JP6962029B2 - A method for manufacturing a semiconductor substrate and an optical circuit manufactured by that method. - Google Patents

Description

The present invention relates to a semiconductor substrate and a method for producing the same. More specifically, the present invention relates to a semiconductor substrate in which semiconductors having different physical characteristic values are integrated, and a method for manufacturing the semiconductor substrate.

Communication traffic continues to increase regardless of whether it is wired or wireless communication, and optical devices for optical communication are widely used from backbone systems to access systems. An optical device for optical communication is configured on a semiconductor chip based on a semiconductor having a single composition (crystal) such as Si or a compound semiconductor such as InP. An optical circuit on a semiconductor chip has many elements such as a laser as a light source, a modulator that encodes information into carrier light from the laser, and an optical waveguide that connects the elements of the laser and the modulator by waveguideing the light. Consists of.

In general, the physical characteristics of semiconductors required to form each element such as an optical laser, a modulator, and a waveguide on an optical circuit are often different. This is because the optimum semiconductor physical property value for constituting each element differs depending on the function to be realized by the element. Therefore, when a plurality of optical circuit elements are monolithically integrated on the same substrate, a technique for forming a plurality of semiconductor regions having different physical property values on the semiconductor substrate is required.

5 and 6 are diagrams showing the manufacturing process of the semiconductor substrate of the prior art, respectively. Each figure shows a top view of the substrate of the rectangular device and a cross-sectional view cut perpendicular to the substrate surface through the AA'line. FIG. 5A shows a state (Step 1) in which a mask is formed on a multilayer film substrate having two layers formed on the substrate 101. The multilayer film substrate is, for example, a semiconductor substrate 101 in which a core layer 102 and a clad layer 103 are epitaxially grown in this order. A mask 104 corresponding to the shape of the element of the optical circuit to be formed is formed on the multilayer film substrate. Next, as shown in FIG. 5B, the core layer 102 and the clad layer 103 are removed in a region other than the mask 104 region by the etching step (Step 2). As described above, the semiconductor region originally included in the multilayer film substrate is completely removed by the etching process, leaving a "partial region" directly under the mask 104.

Further, as shown in FIG. 5 (c), in the next step, the second semiconductor having different physical property values from the initially formed core layer 102 and the clad layer 103 on the multilayer film substrate is grown again. (Step 3). At this stage, the second core layer 105 and the second clad layer 106 are formed in a region other than the mask 104, and the first semiconductor region composed of the core layer 102 and the clad layer 103 is formed on the substrate 101. , A second semiconductor region composed of a second core layer 105 and a second clad layer 106 is configured. After the state of (c) of FIG. 5, the mask 104 is removed so that two semiconductor regions appear on the surface, and optical circuits are continuously produced in each region. As in each step shown in FIGS. 5A to 5C, a plurality of semiconductors having different physical property values are obtained by leaving a part of the initially formed semiconductor and newly regrowth the second semiconductor. A semiconductor substrate in which a region was formed was obtained.

FIG. 6 is a diagram illustrating a process of manufacturing an optical circuit on a substrate having two types of semiconductor regions by a conventional technique. The step following the state of (c) of FIG. 5 starts with the mask 104 of (c) of FIG. 5 being removed. As shown in FIG. 6A, a third clad layer 107 is further formed on the entire surface of the two types of clad layers 103 and 106. The waveguide 107a is formed by etching and removing only a part of the third clad layer 107 by using a mask in the same manner as described with reference to FIG. On the substrate, as shown in FIG. 6B, a waveguide composed of a first semiconductor region composed of a core layer 102 and a clad layer 103 as shown in the cross section of the AA'line, and a waveguide. A waveguide composed of a second semiconductor region composed of a core layer 105 and a clad layer 106, such as a cross section of a BB'line, is produced. In both the first semiconductor region and the second semiconductor region, the light propagated by the third clad layer feels the physical characteristics (refractive index difference) of the core layer and the clad layer, respectively, and the light is confined.

