JP5016653B2 - Manufacturing method of micro movable device - Google Patents

Description

  The present invention relates to a micro movable device manufactured by a micromachining technique such as photolithography and etching, and particularly to a micro movable device including a movable body that is displaced in parallel with a substrate plate surface and a manufacturing method thereof.

Examples of this type of micro movable device include devices such as optical switches, accelerometers, and relay devices, and such micro movable devices generally have a single crystal silicon layer disposed on a single crystal silicon substrate via an insulating layer. 3 layer structure SOI (Silicon
on Insulator) substrate.
FIG. 19 shows a configuration of an optical switch described in Patent Document 1 as an example of a conventional configuration of a micro movable device manufactured using an SOI substrate, and FIG. 20 shows a patent for the optical switch. The manufacturing method (manufacturing process) shown by the literature 1 is shown. First, the configuration of this optical switch will be briefly described with reference to FIG.

Four fiber grooves 12a to 12d are formed in a cross shape on the plate-like base body 11, and the base body 11 between the fiber grooves 12a and 12b perpendicular to each other is used as a driving body forming portion 11 '. A slot 13 that forms 45 ° with respect to each of the fiber grooves 12 a and 12 b is formed in the driver forming portion 11 ′, and a movable rod 14 is disposed in the slot 13.
A mirror 15 is provided at one end of the movable rod 14, and this mirror 15 is positioned at the center 16 of the fiber grooves 12a to 12d having a cross shape. One ends of support beams 17a and 17b are connected to both sides of the intermediate portion in the extending direction of the movable rod 14, and the other ends of these support beams 17a and 17b are connected to fixed support portions 19a and 19b via leaf spring hinges 18a and 18b. It is fixed. Similarly, one ends of the support beams 17c and 17d are connected to both sides of the other end of the movable rod 14 in the extending direction, and the other ends of the support beams 17c and 17d are fixed to the fixed support portion 19a via the leaf spring hinges 18c and 18d. , 19b, whereby the movable rod 14 is supported so as to be movable in the extending direction.

The movable rod 14 is driven by a comb-shaped electrostatic actuator, and movable comb-shaped electrodes 21a to 21d are arranged and fixed on the support beams 17a to 17d, respectively. 22d is fixedly arranged on the driving body forming portion 11 '.
An electrostatic attraction force is generated by applying a voltage between the movable comb electrodes 21a and 21b and the fixed comb electrodes 22a and 22b, and the movable rod 14 approaches the central portion 16 by the electrostatic attraction force. Moving. On the other hand, if a voltage is applied between the movable comb electrodes 21c and 21d and the fixed comb electrodes 22c and 22d, the movable rod 14 moves away from the center portion 16 by electrostatic attraction. Therefore, the mirror 15 can be inserted into and removed from the central portion 16 by driving the movable rod 14 with such a comb-shaped electrostatic actuator.

  In the state where the optical fibers 23a to 23d are respectively disposed in the four fiber grooves 12a to 12d and the mirror 15 is inserted into the center portion 16, for example, light emitted from the optical fiber 23a is reflected by the mirror 15 and is reflected by the optical fiber. The light incident on 23d and emitted from the optical fiber 23b is reflected by the mirror 15 and enters the optical fiber 23c. On the other hand, when the mirror 15 is extracted from the central portion 16, the light emitted from the optical fiber 23a is incident on the optical fiber 23c, and the light emitted from the optical fiber 23b is incident on the optical fiber 23d. Switching is to be performed.

  This optical switch is manufactured by a manufacturing method as shown in FIG. That is, as shown in FIG. 20A, an SOI substrate 30 is prepared in which a single crystal silicon layer 33 is arranged on a single crystal silicon substrate 31 via an insulating layer 32 made of a silicon oxide film. A required mask 34 is formed on the silicon layer 33 by patterning. Then, the portion of the single crystal silicon layer 33 exposed from the mask 34 is etched by reactive ion etching (RIE), and the single crystal silicon layer 33 is exposed until the insulating layer 32 is exposed as shown in FIG. Remove.

A narrow portion 35 of the single crystal silicon layer 33 in FIG. 20 (2) corresponds to a movable body such as the movable rod 14, support beams 17a to 17d, and leaf spring hinges 18a to 18d in FIG. Corresponds to a fixedly arranged structure such as the fixed support portions 19a and 19b. FIG. 20 shows them by way of example.
Next, in FIG. 20B, wet etching is performed on the exposed insulating layer 32, and etching is performed until the insulating layer 32 located under the narrow portion 35 is removed by side etching. As a result, the narrow portion 35 is positioned on the single crystal silicon substrate 31 through the gap as shown in FIG. 20 (3). That is, the narrow portion 35 is formed by removing the insulating layer 32. The movable body is separated from the single crystal silicon substrate 31 and is movable. A reflective film is formed on the side wall surface of the single crystal silicon layer 33 forming the mirror 15 by vapor deposition.

  As described above, in the manufacturing method shown in FIG. 20, the insulating layer 32 of the SOI substrate 30 is used as a sacrificial layer, and the insulating layer 32 positioned under the movable body composed of the single crystal silicon layer 33 is The movable body can be moved by etching away.

US Pat. No. 6,315,462

As described above, a micro movable device including a movable body that is displaced parallel to the substrate plate surface on a single crystal silicon substrate is generally formed using an SOI substrate, and conventionally, the intermediate insulating layer is sacrificed. By using it as a layer, the movable body is separated from the substrate located below it.
However, the thickness of the intermediate insulating layer of the SOI substrate is usually about 3 μm even if it is thick, and the gap formed under the movable body is extremely narrow. Such a malfunction that the body does not work is likely to occur.

  In addition, the insulating layer under the movable body disappears by side etching, and at the same time, the insulating layer under the fixed structure is also side-etched, and is about the same as the width of the side-etched insulating layer under the movable body. Since a gap with a width of 2 mm is formed between the structure and the substrate located thereunder, it is possible that foreign matter enters the gap and gets caught. In this case, there is a possibility that the single crystal silicon substrate and the single crystal silicon layer located above the single crystal silicon layer may be electrically short-circuited through the foreign matter, so that the structures are separated from each other by the foreign matter and the single crystal silicon substrate. There can be a situation where a short circuit occurs through.

Therefore, for example, there is a possibility that two structures made of a single crystal silicon layer used as an electrode for applying a voltage to the comb-shaped electrostatic actuator may be short-circuited in this way, and this also causes the movable body. The operation of was impossible.
In view of such a situation, the object of the present invention is a structure that can be formed using an SOI substrate, and that does not cause a conventional problem that a movable body does not operate due to foreign matter being sandwiched and further an electrical short circuit occurs. It is to provide a micro movable device, and to provide a manufacturing method thereof.

