Halogen-Free Copper Precursors for CVD Adhesion
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Solution Overview
Problem
The deposition of copper thin films in microelectronic devices faces challenges, particularly in achieving pinhole-free seed layers for electrodeposition, due to the difficulty in sputter-depositing copper on shrinking dimensions, and existing copper precursors like copper beta-diketonate complexes suffer from weak adhesion issues with Ta or TaN surfaces due to fluorine contamination.
Innovation Solution
Development of copper precursors without halogen atoms, such as copper borohydrides and cyclopentadienyl-type compounds, which are used in chemical vapor deposition (CVD), atomic layer deposition (ALD), and digital CVD processes to deposit copper films with improved adhesion and reduced contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper beta-diketonate complexes with fluorinated beta-diketonate ligands are used as CVD/ALD precursors, then highly conductive and conformal copper films can be deposited, but weak adhesion occurs due to fluorine contamination on Ta or TaN barrier surfaces
Solution Approach 1:
The patent removes fluorine atoms from the beta-diketonate ligand structure, replacing them with hydrogen or other non-harmful substituents. This extraction of the harmful fluorine element eliminates the source of fluorine contamination while preserving the essential beta-diketonate coordination chemistry that enables effective copper deposition
Solution Approach 2:
The patent transforms the situation by eliminating the harmful fluorine component entirely, converting a harmful precursor into a beneficial one that provides both good adhesion and high conductivity without the adhesion problems caused by fluorine release during deposition
2Manufacturing precision
If sputter deposition is used to deposit copper seed layers on shrinking dimensions, then copper films can be deposited, but pinhole-free seed layers become increasingly difficult to achieve
Solution Approach 1:
The patent replaces the physical sputter deposition process with a chemical vapor deposition process using organometallic precursors. This substitution of mechanical/physical deposition with chemical deposition enables conformal film formation at nanoscale dimensions where sputtering cannot produce pinhole-free seed layers
Solution Approach 2:
The patent changes the deposition parameters by using volatile copper precursors that decompose at lower temperatures and provide atomic-level conformal coverage, enabling seed layer formation on high aspect ratio structures and shrinking dimensions where traditional sputtering fails
3Reliability
If existing copper precursors with halogen atoms are used, then copper films can be deposited, but adhesion to barrier materials is weak and contact resistance increases
Solution Approach 1:
The patent extracts and removes halogen atoms (fluorine, chlorine, bromine, iodine) from the copper precursor structure, creating halogen-free beta-diketonate complexes that eliminate the source of halogen contamination while maintaining the copper deposition functionality
Solution Approach 2:
The patent converts harmful halogen-containing precursors into beneficial halogen-free precursors that provide both excellent adhesion to Ta/TaN barriers and low contact resistance, eliminating the trade-off between deposition efficiency and adhesion quality
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
These new precursors enable the deposition of copper films with enhanced adhesion to barrier materials and reduced contact resistance, facilitating the formation of conformal, high-quality copper layers on microelectronic device substrates, even at lower temperatures below 500°C.
Implementation Method 1
copper precursors useful for deposition of copper, e.g., on a microelectronic device substrate, by techniques such as chemical vapor deposition (CVD)
Implementation Method 2
Atomic layer deposition (ALD), which is a modified CVD process, also provides uniform step coverage which is critical for copper seed layers
Implementation Method 3
From such precursors, copper can be deposited on substrates, e.g., microelectronic device substrates, at temperatures below 500° C.
Data Source
AI summary
Copper precursors useful for depositing copper or copper-containing films on substrates, e.g., microelectronic device substrates or other surfaces. The precursors includes copper compounds of various classes, including copper borohydrides, copper compounds with cyclopentadienyl-type ligands, copper compounds with cyclopentadienyl-type and isocyanide ligands, and stabilized copper hydrides. The precursors can be utilized in solid or liquid forms that are volatilized to form precursor vapor for contacting with the substrate, to form deposited copper by techniques such as chemical vapor deposition (CVD), atomic layer deposition (ALD) or rapid vapor deposition (digital CVD).