Hideki Yagi, Naoko Inoue, Ryuji Masuyama, Takehiko Kikuchi, Tomokazu Katsuyama, Yoshihiro Tateiwa, Katsumi Uesaka, Yoshihiro Yoneda, Masaru Takechi, and Hajime Shoji, “InP-Based pin-Photodiode Array Integrated With 90 ° Hybrid Using Butt-Joint Regrowth for Compact 100 Gb / s Coherent Receiver ”, 2014 IEEE JSTQE, VOL. 20, NO. 6, 3900107 Nobuhiro Kikuchi, Hiroaki Sanjoh, Yasuo Shibata, Ken Tsuzuki, Tomonari Sato, Eiichi Yamada, Tadao Ishibashi, and Hiroshi Yasaka, “80-Gbitls InP DQPSK modulator with an n-p-i-n structure”, 2007 in Proc. Of ECOC 2007, 10.3.1 T. Tsuchiya, J. Shimizu et al., “InGaAlAs selective-area growth on an InP substrate by metalorganic vapor-phase epitaxy”, 2005, Journal of Crystal Growth 276 (2005) 439-445 Yuta Ueda et al., “InP-based compact transversal filter for monolithically integrated light source array”, 2014 Optical Society of America

However, the method of forming a plurality of semiconductor regions having different physical property values in the prior art on a substrate has the following problems.

First, the manufacturing method of the prior art has a problem that the area of the first semiconductor region that can be formed in the "initial semiconductor" is limited. In the steps described with reference to FIGS. 5 to 6, a first semiconductor region having a predetermined shape was produced by using a mask on the initially produced semiconductor layer. In the following description, the semiconductor first formed on the substrate will be referred to as the "initial semiconductor" for the sake of simplicity. In FIGS. 5 to 6, the initial semiconductor corresponds to the core layer 102 and the clad layer 103.

In order to additionally manufacture a second semiconductor having a different physical property value on the substrate in addition to the initial semiconductor, as shown in FIG. 5 (c), the portion corresponding to the initial semiconductor is the first. The second semiconductor (second core layer 105, second clad layer 106) is covered with a mask 104 before growth. As the mask 104, for example, a dielectric mask such as _{SiO 2 is used.} In semiconductor epitaxial growth, no semiconductor is grown on the mask 104. Therefore, during the growth of the second semiconductor, the material molecules that have reached the mask 104 diffuse on the mask, and reach and grow on the substrate 101 that is not covered by the mask 104 or the formed semiconductor layer 105.

FIG. 7 is a diagram illustrating a problem of a method of manufacturing a plurality of semiconductor regions in the prior art. In epitaxial growth of compound semiconductors, semiconductors are grown using a plurality of semiconductor materials. Further, the degree of diffusion of the material molecules during the above-mentioned epitaxial growth differs depending on the semiconductor material. Considering these, it means that the material composition ratio is different between the semiconductor grown in the vicinity of the dielectric mask and the semiconductor grown in a position sufficiently distant from the dielectric mask. That is, the compositions of the second core layer 105 and the second clad layer 106 are different between the region 110 in the vicinity of the striped mask 104 in FIG. 7 and the region 111 in the distance. Fluctuations in the composition ratio in each layer cause fluctuations in various optical characteristics, electrical characteristics, etc. of the optical circuit in manufacturing a monolithic integrated semiconductor chip. In compound semiconductors, all physical property values differ depending on the composition ratio of the constituent materials. Therefore, not only the band gap and mobility of the semiconductor are different, but also the optical characteristics such as the refractive index are changed. For example, the refractive index felt by the propagating light due to fluctuations in the physical property values of the second core layer 105 and the second clad layer 106 on both sides along the length direction of the waveguide 107a configured as shown in FIG. Also fluctuates.

Secondly, there is a problem that the unevenness of the substrate surface after producing the two semiconductor regions becomes large. In addition to the above-mentioned problem of composition ratio fluctuation, a more direct problem is that two semiconductor regions are produced by increasing the growth rate of the semiconductor in the region 110 near the dielectric mask 104 as shown in FIG. The unevenness on the surface of the substrate after that becomes large. Depending on the composition ratio, production conditions, and the like, the film thickness of the formed layer may increase by 10 to 20% in the region 110 near the mask 104 as compared with the region 111 away from the mask 104. This causes deterioration of the accuracy when processing an optical circuit element such as a waveguide with respect to the semiconductor substrate after the two semiconductor regions have been formed. According to Non-Patent Document 3, it is reported that the growth rate on the side of the mask reaches 1.3 times in the case of a mask width of several tens of um.

