JP2004101678A - Micro mirror and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a micro mirror with high exactness in a position and an angle, and to shift from an active alignment to a passive alignment by giving a condensing effect to a micro mirror. <P>SOLUTION: A manufacturing method is composed of a resist process and an etching process. In the resist process, a tapered resist 40 is formed by exposure shifting a focus from a surface of the resist, on a substrate 10 on which optical waveguides 21, 22, and 23 are manufactured. In the etching process, etching of the optical waveguide layers 21, 22 and 23, and the resist 40 is performed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a micro mirror and a method for manufacturing the same. For example, the present invention is applied to an optical component for transmission or reception in optical communication.
[0002]
[Prior art]
With the explosive spread of the Internet, communication backbone traffic has exploded.
Optical communication research using various electric devices and optical devices prepared for the coming ultra-high-speed and large-capacity communication is in progress.
[0003]
In the exchange of optical signals, relatively short distances such as between boards, between chips, and inside chips are performed through optical waveguides, and the optical waveguides are manufactured using various materials such as glass, semiconductor, and polymer. .
It is said that a signal processing IC using a current electric interface has a limit of 40 Gb / s signal processing.
[0004]
This is controlled by the input / output speed of the electric signal of the packaged IC. As a method for solving this problem, a high-speed signal of 40 Gb / s or more is input / output by light, and a low-speed signal of less than 40 Gb / s is an electric signal. It has been studied to input and output signals.
When performing such optical input / output, an optical path changing technique for freely routing optical wiring is required, and there is a method using a micromirror as a method.
[0005]
As a method for manufacturing a micromirror, as shown in FIG. 10, there is a method in which a mirror surface is formed by a dicing blade 3 on an optical waveguide layer 2 formed on a substrate 1 (for example, see Non-Patent Document 1). For example, a dicing error cannot be largely applied to a single-mode waveguide such as a single-mode waveguide which requires extremely high accuracy of several μm or less.
[0006]
In addition, collimating lenses and condensing lenses are often used to obtain the coupling efficiency and tolerance between the optical fiber that performs optical input and output and the optical device, but mounting by active alignment is required, which is a factor that increases the manufacturing cost of optical components It has become.
[0007]
[Non-patent document 1]
Yoshimura, Hikita, Usui, Kaneko, Toshima, Imamura, "Preparation of Polymer Optical Waveguide Film with 45 ° Micromirror", IEICE Technical Report, OCS 96-94, OPE96-94, LQE96-95, pp. 113-119, 1996
[0008]
[Problems to be solved by the invention]
In the present invention, in the manufacture of a micromirror necessary for performing optical path conversion in transmission and reception of an optical signal in optical communication, it is possible to manufacture the micromirror with high positional accuracy and angular accuracy, and by providing the micromirror with a light collecting effect, from active alignment. The problem to be solved is to shift to passive alignment.
[0009]
[Means for Solving the Problems]
A method for manufacturing a micromirror according to claim 1 of the present invention for solving the above-mentioned problems, comprising: a resist step of forming a tapered resist on a substrate on which an optical waveguide is formed by exposure shifted from the resist surface; The method includes at least two steps of an etching step of etching the optical waveguide and the resist.
[0010]
According to a second aspect of the present invention, there is provided a micromirror manufacturing method according to the first aspect, wherein in the resist step, exposure is performed a plurality of times by changing an exposure amount and a focus position using the same exposure mask. The multi-step exposure is performed by performing the step.
[0011]
According to a third aspect of the present invention, there is provided a method of manufacturing a micromirror according to the second aspect, wherein the exposure amount when the focus is most deviated in the multi-stage exposure is larger than the exposure amount when the other focuses. It is characterized by.
[0012]
According to a fourth aspect of the present invention, there is provided a method of manufacturing a micromirror according to the first aspect, wherein the etching ratio between the optical waveguide and the resist is 0.5 to 1.5. And
[0013]
A micromirror according to claim 5 of the present invention that solves the above-mentioned problem is the micromirror manufactured according to claim 1, 2, 3, or 4, wherein a radius of curvature that has been changed to a tapered resist in the resist process is changed. It is characterized by having a light collecting effect by forming a resist having the same.
[0014]
A micromirror according to a sixth aspect of the present invention for solving the above-mentioned problems is the micromirror manufactured in the first, second, third or fourth aspect, wherein the optical waveguide is a single mode waveguide. I do.
