JP2005266482A - Optical switching element and its manufacturing method, and control method for optical switching element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical switching element whose degree of freedom of design can be eased and to provide its manufacturing method, and a control method for the optical switching element. <P>SOLUTION: The optical switching element comprises a silicon substrate 1, a lower clad 9 formed on the silicon substrate 1, an auxiliary core 7a buried in the lower clad 9, 1st and 2nd cores 10a and 10b formed on the lower clad 9 on the auxiliary core 7a at an interval, an upper clad 12a covering the 1st and 2nd cores 10a and 10b, and heaters 13a and 13b which are provided to the upper clad 12a and selectively heat at least one of the 1st core 10a and 2nd core 10b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical switching element, a method for manufacturing the same, and a method for controlling the optical switching element.

  In recent years, with the development of optical communication systems, optical devices such as optical waveguides and optical switching devices have been actively studied. In particular, the optical switching element is used, for example, when an optical signal of a branch network is selectively switched to a plurality of optical fibers of a home network, and is indispensable for the construction of an optical communication system.

Conventionally, when manufacturing such an optical switching element, a raw material gas such as SiCl ₄ is caused to flow into an oxygen burner by a flame hydrolysis deposition method on a silicon substrate, causing an oxidation reaction in the flame, and a glass particle layer. A lower clad and a core material are deposited as follows. Impurities such as TiO ₂ and GeO ₂ are added to the core material in order to obtain a refractive index difference from the cladding. And after heat-processing 1200 degreeC or more and making glass particles adhere | attach, a resist pattern is formed on a core material, and a core is formed by plasma-etching a core material, using this resist pattern as a mask. Thereafter, an upper clad is deposited so as to cover the core by a flame hydrolysis method, and heat treatment at 1200 ° C. or higher is performed so that the glass particles of the upper clad are brought into close contact with each other, thereby forming an element having the same function as an optical fiber. It was formed on the substrate.

  However, when the core material is deposited by the flame hydrolysis and deposition method in this way, the dispersion of the impurity diffusion for adjusting the refractive index is so large that the refractive index of the core varies, and the film thickness distribution of the deposited film is poor. Become.

  Furthermore, when the lower clad, the core, and the upper clad are laminated in this order as described above, the etching selectivity between the clad and the core is small when the core is etched and patterned, so the etching selectivity between them is small. Become. Therefore, it becomes difficult to selectively etch only the core, and even the lower clad below the core is etched, making it impossible to form a core having a desired sidewall shape. In particular, if the side wall of the core is tilted without being perpendicular to the surface of the silicon substrate or if the side wall is skirted, light passing through the core is attenuated.

  In view of these points, the inventor of the present application first invented the optical switch manufacturing method described in Patent Document 1. In this method, the above-described problem is solved by forming the lower cladding, the core, and the upper cladding by chemical vapor deposition instead of the flame hydrolysis deposition method.

In addition, techniques related to the present application are also disclosed in Patent Document 2 and Patent Document 3.
JP 2003-344585 A JP-A-9-318978 JP-A-8-328049

  By the way, in patent document 1 which this inventor applied earlier, only one of two adjacent cores is selectively heated, and the refractive index of the heated core is made lower than the other core. , Switching light from the heated core to the other core.

  However, in this method, the switching time depends on the interval between the cores, and the shorter the interval, the shorter the switching time, and conversely, the longer the core interval, the longer the switching time. Therefore, if an attempt is made to shorten the switching time, the core interval must be reduced, the core interval is limited, and the degree of freedom in designing the optical switching element is reduced.

  The objective of this invention is providing the control method of the optical switching element which can ease a design freedom, its manufacturing method, and an optical switching element.

  According to an aspect of the present invention, a substrate, a lower cladding formed on the substrate, an auxiliary core embedded in the lower cladding, and a gap on the lower cladding above the auxiliary core. The first core and the second core formed in the above, an upper clad covering the first core and the second core, and one of the first core and the second core provided in the upper clad There is provided an optical switching element characterized by having a heat generating part for selectively heating the light.

  According to this, by selectively heating one of the first core and the second core, the light transmitted through the heated core passes through the auxiliary core and is not heated. Move to. As described above, since the switching between the first and second cores is performed via the auxiliary core, it is not necessary to reduce the distance between the first and second cores in order to increase the switching speed. Therefore, the restriction on the distance between the first and second cores is relaxed, and the first and second cores can be freely routed compared with the case where there is no auxiliary core, and the degree of freedom in designing the optical switching element is increased. .

