JPS6033501A - Production of blazed grating - Google Patents

Abstract

PURPOSE:To improve quality of a blazed grating of a transmission type by forming the brazed grating on an org. high polymer film by utilizing the difference in etching speed between a metallic layer and the org. high polymer film with the relief grating formed on a photoresist film as a mask. CONSTITUTION:Electron ray resist film 2 is coated as an org. high polymer film on a substrate 1 and a gold layer 3 which is lower in etching rate with oxygen ion than the electron ray resist film is coated thereon. A photoresist film 4 which is lower than gold in etching rate with argon ion is coated on the surface thereof. A relief grating is formed on the photoresist film and the film is ion- etched with an argon ion beam with said grating as a mask to form a grating having roughly a rectangular section on the layer 3. A grating having roughly a rectangular section is formed on the layer 2 with the grating of the layer 3 as a mask. The resist 4 and the layer 3 are removed and thereafter the resist film is ino-etched from the direction of an arrow 5 by which the blazed grating having high quality is obtd.

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 are used in various applications, such as in holographic scanners and holographic lenses, as wavelength dispersion elements in spectrometers and hologram elements, but they generally have low diffraction efficiency, which poses a practical problem.

A blazed grating has the characteristic that it can theoretically diffract 100% of light to a specific diffraction order, but it is difficult to manufacture because the shape of the grating grooves must be controlled. The method currently considered to be practical is to ion-etch the substrate with an ion beam from an oblique direction using a relief grating made in advance as a shadow mask. Currently known methods for this technique include substrates made of gallium arsenide or polymethyl methacrylate (PMMA) coated on a glass plate.
However, the former is expensive because it is a crystal;
Furthermore, it has the disadvantage that it cannot be used as a transmission type grid because it is opaque.

On the other hand, in the latter case, even if the PMMA coated on the glass plate is sufficiently dried, when forming a relief grid with photoresist on the coating film, the PMMA film is easily dissolved and compatible with the photoresist solvent. There was a drawback that the relief grating itself could not be made of high quality, and therefore a high quality blazed grating could not be manufactured.

The object of the invention is to provide a method for producing a high-quality blazed grating of the transmission type, which eliminates the above-mentioned drawbacks.

The method for manufacturing a blazed grating of the present invention includes the steps of applying an organic polymer film to a substrate, and 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 slower argon ion etching rate than the metal layer to the metal layer; a step of forming the applied photoresist film into a relief-type diffraction grating; ion etching the metal layer with an ion beam to form a diffraction grating with a rectangular cross section on the metal layer; and ion etching the organic polymer film with an oxygen ion beam using the rectangular diffraction grating as a mask. , a blazed grating comprising the steps of 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 an oblique direction to the substrate. This is a manufacturing method.

Next, the present invention will be described in detail with reference to the drawings. 1st
The drawings to FIG. 6 are cross-sectional views for explaining one embodiment of the present invention in the order of steps.

FIG. 1 is a cross-sectional view showing a state in which an organic polymer film 2 is coated on a substrate 1, a metal layer 3 is coated thereon with a cordon, and a photoresist 4 is further coated thereon.

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

As an organic polymer film, as a result of various experiments, we used electron beam resist IL manufactured by Somar Industries, which has a fast ion etch leg speed.
-N type A was used. 5EL-N Type A is a copolymer of glycidyl methacrylate and ethyl acrylate.

The coating was applied to the substrate using a spinner. Coating thickness is approximately 1.5μ
It is m. Thereafter, in the case of a glass substrate, baking was performed at 80° C. for 30 minutes. 6 at 50°C for acrylic board
Baking was performed for 0 minutes. Next, the electron beam resist film 2
The surface of the resist film 2 was coated with gold (Au) 3 to a thickness of about 1000 angstroms by sputtering as a metal having a slower oxygen ion etching rate than the electron beam resist film 2. Subsequently, a photoresist film 4 was applied to the surface of the gold 3. As the photoresist, AZ-1350V manufactured by Sipple Co., Ltd. was used and spin coating was performed using a spinner. Baking is performed under the same conditions as for electron beam resist. Coating thickness is 0.3 μm to 0.5
It was called μIn.

