A method for measuring the thickness of a diffusion layer at a wafer level
By setting metal electrodes on a conductive substrate and measuring the cathode polarization curve, the thickness of the diffusion layer is calculated, which solves the shortcomings in evaluating the mass transfer capacity of different electroplating tanks, improves the uniformity and controllability of the electroplating process, and guides copper electroplating processes such as TSV holes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN UNIV
- Filing Date
- 2024-01-12
- Publication Date
- 2026-06-02
AI Technical Summary
The lack of a clear means to evaluate the mass transfer capacity of different types of electroplating tanks in the same dimension in the current technology leads to significant differences in the electroplating process, which affects the effect of copper electroplating processes such as TSV holes.
By setting metal electrodes on a conductive substrate, measuring the cathodic polarization curve using a multi-channel electrochemical workstation, and calculating the limiting diffusion current to determine the diffusion layer thickness, the mass transfer performance of different types of electroplating baths can be evaluated.
It enables the evaluation of the mass transfer capacity of the electroplating bath in the same dimension, improves the uniformity and controllability of the electroplating process, and guides the electroplating copper processes such as TSV holes, bumps, and RDLs.
Smart Images
Figure CN117870529B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical technology applications, and in particular to a method for measuring the thickness of a wafer-level diffusion layer. Background Technology
[0002] In the post-Moore's Law era, 3D integration technology centered on Through-Silicon-Via (TSV) technology has been widely applied, with the key being the metallization filling of TSV vias. There are three types of TSV via metallization filling technologies: electroplating, electroless plating, and electronic paste filling. Among these, electroless plating and electronic paste filling methods face challenges related to filling efficiency, process complexity, and conductivity, and are still under research and development. Copper possesses excellent ductility, resistivity, and thermal conductivity. Copper electroplating filling processes can leverage accumulated technologies from PCB and silicon CMOS damascus processes, offering low development difficulty and advantages in both performance and cost, making it the current mainstream metallization solution.
[0003] In the field of electroplating, electroplating equipment is one of the factors affecting the electroplating effect of TSV holes. The key lies in how to provide a uniform plating solution and current distribution on the wafer surface, which is often improved through plating tank design and stirring speed. Currently, there is no clear characterization method in the industry to evaluate the mass transfer capacity of different electroplating tanks on the same scale. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for measuring the thickness of a wafer-level diffusion layer.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] A method for measuring the thickness of a wafer-level diffusion layer includes the following steps:
[0007] 1. A method for measuring the thickness of a wafer-level diffusion layer, comprising the following steps:
[0008] S1. Embed a number of metal electrodes onto a conductive substrate;
[0009] S2. The metal electrode is the working electrode, the inert metal is the counter electrode, the saturated calomel electrode is the reference electrode, and a copper electroplating solution is selected.
[0010] S3. The conductive substrate is energized, and the cathodic polarization curve of the conductive substrate and the cathodic polarization curve at different sites on the working electrode are obtained through a multi-channel electrochemical workstation.
[0011] S4. When the cathodic polarization curve of the conductive substrate tends to a stable state, the average value of the limiting diffusion current in the corresponding time interval of the cathodic polarization curve at different points of the working electrode that tends to a stable state is substituted into δ=nFADC / i, where n—the number of charges in the reaction, F—Faraday constant, A—electrode area, D—Cu 2+ diffusion coefficient, C—Cu 2+ The concentration of the diffusion layer is given by i, the limiting diffusion current, and δ, the thickness of the diffusion layer at different sites.
[0012] S5. Apply the above steps S1-S4 to different types of electroplating tanks, so as to evaluate the mass transfer capacity of different types of electroplating tanks in the same dimension by means of the diffusion layer thickness.
[0013] Furthermore, the maximum amplitude of the cathode polarization curve of the conductive substrate does not exceed ±0.1A for at least 500 consecutive seconds, which is the first stable state; the maximum amplitude of the cathode polarization curve of the working electrode does not exceed ±1mA for at least 500 consecutive seconds, which is the second stable state.
[0014] Furthermore, the conductive substrate is a conductive material such as a PCB board, silicon wafer, or copper sheet.
[0015] Furthermore, the metal electrode includes glassy carbon electrode, silver, gold, copper, ruthenium, rhodium, palladium, osmium, iridium or platinum metal and their alloys.
[0016] Furthermore, the inert electrode includes a carbon electrode, gold, titanium, or a platinum group metal.
[0017] Furthermore, the copper electroplating solution comprises one or a combination of several of the following: anions of sulfate, pyrophosphate, aminosulfonate or alkylsulfonate; 0-100 ppm chloride ions; 0.3-100 g / L copper ions; 0.001-2 mol / L hydrogen ions; 1-30 ml / L brightener; 1-50 ml / L inhibitor; and 1-30 ml / L leveling agent.
