A measurement standard sheet and its processing method
By combining ultraviolet light irradiation and protective gas purging, carbon deposits on electron beam microscope measurement standard sheets are removed, solving the problems of inaccurate measurement and reduced production capacity caused by carbon deposition. This achieves efficient cleaning and low-cost maintenance of measurement standard sheets.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NEW RAY MASK TECHNOLOGY CORP
- Filing Date
- 2026-04-17
- Publication Date
- 2026-06-02
AI Technical Summary
During the scanning process, the standard sheet measured by electron beam microscopy is decomposed by hydrocarbon contaminants, resulting in carbon deposition and inaccurate measurement results. Furthermore, the cleaning process affects production capacity and linewidth, and existing technologies are time-consuming and cause physical damage.
A combination of ultraviolet light irradiation at a specific wavelength and protective gas purging is used to remove carbon deposits on the surface of the measurement standard sheet. The chemical bonds are broken and gaseous substances are formed through a photochemical process, avoiding physical damage and linewidth changes.
Quickly remove carbon deposits, extend the lifespan of measurement standard pieces, reduce equipment costs, maintain measurement accuracy and capacity, and avoid data re-collection.
Smart Images
Figure CN122131554A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of integrated circuit photomask manufacturing, specifically relating to a measurement standard wafer and its processing method. Background Technology
[0002] Electron beam metrology is primarily used for precision measurement of critical dimensions in the chip manufacturing process and is an indispensable measurement method in advanced chip manufacturing. Thanks to the high resolution provided by electron beam imaging, it can accurately measure critical dimensions during post-development and post-etching inspections, monitoring the stability of wafer critical dimensions in various production processes on the production line.
[0003] To ensure the accuracy of measurements using an electron beam microscope (SEM), periodic calibration with standard measurement pieces is necessary. However, when scanning standard measurement pieces with an electron beam microscope (SEM), hydrocarbon contaminants present in the scanning area and environment decompose these hydrocarbons during electron beam bombardment, causing electrons to accumulate in the region. The resulting positively charged carbon ions then gather and deposit in this area, ultimately forming carbon deposits that affect the generation of secondary electron signals. These carbon deposits alter the size of the pattern on the standard measurement piece, leading to inaccurate measurement results that fail to reflect the true condition of the measurement equipment, thus affecting the measurement results of the product. Furthermore, this renders the standard measurement pieces unusable after a certain number of measurements.
[0004] Currently, carbon deposits on standard slides measured by electron beam microscopy can be removed by acid washing, which takes about 2 hours. However, the washing process causes changes in the sample linewidth, requiring the re-collection of standard slide data, thus affecting the capacity of the cleaning and measurement equipment. Summary of the Invention
[0005] To overcome the aforementioned deficiencies of the prior art, this invention provides a measurement standard sheet and its processing method. The processing method of this invention employs a relatively mild photochemical process, which can quickly remove carbon deposits from the surface of the measurement standard sheet, thereby extending its service life and reducing the operating cost of the measurement equipment. Furthermore, it causes minimal physical damage to the surface of the measurement standard sheet, does not cause linewidth changes, eliminates the need to recollect standard sheet data, and avoids impacting the cleaning and measurement equipment's capacity.
[0006] The present invention achieves the above objectives through the following technical solutions: This invention provides a method for processing measurement standard pieces, the method comprising the following steps: S1. Place the measurement standard sheet to be processed in the irradiation area of the ultraviolet light generator, and turn on the ultraviolet light to irradiate the measurement standard sheet to remove the carbon deposits on its surface; wherein, the measurement standard sheet to be processed includes a measurement standard sheet scanned by an electron beam microscope; the wavelength of the ultraviolet light is 100-300 nm, and the duration of the irradiation is 120-900 s; S2. The irradiated area is purged with protective gas to obtain the processed measurement standard sheet.
[0007] In this invention, ultraviolet light of a specific wavelength and a specific irradiation time are used to remove carbon deposits on the surface of the measurement standard sheet. The principle of the process is as follows: the photons of ultraviolet light are directly absorbed by hydrocarbon molecules in the carbon deposit layer. The ultraviolet photons have a high energy, about 6.2 Ev, which is sufficient to break the chemical bonds in the molecules, such as C-C bonds (bond energy about 3.6 eV) and CH bonds (bond energy about 4.3 eV). Then, the thermal effect generated during the irradiation process raises the temperature and promotes the reaction, forming gaseous substances.
[0008] In this invention, the ultraviolet light generating device can be a UV machine.
[0009] In some embodiments, in step S1, the wavelength of the ultraviolet light is 200-280 nm; preferably 250-270 nm.
[0010] In one embodiment, the wavelength of the ultraviolet light is 266 nm.
[0011] In some embodiments, the duration of irradiation in step S1 is 180-600 s; preferably 240-360 s.
[0012] In one embodiment, the duration of the irradiation is 240 s.
[0013] In step S2 of the present invention, the purpose of using a protective gas to purge the irradiated area is to remove the gaseous substances formed after ultraviolet irradiation.
