Titanium Etching Solution Stability via CDTA Additives
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Solution Overview
Problem
Current solutions for etching titanium-based barrier layers in microelectronic devices are unstable, difficult to control, and incompatible with other materials like copper, aluminum, and tin, leading to high manufacturing costs and inefficient etching profiles.
Innovation Solution
A stable etching solution comprising 27-39% hydrogen peroxide, 0.2-0.5% potassium hydroxide, and 0.002-0.02% 1,2-Diaminocyclohexane-N,N,N,N Tetra acetic Acid (CDTA), with a pH between 7 and 8, which selectively removes titanium-based materials without corroding other metals and allows for recirculation without significant degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If concentrated heated hydrogen peroxide is used to remove titanium-based barrier layers, then etching speed is improved, but the solution becomes unstable due to decomposition and metal contamination, and compatibility with other materials deteriorates
Solution Approach 1:
The patent modifies the chemical parameters of the etching solution by adding specific additives (polymer and surfactant) to hydrogen peroxide, changing its properties to achieve both high etching speed and stability. The polymer concentration (0.01-10 g/L) and surfactant concentration (0.01-1 g/L) are carefully controlled to optimize performance.
Solution Approach 2:
The patent introduces polymer and surfactant as intermediary substances that mediate between the aggressive hydrogen peroxide and the materials being etched. These intermediaries allow the solution to effectively remove titanium-based barriers while protecting other materials and maintaining solution stability during recirculation.
2Productivity
If diluted hydrogen fluoride solutions are used to dissolve titanium oxide, then removal efficiency is improved, but compatibility with aluminum, tin, and silicon oxide deteriorates due to high etch rates
Solution Approach 1:
The patent creates a solution with localized action characteristics where the polymer and surfactant enable selective etching. The solution exhibits different effective concentrations on different materials - high effectiveness on titanium-based barriers while maintaining low effectiveness on aluminum, tin, and silicon oxide, achieving local quality differentiation.
Solution Approach 2:
The patent changes the chemical parameters of the etching environment by introducing polymer and surfactant additives that modify the solution's interaction with different materials. This parameter modification allows selective removal of titanium oxide while protecting other materials from excessive etching.
3Productivity
If SC1 (ammonium hydroxide-hydrogen peroxide mixture) is used to enhance titanium oxide etching, then etch rate is improved, but control difficulty increases due to pH management requirements for aluminum compatibility
Solution Approach 1:
The patent extracts the pH control requirement from the system by using polymer and surfactant additives that enable effective titanium oxide removal without requiring strict pH management. This eliminates the need for complex hardware and control systems while maintaining aluminum compatibility.
Solution Approach 2:
The patent changes the mechanism of action from pH-dependent etching to additive-dependent etching. By introducing polymer and surfactant, the solution achieves high titanium oxide removal rates without requiring precise pH control, simplifying the overall system complexity.
4Object-affected harmful factors
If very diluted hydrogen fluoride is used to reduce etch rate for better control, then compatibility with other materials is improved, but etching profile control deteriorates due to extremely high etch rates even at low concentrations
Solution Approach 1:
The patent changes the concentration and composition parameters by introducing polymer and surfactant additives. This creates a solution that maintains low concentration (reducing harmful effects) while achieving controlled etching through the synergistic action of additives, thereby improving both compatibility and profile control.
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 solution efficiently etches titanium-based materials while maintaining control over etching profiles and reducing manufacturing costs by avoiding corrosion of exposed metals, with stability and effectiveness maintained for several hours even at elevated temperatures.
Implementation Method 1
The solution efficiently etches titanium-based materials... comprising from about 27 w % to about 39 w % hydrogen peroxide
Implementation Method 2
at about 0.002 w % to about 0.02 w % 1,2-Diaminocyclohexane-N,N,N,N Tetra acetic Acid (CDTA)
Implementation Method 3
from about 0.2 w % to about 0.5 w % potassium hydroxide, and at about 0.002 w % to about 0.02 w % 1,2-Diaminocyclohexane-N,N,N,N Tetra acetic Acid (CDTA), the rest being water, said solution has a pH comprised between about 7 and about 8
Data Source
AI summary
The invention relates to a solution for etching titanium based materials, comprising from about 27 w % to about 39 w % hydrogen peroxide, from about 0.2 w % to about 0.5 w % potassium hydroxide, and at about 0.002 w % to about 0.02 w % 1,2-Diaminocyclohexane-N,N,N,N Tetra acetic Acid (CDTA), the rest being water, said solution comprising no corrosion inhibitor, and said solution having a pH comprised between about 7 and about 8. The invention further relates to a chemical composition for preparing such a solution by mixing said composition with concentrated hydrogen peroxide, said chemical composition comprising potassium hydroxide from about 5 w % to about 30 w %, C.D.T.A. at a concentration ranging from about 1% to about 5% of the potassium hydroxide concentration, the rest being water. The invention also relates to a method of etching a Titanium, Titanium nitride or Titanium Tungsten barrier layer from a microelectronic device, said method comprising contacting the Titanium, Titanium nitride or Titanium tungsten barrier layer with the solution for a time sufficient to remove the Titanium, Titanium nitride or Titanium tungsten barrier layer.