One of the effective means for avoiding the above-mentioned problems of composition fluctuation and unevenness of the substrate surface is to make the area of the dielectric mask as small as possible. The area of the dielectric mask is determined by the area of the initial semiconductor required to create a particular optical circuit. Some optical devices, such as lasers, have an elongated striped shape. As shown in the top view of FIG. 6B, the dielectric mask must be arbitrarily set to the required length according to the predetermined design specifications for the function of the optical circuit to be realized. There is little room for adjustment in reducing the area of the mask in the length direction of the mask along the direction of the waveguide. After all, in many cases, it can be said that the area of the dielectric mask of an optical circuit is determined only by the width of the mask, which is perpendicular to the direction of the waveguide.

If you want to locally re-grow another semiconduct afterwards while leaving as wide an area as possible for the initially formed semiconductor on the substrate, the mask area will be very wide, so the elongated stripes as described above. There is also a problem that the method for manufacturing a semiconductor substrate using a mask cannot be applied. This means that in the conventional method for manufacturing a semiconductor substrate, the order in which semiconductor regrowth is performed is restricted depending on the semiconductor type.

One of the factors that determines the order of regrowth of different semiconductors is the problem of thermal history. In the semiconductor manufacturing process, not only the regrowth of semiconductors, it is ideal that the process temperature is lowered as the process progresses. For example, when the initial semiconductor first formed on the substrate is vulnerable to high temperatures, there is a limit to the growth temperature when the semiconductor is subsequently regrown. Another factor that determines the order of regrowth is the availability of semiconductor substrates. Some semiconductor manufacturing processes can be manufactured by a general-purpose process that is generally easy to carry out, while others need to be manufactured by a process that requires know-how. A semiconductor wafer that can be easily inserted from the outside can be used as a multilayer substrate including the core layer 102 and the clad layer 103 of FIG. 5A that can be manufactured by a general-purpose process. When the semiconductor layer to be re-grown has a special structure that requires know-how, a multilayer film substrate on which a ready-made initial semiconductor is preformed is used at a lower cost than the outside as a preliminary step for manufacturing an optical circuit as a product. It is more rational to get it. As described above, in the conventional method for manufacturing a semiconductor substrate, the mask area is also determined under the constraint of a certain order in the semiconductor manufacturing process.

In fact, in general, the width of the dielectric mask is often in the range of about 10 μm to 100 μm in consideration of the above-mentioned composition fluctuation. This is because the manufacturing process of the semiconductor substrate shown in FIGS. 5 to 6 is inappropriate when the width of the optical circuit element in the first semiconductor region formed by the semiconductor mask in the semiconductor initially exceeds 100 μm. means. As described above, in the method of the prior art, when manufacturing a semiconductor substrate having a plurality of semiconductor regions having different physical property values, it is difficult to form a semiconductor region including element elements of an optical circuit having a wide occupying area, and it is difficult to form a semiconductor region in a plurality of semiconductor regions. It becomes difficult to monolithically integrate optical circuits across the board.

The present invention has been made in view of such a problem, and an object of the present invention is a method of forming a plurality of semiconductor regions having different physical property values on a substrate, including a semiconductor region having a wider occupied area. Is to provide. Further, an optical circuit using a semiconductor substrate manufactured by the method of the present invention is also provided.

In order to achieve such an object, the invention according to claim 1 is a method for manufacturing a semiconductor substrate including two or more semiconductor regions having different physical property values, and is formed on the substrate. Initially, a step of forming a mask layer for processing a part of a semiconductor, a step of forming an opening having a square, rectangular or diamond shape having a side length of 100 μm or more in the mask layer, and the opening. A frame-shaped mask is removed by removing the mask layer, leaving a width GW from the inner circumference of the opening and the step of forming a groove having a predetermined shape in the initial semiconductor by performing etching using the portion. and forming a, a step wherein the width GW is less than greater than 0 20 [mu] m, the initially semiconductor of the groove, a step of growing a semiconductor having different physical properties from the original semiconductor, the initial The method is characterized by comprising a step of removing the semiconductor having different physical property values formed outside the groove of the semiconductor.

The invention according to claim 2 is the method of claim 1, wherein the groove of the initial semiconductor is rectangular, and the initial semiconductor forms a plurality of waveguides in parallel with one side of the rectangle. It is characterized by further providing.

The invention according to claim 3 is the method according to claim 1 or 2 , wherein the two or more semiconductor regions are composed of a compound semiconductor.

According to the present invention, it is possible to form a plurality of semiconductor regions having different physical property values on a substrate, including a semiconductor region having a wider occupied area.

