JP2005096008A - Manufacturing method for semiconductor structure, and optical switching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent side etching at both longitudinal ends of a plate-like structure. <P>SOLUTION: In this manufacturing method for a semiconductor structure, a semiconductor substrate is etched to form the plate-like structure with side faces formed as (111) faces almost perpendicular to the main surface of the substrate. A mask pattern is formed having a pair of slits corresponding to the side faces, and after wet etching is performed to form the side faces formed of the (111) faces, a part other than the plate-like structure is eliminated by dry etching. With the formation of the (111) faces by wet etching and the dissolution of side etching by dry etching, the plate-like structure is accurately formed with a required minimum produced area. The formed plate-like structure is used as a mirror in an optical switching device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor structure manufacturing method for manufacturing a plate-like structure having a Si surface orientation (111) having a high perpendicularity to the main surface of a silicon substrate on its side surface, and further to manufacturing the semiconductor structure The present invention relates to an optical switching device using a plate-like structure manufactured by the method as a mirror.

  With the recent increase in the speed of the Internet, the spread of optical communication systems has rapidly progressed, and research and development have been conducted in various fields regarding optical switching devices that can process optical signals as light. Various types of optical switching devices have been proposed so far, and as one of them, for example, a plate-shaped mirror formed by micromachining technology is arranged in the optical path of the optical fiber, and this is used. 2. Description of the Related Art An optical switching device that switches on and off by moving in and out in the vertical direction is known.

When considering such an optical switching device, it is desired to form a plate-like structure as a mirror accurately and easily, and a manufacturing method using wet etching has been conventionally employed. The manufacturing method of the (111) face plate structure by wet etching will be described. In order to form the (111) face plate structure, a mask is formed by patterning SiO ₂ , SiN _x or the like on the silicon substrate by photolithography or the like. And wet etching with an inorganic alkaline solution such as KOH or NaOH, or an organic alkaline solution such as ethylenediamine / pyrocatechol (EDP), hydrazine, tetramethylammonium hydroxide (TMAH) :( CH ₃ ) 4NOH, or the like. .

  At this time, for example, if a silicon substrate having an etching surface of (110) is used, the (100) surface and the (111) surface having an etching rate of about 1/100 or less of the (110) surface become side surfaces and have vertical side walls. A substantially parallelogram wet etching opening having a high aspect ratio can be easily formed.

In addition, as a method of manufacturing a micromirror having a plate-like structure, for example, a method including a step of forming a mirror surface by performing anisotropic wet etching on a silicon substrate to form a micromirror has also been proposed. (For example, refer to Patent Document 1).
JP 2000-121967 A

  However, in the conventional method, in any case, since the plate-like structure is formed by performing wet etching on surfaces other than the (111) surface, a number of inconveniences occur.

  For example, when the plate-like structure is formed by wet etching, abrupt side etching occurs from both ends in the longitudinal direction of the plate-like structure, and both ends of the plate-like structure disappear and are finally formed. There is a problem that the length of the plate-like structure is shortened. For this reason, it is necessary to perform patterning in consideration of the amount of side etching at the time of wet etching, and a very wide etching region (area) must be ensured compared to the original longitudinal size of the plate-like structure.

  In addition, since both end portions in the longitudinal direction of the plate-like structure are side-etched, the shape of both end portions is disturbed, and there is a problem that it is extremely difficult to form in a desired shape. FIG. 12 schematically shows the shape of the plate-like structure when all the side surfaces constituting the plate-like structure are formed by wet etching.

  When the plate-like structure 102 is formed on the silicon substrate 101 only by wet etching, the side surface 103 which is the (111) surface is formed as a flat surface. On the other hand, at both end faces 104 in the longitudinal direction of the plate-like structure 101, the plate-like structure 101 partially disappears due to side etching, and shape deterioration occurs, resulting in a plate-like structure having high accuracy in the longitudinal direction. It is difficult to form.

  Therefore, the present invention has been proposed in view of the above-described situation, and prevents the side etching at both ends in the longitudinal direction of the plate-like structure, and has a plate shape having a high-aspect (111) surface with high verticality. An object of the present invention is to provide a semiconductor structure manufacturing method capable of easily and accurately forming a structure, and further to provide an optical switching device having the plate-like structure.

