Selective Copper Etchant Composition for TSV Metal Protection
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Solution Overview
Problem
Current techniques fail to selectively etch copper and copper alloys while suppressing the dissolution of nickel, nickel alloys, tin, tin alloys, gold, and gold alloys, particularly in semiconductor substrates with TSVs used in next-generation DRAM and NAND memories.
Innovation Solution
An etchant comprising 5-10.5% hydrogen peroxide, 0.3-6% nitric acid, a nitrogen-containing 5-membered ring compound like triazoles or tetrazoles, and a pH adjuster such as an alkali metal hydroxide or phosphonic acid compounds, with a pH of 0.7-1.3, is used to selectively etch copper and copper alloys while preventing the dissolution of nickel, tin, and gold alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etchants containing hydrogen peroxide and nitric acid are used, then copper etching capability is achieved, but dissolution of nickel and other metals cannot be prevented
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentrations of hydrogen peroxide (5-10.5%) and nitric acid (0.3-6%), and adjusting pH to 0.7-1.3 using phosphonic acid compounds and pH adjusters. These parameter optimizations enable selective copper etching while suppressing dissolution of nickel, tin, and gold alloys, resolving the contradiction between etching effectiveness and metal protection.
Solution Approach 2:
The patent introduces phosphonic acid compounds and nitrogen-containing 5-membered ring compounds as intermediary substances that selectively adsorb onto metal surfaces. These intermediaries form protective complexes with nickel, tin, and gold alloys, preventing their dissolution while allowing copper to be etched by the hydrogen peroxide-nitric acid system.
2Productivity
If etching conditions are optimized for copper, then etching speed improves, but selectivity against other metals deteriorates
Solution Approach 1:
The patent achieves both high etching speed and selectivity by optimizing multiple parameters simultaneously: hydrogen peroxide concentration (5-10.5%), nitric acid concentration (0.3-6%), pH (0.7-1.3), and temperature (20-40°C). This multi-parameter optimization enables the etchant to rapidly etch copper while maintaining selectivity against nickel, tin, and gold alloys, resolving the contradiction between productivity and precision.
Solution Approach 2:
The patent creates a composite etching system combining hydrogen peroxide, nitric acid, phosphonic acid compounds, and nitrogen-containing 5-membered ring compounds. This composite formulation synergistically provides both high etching speed for copper and selective protection for other metals, achieving both productivity and manufacturing precision simultaneously.
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 etchant effectively enables selective etching of copper and copper alloys while suppressing the dissolution of nickel, tin, and gold alloys, making it suitable for wiring formation in semiconductor substrates with bumps like TSVs.
Implementation Method 1
an etchant comprising: (A) 5 to 10.5% by mass of hydrogen peroxide relative to the total mass of the etchant; (B) 0.3 to 6% by mass of nitric acid relative to the total mass of the etchant
Implementation Method 2
An etchant for selectively etching at least one selected from the group consisting of copper and a copper alloy in a semiconductor substrate
Data Source
Figure 1(a)~1(c)
Figure 2~3
Figure 4~5
AI summary
The present invention relates to an etchant capable of selectively etching copper and a copper alloy while suppressing dissolution of nickel, tin, gold, and an alloy thereof. This etchant is characterized by comprising: (A) 5-10.5% by mass of hydrogen peroxide with respect to the total mass of the etchant; (B) 0.3-6% by mass of nitric acid with respect to the total mass of the etchant; (C) at least one nitrogen-containing 5-membered ring compound selected from the group consisting of triazoles and tetrazoles, which may have at least one substituent selected from the group consisting of a C1-6 alkyl group, an amino group, and a substituted amino group having a substituent selected from the group consisting of a C1-6 alkyl group and a phenyl group; and (D) (d1) one or more pH adjusters selected from the group consisting of an alkali metal hydroxide, ammonia, an amine, and an ammonium salt, (d2) a phosphonic acid compound, or (d3) a combination of (d1) and (d2).