As an industry account manager focusing on the semiconductor industry, I’ve come to realize that when it comes to sensors used in semiconductor production equipment, size definitely matters. A semiconductor manufacturing facility, better known as a fab or foundry, can cost thousands of dollars per square foot to construct, not to mention the cost to maintain the facility. Therefore, manufacturers of equipment used to produce semiconductors are under pressure to reduce the footprint of their machines. As the equipment becomes more compact, it becomes more difficult to incorporate optical sensors that are needed for precise object detection.
A self-contained optical sensor that includes the optics along with the required electronics is often much too large. There simply isn’t enough space for mounting in the area where the object is to be detected. An alternative method is to use a remote amplifier containing the electronics with a fiber optic cable leading to the point of detection where the light beam is focused on the target. However, there are some drawbacks to this method that can be difficult to overcome. There are instances where the fiber optic cable is too large and not flexible enough to be routed through the equipment. Also, a tighter beam pattern is often required in semiconductor equipment for precise positioning. To provide a tighter beam pattern with fiber optics, it is necessary to add additional lenses. These lenses increase the size, complexity and cost of the sensor.
The most effective way to overcome the limitations of fiber optic sensors is to use very small sensor heads connected to a remote amplifier by electric cables, as opposed to fiber optic cables. The photoelectric sensor heads are exceptionally small, and because the cables are extremely flexible they can easily accommodate tight bends. Therefore, these micro-optic photoelectric sensors are particularly well suited for use in semiconductor equipment. The extremely small beam angles and sharply defined light spots are ideal for the precise positioning required for producing semiconductors. No supplementary lensing is required.
An excellent example of how this micro-optic sensor technology is utilized in semiconductor equipment is for precision wafer detection needed for automated wafer handling. At the end of a robot arm used for wafer handling there is a very thin end-effector known as a blade. By utilizing a very tightly controlled and focused light spot, the sensor can detect wafers just a few μm thick with extreme precision.
The combination of extremely small optical sensor heads with an external processor unit (amplifier) connected via highly flexible cables is a configuration that is ideal for use in semiconductor production equipment.