  According to another aspect of the present invention, a step of forming a lower clad lower layer on the substrate by chemical vapor deposition, and a step of forming a recess in the lower clad lower layer, A step of forming an auxiliary core in the recess, a step of forming an upper layer of the lower clad on the lower layer of the lower clad and the auxiliary core, and a chemical layer on the upper layer of the lower clad. Forming a core material layer by vapor deposition, patterning the core material layer to form a first core and a second core at an interval above the auxiliary core, and a chemical vapor There is provided a method for manufacturing an optical switching element, comprising: a step of forming an upper clad covering the first and second cores by a phase growth method; and a step of forming a heat generating portion in the upper clad.

  According to this, since the lower cladding, the auxiliary core, the first and second cores, and the upper cladding are all formed by chemical vapor deposition, they are formed by flame hydrolysis deposition as in the past. Compared with, variations in refractive index and film thickness distribution are suppressed, and a high-quality optical switching element is provided.

  Furthermore, according to another aspect of the present invention, a first core and a second core embedded in the cladding at a distance from each other, and the first core and the second core straddle the cladding. An optical switching element control method comprising an embedded auxiliary core and a heat generating part that selectively heats one of the first core and the second core, wherein the heat generating part selects the first core There is provided a method of controlling an optical switching element, characterized in that the light transmitted through the first core is heated to move to the second core via the auxiliary core.

  According to this, of the first core and the second core, the heated core is thermally expanded to lower the refractive index, and the light transmitted through the core moves to the auxiliary core having a higher refractive index. Is switched to the second core.

  According to the optical switching element of the present invention, by embedding the auxiliary core in the lower cladding, the limitation on the distance between the first and second claddings on the auxiliary core is relaxed, and the design flexibility of the optical switching element is increased. Can be bigger.

  In addition, according to the method for manufacturing an optical switching element of the present invention, the lower cladding, the auxiliary core, the first and second cores, and the upper cladding are all formed by chemical vapor deposition, so that the refractive index and film A high-quality optical switching element in which variations in thickness distribution are suppressed can be provided.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

(1) 1st Embodiment FIGS. 1-10 is principal part sectional drawing in the middle of manufacture based on the manufacturing method of the optical switching element which concerns on 1st Embodiment of this invention.

First, as shown in FIG. 1A, a silicon oxide film having a thickness of about 15 μm is formed on a silicon substrate 1 by a plasma CVD method using SiH ₄ as a reaction gas, and is formed under the lower cladding. Side layer 2 is assumed. The refractive index of the lower layer 2 is about 1.46. Note that the lower layer 2 may be formed by a thermal CVD method.

  Next, steps required until a sectional structure shown in FIG.

  First, a resist pattern (not shown) is formed on the lower layer 2 by photolithography, and the lower layer 2 is plasma-etched using the resist pattern as an etching mask to form a hole 2a in the lower layer 2 To do. The hole 2a has a rectangular shape in plan view, and the vertical length of the rectangle is about 1.0 μm and the horizontal length is about 0.6 μm. The depth of the hole 2a is about 0.6 μm. However, the depth of the hole 2a is not limited to this, and can be arbitrarily adjusted by controlling the etching amount with time. Furthermore, the planar size of the hole 2a is not limited to the above, and may be optimized in various ways.

  Subsequently, a TiN (titanium nitride) film having a thickness of about 50 nm is formed as a glue film 3 on the upper surface of the lower layer 2 and in the hole 2a by sputtering, and then W ( Tungsten) film 4 is formed to a thickness of about 600 nm, and hole 2a is completely filled.

  The material for embedding the hole 2a is not limited to the above, and the hole 2a may be embedded with a material that clearly shows a difference in refractive index with the lower layer 2. Examples of such materials include Ti (titanium), Al (aluminum), or alloys thereof, silicon materials such as polysilicon and amorphous silicon, and insulating films such as a silicon nitride film. However, since the metal is thermally diffused depending on the heat treatment in the subsequent process, a material to be embedded by the heat treatment is selected.

  Next, as shown in FIG. 1C, the excess glue film 3 and the W film 4 formed on the upper surface of the lower layer 2 are removed by polishing by CMP (chemical mechanical polishing) method. Is left as the marker material 5 only in the hole 2a.

  Next, steps required until a sectional structure shown in FIG.

  First, a first resist pattern 6 is formed on the lower layer 2 by photolithography, and the lower layer 2 is plasma-etched while using the first resist pattern 6 as an etching mask. Form. The recess 2b has a rectangular shape in plan view, and the vertical length of the rectangle is about 15.0 μm, and the horizontal length is about 10.0 μm. The depth of the recess 2b is about 0.6 μm. However, the depth of the recess 2b is not limited to this. The depth of the recess 2b can be arbitrarily adjusted by obtaining the etch rate of the lower layer 2 in advance and managing the etching time. Furthermore, the planar size of the recess 2b is not limited to the above, and may be optimized in various ways.

  Thereafter, the first resist pattern 6 is removed.

