Titanium Nitride Etchant Composition for Selective Wet Recessing
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Solution Overview
Problem
In semiconductor manufacturing, there is a challenge in achieving selective etching of titanium nitride films without affecting underlying metal conductor layers such as molybdenum, aluminum oxide, and silicon dioxide, particularly in the dual damascene process where precise control of via and trench dimensions is critical as device sizes decrease.
Innovation Solution
A composition comprising water, an oxidizing agent, a fluoride-containing etchant, a metal corrosion inhibitor, and optionally a pH adjustor or water-miscible solvent is used for selective etching of titanium nitride, with specific formulations achieving high selectivity and stability, allowing for uniform recess formation in microelectronic device structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wet etching process is used to remove titanium nitride metal hard masks, then the metal hard mask can be effectively removed, but the underlying metal conductor layer and low-k dielectric material may be affected
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by incorporating specific inhibitors (benzotriazole for copper protection, hydrofluoric acid for dielectric protection) and oxidizing agents (ammonium persulfate, hydrogen peroxide) to achieve selective etching of titanium nitride while protecting underlying layers. The pH and temperature parameters are also optimized to enhance selectivity and prevent damage to sensitive materials.
Solution Approach 2:
The patent introduces intermediary substances into the etching process: benzotriazole acts as an intermediary to selectively inhibit copper dissolution, hydrofluoric acid serves as an intermediary to protect dielectric materials, and oxidizing agents act as intermediaries to facilitate titanium nitride removal while sparing metal conductor layers. These intermediaries enable selective etching by mediating the chemical reactions between the etchant and different materials.
2Productivity
If the etch rate is increased to improve productivity, then the etching process becomes faster, but the selectivity between titanium nitride and other materials decreases
Solution Approach 1:
The patent achieves high etch rates with maintained selectivity by optimizing multiple parameters simultaneously: using ammonium persulfate and hydrogen peroxide as oxidizing agents to accelerate titanium nitride etching, incorporating benzotriazole to suppress copper etching, adjusting pH to enhance selectivity, and controlling temperature to optimize the balance between etch rate and selectivity. This multi-parameter optimization enables fast etching while preserving material selectivity.
3Productivity
If strong etchants are used to achieve high etch rates, then productivity increases, but the stability and compatibility of the composition with other materials decreases
Solution Approach 1:
The patent creates a composite etching composition that combines multiple chemical components with complementary functions: ammonium persulfate and hydrogen peroxide provide oxidizing power for high etch rates, benzotriazole provides selective inhibition for copper protection, hydrofluoric acid provides dielectric protection, and pH adjustors maintain compositional stability. This composite formulation achieves high productivity while ensuring reliability and compatibility with various materials through synergistic interactions among components.
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 enables selective etching of titanium nitride with high etch rates exceeding 3.5 Å/minute, maintaining the integrity of molybdenum and other materials, and providing long bath life and shelf stability, thus ensuring precise pattern formation in microelectronic devices.
Implementation Method 1
a. water; b. at least one oxidizing agent; c. at least one fluoride containing etchant
Implementation Method 2
c. at least one fluoride containing etchant; The selectivity of the compositions depends on process temperature and time
Implementation Method 3
d. at least one metal corrosion inhibitor; maintaining the integrity of molybdenum and other materials
Implementation Method 4
The selectivity of the compositions depends on process temperature and time (i.e., exposure)
Data Source
AI summary
Provided are compositions and methods for selectively etching titanium nitride, generally leaving molybdenum present unaffected by the process, as well as any aluminum oxide, silicon dioxide, and polysilicon which may be present on the device. In general, the compositions of the invention were able to achieve titanium nitride etch rates exceeding 3.5 Å/minute, thereby providing uniform recess top and bottom layers in patterns.