SANYO Semiconductor Manufacturing Co., Ltd. (hereunder『SSMC』, President: Atsushi Bando) and Hayashi Pure Chemical Ind., Ltd. (hereunder『HPC』, President: Masakatsu Irie) succeeded in co-developing high performance silicon etching chemical that does not damage aluminum interconnection in semiconductor process.
Introducing our silicon etching chemical after aluminum interconnection process makes anisotropic etching possible to etch silicon purposely and speedily.
Aiming to improve process accuracy and reliability for SSMC’s IC and LSI, the chemical has been supplied to SSMC by HPC, at the same time the chemical is also been scheduled to recommend to multiple users not only for semiconductor’s use, but also as the chemical which is expected to be applied in the process of MEMS products expected to rise up in coming market.
Recent silicon devices are applied to various MEMS sensor devices, not only to application of usual semiconductor products as IC and LSI etc. Micro machining process technology is introduced to satisfy requirements as high integration, fine pitch, high sensitivity and high performance. In the micro machining technology, the anisotropic etching technology of silicon is introduced to form desired three-dimensional structures. Up until now, aluminum and its alloy have been used for electrode and interconnection material on the silicon semiconductor, but those materials are easily corroded with previous anisotropic etching chemicals.
For silicon anisotropic etching, adding certain kinds of silicon, oxidizer, and reducer into etchant have been tried in order to prevent corrosion of aluminum and its alloy formed on wafer before Si anisotropic etching.
However adding these additives gives anticorrosive effect by sacrificing desired etching rate which greatly dominates productivity on the process.
In view of this background, our joint development by Hayashi Pure Chemical and SANYO Semiconductor Manufacturing was started aiming at High Performance Anisotropic Etching with enough Anti-Corrosive Effect for aluminum and its alloy.
Ⅲ.Results of Development
Our joint development succeeded in development of High Performance Anisotropic Silicon Etchant. The chemical newly developed at last achieved Superior Anisotropic Silicon Etching Performance and excellently Long Life on the process in addition to the performance aimed at the beginning of joint development.
Main performance of this chemical is as follows.
(1) Anti-Corrosive Effect
Achieved enough Anti-Corrosive Effect of aluminum (Al) and its alloy (AlCu etc.)
Comparison of AlCu Etching Rate at 75℃
Previous chemical (including TMAH5% and Si as component)：22 nm/min.
Our Newly Developed Chemical：0 nm/min.
(2) High Etching Rate
Achieved Superior Silicon Etching Rate
Comparison of Silicon Etching Rate at 75℃
Previous chemical(including TMAH5% and Si as component)：47.0 μm/h
Our Newly Developed Chemical：59.0 μm/h
(3) Superior Anisotropic Silicon Etching Performance
1) Micro Pyramid Controllable and Etching with Flat Bottom possible. (Fig.1)
2) Anisotropic Etching is easily available even for silicon surface deteriorated by dry etching process. (Fig.2)
3) Running Cost Reduction is possible by constant etching rate and long life.
Comparison of silicon etching rate after 7 days run at 75℃
Initial state ：59.0 μm/h
After 7 days：59.1 μm/h
Ⅳ.Explanation of items
(1) MEMS (Micro-Electro-Mechanical Systems)
MEMS means the technology that forms minute machine elements on the silicon substrate by micro processing technology of semiconductor, and formed structure with this technology. It is sometimes called Micro Machine.
Applications are acceleration sensors and pressure sensors, also medical application is expected.
(2) Micro pyramid
A pyramidal nodule in micron order which makes problems on silicon trench etching process. (Fig.3)
Hayashi Pure Chemical Ind., Ltd.
Overseas Sales Department, Electronic Material Head Office
3-2-12 Uchihiranomachi, Chuo-ku, Osaka, 540-0037, Japan
TEL +81-6-6910-7336 FAX +81-6-6910-7330
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