Photomask repair apparatus and photomask repair method

Abstract

PURPOSE: To provide a method for self-restoring a pseudo SEM image generated from design data to an original image by selecting a restoring object based on defect data, relating to a photomask restoring device and a photomask inspection method.CONSTITUTION: A method for restoring a pseudo image to an original image comprises: a nozzle that sprays gas onto a surface of a photomask; a stage that holds the photomask; means for detecting and amplifying secondary electrons to obtain a SEM image; a defect database that stores defect data; a design data base storing design data; means for extracting defect data of a photomask to be restored at the time of defect restoration, extracting defective design data, and generating a pseudo SEM image suitable for the photomask process; and restoring means for, based on the pseudo SEM image, injecting gas from a nozzle to a portion corresponding to the SEM image on the defective photomask, and performing one or both of etching and deposition to perform restoring.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photomask repair apparatus and a photomask repair method for repairing defects in a photomask. [Background technology]

[0002] Traditional photomask restoration was not automated; it was more of a semi-automatic process. For example, the restoration required a human to create, select, or copy existing shapes to determine which shapes needed correction. This required skilled craftsmen and resulted in low productivity.

[0003] Furthermore, although there is theoretically only one restoration goal, restorations performed by skilled individuals do not always yield the same results. Secondarily, variations in photomask performance were occurring due to the restoration process. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] As mentioned above, conventional photomask restoration required skilled personnel to create, select, and copy existing shapes to determine which shapes needed correction, and then perform the restoration (cutting, adding). This presented a challenge in that it could not be automated.

[0005] Furthermore, because the restoration was performed by skilled workers, the same results could not always be obtained, and there were issues such as variations in the secondary photomask performance due to the restoration. [Means for solving the problem]

[0006] To solve the aforementioned problems, the present invention aims to automatically perform repair by selecting a target for repair based on defect data, and then repairing (etching and deposition) this target based on a pseudo-SEM image generated from design data, so that the same results are always obtained.

[0007] Furthermore, in order to solve the above-mentioned problems, the present invention aims to automatically repair a target by creating a repair object by removing the defective portion based on defect data, and then repairing or reconstructing (etching, deposition) this repair object based on a pseudo-SEM image generated from the design data so that the same results are always obtained.

[0008] Therefore, the present invention provides a photomask repair device for repairing defects in a photomask, comprising: a nozzle for spraying gas perpendicularly onto the surface of the photomask; a stage for holding the photomask opposite the nozzle; means for irradiating and scanning the photomask with a narrowed electron beam, and detecting and amplifying emitted secondary electrons and reflected electrons to acquire an SEM image; a defect database for storing defect data relating to a pattern on the surface of the photomask; a design database for storing design data for the pattern on the surface of the photomask; means for extracting defect data of the photomask to be repaired from the defect database when repairing defects in the photomask, and based on the defect data, extracting design data containing the defect in the defect data from the design database to generate a pseudo SEM image compatible with the process of the photomask; and repair means for spraying gas from the nozzle to repair a portion of the photomask corresponding to the SEM image on which the defect in the extracted defect data is located, by etching or deposition, or by switching between both, based on the generated pseudo SEM image.

[0009] In this case, the repair means creates a repair target by spraying gas from a nozzle onto the defective area or a slightly larger area corresponding to the SEM image of the photomask surface where the defect data is extracted, based on the generated pseudo-SEM image, and then repairs the repair target by spraying gas from a nozzle onto the defective area or a slightly larger area, or by switching between both.

[0010] In addition, an air curtain is provided outside the nozzle where gas is sprayed onto the photomask to prevent leakage of gas outside the air curtain and to remove any adhering gas.

[0011] Furthermore, the reaction radius or diameter due to the gas, corresponding to the radius or diameter of the area irradiated by the electron beam onto the photomask, is experimentally determined in relation to the acceleration voltage of the electron beam. Then, the electron beam is scanned while irradiating only the area to be repaired, and etching and deposition are performed appropriately. [Effects of the Invention]

[0012] This invention selects the repair target based on defect data, and repairs (etching and deposition) this repair target based on a pseudo-SEM image generated from the design data, making it possible to automatically repair photomasks without relying on skilled personnel.

[0013] Furthermore, by repairing or reconstructing the repair target from which the defective portion has been removed based on a pseudo-SEM image, repair instability that depends on the shape of the defect is eliminated, enabling reliable and consistent automatic repair.

[0014] In addition, the following effects are obtained. 1. Using a low-energy aberration corrector, we were able to achieve a small reaction volume on the order of nm, making extremely fine automatic repair possible. 2. By vertically injecting and recovering the gas, the gas concentration increased and controllability improved. 3. Process control using reaction radius was introduced. 4 The introduction of repair targets that remove defective parts enabled the photomask repair process to be fully automated. 5. Etching and deposition of difficult-to-etch materials is now possible. 6. The process volume can now be easily controlled at the atomic layer level (realization of electron beam digital processing). 7 Arbitrary structure construction was realized. Example 1

[0015] Figure 1 shows a configuration diagram of one embodiment of the present invention. This figure shows the configuration diagram of an apparatus for repairing defects in a pattern formed on a photomask, which is a sample 13. The apparatus irradiates the photomask with an electron beam while injecting gas onto the photomask, and repairs the defects by etching or depositing the area reacted by the electron beam. This will be explained in detail below.

[0016] In Figure 1, electron gun 1 generates electrons.

[0017] The blanking electrode 2 is a parallel plate to which a high voltage is applied, and it 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.

[0018] The blanking aperture 3 is an aperture that blocks the deflected primary electron beam by applying a high voltage to the blanking electrode 2.

[0019] 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.

[0020] 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.

[0021] The electron detection device 6 scans the sample 13 while irradiating it with a narrowly focused primary electron beam, and detects and amplifies the secondary electrons emitted at that time.

[0022] The deflection device 7 deflects the primary electron beam in two stages and scans the sample 13 while irradiating it with the narrowly focused primary electron beam.

[0023] The objective lens 8 focuses the primary electron beam narrowly and illuminates the sample 13. Here, if necessary, aberration correction devices (spherical and chromatic aberration correction devices) are used in conjunction to minimize spherical and chromatic aberration.

[0024] The sample chamber 10 is a container that houses samples 13, such as photomasks, inside a vacuum-sealed chamber.

[0025] The gas injection nozzle 11 is a nozzle for injecting gas (etching gas, deposition gas) perpendicularly onto the surface of the sample 13.

[0026] 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. Sample 13 is a sample such as a photomask, which is a sample targeted for repairing defects in a pattern formed on its surface.

[0027] The sample temperature control 14 automatically adjusts the temperature of the mounted sample 13.

[0028] Laser measurement 14-1 precisely measures the position (XYZ) of sample 13 in real time using a laser interferometer.

[0029] The Z-stage 15 adjusts the height position of sample 13.

[0030] The sample bias voltage control 16 applies a predetermined bias voltage to the sample 13.

[0031] The XY stage 17 moves the sample 13 in the X and Y directions, precisely measuring it using the laser measurement 14-1 while moving it to a predetermined position.

[0032] The vacuum gauge 21 measures the vacuum inside the sample chamber 10.