[0018] Furthermore, the brightener comprises one or more of the following: sodium dithiopropane sulfonate, sodium thiopropane sulfonate, sodium phenyl dithiopropane sulfonate, sodium dimethylformamide propane sulfonate, sodium 3-(benzothio-2-thio)propane sulfonate, sodium 3-thio-1-propane sulfonate, and dimethyl dithiomethylamine sulfonic acid.
[0019] Furthermore, the inhibitor comprises one or a combination of several of polyethylene glycol, fatty alcohol alkoxylates, and ethylene oxide-propylene oxide block copolymers with molecular weights of 400, 1000, 6000, and 20000, respectively.
[0020] Furthermore, the leveling agent is one or a combination of several of thiourea compounds, alkylpyridine compounds, and nicotinic green, as well as one or a combination of several of fatty alcohol polyoxyethylene ether series, ether series, and emulsifier series with different molecular weights.
[0021] Furthermore, the cathode polarization curve is obtained using cyclic voltammetry, linear sweep voltammetry, or chronoamperometry.
[0022] The beneficial effects of this invention are:
[0023] This invention proposes a method for measuring the thickness of a wafer-level diffusion layer, which converts the limiting diffusion current into the diffusion layer thickness. This allows for the evaluation of the mass transfer performance of different types of electroplating tanks in the same dimension, overcoming the significant differences between the electric field, flow field, and concentration field in the electrolytic cell and the wafer-level copper plating process. This method is closer to the actual electroplating process and can provide guidance for understanding the copper plating processes such as TSV holes, bumps, and RDLs. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1A This is one of the schematic diagrams of the working electrode arrangement in the method for measuring the thickness of a wafer-level diffusion layer according to the present invention;
[0026] Figure 1B This is a second schematic diagram of the working electrode arrangement for a method of measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0027] Figure 1C This is the third schematic diagram of the working electrode arrangement style of the method for measuring the thickness of a wafer-level diffusion layer according to the present invention;
[0028] Figure 1D This is the fourth schematic diagram of the working electrode arrangement style of the method for measuring the thickness of a wafer-level diffusion layer according to the present invention;
[0029] Figure 2 This is a schematic diagram of the TSV hole measurement method for a method of measuring the thickness of a wafer-level diffusion layer according to the present invention;
[0030] Figure 3 This is a schematic diagram of a horizontal electroplating tank for measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0031] Figure 4 This is a schematic diagram of a rack-type electroplating tank for measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0032] Figure 5A The cathode polarization curve of the copper sheet surface is shown in Embodiment 1 of the method for measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0033] Figure 5B The cathode polarization curve of the glassy carbon electrode surface is shown in Embodiment 1 of the method for measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0034] Figure 6A The cathode polarization curve of the copper sheet surface is shown in Embodiment 2 of the method for measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0035] Figure 6B The cathode polarization curve of the copper electrode is shown in Embodiment 2 of the method for measuring the thickness of a wafer-level diffusion layer according to the present invention.
[0036] In the figure, 10 is the conductive substrate; 20 is the working electrode; 30 is the counter electrode; 40 is the reference electrode; 50 is the TSV hole; and 60 is the measurement point. Detailed Implementation
[0037] The present invention will now be described in detail with reference to Figures 1-6.
[0038] A method for measuring the thickness of a wafer-level diffusion layer includes the following steps:
[0039] S1. A number of metal electrodes are embedded in the conductive substrate 10;
[0040] S2. The metal electrode is the working electrode 20, the inert metal is the counter electrode 30, the saturated calomel electrode is the reference electrode 40, and a copper electroplating solution is selected.
[0041] S3. The conductive substrate 10 is energized, and the cathodic polarization curve of the conductive substrate 10 and the cathodic polarization curve at different sites on the working electrode 20 are obtained through a multi-channel electrochemical workstation.
[0042] S4. When the cathode polarization curve of the conductive substrate 10 tends to a stable state, the average value of the limiting diffusion current in the corresponding time interval of the cathode polarization curve at different sites of the working electrode 20 that tends to a stable state is substituted into δ=nFADC / i, where n—the number of charges in the reaction, F—Faraday constant, A—electrode area, D—Cu 2+ diffusion coefficient, C—Cu 2+ The concentration of the diffusion layer is given by i, the limiting diffusion current, and δ, the thickness of the diffusion layer at different sites.
[0043] S5. Apply the above steps S1-S4 to different types of electroplating tanks, so as to evaluate the mass transfer capacity of different types of electroplating tanks in the same dimension by means of the diffusion layer thickness.
