1. Field of the Invention
The present invention relates to a method for surface treatment.
2. Description of the Prior Art
In recent years, semiconductor devices, quartz oscillators, and the like are manufactured through processing carried out using photolithography technology or the like, that is, so-called micromachining technology is actively employed. By employing micromachining technology, it is possible to directly process substrates. For example, after one surface of a substrate is subjected to processing, the thickness of the substrate can be reduced or holes can be provided in the substrate by subjecting the other surface of the substrate, which is opposite to the processed surface, to etching or the like.
In such a case where one surface of a substrate is processed (that is, in a case where one surface of a substrate is subjected to etching), there is a necessity to protect the other surface that has been processed (hereinafter, referred to as a “processed surface”) from an etchant. From such a viewpoint, an apparatus for etching capable of subjecting only a surface opposite to a processed surface (hereinafter, referred to as a “surface to be etched”) to etching while protecting the processed surface has been developed (see Japanese Patent Laid-open No. Hei 7-111257, for example). The apparatus for etching disclosed in Japanese Patent Laid-open No. Hei 7-111257 includes a supporting jig and a pressing jig to be detachably attached to the supporting jig. When the pressing jig is attached to the supporting jig with a substrate being placed on the supporting jig, the pressing jig presses the peripheral portion of the substrate. In this way, the substrate is secured to the apparatus for etching.
Further, the apparatus for etching has O-rings provided at predetermined positions. While the substrate is being secured to the apparatus for etching, the O-rings are in close contact with a surface to be etched of the substrate. This makes it possible to prevent an etchant from being reached to a processed surface of the substrate. Therefore, even when the apparatus for etching to which the substrate is secured is immersed in an etchant, only the surface to be etched is subjected to etching.
However, in the case where such an apparatus for etching is used, the outer peripheral portion of the surface to be etched which is pressed by the pressing jig is not exposed to the etchant so that the outer peripheral portion is not treated.
As a result, a difference in level is developed on the etched surface at the boundary between a portion that has been in contact with the pressing jig (that is, an untreated portion) and a portion that has not been in contact with the pressing jig (that is, a treated portion). Such a difference in level causes a problem that it is difficult to evenly carry out various treatments for each area of the substrate in post-steps coming after etching.