[0033] The vibration isolation table 21 is designed to isolate vibrations from the sample chamber 10 and other components, enabling the acquisition of high-resolution SEM images of the sample 13.

[0034] TMP23 is a vacuum evacuation device, which in this case is used to evacuate the inside of the sample chamber 10.

[0035] The dry pump 24 is an oil-free vacuum evacuation device.

[0036] Next, we will explain the configuration shown in Figure 1 in detail.

[0037] The photomask correction apparatus shown in Figure 1 has an electron beam column consisting of an electron gun 1, blanking electrodes 2, aberration correction device 5, electron detector 6, deflection device 7, and objective lens 8, which are necessary to irradiate an electron beam with the desired energy and current at the desired position and timing. The aberration correction device 5 is capable of correcting higher-order chromatic aberrations of third order or higher in addition to normal spherical aberration correction, so that the electron beam size at low energy can be narrowed to the order of nm.

[0038] The system includes an electron detection device 6 for observing the target to be modified and confirming the endpoint of etching or deposition. It is particularly desirable to use an ALD-type MCP with strong contamination resistance. The process endpoint is determined by setting a predetermined threshold for the contrast of secondary electrons or backscattered electrons, or for the output of a mass spectrometer. The objective lens 8 is equipped with a two-stage differential pump to prevent contamination of the column with process gas, and process gas mixed into the sample chamber 10 does not enter 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.

[0039] 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.

[0040] 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.

[0041] While the cleanroom temperature is maintained within approximately ±1 degree Celsius, a separate temperature control device of ±0.1 degrees Celsius or less is installed within the device to prevent large fluctuations in the temperature of the mask correction device chamber.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Since several types of reaction gases are used for each process, they are supplied through multiple pipes. To simplify the apparatus, for gases that can be mixed, the gases can be combined into a single gas through a gas mixing device that can mix the gases in predetermined proportions, thereby simplifying the system by unifying the pipes. Since the gases are not uniform when simply sprayed from multiple nozzles in a chamber as in conventional methods, this method allows for very stable process results. On the other hand, when reactions are performed by mixing gases, it is desirable to have separate gas supply systems for each. Each supply system has multiple independent control systems that allow for digital numerical control of flow rate, pressure, temperature, supply timing, etc. The entire apparatus is controlled by a PC (not shown), and a display (not shown) shows the repair target, repair goal, repair process and results, SEM images, apparatus status, process conditions, and details.

[0049] Next, we will explain the introduction of the reaction gas in detail using Figure 2.

[0050] Figure 2 shows an example of vertical gas introduction according to the present invention.

[0051] Figure 2(a) shows gas introduction example 1, where there is no gas curtain.

[0052] FIG. 2(a-1) shows an example where the distance between the gas inlet and the sample 13 is large, and FIG. 2(a-2) shows an example where the distance between the gas inlet and the sample 13 is small.

[0053] In Figure 2(a-1), the reactive gas inlet 32 ​​injects reactive gas perpendicularly from the outside toward the sample 13 (see Figure 3(a)). Meanwhile, the vacuum 31 draws a vacuum from the inside of the gas injection by the reactive gas inlet 32 ​​(see Figure 3(a)). As a result, gas is injected perpendicularly toward the outside of the ring-shaped nozzle toward the sample 13, and vacuum 31 is drawn from the inner ring-shaped nozzle portion. Therefore, the gas is removed to the outside by vacuum 31 without scattering to the periphery. Then, by scanning the sample 13 while irradiating it with a primary electron beam of a predetermined size, the scanned area is etched or deposited by the gas and the primary electron beam irradiation, thereby repairing defective portions of the pattern. Because the gas inlet becomes hot, it is desirable for it to be thermally and electrically insulated to prevent the temperature rise of the objective lens and other components. The same effect can be achieved with the gas injection section of the ring-shaped nozzle, which has many holes like a gas stove or has pipes protruding from the holes.

[0054] Similarly, in (a-2) of Figure 2, reactive gas inlet 32 ​​injects reactive gas onto sample 13 from the space between sample 13 and the vacuum plate. Meanwhile, vacuum 31 draws a vacuum from the inside near the axis. As a result, gas is injected onto sample 13 from the outside of the ring-shaped nozzle, and vacuum 31 is drawn from the inside, so that the gas is removed to the outside by vacuum 31 without scattering to the periphery. Then, by scanning while irradiating a primary electron beam of a predetermined size with gas being injected onto sample 13, the scanned area is etched or deposited by the gas and the irradiation of the primary electron beam, making it possible to repair defective portions of the pattern.

[0055] Figure 2(b) shows gas introduction example 2, where a gas curtain is present.

[0056] FIG. 2(b-1) shows an example where the distance between the gas inlet and the sample 13 is large, and FIG. 2(b-2) shows an example where the distance between the gas inlet and the sample 13 is small.

[0057] 2(b-1), in this example, a gas curtain 33 is provided below the reactive gas inlet 32, and the reactive gas is sprayed from the ring-shaped nozzle outside the vertical spray from the ring-shaped nozzle onto the sample 13 by the reactive gas inlet 32 ​​to form a curtain, which further prevents the reactive gas from scattering to the outside. The gas curtain has the function of removing the reactive gas adhering to places other than the electron beam irradiation point.

[0058] 2(b-2), in this example, the distance between the injection port and the sample 13 is small, so that the curtain gas is injected from the outer periphery toward the sample 13 through the gap between the injection port and the sample 13, as shown in the gas curtain 33 in the figure, thereby further preventing the reaction gas from scattering outward. The reaction gas is injected perpendicularly toward the sample 13 as shown in the figure.

[0059] FIG. 2 will now be described in detail.

[0060] The present invention utilizes a gas supply channel similar to a flat microduct, made by stacking thin, non-magnetic plates approximately 100 microns thick. This provides high conductance and eliminates the need for gas to pass through narrow spaces like conventional pipes. This reduces gas solidification and ensures sufficient gas pressure to deliver the gas to the surface of the sample 13. Because the gas is blown from the periphery toward the electron beam irradiation point, a high gas concentration can be maintained at the electron beam irradiation point. Furthermore, a differential pumping system connected to a TMP is located above the electron beam irradiation point, allowing the supplied reactant gas to be quickly recovered. This ability to supply only the required amount of reactant gas to the required location prevents side etching with gases that cause spontaneous etching, such as xenon fluoride. This gas supply channel structure can be fabricated using sheet metal, cutting, 3D printing, or semiconductor processes such as MEMS.

[0061] Figure 3 shows an example of vertical gas introduction (part 2) of the present invention.

[0062] FIG. 3(a) shows gas supply example 1, and FIG. 3(b) shows gas supply example 2 (split into two). FIG. 3(c) shows gas supply example 3 (four-way division).

[0063] In FIG. 3(a), the gas curtain holes 34 are holes for injecting gas that is injected onto the sample 13 to form a curtain.

[0064] The electron beam hole 35 is a hole through which the primary electron beam passes.

[0065] The reactive gas holes 36 are holes for injecting reactive (etching, deposition) gases perpendicularly to the sample 13 .

