Photomask modification drift correction apparatus and photomask modification drift correction method

Abstract

PURPOSE: To automatically carry out a drift correction of a modification object having a defect on photomask, based on a SEM image of the modification object, in a photomask modification drift correction apparatus and a photomask modification drift correction method.CONSTITUTION: A photomask modification drift correction apparatus includes: a nozzle; a stage; SEM image acquisition means; photomask modification means for repeating a gas jet from a nozzle to and an electronic irradiation onto a modification object having a defect in a pattern on a photomask, and then a suspension of the gas jet and an electronic irradiation after an elapse of prescribed time; drift calculation means for, at the suspension of the gas jet and the electronic irradiation, acquiring a SEM image by the SEM image acquisition means, comparing a plurality of SEM images thus acquired to calculate a drift amount; and correction means for modifying a location for the electronic irradiation or a location of the stage according to the drift amount thus calculated. A modification object having a defect in a photomask receives drift correction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drift correction device and a drift correction method for repairing defects in a photomask. [Background technology]

[0002] Conventionally, mask repair required drift correction marks 74 to correct drift in the photomask position, as shown in (a) of Figure 13, which will be described later. Mask repair equipment includes an electron beam column and an XY stage, which tend to drift in position due to thermal expansion caused by charging due to electron beam irradiation, heat from the gas supply system, or heat generated by the stage motor.

[0003] The time required to repair a single defect can range from a few minutes to several tens of minutes. The minimum line width of cutting-edge photomasks is extremely narrow, measuring several tens of nanometers. Drift on the order of microns can be avoided by using materials that make up the equipment and by making it less susceptible to charging.

[0004] However, the above method alone is insufficient to achieve the positional accuracy of several nanometers required for cutting-edge photomask repair; it is necessary to observe the image of the object to be repaired during the repair and perform drift correction to ensure that only the desired position is repaired.

[0005] In conventional mask repair devices, for example, when etching is performed, xenon fluoride gas, which is an etching gas, is continuously flowed over the photomask, and the drift correction marks are observed and corrected in this state while the etching process is performed.

[0006] The drift correction mark is etched during image observation, and is deformed during the etching process. Therefore, a material that is resistant to etching with xenon fluoride gas is selected and used as the drift correction mark.

[0007] The explanatory diagram of the prior art shown in FIG. 13 will be briefly explained below.

[0008] FIG. 13 shows an explanatory diagram of the prior art.

[0009] FIG. 13(a) shows an example in which a defective correction target 71 and a drift correction mark 74 are provided on a photomask.

[0010] In FIG. 13(a), a repair target 71 is a repair target that has a defect.

[0011] The photomask 73 is a photomask on which the repair target 71 exists.

[0012] The drift correction marks 74 are marks for calculating the drift of the correction target 71. The drift correction marks 74 are, for example, conical in shape, and four of them are used in the case of rotation correction, while only one is used in the case of translation correction.

[0013] Next, the operation will be described with reference to the flowchart in FIG.

[0014] 13(b), S11 deposits / selects drift correction marks. Before correction, a relatively large area of ​​the pattern created on the photomask 73 is selected as the deposition location for the drift correction marks 74, and the drift correction marks 74 are deposited with a diameter of approximately several tens of nanometers.

[0015] In step S12, electron irradiation and gas injection are performed, and the mask is repaired and the drift correction mark 74 is removed while observing the mask by SEM. This is to repair the repair target 71 while simultaneously observing the drift correction mark 74 during the mask repair.

[0016] In step S13, it is determined whether the mask correction is complete. If the result is YES, the process ends. If the result is NO, the process proceeds to step S14.

[0017] In S14, it is determined whether drift exists. If the result is YES, the amount of drift that occurred between the SEM images acquired in S12 is calculated, and if the calculated amount of drift is equal to or greater than a predetermined threshold value (determined by experiment), it is determined whether drift exists. If the result is YES, the process proceeds to S15. If the result is NO, the process returns to S12 and is repeated.

[0018] In step S15, drift correction (electron beam) is performed. Since it was determined in step S14 that drift exists, the electron beam (or stage movement) is corrected to cancel the determined amount of drift. Then, the process returns to step S12.

[0019] As described above, conventional mask repair devices are required to select the formation position of the drift correction mark 74 and to perform the process of forming or removing the drift correction mark 74, which are essentially completely unrelated to the mask repair process, and they also have the potential to degrade the performance of the repaired photomask. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0020] The above-mentioned drift correction mark pattern cannot be arbitrarily placed at any position on the photomask, and therefore requires a skilled worker to manually place it while taking into consideration minimizing the effect on the existing patterns on the photomask.

[0021] In other words, even if the correction pattern (target of correction) is geometrically very simple, the photomask needs to be corrected manually, taking into consideration various factors such as the arrangement and material of the drift correction mark pattern, and there was a problem in that operation by an experienced person was essential. [Means for solving the problem]

[0022] In order to solve the above-mentioned problems, the present invention aims to automatically perform drift correction on a defective repair target on a photomask based on an SEM image (representing a secondary electron image, a backscattered electron image, etc.; the same applies hereinafter) of the repair target, rather than providing a drift correction mark as in the past and performing drift correction on the repair target.

[0023] Therefore, the present invention provides a drift correction device for correcting drift when repairing defects in a photomask, the drift correction device comprising: a nozzle for spraying gas onto the surface of the photomask; a stage for holding the photomask opposite the nozzle; SEM image acquisition means for scanning the photomask while irradiating it with electrons using a narrow beam to detect and amplify the emitted electrons to acquire an SEM image; photomask repair means for repeating the steps of injecting gas from the nozzle and irradiating it with electrons onto a repair target having a pattern defect on the photomask, and then stopping the gas injection after a predetermined time has elapsed and restarting the electron irradiation; drift calculation means for acquiring SEM images by the SEM image acquisition means when gas injection is stopped and electron irradiation is performed, and calculating the amount of drift by comparing the acquired multiple SEM images; and correction means for correcting the electron irradiation position or the stage position based on the calculated drift amount, thereby performing drift correction on the repair target having a defect in the photomask.

[0024] At this time, the electron irradiation in which gas is jetted from the nozzle and electron irradiation is performed, and the electron irradiation in which gas jetting is stopped after a predetermined time has elapsed and electron irradiation is performed, are performed on the same object to be repaired.

[0025] The gas is selected to etch the object to be repaired or to deposit the object to be repaired.

