Method for coating film on inner wall of micropore

Abstract

The invention discloses a method for coating a film on the inner wall of a micropore, which relates to the technical field of microelectronic packaging, and comprises the following steps: a first stage, placing a workpiece and an ion source oppositely, turning on an asymmetric bipolar pulse power supply, turning on the ion source and an electron gun power supply at the same time, and starting to deposit a metal layer; in the second stage, the negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased, and the current of the electron gun is increased at the same time; and in the third stage, the negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are further increased, deposition is accelerated, the thickness of the metal film meets the electroplating requirement, and the resistance of the upper port and the lower port of the micropore is reduced to be below 200 ohm after film coating is finished. Neutral plasmas provided by the ion source and the electron gun are superposed with the asymmetric bipolar pulse bias power supply, and through the electron-ion coupling effect, the technical problem that the adhesion and coverage rate of a coating in a micropore are insufficient is solved, the quality of a film layer in the micropore is improved, and integration of metal on the surface and metal in the micropore is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of microelectronic packaging, and in particular to a method for coating the inner wall of a micropore. Background Art

[0002] Substrate vertical interconnection technology is an advanced electrical interconnection technology for packaging substrates or PCB printed boards. This technology has a wide range of applications, including but not limited to electronic manufacturing, communication equipment, computer hardware, medical equipment, etc. Substrate vertical interconnection technology requires copper plating in through-holes on non-metallic bases such as glass or other organic materials to achieve circuit connectivity between the upper and lower substrates. The advantage of substrate vertical interconnection technology is that it can systematically reconstruct the packaging structure, improve functional density, shorten the interconnection length, increase integration, and reduce signal transmission delay. Therefore, it is an important technology that is indispensable to modern electronic packaging technology and product design. With the development of technologies such as three-dimensional packaging and heterogeneous integration, the aspect ratio of substrate through-holes is getting larger and larger. It is necessary to develop new micropore inner wall coating technology to improve the coverage and adhesion of the micropore side wall coating to meet the requirements of inner hole side wall coating with high aspect ratio AR>10:1.

[0003] The existing microporous metallization technologies mainly include PVD technology, CVD technology, chemical plating, and electroplating technology. For the metallization needs of the inner walls of through holes on substrates of different materials, the magnetron sputtering and arc ion plating technologies of PVD technology are highly adaptable. Through the combination of magnetic field and electric field with ion beam, the coating quality, uniformity, and coverage can meet most needs. As the aperture of the through holes on the surface of the substrate becomes smaller, especially for substrates of non-metallic materials, the electrostatic shielding caused by the accumulation of charges on the outer surface of the hole during coating prevents ions from entering the interior of the through hole. The coating at the hole mouth is too thick, and the coating coverage and adhesion of the inner side wall of the hole are reduced. Later filling is prone to defects such as voids or clamping in the through hole. The above problems have been improved by combining auxiliary magnetic fields and electric fields with ion beams. However, as the aperture of the through-holes in the substrate continues to decrease, the aspect ratio is higher, from 6:1 and 8:1 to 10:1, 15:1, 20:1, and even 50:1. This problem is particularly prominent when processing insulating materials, i.e. non-metallic substrates such as glass-based or organic materials.

[0004] At present, the common methods used to deposit metal on the inner wall of micropores with an aspect ratio of more than 10:1 are chemical plating, electroplating technology, CVD technology and atomic layer deposition technology (ALD). For non-metallic substrates, the solution is not easy to preserve during the preparation of the metal seed layer by chemical plating and electroplating methods, and is easily contaminated by foreign impurities. The cost of wastewater treatment is high, which does not meet the current requirements of green and environmentally friendly technology development. The use of CVD technology to achieve metal layer deposition on the inner wall of the micropore requires a certain reaction temperature, which is suitable for heat-resistant glass substrates, but not for heat-resistant organic material substrates. ALD has good three-dimensional conformality, but the deposition rate is slow, and it also needs to be carried out at a certain reaction temperature. It is not suitable for organic material substrates with low temperature resistance and high surface flatness requirements. The technical solution of using the metal melting or melting of the capillary effect and the flow of metal copper liquid into the micropores also has the problem of too high process temperature and mismatch of the heat resistance characteristics of organic materials. Secondly, the problem that needs to be solved is the through-hole copper deposition technology with a higher aspect ratio. The existing through-hole copper plating technology is limited by the transport characteristics of ions in the hole and the serious loss of energy. The coverage and adhesion of the hole side walls are insufficient. There is a risk of falling off during later work, which will cause chip connection failure and reduce working reliability. It is also necessary to develop new through-hole copper plating technology to improve the adhesion and coverage of the plating on the inner wall of the micropore.

