Method for representing action volume of beam and material

Abstract

The invention relates to the field of measurement, in particular to a method for representing the action volume of a beam and a material. The method comprises the following steps that a suspended thin film is provided, the suspended thin film is a thin film integrally formed on a supporting substrate with more than one back cavity structure, and a photoresist material layer is formed on the side face, away from the supporting substrate, of the thin film; a beam is incident in the suspended film area of the photoresist material layer in a point or line mode; soaking the photoresist material layer by using a developing solution to obtain a beam current and material action volume; and characterizing the action volume of the beam and the material by using an electron microscope. The method is not limited by factors such as beam intensity and beam types, is suitable for beams of any intensity and any type, and is more accurate in result and higher in precision.

Description

Technical Field

[0001] This invention relates to the field of measurement, and more specifically to a method for characterizing the volume of interaction between a beam and a material. Background Technology

[0002] The interaction volume between a beam (such as a laser, electron beam, or ion beam) and a material, i.e. the volume in which beam energy is deposited into the material, is crucial in fields such as materials processing, analysis, and medicine, as the accuracy of the interaction volume directly affects processing precision, analytical results, and treatment outcomes.

[0003] Existing methods for determining the interaction volume between a beam and a material have several shortcomings. For example, one method involves bombarding the material with a high-dose beam to damage it, and then characterizing the damage using electron microscopy to obtain the interaction volume. However, low-dose beams (such as those used in exploratory and medical applications) do not cause significant damage to the material, so this method cannot accurately characterize the interaction volume between the beam and the material. Another method is to calculate the interaction volume using Monte Carlo methods, but this calculation is complex and the results require further verification.

[0004] Therefore, existing technologies need to be improved. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a method for characterizing the interaction volume between beam and material, aiming to solve the problem that existing methods cannot be adapted to the application of low-dose beams. This invention is achieved through the following technical solution: A method for characterizing the interaction volume between a beam and a material includes the following steps: S01. Provide a suspended thin film, wherein the suspended thin film is integrally formed on a support substrate having one or more back cavity structures, and a photoresist material layer is formed on the side of the thin film away from the support substrate. S02, The beam is incident in a point or line manner in the suspended thin film region of the photoresist material layer; S03. Immerse the photoresist material layer in a developing solution to obtain the interaction volume between the beam and the material. S04. The interaction volume between the beam and the material is characterized using an electron microscope.

[0006] Optionally, the thickness of the film is 1-5000 nm.

[0007] Optionally, the material of the thin film is silicon, silicon nitride, or silicon oxide.

[0008] Optionally, the photoresist material layer is made of positive photoresist or negative photoresist.

[0009] Optionally, when the photoresist material layer is made of positive photoresist, the volume of the beam interaction with the material is the three-dimensional hole formed on the photoresist material layer; When the photoresist material layer is made of negative photoresist, the interaction volume between the beam and the material is a residual three-dimensional photoresist block. Before characterization, the obtained interaction volume between the beam and the material is laid down.

[0010] Optionally, the tilting can be achieved by using ultrasound to tilt the volume of the beam interacting with the material, or by using the probe of an atomic force microscope to tilt the volume of the beam interacting with the material.

[0011] Optionally, the thickness of the photoresist material layer is 1-10000 nm.

[0012] Optionally, the beam is an ion beam, an electron beam, an uncharged beam, or a light beam.

[0013] Optionally, the incident light in a point or line manner can be single-pixel point-based, single-pixel line-scan, or array-area-scan incident light.

[0014] Optionally, the electron microscope is a scanning electron microscope or a transmission electron microscope.

[0015] Optionally, the incident range of the beam is 1.6 × 10⁻⁶. -10 ~ 1×10 -1 nC.

[0016] The present invention has the following beneficial effects: The present invention ingeniously designs a method for characterizing the interaction volume between a beam and a material. First, a suspended thin film is provided, then a photoresist material layer is prepared on the suspended thin film, then a beam is incident, followed by development to obtain the interaction volume between the beam and the material, and finally the interaction volume between the beam and the material is characterized using an electron microscope. The interaction volume between the beam and the material is used to characterize the beam. This method is simple. Since no special processing is required, it can be directly obtained through electron microscope characterization without complex calculations, thus maintaining the original state of the interaction volume between the beam and the material. Moreover, the interaction volume between the beam and the material obtained by the method of the present invention is three-dimensional, which can reflect the relevant information of the interaction volume between the beam and the material in the depth direction. Therefore, the interaction volume between the beam and the material characterized by the method of the present invention is more comprehensive, more accurate, and has higher precision.

