JP2004343131A - Method and device for analyzing sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of preparing a sample and a device therefor wherein only a sample piece including a desired specific area from a semiconductor and a device chip is taken out, and the sample is mounted on the sample stage of an analyzer/measuring device, dispensing with a hand-working sample preparation process which requires experience, skills and time. <P>SOLUTION: The method of analyzing the sample comprises processes for: storing the coordinates information of the desired positions of foreign matters, defects or the like detected by an inspecting means inspecting a sample substrate; taking out the sample piece, including the desired area by the processing of a focusing ion beam from the sample substrate based on the coordinates information of the desired positions, fixing the sample piece taken-out to a sample holder corresponding to at least any of the analyzer, an observation device, and a measuring device, and processing the sample piece fixed to the sample holder into a shape suitable for at least any of the analyzer, the observation device, and the measuring device; and introducing the sample holder which fixes the sample to at least any of the analyzer, the observation device, and measuring device to analyze the desired positions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is to inspect a semiconductor wafer to detect a desired location such as a minute foreign matter or a defect, extract a sample piece including the desired location using a focused ion beam and a transfer means, and observe and analyze the test piece. The present invention relates to a sample analysis method and a sample analysis device which process the sample into a shape corresponding to the measurement device and send it to observation, analysis, and measurement devices.

  In the manufacture of semiconductor devices, it is required to continuously produce good products without stagnation. Since the number of products produced is large, the occurrence of defects in a certain process leads to a reduction in product yield and a stoppage of a production line, which greatly affects profitability. For this reason, at a semiconductor element manufacturing site, a careful inspection is performed after a specific process or after a device is completed, and efforts are made to eliminate defective products and investigate the cause. Actually, in the manufacturing process, wafers and devices are periodically or periodically extracted and inspected for defective portions. In the case of wafers, the inspection location and inspection items are determined in advance, and the inspection location is constantly monitored for each wafer to detect abnormalities in the manufacturing process. If there is an abnormal portion such as a pattern defect or foreign matter, the device is discarded, or a method of pursuing the cause of the abnormality and taking measures is taken.

  As an example of the inspection method, there is an inspection method for detecting the attachment of foreign matter or a defect of a formed circuit pattern or the like on the entire surface or a partial area of a wafer. There are a wafer inspection device (abbreviated as inspection), a wafer inspection electron microscope (hereinafter abbreviated as inspection SEM), and a prober device that detects an electrical failure such as disconnection or short circuit of a circuit.

  Although a high-resolution scanning electron microscope (hereinafter abbreviated as SEM) is used for more detailed sample appearance observation, with the integration of semiconductors, even objects that are too fine to be observed at the SEM resolution are required. It needs to be analyzed. In this case, a transmission electron microscope (hereinafter, abbreviated as TEM) having a high observation resolution is an effective device instead of the SEM.

Here, a method for preparing a TEM sample will be described. FIG. 2 is a view for explaining one of the conventional methods for producing a TEM sample. FIG. 2A shows a semiconductor wafer on which an LSI is formed (hereinafter, simply referred to as a wafer 30), which includes an upper layer portion 31 and a substrate portion 32. It is assumed that a TEM sample is prepared for a specific region of the wafer 30. First, an area to be observed is marked, and the wafer 30 is cut with a diamond pen or the like so as not to destroy the observation area, or cut along a cutting line 33 by a dicing saw, for example. Two pieces of the strip-shaped pellets 34 cut out as shown in FIG. 2 (b) are attached with an adhesive 35 so that the observation areas face each other so that the central part of the TEM sample to be produced becomes the observation area. A bonded sample 36 is made (FIG. 2C). Next, the bonded sample 36 is sliced with a diamond cutter, and a sliced sample 37 is cut out (FIG. 2D). The size of the slice sample 37 is about 3 × 3 × 0.5 mm. Further, the sliced sample 37 is polished thinly on a polishing plate using an abrasive to produce a polished sample 38 having a thickness of about 20 μm, and this is fixed to a single-hole TEM holder 39 mounted on a TEM stage (FIG. 2 (e)). Next, an ion beam 40 is irradiated from both sides of the polishing sample 38 (FIG. 2 (f)) to perform ion thinning (FIG. 2 (g)). Stop and use as TEM sample 41 (FIG. 2 (h)).
Thus, the thin section 42 thinned to about 100 nm or less was used as a TEM observation area (circled in the figure). With such a method, it is very difficult to determine the position when the part to be observed is specified at the micron level.

  As another conventional technique for preparing a TEM sample, there is an example in which focused ion beam (hereinafter, abbreviated as FIB) processing is used. This will be described with reference to FIG. First, the wafer 30 is diced in the vicinity of the region to be observed as shown in FIG. 3A (reference numeral 33 is a cutting line), and a rectangular pellet 34 is cut out (FIG. 3B). The size of the pellet is approximately 3 × 0.05 × 0.5 mm (wafer thickness). The strip-shaped pellet 34 is fixed to a TEM sample holder 37 made of a slightly semicircular thin metal piece (FIG. 3C). The observation area in the strip-shaped pellet 34 is irradiated with the FIB 24 so as to leave a thin section (hereinafter, referred to as a wall section) 43 having a thickness of about 0.1 μm (FIG. 3D) to form a thin wall section. (Hereinafter, it is called wall processing. FIG. 3 (e)). This is used as a TEM sample 41, and a TEM holder is mounted on a TEM stage, introduced into a TEM device, and the wall portion 43 is observed. With this method, it has become possible to locate the observation portion at the micron level. This technique is described in, for example, E.C.G.Kirk et al. In the collection of papers, Microscopy of Semiconducting Materials 1989, Institute of Physics Series No. 100, p.501-506 (known example 1).