[0005] In the post-Moore era, the demand for high-performance, high-density and high-reliability chips is particularly urgent. Whether the chip substrate is used as an interposer, IC carrier or printed circuit board, the substrate through-holes have a larger aspect ratio, higher arrangement density and more stable reliability requirements. At present, non-metallic substrates such as glass-based and organic materials still have the problem of low coating coverage and poor adhesion on the inner wall of high aspect ratio micropores. Summary of the invention

[0006] In view of the low coverage and poor adhesion of non-metallic material substrates with different heat resistance characteristics such as glass and organic materials when coating the inner wall of micropores with high aspect ratio, the present invention aims to propose a new method for coating the inner wall of micropores. This method effectively overcomes the electrostatic shielding effect formed by the accumulation of charges on the surface and at the hole of the non-metallic substrate, as well as the problem of ion beam divergence of the same charge, thereby significantly improving the adhesion and coverage of the coating in the micropores. In addition, this method also solves the technical problem that the coating on the upper and lower ports of the through-hole cannot be continuously penetrated when processing through-holes with high aspect ratios.

[0007] The present invention is achieved through the following technical solutions: The present application provides a method for coating the inner wall of a micropore, comprising the following steps: The first stage of coating: first turn on the asymmetric bipolar pulse power supply, then turn on the ion source and electron gun power supply at the same time, cover the metal layer on the substrate surface and inside the micropores, and when the overall conductivity is weak, the coating enters the second stage; The second stage of coating: increase the negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply, and increase the electron gun current at the same time. After the conductivity of the surface and the inside of the micropores is further improved, the coating enters the third stage; The third stage of coating: further increase the negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply to accelerate deposition, further increase the thickness of the metal film, and reduce the resistance to below 200Ω.

[0008] The coating method is realized by a vacuum coating device, which mainly includes a vacuum chamber, an ion source, an electron gun, an asymmetric bipolar pulse power supply and a workpiece table. The substrate is placed on the workpiece table facing the ion source, and the workpiece table is made of stainless steel. The electron gun is placed in an area close to the workpiece table to ensure that the workpiece is immersed in the electron emission area of ​​the electron gun and that the neutral ion beam can be obtained on the workpiece surface.

[0009] An asymmetric bipolar pulse power supply is used. Its two poles (pole A and pole B) are connected to the workpiece and the vacuum chamber wall respectively. By adjusting the positive and negative pulse widths and working voltages of the asymmetric bipolar pulse power supply, effective deposition of the film layer inside the hole can be achieved for through holes with a high aspect ratio.

[0010] The method uses an electron gun and an asymmetric bipolar pulse power supply composite technology to deposit a metal layer on the inner wall of the micropores on the surface of the insulating material. By configuring an electron gun, an electron beam is provided to neutralize the film-forming ion beam, a neutral plasma is obtained, and the charge accumulation on the surface of the insulating material and the beam divergence angle of the same-charged particles of the ion beam are eliminated, thereby solving the problem of preventing ions from entering the through-hole due to the electrostatic field formed by charge accumulation when processing insulating materials in traditional electrodeposition and physical vapor deposition methods, and the influence of the beam divergence angle between the same-charge on the parallelism of the ion beam, thereby improving the ion density and energy in the hole and improving the adhesion and coverage of the coating. Superimposing an asymmetric bipolar pulse bias, modulating the positive and negative pulse working pulse width and working voltage of the bipolar pulse power supply for through-holes with different aspect ratios, and realizing staged deposition on the inner wall of the through-hole. Implementing different positive and negative pulse widths and voltages, through the coupling of electrons and ions, ions are guided into the micropores, further improving the adhesion and coverage of the coating. At the same time, it also solves the technical problem that the upper and lower port film layers of the through-hole cannot penetrate when processing through-holes with high aspect ratios.

[0011] In a specific embodiment, in the first stage of the coating, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 100V~300V, pulse width is 20μs~100μs; Positive pulse: working voltage is 10~20V, pulse width is 20μs ~60μs.

[0012] In a specific embodiment, in the first stage of the film deposition, the current of the electron gun power supply is set to be more than 1.0 times the current of the ion source, preferably 1.0 to 1.5 times.

[0013] In a specific embodiment, the coating time of the first stage of coating is 5 min to 10 min.

[0014] In a specific embodiment, in the second stage of the coating, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 600V~800V, pulse width is 300μs~400μs; The positive pulse voltage and pulse width are the same as those in the first stage of coating.

[0015] In a specific embodiment, in the second stage of the coating, the current of the electron gun power supply is set to be more than 1.5 times the current of the ion source, preferably 1.5 to 2.0 times.

[0016] In a specific embodiment, the coating time of the second coating stage is 10 min to 30 min.

[0017] In a specific embodiment, in the third stage of the coating, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 900V~1200V, pulse width is 400μs~450μs; Positive pulse: operating voltage is 20V~80V, pulse width is 20μs~40μs.

