JP2005084582A - Method for removing particle from photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cleanly and absolutely remove particles present in several or less number on a photomask by a method except for cleaning. <P>SOLUTION: Particles influencing transfer are cleanly and absolutely removed from a photomask by using dynamic or electromagnetic interaction or chemical reaction between the probe 2 of a scanning probe microscope having high positioning accuracy and the particle 1 on the photomask. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for removing particles from a photomask used in a lithography process.

  The miniaturization of Si semiconductor integrated circuits is remarkable, and accordingly, the pattern dimensions on a photomask or reticle used for transfer are also becoming finer. A photomask is an original of a lithography process, and if a soft defect such as particles is present on the photomask, it is transferred to the wafer as it is, which may cause a device failure and must be removed. As dimensions become smaller, unacceptable particle sizes are becoming smaller.

Conventionally, cleaning using a cleaning liquid has been performed for particle removal. (For example, see Non-Patent Document 1)
Isao Tanabe, Yoichi Takehana, Morihisa Horimoto "The story of photomask technology" pp216-220 (1996), Industrial Research Committee. Jpn. J. Appl. Phys. Vol. 41 (2002) pp.4242-4245

  In the conventional technology, cleaning for particle removal has been devised, but cleaning differs depending on the type of particle. If the number of cleanings is increased, the shading film will decrease (film slippage), the phase will change, etc. There are also secondary problems. Here, the film reduction means that the light-shielding film (including a halftone film) is thinned by cleaning (acid or alkali). If the number of washings is repeated, the film will become thinner and will eventually fail to function as a light-shielding film. The Cr mask has a considerable margin, and it can be said that the film becomes thicker. However, in a halftone mask such as MoSiON, the film thickness is adjusted so that the phase is 180 ° in order to increase the resolving power, so it is not possible to thicken the film with a margin. If the reduction increases, the expected function itself will not be fulfilled, causing a problem.

  If particles are found in the mask inspection process or defect correction process, even if only one particle has been found, no attempt has been made to actively remove the particles by means other than cleaning. Particles found in the mask inspection process and defect correction process also know the position on the mask, and if there are several particles, increasing the number of cleanings may cause a reduction in the thickness of the light-shielding film, change the phase, etc. If the coordinates can be linked and other devices can be removed cleanly and reliably by other approaches than cleaning that also has secondary problems, the quality of the entire photosk manufacturing process can be improved even if the number of processes increases. Is an attractive and necessary way to achieve.

  The present invention intends to remove several or less particles existing on a photomask safely and reliably by a method other than cleaning.

  Particles are removed from the photomask using a mechanical / electromagnetic interaction or chemical reaction between the probe of the scanning probe microscope and the particles on the photomask.

  As described above, in the present invention, particles found in the defect inspection process and the defect correction process are cleaned and cleaned without causing a secondary problem such as a reduction in the thickness of the light shielding film due to cleaning or a phase change. It can be reliably removed from the photomask.

Scanning probe microscopes have strong locality due to the sharp tip and high positioning ability unique to high-resolution microscopes, and do not adversely affect normal patterns using the position information of defect inspection equipment and defect correction equipment. Only targeted particles can be removed from the photomask. Since particles are removed by a method other than cleaning, there is no side problem such as reduction of the light-shielding film due to cleaning or phase change.
Examples using the present invention will be described below.

  The stage of the atomic force microscope is moved to the position where the particle is located according to the position information of the defect inspection apparatus or defect correction apparatus that found the particle. The region including the particle 1 is observed in the observation mode of the atomic force microscope, and the position of the particle on the glass substrate 4 is recognized. As shown in FIG. 1, the atomic force microscope probe 2 is applied to the side surface of the particle 1, and the adhered particle is removed by being pushed and moved. The force gradient at the time of pressing is monitored, and the probe 2 is always controlled in the direction in which the force gradient is maximized to move and remove the particles 1.

  When the particles are positively or negatively charged, the particles are removed using their electrostatic characteristics. The stage of the atomic force microscope equipped with the conductive probe is moved to the position where the particle is located according to the position information of the defect inspection apparatus or defect correction apparatus that found the particle. The region including the particles is observed in the observation mode of the atomic force microscope, and the position of the particle 1 is recognized. As shown in FIG. 2, a positive or negative voltage is applied to the conductive probe 5, and electrostatic repulsion between the charged particles 1 (FIG. 2 (a)) or electrostatic attraction (FIG. 2 ( Use b)) to move and remove the particle 1 on the photomask.

