JP2015227799A - Foreign matter removal method using scan type probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing a fine foreign matter existing on an object surface, using a conventional scan type probe microscope as it is, the scan type probe microscope configured to obtain information on a shape of the surface through scanning the object surface using a probe disposed at a tip of a cantilever.SOLUTION: A surface of a probe 12 is coated with an adhesive agent 26A. The probe coated with the adhesive agent is attached to a scan type probe microscope. The probe is made to have contact with a foreign matter 23 existing on a surface of an object 20 so as to cause the foreign matter adhere to the probe.

Description

  The present invention relates to a method for removing fine foreign matter existing on the surface of an object using a scanning probe microscope.

  A scanning probe microscope scans the surface of an object using a probe (probe) provided at the tip of a cantilever such as an atomic force microscope (AFM) or a scanning tunneling microscope (STM). This is a type of microscope that obtains information on the shape, and includes a multifunctional type microscope that can operate as an AFM mode, an STM mode, or the like by exchanging a cantilever including a probe.

  As a technique for removing fine foreign matters, particularly a method for removing foreign matters on a photomask or a semiconductor wafer in a manufacturing process of a semiconductor integrated circuit or the like, there is a method described in Patent Document 1. This method uses a probe having an adhesive material head at the tip. The adhesive material is discharged from the adhesive material head at the tip of the probe, the excess adhesive material is removed, and the remaining adhesive material is semi-dried. Shape. The adhesive material head from which the semi-dry adhesive material is discharged is moved to the position where the foreign material is detected, pressed against the location where the foreign material is attached, and then the adhesive material head is pulled up. Patent Document 2 also describes a similar foreign matter removal method.

JP-A-6-260464 JP-A-8-250475

  However, these methods first use a special probe having an adhesive material head for discharging an adhesive material at the tip. Secondly, with the recent high definition of workpieces such as semiconductor substrates, there is a high risk of destroying the surrounding resist pattern and the like when an adhesive material is pressed around the foreign matter. Further, when the adhesive material adheres to the substrate itself, the solvent component contained in the adhesive material may be transferred to the substrate and cause haze or the like, which may shorten the work life.

  The present invention provides a foreign matter removing method using a scanning probe microscope that can remove foreign matter without necessarily preparing a special probe.

  The present invention also provides a method capable of removing foreign matter by touching only the foreign matter without damaging the object. For example, the present invention provides a method capable of removing foreign matter without damaging the pattern or the substrate even if the object is a semiconductor substrate having a highly refined pattern.

  The present invention is a method for removing foreign matter existing on the surface of a target by using a scanning probe microscope that scans the surface of the target using a probe provided at the tip of a cantilever and obtains information on the shape of the surface. The surface of the probe is coated with an adhesive, the probe coated with the adhesive is attached to a scanning probe microscope, and the probe is brought into contact with a foreign object existing on the surface of the object to detect the foreign object. It is attached to the needle. The thin film of the adhesive should not affect the normal operation of the scanning probe microscope.

  Since an existing scanning probe microscope can be used and an existing probe of the scanning probe microscope can be used, foreign matter can be removed without necessarily preparing a special probe. Of course, this does not exclude the use of a probe for removing foreign substances.

  In addition, according to the present invention, the foreign matter can be removed by touching only the foreign matter without damaging the object. For example, even if the object is a semiconductor substrate having a highly refined pattern, foreign matter can be removed without damaging the pattern or the substrate. Foreign matter can be removed without destroying or contaminating the substrate.

  Prior to the removal of foreign matter, it is preferable to confirm the position of the foreign matter on the target by scanning the surface of the target with a probe. This makes it possible to reliably remove foreign matter.

  After removing the foreign matter, the surface of the object may be scanned with a probe to confirm that the foreign matter has been removed.

  When the foreign matter adhering to the probe is removed from the probe, the probe can be reused for foreign matter removal, and low-cost operation is possible.