[0018] In a specific embodiment, in the third stage of the coating, the current of the electron gun power supply is set to be more than 1.5 times the current of the ion source, preferably 1.5 to 2.0 times.

[0019] In a specific embodiment, the coating time of the third coating stage is 20 min to 40 min.

[0020] In a specific embodiment, during the coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is insufficient or excessive, and the current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention configures an electron gun to provide an electron beam to neutralize the film-forming ion beam, obtain a neutral plasma, and eliminate the charge accumulation on the surface of the insulating material, thereby solving the problem that the electrostatic field formed by the charge accumulation prevents ions from entering the through hole when the insulating material is processed by the traditional electrodeposition and physical vapor deposition methods, thereby improving the quality of the film coating in the hole.

[0022] (2) The neutral ion beam of the present invention solves the problems of electrostatic field shielding and the beam divergence of ions of the same charge. It superimposes an asymmetric bipolar pulse bias voltage, modulates the positive and negative pulse width and voltage of the asymmetric bipolar pulse power supply for through holes with different aspect ratios, and realizes the spatiotemporal evolution of the discharge plasma. Through the coupling of positive and negative charges, it guides the ions deep into the micropores and accelerates the ions, thereby increasing the depth and energy of ion introduction into the micropores and improving the coverage and adhesion of the micropore sidewall coating. Compared with the prior art, no additional electric or magnetic field is required to guide the plasma. The coating process of micropores with different aspect ratios requires regulating the positive and negative pulse amplitudes and pulse widths of the asymmetric bipolar pulse power supply to achieve the best coating deposition process. The coverage of the micropore sidewall coating reaches 100%, which solves the coating requirements of micropores with aspect ratios greater than 10:1 and realizes the integration of surface and hole metal.

[0023] (3) The temperature of the workpiece can be controlled during coating, and metal deposition can be achieved at low temperature, which is suitable for the preparation of metal films on the surface of temperature-sensitive organic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings: Figure 1 Schematic diagram of the structure of the coating device used in the embodiment of the present invention.

[0025] Reference numerals: 1-vacuum chamber, 2-ion source incident port, 3-workpiece stage, 4-workpiece, 5-electron gun, 6-asymmetric bipolar pulse power supply.

[0026] Figure 2 This is a cross-sectional SEM photograph of a sample of copper plating on the sidewall of a micro-hole with a diameter of 30 μm (aspect ratio of 15:1) on a surface of an optical glass with a thickness of 450 μm in Example 1 of the present invention; Figure 3 This is a cross-sectional SEM photograph of a sample of copper plating on the sidewall of a micro-hole with a diameter of 20 μm (aspect ratio of 30:1) on the surface of a BT substrate with a thickness of 600 μm in Example 2 of the present invention; Figure 4 This is a schematic diagram of test points when the EDS method is used to test the distribution of copper elements in micropores in Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6 of the present invention; Figure 5 This is a cross-sectional SEM photograph of a sample of copper plating on the sidewall of a micro-hole with a diameter of 30 μm (aspect ratio of 15:1) on a surface of an optical glass with a thickness of 450 μm in Comparative Example 1 of the present invention; Figure 6 1 is a process flow chart of coating the inner wall of micropores in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0028] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details need not be employed to practice the present invention. In other embodiments, in order to avoid confusing the present invention, well-known materials or methods are not specifically described.

[0029] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" that appear in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any appropriate combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. In addition, those skilled in the art will be able to combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, without contradicting each other.

[0030] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0032] Example 1

[0033] This embodiment provides a method for coating the inner wall of a micropore, wherein the workpiece is optical glass with a thickness of 450 μm, the diameter of the through holes on the surface is 30 μm, the through hole spacing is 30 μm, and the through hole depth-to-diameter ratio is 15:1.

[0034] like Figure 1 The figure shows the device used in the method, which mainly includes a vacuum chamber 1, an ion source 2, an electron gun 5, an asymmetric bipolar pulse power supply 6 and a workpiece table 3. The substrate is placed on the workpiece table 3 as the workpiece 4, and the workpiece table 3 is made of stainless steel. The electron gun 5 is placed in the area close to the workpiece table 3 to ensure that the workpiece 4 is immersed in the electron emission area of ​​the electron gun 5, so that the surface of the workpiece 4 can obtain a neutral ion beam.

[0035] like Figure 6As shown, follow these steps: S1. Workpiece installation First, fix the cleaned and baked workpiece on the workpiece table. The workpiece faces the ion source, and the electron gun and ion source are located in the common area above the workpiece, and neutral plasma is obtained on the surface of the workpiece. The two poles of the asymmetric bipolar pulse power supply are A and B, with A connected to the workbench and B connected to the vacuum chamber.

[0036] S2. Workpiece coating The workpiece coating process adopts the segmented coating method.

