JP2006023536A - Method of manufacturing optical switch, and optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical switch with which the occurrence of roughness and tapering of a mirror surface is prevented without increasing the production step. <P>SOLUTION: The manufacturing method is provided for the optical switch consisting of at least a substrate section, a movable section on which a mirror section is provided and a beam section which supports the movable section with respect to the substrate section. In the manufacturing method, a dummy structure is formed at the front section of the mirror section and a certain amount of the dummy section is removed by the step in which a silicon active layer of an exposed region is eliminated for a certain amount by dry etching or the dummy structure is removed by the step in which an intermediate layer is removed excluding a portion of the layer by wet etching. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical switch manufacturing method and an optical switch.

  Conventionally, it is known that a silicon substrate is processed using MEMS (Micro Erectro Mechanical Systems) technology to form a micro structure such as an optical switch. FIG. 4 is a perspective view (a) and a top view (b) showing an example of an optical switch manufactured by the MEMS technology. The drive system is an electrostatic drive type, and the movable electrode portion 1a having a comb shape and the beam portion 1b that supports the movable electrode portion 1 are integrally formed to constitute the movable portion 1, and the support electrode portion 3 is used as a base point. The silicon support substrate 2c as the base is held in a hollow state. A fixed electrode portion 4 having comb-tooth electrodes 4a is provided at a position facing the movable electrode portion 1a. When a voltage is applied between the facing electrodes, electrostatic attraction is generated between the comb teeth (between the electrodes). And the entire movable part 1 moves, and functions as an optical switch by deflecting the optical path of light irradiated to the mirror 5 on the prismatic mirror base 5a provided at the tip of the movable part 1.

FIG. 5 is a view for explaining the method of manufacturing the optical switch, and is a cross-sectional view of a main part for each step (cross section AA in FIG. 4), but hatching is omitted. Hereinafter, a conventional method of manufacturing an optical switch will be described with reference to FIG.
Step (a): A masking resistant film 6 is formed on the entire surface of the silicon active layer 2a of the silicon laminate (SOI substrate) 2 including the silicon active layer 2a, the intermediate layer 2b, and the silicon support substrate 2c by sputtering or the like. . The resistant film 6 is made of, for example, chromium (Cr), and is a film that is resistant to silicon deep anisotropic reactive ion etching and hydrofluoric acid (HF).
Step (b): The resistant film 6 is patterned into a desired pattern shape by etching to form a first masking pattern 6a. When patterning, first, a photosensitive resist (positive type) is uniformly applied to the upper surface of the resistant film 6 by spin coating. After coating, the photomask having a desired masking pattern shape is covered, and the resist is exposed to ultraviolet light. After the exposure, the resist in the exposed region is removed using a developer. Thereafter, using the resist pattern formed by the above steps as a mask, the resistant film 6 in the exposed region is removed by wet etching.
Step (c): Using the first masking pattern 6a formed in the previous step (b) as a mask, the exposed region of the silicon active layer 2a is subjected to deep anisotropic reactive ion etching to be an intermediate layer serving as an etching stop layer. Etch until layer 2b is exposed.
Step (d): The first masking pattern 6a used as a mask in the previous step (c) is removed by wet etching.
Step (e): The resistant film 7 made of chromium (Cr) is formed on the entire upper surface of the silicon active layer 2a including the exposed upper surface of the intermediate layer 2b.
Step (f): The resistant film 7 formed in the previous step (e) is patterned into a desired pattern shape by wet etching to form a second masking pattern 7a. The patterning method is the same as that in the step (b) and will not be described.
Step (g): Using the second masking pattern 7a as a mask, the silicon active layer 2a in the exposed region is etched by a certain amount (for example, 50 μm in the depth direction) by deep anisotropic reactive ion etching. (Mirror 5 is formed)
Step (h): The second masking pattern 7a used as a mask in the previous step (g) is removed by wet etching.
Step (i): The intermediate layer 2b is selectively removed by isotropic wet etching except for a part (a connection part between the movable part 1 and the silicon support substrate 2c), and a part of the silicon active layer 2a ( The movable part 1) is separated from the silicon support substrate 2c. As an etchant used for wet etching, for example, hydrofluoric acid (HF) may be used. However, other etchants may be used as long as they selectively etch only the intermediate layer 2b.