  As described above, TEM can be expected to perform high-resolution observation, but has a face that a great deal of effort is required for sample preparation.

Microscopy of Semiconducting Materials 1989, Institute of Physics Series No.100., P.501-506

As described above, the conventional sample analysis method and sample preparation method have the following problems.
(1) Coordinate problem: When analyzing a defective portion such as a foreign substance or a defect found by inspection of the entire surface or a part of the wafer, the coordinates of the defective portion are clarified in an inspection device such as a wafer inspection device or an inspection SEM. Must also be cut into dimensions that can actually fit into an analysis device, observation device, or measurement device (hereinafter, abbreviated as an analysis device) and processed into an analysis sample piece. There is a problem that the position cannot be known and a desired analysis cannot be performed.
(2) Sample preparation problem: Even if a defect is detected at a certain position as a result of inspection of the entire surface or a part of the wafer by a wafer inspection device or an inspection SEM, the purpose of the analysis is to determine the analysis sample piece from the wafer. In some cases, the minute foreign matter that is generated may be lost or deteriorated, or another damage may be caused and superimposed to make it impossible to determine the cause of the originally intended defective portion. This is because the conventional sample preparation method relied on mechanical or chemical methods such as cutting, polishing, and cleaving the sample. Was not expensive. In addition, since such an accurate analysis takes a long time, defective products may occur successively in the final product, causing a great deal of damage.
(3) The problem of wafer breakage: In order to monitor the finish in a certain process during manufacturing, in the continuous inspection of only a specific portion of a wafer, only a few inspection points are periodically performed for each fixed number. , And the wafer is discarded except for the inspection location. In recent years, the wafer diameter has become 200 mm, and the diameter has tended to increase to 300 mm, and even larger.Therefore, a wafer on which many high value-added devices are mounted is cut and cleaved for inspection at several locations. Disposal was very uneconomical.

  Here, a TEM sample will be described as an example relating to any of the above problems (1) to (3). Because TEM has high resolution as described above, it is a powerful tool for analyzing small parts, but it takes a very long time from the identification of a defective area to the analysis result, so when you want to observe It is not as widespread as SEM with immediate results. One of the reasons why it takes a long time for the analysis results is in the sample preparation process before TEM observation. Since the TEM observation region must be thinned to a thickness of about 100 nm, the conventional method involves manual operations such as polishing and machining that require the skill of a sample creator. In addition, when the observation region is specified at the micron level, it becomes extremely difficult to prepare a sample. In addition, the position of the defective area previously specified on the micron order by a microscope is often lost or mistaken during sample preparation. Further, in order to manufacture a desired sample piece from a wafer, mechanical damage such as cleavage or cutting of the wafer is performed, so that new damage to the sample occurs, and it may not be possible to distinguish it from the original defective area. In addition, the sample chamber of a TEM is very small, and the sample piece must be subdivided into millimeter-sized pieces, and the wafer must be cut. Once analysis or observation has been performed, if another analysis or observation is necessary for an adjacent part, the subsequent analysis area may be damaged or damaged due to the disruption of the previous sample preparation. In addition, there arises a problem that an accurate positional relationship is not known and continuous analysis and observation information cannot be obtained.

  With respect to such a conventional technique, with respect to a defective portion obtained by various inspection methods, only a desired portion on the wafer is not subjected to mechanical or chemical damage, while maintaining the wafer shape, There has been a demand for a sample analyzing method and a sample analyzing apparatus capable of processing and analyzing a sample piece that can be introduced into various branching devices.

  In view of the above-mentioned problems, a first object of the present invention is to accurately locate a desired location such as a foreign substance or a defect detected in an entire or partial inspection of a wafer without cutting and separating the wafer, and to perform various analyzes. An object of the present invention is to provide a sample analysis method that can process the sample into a suitable sample piece and analyze the desired region with various analyzers. Further, a second object is to provide a sample analyzer which realizes the first object.

In order to achieve the first object,
A sample analysis method for observing, analyzing, or measuring a target sample piece by at least one of: a step of storing coordinate information of a desired portion such as a foreign substance or a defect detected by the inspection means on the sample substrate; A sample piece including the desired location is extracted from the sample substrate based on coordinate information of the desired location using processing by a focused ion beam, and the extracted sample piece is analyzed by an analyzer, an observation device, or a measurement device. Fixed to the sample holder corresponding to at least one of them, a step of processing the sample piece fixed to the sample holder into a shape suitable for at least one of analysis or observation or measurement, and fixed the sample piece The sample holder is introduced into at least one of an analyzer, an observation device, and a measurement device to analyze the desired portion. Using the sample analysis method consisting of a degree,
In particular, the inspection means uses at least one of an optical wafer inspection apparatus, a scanning electron microscope for wafer inspection, a laser scanning microscope, and an optical microscope.

  Further, before the step of extracting the sample piece using the processing by the focused ion beam, a positioning step by an optical microscope may be accompanied.

  Furthermore, in the sample analysis method, in particular, before the step of extracting the sample piece by using a focused ion beam, a step of marking the desired location near the desired location with the focused ion beam is performed. A desired portion can be reliably processed by adding the above.

  Further, in the sample analysis method, the method further includes a step of subjecting the sample piece fixed to the sample holder to thin-wall processing by focused ion beam irradiation to finish the sample for observation with a transmission electron microscope. The time required for electron microscope observation can be greatly reduced.