Next, as shown in FIG. 2 (b), the plasma CVD method using a mixed gas of SiH ₄ , N ₂ O, and N ₂ is performed on the inside of the recess 2b, on the marker material 5 and on the lower layer 2. A silicon oxynitride film is formed to a thickness of 1.0 μm or more, and this is used as the auxiliary core material layer 7. The refractive index of the auxiliary core material layer 7 is set to be higher than that of the lower layer 2, for example, 1.4965, by adjusting the flow rate of each gas in the mixed gas.

  Subsequently, as shown in FIG. 2C, the auxiliary core material layer 7 is polished by the CMP method while using the marker material 5 as a polishing stopper, and the polishing is stopped at the upper end of the marker material 5. As a result, the extra auxiliary core material layer 7 is removed from the upper surface of the lower layer 2, and the auxiliary core material layer 7 is left as the auxiliary core 7a only in the recess 2b.

  In this CMP, since the marker material 5 is used as a polishing stopper, a slurry in which the polishing rate of the marker material 5 is smaller than that of the lower layer 2 is used. An example of such a slurry is a system in which silica and potassium hydroxide are mixed.

Next, as shown in FIG. 3A, the lower layer 2 and the auxiliary core 7a are etched to reduce their thickness by plasma etching using CHF ₃ + CF ₄ + Ar as an etching gas. . In the present embodiment, this etching reduces the thickness of the auxiliary core 7a to about 0.40 μm. In this etching, the marker material 5 is hardly etched, and the upper end of the marker material 5 protrudes from the upper surface of the lower layer 2.

  Instead of plasma etching, the thickness of the auxiliary core 7a may be reduced by wet etching using HF or the like as an etching solution.

Next, as shown in FIG. 3B, a silicon oxide film is formed on the upper end of the marker material 5, on the auxiliary core 7a, and on the lower layer 2 by plasma CVD using SiH ₄ as a reaction gas. Is formed to a thickness of 0.25 μm, and this is used as the upper layer 8 of the lower cladding. The upper layer 8 has the same refractive index as the lower layer 2, for example a refractive index of about 1.46.

  Subsequently, as shown in FIG. 3C, the upper layer 8 is polished by the CMP method while using the marker material 5 as a polishing stopper to flatten the upper surface of the upper layer 8 and to increase the height of the upper surface. The height is the same as the height of the upper end of the marker material 5. In the present embodiment, the thickness of the upper layer 8 after CMP is 0.225 μm. In this CMP, since the marker material 5 is used as a polishing stopper, a slurry in which the polishing rate of the marker material 5 is smaller than that of the upper layer 8, for example, a system in which silica and potassium hydroxide are mixed is used.

  Through the steps so far, a lower clad 9 having a thickness of about 15 μm formed of the lower layer 2 and the upper layer 8 is formed, and a structure in which the auxiliary core 7a is embedded in the lower clad 9 is obtained. It will be.

Next, as shown in FIG. 4A, a silicon oxynitride film is formed on each of the marker material 5 and the lower clad 9 by plasma CVD using a mixed gas of SiH ₄ , N ₂ O, and N _2. Is formed to a thickness of 1.5 μm, which is used as the core material layer 10. The refractive index of the core material layer 10 is set to be higher than that of the lower cladding 9, for example, 1.4965, by adjusting the flow rate of each gas in the mixed gas.

  Subsequently, as shown in FIG. 4B, a first photoresist 11 is applied on the core material layer 10.

  Thereafter, as shown in FIG. 4C, the first photoresist 11 is exposed and developed to form core-shaped second resist patterns 11a and 11b.

  Next, steps required until a sectional structure shown in FIG.

First, the silicon substrate 1 is put into an unillustrated etching chamber, an etching gas composed of CHF ₃ + CF ₄ + Ar is introduced into the chamber, and the core material layer 10 is formed while using the second resist patterns 11a and 11b as a mask. Start etching. The light emitted from the plasma-ca material in the chamber is monitored by an end point detector (not shown), and the end point detector detects changes in the wavelength and intensity of the plasma light when the etching gas advances and the etching gas reaches the marker material 5. And etching is stopped at the upper end of the marker material 5. As a result, the first and second cores 10a and 10b formed by patterning the core material layer 10 are formed above the auxiliary core 7a. The first and second cores 10a and 10b both have a cross-sectional shape having a height of 1.5 μm and a width of 1.2 μm, and are formed with an interval of 0.8 μm therebetween.

  Further, according to this, since the marker material 5 is used for detecting the end point of etching, the etching is performed on the lower cladding 9 even though the difference in etch rate between the lower cladding 9 and the core material layer 10 is small. Can be stopped. Therefore, it is possible to prevent the lower clad 9 under the first and second cores 10a and 10b from being over-etched and causing skirting under the cores 10a and 10b. The light passing through can be prevented from being attenuated.