  In order to solve the above-described problems, a semiconductor structure manufacturing method of the present invention etches a semiconductor substrate to form a plate-like structure that is substantially perpendicular to the main surface of the substrate and has a (111) side surface. In the semiconductor structure manufacturing method, a mask pattern having a pair of slits corresponding to the side surfaces is formed, wet etching is performed to form side surfaces composed of (111) surfaces, and portions other than the plate-like structure are dry etched. It removes by. The optical switching device of the present invention is characterized in that the plate-like structure manufactured as described above is used as a mirror.

  In the present invention, by using wet etching, a high aspect (111) surface having very high perpendicularity to the main surface of the semiconductor substrate is formed as the side surface of the plate-like structure.

  On the other hand, since both end surfaces in the longitudinal direction of the plate-like structure are formed by dry etching, there is no risk of side etching, and the shape of the both end surfaces does not deteriorate. Further, reduction of the size of the plate-like structure due to side etching is also avoided, and the plate-like formed body can be manufactured with the minimum necessary manufacturing area.

  According to the method for manufacturing a semiconductor structure according to the present invention, wet etching and dry etching are performed in this order when the plate-like structure is formed, so that side etching from both longitudinal ends of the plate-like structure is prevented. be able to. Therefore, a plate-like structure having a desired shape can be accurately formed without deterioration of the shape of both end portions of the plate-like structure, and the plate-like structure can be formed on the semiconductor substrate with the minimum necessary manufacturing area. Can be formed.

  In addition, according to the optical switching device of the present invention, a high-quality plate-like structure that is manufactured by performing wet etching and dry etching in this order and has no side etching from both ends in the longitudinal direction is used as a mirror. Therefore, the optical characteristics can be improved.

  Embodiments to which the present invention is applied will be described below in detail with reference to the drawings.

[First Embodiment]
[Semiconductor Structure Manufacturing Method According to First Embodiment]
The semiconductor structure manufacturing method according to the first embodiment is applied, for example, to a step of forming a plate-like structure having a side surface that reflects light in an optical switching device on a silicon substrate. This plate-like structure is composed entirely of the (111) plane of the silicon crystal.

  In the semiconductor structure manufacturing method according to the first embodiment, first, a silicon substrate 10 is prepared as a semiconductor substrate, as shown in a perspective view in FIG. 1A and a cross-sectional view in FIG. In the present embodiment, a substrate having a silicon (110) upper surface on which a process described later is performed is used as a supporting substrate to be etched.

  Then, as shown in FIGS. 2A and 2B, an oxide film 11 is formed on almost the entire surface of the silicon substrate 10 as a dry etching mask by, for example, CVD (chemical vapor deposition) oxidation. Here, in order to form a plate-like structure having a height of about 600 μm, the thickness of the oxide film 11 is desirably 4 μm or more.

  Next, as shown in FIGS. 3A and 3B, a thick film resist 12 is used so that the oxide film 11 remains in a portion that becomes a plate-like structure when viewed from above, for example, by a photolithography technique or the like. Then, the oxide film 11 is patterned. As a result, a plate-like structure pattern 20 composed of an elongated rectangular oxide film 11 and thick film resist 12 is formed. The thickness of the thick film resist 12 is preferably about 10 μm or more in consideration of the thickness of the oxide film 11.

  Next, after removing the thick resist 12 on the oxide film 11, a nitride film 13 is formed as a wet etching mask so as to cover the patterned oxide film 11 as shown in FIGS. It is laminated on the entire surface of the silicon substrate 10. The film thickness of the nitride film 13 is preferably at least about 1000 mm, considering a long wet etching process to be performed later.

  Subsequently, as shown in FIGS. 5A and 5B, a pair of slit patterns 21 in which the silicon substrate 10 is exposed are formed on both sides in the width direction of the oxide film 11 using the resist 14. The nitride film 13 is patterned. The slit pattern 21 has a substantially parallelogram shape composed of (111) planes.

  Then, after removing the resist 14, the silicon substrate 10 is wet etched with an alkaline aqueous solution using the nitride film 13 as a mask. Since the (110) plane silicon substrate 10 is used as the support substrate, the etching rate for the (111) plane is much smaller than the etching rate for the (110) plane and the (100) plane, and as a result, FIG. And as shown to (b), the wet etching opening part 30 which has the (111) surface 40 perpendicular | vertical to the main surface of the silicon substrate 10 as a side wall is formed in the part corresponding to the slit pattern 21. FIG.