The second object is
A wafer inspection unit for inspecting a wafer and storing coordinate information of a desired location such as a foreign substance or a defect, and including the desired location using a focused ion beam with respect to the sample substrate based on the coordinate information of the desired location A sample preparation unit configured to extract a sample piece and fix it to a sample holder suitable for at least one of analysis, observation, and measurement, and process the wafer; the wafer inspection unit and the sample preparation unit move the wafer Connected by a vacuum transfer path for Or
A wafer inspection unit for inspecting a wafer and storing coordinate information of a desired location such as a foreign substance or a defect, and including the desired location using a focused ion beam with respect to the sample substrate based on the coordinate information of the desired location The sample piece is extracted and fixed to a sample holder suitable for at least one of the analysis device, the observation device, and the measurement device, and the sample piece having a shape suitable for at least one of the analysis device, the observation device, and the measurement device is obtained. A sample preparation unit to be processed, and at least one of an analyzer or an analyzer or an analyzer for analyzing the sample piece, and the wafer inspection unit, the sample preparation unit, and the analysis unit The wafers are connected by a vacuum transfer path for moving the wafers. Or
A wafer inspection unit for inspecting a wafer and storing coordinate information of a desired location such as a foreign substance or a defect, and including the desired location using a focused ion beam with respect to the sample substrate based on the coordinate information of the desired location The sample piece is extracted and fixed to a sample holder suitable for at least one of the analysis device, the observation device, and the measurement device, and the sample piece having a shape suitable for at least one of the analysis device, the observation device, and the measurement device is obtained. The sample preparation unit to be processed and at least one of the analysis unit or the observation unit or the measurement unit for analyzing the sample piece are configured mechanically independently, and at least the wafer inspection unit A sample analyzer may have a structure in which coordinate information of a desired location is connected by an information transmission unit that transmits the coordinate information to the sample preparation unit and the analysis unit. In this structure, the wafer and the sample holder or a jig on which the sample holder is mounted may be transported by a vacuum vessel between the wafer inspection unit, the sample preparation unit, and the analysis unit.

  In the above-mentioned sample analyzer or sample analysis system, in particular, the inspection apparatus is any one of an optical wafer inspection apparatus, a scanning electron microscope for wafer inspection, a laser scanning microscope, and an optical microscope, or observation in an analysis unit. In particular, when the apparatus is any one of an in-lens scanning electron microscope and a transmission electron microscope, the inspection can be efficiently performed.

  The above object is achieved by using such a sample preparation apparatus.

  By using the sample analysis method and apparatus according to the present invention, on the spot where a desired portion is marked, without subdividing the wafer, and, from the wafer, other analysis such as TEM observation without human intervention, A sample for measurement and observation can be prepared, and the time required to obtain an analysis result can be reduced.

  An embodiment of a sample manufacturing apparatus according to the present invention includes a wafer inspection unit that inspects a wafer and stores coordinate information of a desired location such as a foreign substance or a defect, and focuses ions on a sample substrate based on the coordinate information of the desired location. Using a beam, a sample piece including the desired portion is extracted, fixed to a sample holder suitable for at least one of an analyzer, an observation device, and a measurement device, and processed into a shape corresponding to these devices. The wafer inspection unit and the sample preparation unit are connected by a vacuum transfer path for moving the wafer.

  Hereinafter, a specific example of the embodiment will be described.

<First embodiment>
FIG. 1 is a schematic configuration diagram showing one embodiment of a sample analyzer for realizing the sample analysis method according to the present invention.
In the sample analyzer 100, a wafer inspection unit 101 and a sample preparation unit 102 are mechanically connected. The wafer inspection unit 101 corresponds to a wafer appearance inspection device, an inspection SEM, or a prober device. When it is necessary to detect and analyze a defective portion by the wafer inspection, the valve 106 provided between the wafer inspection unit 101 and the sample preparation unit 102 is opened to transfer the wafer 12 to the sample preparation unit 102. The sample piece processed and manufactured by the sample manufacturing unit 102 is carried into another observation device such as a TEM or SEM, an analysis device, a measurement device, or the like, and a defective portion is analyzed. Conversely, if there is no abnormality as a result of the wafer inspection, the wafer 12 does not need to be sent to the sample preparation unit 102, but is transferred to the apparatus in the next manufacturing process.

  As an example of the wafer inspection unit 101, an inspection SEM is shown here, and an electron beam irradiation optical system 103, a secondary electron detector 104, and a sample stage on which the wafer 12 can be mounted and moved in a sample chamber 107. 105 and the like. The secondary electron signal flowing into the secondary electron detector 104 and the beam deflection of the electron beam irradiation optical system 103 can be synchronized to display the wafer surface shape on the display means 13 ', and control of the entire wafer inspection unit 101 can be performed by a calculation processing device. 17 '. The wafer inspection includes a method of comparing a plurality of devices formed on the wafer, a method of comparing cells in the devices, and the like, but is not limited here. Such coordinate information of a desired portion detected by the wafer inspection unit 100 is temporarily stored in the calculation processing unit 17 ′, and can be transmitted to the calculation processing unit 17 of the sample preparation unit 102 by the information transmission unit 110. The external appearance and coordinate information of the wafer under inspection can be displayed on the display means 13 '.

  The sample preparation unit 102 includes a FIB irradiation optical system 2 for processing and observing the sample substrate 12 and the extracted sample, a secondary particle detector 3 for detecting secondary electrons and secondary ions emitted from the sample by the FIB irradiation, and a FIB A deposition gas source 4 for supplying a source gas for forming a deposition film in an irradiation area, a sample stage 5 on which a sample substrate 12 such as a semiconductor wafer or a semiconductor chip is mounted, and a transfer means 8 for transferring an extracted sample to a sample holder. , An optical microscope 9 for observing the sample substrate 12, display means 13 for displaying an image by the optical microscope 26 and an image by the secondary particle detector 3, a calculation processing device 17 for controlling the entire sample preparation unit 102, a sample stage 5 Is provided at least with a sample chamber 18 and the like in which is installed. Further details will be described with reference to FIG.