[0066] In Figure 3(a), gas is supplied from the left side, and reactive gas is injected vertically from the reaction gas hole 36 and curtain gas from the gas curtain hole 34 onto the defective areas of the sample (photomask, etc.) 13. At the same time, a narrowly focused primary electron beam is irradiated and scanned vertically from the electron beam hole 35, making it possible to repair (etch and deposit) the areas irradiated and scanned by the primary electron beam.

[0067] Figure 3(b) shows an example of a two-part division. Here, reaction gas holes 1 and 2 are examples where the reaction gas hole 36 in Figure 3(a) is divided circumferentially into two parts, resulting in two reaction gas holes 1 and 2. Figure 3(c) shows an example of a four-part division. Here, reaction gas holes 1, 2, 3, and 4 are shown as four reaction gas holes 1, 2, 3, and 4, respectively, created by dividing the reaction gas hole 36 in Figure 3(a) circumferentially into four parts. As described above, by dividing the reaction gas hole 36 into multiple sections, it becomes possible to simultaneously inject multiple types of reaction gases almost perpendicularly into the defective areas of the sample 13 for repair (etching, deposition).

[0068] Figure 3 will be explained in detail.

[0069] In this invention, it is desirable to use nozzles and gas supply ports made of non-magnetic materials such as phosphor bronze, titanium, stainless steel, and ceramics so as not to affect the detection of the primary electron beam trajectory or secondary electrons and backscattered electrons generated by the photomask. It is also desirable to make the surface of the ceramic conductive by applying a non-magnetic plating such as amorphous NiP, NiB, or Kanigen plating to prevent static electricity.

[0070] Figure 4 shows a diagram of the system configuration of the present invention.

[0071] In FIG. 4, the mask repair device is a device for repairing defects in a photomask, which is a sample 13, and as shown in the figure, is composed of an image processing device 411, an image recognition device 412, a process procedure generation device 413, and the like.

[0072] The image processing device 411 performs necessary image processing by referring to device design data and the like.

[0073] The image recognition device 412 recognizes images.

[0074] The process procedure generator 413 generates process procedures.

[0075] The process procedure database 42 contains pre-registered process procedures.

[0076] The electron beam information database 43 for reaction radius etc. is a database in which reaction radius etc. associated with the acceleration voltage of the primary electron beam for each material to be repaired or each reactive gas is previously determined by experiment and registered.

[0077] The 3D pattern database 44 contains pre-registered data necessary for creating 3D models of patterns.

[0078] The repair completion criteria database 45 contains data that has been repaired and serves as a standard.

[0079] The design data server 46 registers and manages the design data for the photomask.

[0080] The defect inspection device (or review device) 47 pre-inspects information about defects in the photomask. The present invention automatically repairs defects identified by this defect information.

[0081] Figure 5 shows an explanatory diagram of the reaction radius of the present invention. Here, the horizontal axis represents the energy (acceleration voltage) of the primary electron beam, and the vertical axis represents the reaction radius caused by that primary electron beam, i.e., the radius of etching or deposition (experimental value). The reaction gas is known to mainly react with secondary electrons of several electron volts.

[0082] As shown in Figure 5, the reaction radius increases significantly as the acceleration voltage of the primary electron beam increases. Therefore, when repairing large defects, using a primary electron beam with a high acceleration voltage allows for faster repair. On the other hand, when repairing minute defects, a low voltage is necessary; otherwise, other parts will be etched or deposited, making repair impossible. Thus, it is necessary to select an appropriate primary electron beam acceleration voltage.

[0083] Next, we will explain Figure 7 in detail.

[0084] When the primary electron beam energy is, for example, 1 kV, the electron beam diameter itself is about 1 nm, but the range over which electrons injected into the sample scatter and escape again from the sample surface as secondary electrons extends to several tens of nanometers, and chemical reactions occur in this range. This range is called the reaction radius (Rr). The reaction radius (Rr) can be reduced by lowering the electron beam energy. In this invention, an aberration correction device that can correct higher-order chromatic aberration is used to lower the electron beam energy, achieving a reaction radius of about 2 nm at 200 eV.

[0085] Figure 6 shows an explanatory diagram (part 2) of the reaction radius of the present invention.

[0086] FIG. 6(a) shows an example of a reaction radius, and FIG. 6(b) shows an example of a reaction area.

[0087] In Figure 6(a), if the electron beam scanning coordinate is the center of the black circle shown, the primary electron beam is irradiated at this center. As a result, the primary electron beam enters the inside of the photomask and scatters, and secondary electrons and reflected electrons are emitted from the area with the circular radius shown, resulting in etching and deposition in this area. In other words, even though the radius of the primary electron beam is small, the secondary electrons and reflected electrons generated by scattering within the area spread out, causing etching and deposition in this area (where reactive gas is supplied nearby).

[0088] In Figure 6(b), the reaction region is the region that is generated by scanning the primary electron beam while irradiating it as shown, and is the region that is etched or deposited. By uniformly scanning the entire inside of the illustrated target shape boundary for the reaction region shown, etching or deposition can be performed.

[0089] Figure 6 will be explained in detail.

[0090] For example, if electron beam etching or deposition is performed by simply focusing on the difference between the target shape obtained from the design data and the current shape including defects, the corrected shape will be larger or smaller than the target by the reaction radius Rr. Since the reaction radius ranges from nanometers to tens of nanometers or more, the error is too large considering that the minimum pattern used in photomasks for cutting-edge devices is 50 nm or less, and the correction will fail. In this invention, the electron beam scanning position is calculated from the design data in advance, taking the reaction radius Rr into account, so photomask correction (repair) can be performed accurately based on the installation data.

[0091] Since the patterns that make up a photomask are three-dimensional structures, the use of three-dimensional information as well as two-dimensional information is essential for photomask restoration. For example, controlling the sidewall angle of the pattern is important for photomasks used in EUV and nanoimprint. In EUV, the wavelength is short at 13.5 nm, so even a slight difference of less than 1 degree in the sidewall angle can change the exposure result. Also, in nanoimprint, it is necessary to precisely set a specific angle so that the mask (template) can be easily removed during printing.

[0092] In this invention, in order to obtain a desired sidewall angle, in addition to 2D information from CAD data, 3D information is also input, and the device has a mechanism that can automatically control electron beam irradiation parameters and gas irradiation parameters in 3D or as a function of time in order to obtain a desired sidewall angle or 3D shape profile. In order to perform mask repair automatically, it is necessary to store the unit process processing that serves as a template as a process procedure (ECAM data). In this invention, the process procedure is recorded in the process procedure database, and mask repair is automatically performed by calling the unit process through the ECAM data.

[0093] Figure 7 shows an example of process conditions for the present invention. This shows an example of process conditions when etching or depositing inside the target shape boundary of Figure 6(b) described above.

[0094] Figure 7(a) shows an example of etching process conditions.

[0095] In Figure 7(a), the following illustrated process conditions are those under which etching occurs when scanning the interior of the target shape boundary in Figure 6(b) while irradiating it with a primary electron beam.

[0096] 1. Gas type: XeF2 2. Gas pressure 0.1 Pa 3 Substrate temperature 10℃ 4. Electron beam energy: 400 eV 5. Electron beam current: 10 pA 6 Electron beam ratio 1:10 7 Substrate bias voltage 10V 8 Reaction radius 10nm Here, the electron beam ratio is the proportion of time spent irradiating with the electron beam.

