Selective laser atom deprocessing method for diamond

Abstract

This invention discloses a selective laser atom desorption / removal method for diamond, belonging to the fields of micro / nano manufacturing and atomic-scale manufacturing. The method includes: ion implantation into the diamond region to be removed, causing it to amorphize and form an amorphous carbon region; using the lower laser ablation threshold between diamond and amorphous carbon as the selective desorption threshold; irradiating the amorphous carbon region and the surrounding diamond region with a pulsed laser with an energy density lower than this threshold, utilizing the difference in atomic desorption rates between amorphous carbon and diamond to preferentially remove amorphous carbon until the exposed diamond significantly reduces the desorption rate, achieving self-termination. This invention, through localized amorphization via ion implantation, makes the atomic desorption rate of amorphous carbon more than two orders of magnitude higher than that of diamond, significantly improving processing efficiency; simultaneously, it utilizes the low desorption rate of diamond to achieve self-termination, resulting in controllable processing contours, surface roughness below 1 nm, and no graphite residue or thermal damage.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano manufacturing and atomic-scale manufacturing, and in particular to a method for selective laser atomic deprocessing of diamond. Background Technology

[0002] Diamond is a high-performance material, possessing the highest hardness in nature, ultra-high thermal conductivity and chemical inertness, an ultra-wide bandgap, and an ultra-wide transmission window covering the deep ultraviolet to far-infrared range, making it promising for applications in microelectronics, optics, and quantum information. With advancements in artificial synthesis technology, the size and purity of diamond crystals have continuously improved, driving the research and development and commercialization of related products. High-precision fabrication of micro- and nanostructures is crucial for device performance, and an increasing number of applications demand atomically smooth surfaces while minimizing material damage. However, while diamond possesses many excellent properties, it is also one of the most difficult materials to process; its extreme strength and stability make high-quality machining extremely challenging.

[0003] Laser processing is one of the mainstream technologies for fabricating diamond micro- and nanostructures, with the most common method being material removal through laser pulse ablation. Due to diamond's large band gap and high thermal conductivity, higher pulse energies are typically required than for processing other materials, leading to intense high-temperature plasma jetting and photo-induced stress processes. This results in surface roughness at the tens to hundreds of nanometer level, accompanied by significant mechanical and thermal damage. This ablation method also leaves a graphite layer on the processed surface, severely affecting photoelectric properties. In contrast, another method, known as laser atom desorption, is gentler. When the pulse energy is below the threshold required to initiate ablation, carbon atoms on the diamond surface react chemically with oxygen molecules in the air under the influence of a light field, generating gaseous carbon oxides that detach from the surface. This method is essentially an atomic-scale process, enabling ultra-micro removal at the atomic layer level, effectively reducing material damage and leaving no graphite residue on the surface.

[0004] However, two significant problems hinder the practical application of laser atomic desorption (LAD) methods: First, LAD is highly sensitive to local fluctuations in the optical field, changes in the local chemical state of atoms on the diamond surface, and variations in the oxygen content of the environment. Because these factors cannot be ideally controlled at the atomic scale, the desorption process is highly random, making it difficult to achieve accurate profile dimensions and low roughness in the final structure. Second, material removal is too slow, with each laser pulse only creating an etching depth of 10⁻⁶. -8 -10 -3 The processing time increases rapidly with the increase of the volume to be removed, which cannot meet the efficiency requirements for the large-scale manufacturing of diamond micro-nano structures.

[0005] To overcome these problems, researchers have attempted to increase the atomic desorption rate by increasing the laser energy density. However, this approach easily exceeds the ablation threshold and enters ablation mode, introducing damage and graphitization. Other attempts have focused on heating diamond in an oxygen-containing atmosphere to enhance the oxidation reaction, but the high temperature damages the original structure of the diamond substrate and makes localized selective processing difficult.

[0006] Therefore, there is an urgent need for a new method that can maintain the atomic-level precision and low-damage advantages of laser atomic desorption while significantly improving the controllability and efficiency of the process.

[0007] This invention is proposed in response to the aforementioned technical problems. Summary of the Invention

[0008] This invention proposes a selective laser atomic removal method for diamond, aiming to solve the problems of traditional laser removal in terms of processing accuracy, controllability, and efficiency.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for selective laser atomic deprocessing of diamond includes the following steps:

[0011] Ion implantation is performed on the area to be removed on the surface of diamond. Through the cascade collision effect induced by high-energy ions in the solid, the diamond in the area to be removed undergoes an amorphization transformation to form an amorphous carbon region.