The invention of claim 1, on a single crystal silicon substrate, and the movable body, a movable micro-device and the structure other than the movable member is formed, the structure is a silicon oxide on the single-crystal silicon substrate A single crystal silicon layer of an SOI substrate having a three-layer structure in which a single crystal silicon layer is arranged through an insulating layer made of a film, and is fixed on the single crystal silicon substrate through an insulating layer, and is movable. consists above monocrystalline silicon layer, is held to be displaceable parallel to the plate surface of the single crystal silicon substrate by a structure, the recess in the entire region where the structure of the single crystal silicon substrate top surface is not present is formed, the An insulating layer in which the movable body is located on the concave portion, the structure has an overhang portion projecting on the concave portion, and is fixed to the single crystal silicon substrate below the overhang portion. Periphery is in a position not Kakakara on the recess, whereby a minute gap between the single-crystal silicon substrate and the single crystal silicon layer is assumed to be formed.
A second aspect of the present invention is a method of manufacturing the micro movable device according to the first aspect, wherein a mask layer is formed on an upper surface of a single crystal silicon layer of an SOI substrate having a three-layer structure, and the structure mask and width are formed. A mask for a movable body made of a combination of narrow patterns is formed by patterning the mask layer, and the portion of the single crystal silicon layer exposed from the mask is gas until the insulating layer is exposed perpendicularly to the single crystal silicon substrate. Removed by reactive dry etching, the side wall surface perpendicular to the substrate plate surface of each single crystal silicon layer formed under each mask by the dry etching was covered with a side wall protective film, and exposed by dry etching of the insulating layer portions to expose the upper surface of the etched away monocrystalline silicon substrate, with respect to the upper surface of the single crystal silicon substrate the exposed, lower side of the single mask for the movable body Surface area of the crystal silicon substrate is subjected to isotropic etching crystal silicon until the recess is etched away to form, by which the recesses are formed in all the regions in which the structure of the single-crystal silicon substrate top surface is not present The movable body is located on the concave portion, the structure has an overhang portion projecting on the concave portion, and then the mask and the sidewall protective film are removed , and the insulating layer below the movable body and the overhang are removed. It is produced by etching away the insulating layer below the part .

According to the present invention, a micro movable device comprising a single crystal silicon substrate on which a movable body that is displaced in parallel with the substrate plate surface and a structure other than the movable body is formed. Through which a concave portion is formed in a region where there is no structure on the upper surface of the single crystal silicon substrate, a movable body is positioned on the concave portion, and a component is installed in the concave portion. The part is provided with an installation reference in which the upper surface of the single crystal silicon substrate remains in the recess.
In the present invention, the installation standard is a grid.
In the present invention, the installation standard is two parallel strips, and a V-groove is present between the strips.
In the present invention, the upper surface of the single crystal silicon substrate is the (100) plane, and the installation reference lattice is configured in the <110> direction of the single crystal silicon substrate.
In the present invention, the upper surface of the single crystal silicon substrate is the (100) plane, and the installation reference strip is configured in the <110> direction of the single crystal silicon substrate.

The micro movable device of the present invention includes a structure in which a mask layer is formed on an upper surface of a single crystal silicon layer of an SOI substrate having a three-layer structure in which the single crystal silicon layer is disposed on the single crystal silicon substrate via an insulating layer. The mask for installation, the mask for installation reference, and the mask for movable body are for the structure, the installation reference, and the movable body in order from the widest width of the narrowest part of each mask pattern. The mask layer is patterned so as to be in the order of the mask, and the portion of the single crystal silicon layer exposed from the mask is removed by gas reactive dry etching until the insulating layer is exposed. The sidewall of the single crystal silicon layer perpendicular to the formed substrate plate surface is covered with a sidewall protective film, and the exposed portion of the insulating layer is removed by dry etching. The upper surface of the recon substrate is exposed, and isotropic etching of the single crystal silicon is performed on the exposed upper surface of the single crystal silicon substrate until the lower part of the movable body is etched away, and the mask and the sidewall protective film are formed. After the removal, the insulating layer is manufactured by etching until the upper part of the insulating layer is removed.

In the present invention, both the insulating layer and the mask layer are made of a silicon oxide film, and the thickness of the mask layer is made larger than the thickness of the insulating layer.
The micro movable device of the present invention is formed on the upper surface of a single crystal silicon layer of an SOI substrate having a three-layer structure in which a single crystal silicon layer is disposed via an insulating layer on a single crystal silicon substrate whose upper surface forms a (100) plane. A mask for forming a mask, the outer shape of which is configured by a line parallel to the <110> direction of the single crystal silicon substrate, and the outer shape is configured using a line not parallel to the <110> direction. The mask for the body and the mask for the structure are formed by patterning the mask layer so that the width of the narrowest part of each mask pattern is the mask for the installation reference. The portion exposed from the mask of the single crystal silicon layer is removed by gas reactive dry etching until the insulating layer is exposed, and the portion exposed by dry etching of the insulating layer and the mask The single crystal silicon is thermally oxidized until the entire narrow structure formed under the installation reference mask is thermally oxidized by dry etching, and the thermal oxide film on the upper surface of the single crystal silicon substrate is removed by etching. The upper surface of the crystalline silicon substrate is exposed, and anisotropic etching of the single crystal silicon is performed on the exposed upper surface of the single crystal silicon substrate until the portion under the movable body is etched away, and then the thermal oxidation is performed. It is produced by etching away the formed part.

A third aspect of the present invention is a method for producing a micro movable device according to the first aspect, wherein a single crystal silicon layer is disposed on a single crystal silicon substrate having an upper surface forming a (100) plane via an insulating layer. A mask for a movable body in which a mask layer is formed on an upper surface of a single crystal silicon layer of an SOI substrate having a three-layer structure, and an outer shape is configured using lines that are not parallel to the < 110> direction of the single crystal silicon substrate , and a structure a mask for the body, the width of the narrowest portion in each of the mask pattern, the structure for the order from the large ones, so as to become the mask for the movable body is formed by patterning the mask layer, The portion of the single crystal silicon layer exposed from the mask is removed by gas reactive dry etching until the insulating layer is exposed perpendicular to the single crystal silicon substrate, and exposed by dry etching of the insulating layer. The exposed surface of the single crystal silicon is removed, the exposed surface of the single crystal silicon is thermally oxidized, and the thermal oxide film on the upper surface of the single crystal silicon substrate is etched away perpendicularly to the single crystal silicon substrate to remove the upper surface of the single crystal silicon substrate. to expose the, with respect to the upper surface of the single crystal silicon substrate the exposed, under the portion to be a movable member is removed by side etching, until the recess Ru formed anisotropically etched single crystal silicon, then, insulating It is produced by divided layers and the thermal oxide film on the sidewalls.

According to the micro movable device according to the present invention, an SOI substrate can be used as in the prior art, and the single crystal silicon substrate that has been a problem in the past due to the formation of the concave portion, and the movable body positioned thereon The problem that the movable body becomes inoperable due to foreign matter caught in the gap between the single-crystal silicon substrate and the structure fixedly disposed on the single crystal silicon substrate is electrically connected via the foreign matter. Problems such as short-circuiting can be solved.
Therefore, it is possible to obtain a micro movable device having good operation performance and excellent reliability.

Moreover, according to the micro movable device of the present invention, since the installation reference is provided in which the upper surface of the single crystal silicon substrate remains, the component is mounted and installed with high height accuracy without being influenced by the recess. be able to.
In addition, according to the manufacturing method of the present invention, the above-described micro movable device can be satisfactorily manufactured using, for example, a commercially available SOI substrate.
Note that in one manufacturing method of the present invention, the recess and the installation reference can be simultaneously formed by isotropic etching of single crystal silicon, while in the other manufacturing method of the present invention, single crystal silicon is formed. The recess and the installation reference can be formed simultaneously by anisotropic etching, and in any case, a micro movable device having the recess and the installation reference can be manufactured by a simple process. .

