A method for achieving ultra-smooth surface of parts through plasma enhanced chemical vapor deposition additive technology

Abstract

A method for achieving ultra-smooth surface of parts by plasma enhanced chemical vapor deposition additive technology, which relates to a method for achieving ultra-smooth surface of parts. The present invention aims to solve the problem that the traditional subtractive ultra-smooth method is time-consuming and the existing DLC ​​deposition technology fails to reduce the roughness from nanometer level to sub-nanometer level. Method: The part to be processed is placed in a vacuum chamber and evacuated, and then acetylene gas is introduced, the air pressure in the vacuum chamber is controlled, and then acetylene plasma is generated inside the vacuum chamber by radio frequency glow discharge, the radio frequency power is set, and a pulse voltage is applied to the part to be processed, and plasma enhanced chemical vapor deposition is performed on the surface of the part to obtain a DLC film. The present invention is used to achieve ultra-smooth surface of parts by plasma enhanced chemical vapor deposition additive technology.

Description

Technical Field

[0001] The invention relates to a method for achieving ultra-smooth surface of a part. Background Art

[0002] At present, the requirements for the root mean square (RMS) value of the surface roughness of optical reflectors and other components have reached the sub-nanometer level. Ultra-precision polishing technology characterized by "subtractive material" is mainly used to obtain this ultra-smooth surface, such as chemical mechanical polishing, magnetorheological polishing, jet polishing, airbag polishing and cluster ion polishing. Chemical mechanical polishing uses the alternating action of chemistry and mechanics to achieve the removal of the surface material to be polished, and can make the RMS value of the surface roughness of NiP amorphous alloy coating reach 0.2nm. Magnetorheological polishing has the advantages of high removal rate and sub-nanometer surface roughness by taking advantage of the fact that the rheological properties of magnetorheological polishing fluid change sharply in a strong magnetic field. The RMS value of the roughness of the quartz glass surface can be reduced to 0.163nm. Jet polishing is a polishing method that uses pre-mixed polishing fluid to spray onto the workpiece surface to achieve material removal, which can reduce the RMS value of the surface roughness of quartz glass from 0.635nm to 0.0586nm. Airbag polishing refers to a processing method that uses a rotating airbag covered with a polishing cloth as a polishing tool. It is very suitable for ultra-smooth processing of complex-shaped workpieces, and can reduce the RMS value of the roughness of the Ni-P amorphous alloy coating surface to 0.286nm. Cluster ion polishing is a processing method that uses cluster ions to bombard the surface of the workpiece, and obtains an ultra-smooth surface through the energy and momentum exchange between the ions and the workpiece atoms. The RMS value of the roughness of the optical glass surface can be reduced from 0.24nm to 0.14nm. It can be seen that the above-mentioned ultra-precision polishing methods can all obtain ultra-smooth surfaces with sub-nanometer roughness. However, the efficiency of these ultra-precision polishing methods characterized by "subtractive material" is relatively low, and the polishing time of large parts can be as long as dozens of days. In addition, since there are generally defects inside the matrix material, when these defects are exposed on the polished surface, the surface roughness will increase significantly. Therefore, internal defects of the substrate are also an important factor affecting the surface roughness limit when polishing large parts.

[0003] Additive manufacturing technology has become a research hotspot in the field of advanced manufacturing. Whether additive manufacturing technology can be applied to the field of ultra-smoothness has also attracted the attention of some researchers. At present, some scholars have conducted some explorations using thin film deposition technology and found that after a layer of thin film is deposited on the surface of an ultra-smooth specimen, its surface roughness will change significantly, among which the most common phenomenon is surface coarsening. For example, when a crystalline film is deposited on an ultra-smooth single-crystal Si wafer, its surface roughness often increases by more than one order of magnitude as the thickness of the film increases. This phenomenon is called dynamic coarsening. This phenomenon can be attributed to the fluctuation and shadow effect of the incident particles, that is, the protrusions on the surface of the material will induce the columnar growth of the grains to form a positive feedback and cause the surface roughness to increase significantly. In order to eliminate the influence of columnar crystals, some scholars have studied the effect of depositing amorphous films on surface roughness and found that when carbon-based films such as diamond-like carbon (DLC) are deposited on the surface of ultra-smooth single-crystal Si wafers, their surface roughness can remain unchanged (sub-nanometer level) or even slightly decrease. However, the substrate roughness used in existing research is less than 0.5nm, for example, from 0.5nm to 0.2nm, and from 0.2nm to 0.1nm, etc. There are few studies on rougher substrates. How to change the surface roughness of a substrate with nanometer level to sub-nanometer level by depositing DLC ​​has not been reported yet. Summary of the invention

