JP4361405B2 - Mask black defect correction by applying electrochemical method to AFM - Google Patents

Description

  The present invention relates to a method for correcting a black defect of a photomask used for manufacturing a semiconductor, an apparatus for executing the method, an AFM probe used for the apparatus, and a manufacturing method thereof.

  Recent electronic devices such as personal computers and mobile phones have become smaller and have higher performance due to higher LSI density and systematization. In a situation where more than several million elements are packed in a semiconductor chip of only a few millimeters, the line width for drawing a circuit pattern has been on the order of microns to nanometers, and lithography technology development to realize that It is unfolding. The mainstream of lithography so far has been optical lithography technology, but the wavelength of light used for pattern miniaturization should be as short as possible, and it will be performed using a short wavelength laser. Due to the problems of optical systems and resists, the response to miniaturization by the optical exposure apparatus is almost at the limit. Therefore, the technology that uses electron beams and ultra-short ultraviolet rays as the source of radiation is promising instead of light, and the photomasks used with these technological trends are also becoming increasingly finely patterned. . If defects exist on this photomask, the defects are transferred to the wafer and cause a reduction in yield. Therefore, before transferring the mask pattern to the wafer, the defect inspection device checks the presence and location of the photomask defects. If there is a defect, the defect correcting process is performed by the defect correcting device before transferring the defect onto the wafer. This mask defect correction also requires precise processing as the pattern becomes finer.

  Although the defect correction of the exposure mask used in lithography has also been corrected using a laser beam, now the etching function of a focused ion beam (FIB) apparatus with excellent processing accuracy and work efficiency is provided. Removal of attached foreign matter (black defect correction) and missing portion addition processing (white defect correction) using an ion beam induced deposition function have become mainstream. Conventionally used photomasks form a light-shielding film by sputtering a binary mask material such as chromium or a halftone phase shift mask material such as MoSiON on a glass such as quartz glass, and the mask pattern is used for light transmittance. Recently, Levenson-type phase shift masks that have been dug until glass is in anti-phase, with stronger resolution and depth of focus improvements, are beginning to be put into practical use. . In such a technical situation, the phenomenon of the river bed at the time of correcting the black defect by irradiating the ion beam has become a bigger problem. This river bed is a phenomenon in which, when an ion beam is irradiated to the peripheral portion of a defect, ions reflected by the defect portion are scattered and the substrate around the defect portion is etched. Although the ion beam is finely focused by the optical system, it has a microscopic normal distribution, which also contributes to the river bed phenomenon that etches the substrate around the defect. Since the river bed disturbs the phase of the transmitted light due to the difference in height, it has an adverse effect on the transfer result and is a factor that degrades the processing quality of the black defect correction location. In particular, due to the recent shortening of the wavelength of the light source of the reduction projection exposure apparatus, even a river bed having a depth that does not cause a problem in the past has been affected by the transfer result. In addition, the etching using the FIB has a problem that the material once sputtered and removed is reattached to the glass substrate.

  In light of this problem of FIB processing such as a river bed, the present applicant has previously proposed Patent Document 1 “Method for correcting black defect of mask”. In this first stage, the tail component of the ion beam and the ion beam scattered at a small angle are irradiated only to the inside of the defect area that is recognized so that it does not hit the surrounding glass part, and etching is performed so as to leave the edge of the defect. The black defect is corrected by following a two-step correction procedure in which only the edge of the defect left in the second stage is physically cut with an AFM hard probe fixed to the height of the glass surface. By combining a defect repair apparatus using an ion beam and an atomic force microscope (AFM), it is possible to repair a black defect without a river bed with a practical throughput.

  However, in order to perform defect correction by this method, it is necessary to perform FIB processing in a vacuum chamber and then move out of the chamber and perform work by AFM. This operation has a problem that the probe position is accurately positioned on the remaining peripheral edge of the defect, and the probe is scanned and mechanically scraped off.

  In addition, in order to perform defect correction by this method, a troublesome operation of accurately positioning the probe position on the remaining defect peripheral portion and mechanically scraping it is necessary. Therefore, there has been a problem that the work is considerably troublesome. In addition, there is a problem of damaging the mask surface when scanning the ion beam to obtain a defective charged particle image for observing a defect, and a FIB drift occurs due to a charge-up phenomenon caused by ion beam irradiation, resulting in poor positioning. There was also the problem of becoming accurate.

  Therefore, the applicant of the present invention is conducting the development with the idea of removing the mask defect portion by an electrochemical method because it is a conductive material such as chromium. The reaction that dissolves the defective material in the electrolytic solution by the electrochemical method does not damage the surrounding glass substrate, and the reaction rate can be controlled, so it satisfies the requirements required in that respect, The problem is that this method realizes processing that removes only the defective portion having a fine structure. Considering the current state of photomasks, a local region of 10 to several hundred nanometers must be identified and reacted.

  Furthermore, since the functions of both the focused ion beam (FIB) apparatus and the AFM are necessary to perform defect correction by this method, the apparatus becomes large and the work sample must be transferred to both apparatuses without performing work. Don't be. Even when this is performed by a composite apparatus having both functions, FIB processing must be performed in the vacuum chamber, and then the work must be taken out of the chamber and performed by AFM. In addition, it is a troublesome task of accurately positioning the probe position on the remaining defect peripheral edge and mechanically scraping it. Therefore, there is a problem that neither the apparatus nor the work is simple. In addition, the problem of damaging the mask surface when scanning the ion beam for observing the defect and obtaining the secondary charged particle image, and the positioning becomes inaccurate due to the charge-up phenomenon caused by the ion beam irradiation. There was also a problem.

  Therefore, as will be described later, since the material of the mask defect portion is a conductive substance such as chromium, the present applicant has been concentrating on removing it by an electrochemical method and is developing it. . The reaction that dissolves the defective material in the electrolytic solution by the electrochemical method does not damage the surrounding glass substrate, so it meets the requirements for that point, but the problem is the microstructure It is to realize processing for removing only the defective portion by this method. Considering the current state of photomasks, a local region of 10 to several hundred nanometers must be identified and reacted. In addition, the correction method based on the electrochemical reaction has a disadvantage that it takes a longer processing time than the etching correction by the conventional FIB apparatus.

  By the way, as an example of executing fine processing using an electrochemical technique, there is a technique disclosed in Patent Document 2. This technique is intended to form a semiconductor mask pattern itself by an electrochemical technique. . That is, a conductive cantilever having a conductive probe capable of detecting an atomic force generated between the workpiece and the workpiece, and a displacement caused by the atomic force between the probe and the workpiece are detected. Detecting means for controlling, a control means for maintaining a constant distance between the probe and the sample to be processed in order to keep the atomic force constant when scanning the sample to be processed, a sample to be processed and the probe A fine processing method using an apparatus including an atomic force detection means, and means for applying a potential between the sample and the probe. This is a microfabrication method in which a sample is subjected to microfabrication by applying a voltage to the probe in the presence of a polar solvent. This document mainly uses a processing method for removing the surface layer by an electrochemical reaction, but it is not easy to remove unnecessary regions by this method over the entire mask.

  The present invention presents a technology for accurately correcting next-generation mask defects having a fine pattern structure using an atomic force microscope (hereinafter referred to as electrochemical AFM) having the electrochemical processing function. However, in order to do so, a local region of 10 to several hundred nanometers must be specified to cause a reaction. In order to realize a local reaction, the fineness of the electrode facing the defect, the distance between the two, and the amount of charge are important conditions. Therefore, when using the probe of the probe microscope as an electrode, the tip diameter is set to be several to several tens of nanometers and the conductive probe is used as an electrode, and this thin electrode is positioned at a close distance of 1 to 100 nanometers. By doing so, a desired local reaction can be realized. However, it is not easy to process the tip diameter of the probe to the order of 1 nanometer and to make only the tip portion into a conductive electrode structure.

  By using an atomic force microscope (AFM) which is a kind of probe microscope, an observation image for specifying a defect position can also be obtained without using a focused ion beam.

The present invention provides a method for producing a suitable probe using this electrochemical AFM and a probe produced thereby. Reactions in which a defective material is dissolved in an electrolytic solution by an electrochemical technique does not damage the surrounding glass substrate, and the reaction rate can be controlled. In this respect, the problem of mask correction using a focused ion beam apparatus is solved. However, in the case of using this method, it is important to realize a process for removing only the defective portion having a fine structure. Since the material of the black defect in the mask is also the material of the mask pattern, if the original mask pattern is removed by this electrochemical method, a new white defect is created and the defect is not corrected.
JP 2002-214760, Seiko Instruments Inc., “Method for correcting black defect in mask”, published on July 31, 2002 JP 2002-355799 A, Hokkaido TELEO, "Fine processing method and information recording method", published on December 10, 2002 JP-A-7-174542, Seiko Instruments, “Scanning near-field atomic force microscope, probe used in the microscope, and probe manufacturing method thereof”, published on July 14, 1995

  The basic problem to be solved by the present invention is that the black bed correction of the mask can not be riverbed, black defects in a fine pattern can be corrected neatly, without damaging the mask surface by ion irradiation, Moreover, it is an object of the present invention to provide a black defect correction technique that can be used in a relatively simple and large-sized apparatus and that can perform operations relatively easily, and to provide an apparatus that can execute such a technique.

  Furthermore, a further problem to be solved by the present invention is to provide a black defect correction method that is capable of performing a local fine correction without misalignment due to a charge-up phenomenon and that can be performed relatively simply. In addition, the present invention provides a black defect correction method capable of performing a local fine correction without affecting the surrounding pattern in the mask black defect correction and performing the operation relatively simply, and such a method can be executed. To provide an apparatus.

  Another problem to be solved by the present invention is to provide a probe for electrochemical AFM having a tip diameter of nanometer order in order to realize the above-described method.

  The mask black defect correcting method of the present invention includes a step of grasping a black defect portion position of a mask by an atomic force microscope, a step of moving the probe of the atomic force microscope above the black defect position, and the probe And a step of removing the black defect by an electrochemical reaction with the mask black defect portion as both electrodes and an electrolyte interposed, and a step of confirming the removal of the black defect by the atomic force microscope. .

  Further, another mask black defect correcting method of the present invention includes a step of grasping a defect position of a mask by an AFM observation function, a step of applying an insulating resist film on the mask surface, and a resist film of the defective portion. A step of scratching with the AFM probe, a step of moving the electrochemical AFM probe above the defect position, and an electrochemical reaction with the probe and the mask black defect portion as both electrodes and an electrolyte interposed The step of removing the black defect and the step of removing the insulating film on the mask surface.

  Further, another mask black defect correcting method of the present invention includes a step of grasping a defect portion position of a mask by a scanning microscope, a step of applying an insulating resist film to the mask surface, and a resist film of the defect portion. Irradiating with a charged particle beam, moving the electrochemical AFM probe above the defect position, and interposing an electrolyte with the probe and the mask black defect as both electrodes And removing the black defect by an electrochemical reaction and removing the insulating film on the mask surface.

  In another mask black defect correcting method of the present invention, any one of an AFM, a scanning ion microscope, and a scanning electron microscope is used as a scanning microscope for obtaining defect position information.

  Further, another mask black defect correcting method according to the present invention includes a step of grasping the position of a defective portion of the mask by a scanning microscope function of the FIB apparatus, and irradiating the central portion of the defective area excluding the peripheral portion with FIB in the vicinity of the glass substrate. Etching, leaving the probe and the mask black defect part as both electrodes, removing the black defect remaining by the electrochemical reaction with the electrolytic solution interposed therebetween, and the atomic force microscope to detect the defective part. And confirming the correction.