  The conventional manufacturing method of the optical switch is as described above, but the conventional manufacturing method has the following problems. When the silicon active layer 2a is dry-etched in the step (g), the mirror 5 is formed. However, the surface of the mirror 5 is roughened, and the mirror surface is formed in a tapered shape, so that the mirror accuracy is improved. It cannot be secured.

  The cause is due to a defect of deep anisotropic reactive ion etching using a so-called Bosch process. That is, the Bosch process is a technique in which dry etching is performed by alternately supplying SF6 gas and CF4 gas as an etching gas at intervals of about 10 seconds, and etching proceeds when SF6 gas is supplied. The reaction product generated when CF4 gas is supplied is attached to the wall surface of the etched part, and the etching proceeds while solidifying the reaction product on the wall surface of the etched part. Yes.

  The etched sidewall is vertically etched in the narrow groove portion such as the movable electrode 1a and the comb-tooth electrode 4a shown in FIG. There is a tendency for the lower part to become thinner as it progresses. This seems to be due to so-called microloading in which the etching rate is higher in a wide etching area (opening area) than in a narrow area. (For example, Patent Document 1)

WO01 / 053194

  When the surface of the mirror surface is rough or the mirror surface is tapered, the reflection performance as an optical switch is deteriorated.

  The present invention has been made in view of the above problems, and an object thereof is to prevent the mirror surface from being rough and the mirror surface from being tapered without increasing the number of manufacturing steps.

In a method of manufacturing an optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports the movable part with respect to the base, at least an intermediate layer is a silicon support substrate and a silicon active layer A first masking step of forming a first masking pattern on the surface of the silicon active layer, and using the first masking pattern as a mask, the silicon active layer in the exposed region is The step of removing by dry etching, the step of removing the first masking pattern, the second masking step of forming a second masking pattern on the surface of the silicon active layer, and using the second masking pattern as a mask, Removing a certain amount of the silicon active layer in the exposed region by dry etching;
A method for manufacturing an optical switch, comprising: removing the second masking pattern; and removing the intermediate layer by removing a part of the intermediate layer by wet etching,
A dummy structure is formed in the front part of the mirror part, and the dummy structure is removed by a certain amount in the step of removing a certain amount of the silicon active layer in the exposed region by dry etching, or a part of the intermediate layer is removed by wet etching. It is set as the manufacturing method of the optical switch removed by the process of removing and removing.

In the manufacturing method of an optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports the movable part with respect to the base, at least,
A first masking step of forming a masking pattern on the surface of the silicon active layer of the silicon laminate formed by sandwiching the intermediate layer between the silicon support substrate and the silicon active layer;
A second masking step of forming a second masking pattern so as to cover the first masking pattern, and a step of removing the silicon active layer in the exposed region by dry etching using the second masking pattern as a mask And removing the intermediate layer exposed by dry etching of the silicon active layer by dry etching, removing the second masking pattern, and removing the second masking pattern. Using the first masking pattern as a mask, removing the silicon support substrate and the silicon active layer in an exposed region by a certain amount by dry etching, removing the first masking pattern, and the remaining intermediate Remove all but one layer by wet etching A method of manufacturing an optical switch and a step,
A dummy structure is formed in front of the mirror part, and the dummy structure is removed by a certain amount in a step of removing the silicon support substrate and the silicon active layer in the exposed region by dry etching, or the intermediate layer is wet etched. The manufacturing method of the optical switch that is removed in the step of removing by removing a part by the above.