[0004] The present invention aims to solve the problem that the traditional subtractive ultra-smoothing method is time-consuming and the existing DLC ​​deposition technology cannot reduce the roughness from nanometer level to sub-nanometer level, and provides a method for achieving ultra-smooth surface of parts through plasma enhanced chemical vapor deposition additive technology.

[0005] A method for achieving an ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology is performed in the following steps:

[0006] The parts to be processed are placed in a vacuum chamber and evacuated, and then acetylene gas with a flow rate of 10sccm to 200sccm is introduced, the air pressure in the vacuum chamber is controlled, and then acetylene plasma is generated inside the vacuum chamber by radio frequency glow discharge, the radio frequency power is set to 0.1kW to 2kW, and a pulse voltage with an amplitude of 0.1kV to 10kV, a frequency of 10kHz to 100kHz, and a pulse width of 10μs to 1000μs is applied to the parts to be processed, and plasma enhanced chemical vapor deposition is performed on the surface of the parts to obtain a DLC film, that is, a part with an ultra-smooth surface.

[0007] The beneficial effects of the present invention are:

[0008] The present invention uses plasma enhanced chemical vapor deposition (PECVD) technology to deposit DLC film on the surface of the part, and only 5min to 300min is needed to reduce the surface roughness RMS from nanometer level to sub-nanometer level, which is much lower than the time required by the traditional polishing method. Moreover, since the method is an "additive" ultra-smoothing method, it avoids the sub-surface defects existing in the ultra-precision polishing method characterized by "subtractive" affecting the surface roughness limit value when polishing large parts. The sub-surface defects in the present invention have little effect on the surface roughness, which leads to a significant reduction in the discreteness of the surface roughness. In addition, since the PECVD deposition process can be proportionally amplified, the time for ultra-smoothing treatment of large parts is basically the same as that of small parts, and the limitation that the polishing time of the traditional method is proportional to the workpiece area is also overcome. Therefore, the PECVD additive ultra-smoothing technology proposed in the present invention can overcome the limitations of the conventional polishing method characterized by "subtractive" in terms of low efficiency and large influence of the limit surface roughness value on the substrate, and realize the rapid ultra-smoothing of the surface of the curved structure, thereby providing a reliable technical approach for the efficient ultra-smoothing treatment of the surface of large and complex structural parts.

[0009] The invention is used for a method for realizing ultra-smooth surface of parts through plasma enhanced chemical vapor deposition additive technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a diagram showing the macroscopic morphology change of the part before and after PECVD additive ultra-smoothing in Example 1, where a is the original surface and b is the surface after PECVD additive ultra-smoothing;

[0011] Figure 2 The microscopic morphology and roughness map of the part before PECVD additive ultra-smoothness in Example 1;

[0012] Figure 3 This is the microscopic morphology and roughness diagram of the ultra-smoothed part after PECVD additive manufacturing in Example 1. DETAILED DESCRIPTION

[0013] Specific implementation method 1: This implementation method is a method for achieving ultra-smooth surface of parts by plasma enhanced chemical vapor deposition additive technology, which is carried out in the following steps:

[0014] The parts to be processed are placed in a vacuum chamber and evacuated, and then acetylene gas with a flow rate of 10sccm to 200sccm is introduced, the air pressure in the vacuum chamber is controlled, and then acetylene plasma is generated inside the vacuum chamber by radio frequency glow discharge, the radio frequency power is set to 0.1kW to 2kW, and a pulse voltage with an amplitude of 0.1kV to 10kV, a frequency of 10kHz to 100kHz, and a pulse width of 10μs to 1000μs is applied to the parts to be processed, and plasma enhanced chemical vapor deposition is performed on the surface of the parts to obtain a DLC film, that is, a part with an ultra-smooth surface.