  According to another mask black defect correction method of the present invention, the step of measuring a tunnel current flowing between the probe and the black defect and setting an appropriate close distance before the electrochemical reaction is performed. Adopted.

  The black defect correction method of the present invention specifies the defect correction position from the atomic force microscope image as the first step, and the distance between the probe tip having conductivity and the conductive mask material as the second step. Is set using a tunnel current, and an electrochemical reaction occurs between the black defect portion and the probe, and processing is performed until the glass surface is exposed. As a third step, the atomic force microscope is used to confirm whether the correction has been completed.

  The mask black defect correcting device of the present invention comprises an atomic force microscope probe having a tip as an electrode, a processing cell for storing a mask as an electrolyte and a sample, the tip of the probe, and the mask surface. A power source for applying a predetermined current or voltage between them and a mechanism for moving the position of the tip of the probe in the X, Y and Z directions, and an observation function as an atomic force microscope and mask black defects are electrochemical It has a processing function that removes it by a mechanical reaction. In order to locally limit the electrochemical reaction, the probe was made of a conductive material and its surface was covered with an insulating material so that only the tip portion was exposed.

  Further, another mask black defect correcting device according to the present invention includes an AFM probe using only the tip as an electrode, a processing cell that stores an electrolyte and a mask as a sample, the tip of the probe, and a mask surface. And a mechanism for moving the position of the tip of the probe in the X, Y, and Z directions, and the surface of the sample by two-dimensional scanning of the probe. A function of observing the shape of the probe, a function of moving the probe to the position based on the defect position information obtained by the observation, mechanically removing the resist film on the defect surface, and a tip electrode of the probe It has a processing function to remove mask black defects by electrochemical reaction.

  Further, in another mask black defect correcting apparatus of the present invention, the function of mechanically removing the resist film on the defect surface stores the positional information of the defect region obtained by the observation function, and the resist film is based on the stored information. A computer that issues a drive signal to a mechanism that moves the position of the probe tip in the X, Y, and Z directions so as to scan the removal area and scan the removal area is provided.

  In addition, another mask black defect correcting device of the present invention includes an FIB device comprising a sample stage having an FIB column and at least a three-dimensional drive mechanism in a vacuum chamber, an AFM probe having only the tip as an electrode, A processing cell for storing an electrolyte and a mask as a sample, a power source for applying a predetermined current or voltage between the probe tip and the mask surface, and the position of the probe tip at X, Y, A mechanism for moving in the Z direction, and has an observation function and a processing function for removing mask black defects by an electrochemical reaction.

  In addition, another mask black defect correcting apparatus of the present invention includes an electron beam apparatus including a sample stage having an electron beam column and at least a three-dimensional drive mechanism in a vacuum chamber, and an AFM probe using a tip as an electrode. A processing cell that stores an electrolyte and a mask as a sample, a power source that applies a predetermined current or voltage between the probe tip and the mask surface, and the position of the probe tip X, Y , A mechanism for moving in the Z direction, and has an observation function and a processing function for removing mask black defects by an electrochemical reaction.

  Further, another mask black defect correcting apparatus of the present invention includes a FIB apparatus having a SIM function for grasping a defect position and an etching function by beam irradiation, an atomic force microscope probe having a tip as an electrode, electrolysis A processing cell that stores a liquid and a mask as a sample, a power source that applies a predetermined current or a predetermined voltage between the probe tip and the mask surface, and the position of the probe tip in the X, Y, and Z directions And an electrochemical AFM apparatus having a processing function of removing the mask black defect by an electrochemical reaction based on the defect position information obtained by the FIB apparatus.

  Furthermore, in order to carry out fine correction of minute areas, the tip is made of a sharp conductive material only at the tip and used as an electrode, and the other part is made of an insulator, or the tip of the probe and a mask. The power supply connected to the surface can supply a bias voltage and a pulse of a predetermined current or a predetermined voltage, and an appropriate close distance between the tip of the probe and the mask black defect can be set by the STM function. A configuration was adopted in which an electrochemical reaction was performed locally.

  According to another mask black defect correcting apparatus of the present invention, the power source connected between the probe tip and the mask surface can supply a bias voltage and a pulse of a predetermined current or a predetermined voltage. In addition to a processing function for removing defects by an electrochemical reaction, an STM function for measuring and setting an appropriate close distance between the probe and the mask black defect is provided.

  The method for producing a probe for electrochemical AFM according to the present invention comprises a step of roughing a plate-like cantilever part and a probe part protruding from the tip of an SOI silicon wafer by dry etching, and silicon of the protruding probe part A step of advancing oxidation from the surface by thermal oxidation to sharpen the tip, a step of coating a metal thin film on the surface of the probe and the cantilever, and an insulating layer except for the tip of the probe and the contact hole And a coating step.

  In another method for producing a probe for electrochemical AFM according to the present invention, mask patterning and reactive ion bombardment are performed as a rough process of a plate-shaped cantilever part and a probe part protruding from the tip of the SOI silicon wafer. An etching method was adopted.

  Further, in another method for producing a probe for electrochemical AFM according to the present invention, as a step of covering the tip with the insulating layer except for the tip of the probe and the contact hole, the entire tip is covered with an insulating film, and then the probe tip and the contact are made. A method of removing holes by plasma etching was adopted.

  Further, in another method for producing a probe for electrochemical AFM according to the present invention, as a step of covering the tip with the insulating layer except for the tip of the probe and the contact hole, the entire tip is covered with an insulating film, and then the probe tip and the contact are made. The holes were removed by the FIB etching method.

  Further, in another method for preparing a probe for electrochemical AFM of the present invention, a process of sharpening a hollow glass capillary in a heated state, and a process of bending the sharpened tip by heating and cooling a plurality of times in one direction. And a process of inserting a metal wire into the capillary, a process of sealing both ends of the capillary with resin, and a process of sharpening the tip by electrolytic polishing. Further, a process of dip-coating the probe that has undergone the process in molten Apiezon wax, a process of polishing the back surface of the probe to form a mirror surface, a process of sputter coating a metal thin film around the mirror surface, The process consisted of a process of removing the metal thin film other than the mirror surface by immersing in chloroform to dissolve the apizone wax.

  The probe for electrochemical AFM of the present invention is made of a conductive material, and its surface is covered with an insulating material and only the tip is exposed.

  In the probe for electrochemical AFM of the present invention, the basic structure of the plate-shaped cantilever and the probe protruding from the tip is formed of silicon, and the tip of the cantilever on the side where the probe is formed is sharpened. A metal film was formed on the silicon surface of the probe, and the upper layer of the metal film was covered with an insulating layer except for the sharpened probe tip and contact hole.

In another electrochemical AFM probe of the present invention, a metal wire is inserted into a glass capillary whose tip is sharpened and bent into a bowl shape, and the metal wire is exposed at the tip and rear ends. In addition, the metal wire sealed with resin and exposed at the tip is sharpened to a tip diameter of several hundred nanometers or less.
In addition to the above-described structure, another electrochemical AFM probe of the present invention has a flat surface on the back surface, and a metal thin film is coated on the surface to form a mirror surface.

  The mask black defect correcting method of the present invention comprises a step of grasping a defect position of a mask by an atomic force microscope, a step of moving a probe above the defect position, and an electrolysis using the probe and the mask black defect part as both electrodes. A step of removing the black defect by an electrochemical reaction in a state of interposing a liquid, and a step of confirming the correction of the defect by an atomic force microscope, the correction using a focused ion beam device; Unlike glass substrates, which do not cause the riverbed phenomenon, the decrease in transmittance, the charge-up phenomenon of the mask surface, etc., the black defects are clean even for masks and Levenson type masks whose patterns are becoming increasingly fine. Corrections can be made, and accurate positioning of the corrected part of the nanometer order becomes possible.

  The mask black defect correcting method according to the present invention includes a step of grasping a position of a defective portion of a mask by an AFM observation function, a step of applying an insulating resist film on the mask surface, and a resist film of the defective portion by using an AFM probe. The step of moving the electrochemical AFM probe above the defect position, and the black defect by an electrochemical reaction with the probe and the mask black defect portion as both electrodes and an electrolytic solution interposed therebetween. And the step of removing the insulating film on the mask surface, which removes black defects by an electrochemical reaction. Therefore, the riverbed phenomenon of processing using a focused ion beam is The glass substrate and normal pattern are not damaged, and the resist film covers the area other than the defective part. Not to cause an electrochemical reaction in the non-pass. Since the pattern edge from which the defective portion has been removed is finished in a steep form, a photomask with a clear pattern boundary can be provided.

  The mask black defect correcting method of the present invention includes a step of grasping a defect portion position of a mask by a scanning microscope, a step of applying an insulating resist film on the mask surface, and irradiating the resist film of the defective portion with a charged particle beam. A step of moving the electrochemical AFM probe above the defect position, and the black reaction by an electrochemical reaction in a state where the probe and the mask black defect portion are both electrodes and an electrolyte is interposed. Since it consists of a step of removing defects and a step of removing the insulating film on the mask surface, which removes black defects by an electrochemical reaction, the riverbed phenomenon of processing using a focused ion beam There is no damage to the glass substrate and normal pattern, and the resist film covers the area other than the defective part. Not to cause an electrochemical reaction in the non-pass. Since the pattern edge from which the defective portion has been removed is finished in a steep form, a photomask with a clear pattern boundary can be provided.

  When AFM is used as a scanning microscope to obtain defect position information and information is obtained by its observation function, there is no concern of damaging the mask surface, such as a scanned image by a charged particle beam, and there is a problem of charge charging. And positioning accuracy is high. In addition, a scanning ion microscope image can be obtained if necessary using a focused ion beam for resist removal, and a scanning electron microscope image can be obtained using an electron beam for resist removal.

  The mask black defect correcting method of the present invention includes a step of grasping a defect portion position of a mask by a scanning microscope function of the FIB apparatus, and etching while leaving the vicinity of the glass substrate by irradiating the FIB to the central portion of the defect region excluding the peripheral portion. The step of removing the black defects remaining by the electrochemical reaction with the probe and the mask black defect portion as both electrodes and interposing the electrolyte, and the defect correction is confirmed by an atomic force microscope It consists of steps. That is, in this correction processing, although FIB is used, a river bed cannot be formed by irradiating only the central area of the defect, and all defects in the portion in contact with the glass substrate surface are cleaned by an electrochemical reaction. Correction can be removed. The mask surface is not damaged by ion irradiation, and the operation of removing the remaining portion by FIB processing can be performed by electrolytic processing without placing a burden as in Patent Document 1 on the operator. Further, since most of the black defects are removed by FIB processing as the first stage, the correction processing can be executed in a relatively short correction time.

  In addition, since the tip of the probe of the electrochemical AFM of the present invention is an electrode, an appropriate close distance between the probe and the mask black defect is measured and set by the function of the tunnel microscope before the electrochemical reaction. Is possible.

  In addition, the mask black defect correction method of the present invention, which takes a step of measuring and setting an appropriate close distance between the probe and the mask black defect with the function of a tunnel microscope before the electrochemical reaction, Therefore, since the appropriate close distance between the tip of the probe and the black defect surface, which is an important requirement for the limitation, can be accurately determined by the tunnel current, fine black defects can be repaired cleanly.

  The mask black defect correcting device of the present invention comprises an atomic force microscope probe having a tip as an electrode, a processing cell for storing an electrolyte and a mask as a sample, and between the tip of the probe and the mask surface. In order to use an observation function as an atomic force microscope, a power source that applies a predetermined current or a predetermined voltage to the power source and a mechanism that moves the position of the tip of the probe in the X, Y, and Z directions. The device to be used is relatively simple and does not increase in size without requiring the sample to be set in the vacuum chamber, and the operation can be performed relatively simply, and the mask function is used to remove the mask black defect by electrochemical reaction. It is possible to provide an apparatus that cleanly corrects black defects without damaging them.

