Craig Rollin Yeakle

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.

57.3: Transparent Silicon‐based Low‐k Dielectric Materials for TFT‐LTPS Displays

Silsesquioxane resins are of particular interest for use as insulator materials in flat panel display applications due to their balance of electrical, optical, and mechanical properties. In this study, a series of HSQ and MSQ resins were synthesized and characterized in terms of their structures and thin film properties. These resin systems yielded high quality thin films with high modulus, good adhesion to silicon and glass substrates, high optical transparency (>98 % @ 300 − 800 nm), good planarization properties, excellent gap fill capability, good thermal and chemical stability to various photoresist and ITO etch chemicals necessary for the fabrication of flat panel displays.

Silicone soft and transparent layer for wafer-level fabrication of optical applications

Dow Corning developed a spin-on dielectric polydimethylsiloxane material suitable for wafer-level packaging in optical applications. The product is optically transparent in the visible range and has a very low Young modulus, inducing a low residual stress when applied at a wafer level. The product has been specifically designed for use as a thin protection or passivation layer of devices and it can also be used as permanent bonding adhesive. Specific attention in the formulation of the product was considered in order to minimize the amount of volatiles being released in the processing steps and a volatile-free layer over a broad temperature range is created at the end of the process. In the discussion section of this paper, a first section will explain the processing conditions of this wafer-level packaging solution and the key benefits will be exposed. A second section will present the volatile outgasing study in order to demonstrate that pending proper care is considered in the processing steps, the silicone solution can be used in a manufacturing environment and that a volatile-free layer is created at the end of the process. A third section will deal with the optical properties of this product and the stability after UV exposure will be exposed. The dielectric strength stability of the silicone layer will be investigated in a fourth section, followed by a study of the low mechanical stress induced by this product coated on a silicon wafer. A brief summary of all the benefits brought by this new technology will finally by summarized in the conclusion section.

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.