[0097] Figure 7(a) will be explained in detail.

[0098] Xenon difluoride is used as the etching gas. The gas pressure is controlled to the desired level by controlling the temperature of a heater located around a gas cylinder that generates gas by sublimating xenon fluoride, which is a solid at room temperature. A low vapor pressure mass flow controller may also be used. The substrate temperature is adjusted using a device with excellent temperature control performance, such as a Peltier element. Using a Peltier element allows for both heating and cooling at will. The substrate temperature can be freely controlled by forming a feedback circuit together with a thermometer that measures the substrate temperature. Since the substrate temperature greatly affects the adsorption probability of the reaction gas and the detachment rate of the reaction product, which change exponentially with respect to temperature changes, it is desirable to control it with an accuracy of more than 0.1 degrees. The electron beam energy is increased or decreased as needed to determine the reaction volume (the region enclosed by the reaction radius). In this invention, an aberration correction device that can correct chromatic aberration to a high order is used, making it possible to focus the beam to a few nanometers at low energy. The electron beam current is determined to achieve the required process speed to determine the reaction rate. The electron beam ratio refers to the duty cycle ratio of the time the electron beam is irradiated and the time it is not irradiated.

[0099] For a chemical reaction between the primary electron beam and the gas to occur, reactive gas molecules must be present in the electron beam irradiation area. If the gas supply rate is low relative to the electron beam irradiation time per unit area, the reactive gas will not be present at the electron beam irradiation point, and no chemical reaction will occur. The duty cycle is determined to ensure that the gas diffusion and surface adsorption times are well coordinated with the electron beam irradiation timing. Substrate bias refers to the voltage applied to the photomask. Electron beam-induced etching reactions are known to depend on the substrate voltage. The applied voltage changes the secondary electron distribution on the sample surface, thereby affecting the etching rate and etching anisotropy. A bias voltage that achieves the desired etched shape is selected and used. The bias voltage can also be varied over time as the process progresses. Electron beam size is an important parameter that determines the minimum processing size. The minimum diameter of the electron beam is determined by the electron beam energy, probe current, and aberrations in the electron optical system. The present system is equipped with an aberration correction device, which theoretically eliminates aberrations in the electron beam optical system. Electron beam diameters ranging from 1 nm to several tens of nanometers can be obtained at various energies required for the process. Here, a standard value of 10 nm is used.

[0100] FIG. 7(b) shows an example of deposition process conditions.

[0101] In Figure 7(b), the following illustrated process conditions are those under which deposition occurs when scanning the interior of the target shape boundary in Figure 6(b) while irradiating it with a primary electron beam.

[0102] 1 Gas type W(CO)6 2. Gas pressure 0.1 Pa 3 Substrate temperature 10℃ 4. Electron beam energy: 400 eV 5. Electron beam current: 10 pA 6 Electron beam ratio 1:10 7 Substrate bias voltage 10V 8 Reaction radius 10nm FIG. 7(b) will be explained in detail.

[0103] For example, tungsten carbonyl can be used as the deposition gas. The gas pressure is controlled to the desired pressure by controlling the temperature of a heater installed around a gas cylinder that generates gas by sublimating tungsten carbonyl, which is solid at room temperature. The substrate temperature is controlled using a device with excellent temperature control performance, such as a Peltier element. Using a Peltier element allows for both heating and cooling at will. The substrate temperature can be freely controlled by forming a feedback circuit together with a thermometer that measures the substrate temperature. Since the substrate temperature greatly affects the adsorption probability of the reaction gas and the detachment rate of the reaction product, which change exponentially with respect to temperature changes, it is desirable to control it with an accuracy of more than 0.1 degrees. The electron beam energy is increased or decreased as needed to determine the reaction volume. In this invention, an aberration correction device is used to enable focusing to a few nanometers at low energy. The electron beam current is determined to achieve the required process speed to determine the reaction rate. The electron beam ratio refers to the duty cycle. For the chemical reaction between the electron beam and the gas to occur, the reaction gas molecules must be present in the electron beam irradiation region. If the gas supply rate is small relative to the electron beam irradiation time per unit area, no chemical reaction will occur even if the electron beam is irradiated. The duty cycle is determined so that the gas diffusion and surface adsorption time and the electron beam irradiation timing are well coordinated. The substrate bias indicates the voltage applied to the photomask. It is known that electron beam-excited etching reactions depend on the substrate voltage, and the etching rate and etching anisotropy change depending on the applied voltage. A bias voltage that can obtain the desired etching shape is selected and used. The electron beam size is a parameter that determines the minimum processing size. The minimum diameter of the electron beam is determined by the electron beam energy, irradiation current, and aberration of the electron optical system. The apparatus of the present invention is equipped with an aberration correction device, making it possible to reduce the aberration of the electron beam optical system to zero in principle. Therefore, electron beam diameters from 1 nm to tens of nanometers can be obtained at various energies. Here, 10 nm is set as a standard value. Not only metals can be used as deposition films, but also to create ad hoc structures that can be removed by oxygen plasma etching, such as carbon.In the case of carbon, hydrocarbon compounds such as phenanthrene can be used, which makes it possible to create hollow structures or 3D structures that appear to float above the substrate.

[0104] To ensure process reproducibility, a digital process control system is installed so that numerically given process data (pressure, flow rate, temperature, gas type, electron beam conditions, etc.) can be realized or changed in real time in synchronization with the electron beam scanning. This overall control is carried out by running digital process control software stored in a PC.

[0105] FIG. 8 shows a flow chart of the repair process of the present invention.

[0106] In Figure 8, S1 is alignment. This involves setting a photomask as sample 13 in the device in Figure 1 using a robot and aligning it based on the alignment marks. This makes it possible to position the photomask at any coordinate and automatically acquire an SEM image using the coordinates output by the defect inspection device.

[0107] S2 recognizes the repair target (acquires an SEM image). Based on the defect information of the set photomask, it acquires an SEM image of the surface of the photomask to be repaired, including the defective area (the relevant area of ​​the photomask is scanned with a primary electron beam, and the secondary electrons generated at that time are detected and amplified to acquire an SEM image).

[0108] In step S3, a target image is extracted from the CAD data using the coordinates of the repair points. This extracts a target image by referring to the CAD data (design data) using the coordinates of the repair points on the SEM image where defects are present.

[0109] S4 converts the image from CAD data to the target shape. This converts the target image extracted from the CAD data in S3 into an image of the target shape (pseudo SEM image) that corresponds to the process of the photomask to be repaired. This makes it possible to automatically generate an ideal image (pseudo SEM image) that will be generated when the process of the photomask to be repaired is executed from the CAD data.

[0110] S5 evaluates the difference, which calculates the difference in the defect area between the pseudo SEM image generated in S4 and the SEM image acquired in S2.

[0111] In step S6, a process area is identified, which is a processing target (process area) including the area of ​​the difference calculated in step S5.

[0112] S7 sets the process method, sequence, speed, and conditions for the process area identified in S6.

[0113] S8 executes the process, which executes the repair of the process area according to the process method, order, speed, and conditions set in S7.

