JPH05209849A - Sample analysis apparatus and method - Google Patents

Abstract

PURPOSE: To obtain a device and a method for analyzing a sample by which chamical characteristics and other features of the sample can be identified spatially concerning analysis of sample surface by using the radiation from the sample through a primary beam. CONSTITUTION: This device is provided with a means 51 for displaying a visual picture related to the surface of a sample 1 and means 3 and 5 for changing the beam position oh the sample according to the picture. In addition, the beam quiescent time for each pixcel of the sample can be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample analysis device and a sample analysis method. The present invention is not specifically directed, but in particular to a sample analyzer and a sample analysis method for analyzing the surface of a sample.

[0002]

2. Description of the Prior Art In modern material engineering, there is a demand for analyzing non-uniform patterned samples and anisotropic patterned samples.
Examples of such samples include fiber reinforced plastics,
Examples include polycrystals such as high temperature superconductors and metal alloys, semiconductors and other electronic devices, and layered composites and coated materials. In addition, some samples found in nature, such as ores and animal or plant debris, are also heterogeneously patterned or anisotropically patterned. ,
Or present both.

The above requirements arise in samples where it is necessary to determine both the identity of the sample and the position of the sample with respect to their chemical characteristics, typically with high resolution, eg 1 mm to 100 microns. This requirement arises, for example, in order to know the exact area of the patterned sample to be analyzed, which analysis is limited to a range of arbitrary shape not previously known. Moreover, in the case of patterned samples, the micromachining process needs to expose the area of interest and the shape of the mass that needs to be removed is arbitrary and not known in advance. Micromachining can also be used when repairing damaged parts of a sample. In either case, it is necessary to determine the area within the sample where micromachining has been performed or has been performed.

When mass spectroscopy techniques are used to analyze a sample, such techniques consume material from the sample. Thus, for example, in the case of a semiconductor device where some doping material is present in a very small proportion in a selected part of the sample, this part is repeated on the surface of the sample, so that several of these parts are It is effective for exciting the material of interest from the sample.

[0005]

Known sample analyzers include, for example, secondary ion mass spectrometers (SIMS).
There are generally only rectangular or circular analysis zones in the sample that can be analyzed.

[0006] H. Frenzel et al.
The "I", pages 219 to 224, describes a SIMS instrument in which it analyzes materials from different parts of the analysis zone by using "checker board" gating. It is possible to do it. However, such a device can only analyze material from a predefined and defined shape in a sample, eg an array of adjacent squares or rectangles.

[0007] It is an object of the present invention to provide a sample analyzer and method that allows spatial identification of a sample's chemical properties or other characteristics over the sample.

[0008]

According to a first aspect of the present invention, there is provided a sample analyzer which produces a beam effective for emitting material from a point on a sample surface. Excitation means, an image forming means for forming an image of the sample, and means for controlling the position where the beam and the sample intersect,
Thereby, the material is arranged to be released from a series of different points on the sample according to the image of the sample formed by the image forming means.

According to a second aspect of the present invention, there is provided a method of analyzing a sample, the method comprising the step of producing an excitation beam effective to eject material from a point on the sample; Of the image and controlling the intersection of the beam and the sample so that the material is emitted from a series of different points on the sample according to the image of the sample. Is configured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, the apparatus comprises a charged particle source PS effective to direct a charged particle beam onto a sample 1 mounted on a motorized sample stage MMS. This beam is directed by a scanning device 3 for the X direction and a scanning device 5 for the Y direction, each such device controlling the position where the charged particle beam intersects the sample 1 during a selected dwell time. And is described in detail below. The X-direction and Y-direction scanning devices 3 and 5 are magnetic or electrical charged particle optics effective to give a time-varying electric field or magnetic field to the charged particle beam, or some of these two. Or it can take a combined form.

This beam scanning operation consists of three sets of three numbers known as "three-way vectors".
Controlled by loading into one random access memory 7, 9, 11. Each set of three numbers defines the position where the beam intersects sample 1 according to a function of two orthogonal directions X and Y, as well as the dwell time of the beam at each point or pixel on the sample. The three random access memories 7, 9, 11 together form the electronic device for the scanning devices 3, 5 in the X and Y directions, but in the embodiment shown, for communication purposes. Bus 13
, Which in turn is connected to computer system 15 and optionally to local processing unit 16.

