JPH01264161A - Secondary ion mass spectrographic equipment - Google Patents

Abstract

PURPOSE:To make it possible to carryout identification and detection etc., of a very small amount of impurities resulting from the detection of a secondary ion, while observing a sample with high precision without damaging the sample by radiating a primary electron beam from the same or about the same direction as tie direction from which a primary ion beam is radiated. CONSTITUTION:A charged particle source 3 which is capable of emitting a primary ion beam and a primary electron beam simultaneously or selectively, is provided so that said primary electron beam 5 is radiated onto a sample 2 from the same or about the same direction as the direction from which the primary ion beam 4 is radiated. For example, a negative ion beam and an electron beam are radiated at any time onto the identical part of said sample 2 from the same direction, so that images resulting from the electron beam 5 and the ion beam 4 are mated with each other in a wide region of the sample 2, then the ion beam 4 can be precisely radiated onto a part of the sample 2 to be detected, based upon the image resulting from the electron beam 5 having no sputtering action, etc., on said sample 2. Consequently this makes it possible to carryout identification and detection etc., of a very small amount of impurities resulting from the detection of a secondary ion while observing the sample with high precision without damaging it.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to secondary ion mass spectrometry technology, and is particularly effective when applied to process evaluation technology by detecting trace impurity elements in the manufacturing process of semiconductor integrated circuit devices. related to technology.

[Conventional technology]

In the manufacturing process of semiconductor integrated circuit devices, p
The presence of extremely small amounts of impurity elements on the order of pm and ppt has come to greatly affect the performance and yield of semiconductor integrated circuit devices, and highly accurate detection of trace impurity elements in minute regions has become essential.

In response to such demands, the following secondary ion mass spectrometers and the like have come into use in recent years.

The outline of this method is to use the detection signals of secondary electrons and secondary ions generated when scanning the inspection area of a sample with an ion beam as a brightness modulation signal of a cathode ray tube that is synchronized with the scanning of the ion beam. Construct and observe. After identifying the target analysis location based on this image, the ion beam is intensively irradiated to the analysis location, and the secondary ions generated from the analysis location are guided to a mass spectrometer etc. By precisely detecting the type and amount, it attempts to understand the distribution of trace impurity elements on the surface and in the cross-sectional direction of a specific part of the sample.

Regarding secondary ion mass spectrometers, please refer to "Electronic Materials J.
It is described in the November 1984 special edition, pages 91 to 96.

[Problem that the invention attempts to solve]

However, with the above-mentioned conventional techniques, trace impurity elements are lost due to the sputtering effect caused by ion beam scanning, which is performed prior to detection of secondary ions by a mass spectrometer, for purposes such as identifying analysis locations. This is unavoidable, and there is a problem in that the analysis work itself becomes impossible.

For this reason, for example, by irradiating the sample with an electron beam using an electron optical system that is separate from the ion beam that is irradiated on the sample, the target analysis position can be identified using the principle of a scanning electron microscope. However, since the directions of irradiation of the ion beam and electron beam on the sample are different, it is difficult to match the electron beam image and the ion beam image across the entire sample area, and it is difficult to match the image of the electron beam and the ion beam when the sample is an insulator. This causes new problems such as charging caused by electron beam irradiation, which makes it difficult to analyze secondary ions by subsequent ion beam irradiation.

Therefore, the purpose of the present invention is to provide a secondary ion mass spectrometry technique that can identify and detect impurities without damaging the sample (by detecting secondary ions while observing with high precision). It's about doing.

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 representative inventions disclosed in this application is as follows.

That is, a charged particle source capable of simultaneously or selectively emitting a primary ion beam and a primary electron beam is provided, and the sample is irradiated with the primary electron beam from the same or approximately the same direction as the irradiation direction of the primary ion beam. This is how it was done.

[Effect]

According to the above-mentioned means, for example, by irradiating the same part of the sample from the same direction with a negative ion beam and an electron beam at any time, images produced by the electron beam and ion beam can be made to match over a wide area of the sample. .

This makes it possible to accurately irradiate the ion beam to the inspection area of the sample, which is identified based on the image of the electron beam without causing any sputtering effects on the sample, with high precision without damaging the sample. It is possible to identify and detect trace impurities by detecting secondary ions while observing them.

[Example 1] Fig. 1 is an explanatory diagram showing the main parts of a secondary ion mass spectrometer that is an embodiment of the present invention, and Fig. 2 is a sectional view showing an example of the charged particle source. be.

A sample 2, such as a semiconductor wafer or a semiconductor pellet on which a predetermined pattern A is formed, is placed on a sample stage l that can freely move in a horizontal plane and move up and down.