[0114] S9 evaluates the process result by acquiring an SEM image after the process of S8 is executed, obtaining the difference between the acquired image and a pseudo SEM image, and evaluating the degree of repair.

[0115] By following the steps S1 to S9 above, a pseudo-SEM image containing the defective part is generated based on the defect information of the photomask, the difference between this and the SEM image of the actual photomask is extracted, and repair is performed so that this difference becomes zero, making it possible to automatically repair (etch and deposit) the defective part of the photomask.

[0116] FIG. 9 shows an illustration of the repair process of the present invention.

[0117] FIG. 9(a) shows an example of defect coordinates (S1 in FIG. 8).

[0118] 9(a-1) shows an example of defect coordinates, and FIG. 9(a-2) shows an example of defect coordinate data. This is an example of displaying the coordinates of defects on a photomask.

[0119] FIG. 9(b) shows example images (S2, S3, and S4 in FIG. 8).

[0120] (b-1) in Figure 9 shows an example of an SEM image (S2 in Figure 8), (b-2) in Figure 9 shows an example of a CAD image (S3 in Figure 8), and (b-3) in Figure 9 shows an example of a pseudo-SEM image (S4 in Figure 8).

[0121] Figure 9(c) shows an example of differential image data (S5 in Figure 8), which is an example of an image obtained by subtracting a pseudo-SEM image from an SEM image.

[0122] FIG. 10 shows an explanatory diagram of the repair of the present invention.

[0123] 10(a) shows an example of a defect range. This indicates that the defect center coordinates are (x, y), and the image of the range (Δx, Δy) centered on this is taken as the defect image.

[0124] Figure 10(b) shows an example of a pseudo-SEM image.

[0125] Figure 10(b-1) schematically shows an example of design data (CAD data), and Figure 10(b-2) shows an example of a pseudo-SEM image. This is an ideal image (pseudo-SEM image) generated when a predetermined process is performed based on the design data.

[0126] Figure 10(c) shows an example of restoration.

[0127] (c-1) in Fig. 10 shows an example of a defect image, in which a pattern (defect) protruding to the right is formed in the middle of the pattern.

[0128] Figure 10(b-2) shows an example of a pseudo-SEM image, which is an ideal (defect-free) pseudo-SEM image generated using the same process as the defective photomask, based on the design data of the defect image example in Figure 10(b-1).

[0129] Fig. 10(c) shows an example of a repaired image after performing repair (etching and deposition) of Fig. 10(c-3) so that the difference between the pseudo-SEM image of Fig. 10(c-2) and the defect image (SEM image) of Fig. 10(c-1) becomes zero.

[0130] Next, FIGS. 8 to 10 will be specifically described in detail below.

[0131] First, SEM images of defect positions on the photomask are acquired in order according to the defect position coordinates (KLARF, etc.) output by the defect inspection system (S2 in FIG. 8). The defect position coordinates are used to access the design database for the device to be repaired (S3 in FIG. 8). The range of data to be imported is specified along with the center coordinates of the defects, as shown in FIG. 10(a). The range to be imported should preferably be large enough to include the entire defect to be repaired and a range (e.g., 1 micron) that can absorb the deviation in position coordinates between the defect inspection system and the mask repair system of the present invention (FIG. 1).

[0132] The CAD data to be repaired is transferred to the photomask repair device (Figure 4). Since the CAD data differs from the actual pattern formed on the photomask, as shown in Figure 10(b), image conversion is performed using deep learning such as GANs that have learned the correspondence between the CAD data and the SEM image that reflects the shape formed on the actual photomask, or using image processing that expresses corner rounding and noise specific to SEM images, to convert the CAD data shape into a pseudo-SEM image that resembles the actual pattern on the photomask (Figure 8, S4). The positions of the image of the area to be repaired (defect image) and the pseudo-SEM image (target image for repair) are aligned using pattern matching, and a difference image between the defect image and the pseudo-SEM image is calculated (Figure 8, S5). This difference image corresponds to the shape to be repaired. There are differences in 2D images and differences in 3D structures. The 2D image difference is obtained from the difference between the two images. The 3D difference is obtained by calculating the difference between the 3D profile of the structure obtained using the stereo method, sectioning method, moiré method, or AFM, etc., and the 3D profile of the ideal structure. In this way, the scope, amount and goal of the correction process are determined.

[0133] Electron beam excitation processes have a unique minimum processing resolution distinct from the electron beam size. This repair resolution is defined herein as the reaction radius, and it represents the range of secondary electrons generated when the electron beam is incident on the material. This range is considerably larger than the electron beam probe size, ranging from a few nanometers to tens of nanometers. This value varies depending on the electron beam probe size and the material being repaired, making it a process parameter.

[0134] The patterns used in semiconductor devices have restrictions on their shape to ensure yield, and similar patterns are reused repeatedly. By structuring the repair process for these basic patterns as a single unit and combining these sequences, it is possible to repair patterns of any shape.

[0135] Photomask correction is performed automatically according to an ECAM file that is generated so that the difference between the target shape and the electron beam excitation reaction radius is zero after automatic correction, taking into account the reaction radius of each reaction case (S8 in Figure 8). Repairs vary in difficulty, and there are various procedures for them. Simple repairs can be completed with a single pre-prepared unit process. In this case, a single process condition is set for the repair point, and the electron beam is scanned and deposition or etching is performed to achieve the desired shape in one go. For complex patterns, a method can be adopted in which the unit processes are automatically combined by reducing the pattern to a simple combination, or several passes or layers are considered, and the electron beam and gas conditions used for repair are changed for each pass or layer to gradually make the repair. These process procedures can be generated automatically by a computer, or they can be taught by a human in the same way that complex movements of an industrial robot are taught. The resulting files are named and recorded as ECAM data.

[0136] Taking into consideration the photomask material, repair volume, etc., the optimal process method is selected, or the process sequence, electron beam energy and current values, scanning coordinate position and speed, etc. are automatically generated to create a process execution file (ECAM file).The photomask repair device (Fig. 1, Fig. 4) repairs the photomask fully automatically according to this file.

[0137] As shown in Figure 10(c), the photomask repair device automatically repairs the photomask by controlling the electron beam irradiation position, gas type and amount, and temperature according to the process execution file (ECAM). Finally, the repaired pattern is observed two-dimensionally or three-dimensionally using an SEM to confirm whether the repair was carried out correctly. If necessary, optical simulations can be performed or confirmation can be carried out using a simulation microscope such as AIMS that can realize actual exposure conditions.

[0138] FIG. 11 shows an explanatory diagram (part 2) of the repair method of the present invention.

[0139] Figure 11(a) shows an example of a defective image (convex). This shows an example of a defective image where the defect (convex) is on the right side, as shown in the figure.

[0140] FIG. 11(a-1) shows an example of a defect image (convex).

[0141] Figure 11(a-2) shows the area to be repaired after the defective (convex) portion (or a slightly larger portion) of the defective image example (convex) has been excised.

[0142] Figure 11(a-3) shows the restored image. This shows the restored image of the object to be restored in Figure 11(a-2) after restoration based on a pseudo-SEM image.

[0143] Figure 11(b) shows an example of a defect image (indentation). This shows an example of a defect image where the defect (indentation) is on the right side, as shown in the figure.

