Metrology for Substrate Back Side Contamination

Contamination elements

MRAM elements: Lower limits of detection (LLD) [atoms/cm²]

After etching of MTJ layer and cap layer, those elements cause contamination on the backside of the silicon substrate.

BAC-TXRF

Backside contamination must be measured to avoid cross-contamination of the product line.

BAC-TXRF is a suitable technique for the MRAM application.

Diffusion length of Cu at various temperatures for 1 hr.

About BAC-TXRF

Frontside and backside handling with flipping robot arm

Contamination from the tunnel layer material (MgO)

The W-M excitation source is suitable to measure light-element contamination, such as Na, Mg, and Al.

Contamination from the free and pinned layer material (CoFeB)

Contamination from the Pt and Ru layers

Other detected elements

Results after cleaning