A charged particle source 3 whose axis is inclined at a predetermined angle with respect to the sample 2 placed on the sample stage 1 is provided above the sample stage 1 .

The charged particles 3 are constituted by a gas discharge type ion gun such as a duoplasmatron as shown in FIG. 2, for example.

That is, as shown in FIG. 2, the charged particle source 3 includes a hollow cathode 31, an intermediate electrode 32 having a through hole formed in the central axial direction through which charged particles pass, an anode 33. It is constructed by coaxially arranging the extraction electrode 34, etc.
Around the intermediate electrode 32, a magnet 35 is provided, in which the intermediate electrode 32 and the anode 33 serve as magnetic poles to form a magnetic field in the axial direction.
is located.

Further, a discharge power source 36 and an acceleration power source 37 are connected between the hollow cathode 31 and the intermediate electrode 32, and between the anode 33 and the extraction electrode 34, respectively.

A source gas 39 is introduced between the hollow cathode 31 and the intermediate electrode 32 from a gas nozzle 38 .

Then, this source gas 39 is turned into plasma by arc discharge, and is further focused on the anode 33 with high density by the magnet 35, and then the anode 33 and the extraction electrode 34 are
The target ion species and electrons in the plasma are extracted to the outside as the primary ion beam 4 and the primary electron beam 5 by being accelerated by the potential difference between the hollow cathodes 31 . Intermediate electrode 32. The primary ion beam 4 and the primary electron beam 5 can be obtained individually or simultaneously at any time by mutually adjusting the axes of the anode 33 and the extraction electrode 34, or by making the anode 33 eccentric with respect to the intermediate electrode 32.

The central part of the anode 33 where plasma accumulates and the power of the discharge power source 36 concentrates is an anode button 33a made of, for example, a highly heat-resistant metal with a through hole formed in the central part.
It consists of

On the other hand, the sample 2 placed on the sample 1 from the charged particle source 3
The paths of the primary ion beam 4 and the primary electron beam 5 leading to the point include an electrostatic converging lens 6, a slit 7, an electrostatic converging lens 8. Scanning deflectors 9 are sequentially arranged,
The surface of the sample 20 is configured to be scanned with a primary ion beam 4 and a primary electron beam 5, which are converged to a size of, for example, several tens to hundreds of beams.

Further, in front of the convergent lenses 6 and 8, axis adjustment lenses 10 and 11 are arranged, and the primary ion beam 4
Furthermore, the structure is such that various aberrations that occur when the primary electron beam 5 is converged as described above are eliminated or reduced.

Furthermore, in this case, a magnetic field-type electron beam corrector 12 and An electron beam corrector 13 (magnetic field lens or magnetic field deflection system) is arranged.

A secondary electron detector 14 is installed near the sample 2 placed on the sample stage 1 to detect secondary electrons 5a generated when the primary ion beam 4 or the primary electron beam 5 is incident on the sample 2. is provided, and by inputting the detection signal of the secondary electrons 5a 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 5 with respect to the sample 2, the primary ions of the sample 2 are detected. The image of the incident site of the beam 4 is, for example, the primary ion beam 4.
It is configured so that it can be observed equivalently to an image based on secondary ions 4a generated by scanning only.

Furthermore, in the vicinity of the sample 2, a secondary ion extraction lens 15. Beam correction lens 16. Beam correction deflector 17. Toroidal electric field or spherical electric field generator 1
8. Correction lens that also serves as an aperture 19. Electromagnetic field generator 20.
Electric field generator for removing scattered particles 21. Ion collector slit 22° Secondary electron multiplier tube 23 that converts the secondary ions 4a into secondary electrons and amplifies them. Slit 24. A mass spectrometry system M consisting of a detector 25 and the like is provided, and the type and amount of secondary ions 4a generated from the target inspection site of the sample 20 by the incidence of the primary ion beam 4 can be accurately detected.

Further, although not particularly illustrated, each of the above-mentioned parts is housed in a vacuum chamber that is evacuated to a desired degree of vacuum.

Hereinafter, the operation of the secondary ion mass spectrometer of this embodiment will be explained with reference to the drawings.

First, in the charged particle source 3, with the anode button 33a fixed, the intermediate electrode 32 and the extraction electrode 34 were slightly eccentric, so that only the primary electron beam 5 was emitted and the primary ion beam 4 was hardly emitted. After that, the above-mentioned converging lens 6.8 and axis adjustment deflection lens 10.1L are used, as well as the electron beam corrector 12, so that the primary electron beam 5 irradiated onto the sample 2 is narrowly converged.
．． Adjust 13 etc.