[0012] Determine the minimum energy density for laser ablation removal of diamond and amorphous carbon, and use the smaller of them as the selective desorption threshold energy density.

[0013] The amorphous carbon region and the surrounding diamond region are irradiated with a pulsed laser while keeping the laser energy density below the selective desorption threshold. The difference in atomic desorption rates between amorphous carbon and diamond under the action of the pulsed laser is used to preferentially remove the amorphous carbon region until the exposed diamond surface causes a significant decrease in the atomic desorption rate, thereby achieving self-termination of the processing.

[0014] The principle is as follows: First, the diamond in the area to be removed undergoes an amorphization transformation (carbon atoms change from a diamond arrangement to a disordered arrangement). Since the chemical activity of amorphous carbon is significantly higher than that of diamond, laser atomic desorption can occur at a faster rate. By utilizing this rate difference, the local amorphous carbon can be preferentially removed, and the final structure is formed after sufficient exposure time. After all the amorphous carbon is removed, only normal diamond remains. Due to its extremely low atomic desorption rate, the removal process can be regarded as automatically stopping, ensuring the stability of the processed structure.

[0015] Furthermore, since the insulating properties of diamond affect the ion beam, a step of depositing a conductive film layer on the diamond surface is included before ion implantation, the thickness of which is 2nm~20nm.

[0016] Furthermore, after ion implantation and before pulsed laser irradiation, the step of removing the conductive film layer is also included.

[0017] The ion implantation is performed using focused ion beam scanning implantation: the focused ion beam scanning path, spot spacing, and dwell time are determined based on the target pattern, beam current intensity, and beam spot size.

[0018] Alternatively, large beam ion implantation can be performed: Before implantation, a surface pattern mask is prepared to block the non-implanted area. The mask thickness is greater than the sum of the ion penetration depth and the total etching depth caused by the ion beam and laser beam irradiation. Then, the scanning path and speed are determined according to the ion beam spot size and beam current intensity.

[0019] Furthermore, the material of the conductive film is selected from gold, copper, aluminum, platinum, or carbon, and its deposition method is selected from ion sputtering, magnetron sputtering, vapor deposition, or atomic layer deposition. The film thickness is measured using a scanning probe microscope, a profilometer, or the like.

[0020] Furthermore, the wavelength of the pulsed laser is 200nm~800nm, and the pulse width is 50fs~50ns.

[0021] Furthermore, the pulsed laser employs a focused beam or a structured beam with a specific energy, phase, and polarization state distribution for multiple scans or continuous exposure, and the scanning range or exposure area is larger than the ion implantation region, while maintaining the laser energy density below the selective desorption threshold.

[0022] Furthermore, based on the size of the area to be removed and the measured thickness of the conductive film, ion implantation parameters are designed. These parameters include ion elements, energy, and dosage, and are designed using Monte Carlo or molecular dynamics simulation methods. The ion implantation is achieved through a focused ion beam processing machine, an accelerator, an ion implanter, or a plasma implanter.

[0023] Furthermore, the conductive film layer is removed without damaging the normal diamond and the amorphous carbon formed by ion implantation; if a patterned mask is used, the mask material must also be protected from damage.

[0024] Methods for removing the conductive film include chemical etching, plasma cleaning, or laser etching.

[0025] Furthermore, the selective desorption threshold energy density is obtained by gradually reducing the laser power and performing data fitting processing on the diameter or depth of the surface ablation pits.

[0026] After a specific number of scans or exposure time, the geometry and material state of the formed structure are measured to determine whether the amorphous carbon has been fully removed. If it has been removed, laser irradiation is stopped; if there is any residue, laser irradiation continues until it is fully removed.

[0027] Determine if the structural depth meets the standard. If it does, end the processing. If it does not, start a new round of processing from the deposition of the conductive film layer. When using a patterned mask, if the depth meets the standard, remove the mask and the conductive film layer underneath without damaging the normal diamond. If it does not meet the standard, start a new round of processing from the deposition of the conductive film layer (no need to repeat the mask preparation).

