Method for rapidly screening TSV copper filling inhibitor

Abstract

The invention discloses a method for rapidly screening a TSV copper filling inhibitor. An electrochemical method is utilized, linear sweep voltammetry (LSV) is adopted to research the inhibition performance of the inhibitor, cyclic voltammetry (CV) is adopted to strip copper, chronopotentiometry (CP) is adopted to research the inhibition effect of the inhibitor, and finally, the characteristics of the additive are qualitatively analyzed in combination with an electrochemical test result. By means of the method, the inhibitor with the high inhibition effect can be rapidly screened, subsequent TSV copper filling is facilitated, and the screened inhibitor can achieve TSV copper filling from bottom to top and is free of holes and defects.

Description

Technical Field

[0001] The invention relates to the technical field of TSV copper electroplating, and in particular to a method for quickly screening TSV copper filling inhibitors. Background Art

[0002] In the TSV copper filling process, controlling additives often leads to better electroplating filling effects for optimizing high aspect ratio TSVs.

[0003] Additives are mainly divided into three categories: accelerators, inhibitors and levelers. Accelerators are generally sulfur-containing compounds that can be adsorbed on the cathode surface. Through the coordination effect, they can accelerate the diffusion of copper ions, reduce cathode polarization, accelerate nucleation, and promote copper deposition. Within a certain concentration range, they can affect the copper crystallization mode, making the coating grains refined, the structure dense, and the surface bright. Because the molecular weight of the accelerator is small, it can quickly diffuse to the bottom of the hole and various parts in the hole. When used in conjunction with the inhibitor, it can improve the problem of the clamping defect. The inhibitor is the key to controlling copper deposition. It is generally a long-chain organic polymer with a large molecular weight (>1000). It can usually form a polymer film on the cathode surface, which mainly acts on the position of the orifice to prevent the orifice from closing prematurely and avoid the formation of the clamping defect. The leveler is usually an additive containing nitrogen functional groups, which has a certain inhibitory and leveling effect. Because the leveler generally attaches preferentially to the raised position, inhibiting the copper deposition there, while the deposition in other areas is weakly inhibited, and finally the deposition thickness is the same everywhere, achieving the leveling effect.

[0004] Currently, many researchers have begun to try to fill blind vias with a single inhibitor. Regardless of whether it is a single additive system or a three-additive system, the screening of the inhibitor is extremely important. The present invention mainly focuses on the single inhibitor system to screen a suitable blind via filling inhibitor. Summary of the invention

[0005] The present invention aims to provide a method for quickly screening TSV copper filling inhibitors to solve the TSV copper electroplating problem mentioned in the above background technology.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for rapidly screening TSV copper filling inhibitors, using electrochemical screening methods, including linear sweep voltammetry, cyclic voltammetry and chronopotentiometry; comprising the following steps: S1: cleaning the platinum rotating disk electrode; S2: Fix the platinum rotating disk electrode in the TSV copper filling mother solution and connect the electrodes; S3: Linear sweep voltammetry was used to adjust the speed of the platinum rotating disk electrode through the rotating disk electrode controller to screen out the appropriate inhibitor concentration; S4: Use chronopotentiometry to screen out the best inhibitors; Among them, after each inhibitor is screened, copper will be deposited on the platinum rotating disk electrode. Before screening the next type of inhibitor, cyclic voltammetry is used to strip the copper from the platinum rotating disk electrode, and then S1-S3 are repeated to complete the screening of the next inhibitor. A three-electrode system was used, with the reference electrode being a mercury / mercurous sulfate electrode, the working electrode being a platinum rotating disk electrode, and the counter electrode being a platinum wire.

[0007] S1 described cleaning of the platinum rotating disk electrode, specifically: first soak in 5%-10% sulfuric acid for 0.5-1min, rinse with deionized water, then polish with 0.5-1μm alumina powder, place in deionized water ultrasonic bath for 1-2min to remove residual alumina powder, rinse again with deionized water, and finally blow dry with nitrogen.

