Electron beam processing method and electron beam processing program

Abstract

The present invention relates to an electron beam processing method and an electron beam processing program, and aims to repair defects by irradiating a sample with an electron beam to induce a chemical reaction. [Configuration] This electron beam processing method comprises the steps of: acquiring and storing in advance the reaction radius, which indicates the spatial extent of the chemical reaction that occurs on the sample according to the difference in irradiation conditions; determining at least one of the electron beam irradiation position, scanning interval, number of irradiations, beam current, acceleration voltage, and irradiation time based on the reaction radius; and performing electron beam irradiation based on the determined conditions.

Description

Technical Field

[0001] The present invention relates to an electron beam processing method for irradiating a sample with an electron beam to cause a chemical reaction and an electron beam processing program.

Background Art

[0002] Conventional photomask repair was not automated and was, so to speak, semi-automatic. For example, for repair, it was necessary for a person to create, select the figure to be corrected, or copy an existing figure. Skilled workers were required for repair, resulting in low productivity.

[0003] Also, in principle, there is only one repair target, but the repairs performed by skilled workers do not always result in the same outcome. Variations in photomask performance occurred secondarily due to the repairs.

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] As described above, in the conventional repair of a photomask, since a person creates, selects the figure to be corrected, or copies an existing figure and then performs repair (etching, deposition), skilled workers are required for repair and there is a problem that automatic repair is not possible.

[0005] Also, since the repair was performed by skilled workers, the same result was not always obtained, and there were problems such as variations occurring in the secondary photomask performance due to the repair.

Means for Solving the Problems

[0006] In order to solve the above-described problems, the present invention aims to automatically perform repair by selecting a repair target based on defect data so that the same result is always obtained, and performing repair (etching, deposition) on this repair target based on a pseudo-SEM image generated from design data.

[0007] Furthermore, in order to solve the above-mentioned problems, the present invention aims to create a repair target by removing the defective portion based on defect data so that the same results can always be obtained, and then to automatically repair or reconstruct (etch, deposit) this repair target based on a pseudo-SEM image generated from design data.

[0008] Therefore, the present invention relates to a photomask repair apparatus for repairing defects in a photomask, comprising: a nozzle for blowing gas perpendicularly onto the surface of the photomask; a stage for holding the photomask opposite the nozzle; means for detecting and amplifying secondary electrons and backscattered electrons emitted by scanning the photomask while irradiating it with a narrowly focused electron beam to acquire an SEM image; a defect database storing defect data relating to the pattern on the surface of the photomask; a design database storing design data relating to the pattern on the surface of the photomask; means for retrieving defect data of the photomask to be repaired from the defect database when repairing defects in the photomask, and retrieving design data containing the defect in the defect data from the design database based on the defect data to generate a pseudo-SEM image that is compatible with the process of the photomask; and repair means for performing a repair consisting of etching, deposition, or switching between both, by injecting gas from the nozzle onto the portion of the SEM image on the photomask where the extracted defect data has a defect, based on the generated pseudo-SEM image.

[0009] In this process, the repair method uses the generated pseudo-SEM image to create a repair target by etching the defective portion or a slightly larger area of ​​the photomask surface corresponding to the SEM image of the extracted defective data by spraying gas from a nozzle. Then, the repair method performs etching and deposition, or a combination of both, on the repair target by spraying gas from a nozzle.

[0010] Furthermore, an air curtain is provided outside the nozzle from which the gas is sprayed onto the photomask to prevent gas leakage to the outside of 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 enables automated photomask repair, eliminating reliance on skilled personnel, by selecting a repair target based on defect data and then repairing (etching and deposition) this target based on a pseudo-SEM image generated from design data.

[0013] Furthermore, by repairing or reconstructing the target object, from which the defective parts have been removed, based on pseudo-SEM images, the repair instability dependent on the shape of the defect is eliminated, enabling reliable and consistent automated repair.

