Infrared wafer metrology

What it does

Silicon is opaque to visible light but transparent in the near infrared. The T-Map sends infrared light into the wafer and records the reflections from its front and back faces; the interference between them gives the thickness at that point, and a scan across the wafer turns it into a map.

From the map we read the thickness, its total variation and wedge, and local thin or thick spots, before and after grinding, polishing or etching. Heavily doped silicon absorbs the infrared and needs other methods.

What we use it for

• BULLKID wafers

  Thickness of the silicon wafers for BULLKID detector arrays, before they are diced.

• Thinned and polished crystals

  Uniformity of crystals after thinning and polishing, where thickness sets how a plate bends or how well it diffracts.

Working with us

We can map the thickness of your wafers and thinned crystals in joint projects.