  Thereafter, the second resist patterns 11a and 11b are removed.

Next, as shown in FIG. 5B, a silicon oxide film having a thickness of about 9 μm is formed on the lower clad 9 and the first and second cores 10a and 10b by plasma CVD using SiH ₄ as a reaction gas. The upper clad material layer 12 is formed. The refractive index of the upper cladding material layer 12 is the same as that of the lower cladding 9 and is about 1.46. Further, unevenness reflecting each of the cores 10a and 10b is formed on the upper surface of the upper clad material layer 12.

  Next, steps required until a sectional structure shown in FIG.

First, the second photoresist 13 is applied to the entire surface of the upper cladding material layer 12. Next, the silicon substrate 1 is placed in an etching chamber (not shown), and the silicon substrate is placed on a susceptor in the chamber. Thereafter, CHF ₃ , CF ₄ , and Ar are supplied as etching gases into the etching chamber (not shown) at flow rates of 20, 80, and 400 sccm, respectively, and the pressure in the chamber is stabilized at 800 mTorr. By holding for 8 seconds, the second photoresist 13 is etched back by plasma etching to reduce its thickness. In the above-described etching chamber, the susceptor functions as a lower electrode, and a gas dispersion plate that is provided above the susceptor and releases an etching gas functions as an upper electrode. A high frequency power having a power of 1300 W and a frequency of 13.56 MHz is applied between the susceptor and the gas dispersion plate. The distance between the susceptor and the gas dispersion plate is set to about 11 mm.

  When the second photoresist 13 is applied and etched back in this manner, the irregularities on the upper surface of the second photoresist 13 are leveled, so that the second photoresist 13 has a shape due to the shape of each core 10a, 10b. The size of the undulations appearing on the upper surface is reduced.

  Next, as shown in FIG. 6B, by performing CMP from the upper surface of the second photoresist 13 after the etch back, the excess second photoresist 13 on the upper clad material layer 12 is polished and removed. At the same time, the upper cladding material layer 12 is planarized to form the upper cladding 12a. The upper clad 12 a has a thickness of 8 to 9 μm, for example, on the marker material 5.

  In the present embodiment, CMP is performed from the upper surface of the second photoresist 13 that has been planarized by etch back as described above, so that it is easy to planarize the upper clad 12a.

  Next, steps required until a sectional structure shown in FIG.

  First, a resist pattern (not shown) is formed on the upper clad 12a, and the upper clad 12a is etched using the resist pattern as a mask so that the first and second grooves 12b and 12c are formed above the auxiliary core 7a. Form. The size of each groove 12b, 12c is not limited, but in the present embodiment, the depth is 0.15 μm and the width is 1.2 μm.

  Subsequently, a TiN film is formed as a glue film in each groove 12b, 12c and on the upper clad 12a to a thickness of about 50 nm, and a W film is formed thereon by a CVD method to a thickness of about 100 nm. 12b and 12c are completely embedded. Thereafter, excess glue film and W film on the upper surface of the upper clad 12a are polished and removed by CMP. As a result, the glue film and the W film are left only in the grooves 12b and 12c to form the first and second heaters (heat generating portions) 13a and 13b. Each of the heaters 13a and 13b is provided so as to correspond to the first and second cores 10a and 10b. In the present embodiment, the sheet resistance value is about 2Ω / □.

  In addition, the formation method of the heaters 13a and 13b is not limited to the above. For example, instead of forming the grooves 12b and 12c in the upper clad 12a, a TiN film and a W film are formed on the entire surface of the flattened upper clad 12a, and these films are patterned to form first and second heaters. It is good also as 13a, 13b.

  Next, as shown in FIG. 7B, a Ti film, a TiN film, a Cu-containing Al film, and an anti-reflection TiN film are formed by sputtering in this order at thicknesses of 60 nm, 30 nm, 1.0 μm, and 100 nm, respectively. Thus, the multilayer metal film 14 is obtained.

  Next, as shown in FIG. 8A, a third photoresist 15 is applied on the multilayer metal film 14.

  Subsequently, as shown in FIG. 8B, the third photoresist 15 is exposed and developed to form third resist patterns 15a and 15b having a wiring shape.

  Thereafter, as shown in FIG. 9A, the multilayer metal film 14 is etched using the third resist patterns 15a and 15b as a mask to thereby electrically connect the first and second heaters 13a and 13b. First, second wirings 14a and 14b are formed. Thereafter, the third resist patterns 15a and 15b are removed.

  Next, as shown in FIG. 9B, a silicon oxide film having a thickness of 500 nm is formed by plasma CVD as a cover insulating film 16 that protects the wirings 14a and 14b and the upper cladding 12a. Instead of the silicon oxide film, a silicon oxynitride film, a silicon nitride film, or a laminated film thereof may be formed as the cover insulating film 16.