[0014] Furthermore, it has the following effects: 1. By using a low-energy aberration correction device, it became possible to achieve reaction volumes on the order of nanometers, enabling extremely fine automated repair. 2. By vertically injecting and recovering the gas, the gas concentration increased and controllability improved. 3. We were able to implement process control using reaction radius. 4. By introducing a model to be repaired with the defective portion removed, the photomask repair process was fully automated. 5. Etching and deposition of difficult-to-etch materials has become possible. 6. Process volume can now be easily controlled at the atomic layer level (realization of electron beam digital processes). 7. We were able to achieve arbitrary structure construction. [Example 1]

[0015] Figure 1 shows a configuration diagram of one embodiment of the present invention. This Figure 1 is a configuration diagram of an apparatus for repairing defects in a pattern formed on a photomask, which is sample 13. The apparatus irradiates the photomask with an electron beam while spraying gas, and repairs the defects by etching or deposition in the reaction area of ​​the electron beam. A detailed explanation follows below.

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

[0017] The blanking electrode 2 is a parallel plate that allows the primary electron beam generated by the electron gun 1 to pass through or block at high speeds on the order of nanoseconds, and a high voltage is applied to it. The blanking electrode is designed to prevent the primary electron beam from drifting due to the charge of the blanked electron beam.

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

[0020] The aberration correction device 5 consists of an electron beam deflection element made of an octapole that generates an electromagnetic field in multiple stages and a transfer lens, and is designed to correct chromatic aberration for low-energy primary electron beams up to the third order or higher, and to narrow the beam on sample 13. Here, if necessary, the aberration correction device (chromatic aberration correction device) 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.

[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 while irradiating the sample 13 with a thin and constricted primary electron beam.

[0023] The objective lens 8 constricts the primary electron beam and irradiates it onto the sample 13. Here, an aberration correction device (spherical and chromatic aberration correction device) is used in combination as necessary to minimize spherical and chromatic aberrations.

[0024] The sample chamber 10 is a container for storing samples such as the sample 13 like a photomask inside a vacuum-exhausted interior.

[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. The sample 13 is a sample such as a photomask and is a sample to be repaired for defects in the pattern formed on its surface.

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

[0028] The laser measurement 14-1 precisely measures the position (X, Y, Z) of the sample 13 in real time using a laser interferometer.

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

[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 and moves it to a predetermined position while being precisely measured by the laser measurement 14-1.

[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] It has 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 has an ion pump (not shown) to maintain an ultra-high vacuum of 10⁻⁷ Pascals or more inside the column. Furthermore, it has 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 measurement of the sample position 13, and sample temperature control 14. It has a vacuum chamber (sample chamber 10) made of pure iron or a low thermal expansion material such as Invar or SuperInvar that can achieve a vacuum of 10⁻⁵ Pascals or less so that the electron beam can reach the photomask, and has a dry pump 24 or turbomolecular pump to maintain the desired vacuum level inside the chamber, and a vacuum gauge 21 for measuring the chamber vacuum level.

[0040] The sample position control device, which positions the mirrors and other components of the laser interferometer, is surrounded by materials with an ultra-low thermal expansion coefficient. To suppress vibrations from the surrounding environment that are transmitted into the device, it is equipped with an active vibration isolation system, as well as a device that feeds sample vibrations back into 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 perform photomask modification, it is necessary to ensure that a chemical reaction occurs only at the location irradiated by the electron beam. Therefore, the system has the capability to supply multiple types of reaction gases to the electron beam irradiation point and its surroundings at the required timing, flow rate, gas pressure, and temperature. To avoid spontaneous etching, the system also has a forced gas removal device and a gas supply device to instantaneously remove any excess 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 section using energy supplied by a conventional heater, laser beam, or electron beam, and then using feedback control. 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 area to be corrected by directly directing the beam onto the area to be corrected.

[0044] The reaction gas can also be supplied after being pre-ionized. Currently available ionization methods such as ultraviolet irradiation, electron beam irradiation, and RF excitation can be used for ionization. The ionized gas can be efficiently guided to the correction point using an electric field or the potential difference between the ion source and the electron beam irradiation point. A key feature is the inclusion of bias electrodes and electrostatic lenses for this purpose. Ions accelerated using an ion gun can also be delivered directly to the correction point. This is the opposite of conventional FIBs, which used high-speed, heavy ions such as Ga to perform physical etching; this method delivers lighter gases to the correction point at low energies of less than 100 eV, effectively eliminating physical sputtering effects. Clustered ions can also be delivered. Clustering further reduces the kinetic energy of each molecule, preventing sample damage. If it is preferable to deliver neutral atoms or molecules, neutralization means such as electron beam irradiation can be provided in the ionized reaction gas pathway to remove the ion charge.

