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Silicon Wafer Edge Grinding

Cranfield Precision developed the World’s first silicon wafer edge grinding machine capable of operating in the ductile regime. The machine uses resin bond grinding wheel technology and is so revolutionary that eight patent groupings are covered by more than 30 patents worldwide.

Link to detailed description of each patent grouping.

The SiWEG machine was a completely new concept that was sold to the research and development facilities of the world’s leading silicon wafer manufacturers (mainly in Japan) to develop their 300mm silicon wafer manufacturing processes. It was also sold to a Japanese government funded research organization (Super Silicon or SSi) that is the world’s only 400mm silicon wafer development facility.

The machine was successful in these research and development environments because it was capable of producing wafer edges to a near polish quality finish by grinding silicon (a brittle, glass like material) in the ductile regime. Ductile regime grinding removes material without the brittle fracture normally associated with the grinding of hard materials.

It is a process that has been researched and championed by the precision engineering community many years. However, before SiWEG, the process could only be used to grind simple components, for example those that have flat, or slightly curved faces. The SiWEG machine was the World’s first to be capable of forming complex profiles into the grinding wheel in situ and then grinding the profile into the component in the ductile regime.

The ability to grind complex silicon wafer edge profiles by ductile regime grinding eliminated one or both of the post grinding process steps used in conventional wafer manufacturing. Each of these steps (wafer edge polishing and/or acid etching) required a machine costing over $1million plus ancillary equipment and occupied very expensive clean room floor space.

The SiWEG machine generated such a large number of patents because it transferred so many original concepts from the research environment to a commercially viable machine and process. Many of the patented inventions are important to many disciplines of the precision engineering field, not just silicon wafer grinding. It would have been impossible to invent such a radical machine without the research capabilities available at Cranfield Precision and Cranfield University.

SiWEG specification:

Wafer Diameter Range: 200mm, 300mm, 324mm, 400mm, 450mm.

Sub-Surface Damage: Less than 1micron

Surface finish: 20-80nm RMS

Diameter: 0.1mm

Roundness: 0.03mm

Notch Depth: SEMI standard: +0.25mm/-0.0mm

Notch Angle: SEMI standard: +/-0.5mm

Grinding spindle axes: Flexure mounted, cam driven

Grinding spindles: Aerostatic bearings <0.001mm radial error motions

Grinding (edge and notch) wheels:

  • Resin bond diamond
  • Resin bond CBN
  • Metal bond diamond

In-situ forming of resin bond wheels using metal bond diamond forming wheels

Fully Automatic, cassette to cassette loading

In-situ inspection of diameter, edge profile, notch shape

Published Papers

Silicon Wafer Edge Grinding Machine

Silicon Wafer Edge Grinding Machine

Silicon Sub Surface Damage

Silicon Sub Surface Damage