  Subsequently, as shown in FIG. 10A, a photoresist is applied on the cover insulating film 16, and exposed and developed to form a fourth resist pattern 17. The fourth resist pattern 17 includes hole-shaped first and second windows 17a and 17b on the wirings 14a and 14b.

  Next, as shown in FIG. 10B, the cover insulating film 16 is etched through the first and second windows 17a and 17b of the fourth resist pattern 17 to thereby form the upper surfaces of the first and second wirings 14a and 14b. First and second holes 16a and 16b are formed in the cover insulating film 16, respectively. Thereafter, the fourth resist pattern 17 is removed.

  Thereafter, lead-out wirings electrically connected to the first and second wirings 14a and 14b are formed in the holes 16a and 16b and on the cover insulating film 16, and the basic structure of the optical switching element according to the present embodiment. Is completed.

  FIG. 11 is a plan view of the optical switching element as a single unit, and FIG. 10B corresponds to a cross section taken along line II in FIG. However, in FIG. 11, the routing of the first and second wirings 14a and 14b is omitted.

  As shown in FIG. 11, the auxiliary core 7a has a rectangular planar shape straddling the cores 10a and 10b. The size of the rectangle is not particularly limited, but in this embodiment, the length is 15.0 μm and the width is 10.0 μm. Two first wirings 14a are provided at both ends of the first heater 13a, and a current is supplied to the first heater 13a through the first wiring 14a, so that the first heater 13a generates heat. The second heater 13b and the second wiring 14b have the same structure.

  Each heater 13a, 13b is provided independently above the first core 10a and the second core 10b, respectively, and has a structure capable of selectively heating each core 10a, 10b.

  Next, a method for controlling the optical switching element will be described with reference to FIG.

  FIG. 12 is a cross-sectional view of a main part for explaining the method for controlling the optical switching element according to the present embodiment.

  First, in order to move (switch) the light transmitted through the first core 10a to the second core 10b, only the first heater 13a generates heat by supplying a current from the first wiring 14a to the first heater 13a. . In this case, the second heater 13b is not supplied with current and does not generate heat.

  Thereby, since only the first core 10a close to the first heater 13a is selectively heated, the first core 10a is thermally expanded and its refractive index is lowered. Since the light has a property of moving from the low refractive index side to the high side, when the first core 10a is heated as described above, the light traveling in the first core 10a moves to the auxiliary cladding 7a having a high refractive index. Eventually, it moves to the 2nd core 10b, and switching is completed.

  Similarly, in order to switch light from the second core 10b to the first core 10a, it is only necessary to supply current to the second heater 13b to generate heat and to selectively heat only the second core 10b.

  According to the present embodiment described above, the auxiliary core 7a is embedded in the lower clad 9, and switching between the cores 10a and 10b is performed via the auxiliary core 7a. Therefore, in order to increase the switching speed, the core 10a 10b need not be close to each other. Therefore, the limitation on the interval between the cores 10a and 10b is relaxed, and the cores 10a and 10b can be freely routed compared with the case where the auxiliary core 7a is not provided, and the degree of freedom in designing the optical switching element can be increased. .

  Furthermore, since the lower cladding 9, the auxiliary core 7a, the first and second cores 10a and 10b, and the upper cladding 12a constituting the optical switching element are all formed by chemical vapor deposition, they are conventionally used. Compared with the case of forming by a flame hydrolysis deposition method, variation in refractive index and film thickness distribution is suppressed, and a high-quality optical switching element can be provided.

  In addition, as shown in FIG. 5A, the marker material 5 is formed in the hole 2a of the lower layer 2, and the core material layer 10 is etched and used while the marker material 5 is used for end point detection. Since the first and second cores 10a and 10b are formed, the etching of the core material layer 10 is desired on the upper surface of the lower cladding 9 even though the difference in the etching rate between the core material layer 10 and the lower cladding 9 is small. Can be stopped. As a result, it is possible to prevent the lower cladding 9 under the first and second cores 10a and 10b from being over-etched and causing bottoming under the cores 10a and 10b. The light passing through can be prevented from being attenuated.

  Further, when a semiconductor such as polysilicon or amorphous silicon or an insulator such as silicon nitride is employed as the material constituting the marker material 5, the elements constituting the marker material 5 are heated compared to the case where a metal is employed. Since it is difficult to diffuse into the lower clad 9 during the process, the refractive index of the lower clad 9 can be prevented from fluctuating due to the element, and a highly reliable optical switching element can be provided.

  Then, as shown in FIGS. 6A and 6B, before the upper surface of the upper cladding 12a is flattened by CMP, the second photoresist 13 is etched back and the surface thereof is leveled. 12a can be easily flattened.