[0026] Also, a gas that eliminates the influence of the etching gas or the deposition gas is injected.

[0027] In addition, gas is injected to neutralize the charge to be corrected.

[0028] Furthermore, when the calculated drift amount is equal to or greater than a predetermined threshold value, the position where electrons are irradiated or the position of the stage is corrected. [Effects of the Invention]

[0029] In the present invention, instead of providing a conventional drift correction mark to correct the drift of a defective photomask to be repaired, the drift of the repair target is corrected based on multiple SEM images of the repair target itself, making it possible to automatically correct drift when repairing a photomask without relying on an expert.

[0030] Furthermore, the object to be repaired can be irradiated with electrons while being sprayed with etching or deposition gas, thereby optionally etching or depositing defects in the photomask and repairing them.

[0031] In addition, the following effects are obtained. 1 In addition to the etching or deposition gas, gases that quickly remove the gas (such as water vapor gas) and gases that remove charges caused by electron irradiation (such as nitrogen gas) can be sprayed, making it possible to quickly stop the etching or deposition, neutralize the charges, and obtain SEM images with a high S / N ratio. Example 1

[0032] Figure 1 shows a configuration diagram of one embodiment of the present invention. This Figure 1 shows the configuration of a photomask repair device used in the present invention, which repairs defects in a pattern formed on a photomask, which is a sample 13. The photomask is irradiated with an electron beam while a gas is injected onto it, and the defect is repaired by etching or deposition within the area reacted to the electron beam. This will be explained in detail below.

[0033] In FIG. 1, an electron gun 1 generates electrons.

[0034] The blanking electrode 2 is a parallel plate to which a high voltage is applied, and passes or blocks the primary electron beam generated by the electron gun 1 at high speeds on the order of nanoseconds. It is designed to prevent the blanked electron beam from drifting due to charging.

[0035] The blanking aperture 3 is an aperture that blocks the primary electron beam deflected by applying a high voltage to the blanking electrode 2 .

[0036] The pulse blanking device 4 generates a pulsed high voltage and applies it to the blanking electrode 2. This creates electron beams with different duty ratios.

[0037] The aberration corrector 5 is composed of an electron beam deflection element consisting of an octopole that generates a multi-stage electromagnetic field, and a transfer lens, and is used to correct chromatic aberration of the low-energy primary electron beam up to third order or higher, and to narrow the beam on the sample 13. Here, the aberration corrector (chromatic aberration corrector) 5 can achieve a beam spot diameter of 3 nm when the electron beam energy is 100 V, 2 nm when it is 200 V, and 1 nm when it is 500 V or higher, as needed.

[0038] The electron detector 6 scans the sample 13 while irradiating it with a finely focused primary electron beam, and detects and amplifies the secondary electrons emitted at that time.

[0039] The deflection device 7 deflects the primary electron beam in two stages, and scans the sample 13 while irradiating the finely focused primary electron beam thereon.

[0040] The objective lens 8 narrows the primary electron beam and irradiates it onto the sample 13. Here, an aberration corrector (spherical and chromatic aberration corrector) is used in combination as needed to minimize spherical and chromatic aberrations.

[0041] The sample chamber 10 is a container that contains a sample 13 such as a photomask inside the evacuated chamber.

[0042] The gas injection nozzle 11 is a nozzle for injecting gas (etching gas, deposition gas) perpendicularly onto the surface of the sample 13.

[0043] The low vacuum gas injection nozzle 111 is a nozzle that injects (introduces) gas (nitrogen gas, etc.) into the sample chamber 10 to create a low vacuum (for example, about 10 to 100 Pa) (described later).

[0044] The height sensor 12 measures the height of the sample 13 (such as the distance from the tip of the objective lens 8) in real time. The sample 13 is a sample such as a photomask, and is a specimen for which defects in a pattern formed on the surface are to be repaired.

[0045] The sample temperature control 14 automatically adjusts the temperature of the mounted sample 13 .

[0046] The laser measurement 14-1 measures the position (XYZ) of the sample 13 precisely in real time using a laser interferometer.

[0047] The Z stage 15 adjusts the position of the sample 13 in the height direction.

[0048] The sample bias voltage control 16 applies a predetermined bias voltage to the sample 13 .

[0049] The XY stage 17 moves the sample 13 in the X and Y directions, and moves it to a predetermined position while performing precise measurements using the laser measurement 14-1.

[0050] The vacuum gauge 21 measures the vacuum inside the sample chamber 10 .

[0051] The vibration isolation table 22 is used to isolate the sample chamber 10 and other components from vibrations, thereby enabling the acquisition of a high-resolution SEM image of the sample 13 .

[0052] The TMP 23 is a vacuum pumping device, which here evacuates the inside of the sample chamber 10 to a vacuum.

[0053] The dry pump 24 is an oil-less vacuum pumping device.

[0054] Next, the configuration of FIG. 1 will be described in detail.

[0055] The photomask repair device shown in Figure 1 has an electron beam column that is made up of an electron gun 1, blanking electrode 2, aberration corrector 5, electron detector 6, deflector 7, and objective lens 8, all of which are necessary for irradiating an electron beam with the desired energy and current at the desired position and timing. The aberration corrector 5 is capable of correcting higher-order chromatic aberrations, in addition to the usual spherical aberration correction, so that the low-energy electron beam size can be narrowed down to the nm order.

[0056] An electron detector 6 is provided for observing the target to be repaired and for confirming the endpoint of etching or deposition. It is particularly desirable to use an ALD-type MCP, which is highly resistant to contamination. The endpoint of the process is determined by setting a predetermined threshold for the contrast of secondary electrons or backscattered electrons or the output of a mass spectrometer or similar device. To prevent contamination of the column with process gas, the objective lens 8 is equipped with a two-stage differential pumping device, preventing process gas mixed into the sample chamber 10 from entering the column. Oxygen or nitrogen gas can be introduced separately from the process gas to prevent surface charging of the sample 13 due to electron beam irradiation.

[0057] The system includes an electron beam column control device for controlling the electron beam column and a high-voltage power supply (not shown) for controlling the electron gun. It also includes an ion pump (not shown) for maintaining an ultra-high vacuum of 10-7 Pa or higher inside the column. It also includes an XYZ stage 17 for determining the sample position relative to the electron beam irradiation position, laser measurement 14-1 such as a laser interferometer or laser scale for precise position measurement of the sample 13, and sample temperature control 14. It includes a vacuum chamber (sample chamber 10) made of a low-thermal expansion material such as pure iron, invar, or super invar that can achieve a vacuum of 10-5 Pa or lower so that the electron beam can reach the photomask. It also includes a dry pump 24 or turbomolecular pump for maintaining the desired degree of vacuum inside the chamber, and a vacuum gauge 21 for measuring the chamber vacuum.

