JP2006145333A - Probe regeneration method, and scanning probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a probe regeneration method and a scanning probe microscope capable of maintaining all the time a tip of a probe with a favorable sharpness degree, capable of prolonging a service life of the probe, capable of holding favorably precision for measurement and inspection, capable of reducing cost, and capable of enhancing data reproducibility. <P>SOLUTION: This probe regeneration method is a method executed by the scanning probe microscope provided with a probe part having the probe opposed to a sample, a probe moving mechanism for conducting approach and evacuation moving to/from the probe, and scanning moving for the probe, a measuring part for measuring a physical quantity generated between the probe and the sample when the probe scans a surface of the sample, and a sample stage mounted with the sample, and for scanning the surface of the sample with the probe to measure the surface of the sample, while changing a position of the probe with respect to the sample by the probe moving mechanism while keeping the physical quantity constant by the measuring part. The method has a step for preparing the regeneration working sample, and a step for pushing the probe onto the regeneration working sample under a mounted condition to regenerate the tip of the probe. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a probe regeneration method and a scanning probe microscope, and in particular, for example, a probe regeneration suitable for sharpening and regenerating the tip of a probe when the tip of the probe becomes dull as a result of measuring a large number of samples. The present invention relates to a method and a scanning probe microscope having an apparatus function for carrying out the probe reproducing method.

  A scanning probe microscope is conventionally known as a measurement apparatus having a measurement resolution capable of observing a fine object of atomic order or size. In recent years, scanning probe microscopes have been applied to various fields such as measurement of fine irregularities on the surface of a substrate or wafer on which a semiconductor device is made. There are various types of scanning probe microscopes depending on the detected physical quantity used for measurement. For example, there are scanning tunneling microscopes (STM) that use tunnel current, atomic force microscopes (AFM) that use atomic force, and magnetic force microscopes (MFM) that use magnetic force. It's getting on.

  Of these, the atomic force microscope is particularly suitable for detecting fine irregularities on the surface of a sample with high resolution, and has a proven record in the fields of semiconductor substrates and disks. Recently, it has also been used for in-line automatic inspection processes.

When an atomic force microscope or the like is used in an in-line automatic inspection process, a large number of samples that are semiconductor products must be sequentially and sequentially measured to inspect the semiconductor products. The measurement accuracy of the atomic force microscope largely depends on the sharpness (sharpness) of the tip of the probe. Therefore, if the measurement / inspection of a large number of samples is continued, the tip of the probe gradually becomes dull and its sharp state deteriorates. When the tip of the probe becomes dull, the resolution decreases, and the measurement accuracy decreases, conventionally, the probe is normally replaced (see, for example, Patent Document 1).
JP 2002-323430 A

  In atomic force microscopes used in inline automatic inspection processes, etc., replacing the probe when the tip of the probe becomes dull cannot effectively use the probe, resulting in waste and cost. In addition, there is a problem that data reproducibility deteriorates when measurement / inspection is started again. Therefore, in an atomic force microscope or the like used in an in-line automatic inspection process, when the tip of the probe becomes dull, the probe should not be replaced easily, but to be used effectively. It is desired that the tip of the probe is machined, the sharpness is improved and sharpened, and the probe is reused.

  Accordingly, an object of the present invention is to extend the service life of the probe in a scanning probe microscope while maintaining the tip sharpness of the probe attached to the microscope apparatus in a good condition, and always improve the measurement / inspection accuracy. It is to keep it high and to further reduce costs.

  Furthermore, in view of the above-described problems, the object of the present invention is to improve the tip sharpness of the probe attached to the scanning probe microscope as necessary, to extend the service life of the probe, and to perform measurement / inspection. It is an object of the present invention to provide a probe reproducing method and a scanning probe microscope that can maintain the accuracy of the above-mentioned, reduce the cost, and improve the data reproducibility.

  In order to achieve the above object, a probe reproducing method and a scanning probe microscope according to the present invention are configured as follows.