(2) Second Embodiment In the first embodiment described above, as shown in the plan view of FIG. 11, two cores 10a and 10b are formed in one optical switching element, and each of the cores 10a and 10b is provided. On the other hand, two heaters 13a and 13b were formed. However, in the present invention, the number of cores and the number of heaters are not limited, and as described below, they may be formed more than in the first embodiment.

  FIG. 13 is a plan view of the optical switching element according to the present embodiment. In FIG. 13, the same elements as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted below.

  As shown in FIG. 13, the optical switching element includes a third core 10c and a fourth core 10d in addition to the first and second cores 10a and 10b. The third and fourth cores 10c and 10d are formed by the same process as the first and second cores 10a and 10b described above.

  On the other hand, the auxiliary core 7a is individually arranged in the first to fourth rows, and is common to the first to fourth cores 10a to 10d in each row.

  A plurality of first to fourth heaters 13a to 13d are provided along the extending direction of the first to fourth cores 10a to 10d, respectively.

  14 is a cross-sectional view taken along the line II-II in FIG.

  Next, a method for controlling the optical switching element will be described with reference to FIG.

  In FIG. 13, the light path is indicated by a thick arrow. In order to realize this optical path, in the second row, the first heater 13a and the third heater 13c are heated together to selectively heat the first core 10a and the third core 10c below them. . In this case, the second heater 13b is not heated.

  If it does in this way, since the 1st core 10a and the 3rd core 10c of the 2nd row will thermally expand and those refractive indexes will fall, the light which propagates the 1st core 10a will go to auxiliary core 7a with a higher refractive index. And finally move to the second core 10b.

  In the third row, the first and second cores 10a and 10b are selectively heated by the first and second heaters 13a and 13b, and the fourth heater 13d is not heated.

  As a result, the light transmitted through the second core 10b moves to the fourth core 10d via the auxiliary core 7a by the same principle as in the second row.

  According to this embodiment, it is possible to provide a multi-channel optical switching element having three or more inputs and outputs.

(3) Other Embodiments The optical switching elements described in the first and second embodiments are actually connected to an optical fiber or the like for practical use. Therefore, in the present embodiment, a method for suitably connecting the optical switching element and the optical fiber is provided.

  FIG. 15 is a plan view for explaining a method of joining the optical switching element and the optical fiber according to the first and second embodiments. In the figure, the same elements as those described in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and the description thereof is omitted below.

  As shown in FIG. 15, in the present embodiment, the cores 10 a to 10 d are radially expanded toward the emission end face (or the incident end face) of the optical switch so that the positions match the respective optical fibers 20. Further, the marker material 5 is arranged so that the cross section thereof appears on the emission end face (or the incident end face). The optical fiber 20 includes a core 20a through which light is transmitted and a clad 20b that wraps the core 20a.

  16 is a cross-sectional view taken along line III-III in FIG. As shown, when viewed from the optical fiber 20 side, the marker material 5 appears to be exposed from the optical switching element.

  In this embodiment, the marker material 5 exposed from the optical switching element is used as a reference for alignment between the core 20b of the optical fiber 20 and the first to fourth cores 10a to 10d. In this way, the first to fourth cores 10a to 10d, which are the same color as the lower cladding 9 (see FIG. 10B) and the upper cladding 12a and are difficult to distinguish from these, are aligned with the core 20b of the optical fiber 20. It becomes easy and the connection failure of the optical fiber 20 and an optical switching element can be prevented.

  The features of the present invention are added below.

(Appendix 1) a substrate,
A lower cladding formed on the substrate;
An auxiliary core embedded in the lower cladding;
A first core and a second core formed on the lower cladding on the auxiliary core and spaced apart;
An upper clad covering the first core and the second core;
An optical switching element, comprising: a heat generating portion that is provided on the upper clad and selectively heats one of the first core and the second core.

  (Additional remark 2) The said auxiliary | assistant core is provided under the said heat-emitting part, The optical switching element of Additional remark 1 characterized by the above-mentioned.

  (Supplementary note 3) The optical switching element according to supplementary note 1, wherein the heat generating portion is independently provided above the first core and above the second core.

  (Additional remark 4) The said heat-emitting part is provided with two or more along the extension direction of the said 1st core, and the extension direction of the said 2nd core, The optical switching element of Additional remark 3 characterized by the above-mentioned.

  (Supplementary Note 5) The light according to Supplementary Note 1, wherein a marker material made of a material different from the lower clad is provided in the lower clad, the upper end having the same height as the upper surface of the lower clad. Switching element.

