Active solid-state devices (e.g. – transistors – solid-state diode – Physical configuration of semiconductor – Mesa structure
Patent
1990-09-28
1992-11-24
Hille, Rolf
Active solid-state devices (e.g., transistors, solid-state diode
Physical configuration of semiconductor
Mesa structure
501136, 252520, 427 79, 257920, H01L 2992, C04B 3546, B05D 512, H01B 106
Patent
active
051667592
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a semiconductor-type laminated ceramic capacitor with a grain boundary-insulated structure and a method for producing the same, and more particularly to a ceramic capacitor which absorbs both low voltage noises and high frequency noises under the normal operational conditions as a capacitor, works as a varistor against invading high voltage loads such as pulses and electrostatic charges, thereby protecting built-in semiconductors and electronic equipment from being damaged by abnormal voltage loads such as noises, pulses and electrostatic charges arising from surrounding electronic equipment, wherein characteristics of said ceramic capacitor being stable to temperature changes.
BACKGROUND ART
Recently, semiconductor elements such as IC and LSI are widely used in electronic devices and equipment to realize multifunctional applications of the equipment and to make the equipment light, small and handy. However, the use of many semiconductor elements makes the electronic devices less resistant to disturbance by electric noises. The conventional method to protect the electronic devices from invading electric noises is to integrate by-pass capacitors such as film capacitor, laminated ceramic capacitor and semiconductor ceramic capacitor into the power line of IC and LSI. These capacitors display excellent performances in absorbing low voltage noises and high frequency noises. They are, however, so impotent to high voltage pulses and electrostatic charges that malfunctionings of the equipment, break-down of semiconductors and/or capacitors themselves occur frequently when the electronic equipment are invaded by high voltage pulses or electrostatic charges. Therefore, these technical problems in the conventional capacitors should be improved.
A new type capacitor, which has sufficient resistance and excellent absorbing ability to pulses as well as good noise absorbing ability and stability to temperature and frequency changes, was developed and disclosed in Japanese Laid-Open Patent Publication No. 57-27001 and Japanese Laid-Open Patent Publication No. 57-35303 (corresponding to U.S. Pat. Nos. 4,519,942 and 4,541,974) etc., wherein a varistor function was added to a ceramic capacitor made of SrTiO.sub.3 series of ceramic materials and the capacitor was defined as "a grain boundary insulated, semiconductor type ceramic capacitor having a varistor function" (hereinafter referred to as a ceramic capacitor with varistor function). This ceramic capacitor with varistor function works as a varistor when high voltage pulses and electrostatic charges invade it, and absorbs low voltage noises and high frequency noises as a conventional capacitor, thereby protecting the electronic equipment and built-in semiconductors from abnormal high voltage noises, pulses and electrostatic charges generated by surrounding electronic equipment and devices, and providing wide application fields of the capacitor.
Since the electronic parts are made to be more sophisticated, lighter, smaller, and more handy, ceramic capacitors with varistor function are also required to be smaller but higher in performance. The effective electrode area of the conventional single-plate type ceramic capacitor with varistor function will be, however, decreased when the capacitor is miniaturized, resulting in the reduction of electric capacitance and hence inferior reliability of the capacitor. A capacitor having laminated structure of the electrode is devised to solve the aforementioned problem, wherein the effective electrode area is expected to be increased. However, the ceramic capacitor with varistor function is conventionally manufactured by the process comprising a step coating the surface of SrTiO.sub.3 type semiconductor element with oxides, followed by a thermal diffusion process to form an electric insulating layer in the grain boundaries. It is recognized to be very difficult to manufacture "a laminate type ceramic capacitor having varistor function" (hereinafter referred to as a laminated ceramic
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Kobayashi Kimio
Shiraishi Kaori
Takami Akihiro
Ueno Iwao
Wakahata Yasuo
Hille Rolf
Matsushita Electric - Industrial Co., Ltd.
Saadat Mahshid
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