High-resolution chemical depth profiling of solid material using a miniature laser ablation/ionization mass...

Area of Science:

• Materials Science
• Analytical Chemistry
• Surface Science

Background:

• Electrodeposited copper films are crucial for on-chip interconnects in the semiconductor industry.
• Plating additives influence the properties and performance of these copper interconnects.
• Accurate chemical depth profiling is essential for quality control and process optimization.

Purpose of the Study:

• To develop and demonstrate a high-resolution chemical depth profiling technique for copper films.
• To quantify the inclusion of plating additives (SPS, Imep, PEI, PAG) in electrodeposited copper.
• To assess the capabilities of a miniature laser ablation ionization mass spectrometer (LIMS) for trace-level analysis.

Main Methods:

• High-resolution chemical depth profiling using a miniature laser ablation ionization mass spectrometer (LIMS).
• Quantitative elemental mass spectrometric measurements at trace levels (∼10 ppb).
• Utilized an ultrashort pulsed laser system (τ ∼ 190 fs, λ = 775 nm) for sample ablation and ionization.

Main Results:

• Demonstrated quantitative chemical mass spectrometric analysis with subnanometer ablation depth resolution per laser shot.
• Achieved high detection sensitivity (∼10 ppb) and a high dynamic range (≥10^8).
• Successfully probed the incorporation trend of plating additives into growing copper deposits.

Conclusions:

• The developed LIMS system offers exceptional vertical depth resolution and high sensitivity for chemical analysis.
• This technique is highly valuable for investigating semiconductor wafers and space-weathered samples.
• The LIMS instrument provides accurate and precise measurements for materials requiring high-resolution chemical composition analysis.