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CN-122003131-A - Improved sample damage avoidance in devices and methods for sample processing and sample repair

CN122003131ACN 122003131 ACN122003131 ACN 122003131ACN-122003131-A

Abstract

A method for potential determination in relation to a sample includes positioning a probe over the sample, applying at least a first DC voltage offset and a second DC voltage offset each from a first range, applying an AC voltage to the probe to cause mechanical oscillation of the probe, 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 determining a potential outside an interval spanned by the first DC voltage offset and the second DC voltage offset based at least in part on the first deflection and the second deflection. A method of causing a probe to approach toward a sample includes causing the probe to approach toward the sample, repeatedly determining a deflection of the probe during a process of causing the approach, and determining an approach termination condition for avoiding damage to the sample based at least in part on the deflection of the probe or its oscillation frequency.

Inventors

  • R. Kulock
  • H.H. Piper
  • C. BAUER
  • R. Herbert Ren

Assignees

  • 卡尔蔡司SMT有限责任公司

Dates

Publication Date
20260508
Application Date
20251104
Priority Date
20241105

Claims (20)

  1. 1. A method (510) for potential determination with respect to a sample (160), wherein the method comprises: positioning (511) a probe (150) over the sample (160); -applying (512) at least a first DC voltage offset and a second DC voltage offset (121, 122) each from a first range (221); -applying (513) an AC voltage to the probe (150) to cause mechanical oscillations (141, 142) of the probe (150); Determining (514) a first induced deflection (210, 211, 212, 230) of the probe (150) for the first DC voltage offset (121, 122) and a second induced deflection (210, 211, 212, 230) of the probe (150) for the second DC voltage offset (121, 122), and A potential outside an interval spanned by the first and second DC voltage offsets (121, 122) is determined (515) based at least in part on the first and second deflections (210, 211, 212, 230).
  2. 2. The method according to claim 1, wherein the deflection (210, 211, 212, 230) comprises an amplitude (210, 211, 212) of the mechanical oscillation (141, 142) and/or a phase (230) of the mechanical oscillation (141, 142).
  3. 3. The method according to claim 1 or 2, wherein the first and second deflections (210, 211, 212, 230) comprise an in-phase component (212) and/or a quadrature component (211).
  4. 4. The method of any of the preceding claims, wherein determining (514) the first and second deflections (210, 211, 212, 230) comprises lock-in amplification.
  5. 5. The method according to any of the preceding claims, wherein the AC voltage frequency is substantially equal to the resonance frequency of the probe (150) or is a multiple of the resonance frequency of the probe (150).
  6. 6. The method of any of the preceding claims, wherein the first range (221) extends from-10V to +10v.
  7. 7. The method of any of the preceding claims, wherein determining the potential comprises fitting at least a first data point comprising the first deflection (210, 211, 212, 230) and the first DC voltage offset (121, 122) and a second data point comprising the second deflection (210, 211, 212, 230) and the second DC voltage offset (121, 122) using a fitting function.
  8. 8. The method of claim 7, wherein determining the potential further comprises extrapolating and/or determining a zero point of the fitting function.
  9. 9. The method of claim 7 or 8, wherein the fitting function comprises a linear function, and preferably comprises a correction of the linear function based at least in part on a resonant frequency, an oscillating mass, and/or a spring constant of the probe (150).
  10. 10. The method according to any of the preceding claims, wherein the positioning is performed such that the distance between the probe (150) and the sample (160) is 0.001 to 1000 μιη, preferably 50 to 150 μιη.
  11. 11. A method (530) for causing a probe (150) to approach toward a sample (160), wherein the method comprises: Causing the probe (150) to approach (531) toward the sample (160); Repeatedly determining (532) a deflection (210, 211, 212, 230) of the probe (150) during a process causing an approach (531), and A near termination condition for avoiding sample damage is determined (533) based at least in part on the deflection (210, 211, 212, 230) of the probe (150).
  12. 12. The method according to claim 11, wherein the determining (533) is performed by means of a real-time device configured to determine the approaching termination condition in a time of 2 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less.
  13. 13. The method of claim 11 or 12, further comprising terminating (534) a process that causes the probe (150) to approach (531) toward the sample (160) based at least in part on determining (533) the approach termination condition.
  14. 14. The method according to claim 13, wherein the termination is performed within a time of 2 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less after the approaching termination condition has occurred.
  15. 15. The method according to any one of claims 11 to 14, wherein the process of bringing about the proximity (531) by the probe (150) is performed at a speed of 0.1 μm/s or more, preferably 1 μm/s or more, particularly preferably 2 μm/s or more.
  16. 16. The method of any of claims 11 to 15, wherein the near termination condition comprises exceeding a predefined deflection (210, 211, 212, 230) of the probe (150).
  17. 17. The method of any of claims 11 to 16, further comprising determining a resonant frequency of the probe (150) during a process of causing proximity (531).
  18. 18. The method of claim 17, wherein the near termination condition comprises a predefined frequency shift exceeding the resonant frequency.
  19. 19. The method of claim 17 or 18, wherein the near termination condition comprises the resonant frequency being below a predefined minimum frequency.
  20. 20. A method for processing a sample (160), comprising: the method for potential determination according to any one of claims 1 to 10, and The method for approaching (531) a probe (150) towards a sample (160) according to any of claims 11 to 19, based at least partly on the potential determination.