[0017] Moreover, the method of the present invention is not limited by factors such as beam intensity and beam type, and is applicable to beams of any intensity and type. Furthermore, the results are more accurate and precise. Therefore, the method of the present invention is a universal method that is expected to improve the accuracy and efficiency in fields such as materials processing, analysis, and medicine.

[0018] The method of this invention is particularly suitable for the application of low-dose beams, thus expanding its scope of application and providing guidance for semiconductor exposure, imaging, modification, and medical radiation.

[0019] The beam-material interaction volume characterized by the method of this invention can not only be used to evaluate the size of the beam spot, but also for the research and development of process technologies such as beam spot imaging, beam spot direct etching, beam spot modification, and beam spot exposure. Attached Figure Description

[0020] Figure 1 This is a flowchart of an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the process flow according to an embodiment of the present invention.

[0022] Figure 3 This is a comparison of transmission electron microscope images of the interaction volume between the beam and the material obtained in an embodiment of the present invention.

[0023] Figure 4 These are transmission electron microscope images comparing the interaction volume of the beam and the material obtained in Examples 2-5 of this invention. Detailed Implementation

[0024] This invention provides a method for characterizing the interaction volume between a beam and a material. To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0025] Many existing methods for characterizing the interaction volume between a beam spot and a sample employ numerical simulations. These models typically assume that the material is homogeneous and isotropic, neglecting the microstructure and nonlinear effects of the actual material. For pulsed or high-intensity beams, the accuracy of these methods decreases significantly. Furthermore, these methods rely on complex calculations, and the results require further validation.

[0026] Another method for characterizing the interaction volume between a beam spot and a sample involves first preparing a very thin sheet of material, then incident a certain dose of beam current onto the sidewall of this sheet to induce significant destructive damage. The damage volume is then observed using a high-resolution transmission electron microscope or scanning electron microscope, and this damage volume is approximated as the interaction volume between the beam current and the material. While this method provides helpful guidance for processing, it has limitations. For example, the results may differ when the initial material state is a sheet or a bulk material. Even if the initial material state is bulk, the bulk material needs to be cut during characterization, which can lead to discrepancies between the characterized interaction volume and the actual volume. Furthermore, inducing significant damage requires a very high dose of beam current, which is insufficient for applications such as semiconductor exposure, medical treatment, analysis, and imaging, where the required doses are very low.

[0027] Based on this, embodiments of the present invention provide a method for characterizing the interaction volume between a beam and a material, such as... Figure 1 As shown, it includes the following steps: S01. Provide a suspended thin film, wherein the suspended thin film is integrally formed on a support substrate having one or more back cavity structures, and a photoresist material layer is formed on the side of the thin film away from the support substrate. S02, The beam is incident in a point or line manner in the suspended thin film region of the photoresist material layer; S03. Immerse the photoresist material layer in a developing solution to obtain the interaction volume between the beam and the material. S04. The interaction volume between the beam and the material is characterized using an electron microscope.

[0028] In this embodiment S01, a suspended thin film is provided. This suspended thin film is commercially available, and its preparation method is relatively mature. The preparation method can be summarized as follows: first, a thin film (such as a silicon nitride thin film) is deposited on a supporting substrate (such as silicon); then, the supporting substrate is etched with NaOH or KOH for a certain period of time, resulting in one or more back cavity structures extending from the side away from the thin film to the side of the thin film on the supporting substrate. In other words, this method can obtain a thin film integrally formed on a supporting substrate having one or more back cavity structures, such as... Figure 2 The suspended film shown in (a) is a single suspended film. The suspended film not only supports the photoresist material layer, but also improves the characterization accuracy of the electron microscope.

[0029] In this embodiment S01, a photoresist material layer can be obtained on one side of the thin film away from the supporting substrate by spin coating.

[0030] This embodiment uses a negative photoresist as an example. In S02 of this embodiment, a beam is incident from one side of the back cavity structure supporting the substrate in a point or line manner on the suspended thin film region of the photoresist material layer. The incident beam secondaryly excites electrons, photons, etc. on the photoresist material layer, forming a certain trajectory, thereby ultimately obtaining the interaction volume between the beam and the material, such as... Figure 2 (b)

[0031] In one embodiment, the photoresist material layer is a positive photoresist, and a beam is incident from the side away from the supporting substrate in a point or line manner on the suspended thin film region of the photoresist material layer.