The top view which showed the structure of the optical switch as one Example of the micro movable device by this invention. 1A is a cross-sectional view taken along line AA in FIG. 1, B is a cross-sectional view taken along line BB in FIG. 1, and C is a cross-sectional view taken along line CC in FIG. The figure for demonstrating operation | movement of the optical switch of FIG. The figure for demonstrating operation | movement of the optical switch of FIG. The figure for demonstrating the manufacturing method of the micro movable device by this invention. The top view which showed the structure of the optical switch as one Example of the micro movable device by this invention. The elements on larger scale of FIG. 6A is a cross-sectional view taken along the line A-A in FIG. 6, B is a cross-sectional view taken along the line BB in FIG. 6, and C is a cross-sectional view taken along the line CC in FIG. FIG. 7 is a view for explaining a manufacturing method of the optical switch shown in FIG. 6. 9A and 9B are diagrams showing a mask pattern for installation reference provided in the fiber groove, where A is a continuous pattern and B is an island pattern. The figure for demonstrating the short circuit generation | occurrence | production by dew condensation, A shows the case where there is no recessed part (conventional example), and B shows the case where there is a recessed part. FIG. 7 is a diagram for explaining another method for manufacturing the optical switch illustrated in FIG. 6. The figure for demonstrating the structure and manufacturing method for preventing generation | occurrence | production of a short circuit more reliably. The top view which showed the structure of the optical switch provided with the installation reference | standard as an example of a micro movable device. FIG. 15 is a diagram for explaining a manufacturing method of the optical switch shown in FIG. 14. FIG. 15 is a diagram for explaining a manufacturing method of the optical switch shown in FIG. 14. The top view which showed the structure of the optical switch provided with the installation reference | standard as another example of a micro movable device. FIG. 17 illustrates a method for manufacturing the optical switch illustrated in FIG. 16. FIG. 17 is a view for explaining another manufacturing method of the optical switch shown in FIG. 16. FIG. 17 is a view for explaining another manufacturing method of the optical switch shown in FIG. 16. The top view which shows the prior art example of a micro movable device. FIG. 19 is a diagram showing a method for manufacturing the micro movable device shown in FIG. 18.

An embodiment in which the present invention is applied to an optical switch will be described with reference to the drawings.
FIG. 1 is a plan view of an optical switch. Four fiber grooves 42a to 42d are formed in a cross shape on an upper surface 41a of a plate-like base 41, and one region divided into four by these fiber grooves 42a to 42d is formed. It is set as the drive body formation part 41 '. A rod groove 44 that communicates with the central portion 43 of the fiber grooves 42 a to 42 d is formed in the driver forming portion 41 ′ so as to divide it into two, and a recess 45 is formed that communicates with the other end of the rod groove 44. Has been.
A movable rod 46 is disposed in the rod groove 44, and a mirror 47 is provided at one end on the central portion 43 side of the movable rod 46. Leaf spring hinges 48a and 48b are connected to both sides of the intermediate portion in the extending direction located in the recess 45 of the movable rod 46, and further, leaf spring hinges 48c and 48d are connected to both sides of the other end in the extending direction. The movable rod 46 is supported by the drive body forming portion 41 ′ so as to be movable in the extending direction by the hinges 48 a to 48 d.

Comb-type electrostatic actuators are provided between the leaf spring hinges 48 a and 48 b and 48 c and 48 d, and the movable comb electrodes 49 are fixed to both sides of the movable rod 46. The movable comb electrode 49 has comb teeth on both sides thereof, that is, on both sides in the extending direction of the movable rod 46.
A first fixed comb electrode 51 and a second fixed comb electrode 52 combined with the movable comb electrode 49 are arranged on the leaf spring hinges 48c, 48d and 48a, 48b side with respect to the movable comb electrode 49, respectively. These are fixed to the bottom surface of the recess 45.

2A, 2B, and 2C show the AA, BB, and CC sections in FIG. 1, respectively. A base 41 is an insulating layer 62 made of a silicon oxide film on a single crystal silicon substrate 61. FIG. A single-crystal silicon layer 63 is disposed on the single-crystal silicon substrate 61, and a movable rod 46, a mirror 47, and a leaf spring hinge 48a that are displaced parallel to the substrate plate surface are disposed on the single-crystal silicon substrate 61. A movable body such as ˜48d and a movable comb electrode 49 is constituted by the single crystal silicon layer 63.
In addition to the movable body, the structure defining the fiber grooves 42a to 42d, the hinge groove 44, and the recess 45, including the first and second fixed comb electrodes 51 and 52, has a single crystal silicon layer 63 as in the movable body. These structures are fixedly disposed on the single crystal silicon substrate 61 with an insulating layer 62 interposed therebetween. In this example, the insulating layer 62 is also present below the movable body.

As shown in FIG. 2, a recess 64 is provided between the structures on the upper surface of the single crystal silicon substrate 61, and the movable body is separated from the single crystal silicon substrate 61 by this recess 64. Since the concave portion 64 is formed in such a range in which the movable body is displaced, a sufficient gap is secured between the movable body and the single crystal silicon substrate 61 in this example.
FIG. 3 shows a state in which optical fibers 71a to 71d are arranged in four fiber grooves 42a to 42d, respectively, in the configuration shown in FIG. 1, and in this initial state (first stable state), a mirror is shown. 47 is located in the central portion 43. For example, light emitted from the optical fiber 71a is reflected by the mirror 47 and incident on the optical fiber 71d, and light emitted from the optical fiber 71b is similarly reflected by the mirror 47. Then, the light enters the optical fiber 71c.

The first fixed comb in a state where the driving body forming portion 41 ′ and the second fixed comb electrode 52 that are electrically connected to the movable comb electrode 49 via the movable rod 46 and the leaf spring hinges 48 a to 48 d are grounded. When a voltage is applied to the tooth electrode 51, an electrostatic attraction force acts between the first fixed comb electrode 51 and the movable comb electrode 49, and when the force is larger than the holding force in the first stable state, The spring hinges 48a to 48d are inverted to the second stable state as shown in FIG. 4, and are self-held in that state even when the voltage application is stopped. At this time, the mirror 47 has a central portion 43 as shown in FIG.
In this state, the outgoing lights from the optical fibers 71a and 71b travel straight and enter the optical fibers 71c and 71d, respectively.

The first stable state and the second stable state in the above can be obtained by making the shape of the leaf spring hinges 48a to 48d into an appropriate S shape in the extending direction. In addition, if a voltage is applied to the second fixed comb electrode 52 in a state where the driving body forming portion 41 ′ and the first fixed comb electrode 51 are grounded, the second fixed comb electrode 52, the movable comb electrode 49, In the case where the electrostatic attraction force works during this period and the force is larger than the holding force in the second stable state, the state returns to the first stable state in FIG.
In order to apply a voltage between the first or second fixed comb electrode 51 or 52 and the movable comb electrode 49, for example, a bonding wire is connected to each of the first and second fixed comb electrodes 51 and 52. A voltage may be applied between the bonding wires and the drive body forming portion 41 ′.

