JP2000047015A - Manufacture of digital blazed diffraction grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of the diffraction grating in which no wall-shaped projection is caused. SOLUTION: This manufacturing method comprises: a first stage forming a metallic layer 2 on a substrate 1, further forming a pattern 3 having a first level on the metallic layer 2 and thereafter etching the uncovered parts of the metal layer 2 with the pattern 3 to the substrate 1; a second stage removing the pattern 3 and thereafter etching the exposed parts of the substrate 1 from the metal layer 2 to prescribed depth to form first grooves 5 that become the first level; a third stage forming a pattern 7 slightly longer than a second level, on the metal layer 2 and the first grooves 5 and thereafter etching the uncovered parts of the metal layer 2 with the pattern 7 to the substrate 1; and a fourth stage removing the pattern 7 and thereafter, etching the exposed parts of substrate 1 from the metal layer 2 to prescribed depth to form second grooves 8 that become the second level. By repeatedly performing the above third stage and fourth stage, the objective blazed diffraction grating having (n) levels can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a diffraction grating widely used for an optical pickup or the like of an optical disk device. Particularly, fabrication of a digital blazed diffraction grating in which a diffraction grating cross section is formed into a step (hereinafter referred to as a digital blazed) so that a specific wavelength can be efficiently concentrated and diffracted to a specific order on one side. About the method.

[0002]

2. Description of the Related Art A digital digital blaze diffraction grating is one of diffraction gratings used for an optical pickup of an optical disk device. The digital blaze diffraction grating generates diffracted light in the periodic pattern pitch direction by periodically arranging a pattern of step-like grooves. Here, in general, the number of steps of the digital blaze diffraction grating is called a level. In an optical disk apparatus using a digital blaze diffraction grating, a laser beam is irradiated on an optical disk, and information light reflected from the optical disk is made incident on a digital phrase diffraction grating, and follows a specific order along a periodic pattern pitch direction. An information signal is obtained by detecting the diffracted light. In order to obtain this information signal with high accuracy, it is necessary to produce a digital blaze of a digital blaze diffraction grating according to design values.

[0003] A method of manufacturing a conventional digital blaze diffraction grating will be described below. FIG. 4 is a manufacturing process diagram showing a conventional method for manufacturing a digital blaze diffraction grating. (First Step) First, as shown in FIG. 4A, after a photoresist is applied on the glass substrate 1, the mask portion 22 is formed.
A photoresist pattern 23 is formed on the glass substrate 1 by a photolithography method using a photomask 22 having a basic pitch P having a width obtained by adding the width of a to the width of the non-mask portion 22b. Thereafter, as shown in FIG.
Photoresist pattern 2 by dry etching
The groove 24 is formed by etching the glass substrate 1 other than the one covered with 3 by a predetermined depth.

(Second step) Further, after removing the photoresist pattern 23 with an organic solvent, a photoresist is applied on the glass substrate 1 again. As shown in FIG.
A photoresist pattern is formed on the glass substrate 1 and the groove 24 by photolithography using a photomask 25 having a basic pitch (1/2) P of a width obtained by adding the width of the mask portion 25a and the width of the non-mask portion 25b. 26 is formed.

(Third Step) As shown in FIG. 4D, a photoresist pattern 26 is formed by dry etching.
The grooves 27 and 28 are formed by etching the glass substrate 1 and the grooves 24 other than those covered with the. In this way, a four-level digital blaze diffraction grating can be manufactured on the glass substrate 1.

After the (third step), the 2n-level digital blazed diffraction grating has a basic pitch (1/4) P, which is the sum of the width of the mask portion and the width of the non-mask portion. 1
/ 8) Using a photomask with P,..., (1/2 ⁿ ) (n is an integer), a 2n-level digital blazed diffraction grating can be manufactured by repeating the same process.

