JPS59204877A - Manufacture of hologram - Google Patents

Abstract

PURPOSE:To form a grating having a deep groove in the direction vertical to a substrate on the surface layer of an organic polymer film by providing in order a specified organic polymer film, a metallic layer, and a photoresist film on the substrate to form the photoresist film in the shape of a relief type diffraction grating, and thereafter, executing successively an etching. CONSTITUTION:An organic polymer film 2 is coated to a substrate 1, subsequently, the film 2 is coated with a metallic layer 3 whose oxygen ion etching speed is lower than that of the film 2, and next, a photoresist film 4 whose argon etching speed is lower than that of the layer 3 is coated to the layer 3. This coated film 4 is formed to diffraction grating of the relief type, the layer 3 is ion-etched by an argon beam by using this diffraction grating as a mask, a diffraction grating having a rectangular section is formed on the layer 3, subsequently, the film 2 is ion-etched by an oxygen ion beam by using this diffraction grating having a rectangular section, as a mask, and the diffraction grating having a rectangular section is formed on the surface layer of the film 2. Next, after removing the layer 3, an ion etching is executed from the direction roughly vertical to the base plate. In this way, hologram of a good quality having a deep groove is manufactured, and high diffraction efficiency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a hologram, and more particularly to a method for manufacturing a hologram of this type used for scanning an original beam.

Holograms have a variety of applications in which they are used as optical components, such as holographic scanners, holographic lenses, and splitters. Among these, holographic scanners are already commercially available as barcode reading devices, but in order to use them as original scanners for laser beam printers and the like, they must be able to scan straight lines without curves.

It is known that the most promising method for this purpose is to use simple beam holograms whose grating period is on the order of the wavelength and arranged around the circumference of the disk, whereby a straight scanning line can be obtained with a specific optical arrangement. Good for this linear scanning hologramG)
The point is that high diffraction efficiency is theoretically predicted. In other words, a grating with a sinusoidal grating cross section similar to a holographic grating has a grating period on the order of the wavelength, and if the groove depth is about 1.5 to 2 times the grating period, it can be used as a Bragge grating by more than 90%. It is known to have diffraction efficiency. For example, Figure 1 shows the calculation results of the diffraction efficiency versus the depth of the grating grooves for a grating whose grating period is equal to the wavelength. When the groove depth is 1.75 times the grating period, the maximum diffraction efficiency is 96%. can get. The reason why gratings with such high diffraction efficiency could not be obtained in the past is that with holographic gratings that have a grating period on the order of the wavelength, it is not possible to create a grating with a depth exceeding one grating period using the method of recording interference fringes on photoresist. This is because it is difficult to form, and a high-quality holographic grating cannot be manufactured over a wide area.

An object of the present invention is to provide a method for manufacturing a grating with deep grooves that cannot be formed using holographic techniques alone.

The method for manufacturing a hologram of the present invention includes a step of applying an organic polymer film to a substrate, and a step of coating the applied organic polymer film with a metal layer whose oxygen ion etching rate is slower than that of the organic polymer film. , a step of applying a photoresist film having a lower irgon ion etching rate than the metal layer, a step of forming the applied photoresist film into a relief-type diffraction grating, and using the diffraction grating as a mask, A step of ion etching the metal layer with an argon ion beam to form a diffraction grating with a rectangular cross section on the metal layer, and ion etching the organic polymer film with a single nitrogen beam using the diffraction grating with a rectangular cross section as a mask. and forming a diffraction grating with a rectangular cross section on the surface layer of an organic polymer film, and after removing the metal layer, performing ion etching from a direction substantially perpendicular to the substrate. This is the manufacturing method.

Next, the present invention will be described in detail with reference to the drawings. FIGS. 2 to 7 are cross-sectional views for explaining one embodiment of the present invention in the order of one process. Figure 2 shows 1 board 1
FIG. 2 is a cross-sectional view showing a state in which an organic polymer film 2 is coated on the substrate, a metal layer 3 is coated thereon, and a photoresist 4 is further coated thereon.

A glass board and an acrylic board were used as the substrate.

As an organic polymer film, as a result of various experiments, we used Somar Kogyo's electron beam etchant Cyst 8, which has a high ion etching speed.
EL-N type A was used. -IL-N Type A is a copolymer of glycidyl methacrylate and ethyl acrylate. The coating was applied to the substrate using a spinner.