[0032] In this embodiment, S03, a developing solution is used to develop the photoresist material layer to obtain the interaction volume between the beam current and the material, such as... Figure 2As shown in (c). Since this embodiment uses negative photoresist as an example, areas interacting with the photoresist will not be dissolved by the developer, while areas without interaction with the photoresist will be dissolved. Therefore, the volume of interaction between the photoresist and the material in this embodiment is a residual three-dimensional photoresist block. The volume of interaction between the photoresist and the material obtained in this embodiment will be completely attached to the suspended film and will not be washed away by the developer during development.

[0033] In this embodiment, S04 uses an electron microscope to characterize (photograph) the volume of the beam-material interaction. Since this embodiment uses a negative photoresist as an example, before characterizing the volume of the beam-material interaction, the volume of the beam-material interaction obtained in S03 is first laid upside down, and the result is as follows. Figure 2 As shown in (d). If the microscope is not tilted, only a top view of the volume of the beam interacting with the material can be observed using electron microscopy (e.g., ...). Figure 3 As shown by the white dots above, or in a tilted view, it is impossible to accurately observe the information about the volume of the beam interacting with the material at different depth directions. After being laid down, the volume of the beam interacting with the material can be accurately observed in three dimensions by taking pictures. Moreover, since this embodiment directly takes pictures for characterization, the results are obtained directly, and the measurement results are very accurate.

[0034] In some embodiments, the thickness of the SO1 film is 1-5000 nm, and the film should be flat and uniform. To prevent interference beams from interacting with the material, the thickness of the suspended film should be as thin as possible, preferably 1-100 nm, and specifically 20 nm, 40 nm, 60 nm, 80 nm, or 100 nm.

[0035] In some embodiments, the thin film is made of silicon, silicon nitride, or silicon oxide. The thin film is used to support the photoresist material layer, so its material is not limited, and other materials can also be used.

[0036] In some embodiments, the photoresist material layer of SO2 is made of positive photoresist or negative photoresist.

[0037] The principle of positive photoresist is that the chemical bonds in the exposed areas break or decompose, leading to a decrease in molecular weight and an increase in solubility. During development, the exposed areas are dissolved and removed, while the unexposed areas remain. Its advantages include high resolution, making it suitable for manufacturing intricate patterns (such as advanced process chips). The principle of negative photoresist is that the exposed areas undergo a cross-linking reaction (photopolymerization or photocross-linking) to form a three-dimensional network structure, resulting in reduced solubility. During development, the unexposed areas are dissolved and removed, while the exposed areas remain. Its advantages include better etch resistance and mechanical strength, but lower resolution (light scattering causes pattern expansion). It is less expensive and commonly used in low-to-medium precision processes (such as PCB manufacturing).

[0038] In one embodiment, when the photoresist material layer is made of positive photoresist, the beam-material interaction volume is a three-dimensional hole formed on the photoresist material layer. When characterizing the beam-material interaction volume using an electron microscope (EM), the 3D reconstruction function of the EEM is required. When the photoresist material layer is made of positive photoresist, after development, areas interacting with the beam are dissolved by the developer, while areas not interacting with the beam are not dissolved. Therefore, the resulting beam-material interaction volume is a three-dimensional hole on the photoresist material layer, and the structure of the beam-material interaction volume can be obtained using the 3D reconstruction function of the EEM.

[0039] In some embodiments, the tilting is achieved by using ultrasound to tilt the volume of the beam interacting with the material, or by using a probe of an atomic force microscope to tilt the volume of the beam interacting with the material.

[0040] In some embodiments, the thickness of the photoresist material layer is 1-10000 nm. The preferred thickness is 200-1000 nm, specifically 200 nm, 300 nm, 500 nm, 700 nm, 900 nm, or 1000 nm. The thickness of the photoresist material layer is determined based on a pre-determined depth of the characterization beam-material interaction volume. Too thick a layer will affect the electron microscope observation results, while too thin a layer will allow the beam spot to penetrate, resulting in an incomplete characterization beam-material interaction volume and inaccurate results.

[0041] In some embodiments, the beam is an ion beam, an electron beam, an uncharged beam, or a light beam. Because the method steps of this invention are unique and ingenious, it has a wide range of applications and can be used for various types of beams.

[0042] In some implementations, the point-based incident method can be single-pixel point scanning, single-pixel line scanning, or array area scanning.

