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KR-20260067339-A - IMPROVED SAMPLE DAMAGE AVOIDANCE IN DEVICES AND METHODS FOR SAMPLE PROCESSING AND SAMPLE REPAIR

KR20260067339AKR 20260067339 AKR20260067339 AKR 20260067339AKR-20260067339-A

Abstract

A method for determining a potential for a sample comprises: a step of positioning a probe over a sample; a step of applying at least a first and a second DC voltage offset, respectively, from a first range; a step of applying an AC voltage to the probe to induce mechanical vibration of the probe; a step of determining a first induced deflection of the probe for the first DC voltage offset and a second induced deflection of the probe for the second DC voltage offset; and a step of determining a potential outside the interval spanning the first and second DC voltage offsets based at least partially on the first and second deflections. A method for inducing the probe to approach the sample comprises: a step of inducing the probe to approach the sample; a step of repeatedly determining the deflection of the probe during the process of inducing approach; and a step of determining an approach termination condition to prevent sample damage based at least partially on the deflection of the probe or its vibration frequency.

Inventors

  • 쿨로크, 레네
  • 피퍼, 한스 헤르만
  • 바우어, 크리스토프
  • 헤버라인, 로베르트

Assignees

  • 칼 짜이스 에스엠티 게엠베하

Dates

Publication Date
20260512
Application Date
20251103
Priority Date
20241105

Claims (20)

  1. As a method (510) for determining the potential regarding a sample (160), the method is: Step (511) of positioning the probe (150) on the sample (160); Step (512) of applying at least a first and second DC voltage offset (121, 122) respectively from a first range (221); Step (513) of applying an AC voltage to the probe (150) to induce mechanical vibrations (141, 142) of the probe (150); Step (514) of determining the first induced deflection (210, 211, 212, 230) of the probe (150) for the first DC voltage offset (121, 122) and the second induced deflection (210, 211, 212, 230) of the probe (150) for the second DC voltage offset (121, 122); and A method comprising the step (515) of determining a potential outside the interval spanned by the first and second DC voltage offsets (121, 122) based at least partially on the first and second deflections (210, 211, 212, 230).
  2. A method according to claim 1, wherein the deflection (210, 211, 212, 230) comprises the amplitude (210, 211, 212) of the mechanical vibration (141, 142) and/or the phase (230) of the mechanical vibration (141, 142).
  3. A method according to claim 1 or claim 2, wherein the first and second deflections (210, 211, 212, 230) comprise an in-phase component (212) and/or an orthogonal component (211).
  4. The method of claim 1 or claim 2, wherein the step (514) of determining the first and second biases (210, 211, 212, 230) includes lock-in amplification.
  5. A method according to claim 1 or claim 2, wherein the AC voltage frequency is substantially the same as or a multiple of the resonant frequency of the probe (150).
  6. A method according to claim 1 or claim 2, wherein the first range (221) extends from -10V to +10V.
  7. A method according to claim 1 or claim 2, wherein the step of determining the potential comprises fitting a first data point including at least a first bias (210, 211, 212, 230) and a first DC voltage offset (121, 122) and a second data point including a second bias (210, 211, 212, 230) and a second DC voltage offset (121, 122) using a fit function.
  8. The method of claim 3, wherein the step of determining the potential comprises fitting a first data point including at least a first bias (210, 211, 212, 230) and a first DC voltage offset (121, 122) and a second data point including a second bias (210, 211, 212, 230) and a second DC voltage offset (121, 122) using a fit function.
  9. The method of claim 7, wherein the step of determining the potential also includes the step of extrapolating and/or determining the zeros of the fitting function.
  10. A method according to claim 1 or claim 2, wherein the positioning is performed such that the distance between the probe (150) and the sample (160) is 0.001 μm to 1000 μm, or 50 μm to 150 μm.
  11. A method (530) for allowing the probe (150) to approach the sample (160), wherein the method is: Step (531) of allowing the probe (150) to approach the sample (160); A step (532) of repeatedly determining the bias (210, 211, 212, 230) of the probe (150) during the process of the approaching step (531); and A method comprising the step (533) of determining an access termination condition to prevent sample damage based at least partially on the deflection (210, 211, 212, 230) of the probe (150).
  12. In claim 11, the checking step (533) is performed through a real-time device configured to check the access termination condition for 2ms or less, or 1ms or less, or 0.5ms or less.
  13. A method according to claim 11 or claim 12, further comprising the step (534) of terminating the process of the step (531) of allowing the probe (150) to access the sample (160) based at least partially on the step (533) of checking the access termination condition.
  14. A method according to claim 13, wherein termination is performed within 2ms or less, or 1ms or less, or 0.5ms or less after an access termination condition occurs.
  15. A method according to claim 13, wherein the approach termination condition comprises overshooting a predefined bias (210, 211, 212, 230) of the probe (150).
  16. A method according to claim 13, further comprising the step of determining the resonant frequency of the probe (150) during the process of the step (531) of approaching.
  17. A method according to claim 14, further comprising the step of determining the resonant frequency of the probe (150) during the process of the step (531) of approaching.
  18. A method according to claim 16, wherein the approach termination condition comprises exceeding a predefined frequency shift of the resonant frequency.
  19. A method according to claim 17, wherein the approach termination condition comprises exceeding a predefined frequency shift of the resonant frequency.
  20. As a method of processing the sample (160): Steps of the method for determining potential as described in claim 1; and A method comprising steps of a method in which the probe (150) described in claim 11 approaches (531) a sample (160) based at least partially on a potential determination.