[0007]

However, as shown in FIGS. 4 and 5A, in the (second step),
If the alignment between the photomask 25 and the glass substrate 1 on which the groove 24 is formed is not performed accurately, the photoresist pattern 26 may be formed separately at both ends on the glass substrate 1 and the groove 24. become. As shown in FIG. 5B, when dry etching is performed in this state, grooves 29 and 30 are formed corresponding to the surface of the glass substrate 1 and the groove 24, respectively, and a wall is formed between the grooves 29 and 24. Protrusion T ₁
Protrusion T ₂ between the groove 30 and the side wall 1a of the glass substrate 1
Is formed.

On the other hand, as shown in FIG. 6, the relation between the basic pitch and the diffraction efficiency tends to decrease as the basic pitch decreases. For this reason, when producing a high-level digital braze, if the basic pitch is reduced,
Since the ratio of the wall-shaped protrusions T ₁ and T _{2 to} the basic pitch increases, the wall-shaped protrusions T ₁ and T ₂ are also diffracted.
The desired diffraction efficiency of the diffracted light could not be obtained. Further, the diffraction grating when injection molding a large number of replicated using as a base type, peeling resistance at the wall-like projection T ₁ portion was reduced. The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a method of manufacturing a digital blaze diffraction grating free from occurrence of wall-like projections.

[0009]

According to a first aspect of the present invention, there is provided a method for manufacturing a digital blazed diffraction grating having an n-level digital blazed cross section. A metal layer is formed on a substrate, a first photoresist pattern having a first level digital blaze is formed on the metal layer, and the first photoresist pattern is covered with a cyan-based etchant. A first step of etching the metal layer other than the metal layer to a glass substrate, and after removing the first photoresist pattern, dry etching the glass substrate exposed from the metal layer to a predetermined depth to form the first substrate. A second step of forming a first groove which becomes a digital blaze of a level, and a digital blaze of a second level on the metal layer and the first groove. Forming a second photoresist pattern that is slightly longer than the second photoresist pattern, and then etching the metal layer other than that covered by the second photoresist pattern to the glass substrate using a cyan-based etchant; Removing the second photoresist pattern and etching the glass substrate exposed from the metal layer to a predetermined depth by dry etching to form a second groove which becomes the second level digital blaze. The third step and the fourth step are repeated to form a digital blaze diffraction grating having an n-level digital blaze.

According to a second aspect of the present invention, there is provided a method for manufacturing a digital blazed diffraction grating having an n-level digital blazed cross section. A first photoresist pattern having a digital blaze is formed, and the glass substrate other than the glass substrate covered with the first photoresist pattern is etched to a predetermined depth by dry etching. A first step of forming a first groove serving as a semiconductor substrate, and embedding a polyimide resin in the first groove, and forming a second photo on the glass substrate and the polyimide resin slightly longer than a second-level digital blaze. After forming the resist pattern, the glass substrate other than the glass substrate covered with the second photoresist pattern is dried to a predetermined depth by dry etching. A second step of forming a second groove which becomes the second level digital blaze by etching, and repeating the first and second steps to form a digital having an n level digital blaze. A blazed diffraction grating is formed.

According to a third aspect of the present invention, there is provided a method of manufacturing a digital blazed diffraction grating having an n-level digital blazed cross section. First with blazed grating
After forming a photoresist pattern, by vacuum evaporation method,
A first step of forming a first inorganic material having a refractive index substantially equal to that of the glass substrate on the glass substrate and the first photoresist pattern, and forming a second level digital blaze on the first inorganic material; A second photoresist pattern slightly longer than the first photoresist pattern is formed on the first inorganic material and the second photoresist pattern by a vacuum deposition method.
After repeating the second step of forming the inorganic material and the first step and the second step, the third step of removing the first photoresist pattern and the second photoresist pattern with hot sulfuric acid provides an n level. Digital blur
Forming a digital braze diffraction grating having a pitch.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to FIGS. The same components as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 is a sectional view showing a first embodiment of a method for producing a digital blaze diffraction grating according to the present invention. FIG. 2 is a sectional view showing a second embodiment of the method for producing a digital blaze diffraction grating according to the present invention. FIG. 3 is a sectional view showing a third embodiment of the method for producing a digital blaze diffraction grating according to the present invention. In the first and second embodiments of the present invention, a case where a three-level digital blazed diffraction grating is manufactured will be described. In a third embodiment, a case where a four-level digital blazed diffraction grating is manufactured will be described. . Generally, when an n-level digital blaze diffraction grating is formed by etching a glass substrate, a groove for forming an n-level digital blaze having an equal interval width is etched in the glass substrate. Then, an n level is formed in this groove. When an n-level digital blaze diffraction grating is formed by laminating a material having a refractive index equivalent to the glass substrate on a glass substrate, the n-level digital blaze is formed on the glass substrate. A pattern having a width that can be formed is formed, and a stepwise n-level digital blaze is formed between the patterns.