  A black defect correcting device according to the present invention includes an AFM probe having only the tip as an electrode, a processing cell that stores an electrolyte and a mask as a sample, and a predetermined gap between the probe tip and the mask surface. A power supply for applying a current or voltage and a mechanism for moving the position of the tip of the probe in the X, Y, and Z directions are basically provided only as a structure of an electrochemical AFM apparatus. A function of observing the shape of the sample surface by two-dimensional scanning, a function of moving the probe to the position based on the defect position information obtained by the observation, and mechanically removing the resist film on the defect surface; A mask black defect correcting method having the above-described effect can be realized, which has a processing function of removing a mask black defect by an electrochemical reaction using the tip electrode of the probe.

  Further, the position information of the defect area obtained by the observation function is stored, the resist film removal area is determined based on the stored information, and the position of the probe tip is scanned in the X, Y and Z directions so as to scan the removal area By providing a computer that emits a drive signal in the mechanism for moving to the position, the function of mechanically removing the resist film on the defect surface can be easily exhibited.

  An FIB apparatus comprising an FIB column (or electron beam column) in a vacuum chamber and a sample stage having at least a three-dimensional drive mechanism in a method in which an insulating resist film is coated except for a defective region and is not brought into contact with the electrolyte. (Or an electron beam device), an AFM probe using only the tip as an electrode, a processing cell that stores a mask as an electrolyte and a sample, and a predetermined current between the probe tip and the mask surface Alternatively, a book having a power supply for applying voltage and a mechanism for moving the position of the tip of the probe in the X, Y, and Z directions, and an observation function and a processing function for removing mask black defects by an electrochemical reaction. When using the mask black defect correcting device of the invention, the tip of the atomic force microscope with the tip being a sharp electrode is used as the tip of the electrochemical AFM, the tip of the tip and the mask surface Pulse current between In addition to providing a power supply that applies a pulse voltage, the pattern edge is sharpened in combination with a technique that covers the area other than the defective area with an insulating resist film and prevents contact with the electrolyte. It can be modified into a photomask with a clear boundary.

  The mask black defect correcting apparatus of the present invention includes an FIB apparatus having a SIM function for grasping a defect position and an etching function by beam irradiation, an atomic force microscope probe having a tip as an electrode, an electrolyte and a sample. A processing cell for storing the mask, a power source for applying a predetermined current or voltage between the probe tip and the mask surface, and a mechanism for moving the position of the probe tip in the X, Y, and Z directions And a combination with an electrochemical AFM apparatus having a processing function of removing a mask black defect by an electrochemical reaction based on defect position information obtained by the FIB apparatus. The correction method can be executed smoothly.

  In addition, the mask black defect correcting apparatus according to the present invention adopting a probe configuration in which only the tip portion is formed of a sharp conductive material as an electrode and the other portion is an insulator, the electrochemical reaction region is It is effective for narrowing down.

  Furthermore, the power source connected between the probe tip and the mask surface can supply a bias voltage and a pulse of a predetermined current or a predetermined voltage, and has a processing function for removing mask black defects by an electrochemical reaction. In addition, the mask black defect correcting device of the present invention having the STM function can measure and set an appropriate close distance between the probe and the mask black defect, and can perform electric machining by performing electrolytic processing using pulses. The chemical reaction area can be effectively narrowed and limited, and precise correction processing is possible.

  In addition, the mask black defect correction device of the present invention locally limits the electrochemical reaction by forming the probe with a conductive material and covering the surface with an insulating material so that only the tip is exposed. The mask black defect of the fine structure can be neatly corrected.

  Furthermore, the power source connected between the probe tip and the mask surface can supply pulses of bias voltage and constant voltage. In addition to the processing function to remove mask black defects by electrochemical reaction, the probe is supplied. The mask black defect correcting device of the present invention having the STM function for measuring and setting the appropriate close distance between the needle and the mask black defect does not require a large structural change, and combines the functions of AFM and STM. The mask black defect of the structure can be repaired cleanly.

  The method for producing a probe for electrochemical AFM according to the present invention comprises a step of roughing a plate-shaped cantilever part and a probe part protruding from the tip of an SOI silicon wafer by dry etching, and silicon of the protruding probe part. A step of advancing oxidation from the surface by thermal oxidation to sharpen the tip thereof, a step of coating a metal thin film on the surface of the probe and the cantilever, and an insulating layer excluding the tip of the probe and the contact hole Therefore, it is possible to provide a probe for electrochemical AFM having a tip diameter of the order of nanometers, thereby locally limiting the electrochemical reaction region.

  The rough processing of the plate-shaped cantilever part and the probe part protruding from the tip of the SOI silicon wafer is performed by mask patterning and reactive ion etching, so that a steep columnar body preferable as a probe structure is obtained. Can be formed.

  The method for producing a probe for electrochemical AFM according to the present invention comprises a step of sharpening a hollow glass capillary in a heated state, a step of heating and cooling the sharpened tip portion a plurality of times, and bending in one direction. It is a probe for electrochemical AFM because it consists of a process of inserting a metal wire into the core, a process of sealing both ends of the capillary with resin, and a process of electrolytic polishing and sharpening the tip. It is possible to provide a fine electrode facing a sample surface having a tip diameter of nanometer order.

  Further, a step of dip-coating the probe having undergone the step according to claim 19 in molten Apiezon wax, a step of polishing the back surface of the probe to form a mirror surface, and a metal thin film centered on the mirror surface The method for preparing a probe for an electrochemical AFM according to the present invention comprising a step of sputter coating and a step of removing metal thin film other than the mirror surface by immersing in chloroform to dissolve the apizone wax. As a reflection surface, the mirror surface of the required displacement detection mechanism can be formed only on the specified flat surface, which is structurally simple and does not cause malfunction.

  The electrochemical AFM probe of the present invention is a probe having a plate-shaped cantilever and a probe protruding from the tip formed of silicon, and the tip and tip of the cantilever are sharpened. Since the metal film is formed on the silicon surface of the needle, and the upper layer of the metal film is covered with an insulating layer except for the sharpened probe tip and contact hole, If the mask is attached to the electrochemical AFM and the black defect of the mask is corrected, the river bed cannot be obtained, and even the black defect in a fine pattern can be corrected neatly, and the mask black defect that does not damage the mask surface due to ion irradiation Allows modification. In addition, the probe for electrochemical AFM of the present invention has a structure in which the tip of the probe is formed of a conductive material and can be connected to an external terminal through a contact hole in the metal coating, so it can be used as a probe for a tunnel microscope. can do.

  In addition, since the tip of the probe of the electrochemical AFM of the present invention is an electrode, an appropriate close distance between the probe and the mask black defect is measured and set by the function of the tunnel microscope before the electrochemical reaction. Is possible.

  In the electrochemical AFM probe of the present invention, a metal wire is inserted into a glass capillary whose tip is sharpened and bent into a bowl shape, and the metal wire is exposed at the tip and rear ends. Since the metal wire sealed with resin and exposed at the tip is sharpened to a tip diameter of several hundred nanometers or less, when this is used as an electrode for electrolytic processing, the electrochemical reaction It is possible to realize removal processing of extremely local regions such as tens to hundreds of nanometers. In addition, since it uses an electrochemical reaction, it cannot be riverbed like the conventional defect correction using a focused ion beam device, and even a black defect in a fine pattern can be corrected neatly. This makes it possible to correct a black defect in a mask that does not cause damage due to irradiation.

  As described above, the present invention was started with the intention of eliminating various effects caused by irradiation of an ion beam used for defect correction, in the trend toward a shorter wavelength of a light source used for lithography and a light source used for lithography. For that purpose, it is only necessary to be able to correct defects basically without using a focused ion beam. That is, a method capable of accurately and efficiently executing fine processing instead of defect correction using a focused ion beam must be presented. That is, it is required to be a technique that can remove black defects of the mask relatively quickly and without damaging the surrounding glass substrate. Therefore, it was conceived that a conductive material such as chromium was assumed as the material of the defective portion, and this was removed by an electrochemical method. The method of removing the defective material by dissolving it in the electrolytic solution by an electrochemical method does not damage the surrounding glass substrate, and the reaction rate can be controlled, so that the requirement required in that respect is satisfied. . However, in the case of using this method, it is important to realize a process for removing only the defective portion having a fine structure. Since the material of the black defect in the mask is also the material of the mask pattern, if the original mask pattern is removed by this electrochemical method, a new white defect is created and the defect is not corrected. Considering the current state of photomasks, a local region of 10 to several hundred nanometers must be identified and reacted. In order to realize a local reaction, the fineness, distance, and charge amount of the electrode facing the defect are important conditions. Accordingly, the present invention has been conceived to use a probe of a probe microscope as an electrode. The tip is sharpened from several nanometers to several tens of nanometers, and a probe made conductive is used as an electrode. A desired local reaction can be realized by positioning the thin electrode at a close distance of 1 to 100 nanometers.

  Patent Document 3 discloses an example in which a probe of a probe microscope is used as an electrode and fine processing is performed using an electrochemical technique. This technique is intended to form a semiconductor mask pattern itself by this method. That is, a conductive cantilever having a conductive probe capable of detecting an atomic force generated between the workpiece and the workpiece, and a displacement caused by the atomic force between the probe and the workpiece are detected. Detecting means for controlling, a control means for maintaining a constant distance between the probe and the sample to be processed in order to keep the atomic force constant when scanning the sample to be processed, a sample to be processed and the probe And a microfabrication method using an apparatus having a means for applying a potential between the sample and the probe, with a nonpolar solvent containing water present between the sample to be processed and the probe, This is a fine processing method for applying a fine voltage to the sample to be processed by applying a voltage to the probe. This document mainly presents a processing method for removing the surface layer by an electrochemical reaction. However, it is not easy to remove unnecessary regions over the entire mask by this method. The present invention uses this electrochemical technique to correct black defects on the mask. In addition, this technique is applied to precision machining of extremely local regions, and a practical technique at that time is presented.

  With reference to FIG. 1, description will be given of microelectrolytic machining as the basis of the present invention. In the figure, 1 is an AFM probe that also serves as a machining electrode, 2 is a cantilever, and 3 is a holder that supports the machining electrode. Reference numeral 4 denotes a processing cell, and an electrolytic solution is accommodated in the processing cell. A sample is placed in the electrolytic solution, and defect correction processing is performed here. 5 is an optical displacement detector for detecting the displacement amount of the AFM cantilever, 7 is a PZT scanner for driving the processing electrode holder 3 in a three-dimensional (XYZ) direction, and 6 is processed through the PZT scanner 7. A Z-axis stage for roughly adjusting the position of the electrode holder 3 in the Z direction, and 8 is a base on which the processing cell 4 is placed. This processing apparatus basically has an observation function as well as a processing function, and operates under the computer 10, respectively. In order to operate electrochemically as the former processing function, the sample side is one electrode, the tip of the cantilever tip is the other electrode, and the sample is not in contact with the sample in the electrolyte of the processing cell 4 The reference electrode 9 in a state is arranged, and the lead wire L 1 from the probe electrode, the lead wire L 2 from the sample side electrode, and the lead wire L 0 from the reference electrode are drawn out and connected to the terminal portion of the processing galvanostat 11. This reference electrode 9 is for detecting the ground potential. The electrochemical reaction does not simply depend on the relative potential difference between the two electrodes, but is influenced by the absolute potential of each electrode. In order to measure this absolute potential, a reference electrode 9 is provided. The galvanostat 11 controls the electrochemical reaction with a constant current. Further, as the latter observation function, an AFM controller 12 to which driving position information of the PZT scanner 7 and displacement information of the cantilever 2 detected by the optical displacement detector 5 are input is provided, and the operation as the AFM is controlled.