FIG. 1 is a diagram illustrating a process of a method for manufacturing a semiconductor substrate of the present invention. FIG. 2 is a diagram illustrating a continuation of the process of the method for manufacturing a semiconductor substrate of the present invention. FIG. 3 is a diagram further explaining the process of the method for manufacturing the semiconductor substrate of the present invention. FIG. 4 is a diagram showing a configuration of an IQ modulator in which the LDA of the present invention is integrated. FIG. 5 is a diagram showing a manufacturing process of a semiconductor substrate of the prior art. FIG. 6 is a diagram showing a manufacturing process of an optical circuit on a semiconductor substrate of the prior art. FIG. 7 is a diagram illustrating a problem of a plurality of semiconductor region manufacturing methods of the prior art.

In the method for manufacturing a semiconductor substrate of the present invention, a groove is formed in a part of the initial semiconductor of the semiconductor substrate instead of leaving only a part of the initial semiconductor on the semiconductor substrate to form a semiconductor region for the target optical circuit. It is formed, and an additional semiconductor having a physical property value different from that of the initial semiconductor is formed in this groove by regrowth. Initially, a semiconductor region made of a semiconductor having a physical property value different from that of a semiconductor is formed, and a semiconductor substrate in which a plurality of semiconductor regions having different physical characteristic values are formed is manufactured.

In the method of manufacturing a semiconductor substrate of the prior art, only a part of the initial semiconductor first created on the substrate is left as the first semiconductor region, and the physical property value is different from that of the initial semiconductor instead of the removed initial semiconductor. The semiconductor was regrown over the entire surface of the substrate to form a second semiconductor region. A predetermined optical circuit or circuit element was formed in the first semiconductor region of the initial semiconductor first formed on the substrate and the second semiconductor region formed by regrowth, respectively.

In the method for manufacturing a semiconductor substrate of the present invention, a part of the initially formed semiconductor initially formed on the semiconductor substrate is removed to form a groove, and an additional semiconductor having a physical property value different from that of the initially semiconductor is regenerated in the groove. Grow and regrow the second semiconductor domain. The initial semiconductor, which leaves most of the parts other than the groove, is used as the first semiconductor region. In the present invention, an optical circuit initially configured in the semiconductor region of a semiconductor in the prior art is formed in the semiconductor region formed by regrowth in the groove. As a result, the limitation of the area for forming the optical circuit is greatly relaxed, and the semiconductor region having different physical property values can be formed in a wider occupied area without causing the problem of the fluctuation of the physical characteristic values and the unevenness of the substrate surface. Can be done. The present invention also provides an integrated optical circuit including optical circuit elements formed on each semiconductor region produced by the above method.

Hereinafter, a more specific manufacturing procedure of a method for manufacturing a plurality of semiconductor regions having different physical property values on a substrate will be described with reference to the drawings. The configuration of the integrated optical circuit will also be described.

1 to 3 are diagrams for explaining the method for manufacturing the semiconductor substrate of the present invention, respectively. Each figure shows a top view of the semiconductor substrate and a cross-sectional view cut perpendicular to the substrate through the AA'line. FIG. 4 is a diagram showing a configuration of an IQ modulator in which a light source manufactured on a semiconductor substrate manufactured through the steps of FIGS. 1 to 3 is monolithically integrated. As will be described later, the IQ modulator is monolithically formed on a single substrate by combining a semiconductor laser diode array (LDA) and two Mach-Zehnder modulators (MZM). According to the method for manufacturing a semiconductor substrate of the present invention, a semiconductor region is partially grown in a groove to form an LDA. The LDA occupies a larger area in proportion to the number of lasers to be arrayed. For example, if 100 lasers are arrayed with the width of the waveguide constituting the laser being 2 μm and the distance between adjacent lasers being 5 μm, a width of 700 μm is required as a circuit region for LDA. One of the features of the IQ modulator is that it requires a large area as compared with other optical devices (Non-Patent Document 2).

FIG. 1 is a diagram illustrating a process of a method for manufacturing a semiconductor substrate of the present invention. FIG. 1A shows the initial state (Step 1) in which the mask is formed on the multilayer film substrate. The semiconductor substrate includes a core layer 2 having a 500 nm Multi-Quantum Well (MQW) structure formed on an InP substrate 1 from III-V source materials of In, Al, Ga, and As, and a core layer. A multilayer film substrate in which an InP clad layer 3 having an InP cladding layer of about 100 nm was grown on the 2 was used. The MQW structure described above is transparent to light in the 1.55 μm band, which is important in optical communication. On the other hand, in the optical waveguide having an MQW structure, when a voltage is applied to the core layer 2, its refractive index changes due to the quantum confinement Stark effect. The composition of the core layer 2 having an MQW structure is adjusted so that it can be used as MZM by utilizing this change in the refractive index. Such a multilayer InP substrate may be produced by a usual method for forming a compound semiconductor layer, or a commercially available multilayer InP substrate in which the core layer 2 and the clad layer 3 have already been completed may be used.

