Optical Coatings on ASIC Wafers
CMOS Technology Shifts to Wafer Level Packaging
The use of CMOS (Complementary Metal-Oxide Semiconductor) image sensing technology has grown considerably over the last several years. According to a market report by Yole Development, the CMOS image sensing market will reach $10.4B by 2016 with > 4.1B sensors being manufactured. Much of the volume growth can be attributed to its use in mobile and tablet applications. Beyond mobile, the versatility and functionality of CMOS technology is finding its way into many other applications that will continue to drive growth. Some of these other applications include gesture control and 3D imaging, smart TV, clinical medical applications, wearable devices and automotive controls.
This growth has been enabled by improvements in CMOS technology and a decrease in manufacturing costs. This makes it affordable in some applications, such as mobile, to use multiple sensors in one device. One particular innovation has had a significant impact on cost, as well as on overall package size; that is, the shift from discretely packaged sensors to wafer level packaging. Using this technology, a “window” wafer is bonded directly to the wafer containing the CMOS devices and then diced to create a batch of finished sensors.
Filters Play Key Role in CMOS
Filtering plays an important role in CMOS imaging and sensing. Color filtering is typically generated through the use of organic dyes in the form of a Bayer pattern directly on the device. More complicated spectral filtering and blocking can be achieved in several ways. The first method is to put the filter on the cover wafer prior to bonding. This technique allows for standard dyes to be used for color generation and achieve improved spectral performance through the filter. For purely sensing applications, Materion has developed an exciting new capability to deposit the spectral filter directly onto the device. Through the use of photolithography, we can selectively place the filter on each individual device. Since standard cover glass can then be used, this provides a cost-effective way of achieving targeted spectral performance.
One concern for both wafer level and device level coatings is the defect level in the coating. Close proximity of these coatings to the surface of the device make it extremely important that the defect size and quantity are minimized. For the last several years, Materion has concentrated efforts on developing new low defect optical coatings with much success.
Deposition Capabilities Expanded to 300mm Wafers
Materion has invested heavily in upgrading our photolithographic and coating capabilities for wafer level and device level filter coating. Our completion (in 2014) of a state-of-the-art, Class 1000 clean room facility dedicated to wafer level and device level optical filter manufacturing has uniquely positioned us to provide optical solutions in these areas. We also subsidized semiconductor grade photolithography tools that are capable of handling wafer sizes up to 200mm and create features down to about 10um in size. In keeping with our mission to be the leader in this area, we’ve recently expanded our deposition capabilities to 300mm wafers and plan to expand our photolithography capabilities there as well.
The investments we have made are allowing Materion to bridge the gap between optical coating and semi-conductor grade processing. This is a critical aspect, since in the case of detector level coatings; our customers are submitting fully functional wafers for processing with expectations of very high yields.
Materion for Innovative Optical Coating
As one of the world’s largest manufacturers of precision optical filters, Materion Precision Optics provides high value solutions for our customers’ most demanding applications. These applications include but are not limited to: multispectral imaging, wavelength sorting, machine vision, automotive systems, industrial control & automation, medical devices, consumer electronics, CMOS sensors, Si wafers, biometric detectors, gesture control filters, gas sensing filters, light absorption, and more.
For more information on wafer level and device level optical coatings, please contact David Harrison, Business Development Manager, David.Harrison@Materion.com