  The present invention uses the apparatus described above. As a first step, the drive position information of the PZT scanner 7 and the displacement information of the cantilever 2 detected by the optical displacement detector 5 are obtained, and the black defect position on the sample surface is detected and specified using the observation function as an AFM. To do. The defect position information obtained from the observation result is stored in the computer 10, and the second stage black defect correction is executed based on the stored information. First, the PZT scanner 7 is driven and controlled based on the previous defect position information so that the probe 1 is positioned at the black defect portion. The processing galvanostat 11 is operated in a state where the defect region and the tip of the probe 1 are opposed to each other, and between the conductive mask material and the probe tip having conductivity opposed to each other through the electrolytic solution. A voltage is applied to cause an electrochemical reaction to dissolve black defects in the electrolyte. This electrolytic solution is not particularly limited, but avoids those that are strong in acid or alkali and cause a chemical reaction with the sample. Since electrochemical processing is performed on a fine black defect on a mask, the probe 1 serving as a processing electrode has a fine electrode structure, and the distance from the black defect serving as a counter electrode is also an appropriate close distance. is important. Therefore, in the present invention, the entire probe 1 is not made of a conductive material, but only the tip portion is made of a conductive material. Further, the Z-axis stage 6 is controlled so as to be positioned at an appropriate close distance, and the Z-direction position of the processing electrode holder 3 is adjusted. In the present invention, a region where an electrochemical reaction is caused by a fine electrode structure (tip diameter of several to several tens of nanometers) and an appropriate close distance (1 to several hundred nanometers) is locally (ten to ten to several nanometers). (Several hundred nanometers). As a result, it is possible to realize precise processing that targets only the black defect portion that needs to be removed. This reaction is continued until the glass surface is exposed. However, unlike the ion beam processing, even if the glass surface is exposed, the portion does not react, so that the glass substrate is not damaged. As the final third step, it is confirmed whether the correction is completed by the original observation function of AFM. This is basically the same as the observation operation in the first stage, but it is confirmed whether or not the defect originally discovered is removed by this observation. At that time, it is not always necessary to obtain an image of the entire mask, and it may be confirmed by local scanning only in the vicinity of the defect area detected at the beginning.

  Further, the present invention was started with the intention of eliminating various effects caused by irradiation of an ion beam used for defect correction in the tendency of a finer photomask and a shorter wavelength of a lithography light source as described above. For that purpose, it is basically sufficient to correct a defect without using a focused ion beam, but instead, a method capable of accurately and efficiently executing fine processing must be presented. That is, it is required to be a technique that can remove black defects of the mask relatively quickly and without damaging the surrounding glass substrate.

  In this situation, the present applicant has conceived that the black defect is corrected by an electrochemical reaction, and the electrode facing the defect portion is caused to cause an electrochemical reaction only in a minute defect portion. Research has been conducted on the use of atomic force microscope (AFM) probes. In order to form a finer electrode in the process, the base of the probe is made of an insulator, and only the tip of the probe is made of a conductive material to form a fine electrode. Using the black defect part as one electrode, the fine electrode at the tip of the probe is opposed to the optimum close distance through the electrolyte, and a predetermined current or voltage is applied, and the black defect is brought into the electrolyte by an electrochemical reaction. It is to be dissolved. In this specification, this probe is referred to as an electrochemical AFM probe. In this series of studies, the present applicant has applied a resist (insulating) film over the entire mask surface to remove only black defects by an electrochemical reaction without affecting the normal pattern of the mask to be processed. After that, the method is effective in which the surface is exposed except for the resist of the defective portion, the probe for electrochemical AFM is positioned at the position of the defective portion, and the black defect is removed by an electrochemical reaction. The knowledge that it is. In short, a normal pattern or a region of a glass substrate is protected by being covered with a resist film, and an electrochemical reaction is caused only by a defective portion whose surface is exposed.

  1 shows an embodiment of the present invention. In this embodiment, the AFM function is provided with a function as a scanning tunneling microscope (STM), and an appropriate close distance between the defect surface and the tip of the probe is measured and the distance is easily set. Since the probe of the present invention has an electrochemical action, the tip of the probe 1 is an electrode and the lead wire L1 to the outside is connected, so that it can be used as an STM as it is. The configuration was used. Hereinafter, a method for correcting black defects in the present embodiment will be described in time series along the flowchart of FIG. FIG. 3 shows a model of a black defect to be corrected. The upper part is shown as a plan view near the black defect, and the lower part is a sectional view thereof. In step 1, the position of the black defect is detected by an ordinary AFM observation function of two-dimensional scanning. In step 2, the PZT scanner 7 is driven based on the defect position information obtained here to move the probe 1 above the defect position. The probe microscope that was functioning as the AFM in step 3 is caused to function as the STM. That is, as schematically shown in FIG. 4, a low bias voltage is applied from the power source 11 'between the mask black defect portion and the tip electrode of the probe. A tunnel current flows between the two due to this bias voltage. While the tunnel current is measured by the STM control means 12 ', the Z-axis stage is driven so that the distance between the two becomes an appropriate close distance, and the probe 1 Position it. In step 4, the probe 1 is caused to function as a machining electrode. Therefore, a pulse current (or pulse voltage) is applied from the power supply 11 ′ between the tip electrode portion of the probe 1 and the mask. In this embodiment, a conductive probe is formed, and an insulating material is coated on the surface thereof so that only the tip is exposed. Here, pulse current (or pulse voltage) is used instead of constant current or constant voltage application using a galvanostat. The reason is that between constant electrode and electrolyte solution when constant current or constant voltage is used. An electric double layer can be formed on the entire electrode surface and the electrochemical reaction area becomes wide. On the other hand, when this pulse current (or pulse voltage) is used, an alternating element acts and the electric double layer is at the tip. This is because it concentrates and the electrochemical reaction area becomes narrow. The amount of charge that flows when a single pulse voltage is applied is quantified. In step 5, a predetermined amount of a mask material in a narrow region centering on the tip end position is dissolved in the electrolyte by an electrochemical reaction. Incidentally, the electrolytic solution used here is an aqueous solution of NaCl, and this electrochemical reaction is as follows.

Black defect surface _{^{Cr → Cr 2 + + 2e -}} → Cr 3 + + 3e -
Probe side electrode 2H + + 2e ⁻ → H ₂ ↑
The operation form at this time is schematically shown in FIG. That is, a pulsed voltage is applied from the pulse power source 11 ′ between the mask and the electrode at the tip of the probe, and a local electrochemical reaction occurs on the defective portion. In step 6, the probe 1 is scanned two-dimensionally over the defect area, and the operations in steps 4 and 5 are repeatedly executed over the entire defect area.

  When the processing at one point in all the defect areas is completed, the Z stage 6 is driven by the amount ΔZ corresponding to the thickness of the mask material removed by one processing in Step 7 to move the probe 1 downward. Then, the defect surface and the tip position of the probe are set to an appropriate close distance again. The operation form at this time is schematically shown in FIG. In response to a command from the control means (AFM controller 12), the Z-axis stage is displaced in the Z direction by ΔZ. The amount of displacement is detected by a displacement detector and fed back to the control means. This position control mechanism is the same for positioning in the X and Y directions by the PZT scanner 7. In step 8, it is determined whether or not the tip of the probe has reached the glass substrate surface by the displacement of ΔZ. If it has not yet reached that position, the process returns to step 4 to repeat the electrochemical processing. When the tip of the probe reaches the glass substrate, the black defect has already been removed, and the processing ends here. In step 9, the processed sample surface is observed by the AFM function, and it is confirmed that the black defect has been corrected and removed. The black defect correcting operation according to the method of the present invention is completed through the above steps.

  Next, the black defect correction procedure of the present invention will be described with reference to the flowchart shown in FIG. First, in step 1, the defect position on the mask surface is grasped. A microscope image is obtained by the observation function of the AFM, and the position information of the defective portion is stored. The defect is, for example, a black defect adjacent to a normal pattern as schematically shown in the upper plan view of FIG. In step 2, a resist film is applied to the entire mask surface as shown in the upper side view of FIG. In this case, the resist material needs to be insulating. In step 3, as shown in the middle part of FIG. 8, the AFM probe is moved to the defect position and scanned in accordance with the defect area, and the resist film in the defect area to be processed is scratched, that is, mechanically scratched and removed. The resulting state is shown in the lower part of FIG. The AFM probe is controlled to drive the sample stage based on the previous defect position information, and the position of the probe tip is aligned with the defect. As shown schematically in the figure, the exposed region should be slightly narrower than the defective region. There are methods for removing the resist film, such as etching using a focused ion beam and electron exposure using an electron beam. In that case, a focused ion beam device or an electron beam device must be prepared separately. In the present invention, all processes can be processed only by an electrochemical AFM apparatus.

  In step 4, the defect is corrected and processed by the electrochemical reaction of the electrochemical AFM apparatus in the processing cell containing the electrolytic solution. First, based on the previous defect position information, the electrochemical AFM probe is driven and controlled above the defect position. Then, since the surface of the black defect portion is exposed in the previous process, as shown in FIG. 9, the surface of the black defect and the tip of the probe face each other at a close distance through the electrolytic solution. In order to concentrate the electrochemical reaction locally, the diameter of the counter electrode (the conductive member at the tip of the probe), the distance between the black defect surface and the tip of the probe, and how to apply the charge are important factors. In the present invention, a probe for electrochemical AFM is used in which the base is an insulating member and only the tip has a conductive structure and the tip is sharpened. Further, the distance is measured by detecting a tunnel current in a state where a bias voltage is applied between both electrodes, and the separation distance is set to the optimum closest distance by performing Z-direction control or the like.

The present invention is characterized in that this electrochemical reaction is caused only at the defective portion, and the other region is covered with a resist film. Since this resist film is insulative, an electrochemical reaction does not occur in that portion, and a local reaction occurs between the black defect surface and the probe tip electrode. In step 5, the distance between the two is set to an appropriate close distance and a pulse current or pulse voltage is applied. The reason why the pulse is used without using a constant current or a constant voltage is that the electric double layer formed on the probe tip electrode surface does not spread over the whole but concentrates on the tip, thereby narrowing the reaction region. In step 6, the black defect portion dissolves in the electrolytic solution by an electrochemical reaction, and the form at that time is conically shaped as shown in FIG. As described above, the electrochemical reaction is
Black defect surface _{^{Cr → Cr 2 + + 2e -}} → Cr 3 + + 3e -
Probe side electrode 2H + + 2e ⁻ → H ₂ ↑
Therefore, the chromium in the black defect portion is ionized and dissolved in the electrolyte, and water is decomposed at the probe side electrode to generate hydrogen gas.

  In Step 7, it is confirmed whether or not the conical hole has reached the glass substrate. If not, the process proceeds to Step 8 where the probe is displaced in the Z direction by the depth dissolved by one pulse process, Returning to Step 5, the operations up to Step 6 are repeated. As shown in the partial diagram in the lower right circle of FIG. 10, the melting state at this time is such that the defective portion is melted in a conical shape, and the conical tip reaches the glass substrate surface by several repeated reactions. Then, the melting proceeds rapidly so as to push open the glass surface of the hole bottom, and the edge of the pattern is sharply finished. This phenomenon is a remarkable phenomenon in the method of the present invention in which a resist coating is applied. Finishing the pattern with sharp edges means that the boundary is sharp as a photomask, which is a very desirable phenomenon. Incidentally, when this angle was measured, it was about 85 °. It is understood that the reason why the edge stands when the resist film is applied is that the normal pattern region is covered with the resist, so that the electrochemical reaction is completely suppressed without contact with the electrolytic solution. The Since the potential to the defective portion is supplied via the normal pattern, it is preferable to start the processing from the outer portion not in contact with the normal pattern in the case of a large black defect having a wide defective portion area. This is because if the black defect is separated from the normal pattern and becomes an isolated form, charge supply becomes troublesome.