In Step 1 of FIG. 1A, the mask layer 4 is formed on the clad layer 3 of the multilayer film substrate. As the material of the mask layer 4, for example, SiO ₂ can be used. The mask material is opened by a photolithography step and an insulating film etching step to form an opening mask having an opening 5a and having a predetermined shape.

In Step 2 of FIG. 1 (b), the InP clad layer 3 and the MQW core layer 2 on the substrate are removed by a semiconductor etching step using the mask layer 4 processed into an aperture mask, and the mask layer 4 is placed on the semiconductor substrate 1. A groove 5b is formed. In the top view of the groove 5b, the longitudinal direction is the direction of the laser waveguide of the LDA. Therefore, the width of the groove 5b in the cross-sectional view corresponds to the width direction of a large number of guided waveguides arranged in an array. Here, the term "groove" is not limited to a striped shape or a rectangular shape, but has an arbitrary shape, and is perpendicular to the substrate surface from the top surface of the substrate formed by removing a part of the semiconductor by etching. Refers to the recess formed in. In the example of FIG. 1B, the groove removes all the two semiconductor layers 2 and 3 and reaches the upper surface of the substrate 1 which is the base of the semiconductor substrate. Further, the "groove" may be one in which the middle of one or more semiconductor layers is removed by etching in the direction perpendicular to the substrate surface (groove depth direction).

FIG. 2 shows a step following from FIG. 1, and FIG. 2A shows a step (Step 3) of forming a mask for regrowth, which is characteristic of the method for manufacturing a semiconductor substrate of the present invention. As described in the prior art, it is preferable that the area of the insulating film serving as a mask on the substrate is small during semiconductor growth. Therefore, the mask layer 4 is removed leaving the width GW from the inner circumference including the end face of the opening 5a forming the groove. The _{mask layer 4 is removed from the SiO 2} mask by a photolithography step and an insulating film etching step to form a frame-shaped mask 6 having a side surface perpendicular to the substrate surface inside the groove 5b and having a continuous side surface. It becomes the state of Step 3 of (a).

Here, the width GW of the frame-shaped mask 6 has a certain selection width. If the width GW of the frame-shaped mask 6 is too wide, as described in the prior art, the semiconductor composition grown in the subsequent semiconductor regrowth _{fluctuates in the vicinity of the SiO 2} mask, or the unevenness of the substrate obtained by the regrowth becomes uneven. There is a problem of growing up. On the other hand, if all the mask layer 4 is removed after the groove 5b is formed (that is, GW = 0), the step of removing the surplus semiconductor described below may become difficult depending on the subsequent regrowth conditions. Considering the above conditions, the width GW of the frame-shaped mask 6 includes the case of 0, and is preferably in the range of 0 to approximately 20 μm. Within this range, the width of the dielectric mask can be suppressed to 20 μm at the maximum, so that the semiconductor composition in the vicinity of the mask does not fluctuate and the substrate obtained by regrowth does not have irregularities.

FIG. 2B shows a subsequent step, showing an additional semiconductor regrowth step (Step 4). After forming the frame-shaped mask 6 in Step 3, an additional semiconductor having a physical property value suitable for forming the LDA is re-grown. Specifically, the MQW core layers 7a and 7b formed from the III-V source materials of In, Al, Ga, and As, and the MQW core layer in order to match the height of the uppermost surface of the original semiconductor substrate. InP clad layers 8a and 8b as overclads are grown on the top. The composition of this MQW core layer is adjusted so as to emit light in the 1.5 μm band when an electric current is injected.