[0144] FIG. 11(b-1) shows an example of a defect image (concave).

[0145] Figure 11 (b-2) shows the area to be repaired after the defective (concave) portion (or a slightly larger portion) of the defective image example (concave) has been excised.

[0146] Figure 11(b-3) shows the restored image. This shows the restored image of the object to be restored in Figure 11(b-2) after restoration based on a pseudo-SEM image.

[0147] Next, we will explain Figure 11 in detail.

[0148] Photomask repair is not always successful. For example, even if deposition is performed on the area corresponding to the difference, a boundary will form between the repair target and the deposited area. The deposited structure has poor adhesion, resulting in detachment after several photomask cleanings. Alternatively, the structure may be too small compared to the process resolution and cannot be realized with the deposition resolution. Furthermore, since the target structure is arbitrary, it is theoretically impossible for a computer to automatically repair it while taking into account its structure. In such cases, it is effective to etch a slightly larger area including the deposition area to create a fresh area with a fixed shape. Removing the defective area in this way can ensure consistent work and increase or stabilize the adhesion of the deposition process. Furthermore, since the shape before the deposition process can be set to the desired shape or a fixed standard shape, preparing ECAM data for several automated processing shapes as templates in advance allows for automatic mask repair by performing optimal deposition and etching processes using automated processing without being affected by the surrounding area where the repair target is located.

[0149] As an application of the ablation process, by combining offset deposition, which deposits excess material, with etching, which removes the excess material, it is possible to obtain a more desirable photomask repair shape by removing the unwanted shape created by the deposition process again by etching. These process flows can be stored in a process procedure database.

[0150] For example, if deposition is simply performed, the pattern edges obtained from the deposition may not be vertical but drooping. In EUV photomasks using 13.5nm, the reflectivity changes if the edges are drooping, so the edges need to be sharp at 90 degrees. In such cases, a deposition offset of Xnm is used. By first performing deposition over an area Xnm wider than the final correction target, and then performing an etching process that makes it easier to obtain a relatively vertical cross-section than deposition to form the final shape, it is possible to achieve photomask correction with sharp 90-degree edges. Specifically, deposition is performed with the target shape being a figure that is X nanometers larger than the design data. Then, etching is performed to create the figure that will become the final repair target obtained from the CAD data. If necessary, the correction process may be performed by combining deposition and etching multiple times. Since many integrated circuit patterns are similar, the relationship between various patterns and ranges can be learned through training, and the appropriate range can be automatically selected for the various patterns that appear during photomask correction.

[0151] FIG. 12 shows an overall flow chart of the repair process of the present invention.

[0152] In Fig. 12, S21 loads mask, which commands the photomask to be repaired to be loaded as sample 13 of the device (Fig. 1).

[0153] In step S22, the robot transports the photomask to the XY stage. In response to the mask load command in step S21, the robot transports the photomask to the XY stage of the apparatus shown in FIG.

[0154] In S23, the XY stage is moved so as to enter the electron beam processing range. After the photomask is transported to the XY stage and fixed in S22, the photomask is scanned while being irradiated with a finely focused primary electron beam, and the XY stage is moved so as to enter the processing range by the primary electron beam.

[0155] This completes the preparations for scanning the photomask while irradiating it with the primary electron beam, and for etching or deposition.

[0156] S24 starts the data reading process.

[0157] S25 is deposited or etched inside the X1Y1-X2Y2 region. As shown in Figure 13 (a-2) below, a wide primary electron beam is used to process (deposit or etch) the area slightly inside the area to be repaired. This allows the entire area slightly inside the area to be repaired to be rapidly deposited or etched with the wide primary electron beam, enabling the process to be completed in a short time.

[0158] S26 deposits or etches material onto the edges (boundaries) of the X1Y1-X2Y2 region. As shown in Figure 13 (a-2) later, this process involves processing (depositing or etching) the outer boundary of the area to be repaired by taking fine scanning steps with a narrow primary electron beam. This allows for precise deposition or etching of the boundary area of ​​the area to be repaired with the primary electron beam, resulting in a process that improves the accuracy of the boundary area of ​​the area to be repaired.

[0159] S27 is where the purge gas is introduced, which allows the reactive gases used in deposition and etching to be completely exhausted to the outside or neutralized.

[0160] S28 removes the mask from the XY stage.

[0161] S29 unloads the mask.

[0162] As a result of the above, the photomask to be repaired is transported to the stage of the equipment (Fig. 1) and fixed in place, and the boundary portion of the object to be repaired is scanned while irradiating it with a thin primary electron beam, and the entire inner portion is scanned while irradiating it with a thick primary electron beam.By simultaneously injecting reactive gas, deposition or etching can be performed accurately on the boundary portion of the object to be repaired and quickly on the interior, making it possible to automatically repair defects in the photomask.

[0163] Next, we will explain Figure 12 in detail.

[0164] The edge region of the pattern on the photomask requires a steep pattern edge with little edge roughness. The edge region of the pattern is extracted from the design data to be repaired, and a predetermined range slightly inside the edge region is defined as the boundary region (see Figure 13 (a-2)). The deposition (etching) process is performed on the edge region under conditions where the primary electron beam is narrowed to, for example, about 2 nm. For other inner regions, conditions are applied where the primary electron beam size is 2 nm or more and the current value is increased to 10 pA, allowing for high-speed deposition (etching).

[0165] This allows for accurate repair and shortens the repair time. By storing these in a process flow database, they can be used for automatic mask repair using ECAM.

[0166] Figure 13 shows an explanatory diagram of electron beam scanning in the repair process of the present invention.

[0167] FIG. 13(a) shows an example of a scanning beam.

[0168] 13(a-1) shows a repair target. The repair target shown in the figure is a defective target (pattern example) identified by the coordinates (center coordinates) of a defective pattern on a photomask.

[0169] Figure 13(a-2) shows the edge region (boundary region). This is the area slightly inside the outer boundary of the defect target (pattern) in Figure 13(a-1). This edge region is scanned while irradiating with a narrow primary electron beam and processed (deposited or etched) with good precision. The area inside the edge region is scanned while irradiating with a wide primary electron beam in large steps and processed (deposited or etched) in a short time.

[0170] FIG. 13(b) shows an example of a beam scanning method.

[0171] Figure 13(b-1) shows a vector scan. A vector scan involves scanning the pattern to be repaired, for example, by irradiating it with a primary electron beam in the direction of the arrows shown, and then irradiating the boundary areas (edge ​​regions) to repair it by deposition or etching.

[0172] Figure 13(b-2) shows a raster scan. Raster scanning involves scanning the pattern to be repaired in a specific direction, for example, as shown by the arrows in the figure, illuminating only the necessary parts (in this case, only the boundary regions (edge ​​regions)), and then repairing them by deposition or etching.

[0173] Figure 14 shows an explanatory diagram of the damageless etching method of the present invention. This method involves etching sequentially from the highest to the lowest areas of the defect on the photomask, preventing over-etching and damage to the substrate.

[0174] Figure 14(a) shows a state with a two-layer defect pattern.

[0175] FIG. 14(b) shows the pattern after the pattern of the first layer has been removed by etching.

[0176] Figure 14(c) shows the pattern after the pattern of the second layer has been removed by etching.