In this state, by operating the scanning deflector 9,
A target area of the sample 2 is scanned by the primary electron beam 5 without causing any damage or disappearance of existing foreign matter, and at this time, signals of secondary electrons 5a generated from the sample 2 are detected by the secondary electron detector 14. measure.

By using the signal of the secondary electrons 5a as a brightness modulation signal of a cathode ray tube (not shown) synchronized with the scanning deflector 9, for example, the target region of the sample 2 can be enlarged as shown in FIG. Pattern 8, which forms image 2a and is formed on sample 2, is observed.

Next, the intermediate electrode 32 in the charged particle source 3. Anode 3
3. The position of the extraction electrode 34 is returned to the original coaxial state, and the primary ion beam 4 and primary electron beam 5 are simultaneously applied to the sample 2.
0 Irradiate the target area.

At this time, the secondary ions 4a generated from the sample 2 by the incidence of the primary ion beam 4 are guided to the mass spectrometry system M and measured, so that the secondary ions 4a are delivered to the target region of the sample 2 as shown in FIG. Detects the type of substance present.

Further, the charged particle source 3 is adjusted as described above, and the sample 2 is irradiated with only the primary electron beam 5 again, so that an enlarged image 2 of the same part of the sample 2 as shown in FIG. 4 is obtained.
Observe b.

In this way, when the enlarged images 2a and 2b of the sample 2 before and after irradiation with the primary ion beam 4 are compared, the area sputtered by the incidence of the primary ion beam 4 is observed as, for example, a black spot 21b, and the above-mentioned fifth It is known that the data in the figure is the outer edge data to the pattern.

Furthermore, by repeating the above-mentioned series of operations, for example, in the enlarged image 2C shown in FIG.
1c was observed, and the analysis results in the mass spectrometry system M at that time are obtained as shown in FIG.

Here, when comparing FIG. 5, which is the secondary ion analysis result at the sunspot 21b located at the outer edge of the pattern, and FIG. 7, which is the analysis result at the sunspot 2IC located in the center of the pattern A, the sunspot The area of 21b is more than the area of sunspot 21c,
It is known that there are many impurities such as Na, Al, and C.

In other words, no contamination is observed in the center of the pattern, but contamination with alkaline earth metal elements is known to occur at the outer edges, for example due to insufficient cleaning treatment in the manufacturing process of semiconductor integrated circuit elements. It becomes clear that edge contamination of the pattern has occurred.

As a result, as a countermeasure against the occurrence of contamination, appropriate measures such as extending the cleaning time are taken in the manufacturing process of semiconductor wafers and the like constituting the sample 2.

In this way, in this embodiment, the target part of the sample 2 can be searched and observed by irradiating it from almost the same direction as the primary ion beam 4, with less risk of damaging the sample 2 due to sputtering action, etc. , secondary ion 4a
Since this is performed by scanning the primary electron beam 5, which forms an image equivalent to the image formed by is detected with high accuracy without being lost.

In addition, since the primary ion beam 4 and the primary electron beam 5 can be accurately irradiated to the same part of the sample 2, even if the sample 2 is insulating, the charge cancellation phenomenon caused by simultaneous irradiation with both , it is possible to prevent potential increase due to charging of the target analysis site, and it is possible to easily realize stable image observation by detecting secondary electrons 5a and highly accurate analysis by detecting secondary ions 4a. can.

As a result, for example, in response to the miniaturization and high integration of semiconductor integrated circuit elements, it is possible to accurately detect minute amounts of impurity elements, which are important for evaluating the manufacturing process of semiconductor integrated circuit elements. By promptly implementing improvements through appropriate evaluation of the manufacturing process, productivity in manufacturing semiconductor integrated circuit devices can be improved.

In the above description, the case where a toroidal electric field or a spherical electric field generator 18 is used as the mass spectrometry system M is described, but the present invention is not limited to this. For example, as shown in FIG. , quadrupole mass spectrometer 2
7. Mass spectrometer Ml consisting of a secondary ion detector 28, etc.
It is also possible to provide a secondary ion 4a, the type of the sample 2, etc., and use it appropriately.

Furthermore, it goes without saying that the mass spectrometry system M provided with the quadrupole mass spectrometer 27 may be provided in place of the mass spectrometry system M in the description of the embodiments.

Furthermore, charged particles 1! ! 3 may be provided separately for each of the primary ion beam 4 and the primary electron beam 5, and the incident path to the sample 2 may become the same from the middle.