  A first probe regenerating method (corresponding to claim 1) includes a probe portion having a probe facing a sample, a probe moving mechanism for causing the probe to approach, retract and scan, and a probe Has a measuring unit that measures the physical quantity generated between the probe and the sample when scanning the surface of the sample, and a sample stage on which the sample is placed, and the probe moving mechanism keeps the physical quantity constant at the measuring unit. A method executed by a scanning probe microscope that changes the position of the probe with respect to the sample and scans the surface of the sample with the probe to measure the surface of the sample, comprising the steps of preparing a sample for reproduction processing, And a step of regenerating the tip of the probe by pressing it against the sample for regeneration processing while the needle is attached.

  In the above-described probe regeneration method, for example, when a scanning probe microscope is provided in an in-line automatic inspection process in a semiconductor manufacturing process and the measurement / inspection is performed, the probe life is extended and the probe is effectively used. Therefore, the cost can be reduced and the data can be maintained with good reproducibility. The prepared sample for regeneration processing is set on the sample stage, for example, in the same manner as a normal sample, when the probe is reproduced, and the probe is set against the inclined surface formed on the surface of the sample for regeneration processing. The tip is sharpened by bringing the tip of the tip into contact and causing friction.

  The second probe regeneration method (corresponding to claim 2) is preferably the above-described probe regeneration method, wherein the probe is preferably repeatedly moved toward and away from the sample for reprocessing by the probe moving mechanism, It is characterized by sharpening the tip. The sample for reprocessing has an inclined surface covered with a hard film, and the tip of the probe is sharpened by repeatedly pressing the tip of the probe toward and away from the inclined surface. To do.

  According to a third probe regeneration method (corresponding to claim 3), in the above-described probe regeneration method, the probe is preferably moved by a probe moving mechanism in a specific direction while being pressed against the sample for regeneration processing. It is characterized by sharpening the tip of the probe. In this method, the tip of the probe is sharpened by selectively wearing one side of the tip of the probe.

  A first scanning probe microscope (corresponding to claim 4) includes a probe portion having a probe facing a sample, a probe moving mechanism for causing the probe to approach, retract and scan, and a probe Has a measuring unit that measures the physical quantity generated between the probe and the sample when scanning the surface of the sample, and a sample stage on which the sample is placed, and the probe moving mechanism keeps the physical quantity constant at the measuring unit. This is a scanning probe microscope that changes the position of the probe with respect to the sample and scans the surface of the sample with the probe to measure the surface of the sample. Further, the sample installation section including the sample for reprocessing and the tip of the probe are dull. When using the sample for regeneration processing provided in the sample installation unit, the probe regeneration is performed to regenerate the tip of the probe by pressing the tip of the probe with a moving mechanism against the sample for regeneration processing. I have a part Configured.

  In the above scanning probe microscope, preferably, a sample setting part is provided in the vicinity of the sample stage, and when the tip of the probe becomes blunt during continuous sample measurement and the measurement accuracy decreases, the sample setting part is provided. Using the reclaimed processing sample, the tip of the probe is polished and sharpened by performing the required operation so that the tip of the probe is brought into contact with the reprocessing sample. Do. Thereafter, again, the probe continues measurement / inspection of the sample on the sample to be originally measured / inspected on the sample stage. As for how to use the sample for reprocessing, the necessary operation control is performed so that the sample for reprocessing is placed on the sample stage instead of the sample and the probe is brought into contact with the sample for reprocessing. It is desirable to do so. In addition, it is possible to provide a sample setting part for fixing the sample for reprocessing on the sample stage, and automatically move the probe to the sample setting part to perform the same regenerating process operation.

  In the second scanning probe microscope (corresponding to claim 5), in the first configuration described above, the reproduction processing sample preferably has an inclined surface with which the tip of the probe contacts, Characterized by the surface being coated with a hard film. In this configuration, the sample for reprocessing is coated with a hard film, and the tip of the probe is positively shaped into a specific shape by the tip of the tip contacting and rubbing against the inclined surface of the sample. It becomes possible to sharpen the probe. The method of forming the inclined surface of the surface of the sample for reprocessing can be arbitrarily made according to the purpose of polishing the tip of the probe.