  FIG. 4 shows, in addition to the constituent parts shown in FIG. 1, a sample holder 6 for fixing a small extracted sample obtained by extracting a part of the sample substrate 12, and a holding means 7 for holding the sample holder (hereinafter also referred to as a holder cassette). ), A stage control device 10 for controlling the position of the sample stage 5, a transfer device control device 11 for driving the transfer means 8 independently of the sample stage 5, a sample holder 6, a sample substrate 12, a transfer means 8 and the like. An image display means 13 for imaging by secondary electrons or secondary ions generated by ion beam irradiation, a FIB control device 14 of the FIB irradiation optical system 2 and the like are also configured. In addition, a deposition gas source control device 15, secondary particle detection The control unit 16, the image display unit 13, the transfer unit control unit 11, and the like are controlled by the calculation processing unit 17.

  The FIB irradiation optical system 2 forms the FIB 24 having a diameter of about 10 nm to about 1 μm by passing ions emitted from the liquid metal ion source 20 through a beam limiting aperture 21, a focusing lens 22, and an objective lens 23. By scanning the FIB 24 over the sample substrate 12 using the deflector 25, the sample substrate 12 can be processed in a scanning shape on a micron to submicron level. The processing here refers to an operation of changing the shape of the sample substrate by using a concave portion formed by sputtering, a convex portion formed by FIB assist deposition, or a combination thereof. The deposition film formed by the FIB irradiation is used to connect the contact portion at the tip of the transfer means 8 to the sample substrate 12 and to fix the extracted sample to the sample holder. In addition, by processing secondary electrons and secondary ions generated during FIB irradiation with the secondary particle detector 3 and forming an image, it is possible to observe a processed region and the like.

  The sample stage 5 is installed in a sample chamber 18, and the FIB irradiation optical system 2 and the like are also arranged in a vacuum vessel. A holding means (sample holder cassette) 7 on which a sample holder 6 is mounted can be attached to and detached from the sample stage 5, and movement, inclination, and rotation in three-dimensional (X, Y, Z) directions are controlled by a stage control device 10. You. The sample substrate 12 enters and exits using the sample substrate transport path 19 as necessary.

  The sample holder 6 is a strip-shaped silicon piece 27 having a convex cross section as shown in FIG. This strip-shaped silicon piece 27 was formed by cleaving from a silicon wafer or using a dicing saw. The size of the sample holder used in this embodiment is 2.5 mm in length, 50 μm in upper width, 200 μm in lower width, and 0.5 mm in height (silicon wafer thickness), and the fixed surface of the extracted sample is the silicon wafer surface or the cleavage surface. Accordingly, even if the extracted sample 70 is fixed to the fixed surface and observed by TEM, the unevenness of the fixed surface does not hinder electron beam irradiation. Although the shape of the sample holder is not limited to the dimensions shown here, it is necessary to make the fixing surface a wafer surface or a cleavage surface and make the width as thin as possible in order to facilitate TEM observation. FIG. 5 shows an example in which three extracted samples 70 are mounted on one sample holder 6. On the other hand, a conventional sample holder for TEM is a single hole type shown in FIG. 6 (a) or a mesh type shown in FIG. 6 (b). The single hole type has a single hole 75 having a diameter of about 1 mm at the center and has a diameter of about 3 mm. Although it is a thin metal disk 76, if it is as small as 10 to 20 microns like the extracted sample 70 obtained by the sample preparation method according to the present invention, it is very difficult to accurately attach the extracted sample 70 to the side wall of the single hole 75. . In the case of the mesh type, a mesh 77 is attached to the thin metal disk 76, and the mounting position can be selected arbitrarily to some extent by using the mesh 77 at intervals according to the size of the sample. There was a very high risk that the line path would be shaded by the mesh 77 and TEM observation would not be possible.

  The holder cassette (holding means) 7 is a jig for supporting the sample holder 6 and is mounted on the sample stage 5. The sample stage 5 refers to a general-purpose large stage on which a wafer can be mounted, or a small stage on which device chips can be mounted. The number of sample holders 6 mounted on one holder cassette 7 may be one or more. The number of holder cassettes 7 that can be set on the sample stage 5 may be one or more.

As the optical microscope 9, a laser scanning microscope that can be expected to have higher resolution than a conventional optical microscope was used. The laser scanning microscope focuses the laser beam emitted from the oscillator 28 by the objective lens and irradiates the sample with the fluorescence. The fluorescence from the focal point excited by the minute laser spot passes through the dichroic mirror and is confocal with the focal point of the sample. And reaches the CCD 29 through the aperture set at the position (1), an image is formed only by the fluorescence from the focal point of the sample. Compared with the method of uniformly exciting the field of view, the amount of stray light is extremely small, and even if fluorescence from other than the focus is generated, the image is obstructed by the aperture and does not reach the CCD 29 to obtain a clear image. By installing two mirrors between the sample substrate 12 and the dichroic mirror and scanning in the X and Y directions, a sample surface image can be obtained and displayed on the display means 13. The optical microscope 9 is based on the relationship between the coordinates of marks (not shown) previously set on the sample substrate 12 and the coordinate information obtained by the inspection unit 101. Is disclosed in Japanese Patent Application Laid-Open No. 9-134699, “Focused Ion Beam Apparatus” (known example 3), but does not disclose the existence of the transfer means 8 for extracting a specific region of the sample substrate 12. .

