JP4739244B2 - Particle removal method - Google Patents

Description

  The present invention relates to a method for removing fine particles in units of μm generated in various processes of manufacturing an electronic product such as a semiconductor integrated circuit.

  In order to improve the performance of electronic products as well as semiconductor integrated circuits, the miniaturization of parts has progressed, and particles of a size that has been a problem in the manufacturing process have greatly affected the performance of products. Yes. Therefore, particle removal technology generated in various processes is becoming more important than ever in order to increase the yield of products. For example, particles of several μm on the microlens generated in the final assembly process of the CCD camera lowered the CCD's local incident light intensity, reducing the performance as a camera, and reducing the yield.

  Particles have been removed by conventional cleaning, but the number of particles that cannot be removed by cleaning has increased, and there is a need for a method that can cope with cases where the cleaning process cannot be performed in the final assembly process. Even if particles are removed by washing, the particles may increase due to reattachment or new contamination, and when the number of particles is small, a method that can be directly removed by pinpoint is required.

  As a method to remove fine particles directly by pinpoint, move or remove particles on the photomask with an AFM probe and then remove them by cleaning (Patent Document 1), or grab particles on the wafer with tweezers (Non-Patent Document 1) has been proposed. When removing with an AFM probe, a cleaning process is required after removal, and the method of grasping with tweezers cannot be used due to interference with samples with large irregularities, and in order to pinch them securely so as not to drop even if there are no irregularities, Accurate alignment is required, and when combined with the sandwiching process, it takes time and the throughput cannot be increased. Furthermore, the tweezers have a problem that the sandwiched particles cannot be dropped even if the tweezers are opened. Therefore, there is a need for a high-throughput particle removal method that does not require a cleaning step after removal.

Pipettes with heated glass pipettes that have been stretched to make their tips thinner are widely used in the biological and medical fields due to the patch clamp method. Recently, pipette tips with smooth end faces have been obtained by removal using a focused ion beam (FIB) device. It is also known that a fine desired shape can be produced at the pipette tip by FIB deposition on a smooth pipette end face (Non-patent Document 2).
JP 2005-084582 ([0007], FIG. 1) Tsutomu Osaka, Kuniyasu Yasushi, Jun Hattori, Honor Munekane, Koji Iwasaki, Hiroki Hayashi, Takashi Konno, Proceedings of the 52nd Joint Conference on Applied Physics, p880 (2005) Shinji Matsui, Optical Technology Contact, 41 356-363 (2003)

  The present invention solves the above-described problems, and aims to remove particles having a size of 2 to 40 μm adhering to a photomask, a wafer, a microlens, or the like at high throughput without post-cleaning. .

By heating and stretching the glass pipette by a known technique, it is possible to produce a pipette having a tapered frustoconical end having an inner diameter of about 100 nm to several tens of μm. The expanded pipette tip is processed by FIB so that there is no gap between the particles when they are brought into contact with the particles, so that the end surface has no unevenness.
A pipette whose tip is sharpened in a tapered truncated cone shape is brought close to contact with the particles, and the inside of the pipette is evacuated to adsorb the particles, then lifted and moved to the outside of the sample, and the inside of the pipette is moved to the atmosphere or pressurized to discard the particles.

  When the particle is small, a pipette having a small inner diameter is used, and when the particle is large, the pipette having a large inner diameter is vacuum sucked with a pipette having a large inner diameter so as to increase the adsorption force, and the particle is discarded.

Using a pipette containing a fine metal wire in the pipette, using a pipette that is stretched and protruding from the tip, press the tip of the grounded fine metal wire against the particle to remove the charge of the particle, and then vacuum the particle After being adsorbed, the sample is lifted and moved out of the sample, and the inside of the pipette is made atmospheric or pressurized to discard the particles. When the fine metal wire is not exposed, the glass part is removed by FIB processing to expose the fine metal wire.
If the glass wall thinned by raising the vacuum to a reduced pressure atmosphere cannot be tolerated and damaged, the glass at the tip is removed by FIB etching to give a smooth surface without irregularities, and then the FIB deposit film on the pipette tip Make a hard, durable and smooth tip without irregularities. Using this FIB-modified pipette, the particles are vacuum-adsorbed and then lifted and moved out of the sample, and the inside of the pipette is placed in the atmosphere or under pressure to discard the particles.

  After removing the stretched pipette tip by FIB etching to give a smooth surface without unevenness, an end portion having a sharply sharp wall tip that is harder than the sample by the FIB deposition film is formed on the smooth surface. Make it. Using a pipette repaired with this FIB deposition film, the tip of the particle is pierced and then vacuum-adsorbed, then lifted and moved out of the sample, and the inside of the pipette is set to the atmosphere or pressurized to discard the particle.