[0028] Advantages and benefits of the present invention

[0029] 1. Localized amorphization significantly improves the controllability and efficiency of atomic desorption. As described in the background section, traditional atomic desorption is sensitive to changes in various factors, and differences in removal rates inevitably exist at different locations on the surface, leading to uncontrollable final morphology under continuous laser irradiation. This invention amorphizes the area to be removed. Although the desorption process in the amorphous carbon region also exhibits inherent randomness, the surrounding normal diamond region acts as a barrier. As the amorphous carbon is gradually consumed and the diamond is exposed to the laser, the rapid decrease in the desorption rate is equivalent to the removal process almost stopping. The surface profile under continuous exposure can still remain stable without strict control of the pulse number and exposure time. Furthermore, under the same laser parameters, the amorphous carbon atomic desorption rate can be more than two orders of magnitude higher than that of diamond, significantly improving processing efficiency.

[0030] 2. Atomic-scale mechanisms ensure high-precision, low-damage processing. The ion implantation and laser atom desorption processes in this invention are both atomic-scale processes. The former disrupts the arrangement of carbon atoms in diamond through the collision of high-energy ions, resulting in a small-sized and smooth-boundary amorphous carbon structure. The latter removes the amorphous carbon through a photochemical reaction mechanism, preserving the smooth interface morphology of the amorphous carbon structure. The surface roughness can reach below 1 nm, minimizing the mechanical and thermal damage to the material during ablation processing.

[0031] 3. Highly scalable and suitable for mass production. Multiple micro / nano structural units can be fabricated simultaneously using patterned masks, large-aperture ion beams, and high-power laser beam expansion and shaping, and even large-scale parallel processing can be carried out within the wafer-level area. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process flow of the technical solution of the present invention.

[0033] Figure 2 This is an atomic force microscope thickness measurement image of the diamond surface after aluminum film deposition in Example 1.

[0034] Figure 3 This is an atomic force microscope image of the diamond micro / nano structure after processing in Example 1.

[0035] Figure 4 This is a comparison of the Raman spectra of the diamond surface before and after processing in Example 1. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0037] Example 1: Selective laser atom deprocessing without a mask

[0038] This embodiment uses a single-crystal diamond substrate as the processing object and employs a maskless method to process micro-nano structures on its surface. The specific steps are as follows.

[0039] (1) Deposition of conductive film layer

[0040] An aluminum film was deposited as a conductive layer on the diamond surface using ion sputtering. The thickness of the deposited film was measured by atomic force microscopy (AFM) and found to be 12 nm (see [link to AFM]). Figure 2 ).

[0041] (2) Design of ion implantation parameters

[0042] Based on the size of the area to be removed and the measured thickness of the conductive film, ion implantation parameters were designed using SRIM (Monte Carlo simulation software). The ion source was gallium (Ga), the implantation energy was 30 keV, and the implantation dose was 1 × 10⁻⁶. 15 cm -2 .

[0043] (3) Perform ion implantation

[0044] Using a focused ion beam (FIB) machine, the area to be removed on the diamond surface was scanned and implanted according to the designed parameters. The scanning area of ​​the focused ion beam was 10 μm × 10 μm.

[0045] (4) Remove the conductive film layer

[0046] Without damaging the normal diamond and the formed amorphous carbon region, the aluminum film on the surface is removed by etching with hydrochloric acid solution.

[0047] (5) Determine the selective desorption threshold energy density

[0048] The threshold energy density is 0.3 J / cm³. 2 .

[0049] (6) Perform laser atom desorption

[0050] A pulsed laser with a wavelength of 266 nm and a pulse width of 100 fs was used, and the laser energy density was controlled to be 0.2 J / cm². 2 The laser employs a focused beam scanning method, scanning an area of ​​18μm × 18μm, and is repeated three times. During the scanning process, the sample surface is monitored in real time using an optical microscopy system.

[0051] (7) Inspection of processing results

[0052] After processing, the diamond micro / nano structure formed after three laser scans was measured using atomic force microscopy (AFM). For example... Figure 3 As shown, only the ion-implanted region was removed, and the surface roughness was 0.67 nm; the crystal structure was characterized using Raman spectroscopy, as shown... Figure 4 As shown, 1332cm -1 The intensity of the characteristic peak representing the diamond structure did not decrease after processing compared to the initial state, and no characteristic peaks representing defects and graphitization appeared, demonstrating the high-precision and low-damage processing advantages of the selective laser atom desorption method. Furthermore, the amorphous carbon atom desorption rate in the examples was 196 times that of diamond atom desorption, demonstrating the advantage of this invention in improving processing efficiency.