[0058] The sample position control device, which positions the mirrors that make up the laser interferometer, is surrounded by an ultra-low thermal expansion material.The device is also equipped with an active vibration isolation system to prevent vibrations from the environment around the device from being transmitted to the inside of the device, and a system that feeds back sample vibrations to the electron beam to stop electron beam vibrations.

[0059] The clean room temperature is maintained at approximately ±1 degree, but a separate temperature control device that controls the temperature to within ±0.1 degrees is installed within the mask repair equipment chamber to prevent large fluctuations in temperature.

[0060] To repair a photomask, it is necessary to ensure that a chemical reaction occurs only at the location irradiated by the electron beam, and a system is provided to supply multiple types of reactive gases to the electron beam irradiation point and its surroundings at the required timing, flow rate, gas pressure, and temperature.To prevent spontaneous etching, etc., a forced gas exhaust device and gas supply device are provided to instantly remove unnecessary gas from the electron beam irradiation point at the same time as gas injection.

[0061] The gas temperature can be adjusted by measuring the temperature of the supply point using energy supplied by a conventional heater, laser beam, or electron beam and then feedback controlling it. Heaters can be used to control the temperature of the photomask and to keep the gas supply pipe warm. Laser beams or electron beams can be used to control the gas temperature at the repair site by directing the beam at the repair site.

[0062] The reactive gas can be pre-ionized before supply. Ionization can be achieved using currently available ionization methods, such as ultraviolet irradiation, electron beam irradiation, and RF excitation. The ionized gas can be efficiently guided to the repair site using an electric field or the potential difference between the ion source and the electron beam irradiation point. This method also features a bias electrode and electrostatic lens. Accelerated ions can also be delivered directly to the repair site using an ion gun. This method is distinct from conventional FIBs, which use high-speed, heavy ions such as Ga to perform physical etching. It delivers light gas to the repair site with low energies of less than 100 eV, which essentially eliminates the physical sputtering effect. Clustered ions can also be delivered. Clustering further reduces the kinetic energy of each molecule, preventing sample damage. If it is preferable to deliver the ions as neutral atoms or molecules, a neutralization method, such as electron beam irradiation, can be installed in the ionized reactive gas path to remove the ion charge.

[0063] Electron beam excited reaction gases generally use chemical substances (solid sources) that are solid at room temperature. The gas supply system includes a heater and temperature control circuit to sublimate the solid source contained in a Swagelok cylinder into a gas with the appropriate gas pressure, a pressure sensor or mass flow meter to measure the supply pressure, and a reservoir tank to temporarily store the sublimated gas. It is desirable to control the temperature with an accuracy of about 0.1 degrees.

[0064] Gas generated by the gas supply system is injected into the chamber through a pipe while maintained at the desired temperature. The nozzle has a built-in heater or other device that adjusts the gas temperature. The gas delivery components inside the vacuum chamber are insulated by the chamber vacuum, so they are maintained at the nearest heater temperature.

[0065] To achieve electron beam ALD and ALE, a high-speed response valve is incorporated to turn the diaphragm valve on and off in a short time of less than a millisecond to deliver pulsed gas. The valve is equipped with a temperature control mechanism. Solenoid valves, piezoelectric valves, or electrostatic valves made with MEMS can be used. To improve response, the valve can also be installed inside the chamber. Because gases tend to solidify easily, functions include periodically flowing inert gas at a constant temperature to prevent clogging in the pipes, or momentarily increasing the pressure to flush the reactant gas. Because reactant gases have low vapor pressures, their supply pressures tend to be lower than those of gases such as nitrogen and oxygen, which are gases at room temperature. To compensate for this pressure, inert gases such as nitrogen, argon, or helium can be used as a booster gas along with the reactant gas. The booster effect can be achieved by directly injecting the booster gas into the gas source vessel. These booster gases generate ions upon collision with the primary electron beam and also function as antistatic gases. The use of booster gas allows for higher pressures, thereby increasing the flexibility of gas supply methods. Since it is no longer necessary to use a nozzle with a small hole like a syringe needle to obtain a gas flow as in the past, problems caused by gas solidification are reduced.

[0066] Several types of reaction gases are used for each process, and are supplied through multiple pipes. To simplify the equipment, for gases that can be mixed, a single gas can be supplied through a gas mixer capable of mixing gases in predetermined ratios, sharing a common pipe. Conventional methods of simply spraying gas from multiple nozzles into a chamber do not result in uniform gas distribution, so this method significantly stabilizes process results. On the other hand, when reactions involve gas mixtures, it is desirable to have independent gas supply systems for each. Each supply system has multiple independent control systems that enable digital numerical control of flow rate, pressure, temperature, supply timing, etc. The entire equipment is controlled by a PC (not shown), and a display (not shown) displays SEM images of the repair target, repair target, repair status, and results, as well as the equipment status, process conditions, and details.

[0067] Next, drift correction in the photomask repair apparatus of the present invention will be explained in detail with reference to FIGS.

[0068] FIG. 2 shows a configuration diagram (part 1) of the present invention.

[0069] In FIG. 2, an electron beam 31 is an electron beam (primary electron beam) emitted from an electron gun.

[0070] The electron beam column 32 is a lens barrel that generates the electron beam 31, narrows it by the objective lens 8, and irradiates the photomask 131 while scanning the photomask 131 in a plane.

[0071] The gas pipe 33 is a pipe for supplying gas and is a pipe that can be heated.

[0072] The gas injection nozzle 11 injects gas toward the photomask 131 .

[0073] The photomask 131 is a photomask having a defect and to be repaired.

[0074] The Z stage 15 moves in the Z direction and is a high-speed response device such as a piezoelectric element.

[0075] The XY stage 17 moves the photomask 131 in the X and Y directions. The Z stage 15 and the XY stage 17 are precisely position-controlled in real time by a laser interferometer (not shown).

[0076] XeF2 is a gas, and in this case, it is an etching gas. Alternatively, it may be a deposition gas.

[0077] Next, the configuration of FIG. 2 will be specifically described.

