TWI464305B - (TSV) electroplated copper filler inhibitor and electroplating copper filling formula - Google Patents

Description

Electroplated copper hole filling inhibitor and electroplating copper filling formula for through hole (TSV)

The present invention relates to an electroplated copper formulation for filling vias (TSV), and more particularly to inhibitors in the formulation. The inhibitors selected for use in the present invention are functional polyalcohols (PEG-derived). ()).

Copper has a low resistivity and a high resistance to electromigration and is widely used in integrated circuits. It is known that the through-silicon via (TSV) conductive fill hole can be completed by electroplating copper. The best hole filling mode is Bottom Up, non-porous superfilling. . To achieve the above optimal pore filling mode, it is extremely important to select and control the concentration of additives in the plating solution. The additives mainly include Accelerator/Brighter, Leveler, and Suppressor. , hydrogen ions and chloride ions.

The commonly used accelerators are thiol series compounds such as bis(3-sulfonylpropyl) disulfide [Bis Disulfide, SPS], 3-thiol-1-propanesulfonic acid [3-Mercapto-l -Propane Sulfonate, MPS]. The accelerator acts synergistically with chloride ions to accelerate the rate of copper ion reduction and impart gloss to the coating.

Conventional leveling agents are mostly organic nitrogen-containing heterocyclic compounds, and are generally classified into heterocyclic organic compounds (non-dye systems) having a tertiary amine and heterocyclic organic compounds (dye systems) having a quaternary amine salt. Commonly used leveling agents are JGB (Janus Green B) and BTA (Benzotriazole). The leveling agent has the effect of suppressing the reduction rate of copper ions on the surface of the electrode. Because of its N ⁺ relationship, its adsorption behavior is easily affected by the current distribution, preferentially adsorbed in the high current dense area, and the TSV orifice is due to the geometric relationship. It is easy to make the reduction rate of copper ions too fast to form a sealing phenomenon earlier, and to make a TSV hole to create a void. If a leveling agent is added to the plating solution, a good adsorption site of the leveling agent is given at the orifice, and the reduction deposition of the copper ions in the orifice is suppressed, and the copper deposition rate at the bottom of the pore is accelerated, and the filling purpose of the bottom of the pore is shifted up.

Conventional inhibitors, such as polyethylene glycol (PEG) (Polyethlene glycol, PEG) and chloride ions are present in the plating solution to synergistically achieve the effect of inhibiting copper deposition.

Related to the present invention is an inhibitor, and thus a related discussion on the selection of inhibitors.

The Chinese Journal of Chemistry, Vol. 67 (ACTA CHIMICA), in 2009, revealed that the diffusion coefficient and low consumption of PEG-6000 or PEG-8000 in the plating solution are such that the surface concentration of the micropores is greater than the concentration of the bottom of the well. Thereby, the copper deposition rate of the orifice is suppressed, and the filling mode of the bottom of the pore is shifted up. And the larger the molecular weight of PEG, the relatively increased inhibition.

The inhibitor mentioned in the Republic of China Invention Patent Publication No. 201040322 is a mixture of an amine compound containing at least three reactive amine functional groups and at least one compound selected from the group consisting of ethylene oxide and at least one compound selected from the group consisting of C3 and C4 alkylene oxide.

The Republic of China Invention Patent Publication No. 201207159 mentions the use of the dual-state inhibitor DSI in conjunction with the control of the critical potential to achieve a filling pattern at the bottom of the hole. DSI additives cause "DSI behavior" during the hole-filling process. The so-called DSI behavior means that when the potential reaches a critical value, substantial metal deposition is allowed. When the critical potential is not reached, DSI will inhibit metal deposition. The DSI is a quaternary ammonium salt compound, preferably selected from the group consisting of a benzalkonium salt, a thonzonium salt, and a dodecyltrimethylammonium salt.

The selection of the inhibitor can effectively control the pore filling mode of the through hole, and therefore, the present invention That is, the goal of developing new inhibitors is to expand the range of inhibitors, so that there are more inhibitors available in the limited conditions of the ruthenium-filled plating, and a more optimized filling effect can be achieved.

SUMMARY OF THE INVENTION The object of the present invention is to provide a copper-filled hole-filling inhibitor for a through-hole (TSV). The selected inhibitor is a multifunctional polyethylene Glycols, hereinafter referred to as a PEG derivative.

The beneficial effect of the invention is that compared with the traditional inhibitor polyethylene glycol (PEG), the PEG derivative-based inhibitor of the invention is used in the TSV electroplating copper hole filling experiment under the synergistic action of chloride ions. It shows less dosage and stronger inhibition.

An electroplated copper formulation using the above-mentioned PEG derivative-based inhibitor, allowing the 矽 perforation with an aspect ratio (AR ratio) of at least 3:1 to be Bottom Up and void-free Superfilling mode Fully filled.

The TSV plating fill formulation using the above PEG derivative as an inhibitor can be used without the use of a leveling agent, but still exhibits Bottom Up and void-free Superfilling.