[0045] The electron beam excitation reaction gas is generally a chemical substance that is solid at room temperature (solid source). The gas supply system includes a heater and temperature control circuit to sublimate the solid source, which is placed in a Swagelok cylinder, into a gas at the appropriate gas pressure, as well as 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] The gas generated by the gas supply device is injected into the chamber through a pipe while maintaining the desired temperature. The nozzle incorporates a heater or other function to regulate the gas temperature. The gas delivery components inside the vacuum chamber are insulated by the chamber vacuum and are therefore maintained at the temperature of the nearest heater.

[0047] To realize electron beam ALD and ALE, a high-speed response valve is incorporated to switch the diaphragm valve on and off in a short time of less than ms in order to deliver the gas in a pulsed manner. The valve is equipped with a temperature control mechanism. Solenoid valves, piezoelectric valves, or electrostatic valves made with MEMS can be used. The valve can also be installed inside the chamber to improve the response. Since the gas is prone to solidification, the system has functions to periodically flow an inert gas at a constant temperature to prevent clogging of the pipes, and to briefly increase the pressure to flush the reaction gas. Because the reaction gas has a low vapor pressure, the supply pressure tends to be lower compared to nitrogen and oxygen, which are gases at room temperature. To compensate for this pressure, an inert gas such as nitrogen, argon, or helium can be used simultaneously as a pressurizing gas along with the reaction gas. The pressurizing effect is obtained by directly injecting the pressurizing gas into the gas source container. These pressurizing gases generate ions through collision with the primary electron beam and also function as antistatic gases. Using pressurizing gases allows for higher pressure, increasing the flexibility of the gas supply method. Since it is no longer necessary to use a nozzle with a small hole like a hypodermic needle to obtain a gas flow, as in conventional methods, the occurrence of problems due to gas solidification is 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] Figure 2(a-1) shows an example where the distance between the gas inlet and sample 13 is large, and Figure 2(a-2) shows an example where the distance between the gas inlet and sample 13 is small.

[0053] In Figure 2(a-1), the reaction gas introduction 32 injects the reaction gas perpendicularly onto the sample 13 from the outside (see Figure 3(a)). Meanwhile, the vacuum 31 evacuates from the inside of the gas injection by the reaction gas introduction 32 (see Figure 3(a)). As a result, the gas is injected perpendicularly onto the sample 13 from the outside of the ring-shaped nozzle, and vacuum 31 is applied from the inside of the ring-shaped nozzle, so the gas is removed to the outside by vacuum 31 without scattering to the outer circumference. Then, by scanning while irradiating the sample 13 with a primary electron beam of a predetermined size while the gas is being injected perpendicularly, the scanned area is etched or deposited by the gas and primary electron beam irradiation, making it possible to repair defects in the pattern. The gas introduction section becomes hot, so it is desirable that the objective lens and other components be thermally and electrically insulated to prevent temperature rise. The same effect can be obtained even if the gas ejection section of the ring-shaped nozzle has a structure with many holes like a gas stove or a structure with pipes protruding from the holes.

[0054] Similarly, in Figure 2(a-2), the reaction gas introduction 32 injects the reaction gas into the sample 13 from the space between the sample 13 and the vacuum plate. On the other hand, the vacuum 31 evacuates from the inside, closer to the axis. As a result, the gas is injected onto the sample 13 from the outside of the ring-shaped nozzle and vacuumed from the inside by the vacuum 31, so the gas is removed to the outside by the vacuum 31 without scattering to the outer circumference. Then, by scanning while irradiating the sample 13 with a primary electron beam of a predetermined size while the gas is being injected, the scanned area is etched or deposited by the gas and the irradiation of the primary electron beam, making it possible to repair defects in the pattern.

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

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

[0057] In Figure 2(b-1), in this example, the gas curtain 33 is provided below the reaction gas introduction 32 as shown in the figure. The gas curtain is sprayed outside the vertical injection of the ring-shaped nozzle onto the sample 13 by the reaction gas introduction 32, further preventing the reaction gas from scattering outwards. The gas curtain has the function of removing reaction gas that has adhered to locations other than the electron beam irradiation point.

