TW201424492A - Electronic device copper micro-electroplating fast monitoring method - Google Patents

Abstract

The present invention provides an electronic device copper micro-electroplating fast monitoring method, according to this invention, the variation of the electroplating copper deposition can be quickly determined by using the variation of the current difference of different additive in the plating solution under a condition of constant voltage. The monitoring method includes the following steps: a step of preparing additives: to prepare gloss agent, inhibitors, and leveling agent that are scheduled to be adopted by the electroplating solution; s tep of measuring current difference: measuring the voltage difference value between adding all additives to the electroplating solution and neglecting adding one of the additives ; and a step of determining changes in the additives content and form of thecopper deposition: to monitor changes in the current difference in order to determine whether the content of the additives is inadequate, and accordingly to quickly determine whether the electroplating hole-filling form of electronic components meets the requirement.

Description

Rapid monitoring method for copper micro-electroplating of electronic components

The invention relates to the copper micro-plating technology of electronic components, and more specifically to a method for rapid monitoring of copper micro-electroplating of electronic components.

According to the current printed circuit board, most of the printed circuit boards are made of copper to form the via holes for the metal connection. In order to improve the filling result of the electroplated copper, special additives are added to the plating solution to regulate the bottom holes and holes of the blind holes. The technique of the deposition rate of copper at the top of the top can suppress the deposition of copper on the top of the pores on the one hand in the electroplating process, and accelerate the deposition of copper in the pores on the one hand to achieve the best explosive hole filling effect.

According to the different functions of the additives in the plating solution, the brightener (accelerator), the carrier (inhibitor), the leveling agent, etc., and the effectiveness thereof is affected by the rotational speed (flow force), adsorption, plating potential, concentration in the plating The influence of factors such as holes (aspect ratio), especially at different potentials, has a great influence on the function. Since the leveling agent and the brightening agent in the formulation are generally added in a small amount, and the left and right filling ability is greatly affected, the concentration must be carefully monitored to avoid poor quality. The concentration analysis methods of the conventional additives include cyclic voltammetry stripping (CVS), ultraviolet visible light spectrometer (UV), ion chromatography (IC), etc., although these methods have more precise advantages, the analysis process takes a long time. It is necessary to make a calibration curve first, which is not suitable for the On Line program.

Secondly, the current method of monitoring the filling holes is to monitor the change of the concentration of a single additive. When one of the additives is insufficient, the effect of the hole filling may be affected; but in fact, the behavior of the hole filling is not only caused by a single additive. The behavior is generated by the interaction between each other. Therefore, it is necessary to monitor the interaction that causes the result of this filling to meet the actual situation, so as to achieve the positive purpose of improving plating quality, controlling cost and improving productivity. For example, the Republic of China invented the No. I292295 "Method for Monitoring the Filling Capability of Copper Electroplating Solution", which is mainly used to determine the filling ability by the measurement of the potential difference. However, the patent measures the potential difference made at a constant current density. When the concentration of the additive changes, the voltage position of the potential difference will change rapidly, that is, the voltage position of the additive has changed, so the potential difference varies greatly, and is not suitable for rapid stabilization. monitor.

The main object of the present invention is to provide a rapid monitoring method for copper micro-electroplating of electronic components, which is to monitor the change of the current difference of different mixed additives in the plating solution under a constant voltage, and to quickly determine the change of the additive content and the copper deposition form. Very practical value.

Therefore, in order to achieve the foregoing object, the present invention provides a rapid monitoring method for copper micro-electroplating of electronic components, which is to quickly determine the additive content and the copper deposition form by using a change in current difference of different additives in the plating solution under a constant voltage. Variety.

Further, the method comprises the following steps: preparing an additive: preparing Additives such as predetermined gloss agent, inhibitor and leveling agent used in the plating solution; measuring current difference: measuring the current difference between adding all additives in the plating solution and omitting an additive at a constant voltage; judging the content of the additive Changes with the deposition pattern of copper: monitor the change in the current difference to determine whether the content of the additive is insufficient, and to quickly determine whether the form of the electroplated fill hole of the electronic component meets the requirements.

Further, the brightener is sodium 3-Mercapto-1-propanesulfonate (MPSA), the inhibitor is polyethylene glycol (PEG), and the leveling agent is 2-thiol. Pyridine (2-MP).