[0015]
A micromirror according to a seventh aspect of the present invention for solving the above-mentioned problems is the micromirror manufactured in the first, second, third or fourth aspect, wherein the optical waveguide is made of an organic material.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Example 1]
1 to 4 show a micromirror and a method of manufacturing the same according to a first embodiment of the present invention.
FIG. 1 shows a substrate 10 on which an optical waveguide is manufactured, before a mirror structure is manufactured. An optical waveguide 20 including a lower clad 21, a core 22, and an upper clad 23 is formed on the substrate 10. I have.
[0017]
The substrate 10 is not limited to a semiconductor substrate, but may be glass, metal, ceramic, or any other material, and the type is not limited.
Further, not only a bare substrate but also a substrate which has undergone a semiconductor process such as an IC may be used.
[0018]
In FIG. 1, a buried waveguide is shown as a representative, but the waveguide may be any type such as a rib-type waveguide or a waveguide using a photonic crystal, and the type and material are not limited.
FIG. 2 shows a state in which a resist 40 serving as a mask is applied on the substrate 10 of FIG.
FIG. 3 shows a state in which the resist 40 of FIG. 2 is exposed using the reticle 80.
[0019]
The position of the mirror is determined by the accuracy of the exposure apparatus (0.1 μm or less for a stepper), and is much higher in accuracy than the mechanical alignment of a normal microlens or micromirror.
Here, it is assumed that a thick film resist has a thickness of 10 μm as an example of the resist 40.
Exposure is performed in three stages, and the focus in the first exposure is shifted upward from the surface of the resist 40 by a distance a (hereinafter referred to as F = −a), and as shown in FIG. m ² ) (hereinafter referred to as E = A), F = −b, E = B in the second exposure as shown in FIG. 3B, and the third exposure as shown in FIG. 3C. , F = 0 and E = C.
Here, there is a relationship of a>b> 0.
[0020]
FIG. 4 shows the shape after resist development.
In the above case, as shown in FIG. 4A, it is possible to perform a flat taper processing at an angle of 45 degrees.
By changing the values of a and b and the values of A, B and C in the above exposure conditions, it is possible to control the taper angle and to give a certain radius of curvature as shown in FIG. It is.
For example, when the value of a in the first exposure in FIG. 3 is increased, the mirror angle θ is reduced, and conversely, when the value is reduced, the mirror angle θ is increased.
It is also possible to make the exposure amount when the focus is most shifted larger than the exposure amount at other focuses.
[0021]
Further, if a curved surface pattern is previously inserted as a reticle pattern, resist processing having a curvature in the horizontal direction can be performed.
When these are combined, a curved surface having a desired curvature can be processed, and a semicircular convex portion can be formed in the thick film resist 41 as shown in FIG.
[0022]
FIG. 5A shows a shape obtained by etching the pattern of FIG.
If reactive ion etching (RIE) is performed by setting the etching rate ratio (selectivity) between the organic material constituting the optical waveguide layer and the resist 40 to 1, a micromirror shape reflecting the shape of the resist 40 can be obtained.
If the selection ratio between the organic material and the resist 40 is larger than 1, the etching rate of the optical waveguide layer is increased and the mirror angle θ is increased.
[0023]
Conversely, if the selectivity is smaller than 1, the etching rate of the thick film resist is increased and the mirror angle θ is reduced.
When the selection ratio is 0.5 to 1.5, the shape of the mirror can be controlled by RIE while reflecting the shape of the resist 40.
If any resist remains, it is removed by organic washing or the like.
[0024]
Thus, as shown in FIG. 5A, a mirror is completed in which incident light coming from the left is reflected by the tapered surface and travels downward.
In the case of a resist pattern having a curved surface shape as shown in FIGS. 4B and 4C, the resist pattern is similarly etched and the curved surface pattern is transferred.
In this case, as shown in FIG. 5B, the micro mirror has a light collecting effect.
[0025]
[Example 2]
FIG. 6 shows an example in which the mirror structure shown in the first embodiment is applied to a surface light receiving device. The surface-type light receiving element 50 capable of top-surface incidence manufactured on the substrate 10 is a device such as a surface-type photodiode (Photodiode: PD), in which the PD anode electrode is capable of top-surface incidence like an annular or ITO transparent electrode. Can be applied to
[0026]
In addition, the device is applicable not only to a photodiode but also to a surface-emitting laser such as a vertical cavity surface-emitting laser diode (VCSEL). As shown in FIG. The surface light emitting element 60 can be provided, and light is propagated through a path opposite to the PD.