[0037] S2-1, in the first stage of coating, the surface of the workpiece is insulated. First, the asymmetric bipolar pulse power supply is turned on. The working parameters of the pulse power supply are: set the negative pulse voltage to 300V, the pulse width to 20μs, the positive pulse voltage to 20V, and the pulse width to 60μs. Then turn on the ion source and the electron gun power supply at the same time. The ion source needs to have a high ionization rate. It can be a cathode arc ion source or a high-power pulse magnetron sputtering ion source. The electron gun can be a hollow cathode or other types of discharge methods. The current of the electron gun power supply is set to 1.2 times the current of the ion source. Obtain a fully neutralized ion beam. Under the positive and negative electric field modulation of the asymmetric bipolar pulse power supply, when a positive pulse is applied, the electron mass and the moving speed are small. Under the action of the positive pulse, the electron quickly enters the inside of the through hole, forms a spatial electric field in the micropore, attracts ions to move into the micropore, and then electron-ion coupling occurs, avoiding the electrostatic shielding effect, guiding the ions to penetrate into the micropore, and then collide with the side wall under the negative pulse of the pulse power supply to deposit into a film, and repeats over and over again. After 5 minutes, the coating enters the second stage.

[0038] S2-2, in the second stage of coating, when the workpiece substrate surface and the inside of the micropores are conductive, the electric field strength inside the micropores is weak due to the micropore electric field effect, and the density of ions entering is lower than the surface. The negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased to increase the energy of the ions. At the same time, the electron gun current is increased to 1.5 times the ion flow. By increasing the electron density, the electron-ion coupling effect is improved, and the ion density deep into the hole is increased. The negative pulse voltage and pulse width are increased to 600V and 300μs respectively, and the positive pulse voltage and pulse width remain unchanged. The ions obtain higher energy, bombard the surface of the film layer, and improve the density and adhesion of the film layer. After 10 minutes, the coating enters the third stage.

[0039] S2-3, the third stage of coating, the negative pulse voltage and pulse width are 900V and 400μs respectively, accelerating the deposition stage. The positive pulse voltage is 20V, the pulse width is adjusted to 20μs, and the electron gun current is adjusted to 1.5 times the ion current. In this stage, the thickness of the metal film increases further, and after 30 minutes, the coating is completed.

[0040] In the above coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0041] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through-holes was tested with a multimeter. The resistance was less than 200Ω, which showed good electroplating characteristics. Figure 2 The cross-sectional photo shows that the metal layer coverage is 100%. The weight percentage distribution of copper element in the micropores of sample 1# in Table 1 shows that the copper layer coverage in the micropores is 100%.

[0042] Example 2

[0043] This embodiment provides a method for coating the inner wall of a micropore. The difference from Embodiment 1 is that the workpiece of this embodiment is a BT substrate with a thickness of 600 μm, a surface through hole diameter of 20 μm, a hole spacing of 20 μm, and a depth-to-diameter ratio of 30:1.

[0044] In the first stage of coating process, the working parameters of asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 100V, pulse width is 100μs; Positive pulse: The operating voltage is 10V and the pulse width is 20μs.

[0045] like Figure 6 As shown, follow these steps: S1. Workpiece installation First, fix the cleaned and baked workpiece on the workpiece table. The workpiece faces the ion source, and the electron gun and ion source are located in the common area above the workpiece, and neutral plasma is obtained on the surface of the workpiece. The two poles of the asymmetric bipolar pulse power supply are A and B, with A connected to the workbench and B connected to the vacuum chamber.

[0046] S2. Workpiece coating The workpiece coating process adopts the segmented coating method.

[0047] S2-1, in the first stage of coating, the surface of the workpiece is insulated. First, the asymmetric bipolar pulse power supply is turned on. The working parameters of the pulse power supply are: set the negative pulse voltage to 100V, the pulse width to 100μs, the positive pulse voltage to 10V, and the pulse width to 20μs. Then turn on the ion source and the electron gun power supply at the same time. The ion source needs to have a high ionization rate. It can be a cathode arc ion source or a high-power pulse magnetron sputtering ion source. The electron gun can be a hollow cathode or other types of discharge methods. The current of the electron gun power supply is set to 1.2 times the current of the ion source. Obtain a fully neutralized ion beam. Under the positive and negative electric field modulation of the asymmetric bipolar pulse power supply, when a positive pulse is applied, the electron mass and the moving speed are small. Under the action of the positive pulse, the electrons and ions of the neutral ion beam quickly enter the through hole, forming a spatial electric field in the micropore, attracting ions to move into the micropore, and then electron-ion coupling occurs, avoiding the electrostatic shielding effect, guiding the ions to penetrate into the micropore, and then collide with the side wall under the negative pulse of the pulse power supply to deposit into a film, and repeat over and over again. After 10 minutes, the coating enters the second stage.