[0177] As described above, when there are multiple layers or defect patterns with varying heights, etching can be performed without damaging other patterns by etching and removing the patterns in order from the highest layer upwards.

[0178] Next, FIG. 14 will be described in detail.

[0179] Etching in photomask repair must be performed carefully, as it can damage the photomask itself. The height of a typical pattern formed on a photomask is consistent on the order of nanometers, as it is formed using a precision thin-film deposition process. However, if a foreign object or process abnormality occurs from the exposure tool or other process equipment, the height of the object on the photomask is not necessarily consistent, and is even unknown.

[0180] In such cases, if electron beam etching is performed uniformly, the thicker areas of the film remain, while the thinner areas are etched down to the underlying layer, damaging the mask. This makes it impossible to perform repair correctly. In this embodiment, taking advantage of the ability to irradiate the electron beam at any location, the height of the object to be etched is measured in advance to clarify the 3D structure, and then areas of the same height are grouped together so that the height is consistent, starting from the highest point, and etching is performed layer by layer in order. In this way, even if there is height variation in the defect area to be repaired, etching can be performed without damaging the boundary of the underlying layer.

[0181] Height can be estimated from stereo images obtained using a SEM or from the moiré method, or data measured with other devices such as an AFM can be used. An AFM can also be built into the mask correction device. By storing and retrieving these measured 3D shapes in a database, the height can be known during processing. If stereo SEM images are used, the height can be measured on the spot, so it is possible to know the height of the object to be repaired during processing and perform etching while measuring the height. As shown in Figure 13, etching is performed sequentially from the highest point, and finally the lowest point is etched to complete the process. Processing in this way does not damage the substrate, and selective etching is possible without using an etching gas with a very high selectivity ratio with the substrate.

[0182] Figure 15 shows an explanatory diagram of the digital electron beam etching and deposition process according to the present invention.

[0183] Figure 15(a) shows electron beam atomic layer etching (electron beam ALE). This is a technique in which a layer of oxygen molecules is formed in advance on a conventionally difficult-to-etch material (see Figure 15(a-2)), enabling precise etching of each atomic layer at the location irradiated with the electron beam.

[0184] Figure 15(a-1) shows a schematic cross-sectional view of a photomask with a defect.

[0185] Figure 15(a-2) shows a schematic cross-sectional view of the oxygen molecular layer of the defect pattern formed on the photomask.

[0186] Figure 15(a-3) shows a schematic cross-sectional view of a state in which a hexafluoroacetylacetone layer is formed on top of the oxygen molecular layer, which is a defect pattern formed on the photomask shown in Figure 15(a-2), and an electron beam is irradiated from above. As shown in the figure, when the primary electron beam is irradiated, the hexafluoroacetylacetone layer and the oxygen molecular layer beneath it react to form a complex, which becomes volatile and can be etched. As a result, etching occurs as shown in Figure 15(a-4).

[0187] FIG. 15(a-4) is a schematic cross-sectional view showing the state after the oxygen molecule layer on the photomask has been etched.

[0188] As described above, even conventional materials that are difficult to etch can be etched by supplying oxygen or ozone to convert them into volatile materials.

[0189] Next, (a) of FIG. 15 will be described in detail.

[0190] For etching transition metals that cannot be etched using conventional xenon fluoride etching, beta-diketones such as hexafluoroacetylacetone can be used. When this gas is used, the compounds formed after etching transition metals such as Ni, Co, Pt, Cu, Ru, Pd, Fe, Mn, Ir, Tb, Ta, and Ti become volatile, facilitating etching of Ni and other metals. Because hexafluoroacetylacetone has the ability to form complexes with nickel or nickel oxide, a pre-oxidation process for nickel can be included. This can be achieved by supplying oxygen or ozone to oxidize the nickel beforehand, or by simultaneously supplying oxygen and hexafluoroacetylacetone to the photomask surface during electron beam irradiation. The oxidation process is carried out by supplying pulses of reactive gas to the photomask surface using a fast-response valve.

[0191] Similar etching can also be performed on cobalt and copper. This invention thus enables seamless etching of difficult-to-etch materials, including those used in future high-NA EUV exposure tools, and allows for mask repair. Because metal oxide film formation is the reaction-limiting process, the oxide film is first formed, followed by the formation of a metal complex by the introduction of hexafluoroacetylacetone, and finally by electron beam irradiation to evaporate and remove the film, forming a single etching process. Therefore, the gas introduced into the chamber is pulsed to ensure the reaction-limiting rate. Furthermore, the etching volume can be precisely controlled by specifying the number of gas introduction cycles. This eliminates the need to control the etching endpoint and enables damage-free local etching. Unlike conventional ALE processes, only the areas irradiated by the electron beam are etched, allowing for maskless pattern formation.

[0192] Figure 15(b) shows electron beam atomic layer deposition (electron beam ALD). This method allows for precise deposition of single atomic layers at a time in the location irradiated with an electron beam, by pre-forming a metal complex layer (see Figure 15(b-2)) for conventionally difficult-to-deposit materials.

[0193] Figure 15(b-1) shows a schematic cross-sectional view of a photomask with a defect.

[0194] Figure 15(b-2) shows a schematic cross-sectional view of the metal complex layer with a defect pattern formed on a photomask.

[0195] Figure 15(b-3) is a schematic cross-sectional view of a hydrogen layer formed on a metal complex layer, which is a defect pattern formed on the photomask of Figure 15(b-2), and then irradiated with an electron beam from above. As shown in the figure, when irradiated with a primary electron beam, the hydrogen layer and the underlying metal complex layer interact with each other and are reduced to form metal, which can then be deposited. As a result, deposition occurs as shown in Figure 15(b-4).

[0196] Figure 15(b-4) shows a schematic cross-sectional view of the metal complex layer on the photomask after it has been hydrogen-reduced and deposited.

[0197] As described above, it has become possible to reduce and deposit metal complex layers even in conventionally difficult-to-deposit materials.

[0198] Next, we will explain Figure 15(b) in detail.

[0199] Electron beam deposition of transition metals, particularly nickel, cobalt, and copper, can also be achieved by using hexafluoroacetylacetone complexes of these difficult-to-etch transition metals as precursors for electron beam-excited deposition reactions. Contrary to etching, a reducing agent such as hydrogen is required. Hydrogen can be used as a reducing gas. Chemicals such as diethylene glycol dimethyl ether can be added to the main reaction gas to stabilize the reaction. Argon, helium, nitrogen, and ammonia gases can also be used in addition to hydrogen gas to ensure effective delivery of hydrogen to the photomask surface. Pretreatment gases can also be added to stabilize metal deposition. Examples include hydrogen-containing gases such as H2, H2O, and H2O2; inert gases such as Ar, He, and Kr; and nitrogen-containing gases such as N2, NH3, NO2, and NO2. Because the metal reduction reaction by hydrogen is the rate-determining reaction, a single deposition process is determined by the initial introduction of the metal complex to the sample surface, followed by hydrogen introduction and subsequent reduction to metal by electron beam irradiation. Reducing gases such as hydrogen are supplied to the photomask surface in pulses using a fast-response valve. As with etching, a metal film of the desired thickness can be obtained by determining the number of cycles without end-point detection. Because the reaction occurs only in the area irradiated by the electron beam, unlike the commonly known ALD process, pattern formation can be achieved without a mask by scanning the electron beam.