(First Step) As shown in FIG. 1A, Au and Al are deposited on a quartz glass substrate 1 by vacuum evaporation.
The metal layer 2 is formed. A photoresist is applied on the metal layer 2, and is exposed and developed using a photomask 4 on the photoresist to form a photoresist pattern 3 for forming a one-level digital blaze. Here, the photomask 4 has a width P _{1 of the} mask portion 4a.
And 1 level of the digital blur width of the combination of the width P ₂ of the unmasked portion 4b and the base pitches P - a mask for's formation, the width P ₁ of the mask portion 4a is, (2/3) P, width P ₂ of the unmasked portion 4b is (1/3) P. Therefore, the width of the portion other than the portion where the metal layer 2 is covered with the photoresist pattern 3 is (１ ／) P. Next, using a cyan-based etchant, the metal layer 2 other than the one covered with the photoresist pattern 3 is etched to the glass substrate 1 to obtain (2
/ 3) Form a metal layer 2 having a P width. By the way, since the cyan-based etchant is a selective etchant that etches a metal but does not etch glass, the etching can be stopped at the glass substrate 1. Metal layer 2 is A
In the case of 1, the metal layer 2 can be etched by a dry etching method using a phosphoric acid-based etching solution or a chlorine-based gas.

(Second Step) As shown in FIG. 1B, after removing the photoresist pattern 3 with an organic solvent,
Using a fluorine-based gas, the glass substrate 1 other than the one covered with the metal layer 2 is etched to a predetermined depth by a dry etching method to form a groove 5 having a width d ₁ and a one-level digital blaze. I do. Here, the width d ₁ of the groove 5 is (1 /
3) P, and the width d ₂ of the metal layer ₂ is (2/3) P. Incidentally, since the fluorine-based gas is a selective etching gas that etches glass and does not etch metal, the glass substrate 1 is etched without etching the metal layer 2.
Only can be etched.

(Third Step) Next, as shown in FIG. 1C, a photoresist is applied, and alignment with the glass substrate 1 on which the metal layer 2 is formed is performed using a photomask 6. After that, exposure and development are performed to form a photoresist pattern 7. Here, the photomask 6 described above is
2-level digital blur width of the combined width P ₃ of the mask portion 6a and the width P ₄ of the non-masked portion 6b and the fundamental pitch P -
The mask portion width P ₃ and the non-mask portion width P ₄ are (1+ (１ ／)) (１ ／) P.
The mask portion width P ₃ is (1/2) than the width d ₂ of the metal layer 2 of the photomask 6 (1/3) of P only longer, the photo resist pattern 7 is metal layer 2 and the groove This is to allow half of the width d1 of the _No. 5 to be continuously covered.

Here, in order to form the photoresist pattern 7 so as to be continuous with the metal layer 2 and the groove 5, the photomask 6 has a mask portion width P ₃ that is equal to the width d ₁ of the groove 5. However, since it is sufficient that the photoresist pattern 7 is formed continuously with the metal layer 2 and the groove 5, (1/1)
3) It is only necessary that the length is slightly longer than P. As a result, only the metal layer 2 in the width (１ ／) P portion other than the portion covered with the photoresist pattern 7 and the groove 5 having the width (１ ／) (１ ／) P are exposed.

(Fourth Step) Further, as shown in FIG. 1 (D), the metal layer 2 other than that covered with the photoresist pattern 7 is etched off to the glass substrate 1 using a cyan-based etching solution. As described above, since the cyan-based etchant does not etch the glass, the glass substrate 1
Is not etched, and only the metal layer 2 is etched.

