Measuring Focus in Multi-Beam Tools for Tiny Electronics Manufacturing

This patent describes a method to precisely measure how focused tiny particle beams are in advanced manufacturing machines by slightly tilting them and observing where they hit a target.

What it covers

This patent details a method for figuring out how well focused the individual tiny beams, called beamlets, are in a charged-particle multi-beam processing apparatus. To do this, the system slightly changes an electrostatic voltage in a lens, or another setting in its projection optics, which causes the beamlets to tilt. This tilt makes the beamlets land in slightly different spots on the target surface. By measuring how much the landing positions shift and knowing how much the beamlets tilted, the system creates a map. This map, often made using a mathematical model, then allows the system to extract specific focal properties like the height of focus, astigmatic length, or the size of any blur, which can then be used to correct imaging errors.

What it doesn't cover

• —Does not cover single-beam charged-particle processing apparatus, as it specifically addresses 'multi-beam' systems.
• —Does not cover determining focal properties using methods other than tilting beamlets and measuring their displacement.
• —Does not cover the actual correction of imaging errors, only the process of determining the focal properties that can then be used for correction.
• —Does not cover determining other types of imaging errors beyond focal properties like height of focus, astigmatic length, or blur size.
• —Does not cover apparatuses that do not modify an electrostatic voltage of a lens or a similar operating parameter to tilt the beamlets.

The clever bit

The clever bit is using a small, controlled tilt of the beamlets and precisely measuring their displacement to indirectly calculate complex focal properties. This avoids needing direct, difficult-to-obtain measurements of the beam's focus at the target itself.

Why it matters

In advanced manufacturing, especially for computer chips, tools that use charged particles need extreme precision to create tiny features. If the particle beams aren't perfectly focused, the resulting products can have flaws. This method provides a way to accurately measure these focusing issues, allowing machines to be tuned for optimal performance and ensuring the quality of very small components.

Real-world examples

• 1.Electron beam lithography tools for semiconductor manufacturing
• 2.Ion beam etching systems
• 3.Multi-beam inspection tools for wafer defects
• 4.Advanced microscopy systems using multiple charged-particle beams