[0058] Similarly, in Figure 2(b-2), since the distance between the nozzle and the sample 13 is small in this example, the scattering of reaction gas outwards can be further prevented by injecting the curtain gas from the outer periphery toward the sample 13 through the gap between the curtain gas and the sample 13, as shown in the gas curtain 33. The reaction gas is injected vertically toward the sample 13, as shown in the figure.

[0059] Figure 2 will be explained in detail.

[0060] This invention features a gas supply path resembling a flat microduct, made by stacking thin, non-magnetic plates approximately 100 microns thick. Because of its high conductance, the gas does not pass through narrow spaces like conventional pipes. Therefore, gas solidification is less likely, and the gas can be delivered to the surface of sample 13 with sufficient pressure. Since the gas is blown from the periphery towards the electron beam irradiation point, a high gas concentration can be maintained at the electron beam irradiation point. Furthermore, a differential pump connected to the TMP is located above the electron beam irradiation point, allowing for rapid recovery of the supplied reaction gas. This ability to supply the necessary amount of reaction gas to the necessary location prevents side etching for gases that cause spontaneous etching, such as xenon fluoride gas. This gas supply path 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] Figure 3(a) shows gas supply example 1, and Figure 3(b) shows gas supply example 2 (divided into two parts). Figure 3(c) shows gas supply example 3 (divided into 4 sections).

[0063] In Figure 3(a), the gas curtain holes 34 are holes through which gas 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 reaction gas hole 36 is a hole through which reactive (etching, deposition) gases are injected perpendicularly onto 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 Figure 4, the mask repair device is a device for repairing defects in the photomask, which is sample 13, and consists of an image processing device 411, an image recognition device 412, a process procedure generator 413, and the like, as shown in the figure.

[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 Reaction Radius and Other Electron Beam Information Database 43 is a database in which the reaction radius and other information, corresponding to the acceleration voltage of the primary electron beam, are pre-determined experimentally and registered for each material to be repaired or reaction gas.

[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] Figure 6(a) shows an example of the reaction radius, and Figure 6(b) shows an example of the reaction region.

[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 to this center. As a result, the primary electron beam enters the inside of the photomask and scatters, and secondary electrons and backscattered electrons are emitted from the region with the radius of the circle shown, resulting in etching and deposition in this region. In other words, even if the radius of the primary electron beam is small, the secondary electrons and backscattered electrons generated by scattering inside it spread out, and etching and deposition (reaction gas is supplied to this vicinity) occur in this region.

[0088] In Figure 6(b), the reaction region is the area generated by scanning while irradiating with a primary electron beam as shown, and is the region to be etched and deposited. By uniformly scanning the entire interior of the shown target shape boundary within the shown reaction region, 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 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, considering that the minimum pattern used for photomasks for state-of-the-art devices is 50 nm or less, the error becomes too large, resulting in a correction failure. In this invention, the electron beam scanning position, which takes the reaction radius Rr into account, is calculated from the design data in advance and used, so that 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. Board bias voltage: 10V 8. Reaction radius: 10 nm 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 levels. 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 to occur between the primary electron beam and the gas, the reaction gas molecules must be present in the electron beam irradiation area. If the gas supply rate is small relative to the electron beam irradiation time per unit area, the chemical reaction will not occur because there is no reaction gas at the electron beam irradiation point even when 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. Electron beam-induced etching reactions are known to be dependent on the substrate voltage, and since the secondary electron distribution on the sample surface changes depending on the applied voltage, the etching rate and etching anisotropy change. A bias voltage that yields the desired etching shape is selected and used. The bias voltage can also be varied over time in accordance with the progress of the process. The 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, irradiation current, and aberrations of the electron optical system. The apparatus of the present invention is equipped with an aberration correction device, making it possible to reduce the aberrations of the electron beam optical system to zero in principle. Electron beam diameters from 1 nm to tens of nanometers can be obtained at various energy levels required for the process. Here, 10 nm is set as a standard value.

[0100] Figure 7(b) shows an example of sedimentation 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. Board bias voltage: 10V 8. Reaction radius: 10 nm Figure 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 phenanthrenes can be used. Using these, it becomes possible to create hollow structures and 3D structures that appear to float above the substrate.

[0104] To ensure process reproducibility, a digital process control system is in place that allows numerically provided process data (pressure, flow rate, temperature, gas type, electron beam conditions, etc.) to be implemented or modified in real time in synchronization with the electron beam scanning. This overall control is performed by running digital process control software stored on a PC.