[0078] (1) In FIG. 2, when repairing a mask, for example, when etching a pattern (defect) on a photomask 131, xenon fluoride gas (XeF2) is used. Xenon fluoride gas is a solid substance at room temperature and has the property of slightly sublimating. Because its vapor pressure is low and difficult to handle as is, a container containing the xenon fluoride gas is heated to about 100°C to provide sufficient vapor pressure, and after controlling the flow rate to the desired level using a mass flow controller (not shown), the gas is introduced onto the surface of the photomask 131 through the gas injection nozzle 11. The gas pipe 33 is kept warm to create a temperature gradient at each location to prevent the xenon fluoride from solidifying.

[0079] When a mass flow controller is not used, there is also a method of directly controlling the temperature of the xenon fluoride gas container and measuring the pressure inside the mass flow meter or gas pipe 33 to perform flow rate feedback control.

[0080] (2) When the introduced gas is irradiated with the electron beam 31, fluorine is liberated and undergoes a chemical reaction with the metal film on the photomask 131, converting it into a volatile substance. Because the photomask 131 is placed in a high-vacuum environment, the metal that has converted into a volatile substance evaporates into the vacuum and can be removed by etching. The targeted etching can be achieved by irradiating the electron beam 31 in a desired pattern.

[0081] (3) A high-speed valve (1) for turning the gas introduction on and off is placed between the gas supply source and the gas injection nozzle 11. This high-speed valve (1) opens and closes very frequently, so a high-speed valve (1) for ALD (called an ALD valve) that guarantees high speed and high durability is desirable. The ALD valve is resistant to high-temperature gases and can open and close the valve 100 million times at a speed of the order of 10 ms.

[0082] (4) The shorter the distance from the ALD valve to the gas injection nozzle 11, the faster the response time for turning the gas on and off. For example, if the ALD valve is placed near the top plate of the sample chamber 10, the distance from the ALD valve to the tip of the gas injection nozzle 11 can be several tens of centimeters. If even higher speed is required, it is also possible to place the ALD valve inside the sample chamber 10.

[0083] (5) When the degree of vacuum in the sample chamber (vacuum chamber) 10 is 10-3 Pascals, if 10 sccm of gas is flowed through the nozzle of the present invention, the gas pressure at the tip of the nozzle will reach 10 Pa several tens of milliseconds after the ALD valve is opened. When the pressure at the electron beam irradiation point reaches 10 Pa or more, even etching gases will exhibit an antistatic effect.

[0084] (6) Conversely, when the ALD valve is closed, the gas pressure drops to almost 0 Pa after several tens of milliseconds.

[0085] (7) As described above, when the end of the pipe connected to the ALD valve (high-speed valve (1)) is in a high vacuum, the gas exists in a molecular flow state and diffuses and moves at nearly the speed of sound.

[0086] (8) The device of the present invention allows observation of SEM images at almost any timing without adversely affecting the photomask 131. Furthermore, since it has a mechanism for realizing a low-energy, high-definition beam using an aberration correction device (not shown), there is absolutely no need to worry about column discharge. Because it can supply a large amount of gas onto the photomask to achieve high gas pressure, it can achieve high-speed etching and deposition that cannot be compared with conventional electron beam mask repair devices.

[0087] (9) The amount of drift that affects the accuracy of correction tends to increase with time, but in the present invention, the correction time can be made extremely short, which has the effect of reducing the amount of drift.

[0088] Next, the operation of the configuration in FIG. 2 will be described with reference to FIG.

[0089] FIG. 3 shows an example (part 1) of a timing chart of electron irradiation and gas injection in the present invention and the prior art.

[0090] FIG. 3(a) shows an example of a timing chart of the present invention, and FIG. 3(b) shows an example of a timing chart of the prior art (see FIG. 13).

[0091] In FIG. 3A, t0, t1, t2, t3, t4, etc. in the upper row are times, and represent the time for repair 1 of the defect (repair target 51) on the photomask 131, the time for acquiring SEM1 (SEM image 1), etc.

[0092] (a-1) denotes electron irradiation, which indicates that electrons are irradiated for the times t0, t1, t2, t3, t4, . . . as shown in the figure.

[0093] (a-2) indicates gas injection, which is performed for the times t0, t2, t4, etc. shown in the figure.

[0094] In FIG. 3(b), (b-1) denotes electron irradiation, which is performed while the correction is being performed continuously as shown.

[0095] (b-2) is gas injection, which indicates that gas is injected while continuously correcting as shown in the figure.

[0096] Next, the operation of the configuration in FIG. 3 will be described.

[0097] (1) In the present invention, as shown in Figure 3(a), when mask repair is being performed, the ALD valve described above is opened to inject xenon fluoride gas onto the photomask surface (rectangle (a-2)), and the repaired area is irradiated with an electron beam (rectangle (a-1)). Meanwhile, to observe the repair results, the ALD valve for supplying the reaction gas is closed in synchronization with switching to SEM observation mode (no rectangle (a-2)).

[0098] (2) The supply of xenon fluoride gas stops after a few tens of milliseconds, and the xenon fluoride gas in the piping is removed by the vacuum pump, so that almost no xenon fluoride gas reaches the surface of the photomask. In this state, an electron beam is irradiated and SEM observation is performed (such as SEM1 in (a-1)). In other words, since there is no etching gas on the photomask, the photomask will not be etched even if it is irradiated with an electron beam.

[0099] (3) By using the above method, drift correction can be performed using the SEM image position of the correction target without using conventional drift correction marks (see Figure 13(a)). Since there is no need to form conventional drift correction marks, the operation is extremely simple.

[0100] Next, drift correction using the configurations shown in FIGS. 2 and 3 will be described in detail with reference to FIG.

[0101] FIG. 4 shows a flowchart illustrating the operation of the present invention.

[0102] In Fig. 4, S1 performs gas injection and electron irradiation to repair the mask. In the case of mask repair, for example, etching, gas (etching gas injection) and electron irradiation are directed toward a defect (defective portion) 52 in a repair target 51 in Fig. 5(a) (described later), etching the defect 52 and performing mask repair (see Fig. 3(a)). For example, mask repair is performed using repairs 1, 2, etc. in Fig. 3(a), and SEM image data such as SEM1, SEM2, etc. are recorded.

[0103] S2 determines whether it is finished. This determines whether the mask correction of S1 is finished. If it is YES, it ends. If it is NO, it proceeds to S3.

[0104] In step S3, a defect-free location is selected. This is done by referring to the SEM images (SEM1, SEM2, etc.) recorded in step S1 described above, and a defect-free location (for example, four locations at the four corners of the rectangle shown) of the correction target 51 in FIG. 5(a) is selected. Note that two or more locations are sufficient for rotational correction, and only one location is sufficient for translational correction.

