JPH05281885A - Formation of hologram - Google Patents

Abstract

PURPOSE:To form a hologram of desired depth and duty in good reproducibility. CONSTITUTION:The forming method of the hologram includes the following processes. A resist film 2 is applied to specified film thickness on a substrate 1 and exposed to specified exposure by interferencial exposure method (first process). The resist film 2 is developed to form a resist pattern 3 (second process). Then the resist pattern 3 is used as a mask to etch the substrate 1 (third process).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram producing method. Holograms are widely used in bar code reading scanners, printer scanners, and the like, and it is required to create holograms with high diffraction efficiency and stable performance.

[0002]

2. Description of the Related Art FIG. 7 is a process diagram showing a conventional hologram forming process. First, apply the resist film 12 to the substrate 11,
Two-beam interference exposure using object light and reference light is performed on the resist film 12 (A). Then, the resist film 12 is developed to form a resist pattern 13 (B). Then, a Ni film is formed on the surface of the resist pattern 13 by vapor deposition or the like, and a sufficiently thick Ni layer 14 is formed by electroforming (C). Then, the resist pattern 13 and the substrate 11 are separated from the Ni layer 14, the photopolymer 15 is dropped on the surface of the Ni layer 14, and the glass substrate 16 is overlaid (D). Then Ni layer
14 is peeled off, and ultraviolet rays are irradiated from the glass substrate 16 side to UV cure the photopolymer 15 (E).

The shape of the hologram formed by the above method is determined by the shape of the resist pattern 13 as is clear from the above steps.

[0004]

On the other hand, FIG. 4 shows an ideal cross-sectional shape of a resist pattern, where m is the pattern width, v is the inter-pattern distance, and t is the depth. Further, the duty of the resist pattern is D = m from m and v
/ (M + v).

Generally, the diffraction efficiency of a hologram has a depth t,
These values have to be set so as to maximize the diffraction efficiency, because they are greatly affected by the duty D. However, the cross-sectional shape of the resist pattern that is actually formed is complicated as shown in FIG. 5 and is composed of a curved line.
Are different. Therefore, even if the duty D that maximizes the diffraction efficiency is calculated, it is difficult to accurately form a resist pattern having such a duty D.

Further, the resist pattern is relatively brittle and susceptible to deformation. As a result, when the groove is deepened or the duty D is reduced to maximize the diffraction efficiency,
As shown in FIG. 8, the resist pattern is deformed, and even if the process shown in FIG. 7 is performed based on such a resist pattern, the expected improvement in diffraction efficiency cannot be obtained.

Therefore, an object of the present invention is to create a hologram having an arbitrary depth and duty with good reproducibility.

[0008]

The first object of the present invention is to apply a resist film 2 having a predetermined film thickness to a substrate 1 and expose the resist film 2 with a predetermined exposure amount by an interference exposure method. Hologram production characterized by including a step, a second step of developing the resist film 2 to form a resist pattern 3, and a third step of etching the substrate 1 using the resist pattern 3 as a mask. Method, or prior to the first step, the first pattern is formed based on the relationship between the duty and the depth of the resist pattern obtained by forming a resist pattern exposed by an interference exposure method and measuring the cross-sectional shape thereof. This is achieved by the hologram forming method described above, which comprises setting the resist film thickness and the exposure amount in the step of.

[0009]

The hologram pattern obtained by etching the substrate 1 using the resist pattern 3 as a mask is less likely to be deformed than the resist pattern 3. Therefore,
A stable hologram can be created regardless of the pattern shape.

Further, prior to the first step, the resist film thickness and the exposure amount for obtaining a predetermined duty are obtained from the measurement of the sectional shape of the resist pattern prepared in advance,
Since the resist pattern for hologram production is formed by using the resist film thickness and the exposure amount obtained in this way, it is possible to obtain a hologram having the above-mentioned predetermined duty with good reproducibility.