According to the optical switch having the above structure, a movable body (movable rod 46, mirror 47, leaf spring hinges 48a to 48d, movable comb electrode 49) that is displaced in parallel with the plate surface of the single crystal silicon substrate 61. And the single crystal silicon substrate 61 are largely separated by the presence of the concave portion 64, that is, the void can be greatly widened by providing the concave portion 64 as compared with the conventional gap of about 3 μm. It is possible to solve the problem that the movable body does not operate due to entering the gap.
Next, as in the optical switch described above, a movable body that is displaced on a single crystal silicon substrate in parallel with the substrate plate surface and a structure other than the movable body is provided, and the movable body on the upper surface of the single crystal silicon substrate. A method of manufacturing a micro movable device having a structure in which a concave portion is formed in a portion where the displacement is made will be described. 5 (1) to 5 (5) show the manufacturing method in the order of steps, and each step (1) to (5) will be described below.

(1) An SOI substrate 60 having a three-layer structure in which a single crystal silicon layer 63 is disposed on a single crystal silicon substrate 61 via an insulating layer 62 made of a silicon oxide film is prepared. A resist is applied to the upper surface of the single crystal silicon layer 63 to form a mask layer, and the mask layer is patterned using a photolithography technique and movable with the structure mask 65 fixed on the single crystal silicon substrate 61. A body mask 66 is formed.
As shown in the plan view of the optical switch in FIG. 1, the movable body is viewed as individual elements, that is, the movable rod 46, the mirror 47, the leaf spring hinges 48a to 48d, and the movable comb electrode 49 are individually provided. When viewed, at least one direction is narrow in the in-plane direction of the substrate plate surface, and thus the movable body mask 66 is constituted by a combination of narrow patterns as a whole. In contrast, the structure mask 65 is wide.

  (2) The portion of the single crystal silicon layer 63 exposed from the masks 65 and 66 is removed by deep gas reactive dry etching until the insulating layer 62 is exposed. In this etching, an ICP (Inductively Coupled Plasma) -RIE apparatus is used. At that time, in order to improve the verticality of the side wall surface to be formed, the etching process and the polymer precipitation process are alternately repeated to advance the vertical digging. It is preferable to use a technique. Both of these processes are performed in the plasma chamber of the ICP apparatus, a mixed gas of sulfur hexafluoride (SF6) and argon is used in the etching process, and a mixed gas of octafluorocyclobutane (C4F8) and argon is used in the polymer deposition process. It can be done by supplying each.

When the process of alternately repeating the etching of the single crystal silicon layer 63 is completed, the polymer layer remaining and deposited is formed on the side wall surface every cycle of the process, so that the side wall protective film 67 covering the side wall surface as it is. Use as
(3) The exposed portion of the insulating layer 62 is removed by etching to expose the upper surface of the single crystal silicon substrate 61. This etching may be wet etching with about 50% fluoric acid (HF) solution, but here RIE (Reactive Ion)
Etching) is used to perform dry etching using a mixed gas of trifluoromethane (CHF3) and argon.

(4) Isotropic etching of single crystal silicon is performed on the exposed upper surface of the single crystal silicon substrate 61. Here, isotropic dry etching using a mixed gas of sulfur hexafluoride (SF6) and argon is performed by an RIE apparatus.
Since isotropic etching also proceeds in the lateral direction, by selecting an appropriate etching time, single crystal silicon remains under the wide portion that forms the structure of the single crystal silicon layer 63 and the insulating layer 62, and the narrow portion Below, the single crystal silicon is completely etched away. By performing isotropic etching in this manner, a concave portion 64 is formed on the upper surface of the single crystal silicon substrate 61, and the concave portion 64 is sufficient between the narrow portion serving as a movable body and the single crystal silicon substrate 61. A void is formed. On the other hand, although the concave portion 64 is formed so as to slightly enter below the wide portion, the wide portion is fixed on the single crystal silicon substrate 61 by the remaining single crystal silicon. Note that the depth of the recess 64 is, for example, about 10 μm.

(5) The masks 65 and 66 and the sidewall protective film 67 are removed. Thereby, the structure 82 other than the movable body 81 is fixed on the single crystal silicon substrate 61 via the insulating layer 62, and the movable body 81 is provided with a large gap between the single crystal silicon substrate 61 and the recess 64. The structure is complete. The groove 83 corresponds to the fiber groove 42a (42b to 42d) in the optical switch shown in FIG.
The removal of the masks 65 and 66 made of resist and the side wall protective film 67 made of polymer precipitate can be simultaneously performed by dry etching using O 2 plasma or sulfuric acid.

In addition, in the mirror 47 of the optical switch shown in FIG. 1, in the case where a required film formation is required on the surface (side wall surface) of the movable body 81 or the structure 82 so that a reflection film needs to be formed on the mirror surface, The film is formed last.
According to the manufacturing method as described above, a commercially available substrate can be used as the SOI substrate 60 as in the conventional case. However, the intermediate insulating layer 62 of the three-layer structure is not used as a sacrificial layer for forming a movable body as in the prior art, but is used for the etching stop layer of the upper single crystal silicon layer 63 and electrical insulation.

  The etching for forming the recess 64 on the upper surface of the single crystal silicon substrate 61 in the step (4) may be essentially isotropic etching, and is not limited to the dry etching. For example, nitric hydrofluoric acid is used as an etchant. Wet etching may be used. However, as described above, the etching of the insulating layer 62 in the step (3) and the etching of the single crystal silicon in the step (4) are both dry etching by an RIE apparatus, so that only these gases are replaced and the two steps are performed. It can be performed continuously, and in that respect, the apparatus used and the process can be simplified.

The formation of the sidewall protective film 67 in the step (2) is most convenient using the polymer precipitation layer as described above. However, as another method, the anisotropic etching of the single crystal silicon layer 63 is completed. Separately, silicon oxide is deposited on the sidewall surface, or the substrate is exposed to high temperature water vapor to thermally oxidize the sidewall surface, and an oxide film is formed on the surface to form the sidewall protective film 67 of silicon oxide. Is also possible.
However, in this case, the side wall protective film 67 becomes the same silicon oxide film as the intermediate insulating layer 62 of the SOI substrate 60. Therefore, the side wall protective film 67 is left exposed in the step of removing the insulating layer 62 in the step (3). The insulating layer 62 that is present must be selectively removed. This can be done, for example, as follows.

That is, a pair of parallel plate electrodes are provided in the RIE apparatus, and the substrate shown in FIG. 5 (2) is placed between the electrodes, with the substrate plate surface parallel to the electrodes. Then, a reactive gas containing trifluoromethane (CHF 3) or the like is supplied to the plasma chamber of the apparatus, and ions in the plasma are accelerated by a direct current electric field generated by an ion sheath on the electrode surface. The insulating layer 62 exposed at the bottom of the etching groove of the crystalline silicon layer 63 is bombarded to cause an ion-promoted chemical reaction. As a result, the etching proceeds only in the ion incident direction, and only the insulating layer 62 can be effectively removed while the sidewall protective film 67 is maintained.