  The transfer means 8 includes a coarse moving section 60 having a fast moving speed and a large stroke, and a moving resolution of the coarse moving section in order to realize quick sampling from an arbitrary position even when the sample substrate is a large-diameter wafer. And a fine movement unit 61 having a high moving resolution with the same stroke as that described above. The entire transfer means is installed independently of the sample stage, and a large movement of the sampling position is shared by the movement of the sample stage. The driving of the coarse moving section in the XYZ directions is constituted by a motor, a gear, a piezoelectric element and the like, and has a moving resolution of several microns with a stroke of several mm. Since the fine movement section is required to be as compact as possible and to move with precision, a bimorph piezoelectric element is used to obtain a submicron movement resolution. FIG. 7 shows a configuration example of the coarse moving section 60 and the fine moving section 61 of the transfer means 8. The coarse movement part 60 can move in the XYZ-axis direction by using three encoders 64X, 64Z, and 64Y (not shown) with the support 63 using the stenosis part 62 as a fulcrum. The drive system of the coarse movement unit 60 is on the atmosphere side through a lateral port of the sample chamber wall 66, and the vacuum is shut off by the bellows 65. The tip of the bimorph piezoelectric element 67 was connected to a thin and sharpened tungsten probe 68 having a diameter of about 50 μm, and was connected to the coarse movement part 60 by an extension rod 69. By applying a voltage to the bimorph piezoelectric element 67, the tip of the probe 68 moves slightly. As described above, the structure, size, and installation position of the transfer means 8 must be sufficiently considered, and the sample preparation apparatus according to the present invention solves all of them.

As a conventional technique similar to the transfer means 8, there is Japanese Patent Application Laid-Open No. 5-52721, "Method of Separating Sample and Method of Analyzing Separated Sample Obtained by This Separation Method" (Known Example 2).
According to this prior art, the transport means for transporting the separation sample is configured with three bimorph piezoelectric elements corresponding to the XYZ axes, but the installation position of the transport means is unknown, and only FIG. It can be read that it is set on the stage. In this way, when the transfer means is set on the sample stage, when the target sample is located at the center of a wafer having a diameter of, for example, 300 mm, the moving stroke of the tip of the transfer means increases from the transfer means position to a desired position of the sample. Since it is much smaller than the distance, it has a fatal problem that it cannot be reached by the transport means installed on the sample stage. Further, in the case where the three axes constitute a bimorph piezoelectric element, the bimorph piezoelectric element bends at one end as a fulcrum, so that the other end draws an arc according to the applied voltage. That is, in the movement in the XY plane, the probe at the tip of the transfer means does not linearly move in one axial direction only by the operation of one bimorph piezoelectric element. Therefore, the three bimorph piezoelectric elements must be very complicatedly controlled in order to move the tip of the probe to a desired position by forming a fine movement section with the three bimorph piezoelectric elements. .

<Embodiment 2>
In the first embodiment, an example has been described in which the wafer inspection unit 101 and the sample preparation unit 102 are mechanically coupled to each other, and the wafer serving as the sample substrate 12 is carried between the two apparatuses. As shown in FIG. 8, the second embodiment is an example in which the wafer inspection unit 101 and the sample preparation unit 102 are mechanically independent, and the coordinate information of the defective portion is transmitted and received between the calculation processing devices 17 and 17 ′. . The wafer 12, which is a sample substrate, is transported by being enclosed in a transport container 107 which is small and can be evacuated. The coordinate information and the like in the wafer inspection unit 101 can be transmitted from the calculation processing device 17 ′ to the calculation processing device 17 in the sample preparation unit 102 through the information transmission unit 110. With such a configuration, a defective portion of the wafer 12 detected by the wafer inspection unit 101 is processed and manufactured in the sample manufacturing unit 102 into a shape that can be easily analyzed by various analyzers.

<Embodiment 3>
Next, an embodiment of a sample analysis method according to the present invention will be described. Here, as an example of a sample, a method of preparing a sample piece to be observed by TEM will be described, and a specific description will be given of a sample analysis method from wafer observation to sample piece processing to TEM observation. In addition, in order to clarify the procedure, the procedure will be divided into several steps and described with reference to the drawings.
(1) Appearance inspection process:
First, the entire surface of a wafer to be inspected or a part thereof is inspected for abnormalities. The inspection contents include an appearance inspection such as a wafer inspection device using light (laser) and an inspection SEM using an electron beam, and an electric circuit inspection using a probe device. By this inspection, the position of a defective portion such as a foreign matter, a defect, and a wiring abnormality can be known. At this time, the corresponding device coordinates of the above-described defective portion are stored in the calculation processing device as coordinates based on the mark previously set on the corresponding device, based on a mark (wafer mark) set on the wafer in advance.
(2) Sample preparation process
(a) Marking process:
The wafer is introduced into the sample preparation unit, and first, a mark (device mark) of the corresponding device is searched for. Here, the device mark is searched for with a laser microscope installed in the sample preparation unit. A more detailed search is performed to find the above-mentioned defective portion.In this case, when searching by a secondary electron image by FIB irradiation, the sample surface is sputtered by the FIB, so that the surface is damaged, and in the worst case, a desired defective object to be analyzed is obtained. May be lost. Therefore, based on the coordinates of the wafer mark, the device mark, and the defective portion during the wafer inspection, and the coordinates of the wafer mark and the device mark in the sample preparation unit, the coordinates of the defective portion in the sample preparation apparatus were derived by calculation. Later, multiple locations are marked by the FIB so that defective locations can be confirmed.

  In this example, as shown in FIG. 9A, two + marks 80 were formed at 10-micron intervals across the observation region. The rotation of the sample stage is adjusted in advance so that the straight line connecting the two marks is parallel to the tilt axis of the sample stage.