Next, to form a relief grating in the photoresist,
The interference fringes were exposed onto the resist film using an interferometer using a He-Cd laser as a light source, and the resist film was developed with a developer. Second
The figure is a sectional view showing the state after development.

Instead of using a laser interferometer, a relief grating as shown in FIG. 2 can also be formed by contact printing using an emulsion mask. Next, as shown in FIG. 2, the 5-mm sample was ion-etched with an argon ion beam using an ion etching apparatus. The ion etching conditions were an argon gas pressure of 10') and an acceleration voltage of 500V. The ion etch leg rate of photoresist AZ-1350J is 300 A/min for 1 mA/cyy/' argon ion, whereas gold is approximately 1000 A/min.
It was A/min. By utilizing this difference in the cutting speed, a grating with a substantially rectangular cross section can be fabricated on the gold layer 3 using the relief grating 4 as a mask, as shown in FIG. Next, using the lattice of the gold layer 3 shown in FIG. 3 as a mask, the electron beam resist layer 2 was ion-etched with an oxygen ion beam. The ion etching conditions were an oxygen gas pressure of 2×10')-I and an acceleration voltage of 500V. The ion etch leg rate for gold is about 1000 Å/min for oxygen ions at 1 mA/m2, whereas for electron beam resist SE
L/N-A is 5330 angstroms/min, photoresist AZ-1350J is 3000 angstroms/min.
It was a minute. By utilizing this difference in etching speed, the remaining dots 4 shown in FIG. 4 can be removed by melting the gold in the next gold removal process. Potassium iodide (KI) is used to remove gold.
) and iodine (I) by dissolving the gold in a saturated solution. FIG. 5 shows a cross-sectional view after gold has been removed. Next, when the rectangular lattice shown in FIG. 5 is ion-etched with argon ions or oxygen ions from the direction shown by arrow 5,
The grating itself acts as a shadow mask for the ion beam, resulting in a blazed grating as shown in FIG.

At this time, if the ion etching time is short, a portion of the rectangular lattice will remain, and if the ion etching time is too long, the corners of the blazed lattice will become rounded, so it is important to control the ion etching time.

1 In this example, the case where 5EL-N and 1 □ 1 Eve A were used as the organic polymer film was explained.6 Other organic polymer film materials suitable for this method include 8BL-N type. 1 Electron beam resist BBR-9 similar to BBR-9, or a polymer (electron beam resist) COP) in which the two methyl groups of methacrylate are substituted with C1 and CH2CF37-, r or polymethyl methacrylate (PMMA) , polyvinyl alcohol (PVA), polyvinyl formal (PVF), or polyacetal (POM). Since these materials all have a faster oxygen ion etching rate than gold (Au), a blazed lattice can be manufactured using this method.

As described above, according to the present invention, a transmission type blazed grating of high quality can be obtained.

FIG. In the figure, l represents a substrate, 2 an organic polymer film, 3 a metal layer, 4 a photoresist, and an arrow 5 the direction of incidence of the ion beam.

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Claims (1)

[Claims] 1. A step of applying an organic polymer film to a 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 applied organic polymer film with a metal layer having a slower oxygen ion etching rate than the organic polymer film. A step of applying a photoresist film whose argon ion etching rate is slower than that of the metal layer, a step of forming the applied photoresist film into a relief-type diffraction grating, and a step of ionizing the metal layer with an argon ion beam using the diffraction grating as a mask. etching to form 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 oxygen ion beam to form a surface layer of the organic polymer film. A method for manufacturing a blazed grating, comprising the steps of forming a diffraction grating with a rectangular cross section, and after removing the metal layer, performing ion etching from an oblique direction on the substrate.