At the stage (b) of FIG. 2, a substrate structure in which a core layer and a clad layer, which are new semiconductors, are regrown both inside and outside the groove 5b. In applying this semiconductor substrate to the production of an actual concrete optical circuit, the core layer 7a and the clad layer 8a outside the groove 5b are unnecessary as semiconductors for LDA, for example, and are surplus semiconductors. Therefore, by a photolithography process, a second mask is formed so as to cover the regrown semiconductor necessary for manufacturing the optical circuit, that is, the core layer 7b and the clad 8b in the groove 5b, and the core layer 7a and the clad which are surplus semiconductors are formed. It is preferable to remove 8a. As the second mask, for example, a resist mask can be used. That is, the resist may be applied to the wafer in the state of FIG. 2B, and the photolithography step may be performed so that the resist remains only in the groove 5b. After that, the core layer 7a and the clad 8a, which are surplus semiconductors, are removed.

As described above, if the width GW of the frame-shaped mask 6 is 0 in this removing step, it may be difficult to selectively etch only the semiconductor, the core layer 7a, and the clad 8a outside the groove 5b. Therefore, the width GW of the frame-shaped mask 6 includes the case where the width GW is 0, and the width GW is preferably in the range of 0 to approximately 20 μm.

FIG. 3 shows a subsequent step, and FIG. 3A shows a state (Step 5) in which the surplus semiconductor outside the groove is removed. FIG. 3A shows a state after the core layer 7a and the clad 8a, which are surplus semiconductors, and the second mask for removing the surplus semiconductor have already been removed. Therefore, the core layer 7b and the clad 8b layer are formed inside the frame-shaped mask 6 by the regrown additional semiconductor, and the core which is the initial semiconductor is continuously connected to these two layers along the substrate surface. The layer 2 and the clad layer 3 are configured. When the frame-shaped mask 6 is removed in the state of FIG. 3A, an additional regrown semiconductor for LDA is produced only inside the groove 5b, and the outside of the groove 5b becomes the initial semiconductor for MZM. The semiconductor substrate is in the manufactured state.

In each of the steps of FIGS. 1 to 3 described above, the opening 5a has a rectangular shape, a rectangular groove 5b is formed, and a frame-shaped mask 6 having a rectangular outline is formed. .. The shape of the opening 5a for regrowth of the additional semiconductor may be any shape as long as there is no problem in device fabrication in other steps. However, shapes such as squares, rectangles, and rhombuses are often preferred. This is because semiconductors are generally materials with strong plane orientation in fabrication. This is because it is more convenient for the above-mentioned step of removing the surplus semiconductor that the outer circumference of the opening 5a is parallel to a predetermined plane direction or has a specific angle. For example, in the case of performing wet etching with a chemical solution that is particularly susceptible to the plane orientation, if the outer circumference of the opening 5a has a relationship consistent with the plane orientation, the surplus up to the state of FIG. 3 (a) is reached. The semiconductor removal step can be carried out more easily.

In the method for manufacturing a semiconductor substrate of the present invention, the semiconductor region for manufacturing a specific optical circuit is not limited (10 μm to 100 μm) as in the prior art due to the limitation of the mask width. Therefore, with respect to the size of the opening 5a, an arbitrary optical circuit having a larger size can be configured according to the required specifications. However, in the present invention, considering that optical circuits are integrated over different types of semiconductors over a wide area on a single substrate, when the shape of the opening 5a such as a square, a rectangle, or a rhombus is adopted, one side is per. When is 100 μm or more, the effect of the method for manufacturing a semiconductor substrate of the present invention is exhibited. Considering the case of this embodiment, the mask width of the rectangular LDA portion formed in the first semiconductor region by leaving the semiconductor initially in the prior art is limited to 100 μm at the maximum. However, when the LDA portion is formed in the first semiconductor region by the additional semiconductor regrown in the groove by the manufacturing method of the present invention, the mask width can exceed 100 μm, of course, and reaches 700 μm. Everything can be created.

FIG. 3B shows the final step of the method for manufacturing a semiconductor substrate of the present invention, which is a state (Step 6) in which an overclad is formed to form a semiconductor substrate that can be made into a device. A layer necessary for forming a device is produced on a semiconductor substrate on which two types of semiconductors having different physical property values are produced. If necessary, an InP layer 9 as an overclad and a contact layer such as InGaAs that makes contact with an electrode (not shown) can be further grown to obtain a semiconductor substrate that can be made into a device.

Therefore, the present invention is a method for manufacturing a semiconductor substrate including two or more semiconductor regions having different physical property values, the step of forming a mask layer for processing a part of the initial semiconductor formed on the substrate, and the above-mentioned step. From the step of forming an opening having a predetermined shape in the mask layer, the step of performing etching using the opening to form a groove having a predetermined shape in the initial semiconductor, and the inner circumference of the opening. A step of removing the mask layer to form a frame-shaped mask while leaving a width GW, and a step of growing a semiconductor having a physical property value different from that of the initial semiconductor in the groove of the initial semiconductor. It can be carried out as a method characterized by providing.