  According to the probe regeneration method of the present invention, when a scanning probe microscope is provided in, for example, an in-line automatic inspection process in a semiconductor manufacturing process and the measurement / inspection is performed, the life of the probe is extended, Can be used effectively, and further, the cost can be reduced and the reproducibility of data can be maintained well. Further, the tip of the probe can be selectively polished and sharpened in a short time. Furthermore, according to the scanning probe microscope according to the present invention, since the device configuration that sharpens the blunting of the tip of the probe in use during measurement / inspection is provided, the measurement can be performed while effectively utilizing the probe. -Inspection work can be performed efficiently.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a scanning probe microscope according to the present invention, and shows a front view of the scanning probe microscope. This scanning probe microscope is an atomic force microscope as an example. A scanning probe microscope is not limited to an atomic force microscope. In FIG. 1, 11 is a sample stage, and 12 is a coarse movement mechanism provided on the sample stage 11, for example. The coarse movement mechanism 12 is configured to relatively move a sample 13 such as a wafer on which a semiconductor device or the like is formed in the horizontal plane (each direction of the X axis and the Y axis) and the vertical direction (vertical direction: Z axis direction) in FIG. This is a moving mechanism that moves the robot at a large distance. In the coarse movement mechanism 12, the movement mechanism in each direction of the X axis and the Y axis is configured using, for example, a pulse motor. The coarse movement mechanism 12 also has a function as a sample holder. The sample 13 is a semiconductor substrate having a flat plate shape having a relatively large area, for example. In FIG. 1, the sample 13 is drawn with exaggerated thickness unlike the actual case. The sample 13 is fixedly arranged on the coarse movement mechanism 12 via a fixing means (not shown).

  Although the coarse movement mechanism 12 is provided on the sample stage 11, it can be incorporated into the sample stage 11 as a moving function part of the sample stage 11.

  A cantilever 22 having a probe 21 facing the measurement surface of the sample 13 is disposed above the sample 13. The cantilever 22 has a cantilever shape characteristic having a relatively soft elastic characteristic, and a base end portion thereof is attached to a lower end of a cylindrical Z-axis fine movement actuator 23. The Z-axis fine movement actuator 23 is a cylindrical member made of a piezoelectric member. The Z-axis fine movement actuator 23 has at least two electrodes (not shown) at predetermined positions. By applying a required voltage to these electrodes, the Z-axis fine movement actuator 23 has a characteristic of expanding and contracting in the Z-axis direction at a relatively small distance. Have.

  The Z-axis fine movement actuator 23 is attached to a central movable portion 24 a of a parallel plate type XY fine movement actuator 24. The XY fine movement actuator 24 includes an X-axis fine movement mechanism and a Y-axis fine movement mechanism. The XY fine movement actuator 24 has a function of finely moving the Z-axis fine movement actuator 23, and by extension, the cantilever 22 and the probe 21 in the XY plane by receiving a scanning control signal from the control unit 25. Yes. The movement of the probe 21 in the scanning direction along the surface of the sample 13 is performed based on the fine movement operation of the parallel plate type XY fine movement actuator 24.

  The control unit 25 also has a function of controlling the operation of the coarse movement mechanism 12 described above, and is configured by a computer and has a function of performing signal processing.

  An optical microscope 26 is provided inside the cylinder of the cylindrical Z-axis fine movement actuator 23 so as to be inserted from above. With the optical microscope 26, the positional relationship between the probe 21 and the measurement surface of the sample 13 can be observed. An observation image obtained by the optical microscope 26 is picked up by a CCD camera 27 or the like.