[0015] The beneficial effects of this embodiment are:

[0016] In this embodiment, when the DLC film is deposited on the surface of the part by plasma enhanced chemical vapor deposition (PECVD) technology, it only takes 5min to 300min to reduce the surface roughness RMS from the nanometer level to the sub-nanometer level, which is much lower than the time required for the traditional polishing method. Moreover, since this method is an "additive" ultra-smoothing method, it avoids the sub-surface defects existing in the ultra-precision polishing method characterized by "subtractive" affecting the surface roughness limit value when polishing large parts. In this embodiment, the sub-surface defects have little effect on the surface roughness, which leads to a significant reduction in the discreteness of the surface roughness. In addition, since the PECVD deposition process can be amplified proportionally, the time for ultra-smoothing treatment of large parts is basically the same as that of small parts, and the limitation of the polishing time of the traditional method is proportional to the workpiece area. Therefore, the PECVD additive ultra-smoothing technology proposed in this embodiment can overcome the limitations of the conventional polishing method characterized by "subtractive" with low efficiency and the large influence of the substrate on the limit surface roughness value, and realize the rapid ultra-smoothing of the surface of the curved structure, thereby providing a reliable technical approach for the efficient ultra-smoothing treatment of the surface of large and complex structural parts.

[0017] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the surface roughness of the part to be processed is at the nanometer level. The rest is the same as the specific implementation method 1.

[0018] Specific implementation method three: This implementation method is different from the specific implementation method one or two in that: vacuuming to 1×10 -2 Pa or 1×10 -2 Pa or less. Other aspects are the same as those of the first or second specific implementation.

[0019] Specific implementation method 4: This implementation method is different from specific implementation methods 1 to 3 in that the air pressure in the vacuum chamber is controlled to be 0.1 Pa to 1 Pa. The rest is the same as specific implementation methods 1 to 3.

[0020] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: plasma enhanced chemical vapor deposition is performed on the surface of the part for 5 minutes to 300 minutes to obtain a DLC film. The rest is the same as specific embodiments 1 to 4.

[0021] Specific implementation example 6: This implementation example is different from specific implementation examples 1 to 5 in that the surface roughness of the ultra-smooth part is sub-nanometer level. The rest is the same as specific implementation examples 1 to 5.

[0022] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 5 in that: acetylene gas with a gas flow rate of 50 sccm to 200 sccm is introduced, and the pressure in the vacuum chamber is controlled to be 0.5 Pa to 1 Pa. The rest is the same as specific embodiments 1 to 5.

[0023] Specific implementation example 8: This implementation example is different from specific implementation examples 1 to 5 in that the radio frequency power is set to 0.4 kW to 2 kW. The rest is the same as specific implementation examples 1 to 5.

[0024] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 5 in that a pulse voltage with an amplitude of 5 kV to 10 kV, a frequency of 10 kHz to 100 kHz and a pulse width of 10 μs to 20 μs is applied to the part to be processed. The rest is the same as specific embodiments 1 to 5.

[0025] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 5 in that a pulse voltage with an amplitude of 5 kV, a frequency of 10 kHz and a pulse width of 20 μs is applied to the part to be processed. The rest is the same as specific embodiments 1 to 5.

[0026] The following examples are used to verify the beneficial effects of the present invention:

[0027] Embodiment 1:

[0028] A method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology, which is carried out in the following steps:

[0029] Place the part to be processed in a vacuum chamber and evacuate it to 1×10 -2 Pa, and then acetylene gas with a flow rate of 50 sccm is introduced, the air pressure in the vacuum chamber is controlled to be 0.5 Pa, and then acetylene plasma is generated inside the vacuum chamber by radio frequency glow discharge, the radio frequency power is set to 400 W, and a pulse voltage with an amplitude of 5 kV, a frequency of 10 kHz and a pulse width of 20 μs is applied to the parts to be processed, and plasma enhanced chemical vapor deposition is performed on the surface of the parts for 15 minutes to obtain a DLC film, that is, a part with an ultra-smooth surface.