In the manufacturing method of an optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports the movable part with respect to the base, at least,
A first masking step of forming a first masking pattern on the surface of the silicon active layer of the silicon laminate formed by sandwiching the intermediate layer between the silicon support substrate and the silicon active layer; and covering the first masking pattern A second masking step of forming a second masking pattern, a step of removing the silicon active layer in the exposed region by dry etching using the second masking pattern as a mask, and the second masking pattern Removing only the intermediate layer exposed by dry-etching the silicon active layer by dry etching, and exposing the second masking pattern by removing the second masking pattern Using the first masking pattern as a mask, the silicon support substrate in the exposed area And a step of removing a predetermined amount of the silicon active layer by dry etching, a step of removing the first masking pattern, and a step of removing a remaining portion of the intermediate layer by wet etching. In this manufacturing method, a dummy structure is formed in the front part of the mirror part, and the dummy structure is removed in a certain amount in the step of removing the silicon support substrate and the silicon active layer in the exposed region by dry etching. Or a method of manufacturing an optical switch in which the intermediate layer is removed in a step of removing part of the intermediate layer by wet etching.

  The first masking pattern is made of Cr, and the second masking pattern is a method of manufacturing an optical switch made of a photosensitive resist.

  An optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports one end of the movable part with respect to the base, the other end of the movable part being a key type Thus, the mirror part is an optical switch formed at the key-shaped tip part.

  An optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports one end part of the movable part with respect to the base part. The optical switch forms a box-shaped mirror part base having a through hole in which a mirror part is formed.

  According to the present invention, when forming the mirror portion, the dummy structure is formed in the vicinity of the mirror surface forming portion, thereby ensuring the verticality of the mirror surface and preventing the mirror surface from being roughened. Since part or all of the dummy structure is removed, a high-quality optical switch can be manufactured without increasing the manufacturing process.

  A method for manufacturing an optical switch is provided in which a dummy structure is formed in front of the mirror part, and a part or all of the dummy structure is removed in a subsequent process.

FIG. 1 is a view for explaining a method of manufacturing an optical switch according to the present invention, and is a cross-sectional view of a main part for each step (cross section BB in FIG. 6B). The same steps as those of the prior art shown in FIG. 5 are omitted. 6A is a completed perspective view of the mirror portion of the optical switch, and FIG. 6B is a top view of the optical switch. Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 6.
Step (a): A masking resistant film 6 is formed on the entire surface of the silicon active layer 2a of the silicon laminate (SOI substrate) 2 including the silicon active layer 2a, the intermediate layer 2b, and the silicon support substrate 2c by sputtering or the like. . The resistant film 6 is made of, for example, chromium (Cr), and is a film that is resistant to silicon deep anisotropic reactive ion etching and hydrofluoric acid (HF).
Step (b): The resistant film 6 is patterned into a desired pattern shape by etching to form a first masking pattern 6a. At this time, a pattern is formed so that the optical switch becomes a completed drawing shown in FIG. 6, and a pattern 6b for forming a dummy structure is formed in the front part of the mirror part. When patterning, first, a photosensitive resist (positive type) is uniformly applied to the upper surface of the resistant film 6 by spin coating. After coating, the photomask having a desired masking pattern shape is covered, and the resist is exposed to ultraviolet light. After the exposure, the resist in the exposed region is removed using a developer. Thereafter, using the resist pattern formed by the above steps as a mask, the resistant film 6 in the exposed region is removed by wet etching.
Step (c): Using the first masking patterns 6a and 6b formed in the previous step (b) as a mask, the exposed region of the silicon active layer 2a is etched by a deep anisotropic reactive ion etching to form an etching stop layer. Etching is performed until an intermediate layer 2b is exposed. In this step, the dummy structure 8 is also formed. However, by appropriately determining the distance between the dummy structure 8 and the mirror portion, the mirror surface can be formed as a vertical surface without roughening the surface.
Step (d): The first masking patterns 6a and 6b used as a mask in the previous step (c) are removed by wet etching.
Step (e): A resistant film 7 made of chromium (Cr) is formed on the entire upper surface of the silicon active layer 2a.
Step (f): The resistant film 7 formed in the previous step (e) is patterned into a desired pattern shape by wet etching to form a second masking pattern 7a (in this embodiment, only the upper surface of the mirror portion). The patterning method is the same as that in the step (b) and will not be described.
Step (g): Using the second masking pattern 7a as a mask, the silicon active layer 2a in the exposed region is etched by a certain amount (for example, 50 μm in the depth direction) by deep anisotropic reactive ion etching. (The mirror part 5 is not etched and has a shape protruding from the other part as shown in the figure)
Step (h): The second masking pattern 7a used as a mask in the previous step (g) is removed by wet etching.
Step (i): The intermediate layer 2b is selectively removed by isotropic wet etching except for a part, and the movable portion 1 (beam portion 1b, movable electrode 1a, mirror base 5a) is separated from the silicon support substrate 2c. . At this time, the dummy structure 8 is also separated and removed from the optical switch structure. As an etchant used for wet etching, for example, hydrofluoric acid (HF) may be used. However, other etchants may be used as long as they selectively etch only the intermediate layer 2b.
In this embodiment, the dummy structure 8 is formed in the mirror pedestal 5a to increase the accuracy of the mirror 5, and a part of three sides excluding the mirror 5 is removed to form a mirror pedestal. As an alternative to the dummy structure 8, the side 5 b facing the mirror 5 can be used.
By making the mirror pedestal into a box shape, the mirror pedestal can be reduced in weight.