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 was mainly applied to the secondary ion mass spectrometry technique used for evaluating the manufacturing process of semiconductor integrated circuit elements, which is the field of application that formed the background of the invention. The present invention is not limited to this, and can be applied to a wide variety of techniques that require highly accurate detection of trace amounts of elements.

〔Effect of the invention〕

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

That is, a charged particle source capable of simultaneously or selectively emitting a primary ion beam and a primary electron beam is provided, and the primary electron beam is irradiated onto the sample from the same or approximately the same direction as the irradiation direction of the primary ion beam. For example, by irradiating the same part of the sample from the same direction with a negative ion beam and an electron beam at any time, images produced by the electron beam and ion beam can be made to match over a wide area of the sample.

This makes it possible to accurately irradiate the ion beam to the inspection area of the sample, which is identified based on the image of the electron beam without causing any sputtering effects on the sample, with high precision without damaging the sample. It is possible to identify and detect impurities by detecting secondary ions while observing them.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the main parts of a secondary ion mass spectrometer that is an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a charged particle source, and Fig. 3 is an enlarged image of a sample. A diagram showing an example, FIG. 4 is a diagram showing an example of an enlarged image of the sample, FIG. 5 is a diagram showing an example of the mass spectrometry result of the sample, and FIG. 6 is a diagram showing an example of the enlarged image of the sample. Figure 7 is a diagram showing an example of the mass spectrometry results of a sample;
The figure is an explanatory diagram showing a modification of the secondary ion mass spectrometer. 1... Sample stand, 2... Sample, 2a, 2b. 2C... Enlarged image of sample, 21b, 2IC... Black dot, 3... Charged particle source, 31... Hollow cathode, 3
2... Intermediate electrode, 33... Anode, 33a...
Anode button, 34... Extraction electrode, 35...
Magnet, 36... Discharge power source, 37... Acceleration power source, 38
...Gas nozzle, 39...Source gas, 4...Primary ion beam, 4a...Secondary ion, 5...Primary electron beam, 5a...Secondary electron, 6...Convergent lens , 7... Slit, 8... Converging lens, 9... Scanning deflector, 10.11... Axis adjustment lens, 12.1
3... Electron beam corrector, 14... Secondary electron detector, 15... Secondary ion extraction lens, 16... Beam correction lens, 17... Beam correction deflector, 18.
...Toroidal electric field or spherical electric field generator, 19...
Correction lens that also serves as an aperture, 20... Electromagnetic field generator, 2
1... Electric field generator for removing scattered particles, 21b. 21c...Sunspot, 22...Ion collector slit, 23...Secondary electron multiplier, 24...Slit, 2
5...Detector, 26...Correction lens, 27...Quadrupole mass spectrometer, 28...Secondary ion detector, M, M
l...Mass spectrometry system, A#...Pattern. Agent Patent Attorney Daiwa Tsutsui Figure 3 Figure 4 Figure 5 M/e -One- No. Go to Figure 1 2-13... Charged particle source 4... Ion beam 5... Electron beam 14...Secondary electron detector M...Mass spectrometry system 32...Intermediate electrode 33...Anode 3734...Extraction electrode 39...Source gas Figure 6 Figure 7 M/e- + 27...quadrupole mass spectrometer

Claims (1)

[Claims] 1. A charged particle source capable of emitting a primary ion beam and a primary electron beam simultaneously or selectively, the sample being irradiated with the primary ion beam in the same or almost the same direction as the irradiation direction of the primary ion beam. A secondary ion mass spectrometer, characterized in that the primary electron beam is irradiated from. 2. The secondary ion mass spectrometer according to claim 1, wherein the primary electron beam and the primary ion beam are simultaneously irradiated to the same location on the sample to eliminate electrical charges on the sample. 3. Detecting a signal of secondary electrons emitted from the sample,
By using the signal of the secondary electron as a brightness modulation signal of the cathode ray tube that is synchronized with the scanning of the primary electron beam,
3. The secondary ion mass spectrometer according to claim 2, wherein the shape of the sample surface is observed and the irradiation site of the primary ion beam is observed and the position specified. 4. The secondary ion mass spectrometer according to claim 1, wherein convergence and scanning of the primary ion beam and the primary electron beam are controlled by the same lens system and deflection system. 5. The secondary ion mass spectrometer according to claim 4, wherein aberrations of the primary electron beam are corrected by a magnetic field lens or a magnetic field deflection system. 6. The secondary ion mass spectrometer according to claim 1, wherein the charged particle source comprises a gas discharge ion gun.