Description

Improved sample damage avoidance in devices and methods for sample processing and sample repair RELATED APPLICATIONS The present application claims priority from German patent application No.102024132213.6 filed on 5/11/2024, which is incorporated herein by reference in its entirety. Technical Field The present invention relates to a method for potential determination with respect to a sample, a method for causing a probe to approach towards a sample, a method for processing a sample, and a corresponding apparatus and computer program. Background Due to the ever increasing integration density in microelectronics, substrates (e.g., photolithographic masks, mask blanks, or wafers) are required to have increasingly good surfaces. For example, photolithographic masks are intended to image smaller features into the photoresist layer of a wafer. The same applies to templates used in nanoimprint lithography. To meet these requirements, the exposure wavelength is shifted to shorter wavelengths. The trend is towards shorter and shorter wavelengths extending into the Extreme Ultraviolet (EUV) wavelength range (10 nm to 15 nm) and towards the corresponding EUV mask. It is often the case that defects occur in the production of masks due to the ever decreasing size of the structural elements. Since production is associated with high costs, it is possible to repair defective photomasks, photolithographic masks and templates used in nanoimprint lithography as well, whenever possible. In the repair of the photomask, the portion of the absorber pattern that is present on the mask at the location where the design was not envisaged may be removed. In addition, even if the mask design envisages absorbing pattern elements, absorbing material may be deposited on the mask at locations where no absorbing material is present. Both types of repair processes may produce debris fragments or particles that may settle at opaque, transparent, or reflective sites on the photomask and cause imaging aberrations in the lithographic exposure visible on the structured wafer. Another problem is that particles from the environment settle on the surface of the mask or another substrate or on components of the lithographic exposure system. Furthermore, the handling of the mask during its production and/or operation may produce particles that may deposit on the mask. In the case of a lithographic exposure system operating with electromagnetic radiation in the EUV wavelength range, there are two further difficulties. For EUV masks, there is currently no satisfactory protection (e.g. pellicle) for the surfaces of the carrying structural elements. Thus, EUV masks are particularly prone to particle settling on this structured surface. Second, EUV radiation sources typically use a tin plasma to generate EUV radiation. Particles from the thermal plasma may deposit on components of the EUV exposure system, in particular on optical components or elements thereof, including the EUV mask, and may impair its function. The reduction in the structural dimensions of the photolithographic mask increases the difficulty of the cleaning process. Furthermore, due to the reduction of the exposure wavelength, smaller and smaller foreign particles or dirt particles adhering to the surface of the mask or the optical element of the exposure system become visible on the wafer during the exposure process. In view of the smaller and smaller structures, custom solutions are becoming increasingly important for the processing and cleaning of masks and, more generally, substrates. In particular, it may be desirable to eliminate various defects on the same substrate at an acceptable level of cost and inconvenience. The treatment of surfaces, particularly the movement of particles and lifting and/or removing individual particles from the surface, is often a difficult and time-consuming process. External constraints may limit the available tools and treatment options. In addition, it may be expensive and inconvenient to completely remove particles adhering to the surface of the substrate from the substrate. Typically, handling the sample requires bringing the probe towards the sample, although this is not always problematic for the following reasons: During the process for loading the sample into vacuum, for example, the evacuation and measurement processes may cause the sample to become electrostatically charged. During observation of a sample (e.g., a photomask) in a Scanning Electron Microscope (SEM), the sample may likewise be charged by the incoming electrons of the primary beam as well as Secondary Electrons (SE). The charging behavior may here depend mainly on the SE yield (SEY). Samples with large conductive structures that are not or cannot be electrically contacted are critical in both cases. These include, for example, so-called "chrome on glass blanks" for particle monitoring tests and EUV masks. EUV masks, which are high-end mask types, are particularly expensive and,