(Additional remark 6) The process of forming the lower layer of a lower clad by a chemical vapor deposition method on a substrate,
Forming a recess in the lower layer of the lower cladding;
Forming an auxiliary core in the recess;
Forming an upper layer of the lower cladding on the lower layer of the lower cladding and the auxiliary core;
Forming a core material layer on the upper layer of the lower cladding by chemical vapor deposition;
Patterning the core material layer to form a first core and a second core at an interval above the auxiliary core;
Forming an upper clad covering the first and second cores by chemical vapor deposition;
Forming a heat generating portion in the upper clad. A method of manufacturing an optical switching element, comprising:

(Appendix 7) Before forming the auxiliary core, there is a step of forming a hole in the lower layer of the lower clad, and a step of forming a marker material made of a material different from the lower clad in the hole. And
The step of forming the auxiliary core includes a step of forming an auxiliary core material layer in the recess, on the marker material, and on a lower layer of the lower clad, and using the marker material as a polishing stopper. Polishing the auxiliary core material layer by a mechanical polishing method, stopping the polishing at the upper end of the marker material, and leaving the auxiliary core material layer only in the recess to form the auxiliary core. The manufacturing method of the optical switching element of Claim 6.

(Appendix 8) After forming the auxiliary core, reducing the thickness of the lower layer of the auxiliary core and the lower cladding by etching, and projecting the upper end of the marker material from the upper surface of the lower layer; ,
Forming an upper layer of the lower cladding on an upper end of the marker material, on the auxiliary core, and on a lower layer of the lower cladding;
While using the marker material as a polishing stopper, the upper layer of the lower cladding is polished by a chemical mechanical polishing method to flatten the upper surface of the upper layer, and the height of the upper surface is set to the height of the upper end of the marker material. The manufacturing method of the optical switching element of Claim 7 characterized by having the same process as these.

  (Supplementary Note 9) The step of forming the first and second cores is performed by etching the core material layer by plasma etching, and the marker material is used for detecting the end point of the plasma etching. The method for manufacturing an optical switching element according to appendix 7.

  (Additional remark 10) The manufacturing method of the optical switching element of Additional remark 7 characterized by forming any of a metal film, a semiconductor film, and an insulating film as said marker material.

  (Additional remark 11) The manufacturing method of the optical switching element of Additional remark 10 characterized by forming a polysilicon film or an amorphous silicon film as said semiconductor film.

(Supplementary Note 12) The step of forming the upper cladding includes:
Forming an upper clad material layer covering the first and second cores, and flattening an upper surface of the upper clad material layer, and using the flattened upper clad material layer as the upper clad. The manufacturing method of the optical switching element according to appendix 6, which is characterized by the above.

  (Supplementary note 13) The method for manufacturing an optical switching element according to supplementary note 12, wherein the step of planarizing the upper cladding material layer is performed by polishing the upper cladding material layer by a chemical mechanical polishing method.

  (Additional remark 14) It has the process of apply | coating a resist on the said upper clad material layer before the said grinding | polishing, and the process of etching back the said resist, The said grinding | polishing is carried out from the upper surface of this resist after the said etch back. 14. The method for manufacturing an optical switching element according to appendix 13, wherein the optical switching element is manufactured.

(Additional remark 15) The process of forming the wiring electrically connected with the said heat-emitting part on the said upper clad,
Forming an insulating film covering the wiring;
The method for producing an optical switching element according to appendix 6, further comprising: forming a hole having a depth reaching the wiring in the insulating film.

(Supplementary Note 16) The step of forming the heat generating portion includes:
Forming a first groove and a second groove in the upper cladding on the first core and the second core, respectively;
The light according to claim 6, further comprising: forming a metal film in each of the first groove and the second groove, and using the metal film in the first and second grooves as the heat generating portion. A method for manufacturing a switching element.

  (Supplementary note 17) The method of manufacturing an optical switching element according to supplementary note 7, comprising a step of connecting an optical fiber to the first core or the second core while using the marker material as a reference for alignment. .

(Supplementary Note 18) A first core and a second core embedded in a clad at a distance from each other, an auxiliary core embedded in the clad across the first core and the second core, and A control method of an optical switching element comprising a heat generating part that selectively heats one of the first core and the second core,
A method for controlling an optical switching element, wherein the first core is selectively heated by the heat generating portion, and light transmitted through the first core is moved to the second core via the auxiliary core. .

  (Supplementary note 19) The method for controlling an optical switching element according to supplementary note 18, wherein the auxiliary core is provided apart from the first and second cores.

  (Supplementary Note 20) The third core is provided in the clad so as to be arranged in the order of the third core, the first core, and the second core, and the third core and the first core are heated by the heating portion. The light switching element control method according to appendix 18, wherein light transmitted through the first core is moved to the second core via the auxiliary core.

