When a high-precision metal microstructure is mass-produced, a process of lithographie galvanoformung abformung (LIGA) is useful. The LIGA process, which uses synchrotron radiation (SR) ray among X-rays for its high directivity, is characterized in that it allows deep lithography, processing of a structure having a height of several hundreds of micrometers with a precision on the order of micrometers, easy manufacturing of a metal microstructure having high aspect ratio, and the like. Therefore, the LIGA process is expected to find application in various fields.
The LIGA process is a processing technique combining lithography, plating such as electroforming, and molding. According to the LIGA process, a resist film is formed on a conductive substrate, for example, and then is irradiated with SR ray through an absorbent mask having a pattern of predetermined shape to perform lithography. Such lithography allows a resist structure (resin mold) to be formed corresponding to the pattern shape of the absorbent mask. A vacant portion of the resist structure is then electroformed to obtain a metal microstructure. Furthermore, a high-precision metal microstructure obtained by further electroforming may be used as a mold to perform molding such as injection molding so as to obtain a micromolded article made of resin. For example, Japanese Patent Laying-Open No. 2002-217461 discloses a method of manufacturing a metal microstructure as a mold by the LIGA process to form a micromolded article.
However, when lithography is used to form a metal microstructure, it can produce only one resist structure (resin mold) at a time. Therefore, lithography is not suitable for mass production. Furthermore, if a resin mold to be electroformed to form a metal microstructure is not fixed firmly with high precision onto a conductive substrate with an adhesive or the like, dimensional change or separation between the resin mold and the conductive substrate occurs in a subsequent step, disadvantageously resulting in a product of lower precision, a product not suitable for commercial use, and the like. Furthermore, in the case where a typical adhesive is applied to the conductive substrate to fix the resin mold thereon so as to solve the problem of a product of lower precision and a defective product, if the adhesive remains at a vacant portion of the layered structure having the resin mold, electromolding cannot be performed or insufficiently performed thereon, disadvantageously resulting in an uneven metal layer formed thereby. Furthermore, if the entire layered structure having the resin mold is etched to remove the adhesive remaining at a vacant portion thereof, the resin mold itself is damaged accordingly to a certain degree.
An object of the present invention is to provide a method of manufacturing a metal microstructure by using a resin mold, in which a mild condition can be set so as to cause less damage to a resin mold and a high-precision metal microstructure can be mass-produced by uniform electroforming.