(b) Large rectangular hole machining process:
On the straight line connecting the two marks 80, two rectangular holes 82 are provided by FIB 81 on both sides of the two marks. The opening size was, for example, about 10 × 7 μm and the depth was about 15 μm, and the distance between the rectangular holes was 30 μm. In each case, processing was performed with a large current FIB having a diameter of about 0.15 μm and a current of about 10 nA in order to complete the process in a short time.
Processing time was approximately 5 minutes.

(c) Vertical groove machining process:
Next, as shown in FIG. 9b, the line is separated from the straight line connecting the marks 80 by about 2 μm, and has a width of about 2 μm and a length of 2 μm so as to cross one rectangular hole 82 and not to cross the other rectangular hole. An elongated vertical groove 83 of about 30 microns and a depth of about 10 microns is formed. The scanning direction of the beam should be such that sputter particles generated when the FIB irradiates the sample do not fill the vertical grooves or large rectangular holes formed. A small area that does not intersect with one of the rectangular holes 82 becomes a support portion 84 that supports a sample to be extracted later.

(d) Slant groove processing:
After the above steps (b) and (c), the sample surface is slightly inclined (20 ° in this embodiment). Here, the straight line connecting the two marks 80 is set parallel to the tilt axis of the sample stage. Therefore, as shown in FIG. 9C, the two rectangular holes 82 are connected to each other at a distance of about 2 μm from the straight line connecting the marks 80 and opposite to the elongated vertical grooves 83 so as to connect the rectangular holes 82. A groove having a depth of about 32 microns and a depth of about 15 microns is formed. The rectangular holes 82 formed by the sputtered particles due to the FIB irradiation are not filled. An elongated slanted groove 85 is formed by the FIB 81 obliquely incident on the sample substrate surface, and intersects the slender vertical groove 83 formed earlier. By the steps (b) to (d), the wedge-shaped excised specimen having a right-angled triangular cross section having the apex angle of 70 ° including the mark 80 except the support portion 84 is held in a cantilever state. .

(e) Depot process for probe fixation:
Next, as shown in FIG. 9D, the sample stage is returned to a horizontal position, and the probe 87 at the tip of the transfer means is brought into contact with the end opposite to the support 84 of the sample 86 to be extracted. Contact can be sensed by conduction between the sample and the probe or by a change in capacitance between the two. In addition, in order to prevent the sample 86 to be extracted or the probe 87 from being damaged by careless pressing of the probe 87, a function of stopping the + Z direction driving when the probe comes into contact with the sample is provided. Next, in order to fix the probe 88 to the sample 86 to be extracted, the FIB is scanned while flowing out a deposition gas into an area of about 2 μm square including the tip of the probe. In this way, the deposition film 88 is formed in the FIB irradiation area, and the probe 87 and the sample 86 to be extracted are connected.

(f) Extraction sample extraction process:
In order to extract the extracted sample from the sample substrate, the supporting portion 84 is released from the supported state by performing FIB irradiation and sputtering. Since the support portion 84 has a square of 2 microns and a depth of about 10 microns when viewed from above the sample surface, it can be removed by FIB scanning for 2 to 3 minutes.
(Fig. 9e, f)
(g) Extracted sample transfer (sample stage movement) process:
The extracted sample 89 connected to the tip of the probe 87 and extracted is moved to the sample holder, but actually, the sample stage is moved, and the sample holder 90 is moved within the FIB scanning area. At this time, in order to avoid an unexpected accident, the probe may be retracted in the + Z direction. Here, the installation state of the sample holder 90 has various forms as described later, but in this example, it is assumed that the sample holder 90 is installed on a side entry type TEM stage. (Fig. 9g)
(h) Extraction sample fixing step:
When the sample holder 90 enters the FIB scanning area, the movement of the sample stage is stopped, and the probe is moved in the −Z direction to approach the sample holder 90. When the extracted sample 89 comes into contact with the sample holder 90, the contact portion between the extracted sample 89, the sample holder 90, and the FIB is irradiated while introducing the deposition gas. By this operation, the extracted sample can be connected to the sample holder. In this embodiment, a deposition film 92 is formed on the end surface of the extracted sample 89 in the longitudinal direction.
The FIB irradiation area is about 3 μm square, a part of the deposition film 92 adheres to the sample holder 90 and a part adheres to the side surface of the extracted sample, and both are connected. (Fig. 9h)
(i) Probe cutting step:
Next, after the introduction of the deposition gas is stopped, the probe 87 can be separated from the extracted sample 89 by irradiating the FIB 81 onto the deposition film connecting the probe 87 and the extracted sample 89 to remove the sputter. The sample 89 stands free on the sample holder 90. (Fig. 9i)
(j) Sample piece processing step (wall processing):
Finally, the TEM sample is obtained by irradiating with FIB and finally finishing the observation region so that the observation region becomes a wall 93 having a thickness of about 100 nm or less. At this time, since one of the side surfaces in the longitudinal direction of the extracted sample is a vertical surface, when the FIB irradiation area is determined for wall processing, the wall substantially perpendicular to the surface of the sample substrate 89 is determined by using this vertical surface as a reference. 93 can be formed. Further, prior to the FIB irradiation, an FIB deposition film is preferably formed on the upper surface including the wall formation region in order to process the wall surface more planarly. This method is already well known. As a result of the above-described processing, a wall having a width of about 15 microns and a depth of about 10 microns can be formed, and a TEM observation region is completed. As described above, the time from the marking to the completion of the wall processing was reduced to about one hour and 30 minutes, which was several times shorter than the conventional TEM sample manufacturing method. (Figure j)
(3) Analysis process (TEM observation):
After the wall processing, the side entry type TEM stage is pulled out and introduced into the TEM sample chamber. At this time, the TEM stage is rotated and inserted so that the electron beam path and the wall surface intersect perpendicularly. Subsequent TEM observation techniques are well known and will not be described here.