  The suction force of the vacuum is reduced by making the tip thin, but by processing the tip surface of the glass pipette so that there is no irregularity with FIB, the gap between the particles can be reduced and the particles can be absorbed even with a weak suction force. it can.

  Since the particles are adsorbed, lifted as they are, and taken out of the sample, a cleaning step after removing the particles is not necessary.

  Throughput can be improved because there is no need for more accurate alignment and pinching with tweezers than with tweezers. Moreover, it is only necessary to insert the tip of the pipette, so it can be applied even if there is a slight unevenness.

  Since the particles adsorbed on the pipette can be discarded by applying air or pressurizing outside the sample, there is no possibility that particles will not remain attached like tweezers. If it remains, check the degree of vacuum by vacuum suction and replace the pipette if particles remain on the pipette tip.

  By removing the charge accumulated in the particles, the adsorption force of the particles to the sample can be weakened and can be easily removed by vacuum adsorption of the pipette.

  Replacing the thin end of the glass wall with a strong FIB deposition film can increase the vacuum of the particles because it can be sucked to a higher degree of vacuum.

  By piercing the tip of a hard, sharp and sharp wall made with FIB, the gap can be reduced and particles can be adsorbed even with a weak suction force.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIGS. 1a to 1d illustrate a case where a pipette whose tip best represents the characteristics of the present invention is sharpened into a tapered truncated cone is brought close to contact with the particle until the inside of the pipette is evacuated to adsorb the particle, and then discarded after being moved. It is a figure to do.

  Prepare a thin pipette with an inner diameter of 100nm to 5μm by heating and stretching the glass pipette. To eliminate gaps between particles, use a pipette tip processed with FIB so that it has a smooth end face without irregularities. This smooth cross section can be obtained by, for example, etching by irradiating a beam focused with a small amount of current (several tens of pA or less) from the direction perpendicular to the pipette axis.

  Samples found in particle inspection equipment in a high magnification optical microscope having an objective lens 8, a high precision stage on which the specimen 3 is placed, a manipulator 4 to which the stretched pipette 1 is attached, and a particle removal apparatus having a vacuum exhaust system. 3. For example, introduce a CCD camera micro lens. The stage is moved so that the position where the particle is found by the particle inspection device is at the center of the visual field of the particle removal device, and the particle is observed with an optical microscope. Since a strong adsorption force is required to remove large particles, the inner diameter of the pipette is selected according to the particle size.

  Using a manipulator 4, bring the pipette 1 with its tip sharpened into a tapered truncated cone while observing with an optical microscope to the particle 2 just below the objective lens 8 of the optical microscope until it comes into contact (Fig. 1a). After vacuuming 1 and adsorbing particle 2 (Fig. 1b), pipette 1 is pulled up and particle 2 is pulled away from the sample. Move to a position where particles 2 can be discarded outside the sample while adsorbing particles 2, for example, to the exhaust duct (Fig. 1c), and discard the adsorbed particles 2 in the pipette 1 in the atmosphere or under pressure (Fig. 1c) 1d). The suction of particle 2 is performed by evacuating the pipette so that it does not break.

  FIGS. 2A and 2B are diagrams for explaining a case in which particles are vacuum-adsorbed after the grounded metal wire 5 is pressed against the particles to remove the charge of the particles.

  Using a pipette containing a fine metal wire 5 with a metal part protruding from the tip, using a manipulator 4 while observing with an optical microscope, the pipette 1 is brought into contact with the particle 2 immediately below the objective lens 8 of the optical microscope. (Fig. 2 (a)). After pressing the grounded metal wire 5 against the particle 2 to remove the charge accumulated in the particle (Fig. 2 (b)), the particle 2 is vacuum-sucked in the same procedure as above, then the pipette 1 is pulled up and the particle is removed from the sample. Pull 2 apart. The particle 2 is moved to a position where the particle can be discarded outside the sample while the particle 2 is adsorbed, and the adsorbed particle 2 is discarded by making the inside of the pipette 1 atmospheric or pressurized.

  FIGS. 3 (a) and 3 (b) are diagrams for explaining a case where a hard and durable tip is produced at the tip of the pipette with a FIB deposition film and vacuum-adsorbed at a higher degree of vacuum.

