Tin-Silver Electroplating Complexing Agents for Void-Free Deposits
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Solution Overview
Problem
Existing tin-silver alloy electroplating compositions face challenges in stability and effectiveness, particularly in maintaining the quality of deposits over time without significant deterioration or void formation when used for semiconductor substrates.
Innovation Solution
An aqueous composition comprising tin ions, silver ions, and specific complexing agents of formulas C1, C2, and C3, which are capable of forming stable complexes to ensure long-term stability and effective electroplating of tin-silver alloys on semiconductor substrates, particularly for solder bumps with aperture sizes ranging from 500 nm to 500 µm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional tin-silver plating solutions are used, then silver can be deposited in parallel to tin, but the solution shows significant deterioration and coloring over time
Solution Approach 1:
The patent changes the chemical parameters of the plating solution by introducing specific complexing agents (formulae C1, C2, C3) with particular molecular structures containing sulfur and nitrogen atoms. These complexing agents form stable complexes with silver ions, preventing their premature deposition and maintaining solution stability for at least 6 months while ensuring consistent plating quality.
Solution Approach 2:
The complexing agents act as intermediaries between the silver ions and the electrode. They temporarily bind with silver ions in the solution, controlling their release during electroplating and preventing direct interaction between silver ions and other solution components that would cause deterioration or coloring over time.
2Productivity
If conventional plating compositions are used, then electroplating can be performed, but void formation occurs in the deposited alloy
Solution Approach 1:
The patent modifies the chemical environment by introducing complexing agents with specific formulae (C1, C2, C3) that control the deposition kinetics. These agents ensure uniform distribution of metal ions during electroplating, preventing void formation while maintaining efficient deposition rates for semiconductor substrates with aperture sizes from 500 nm to 500 µm.
3Productivity
If the plating bath is used for a long duration, then productivity increases, but significant coloring and deposits are generated
Solution Approach 1:
The complexing agents enable continuous operation of the plating bath for at least 6 months without significant deterioration. The agents continuously bind with silver ions, preventing their participation in side reactions that would cause coloring or deposit formation, thus allowing prolonged productive use of the bath.
Solution Approach 2:
The patent converts the potential harmful interaction between silver ions and other solution components into a beneficial complex formation. The complexing agents deliberately bind with silver ions to create stable, non-reactive complexes that prevent harmful side reactions and coloring, while still allowing controlled silver deposition during electroplating.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition maintains stability for at least six months and enables uniform deposition of tin-silver alloys, preventing significant deterioration and void formation, thereby ensuring high-quality electroplating on semiconductor substrates.
Implementation Method 1
complexing agents that are capable of forming a complex with silver in order to allow silver to be (a) stable in the solution in combination with tin
Implementation Method 2
capable of electrodepositing tin-silver alloys on semiconductor substrates
Implementation Method 3
applying a current to the substrate for a time sufficient to deposit a tin or tin alloy layer onto the substrate
Data Source
AI summary
An aqueous composition comprising (a) metal ions comprising tin ions and silver ions and (b) at least one complexing agent of formula (C1) R1-X1-S-X21[D1-X22-]nS-X3-R2, (C2) R1-X1-S-X31-D2-[X32-S-]nX3-R2, (C3) R3-X1-S-X41-[D3-X42-]nS-X3-R4 wherein X1, X3 are independently selected from a linear or branched C1-C12 alkanediyl, which may be unsubstituted or substituted by OH; X21, X22 are independently selected from X1, which may be further substituted by -X5-COOR12, -X5-SO2-O-R12, a C2 to C6 polyoxyalkylene group of formula -(O-CH2- CHR11)z-OH, or a combination thereof, and -X1-NH-CO-X6-CO-NH-X1-; X31, X32 are independently selected from a chemical bond and X1; X41, X42 are independently selected from X1; X5 is a linear or branched Ci to C10 alkyl; X6 is selected from X1 and a divalent 5 or 6 membered aromatic group; R1, R2 are independently selected from a monovalent 5 or 6 membered aromatic N- heterocyclic group comprising one N atom or two N atoms which are separated by at least one C atom, and its derivatives received by N-alkylation with a C1-C6- alkyl group, which may be substituted by --COOR12 or -SO2-O-R12, and which aromatic N- heterocyclic group may optionally further comprise, under the proviso that X21 is substituted by at least one OH, one S atom; R3, R4 are independently selected from a monovalent 5 or 6 membered aliphatic N- heterocyclic group comprising one N atom and one O atom; D1 is independently selected from S, O and NR10-; D2 is (a) a divalent 5 or 6 membered aliphatic heterocyclic ring system comprising 1 or 2 S atoms, or (b) a 5 or 6 membered aromatic heterocyclic ring system comprising at least two N atoms and optionally one or two S atoms; D3 is independently selected from S and NR10-; n is an integer of from 0 to 5; z is an integer from 1 to 50; R10 is selected from H and a linear or branched C1-C12 alkyl; R11 is selected from H and a linear or branched C1 to C6 alkyl; and R12 is selected from R10 and a cation.