[0048] S2-2, in the second stage of coating, when the workpiece substrate surface and the inside of the micropores are conductive, the electric field strength inside the micropores is weak due to the micropore electric field effect, and the density of ions entering is lower than the surface. The negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased to increase the energy of the ions. At the same time, the electron gun current is increased to 1.5 times the ion flow. By increasing the electron density, the electron-ion coupling effect is improved, and the ion density deep into the hole is increased. The negative pulse voltage and pulse width are increased to 600V and 300μs respectively, and the positive pulse voltage and pulse width remain unchanged. The ions obtain higher energy, bombard the surface of the film layer, and improve the density and adhesion of the film layer. After 15 minutes, the coating enters the third stage.

[0049] S2-3, the third stage of coating, the negative pulse voltage and pulse width are 900V and 400μs respectively, accelerating the deposition stage. The positive pulse voltage is 20V, the pulse width is adjusted to 20μs, and the electron gun current is adjusted to 1.5 times the ion current. In this stage, the thickness of the metal film increases further, and after 40 minutes, the coating is completed.

[0050] In the above coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0051] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through-holes was tested with a multimeter, which was less than 200Ω, indicating good electroplating characteristics. Figure 3The cross-sectional photo shows that the metal layer coverage is 100%. The weight percentage distribution of copper in the micropores of sample 2# in Table 1 shows that the copper layer coverage in the micropores is 100%. No obvious warping or deformation was found in the BT board, and this method meets the low-temperature deposition requirements of organic substrates during the metallization process.

[0052] Example 3

[0053] This embodiment provides a method for coating the inner wall of a micropore. The difference from Embodiment 1 is that the workpiece is 480 μm thick glass, the pore diameter is 40 μm, the pore spacing is 40 μm, and the aspect ratio is 12:1.

[0054] In the second stage of the coating process of this embodiment, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 800V, pulse width is 300μs; The positive pulse voltage and pulse width are the same as those in the first stage of coating.

[0055] like Figure 6 As shown, follow these steps: S1. Workpiece installation First, fix the cleaned and baked workpiece on the workpiece table. The workpiece faces the ion source, and the electron gun and ion source are located in the common area above the workpiece, and neutral plasma is obtained on the surface of the workpiece. The two poles of the asymmetric bipolar pulse power supply are A and B, with A connected to the workbench and B connected to the vacuum chamber.

[0056] S2. Workpiece coating The workpiece coating process adopts the segmented coating method.

[0057] S2-1, in the first stage of coating, the surface of the workpiece is insulated. First, the asymmetric bipolar pulse power supply is turned on. The working parameters of the pulse power supply are: set the negative pulse voltage to 300V, the pulse width to 20μs, the positive pulse voltage to 20V, and the pulse width to 60μs. Then turn on the ion source and the electron gun power supply at the same time. The ion source needs to have a high ionization rate. It can be a cathode arc ion source or a high-power pulse magnetron sputtering ion source. The electron gun can be a hollow cathode or other types of discharge methods. The current of the electron gun power supply is set to 1.2 times the current of the ion source. Obtain a fully neutralized ion beam. Under the positive and negative electric field modulation of the asymmetric bipolar pulse power supply, when a positive pulse is applied, the electron mass and the moving speed are small. Under the action of the positive pulse, the electron quickly enters the inside of the through hole, forms a spatial electric field in the micropore, attracts ions to move into the micropore, and then electron-ion coupling occurs, avoiding the electrostatic shielding effect, guiding the ions to penetrate into the micropore, and then collide with the side wall under the negative pulse of the pulse power supply to deposit into a film, and repeats over and over again. After 5 minutes, the coating enters the second stage.

[0058] S2-2, in the second stage of coating, when the workpiece substrate surface and the inside of the micropores are conductive, the electric field strength inside the micropores is weak due to the micropore electric field effect, and the density of ions entering is lower than the surface. The negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased, and the electron gun current is increased to 1.5 times the ion flow. By increasing the electron density, the electron-ion coupling effect is improved, and the ion density extending into the hole is increased. The negative pulse voltage and pulse width are increased to 800V and 300μs respectively, and the positive pulse voltage and pulse width remain unchanged. The ions obtain higher energy, bombard the surface of the film layer, and improve the density and adhesion of the film layer. After 10 minutes, the coating enters the third stage.

[0059] S2-3, the third stage of coating, the negative pulse voltage and pulse width are 900V and 400μs respectively, accelerating the deposition stage. The positive pulse voltage is 20V, the pulse width is adjusted to 20μs, and the electron gun current is adjusted to 1.5 times the ion current. In this stage, the thickness of the metal film increases further, and after 20 minutes, the coating is completed.