[0053] If the detection finds that the structural depth does not meet the standard, you can return to step (1) to carry out a new round of processing (depositing conductive film, ion implantation, removing film, laser irradiation) until the target depth is reached.

[0054] Example 2: Selective laser atom deprocessing with a mask

[0055] The difference from Example 1 is that the steps of preparing the patterned mask and removing the mask and residual conductive film layer are added, specifically:

[0056] (1) Deposition of conductive film layer

[0057] (2) Preparation of pattern mask

[0058] Pattern masks are fabricated on conductive films using techniques such as photolithography, electron beam etching, and laser direct writing.

[0059] (3) Design of ion implantation parameters

[0060] (4) Perform ion implantation

[0061] (5) Remove the conductive film layer

[0062] (6) Determine the selective desorption threshold energy density

[0063] (7) Perform laser atom desorption

[0064] (8) Inspection of processing results

[0065] (9) Remove the mask and residual conductive film layer

[0066] If the structural depth is not met in step (8), return to step (1) for a new round of processing, but there is no need to repeat the mask preparation (the mask is still retained). After the structural depth meets the standard, remove the mask and the residual conductive film layer below it.

[0067] The above detailed embodiments describe two typical implementations of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for selective laser atomic removal of diamond, characterized in that, Includes the following steps: Ion implantation is performed on the area to be removed on the surface of the diamond to cause the diamond in the area to undergo an amorphization transformation, forming an amorphous carbon region. Determine the minimum energy density for laser ablation removal of diamond and amorphous carbon, and use the smaller of them as the selective desorption threshold energy density. The amorphous carbon region and the surrounding diamond region are irradiated with a pulsed laser while keeping the laser energy density below the selective desorption threshold. The difference in atomic desorption rates between amorphous carbon and diamond under the action of the pulsed laser is used to preferentially remove the amorphous carbon region until the exposed diamond surface causes a significant decrease in the atomic desorption rate, thereby achieving self-termination of the processing.

2. The diamond selective laser atomic deprocessing method according to claim 1, characterized in that, Prior to ion implantation, a step of depositing a conductive film layer on the diamond surface is included, wherein the thickness of the conductive film layer is 2 nm to 20 nm.

3. The diamond selective laser atomic deprocessing method according to claim 2, characterized in that, The process includes removing the conductive film layer after ion implantation and before pulsed laser irradiation.

4. The method according to claim 2, characterized in that, When using large-spot ion implantation, a patterned mask is prepared after depositing a conductive film layer and before ion implantation; the mask covers the non-implanted area and its thickness is greater than the sum of the ion penetration depth and the total etching depth caused by ion beam and laser beam irradiation.

5. The diamond selective laser atomic deprocessing method according to claim 2, characterized in that, The conductive film is made of gold, copper, aluminum, platinum or carbon, and its deposition method is selected from ion sputtering, magnetron sputtering, vapor deposition or atomic layer deposition.

6. The diamond selective laser atomic de-processing method according to claim 1, characterized in that, The wavelength of the pulsed laser is 200nm~800nm, and the pulse width is 50fs~50ns.

7. The diamond selective laser atomic de-processing method according to claim 1, characterized in that, The pulsed laser uses a focused beam or a structured beam with a specific energy, phase, and polarization state distribution to perform multiple scans or continuous exposures, and the scanning range or exposure area is larger than the ion implantation region.

8. The diamond selective laser atomic deprocessing method according to claim 1, characterized in that, The parameters of the ion implantation include ion element, energy and dose, and are designed using Monte Carlo or molecular dynamics simulation methods; the ion implantation is achieved by a focused ion beam processing machine, accelerator, ion implanter or plasma implanter.

9. The diamond selective laser atomic deprocessing method according to claim 3, characterized in that, Methods for removing the conductive film include chemical etching, plasma cleaning, or laser etching.

10. The diamond selective laser atomic deprocessing method according to claim 1, characterized in that, The selective desorption threshold energy density is obtained by gradually reducing the laser power and performing data fitting on the diameter or depth of the surface ablation pits.

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