  The cantilever 22 is provided with a cantilever displacement detection unit that detects bending or twisting of the cantilever 22. The cantilever displacement detector is composed of a laser light source 28 and a photodetector 29 arranged in a predetermined arrangement relationship. The cantilever displacement detector and the cantilever 22 are held in a fixed positional relationship, and the laser light 30 emitted from the laser light source 28 is reflected by the back surface of the cantilever 22 and is incident on a photodetector (such as a four-division photodiode) 29. It is like that. The cantilever displacement detector constitutes an optical lever type optical detector. When the cantilever 22 undergoes deformation such as twisting or bending by the optical lever type optical detection device, the displacement due to the deformation can be detected.

  A detection signal output from the photodetector 29 is input to the Z-axis control unit 31. The Z-axis control unit 31 adjusts the expansion / contraction amount of the Z-axis fine movement actuator 23 so that the detection signal output from the photodetector 29 becomes a predetermined signal, and is generated between the probe 21 and the surface of the sample 13. Control is performed to maintain the distance between the probe and the sample at a constant set distance so that the atomic force (an example of a physical quantity) becomes a constant value. The control signal output from the Z-axis control unit 31 is also given to the control unit 25 that performs signal processing.

  3, the XY fine movement actuator 24, the Z-axis fine movement actuator 23, the cantilever 22 and the probe 21, the laser light source 28, the photodetector 29, and the laser beam 30 are shown in more detail. FIG. 3 shows a specific example of the XY fine movement actuator 24 including the Z-axis fine movement actuator 23, the X-axis fine movement mechanism 129, and the Y-axis fine movement mechanism 130. The Z-axis fine movement actuator 23 is formed of a cylindrical piezoelectric element, and its base portion is fixed to the movable portion 24a. A cantilever 22 having a probe 21 is attached to the lower end of the Z-axis fine movement actuator 23. The Z-axis fine actuator 23 causes displacement in the Z-axis direction as indicated by an arrow 301. This displacement is, for example, about 5 μm. The movable portion 24a is displaced in the X-axis direction (arrow 302) by the X-axis fine movement mechanism 129 which is a rod-shaped piezoelectric element disposed on both sides. An X-axis displacement meter 129a is added to the X-axis fine movement mechanism 129. The X axis displacement meter 129a measures the amount of displacement generated in the X axis fine movement mechanism 29 and generates an X feedback signal. Further, the movable portion 24a is displaced in the Y-axis direction (arrow 303) by the Y-axis fine movement mechanism 130 which is a rod-shaped piezoelectric element disposed on the other side. Further, a Y-axis displacement meter 130 a is added to the Y-axis fine movement mechanism 130. The amount of displacement generated in the Y-axis fine movement mechanism 130 is measured by the Y-axis displacement meter 130a, and a Y feedback signal is generated. The amount of displacement in the X-axis direction and the Y-axis direction is, for example, 10 μm.

  In FIG. 1 again, a sample processing portion 32 for reprocessing is provided on the sample stage 11, and a sample 33 for regenerating processing is disposed on the setting portion 32. A specific example of the reprocessing sample 33 is shown in FIG. In FIG. 2, (A) shows a sample 33A for reproduction processing in which the shape of a triangular mountain 34 continuous in cross-sectional shape is formed, and (B) is for reproduction processing in which an array of a plurality of quadrangular pyramid depressions 35 is formed. A sample 33B is shown, and (C) shows a sample 33C for reproduction processing in which an array of a plurality of quadrangular pyramidal projections 36 is formed. Each of the samples 33A, 33B, and 33C for reprocessing has an inclined surface having a required angle. In particular, the sample 33A for reprocessing has two inclined surfaces that form a straight valley in a specific direction, and the sample 33B for regenerating processing has four inclined surfaces that form a quadrangular pyramid-shaped recess for reprocessing. The sample 33C has four inclined surfaces that form a quadrangular pyramidal projection. Each inclined surface of the samples 33A, 33B, and 33C for reprocessing is covered with a hard film so as to have a hardness higher than the hardness of the probe 21. As this hard film, a DLC (diamond-like carbon) film, a TiN (titanium nitride) film, or the like is used.