1 shows a schematic configuration of an atomic force microscope. A state in which surface treatment is performed on the probe surface is shown. A state where the probe is dipped in the adhesive is shown. The probe having an adhesive layer formed on the surface is shown. A state in which the probe scans the substrate surface by feedback control is shown. A state in which the probe is brought into contact with a foreign object without feedback control is shown. A probe with foreign matter attached is shown. The state which stabbed the probe in the adhesive sheet for the foreign material removal is shown. The state which the foreign material moved to the adhesive sheet side is shown. The foreign substance removal process flow is shown. The modification of a probe is shown. The state which adhered the foreign material to the probe of a modification is shown. Another modification of the probe will be described. The state in which the foreign material has adhered in the probe of another modification is shown.

  FIG. 1 shows a schematic configuration of a scanning probe microscope having an atomic force microscope or an atomic force microscope mode. As an example, the object is a substrate (for example, a semiconductor substrate) 20, and a pattern (for example, a photoresist pattern, a photomask pattern) 21 is formed on the surface of the semiconductor substrate.

  The substrate 20 is placed on the XY stage 17 and moved (displaced) in the X and Y directions (relatively scanned in the X and Y directions) by the XY stage 17. A cantilever 11 having a probe 12 at the tip is fixed to a holder (not shown) of a driving device (actuator) 15 at its base and is driven in the vertical direction (Z direction). The driving device 15 is fixed to the support member 18. The driving device 15 includes a piezoelectric element. The movement (vibration) in the vertical direction (Z direction) of the tip of the cantilever 11 is detected by the optical detection device 16. For example, the optical detection device 16 detects the vertical position of the cantilever 11 by irradiating the surface of the cantilever 11 and receiving the reflected light. The detection signal of the optical detection device 16 is given to the control device 13, and the control device 13 controls driving (vertical movement or vibration) by the driving device 15 based on this signal. The optical detection device 16, the control device 13, and the drive device 15 constitute a feedback control system. The control device 13 also controls scanning in the X and Y directions by the XY stage 17. The XY stage 17 may be provided with a vertical (Z direction) drive device, and a feedback control system may be provided between the optical detection device 16 or the drive device 15, the control device 13, and the XY stage 17 (Z direction drive). A storage device 14 is connected to the control device 13 and stores a control result by the control device 13, that is, a position in the X and Y directions and a position in the Z direction. Based on the stored data, an image (microscopic image) of the shape (including irregularities) of the surface of the substrate 20 (object) is created.

  Atomic force microscopes have various modes of operation, which are well known and will be briefly described. In the contact mode, the probe is moved closer to the object as the repulsive force acts between the probe and the object, and the feedback circuit is operated so that the repulsive force becomes a constant value in XY two-dimensional scanning. On the other hand, in non-contact modes such as tapping mode (trademark) (intermittent contact mode or cyclic contact mode), a large-amplitude forced vibration is generated near the resonance frequency using an excitation piezoelectric element attached to the holder. By utilizing the fact that changes in the vibration amplitude or frequency of the cantilever occur when approaching the object while moving, the cantilever or XY ( Z) Move stage 17 up and down. There are an atomic force microscope in which the object and the cantilever 11 are placed in the atmosphere, and an atomic force microscope in the vacuum, but since an adhesive is used as described later, it is preferable to operate in the atmosphere.

  A method for detecting (confirming) and removing foreign matter existing on the object (substrate) using the atomic force microscope will be described in detail below. The atomic force microscope is capable of high-precision positioning, and removes only foreign objects without damaging surrounding patterns or the substrate, even on highly detailed patterns (resist patterns, etc.) on the substrate. be able to.

  In this foreign matter removal method, an adhesive is coated on the surface of the probe, the probe coated with the adhesive is attached to a scanning probe microscope, and the probe is brought into contact with the foreign matter existing on the surface of the object to remove the foreign matter. It is attached to the probe. Of course, an adhesive coating layer (thin film) that is thin enough not to impair the function of the scanning probe microscope is formed on the probe.

  As the cantilever having the probe to be used, known ones such as silicone, silicone nitride, carbon nanotube, diamond and the like can be used. Further, the surface of the probe or cantilever may be coated with diamond, diamond-like carbon (DLC), gold or platinum.

  In the case of a substrate or the like on which an object pattern is formed, the radius of curvature of the tip of the probe is determined by the line width of the target pattern and the size of foreign matter to be removed. There is no particular limitation as long as the target foreign matter can be confirmed by scanning with an atomic force microscope and the probe can come into contact, but the radius of curvature at the tip of the probe is preferably in the range of 2 to 100 nm.