Three random access memories 7,
The numerical values loaded in 9, 11 are taken out successively by suitable electronic means (not shown) and then for each digital / digital device for the scanning devices 3, 5 for the X and Y directions.
It is input to the analog converters 17 and 19. timing·
The system 21 is responsible for controlling this downtime. The outputs from the digital / analog converters 17 and 19 are connected to the scanning devices 3 and 5 for the X direction and the Y direction via the amplifiers 23 and 25, respectively, and apply appropriate voltages to the scanning devices 3 and 5. .. The gain of this amplifier 23, 25 is controlled by an individual gain device 27, 29, each gain adjuster 27, 29 including the actual or pixel spacing between successive points where the beam intersects the sample, as well as the sample 1 Determine the maximum displacement of the upper beam and the actual spacing or area size of the continuous points where the beams intersect.

The additional control relating to the alignment of the charged particles with respect to the sample 1 is performed under the control of the computer 15 via the bus 13 through the positioning buffers 35 and 37 for the X direction and the Y direction. Further numerical values for X-direction and Y-direction digital-analog converter 3
It is executed by loading in 1, 33.

The apparatus further comprises a suitable signal detecting means with a pulse counter 39 and an analog detector 41, said signal detecting means being caused by the impingement of the primary particle beam on the sample. It operates to measure the signal corresponding to the charged particles emitted from sample 1. Total ion or total electron detector 43
Are provided for integrating the measured signals and accumulate the signals from the individual analysis zones of sample 1. Each analysis zone is defined by the analysis zone random access memory 45 and the analysis zone indicating random access memory 47 under the control of the pixel counter 49 connected to the pixel pause timer 21. .. The apparatus also includes an optical image processing unit 51 that captures an optical image of the illuminant of Sample 1.

Thus, when using this device, the position of the charged particle beam on the sample 1 is controlled by the initially selected point or series of points, which is selected on the optical image plane of the sample 1. It corresponds to one or more areas. After being produced by the image processing unit 51, this optical image is displayed on a visual display device connected to the computer 15 while using a computer chain type pointing device PD such as a mouse. Feedback to the motorized sample stage is provided via the stage controller 53 and is used to position each selected point in the image plane of the sample in the middle of the field of view of the device. In addition, after the preselected pattern or image is loaded into the image recording unit 55 combined with the computer 15, the pattern or image and the sample 1 are read from the sample 1 using a sample stage that decodes the sample on the inspection pattern surface. The correlation with the captured image may be sought until the correlation is found.

The computer-linked pointing device PD is also used to generate an outline of each selected area on the image plane of the sample.

With this sample positioning, the three vector values loaded into the memories 7, 9, 11 control the points of intersection of the beam and the sample and the dwell time, and thus are predetermined. The beam can be scanned over the pixels contained within the selected area while following the scanning operation.

When the dwell time for any of the pixels has expired, this cycle is repeated until the scan operation is complete, since the next set of three vector values are input into the memories 7, 9, 11.

Referring now to FIGS. 2-11, FIG.
Shows a method in which a device such as Sample 1 can be used for some distance up to a predetermined maximum in any direction in a plane orthogonal to the optical axis of the beam transport system.
Used to displace the particle beam above. When the dwell time for any pixel has expired, the next set of three vector values are entered into the three random access memories 7, 9, 11.

The beam displacement on sample 1 was performed in an ordered sequence, as illustrated in FIG. 3, which shows the pixel order in the form of a 10 × 10 flyback raster. ing. Typically, the beam scanner incorporates means (not shown) for positioning the beam in an area outside the area to be identified by the unique identification code, which is typically remote from the sample. So it produces a blank time. The beam may also be switched off for a controlled time at the end of each scanning cycle to produce a blank time.

An example of a pixel pattern in a crowded area is shown in FIG. Sequential displacement of the beam in the sample, e.g. displacement such as uniform or non-uniformly dimensioned distance width in either direction
Form a pixel pattern shown as an "inner raster".

Referring now to FIG. 5, this figure shows two examples for regions with excluded internal areas (IA). Such areas can find their application in the analysis of semiconductor devices, for example. Thus, for example, an image of interconnected tracks on a semiconductor device is enclosed within a polygonal area, which area has parts of the device that do not have excluded tracks. Only the pixels in this region are scanned by the ion beam and move all or part of the track, so that they do not substantially affect the peripheral portion of the device.