FIG. 2 is a view for explaining a method of manufacturing an optical switch according to the present invention, and is a cross-sectional view of a main part for each process (CC cross section in FIG. 7B). FIG. 7A is an optical switch. FIG. 7B is a top view of the optical switch. Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.
Step (a): A masking resistant film 20 is formed on the entire surface of the silicon active layer 2a of the silicon laminate (SOI substrate) 2 including the silicon support substrate 2c, the intermediate layer 2b, and the silicon active layer 2a by sputtering or the like. The resistant film 20 is made of, for example, chromium (Cr), and is a film that is resistant to silicon's deep anisotropic reactive ion etching and hydrofluoric acid (HF).
Step (b): The resistant film 20 formed in the previous step (a) is patterned into a desired pattern shape by wet etching to form a first masking pattern 20a (for mirror portion formation). When patterning, first, a photosensitive resist (positive type) is uniformly applied to the upper surface of the resistant film 20 by spin coating. After coating, the photomask having a desired masking pattern shape is covered, and the resist is exposed to ultraviolet light. After the exposure, the resist in the exposed region is removed using a developer. Thereafter, the resistant film 20 in the exposed region is removed by wet etching using the resist pattern formed by the above steps as a mask. (First masking process)
Step (c): A masking resistant film 21 is newly formed on the entire surface of the silicon active layer 2a including the upper surface of the first masking pattern 20a formed in the previous step (b). The resistant film 21 is made of, for example, a photosensitive resist (positive type) and is uniformly applied by spin coating.
Step (d): The resist film 21 formed in the previous step (c) is patterned into a desired pattern shape by exposure / development in the same manner as in the step (b) to form second masking patterns 21a and 21b (dummy structures). Forming). (Second masking process)
Step (e): Using the second masking patterns 21a and 21b formed in the previous step (d) as a mask, the exposed region of the silicon active layer 2a is etched by a deep anisotropic reactive ion etching to form an etching stop layer. Etching is performed until an intermediate layer 2b is exposed. At this point, a dummy structure and a mirror are formed. Since there is a facing surface by the dummy structure, the mirror surface can be formed without being rough and a vertical surface can be formed.
Step (f): The intermediate layer 2b exposed by the etching in the previous step (e) is removed by anisotropic dry etching.
Step (g): The second masking patterns 21a and 21b used as masks in the previous steps (e) and (f) are removed by an organic solvent (such as acetone) or O ₂ ashing.
Step (h): Using the first masking pattern 20a exposed by removing the second masking patterns 21a and 21b in the previous step (g) as a mask, the exposed silicon active layer 2a and the silicon support substrate 2c is etched by a certain amount (for example, 50 μm in the depth direction) by deep anisotropic reactive ion etching. As a result, the mirror portion formed in the silicon active layer 2a is exposed and, if necessary, the mirror base 5 is formed, and at the same time, recesses 22a and 22b are formed in a part of the silicon support substrate 2c. In the first embodiment, there is a possibility that the concave portion 22b in the narrow area is filled with the resist or the resistant film. In this embodiment, the resist or the resistant film is formed after this step, that is, after the concave portions 22a and 22b are formed. Since they are not formed, no residual foreign matter remains in the recesses 22a and 22b. Therefore, the effect as a concave portion that allows the cleaning liquid to escape and reduces the surface tension is sufficiently exerted.
Step (i): The first masking pattern 20a used as a mask in the previous step (h) is removed by wet etching.
Step (j): The remaining intermediate layer 2b is selectively removed by isotropic wet etching except for a part, and the movable portion 1 (beam portion 1b, movable electrode 1a, mirror base 5a) is removed from the silicon support substrate 2c. By further separating, the optical switch shown in FIG. 7 is completed.
In the present embodiment, the mirror portion is formed at the tip portion where the tip of the movable portion is a key shape.
By forming the dummy structure in the key-shaped space F, the mirror surface can be prevented from being rough and the verticality can be secured.

