JPH06258511A - Mold for producing diffraction grating and its production - Google Patents

Abstract

PURPOSE:To reduce the production cost of the mold for producing a diffraction grating having the decreased for product deviation in blazed wavelengths. CONSTITUTION:Grooves 2 having level differences 2a are formed by etching on the surface of a substrate 1 made of quartz, etc., and thereafter, the substrate 1 is subjected to a film-forming treatment by sputtering, by which thin films 3a to 3c are formed on the bases 2b of the grooves 2, the surfaces of the level differences 2a and the remaining flat surfaces 2c of the substrate 1, respectively. The thicknesses of the respective thin films 3a to 3c are increased from the center of the length of the grooves 2 toward both ends by controlling the moving speed of a moving shutter in sputtering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffraction grating manufacturing mold for manufacturing a blazed diffraction grating used for color separation of a digital color reader by a replica method, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, color image information on a document surface is imaged on a line sensor surface such as a CCD through an optical system, and color image information is output by using an output signal from the line sensor. Various devices have been proposed for digitally reading. In particular, as disclosed in Japanese Patent Laid-Open No. 3-181269, when a light flux from a color image on the surface of a document is condensed by an imaging optical system and focused on the line sensor, the light flux is For example, as a device for color separation into three colors of red, green and blue, one using a 3p prism, one using two beam splitters for color separation, and one using a transmission type blazed diffraction grating Has recently been developed, and recently, an apparatus using a reflection type blazed diffraction grating has attracted attention because it can be easily simplified and highly accurate reading is possible.

When a reflection type blazed diffraction grating is used, color shift may occur depending on the incident angle when the color-separated light flux enters the line sensor.
An emission type telecentric system in which the incident angle is always zero is used in the imaging optical system, or as shown in FIG. 6, the pitch P of the diffraction grating G is increased from the center to the periphery of the diffraction grating substrate and the diffraction grating is used. The height h of G and the step are reduced from the center to the periphery of the diffraction grating substrate, and in particular, in the latter case, the imaging optical system does not have to be complicated, and the diffraction grating substrate is a curved plate. Since there is no need to use the above, there is a great advantage that the manufacturing cost is low, and both the blazed wavelength shift and the diffraction imaging position shift can be eliminated. Further, as a method of mass-producing such a diffraction grating in a large amount at low cost, a molding die for manufacturing the diffraction grating is produced by etching a quartz substrate or the like, and is used to diffract an ultraviolet curable resin material. A replica method has been developed in which a grating is transferred and then its surface is covered with a reflective film.

[0004]

However, according to the above-mentioned conventional technique, in order to inexpensively manufacture the diffraction grating by the replica method, it is desired to manufacture the molding die at low cost first. In order to prevent the blazed wavelength shift, it is necessary to lower the height and step of the diffraction grating from the center to the periphery of the diffraction grating substrate, which complicates the manufacturing process of the mold and may increase the manufacturing cost. is there. That is, although such a mold is usually manufactured by a well-known photolithography patterning process and etching process, a highly accurate gradient is provided on the bottom surface or step of the diffraction grating transfer recess by controlling the etching depth. Are extremely difficult to manufacture, and the complexity of control causes a significant increase in the manufacturing cost of the mold.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a highly accurate gradient on the bottom surface and steps of the diffraction grating transfer recess without increasing the manufacturing cost. An object of the present invention is to provide a mold for manufacturing a diffraction grating and a method for manufacturing the same.

[0006]

In order to achieve the above object, a mold for manufacturing a diffraction grating according to the present invention comprises a substrate having a recess having the shape of at least one diffraction grating, and The thin film is formed on each of the bottom surface and the step, and the film thickness of the thin film changes in the length direction of the recess.

The method for manufacturing a mold for manufacturing a diffraction grating according to the present invention comprises a step of forming a recess having at least one diffraction grating shape on the surface of the substrate, and a step of forming a recess on the substrate. The method comprises depositing a thin film on the surface, and changes the deposition amount of the thin film in the length direction of the recess.