[0105] S4 acquires multiple SEM images, which are the SEM images recorded in S1 (SEM1, SEM2, etc. in FIG. 3(a) are acquired).

[0106] S5 calculates the amount of drift from the SEM image. This calculates the amount of drift (for example, the amount of drift including rotation in S3) between defect-free locations (parts) in the SEM images acquired in S3 and S4 (for example, the images of the correction targets 51 and 511 in Figure 5).

[0107] In S6, it is determined whether the drift is greater than the drift threshold. For example, it is determined whether the amount of drift calculated in S5 is between 1 nm and 1 micron (the optimum value is determined through experiments). If the answer is YES, proceed to S7. If the answer is NO, repeat S1 and subsequent steps.

[0108] S7 performs drift correction (electron beam), which corrects the electron beam or moves the stage to cancel the drift amount calculated in S5.

[0109] As described above, it is now possible to repair the mask by injecting gas and irradiating electrons onto the defective portion of the repair target 51, 511, and at the same time, acquire multiple SEM images of the repair target 51, 511, calculate the amount of drift, and automatically perform drift correction of the repair target 51, 511 on the photomask (see Figures 5 and 3). Note that the acquired SEM images do not have to be the entire repair target 51, 511, but may be only a portion of it (as long as it is an area without defects). Here, SEM images include secondary electron images, backscattered electron images, etc.

[0110] FIG. 5 shows an illustration of the defect repair of the present invention.

[0111] FIG. 5(a) shows a schematic example of etching.

[0112] In FIG. 5(a), a photomask 131 is a photomask on which a repair target 51 is located.

[0113] The repair target 51 is a schematic example in which a defect 52 to be etched is outside the original pattern, as shown in the figure.

[0114] Defect 52 is a schematic representation of a defect in which a protrusion as shown is located outside the original pattern.

[0115] FIG. 5(b) shows a schematic example of the deposition.

[0116] In FIG. 5B, a photomask 131 is a photomask on which a repair target 51 is located.

[0117] The repair target 511 is a schematic example in which a defect 53 to be deposited is located inside the original pattern, as shown in the figure.

[0118] A defect 53 is a schematic representation of a defect in which there is a depression inside the original pattern as shown in the figure.

[0119] As described above, when the defect 52 is on the outside, as in the case of the repair target 51 (FIG. 5(a)), or when the defect 53 is on the inside, as in the case of the repair target 511 (FIG. 5(b)), the mask can be repaired by performing etching and deposition.

[0120] Figure 6 shows a diagram (part 2) of the configuration of the present invention, which adds a configuration for spraying water vapor gas (H2O) that reliably stops etching and does not adversely affect SEM observation, in addition to the etching gas (XeF2) shown in Figure 2.

[0121] In Fig. 6, H2O (water vapor gas), gas pipe (2), and high-speed valve (2) are added to Fig. 2. The configuration will be explained below.

[0122] (1) For example, xenon fluoride gas (XeF2) is used when etching the pattern of the photomask 131. Xenon fluoride gas is a solid substance at room temperature and has the property of slightly sublimating. A container containing xenon fluoride is heated to about 100°C to provide sufficient vapor pressure, and after controlling the flow rate to the desired level using a mass flow controller, the gas is introduced onto the surface of the photomask 131 through the gas injection nozzle 11.

[0123] (2) When the introduced xenon fluoride gas is irradiated with an electron beam, fluorine is liberated and undergoes a chemical reaction with the metal film on the photomask 131, converting it into a volatile substance. Because the photomask 131 is placed in a high-vacuum environment, the metal that has converted into a volatile substance evaporates into the vacuum and can be removed by etching. The desired etching can be achieved by irradiating the electron beam to form the desired pattern (repair defects).

[0124] (3) On the other hand, it is known that water vapor (H2O) reacts with xenon fluoride gas and inhibits etching. Therefore, a separate gas pipe (2) and gas injection nozzle are prepared for introducing water vapor onto the photomask 131, and this is used to completely stop etching.

[0125] (4) Two independent high-speed valves (1) and (2) are installed between the gas supply system and the gas injection nozzle 11 to turn on and off the introduction of etching gas and water vapor gas. Because these high-speed valves (1) and (2) are opened and closed very frequently, high-speed valves designed for ALD, which guarantee high speed and high durability, are desirable. Valves designed for ALD are resistant to high-temperature gases and can open and close at speeds on the order of 10 ms.

[0126] (5) The shorter the distance from the ALD valve to the gas injection nozzle 11, the faster the response. For example, if the ALD valve is placed near the top plate of the chamber (sample chamber 10), the distance from the high-speed valve to the tip of the gas injection nozzle 11 can be several tens of centimeters. If the degree of vacuum in the vacuum chamber is 10-3 Pascals, and 10 sccm of gas is flowed through the nozzle of the present invention, the gas pressure at the tip of the gas injection nozzle 11 will reach 10 Pa several tens of milliseconds after the ALD valve is opened. Conversely, if the ALD valve is closed, the gas pressure will drop to nearly 0 Pa several tens of milliseconds after the ALD valve is closed.

[0127] (6) As described above, when the environment connecting the high-speed valves (1) and (2) is a high vacuum, the gas exists in a molecular flow state, and therefore moves and diffuses at nearly the speed of sound.

[0128] Figure 7 shows an example (part 2) of the timing chart of electron irradiation and gas injection in the present invention and the prior art. This Figure 7 corresponds to the addition of water vapor gas in Figure 6, and adds the gas injection (water vapor gas) in Figure 7 (a-3) to the already described Figure 3. Since the rest is the same, the explanation will be omitted.

[0129] In Figure 7, the gas injection (water vapor) in Figure 7(a-3) is, as shown, a gas injection (water vapor) performed when observing SEM images (SEM1, 2, 3, etc.), and inhibits (stops) etching. As shown in the figure, gas injection (water vapor gas injection) is not required for the entire time when observing SEM images, and gas injection may be performed only for a short period at the beginning (the optimal time can be determined through experiments). The configuration will be explained in detail below.

