Toray Industries, Inc. (headquarters: Chuo-ku, Tokyo, Japan; President: Akihiro Nikkaku; hereinafter referred to as “Toray”) today announced that it has successfully developed the world’s first positive-tone photosensitive polyimide curable at 170°C and has residual stress of 13MPa or less, which is a half of existing low-temperature curable polyimide and PBOs, by harnessing innovative molecular design and cross-linking technologies. The newly developed material, in addition to high chemical and heat resistance, has superior resolution and can be developed using conventional alkaline aqueous developer.
The new material is currently being evaluated by a number of major semiconductor manufacturers for use in next-generation semiconductors that especially require low-temperature curing and low residual stress. Toray will speed up its efforts to offer the product for full-scale marketing under the LT Series name, a new line of its photosensitive polyimide coating Photoneece®.
As IT tools such as mobile information terminals become more sophisticated and multifunctional, semiconductors, which is a key component of these tools, are required to have higher signal-processing abilities. Manufacturers have been introducing low-dielectric insulating layers and high-dielectric gate insulator films in circuit formation for making semiconductors smaller and faster, but these efforts have been hampered by issues such as deterioration in heat resistance resulting from weakened film structure and changes in performance caused by heat. While stacking of semiconductor chips and TSV structure have been increasingly adopted to increase packaging density, the bending of the wafer due to residual stress after curing as chips become thinner has been an issue.
Low-temperature curing positive photosensitive protective coating with low residual stress and fine resolution is required to boost reliability of these next-generation semiconductors.
Toray developed the new positive-tone photosensitive polyimide in response to such demand. The new molecular structure design and cross-linking design of polyimide enabled high-level chemical and heat resistance while realizing low-temperature curing at 170°C on par with epoxy resin for the first time in the world. At the same time, Toray also achieved residual stress of 13MPa, which is about half of the existing low-temperature curing materials. The new material also has superior resolution and can be developed using conventional alkaline developer, which is an environmentally friendly feature.
This material is expected to contribute to improving reliability and yields of next-generation semiconductor devices.
The market for semiconductor protective coating materials is currently estimated at about 20 billion yen and is expected to continue with the growth trend in the future. Photoneece®, Toray’s positive-tone photosensitive polyimide coating materials, has been widely adopted for its world-class photosensitivity and high dimension accuracy, and the product has the top global market share among positive-tone photosensitive polyimide products.
By adding the newly developed low-temperature curing positive-tone photosensitive polyimide to the product lineup, Toray will actively pursue new applications for the product such as protective coating, rewiring and TSV for semiconductors following next-generation semiconductors and aim for a market share in excess of 50% for positive-tone photosensitive polyimide.
Under its medium-term management program “Project AP-G 2013” launched in April 2011, Toray sets Information, Telecommunications and Electronics as one of the four major growth business fields. The company will continue to offer advanced materials by putting into practice its corporate slogan “Innovation by Chemistry” and combining resin design, micro-fabrication techniques and nanotechnology with chemistry.
The technological details of Toray’s newly developed low-temperature curing positive-tone photosensitive polyimide are as follows.