  When the glass substrate is exposed, the correction process is finished, and in step 9, the resist film is removed to expose the entire mask surface. It is possible to confirm that the black defect has been removed by detecting the image of the concavo-convex shape with the original AFM function and imaging the processed mask.

  In addition, the present invention started as an object to eliminate various effects caused by irradiation of an ion beam used for defect correction in the tendency of a finer photomask and a shorter wavelength of a lithography light source as described above. For that purpose, it is basically sufficient to correct a defect without using a focused ion beam, but instead, a method capable of accurately and efficiently executing fine processing must be presented. That is, it is required to be a technique that can remove black defects of the mask relatively quickly and without damaging the surrounding glass substrate.

  In this situation, the present applicant has conceived that the black defect is corrected by an electrochemical reaction, and the electrode facing the defect portion is caused to cause an electrochemical reaction only in a minute defect portion. Research has been conducted on the use of atomic force microscope (AFM) probes. In order to form a finer electrode in the process, the base of the probe is made of an insulator, and only the tip of the probe is made of a conductive material to form a fine electrode. Using the black defect as one electrode, the fine electrode at the tip of the probe is opposed to the optimum close distance through the electrolyte, and a predetermined current or voltage is applied to dissolve the black defect in the electrolyte by an electrochemical reaction. It is something to be made. In this specification, this probe is referred to as an electrochemical AFM probe. In this series of studies, the present applicant has applied a resist (insulating) film over the entire mask surface to remove only black defects by an electrochemical reaction without affecting the normal pattern of the mask to be processed. After that, the method is effective in which the surface is exposed except for the resist of the defective portion, the probe for electrochemical AFM is positioned at the position of the defective portion, and the black defect is removed by an electrochemical reaction. The knowledge that it is. In short, a normal pattern or a region of a glass substrate is protected by being covered with a resist film, and an electrochemical reaction is caused only by a defective portion whose surface is exposed.

  Next, according to the flowchart shown in FIG. 11, a deformation procedure for black defect correction according to the present invention will be described. First, in step 1, the defect position on the mask surface is grasped. A microscope image is obtained by an observation function of a scanning electron microscope (SEM), a scanning ion microscope (SIM), or a scanning AFM, and positional information of a defective portion is stored. The defect is, for example, a black defect adjacent to a normal pattern as schematically shown in the upper plan view of FIG. In step 2, a resist film is applied to the entire mask surface as shown in the upper side sectional view of FIG. In this case, the resist material must be insulative, and an electron beam resist is used when an electron beam is used. In step 3, a focused charged particle beam is irradiated as shown in the middle part of FIG. 12, and the resist film in the defect region to be processed is removed as shown in the lower part of FIG. A focused ion beam or electron beam is used as the focused charged particle beam, and the sample stage is driven and controlled based on the previous defect position information with respect to one of the lens barrels, and the position of the beam irradiation is aligned with the defect portion. To do. The resist film at the defective part is removed by beam irradiation. When focused ion beam is used, sputter etching or gas assisted etching is used. When electron beam is used, the resist is exposed to electron beam and developed and removed. The surface of the black defect is exposed by gas assisted etching. As shown schematically in the figure, the exposed region should be slightly narrower than the defective region. The work at this time is a work in the vacuum chamber of the charged particle beam apparatus.

  In step 4, the sample is transferred from the vacuum chamber into the processing cell of the electrochemical AFM apparatus, and defect correction processing is executed. First, based on the previous defect position information, the electrochemical AFM probe is driven and controlled above the defect position. Then, since the surface of the black defect portion is exposed in the previous process, as shown in FIG. 9, the surface of the black defect and the tip of the probe face each other at a close distance through the electrolytic solution. In order to concentrate the electrochemical reaction locally, the diameter of the counter electrode (the conductive member at the tip of the probe), the distance between the black defect surface and the tip of the probe, and how to apply the charge are important factors. In the present invention, a probe for electrochemical AFM is used in which the base is an insulating member and only the tip has a conductive structure and the tip is sharpened. Further, the distance is measured by detecting a tunnel current in a state where a bias voltage is applied between both electrodes, and the separation distance is set to the optimum closest distance by performing Z-direction control or the like.

  The present invention is characterized in that this electrochemical reaction is caused only by a defective portion, and therefore other regions are covered with a resist film. Since this resist film is insulative, no electrochemical reaction occurs at that portion, and a local reaction occurs between the black defect surface and the probe tip electrode. In step 5, the distance between the two is set to an appropriate close distance and a pulse current or pulse voltage is applied. The reason why the pulse is used without using a constant current or a constant voltage is that the electric double layer formed on the probe tip electrode surface does not spread over the whole but concentrates on the tip, thereby narrowing the reaction region. In step 6, the black defect portion dissolves in the electrolytic solution by an electrochemical reaction, and the form at that time is conically shaped as shown in FIG. That is, chromium in the black defect portion is ionized and dissolved in the electrolytic solution, and water is decomposed at the probe side electrode to generate hydrogen gas.

  In Step 7, it is confirmed whether or not the conical hole has reached the glass substrate. If not, the process proceeds to Step 8 where the probe is displaced in the Z direction by the depth dissolved by one pulse process, Returning to Step 5, the operations up to Step 6 are repeated. As shown in the partial diagram in the lower right circle of FIG. 10, the melting state at this time is such that the defective portion is melted in a conical shape, and the conical tip reaches the glass substrate surface by several repeated reactions. Then, the melting proceeds rapidly so as to push open the glass surface of the hole bottom, and the edge of the pattern is sharply finished. This phenomenon is a remarkable phenomenon in the method of the present invention in which a resist coating is applied. Finishing the pattern with sharp edges means that the boundary is sharp as a photomask, which is a very desirable phenomenon. Incidentally, when this angle was measured, it was about 85 °. It is understood that the reason why the edge stands when the resist film is applied is that the normal pattern region is covered with the resist, so that the electrochemical reaction is completely suppressed without contact with the electrolytic solution. The Since the potential to the defective portion is supplied via the normal pattern, it is preferable to start the processing from the outer portion not in contact with the normal pattern in the case of a large black defect having a wide defective portion area. This is because if the black defect is separated from the normal pattern and becomes an isolated form, charge supply becomes troublesome.

  When the glass substrate is exposed, the correction process is finished, and in step 9, the resist film is removed to expose the entire mask surface. It is possible to confirm that the black defect has been removed by detecting the image of the concavo-convex shape with the original AFM function and imaging the processed mask.

  In addition, as described above, the present invention researches to eliminate various effects caused by irradiation of an ion beam used for defect correction in the trend of shortening the wavelength of a photomask and the lithography light source as described above. It was. For that purpose, it is basically sufficient to correct a defect without using a focused ion beam, but instead, a method capable of accurately and efficiently executing fine processing must be presented. That is, it is required to be a technique that can remove black defects of the mask relatively quickly and without damaging the surrounding glass substrate. Therefore, it was conceived that a conductive material such as chromium was assumed as the material of the defective portion, and this was removed by an electrochemical method. The reaction that dissolves the defective material in the electrolytic solution by the electrochemical method does not damage the surrounding glass substrate, so it meets the requirements for that point, but the problem is the microstructure It is to realize processing for removing only the defective portion by this method. Since the material of the black defect in the mask is also the material of the mask pattern, if the original mask pattern is removed by this electrochemical method, a new white defect is created, and the defect is not corrected. Considering the current state of photomasks, a local region of 10 to several hundred nanometers must be identified and reacted. In order to realize a local reaction, structural conditions such as the fineness and distance of the electrode facing the defect and the amount of charge applied between the two electrodes are important conditions. Accordingly, the present invention has been conceived to use a probe of a probe microscope as an electrode. The tip is pointed to several to several tens of nanometers, and a conductive probe is used as an electrode. By positioning this thin electrode at a close distance of 1 to 100 nanometers, a desired local reaction can be realized.

  The black defect correction process using this electrochemical reaction does not cause a riverbed phenomenon, and enables the precise processing of fine structures by adopting the above structure as an AFM probe. However, there is a drawback that it takes a lot of time for correction processing as compared with the method using the conventional FIB apparatus. Therefore, in the present invention, it has been conceived that processing of the region where the river bed phenomenon does not occur is performed by FIB etching, and only processing of the remaining portion is performed by this electrochemical reaction. This is the same as the above-mentioned Patent Document 1 in that the region where the river bed phenomenon does not occur is processed by FIB etching. In view of the fact that the river bed phenomenon is caused by the fact that the ion irradiated to the defective part hits the glass substrate surface near where it was repelled or that the ion beam has a normal distribution and its skirt part hits the glass substrate surface in the vicinity. If only the central part excluding the peripheral part of the region is processed, the occurrence of the river bed phenomenon can be avoided. This idea is the same as in Reference 1 above, but in the present invention, the vicinity of the glass substrate is also left in the central portion to be processed. This is because if the glass substrate is etched with FIB, the glass substrate will be damaged. Defects left by FIB processing including this part were removed by electrochemical reaction. Since most of the black defects have already been removed by FIB processing, the time required for this processing is not so much.

  The following correction processing method of the present invention uses a FIB apparatus as a first step, obtains a microscope image of a mask, captures and stores defect position information, and removes the peripheral portion of the defect area by this FIB apparatus. Most of the part is etched. Thereafter, the remaining black defects are electrochemically subjected to electrolytic treatment using the apparatus shown in FIG. 1 as the second stage. Next, the black defect correction procedure will be described with reference to the flowchart shown in FIG. First, in step 1, the defect position on the mask surface is grasped. A microscope image is obtained by an observation function of a scanning ion microscope (SIM), and position information of a defective portion is stored. The defect is, for example, a black defect adjacent to a normal pattern as schematically shown in the upper plan view and the side sectional view of FIG. In step 2, a focused ion beam (FIB) is irradiated to the defect area as shown in the middle part of FIG. 14 to remove the black defect by etching. In this case, it is important that the irradiation region avoids the peripheral portion of the defect region and leaves the portion near the glass substrate not to be etched in the defect central region to be irradiated. The reason for not irradiating the peripheral edge with FIB is to avoid the river bed phenomenon, and the reason for leaving the vicinity of the glass substrate is to prevent the glass substrate from being damaged by the FIB. As an etching method, sputter etching or gas assist etching can be used. The above operation is a first stage process performed by the FIB apparatus.

  In step 3, the mask, which is a sample to be processed, is transferred to an electrolytic processing apparatus (hereinafter referred to as an electrochemical AFM apparatus) that performs processing by an electrochemical reaction, and the subsequent second stage processing is executed. In step 3, as shown in the lower part of FIG. 14, the tip of the electrochemical AFM probe is moved to the XY two-dimensional position of the peripheral edge of the black defect without performing the FIB irradiation in the previous step 2. This position is positioned farthest from the normal pattern. This is because it becomes difficult to supply charges when this portion becomes an isolated region by processing. Since the distance between the black defect and the tip electrode at the time of electrochemical machining affects the region where the electrochemical reaction occurs, it is important to set it to an appropriate close distance. In step 4, an appropriate close distance is set. In the present invention, it is appropriate to set a Z-direction position while measuring a tunnel current by applying a bias voltage between the two. In step 5, a predetermined current or a predetermined voltage pulse is applied between the determined positions, and the remaining black defects are dissolved in the electrolytic solution by an electrochemical reaction. The reason why the pulse is used without using a constant current or a constant voltage is that the electric double layer formed on the probe tip electrode surface does not spread over the whole but concentrates on the tip, thereby narrowing the reaction region. Electrochemical machining of the black defect left in step 6 is executed, and the chromium in the black defect part is ionized and dissolved in the electrolytic solution, and water is decomposed at the probe side electrode to generate hydrogen gas. If the defect area is wide, steps 5 and 6 are repeated while driving the PZT scanner 7 and raster scanning the stylus 1 in the XY direction in a direction gradually approaching the normal pattern.

