Wafers are thin slices of silicon that are used in many types of electronics applications. The wafers are grown in a lab setting in which purity is controlled and altered depending on the destined use of the wafer. Wafer dicing is a process used to separate die from a layer of semiconductor after the wafer has been processed. Diamond sawing is a process that is often used for wafer dicing, as it holds advantages to other methods.
Advantages of Diamond Blades over Scribing
Wafers can be scribed with a diamond point, and then carefully broken along the scribe line as opposed to diced with a diamond saw. This process is still used for certain applications. However, the majority of wafer dicing needs are taken care of with a diamond saw. A diamond saw can be used to dice materials such as amorphous or polycrystalline silicon that don’t fracture neatly, whereas scribing cannot be used on these materials. Scribing is not as consistent as diamond dicing and 100 percent break out yield can’t be guaranteed.
Even with the most well-maintained scribe diamond, some components are bound to be chipped or damaged. Diamond scribing also follows the natural contours of the material, so the edges tend to be angles as opposed to vertical as they are with diamond saw wafer dicing. The angled edges allow the wafers to move over one another during transport, which can cause chipping and damage, whereas the vertical edges keep the finished products firmly in place.
Diamond Blade Wafer Dicing Process
To dice thinned wafers, the wafers must be mounted securely. This keeps the wafer securely in place through the dicing process and keeps the die aligned so that it can be easily moved to the next step in processing. There are a few different options that can be used to secure the wafer.
Dicing tape is made from plastic film covered with an adhesive film, which is then covered with a release film. There are two main types of dicing tape available, standard tape (also called blue tape) and UV tape. Wafers are mounted onto the release tape and fixed to a steel ring. Unfortunately, it is sometimes difficult to remove the die from the tape after processing. The tape is also sometimes cut or damaged during processing.
When dicing in high-volume, it may be beneficial to use a jig-based system for mounting. This system relies on vacuum pressure to secure and transport the wafer. A jig is matched to the material and the wafer is held in place with rubber and the pressure from vacuum holes that are underneath the die.
Alternative types of adhesion may also be used in place of tape, such as wax on glass. When using this method, the saw dices through the substrate and into the glass, which eliminates movement. This method is most commonly used for low-volume production when the material being used is very expensive.