[0060] In the above coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0061] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through-holes was tested using a multimeter, which was less than 200Ω, indicating good electroplating characteristics. The distribution of the weight percentage of copper elements in the micropores of sample 3# in Table 1 shows that the coverage of the copper layer in the micropores is 100%.

[0062] Example 4

[0063] This embodiment provides a method for coating the inner wall of a micropore. The workpiece is the same as that in Embodiment 1. The difference from Embodiment 1 is that in the second stage of coating in this embodiment, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 600V, pulse width is 400μs; The positive pulse voltage and pulse width are the same as those in the first stage of coating.

[0064] like Figure 6 As shown, follow these steps: S1. Workpiece installation First, fix the cleaned and baked workpiece on the workpiece table. The workpiece faces the ion source, and the electron gun and ion source are located in the common area above the workpiece, and neutral plasma is obtained on the surface of the workpiece. The two poles of the asymmetric bipolar pulse power supply are A and B, with A connected to the workbench and B connected to the vacuum chamber.

[0065] S2. Workpiece coating The workpiece coating process adopts the segmented coating method.

[0066] S2-1, in the first stage of coating, the surface of the workpiece is insulated. First, the asymmetric bipolar pulse power supply is turned on. The working parameters of the pulse power supply are: set the negative pulse voltage to 300V, the pulse width to 20μs, the positive pulse voltage to 20V, and the pulse width to 60μs. Then turn on the ion source and the electron gun power supply at the same time. The ion source needs to have a high ionization rate. It can be a cathode arc ion source or a high-power pulse magnetron sputtering ion source. The electron gun can be a hollow cathode or other types of discharge methods. The current of the electron gun power supply is set to 1.2 times the current of the ion source. Obtain a fully neutralized ion beam. Under the positive and negative electric field modulation of the asymmetric bipolar pulse power supply, when a positive pulse is applied, the electron mass and the moving speed are small. Under the action of the positive pulse, the electron quickly enters the inside of the through hole, forms a spatial electric field in the micropore, attracts ions to move into the micropore, and then electron-ion coupling occurs, avoiding the electrostatic shielding effect, guiding the ions to penetrate into the micropore, and then collide with the side wall under the negative pulse of the pulse power supply to deposit into a film, and repeats over and over again. After 5 minutes, the coating process enters the second stage.

[0067] S2-2, in the second stage of coating, when the workpiece substrate surface and the inside of the micropores are conductive, the electric field strength inside the micropores is weak due to the micropore electric field effect, and the density of ions entering is lower than the surface. The negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased to increase the energy of the ions. At the same time, the electron gun current is increased to 1.5 times the ion flow. By increasing the electron density, the electron-ion coupling effect is improved, and the ion density deep into the hole is increased. The negative pulse voltage and pulse width are increased to 600V and 400μs respectively, and the positive pulse voltage and pulse width remain unchanged. The ions obtain higher energy, bombard the surface of the film layer, and improve the density and adhesion of the film layer. After 10 minutes, the coating enters the third stage.

[0068] S2-3, the third stage of film coating, the negative pulse voltage and pulse width are 900V and 400μs respectively, accelerating the deposition stage. The positive pulse voltage is 20V, the pulse width is adjusted to 20μs, and the electron gun current is adjusted to 1.5 times the ion current. In this stage, the thickness of the metal film increases further, and the coating is completed after 30 minutes of deposition.

[0069] In the above coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0070] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through-holes was tested using a multimeter, which was less than 200Ω, indicating good electroplating characteristics. The weight percentage distribution of the copper element in the micropores of sample 4# in Table 1 shows that the coverage of the copper layer in the micropores is 100%.

[0071] Example 5

[0072] This embodiment provides a method for coating the inner wall of a micropore. The workpiece is the same as that in Embodiment 1. The difference from Embodiment 1 is that in the third stage of coating in this embodiment, the working parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 900V, pulse width is 450μs; Positive pulse: The operating voltage is 40V and the pulse span is 30μs.

[0073] like Figure 6 As shown, follow these steps: S1. Workpiece installation First, fix the cleaned and baked workpiece on the workpiece table. The workpiece faces the ion source, and the electron gun and ion source are located in the common area above the workpiece, and neutral plasma is obtained on the surface of the workpiece. The two poles of the asymmetric bipolar pulse power supply are A and B, with A connected to the workbench and B connected to the vacuum chamber.

[0074] S2. Workpiece coating The workpiece coating process adopts the segmented coating method.