FIG. 3 is a view for explaining a method of manufacturing an optical switch according to the present invention, and is a cross-sectional view of a main part for each process. Hereinafter, a third embodiment of the present invention will be described with reference to FIG. The description will be made only for the characteristic part in the present invention, and the conventional well-known part and the same part as the second embodiment will be omitted. As a feature of the third embodiment, when the intermediate layer 2b is removed in the step (f) of the second embodiment, only the intermediate layer 2b is selectively used without using the second masking pattern 21a which is a mask for etching. It is to remove by etching. That is, in Example 2, when the intermediate layer 2b is removed, the second masking pattern 21a is used as a mask to prevent the silicon active layer 2a from being etched together with the intermediate layer 2b. In Example 2, instead of using the second masking pattern 21a, an etching solution (for example, hydrofluoric acid (HF)) that reacts only with the intermediate layer 2b so as not to etch the silicon active layer 2a, or etching is used. A gas (for example, CHF ₃ ) is used to make the etching selective. Details are as follows.
Steps (a) to (e): Omitted because they are the same as those in Example 2. Step (f): The second masking pattern 21a used as a mask in the previous step (e) is treated with an organic solvent (such as acetone) or O ₂ ashing. Remove.
Step (g): Only the intermediate layer 2b exposed by the etching in the previous step (e) is selectively removed by anisotropic dry etching.
Steps (h) to (j): Since they are the same as those in Example 2, they are omitted.

  As described above, in the method of manufacturing an optical switch according to the present invention, a dummy structure is formed in the vicinity of the mirror forming portion at the time of mirror formation to prevent the mirror surface from being roughened and to ensure the verticality of the mirror surface. An excellent optical switch can be manufactured by removing the body. It goes without saying that the optical switches of FIGS. 6 and 7 can be manufactured by any of the manufacturing methods of the first to third embodiments.

It is a figure for demonstrating the manufacturing method of the optical switch by this invention, and is principal part sectional drawing for every process It is a figure for demonstrating the manufacturing method of the optical switch by this invention, and is principal part sectional drawing for every process It is a figure for demonstrating the manufacturing method of the optical switch by this invention, and is principal part sectional drawing for every process Perspective view (a) and top view (b) showing an example of an optical switch manufactured by MEMS technology. It is a figure for demonstrating the manufacturing method of the said optical switch, and principal part sectional drawing for every process (AA cross section of FIG. 4). (A) is a completed perspective view of the mirror part of the optical switch, (b) is a top view of the optical switch. (A) is a completed perspective view of the mirror part of the optical switch, (b) is a top view of the optical switch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Movable part 1a Movable electrode 1b Beam part 2 Silicon laminated body (SOI substrate)
2a Silicon active layer 2b Intermediate layer 2c Silicon support substrate 3 Support electrode part 4 Fixed electrode part 4a Comb electrode 5 Mirror 5a Base 6 Resistance film 6a First masking pattern 6b Pattern for forming dummy structure 7 Resistance film 7a Second masking pattern 8 Dummy structure 20 Resistant film 20a First masking pattern 21 Resistant film 21a Second masking pattern 21b Second masking pattern 22a Concavity (large area)
22b recess (narrow area)