  The particles firmly adhered (fixed) on the photomask are removed by scratching with an atomic force microscope probe. The atomic force microscope stage having a probe made of a material harder than the particle is moved to a position where the particle is present in accordance with the position information of the defect inspection apparatus or defect correction apparatus that has found the particle. The region including the particle 1 is observed in the observation mode of the atomic force microscope, and the position of the particle is recognized. As shown in FIG. 3, the particles 1 firmly adhered on the photomask are scraped off with the probe 2 that is harder than the particle, thereby removing the particles 1 adhered on the photomask.

  When the particles are small and the adhesion force to the substrate is not so strong, the particles can be removed by using nanotweezer technology. In accordance with the position information of the defect inspection apparatus or defect correction apparatus that has found the particle, the stage of the atomic force microscope having both the probe having the tweezers function and the ordinary probe is moved to the position where the particle is present. A region including particles is observed in an observation mode of an atomic force microscope with a normal probe, and the position of the particle is recognized. As shown in FIG. 4, fine tweezers 6 made of carbon nanotubes as shown in Non-Patent Document 2, for example, are moved to the position of the particles as nanotweezers, and the adhered particles 1 are sandwiched and picked up and removed.

  A technique applying a transmission electron microscope sample preparation technique performed in a focused ion beam apparatus can also be used for particle removal. Move the atomic force microscope stage combined with an electron beam device or ion beam device with a deposition function and an etching function in vacuum according to the position information of the defect inspection device or defect correction device that found the particle to the position where the particle is located To do. In the observation mode of the atomic force microscope, the region including the particles is observed to recognize the position of the particles. As shown in FIG. 5 (a), an electron beam or an ion beam is first introduced while flowing the deposition source gas from the deposition gas supply system 8 with the scanning probe microscope probe 2 in contact with the particles adhering to the photomask. In step 7, a deposition film 9 is formed and bonded. With the particles adhering to the probe, the particles 1 are moved away from the glass substrate with a strong force, and the particles 1 are moved. As shown in FIG. 5B, the deposition film 9 is etched by the electron beam or ion beam 7 while flowing the etching gas from the etching gas supply system 10 at the particle movement destination, and the particles 1 are separated.

  It is also possible to liberate and remove particles by controlling the zeta potential at the interface between the solution and the glass substrate. The stage of the electrochemical scanning tunneling microscope filled with the acidic or alkaline solution 11 having an appropriate pH is moved to the position where the particles are located in accordance with the position information of the defect inspection apparatus or defect correction apparatus where the particles are found. The region including the particle 1 is observed in the observation mode of the electrochemical scanning tunneling microscope, and the position of the particle 1 is recognized. As shown in FIG. 6, the probe 5 of the electrochemical scanning tunneling microscope is placed near the particle 1 while monitoring the voltage with the reference electrode 12, and the zeta potential at the interface between the solution and the glass substrate is controlled by the conductive probe 5. Then, the particles 1 adhering to the photomask are released and removed.

  For particles made of magnetic metal, the magnetic properties are used for particle removal. In accordance with the position information of the defect inspection apparatus or defect correction apparatus that found the particle, the stage of the apparatus including the nonmagnetic atomic force microscope probe and the scanning magnetic force microscope probe is moved to the position where the particle is present. A region containing particles is observed with a non-magnetic atomic force microscope probe to recognize the position of the particles. Next, as shown in FIG. 7 (a), the ferromagnetic probe 13 is brought close to the particle 1 made of a magnetic material, and the particle 1 attached on the photomask is moved and removed using a magnetic attraction. As shown in FIG. 7 (b), the particles can be similarly removed by using the magnetic repulsive force of the particles 1 made of the ferromagnetic probe 13 and the magnetic material.

