Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
2002-03-28
2004-03-23
Chen, Kin-Chan (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C216S013000, C438S756000
Reexamination Certificate
active
06709988
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing an electronic component, comprising the steps of providing a laminate having a layer construction of a conductive inorganic material layer—insulating layer—conductive inorganic material layer or a layer construction of conductive inorganic material layer—insulating layer, in which the insulating layer can be patterned by wet process, and wet etching the insulating layer to pattern the insulating layer, an electronic component per se produced by said process, and a suspension for a hard disk drive.
BACKGROUND ART
In recent years, rapid development of semiconductor technology has led to rapid progress of a reduction in size of semiconductor packages, the adoption of multipin, the adoption of fine pitch, minimization of electronic components and the like. That is, the semiconductor field has entered the so-called “age of high density packaging.” Regarding printed wiring boards, the above tendency has also led to a change from single side wiring to double side wiring and, in addition, the adoption of a multilayer structure and a thickness reduction (Iwata and Harazono, “Denshi Zairyo (Electronic Material),” 35 (10), 53 (1996)).
A pattern formation method used in the formation of wiring and circuits in such electronic components comprises etching a conductive inorganic material layer on a substrate in a layer construction of conductive inorganic material layer (mainly metal layer)—insulating layer—conductive inorganic material layer (mainly metal layer) with an acidic solution, such as a ferric chloride solution, to form wiring, then subjecting the insulating layer, for example, to dry etching such as plasma etching, or wet etching such as etching with hydrazine, to remove the insulating layer to form a desired shape for layer-to-layer continuity purposes (Japanese Patent Laid-Open No. 164084/1994), and connecting the wirings to each other, for example, through plating or electrically conductive paste. Another pattern formation method (Proceedings of the 7th Symposium of Japan Institute of Electronics Packaging, issued in 1999) comprises providing an insulating layer in a desired form using a photosensitive polyimide (Japanese Patent Laid-Open No. 168441/1992) or the like and then plating gaps to form wiring.
In recent years, for electrical appliances, particularly personal computers, there is a tendency toward lower prices. For members, components and the like used in them as well, there is a tendency toward lower prices. Therefore, how to produce electronic components at low cost is a great issue.
At the present time, rapid expansion of production of personal computers has led to increased production of hard disk drives incorporated in the personal computers. A component, in the hard disk drive, called a “suspension,” which supports a head for reading magnetism, is being shifted in its main products from one, wherein copper wiring is connected to a stainless steel plate spring, to one called a “wireless suspension” comprising copper wiring which has been connected directly to a stainless steel plate spring, from the viewpoint of coping with the size reduction.
The above wireless suspension is mainly prepared using a three-layer material of conductive inorganic material layer (mainly metal layer)—insulating layer—conductive inorganic material layer (mainly metal layer). An example of the layer construction of the three-layer material is such that a copper alloy foil is stacked on one side of an insulating layer and a stainless steel foil is stacked on the other side of the insulating layer. The wireless suspension is a member, which is scanned on a disk being rotated at a high speed, and, thus, fine vibration is applied to the wireless suspension. For this reason, the adhesive strength of wiring (conductive inorganic material layer) to the insulating layer is very important, and the wireless suspension should satisfy strict specifications. Since hard disks are devices for recording information thereon, a high level of data read/write reliability is required and strict specifications should also be satisfied for the adhesive strength of wiring and useless materials, such as dust, and outgas produced from the suspension.
In the laminate such as the three-layer material used in electronic components, in general, in order to render the coefficient of thermal expansion of the conductive inorganic material layer and the coefficient of thermal expansion of the insulating layer identical to each other for preventing the warpage of the substrate, a low-expansion insulating layer, particularly a low-expansion polyimide, is in many cases included. In the laminate in which only a low-expansion polyimide is used in the insulating layer, polyimide films, for example, KAPTON (tradename; manufactured by Du Pont-Toray Co., Ltd.), Upilex (tradename; manufactured by Ube Industries, Ltd.), and APIKAL (tradename; manufactured by Kanegafuchi Chemical Ind. Co., Ltd.), are used as the low-expansion polyimide. A metal layer (mainly copper) is formed, for example, by sputtering or electroless plating on the surface of the low-expansion polyimide film, and, thereafter, the thickness of the conductor layer is increased by electroplating (hereinafter referred to as “type-I laminate”). Another type of laminate is such that an insulator having a three-layer structure, wherein a layer of an adhesive (for example, an epoxy adhesive) other than polyimide is formed on the surface of a low-expansion polyimide, that is, having a layer construction of adhesive other than polyimide—low-expansion polyimide—adhesive other than polyimide, is provided and a conductor foil is adhered to the insulating layer by thermocompression bonding (hereinafter referred to as “type-II laminate”). A further type of laminate is such that an insulator having a three-layer structure, wherein an adhesive polyimide layer is formed on the surface of a low-expansion polyimide, that is, having a layer construction of adhesive polyimide—low-expansion polyimide—adhesive polyimide, is provided and a conductor foil is adhered to the insulating layer by thermocompression bonding (hereinafter referred to as “type-III laminate”).
In the type-I laminate, since the insulating layer is formed of a polyimide having a single composition, the warpage is less likely to occur. Further, a thin metal layer can be formed. Therefore, this is advantageous for the formation of fine wiring. On the other hand, in the type-II laminate and the type-III laminate, since the conductor layer is formed by thermocompression bonding, the conductor layer can be selected from various types. For example, the preparation of a laminate using a rolled copper foil, a stainless steel foil or the like is possible. The type-II laminate advantageously has good adhesion. For the type-III laminate, since the adhesive layer is formed of highly heat-resistant polyimide, the heat resistance is advantageously good. Further, both the type-II and type-III laminates have an additional advantage that the thickness of the metal layer can be increased.
Since spring properties are required of the wireless suspension, a stainless steel foil is in many cases used as the metal layer. An example of the laminate structure is copper foil—adhesive polyimide—low-expansion polyimide—adhesive polyimide—stainless steel. In the conventional wireless suspension, since the etching area of the insulating layer is large, instead of laser beam etching, plasma etching, which belongs to the same category of process, i.e., dry process, is mainly used for patterning of the insulating layer. In the plasma etching, however, the etching rate is low, and, thus, the time necessary for etching is long. Further, since sheet-by-sheet production is adopted, the productivity is low. Moreover, the apparatus for plasma etching is so expensive that the production cost is disadvantageously very high.
For the above reason, patterning of the insulating layer by a wet process, which is high in etching rate and thus is high in productivity and can realize low appara
Amasaki Hiroko
Kawano Shigeki
Momose Terutoshi
Sakayori Katsuya
Togashi Tomoko
Chen Kin-Chan
Dai Nippon Printing Co. Ltd.
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