Ranjith Samuel John

Graded index silicone waveguides for high performance computing

We report on the optical functionality and key performance metrics of graded and step index multimode silicone waveguides. Results demonstrate optical losses of <;0.01 dB/crossing for graded index waveguides and 0.19-0.024 dB/crossing for step index.

Low cost, room temperature debondable spin-on temporary bonding solution: A key enabler for 2.5D/3D IC packaging

We report the development of a bi-layer spin on temporary bonding solution (TBS) which eliminates the need for specialized equipment for wafer pretreatment to enable bonding or wafer post treatment for debonding. Thus it greatly increases the throughput of the temporary bonding/debonding process. It also provides a total thickness variation (TTV) of less than 1 μm for spin coated films on both 200 mm and 300 mm wafers which enable the TTV of 300 mm bonded pairs to be 2-3 μm for bumped wafers using 70 and 100 μm thick adhesive films after backgrinding for an unoptimized bonding process. Furthermore, we have demonstrated the chemical and thermal stability of both the material and the bonded pair by exposing the bonded wafer pair to common chemicals (phosphoric acid, nitric acid, organic solvents etc.) and temperature conditions (up to 300 C) used in the TSV process. Additionally, the time taken for the entire spin coat-bond-debond process was less than 15 minutes with room for further improvement. Based on the current results, it is expected that the current bi-layer based temporary bonding solution has the potential to play an important role in enabling the high volume manufacturing of 2.5D/3D IC stacking.

Thermally Stable, Low Loss Optical Silicones: A Key Enabler for Electro-Optical Printed Circuit Boards

We report the development and characterization of a low loss polymer waveguide material with a polysiloxane backbone for enabling the new generation electrooptical printed circuit boards (PCBs). The polymer was designed to have low optical loss of <;0.05 dB/cm at 850 nm and low residual stress to withstand the harsh reliability requirements during PCB integration. The thermomechanical properties of the polymer were tuned to exhibit a residual stress of ~1 MPa over a temperature range of 25 °C to 200 °C in ambient air. Multimode polymer waveguides were fabricated using the polysiloxane polymer and embedded in a six-layer PCB architecture that was subjected to lamination, through-hole via drilling, plating, and IPC shock test (immersion) in solder bath at 288 °C. Eight channels of multimode polymer waveguide spirals of length 1.2 m were fabricated and the insertion loss measured after waveguide fabrication, lamination, and solder reflow. The deviation in insertion loss as a function of the PCB fabrication process was less than 3% with final insertion loss after solder reflow being 0.052 +/- 0.002 dB/cm. This finding presents an optical waveguide material which when embedded in a PCB fabricated using an industry standard process meets reliability requirements while maintaining optical performance.

Advances in manufacturing of optical silicone waveguides for high performance computing

We report recent advances of polymer waveguide silicone materials for the scaled production of optical waveguides. The development of materials is described with the latest generation achieving low loss waveguides of <;0.04 dB/cm at 850 nm and fabrication times of less than 10 minutes.

Cost-effective temporary bonding and debonding material solution towards high-volume manufacturing 2.5D/3D through-silicon via integrated circuits

Dow Corning developed a silicone-based room temperature temporary bonding and mechanical debonding solution to overcome the current limitations of existing materials and processes for next generation of 2.5D & 3D IC packages; The material properties make possible the use of a simple process sequence which includes material spin coating, room temperature bonding and mechanical debonding. Whereas the Dow Corning bi-layer approach has been reported recently [1], this study focuses on bonding and debonding performance obtained with SUSS MicroTec automated bonding and debonding equipment and for adhesive layer thickness in the range of 100 μm. The results reported in this study, particularly the good process control and ability to debond with a low force (<;30 N) while keeping the overall sequence short and thus cost-effective, make the Dow Corning temporary bonding and debonding approach a versatile solution towards the validation of the TSV technology for a wide range of 2.5D and 3D stacked ICs applications.

An innovative and low cost Bi-layer method for temporary bonding

The purpose of this work was to demonstrate the compatibility of Dow Cornings temporary bonding solution with EVGs 850XT universal temporary bonding and debonding platform. The proposed process made use of well-known processing steps and processing modules like spin coating. The process consisted of a release layer (Dow Corning® WL-3001 Bonding Release) and an adhesive layer (Dow Corning® WL-4050 or WL-4030 Bonding Adhesive) using an EVG® 850TB - 300 mm XT frame. Both layers of material were applied by spin coating on the device wafer side. In the frame of this study, silicon carriers were used. Bonding was performed under vacuum at room temperature. A post bonding bake step was applied using a hotplate. After subsequent backside processing steps, the room temperature debonding was performed.