  If the particles are organic, use the principle of VUV light cleaning in an ozone gas atmosphere. The stage of the scanning near-field microscope is moved to a position where particles are present according to the position information of the defect inspection apparatus or defect correction apparatus that has found the particles. The region including the particles is observed in the shear force mode of the scanning near-field microscope observation, and the position of the particles is recognized. As shown in FIG. 8, organic particles 1 adhered to the photomask by supplying evanescent light from the scanning near-field microscope probe tip 14 to the particles 1 immediately below while flowing ozone gas from the ozone gas supply system 16 to the particles 1 immediately below. To sublimate and remove.

  When the particle is conductive and the particle size is very small, the electric field evaporation phenomenon by the conductive probe is used. In accordance with the position information of the defect inspection apparatus or defect correction apparatus that found the particle, the stage of the atomic force microscope equipped with the conductive probe is moved to the position where the particle is present. The region including the particle 1 is observed in the observation mode of the atomic force microscope, and the position of the particle 1 is recognized. As shown in FIG. 9, a strong pulsed electric field is applied to the conductive probe 5 by a pulse power source 17, and the particles 1 adhering to the photomask are removed by field evaporation.

It is explanatory drawing in the case of moving and removing the particle which adhered by pressing a probe tip to the side of a particle, and moving. It is explanatory drawing in the case of applying a voltage to a probe and removing using the electrostatic interaction between particles. It is explanatory drawing in the case of removing particles by scratching the probe. It is explanatory drawing in the case of picking up and removing a particle with the probe which has a tweezers function. It is explanatory drawing when adhere | attaching by the deposition function of an electron beam or an ion beam in the state which contacted the particle, and pulling apart and removing with a strong force. It is explanatory drawing in the case of controlling the zeta potential with an electroconductive probe in an electrolyte solution, and removing the adhering particles. It is explanatory drawing in the case of removing the adhering particle using the magnetic interaction of the scanning probe microscope probe provided with ferromagnetism. It is explanatory drawing in the case of converting and removing the organic particle adhering with the VUV evanescent light of the scanning near-field microscope in the ozone gas atmosphere to the sublimation. It is explanatory drawing in the case of applying the strong pulse-like electric field to a conductive scanning probe microscope probe, and removing the particles adhering by electric field evaporation.

Explanation of symbols

1 Particle 2 Atomic Force Microscope Probe 3 Glass Substrate 4 Normal Pattern 5 Conductive Atomic Force Microscope Probe 6 Probe with Tweezer Function 7 Electron Beam or Ion Beam 8 Deposition Gas Supply System 9 Deposition Film DESCRIPTION OF SYMBOLS 10 Etching gas supply system 11 Electrolyte solution 12 Reference electrode 13 Scanning probe microscope probe provided with ferromagnetism 14 Scanning near-field microscope probe 15 VUV light source 16 Ozone gas supply system 17 Pulse power supply

Claims (9)

  A method for removing particles from a photomask, wherein the particles removed from the photomask are moved by pressing a scanning probe microscope probe against a side surface of the particles to move the particles.   Applying positive or negative voltage to the conductive scanning probe microscope probe to remove particles by moving the particles on the photomask using electrostatic attraction or repulsion between charged particles A feature of a photomask particle removal method.   A particle removal method for a photomask, characterized in that particles fixed on the photomask are removed by scraping the particles fixed on the photomask with a scanning probe microscope probe harder than the particles.   A photomask particle removal method comprising picking up and removing particles adhering to a photomask with a scanning probe microscope probe having a tweezers function.   The scanning probe microscope probe is bonded with the electron beam or ion beam deposition function in contact with the particles adhering to the photomask, and the particles are moved while they are adhered to the probe to remove the particles. A feature of a photomask particle removal method.   A photomask characterized by filling the periphery of the particles with an acidic or alkaline solution having an appropriate pH and controlling the zeta potential with a conductive scanning probe microscope probe to release and remove particles adhering to the photomask. Particle removal method.   A method of removing particles from a photomask, comprising removing particles adhering to the photomask using a magnetic interaction of a scanning probe microscope probe provided with ferromagnetism.   Particle removal from a photomask characterized by supplying VUV evanescent light from the tip of a scanning near-field microscope probe to the particles directly below it in an ozone gas atmosphere to convert organic particles adhering to the photomask to sublimates. Method.   A photomask particle removal method comprising applying a strong pulsed electric field to a conductive scanning probe microscope probe and removing particles adhering to the photomask by field evaporation.

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