Glass carriers have proven to provide a solution for carriers during wafer thinning operations for 3D-IC (Three-Dimensional Integrated Circuit). The attributes of the glass carrier, such as total thickness variation (TTV), flatness and properties such as coefficient of thermal expansion (CTE), are extremely important in their functional performance. Optimization of Corning's fusion forming process gives a platform that is very well suited to generate high precision glass carriers. This process provides glass at target thickness (no grind/polish required) with a pristine surface, extremely tight TTV, low warp/bow, and thickness tolerance over large volumes of material. Given that this material is formed in sheets as large as three meters in size, there is tremendous flexibility in the size of the wafers; as well as ability to scale to high volume manufacturing in a cost effective way. Furthermore, the ability to alter glass composition provides the opportunity to optimize material properties, such as CTE. This is important to accommodate the needs of various device structures which require thinning. Non-uniformities (TTV, flatness) in the carrier directly impact the accuracy of the thinned wafer TTV. As important as the low TTV and warp/bow provided by Corning's optimized fusion process, is the method in which these attributes are characterized. Corning ® Tropel ® has developed a novel distance measuring interferometer based on a frequency stepping laser that is well-suited to characterize the flatness and TTV of glass wafers. The work presented here will highlight the importance of high precision carriers and metrology techniques used to characterize and qualify these materials. The impact these have on the TTV of a bonded stack is just as critical. The ability to leverage all of these tools to provide bonded stacks with extremely low TTV and highly uniform silicon wafers after thinning operations will be demonstrated.