  As is clear from the above specific example, a large number of inclined surfaces having a required inclination angle are formed on the surface of the sample 33 for reprocessing. As a method for forming these inclined surfaces of the sample 33 for reprocessing, for example, surface orientation etching using a difference in etching rate on the Si crystal surface can be mentioned. For example, there is a substrate in which a <111> plane is exposed by etching a Si substrate having a <100> crystal plane with an alkaline aqueous solution or the like. As another example, an Si substrate is etched using F radicals in a plasma atmosphere using an organic film as a mask material. As described above, a Ti or Ta nitride film is formed on the etched Si substrate by the PVD method. For example, when the tip of the probe is sharpened to a radius of 20 nm, a reproduction processing sample 33B having an opening of about 100 nm and an opening angle of 70 ° is produced for each recess. The size of the inclined surface of the sample 33 for reproduction processing is determined according to the size of the tip of the probe 21 to be sharpened and reproduced.

  Note that the shape of the reprocessing sample 33 is not limited to the above shape. For example, instead of a quadrangular pyramid depression or a quadrangular pyramidal protrusion, a conical shape or other polygonal pyramid shapes can be adopted. Further, the sample 13 to be measured / inspected by the scanning probe microscope is usually a sample having a relatively large number of flat portions such as a step measurement and a surface roughness measurement. On the other hand, the sample 33 for reproduction processing for increasing the sharpness of the tip of the probe 21 may be a sample in which more inclined surfaces are formed than the flat portion.

  For example, as shown in FIG. 4, the scanning probe microscope as described above is incorporated as an automatic inspection process 42 for inspecting a substrate (wafer), for example, at an intermediate stage of an inline manufacturing apparatus for a semiconductor device (LSI). When the substrate to be inspected (sample 13) is unloaded from the production process step 41 in the previous stage by a substrate transfer device (not shown) and placed on the substrate holder of the scanning probe microscope (SPM) in the automatic inspection step 42, a scanning type is obtained. A probe microscope automatically measures the fine unevenness of a predetermined area on the substrate surface, determines whether or not the processing content of the substrate manufacturing in the previous stage is acceptable, and then transports it again to the subsequent manufacturing processing step 43 by the substrate transport device. .

  In the above scanning probe microscope, the movement operation of the coarse movement mechanism 12 and the movement operation of the XY fine movement actuator 24 are controlled by the control unit 25. The control unit 25 is configured by a computer as described above, and the storage unit includes a probe reproduction operation program for executing the reproduction operation of the probe 21 in addition to the normal measurement operation program. The details of the probe regeneration operation executed based on the probe regeneration operation program will be described in detail below with reference to FIGS.

  In the probe regeneration shown in FIG. 5, any one of the above samples 33A to 33C is used as the regeneration processing sample 33 in order to sharpen the probe 21 having a blunt tip. The tip of the probe 21 is brought into contact with, pressed against, and polished on the regenerative processing sample 33 on the basis of a scanning operation 54 configured by combining an approach operation 51, a retreat operation 52, and a horizontal movement operation 53. Is done. The tip portion of the probe 21 is selectively polished from both sides by the inclined surfaces 33-1 on both sides forming the valleys in the sample 33 for reproduction processing, and two wear portions 55 are formed. As shown in the scanning operation 54, the probe 21 is repeatedly polished by the approach / retreat operation while moving in the horizontal direction with respect to the sample 33 for reprocessing. As a result, the tip of the probe 21 is selectively polished, sharpened and regenerated as indicated by reference numeral 56.

  In the probe regeneration shown in FIG. 6, the above-described sample 33A is used as the regeneration processing sample 33 in order to sharpen the probe 21 having a blunt tip. In the reproduction processing sample 33A, the inclined surface is linearly formed in a specific direction. The tip of the probe 21 is brought into contact with, pressed against, and polished on the reproduction processing sample 33A based on the scanning operation 61 in the specific direction in which the inclined surface is formed. The tip portion of the probe 21 is selectively polished from both sides by the inclined surfaces 33A-1 on both sides forming a valley in the reproduction processing sample 33A, and two wear portions 62 are formed. As shown in the scanning operation 61, the probe 21 is polished while moving in a specific horizontal direction with respect to the sample 33A for reprocessing. As a result, the tip of the probe 21 is selectively polished, sharpened and regenerated as indicated by reference numeral 63.