[0011]

FIG. 1 is a process drawing showing an embodiment of the present invention.
In this embodiment, before entering the hologram forming process shown in FIG. 1, the resist film is exposed and developed with a constant exposure amount by the two-beam interference exposure method using the object light and the reference light, and the above-described FIG.
A resist pattern as shown in is created. And
The cross-sectional shape is measured. FIG. 5 shows the pattern width m and the inter-pattern distance v corresponding to each depth t.
FIG. 2 shows the relationship between t, m, v measured from the resist pattern shown in FIG. 5 and the duty D and the depth t, and FIG. 3 shows the relationship between the exposure amount L and the depth t. It shows the relationship.

On the other hand, the duty D that gives the maximum diffraction efficiency
Is calculated in advance, and the depth t corresponding to this duty D is read from FIG. 2 and used as the resist film thickness. Further, the exposure amount that gives the depth t obtained as described above is read from FIG. 3 and is used as the actual exposure amount.
For example, if the duty that gives the maximum diffraction efficiency is D ₁ , the resist film thickness may be set to t ₁ and the exposure amount may be set to L ₁ from FIGS. 2 and 3, respectively.

After the above preparation, as shown in FIG. 1, a resist film 2 having a film thickness t ₁ is applied to the substrate 1. The resist film thickness t ₁ can be accurately set by adjusting the viscosity of the resist and the rotation speed of the spinner used for applying the resist film. Then, exposure is performed with an exposure amount L ₁ by the two-beam interference exposure method using the object light and the reference light (A). Then, the resist film 3 is developed to form a resist pattern 3 (B). The width of the resist pattern 3 and the distance between the patterns are m ₁ and v ₁ , respectively, as is clear from the above-mentioned conditions.

Then, using the resist pattern 3 as a mask, CF ₄ gas is flown to perform reactive ion etching (RIE) (C). According to the RIE method, since the lateral etching is suppressed, the pattern width does not deviate from m ₁ even when the groove is deep, and the duty D ₁ does not change. Then, the resist pattern 3 is removed by O ₂ gas plasma to obtain a hologram (D).

According to the above process, by controlling the resist film thickness and the exposure amount, a hologram having an arbitrary duty can be created with good reproducibility. FIG. 7 shows a sectional shape of the hologram obtained as described above.

[0016]

As described above, according to the present invention, it is possible to create a hologram having an arbitrary duty and depth with good reproducibility without being restricted by the pattern shape. Useful for improving performance.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of the present invention,

FIG. 2 is a diagram showing a relationship between duty and depth of a resist pattern,

FIG. 3 is a diagram showing a relationship between a depth of a resist pattern and an exposure amount,

FIG. 4 is a view showing a cross-sectional shape of an ideal resist pattern,

FIG. 5 is a diagram showing a cross-sectional shape of an actual resist pattern,

FIG. 6 is a diagram showing a cross-sectional shape of a hologram,

FIG. 7 is a process chart showing a conventional example,

FIG. 8 is a cross-sectional view showing the problems of the conventional example,

[Explanation of symbols]

1, 11 substrate, 14 Ni layer,
2, 12 resist film, 15 photopolymer, 3, 13 resist pattern, 16 glass substrate,

Claims (2)

[Claims] 1. A resist film having a predetermined film thickness on a substrate (1)
The first step of applying (2) and exposing the resist film (2) with a predetermined exposure amount by an interference exposure method, and developing the resist film (2) to form a resist pattern (3)
A method for producing a hologram, comprising: a second step of forming a substrate; and a third step of etching the substrate (1) using the resist pattern (3) as a mask. 2. Prior to the first step, a resist pattern exposed by an interference exposure method is formed, and the cross-sectional shape is measured to obtain the resist pattern based on the relationship between the duty and the depth of the resist pattern. The hologram forming method according to claim 1, wherein the resist film thickness and the exposure amount in step 1 are set.