In addition, in the above-mentioned sample analysis method, there is known example 2 as a prior art similar to the sample preparation process. The conventional method will be described with reference to FIG. 10 in order to show that this sample preparation process is completely different from the conventional method. First, the posture of the sample 50 is maintained such that the FIB 24 irradiates the surface of the sample 50 at right angles, and the FIB 24 is scanned in a rectangular shape on the sample to form a square hole 51 of a required depth on the sample surface (FIG. 10). (a)). Next, the sample is tilted so that the axis of the FIB with respect to the sample surface is tilted by about 70 °, and a bottom hole 52 is formed. The tilt angle of the sample is changed by a sample stage (not shown) (FIG. 10B). The posture of the sample is changed, and the sample is set so that the surface of the sample is perpendicular to the FIB again, and the notch groove 53 is formed (FIG. 10C). The manipulator (not shown) is driven, and the tip of the probe 54 at the tip of the manipulator is brought into contact with the part for separating the sample 50 (FIG. 10 (d)). A deposition gas 56 is supplied from a gas nozzle 55, and FIB is locally irradiated to a region including the tip of the probe to form an ion beam assisted deposition film (hereinafter abbreviated as a deposition film 57). The separated portion of the sample in contact with the tip of the probe 44 is connected by a deposition film 46 (FIG. 10E). The remaining portion is cut out by the FIB 24 (FIG. 10F), and a separated sample 58 is cut out from the sample 50.
The cut-out separated sample 58 is supported by the connected probe 54 (FIG. 10 (g)). The separated sample 58 is processed by FIB in the same manner as in the second conventional method, and a region to be observed is processed into a wall to be a TEM sample (not shown).

In order to extract a micro sample from a sample substrate, it is essential to separate the micro sample from the substrate, and this involves a step of separating the substrate serving as the bottom surface of the extracted sample from the substrate (hereinafter referred to as a bottom dredge). In the bottom dredging method using the FIB shown in the publicly known example 2, since the FIB is incident on the substrate surface from an oblique direction and processed, the ion beam incident angle and the processing aspect at the time of the bottom dredging are provided on the bottom surface of the extracted sample piece. There is a slope consisting of the ratio. Further, the square hole 51 for realizing the oblique FIB irradiation shown in FIG. 10B must be very large. This indicates that it takes a lot of time to form the square hole 51. In this known example, the sample is largely tilted by about 70 ° in order to perform oblique FIB irradiation. Considering the distance between the objective lens and the sample required from the convergence of the FIB, it is expected that such a large inclination will degrade the FIB performance and that satisfactory processing cannot be performed. To maintain the performance of the generally used FIB device, the limit is about 60 °. Further, it is very difficult mechanically to tilt the sample stage for a large-diameter wafer such as 300 mm in diameter by as much as 70 °. Even if a large tilt of 70 ° is possible, the bottom surface of the extracted sample has a tilt of 70 °, and when placed on a horizontal sample holder, the original sample surface is tilted as much as 20 ° with respect to the sample holder surface. It is difficult to form a cross section or a wall almost perpendicular to the surface. In order to form a cross section or wall almost perpendicular to the surface of the sample substrate, it is essential to make the bottom slope smaller and make the bottom parallel to the surface.To achieve this, the sample slope must be further increased. Rather, this is made more difficult by the limitations of the device described above. Therefore, in order to place the extracted sample as another object of the present invention in another member (sample holder) and to introduce it into another observation device or analysis device, a different bottom dredge method capable of forming a vertical cross section is studied. Must. (However, in the publicly known example 2, since the separated sample is not placed on a sample holder or the like and is observed while attached to the probe of the transport means, the shape of the bottom surface does not affect.)
As described above, the sample preparation process according to the present invention and the sample separation method according to the known example 2 are significantly different from each other in that (1) the beam irradiation method at the time of extracting (separating) the sample is completely different, and the extracted sample is made as thin as possible. In addition, the side surface in the longitudinal direction (parallel to the TEM observation surface) was machined to simplify the separation of the bottom surface and to minimize the inclination of the sample stage. (2) The extracted sample is separate from the transfer means. The present invention provides a sample preparation apparatus and a sample preparation method capable of extracting a sample piece from a wafer by fixing the sample piece to a sample holder as a member.

<Embodiment 4>
The sample analysis step of the above embodiment is not limited to the TEM analysis, and can be used for other observation methods, analysis methods, and observation methods.

For example, the present invention can be applied to a case where the analyzer is an in-lens type high-resolution SEM.
The in-lens type SEM is a method that puts the observation sample in the objective lens, and is a powerful tool for surface observation because the resolution is very good compared to the out lens. Must be smaller. Therefore, even if a defective part is found by a wafer inspection device or the like, and the part is to be observed in more detail, the wafer cannot be introduced into an in-lens type scanning electron microscope as it is, and the wafer is divided and subdivided. I had to help. According to the sample analysis method of the present invention, a sample piece in a desired region can be extracted from a wafer, so that high-resolution observation can be performed with an in-lens type SEM. Since the observation area can observe not only the wafer surface but also a cross section that can be formed at the time of extracting, if the FIB irradiation direction at the time of extracting a sample piece is appropriately set, the cross section of a defective portion can also be observed. According to such a method, the problem of coordinates, the problem of sample preparation, and the problem of wafer division can be solved to perform sample analysis. In addition, sample analysis for performing elemental analysis such as Auger electron spectroscopy and secondary ion mass spectrometry can be similarly performed.