  At this time, the wet etching solution used is a 40% strength aqueous potassium hydroxide solution, and the solution temperature is 75 ° C. Other wet etching solutions include inorganic alkaline solutions such as NaOH, organic alkaline solutions such as ethylenediamine / pyrocatechol (EDP), hydrazine, tetramethylammonium hydroxide (TMAH) :( CH3) 4NOH, and the like. Can do.

  Next, as shown in FIGS. 7A and 7B, the nitride film 13 is removed, and further, as shown in FIGS. 8A and 8B, dry etching is performed using the oxide film 11 as a mask. As a result, the plate-like structure exterior 31, which is a region where the oxide film 11 is not formed, is etched to form plate-like structures 50 having (111) surfaces 40 perpendicular to the main surface of the substrate surface 10 on both sides. Is done.

[Effect of the first embodiment]
As described above in detail, in the semiconductor structure manufacturing method according to the first embodiment, wet etching is performed with the slit patterns 21 where the silicon substrate 10 is exposed on both sides of the portion to be the side surface of the plate-like structure 50. The wet etching opening 30 having the (111) surface 40 is formed. Thereafter, the plate-like structure exterior 31 is removed by dry etching using the oxide film 11 as a mask, and the plate-like structure 50 is formed. For this reason, there is no side etching from both ends in the longitudinal direction of the plate-like structure 50 as in the case where all the etching is wet etching, and the high aspect ratio has good perpendicularity to the main surface of the silicon substrate 10. The plate-like structure 50 can be formed in a desired shape.

[Second Embodiment]
Next, a semiconductor structure manufacturing method according to the second embodiment will be described. In addition, since the basic manufacturing process of the plate-like structure in the second embodiment is the same as the manufacturing process in the semiconductor structure manufacturing method according to the first embodiment described above, the description thereof is omitted here.

  The semiconductor structure manufacturing method according to the second embodiment includes a length in the longitudinal direction of the plate-like structure 50, a slope at the longitudinal end portion of the wet etching opening 30 grown by crystal anisotropy of the silicon substrate 10, and a wet structure. In consideration of the etching depth, the length of the slit pattern 21 (the length of the opening of the wet etching opening 30) is determined.

  When the plate-like structure 50 is manufactured by the method shown in the first embodiment, the plate-like structure 50 is formed at the ends in the longitudinal direction of the two slit patterns 21 (openings of the wet etching openings 30). That is, as shown in FIG. 9A, when the wet etching opening 30 is formed by wet etching the parallelogram slit pattern 21 having the (111) plane, both ends in the longitudinal direction of the slit pattern 21 are formed. Etching at the portion does not proceed perpendicularly to the main surface, but proceeds obliquely inward from the acute angle portion toward the bottom surface of the wet etching opening 30 to form the (111) slope 60.

  For this reason, the length of the bottom part of the finally formed plate-like structure 50 is shorter than the length of the slit pattern 21, and the area of the (111) surface 40 formed by wet etching is small. turn into. The formation of the (111) slope 60 in this way depends on the crystal anisotropy and the shape of the slit pattern 21 serving as a mask.

  Here, the size of the (111) slope 60 that grows in the wet etching opening 30 depends on the depth of the wet etching opening 30. Therefore, when the plate-like structure 50 is formed, the length of the opening in the longitudinal direction of the wet etching opening 30 is determined in consideration of the (111) slope 60 in advance.

  That is, as shown in FIG. 9B, the length in the longitudinal direction of the finally formed plate-like structure 50 is defined as a plate-like structure pattern length A, and (111 ) The length of the slope 60 is a (111) plane length B, and the length of the opening (slit pattern 21) of the wet etching opening 30 in the longitudinal direction is a slit length C. When the plate-like structure 50 having a height of 600 μm and a length of 600 μm in the longitudinal direction is formed, the slit length C is changed to the plate-like structure pattern length A and the (111) surface length B. More specifically, the value may be taken into account. Specifically, the length (111) of the (111) plane from the silicon crystal orientation plane is determined by √3 × etching depth, and is therefore 1678 μm or more.

  In the semiconductor structure manufacturing method according to the second embodiment, in order to form the plate-like structure 50 by determining the slit length C in consideration of the (111) plane 60 that grows in the wet etching opening 30. A region (area) to be secured can be predicted in advance, and the plate-like structure 50 can be formed with a minimum production area.