The coating thickness is approximately 1.5 μm. After that, in the case of a glass substrate, baking was performed at 80"C for 30 minutes. In the case of an acrylic substrate, baking was carried out for 6θ minutes at 50"C.Next, electron beam resist was applied to the surface of M2 (electron beam resist). Gold (Au) is a metal whose oxygen ion etching rate is slower than that of film 2.
)3 by sputtering to a thickness of approximately 1000 angstroms. Next, a photoresist film 4 is applied to the surface of the gold 3.
was applied. As a photoresist, AZ manufactured by Silapray Co., Ltd.
-1350V was used, and spin coating was performed using a spinner. Baking was performed under the same conditions as for electron beam resist. The coating thickness was 0.3 μm to 0.5 μm.Next, in order to form a relief grating on the photoresist film, interference fringes were exposed to the photoresist film using an interferometer using a He-Cd laser as a light source, and a developer was applied. It was developed with FIG. 3 is a sectional view showing the state after development.

Alternatively, a relief grating as shown in FIG. 3 can be formed by contact printing using emulsion masses (using a laser interferometer). Next, the sample shown in FIG. 3 was etched with an argon ion beam using an ion etching apparatus. The ion etching conditions were an argon gas pressure xo-'torr and an acceleration voltage of 500V. The ion etching rate of photoresist AZ-1350J is 1 mA/
For crj argon ion, it was 300λ/min, whereas for gold it was about 1000νmin.

By utilizing this difference in etching speed, as shown in Figure S@4, a grating with a substantially rectangular cross section can be fabricated on the metal 3 using the relief grating 4 as a mask. Next, using the metal 3 grid shown in FIG. 4 as a mask, electron beam resist #2 was ion-etched with an rR:A ion beam. The ion etching conditions were an oxygen gas pressure of 2XlO-4 Torr and an acceleration voltage of 5oo.
v. Gold ion etching rate is 1 mA/ci
AO) About 1000 angstroms/min for acid Z ions, whereas for electron beam resist 5EL-L”J
-A is 5330 mm/min, photoresist AZ-1350J is 300 mm/min.

The distance was 7 angstroms. By making use of the difference in etching speed, a lattice with a rectangular cross section can be produced in the electron beam resist layer 2, as shown in Figure 5. Metal 3C+
Although photoresist 4 remains on the surface, it can be removed by melting the gold in the next gold removal step. To remove gold,
Iodide power! This was done by dissolving gold in a saturated solution of J (KI) and iodine (1).

FIG. 6 shows a cross-sectional view after the gold has been removed. Next, when the rectangle 4.b shown in FIG. 6 is ion-etched with 40,000 ions of argon or acidic ions from a direction almost perpendicular to the substrate surface,
The grating itself is etched with an ion beam to obtain a grating having a sinusoidal cross-sectional shape as shown in FIG. At this time, if the ion etching time is short, part of the rectangular lattice will be cut off, so it is important to control the ion etching time.

In this example, a case was explained in which 8FiL-N type A was used as the organic polymer film, but other organic polymer film materials suitable for this method may be similar to 5EL-N type A. electron beam resist BBR-9, or a polymer in which two methyl groups of methacrylic acid are substituted with CJi6 and CHtCF'a (111 electron beam resist C0P), or itpo IJ
Methyl methacrylate (PMMA), or polyvinyl alcohol (PVA), or polyvinyl formal (
PVF) or POM force.

Since both of these materials have a faster oxygen ion etching speed than gold (U), a hologram with one groove can be manufactured using this method.

As described above, according to the present invention, a deep one-groove σ) high quality σ] hologram can be manufactured and a high diffraction efficiency can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing calculation results of the diffraction efficiency O with respect to the depth of grating grooves, and FIGS. 2 to 7 are cross-sectional views showing the present invention in the order of steps. In the figure, l represents a substrate, 2 represents an organic polymer film, 3 represents a metal film, and 4 represents a photoresist. No. 7 5 bags in the groove / Kaku J synchronization

Claims (1)

[Claims] 1. A step of adhering a 4F5 polymer film on the substrate, a step of coating the applied organic polymer film with a metal layer having a slower oxygen ion etching rate than the organic polymer film, and a step of coating the gold PISN. a step of applying a photoresist film having a slower argon ion etching rate than the metal layer; a step of forming the applied photoresist film into a relief shop's diffraction grating; and using the diffraction grating as a mask, the metal layer is etched with an alcone ion beam. Ion-etch the layer,
A step of forming a diffraction grating with a rectangular cross section on the metal layer, and using the diffraction grating with the rectangular cross section as a mask, ion etching the organic polymer film with an rR complex ion beam to form a rectangle-1 on the surface layer of the organic polymer film. forming a surface diffraction grating;
A method for manufacturing a hologram, comprising: after removing the metal layer, performing ion etching in a direction substantially perpendicular to the substrate.