[0043] Conventional irradiation uses area scanning, and the results obtained from area scanning are a comprehensive result of all factors. Therefore, it cannot be used to study the influence of a specific factor on the result. The most basic unit of area scanning is a single pixel. A single pixel incident beam can shield the influence of factors such as pixel pitch, making the beam spot and sample interaction volume obtained from single-pixel scanning the most instructive. Single-pixel line scanning, based on point incident beam, introduces the pixel pitch factor along the line length, facilitating the study of the influence of pixel pitch on the interaction volume. Array area scanning, based on single-pixel line scanning, introduces the pixel pitch factor in another direction, allowing for a comprehensive decomposition of various influencing factors from point, line, and area perspectives. This enables detailed studies of the impact of each factor on the final result, and ultimately, optimization of process parameters.

[0044] In some implementations, the incident dose of the SO2 beam is determined based on the application, with an incident range of 1.6 × 10⁻⁶. -10 ~ 1×10 -1 If the incident dose is too low, the photoresist will not be modified and the volume of the beam interaction with the material cannot be visualized.

[0045] In some implementations, since the characteristic size of the volume in which the beam interacts with the material is about 5-100 nm, the best means of characterization is a high-resolution transmission electron microscope, but a scanning electron microscope can also be used.

[0046] The present invention will be further described below with reference to specific embodiments.

[0047] Example 1 This invention provides a method for characterizing the interaction volume between a beam and a material, comprising the following steps: Provides a suspended thin film (commercially available, comprising a 20nm thick silicon nitride film integrally formed on a support substrate (material: silicon) having one or more back cavity structures, with a photoresist layer (a 500nm thick negative photoresist, hydrosilsesquioxane) spin-coated on the side of the film away from the support substrate), such as... Figure 2 As shown in (a); A helium ion beam (beam current of 4997 helium ions) is incident on the back cavity structure of the supporting substrate from the photoresist material layer in a single pixel-like manner, such as Figure 2 As shown in (b); The photoresist material layer was immersed in a developer solution (2.38 wt.% tetramethylammonium hydroxide) for 10 min to obtain the interaction volume between the beam current and the material. Figure 2 As shown in (c); The volume of the beam interacting with the material is shaken by ultrasound, such as... Figure 2 As shown in (d), the interaction volume between the beam and the material after ultrasonic vibration was characterized by a transmission electron microscope.

[0048] Figure 3 This is a comparison of transmission electron microscope images of the interaction volume between the beam and the material obtained in an embodiment of the present invention. Figure 3 The middle arrow indicates the volume of the beam and material interaction obtained in Embodiment 1 of the present invention. After being laid down, the three-dimensional dimensions can be obtained comprehensively and accurately. Figure 3The difference between the other beam-material interaction volumes in this embodiment and those in Example 1 is that the white dots represent the beam-material interaction volumes in an upright state, i.e., the beam-material interaction volumes before being laid down. Since the photoresist in this embodiment is a negative photoresist, hydrosilyl silsesquioxane, characterizing the laid-down beam-material interaction volumes using transmission electron microscopy (TEM) allows for accurate, three-dimensional observation of the beam-material interaction volumes. Furthermore, because the images are taken directly, the results are obtained directly, resulting in highly accurate measurements. The beam-material interaction volumes before being laid down, when characterized by direct TEM imaging, cannot directly display their three-dimensional information. In comparison, the beam-material interaction volumes obtained before being laid down cannot have their three-dimensional information displayed through photography, but their three-dimensional information can be obtained using the 3D reconstruction function of an electron microscope.

[0049] Figure 3 The doses of the beams used in the interaction volumes with the materials differ for each beam. The doses used in each interaction volume, counted vertically from the upper right to the lower left, are 167, 333, 499, 666, 832, 999, 1332, 1666, 1998, 2331, 2665, 2998, 3331, 3664, 3998, 4330, 4664, 4997, 5330, 5663, 5996, 6329, 6662, 8328, 9993, 13325, and 16656 helium ions, with each ion carrying a charge of 1.6 × 10⁻⁶. -19 C. Of these, 167 helium ions, due to their low dosage, did not form a significant beam-material interaction volume, therefore... Figure 3 The image displayed is not very clear.

[0050] Example 2 The difference between this embodiment and Embodiment 1 is that the dose of helium ions in this embodiment is 250 helium ions.

[0051] Example 3 The difference between this embodiment and Embodiment 2 is that the dose of helium ions in this embodiment is 500 helium ions.

[0052] Example 4 The difference between this embodiment and Embodiment 2 is that the dose of helium ions in this embodiment is 1000 helium ions.

