O1s photoelectrons and Si2p photoelectrons emitted from the insulating film at the time of X-ray irradiation is obtained, and this ratio is compared with the intensity ratio obtained in the case of the thermal oxide film to obtain the SiOx film. The composition was evaluated. It was found that x was 2.2 to 2.3 in the film formed by the plasma organic CVD method, and oxygen was larger than the stoichiometric composition x = 2.0 of the Si oxide film. On the other hand, in the case of the chemical mechanically polished oxide film, x was varied from 1.8 to 2.2 depending on the irradiation position, and it was found that there were places where Si was large and places where Si was small. These corresponded well with the scattered electron or hole traps shown by the current-voltage characteristics. It was found that when heat treatment was performed in the apparatus of this example at 450 ° C. for 60 minutes in an oxygen atmosphere and a hydrogen atmosphere, traps were reduced and x was close to the stoichiometric composition in both cases.

(Embodiment 5) The apparatus configuration is the same as that in Embodiment 1. However, in this case, a sample stage that can take out the current flowing from the back surface of the semiconductor device and a measurement system for the current are provided. The in-plane distribution of the sample in which the electric current generated by the electric charges generated in the semiconductor such as the Si substrate when the X-ray was irradiated was measured, and the irradiation position and the current value extracted from the back side of the substrate were made to correspond to each other is shown in FIG. It can be stopped with a data processor.

In the dynamic random access memory,
The device of the present embodiment was applied to the failure analysis of an element in which the accumulated charge amount rapidly decays. FIG. 2 shows the cross-sectional structure of this memory, and the size of the memory capacity portion of the sample evaluated is 1 μm × 2.
The irradiation X-ray energy was 5 keV, and the beam diameter was 0.1 μm. The two-dimensional in-plane distribution of the current value when the irradiation position was moved was obtained by irradiating the vicinity of the memory capacity portion with X-rays from the direction perpendicular to the upper surface of the sample. X in this measurement
Attenuation characteristics of the current immediately after the irradiation were obtained at the same time as the current flowing during the line irradiation.

It has been found that in a defective element in which the accumulated charge in the memory capacitor portion is rapidly attenuated, the amount of current flowing to the back surface side of the substrate due to X-ray irradiation is small, and the current decay rate after X-ray irradiation is fast. In particular, the attenuation speed was remarkably short in the portion where the memory capacity electrode was in contact with the Si substrate. From these measurement results, it was found that there is some cause for promoting recombination of electrons and holes generated by X-ray irradiation in this portion.

When fluorescent X-ray analysis was performed by irradiating X-rays from the same low angle as described above, a trace amount of Fe or Cu was detected in this portion. Further, when the distribution of strain in the Si substrate in the vicinity of the memory portion was obtained by the X-ray diffraction measurement method similar to that described in the previous embodiment, the strain in the portion where the memory capacitor electrode is in contact with the Si substrate is the highest. I found it big. From these results, it is considered that some impurities enter the substrate during the manufacturing process of the memory, and these impurities are segregated in the process of the heat treatment in the electrode contact portion where the stress concentration is the most complicated in the memory portion.

As a method similar to that of this embodiment, there is already a method in which an electron beam is applied to the substrate and the defects in the substrate are examined from the two-dimensional distribution of the substrate current generated at this time. However, in this method, many layers on the substrate, such as the memory part of the LSI,
In particular, it could not be applied if there was an electrode wiring layer. In addition, it was not possible to evaluate impurities, crystal structure, strain, etc. with the same device, and it was difficult to elucidate the cause even if the defect part was clarified.

In the above examples, various electrical and material properties were evaluated by utilizing the electric charges generated when the oxide film and the Si substrate were irradiated with X-rays. According to the present invention,
By irradiating a metal layer such as wiring with a fine X-ray beam, it is possible to evaluate the crystal structure and element distribution in the minute portion by X-ray diffraction and fluorescent X-ray analysis.

Although the glass capillary is used for forming the fine X-ray beam in the above-described embodiment, a Fresnel lens or various mirrors may be used. Further, if a synchrotron radiation facility is applied to the X-ray source, a fine X-ray beam with high brightness can be formed over a wide energy range.
The measurement can be performed in a short time.

[0050]

According to the present invention, it is possible to specify the location of occurrence of an electrical characteristic defect in a minute portion such as an LSI, which is an aggregate of fine elements having a multi-layered structure, and to determine the material characteristics that cause the defect. Can be evaluated while associating with. Further, these evaluations can be performed nondestructively without breaking or cutting the LSI. For this reason, the cause of the defect can be easily clarified and the accuracy can be improved. As a result, it is possible to take countermeasures in the manufacturing process for defects such as LSI, so that the highly reliable LSI
And the manufacturing yield can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment showing the basic structure of the present invention.