Another treatment of regions that incorporate excluded internal areas is when a brightness threshold is set for the sample image, so that all pixels with a brightness greater than the threshold are included in the region. Is. For example, if the interconnect tracks on a semiconductor device were made of aluminum and the image was taken in contrast mode, it would distinguish the aluminum from the surrounding area, so that all pixels on the track would be contained within the area. It will be. Also, an intensity threshold is set for the image,
All pixels with intensities below this threshold may be incorporated into the region. Thus, for a semiconductor device with an interconnect track made of aluminum, if the image was made in a contrast mode that distinguishes aluminum from its surroundings, all pixels except this track will be included in the area. ..

The transformed image can be formed by some mathematical transformation on the sample image, using a contrasting technique similar to that described above or other contrasting techniques. In this converted image, the pixels set in the area can be defined by overlapping the polygonal areas based on the above method. On the other hand, an intensity threshold value may be set so that pixels larger or smaller than the above intensity are included in the region. In the case of a semiconductor with a track made of aluminum, if the track is dirty,
When there is noise, a mathematical denoising method can be applied before the area selection processing.

The three vectors corresponding to the desired internal raster can be computed by computer 15 or local processing unit 16. As shown in FIG. 6, these rasters can take the form of at least one of several contiguous regions, non-contiguous regions and overlapping regions, these regions being “sub-rasters”. Is called. Referring now to FIG. 7, the beam positioning is
Positioning buffers 35 and 37 for X-direction and Y-direction components
Is reprogrammed by the computer 1 or device 16 via the so that the inner raster is itself scanned laterally over the sample within the boundaries of the "outer raster". If the dimensions of the inner raster are larger than the displacement of the inner raster, then the outer raster can be said to be "nested" within the inner raster. As can be seen from FIG. 7, by appropriately displacing the inner raster in this method, the brightness of the pixels in the region is temporarily increased, so that a high resolution image can be generated.

Here, the inner raster can be said to be "nested" within the outer raster if the dimensions of the inner raster are smaller than the overall displacement width of the inner raster. This state is shown in Fig. 8, where the sub
The raster has been displaced to seven positions within the area.

The beam scanning devices 3, 5 are arranged to move the region in the X and Y directions by electrically floating the voltage used to generate the internal raster. Therefore, at least one of the region and the inner raster can be positioned in the sample 1 with suitable features. Here, this device is a SIMS device, which is, for example, a high extraction field for collecting secondary ions from sample 1.
eld) is used and the extraction field polarity is reversed and changes from positive ion analysis to negative ion analysis, such beam positioning preserves the registration between the internal raster and selected characteristics of the sample. Can be used for.

The spacing of all pixels, and therefore the overall size of the area, can be varied by changing the gain of the amplifiers 23, 25 in the X and Y directions, and the size of the various areas. An example of is shown in FIG.

It will be appreciated that the time the beam is present at any pixel in sample 1 can be individually controlled. Therefore, the milling operation is as shown in FIG.
And performed by the beam at the sample surface as shown in FIG. 11 to create a surface profile such as a bevel. In the operation shown in FIG.
This bevel is obtained by increasing the dwell time of the beam at the sample plane for pixels towards the right-hand end of the sample. Similar results are obtained by the processing shown in FIG. 11, and the pixel density is increased with respect to the pixels in the right-hand direction of the sample.

It can be seen here that when the sputter rate varies within the visible range, the pixel spacing, the pixel dwell time, or both are alternatively controlled so that the eroded area remains flat. Will.

The resolution of the apparatus described above is, by way of example, that if the internal raster comprises a maximum of 65,536 pixels, the position of each pixel is determined with a precision of 65,536. It Downtime is 16,000 eligible
It is confirmed with a precision of 1/0. The analysis zone random access memory 45 built into the device generally
It has sufficient memory to store up to 256 data from the analysis zones with 32-bit precision for each zone.

It should be appreciated that the image of the sample can be captured by other suitable means. These include the phase and intensity contrast produced by the light source. In addition, a visually displayable map of the sample surface is generated for each atomic symbol and topographical contrast, which topographical contrast is caused by the focused primary electron beam secondary electron (SEM). Generated by. The primary electron beam may be used to create a chemical or other contrast by ion emission from the sample. The focused primary electron beam or fast atomic beam is thus emitted from the sample,
It can be used to create atomic symbols and topographical contrasts, ie, chemical or other contrasts from secondary ions emitted from the sample.

The image thus formed can then be used to select the analysis zone and the shape of the current density distribution over the sample area range illuminated by the beam.