[0200] Figure 16 shows an explanatory diagram of electron beam formation according to the present invention.

[0201] FIG. 16(a) shows a first example of the support structure.

[0202] Fig. 16(a-1) shows an example of a support structure, in which four cubes are arranged horizontally as shown in the figure.

[0203] An example of deposition is shown in Fig. 16(a-2), which shows the structure after deposition as shown around the support structure of Fig. 16(a-1).

[0204] Fig. 16(a-3) shows an example of support structure removal, which shows the structure after the deposition of Fig. 16(a-2) and subsequent removal of the internal support structure.

[0205] FIG. 16(b) shows a second example of the support structure.

[0206] Figure 16(b-1) shows an example of a support structure. As shown in the figure, this structure has 10 cubes arranged in a staircase pattern.

[0207] Fig. 16(b-2) shows an example of deposition, which shows the structure after deposition (deposition) as shown around the support structure of Fig. 16(b-1).

[0208] Fig. 16(b-3) shows an example of support structure removal, which shows the structure after the internal support structure is removed after the deposition of Fig. 16(b-2).

[0209] Next, (a) and (b) of FIG. 16 will be described in detail.

[0210] The apparatus of the present invention can create arbitrary patterns in mid-air, similar to a 3D printer. For example, in the case of a structure where the area beneath the pattern is open, as is done with a 3D printer, a method can be used in which a support structure is created, the target structure is created on top of it, and then the support structure is removed.

[0211] For example, if the support structure is made of carbon, this can be achieved by introducing a hydrocarbon compound such as phenanthrene into the chamber and irradiating it with an electron beam. Carbon support structures can be easily removed by oxygen plasma etching. Similarly, silicon oxide or other materials can be used for the support structure. In this case, the support structure can be removed using fluorine gas or other gases.

[0212] Using the above method, it is possible to create any structure at the nm order, just like a 3D printer. As with a 3D printer, deposition can be performed at any position, so it goes without saying that walls and holes at any angle can be created. Because each block is large, it looks rough, but by reducing the size of each block or stacking them in sub-pixel positions, it is possible to create structures with an infinitely smooth shape. [Brief explanation of the drawings]

[0213] [Figure 1] FIG. 1 is a configuration diagram of an embodiment of the present invention. [Figure 2] This is an example of vertical gas introduction according to the present invention. [Figure 3] This is an example (part 2) of vertical gas introduction according to the present invention. [Figure 4] This is a system configuration diagram of the present invention. [Figure 5] This is an explanatory diagram of the reaction radius of the present invention. [Figure 6] This is a diagram (part 2) illustrating the reaction radius of the present invention. [Figure 7] This is an example of process conditions for the present invention. [Figure 8] 3 is a flowchart of the repair process of the present invention. [Figure 9] This is an explanatory diagram of the repair process of the present invention. [Figure 10] This is a diagram illustrating the restoration of the present invention. [Figure 11] This is a diagram illustrating the restoration process of the present invention (part 2). [Figure 12] This is an overall flowchart of the repair process of the present invention. [Figure 13]FIG. 2 is an explanatory diagram of electron beam scanning in the repair process of the present invention. [Figure 14] FIG. 2 is an explanatory diagram of damage-less etching according to the present invention. [Figure 15] FIG. 1 is an explanatory diagram of electron beam etching and deposition according to the present invention. [Figure 16] FIG. 2 is an explanatory diagram of electron beam formation according to the present invention. [Explanation of symbols]

[0214] 1: Electronic gun 2: Blanking electrode 3: Blanking Aperture 4: Pulse blanking device 5: Aberration correction device 6: Electronic detection device 7: Deflection device 8: Objective lens 10: Sample Room 11: Gas injection nozzle 12: Height sensor 13: Sample 14: Sample temperature control 14^1: 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: Vacuuming 32: Reaction gas introduction 33: Gas Curtain 34: Gas curtain hole 35: Electron beam hole 36: Reaction gas hole 41: Mask repair device 411: Image processing device 412: Image recognition device 413: Process procedure generator 42: Process procedure database 43: Reaction Radius and Other Electron Beam Process Information Database 44: 3D pattern database 45: Repair completion criteria database 46: Design data server 47: Defect inspection equipment

Claims

1. A photomask repair apparatus for repairing defects in a photomask, a nozzle for spraying gas onto the surface of the photomask; a stage for holding the photomask facing the nozzle; a means for detecting and amplifying emitted secondary electrons while scanning the photomask with a narrowed electron beam to obtain an SEM image; A defect database containing defect data obtained by pre-inspecting the photomask with a defect inspection device, relating to the pattern on the surface of the photomask, a design database storing design data of a pattern on the surface of the photomask; a means for extracting defect data of a photomask to be repaired from the defect database when repairing defects in the photomask, and extracting design data having the defect data from the design database based on the defect data, thereby generating a pseudo SEM image suited to the process of the photomask; Based on the generated pseudo-SEM image, a repair means performs a repair consisting of etching, deposition, or switching between both, by injecting gas from the nozzle into the portion of the photomask corresponding to the SEM image on which the extracted defect data has defects. A photomask repair device comprising:

2. The repair means creates a repair target by injecting gas from the nozzle onto the defective portion or a slightly larger area on the photomask where the defect of the extracted defect data is present, corresponding to the SEM image, based on the generated pseudo SEM image, and then repairs the repair target by injecting gas from the nozzle onto the repair target by either etching or deposition, or by switching between both.

2. The photomask repair apparatus according to claim 1.

3. The photomask repair apparatus according to claim 1, characterized in that an air curtain is provided outside the nozzle from which gas is injected onto the photomask to prevent gas leakage to the outside of the air curtain and to remove adhering gas.

4. A photomask repair device as described in any one of claims 1 to 3, characterized in that the reaction radius or reaction diameter of the gas corresponding to the radius or diameter of the portion irradiated by the electron beam on the photomask is determined by experiment in correspondence with the acceleration voltage of the electron beam, and the electron beam is scanned while being irradiated so as to repair only the repaired portion, thereby appropriately performing the etching and deposition.

5. A photomask repair method for repairing defects in a photomask, comprising: a nozzle for spraying gas onto the surface of the photomask; a stage for holding the photomask facing the nozzle; A means for irradiating and scanning a photomask with a narrowed electron beam, detecting and amplifying the emitted secondary electrons, and acquiring an SEM image; A defect database containing defect data obtained by pre-inspecting the photomask with a defect inspection device, relating to the pattern on the surface of the photomask, a design database storing design data of a pattern on the surface of the photomask; We have established The pseudo SEM image generating means, when repairing defects in the photomask, retrieves defect data of the photomask to be repaired from the defect database, and based on the defect data, retrieves design data having the defect in the defect data from the design database, and generates a pseudo SEM image suited to the process of the photomask; The repair means performs repair by injecting gas from the nozzle to a portion of the photomask corresponding to the SEM image, which has a defect in the extracted defect data, and by performing either etching or deposition, or by switching between both, based on the generated pseudo SEM image. A photomask repair method comprising:

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