[0008]

By changing the thickness of the thin film, it is possible to provide highly accurate gradients on the bottom and steps of the recess. Since complicated control such as control of the etching depth is not required, there is no fear of increasing the manufacturing cost.

[0009]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partial perspective view showing a part of one embodiment, in which a mold M ₁ for manufacturing a diffraction grating of this embodiment is
A groove 2 having a shape of a plurality of diffraction gratings each having a step 2a is formed on the surface of a substrate 1, and a step 2a of each groove 2, a bottom surface 2b and a flat surface 2c between each groove 2 are formed with SiO. _{The second} thin films 3a to 3c are formed. The width of the step 2a of each groove 2 of the substrate 1, the bottom surface 2b and the width of the flat surface 2c between each groove 2 are from the center of the substrate 1 to each edge 1 respectively.
The height of the bottom surface 2b of each groove 2 from the back surface of the substrate 1, the height of the step 2a, and the height of the flat surface 2c are constant from the back surface of the substrate 1. Thin film 3a deposited on step 2a, bottom surface 2b and flat surface 2c
As shown in FIG. 3, the film thicknesses of .about.3c increase with a predetermined gradient from the center of the substrate 1 indicated by the line C--C toward each edge 1e. Therefore, the heights h ₁ to h ₃ of the surfaces of the thin films 3a to 3c also increase from the center of the substrate 1 toward the edges 1e. That is, the substrate 1 and the thin films 3a to
The diffraction grating transfer recess S ₁ of the molding die M ₁ for manufacturing a diffraction grating composed of 3c has a groove and a step that become shallower with a predetermined gradient from the center to each end edge, and the adjacent groove and the step Each pitch gradually increases from the center of the substrate 1 to each edge 1e, and the diffraction grating transferred to the substrate of the ultraviolet-curing resin material diffraction grating substrate using this pitch has a predetermined distance from the center to the periphery. There is a step whose height decreases due to the gradient, and the pitch of the adjacent steps increases from the center to the periphery of the diffraction grating. A color separation device using such a diffraction grating can prevent color shift due to a blazed wavelength shift or a diffraction grating image shift position without using a complicated image forming optical system.

The mold M ₁ for making a diffraction grating was manufactured by the following method.

First, the length is 70 mm, the width is 30 mm, and the thickness is 3.
4 (a) and FIG. 4 (a) by a known photolithographic patterning process and etching process on a quartz substrate 1 having a surface precision and a surface roughness of 10 Å (rms) of 3 Newtons in mm, φ50. As shown in (b), a predetermined number of grooves 2 having a step 2a and a bottom surface 2b were formed. The width of each flat surface 2c formed between the step 2a of each groove 2 and the bottom surface 2b and the adjacent groove 2 is gradually increased from the center of the substrate 1 indicated by the line C-C toward each edge 1e. On the other hand, the heights of the bottom surface 2b, the step 2a, and the flat surface 2c of the groove 2 from the back surface of the substrate 1 are constant.

The etching process was performed under the following conditions.

Etching depth 620 nm Power consumption 100 W Etching time 16 minutes Etching gas CF ₄ Etching gas pressure 40 mTorr Etching gas flow rate 15 SCCM Then, the steps 2a, the bottom surface 2b and the flat surface 2c of each groove 2 are respectively formed by a known sputtering process. SiO whose thickness gradually increases from the center to the periphery of the substrate 1.
₂ thin films 3a to 3c were deposited. The film thicknesses of the thin films 3a to 3c are 20 nm at the center of the substrate 1 and 40 nm at both ends, respectively.