  In Step 7, it is confirmed whether or not the black defect has been removed and the glass substrate has been reached. If not, the process proceeds to Step 8 where the probe is displaced in the Z direction by the depth dissolved by one pulse process, Returning to step 5, the operations up to step 6 are repeated. In this case, the periphery of the defect region is melted in a V shape, and the V-shaped tip reaches the glass substrate surface by several repeated reactions. The black defect left at the bottom of the hole at the center is rapidly dissolved so as to push open the glass surface when the layer is as thin as several nanometers, but if a certain thickness remains, the probe 1 is rastered. Dissolves in the process of scanning. FIG. 15 schematically shows where the black defects are dissolved and disappeared cleanly. In step 9, the AFM observation function is used as a third stage, and the mask surface is scanned to take a surface shape image to confirm that the black defect has been corrected and removed. Thus, a series of operations according to the present invention is completed.

  The apparatus for carrying out the defect correcting method of the present invention is an FIB apparatus that performs the first stage, but basically there is no significant difference from the conventional FIB apparatus for mask repair. However, based on the defect position information grasped by this apparatus, the peripheral area of the defect area is avoided and the FIB is irradiated, and the defect central part area to be irradiated is also operated so as not to etch the vicinity of the glass substrate. It is necessary to have a function of transmitting information to the electrochemical AFM apparatus that performs the second stage work. The former can be dealt with by preparing software for executing the calculation operation and the drive control based on the result, and the latter can be controlled by providing an export / import function between the control units of the FIB apparatus and the electrochemical AFM apparatus. This can be handled by adopting a personal computer form common to both devices as a unit.

  Regarding the electrochemical AFM apparatus for performing the second stage operation, as a basic configuration, an AFM probe having a tip portion as an electrode, a processing cell for storing an electrolyte and a mask as a sample, the tip portion of the probe and the mask And a power source for applying a predetermined current or a predetermined voltage between the surface and a mechanism for moving the position of the tip of the probe in the X, Y, and Z directions, and a mask based on defect position information obtained by the FIB apparatus. It is necessary to have a processing function to remove black defects by electrochemical reaction. And in order to implement | achieve fine electrolytic processing, what employ | adopted the AFM probe which formed only the front-end | tip part with the sharp electrically conductive material as an electrode, and comprised the other part with the insulator. In such a probe structure, the probe is formed of a conductive material, and the tip other than its tip is covered with an insulator, or a thin conductive wire is inserted into an insulating capillary, and the tip is exposed to sharpen it. It can be produced by a technique.

  The power source connected between the tip of the probe and the mask surface can supply a bias voltage and a constant current or constant voltage pulse. By supplying the bias voltage, the probe and the mask black defect By measuring the tunnel current generated between them, it is possible to measure and set an appropriate close distance when an electrochemical reaction occurs. In addition to the function as an AFM, an STM function can be provided. Further, by providing a function of supplying a pulse of a predetermined current or a predetermined voltage, it is possible to locally limit the electrochemical reaction region as described above.

  Now, as described above, the present applicant has studied to remove various effects caused by irradiation of ion beams used for defect correction in the trend of short-wavelengths of photomasks and lithography light sources as described above. Has advanced. As a material for the defect portion, a conductive substance such as chromium was assumed, and the inventors came up with the idea of removing this by an electrochemical method. It is to realize a process for removing only the defective portion having a fine structure by this method. Considering the current state of photomasks, a local region of 10 to several hundred nanometers must be identified and reacted. In order to cause the electrochemical reaction to be locally limited, the fineness, distance and charge amount of the electrode facing the defect are important conditions. In order to realize a local reaction that does not affect the normal mask pattern, it is necessary to insulate the part other than the most advanced part of the probe of the sharp probe microscope. That is, the present invention described below is a technical idea of how to reduce the exposed area of the probe tip serving as the counter electrode and realize sharpening.

  This electrolytic processing uses the above-mentioned apparatus, and as a first step, obtains the driving position information of the PZT scanner 7 and the displacement information of the cantilever 2 detected by the optical displacement detector 5 and uses the observation function as an AFM on the sample surface. The black defect position is detected and specified. The defect position information obtained from the observation result is sent from the observation computer to the processing computer, and black defect correction is executed as the second stage. First, the PZT scanner 7 is driven and controlled based on the previous defect position information so that the probe 1 is positioned at the black defect portion. The processing galvanostat 11 is operated in a state where the defect region and the tip of the probe 1 are opposed to each other, and between the conductive mask material and the probe tip having conductivity opposed to each other through the electrolytic solution. A voltage is applied to cause an electrochemical reaction to dissolve black defects in the electrolyte. This electrolytic solution is not particularly limited, but avoids those that are strong in acid or alkali and cause a chemical reaction with the sample. Since electrochemical processing is performed on a fine black defect on a mask, the probe 1 serving as a processing electrode has a fine electrode structure, and the distance from the black defect serving as a counter electrode is also an appropriate close distance. It becomes important. The Z-axis stage 6 is controlled so as to be positioned at an appropriate close distance, and the Z-direction position of the processing electrode holder 3 is adjusted. In the present invention, a region where an electrochemical reaction is caused by a fine electrode structure (tip diameter of several to several tens of nanometers) and an appropriate close distance (1 to several hundred nanometers) is locally (ten to ten to several nanometers). (Several hundred nanometers). As a result, it is possible to realize precise processing that targets only the black defect portion that needs to be removed. This reaction is continued until the glass surface is exposed. Unlike ion beam processing, even if the glass surface is exposed, the portion does not react, so the glass substrate is not damaged. As the final third step, it is confirmed whether the correction is completed by the original observation function of AFM. This is basically the same as the first stage observation operation. It will be confirmed whether the defect discovered initially is removed by this observation.

  Next, a method for producing a probe for electrochemical AFM according to the present invention will be described in accordance with the procedure with reference to the flowchart shown in FIG.

  Step 1: An SOI wafer substrate having an insulating layer sandwiched between the upper and lower layers as a material and a silicon layer sandwiched between the upper and lower sides is used, and the surface is mask-patterned with silicon dioxide (SiO2) as shown in FIG.

  Step 2: A portion of silicon not covered with a mask is dry-etched by a reactive ion etching (RIE) method using plasma ions on a silicon substrate subjected to mask patterning. Since this processing is RIE using SF6 gas, the etching progresses in the depth direction of the silicon layer, and at the same time, the lower part of the mask is under-etched. As a result, as shown in FIG. The remaining silicon is left in a steep columnar shape. In the present invention, this portion is used as a probe portion, and a portion etched into a wide and thin layer is used as a cantilever. In this step, the basic structure is roughly processed.

Step 3: When the dry etching process is completed, the SiO ₂ mask is removed as shown in FIG. This is done by conventional chemical processing.

Step 4: Next, this rough-processed silicon is subjected to a thermal oxidation treatment. Although silicon has gradually become SiO ₂ oxide from the surface it is possible to repeatedly advanced in being heated as shown in d of FIG. 17, the silicon area which is not oxidized in the probe portion protruding columnar shape core It becomes thinner in the part, and the tip part remains sharpened. This sharpening process realizes the formation of a probe having a tip diameter of nanometer order required as a probe for electrochemical AFM, which is an important point of the present invention.

  Step 5: Subsequently, when the oxidized silicon layer is removed by chemical treatment, the silicon remaining in the core portion appears in a sharpened probe shape as shown in FIG.

Step 6: A large number of silicon probes subjected to the above processing are formed in a matrix arrangement on a silicon wafer, and the individual silicon probes formed in this step are separated and processed. The processing of the silicon at the boundary is exposed on coating the resist film by conventional means for etching away to independently separated on the insulating layer SiO ₂ as shown in f in Figure 17. With the above process, the processing of the silicon serving as the basic structure of the probe is completed.

  Next, an electrode structure at the tip of the probe necessary as a probe for electrochemical AFM and a lead structure for supplying charges to the electrode are formed.

Step 7: First, as shown in FIG. 17g, a resist is applied to the boundary portion of each independently separated silicon probe where the insulating layer SiO ₂ is exposed.

  Step 8: A metal coating is applied to the silicon surface including the probe portion in a state in which each probe is surrounded by a resist. For example, platinum Pt is used as the metal material. However, since the affinity with silicon is not good, first, a titanium Ti thin film is coated as an S8A underlayer, and a platinum Pt thin film suitable as an S8B electrode material or a lead member is formed thereon. Coating. The state of the probe at this time is that the silicon surface exposed on the surface and the resist surface are coated with metal as shown in a cross-sectional view in FIG.

  Step 9: When the resist material around each probe is removed when the metal thin film is coated, the metal thin film is coated on the entire surface of the probe side of the silicon probe including the probe portion as shown in i of FIG. It has become.

Step 10: A SiO ₂ thin film as an insulating film is formed on the entire surface of the probe in this state by a chemical vapor deposition (CVD) technique. The state at this time is shown in a sectional view in FIG.

  Step 11: Following the formation of the insulating film, a resist film is applied to the upper layer, and patterning is performed to form a contact hole in the vicinity of the end opposite to the partial probe serving as a cantilever. This contact hole is a hole for connecting an electric power supply lead to the tip of the probe that becomes an electrode for electrochemical AFM and an external terminal. The state at this time is shown by k in FIG.

Step 12: In order to realize a structure in which only a minute region at the tip of the probe is exposed as a metal electrode, first, a resist film covering the tip of the probe is applied with O ₂ plasma as shown in FIG. Use to remove.

Step 13: Following the removal of the resist film at the tip of the probe, the insulating film SiO ₂ in the region of the tip of the probe and the contact hole is removed by carbon fluoride (CF ₄ or C ₂ F ₆ ) plasma. The configuration at this time is shown in FIG.

  Step 14: When the resist that is the uppermost layer and covers the probe is removed, the probe is entirely covered with an insulating layer as shown in FIG. The insulating layer is removed only in the region, and the metal thin film is exposed. The above is the step of forming a microelectrode at the tip of the probe as an electrochemical AFM probe.

  Step 15: Finally, in order to form the back surface portion of the probe, the unnecessary silicon layer and insulating layer on the back surface are removed. For this purpose, first, a mask as shown in FIG. 18O is formed for silicon etching.

  Step 16: Subsequent to mask formation, unnecessary portions of silicon are removed from the back surface by alkali etching. The silicon is left by the mask in the boundary area between the back surface end portion on the opposite side to the probe portion of the cantilever which becomes a holding portion when the probe is attached to the AFM and the adjacent probe which is separated and independent. The form at this time is shown by p in FIG.

Step 17: Next etched using hydrofluoric acid to remove the insulating layer SiO _2. The insulating layer SiO ₂ is individual probes by a buried oxide film of the SOI wafer substrate is a material the insulating film is removed is separated into pieces. The probe produced by the above steps is shown in q of FIG. On the probe-side surface, the conductive material is exposed only at the sharpened tip of the probe and the contact hole provided at the base of the cantilever, the other is covered with an insulating material, and the back is a silicon layer. It is in an exposed state.