[0030] The part to be processed is conductive glass with a surface roughness RMS of 1.0 nm.

[0031] The surface roughness RMS of the part with ultra-smooth surface drops to 0.5 nm.

[0032] Under the action of pulse bias, carbon ions are deposited on the material surface with high energy, and then a DLC film is formed on the material surface, such as Figure 1 As shown, Figure 1 This is a diagram of the macroscopic morphology change of the part before and after PECVD additive super-smoothing in Example 1. a is the original surface, and b is the surface after PECVD additive super-smoothing. The morphology and roughness of the original surface of the material and the surface after DLC deposition were tested using a white light interferometer. The results are as follows Figure 2 and 3 As shown, Figure 2 This is the microscopic morphology and roughness diagram of the part before PECVD additive ultra-smoothness in Example 1. Figure 3 This is the microscopic morphology and roughness diagram of the ultra-smoothed part after PECVD additive manufacturing in Example 1. Figure 2 and 3 It can be seen that after DLC deposition, the undulation of the material surface is reduced, the height difference between the highest and lowest points is reduced from about 9nm to about 5nm, and the root mean square roughness is reduced from 1.0nm to 0.5nm. The material surface roughness test refers to the standard ISO 25178, and the average of three points is obtained. The results are shown in Table 1.

[0033] Table 1. Roughness change of parts before and after PECVD additive ultra-smoothing in Example 1

[0034] Test point 1 Test point 2 Test point 3 average value Original surface 1.158nm 1.075nm 0.940nm 1.058nm After adding ultra-smooth 0.553nm 0.528nm 0.558nm 0.546nm

[0035] Comparative Experiment 1: This comparative experiment is different from Example 1 in that: plasma enhanced chemical vapor deposition is performed on the surface of the part for 2 minutes to obtain the DLC film. The rest is the same as Example 1.

[0036] Comparative Experiment 2: This comparative experiment is different from Example 1 in that the part to be processed is a conductive glass with a surface roughness RMS of 0.45 nm. Others are the same as Example 1.

[0037] Table 2 Comparison of the roughness changes of parts before and after PECVD additive ultra-smoothing

[0038]

Claims

1. A method for achieving ultra-smooth surface of parts by plasma enhanced chemical vapor deposition additive technology, Features It is carried out in the following steps: The parts to be processed are placed in a vacuum chamber and evacuated, and then acetylene gas with a flow rate of 10sccm~200sccm is introduced, and the pressure in the vacuum chamber is controlled, and then acetylene plasma is generated inside the vacuum chamber by radio frequency glow discharge, and the radio frequency power is set to 0.1kW~2kW, and a pulse voltage with an amplitude of 5kV~10kV, a frequency of 10kHz~100kHz, and a pulse width of 10µs~1000µs is applied to the parts to be processed, and plasma enhanced chemical vapor deposition is performed on the surface of the parts to obtain a DLC film, that is, a part with an ultra-smooth surface is obtained; The part to be processed is conductive glass with a surface roughness RMS of 1.0 nm; The surface roughness RMS of the part with ultra-smooth surface drops to 0.5 nm.

2. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 1, Features Vacuum to 1×10 -2 Pa or 1×10 -2 Below Pa.

3. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 2, Features Control the air pressure in the vacuum chamber to 0.1Pa~1Pa.

4. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 1, Features Plasma enhanced chemical vapor deposition is carried out on the surface of the part for 5 minutes to 300 minutes to obtain the DLC film.

5. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 1, Features Acetylene gas with a flow rate of 50 sccm~200 sccm is introduced, and the pressure in the vacuum chamber is controlled to be 0.5Pa~1Pa.

6. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 1, Features Set the RF power to 0.4kW~2kW.

7. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 1, Features A pulse voltage with an amplitude of 5kV~10kV, a frequency of 10kHz~100kHz and a pulse width of 10µs~20µs is applied to the parts to be processed.

8. The method for achieving ultra-smooth surface of a part by plasma enhanced chemical vapor deposition additive technology according to claim 1, Features A pulse voltage with an amplitude of 5 kV, a frequency of 10 kHz and a pulse width of 20 µs is applied to the part to be treated.

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