FIG. 5 shows a sputtering apparatus for producing such thin films 3a to 3c by sputtering deposition. The apparatus comprises a decompression chamber 10 having a gas inlet 10a and an exhaust port 10b, and a decompression chamber. The substrate 1 is held by the anode 11, which is composed of an anode 11, a cathode 12, and a movable shutter 13 which are provided inside the substrate 10. The cathode 12 is held by a water cooling holder 14, and the water cooling holder 14 is a decompression chamber 10.
Through the insulator 15 provided on the wall of the wall, and is connected to a supply source of cooling water (not shown). The cathode 12 is connected to a high voltage power supply 17 by a wiring 16 penetrating the water cooling holder 14. After the decompression chamber 10 is decompressed to a predetermined vacuum pressure by a vacuum pump connected to the exhaust port 10b, a sputtering gas such as Ar gas is introduced from the gas introduction port 10a to form a plasma formed between the anode 11 and the cathode 12. Activated and collided with the cathode 12, and the surface of the cathode 12 is sputtered.
It vapor-deposits on the board | substrate 1 through the slit 13a. At this time, the moving shutter 13 is reciprocally moved in the width direction of the substrate 1, and the moving speed is set so that the slit 13a moves to the substrate 1
It is delayed at a predetermined rate as it approaches each edge 1e from the center. Thereby, the deposition amount of the particles is increased from the center of the substrate 1 toward each edge 1e with a predetermined gradient.

According to this embodiment, a predetermined gradient can be provided on the bottom surface and the step of the diffraction grating transfer recess by changing the deposition amount of each thin film, so that complicated control is required for the etching process and the like. Therefore, it is possible to inexpensively manufacture a mold for manufacturing a diffraction grating with a small blaze wavelength shift.

Needless to say, the number of steps of the mold for manufacturing the diffraction grating is not limited to one, and two or more steps can be provided if necessary.

[0018]

Since the present invention is configured as described above, it has the following effects.

It is possible to provide highly accurate gradients on the bottom surface and the step of the diffraction grating transfer recess without increasing the manufacturing cost. As a result, it is possible to reduce the manufacturing cost of the molding die for manufacturing the diffraction grating with less blaze wavelength shift. As a result, it is possible to reduce the manufacturing cost of the diffraction grating having a small blazed wavelength shift and to realize an inexpensive and high-performance digital color reader.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing a part of a mold for manufacturing a diffraction grating according to an embodiment.

FIG. 2 is a partial cross-sectional view showing a part of the mold for manufacturing the diffraction grating of FIG.

FIG. 3 is an elevational view showing the entire mold for manufacturing the diffraction grating shown in FIG.

FIG. 4 shows a mold for manufacturing a diffraction grating before vapor deposition of a thin film, (a) is a partial sectional view showing a part thereof,
(B) is an elevation view showing the whole.

FIG. 5 is an explanatory diagram illustrating a sputtering apparatus that deposits a thin film.

FIG. 6 is an explanatory diagram illustrating a blazed diffraction grating.

[Explanation of symbols]

 1 Substrate 2 Groove 2a Step 2b Bottom 2c Flat 3a-3c Thin film

Claims (6)

[Claims] 1. A substrate comprising a recess having at least one diffraction grating shape, and a thin film formed on each of the bottom surface and the step of the recess, wherein the thickness of the thin film is Mold for manufacturing a diffraction grating, characterized in that the recess changes in the length direction. 2. The film thickness of the thin film increases from the center in the lengthwise direction of the recess toward each end.
Mold for manufacturing the diffraction grating described above. 3. The method comprises the steps of forming a recess having at least one diffraction grating shape on the surface of a substrate, and depositing a thin film on the surface of the substrate on which the recess is formed. A method of manufacturing a mold for manufacturing a diffraction grating, wherein the amount is changed in the length direction of the recess. 4. The method of manufacturing a mold for manufacturing a diffraction grating according to claim 3, wherein the recess is formed by etching. 5. The method of manufacturing a mold for manufacturing a diffraction grating according to claim 3, wherein the thin film is deposited by sputtering. 6. The diffraction according to claim 5, wherein in the sputtering for depositing the thin film, the deposition amount of the thin film is changed by controlling the moving speed of a moving shutter provided between the cathode and the substrate. Manufacturing method of forming die for lattice production.