The slanted or rounded edge between the bottom of a wafer and the side of a wafer is the bevel region. Beveling is achieved by edge grinding, or pressing the edge of a grooved grinding wheel against the wafer as it rotates. Beveling wafers can help to prevent chipping and can have an impact on the function of the semiconductor when it is finished.
Bevel Angle and Semiconductor Function
The bevel angle of a wafer is very important to the function of the finished semiconductor. Differing bevel angles create differing amounts of surface electrical fields. For example, a shallow negative bevel angle will reduce the surface electrical field significantly. This may affect the life, quality, and function of electronics devices created using the finished semiconductor.
Outsourcing Beveling Needs
In order to achieve specific bevel angles, it is important that precision equipment be used. Innovative Fabrication’s precision lapping equipment allows fabricators to adjust the angle between the wafer surface and the polishing pad to very precise constraints. This allows electronic manufacturers to have greater control over the breakdown voltage and the way the voltage is divided among junctions without having to fabricate and bevel wafers in-house.
Edge Defects and Semiconductor Performance
When there are defects in wafer edges, it may affect the performance of the semiconductor. Blemishes may cause airborne particles or liquid to become trapped against the surface of the wafer. Protrusions may also become detached from the wafer during processing, causing debris that may damage the semiconductor and other sensitive electronic components. It is important that beveled wafer edges be inspected for microroughness after processing to protect against these types of issues. Wafer edges may also be polished to remove blemishes after beveling.
Wafer Edge Types
There are two typical wafer edge types that are used in the semiconductor industry, beveled or bullet shaped edges and rounded or blunted edges. Bullet shaped wafers usually have an edge that is at a 22 degree angle to the wafer surface. Blunt edged wafers have a smooth transition between the wafer surface and the edge. The shape of the edge has an impact on the way that electricity is conducted through the component of the finished product.
Wafer Edge Regions
There are five regions that constitute the edge of a wafer after it has been beveled:
- The transition area between the edge and the polished side
- The bevel or rounded area of the front side
- The crown
- The rounded are of the back side
- The transition area between the edge and the back side