It will be appreciated that a particular application for the device and method according to the invention is that the signal from a particular analysis zone in a sample is required to be added in real time to the next signal. For example, a semiconductor device made up of a transistor array comprises many correspondingly doped portions, each portion containing a doped material, but at the SIMS depth cross-section. For rigorous vertical analysis, the amount is extremely small. If similarly doped portions are visible from an image of the sample displayed on the computer through a visual display device, a set of individual polygons are drawn around each doped portion, The signals from the pixels in that polygon can be summed in the next depth section to give one analytical signal. As described above, the distribution of the doping material in the depth direction in the target portion can be obtained with excellent statistical accuracy regardless of the distribution of the doping material in the peripheral portion.

[0035]

As described above, according to the present invention, it is possible to provide a sample analyzer and a method thereof which enable spatial discrimination of chemical properties or other characteristics of a sample over the sample. ..

[Brief description of drawings]

1 is a schematic block diagram of an embodiment of an apparatus according to the present invention.

FIG. 2 illustrates a method according to the present invention, in which pixels of a sample image are addressed.

FIG. 3 is an explanatory diagram showing a pixel order of a raster scanning array.

FIG. 4 is an explanatory diagram showing a pixel pattern surrounded by a region.

FIG. 5 is an explanatory diagram showing two types of areas.

FIG. 6 is an explanatory diagram showing a plurality of adjacent sub-rasters and a non-adjacent sub-raster in a sample image.

FIG. 7 is an explanatory diagram showing an external raster assembled in an internal raster.

FIG. 8 is an explanatory diagram showing an internal raster assembled in a random external raster.

FIG. 9 is an explanatory diagram showing the effect of analog gain on the size of a region.

FIG. 10 is an illustration showing a first method for milling the surface profile of a sample according to an embodiment of the present invention.

FIG. 11 is an illustration showing a second method for milling the surface profile of a sample according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Sample 3 ... X-direction scanning device 5 ... Y-direction scanning device 7, 9, 11 ... Random access memory 15 ... Computer system 17, 19 ... Digital / analog converter 27, 29 ... Gain device 31, 33 ... Positioning digital / analog converters 35, 37 ... Positioning buffer / RAM 51 ... Optical image processing unit

 ─────────────────────────────────────────────────── ————————————————————————————————————————————————————————————————————————————————— YorkWay_179 RG, Malton, Akram, Lakeview (No Address)

Claims (16)

[Claims] 1. Excitation means (P) for producing a beam effective to emit material from a point on the sample (1) surface.
S), image forming means (51) for forming an image of the sample (1), and means (3, 5) for controlling the crossing position of the beam and the sample (1). A sample analyzer, whereby the material is released from a series of different points on the sample according to the image of the sample formed by the image forming means (51). 2. The control means (3, 5) according to claim 1, which is effective for defining an analysis zone corresponding to each point contained within a polygonal zone on the sample. apparatus. 3. The polygonal zone is a recessed zone.
The device according to claim 2. 4. Apparatus according to claim 2 or 3, wherein at least one area (IA) of the polygonal zone is excluded from the analysis zone. 5. The control means (3, 5) according to any one of claims 2 to 4, wherein the control means (3, 5) includes a computer-linked pointing device (PD) effective for defining the analysis zone. apparatus. 6. An apparatus according to claim 2, comprising means effective for determining a brightness curve of the image and means for determining the analysis zone according to the brightness curve. .. 7. A device according to claim 2, comprising algorithm generating means effective to define the analysis zone. 8. A means (45) for storing a set of three numbers, each set defining a position and a beam dwell time for a pixel corresponding to each point on the sample, and a predetermined (45) for the pixel. 8. A device as claimed in any one of claims 1 to 7, comprising means for addressing any pixel in any order during the dwell time. 9. Device according to claim 8, comprising means (43) for accumulating signals from different pixels. 10. An effective means for generating a set of three numbers from the sample image.
The device according to. 11. The apparatus of claim 8 comprising processing means effective to generate a set of three numbers independent of the image of the sample. 12. The electrical storage means is arranged such that the position of each pixel in the analysis zone determines the address of the storage and the signal from the pixel is stored in the storage. 11. The device according to any one of 1 to 11. 13. Displacement means (31, 3) for acting on the beam scanning mechanism to displace the position of each pixel by the same amount.
The device according to claim 8, comprising 3, 35, 37). 14. Apparatus according to claim 13, comprising means for varying the displacement caused by said displacement means as a function of time. 15. Apparatus according to claim 8 comprising means for varying the dwell time of the beam as a function of time. 16. Generating an excitation beam effective to eject material from a point on the sample; forming an image of the sample; controlling the intersection of the beam and the sample. A sample analysis method, wherein the material is released from a series of different points on the sample according to an image of the sample.