FIG. 4 is a diagram showing a configuration of an IQ modulator manufactured on a semiconductor substrate manufactured through the steps of FIGS. 1 to 3 described above. A top view of the substrate surface and a cross-sectional view taken through the XX'and YY'lines and perpendicular to the substrate surface are shown. The IQ modulator 20 in which a plurality of light sources are monolithically integrated is composed of an LDA unit 21 and an IQM unit 22. The LDA unit 21 includes a plurality of semiconductor laser arrays 25 formed in the first semiconductor region 10 (core layer 7b and clad layer 8b) formed by the regrowth semiconductor layer formed in the groove by the substrate manufacturing method of the present invention. It is composed of a wave portion 27. As can be seen from the cross section passing through the XX'wire, the semiconductor laser array 25 is composed of a waveguide of the core layer 7b defined by each of the striped electrodes of the overclad layer 9.

The IQM unit 22 includes the first MZM23 and the second MZM24, and outputs the modulated light 28 from the end portion of the substrate. The IQM is composed of an interference circuit including an arm waveguide manufactured in a second semiconductor region made of a semiconductor initially by the substrate manufacturing method of the present invention. As can be seen from the cross-sectional view passing through the YY'line, the arm waveguide of each MZM is composed of the core layer 2 defined by the striped electrodes 26a to 26d. In the semiconductor substrate obtained by the manufacturing method of the present invention, an additional semiconductor (second semiconductor region) that is re-grown in the groove and has a physical property value suitable for LDA is used, and the physical property value fluctuates and the surface is uneven. LDA with a larger occupied area can be produced without causing the problem of. On the other hand, LDA in the second semiconductor region having a large occupied area is monolithically integrated by using the initial semiconductor (first semiconductor region) having a physical characteristic value different from that of the additional semiconductor and having a physical characteristic value suitable for MZM. It is possible to realize an optical circuit.

A substrate having a plurality of semiconductor regions according to the substrate manufacturing method of the present invention includes an IQ modulator in which a plurality of light sources are monolithically integrated as shown in FIG. 4, a plurality of light sources (LD array), and a combiner circuit (transversal by MMI). It can also be applied to an optical circuit or the like in which a filter) is combined (Fig. 3 of Non-Patent Document 4).

The present invention also has an aspect of a monolithic integrated optical circuit, which is an optical circuit formed on a semiconductor substrate including two or more semiconductor regions having different physical property values, and is formed on the substrate. It was manufactured on a regrown semiconductor having a physical property value different from that of the initially semiconductor in the first optical circuit initially manufactured on the semiconductor and in the groove formed by removing a part of the initially semiconductor. It can also be implemented as an optical circuit including a second optical circuit, wherein the shape of the groove is a square, a rectangle, or a diamond having a side length of 100 μm or more. Preferably, the first optical circuit includes an optical modulator that includes two Mach-Zehnder interferometers, and the second optical circuit includes an LDA that is an array of multiple lasers.

In addition to the IQ modulator in which multiple light sources are monolithically integrated as in the embodiment, in various optical circuits including a Mach-Zehnder interferometer (MZI), a semiconductor region in which an optical circuit having a very large occupied area is formed is formed on a substrate. A plurality of semiconductor regions having different physical property values including the above are required. According to the method for manufacturing a semiconductor substrate of the present invention, a semiconductor region capable of forming an optical circuit element having a wider area without being limited by the mask width of the prior art and causing problems of fluctuations in physical characteristics and surface irregularities. A semiconductor substrate having a plurality of semiconductor regions having different physical property values including the above can be obtained. An optical circuit in which circuit elements having various functions can be combined can be configured over a plurality of semiconductor regions on the semiconductor substrate.

The method for manufacturing a semiconductor substrate of the present invention requires a large area in a semiconductor region to be newly regrown and formed in order to fabricate a specific optical circuit, and is a region that can be formed by a mask by a conventional method. It is very effective when the optical circuit does not fit. According to the embodiment, in the conventional method for manufacturing a semiconductor substrate, the LDA portion is formed by leaving a part of the semiconductor initially with a striped mask. However, the area where the LDA portion can be produced is limited due to the limitation of the mask width due to the fluctuation of the physical property value and the problem of surface unevenness. In contrast, in the method for manufacturing a semiconductor substrate of the present invention, a groove is initially formed in the semiconductor by a mask having an opening, and a new additional semiconductor is re-grown in the groove, so that there is no size limitation. The LDA portion can be formed.

