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Packaging practices are conducted on work unit substrates while they are temporarily held in place. This requires a simple adhesion process that enables easy removal without the burdens of complex cleaning. Substrates may be wafers, flexible displays, or components, organic or inorganic, and may contain topography such as solder bumps. The choice of a temporary bonding medium is dependent upon its ability to resist exposure to heat and chemicals. Thermal resistant materials as polyimide (PI), bisbenzocyclobutene (BCB, DOW CycloteneTM), or silicone can support processes that exceed 300°C, depending upon exposure conditions. In building flexible displays, PI materials are popular choices as a substrate processed from liquid and film forms. [1] These products may use silicone polymers, providing low outgas and inert character with an adhesive force tuned to allow substrate removal by peeling without a loss of integrity. Similar approaches are used for discrete, thin, fragile components, attached by dry bonding, processed, and removed by simple peeling practices without observed residue. Examples of die temporary bonding include encapsulation during bumping, permanent bonding, or vacuum deposition of EMI/RFI shielding. [2] The success in these and other technologies depend upon the use of the proper adhesive but most importantly, the tuning of the adhesion force. Successful tuning depends upon many factors, including substrate surface energy, texture, and the bonding process. Daetec has created adhesives used in temporary bonding processes for nearly 20yrs, applying to multiple wafer types, OLED and TFT displays, printed electronics, solar, thinning down to 4um, and thermal resistance >600°C. [3] Our experience in creating solutions for these and other industry needs will be discussed as well as the criteria to temporarily support flexible and rigid substrates of all types, sizes, and shapes.

Although several materials are commercially available as temporary adhesives in 3-D packaging, few candidates satisfy processes of elevated temperature and extreme vacuum. Whether these include thermoplastic or thermosetting polymers, success is met by their being processed in a manner that meets the customer’s low vacuum conditions. This paper presents data on several products and methods of modeling a customer’s process. Low-cost alternatives will be presented which may be easily integrated, provided that a customer’s process can be tuned to accept such materials. Low-cost temporary support materials allow grinding and polishing to <20um while also protecting front side devices from backside processing to include through silicon vias (TSVs) and the associated cleans and metallization steps. Temporary adhesives must sustain thermal resistance to 250C, vacuum conditions of 10-6 Torr, and shear forces of grinding processes. These properties are required for via etch, CVD processing (e.g. oxide deposition), and chemical use during cleaning. These efforts are aimed at simplifying the overall process, aligning chemistry, and many times, eliminating the need for complicated cleans. By tailoring a customer’s process to accept a lower-cost adhesive, new ways of simple and rapid cleaning or even detergent washable systems may be integrated. Using these approaches, a safer working environment, or green factory, may be achieved while reducing the use of organic solvents and eliminating waste. Several options will be presented for using low-cost adhesives in thinning and backside processing towards increasing throughput and reducing cost. Examples will include semiconductor wafer and die thinning and at least one non-semiconductor thin substrate practice.

Temporary adhesives are a key part to 3DIC integration. Choosing the right adhesive is critical as it defines your process, tooling needs, and by virtue of its chemistry, will control throughput and yield. Although several products and tooling exist in the market, few offer a clear path to achieve HVM at an affordable cost. [1] A wide range in materials and processes are available, most which can be tailored to a specific design or tooling objective. Multiple options in adhesives allow grinding and polishing to <20um, protection during backside processing (e.g. TSVs), thermal resistance to >400C, [2] CVD acceptance (Fig. 1), and rapid removal with cleans on a film frame (Fig. 2). Using batch processing, throughput is increased by a factor of 5 while cost is reduced by 50%, suggesting a COO that is 10% relative to current practice. Instituting simple materials and processes matched to a customer's design will provide benefits beyond cost savings, including “green factory” certification. This presentation reviews several current practices in the market and contrasts these options with alternative low-cost adhesives and processes that are tuned to a customer's product design and tooling. Examples include excerpts from handling thin substrates in semiconductor, solar, and TFT/LCD fabrication lines.