Tight bond

Advanced adhesive dry-film materials will help drive production of the next generation of miniature electronic devices, according to an international consortium of companies developing the technology.

The materials are aimed at the emerging use of wafer-level packaging (WLP) and 3D/through-silicon via (TSV) packaging production processes in the semiconductor industry. Both of these technologies are tipped to see strong growth over the coming years, with some estimates putting the global market for the two at $600m (£420m) by 2013 and more than $1bn just a few years after that. Some analysts expect 3D/TSV wafers to make up 6 per cent of the entire semiconductor industry by 2015.

Packaging — enclosing and interconnecting the chip and any other devices into a complete assembly — is a crucial element of the manufacturing process. WLP and 3D/TSV are designed to enable the production of the smaller, more powerful and more efficient semiconductor packages needed to help keep the electronics industry on course to meet Moore's Law of continually increasing processing power.

The concept of 3D stacking, which involves placing elements on top of each other that would previously have sat side by side on a 2D silicon wafer, is at the heart of the push towards these more powerful chips.

One of the first materials designed to meet the needs of these emerging processes is a photodielectric adhesive dry film. It is about to be commercialised under the name of DuPont PerMX 3000 and is the first fruit of co-operation between a division of the global chemicals and materials giant DuPont and MicroChem, part of the Nippon Kayaku Company, a major supplier of epoxy resins to the microelectronics industry.

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have just signed an agreement to develop photo-definable epoxy-based materials for the emerging markets and said that they expect to launch a series of such materials over the next five years.

Under WLP, rather than the packaging and testing of single components, the packaging process takes place on the semiconductor wafer. According to DuPont, photodielectric adhesive dry films can allow WLP of new complementary metal oxide semiconductor cameras or radio-frequency components by creating a protective cavity around each chip in a single process involving thousands of components on a wafer.

PerMX 3000 comes in 10-, 15- and 20-micron thicknesses and, according to DuPont, gives low-temperature curing at 150C and excellent adhesion to silicon or glass. Glass or a second layer of the adhesive dry film can then be bonded on top without the need for an additional adhesive before each component is singulated (separated into individual semiconductor packages as part of the production process).

Other applications for the material include wafer-level cavity packages for electronic components, microelectromechanical systems and light-emitting diode displays and bonding for 3D packaging.

DuPont is just one of many companies seeking to create bonding and adhesives technologies that can meet the needs of the changing semiconductor industry. For example, Brewer Science, a US specialist supplier to the industry, has developed a range of materials designed to help the production of 3D stacked devices.

According to the company, the material — called WaferBond HT-10.10 — can bond a fragile device wafer to a temporary carrier, allowing the thinning and processing necessary as part of the TSV production process.

Brewer Science claims that the material's ability to withstand high-temperature processing will help the industry move towards robust, high-volume production processes needed for the future.