Claims (6)

In a method for manufacturing an optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports the movable part with respect to the base,
at least,
A first masking step of forming a first masking pattern on the surface of the silicon active layer of the silicon laminate formed by sandwiching the intermediate layer between the silicon support substrate and the silicon active layer;
Using the first masking pattern as a mask, removing the silicon active layer in the exposed region by dry etching;
Removing the first masking pattern;
A second masking step of forming a second masking pattern on the surface of the silicon active layer;
Using the second masking pattern as a mask, removing a certain amount of the silicon active layer in the exposed region by dry etching;
Removing the second masking pattern;
Removing the intermediate layer by removing part of it by wet etching;
An optical switch manufacturing method comprising:
A dummy structure is formed in the front part of the mirror part, and the dummy structure is removed by a certain amount in the step of removing a certain amount of the silicon active layer in the exposed region by dry etching, or a part of the intermediate layer is removed by wet etching. A method of manufacturing an optical switch, characterized in that the optical switch is removed in a removing step. In a method for manufacturing an optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports the movable part with respect to the base,
at least,
A first masking step of forming a masking pattern on the surface of the silicon active layer of the silicon laminate formed by sandwiching the intermediate layer between the silicon support substrate and the silicon active layer;
A second masking step of forming a second masking pattern so as to cover the first masking pattern;
Using the second masking pattern as a mask, removing the silicon active layer in the exposed region by dry etching;
Removing the intermediate layer exposed by dry etching of the silicon active layer by dry etching;
Removing the second masking pattern;
Using the first masking pattern exposed by removing the second masking pattern as a mask, removing a predetermined amount of the silicon support substrate and the silicon active layer in an exposed region by dry etching;
Removing the first masking pattern;
Removing the remaining intermediate layer except for a portion by wet etching;
An optical switch manufacturing method comprising:
A dummy structure is formed in front of the mirror part, and the dummy structure is removed by a certain amount in a step of removing the silicon support substrate and the silicon active layer in the exposed region by dry etching, or the intermediate layer is wet etched. A method of manufacturing an optical switch, characterized in that the optical switch is removed in a step of removing by removing part of the optical switch. In a method for manufacturing an optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports the movable part with respect to the base,
at least,
A first masking step of forming a first masking pattern on the surface of the silicon active layer of the silicon laminate formed by sandwiching the intermediate layer between the silicon support substrate and the silicon active layer;
A second masking step of forming a second masking pattern so as to cover the first masking pattern;
Using the second masking pattern as a mask, removing the silicon active layer in the exposed region by dry etching;
Removing the second masking pattern;
Selectively removing only the intermediate layer exposed by dry etching the silicon active layer by dry etching;
Using the first masking pattern exposed by removing the second masking pattern as a mask, removing a predetermined amount of the silicon support substrate and the silicon active layer in an exposed region by dry etching;
Removing the first masking pattern;
Removing the remaining intermediate layer except for a portion by wet etching;
An optical switch manufacturing method comprising:
A dummy structure is formed in front of the mirror part, and the dummy structure is removed by a certain amount in a step of removing the silicon support substrate and the silicon active layer in the exposed region by dry etching, or the intermediate layer is wet etched. A method of manufacturing an optical switch, characterized in that the optical switch is removed in a step of removing by removing part of the optical switch. 4. The method of manufacturing an optical switch according to claim 2, wherein the first masking pattern is made of Cr, and the second masking pattern is made of a photosensitive resist. An optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports one end of the movable part with respect to the base part,
The other end of the movable part is a key type, and the mirror part is formed at the tip of the key type. An optical switch having at least a base, a movable part provided with a mirror part, and a beam part that supports one end of the movable part with respect to the base part,
An optical switch, wherein a box-shaped mirror part base having a through hole with a mirror part formed on one side is formed at the other end of the movable part.

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