[0130] (1) The opening and closing of the ALD valve for supplying etching gas and the ALD valve for supplying water vapor are synchronized with the timing of SEM observation of the mask to be repaired. In other words, when the mask is being repaired, the etching gas supply valve is open to supply xenon fluoride gas to the surface of the photomask. Meanwhile, to observe the repair results, the ALD valve for supplying etching gas is closed in synchronization with switching to SEM observation mode. The supply of xenon fluoride gas is stopped within a few tens of milliseconds, and the xenon fluoride gas in the piping is drawn away by the vacuum pump, so that almost no xenon fluoride gas reaches the surface of the photomask.

[0131] (2) The xenon fluoride gas valve is closed, and at the same time, the water vapor supply ALD valve in the water vapor supply pipe is opened to introduce water vapor onto the photomask. The xenon fluoride gas adsorbed on the photomask surface reacts with the water vapor, converting the xenon fluoride into an inactive state.

[0132] (3) On the other hand, if water vapor is flowed at a rate of 10 sccm or more, the pressure at the electron beam irradiation point will be 10 Pa or more, and a low vacuum state will be achieved. In other words, it is possible to create a low vacuum state with an anti-static effect using water vapor.

[0133] (4) In this inactive etching state, an electron beam is irradiated to observe the repaired area, and SEM observation is performed. In other words, since there is no etching gas on the photomask and the xenon fluoride gas present on the surface of the photomask has been inactivated by water vapor, the photomask will not be etched even if it is irradiated with an electron beam. When the water vapor pressure is 10 Pa or higher, a low vacuum state is created, which can also be expected to prevent charging on the photomask.

[0134] (5) As described above, in the present invention, drift correction can be performed using the position of the SEM image to be corrected, without using conventional drift correction marks.

[0135] Fig. 8 shows a third explanatory diagram of the configuration of the present invention. In Fig. 8, in addition to the etching gas (XeF2) and H2O shown in Fig. 6, a configuration for injecting (supplying) N2 (nitrogen gas) to remove charges during SEM observation is added.

[0136] In Fig. 8, N2 (nitrogen gas), gas pipe (3), and high-speed valve (3) are added to Fig. 6. The other configurations are the same as Fig. 6, so the explanation will be omitted.

[0137] Next, the operation of the configuration in FIG. 8 will be described in detail with reference to FIG.

[0138] FIG. 9 shows an example (part 3) of a timing chart of electron irradiation and gas injection according to the present invention.

[0139] (1) In Figure 9, N2, gas piping (3), and high-speed valve (3) are added to the configuration of Figure 6. To achieve a low vacuum state that prevents static buildup during SEM observation, a nitrogen gas supply ALD valve (high-speed valve (3)) or a high-speed valve for oxygen gas, which is easily ionized but does not directly react with the photomask, is opened and gas is separately supplied to the photomask 131 from the gas injection nozzle 11. In the case of this gas injection nozzle 11, a low vacuum state of approximately 10 Pa can be achieved directly above the photomask 131 by supplying gas to the nozzle at a gas flow rate of approximately 10 sccm. Nitrogen gas (N2) is inert to xenon fluoride gas and water vapor, so it can also be supplied from a common nozzle. Using a common nozzle also has the effect of flushing and cleaning out any reaction gases that may be accumulating in the nozzle.

[0140] (2) In this state, an electron beam is irradiated and SEM observation is performed. In other words, there is no etching gas on the photomask 131. The xenon fluoride gas adsorbed on the photomask 131 is inactivated by water vapor, so the photomask 131 is not etched even when irradiated with an electron beam. Furthermore, because a low vacuum state is achieved by nitrogen gas (N2), ionization of the nitrogen gas occurs, which helps prevent charging, and it is possible to prevent charging of the photomask surface, which is a cause of electron beam drift.

[0141] (3) The anti-static effect begins at a vacuum level of about -1 Pa, and the effect becomes stronger as the vacuum level becomes lower. However, if the vacuum level is too low, the collision and scattering between the primary electron beam and the introduced low-vacuum gas becomes too great, reducing the percentage of the electron beam that reaches the photomask 131 and causing the beam to spread, so the effect is only seen up to about several tens of Pa. This effect prevents the electron beam irradiating the photomask from drifting due to charging.

[0142] (4) As described above, SEM observation can be performed without damaging the object to be repaired, so drift correction can be performed using the position of the SEM image of the object to be repaired without using conventional drift correction marks.

[0143] FIG. 10 shows an example (part 1) of the annular nozzle of the present invention.

[0144] FIG. 10(a) shows a top view, and FIG. 10(b) shows a cross-sectional view.

[0145] In FIG. 10, the annular nozzle 61 forms a chamber (gas chamber) together with the lower surface of the objective lens 8, the annular nozzle 61, and the photomask 131, as shown in the figure.

[0146] Gas 62 is a gas supplied to a chamber (gas chamber) formed by the lower surface of objective lens 8, annular nozzle 61, and an adjacent photomask 131, and is a variety of gases (etching gas, deposition gas, purge gas, charge removal gas, etc.).

[0147] The gas pipe 33 is a pipe for introducing gas.

[0148] In this case, the differential pumping 34 is a system in which two stages of small holes are provided in the area where the electron beam passes, and vacuum is evacuated from above between the holes, so that the gas inside the annular nozzle 61 does not diffuse into the upper lens barrel or further into the electron gun.

[0149] Next, the configuration of FIG. 10 will be described in detail.

[0150] (1) Conventional gas nozzles were long, thin pipes, each with a different gas type. This was thought to be because the objective lens attached to the electron beam column used in conventional repair equipment had a sharp tip, making it easy to run the pipe along the outer shape of the objective lens. Since there was nothing obstructing the area around the nozzle, the gas emitted from the nozzle was released into the large vacuum chamber space. In order to increase the gas concentration at the electron beam irradiation point with a conventional nozzle to a practically sufficient level, it was theoretically necessary to bring the distance between the nozzle and the photomask close to 1 mm or less, and to install the nozzle so that the gas ejected from the nozzle was accurately directed toward the irradiation point. This was extremely troublesome when considering operability and maintenance.

[0151] (2) The nozzle used in the present invention in Figure 10 is annular and is arranged to surround the electron beam irradiation point. It is made of a non-magnetic material. The bottom surface of the objective lens 8 has a flat area, and a small chamber (gas chamber) is formed by the annular member, the surface of the photomask 131, and the bottom of the objective lens 8. The required number of nozzles are provided in part of the annular member. The same type of gas may be sprayed in opposite directions, or different gases may be arranged opposite each other to ensure good mixing. The size, number, and arrangement of the nozzles are optimized depending on the purpose. The nozzle's mmΦ size is selected to increase conductance.