  The pipette 1 has a tip end that is formed into a smooth, truncated cone-shaped end 6 that is hard, durable, and without unevenness that can be endured in a reduced pressure atmosphere with a FIB deposition film after the tip is removed by FIB etching. Use the manipulator 4 while observing the tip of the tip with an optical microscope until it comes into contact with the particles 2 immediately below the objective lens 8 (FIG. 3 (a)). After the particles 2 are vacuum-adsorbed at a higher degree of vacuum than before (FIG. 3 (b)), the pipette 1 is pulled up and the particles 2 are pulled away from the sample in the same procedure as described above. The particle 2 is moved to a position where the particle can be discarded outside the sample while the particle 2 is adsorbed, and the adsorbed particle 2 is discarded by making the inside of the pipette 1 modified with the FIB air or pressurized.

  FIGS. 4 (a) and 4 (b) are diagrams for explaining a case where an end portion 7 having a hard pointed wall tip is formed at the tip of a pipette and pierced with particles and then vacuum-adsorbed.

Using pipette 1 tip with end 7 with hard sharp pointed wall tip made of FIB deposition film, using manipulator 4 while touching particle 2 directly under objective lens 8 while observing with optical microscope Move closer (Fig. 4 (a)). After piercing the particle 2 with the end 7 having the tip of the wall with a sharp pipette and vacuum-adsorbing the particle 2 (FIG. 4 (b)), the pipette 1 is pulled up and the particle 2 is pulled away from the sample in the same procedure as described above. Move to a position where particles can be discarded outside the sample with particles 2 adsorbed, and discard the particles 2 by making the inside of the pipette 1 with the end 7 having a sharp wall tip formed into the atmosphere or pressure. .
After discarding the particles, the degree of vacuum in the pipette is checked by vacuum suction. If this degree of vacuum is higher than the pipette when particle removal is not used, the pipette is replaced because the particles remain at the tip of the pipette.

It is a figure explaining the case where the pipette sharpened in the shape of a tapered truncated cone is brought close to contact with a particle, the inside of the pipette is evacuated, the particle is adsorbed, moved and discarded. It is a figure explaining the case where the pipette sharpened in the shape of a tapered truncated cone is brought close to contact with a particle, the inside of the pipette is evacuated, the particle is adsorbed, moved and discarded. It is a figure explaining the case where the pipette sharpened in the shape of a tapered truncated cone is brought close to contact with a particle, the inside of the pipette is evacuated, the particle is adsorbed, moved and discarded. It is a figure explaining the case where the pipette sharpened in the shape of a tapered truncated cone is brought close to contact with a particle, the inside of the pipette is evacuated, the particle is adsorbed, moved and discarded. It is a figure explaining the case where a particle is vacuum-sucked after pressing the particle to the metal part which earthed and removing the charge of a particle. It is a figure explaining the case where a strong durable tip is produced with a FIB deposit membrane at the tip of a pipette, and it is made to vacuum-suck with a higher degree of vacuum. It is a figure explaining the case where the edge part which has the hard-pointed wall part tip with a FIB deposit film at the tip of a pipette is produced, and is vacuum-sucked after piercing particles.

Explanation of symbols

1 Pipette 2 Particle 3 Specimen 4 Manipulator 5 Metal fine wire 6 Tapered truncated cone-shaped strong tip formed by FIB deposition 7 Tip with sharp sharpened wall formed by FIB deposition 8 Objective lens

Claims (7)

  A method for removing particles generated in various steps of manufacturing an electronic product such as a semiconductor integrated circuit, and heating and stretching the end of a glass pipette to form a tapered truncated cone, and then the tip of the glass pipette A method for removing particles, comprising processing an end face with FIB to form a smooth end face with less unevenness, and then removing the particles by vacuum suction using the pipette.   2. The particle removal method according to claim 1, wherein an inner diameter of the tip of the pipette is changed in accordance with a size of the particle to be removed.   The pipette contains a grounded fine metal wire, the tip of the fine metal wire protruding from the tip of the pipette is pressed against the particle to remove the charge of the particle, and then the particle is vacuum adsorbed and removed. The particle removal method according to claim 1 or 2.   3. The particle removal method according to claim 1 or 2, wherein a tip end portion having a smooth end face without unevenness is made of an FIB deposition film on a smooth end face without unevenness made by processing with the FIB. .   On the smooth end face with few irregularities made by the FIB, a FIB deposit film is used to produce a tip with a sharply sharp wall, and after piercing the particles, it is removed by vacuum adsorption. The particle removal method according to claim 1 or 2.   5. The particle removal method according to claim 1, wherein the particles adsorbed on the pipette are discarded outside the sample with the inside of the pipette in the atmosphere.   6. The particle removal method according to claim 1, wherein the particles adsorbed by the pipette are pressurized and discarded outside the sample.

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