Subsequently, as shown in FIG. 1E, after removing the photoresist pattern 7 with an organic solvent, the glass substrate 1 is etched to a predetermined depth by a dry etching method using a fluorine-based gas. Thus, the glass substrate 1 exposed from the metal layer 2 has a (1/3) P width of 2
A groove 8 for forming a level digital blaze and a groove 9 in which the groove 4 is deeply etched are formed. Since the width of the groove 9 is the same as the width d _{1 of the} groove 4, it is (１ ／) P. After this,
By removing the metal layer 2 by etching with a cyan-based etchant, a three-level digital blaze diffraction grating can be manufactured. At this time, the surface of the glass substrate 1 becomes a three-level digital blaze.

An n-level digital blaze diffraction grating is:
The width obtained by adding the width of the mask portion and the width of the non-mask portion is the basic pitch P, and the width of the non-mask portion is (1 / n) P,
((1+ (1/2)) P / n,..., ((N−2) + (1
/ 2)) (n) for forming each digital blaze which is P / n
-1) By repeating the above (second step) to (fourth step) using the photomasks in order, a n-level digital blaze can be formed. This n
Also in the case of producing a digital blaze diffraction grating of a level, the surface of the glass substrate 1 becomes a digital blaze of an n level as described above, and the groove 5 is formed by (n-1) times of etching. And a one-level digital blaze.

As described above, in (third step), the photoresist pattern 7 covering the metal layer 2 is formed continuously up to the groove 5, so that the photoresist pattern 7 between the glass substrate 1 and the photomask 6 can be compared. Even if the alignment is slightly shifted, the metal layer 2
Is not exposed outside the photomask pattern 7. For this reason, even if the glass substrate 1 is etched after the metal layer 2 is etched, the wall-like projections generated by the conventional method for manufacturing a digital blaze diffraction grating can be prevented. The digital blazed diffraction grating manufactured in this way can collect the diffracted light corresponding to the specific order on one side, and can accurately detect the information signal from the optical disk. Further, when a large number of replicas are injection-molded using the digital blaze diffraction grating of the present invention as a matrix, since no wall-like projections are generated, the digital blaze diffraction grating is separated from the replica. Performance can be improved. Therefore, the digital blaze diffraction grating of the present invention can be used as a master block having mass productivity.

Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those of the first embodiment of the present invention are denoted by the same reference numerals, and description thereof is omitted. The second embodiment of the present invention corresponds to (first step) and (second step) of the first embodiment of the present invention.
After removing the photoresist pattern 3 with an organic solvent, a polyimide resin is buried in the groove 5, and the steps are performed in the same steps as (3rd step) and (4th step) of the first embodiment.

Hereinafter, a second embodiment of the present invention will be described in detail. (First Step) As shown in FIG. 2A, after performing the same steps as (First Step) and (Second Step) of the first embodiment of the present invention and removing the photoresist pattern 3, A polyimide resin 10 is buried in a groove 5 which becomes a one-level digital braze.

(Second Step) Thereafter, using the same two-level photomask 6 for forming a digital blaze as used in the first embodiment of the present invention, the glass substrate 1 in which the polyimide resin 10 is embedded is used. After aligning with
Development is performed to form a two-level photoresist pattern 11 for digital blaze formation. In this case, the polyimide resin 10, so embedded in the groove 5, the width of the polyimide resin 10 is d _1. That is, polyimide resin 1
The width of 0 is (1/3) P. The alignment between the photomask 6 and the glass substrate 1 in which the polyimide resin 10 is embedded is determined by the photoresist pattern 11 having a width (１ ／).
This is performed so as to continuously cover half of the width d ₁ of the P glass substrate 1 and the polyimide resin 10, that is, (（) (（) P. Since the photoresist pattern 11 may be formed continuously on the glass substrate 1 and the polyimide resin 10, the width of the photoresist pattern 11 is (1
/ 3) It is sufficient that the length is slightly longer than P.

