JPS6332361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a blazed grating used as a wavelength dispersion element or hologram element in a spectrometer.

Diffraction gratings have various applications as wavelength dispersion elements in spectrometers and hologram elements, but they generally have low diffraction efficiency, which poses a practical problem.

The blazed grating theoretically
Although it has the feature of being able to diffract 100% of light, it is difficult to manufacture because it requires controlling the shape of the grating grooves. Currently, what seems to be the most realistic
This method involves ion milling from an oblique direction on a relief grating made in advance, but the ion milling device is a large and expensive device that includes a vacuum system, and is not an easy manufacturing method.

An object of the present invention is to provide a simple method for manufacturing a blazed grating that does not involve ion milling.

The method for producing a blazed grating of the present invention includes a photoconductor whose exposed portion is removed by a development process, and a relief of a grating original plate having a surface relief grating that is opaque to light at the exposure wavelength of the photoconductor. A method for producing a blazed grating by the following steps: coating the photoreceptor so as to fill it in, exposing the photoreceptor coated as described above obliquely from the photoreceptor side, and developing the photoreceptor after exposure. be.

Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a sectional view showing exposure from the photoreceptor side in a state in which the photoreceptor is applied so as to substantially fill the relief of the grating original plate in the method for manufacturing a plased grating of the present invention. Figure 1 shows
This shows the case where a holographic grating is used as the grating original plate. In FIG. 1, a photoresist is applied to a substrate 1, interference fringes of laser light are recorded thereon, and a development process is performed to obtain a sinusoidal relief grating 2. Next, to make the relief grid 2 opaque,
For example, a metal film 3 is applied to the surface by vacuum deposition, plating, etc. to form an opaque surface relief grating. Next, the photoreceptor 4 referred to in the present invention is applied onto the relief to fill in the depressions on the surface of the relief. Next, in this state, exposure is performed from the direction of arrow 5. Angle 6 corresponds approximately to the blaze angle.

FIG. 2 is a diagram showing a cross section of the photoreceptor after development processing. When the photoreceptor 4 is developed after exposure as shown in FIG. 1, the hatched area 4 in FIG. This remains behind, yielding a blazed grating in the form of sawtooth grooves. A group of dotted lines 7 indicates the direction of exposure light.

The blazed grating shown in Figure 2 can be used as a reflective grating by attaching a reflective film to its surface by vapor deposition or the like. Also, if a replica is taken, it can be made into a transparent grid. In the above explanation, a case has been described in which a holographic grating is used as a grating original plate, but it is of course possible to use a grating made by photolithography as an original plate.

Figure 3 shows a cross section of a grating made by photolithography. A grid 8 is formed on the substrate 1 using metal or the like. In this case, it is desirable to use a grating in which the width of the protrusions of the grating is smaller than the period of the grating.

In the exposure process of the present invention, short wavelength light (ultraviolet rays,
It is necessary to use As the photoreceptor 4 used in the present invention, a positive resist used in the manufacture of ICs, for example AZ1350J manufactured by Shippray Co., Ltd. may be used. In this case, the exposure involves the ultraviolet rays (wavelength) of a mercury lamp.
300-400nm) with better collimation properties
Cd laser (wavelength 442nm) or Ar laser (wavelength
458 nm), it is possible to reduce the amount of light that enters the shadow part of the opaque relief 3, resulting in a good sawtooth groove shape. However, even if a laser beam is used, the light may wrap around the shadow part of the opaque relief 3 due to light diffraction. Therefore, in the second embodiment of the present invention, a positive type X-ray resist, such as PMMA (polymethyl methacrylate), is used as the photoreceptor 4, and exposure is performed with X-rays. The wavelength of X-rays is 0.5 to 3 nm, which is more than two orders of magnitude shorter than the wavelength of light (several 100 nm), so wraparound due to diffraction is small and the sawtooth groove shape is good. or,
In the case of PMMA, the deuterium discharge tube uses far ultraviolet light (wavelength 200 to 300 nm) using a xenon mercury arc lamp.
Good results can also be obtained with exposure. In the above description with reference to the drawings, a simple lattice diagram was used for convenience of explanation, but implementation of the present invention is not limited to a simple lattice diagram.
For example, even with gratings in which both the grating period and the grating direction have a distribution within the hologram, such as a zone plate used in a holographic scanner, the method of the present invention can be applied by selecting the direction of the exposure light and the angle of the exposure light. Needless to say, it can easily be made into a blazed lattice. That is, instead of exposing the entire surface of the hologram at once to the size of the hologram, an exposure method may be used that uses narrow exposure light or moves the photoreceptor so that a blaze angle is always formed.

As explained above, according to the present invention, a blazed grating having an arbitrary blaze angle can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the exposure process of the present invention;
FIG. 2 is a cross-sectional view showing the photoreceptor after development processing, and FIG. 3 is a cross-sectional view showing the original plate grating produced by photolithography. In the figure, 1 is a substrate, 2 and 8 are relief gratings, 3 is a metal film, 4 is a photoreceptor, 5 and 7 are directions of exposure light, and 6 is an angle of exposure light.

Claims (1)

[Claims] 1. A step of applying a photoreceptor whose exposed areas are removed by a development process so as to substantially fill the relief of a grating original plate having a surface relief grating that is opaque to light at the exposure wavelength of the photoreceptor. A method for manufacturing a plased grating, comprising at least the steps of: exposing the photoreceptor coated as described above obliquely from the photoreceptor side; and developing the photoreceptor after exposure.