When the sidewall protective film 67 is formed of silicon oxide in this way, the removal is performed using hydrofluoric acid. In this case, the side wall protective film 67 on the vertical side wall surface and the insulating layer 62 below the movable body 81 are removed simultaneously, but the side wall protective film 67 is removed very quickly from the insulating layer 62 below the structure 82. Therefore, the lateral etching occurring in the insulating layer 62 at the same time is slight and does not cause a problem.
In the example described above, the edge portion (overhang portion) located on the concave portion 64 of the movable body 81 and the structure body 82 is composed of two layers of the single crystal silicon layer 63 and the insulating layer 62 as shown in FIG. In particular, since the insulating layer 62 is provided in the overhang portion of the structure 82, the single crystal silicon layer 63 is electrically connected to the single crystal silicon substrate 61 by the conductive foreign matter that has entered the gap below the structure 82. It is possible to prevent a short circuit from occurring.

However, when the depth of the concave portion 64 is secured to about 10 μm and the insulating layer (for example, 3 μm thickness) in the overhang portion is removed, a depth of about 13 μm is formed from the lower surface of the structure 82 to the bottom of the concave portion 64. Will do. Therefore, for example, if the device is used in an environment where it can be determined that there is no possibility that foreign matter with such a size as to short-circuit such a gap will be possible, the purpose of preventing the short-circuit only by the size of the gap is sufficiently achieved. Therefore, the insulating layer in the overhang portion is not always necessary.
In addition, for example, when the movable body 81 is made more flexible, or when stress or the like generated at the interface due to the two-layer structure becomes a problem in the movable body 81, the movable body 81 and the structural body are further changed from the state of FIG. The insulating layer 62 in the 82 overhang portion may be removed with hydrofluoric acid.

By the way, in the above-described example, the recess 64 is formed not only below the movable body 81 but also between each of the fixedly arranged structures 82 other than the movable body 81, that is, the structure 82 on the upper surface of the single crystal silicon substrate 61. The concave portions 64 are formed in all the regions where the optical fibers 71 do not exist, and therefore the concave portions 64 also exist in the fiber grooves 42a to 42d in which the optical fibers 71a to 71d are installed.
However, it is generally not easy to control the height of the bottom surfaces of the recesses 64 formed by etching with high accuracy, and when the plurality of recesses 64 are present on the single crystal silicon substrate 61, the bottom surfaces of the recesses 64. It is not easy to make the heights of the same and uniform.
Accordingly, the optical fibers 71a to 71d installed on the concave portion 64 are inevitably deteriorated in height accuracy and variations in height, and the optical coupling efficiency is deteriorated due to an optical axis shift.

Next, in order to solve such a problem, a configuration will be described in which components can be mounted and installed with high accuracy and high accuracy regardless of the formation state of the recess 64.
FIG. 6 shows an example of an optical switch as a micro movable device having such a configuration, and FIGS. 7A and 7B are partially enlarged views thereof. 8A to 8C show an AA section, a BB section, and a CC section in FIG. 6, respectively. Parts corresponding to those of the optical switch shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this example, as illustrated in FIG. 8C, an installation reference 91 is provided in the recess 64 of each of the fiber grooves 42a to 42d, and the optical fibers 71a to 71d are installed on the installation reference 91. Yes. The installation reference 91 is the one in which the upper surface of the single crystal silicon substrate 61 remains without being etched in the recess 64, and has extremely high surface accuracy.
Therefore, the height of each of the optical fibers 71a to 71d can be matched with high accuracy, and the relative height between the mirror 47 constituted by the single crystal silicon layer 63 and the optical fibers 71a to 71d is also a single crystal silicon substrate. Since the height can be controlled with reference to the upper surface of 61, it can be controlled with high accuracy.

  On the other hand, in this example, as shown in FIG. 6, conductive paths 53 and 54 are formed which are respectively connected to the first fixed comb electrode 51 and the second fixed comb electrode 52 and reach the peripheral side of the drive body forming portion 41 ′. The peripheral portion (the portion surrounded by a two-dot chain line in FIG. 6) of the driver forming portion 41 ′ that crosses the conductive paths 53 and 54 is defined as an electrode pad forming region 55. As shown in FIG. 8A, an electrode pad 56 is formed. The electrode pad 56 is made of, for example, an Au / Pt / Ti film with a Ti film as a base, and is formed by sputtering. 7A indicates a fiber pressing spring, and the optical fibers 71a to 71d installed in the fiber grooves 42a to 42d are pressed and positioned by the fiber pressing spring 57.

FIG. 9 shows a manufacturing method of the optical switch having the above-described structure in the order of steps, and shows three positions of the AA cross section, the BB cross section, and the CC cross section of FIG. Hereinafter, each process (1)-(6) is demonstrated.
(1) An SOI substrate 60 is prepared.
(2) A resist mask is applied to the upper surface of the single crystal silicon layer 63 to form a mask layer, and the mask layer is patterned on the single crystal silicon substrate 61 by patterning the mask layer using a photolithography technique. 65 and a movable body mask 66 are formed. At this time, an installation reference mask 68 formed in the fiber groove is also formed at the same time.
The mask 65 for structure, the mask 66 for movable body, and the mask 68 for setting reference are arranged in order from the widest width of the narrowest part in each mask pattern, and the mask 65 for setting. The reference mask 68 and the movable body mask 66 are arranged in this order.

The installation reference mask 68 may be a continuous pattern along the extending direction of the fiber groove as shown in FIG. 10A or an island-like pattern as shown in FIG. 10B. In the case of an island-shaped pattern, a concave portion is formed between the island and the island on the upper surface of the single crystal silicon substrate 61 in the step (4) to be described later. It is possible to inject, and the fixing strength of the optical fiber can be increased.
Subsequently, portions of the single crystal silicon layer 63 exposed from the masks 65, 66, and 68 are etched away by deep gas reactive dry etching until the insulating layer 62 is exposed. At this time, although not shown in the drawing, a film is deposited on the etching side wall as in the case of FIG. 5B described above, and a side wall protective film is formed.

(3) The exposed portion of the insulating layer 62 is removed by etching to expose the upper surface of the single crystal silicon substrate 61.
(4) Isotropic etching of the single crystal silicon is performed on the exposed upper surface of the single crystal silicon substrate 61 until the lower portion of the movable body is etched away. Thereby, the recessed part 64 is formed. The steps (3) and (4) may be wet etching, but if dry etching is used, the steps (2) to (4) can be performed continuously in the same apparatus, which is convenient.
(5) After removing the masks 65, 66, 68 and the sidewall protective film, the insulating layer 62 is etched until the portion above the installation reference 91 is removed, and the single crystal silicon layer 63 on the installation reference 91 is removed. .
(6) An Au / Pt / Ti film is formed by sputtering using a mechanical mask in the electrode pad formation region 55 and the mirror 47 region. Thereby, the optical switch shown in FIGS. 6 to 8 is completed.

If the width of the fiber grooves 42a to 42d is, for example, a few tens of micrometers, the width of the installation reference 91 is set to, for example, about 50 μm. In this case, if the depth of the concave portion 64 is 10 μm, the isotropic etching at the time of forming the concave portion 64 proceeds in the same direction as the depth direction in the lateral direction. Therefore, the width of the mask 68 for installation reference is 70 μm. Become.
As described above, by setting the shape of the installation reference 91 as an island shape, the fixing strength of the optical fiber can be increased by the recess formed between the islands. In addition to this, as shown in FIG. When the reference mask 68 is formed in a continuous pattern, the recess 64 in the fiber groove is separated into two, whereas the two recesses 64 are communicated with each other. The flow of the adhesive such as the UV curable adhesive is improved, and the uniform liquid level of the adhesive can be immediately obtained over the entire fiber groove.