Further, the comparison of the current difference is compared with the current curve of the MPSA & PEG & 2-MP additive in the plating solution with no added MPSA and only PEG & 2-MP, and the current difference is about 1.85×10 ^{− 3} Amps/cm ² , which can be used as the basis for the normal concentration of the gloss agent (MPSA) in the plating solution. If the difference is less than 1.85×10 ^-3 Amps/cm ² , it means that the MPSA content in the plating solution is insufficient or It must be replenished after consumption.

Further, the comparison of the current difference is compared with the current curve of the MPSA & PEG & 2-MP additive in the plating solution with the addition of 2-MP and only MPSA & PEG, and the current difference is about 1.33×10 ^{− 2} Amps / cm ^2, can be used as the basis for this difference leveling agent in the plating solution (2-MP) concentration is normal, if the difference is less than 1.33 × 10 ^-2 Amps / cm ^2, the plating solution represents 2- If the MP content is insufficient or consumed, it must be replenished.

Further, the mother liquor in which the plating solution is not added with an additive contains a predetermined amount of copper sulfate (CuSO ₄ ‧5H ₂ O), sulfuric acid (H ₂ SO ₄ ) and chloride ion (Cl ⁻ ) additives.

Further, the plating solution is a low copper high acid mother liquid (the ratio of each component is: CuSO ₄ ‧5H ₂ O: 75 g/l, H ₂ SO ₄ : 190 g/l, Cl ⁻ : 46 ppm) or high copper low The mother liquor (the ratio of the components was: CuSO ₄ ‧5H ₂ O: 200 g/l, H ₂ SO ₄ : 50 g/l, Cl ⁻ : 46 ppm).

In the following, a number of preferred embodiments of the present invention will be described in detail with reference to the drawings. First, referring to FIG. 1 , a method for quickly monitoring copper micro-electroplating of electronic components according to a preferred embodiment of the present invention is provided. The main method is to use the current difference of different additives in the plating solution to quickly determine the change of the additive content and the copper deposition form under a constant voltage. The first step is to prepare the additive 110: the predetermined gloss used for preparing the plating solution. Additives such as an inhibitor, a leveling agent, etc., the glossing agent is 3-sodium 3-mercapto-1-propanesulfonate (MPSA) (HS(CH ₂ ) ₃ SO ₃ Na), the inhibition The agent is polyethylene glycol (PEG), the leveling agent is 2-thiol pyridine (full name: 2-Mercaptopyridine N-oxide; 2-MP) (C ₅ H ₅ NS), and the plating solution is not added with additives The mother liquor comprises copper sulfate (CuSO ₄ ‧5H ₂ O), sulfuric acid (H ₂ SO ₄ ) and chloride ion (Cl ^- ) additives, such as low copper high acid mother liquor (the ratio of each component is: CuSO ₄ ‧5H ₂ O: 75 g/l, H ₂ SO ₄ : 190 g/l, Cl ^- : 46 ppm), or high copper low acid mother liquor (the ratio of each component is: CuSO ₄ ‧5H ₂ O: _{200 g / l, H 2 SO} 4: 50 g / l, Cl -: 46 ppm).

The second step is to measure the current difference 120: measure the current difference between adding all the additives in the plating solution and omitting an additive at a constant voltage, for example, additives in different mixing ratios such as MPSA & PEG & 2-MP Observe the current difference with PEG & 2-MP (omitting MPSA).

Finally, it is judged that the additive content and the copper deposition form change 130: monitor the change in the current difference, thereby judging whether the content of the additive (such as the aforementioned MPSA) is insufficient, and quickly determining whether the electronic component plating and filling form conforms to the requirements.

Therefore, the electronic component copper micro-electrode rapid monitoring method 100 of the present invention can use the method of monitoring the change of the current difference to determine the degree of additive consumption, thereby simplifying the complicated additive analysis program to achieve time-saving and cost-saving. Electronic components copper micro-plating for rapid monitoring of benefits.

The following is a detailed embodiment of the present invention: firstly, 1 liter of low copper high acid plating mother liquid and high copper low acid plating mother liquid are respectively arranged, and then 100 ml of each plating mother liquid is added with different trace additives to form an analysis sample liquid. Place it in a constant temperature water tank at a temperature of 25 ° C and place it in a rotating electrode tank. Turn the electrode (working electrode) VS. Saturated calomel electrode (SCE, when reference electrode) with platinum, and make a constant current with an electrochemical analyzer -0.0035 A, 60 sec timed deposition, making copper available It is uniformly plated on the rotating electrode, and then the rotating electrode is turned into a copper electrode, and then the potential is changed to scan at a time of 100 seconds to understand the reaction mechanism of various additives in electroplating copper.

