Logic / Memory

A variety of memory and logic devices, including DRAM (dynamic random access memory), SDRAM (synchronous dynamic random access memory), Flash memory (NAND or NOR), CPU (central processing unit), GPU (graphics processing unit), etc., are widely used in computers, digital music players, gaming consoles and mobile internet devices. For instance, since SDRAM was introduced to computers, further generations of SDRAM (DDR1, DDR2 and DDR3) have entered the mass market, with DDR4 currently being designed and anticipated to become available in the coming years.

Wafer-to-Wafer (W2W) Bonding
Wafer alignment and bonding are well-established technologies originating from MEMS manufacturing. Wafer-to-wafer bonding is suitable for stacking two or multiple devices with the same size, matched CTE (coefficient of thermal expansion), stringent topography control and good alignment accuracy. Aligned wafer bonding consists of three process steps; in the first step the wafer surface is prepared in terms of cleanliness, surface chemistry and intermediate layer properties, in the second step two wafers are aligned according to the alignment specification. In the last step the actual permanent bonding process takes place. For production purposes the individual processes are separated into different process modules. In the case of silicon direct bonding, an additional batch annealing step is required to increase the bond strength.

Due mainly to thermal budget issues, bonding processes compatible with TSV-interconnected CMOS wafers are limited to direct oxide bonding, metal bonding (Cu-Cu or Cu-Solder-Cu), adhesive bonding and various hybrids of those methods. The SmartView® alignment method, an indirect face-to-face alignment scheme, is designed for 3D integration. This technique uses dual microscopes with a common focal plan, enabling the use of any unique features on the front side of non-IR transparent wafers for face-to-face precision bonding.

Please see our related products EVG®540 , EVG®560 , SmartView® ,  and GEMINI® for detailed information.