Such an installation reference 91 may be formed in a state of being surrounded by the structure, that is, surrounded by the recess 64, or reaching the edge of the substrate as in the example of the fiber groove and the structure of the recess 64 or the structure. You may have the side part which is not enclosed by a body.
In addition to the surface on which the optical fiber is mounted as in this example, the installation reference 91 is used as a surface on which a chip element such as a lens, a semiconductor light emitting element, or a semiconductor optical modulator is mounted. When the chip element is mounted, a metal layer serving as an electrode pad is formed on the surface of the installation reference 91 in the same process as the electrode pad of other portions.
As described above, the provision of the concave portion 64 can solve the problem that the movable body becomes inoperable due to the foreign object being caught or an electrical short circuit occurs. However, the short circuit due to condensation (included in a broad sense foreign object) is here. Will be described.

FIG. 11A shows the state of condensation when there is no recess 64 as a comparative example (conventional example). In the figure, 75 indicates condensation. Condensation 75 tends to occur selectively near the boundary between silicon and metal (Au). In the film formation of the electrode pad 56 using the mechanical mask, the metal layers 56a and 56b are also formed on the side wall surface of the single crystal silicon layer 63 and the exposed upper surface of the single crystal silicon substrate 61. As shown, dew condensation 75 occurs, which causes a state where the electrode pads 56-1 and 56-2 are short-circuited.
On the other hand, FIG. 11B shows a case where there is a concave portion 64, and it can be seen that a short circuit can be prevented even if condensation 75 occurs due to the presence of the concave portion 64.
In addition, not only an optical switch but a micro movable device manufactured using this kind of SOI substrate is generally stored in a package. However, it is difficult to realize a completely sealed structure, and water vapor gradually enters over time. Condensation can occur on the device surface due to changes in the temperature environment.

Next, another method for manufacturing the optical switch shown in FIGS. FIG. 12 shows the manufacturing method in the same order as in FIG. 9, and the steps (1) to (6) will be described below.
(1) An SOI substrate 60 is prepared.
(2) A silicon oxide film is formed on the upper surface of the single crystal silicon layer 63, and the silicon oxide film is patterned by using a photolithography technique, and the structure mask 65 and the movable body are formed as in the case of FIG. A mask 66 for installation and a mask 68 for installation reference are formed. Note that the thickness of the silicon oxide film forming the mask layer is larger than the thickness of the insulating film 62 made of the silicon oxide film.
Subsequently, the portions of the single crystal silicon layer 63 exposed from the masks 65, 66, and 68 are etched away by deep digging gas reactive dry etching until the insulating layer 62 is exposed. At this time, although not shown in the drawing, a sidewall protective film is formed on the etched sidewall.
(3) The exposed portion of the insulating layer 62 is removed by etching to expose the upper surface of the single crystal silicon substrate 61. At this time, the masks 65, 66, and 68 are similarly etched, but remain because they are thicker than the insulating layer 62.
(4) Isotropic etching of single crystal silicon is performed on the exposed upper surface of the single crystal silicon substrate 61 as in FIG. 9 (4).
(5) After removing the sidewall protective film, the insulating layer 62 is etched in the same manner as in FIG. 9 (5), and the single crystal silicon layer 63 on the installation reference 91 is removed. At this time, the masks 65, 66, and 68 are also etched and removed at the same time.
(6) An Au / Pt / Ti film is formed by sputtering in the electrode pad formation region 55 and the mirror 47 region, thereby completing the optical switch.

In the manufacturing method described above, the masks 65, 66, and 68 are formed by silicon oxide films instead of the resist, and the number of processes is increased for the patterning. However, in terms of etching resistance in dry etching, the resist is used. The advantage is that it is stronger and more reliable.
In the two manufacturing methods shown in FIGS. 9 and 12, a film (polymer deposition layer) deposited on the sidewall by gas reactive dry etching in step (2) is used as the sidewall protective film in the etching in step (4). Although being used, in the manufacturing method shown in FIG. 12, the sidewall protective film can be made into a silicon oxide film by performing thermal oxidation after the step (2).

Thus, when the sidewall protective film is a silicon oxide film,
a) The reliability as a protective film in the etching process of the single crystal silicon substrate 61 is higher than that of the polymer deposition layer. b) When a smooth vertical surface (side wall surface) such as a mirror surface is required, the vertical surface in the oxide film generation process C) Planarization is a secondary effect. C) Since there is no need to generate and retain the desired polymer deposition layer, the etching process and polymer deposition in the deep gas reactive dry etching are repeated alternately. There is an advantage that the degree of freedom is expanded.

Incidentally, in the manufacturing method shown in FIGS. 9 and 12, the single crystal silicon layer 63 on the installation reference 91 can be removed by etching the insulating layer 62 in the step (5). The peripheral portion of the layer 62 is also etched, so that a minute gap is formed between the single crystal silicon substrate 61 and the single crystal silicon layer 63 as indicated by a dotted line 76 in FIG. 11B.
If such a void exists, the condensation 75 may be trapped in the void, and foreign substances other than the condensation 75 may be trapped, whereby the single crystal silicon substrate 61 and the single crystal silicon layer 63 are separated. A situation such as a short circuit can occur. FIG. 13 shows a configuration and a manufacturing method capable of preventing a short circuit due to the presence of such voids, and the manufacturing process shown in FIG. 13 will be described below.

Steps (1) to (5) are performed by any one of steps (1) to (5) shown in FIG. 9 or FIG.
(5 ') A silicon oxide film 69 is formed by oxidizing the entire surface of the exposed single crystal silicon surface by thermal oxidation.
(5 ″) Conductive windows 70 are formed by patterning the silicon oxide film 69 on the single crystal silicon layer 63 in the electrode pad formation region 55.
(6) An Au / Pt / Ti film is formed by sputtering in the electrode pad formation region 55 and the mirror 47 region.
By adopting such a process and forming the silicon oxide film 69 by thermal oxidation, it is possible to reliably prevent a short circuit in the above-described gap portion.

  As described above, taking the optical switch as an example, the configuration including the concave portion 64 that prevents the short circuit and the malfunction of the movable body and the installation reference 91 in which the upper surface of the single crystal silicon substrate 61 remains in the concave portion 64 are excellent. A description has been given of a configuration in which components can be mounted and installed with high accuracy, and a method of manufacturing such a recess 64 and installation reference 91 by isotropic etching of single crystal silicon has been described. A structure in which the recess and the installation standard are manufactured by anisotropic etching of single crystal silicon and a manufacturing method thereof will be described.