(Third Step) Thereafter, as shown in FIG. 2B, the glass substrate 1 and the polyimide resin 10 other than those covered with the photoresist pattern 11 are dry-etched using a fluorine-based gas. Is etched to a predetermined depth to form a groove 12 which becomes a two-level digital blaze. At this time, since the etching rate of the polyimide resin 10 is very small, the polyimide resin 10 is hardly etched.

(Fourth Step) Thereafter, the polyimide resin 10 together with the photoresist pattern 7 is removed by etching with hot sulfuric acid, whereby a three-level digital blaze diffraction grating can be manufactured. At this time, the surface of the glass substrate 1 becomes a digital blaze of three levels. Here, the photoresist pattern 11 and the polyimide resin 10 are removed using hot sulfuric acid, but may be removed by a dry etching method using O ₂ gas.

An n-level digital blaze diffraction grating is:
As in the first embodiment of the present invention, the width obtained by adding the width of the mask portion and the width of the non-mask portion is the basic pitch P, and the width of the non-mask portion is (1 / n) P, ((1+ ( 1/2)) P /
n,..., ((n−2) + (１ ／)) P / n (n−1) photomasks for forming each digital blaze are used in order, and one photomask is used. By repeating the (first step), (second step), and (third step) of the second embodiment of the present invention while using each of them, an n-level digital blaze can be formed. Also in the case of producing this n-level digital blazed diffraction grating, the surface of the glass substrate 1 becomes an n-level digital blazed in the same manner as described above, and the groove 5 is etched by (n-1) times. The grooves formed are one-level digital blaze.

As described above, the (first embodiment) of the second embodiment of the present invention
In the step), the photoresist pattern 11
/ 3) From P glass substrate 1 part (1/2) (1/3)
Since it is continuously formed up to the P width groove 5 part,
Even if the alignment between the glass substrate 1 and the photomask 6 is shifted, the glass substrate 1 is not exposed outside the photomask pattern 11. For this reason, even when the glass substrate 1 is etched, the wall-like projections generated by the conventional method for manufacturing a digital blaze diffraction grating can be prevented.
The digital blazed diffraction grating manufactured in this manner enables the condensing of diffracted light according to a specific order on one side similarly to the first embodiment of the present invention, and accurately detects information signals from an optical disk. can do.

When a large number of replicas are injection-molded using the digital blaze diffraction grating of the present invention as a matrix, there is no occurrence of wall-like projections. Can be improved. For this reason, the digital blaze diffraction grating of the present invention
It can be used as a matrix having mass productivity.

Next, a third embodiment of the present invention will be described with reference to FIG. The same components as those of the first and second embodiments of the present invention are denoted by the same reference numerals, and description thereof will be omitted. In the third embodiment of the present invention, a digital blazed diffraction grating is manufactured by laminating a material having a refractive index equivalent to that of glass on a glass substrate 1. In the third embodiment of the present invention, the surface of the glass substrate 1 has one level of digital blaze.

(First Step) First, as shown in FIG. 3A, a photoresist is applied on a glass substrate 1,
Exposure and development are performed on the photoresist using a photomask 13 to form a photoresist pattern 14. Here, the photo mask 13, two-level digital blurring of the width of the combined width P ₅ of the mask portion 13a and the width P ₆ unmasked portion 13b and the base pitch P - a mask for's formation, mask width P ₅ parts 13a is, (1/4) P,
The width P ₆ of the non-mask portion 3b is (3/4) P. Therefore, the width of the portion where the glass substrate 1 is covered with the photoresist pattern 14 is (1/4) P.

(Second Step) Next, SiO ₂ having a refractive index substantially equal to that of the glass substrate 1 is deposited on the photoresist pattern 14 by SiO ₂ 15 and a two-level digital blur on the glass substrate 1 by vacuum evaporation. SiO ₂ layer 1
5 is formed. Thereafter, as shown in FIG.
A photoresist is applied on the O ₂ layers 15a and 15b,
Exposure and development are performed on the photoresist using a photomask 16 to form a photoresist pattern 17. Here, the photomask 16 is a width of the combined width P ₇ of the mask portion 16a and the width P ₈ unmasked portion 16b a mask having a basic pitch P, the width P of the mask portion 16a
₇ is (1+ (1/2)) (1/4) P, non-mask part 1
6b has a width P ₈ (2+ (１ ／)) (１ ／) P.