[0053] Example 5 The difference between this embodiment and Embodiment 2 is that the dose of helium ions in this embodiment is 1500 helium ions.

[0054] Figure 4These are comparative transmission electron microscope (TEM) images of the beam-material interaction volume obtained in Examples 2-5 of this invention, corresponding from left to right to the TEM images obtained in Examples 2, 3, 4, and 5, respectively. Figure 4 As can be seen, the interaction volume between the beam and the material varies with different doses of single-point incidence. At low doses, it is an inverted cone shape, which becomes cylindrical as the dose increases, and then becomes baseball-shaped as the dose increases further.

[0055] By extracting the dimensional parameters of the beam-material interaction volume at different doses, exposure process parameters can be guided. For example, the diameter at different depths within the beam-material interaction volume can determine the limiting resolution of the helium ion beam; the maximum diameter of the beam-material interaction volume can predict the degree of proximity effect; the height of the beam-material interaction volume can determine the exposure depth at that dose, and combined with the diameter at different depths, the aspect ratio after exposure can be predicted; and the tilt of the beam-material interaction volume can determine the verticality after exposure. Therefore, this has guiding significance for semiconductor exposure, imaging, modification, and medical radiation.

[0056] In summary, this invention ingeniously designs a method for characterizing the interaction volume between a beam and material. First, a suspended thin film is provided. Then, a photoresist material layer is prepared on the suspended thin film. Next, a beam is incident, followed by development to obtain the interaction volume between the beam and material, which is used to characterize the beam. Finally, an electron microscope is used to characterize the interaction volume. This method is simple; since no special processing is required, it can be directly obtained through electron microscopy without complex calculations, maintaining the original state of the interaction volume. Moreover, the interaction volume obtained by this invention is three-dimensional, reflecting relevant information in the depth direction. Therefore, the interaction volume characterized by this invention is more comprehensive, accurate, and precise.

[0057] Moreover, the method of the present invention is not limited by factors such as beam intensity and beam type, and is applicable to beams of any intensity and type. Furthermore, the results are more accurate and precise. Therefore, the method of the present invention is a universal method that is expected to improve the accuracy and efficiency in fields such as materials processing, analysis, and medicine.

[0058] The method of this invention is particularly suitable for the application of low-dose beams, thus expanding its scope of application and providing guidance for semiconductor exposure, imaging, modification, and medical radiation.

[0059] The beam-material interaction volume characterized by the method of this invention can not only be used to evaluate the size of the beam spot, but also for the research and development of process technologies such as beam spot imaging, beam spot direct etching, beam spot modification, and beam spot exposure.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for characterizing the volume of interaction between a beam and a material, characterized in that, Includes the following steps: A suspended thin film is provided, wherein the suspended thin film is integrally formed on a support substrate having one or more back cavity structures, and a photoresist material layer is formed on the side of the thin film away from the support substrate. A beam is incident in a point or line manner in the suspended thin film region of the photoresist material layer; The photoresist material layer is immersed in a developer solution to obtain the interaction volume between the beam and the material. The interaction volume between the beam and the material was characterized using electron microscopy.

2. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, The thickness of the film is 1-5000 nm.

3. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, The photoresist material layer is made of either positive or negative photoresist.

4. The method for characterizing the interaction volume between a beam and a material according to claim 3, characterized in that, When the photoresist material layer is made of positive photoresist, the interaction volume between the beam and the material is the three-dimensional hole formed on the photoresist material layer; When the photoresist material layer is made of negative photoresist, the interaction volume between the beam and the material is a residual three-dimensional photoresist block. Before characterization, the obtained interaction volume between the beam and the material is laid down.

5. The method for characterizing the interaction volume between a beam and a material according to claim 4, characterized in that, The "tilting" refers to using ultrasound to tilt the volume of the beam interacting with the material, or using the probe of an atomic force microscope to tilt the volume of the beam interacting with the material.

6. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, The thickness of the photoresist material layer is 1-10000 nm.

7. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, The beam is an ion beam, an electron beam, an uncharged beam, or a light beam.

8. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, Incident light can be categorized into single-pixel point-based, single-pixel line-scan, and array-area-scan incident light, either as points or lines.

9. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, The electron microscope is a scanning electron microscope or a transmission electron microscope.

10. The method for characterizing the interaction volume between a beam and a material according to claim 1, characterized in that, The incident dose of the beam is 1.6 × 10⁻⁶. -10 ~ 1×10 -1 nC.

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