[0105] Figure 8 shows a flowchart of the repair process of the present invention.

[0106] In Figure 8, S1 performs alignment. This involves setting the photomask as sample 13 using a robot in the apparatus shown in Figure 1, and aligning it based on the alignment marks. This allows for positioning at any coordinate on the photomask and automatically acquiring SEM images using the coordinates output by the defect inspection device.

[0107] S2 recognizes the target for repair (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 primary electron beam scans the corresponding region of the photomask, and the secondary electrons generated at that time are detected and amplified to acquire the SEM image).

[0108] S3 extracts the target image from the CAD data using the repair point coordinates. This involves using the repair point coordinates of the defects on the SEM image acquired in S2 and referencing the CAD data (design data) to extract the target image.

[0109] S4 converts CAD data into an image of the target shape. Based on the target image extracted from the CAD data in S3, it converts it into an image of the target shape (pseudo-SEM image) corresponding to the process of the photomask to be repaired. This makes it possible to automatically generate an ideal image (pseudo-SEM image) that would be produced when the process of the photomask to be repaired is executed from the CAD data.

[0110] S5 evaluates the difference. This calculates the difference in defects between the pseudo-SEM image generated in S4 and the SEM image acquired in S2.

[0111] S6 identifies the process region. This identifies the processing target (process region) that includes the region of the difference calculated in S5.

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

[0113] S8 executes the process. This performs process area repair using the process method, order, speed, and conditions set in S7.

[0114] S9 evaluates the process results. This involves acquiring an SEM image after the process in S8, obtaining the difference between it and a pseudo-SEM image, and evaluating the degree of repair.

[0115] By following the steps S1 to S9 described above, a pseudo-SEM image containing the defective areas is generated based on the defect information of the photomask. The difference between this pseudo-SEM image and the actual SEM image of the photomask is extracted, and the defective areas of the photomask are automatically repaired (etched and deposited) by repairing them so that this difference becomes zero.

[0116] Figure 9 shows an explanatory diagram of the repair process of the present invention.

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

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

[0119] Figure 9(b) shows an example image (S2, S3, S4 in Figure 8).

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

[0121] Figure 9(c) shows an example of difference image data (S5 in Figure 8). This is an example of the difference image between a pseudo-SEM image and an SEM image.

[0122] Figure 10 shows an explanatory diagram of the restoration method according to the present invention.

[0123] Figure 10(a) shows an example of a defect area. This indicates that the defect center coordinates are (x, y), and the image of the area (Δx, Δy) centered on this point is considered 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] Figure 10(c-1) shows an example of a defect image. Here, a pattern (defect) that is convex to the right is formed in the middle of the pattern.

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

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

[0130] Next, Figures 8 through 10 will be explained in detail below.

[0131] First, SEM images of the defect locations on the photomask are acquired sequentially according to the defect location coordinates (KLARF, etc.) output by the defect inspection device (S2 in Figure 8). The design database of the device to be corrected is accessed using the above defect location coordinates (S3 in Figure 8). As shown in Figure 10(a), the range of data to be acquired is specified along with the center coordinates of the defect. It is desirable that the range to be acquired be large enough to include the entire defect to be corrected and a range (e.g., 1 micron) that can absorb the positional difference between the defect inspection device and the mask correction device of the present invention (Figure 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 goals 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 automatically adjusts the reaction radius of the electron beam excitation reaction for each reaction case, and then generates an ECAM file so that the difference from the target shape becomes zero. This is then automatically executed (S8 in Figure 8). The difficulty of the correction varies, and there are various procedures for making the correction. For simple repairs, it may be possible to complete the process in a single pre-prepared unit process. In this case, one process condition is set for the correction point, and the electron beam is scanned to perform deposition or etching, thereby achieving the target shape in one go. For complex patterns, it is possible to reduce them to combinations of simple patterns and automatically combine unit processes, or to consider several passes or layers and gradually make the correction by changing the electron beam and gas conditions used for correction for each pass or layer. These process procedures can be automatically generated by a computer, or they can be taught by a human in the same way that complex movements are taught to industrial robots. As a result, the obtained files are each named and recorded as ECAM data.