  The surface roughness of the probe is not particularly limited as long as the pressure-sensitive adhesive is uniformly coated.

  As the pressure-sensitive adhesive to be used, known ones such as an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and a rubber pressure-sensitive adhesive can be used.

  As the method of coating the probe with adhesive, spray coating, dip coating, spin coating, and the like can be used. Alternatively, a method may be used in which an adhesive is applied in a sheet shape, a probe is inserted into the sheet, and the adhesive is attached to the probe. There is no particular limitation on the film thickness of the adhesive, but there is a fine uneven pattern on the substrate, and even if the target foreign matter exists in the concave portion, it is only necessary to approach the foreign matter without hitting the convex portion. As an example, the film thickness of the pressure-sensitive adhesive will be about 10 to several tens of nm.

  For the probe, if necessary, pretreatment with adhesive coating, cleaning of surface contamination, and surface treatment to facilitate adhesion of adhesive, metal sputtering, UV ozone treatment, silane coupling agent treatment, corona Treatment, fluorine gas treatment, etc. may be performed. These pretreatments are not limited to one type as long as uniform coating is finally possible, and a plurality of them may be combined.

  Set a cantilever with a probe coated with an adhesive as described above on an atomic force microscope, scan the object (substrate) on which foreign matter to be removed exists (for example, non-contact mode under feedback control), The position (X, Y, Z coordinates) of the foreign matter to be removed is specified. Next, the probe coated with the adhesive is brought close to the position of the specified foreign object (for example, contact mode without feedback control), and the probe is brought into contact with the foreign object. Foreign matter adheres (adheres) to the adhesive. If the contact or adhesion (adhesion) of a foreign object fails, the above operation may be repeated until the foreign object can be removed many times.

  After the target foreign matter has adhered (attached) to the probe, remove the cantilever from the atomic force microscope and remove the foreign matter attached to the probe. As a method of removing the foreign matter adhering to the probe, there is a removal method by pressing or piercing the probe to the coated adhesive sheet and transferring the foreign matter to the adhesive sheet side. The material of the pressure-sensitive adhesive used for removing foreign substances from the probe is not particularly limited, and the above-described general pressure-sensitive adhesive can be used. Moreover, the silicone gel etc. which are used for fixing a cantilever as another example of what has adhesiveness may be used. In order to use the cantilever with the probe again after removing the foreign matter, it is desirable that the adhesive is made of the same material in consideration of recoating the adhesive.

  FIGS. 2 to 9 specifically show the above-described series of operations (operations or methods), and FIG. 10 shows the operation of the operator and the flow of processing by the control device 13.

  FIG. 2 shows a state in which the surface of the probe 12 is chemically decorated by dripping the silane coupling agent 24 as a pretreatment on the probe 12 portion of the cantilever 11 in which the probe 12 is integrally formed. ing. The silane coupling agent 24 makes it easy to attach an adhesive to the probe 12.

  Next, as shown in FIG. 3, an adhesive 26 is placed in a container 25, the probe 12 is dipped in the adhesive 26, and an adhesive layer 26A is formed on the surface of the probe 12 (adhesive coating method). ). FIG. 4 shows the tip of the probe 12 on which the adhesive layer 26A is formed.

  An image processing apparatus using laser light or other appearance inspection apparatus is used to check whether there is a foreign substance to be removed on the substrate (object) on which the pattern is formed (FIG. 10, S31). Only the substrate on which the foreign matter to be removed is present is taken as a target for foreign matter removal.

  The cantilever 11 in which the adhesive layer 26A is formed on the probe 12 as described above is attached to an atomic force microscope, the target substrate is set, and the surface of the substrate 20 on which the foreign matter 23 exists has the adhesive layer 26A. The probe 12 scans two-dimensionally (FIG. 10, S32). Thereby, a microscopic image of the pattern 21 and the foreign matter 23 on the substrate 20 is obtained. This is shown in FIG. This is performed, for example, in a non-contact mode with feedback control. The broken line shows the outline of the locus of the tip of the probe 12. Since the position on the substrate 20 where the foreign material 23 exists is known by the prior inspection by the appearance inspection apparatus, scanning is not performed on the entire surface of the substrate 20 but only in the vicinity of the position where the foreign material 23 exists. Good. Thereby, the exact position (X, Y, Z coordinate) where the foreign material 23 exists can be confirmed. Scanning of foreign matter detection (confirmation of the presence of foreign matter) may be performed using a probe on which no adhesive layer is formed.