Compared with the traditional inhibitor polyethylene glycol (Polyethlene glycol, PEG), the TSV electroplating and filling formula using the above PEG derivative as an inhibitor has the application advantages of micro TSV filling.

The invention selects functional polyethylene glycol as an inhibitor of electroplating copper. The polyethylene glycol has the general formula of formula 1, and each end has a hydroxyl group. Functional polyethylene glycol is the introduction of a functional group into both ends of the polyethylene glycol chain, as in Formula 2. In Formula 2, the functional groups are represented by X and Y, respectively, and the functionalized groups introduced include an acid group, a thio group, an amine group, a sulfonic acid group, and an alkyl group. Wherein, X and Y may be the same functional group, referred to as "homofunctional PEG derivative"; X and Y may also be different functional groups, referred to as "heterobifunctional PEG derivatives" . X is a hydrogen group (-H), a methyl group (-CH ₃ ), a vinylamine group (-C ₂ H ₄ NH ₂ ), a methylsulfonyl group (-SO ₂ CH ₃ ); Y is a hydrogen group ( -H), vinylamino (-C ₂ H ₄ NH ₂ ), methylsulfonyl (-SO ₂ CH ₃ ), thiopropionylamino (-C ₂ H ₄ NHCOC ₂ H ₄ SH), Propionic acid group (-C ₂ H ₄ COOH), maleic imido group (C ₂ H ₄ NC ₄ H ₂ O ₂ ), benzyl alcohol group (-C ₆ H ₄ CH ₂ OH).

In order to prove the feasibility of functional polyethylene glycol as an inhibitor of electroplating copper, the present invention designs two electroplating solution formulations, the composition of which is: copper sulfate (CuSO ₄ ) 0.88 M, sulfuric acid (H) ₂ SO ₄ ) 0.54M, chloride ion (Cl-) 60ppm, Bis (3-Sufopropy) Disulfide (SPS) 1ppm, functional polyethylene glycol (PEG derivative) 10 ppm, 20 ppm, 30 ppm, 40 Ppm, 50ppm. The composition of the second plating solution formulation was the same as described above, and only the functional polyethylene glycol (PEG derivative) was replaced by polyethylene glycol at the same concentration. Both the first plating solution formulation and the second plating solution formulation were in contact with a substrate having the same feature through-hole (TSV) under the same plating conditions. The plating conditions were current density: 2.5 ASF, constant temperature: 25 ° C, plating time: 5 hr. The hole diameter of the substrate through hole is 30 μm, 40 μm, and 50 μm.

The functional polyethylene glycol (PEG derivative) used in the first plating solution formulation includes any of the following:

(1) Methoxypolyethylene glycol amine 5000 {methoxypolyethylene glycol amine (MPEGA)}

(B) Polyoxyethylene bis (amine) 6000 {polyoxyethylene diamine (PEGBA)}

(3) O-[2-(3-Mercaptopropionylamino)ethyl]-O'-methylpolyethylene Glycol 5000{O-[2-(3-thiolpropionamido)ethyl]-O'-methylpolyethylene alcohol}

(4) Polyethylene glycol monomethyl ether mesylate 5000 {polyethylene glycol monomethyl ether mesylate}

(5) Methoxypolyethylene glycol propionic acid 5000 {polyethylene glycol monomethyl ether propionate}

(6) Polyethylene glycol dimesylate 4000 {polyethylene glycol dimethanesulfonic acid}

(7) Methoxypolyethylene glycol maleimide 5000 {maleimide-based polyethylene glycol monomethyl ether}

(8) O-[4-(Hydroxymethyl)benzoyl]-O'-methyl-polyethylene glycol 5000{O-[4-benzyl alcohol]-O'-methyl polyethylene glycol}

The first figure depicts an SEM image of the cross section of each of the first electroplating solution functional polyethylene glycols (PEG derivatives) filled with pores per aperture. The second figure depicts an SEM image of the cross section of each of the above electroplating solutions of polyethylene glycol filled with respective pore sizes. It can be seen from the experimental results that the first plating solution formulation containing 20 ppm of functional polyethylene glycol can obtain Bottom Up and Poreless Superfilling filling of 30 μm, 40 μm, 50 μm 矽 through holes. . Other concentrations of functional polyethylene glycols of 10 ppm, 30 ppm, 40 ppm, and 50 ppm did not completely fill the pores, but it was clearly seen to be carried out by Bottom Up. The second plating solution formulation containing polyethylene glycol allows a 50 μm 矽 through-hole to obtain a Bottom Up and a non-porous Superfilling at a concentration of 50 ppm.

In the above-mentioned hole-filling experiment, functional polyethylene glycol exhibits a pore-filling effect of Bottom Up and non-porous superfilling, showing the functionality selected for the present invention. Polyethylene glycol can indeed be used in TSV electroplated copper fill-in formulations.