For this reason, the photoresist pattern 17
Is a Si (3/4) P width formed on the glass substrate 1.
O ₂ layer 15a portion and the photoresist pattern 14 on the formed width (1/2) (1/4) P of the SiO ₂ layer 15b
The part is formed continuously. The photoresist pattern 17 is formed on the SiO ₂ layer 1 formed on the glass substrate 1.
Since the 5a partial photoresist pattern 14 formed SiO ₂ layer 15a portion on may be formed in succession, the width formed on the glass substrate 1 (3/4) P of the SiO ₂ layer 15a Only slightly longer. Thereafter, SiO ₂ is deposited by a vacuum deposition method to form an SiO ₂ layer 18b on the photoresist pattern 17 and an SiO ₂ layer 18a on the SiO ₂ layer 15 which becomes a digital blaze of three levels.

(Third Step) Next, as shown in FIG. 3C, a photoresist is applied on the SiO ₂ layers 18a and 18b, and is exposed and developed by using a photomask 19 on the photoresist. Is performed to form a photoresist pattern 20. Here, the photomask 19 is
The combined width of the width P ₉ of a width P ₁₀ of the non-masked portion 19b is a mask which is based pitch P, the width P ₉ of the mask portion 19a is, (2/4) P, unmasked portion 19b Width P
₁₀ is (2/4) P. Therefore, the photoresist pattern 20 becomes the width (2/4) SiO ₂ layer 18a and the width of the P (1+ (1/2)) to be formed on the P of the SiO ₂ layer 18b.

(Fourth Step) Next, as shown in FIG. 3 (D), SiO ₂ is deposited on the photoresist pattern 20 on the SiO ₂ layer 21b and on the glass substrate 1 by vacuum evaporation.
On the iO ₂ layer 18a, an SiO ₂ layer 21a which becomes a digital blaze of four levels is formed. Then, with hot sulfuric acid,
Along with the photoresist patterns 14, 17, 20 the SiO ₂ layers 15, 18, ₂ formed on these patterns
Remove one. Thus, a three-level digital blaze diffraction grating can be manufactured.

An n-level digital blaze diffraction grating is
The width obtained by adding the width of the mask portion and the width of the non-mask portion is the basic pitch P, and the width of the mask portion is P / (n + 1);
((1+ (1/2)) P / (n + 1),..., ((N−
1) + (1/2)) P / (n + 1) and (n + 1) photomasks having the basic pitch P are used in order,
By repeating the above (first step) to (third step), n
After forming digital blaze of level (fourth step)
Can be carried out.

Thus, as shown in (second step),
The photoresist pattern 17 is SiO ₂ layer 15 formed on the SiO ₂ layer 15 and the photoresist pattern 14
Therefore, even if the alignment between the photomask 16 and the photoresist pattern 14 on which the SiO ₂ layer 15b is formed is slightly shifted, the SiO ₂ layer 15a
And the SiO ₂ layer 18a and 15b is laminated on the SiO ₂ layer 15b, conventional digital motion - it is possible to prevent the wall-like protrusions that occurred in the manufacturing method of's diffraction grating.
The same applies to the SiO ₂ layer 21a and the SiO ₂ layer 21b. Like the first and second embodiments, the digital blazed diffraction grating manufactured as described above can condense diffracted light according to a specific order on one side and accurately detect information signals from an optical disk. can do. Further, when a large number of replicas are injection-molded using the digital blaze diffraction grating of the present invention as a matrix, since no wall-like projections are generated, the digital blaze diffraction grating is separated from the replica. Performance can be improved. Therefore, the digital blaze diffraction grating of the present invention can be used as a master block having mass productivity.