[0152] (3) A feature of the present invention is the creation of a narrow chamber (gas chamber) in which the gas ejected from the nozzle can remain. Because the chamber's volume is less than a few cc, it can be instantly filled with gas with a small amount of gas supplied. Meanwhile, this space (gas chamber) is constantly evacuated by a differential pump via a differential pumping aperture, so that if the gas supply from the nozzle ceases, the gas present in the space is instantly sucked away by the pump. Furthermore, this differential pumping action prevents the gas ejected from the nozzle from entering the electron beam column, causing contamination or corrosion.

[0153] (4) In the electron beam column of the present invention, the high voltage section for retarding or braking, which is found in the conventional intermediate acceleration type electron beam column, is not exposed to the low vacuum section. No discharge occurs even when a large amount of gas is released from the annular nozzle 61 near the electron beam irradiation point. In other words, the nozzle of the present invention has a very large conductance and a structure that is very suitable for supplying high-concentration gas and for quickly turning the gas supply on and off.

[0154] (5) As a result, this column is designed to withstand large gas supply volumes. When approximately 10 sccm of gas is released into this space (gas chamber), an average pressure of approximately 10 Pa is achieved within this space. While this is impossible with conventional devices due to electrical discharge, the device of the present invention can easily raise the electron beam irradiation point pressure to 100 Pa or higher by increasing the gas supply rate (it goes without saying that the mask adjustment speed increases in proportion to the gas pressure). Even if only the gas chamber of the present invention is set to 100 Pa, very little gas escapes to the external sample chamber 10 (i.e., conductance is very small (exhaust resistance is very large)), allowing the pressure in the sample chamber 10 to remain at a high vacuum. This is presumably because the mean free path of gas is long in the pressure range of 10 Pa to 100 Pa or less, resulting in very large exhaust resistance (very small conductance) between the gas chamber of the present invention and the external sample chamber.

[0155] FIG. 11 shows an example (part 2) of the annular nozzle of the present invention.

[0156] Figure 11(a) shows a top view, and Figure 11(b) shows a cross-sectional view. Figure 11 shows an additional gas pipe (2). The rest is the same as Figure 10, so the explanation will be omitted.

[0157] In Figure 11, gas pipe (2) is an added gas pipe. By adding gas pipe (2), gas is supplied to the gas chamber from three directions through the environment nozzle 611 as shown in the figure. This will be explained in detail below.

[0158] (1) Figure 11 shows a system in which an inert gas such as nitrogen gas is introduced separately to achieve a low vacuum. It is characterized by the fact that the introduced gas is concentrated as much as possible only on the surface of the photomask 131. Conventionally, the anti-static effect of gas ionization on the surface of the photomask was thought to occur mainly because ions generated by collisions between primary electrons and the gas neutralized the charge on the surface of the photomask 131.

[0159] (2) On the other hand, it is known that the reaction between gas and electrons in mask repair is not a reaction between primary electrons and gas, but rather a reaction between low-energy secondary electrons generated by primary electrons irradiated onto the surface of the photomask 131 and the gas, resulting in etching and deposition. This can be inferred from the fact that the activation energy of the chemical reaction is several electron volts and that the collision cross section between electrons and gas peaks at a voltage lower than 100 eV.

[0160] The energy levels used in etching and deposition are several eV, and the gas ionization energy is also several eV. Therefore, it is thought that it is not the primary electrons that actually contribute to the gas ionization, but the secondary electrons generated on the photomask surface.

[0161] In either case, irradiation of the repair area with primary electrons causes etching or deposition of the repair area.

[0162] (3) If the primary electron beam and antistatic gas are scattered at a location far from the photomask, not only will the beam widen and the resolution deteriorate, but the antistatic effect on the surface of the photomask 131 will also be reduced. The higher the antistatic gas pressure, the greater the antistatic effect. However, if the high gas pressure is present only on the surface of the photomask, not only will a greater antistatic effect be obtained, but an increase in the beam size due to scattering of the primary electron beam can be avoided. Yes, it is possible.

[0163] (4) As shown in Figure 11, the lower part of the annular nozzle 611 is extended to a position close to the surface of the photomask 131. The aperture of the lower differential exhaust 34 is positioned as close as possible to the surface of the photomask 131. The antistatic gas is designed to be sprayed only onto the surface of the photomask 131, and has the greatest pressure at the outermost surface of the photomask 131. If the gas moves even slightly away from the surface of the photomask 131, the gas pressure rapidly drops to about 10 to the minus 3 Pascals, which is the back pressure, and the probability of collision with primary electrons can be made extremely small.

[0164] (5) As a result of the above, it is possible to effectively prevent photomask charging without adversely affecting the primary electron beam while maximizing the anti-static effect. It goes without saying that this can be used not only in repair systems but also in SEMs with differential pumping systems. While we are talking about the anti-static effect here, it goes without saying that increasing the gas concentration also leads to improved repair speed.

[0165] (6) Although the gas control on the photomask by gas injection from the nozzle has been described above, the gas pressure on the surface of the photomask 131 can also be controlled by controlling the pressure in the sample chamber 10 shown in Figure 1 with an inert gas such as nitrogen gas. The sample chamber 10 in Figure 1 is provided with a low-vacuum gas injection nozzle 111 in addition to the gas injection nozzle 11 for creating a low-vacuum state in the sample chamber 10. The desired pressure can be achieved by introducing gas from this low-vacuum gas injection nozzle 111 via mass flow.

[0166] Figure 12 shows an example (part 4) of the timing chart of electron irradiation and gas injection according to the present invention. This Figure 12 is the same as Figure 9 already mentioned, with the addition of the low-vacuum gas injection of Figure 12 (a-5). The rest is the same as Figure 9, so the explanation will be omitted.

[0167] In FIG. 12, (a-5) low vacuum gas injection in FIG. 12 is for injecting gas to create a low vacuum in the sample chamber 10.

[0168] Next, the operation will be described.

[0169] (1) In Figure 12, the back pressure of the sample chamber 10 is controlled by introducing a low-vacuum gas, such as nitrogen, into the sample chamber 10 in synchronization with the flow of gas (etching gas, deposition gas, etc.). The back pressure of the sample chamber 10 can be controlled extremely accurately because it is measured with a pressure gauge. For example, if the pressure in the sample chamber 10 is set to about 10 Pa, the gas pressure on the surface of the photomask 131 increases by 10 Pa. In other words, an offset effect is achieved, resulting in a higher pressure even though the gas flow rate from the nozzle is the same. When the back pressure of the sample chamber 10 is increased to 10 Pa, the pressure difference between the nozzle and the sample chamber 10 is almost eliminated, and the amount of gas diffusing toward the sample chamber 10 from the gap between the nozzle and the photomask is reduced, which is thought to be why the pressure above the photomask 131 increases.