As shown in FIG. 8, when an optical waveguide layer is provided on the back surface of the chip, the distance from the reflection surface to the surface-type light receiving element 50 becomes long, and the diffusion of the reflected light cannot be ignored. It is considered that light collection by the curved mirror shown in FIG.
[0027]
When the present invention is applied to the substrate 10 on which the devices 50 and 60 are manufactured as described above, the optical waveguide can be manufactured by applying an organic material by a spin coating method.
In the case of an ultra-high speed optical device, the optical waveguide becomes a single mode waveguide.
In the case of a next-generation super 100G-compatible OIEC, the PD, which is the light receiving element, has a small area and is smaller than an optical fiber beam.
In these cases, it is considered essential to collect light using the curved mirror shown in FIG. 5B of the first embodiment.
[0028]
[Example 3]
The micromirror according to the above embodiment reflects light by utilizing the total reflection of the waveguide material and air.
However, when the refractive index of the optical waveguide layer falls below sin 45 ° with a 45-degree mirror, or when a mirror angle larger than 45 degrees is required, the total reflection condition is broken and the reflection efficiency cannot be obtained.
[0029]
In such a case, after the last step of the first embodiment, as shown in FIG. 9, it is possible to increase the reflection efficiency by coating the metal thin film 70 by vapor deposition or sputter deposition.
[0030]
As described above, the present embodiment relates to a method and a structure for manufacturing a micromirror.By performing exposure of the resist in multiple stages, the resist is tapered or further has a curvature. There is an advantage that various micromirrors can be formed by transferring the shape as it is to the optical waveguide.
[0031]
【The invention's effect】
As described above in detail, based on the embodiments, the present invention is a technology for manufacturing a micromirror capable of condensing light in an optical waveguide layer, and has a manufacturing accuracy and a reflection efficiency that are not available in a conventional micromirror. It is expected to contribute to the realization of optical device mounting with a fine structure in the future, as well as being an interface for current planar optical devices.
[Brief description of the drawings]
FIG. 1 is a side view showing a substrate before a micromirror is manufactured.
FIG. 2 is a side view showing a photoresist on a substrate.
3A is a side view showing a first exposure in which a focus is shifted by a distance a, FIG. 3B is a side view showing a second exposure in which a focus is shifted a distance b, and FIG. () Is a side view showing the third exposure without shifting the focus.
4A is a side view showing a planar tapered resist after resist development, FIG. 4B is a side view showing a curved tapered resist after resist development, and FIG. 4C is resist development. FIG. 5A is a side view showing a plane mirror shape, and FIG. 5B is a side view showing a curved mirror shape having a light condensing effect. is there.
FIG. 6 is a side view showing a state in which incident light propagating through an optical waveguide is reflected by a mirror and enters a surface-type light receiving element.
FIG. 7 is a side view showing a state in which light emitted from a surface light emitting element is reflected by a mirror and propagates through an optical waveguide.
FIG. 8 is a side view showing a state in which incident light propagating through an optical waveguide formed on the back surface is reflected by a mirror, and is incident on a light receiving element on the front surface while being collected.
FIG. 9 is a side view showing a state in which a metal thin film coat for improving the reflection efficiency of a mirror that does not totally reflect is formed.
FIG. 10 is a side view showing a micro mirror manufactured by dicing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 10 Substrate 2, 20 Optical waveguide 21 Lower clad 22 Core 23 Upper clad 3 Dicing blade 40 Resist 41 Thick film resist 50 Surface light receiving element 60 which can be incident on the upper surface Surface light emitting element 70 Metal thin film 80 Reticle

Claims (7)

A micromirror comprising a resist step of forming a tapered resist by exposure shifted from the resist surface on a substrate on which an optical waveguide is manufactured, and an etching step of etching the optical waveguide and the resist. Production method. 2. The method according to claim 1, wherein, in the resist step, multi-stage exposure is performed by performing a plurality of times of exposures with different exposure amounts and focus positions using the same exposure mask. 3. The method according to claim 2, wherein the exposure amount when the focus is shifted most in the multi-stage exposure is larger than the exposure amount when the other focus is performed. 2. The method according to claim 1, wherein a selectivity in etching the optical waveguide and the resist is 0.5 to 1.5. 5. The micromirror manufactured according to claim 1, wherein the micromirror has a condensing function by forming a resist having a certain radius of curvature instead of the tapered resist in the resist process. Micro mirror to do. The micromirror manufactured according to claim 1, 2, 3, or 4, wherein the optical waveguide is a single mode waveguide. The micromirror manufactured according to claim 1, 2, 3, or 4, wherein the optical waveguide is made of an organic material.

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