[0075] S2-1, in the first stage of coating, the surface of the workpiece is insulated. First, the asymmetric bipolar pulse power supply is turned on. The working parameters of the pulse power supply are: set the negative pulse voltage to 300V, the pulse width to 20μs, the positive pulse voltage to 20V, and the pulse width to 60μs. Then turn on the ion source and the electron gun power supply at the same time. The ion source needs to have a high ionization rate. It can be a cathode arc ion source or a high-power pulse magnetron sputtering ion source. The electron gun can be a hollow cathode or other types of discharge methods. The current of the electron gun power supply is set to 1.2 times the current of the ion source. Obtain a fully neutralized ion beam. Under the positive and negative electric field modulation of the asymmetric bipolar pulse power supply, when a positive pulse is applied, the electron mass and the moving speed are small. Under the action of the positive pulse, the electron quickly enters the through hole, forms a spatial electric field in the micropore, attracts the ions to move into the micropore, and then electron-ion coupling occurs, avoiding the electrostatic shielding effect, guiding the ions to penetrate into the micropore, and collide with the side wall under the negative pulse of the pulse power supply to deposit into a film, and repeats over and over again. After 5 minutes, the coating enters the second stage.

[0076] S2-2, in the second stage of coating, when the workpiece substrate surface and the inside of the micropores are conductive, the electric field strength inside the micropores is weak due to the electric field effect, and the density of ions entering is lower than that on the surface. The negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased to increase the energy of the ions. At the same time, the electron gun current is increased to 1.5 times the ion flow. By increasing the electron density, the electron-ion coupling effect is improved, and the ion density deep inside the hole is increased. The negative pulse voltage and pulse width are increased to 600V and 300μs respectively, and the positive pulse voltage and pulse width remain unchanged. The ions obtain higher energy, bombard the surface of the film layer, and improve the density and adhesion of the film layer. After 10 minutes, the coating enters the third stage.

[0077] S2-3, the third stage of coating, the negative pulse voltage and pulse width are 900V and 450μs respectively, accelerating the deposition stage. The positive pulse voltage is 40V, the pulse width is adjusted to 30μs, and the electron gun current is adjusted to 1.5 times the ion current. In this stage, the thickness of the metal film increases further, and the coating is completed after 30 minutes of deposition.

[0078] In the above coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0079] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through-holes was tested using a multimeter, which was less than 200Ω, indicating good electroplating characteristics. The distribution of the weight percentage of copper elements in the micropores of sample 5# in Table 1 shows that the coverage of the copper layer in the micropores is 100%.

[0080] Example 6

[0081] This embodiment provides a method for coating the inner wall of a micropore. The workpiece is the same as that in Embodiment 1. The difference from Embodiment 1 is that in the third stage of coating in this embodiment, the working parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 1200V, pulse width is 400μs; Positive pulse: The operating voltage is 80V and the pulse span is 20μs.

[0082] like Figure 6 As shown, follow these steps: S1. Workpiece installation First, fix the cleaned and baked workpiece on the workpiece table. The workpiece faces the ion source, and the electron gun and ion source are located in the common area above the workpiece, and neutral plasma is obtained on the surface of the workpiece. The two poles of the asymmetric bipolar pulse power supply are A and B, with A connected to the workbench and B connected to the vacuum chamber.

[0083] S2. Workpiece coating The workpiece coating process adopts the segmented coating method.

[0084] S2-1, in the first stage of coating, the surface of the workpiece is insulated. First, the asymmetric bipolar pulse power supply is turned on. The working parameters of the pulse power supply are: set the negative pulse voltage to 300V, the pulse width to 20μs, the positive pulse voltage to 20V, and the pulse width to 60μs. Then turn on the ion source and the electron gun power supply at the same time. The ion source needs to have a high ionization rate. It can be a cathode arc ion source or a high-power pulse magnetron sputtering ion source. The electron gun can be a hollow cathode or other types of discharge methods. The current of the electron gun power supply is set to 1.2 times the current of the ion source. Obtain a fully neutralized ion beam. Under the positive and negative electric field modulation of the asymmetric bipolar pulse power supply, when a positive pulse is applied, the electron mass and the moving speed are small. Under the action of the positive pulse, the electron quickly enters the inside of the through hole, forms a spatial electric field in the micropore, attracts ions to move into the micropore, and then electron-ion coupling occurs, avoiding the electrostatic shielding effect, guiding the ions to penetrate into the micropore, and then collide with the side wall under the negative pulse of the pulse power supply to deposit into a film, and repeats over and over again. After 5 minutes, the coating enters the second stage.

[0085] S2-2, in the second stage of coating, when the workpiece substrate surface and the inside of the micropores are conductive, the electric field strength inside the micropores is weak due to the micropore electric field effect, and the density of ions entering is lower than the surface. The negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply are increased to increase the energy of the ions. At the same time, the electron gun current is increased to 1.5 times the ion flow. By increasing the electron density, the electron-ion coupling effect is improved, and the ion density deep into the hole is increased. The negative pulse voltage and pulse width are increased to 600V and 300μs respectively, and the positive pulse voltage and pulse width remain unchanged. The ions obtain higher energy, bombard the surface of the film layer, and improve the density and adhesion of the film layer. After 10 minutes, the coating enters the third stage.