[0014] In some embodiments, the protective gas in step S2 includes nitrogen.
[0015] In some embodiments, the processing method further includes step S3: detecting the carbon removal result of the processed measurement standard sheet using an electron beam microscope; and determining whether to repeat steps S1 and S2 based on the carbon removal result.
[0016] Preferably, when the treated measurement standard sheet does not achieve the expected carbon deposit removal effect, steps S1 and S2 are repeated; when the treated measurement standard sheet achieves the expected carbon deposit removal effect, the measurement standard sheet is removed from the ultraviolet light generating device.
[0017] In some embodiments, the measurement standard includes a phase-shifted photomask that has been exposed, developed, etched, and cleaned.
[0018] In a specific implementation, the measurement standard piece is 6 inches in size.
[0019] The present invention also provides a measurement standard sheet, which is obtained by the processing method described above.
[0020] Compared with the prior art, the present invention has the following significant advantages: This invention removes carbon deposits caused by over-scanning from the surface of measurement standard sheets by directly photolytically degrading them or creating a thermal effect through ultraviolet light irradiation. This method employs a relatively gentle photochemical process to quickly remove carbon deposits from the surface of the measurement standard sheets, thereby extending their service life, increasing the number of times they can be used, and reducing the operating costs of the measurement equipment. Furthermore, it causes minimal physical damage to the surface of the measurement standard sheets, does not cause linewidth changes, eliminates the need to recollect data from the standard sheets, and avoids impacting the cleaning and measurement equipment's capacity. Attached Figure Description
[0021] Figure 1 This is a view of the measurement standard piece to be processed in the processing method of Embodiment 1 of this application; Figure 2 This is a view of the measurement standard sheet after carbon deposit removal in the processing method of Embodiment 1 of this application. Detailed Implementation
[0022] The present invention will be further described in detail below through preferred embodiments, but the scope of protection of the present invention is not limited thereto.
[0023] Example 1 This embodiment discloses a measurement standard sheet and its processing method.
[0024] Figure 1 This is a view of the measurement standard piece to be processed in this embodiment; as shown Figure 1 As shown, after multiple electron beam measurements, the surface of the measurement standard sheet to be processed has carbon deposits (or "carbon deposition"). The diagonal lines in the figure represent the carbon deposits.
[0025] The measurement processing method includes the following steps: S1. Place the measurement standard sheet to be processed in the irradiation area of the UV machine and irradiate it with 266nm ultraviolet light for 240s to remove the carbon deposits on its surface. S2. Nitrogen gas is used to purge the irradiated area to remove the gaseous substances formed after ultraviolet irradiation, thus obtaining the processed measurement standard sheet.
[0026] Figure 2 This is a view of the measurement standard sheet after carbon deposit removal in this embodiment; and... Figure 1 compared to, Figure 2 The significantly lighter slant line indicates a marked reduction in surface carbon deposits on the treated measurement standard. While this method cannot achieve 100% removal, it significantly improves the surface quality of the measurement standard. Furthermore, compared to... Figure 1 The vertical line in the middle, Figure 2 The vertical lines in the measurement standard remain largely unchanged, indicating that the line width of the measurement standard has not changed.
[0027] As can be seen, this embodiment uses a relatively mild photochemical process that can quickly remove carbon deposits on the surface of the measurement standard sheet; moreover, it causes minimal physical damage to the surface of the measurement standard sheet and does not cause changes in linewidth.
[0028] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.
Claims
1. A method for processing measurement standard pieces, characterized in that, The processing method includes the following steps: S1. Place the measurement standard sheet to be processed in the irradiation area of the ultraviolet light generator, and turn on the ultraviolet light to irradiate the measurement standard sheet to remove the carbon deposits on its surface; wherein, the measurement standard sheet to be processed includes a measurement standard sheet scanned by an electron beam microscope; the wavelength of the ultraviolet light is 100-300 nm, and the duration of the irradiation is 120-900 s; S2. The irradiated area is purged with protective gas to obtain the processed measurement standard sheet.
2. The processing method as described in claim 1, characterized in that, In step S1, the wavelength of the ultraviolet light is 200-280 nm.
3. The processing method as described in claim 2, characterized in that, The wavelength of the ultraviolet light is 250-270 nm.
4. The processing method as described in claim 1, characterized in that, In step S1, the duration of the irradiation is 180-600 s.
5. The processing method as described in claim 4, characterized in that, The duration of the irradiation is 240-360 s.
6. The processing method as described in claim 1, characterized in that, In step S2, the protective gas includes nitrogen.
7. The processing method as described in claim 1, characterized in that, The processing method further includes step S3: using an electron beam microscope to detect the carbon removal result of the processed measurement standard sheet; and determining whether to repeat steps S1 and S2 based on the carbon removal result.
8. The processing method as described in claim 1, characterized in that, The measurement standard includes a phase-shifted photomask that undergoes exposure, development, etching, and cleaning.
9. The processing method as described in claim 8, characterized in that, The measurement standard piece is 6 inches in size.
10. A measurement standard sheet, characterized in that, It is obtained by the processing method described in any one of claims 1-9.