  The AFM probe generally forms a mirror on the back surface of the cantilever to detect displacement. Since this probe is not only used for an electrochemical reaction but also has a function as a normal AFM, it is preferable in terms of displacement detection to form a mirror. However, in order to locally limit the electrochemical reaction region, it is not preferable to dispose a metal film in the vicinity of the probe. Therefore, in the case of the present invention, a silicon surface is used as a mirror surface without forming a metal mirror surface on the back surface of the cantilever near the probe portion.

Next, FIG. 19 shows the modified fabrication method described above as a fabrication method of the probe for electrochemical AFM of the present invention. The process from step 1 to mask patterning to formation of the insulating film at step 10 is the same as that shown in the flowchart of FIG. In step 11, the plasma etching is not used for removing the insulating film at the tip of the probe and the contact hole region, but the removal is performed by sputter etching or gas assist etching using a focused ion beam (FIB) apparatus. Is different. That is irradiated while scanning the S11AFIB the pattern area of the contact hole to remove the insulating layer of SiO ₂ that portion. Subsequently, the tip of the S11B probe is irradiated with an ion beam to remove the insulating layer SiO ₂ at that portion. Then, the operation after step 15 in FIG. 16 is executed after step 12 to produce the probe for electrochemical AFM of the present invention.

  The black defect correction processing by the apparatus using the electrochemical AFM probe thus manufactured will be described with reference to FIG. A black defect model to be corrected is shown in a plan view and a sectional view in the upper part of FIG. This is a form in which a pattern material such as chromium is attached to a glass substrate adjacent to a normal pattern. In step 1, the position of the black defect is detected by an ordinary AFM observation function of two-dimensional scanning. In step 2, the PZT scanner 7 is driven based on the defect position information obtained here to move the probe 1 above the defect position. This state is shown in the middle part of FIG. In step 3, the Z-axis stage is driven to position the probe 1 so that the distance between the tip of the probe 1 and the sample surface is an appropriate close distance. For example, a probe microscope that has been functioning as an AFM is caused to function as an STM. That is, the probe 1 is positioned by driving the Z-axis stage so that the separation distance between the two becomes an appropriate close distance while measuring the tunnel current flowing between the tip of the probe 1 and the sample surface. In step 4, the probe 1 is caused to function as a machining electrode. Therefore, a predetermined current or voltage is applied from the power source 11 ′ between the tip electrode portion of the probe 1 and the mask. In step 5, a predetermined amount of a mask material in a narrow region centering on the probe tip position is dissolved in the electrolytic solution by an electrochemical reaction. That is, for example, a pulsed current or voltage is applied from the power source 11 'between the mask and the electrode at the tip of the probe, and a local electrochemical reaction occurs on the defective portion. In step 6, the probe 1 is scanned, and the operations of steps 4 and 5 are executed at each point of all defective areas.

  When the processing at one point in all the defect areas is completed, the Z stage 6 is driven by the amount ΔZ corresponding to the thickness of the mask material removed by one processing in Step 7 to move the probe 1 downward. Then, the defect surface and the tip position of the probe are set to an appropriate close distance again. The operation mode at this time, that is, the probe scanning is schematically shown in the lower part of FIG. In response to a command from the control means (AFM controller 12), the Z-axis stage is displaced in the Z direction by ΔZ. The amount of displacement is detected by a displacement detector and fed back to the control means. This position control mechanism is the same for positioning in the X and Y directions by the PZT scanner 7. In step 8, it is determined whether or not the tip of the probe has reached the glass substrate surface by a displacement of ΔZ. If the probe tip has not yet reached that position, the process returns to step 4 and the electrochemical processing is repeated. When the tip of the probe reaches the glass substrate, the black defect has already been removed, and the processing ends here. In step 9, the processed sample surface is observed by the AFM function, and it is confirmed that the black defect has been corrected and removed. The black defect correcting operation according to the method of the present invention is completed through the above steps.

  In addition, as described above, the present applicant has studied to remove various effects caused by irradiation of ion beams used for defect correction in the trend of short-wavelength photomasks and lithography light sources as described above. did. As a material of the defect portion, a conductive substance such as chromium oxide was assumed, and the inventors have come up with the idea of removing this by an electrochemical method. It is to realize a process for removing only the defective portion having a fine structure by this method. Considering the current state of photomasks, a local region of 10 to several hundred nanometers must be identified and reacted. In order to cause the electrochemical reaction to be locally limited, the fineness, distance and charge amount of the electrode facing the defect are important conditions, and the local reaction that does not affect the normal mask pattern. In order to realize the above, it is necessary to further sharpen the probe of the sharp probe microscope. That is, the present invention is a technical idea of how to realize the sharpening of the probe tip serving as the counter electrode.

  The following electrolytic processing uses the above-described apparatus, and obtains the driving position information of the PZT scanner 7 and the displacement information of the cantilever 2 detected by the optical displacement detector 5 as the first step, and the sample surface with the observation function as the AFM The upper black defect position is detected and specified. The defect position information obtained from the observation result is accumulated in the storage means in the computer 10, and the second stage black defect correction is executed based on the accumulated information. First, the PZT scanner 7 is driven and controlled based on the previous defect position information so that the probe 1 is positioned at the black defect portion. The processing galvanostat 11 is operated in a state where the defect region and the tip of the probe 1 are opposed to each other, and between the conductive mask material and the probe tip having conductivity opposed to each other through the electrolytic solution. A voltage is applied to cause an electrochemical reaction to dissolve black defects in the electrolyte. This electrolytic solution is not particularly limited, but avoids those that are strong in acid or alkali and cause a chemical reaction with the sample. Since electrochemical processing is performed on a fine black defect on a mask, the probe 1 serving as a processing electrode has a fine electrode structure, and the distance from the black defect serving as a counter electrode is also an appropriate close distance. It becomes important. The Z-axis stage 6 is controlled so as to be positioned at an appropriate close distance, and the Z-direction position of the processing electrode holder 3 is adjusted. In the present invention, a region in which an electrochemical reaction is caused by a fine electrode structure (tip diameter of several to several tens of nanometers) and an appropriate close distance (1 to several hundred nanometers) is locally (ten to ten to several nanometers). (Several hundred nanometers). As a result, it is possible to realize precise processing that targets only the black defect portion that needs to be removed. This reaction is continued until the glass surface is exposed. However, unlike the ion beam processing, even if the glass surface is exposed, the portion does not react, so that the glass substrate is not damaged. As the final third step, it is confirmed whether the correction is completed by the original observation function of AFM. This is basically the same as the observation operation in the first stage, but it is confirmed whether or not the defect originally discovered is removed by this observation. At that time, it is not always necessary to obtain an image of the entire mask, and it may be confirmed by local scanning only in the vicinity of the defect area detected at the beginning.

  Next, a method for preparing a probe for electrochemical AFM according to the present invention, which is different from the above, will be described in accordance with the procedure.

  Step 1. A metal wire such as tungsten: W or platinum: Pt with a diameter of 50 μm is prepared by reducing the diameter by electropolishing to a diameter of about 10 μm.

  Step 2. A hollow glass capillary (φout is 120 μm, φin is 75 μm) as shown in FIG. 21a is sharpened by heating with laser irradiation as shown in b, and the tip as shown in c Two glass capillaries with sharpening are obtained. The right side of the figure shows a sketch of a microscope image. The original photomicrograph was taken as a sketch because it was not halftone when converted to a binary image. The bottom is an enlarged view of the tip.

  Step 3. The tip of the glass capillary thus obtained is irradiated with laser light from one side as shown in FIG. 22a, and heating and cooling are repeated. As a result, the tip of the glass capillary is bent in one direction as shown in FIG. The microscopic image sketch is shown on the right side. The sharpened tip portion is a probe portion and the straight tube portion is a cantilever to constitute an AFM probe.

  Step 4. The metal wire prepared and prepared in Step 1 is passed through a glass capillary having a sharpened tip as shown in FIG.

  Step 5. With the metal wire inserted in the glass capillary, the tip and end portions of the glass capillary are sealed with an epoxy resin.

  Step 6. The tip of the probe after the sealing step is electropolished to sharpen the exposed end of the metal wire. A microscope image sketch of the tip is shown in the upper part of FIG. The exposed tip portion of the metal serves as a counter electrode in the electrochemical reaction.

  The above process is to produce a configuration as an AFM probe responsible for the electrochemical processing function according to the present invention. Subsequently, since the AFM has the original displacement detection function, a mirror is formed on the back surface of the cantilever. The method will be explained step by step.

  Step 7. The glass probe that has been processed up to step 6 is dipped in molten Apiezon wax to perform dip coating.

  Step 8. A part of the back surface of the probe to be a cantilever with dip coating is mechanically polished to form a flat mirror surface. By this processing, the coating of the apizon wax is removed only in this portion. The situation at this time is shown on the left side of FIG. 24, and the microscope image sketch of the back side of the probe on which the mirror surface is formed is shown on the right side. The lower part is a partially enlarged view.

  Step 9. A thin film of titanium Ti (t75 nm) / gold Au (t50 nm) is formed by sputtering around the flat mirror surface on the back surface of the probe, and the mirror surface is coated. The microscope image sketch at that time is shown in the upper right part of FIG.

  Step 10. The probe that has completed step 9 is immersed in a chloroform solution to dissolve the apiezone wax. By this treatment, the thin film sputtered on the surface other than the mirror surface can be removed together with Apiezon wax. This is to prevent the laser light from being reflected in a region other than the flat mirror surface and causing noise in optical displacement detection. A microscope image sketch of the probe subjected to this processing is shown in the lower right part of FIG.

  A processing method similar to the above steps 2, 3 and steps 8, 9 is also disclosed in Patent Document 2 “Scanning near-field atomic force microscope, probe used in the microscope, and probe manufacturing method thereof”. This is basically a combination of the AFM function and the optical near-field microscope function, and the glass material used for the probe is not a capillary as in the present invention but a core and cladding. It is an optical fiber consisting of: similar to the work method of sharpening the rod-shaped glass material and bending the tip, and the process for forming the mirror surface on the back of the cantilever as a function of AFM is only partially similar belongs to.

  Through the above steps, the electrochemical AFM probe according to the present invention as shown in FIG. 26 is produced. The tip portion of the glass capillary is bent and sharpened, and this portion is a probe portion of the probe microscope, and the straight tube portion of the glass capillary is a cantilever portion. A fine metal wire such as platinum is penetrated into the capillary, and the tip diameter of the fine metal wire exposed on the probe side is sharpened to the nanometer order to constitute the tip of the probe. The base of the probe is made of insulating glass, and the exposed tip of this fine metal wire is the tip of the probe. Therefore, an extremely small electrode can be formed, and the electrochemical reaction is locally performed. It is effective in waking up. The probe for electrochemical AFM according to the present invention has an electrochemical processing function in addition to an observation function and a distance detection function as an AFM or a scanning tunneling microscope (STM). That is, when the tip receives an atomic force acting between the sample surface and the sample surface, the shape of the sample surface can be detected, and a bias voltage is applied across the tip facing the sample surface at a close distance. The distance between the two can be accurately detected from the flowing tunnel current, and it acts as an electrode for electrolytic processing by applying a voltage with the electrolyte interposed between the sample surface and this tip. It is possible to cause an electrochemical reaction to a limited extent.

  In addition, a mirror surface is formed on the back surface of the glass capillary straight tube portion serving as a cantilever, and constitutes a part of a displacement detection mechanism as an AFM.