FIG. 14 shows an example of a small movable device having such a configuration by taking an optical switch as an example. Parts corresponding to those of the optical switch shown in FIGS. Omitted.
In this example, the optical switch uses an SOI substrate 60 in which a single crystal silicon layer 63 is disposed on a single crystal silicon substrate 61 whose upper surface (front surface) forms a (100) surface through an insulating layer 62 made of a silicon oxide film. The four fiber grooves 42 a to 42 d are formed along the <110> direction of the single crystal silicon substrate 61.
On the other hand, the movable bodies such as the mirror 47, the movable rod 46, the leaf spring hinges 48a and 48b, and the movable comb electrode 49 are mainly configured using lines that are not parallel to the <110> direction. It is supported by a pair of leaf spring hinges 48a, 48b. A hollow 58 is provided in a thick portion of the movable body, and the hollow 58 is mainly configured using a line that is not parallel to the <110> direction. However, all of these may include a line portion that is partially parallel to the <110> direction in the details of the outer shape.

In this example, the electrostatic actuator is composed of a pair of movable comb electrodes 49 and a fixed comb electrode 51, and a rod groove 44 in which the fixed comb electrodes 51 and the movable rod 46 are located, The subsequent concave portion 45 is also configured mainly using a line that is not parallel to the <110> direction. In this example, the mirror 47 is positioned at the central portion 43 in the initial state, and the mirror 47 is retracted from the central portion 43 by applying a voltage between the movable comb electrode 49 and the fixed comb electrode 51. The retracted state is maintained while the voltage is applied.
In each of the fiber grooves 42a to 42d, there is provided an installation reference 101 in which the upper surface of the single crystal silicon substrate 61 remains. The installation reference 101 has a lattice shape in this example, and the lattice is the single crystal silicon substrate 61. In the <110> direction. The optical fiber is mounted and installed on the installation reference 101 having the lattice shape.

FIGS. 15A and 15B schematically show a method of manufacturing an optical switch having the above structure in the order of steps, and each step will be described below.
(1) An SOI substrate 60 is prepared in which a single crystal silicon layer 63 is disposed on an insulating layer 62 on a single crystal silicon substrate 61 whose upper surface forms a (100) plane. For a structure in which the upper surface of the single crystal silicon layer 63 is oxidized to form a silicon oxide film, and a mask layer made of this silicon oxide film is patterned using a photolithography technique to be fixedly disposed on the single crystal silicon substrate 61 The mask 65, the movable body mask 66, and the installation reference mask 111 are formed.
The mask 111 for installation reference is configured by a line parallel to the <110> direction of the single crystal silicon substrate 61, and the mask 66 for the movable body is mainly configured using a line not parallel to the <110> direction. Composed. Further, the narrowest portion of each mask pattern has the narrowest width as the installation reference mask 111. Specifically, the pattern width of the installation reference mask 111 is about 1 to 2 μm. The mask 111 is designed so that the width of the mask 111 is larger than the thickness of the insulating layer 62.

(2) The portions of the single crystal silicon layer 63 exposed from the masks 65, 66, and 111 are etched away by deep gas reactive dry etching until the insulating layer 62 is exposed. As a result, the movable body 81 and the structure 82 are formed, and the narrow structure 112 is formed under the installation reference mask 111.
(3) The exposed portion of the insulating layer 62 is removed by etching to expose the upper surface of the single crystal silicon substrate 61. This etching is performed in a short time using a hydrofluoric acid aqueous solution. For example, a 50 wt% hydrofluoric acid aqueous solution takes about 3 minutes. Here, the etching time is not excessively long so that the insulating layer 62 below the narrow structure 112 is not completely lost. This step is performed to minimize the removal of the oxide film by RIE in the following step (5), and at the same time, the masks 65, 66, and 111 made of the silicon oxide film are also removed by etching.
(4) The single crystal silicon is thermally oxidized. The amount of oxidation is equal to or greater than the amount by which the entire narrow structure 112 is oxidized. A thermal oxide film 113 is formed on the surface of the single crystal silicon, and the thermal oxide film 113 formed on the sidewalls of the movable body 81 and the structure 82 is formed by the movable body 81 and the anisotropic body in the anisotropic etching in the following step (6). It functions as a sidewall protective film of the structure 82.

(5) The thermal oxide film 113 on the upper surface of the single crystal silicon substrate 61 and the upper surface of the single crystal silicon layer 63 is removed by etching to expose the upper surface of the single crystal silicon substrate 61 and the upper surface of the single crystal silicon layer 63. This etching is performed, for example, by RIE using a mixed gas of CHF3 and Ar. Since RIE has almost no etching action on a surface parallel to the incident direction of ions, the thermal oxide film 113 on the side walls of the movable body 81 and the structure 82 is not removed.
(6) Anisotropic etching of single crystal silicon is performed using a KOH aqueous solution. The upper surface of the single crystal silicon substrate 61 and the upper surface of the single crystal silicon layer 63 exposed by removing the thermal oxide film 113 are etched. Etching is performed until the bottom of the portion that becomes the movable body 81 is removed by etching. Under the movable body 81, side etching is generated by the (100) plane, the (110) plane, the (311) plane, etc., and the recess 64 is formed.

On the other hand, since the narrow structure 112 has a lattice shape parallel to the <110> direction of the single crystal silicon substrate 61 in the fiber groove, an inverted pyramid hole 102 is formed by the (111) plane. Since side etching does not occur under the narrow structure body 112, the surface of the single crystal silicon substrate 61 remains. As a result, a concave portion 64 made up of a set of inverted pyramid type holes 102 and an installation reference 101 having a lattice shape within the concave portion 64 are formed.
(7) The portions remaining after being thermally oxidized in step (4), that is, the movable body 81, the thermal oxide film 113 on the side walls of the structure 82 and the narrow structure 112 are removed with hydrofluoric acid. Then, although not shown in the figure, an electrode pad is formed and a metal is also formed on the mirror at the same time. The metal surface is preferably Au.

The optical switch shown in FIG. 14 is completed by the manufacturing process as described above. FIG. 15-2 (8) shows a state in which the optical fiber 71 is mounted and installed in the fiber groove, and the height of the optical fiber 71 is such that the upper surface of the single crystal silicon substrate 61 remains. It is determined with high accuracy by the grid-like installation reference 101. Although not shown in the drawing, the optical fiber 71 is fixed with an adhesive.
Thus, according to this example, the recess 64 can be formed between the structures fixedly arranged on the single crystal silicon substrate 61 by anisotropic etching of single crystal silicon, and the optical fiber 71 is installed. A grid-like installation reference 101 in which the upper surface of the single crystal silicon substrate 61 is left can be provided in the recess 64 at the portion.

In the example described above, the optical fiber 71 is mounted with the upper surface of the installation reference 101 having a lattice shape as the mounting surface. Next, the installation reference is set to two parallel strips, and between these strips. Next, a description will be given of a configuration in which a V-groove is formed and an optical fiber can be mounted with high accuracy by the V-groove.
FIG. 16 shows an optical switch having such a configuration, and parts corresponding to those in FIG. 14 are denoted by the same reference numerals.
In this example, in each of the fiber grooves 42a to 42d, there is provided an installation reference 104 composed of two parallel strips 103 in which the upper surface of the single crystal silicon substrate 61 remains, and these strips 103 are respectively provided with the fiber grooves 42a. It extends in parallel with ˜42d, that is, it is configured in the <110> direction of the single crystal silicon substrate 61. By setting the installation standard 104 to such two strips 103, a V-groove is formed between the two strips 103.