[0008] S2 The TSV copper filling mother solution includes 150-200 g / L CuSO4·5H2O, 10-40 g / L H2SO4 and 50-80 ppm Cl - ; The rotation speed of the platinum rotating disk electrode described in S3 is 0-20000RPM.

[0009] The parameters of the linear sweep voltammetry are: a scan rate of 3-5 mV / s, a maximum current of 8-10 mA, and the parameters of the chronopotentiometry are: a scan time of 500-1000 s, a current of -0.5-0.1 mA.

[0010] The inhibitor is a TSV inhibitor, including polyethylene glycol PEG with a molecular weight of 1000-6000 or a polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol polymer with a molecular weight of 2000-15000; the concentration of the inhibitor is 0-1000 ppm.

[0011] The parameters for copper stripping by cyclic voltammetry are: scanning number of 50-100 circles, scanning starting potential of -0.9V-0V, scanning speed of 300-500mV / s; When the speed of the platinum rotating disk electrode was 0 RPM, the optimal concentrations of different types of inhibitors screened were: PEG1000: 20 ppm, PEG3000: 10 ppm; When the rotation speed of the platinum rotating disk electrode was 1000RPM, the optimal concentrations of different types of inhibitors screened out were: PEG1000: 500 ppm, PEG3000: 300 ppm, PEG6000: 500 ppm, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 2700: 500 ppm, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 8400: 100 ppm, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 14600: 100 ppm; Preferably, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 8400 has the best inhibitory effect on TSV copper filling; The inhibitor is convection-dependent and has a stronger inhibitory effect at high speeds than at low speeds.

[0012] The selected inhibitor is used for wafer TSV copper filling; the wafer hole size is 100-150m deep and 10-15m wide; the copper filling process parameters are: rotation speed is 0-1000RPM, current density is 0.1-0.3A / dm 2 , time is 0.5-3h.

[0013] The beneficial effects of the present invention are as follows: The present invention can quickly screen out inhibitors suitable for TSV copper filling by using electrochemical methods: screen out the appropriate inhibitor concentration through LSV, strip the copper deposited on the platinum disk electrode through CV, and finally screen out the optimal inhibitor through CP. Linear voltammetry can quickly confirm the optimal concentration of the inhibitor. At the same time, by adjusting the rotation speed of the rotating disk electrode and combining the linear voltammetry curve, it can be understood whether the inhibitor has convection-dependent adsorption characteristics. In the TSV electroplating process, the chronopotentiometry is mainly used to apply a constant current for copper filling, so the chronopotentiometry is finally combined to screen the optimal additive, which can better reflect the process of TSV copper filling under constant current; through the above method, the present invention can quickly screen inhibitors with strong inhibitory effects, which is convenient for the subsequent TSV copper filling. The screened inhibitors can achieve TSV copper filling from bottom to top without holes and defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The inhibitory effect of PEG1000 on LSV screening at 0 RPM in Example 1; Figure 2 The inhibitory effect of PEG1000 on LSV screening at 1000 RPM in Example 2; Figure 3 The inhibitory effect of PEG3000 on LSV screening at 0 RPM in Example 3; Figure 4 The inhibitory effect of PEG3000 on LSV screening at 1000 RPM in Example 4; Figure 5 The inhibitory effect of PEG6000 on LSV screening at 1000 RPM in Example 5; Figure 6 The inhibition of QAQ1 at 1000RPM for LSV screening in Example 6; Figure 7 The inhibition of QAQ2 at 1000RPM for LSV screening in Example 7; Figure 8 The inhibition of QAQ3 at 1000RPM for LSV screening in Example 8; Fig. 9 Screening the inhibitory strength of PEG3000, QAQ2, and QAQ3 for CP in Example 9; Fig.10 This is a diagram showing the TSV copper filling effect of adding QAQ2 in Example 10. DETAILED DESCRIPTION

[0015] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0016] Example 1 A method for quickly screening TSV copper filling inhibitors, the screening method comprising the following steps: Step S1: cleaning the platinum rotating disk electrode; Step S2: Turn on the computer, electrochemical workstation and rotating disk electrode, and set the parameters of the screening method Step S3: fix the platinum rotating disk electrode in the TSV copper filling mother solution and connect the electrode; Step S4: Screening inhibitors by adjusting the rotation speed through a rotating disk electrode controller; Step S5: After each inhibitor is screened, copper is deposited on the platinum rotating disk electrode. When the next type of inhibitor is screened, the corresponding parameters should be set by cyclic voltammetry (CV) to strip the copper, and then proceed to steps S1 to S4.