  The black defect correction processing by the apparatus using the electrochemical AFM probe thus manufactured will be described with reference to FIG. A black defect model to be corrected is shown in a plan view and a sectional view in the upper part of FIG. This is a form in which a pattern material such as Cr is attached to a glass substrate adjacent to a normal pattern. In step 1, the position of the black defect is detected by an ordinary AFM observation function of two-dimensional scanning. In step 2, the PZT scanner 7 is driven based on the defect position information obtained here to move the probe 1 above the defect position. This state is shown in the middle part of FIG. In step 3, the Z-axis stage is driven to position the probe 1 so that the distance between the tip of the probe 1 and the sample surface is an appropriate close distance. For example, the probe microscope that has been functioning as an AFM is functioned as an STM, and the probe 1 is positioned by driving the Z-axis stage so that the separation distance between the two becomes an appropriate close distance while measuring the tunnel current flowing between them. To do. In step 4, the probe 1 is caused to function as a machining electrode. Therefore, a predetermined current or voltage is applied from the power source 11 ′ between the tip electrode portion of the probe 1 and the mask. In step 5, a predetermined amount of a mask material in a narrow region centering on the probe tip position is dissolved in the electrolytic solution by an electrochemical reaction. That is, for example, a pulsed current or voltage is applied from the power source 11 'between the mask and the electrode at the tip of the probe, and a local electrochemical reaction occurs on the defective portion. In step 6, the probe 1 is scanned, and the operations of steps 4 and 5 are executed at each point of all defective areas.

  When the processing at one point in all the defect areas is completed, the Z stage 6 is driven by the amount ΔZ corresponding to the thickness of the mask material removed by one processing in Step 7 to move the probe 1 downward. Then, the defect surface and the tip position of the probe are set to an appropriate close distance again. The operation mode at this time, that is, the probe scanning is schematically shown in the lower part of FIG. In response to a command from the control means (AFM controller 12), the Z-axis stage is displaced in the Z direction by ΔZ. The amount of displacement is detected by a displacement detector and fed back to the control means. This position control mechanism is the same for positioning in the X and Y directions by the PZT scanner 7. In step 8, it is determined whether or not the tip of the probe has reached the glass substrate surface by the displacement of ΔZ. If it has not yet reached that position, the process returns to step 4 to repeat the electrochemical processing. When the tip of the probe reaches the glass substrate, the black defect has already been removed, and the processing ends here. In step 9, the processed sample surface is observed by the AFM function, and it is confirmed that the black defect has been corrected and removed. The black defect correcting operation according to the method of the present invention is completed through the above steps.

It is a figure which shows the basic composition of the apparatus which performs the method of mask black defect correction of this invention. It is a flowchart explaining the action | operation of the Example of this invention. It is a figure explaining the structure of the mask black defect used as the object of the present invention. It is a figure which shows the form which the apparatus of this invention measures the distance between a probe tip and a black defect by a STM function. It is a figure which shows the form which the apparatus of this invention raise | generates an electrochemical reaction by a probe tip part and a black defect becoming both electrodes. It is a figure explaining the mechanism which moves a probe to a X, Y, Z direction in the correction process of this invention. It is a flowchart explaining the action | operation of the Example of this invention. The upper plan view is a diagram for explaining the structure of the mask black defect that is the subject of the present invention, the upper side sectional view is a diagram showing a state where a resist film is applied, and the middle stage is a state in which the resist film on the surface of the defective portion is scratched by a probe. The lower part is a figure which shows a mode that the resist film of the defective part was removed. It is a figure which shows the form which positions the electrode for electrochemical AFM above a black defect position, and raise | generates an electrochemical reaction. It is a figure which shows the form which a defect part melt | dissolves by the electrochemical reaction in which the apparatus of this invention becomes a probe tip part and a black defect become both electrodes. It is a flowchart explaining the action | operation of this invention. The upper plan view is a diagram for explaining the structure of the mask black defect that is the subject of the present invention, the upper side sectional view is a view showing a state where a resist film is applied, and the middle stage is a view showing a state in which a charged particle beam is irradiated to the defective portion. The lower part is a view showing a state where the resist film in the defective part is removed. It is a flowchart explaining the action | operation of the Example of this invention. It is a figure explaining the structure of the mask black defect used as the object of this invention, and its correction form. It is a figure which shows the state from which the black defect was removed by the process by the probe for electrochemical AFM of this invention. It is a flowchart explaining the process of producing the probe for electrochemical AFM of this invention. It is a figure which shows the form in each process of the first half which produces the probe for electrochemical AFM of this invention. It is a figure which shows the form in each process of the latter half which produces the probe for electrochemical AFM of this invention. It is a flowchart explaining the other Example of the process of producing the probe for electrochemical AFM of this invention. It is a figure explaining the black defect correction process by the micro electrolytic processing apparatus using the probe for electrochemical AFM of this invention. It is a figure which shows the sharpening process form of the glass capillary which is the raw material of the probe of this invention. It is a figure which shows the bending process form of a glass capillary. It is a figure explaining the form which inserts a metal wire in a glass capillary. It is a figure explaining the form which forms the plane used as the mirror surface of a probe. It is a figure explaining the form which coats a metal thin film on the mirror surface of a probe. It is a figure which shows the probe for electrochemical AFM of this invention completed. It is a figure explaining the black defect correction process by the electrolytic processing apparatus using the probe for electrochemical AFM of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AFM probe 2 Cantilever 3 Processing electrode support holder 4 Processing cell 5 Optical displacement detector 6 Z-axis stage 7 PZT scanner 8 Base 9 on which processing cell 4 is placed Reference electrode 10 Computer 11 Processing 12 AFM controller 12
L1 Lead wire from probe electrode L2 Lead wire from sample side electrode L0 Lead wire from reference electrode

Claims (17)

  The step of grasping the position of the black defect portion of the mask with an atomic force microscope, the step of moving the probe of the atomic force microscope above the black defect position, and the probe and the mask black defect portion as both electrodes A mask black defect correction method comprising: a step of removing the black defect by an electrochemical reaction in a state where an electrolytic solution is interposed; and a step of confirming the removal of the black defect by the atomic force microscope.   The step of grasping the position of the defective portion of the mask by the observation function of the AFM, the step of applying an insulating resist film on the mask surface, the step of scratching the resist film of the defective portion with the probe of the AFM, and above the defect position A step of moving a probe of electrochemical AFM, a step of removing the black defect by an electrochemical reaction in a state where the probe and the mask black defect portion are both electrodes and an electrolyte is interposed, and insulation of the mask surface A method for correcting a mask black defect comprising the step of removing a film.   A step of grasping a defect position of a mask by a scanning microscope, a step of applying an insulating resist film on the mask surface, a step of irradiating a charged particle beam to remove the resist film of the defect portion, Moving an electrochemical AFM probe above the defect position; removing the black defect by an electrochemical reaction in a state where the probe and the mask black defect portion are both electrodes and an electrolyte is interposed; and And a method for correcting a mask black defect, comprising: removing an insulating film on the mask surface.   The mask black defect correction method according to claim 3, wherein the scanning microscope for obtaining the defect position information uses any one of an AFM, a scanning ion microscope, and a scanning electron microscope.   The step of grasping the position of the defective part of the mask by the scanning microscope function of the FIB apparatus, the step of irradiating the FIB to the central part of the defective area excluding the peripheral part and etching while leaving the vicinity of the glass substrate, the probe and the mask black defect A method of correcting a mask black defect comprising a step of removing black defects left by an electrochemical reaction in a state where both portions are electrodes and an electrolyte is interposed, and a step of confirming defect portion correction by an atomic force microscope.   6. The method of correcting a mask black defect according to claim 1, wherein a step of measuring a tunnel current flowing between the probe and the black defect and setting an appropriate close distance before the electrochemical reaction is performed. .   Applying a predetermined current or a predetermined voltage between the probe of the atomic force microscope using the tip as an electrode, a processing cell storing a mask as an electrolyte and a sample, and the tip of the probe and the mask surface Equipped with a power source and a mechanism for moving the position of the tip of the probe in the X, Y, and Z directions, and has an observation function as an atomic force microscope and a processing function for removing mask black defects by an electrochemical reaction A mask black defect correcting apparatus characterized by the above.   An AFM probe using only the tip as an electrode, a processing cell that stores an electrolyte and a mask as a sample, a power source that applies a predetermined current or voltage between the probe tip and the mask surface, A function of observing the shape of the X, Y, Z surface of the position of the tip of the probe, and moving the probe to the position based on the defect position information obtained by the observation, A mask black defect correcting device characterized by having a function to remove the mask and a processing function to remove the mask black defect by an electrochemical reaction using the tip electrode of the probe.   The function of mechanically removing the resist film on the defect surface stores the positional information of the defect area obtained by the observation function, determines the resist film removal area based on the stored information, and scans the removal area. 9. The mask black defect correcting device according to claim 8, further comprising a computer that issues a drive signal to a mechanism that moves the position of the needle tip in the X, Y, and Z directions.   An FIB device comprising a sample stage having an FIB column and at least a three-dimensional drive mechanism in a vacuum chamber, an AFM probe having only the tip as an electrode, a processing cell for storing an electrolyte and a mask as a sample, A power source for applying a predetermined current or voltage between the probe tip and the mask surface, and a mechanism for moving the position of the probe tip in the X, Y, and Z directions. A black defect correcting apparatus having an observation function and a processing function for removing mask black defects by an electrochemical reaction.   An electron beam device comprising an electron beam column and a sample stage equipped with at least a three-dimensional drive mechanism in a vacuum chamber, an AFM probe having a tip as an electrode, a processing cell for storing an electrolyte and a mask as a sample And a power source for applying a predetermined current or voltage between the probe tip and the mask surface, and a mechanism for moving the position of the probe tip in the X, Y, and Z directions. And a black defect correcting apparatus characterized by having an observation function and a processing function for removing mask black defects by an electrochemical reaction.   An FIB apparatus having a SIM function for grasping a defect position and an etching function by beam irradiation; an atomic force microscope probe having a tip as an electrode; a processing cell for storing an electrolytic solution and a mask as a sample; A power source for applying a predetermined current or voltage between the probe tip and the mask surface, and a mechanism for moving the position of the probe tip in the X, Y, and Z directions, obtained by the FIB apparatus. A mask black defect correcting apparatus comprising a combination with an electrochemical AFM apparatus having a processing function of removing a mask black defect by an electrochemical reaction based on defect position information. A power source connected between the probe tip and the mask surface can supply a bias voltage and a pulse of a predetermined current or a predetermined voltage, and in addition to a processing function for removing a mask black defect by an electrochemical reaction, 13. The mask black defect correcting apparatus according to claim 7 , further comprising an STM function for measuring and setting an appropriate close distance between the probe and the mask black defect. The mask black defect correcting device according to claim 7, wherein the probe is formed of a conductive material, the surface thereof is covered with an insulating material, and only the tip portion is exposed. The probe is provided in a plate-shaped cantilever formed by dry etching an SOI silicon wafer, and the tip of the probe is sharpened, and a metal thin film is continuous from the surface of the cantilever. The mask correction device according to claim 7, wherein the probe is an electrode having a tip portion coated only with a tip and having a portion excluding the tip portion covered with an insulating layer. The probe is a hollow glass capillary with a sharpened tip and formed into a bowl shape, a metal wire is inserted into the capillary, and the tip of the wire is sharpened to a few hundred nanometers or less. The mask correction device according to claim 7, wherein the mask correction device is a probe using only a portion as an electrode. The mask correction device according to claim 16, wherein the hollow glass capillary has a flat surface processed on the back surface of the curved portion, and the surface of the flat surface is coated with a metal thin film to form a mirror surface.

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