  In the above, when the probe 21 is pressed against the sample for reprocessing, the pressing force is set to be larger than the pressing force in normal sample measurement. In the case of probe regeneration in the case of FIG. 6, the tip of the probe is sharpened at a relatively high scanning speed that is not used for normal measurement as the scanning speed of the probe 21 with respect to the sample for reproduction processing.

  The configurations, shapes, sizes, and arrangement relationships described in the above embodiments are merely shown to the extent that the present invention can be understood and implemented, and the numerical values and the compositions (materials) of the respective configurations are as follows. It is only an example. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

  INDUSTRIAL APPLICABILITY The present invention is used for sharpening the tip of a probe when the tip of the probe is worn out and blunted in a scanning probe microscope to effectively use the probe and increase measurement / inspection accuracy.

1 is a front view showing a typical embodiment of a scanning probe microscope according to the present invention. It is a perspective view which shows the example of the sample for reproduction | regeneration processing used by this embodiment. It is a perspective view of an XY fine movement actuator provided in the scanning probe microscope of the present embodiment. It is process drawing which shows the step in which the scanning probe microscope which concerns on this embodiment is used. It is a figure explaining the 1st example of operation content of probe reproduction performed based on a probe reproduction operation program. It is a figure explaining the 2nd example of operation content of probe reproduction performed based on a probe reproduction operation program.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Sample stage 12 Coarse movement mechanism 13 Sample 21 Probe 22 Cantilever 23 Z-axis fine movement actuator 24 XY fine movement actuator 28 Laser light source 29 Photo detector 32 Probe reproduction sample setting part 33 Probe reproduction sample

Claims (5)

A probe portion having a probe facing the sample, a probe moving mechanism for causing the probe to approach, retreat, and scan; and when the probe scans the surface of the sample, the probe and the A measurement unit that measures a physical quantity generated between samples; and a sample stage on which the sample is placed, and the probe moving mechanism moves the probe with respect to the sample while keeping the physical quantity constant. Executed by a scanning probe microscope that changes the position and scans the surface of the sample with the probe to measure the surface of the sample,
Preparing a sample for reprocessing,
Regenerating the tip of the probe by pressing against the sample for regeneration processing while the probe is mounted;
A probe reproducing method characterized by comprising:   2. The probe regeneration method according to claim 1, wherein the probe moving mechanism repeats the probe approaching and retracting the regeneration processing sample to sharpen the tip of the probe.   2. The probe reproducing method according to claim 1, wherein the probe moving mechanism moves the probe in a specific direction in a state in which the probe is pressed against the sample for reproduction processing, and sharpens the tip of the probe. . A probe portion having a probe facing the sample, a probe moving mechanism for causing the probe to approach, retreat, and scan; and when the probe scans the surface of the sample, the probe and the A measurement unit that measures a physical quantity generated between samples; and a sample stage on which the sample is placed, and the probe moving mechanism moves the probe with respect to the sample while keeping the physical quantity constant. In a scanning probe microscope that changes the position and scans the surface of the sample with the probe to measure the surface of the sample,
A sample installation section comprising samples for reprocessing,
When the tip of the probe is dull, the tip of the probe is pressed by the moving mechanism against the sample for regeneration processing using the sample for regeneration processing provided in the sample setting portion. Probe regeneration execution means for regenerating the tip of the probe;
A scanning probe microscope comprising: 5. The scanning probe microscope according to claim 4, wherein the sample for reproduction processing has an inclined surface with which the tip of the probe contacts, and the surface of the inclined surface is coated with a hard film.

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