  Subsequently, the operation proceeds to the foreign substance removal operation. Since the position of the foreign material 23 is known, this may be performed, for example, in a contact mode that does not involve feedback control (turned off). As shown in FIG. 6, the probe 12 having the adhesive layer 26A formed on the surface is moved toward the foreign object 23 and brought into contact with it (FIG. 10, S33). The foreign matter 23 adheres to the probe 12. When there are a plurality of foreign matters, the above foreign matter removing operation can be repeated for each foreign matter. At this time, it is preferable to replace the cantilever 11 having the adhesive layer 26A formed on the surface.

  Finally, in order to confirm that the foreign matter has been removed, the surface of the substrate is scanned again using a probe (which may or may not have an adhesive layer), and the microscopic image is displayed. It is created and compared with the previous image (image obtained in S32), it is confirmed that the foreign matter has been removed (FIG. 10, S34, S35). This confirmation can be made without necessarily comparing with the previous image, or only a limited range of images centering on the position where the foreign matter exists may be obtained. If foreign matter has not been removed, the process returns to S33 for removing foreign matter. When there are a plurality of foreign matters on one substrate 20, S33 and S34 may be repeated for each foreign matter.

  FIG. 7 shows a state in which foreign matter adheres to the adhesive layer 26 </ b> A at the tip of the probe 12. As shown in FIG. 8, the probe 12 having the foreign matter 23 attached to the adhesive layer 26A is pressed against or pierced to the adhesive sheet 27 having another adhesive layer, thereby moving the foreign matter 23 to the adhesive sheet 27 and removing it. can do. FIG. 9 shows a state in which the foreign matter 23 has been removed from the probe 12. The probe from which the foreign matter 23 has been removed can be used again. The probe may be discarded without removing the foreign matter.

  The probe of the above embodiment is for removing foreign matter using a probe conventionally used in an atomic force microscope, but a probe for removing foreign matter may be used. For example, a probe 12A shown in FIG. 11 has a V-shaped recess 12a formed at the tip. In this recess 12a, an adhesive thin film 26A is formed on the probe 12A. If such a cantilever having a probe 12A is attached to an atomic force microscope, the probe 12A is positioned immediately above the position where the foreign matter is present, and the probe 12A is lowered as it is, the foreign matter as shown in FIG. 23 adheres to the adhesive layer 26A in the recess 12a.

  In another modification, as shown in FIG. 13, two tapered protrusions having different protrusion amounts are formed at the tip of the probe 12B, and a V-shaped recess 12a is formed between the two protrusions. . The adhesive layer 26A is formed on the entire surface of the probe 12B. In this case, the foreign object 23 can be attached anywhere on the probe 12B as shown by a solid line and a chain line in FIG. 14, so that the moving operation of the probe for removing the foreign object becomes easy.

10 Atomic force microscope
11 Cantilever
12, 12A, 12B
13 Control device
15 Drive unit
20 Substrate (object)
21 patterns
23 Foreign object
26 Adhesive
26A adhesive layer
27 Adhesive sheet

Claims (4)

It is a method of removing foreign matter existing on the surface of the object using a scanning probe microscope that scans the surface of the object using a probe provided at the tip of the cantilever and obtains information on the shape of the surface,
Coating the surface of the probe with an adhesive,
A probe coated with an adhesive is attached to a scanning probe microscope, and the probe is brought into contact with a foreign substance existing on the surface of the object to attach the foreign substance to the probe.
A foreign matter removing method using a scanning probe microscope.   2. The foreign matter removing method using a scanning probe microscope according to claim 1, wherein prior to removing the foreign matter, the surface of the subject is scanned with a probe to confirm the position of the foreign matter on the subject.   The foreign matter removal method using the scanning probe microscope according to claim 1 or 2, wherein after removing the foreign matter, the surface of the object is scanned with a probe to confirm that the foreign matter has been removed.   The foreign matter removal method using the scanning probe microscope according to any one of claims 1 to 3, wherein the foreign matter attached to the probe is removed from the probe.

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