  In the semiconductor structure manufacturing method according to the second embodiment, a region to be secured for forming the plate-like structure 50 by taking into account the depth of wet etching when the wet etching opening 30 is formed. (Area) can be predicted in advance, and the plate-like structure 50 can be formed with a minimum necessary area.

[Third Embodiment]
Next, a semiconductor structure manufacturing method according to the third embodiment will be described. Note that the basic manufacturing process of the plate-like structure in the third embodiment is also the same as the manufacturing process in the semiconductor structure manufacturing method according to the first embodiment described above, and the description thereof is omitted here.

  In the semiconductor structure manufacturing method according to the third embodiment, a large number of plate-like structures are formed on a single silicon substrate.

  In the semiconductor structure manufacturing method according to the third embodiment, a pair of slit patterns 21 for forming the side surfaces of the plate-like structure 50 is formed on one silicon substrate 10 as shown in FIG. × N matrix shapes are formed, and then wet etching and dry etching are performed in this order in the same manner as in the first and second embodiments, and as shown in FIG. Many are formed.

  In the semiconductor structure manufacturing method according to the third embodiment, when a pair of slit patterns 21 are arranged in a matrix of N × N on one silicon substrate 10, side etching in the longitudinal direction of the plate-like structure 50 is performed. Since it is not necessary to consider the amount, the mask pattern region 70 occupied by each plate-like structure 50 can be relatively small, and a large number of slit patterns 21 can be formed on the semiconductor substrate. Therefore, the number of plate-like structures 50 formed on one silicon substrate 10 can be increased.

For example, when a plate-like structure having a height of 600 μm and a length of 600 μm is produced, the area of the mask pattern region 70 indicated by one matrix-like plate-like structure 50 is used only by wet etching. In the case of forming this, a production area of at least 4200 × 4200 μm ² is necessary in consideration of the amount of side etching from the corner, whereas in this embodiment, the production area is greatly reduced to 1893 × 1893 μm ^2. Can do.

  Further, as shown in FIG. 10B, all the plate-like structures 50 formed on one silicon substrate 10 are collectively formed by anisotropic etching using crystal orientation planes that are difficult to wet-etch. Therefore, there is no dimensional variation for each plate-like structure 50, and the plate-like structure 50 can be formed with high accuracy.

[Configuration of optical switching device]
The optical switching device according to the present embodiment has a large number of plate-like structures 50 formed by the semiconductor structure manufacturing method according to any of the first to third embodiments as mirrors of the optical switch. Is.

  The optical switching device shown in FIG. 11 includes a mirror unit 90 having, as a mirror 70, a plate-like structure formed by the semiconductor structure manufacturing method according to any of the first to third embodiments described above. N × N mirror units 90 are arranged in a matrix to form an N × N mirror unit 91. Further, the optical switching device has three sides of the outer periphery with the N × N mirror unit 91 in the center, and at a position where light can enter or exit at an angle of 45 ° with respect to the side surface of each mirror 70, A plurality of fibers 80 are provided.

  Each mirror unit 90 includes, for example, a fixed electrode, a movable electrode formed on the fixed electrode, and a mirror 70 formed on the movable electrode. The movable electrode has a structure in which the periphery is supported by a fixed electrode and at least the lower side of the mirror 70 is dug to enable vertical movement.

  In such an optical switching device, the light is switched by moving the movable electrode in the vertical direction by applying a voltage between the fixed electrode and the movable electrode, for example, and inserting / removing the mirror 70 with respect to the optical axis of the fiber 80. Accordingly, the light incident from the input-side fiber 80 is transmitted or reflected and output from the output-side fiber 80, and the like.

  In this optical switching device, a plate-like structure manufactured by the semiconductor structure manufacturing method according to any of the first to third embodiments described above is used as the mirror 70 of the mirror unit 90. Accordingly, the side surfaces of all the mirrors 70 included in the N × N mirror unit 91 are formed in the same orientation plane by anisotropic etching in consideration of crystal orientation, so that each individual side like a conventional optical switching device is manufactured. A step of sequentially aligning the optical fibers with respect to the mirror is not necessary, and alignment can be easily performed.

  Further, according to this optical switching device, since the mirror 70 can be formed without considering the side etching amount of the mirror 70, the area necessary for forming the mirror 70 can be relatively small. As a result, one substrate Since a large number of mirrors can be arranged on the top, it is possible to reduce the size and integration. Therefore, large-scale optical switching can be realized.

