Semiconductor Wafer Etchant Composition for Flat Transition Metal Surfaces
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Solution Overview
Problem
Conventional treatment liquids for etching transition metals like ruthenium, tungsten, and molybdenum in semiconductor manufacturing face challenges in achieving precise etching rates and maintaining surface flatness, leading to difficulties in forming precise wiring structures in semiconductor devices.
Innovation Solution
A treatment liquid comprising hypohalite or periodate ions and an alkylammonium salt, specifically designed to control the etching rate and maintain surface flatness by forming a protective layer on the metal surface, is developed, allowing for precise etching of transition metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching is used to etch transition metals (ruthenium, tungsten, molybdenum, chromium), then etching precision is improved, but control of etching rate and surface flatness becomes difficult
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pH value within a specific range (2.0-4.0) and the concentration of oxidizing agents to achieve precise etching rate control. By adjusting these chemical parameters, the etching process can be optimized to maintain both precision and surface flatness without the problems of conventional wet etching
Solution Approach 2:
The patent uses a composite treatment liquid containing multiple components including oxidizing agents (such as hypochlorite, bromate, or periodate), complexing agents, and buffers. This composite formulation works synergistically to provide controlled etching while maintaining surface flatness, resolving the contradiction between etching precision and rate control
2Quantity of substance
If conventional treatment liquids (pH 12 or higher with hypochlorite, chlorite, or bromate) are used to etch ruthenium, then ruthenium can be dissolved and removed, but precise etching is difficult and surface flatness is not maintained
Solution Approach 1:
The patent fundamentally changes the pH parameter from conventional high pH (12 or higher) to a moderate pH range (2.0-4.0). This parameter change enables precise etching of ruthenium while maintaining surface flatness, overcoming the limitations of conventional treatment liquids that could remove ruthenium but created surface irregularities
Solution Approach 2:
The patent introduces complexing agents as intermediaries that mediate between the oxidizing agents and the ruthenium metal. These complexing agents form stable complexes with ruthenium during etching, enabling controlled dissolution while maintaining surface flatness, thus resolving the contradiction between removal efficiency and precision
3Ease of manufacture
If dry etching is used to etch transition metals, then wiring can be formed, but precise etching is difficult due to plasma distribution non-uniformity and etching rate variations
Solution Approach 1:
The patent replaces the mechanical/physical dry etching process with a chemical wet etching process using a specially formulated treatment liquid. This substitution eliminates the plasma distribution non-uniformity and etching rate variations inherent in dry etching, achieving both ease of manufacture and high precision with uniform etching across the substrate
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 treatment liquid enables precise control of the etching rate and maintains surface flatness, making it suitable for semiconductor manufacturing processes, particularly for forming multilayer wiring structures with features down to 10 nm or less.
Implementation Method 1
the flatness of a transition metal surface after etching can be maintained, and the etching rate of the transition metal can be precisely controlled by adding a specific alkylammonium salt
Implementation Method 2
A treatment liquid comprising hypohalite or periodate ions and an alkylammonium salt, specifically designed to control the etching rate
Data Source
AI summary
Provided is a treatment liquid for etching a transition metal on a semiconductor wafer, the treatment liquid comprising: (A) a hypohalite ion or periodate ion; and (B) an alkylammonium salt represented by the following Formula (1).(wherein a is an integer from 6 to 20, R1, R2, and R3 are independently a hydrogen atom or an alkyl group having carbon number from 1 to 20, and X− is a bromine-containing ion), and a method of etching a transition metal by bringing the treatment liquid for semiconductor wafers into contact with the transition metal used in a semiconductor formation process.