  FIG. 17A shows how this V-groove is formed in correspondence with step (6) of FIG. 15-2. In this example, two parallel narrow structures are formed in the fiber groove. 112 'is formed through steps similar to steps (1) to (5) in FIGS. 15-1 and 15-2, and between these narrow structures 112' by anisotropic etching of single crystal silicon. A V-groove 105 having a (111) plane is formed on the upper surface of the single crystal silicon substrate 61. Note that V-grooves 106 are also formed on the outer sides of both narrow structures 112 '.

FIG. 17 (a) shows a state in which the optical fiber 71 is mounted and installed in the V groove 105 formed between the strips 103 by setting the installation reference 104 to be two parallel strips 103. The optical fiber 71 can be positioned with high accuracy by the V groove 105. Note that the V groove 105 can accurately position not only in the height direction but also in the lateral direction, and the distance between the two strips 103 formed by the design of the V groove 105, that is, the upper surface of the single crystal silicon substrate 61 remains. By selecting, the height of the optical axis of the optical fiber 71 can be easily adjusted.
Note that, in addition to the method described with reference to FIG. 17 described above, the manufacturing method in the form in which the installation standard 104 is the two strips 103 and the V-groove 105 is provided between the strips 103 is an order of increasing or decreasing the mask pattern width. The installation reference mask and the movable body are replaced, that is, the pattern width of the installation reference mask is made wider than the pattern width of the movable body mask, and the narrow structure formed under the installation reference mask as a whole Alternatively, it is also possible to adopt a method in which only the surface is thermally oxidized, and the insulating layer portion under the surface is removed by etching to remove and remove the upper narrow structure portion. 18A and 18B show this manufacturing method in the order of steps corresponding to FIGS. 15A and 15B.

In this example, as shown in step (1) of FIG. 18A, the pattern width of the mask 111 for installation reference is made larger than the pattern width of the mask 66 for movable body. The surface of the narrow structure 112 'is thermally oxidized by thermal oxidation. Steps (1) to (6) are the same as steps (1) to (6) in FIGS. 15A and 15B, and a V-groove 105 is formed between the two narrow structures 112 ′. Is done. The anisotropic etching of single crystal silicon in the step (6) is completed by forming the V groove 105 in a desired size.
In step (7), the insulating layer 62 is removed by etching until the insulating layers 62 on the two strips 103 constituting the installation standard 104 are removed, and at the same time, the thermal oxide film 113 is also removed by etching. By removing the insulating layer 62 by etching in this manner, the narrow structure 112 'is also removed and removed at the same time. In this example, unlike the case of FIG. 17, the insulating layer 62 under the movable body 81 is also removed by etching.
As described above, taking the optical switch as an example, the concave portion 64 is formed by anisotropic etching of the single crystal silicon substrate 61, and the upper surface of the single crystal silicon substrate 61 for component placement remains in the concave portion 64 simultaneously with the formation of the concave portion 64. The manufacturing method for providing the installation standards 101 and 104 has been described. However, compared to the formation of the recesses 64 and the installation standards 91 by the isotropic etching described above, there is a difference in the stability and accuracy of the formed shape. It is preferable to use isotropic etching.

Claims (2)

Comprising a movable body and a structure other than the movable body,
The structure includes a single crystal silicon layer of an SOI substrate having a three-layer structure in which a single crystal silicon layer is disposed on a single crystal silicon substrate via an insulating layer made of a silicon oxide film. Fixed on the single crystal silicon substrate,
The movable body is composed of the single crystal silicon layer, and is held by the structure so as to be displaceable parallel to the plate surface of the single crystal silicon substrate.
A recess is formed in the entire area where the structure does not exist on the upper surface of the single crystal silicon substrate, and the movable body is located on the recess,
The structure has an overhang portion projecting over the recess, and a peripheral edge of the insulating layer that is below the overhang portion and fixes the structure to the single crystal silicon substrate is on the recess. A method of manufacturing a micro movable device in which a micro air gap is formed between the single crystal silicon substrate and the single crystal silicon layer .
Forming a mask layer on the upper surface of the single crystal silicon layer of the three-layer SOI substrate;
Forming the mask for the structure and the mask for the movable body made of a combination of narrow patterns by patterning the mask layer;
The portion of the single crystal silicon layer exposed from the mask is removed by gas reactive dry etching until the insulating layer is exposed perpendicular to the single crystal silicon substrate,
A side wall surface perpendicular to the single crystal silicon substrate plate surface of each single crystal silicon layer formed under each mask by the dry etching is covered with a side wall protective film,
Etching and removing the exposed portion of the insulating layer by the dry etching to expose the upper surface of the single crystal silicon substrate,
To the exposed upper surface of the single crystal silicon substrate, isotropic etching of the monocrystalline silicon to the bottom side of the surface region of the single crystal silicon substrate is removed by etching the recessed portion of the movable body mask is formed alms, thereby, the above-mentioned recesses in all areas where the structure is not present in the single crystal silicon substrate top surface is formed, the movable body is located on said recess, said structure protrudes on the recess above With an overhang,
Thereafter, the mask and removing the side wall protective film, a method for manufacturing a micro movable device, characterized in that the lower the insulating layer of the insulating layer and the overhanging portion of the lower side of the movable member is removed by etching. Comprising a movable body and a structure other than the movable body,
The structure includes a single crystal silicon layer of an SOI substrate having a three-layer structure in which a single crystal silicon layer is disposed on a single crystal silicon substrate via an insulating layer made of a silicon oxide film. Fixed on the single crystal silicon substrate,
The movable body is composed of the single crystal silicon layer, and is held by the structure so as to be displaceable parallel to the plate surface of the single crystal silicon substrate.
A recess is formed in the entire area where the structure does not exist on the upper surface of the single crystal silicon substrate, and the movable body is located on the recess,
The structure has an overhang portion projecting over the recess, and a peripheral edge of the insulating layer that is below the overhang portion and fixes the structure to the single crystal silicon substrate is on the recess. A method of manufacturing a micro movable device in which a micro air gap is formed between the single crystal silicon substrate and the single crystal silicon layer .
Forming a mask layer on the upper surface of the single crystal silicon layer of the three-layer SOI substrate in which the single crystal silicon layer is disposed on the single crystal silicon substrate having an upper surface of the (100) plane through an insulating layer;
The movable body mask whose outer shape is configured by using a line that is not parallel to the <110> direction of the single crystal silicon substrate, and the structural mask, the narrowest portion of each mask pattern. The mask layer is patterned to form the mask for the structure and the movable body in order from the widest width,
The portion of the single crystal silicon layer exposed from the mask is removed by gas reactive dry etching until the insulating layer is exposed perpendicular to the single crystal silicon substrate,
Removing the portion of the insulating layer exposed by the dry etching and the mask;
Thermally oxidize the exposed surface of single crystal silicon,
The thermal oxide film on the upper surface of the single crystal silicon substrate is etched away perpendicularly to the single crystal silicon substrate to expose the upper surface of the single crystal silicon substrate,
To the exposed upper surface of the single crystal silicon substrate under the portion to be the above-mentioned movable member is removed by side etching, subjected to anisotropic etching of single crystal silicon until said recesses are formed,
Then, a method for manufacturing a micro movable device and removing the thermal oxide film of the insulating layer and on the side walls.

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