[0086] S2-3, the third stage of film deposition, the negative pulse voltage and pulse width are 1200V and 400μs respectively, accelerating the deposition stage. The positive pulse voltage is 80V, the pulse width is adjusted to 20μs, and the electron gun current is adjusted to 1.5 times the ion current. In this stage, the thickness of the metal film increases further, and the film deposition ends after 30 minutes of deposition.

[0087] In the above coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

[0088] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through hole was tested with a multimeter, which was less than 200Ω, and had good electroplating characteristics. The weight percentage distribution of the copper element in the micropores of the 6# sample in Table 1 shows that the coverage of the copper layer in the micropores is 100%.

[0089] The test results of the weight percentage of copper element at different positions in the micropores of the samples prepared in Examples 1 to 6 using the EDS method are shown in Table 1 below. Figure 4 As shown, it is a schematic diagram of the test points when the EDS method is used to test the distribution of copper elements in micropores in Example 1 (1#), Example 2 (2#), Example 3 (3#), Example 4 (4#), Example 5 (5#), and Example 6 (6#) of the present invention.

[0090] Table 1 EDS method test copper content at different positions of the microporous section of samples 1#-6# (wt%)

[0091] Comparative Example 1 This comparative example provides a method for coating the inner wall of a micropore. The workpiece is the same as that in Example 1. The difference from Example 1 is that this comparative example does not involve an electron gun power supply.

[0092] The samples prepared by the above method were tested, and the resistance of the upper and lower ports of the through hole was tested with a multimeter. The resistance value was greater than 2000Ω, which did not meet the requirements of electroplating. Figure 5 As can be seen from the cross-sectional photograph, the metal layer does not completely cover the sidewalls of the microvia, and the copper layer is disconnected in the middle area of ​​the microvia.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that it is still possible to modify the technical solutions described in the aforementioned embodiments, or to replace some or all of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for coating the inner wall of a micropore, characterized in that: The following steps are involved: The first stage of coating: first turn on the asymmetric bipolar pulse power supply, then turn on the ion source and electron gun power supply at the same time, cover the metal layer on the substrate surface and inside the micropores, and when the overall conductivity is weak, the coating enters the second stage; The second stage of coating: increase the negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply, and increase the electron gun current at the same time. After the conductivity of the surface and the inside of the micropores is further improved, the coating enters the third stage; The third stage of coating: further increase the negative pulse amplitude and pulse width of the asymmetric bipolar pulse power supply to accelerate deposition, further increase the thickness of the metal film, and reduce the resistance to below 200Ω.

2. A method for coating the inner wall of a micropore according to claim 1, characterized in that: In the first stage of the coating, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 100V~300V, pulse width is 20μs~100μs; Positive pulse: working voltage is 10~20V, pulse width is 20μs ~60μs.

3. A method for coating the inner wall of a micropore according to claim 1, characterized in that: In the first stage of the coating, the current of the electron gun power supply is set to be more than 1.0 times the current of the ion source.

4. A method for coating the inner wall of a micropore according to claim 1, characterized in that: The coating time of the first coating stage is 5 min to 10 min.

5. The method for coating the inner wall of a micropore according to claim 1, characterized in that: In the second stage of the coating, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 600V~800V, pulse width is 300μs~400μs; The positive pulse voltage and pulse width are the same as those in the first stage of coating.

6. A method for coating the inner wall of a micropore according to claim 1, characterized in that: In the second stage of the coating, the current of the electron gun power supply is set to be more than 1.5 times the current of the ion source.

7. A method for coating the inner wall of a micropore according to claim 1, characterized in that: The coating time of the second coating stage is 10 min to 30 min.

8. A method for coating the inner wall of a micropore according to claim 1, characterized in that: In the third stage of coating, the operating parameters of the asymmetric bipolar pulse power supply are: Negative pulse: working voltage is 900V~1200V, pulse width is 400μs~450μs; Positive pulse: operating voltage is 20V~80V, pulse width is 20μs~40μs.

9. A method for coating the inner wall of a micropore according to claim 1, characterized in that: In the third stage of the coating, the current of the electron gun power supply is set to be more than 1.5 times the current of the ion source.

10. The method for coating the inner wall of a micropore according to claim 1, characterized in that: The coating time of the third coating stage is 20 minutes to 40 minutes.

11. A method for coating the inner wall of a micropore according to claim 1, characterized in that: During the coating process, an oscilloscope is used to detect the loading voltage waveform of the workpiece table in real time. When the detected voltage is inconsistent with the set voltage of the asymmetric bipolar power supply, the electron neutralization effect is poor. The current of the electron gun is adjusted to ensure that the loading voltage of the workpiece table is consistent with the output voltage of the asymmetric bipolar power supply.

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