[0136] The optimal process method is selected based on the photomask material, the amount of repair required, etc., or the process sequence, electron beam energy and current values, and scanning coordinate position and velocity are automatically generated to create a process execution file (ECAM file). The photomask repair device (Figures 1 and 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 quantity, and temperature according to the process execution file (ECAM). Finally, the repaired pattern is observed in planar or three-dimensional form using a SEM to confirm whether the repair was performed correctly. If necessary, optical simulations are performed or confirmation is made using a simulation microscope that can realize actual exposure conditions such as AIMS.

[0138] Figure 11 shows a diagram illustrating the restoration process of the present invention (part 2).

[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] Figure 11(a-1) shows an example of a defective 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] Figure 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, no matter how it is performed. For example, even if deposition is performed at the difference area, a boundary will be created between the area to be repaired and the deposited area, and because the deposited structure has weak adhesion, it will detach after several photomask cleanings. Alternatively, the structure may be too small compared to the process resolution to be realized with the deposition resolution. Furthermore, since the structure to be repaired is arbitrary, it is fundamentally impossible for a computer to automatically repair it while considering its structure. In such cases, it is effective to etch a slightly wider area including the area to be deposited, thereby creating a fresh area of ​​a fixed shape. By removing the defective area in this way, the work can be made more consistent, and the adhesion of the deposition process can be increased or stabilized. In addition, since the shape before the deposition process can be set to a desired shape or a always-defined standard shape, if ECAM data for several automated processing shapes is prepared in advance as templates, the mask can be automatically repaired using automated processing to perform the optimal deposition and etching process without being affected by the surrounding area where the area to be repaired is located.

[0149] As an application of the excision process, by combining offset deposition, which involves performing extra deposition, with etching, which removes excess material, an even more desirable photomask restoration shape can be obtained by further etching away unwanted shapes created by the deposition process. 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 a target shape that is X nanometers larger than the design data. Then, etching is performed to create the shape 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] Figure 12 shows the overall flowchart of the repair process of the present invention.

[0152] In Figure 12, S21 loads the mask. This commands the device (Figure 1) to load the photomask to be repaired as sample 13.

[0153] S22 involves the robot transporting the photomask to the XY stage. In response to the mask load command in S21, the robot transports the photomask to the XY stage of the apparatus shown in Figure 1.

[0154] In S23, the XY stage is moved to enter the electron beam processing range. This is because, after the photomask is transported to and fixed on the XY stage in S22, a narrowly focused primary electron beam is irradiated onto the photomask while scanning, and the XY stage is moved to enter the processing range of the primary electron beam.

[0155] With the above steps completed, the photomask is ready to be scanned while being irradiated with a primary electron beam, and then etched or deposited.

[0156] S24 initiates 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 involves introducing purge gas. This allows for the complete exhaust or neutralization of the reactive gases used in deposition and etching.

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

[0161] S29 unloads the mask.

[0162] As described above, the photomask to be repaired is transported and fixed onto the stage of the apparatus (Figure 1), and the boundary area of ​​the area to be repaired is scanned while irradiating it with a narrow primary electron beam, while the entire inner part is scanned while irradiating it with a wide primary electron beam. Simultaneously, reactive gas is injected, allowing for high-precision deposition or etching of the boundary area and high-speed deposition or etching of the interior, thereby enabling the automatic repair of defects in the photomask.

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

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

[0165] By following these steps, accurate repairs can be performed while also reducing repair time. These steps can then be stored in a process procedure database and used for automated mask repair with ECAM.

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

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

[0168] Figure 13(a-1) shows the target for repair. The target for repair shown is a defective object (pattern example) identified by the coordinates (center coordinates) of the defective pattern on the 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] Figure 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] Figure 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, we will explain Figure 14 in detail.

[0179] Etching in photomask modification is a process that can damage the photomask itself and therefore must be performed carefully. The height of normal patterns formed on a photomask is constant on the order of nanometers because they are formed by a precision thin-film deposition process. However, if foreign matter or process abnormalities occur from the exposure equipment or other process equipment, the height of objects on the photomask is not necessarily constant, and may even be unknown.

[0180] In such cases, if electron beam etching is performed uniformly, the thicker parts of the film will remain intact, while the thinner parts will be etched down to the substrate, damaging the mask. This prevents proper repair. In this embodiment, taking advantage of the characteristic that the electron beam can be irradiated to any location, the height of the object to be etched is measured in advance to clarify the 3D structure, and then areas with the same height are grouped together so that the height becomes constant, starting from the highest point, and etching is performed one layer at a time in sequence. In this way, even if there are height variations in the defective area to be repaired, etching can be performed without damaging the substrate boundary.