Description

Improved Sample Damage Avoidance in Devices and Methods for Sample Processing and Sample Repair This application claims priority to German patent application No. 102024132213.6 filed on November 5, 2024, the full text of which is incorporated herein by reference. Technology field The present invention relates to a method for determining the potential of a sample, a method for allowing a probe to approach a sample, a method for processing a sample, and a corresponding apparatus and computer program. As the integration density of microelectronics continues to increase, there is a growing need for further improvements to the surfaces of substrates, such as lithography masks, mask blanks, or wafers. For example, lithography masks are intended to image increasingly smaller structural elements onto the photoresist layer of a wafer. The same applies to templates used in nanoimprint lithography. To meet these requirements, exposure wavelengths are shifting toward increasingly shorter wavelengths. There is a trend toward transitioning to increasingly shorter wavelengths and corresponding EUV masks, extending to the extreme ultraviolet (EUV) wavelength range (10 nm to 15 nm). As the dimensions of structural elements become increasingly smaller, defects frequently occur during mask production. Due to high manufacturing costs, defective photomasks, photolithography masks, and templates used in nanoimprint lithography are repaired whenever possible. During photomask repair, portions of the absorber pattern present at mask locations not intended by the design may be removed. Additionally, even if the mask design includes absorption pattern elements, absorbers may be deposited at mask locations where absorbers are not present. Both types of repair processes can generate debris fragments or particles deposited in the opaque, transparent, or reflective areas of the photomask, which can cause imaging aberrations during lithography exposure visible on structured wafers. Another problem is particles from the surrounding environment that settle on the surface of the mask or other substrates, or on components of the photolithography exposure system. Additionally, particles that can be deposited on the mask may be generated when the mask is handled during the manufacturing and/or operation processes. There are two additional challenges for photolithography exposure systems operating with electromagnetic radiation in the EUV wavelength range. For EUV masks, there are currently no suitable protective devices (e.g., pellicles) to protect surfaces containing structural elements. Consequently, EUV masks are particularly prone to particle deposition on these structured surfaces. Secondly, EUV radiation sources typically use tin plasma to generate EUV radiation. Particles generated from high-temperature plasma can be deposited on the components of the EUV exposure system, particularly optical components including the EUV mask, which can impair the system's functionality. As the structural dimensions of photolithography masks decrease, the difficulty of the cleaning process increases. Furthermore, as the exposure wavelength decreases, smaller foreign substances or dust particles attached to the mask surface or optical elements of the exposure system become visible on the wafer during the exposure process. Due to increasingly smaller structures, customized solutions for the processing and cleaning of masks, and furthermore substrates, are becoming increasingly important. In particular, various defects on the same substrate may need to be removed at an acceptable cost and with minimal inconvenience. Surface processing, especially particle transport and the lifting and/or removal of individual particles from the surface, is generally a difficult and time-consuming process. External constraints may limit the available tools and processing options. Moreover, completely removing particles attached to the substrate surface can be costly and inconvenient. Generally, to process a sample, a probe must be brought close to the sample, but this is not always possible without problems for the following reasons. Samples can become electrostatically charged during the process of loading them into a vacuum (e.g., evacuation and measurement processes). During the process of observing samples (e.g., photomasks) in a scanning electron microscope (SEM), samples can also become charged by introduced electrons and secondary electrons (SE) from the primary beam. The charging behavior can depend primarily on the SE yield (SEY). In both cases, samples with large conductive structures that are not or cannot be electrically contacted are important. These include, for example, so-called "chrome-on-glass blanks" for particle monitoring tests and EUV masks. EUV masks, which are a high-end mask type, are particularly expensive and, due to their small structure, are particularly sensitive to particle contamination and electrostatic discharge (ESD). For example, if a pro