[0017] Step S6: performing TSV copper filling using the screened inhibitor.

[0018] In the electrochemical reaction process, a three-electrode system is used, the reference electrode is a mercury / mercurous sulfate electrode, the working electrode is a platinum rotating disk electrode, and the counter electrode is a platinum wire.

[0019] The specific operation of cleaning the platinum rotating disk electrode is as follows: first soak it in 5% sulfuric acid for 1 min, rinse it with deionized water, then polish it with 0.5 μm alumina powder, place it in an ultrasonic bath in deionized water for 1 min to remove the residual alumina powder, rinse it with deionized water again, and finally blow it dry with nitrogen.

[0020] The TSV copper filling mother solution includes 180 g / L CuSO4·5H2O, 30 g / L H2SO4, 70 ppm Cl - .

[0021] During the screening process, the rotating disk electrode controller adjusted the rotation speed to 0 RPM, and the screening method adopted was linear sweep voltammetry (LSV), with a scan speed of 5 mV / s and a maximum current of 10 mA.

[0022] The inhibitor screened in this example is PEG1000, and the concentrations are 0 ppm, 10 ppm, 20 ppm, 50 ppm, 100 ppm, and 300 ppm, respectively. The test results are shown in Figure 1 . Figure 1 It shows that when the concentration of PEG1000 increases to 20ppm or higher at 0RPM, the inhibitory effect remains basically unchanged, because at this speed the inhibitor mainly relies on diffusion, so the adsorption process is slow and there is little difference between low and high concentrations.

[0023] Example 2 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 1, and copper stripping is performed by cyclic voltammetry (CV) before screening, and the parameters are set as follows: the number of scans is 100, the scan start potential is -0.7V, and the scan speed is 400mV / s; the inhibitor screened in this example is PEG1000, the rotation speed is 1000RPM, and the concentrations are 5 ppm, 10 ppm, 30ppm, 50 ppm, 100 ppm, 150 ppm, 300 ppm, 500 ppm, and 700 ppm. The results are shown in FIG. Figure 2 . Figure 2 It shows that as the concentration of PEG1000 increases, the potential gradually shifts negatively until it stops shifting negatively at 500 ppm, at which concentration the inhibition is strongest. Figure 1 The results show that the inhibitor has convection-dependent adsorption, and selects the position with strong adsorption convection to enhance the inhibitory effect on Cu reduction. The inhibitor PEG1000 has a stronger inhibitory effect at high speed than at low speed.

[0024] Example 3 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 2, and copper stripping is performed by cyclic voltammetry (CV) before screening, and the parameters are set as follows: the number of scans is 100, the scan start potential is -0.7V, and the scan speed is 400mV / s; the inhibitor screened in this example is PEG3000, the rotation speed is 0 RPM, and the concentrations are 0 ppm, 5 ppm, 10 ppm, 50 ppm, 100 ppm, and 300 ppm. The results are shown in FIG. Figure 3 . Figure 3 When 0 RPM is displayed, when PEG3000 is added to 10 ppm or higher, the inhibitory effect remains basically unchanged, and the main reason is the same as in Example 1.

[0025] Example 4 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 2, and copper stripping is performed by cyclic voltammetry (CV) before screening, and the parameters are set as follows: the number of scans is 100, the scan start potential is -0.7V, and the scan speed is 400mV / s; the inhibitor screened in this example is PEG3000, the rotation speed is 1000 RPM, and the concentrations are 0 ppm, 10 ppm, 30 ppm, 50 ppm, 100 ppm, 300 ppm, and 500 ppm. The results are shown in FIG. Figure 4 . Figure 4 It shows that the inhibitory effect of PEG3000 reaches saturation at 300 ppm. Similar to Example 2, PEG3000 also has convection-dependent adsorption.