[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 method allows for precise etching of one atomic layer at a time in areas irradiated with an electron beam, by pre-applying an oxygen molecular layer (see Figure 15(a-2)).

[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] Figure 15(a-4) shows a schematic cross-sectional view after the oxygen molecular layer on the photomask has been etched.

[0188] As described above, even conventionally difficult-to-etch materials can now be etched by supplying oxygen or ozone and converting them to volatile substances.

[0189] Next, we will explain Figure 15(a) in detail.

[0190] For etching metals that cannot be etched by conventional xenon fluoride etching methods, such as transition metals, β-diketones like hexafluoroacetylacetone can be used. When this gas is used, the compounds formed after the etching of transition metals such as Ni, Co, Pt, Cu, Ru, Pd, Fe, Mn, Ir, Tb, Ta, and Ti become volatile, allowing for easy etching of Ni and other metals. Since hexafluoroacetylacetone has the property of forming complexes with nickel or nickel oxides, a process of pre-oxidizing nickel can be included. In this case, it can be achieved by supplying oxygen or ozone beforehand to oxidize the nickel, or by simultaneously supplying oxygen and hexafluoroacetylacetone during electron beam irradiation. The oxidation process is carried out by supplying the reaction gas in a pulsed manner to the photomask surface using a high-speed response valve.

[0191] Similar etching can be performed on materials such as cobalt and copper. Thus, this invention enables etching and mask correction without problems even on difficult-to-etch materials that will be used in future High NA EUV lithography systems. Since metal oxide film formation is the rate-limiting step in the reaction, the process involves first forming an oxide film, then introducing hexafluoroacetylacetone to form a metal complex, and finally irradiating with an electron beam to evaporate and remove the film, thus forming a single etching process. Therefore, the amount of gas introduced into the chamber is pulsed so that the amount of gas introduced is the rate-limiting step in the reaction, and the etching amount can be precisely controlled by specifying the number of gas introduction cycles. This eliminates the need to manage the etching endpoint and enables damageless local etching. Unlike conventional ALE processes, only the area irradiated with the electron beam is etched, so patterns can be formed without a mask.

[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) shows a schematic cross-sectional view of a hydrogen layer formed on a metal complex layer, which is a defect pattern formed on the photomask shown in Figure 15(b-2), and then irradiated with an electron beam. As shown in the figure, when irradiated with a primary electron beam, the hydrogen layer and the underlying metal complex layer interact and are reduced to form a 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] By using hexafluoroacetylacetone complexes of difficult-to-etch transition metals, particularly nickel, cobalt, or copper, as precursors for electron beam-excited deposition reactions, nickel, cobalt, and copper can also be deposited using electron beams. Conversely to etching, it is necessary to include a reducing agent such as hydrogen. Hydrogen can be used as the reducing gas. In addition to the main reaction gas, chemicals such as diethylene glycol dimethyl ether may be used to stabilize the reaction. To ensure that hydrogen gas effectively reaches the photomask surface, argon, helium, nitrogen, or ammonia gases may also be used in addition to hydrogen gas. Pretreatment gases can also be supplied 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, N2O, and NO2. Since the rate-determining reaction is the metal reduction reaction by hydrogen, one deposition process consists of one cycle: first, the introduction of the metal complex to the sample surface, followed by hydrogen introduction, and then reduction to the metal by electron beam irradiation. The reducing gas, such as hydrogen, is supplied to the photomask surface in a pulsed manner using a high-speed response valve. Similar to etching, by determining the number of cycles, a metal film of the desired thickness can be obtained without endpoint detection. Unlike the generally known ALD process, since the reaction occurs only where the electron beam is irradiated, maskless pattern formation can be achieved by electron beam scanning.

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

[0201] Figure 16(a) shows example of a support structure 1.

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

[0203] Figure 16(a-2) shows an example of deposition. This shows the structure after deposition around the supporting structure in Figure 16(a-1), as illustrated.

[0204] Figure 16(a-3) shows an example of support structure removal. This shows the structure after the internal support structure has been removed following the deposition shown in Figure 16(a-2).

