Application Note

Semiconductor Metrology

Application Note

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Semiconductor Metrology

Electronic components are everywhere in our modern world. These components must be reliable, as they control critical systems from everyday items to electronically controlled military equipment and various aerospace equipment. To assure this reliability, components must go through a battery of tests. XRF analysis is an irreplaceable tool for the semiconductor industry to guarantee and certify their products. Electrical or photonic circuits are one of these components that are the foundation for so many other products. These circuits begin their lives on silicon wafers. As the wafers and associated circuits and boards become more specialized, they require different types of testing.

IXRF Systems’ ATLAS SEMI can analyze for:

  • bump inspection
  • CMOS image sensors (CIS)
  • corrosion resistance coating
  • Cu CMP control at BEOL
  • film stack
  • light elements
  • metal film stack composition such as CIGS
  • multi-stack structures
  • Pb measurement for Whiskers
  • redistribution layer (RDL)
  • Sn/Ag Bump/Pillar measurements
  • sputtering targets
  • thermal barrier coating
  • thick mono-layers
  • thickness and composition control
  • thin Film/Coating thickness measurements
  • ultra-thin films
  • under bump metallization (UBM)
  • wafer-level packaging (WLP)
Semi Wafer

Atlas in Semi Fab

Atlas Semi

IXRF Systems offers a 5µm spot size, the smallest on the market, allowing for extremely high resolution maps, analysis of small leads or pillars. Though SnPb solder has its place in technology, there is now a shift to use SnAg due to environmental, health and safety concerns. These solder points must also be tested.

Current technologies include Pb-free bumps of SnAg, as well as Pb-free SnAg pillars on Cu seed. Current bump/pillar and seed sizes are about 50 to 150µm. However, next-generation technology is pushing towards smaller pillar/seed sizes of 20- 30µm.

Leads on electronic components cannot fail, less the whole system will fail. A well-known phenomenon known as ‘whiskers’ can cause these components to fail. The whiskers come from tin used in electronic component surfaces.

It has been found that adding lead to the tin can prevent the growth of whiskers. This addition of lead must be analytically measured to ensure expected and required concentrations. Most aerospace companies require a minimum of 3% Pb to prevent tin whiskers.

XRF is the preferred method for lead testing in tin. XRF is more accurate than EDS based on the larger area and depth of measurement.

IXRF Systems’ powerful software can quickly identify, measure, and analyze multiple solder bumps on a board.

Quantitative analysis was done on one of the SnPb solder bumps in the center trio section, a circled portion in the elemental map to the right.

Below is an elemental map of a large wafer area with pillars, collected with a 5µm spot size.

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