[0026] Example 5 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as in Example 1, and copper stripping is first performed by cyclic voltammetry (CV), and the parameters are set as follows: the number of scans is 100, the scan starting potential is -0.7V, and the scan speed is 400mV / s; in combination with Examples 1 to 4, it can be seen that the inhibitors basically have convection-dependent adsorption, so the subsequent examples are all screened at 1000RPM. The inhibitor screened in this example is PEG6000, the rotation speed is 1000 RPM, and the concentrations are 0 ppm, 10 ppm, 30ppm, 50 ppm, 100 ppm, 200ppm, 300 ppm, 500 ppm, and 1000ppm. The results are shown in Table 1. Figure 5 . Figure 5 The results showed that PEG6000 had the strongest inhibitory effect when the concentration was 500 ppm.

[0027] Example 6 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 1, and copper stripping is performed by cyclic voltammetry (CV) before screening, and the parameters are set as follows: the number of scans is 100, the scan starting potential is -0.7V, and the scan speed is 400mV / s; the inhibitor screened in this example is QAQ1, which is mainly a triblock polymer of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol), with an average molecular weight of 2700, a rotation speed of 1000RPM, and a concentration of 0 ppm, 5ppm, 10ppm, 20ppm, 30ppm, 50 ppm, 70ppm, 100 ppm, 150ppm, 200ppm, 300ppm, 500ppm, and 1000ppm. The results are shown in FIG. Figure 6 . Figure 6 The results showed that QAQ1 had the strongest inhibitory effect at a concentration of 500 ppm.

[0028] Example 7 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 1, and copper stripping is performed by cyclic voltammetry (CV) before screening, and the parameters are set as follows: the number of scans is 100, the scan start potential is -0.7V, and the scan speed is 400mV / s; the inhibitor screened in this example is a triblock polymer QAQ2, with an average molecular weight of 8400, a rotation speed of 1000RPM, and a concentration of 0 ppm, 5 ppm, 10ppm, 20 ppm, 30 ppm, 50 ppm, 100 ppm, and 300ppm. The results are shown in FIG. Figure 7 . Figure 7 It shows that the inhibition effect of QAQ2 reaches saturation at a concentration of 100ppm, and then the inhibition effect increases very slowly.

[0029] Example 8 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 1, and copper stripping is performed by cyclic voltammetry (CV) before screening, and the parameters are set as follows: the number of scans is 100, the scan start potential is -0.7V, and the scan speed is 400mV / s; the inhibitor screened in this example is a triblock polymer QAQ3, with an average molecular weight of 14600, a rotation speed of 1000RPM, and a concentration of 5 ppm, 10ppm, 20 ppm, 30 ppm, 50ppm, 70ppm, 100ppm, and 150ppm. The results are shown in FIG. Figure 8 . Figure 8 The results showed that QAQ3 had the strongest inhibitory effect at a concentration of 100 ppm.

[0030] Example 9 A method for rapidly screening TSV copper filling inhibitors, the screening steps are the same as those in Example 1, the electrochemical method used in this example is chronopotentiometry (CP), the scanning time is 1000s, the current is -0.4mA, and electrochemical tests are performed on the three additives PEG3000, QAQ2, and QAQ3 with better inhibitory effects in Examples 1-9 to confirm which of the three inhibitors has the best inhibitory effect. The rotation speed is 1000RPM, and the inhibitor with the optimal concentration is added when the time is 500s. The results are shown in FIG. Fig. 9 . Fig. 9 The results showed that among the three inhibitors, QAQ2 had the strongest inhibitory effect, while QAQ1 and PEG3000 had basically the same inhibitory effects. Example 10 The screened inhibitor QAQ2 was used to fill TSV copper. The electroplating mother solution was the same as in Example 1. The wafer hole size was 100 mm in depth and 10 mm in width. The rotation speed was 1000 RPM and the current density was 0.2 A / dm 2 , time is 2.5h, and the addition amount of additive QAQ2 after screening is 100ppm. Fig.10 This is the effect diagram after filling. It can be seen from the figure that under this inhibitor, TSV copper filling can achieve no holes and no defects.