[0044] In this embodiment, the cathodic polarization curve of the conductive substrate 10 has a maximum amplitude not exceeding ±0.1A for at least 500 consecutive seconds, which constitutes a first stable state; the cathodic polarization curve of the working electrode 20 has a maximum amplitude not exceeding ±1mA for at least 500 consecutive seconds, which constitutes a second stable state. In this embodiment, the conductive substrate 10 is made of conductive materials such as a PCB board, silicon wafer, or copper sheet.
[0045] In this embodiment, the metal electrode includes glassy carbon electrode, silver, gold, copper, ruthenium, rhodium, palladium, osmium, iridium or platinum metal and their alloys.
[0046] In this embodiment, the inert electrode includes a carbon electrode, gold, titanium, or a platinum group metal.
[0047] In this embodiment, the copper electroplating solution includes one or a combination of several of the following: anions of sulfate, pyrophosphate, aminosulfonate or alkylsulfonate, 0-100 ppm chloride ions, 0.3-100 g / L copper ions, 0.001-2 mol / L hydrogen ions, 1-30 ml / L brightener, 1-50 ml / L inhibitor, and 1-30 ml / L leveling agent.
[0048] In this embodiment, the brightener comprises one or more of the following: sodium polydithiopropane sulfonate, sodium thiopropane sulfonate, sodium phenyl dithiopropane sulfonate, sodium dimethylformamide propane sulfonate, sodium 3-(benzothio-2-thio)propane sulfonate, sodium 3-thio-1-propane sulfonate, and dimethyl dithiomethylamine sulfonic acid.
[0049] In this embodiment, the inhibitor comprises one or a combination of several of polyethylene glycol, fatty alcohol alkoxylates, and ethylene oxide-propylene oxide block copolymers with molecular weights of 400, 1000, 6000, and 20000, respectively.
[0050] In this embodiment, the leveling agent is one or a combination of several of the following: thiourea compounds, alkylpyridine compounds, and nicotinic acid green, as well as one or a combination of several of the following: fatty alcohol polyoxyethylene ether series, ether series, and emulsifier series with different molecular weights.
[0051] In this embodiment, the cathode polarization curve is obtained using cyclic voltammetry, linear sweep voltammetry, or chronoamperometry.
[0052] In this embodiment, the electroplating tank types include horizontal electroplating tanks and rack-type electroplating tanks.
[0053] In this embodiment, as Figure 2 As shown, a measurement point 60 is located at the bottom of the TSV orifice 50, and two measurement points 60 are located at the orifice opening of the TSV orifice 50. Electrochemical tests are performed on the measurement points using a multi-channel electrochemical workstation to extract the limiting diffusion current at the orifice opening and bottom of the TSV orifice. The current is calculated using the formula δ=nFADC / i, where n is the charge of the reaction, F is the Faraday constant, A is the electrode area, and D is the Cu. 2+ diffusion coefficient, C—Cu 2+ The concentration of the diffusion layer is given by i, the limiting diffusion current, and δ, the diffusion layer thickness at the corresponding measurement point is calculated from the limiting diffusion current.
[0054] To illustrate the above-mentioned invention, the following embodiments are provided.
[0055] Example 1
[0056] Select 6 / 8 / 12-inch copper sheets as the conductive substrate 10. Drill a number of mounting holes on the surface of the copper sheets using an electric drill. After drilling, clean the copper sheets with acid, alkali, and deionized water for a total of 30 minutes. Embed a 3mm diameter L-shaped glassy carbon electrode into the mounting holes and insulate and fix it with epoxy resin. Before each electrochemical test, draw an 8-shaped pattern 100 times on the glassy carbon electrode on the moistened Al2O3 powder, polish it, and then clean it with deionized water.
[0057] A glassy carbon electrode (20) was selected as the working electrode, a titanium mesh as the counter electrode (30), and a saturated calomel electrode as the reference electrode (40) to form a three-electrode system. Electrochemical tests were conducted using a copper electroplating solution.
[0058] Based on the energized copper sheet, the LSV curve of the glassy carbon electrode was measured using a multi-channel electrochemical workstation. The limiting diffusion voltage, used to measure the limiting diffusion current of the glassy carbon electrode, was obtained from the LSV curve. According to the cathodic polarization curve of the glassy carbon electrode, the limiting diffusion current at different sites was extracted, and the diffusion layer thickness at the corresponding sites was calculated using the formula δ=nFADC / i.
[0059] The electroplating solution was sourced from Shanghai Saft Co., Ltd., and its main components were 50 g / L H2SO4 and 40 g / L Cu. 2+ 60 ppm chloride ions. The current range for multi-channel electrochemical operation is 0.01 μA-10 A, with a more preferred range of 0.01 μA-5 A. In this embodiment, the cathodic polarization curves on the copper sheet surface and at a certain location on the glassy carbon electrode surface are obtained using the chronoamperometry method, as shown below. Figure 5A and Figure 5B As shown. By Figure 5AIt can be seen that the cathodic polarization curve on the copper sheet surface changes by less than 0.1A from 500 to 1000 seconds, indicating that the cathodic polarization curve on the copper sheet surface is in the first stable state; Figure 5B It can be seen that the cathodic polarization curve on the surface of the glassy carbon electrode changes by less than 1 mA from 1000 to 1600 seconds, and the cathodic polarization curve on the surface of the glassy carbon electrode is in the second stable state.