[0170] (2) Normally, gases used in reactions are expensive, so it is desirable to reduce their consumption as much as possible. By maintaining a high back pressure in the sample chamber 10 as described above, the consumption of expensive gases can be dramatically reduced.

[0171] (3) On the other hand, when rapidly exchanging gases that react with the electron beam, such as during SEM observation, stopping the introduction of low-vacuum gas and lowering the back pressure of the sample chamber 10 to 10-3 Pa or less makes it possible to bring the degree of vacuum in the nozzle into a molecular flow state and quickly release the gas that remains in the nozzle that supplies the gas that reacts with the electron beam. It is desirable to perform these operations automatically in synchronization with the gas switching signal.

[0172] (4) Gas switching can be performed in the deposition process as well.

[0173] (5) The same effect can be obtained by replacing the etching gas, for example, xenon fluoride gas, with a deposition gas consisting of a volatile organometallic compound such as metal carbonyl.

[0174] (6) This can be achieved by replacing the deactivating gas, water vapor, with a gas that inhibits the deposition reaction, such as oxygen, an oxidizing agent, or hydrogen, a reducing agent.

[0175] (7) Back pressure control can be achieved by using inert gases such as nitrogen and argon, which do not react with the reactant gas.

[0176] (8) As described above, the present invention provides a method for rapidly switching to a different gas during an etching or deposition process. This method allows the operator to perform SEM observation at any time and enables drift correction without using conventional drift correction marks. [Brief explanation of the drawings]

[0177] [Figure 1] FIG. 1 is a configuration diagram of an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram (part 1) illustrating the configuration of the present invention. [Figure 3] 1 is a timing chart (part 1) showing an example of electron irradiation and gas injection timing in the present invention and the prior art. [Figure 4] 1 is a flowchart illustrating the operation of the present invention. [Figure 5] FIG. 2 is an explanatory diagram of defect repair according to the present invention. [Figure 6] FIG. 2 is a diagram (part 2) illustrating the configuration of the present invention. [Figure 7] 10 is a timing chart showing examples of electron irradiation and gas injection in the present invention and the prior art. [Figure 8] FIG. 3 is a diagram (part 3) illustrating the configuration of the present invention. [Figure 9] 10 is a timing chart (part 3) showing an example of the electron irradiation and gas injection timing according to the present invention. [Figure 10] 1 is an example (part 1) of an annular nozzle according to the present invention. [Figure 11] 2 is a second example of the annular nozzle of the present invention. [Figure 12] 10 is a fourth example of a timing chart of electron irradiation and gas injection according to the present invention. [Figure 13] FIG. 1 is an explanatory diagram of a conventional technique. [Explanation of symbols]

[0178] 1: Electron gun 2: Blanking electrode 3: Blanking aperture 4: Pulse blanking device 5: Aberration corrector 6:Electron detection device 7: Deflection device 8: Objective lens 10: Sample chamber 11: Gas injection nozzle 111: Low vacuum gas injection nozzle 12: Height sensor 13: Sample 131: Photomask 14: Sample temperature control 141: Laser measurement 15: Z Stage 16: Sample bias voltage control 17: XY Stage 21: Vacuum gauge 22: Vibration isolation table 23:TMP 24: Dry pump 25: Vibration isolator 26: Gas flow control device 27: Gas supply equipment 31: Electron beam 32: Electron beam column 33: Gas piping 34: Differential pumping 51, 511: To be corrected 52, 53: Defects 61, 611: Annular nozzle 62, 621: Gas

Claims

1. A drift correction apparatus for correcting drift when repairing defects on a photomask, a nozzle for spraying gas onto the surface of the photomask; a stage for holding the photomask facing the nozzle; an SEM image acquisition means for acquiring an SEM image by scanning the photomask while irradiating it with electrons through a narrow beam and detecting and amplifying the emitted electrons; a photomask repairing means for repeatedly injecting gas from the nozzle and irradiating electrons onto a target to be repaired that has a defect in a pattern on the photomask, and stopping the gas injection after a predetermined time has elapsed and then irradiating electrons; a drift calculation means for acquiring SEM images by the SEM image acquisition means when the gas injection is stopped and the electron irradiation is performed, and for calculating a drift amount by comparing a plurality of acquired SEM images; a correction means for correcting the electron irradiation position or the stage position based on the calculated drift amount; Equipped with A drift correction device for photomask repair, which corrects drift of a defective photomask to be repaired.

2. 2. The photomask repair drift correction device according to claim 1, wherein the electron irradiation in which gas is injected from the nozzle and the electron irradiation in which the gas injection is stopped after a predetermined time has elapsed are directed to the same object to be repaired.

3. 3. The photomask repair drift correction device according to claim 1, wherein the gas is a gas that etches the object to be repaired or a gas that deposits the object to be repaired.

4. 4. The apparatus for correcting drift in photomask repair according to claim 3, wherein a gas for eliminating the influence of said etching gas or said deposition gas is injected.

5. 5. The drift correction device for photomask repair according to claim 1, wherein a gas for neutralizing charges on the object to be repaired is injected.

6. 6. The drift correction device for photomask repair according to claim 1, wherein when the calculated drift amount is equal to or greater than a predetermined threshold, the position of the electron irradiation or the position of the stage is corrected.

7. A drift correction method for correcting drift when repairing defects on a photomask, comprising: a nozzle for spraying gas onto the surface of the photomask; a stage that holds the photomask facing the nozzle; Established an SEM image acquisition step of detecting and amplifying emitted secondary electrons by scanning the photomask while irradiating it with electrons through a narrow aperture, and acquiring an SEM image; a photomask repair step of repeatedly injecting gas from the nozzle and irradiating electrons onto a target to be repaired that has a defect in a pattern on the photomask, and stopping the gas injection after a predetermined time has elapsed and irradiating electrons; a drift calculation step of acquiring SEM images by the SEM image acquisition step when the gas injection is stopped and the electron irradiation is performed, and calculating a drift amount by comparing the acquired SEM images; a correction step of correcting the electron irradiation position or the stage position based on the calculated drift amount; and A drift correction method for photomask repair, comprising correcting the drift of a defective photomask to be repaired.

Images