Figure 2 is a current-time analysis of the constant voltage (-0.22 V) of different additives in a low copper high acid plating mother liquor. It can be seen from the figure that the analysis sample liquid containing only the PEG & 2-MP additive enhances the suppression effect of the cathode surface due to the synergistic relationship between the two additives, and the result is that the current is almost 0 Amps/. Cm ² , and when the additive in the sample liquid is changed to MPSA & PEG, it can be found that the current seems to be affected by the addition of MPSA, so that the uniform inhibition of the inhibitor PEG disappears, so that the overall current is larger than the mother liquid, which also indicates chlorine. The synergy between ion (Cl ^- ) and MPSA is stronger than that between chloride and PEG. When all additives MPSA & PEG & 2-MP are added, the stable current will drop to about -1.87 × 10 ^-3 Amps / Cm ² , indicating that the overall inhibition of 2-MP is strong, but due to the influence of MPSA, the current does not fall to 0 Amps/cm ² .

Comparing the MPSA & PEG & 2-MP curve with the current of the PEG & 2-MP curve, the current difference is about 1.85 × 10 ^-3 Amps / cm ² , which can be used as a brightener in the plating solution ( Whether the concentration of MPSA) is normal, as long as the difference is less than 1.85×10 ^-3 Amps/cm ² , it means that the MPSA is insufficient or needs to be replenished. Similarly, according to the current difference method, the MPSA & PEG & 2-MP curve is compared with the current value of the MPSA & PEG curve, and the current difference is relatively large, about 1.33×10 ^-2 Amps/cm ² . This difference can be used as the basis for whether the concentration of the leveling agent (2-MP) in the plating solution is normal. If the difference is less than 1.33×10 ^-2 Amps/cm ² , it means that the 2-MP is insufficient or has been consumed. Must be added again.

Annex 1 is the SEM (500X) morphology of the lower hole (100 μm) coating of the low-copper high-acid DC plating wafer with different formulations. It can be seen that the plating profile (a part) in the absence of the additive MPSA can also be seen. The plating pattern (part b) in the absence of the additive 2-MP, and the actual plating pattern of the normal MPSA & PEG & 2-MP curve is shown in part c.

In addition, the Relative Deposition Thickness (RDT) (h ₂ /h ₁ , h ₁ : surface deposition thickness, h ₂ : deep hole deposition thickness) in the part c of Annex I is the largest, representing the deep hole plating efficiency. The best, although the RDT value is also close to the b part, but the Contingation coating is quite good, the side also has a fairly good high resolution, and the effect of the edge suppression is quite good, let the copper ion Reducing the reduction deposition near the hole, because this is a planar formulation mother liquid, although there is no protrusion on the hole, the configuration coating is quite good.

In order to explore whether the accumulation phenomenon of MPSA in the cave will cause accelerated deposition, the analysis of different speeds is shown in Figure 3. In theory, the slow speed of the gloss agent (MPSA) will form a thicker adsorption on the cathode surface. Layer (similar to cumulative effect), a thicker adsorption layer may cause an increase in the resistance of copper ion reduction or an increase in the amount of cuprous ions, promoting reduction deposition (increased current value). Figure 3 shows the test at different speeds (-0.22 V) with a plating solution containing only 5 ppm of MPSA. The results show that the acceleration effect dominated by MPSA is stronger and the current value is larger than that of the mother liquor. Therefore, the current between the two can be utilized. The difference is used for quantization. It can be seen from the figure that the current difference between the two curves at 1000 rpm is about 1.82×10 ^-3 Amps/cm ² , and the current difference between the two curves at 100 rpm is 2.23×10 ^{− 3} Amps/cm ² , it can be found that MPSA has a good cumulative effect at low speed and accelerates the reduction of copper ions on the surface of the cathode, so the difference in current is greater than the difference in current at high speed, and the additive is added by Annex II. MPSA in the low-copper high acid solution in the SEM (500X) form of DC-plated wafer hole (100 μm) coating, it can be seen that the RDT value is larger in the case of adding MPSA, which means that the surface of the wafer and the hole are both because of MPSA. The effect is to accelerate the deposition, but there is a cumulative acceleration effect in the hole, so the RDT value is large.