[0060] Example 2
[0061] In this embodiment, the difference from Embodiment 1 is that the glassy carbon electrode is replaced with a copper electrode, while everything else remains the same. The cathodic polarization curves on the copper sheet surface and the copper electrode surface are obtained using the chronoamperometry method, as shown below. Figure 6A and Figure 6B As shown. By Figure 6A It is evident that the cathodic polarization curve on the copper sheet surface exhibits an amplitude variation of less than 0.1A within at least 1000-1600 seconds, indicating that the cathodic polarization curve on the copper sheet surface is in its first stable state. Figure 6B It can be seen that the cathodic polarization curve on the surface of the copper electrode changes by less than 1 mA from 1000 to 1600 seconds, and the cathodic polarization curve on the surface of the copper electrode is in the second stable state.
[0062] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand and implement the present invention. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for measuring the thickness of a wafer-level diffusion layer, characterized in that, Includes the following steps: S1. Embed a number of metal electrodes onto a conductive substrate; S2. The metal electrode is the working electrode, the inert metal is the counter electrode, the saturated calomel electrode is the reference electrode, and a copper electroplating solution is selected. S3. The conductive substrate is energized, and the cathodic polarization curve of the conductive substrate and the cathodic polarization curve at different sites on the working electrode are obtained through a multi-channel electrochemical workstation. S4. When the cathode polarization curve of the conductive substrate tends to the first stable state, the average value of the limiting diffusion current in the corresponding time interval of the cathode polarization curve at different points of the working electrode that tends to the second stable state is substituted into... δ =nFADC / i Where, n—the charge number of the reaction, F—Faraday constant, A—electrode area, D—Cu 2+ diffusion coefficient, C—Cu 2+ concentration, i —Limiting diffusion current, δ —Diffusion layer thickness, thereby calculating the diffusion layer thickness at different sites using the limiting diffusion current; S5. Apply the above steps S1-S4 to different types of electroplating tanks, so as to evaluate the mass transfer capacity of different types of electroplating tanks in the same dimension by means of the diffusion layer thickness. The first stable state is characterized by the maximum amplitude of the cathodic polarization curve of the conductive substrate not exceeding ±0.1A for at least 500 consecutive seconds; the second stable state is characterized by the maximum amplitude of the cathodic polarization curve of the working electrode not exceeding ±1mA for at least 500 consecutive seconds.
2. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 1, characterized in that, The conductive substrate is made of conductive materials such as PCB board, silicon wafer, or copper sheet.
3. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 1, characterized in that, The metal electrode includes glassy carbon electrode, silver, gold, copper, ruthenium, rhodium, palladium, osmium, iridium or platinum metal and their alloys.
4. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 1, characterized in that, The inert metals mentioned include carbon electrodes, gold, titanium, or platinum group metals.
5. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 1, characterized in that, The copper electroplating solution comprises one or a combination of several of the following: anions of sulfate, pyrophosphate, aminosulfonate or alkylsulfonate, 0-100 ppm chloride ions, 0.3-100 g / L copper ions, 0.001-2 mol / L hydrogen ions, 1-30 ml / L brightener, 1-50 ml / L inhibitor, and 1-30 ml / L leveling agent.
6. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 5, characterized in that, The brightener comprises one or more of the following: sodium polydithiopropane sulfonate, sodium thiopropane sulfonate, sodium phenyl dithiopropane sulfonate, sodium dimethylformamide propane sulfonate, sodium 3-(benzothio-2-thio)propane sulfonate, sodium 3-thio-1-propane sulfonate, and dimethyl dithiomethylamine sulfonic acid.
7. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 5, characterized in that, The inhibitor comprises one or a combination of several of polyethylene glycol, fatty alcohol alkoxylates, and ethylene oxide-propylene oxide block copolymers with molecular weights of 400, 1000, 6000, and 20000, respectively.
8. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 6, characterized in that, The leveling agent is one or a combination of several of thiourea compounds, alkylpyridine compounds, and nicotinic acid green, as well as one or a combination of several of fatty alcohol polyoxyethylene ether series, ether series, and emulsifier series with different molecular weights.
9. The method for measuring the thickness of a wafer-level diffusion layer as described in claim 1, characterized in that, The cathode polarization curves were obtained using cyclic voltammetry, linear sweep voltammetry, or chronoamperometry.