FIG. 1 is a configuration block diagram illustrating an embodiment of a sample analyzer according to the present invention. FIG. 7 is a view for explaining a conventional procedure for manufacturing a TEM sample. FIG. 7 is a diagram for explaining another procedure for manufacturing a conventional TEM sample. FIG. 2 is a configuration block diagram for explaining an embodiment of a sample preparation unit in the sample analyzer according to the present invention. FIG. 3 is a diagram for explaining a sample holder in the embodiment of the sample analyzer according to the present invention. FIG. 9 is a view for explaining a conventional TEM holder. FIG. 3 is a diagram for explaining an embodiment of a transfer unit in a sample preparation unit in the embodiment of the sample analyzer according to the present invention. FIG. 4 is a block diagram showing the configuration of another embodiment of the sample analyzer according to the present invention. FIG. 4 is a view for explaining a sample preparation step in the sample analysis method according to the present invention. FIG. 9 is a view for explaining a conventional TEM sample holder.

Explanation of reference numerals

2 FIB irradiation optical system, 3 secondary particle detector, 4 deposit gas source, 5 sample stage, 6 sample holder, 7 holding means (holder cassette), 8 transfer means, 9 optical microscope, 100 .., Sample analyzer, 101, wafer inspection unit, 102, sample preparation unit, 103, electron beam irradiation system, 104, secondary electron detector, 105, sample stage, 107, transport container, 110, information transmission means.

Claims (11)

  A sample analysis method for observing, analyzing, or measuring a target sample piece by at least one of: a step of storing coordinate information of a desired portion such as a foreign substance or a defect detected by the inspection means on the sample substrate; A sample piece including the desired location is extracted from the sample substrate based on coordinate information of the desired location using processing by a focused ion beam, and the extracted sample piece is analyzed by an analyzer, an observation device, or a measurement device. Fixed to the sample holder corresponding to at least one of them, a step of processing the sample piece fixed to the sample holder into a shape suitable for at least one of analysis or observation or measurement, and fixed the sample piece The sample holder is introduced into at least one of an analyzer, an observation device, and a measurement device to analyze the desired portion. Sample analyzing method characterized by comprising a degree.   2. The sample analysis method according to claim 1, wherein the inspection means uses at least one of an optical wafer inspection apparatus, a scanning electron microscope for wafer inspection, a laser scanning microscope, and an optical microscope. analysis method.   3. The sample analysis method according to claim 1, further comprising, before the step of extracting the sample piece by using a focused ion beam, a positioning step using an optical microscope. .   4. The sample analysis method according to claim 1, wherein, before the step of extracting the sample piece by using a focused ion beam, the focused ion beam is used near the desired location. A method for analyzing a sample, which comprises a step of attaching a mark for confirming a location.   The sample analysis method according to any one of claims 1 to 4, wherein the sample piece fixed to the sample holder is further subjected to thin-wall processing by focused ion beam irradiation, and the sample for transmission electron microscope observation is further provided. A method for analyzing a sample, comprising a step of finishing the sample. A wafer inspection unit that inspects the wafer and stores coordinate information of a desired location such as a foreign substance or a defect;
Using a focused ion beam on the sample substrate based on the coordinate information of the desired portion, extracting a sample piece including the desired portion and analyzing or observing or measuring it into a sample holder suitable for at least one of the following: And a sample preparation part that is fixed and processed,
A sample analyzer, wherein the wafer inspection section and the sample preparation section are connected by a vacuum transfer path for moving the wafer. A wafer inspection unit that inspects the wafer and stores coordinate information of a desired location such as a foreign substance or a defect;
Using the focused ion beam on the sample substrate on the basis of the coordinate information of the desired location, a sample piece including the desired location is extracted and suitable for at least one of an analyzer, an observation device, and a measurement device. A sample preparation unit that is fixed to the sample holder and is processed into a sample piece having a shape suitable for at least one of the analysis device or the observation device or the measurement device,
Having at least one of an analyzer or an analyzer or an analyzer for analyzing the sample piece,
A sample analyzer, wherein the wafer inspection unit, the sample preparation unit, and the analysis unit are connected by a vacuum transfer path for moving the wafer. A wafer inspection unit that inspects the wafer and stores coordinate information of a desired location such as a foreign substance or a defect;
Using the focused ion beam on the sample substrate on the basis of the coordinate information of the desired location, a sample piece including the desired location is extracted and suitable for at least one of an analyzer, an observation device, and a measurement device. A sample preparation unit that is fixed to the sample holder and is processed into a sample piece having a shape suitable for at least one of the analysis device or the observation device or the measurement device,
An analyzer or an analyzer for performing the analysis of the sample piece or at least one of the analyzers of the measurement device is configured mechanically independently,
A sample analyzer having a structure in which at least coordinate information of the desired location in the wafer inspection unit is connected by an information transmission unit that transmits the coordinate information to the sample preparation unit and the analysis unit. The sample analyzer according to claim 8, further comprising:
A sample analyzer, comprising a structure in which the wafer and the sample holder or a jig on which the sample holder is mounted are transported by a vacuum vessel between the wafer inspection unit, the sample preparation unit, and the analysis unit.   The sample analyzer according to any one of claims 6 to 9, wherein the inspection device is any one of an optical wafer inspection device, a scanning electron microscope for wafer inspection, a laser scanning microscope, and an optical microscope. A sample analyzer characterized by the above-mentioned. The sample analyzer according to any one of claims 6 to 9, wherein the observation device in the analyzer is any one of an in-lens scanning electron microscope and a transmission electron microscope. Sample analyzer.

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