Figure 4 shows the mixing formula for different speeds at a constant voltage (-0.22 V). It can be found that the cathode current value at the high electrode speed (2000 rpm) is smaller than the low speed (1000 rpm). The shearing force of the fluid on the surface of the cathode is small, and the thickness of the mixed misaligned film formed by surface copper reduction should be thicker, so the resistance is stronger and the current value is smaller. However, the results are different, and the reason may be additive. The adsorptivity is different. The additives adsorbed on the surface layer compete with each other at low rotation speeds, and the effect of MPSA is easy to appear at low rotation speed, resulting in higher current value, and oppositely at high rotation speed. -MP suction The adhesion may be strong, preferentially adsorbed on the surface layer, forming a dense barrier layer, while other additives adsorbed on the outer layer may be washed away by shear force or accumulated in the hole with large aspect ratio, such as this The situation is very beneficial for commercial plating.

Figure 5 shows the analysis of different additives in a high copper low acid mother liquor at a constant voltage of -0.23 V. It can be seen that the additive exhibits competitive and synergistic properties similar to the addition of additives in low copper high acid mother liquor, but the difference in current is greater, in MPSA & PEG & 2-MP curves with PEG & 2 The current difference between the -MP curves is approximately 2.01 × 10 ^-3 Amps/cm ² , while the current difference between the MPSA & PEG & 2-MP curve and the MPSA & PEG curve is 2.26 × 10 ^-2 Amps/cm ² , the difference The large possible cause is the higher concentration of copper ions and the effect of the additive MPSA, so the accelerated copper ion reduction deposition effect can be displayed.

Annex III is the SEM (500X) form of different formulations in high-copper low-acid solution with DC plating wafer hole (100 μm). It can be seen that the filling effect of c part is very good, and the RDT value can be as high as 3.002. Filled form

As shown in Figure 6, the constant voltage (-0.23 V) test was performed at a plating speed of only 5 ppm MPSA. Due to the acceleration effect of the MPSA, the current was larger than the mother liquid, and the current between the two curves at 1000 rpm. The difference is about 2.96 × 10 ^-3 Amps / cm ² , and the current difference between the two curves at 100 rpm is 3.48 × 10 ^-3 Amps / cm ² , which is lower than the gloss agent MPSA in low copper. The difference in current in the high acid mother liquor is large, which further indicates that the MPSA accelerates better under high copper and low acid.

It can be seen from the SEM (500X) form of the coating of the high-potassium low-acid solution in the high-copper low-acid solution with the DC-plated wafer hole (100 μm). The RDT value is relatively large in the case of adding MPSA, which indicates that the wafer surface and the hole are inside. Because the effect of MPSA has an accelerated deposition effect, but there is a cumulative acceleration effect in the hole, the RDT value is large.

Figure 7 shows the mixed formula of different speeds at a constant voltage (-0.23 V). It can be found that the cathode current value at the high electrode speed (2000 rpm) is lower than that of the low copper high acid mother liquor. (1000 rpm) is small, the presumed reason may be that the additive adsorption is different, but the competitive behavior of the additives that adsorb the surface layer at low rotation speed is intensified, because the effect of MPSA is easier to show except at low rotation speed. It may be more pronounced in sample liquids with high copper ion concentrations (compared to Figure 6).

Judging from the curves of Fig. 6 and Fig. 7, for example, the curve of MPSA & PEG & 2-MP (2000 rpm) is the theoretical perfect outside (surface) condition, and the curve is perfect with MPSA only curve (100 rpm). In the condition of the hole, the current values of the two curves represent the proportional deposition rate, so under the ideal additive ratio, the theoretical aspect ratio of the wafer can be calculated to be 11:1, thus indicating that the plating fills the hole depth. The aspect ratio ideally achieves a high aspect ratio.

Attachment 5 is the SEM morphology of the profile coating of the blended formula wafer. It can be seen from the figure that whether it is low copper high acid or high copper low acid, it can show the filling tendency, and the suppression effect at the orifice is better, let the copper ion (Cu ²⁺ ) is firstly deposited on the side and the bottom of the hole, so it has a good filling phenomenon, but the high copper and low acid filling effect is superior, like the Super Filling form, which may be the concentration of this additive. The ratio is suitable for the addition of high copper and low acid, and the smaller the pore size, the larger the RDT value, and the low copper high acid filling form is like the Conformation coating.