FIGS. 1A to 1C are main part cross-sectional views (part 1) in the course of manufacturing according to the method for manufacturing an optical switching element according to the first embodiment of the present invention. FIGS. 2A to 2C are cross-sectional views (No. 2) of main parts in the course of manufacturing according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. FIGS. 3A to 3C are cross-sectional views (No. 3) of the main part in the course of manufacture according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. 4A to 4C are principal part cross-sectional views (part 4) in the course of manufacturing according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. FIGS. 5A and 5B are cross-sectional views (No. 5) of the main part in the course of manufacture according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. FIGS. 6A and 6B are cross-sectional views (No. 6) of main parts in the course of manufacturing according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. FIGS. 7A and 7B are cross-sectional views (No. 7) of main parts in the course of manufacturing according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. FIGS. 8A and 8B are cross-sectional views (No. 8) of the main part in the course of manufacture according to the method for manufacturing the optical switching element according to the first embodiment of the present invention. FIGS. 9A and 9B are cross-sectional views (No. 9) showing the principal part of the optical switching element according to the first embodiment of the present invention in the course of manufacturing. FIGS. 10A and 10B are cross-sectional views (No. 10) showing the main part of the optical switching element according to the first embodiment of the present invention during the manufacturing process. FIG. 11 is a plan view of the optical switching element according to the first embodiment of the present invention. FIG. 12 is a cross-sectional view of relevant parts for explaining the control method of the optical switching element according to the first embodiment of the present invention. FIG. 13 is a plan view of an optical switching element according to the second embodiment of the present invention. FIG. 14 is a cross-sectional view of a main part of an optical switching element according to the second embodiment of the present invention. FIG. 15 is a plan view for explaining a method of joining the optical switching element and the optical fiber according to the first and second embodiments of the present invention. FIG. 16 is a cross-sectional view of an essential part for explaining a method of joining the optical switching element and the optical fiber according to the first and second embodiments of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Lower layer of lower clad, 2a ... Hole, 2b ... Recess, 3 ... Glue film, 4 ... W film, 5 ... Marker material, 6 ... First resist pattern, 7 ... Auxiliary core material layer , 7a ... auxiliary core, 8 ... upper clad of lower clad, 9 ... lower clad, 10 ... core material layer, 10a, 10b ... first and second cores, 11 ... first photoresist, 11a, 11b ... second resist Pattern: 12 ... Upper clad material layer, 12a ... Upper clad, 13 ... Second photoresist, 13a, 13b ... First, second heater, 14 ... Multi-layer metal film, 14a, 14b ... First, second wiring, 15 3rd photoresist, 15a, 15b ... 3rd resist pattern, 16 ... Cover insulating film, 16a, 16b ... 1st, 2nd hole, 17 ... 4th resist pattern, 17a, 17b ... 1st, 2nd window, 20 ... Hikari Fiber, 20a ... core, 20b ... clad.

Claims (5)

A substrate,
A lower cladding formed on the substrate;
An auxiliary core embedded in the lower cladding;
A first core and a second core formed on the lower cladding on the auxiliary core and spaced apart;
An upper clad covering the first core and the second core;
An optical switching element, comprising: a heat generating portion that is provided on the upper clad and selectively heats one of the first core and the second core. Forming a lower clad lower layer on the substrate by chemical vapor deposition;
Forming a recess in the lower layer of the lower cladding;
Forming an auxiliary core in the recess;
Forming an upper layer of the lower cladding on the lower layer of the lower cladding and the auxiliary core;
Forming a core material layer on the upper layer of the lower cladding by chemical vapor deposition;
Patterning the core material layer to form a first core and a second core at an interval above the auxiliary core;
Forming an upper clad covering the first and second cores by chemical vapor deposition;
Forming a heat generating portion in the upper clad. A method of manufacturing an optical switching element, comprising: Before forming the auxiliary core, forming a hole in the lower layer of the lower clad, and forming a marker material made of a material different from the lower clad in the hole,
The step of forming the auxiliary core includes a step of forming an auxiliary core material layer in the recess, on the marker material, and on a lower layer of the lower clad, and using the marker material as a polishing stopper. Polishing the auxiliary core material layer by a mechanical polishing method, stopping the polishing at the upper end of the marker material, and leaving the auxiliary core material layer only in the recess to form the auxiliary core. The manufacturing method of the optical switching element of Claim 2.   The step of forming the first and second cores is performed by etching the core material layer by plasma etching, and the marker material is used for detecting an end point of the plasma etching. The manufacturing method of the optical switching element of description. A first core and a second core embedded in the cladding at a distance from each other; an auxiliary core embedded in the cladding across the first core and the second core; and the first core and A control method of an optical switching element comprising a heat generating part that selectively heats one of the second cores,
A method for controlling an optical switching element, wherein the first core is selectively heated by the heat generating portion, and light transmitted through the first core is moved to the second core via the auxiliary core. .

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