  Further, in this optical switching device, a plate-like structure having a good verticality and a high aspect ratio manufactured by the semiconductor structure manufacturing method according to any of the first to third embodiments is used as the mirror 70 of the mirror unit 90. Used as Thus, since the mirrors of all the mirror units 90 are collectively formed by anisotropic etching using the crystal orientation plane, there is no dimensional variation for each mirror 70, and excellent optical characteristics can be realized. it can.

  Each of the above-described embodiments is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and even if it is a form other than this embodiment, as long as it does not depart from the technical idea of the present invention, it depends on the design and the like. Of course, various modifications are possible.

An example of the manufacturing process in the semiconductor structure manufacturing method to which this invention is applied is shown, (a) is a perspective view of a semiconductor substrate, (b) is the sectional drawing. The oxide film formation process is shown, (a) is a perspective view, (b) is a sectional view. The oxide film patterning process is shown, (a) is a perspective view, (b) is a sectional view. The nitride film formation process is shown, (a) is a perspective view, (b) is a sectional view. The nitride film patterning process is shown, (a) is a perspective view, and (b) is a sectional view. The wet etching process is shown, (a) is a perspective view, (b) is a sectional view. The nitride film removal process is shown, (a) is a perspective view, (b) is a sectional view. The dry etching process is shown, (a) is a perspective view, (b) is a sectional view. It is a figure for demonstrating the manufacturing method of the semiconductor structure which concerns on 2nd Embodiment of this invention, (a) is a perspective view which shows the state in which a pair of wet etching opening part was formed in the both sides of a plate-shaped structure pattern (B) is a plan view. It is a figure for demonstrating the manufacturing method of the semiconductor structure which concerns on 3rd Embodiment of this invention, (a) is a perspective view which shows the state in which a pair of slit pattern was formed in the matrix form on one silicon substrate. (B) is a perspective view showing a state in which plate-like structures are formed in a matrix on one silicon substrate. It is a top view which shows an example of the optical switching device to which this invention is applied. It is a perspective view of the plate-shaped structure formed by the conventional manufacturing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Silicon substrate 11 Oxide film 12 Thick film resist 13 Nitride film 14 Resist 20 Plate-like structure pattern 21 Slit pattern 30 Wet etching opening 31 Plate-like structure exterior 40 (111) surface 50 Plate-like structure 60 (111) Slope 70 mirror 80 fiber 90 mirror unit 91 N × N mirror unit

Claims (7)

In a semiconductor structure manufacturing method of etching a semiconductor substrate to form a plate-like structure that is substantially perpendicular to the main surface of the substrate and has a side surface of (111).
After forming a mask pattern consisting of a pair of slits corresponding to the side surfaces and performing wet etching to form side surfaces consisting of (111) planes,
A method for manufacturing a semiconductor structure, wherein portions other than the plate-like structure are removed by dry etching.   The method of manufacturing a semiconductor structure according to claim 1, wherein the semiconductor substrate is a silicon substrate. Forming a dry etching mask in a region corresponding to the plate-like structure of the semiconductor substrate;
Forming a wet etching mask so that slits for exposing the semiconductor substrate are formed on both sides of the dry etching mask in the width direction;
Performing wet etching on the semiconductor substrate to form wet etching openings having (111) surfaces as side surfaces on both sides in the width direction of the dry etching mask;
Performing dry etching on the semiconductor substrate, etching the semiconductor substrate in a region where the mask for dry etching is not formed, and forming a plate-like structure having a (111) plane as a side surface. The method of manufacturing a semiconductor structure according to claim 1.   4. The method of manufacturing a semiconductor structure according to claim 3, wherein the length of the slit is determined in consideration of a (111) slope formed at an end of the slit and a depth of a wet etching opening.   The length of the slit is set so that the length of the bottom of the wet etching opening excluding the (111) slope portion generated at the end of the slit is equal to or longer than the length of the plate-like structure. The method of manufacturing a semiconductor structure according to claim 4, wherein:   6. The semiconductor structure manufacturing method according to claim 1, wherein a plurality of the plate-like structures are formed by arranging the slits in a matrix.   The optical switching device which makes the plate-shaped structure manufactured by the semiconductor structure manufacturing method in any one of Claims 1-6 a mirror.

Images