In the previous hole-fill plating experiments and literature (for example, JJKelly, and ACWest "Leveling of 200nm Feature by Organic Additives" Electrochem. Soc., 2) pointed out that PEG + Cl ^- (inhibitor) + SPS (accelerator) + JGB ( The mixing formula of the leveling agent is easier to achieve the hole filling mode of Bottom UP and the filling rate can reach more than 90%. In the absence of a leveling agent, it is prone to early sealing and cannot be completely filled. Although the use of a leveling agent can improve the ability to fill the hole, the concentration of the leveling agent must be properly controlled. Too high or too low will result in voids in the hole.

The first and second plating solutions described above all use copper ions (CuSO ₄ ), hydrogen ions (H ₂ SO ₄ ), chloride ions (Cl ^- ), inhibitors (PEG or PEG derivatives), accelerators ( A mixed formulation of SPS) in which no leveling agent is used. From the above experimental results, it can be seen that the 20 ppm concentration of the PEG derivative can make the 30 μm, 40 μm, and 50 μm 矽 through holes exhibit superfilling without voids, but the 20 ppm conventional PEG cannot fill the holes. It can be inferred that under the condition of synergistic action with chloride ions, the inhibition effect of PEG derivatives is stronger than that of traditional PEG. In the plating solution formulation without using leveling agent, Bottom Up and non-porosity can be obtained. Superfilling.

The first figure is an SEM image of the cross section of each of the apertures of the first electroplating solution functional polyethylene glycol filled with each aperture.

The second figure is an SEM image of the cross section of each of the two apertures filled with polyethylene glycol at each concentration.

Claims (9)

An electroplated copper hole-filling inhibitor of a through-hole (TSV), the inhibitor being mixed in a plating solution, the plating solution containing an accelerator, a chloride ion, a hydrogen ion, and a copper ion; characterized in that: the suppression The agent is selected from the group consisting of functional polyethylene glycols. The electroplated copper hole-filling inhibitor of the through-hole (TSV) according to claim 1, wherein the inhibitor is a homobifunctional polyethylene glycol derivative. The electroplated copper hole-filling inhibitor of the through-hole (TSV) according to the first aspect of the invention, wherein the inhibitor is a heterobifunctional polyethylene glycol derivative. An electroplated copper hole-filling inhibitor of a through-hole (TSV) according to claim 1, wherein the inhibitor is represented by Formula 1. Wherein, X and Y are respectively a functional group introduced into a hydroxyl group at both ends of the polyethylene glycol, and the functional group is selected from the group consisting of an acid group, a sulfur group, an amine group, a sulfonic acid group, and an alkyl group. An electroplated copper hole-filling inhibitor of a through-hole (TSV) according to claim 4, wherein X may be a hydrogen group (-H), a methyl group (-CH ₃ ), or a vinyl amine group (-C _{2 )} H ₄ NH ₂ ), methylsulfonyl (-SO ₂ CH ₃ ). An electroplated copper hole-filling inhibitor of a through-hole (TSV) according to claim 5, wherein Y is a hydrogen group (-H), a vinylamine group (-C ₂ H ₄ NH ₂ ), or a methylsulfonate (-SO ₂ CH ₃ ), thiopropionylamino (-C ₂ H ₄ NHCOC ₂ H ₄ SH), propionic acid (-C ₂ H ₄ COOH), maleimine (C ₂ H ₄ NC ₄ H ₂ O ₂ ), benzyl alcohol (-C ₆ H ₄ CH ₂ OH). An electroplated copper hole-filling inhibitor of a through-hole (TSV) according to claim 1 of the patent application, wherein The inhibitor is selected from the group consisting of Methoxypolyethylene glycol amine {methoxypolyethylene glycol amine (MPEGA)}, Polyoxyethylene bis (amine) {polyoxyethylene diamine (PEGBA)}, O-[2-(3-Mercaptopropionylamino)ethyl ]-O'-methylpolyethylene Glycol{O-[2-(3-thiol propylamino)ethyl]-O'-methyl polyethylene glycol}, Polyethylene glycol monomethyl ether mesylate {polyethylene glycol monomethyl Ether mesylate}, Methoxypolyethylene glycol propionic acid 5000 {polyethylene glycol monomethyl ether propionate}, Polyethylene glycol dimesylate {polyethylene glycol dimethanesulfonate}, Methoxypolyethylene glycol maleimide {maleimide polyethylene Glycol monomethyl ether}, O-[4-(Hydroxymethyl)benzoyl]-O'-methyl-polyethylene glycol {O-[4-benzyl alcohol]-O'-methyl polyethylene glycol}. The electroplated copper hole-filling inhibitor of the through-hole (TSV) according to claim 7 of the patent application, wherein the inhibitor has a molecular weight of 4000 to 6000. An electroplated copper hole filling formula for a through hole (TSV), comprising: a copper ion source, a hydrogen ion source, a chloride ion source, an inhibitor, and an accelerator; wherein the inhibitor is a functional polyethylene glycol.