FIG. 2 is an LS used as a measurement sample in each example of the present invention.
Sectional drawing of I.

FIG. 3 is an explanatory diagram showing the relationship between the planar structure of a MOS transistor evaluated in Example 1 of the present invention and the irradiation position of a fine X-ray beam.

FIG. 4 is a measurement result of Example 1 of the present invention, showing an X-ray irradiation position on a MOS transistor, a change rate of mutual conductance due to X-ray irradiation (Δgm / gm), and a change rate of interface state (ΔDit / Dit). FIG. 6 is a characteristic diagram showing the relationship between the strain and the strain (ε).

FIG. 5 is a characteristic diagram showing the relationship between the X-ray irradiation position on the MOS transistor and the strain in the Si substrate, which is the measurement result of the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of an apparatus according to a second embodiment of the present invention.

FIG. 7 is a current-voltage characteristic diagram of interlayer and inter-wiring insulating films obtained in Examples 2 and 4 of the present invention.

FIG. 8 is an explanatory diagram of an apparatus according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram of an apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... X-ray generator, 2 ... Fine X-ray beam, 3 ... Glass capillary, 4 ... Sample, 5 ... X-ray irradiation angle, 6 ... Sample stand, 7 ...
Imaging plate, 8 ... Diffractive X-rays, fluorescent X-rays, etc.
9 ... Semiconductor X-ray detector, 10 ... Electrical characteristic measuring device, 11
... data processing device, 12 ... computer and display device, 2
5 ... Electron detector, 36 ... X-ray transmitted through sample.

Claims (11)

[Claims] 1. A semiconductor evaluation using X-rays, which has a function of irradiating a desired portion of a semiconductor device with an X-ray beam having a minute diameter and a function of detecting a change in electrical characteristics of an element caused by the irradiation. apparatus. 2. The brightness and energy of irradiation X-rays, irradiation time, beam incident angle, energy of X-rays and electrons diffracted or radiated from the X-ray irradiation portion, number, irradiation angle or emission angle. X-ray utilizing semiconductor evaluation device having a function of detecting at least one of the characteristic items consisting of. 3. The electric characteristics to be detected according to claim 1, wherein the electric charge in the vicinity of the interface between the electrode and the insulating film, the electric charge existing in the insulating film, the interface state of the semiconductor element, the flat band voltage, the threshold voltage of the transistor, and the amplification. Rate, capacity, carrier mobility,
An X-ray-based semiconductor evaluation device capable of detecting at least one of these characteristics, which is a leak current of a junction, a leak current between wirings, and a charge generated in a semiconductor material. 4. An X-ray utilizing semiconductor evaluation apparatus having a function of obtaining the correspondence between the detected contents obtained in claim 2 or the semiconductor characteristics obtained in claim 3. 5. The X-ray utilizing semiconductor evaluation apparatus according to claim 1, 2, 3 or 4, wherein the semiconductor characteristics can be measured while irradiating with X-rays. 6. An X, which comprises means for intermittently irradiating a DUT with a fine X-ray beam and means for measuring each semiconductor characteristic of the DUT during a rest period of the X-ray beam. Wire-based semiconductor evaluation system. 7. The method according to claim 6, wherein X-ray irradiation is repeated, data accumulated during the irradiation period is accumulated and accumulated,
An X-ray utilizing semiconductor evaluation device having a function of obtaining a relationship between any one of the characteristic items and the electric characteristic according to claim 2 after measuring a desired time. 8. An electrode wiring or a semiconductor is irradiated with X-rays without applying a voltage from the outside, and a current generated by holes or electrons generated in the insulating film or the semiconductor substrate by the irradiation or the electrode wiring or the semiconductor substrate An X-ray utilizing semiconductor evaluation device having a function of detecting potential fluctuations. 9. The X-ray of each of the above-mentioned items and the electrical characteristics of the electron or semiconductor were measured at each moving point while moving the fine X-ray irradiation position on the semiconductor device, and obtained at each of these points. An X-ray-based semiconductor evaluation device characterized in that characteristics are arranged so as to correspond to irradiation positions on a semiconductor device so that a two-dimensional distribution of each property can be obtained. 10. An X-ray utilizing semiconductor evaluation apparatus according to claim 9, wherein a singular point in a two-dimensional distribution of semiconductor characteristics is extracted to detect a defective portion of a semiconductor device. 11. Claims 1, 2, 3, 4, 5, 6, 7,
In 8, 9, or 10, after the measurement is completed, the semiconductor device irradiated with X-rays is subjected to heat treatment in an atmosphere containing ultraviolet rays or hydrogen to remove X-ray irradiation damage and restore a semiconductor device having normal characteristics. An X-ray-based semiconductor evaluation device having a function capable of performing.