[0205] Figure 16(b) shows example of support structure 2.

[0206] Figure 16(b-1) shows an example of a support structure. Here, as shown in the figure, there is a structure in which 10 cubes are arranged in a staircase pattern.

[0207] Figure 16(b-2) shows an example of deposition. This shows the structure after deposition around the supporting structure in Figure 16(b-1), as illustrated.

[0208] Figure 16(b-3) shows an example of support structure removal. This shows the structure after the internal support structure has been removed following the deposition shown in Figure 16(b-2).

[0209] Next, we will explain Figures 16(a) and 16(b) 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 hydrocarbon compounds such as phenanthrene into a chamber and irradiating it with an electron beam. The carbon support structure can be easily removed by oxygen plasma etching. Similarly, silicon oxide and the like can be used for the support structure. In this case, the support structure can be removed using fluorine gas or the like.

[0212] By using the methods described above, it is possible to create any structure on the nanometer scale, just like with a 3D printer. Since deposition can be performed at any position, just like with a 3D printer, it goes without saying that walls and holes at any angle can be created. While the large size of each block may make the result appear rough, by reducing the size of each block or stacking them at sub-pixel positions, it is possible to create structures with any smooth shape. [Brief explanation of the drawing]

[0213] [Figure 1] This is a diagram illustrating one 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 the vertical gas introduction method of 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] This 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]This is an explanatory diagram illustrating the scanning of an electron beam in the repair process of the present invention. [Figure 14] This is an explanatory diagram of the damageless etching method of the present invention. [Figure 15] This is an explanatory diagram of electron beam etching and deposition according to the present invention. [Figure 16] This 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: Introduction of reaction gas 33: Gas Curtain 34: Gas curtain hole 35: Electron beam hole 36: Reaction gas hole 41: Mask Correction 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: Database of criteria for completion of restoration 46: Design data server 47: Defect inspection device

Claims

1. An electron beam treatment method that involves irradiating a sample with an electron beam to induce a chemical reaction, A step of acquiring and storing in advance the reaction radius, which indicates the spatial extent of the chemical reaction occurring on the sample according to the differences in irradiation conditions, A step of determining at least one of the electron beam irradiation position, scanning interval, number of irradiations, beam current, acceleration voltage, and irradiation time based on the reaction radius, A step of performing electron beam irradiation based on the conditions determined above. An electron beam processing method characterized by having the following features.

2. The electron beam processing method according to claim 1, characterized in that the reaction radius is obtained from measured data based on the results of test irradiation on a sample.

3. The electron beam processing method according to claim 1, characterized in that the reaction radius is calculated based on an electron scattering simulation or a reaction-diffusion model.

4. The electron beam processing method according to claim 1, characterized in that the reaction radius is estimated by a learning process using past processing history data.

5. The electron beam processing method according to claim 1, characterized in that the reaction radius is controlled as a value that changes depending on at least one of the acceleration voltage, beam current density, reaction gas species, substrate bias voltage, and substrate temperature.

6. The electron beam processing method according to claim 1, characterized in that the scanning interval is corrected based on the reaction radius so that the reaction regions of adjacent irradiation points do not overlap too much.

7. The electron beam processing method according to claim 1, characterized in that the number of overlapping shots when irradiating the same position multiple times is controlled based on the reaction radius.

8. The electron beam processing method according to claim 1, characterized in that the irradiation amount is corrected at the edge portion of the target processed shape based on the reaction radius.

9. The electron beam processing method according to claim 1, characterized in that the step of performing the electron beam irradiation is any of electron beam-induced etching, electron beam-induced deposition, electron beam atomic layer etching, or electron beam atomic layer deposition.

10. The electron beam processing method according to claim 1, characterized in that the step of performing the electron beam irradiation is applied to any of photomask modification, semiconductor device processing, or three-dimensional nanostructure formation.

11. An electron beam processing program that performs a process to induce a chemical reaction by irradiating a sample with an electron beam, A step of acquiring and storing in advance the reaction radius, which indicates the spatial extent of the chemical reaction occurring on the sample according to the differences in irradiation conditions, A step of determining at least one of the electron beam irradiation position, scanning interval, number of irradiations, beam current, acceleration voltage, and irradiation time based on the reaction radius, A step of performing electron beam irradiation based on the conditions determined above. An electron beam processing program that executes this process.

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