[0037]

According to the method of manufacturing a digital blaze diffraction grating according to the present invention, it is possible to manufacture a good digital blaze diffraction grating free from occurrence of wall-like projections. For this reason, it becomes possible to condense the diffracted light corresponding to the specific order on one side, and it is possible to accurately detect the information signal from the optical disc. Also, when injection molding a large number of replicas using the master mold,
Since there is no generation of wall-like projections, the releasability between the digital blaze diffraction grating and a copy thereof can be improved. As a result, it can be used as a matrix having mass productivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a method for producing a digital blaze diffraction grating according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the method for producing a digital blaze diffraction grating according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the method for producing a digital blaze diffraction grating according to the present invention.

FIG. 4 is a sectional view showing a third embodiment of a conventional method for manufacturing a digital blaze diffraction grating.

FIG. 5 is a view for explaining a problem of a conventional method for manufacturing a digital blaze diffraction grating.

FIG. 6 is a diagram showing the basic pitch dependence of the diffraction efficiency of a conventional digital blaze diffraction grating.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Metal layer, 3 ... Photoresist pattern (1st photoresist pattern), 4 ... Photomask, 5 ... Groove (1st groove), 6 ... Photomask, 7 ... Photoresist pattern (2nd) Photoresist pattern), 8
... grooves (second grooves), 9 ... grooves, 10 ... polyimide resin, 11
... Photoresist pattern, 12 ... Groove, 13, 19 ... Photomask, 14 ... Photoresist pattern, 15, 1
8, 21: SiO ₂ layer (inorganic material), 16: photoresist pattern, 17: photoresist pattern

Claims (3)

[Claims] 1. A method of manufacturing a digital braze diffraction grating having an n-level digital braze cross section, comprising: forming a metal layer on a glass substrate; and forming a first level digital braze on the metal layer. Forming a first photoresist pattern having the first photoresist pattern, using a cyan-based etchant to etch the metal layer other than the metal layer covered with the first photoresist pattern to a glass substrate; A second step of etching the glass substrate exposed from the metal layer to a predetermined depth by dry etching to form a first groove serving as the first-level digital braze; and After forming a second photoresist pattern slightly longer than the digital blaze of the second level on the first groove, a cyan-based etchant is used. A third step of etching the metal layer other than the metal layer covered with the second photoresist pattern up to the glass substrate; and removing the second photoresist pattern, and then performing dry etching to expose the metal layer from the metal layer. A fourth step of etching the glass substrate to a predetermined depth to form a second groove which becomes the second level digital brazing. The third to fourth steps are repeated to form an n level digital blur. Forming a digital blazed diffraction grating having a blazed structure. 2. A method of manufacturing a digital blazed diffraction grating having an n-level digital blazed cross section, comprising: forming a first photoresist pattern having a first level digital blazed on a glass substrate. By dry etching, the glass substrate other than covered with the first photoresist pattern is etched to a predetermined depth,
A first step of forming a first groove serving as a first-level digital blaze; and embedding a polyimide resin in the first groove, the second groove being formed on the glass substrate and the polyimide resin more than a second-level digital blaze. After forming a slightly longer second photoresist pattern, the glass substrate other than the glass substrate covered with the second photoresist pattern is etched to a predetermined depth by dry etching to obtain the second level digital blur. A second step of forming a second groove, which is to be closed, wherein the first and second steps are repeated to form a digital braze diffraction grating having an n-level digital blaze. Of producing a digital blaze diffraction grating. 3. A method for manufacturing a digital blazed diffraction grating having an n-level digital blazed cross section, comprising: forming a first photoresist pattern having a first digital blazed grating on a glass substrate. Forming a first inorganic material having a refractive index substantially equal to that of the glass substrate on the glass substrate and the first photoresist pattern by a vacuum deposition method; and forming a second level on the first inorganic material. Forming a second photoresist pattern that is slightly longer than the digital blaze, and forming a second inorganic material on the first inorganic material and the second photoresist pattern by vacuum deposition. After repeating the first and second steps, removing the first and second photoresist patterns with hot sulfuric acid. n-level digital blur by step - a method for manufacturing a's diffraction grating - digital blur and forming a's diffraction grating - digital blur with's.