[0031] The conclusion drawn from the above embodiments is that: combined with electrochemical testing, inhibitors with strong inhibitory effects can be quickly screened to facilitate subsequent TSV copper filling, and the screened inhibitors can achieve TSV copper filling from bottom to top without holes or defects.

Claims

1. A method for rapid screening of TSV copper filling inhibitors, characterized in that: Electrochemical screening methods were used, including linear sweep voltammetry, cyclic voltammetry, and chronopotentiometry.

2. The method for rapid screening of TSV copper filling inhibitors according to claim 1, characterized in that: The following steps are involved: S1: cleaning the platinum rotating disk electrode; S2: Fix the platinum rotating disk electrode in the TSV copper filling mother solution and connect the electrodes; S3: Linear sweep voltammetry was used to adjust the speed of the platinum rotating disk electrode through the rotating disk electrode controller to screen out the appropriate inhibitor concentration; S4: Use chronopotentiometry to screen out the best inhibitors; Among them, after each inhibitor is screened, copper will be deposited on the platinum rotating disk electrode. Before screening the next type of inhibitor, cyclic voltammetry is used to strip the copper from the platinum rotating disk electrode, and then S1-S3 are repeated to complete the screening of the next inhibitor.

3. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: A three-electrode system was used, with the reference electrode being a mercury / mercurous sulfate electrode, the working electrode being a platinum rotating disk electrode, and the counter electrode being a platinum wire.

4. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: S1 described cleaning of the platinum rotating disk electrode, specifically: first soak in 5%-10% sulfuric acid for 0.5-1min, rinse with deionized water, then polish with 0.5-1μm alumina powder, place in deionized water ultrasonic bath for 1-2min to remove residual alumina powder, rinse again with deionized water, and finally blow dry with nitrogen.

5. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: S2 The TSV copper filling mother solution includes 150-200 g / L CuSO4·5H2O, 10-40 g / L H2SO4 and 50-80 ppm Cl - ; The rotation speed of the platinum rotating disk electrode described in S3 is 0-20000RPM.

6. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: The parameters of the linear sweep voltammetry are: a scan rate of 3-5 mV / s, a maximum current of 8-10 mA, and the parameters of the chronopotentiometry are: a scan time of 500-1000 s, a current of -0.5-0.1 mA.

7. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: The inhibitor is a TSV inhibitor, including polyethylene glycol PEG with a molecular weight of 1000-6000 or a polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol polymer with a molecular weight of 2000-15000; the concentration of the inhibitor is 0-1000 ppm.

8. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: The parameters of the cyclic voltammetry method for copper stripping are: the number of scans is 50-100, the scan starting potential is -0.9V-0V, and the scan speed is 300-500mV / s.

9. The method for rapid screening of TSV copper filling inhibitors according to claim 2, characterized in that: When the rotation speed of the platinum rotating disk electrode was 0 RPM, the optimal concentrations of different types of inhibitors screened were: PEG1000: 20 ppm, PEG3000: 10 ppm; When the rotation speed of the platinum rotating disk electrode was 1000RPM, the optimal concentrations of different types of inhibitors screened out were: PEG1000: 500 ppm, PEG3000: 300 ppm, PEG6000: 500 ppm, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 2700: 500 ppm, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 8400: 100 ppm, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 14600: 100 ppm; Preferably, polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol with an average molecular weight of 8400 has the best inhibitory effect on TSV copper filling; The inhibitor is convection-dependent and has a stronger inhibitory effect at high speeds than at low speeds.

10. Application of the method according to claims 1-9 in screening TSV copper filling inhibitors, characterized in that: The selected inhibitor is used for wafer TSV copper filling; the wafer hole size is 100-150m deep and 10-15m wide; the copper filling process parameters are: rotation speed is 0-1000RPM, current density is 0.1-0.3A / dm 2 , time is 0.5-3h.

Images