As described in the prior art, the application of the method for manufacturing a semiconductor substrate of the present invention is more preferable from the viewpoint of the order of regrowth of semiconductors when manufacturing a plurality of semiconductor regions having different physical property values on a semiconductor substrate. Can be considered. When a large area is required for a circuit element to be manufactured on a semiconductor by regrowth at a low temperature, it is difficult to use a conventional method for manufacturing a semiconductor substrate due to problems of fluctuations in physical property values and surface irregularities. .. Since the method for manufacturing a semiconductor substrate of the present invention has no size limitation on the semiconductor region to be regrown, it is suitable when a large area is required for a circuit element to be manufactured on a semiconductor by regrowth at a low temperature. Further, the method for manufacturing a semiconductor substrate of the present invention is also suitable when it is necessary to prepare a circuit element having a large area in a semiconductor to be regrown and a special process requiring know-how is required for the regrowth.

In the method for producing the semiconductor substrate of Example 1 described with reference to FIGS. 1 to 4, a case where a core layer and a clad layer are formed on the InP substrate has been described as an example. In a compound semiconductor such as InP, the composition fluctuation around the dielectric mask as described above occurs, so that the method for producing a semiconductor substrate of the present invention is very effective. However, the present invention is not limited to compound semiconductors, but is also applicable to single crystal substrates such as Si. For example, when a groove is dug in Si and Ge that is compatible with Si is grown in the groove, the method for producing a semiconductor substrate of the present invention can be applied. In the case of a single crystal substrate such as a Si substrate, fluctuations in physical properties are generally less likely to occur than in a compound semiconductor. However, a mask exists when forming a semiconductor region having different physical property values, and if the growth rate around the mask changes, the lattice constant of a single crystal is distorted and grows. Therefore, even in the case of a Si substrate, so-called defective abnormal growth may occur. Further, the problem of unevenness of the substrate can occur even in a single crystal substrate. The method for producing a semiconductor substrate of the present invention is also applicable to a single crystal substrate such as Si.

Further, in the above-described embodiment, a case where two types of semiconductors, an initial semiconductor and an additional semiconductor to be regrowth, are manufactured and two semiconductor regions are formed on the substrate has been described as an example. However, it can also be applied to the case of forming three or more kinds of semiconductors having more complicated and different physical characteristic values on a substrate. That is, after removing the frame-shaped mask 6 in the state of FIG. 3 (a), the steps from Step 1 of FIG. 1 (a) to Step 5 are further carried out at a new location on the substrate. Therefore, a third semiconductor region can be formed.

As described in detail above, according to the method for manufacturing a semiconductor substrate of the present invention, a plurality of semiconductor regions including a semiconductor region having a wider occupied area and having different physical property values can be formed on the substrate.

The present invention can generally be used for optical communication devices.

1, 101 Substrate 2, 7a, 7b, 102, 105 Core layer 3, 8a, 8b, 9, 104, 106 Clad layer 5a Opening 5b Groove 6 Frame mask 20 Monolithic integrated IQ modulator 21 LDA
22 IQM section 23, 24 MZM
27 Wave section

Claims (3)

A method for manufacturing a semiconductor substrate containing two or more semiconductor regions having different physical property values.
A step of forming a mask layer for processing a part of the initially semiconductor formed on the substrate, and
A step of forming an opening having a square, rectangular or rhombic shape having a side length of 100 μm or more in the mask layer.
A step of performing etching using the opening to form a groove having a predetermined shape in the initial semiconductor, and
A step of removing the mask layer while leaving a width GW from the inner circumference of the opening to form a frame-shaped mask, wherein the width GW is greater than 0 and 20 μm or less.
A step of growing a semiconductor having a physical characteristic value different from that of the initial semiconductor in the groove of the initial semiconductor ,
A method comprising: removing a semiconductor having different physical characteristic values formed outside the groove of the initially semiconductor . The method according to claim 1, wherein the groove of the initial semiconductor is rectangular, and further comprises a step of forming a plurality of waveguides in parallel with one side of the rectangle by the initial semiconductor. The method according to claim 1 or 2 , wherein the two or more semiconductor regions are composed of a compound semiconductor.

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