It can be seen from the above that the present invention changes the rotational speed under a constant voltage, and the additive adsorption state at the different rotational speeds will also be different, thus affecting the current change. By observing the change of current, it is predicted whether the pattern of the plating layer conforms to the form we want when actually plating. Furthermore, the concentration of the additive in the plating solution is changed by the consumption of the long-term use or the decomposition of the organic molecular structure, so that the plating layer changes due to the change of the additive concentration, and the degree of the additive consumption can be judged by the method of the present invention, thereby simplifying the old There are complex and cumbersome analytical procedures to achieve time and cost savings.

In summary, the invention provides a rapid monitoring method for copper micro-electroplating of electronic components, which simplifies the traditional complex chemical composition analysis program with a fast and simple physical signal (current difference under constant potential) monitoring mode, and the signal thereof It can be as small as microamperes, so it is very sensitive and can speed up the online verification procedure of electronic components. Compared with the potential difference monitoring technology made by the conventional constant current, the present invention does not need a calibration curve and does not require a trivial front-end. Homework, only need to be normal formula at constant voltage Controlling different speeds and temperatures to represent different aspect ratios, the normal current difference (current density difference can also be) can be quickly monitored when the additive concentration is abnormal, which is obviously more practical.

100‧‧‧Electronic components copper micro-plating rapid monitoring method

110‧‧‧Prepared additives

120‧‧‧Measure current difference

130‧‧‧Review the change of additive content and copper deposition morphology

1 is a flow chart of a preferred embodiment of the present invention.

Figure 2 is a graph of the constant voltage (-0.22 V) of the different additives of the present invention.

Figure 3 is a graph showing the different rotational speeds of the glossing agent MPSA constant pressure (-0.22 V) of the present invention.

Figure 4 is an analysis diagram of the mixed formula of different speeds under the constant voltage (-0.22 V) of the present invention.

Figure 5 is a graph of the constant voltage (-0.23 V) of the different additives of the present invention.

Fig. 6 is a graph showing different rotational speeds of the glossing agent MPSA constant pressure (-0.23 V) of the present invention.

Figure 7 is an analysis of the mixing formula of different speeds under the constant voltage (-0.23 V) of the present invention.

100‧‧‧Electronic components copper micro-plating rapid monitoring method

110‧‧‧Prepared additives

120‧‧‧Measure current difference

130‧‧‧Review the change of additive content and copper deposition morphology

Claims (5)

A rapid monitoring method for copper micro-electroplating of electronic components is to quickly determine the change of the additive content and the shape of the copper depositing and filling holes by using the current difference of the different proportions of the additives in the plating solution under constant voltage conditions. The method for monitoring copper micro-electroplating of an electronic component according to claim 1, wherein the method comprises the following steps: preparing an additive: preparing a predetermined brightener, an inhibitor, a leveling agent and the like for using the plating solution; Current difference: measure the current difference between adding all additives in the plating solution and omitting an additive at a constant voltage; and judging the change of the additive content and the copper deposition form: monitoring the change of the current difference, thereby judging the additive Whether the content is insufficient, and according to the rapid determination of whether the electronic component plating hole shape meets the requirements. The method for monitoring copper micro-electroplating of an electronic component according to claim 2, wherein the glossing agent is 3-sodium 3-mercapto-1-propanesulfonate (MPSA), the inhibitor It is a polyethylene glycol (PEG) and the leveling agent is 2-thiol pyridine (2-MP). The method for monitoring copper micro-electroplating of electronic components according to claim 3, wherein the comparison of the current difference is performed by using MPSA & PEG & 2-MP additive in the plating solution with no added MPSA, only adding PEG & 2- The current curve of the MP is compared, and the current difference is about 1.85×10 ^-3 Amps/cm ² , and the difference can be used as a basis for whether the concentration of the gloss agent (MPSA) in the plating solution is normal, if the difference is less than 1.85× At 10 ^-3 Amps/cm ² , it means that the MPSA content in the plating solution is insufficient or consumed and needs to be replenished. The method for monitoring copper micro-electroplating of an electronic component according to claim 3, wherein the comparison of the current difference is performed by adding MPSA & PEG & 2-MP additive to the plating solution without adding 2-MP, adding only MPSA & The current curve of PEG is compared, and the current difference is about 1.33×10 ^-2 Amps/cm ² . This difference can be used as the basis for whether the concentration of the leveling agent (2-MP) in the plating solution is normal. 1.33×10 ^-2 Amps/cm ² means that the 2-MP content in the plating solution is insufficient or consumed and needs to be replenished.