Stacking of Known Good Rebuilt Wafers without TSV - Applications to Memories and SiP

Abstract

The 3-D interconnection started at 3D PLUS in 1996 and led to the stacking of nearly all types of analogical and logical components, sensors, MEMS, etc for the Hi-Rel field (Space, Defence, Medical, Industrial). This technology is extremely robust (−130°C +175°C, 40000g), and is fully qualified by all worldwide most important Space Agencies and for Defence applications. A technological break started in 2002 ; It consisted in another 20 to 30 reduction factor of the weight and volume of these 3-D modules.The Z pitch is 100μm and the X Y size is given by the size of the larger die plus 100μm of polymer around it. This is a stacked of Known Good Rebuilt Wafer of full wafer level technique. The dice are received in wafers and following operations are carried out :- Pick, flip and place of the good dice on a “sticking skin”- Moulding of the whole of this « pseudo wafer » in order to obtain what we call a « Known Good Rebuilt Wafer (KGRW) ». These two first steps are already developed by Infineon and mainly Freescale (RCP technique up to 300mm)- Stacking and gluing of KGRW 1, 2, 3…, n, by means of an adhesive film- Dicing of these stacked rebuilt wafers by techniques identical to the dicing of standard wafers- Metallization of the dicing streets with nickel + gold by electroless chemical plating identical to the UBM plating technique- Direct laser patterning by laser with our edge connection technique up to 100μm pitch. Below this pitch, the Thru Polymer Via (TPV) are made through the stacked wafers. The equivalent pitch will be 20μm. it can be noticed that the shielding can be made on the dicing street.- Electrical test at the stacked wafer level- Singulation of the 3D modules This approach allows using standard dice without any modification. It is multi sources and the stacking of the good rebuilt wafers allows to get an excellent yield. A development agreement has been signed with a semiconductors manufacturer. A development is in progress with the most worldwide important manufacturer of smart cards in order to integrate 5 levels of dice (including a MEMS) within a cavity of 550 μm inside the 800μm SIM card. Other applications with MEMS will be presented:- “Abandoned Sensors” for Heath Monitoring of the aircraft structure developed during the European Program: “e-Cubes” ,- Gyroscope with 6 MEMS,- Micro camera for endoscopy…- Medical applications with an important development made for 3 major pacemaker manufacturers. This « full wafer level » approach will allow to build System in Package (SiP) or “Abandoned Sensors” at very low costs, since the process uses mainly the steps of wafers building; the “panelization” allows to be in parallel processing from A to Z steps. Moreover, the use of Known Good Rebuilt Wafer like the RCP allows stacking Good wafer at the reverse what is impossible with the wafer to wafer approach.