Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal
Reexamination Certificate
2000-06-27
2001-10-16
Lebentritt, Michael (Department: 2824)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
C438S158000, C438S161000
Reexamination Certificate
active
06303402
ABSTRACT:
This application is based on an application No. 11-189131 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming a microscopic opening serving as a near field light generating device by a photolithographic technique using illumination light.
2. Description of the Background Art
In conventional optical recording, a recording density has an upper limit determined by the diffraction limit (which means that the size of a spot focused by diffraction of light is not infinitesimal), and hence only marks having a size on the order of magnitude of the wavelength of light (hundreds of nanometers) can be read or written.
In recent years, a technique which utilizes near field light (evanescent light) to increase the recording density in optical recording has attracted particular attention. A recording method which utilizes the near field light makes it possible to read marks as small as tens of nanometers in size beyond the diffraction limit of light by reducing a spacing between an optical head and a recording medium down to tens of nanometers. On similar principles, it also becomes possible to form microscopic patterns beyond the diffraction limit by using the near field light.
In these techniques using the near field light, an optical probe is desired which can form a microscopic light spot with as high an intensity as possible. To this end, there has been proposed a fiber probe having an opening at a sharp-pointed tip of a fiber. However, the size of the opening of a probe on the order of 100 nm causes an extremely low intensity of transmitted light, for example, on the order of {fraction (1/100)} or below, resulting in low efficiency of use of light.
To overcome this problem, a technique has been proposed which produces a tapered microscopic opening by anisotropically etching a thin film of single crystalline silicon and directs light into the microscopic opening to generate near field light from the microscopic opening (as disclosed in U.S. Pat. No. 5,689,480).
Unfortunately, the technique disclosed in U.S. Pat. No, 5,689,480, in which etching is used to produce the tapered microscopic opening, has poor reproducibility of the microscopic opening, presenting difficulties in maintaining good product quality. This technique also requires precise control of etching time, resulting in low yields.
SUMMARY OF THE INVENTION
The present invention is intended for a method of manufacturing a near field light generating device. According to the present invention, the method comprises the steps of: forming a first opaque layer on a transparent substrate, the first opaque layer having a first opening and an opaque portion; forming a transparent layer on the first opaque layer; forming a photosensitive layer on the transparent layer; exposing the photosensitive layer to illumination light transmitted through the first opening to form a microscopic region of an exposed photosensitive material; forming a second opaque layer on the transparent layer and the microscopic region; and removing the microscopic region and a portion of the second opaque layer overlying the microscopic region to form a second opening in the second opaque layer.
The method of the present invention uses the first opening as a photomask for the formation of the second opening, to accurately form the second opening, thereby easily forming a microscopic opening having good product quality. Furthermore, when forming a plurality of microscopic openings in parallel, this method eliminates the need for the positioning of a plurality of photomasks relative to each other in the step of forming the second openings, to easily form a large number of microscopic openings.
Preferably, the transparent layer is transparent to light for use in generating near field light.
The microscopic opening thus formed can generate near field light.
Preferably, the transparent layer has a thickness ranging from about one-tenth to about twice the wavelength of the illumination light.
This allows the first opening and the second opening to differ in size.
According to another aspect of the present invention, the method comprises the steps of: forming a first opaque layer on a transparent substrate; forming a first opening in the first opaque layer; forming a transparent layer on the first opaque layer; forming a photosensitive layer on the transparent layer; exposing the photosensitive layer to illumination light transmitted through the first opening to form a microscopic region of an exposed photosensitive material; forming a second opaque layer on the transparent layer and the microscopic region; and removing the microscopic region and a portion of the second opaque layer overlying the microscopic region to form a second opening in the second opaque layer.
The present invention is also intended for a device for generating near field light, the device being manufactured by the steps consisting essentially of: forming a first opaque layer on a transparent substrate, the first opaque layer having a first opening and an opaque portion; forming a transparent layer on the first opaque layer; forming a photosensitive layer on the transparent layer; exposing the photosensitive layer to illumination light transmitted through the first opening to form a microscopic region of an exposed photosensitive material; forming a second opaque layer on the transparent layer and the microscopic region; and removing the microscopic region and a portion of the second opaque layer overlying the microscopic region to form a second opening in the second opaque layer.
It is therefore an object of the present invention to provide a method of easily forming a large number of microscopic openings having good product quality.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
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Hatano Takuji
Sato Akira
Lebentritt Michael
Minolta Co. , Ltd.
Morrison & Foerster / LLP
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